Rozprawy doktorskie: „AFM Modes”

1

Devailly, Clémence. "Fluctuations thermiques - un outil pour étudier les fluides simples et binaires à l'échelle du micron". Thesis, Lyon, École normale supérieure, 2014. http://www.theses.fr/2014ENSL0976.

Pełny tekst źródła

Streszczenie:

Les transitions de phase près d'un point critique - dites du second ordre - sont un sujet toujours d'actualité en raison des nombreux phénomènes critiques intéressants tels que la force de Casimir critique, les problèmes de confinements ou les phénomènes hors d'équilibre suivant une trempe au point critique. Cette thèse vise à étudier expérimentalement certains phénomènes engendrés près d'un point critique. La thèse est divisée en deux axes : le premier consiste à développer plusieurs systèmes expérimentaux qui permettront de mesurer essentiellement la viscosité, par l'intermédiaire des fluctuations thermiques à l'échelle micrométrique. Le deuxième axe consiste à trouver et caractériser des mélanges binaires présentant une transition de phase du second ordre dans lesquelles on souhaite faire des mesures. Les enjeux de ces systèmes expérimentaux sont d'avoir une régulation en température précise, une sonde de mesure sensible aux fluctuations thermiques et/ou à des forces de l'ordre du pN, et un échantillon fiable et reproductible présentant un point critique accessible expérimentalement. Nous avons ainsi monté à partir d'un microscope à force atomique (AFM) déjà présent au laboratoire, un système de mesure de viscosité à sonde AFM fibrée. Malgré sa faible efficacité en terme de sonde de mesure métrologique, nous avons pu décrire et développer un modèle de couplage de modes de vibration permettant de comprendre la mécanique de microleviers AFM fibrés. J'ai également développé au laboratoire la mesure de microscopie dynamique différentielle qui permet de faire des mesures à sondes multiples contrairement au premier montage. J'ai discuté de la précision de la mesure dans le cadre de notre objectif d'étude des fluctuations critiques. En ce qui concerne l'échantillon de mesure, nous avons étudié plusieurs mélanges binaires que nous avons caractérisés par des méthodes classiques de turbidité et diffusion statique de la lumière. Cette caractérisation nous a permis de connaître les mélanges binaires pour les utiliser dans un troisième système de mesure : billes micrométriques piégées dans des pinces optiques déjà monté au laboratoire. Nous y avons rajouté un système de régulation thermique fait maison pour être exploité avec les contraintes de la pince optique. Ces tests ont fait apparaître un phénomène inattendu d'oscillations de transition de phase induites par laser. Nous avons développé un modèle pour les décrire. Enfin, des expériences préliminaires - toujours avec les pinces optiques dans les mélanges binaires - nous ont permis d'observer qualitativement des effets de l'approche au point critique par des mesures de viscosité et d'interaction type force de Casimir critique
Phase transitions near a critical point, or second order phase transitions, are still a recent object of studies because of the large amount of interesting critical phenomena as the critical Casimir force, confinements problems or out of equilibrium phenomena following a quench at the critical point. This thesis experimentally studies phenomena near a critical point. This manuscript is divided in two parts : the first one consists in building several experimental set-up which measure viscosity through thermal fluctuation at micrometric scale. The second part consists in finding and characterize binary mixtures which show a second order phase transition. Preliminary results have been done in these samples. One of the principal points of these experimental set-up are a well regulated temperature, a probe sensitive to thermal fluctuation and/or pN forces and a reproducible binary mixture which presents a critical point easy to reach experimentally. We mounted from an Atomic Force Microscope (AFM) already built in the laboratory, a hanging-fiber probe to measure viscosity of liquids. Despite its weak efficiency as a metrologic probe, we described and developed a mode coupling model which let us understand mechanics of hanging-fiber probes. I also developed in the lab the dynamic differential microscopy technique (DDM) which do measurements with several probes. I discussed about the measure precision with in mind the aim of studying critical fluctuations. For the choice of the sample, we studied several binary mixtures. We characterized them by classical methods as turbidity measurements and static light scattering. These characterizations let us learn about binary mixtures in order to use them in a third experimental set-up : beads trapped in an optical tweezers already built in the lab. We added to it a home-made thermal regulation which can be used with the constraints of optical tweezers. These tests showed an unexpected phenomenon of oscillating phase transition induce by laser. We developed a model to describe it. At last, preliminary experiments with optical tweezers in binary mixtures showed qualitative effects of an approach near a critical point on the viscosity and on interactions between beads as critical Casimir force

Style APA, Harvard, Vancouver, ISO itp.

2

Oral, Hasan Giray. "Modeling time-resolved interaction force mode AFM imaging". Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43691.

Pełny tekst źródła

Streszczenie:

Intermittent contact mode atomic force microscopy has been widely employed for simultaneous topography imaging and material characterization. The work in the literature includes both qualitative and quantitative methods. Regular AFM cantilevers are generally used in these methods, yet these cantilevers come with certain limitations. These limitations result from the very nature of cantilever probes. They are passive force sensors with insufficient damping. This prevents having active and complete control on tip-sample forces, causing sample damage and inaccurate topography measurement. Ideally, an AFM probe should offer high bandwidth to resolve interaction forces, active control capability for small interaction force and stable operation, and sufficient damping to avoid transient ringing which causes undesired forces on the sample. Force sensing integrated readout and active tip (FIRAT) probe offers these properties. A special imaging mode, time-resolved interaction force (TRIF) mode imaging can be performed using FIRAT probe for simultaneous topography and material property imaging. The accuracy of topography measurement of samples with variations in elastic and adhesive properties is investigated via numerical simulations and experiments. Results indicate that employing FIRAT probe's active tip control (ATC) capability during TRIF mode imaging provides significant level of control over the tip-sample forces. This improves the accuracy of topography measurement during simultaneous material property imaging, compared to conventional methods. Moreover, Active tip control (ATC) preserves constant contact time during force control for stable contact while preventing loss of material property information such as elasticity and adhesive forces.

Style APA, Harvard, Vancouver, ISO itp.

3

Billingsley, Daniel Jeffrey. "Convergent transcription and nested gene models studied by AFM". Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/3149/.

Pełny tekst źródła

Streszczenie:

Genomic DNA is organised in complex spatial arrangements, and a given stretch of DNA may encode more than one gene. In some cases one gene may be entirely contained within a region of the DNA already occupied by another larger gene. The presence of these nested genes, often situated in introns and in the opposite orientation, poses important implications with regards to gene expression, function and regulation. A consequence of the nested gene arrangement is convergent transcription, occurring when two promoters on opposite DNA strands are active. Elucidating the mechanics of multiple interacting proteins on single DNA templates requires single molecule methods such as atomic force microscopy (AFM). AFM can accurately determine the relative positions of enzymes, such as RNA polymerase (RNAP), on individual DNA templates. The central aim of this thesis is to use AFM to study the outcomes of convergent transcription, using linear DNA templates that function as models for nested genes. Fundamental aspects of imaging DNA on mica with AFM were investigated, with a view to optimising sample preparation. The main processes involved with preparing DNA samples, ready for scanning, were examined in turn. Effective binding was achieved by introducing divalent cations into a deposition buffer. Mica ion exchanged with Ni(II) usually gave rise to kinetically-trapped DNA molecules, however short linear fragments (< 800bp) were seen to deviate from the expected behaviour, indicating that ion-exchanged mica is heterogeneous, and contains patches or domains. These findings can be used to more readily control binding of DNA to substrates. The outcomes of varying the relative humidity while imaging biomolecular systems are largely unexplored to date. Various DNA samples were imaged in conditions of varying humidity. In particular when supercoiled plasmids are scanned at very high relative humidity (> 90% RH), localised DNA backbone motions or conformational changes were observed. Humidity controlled AFM will be a useful technique for probing DNA topology without some of the drawbacks of imaging under bulk solution. Initial studies of transcription utilised templates containing two promoter sites and E. Coli RNAP. Two promoter arrangements were studied: a convergent template containing the promoter sites on opposite strands directed towards each other, and a tandem template containing the promoters in the same direction, on the same stand. It was shown that collisions between RNAPs led to similar outcomes in both cases: RNAPs are unable to pass each other and remain stalled against each other. In the convergent case, it was observed that after collision one RNAP could cause another to backtrack along the template. By end-labelling double-stranded (ds) DNA templates with a single-stranded DNA loop, the polarity of the molecules can be established in the AFM. It allowed better discrimination between outcomes of collision events on single DNA molecules and importantly, it enabled a quantitative comparison of the relative frequencies of the outcomes. The most common outcome is a collision between an actively transcribing elongation complex (EC) and a “sitting duck” (SD), which is a stalled RNAP or open promoter complex (OPC). In collisions initiated from OPCs, the most likely outcome, a collision between an EC and an SD occurs ~74% of the time. This causes sizeable back-tracking of the inactive RNAP, on average 59 nm upstream of the promoter. A significant fraction of the collisions (~15%) are between actively transcribing RNAP while the remainder (~11%) are undetermined. End-labelling of dsDNA using nucleic acid structures did not interfere with AFM sample preparation and can be used as a generic approach to studying interactions of multiple proteins on DNA templates at the single molecule level.

Style APA, Harvard, Vancouver, ISO itp.

4

Yurtsever, Ayhan. "Nanotribological surface characterization by frequency modulated torsional resonance mode AFM". Diss., kostenfrei, 2008. http://edoc.ub.uni-muenchen.de/8718/.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

5

Stone, Peter (Peter Robert). "A new model for electric force microscopy and its application for electrostatically generated phase difference in tapping mode AFM". Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32855.

Pełny tekst źródła

Streszczenie:

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.
Includes bibliographical references (leaf 37).
The harmonic force balance method was used to model and simulate electric force microscopy (EFM) and electrostatically generated phase difference in tapping mode AFM (EPTA) measurements. Simulations show that the harmonic force balance approach matches and explains EFM and EPTA experimental results well. Simulations also show that the model depended on both geometric and materials parameters. The harmonic force balance model was subsequently used to directly simulate a previously performed EPTA experiment. Data obtained from the model showed a remarkable similarity to the experimentally obtained data, thus validating the use of the harmonic force balance model to simulate EPTA data.
by Peter Stone.
S.B.

Style APA, Harvard, Vancouver, ISO itp.

6

Nasrallah, Hussein. "Capillary adhesion and friction : an approach with the AFM Circular Mode". Phd thesis, Université du Maine, 2011. http://tel.archives-ouvertes.fr/tel-00651818.

Pełny tekst źródła

Streszczenie:

The aim of this thesis is concerned with the influence of sliding velocity on capillary adhesion at the nanometer scale. In ambient conditions, capillary condensation which is a thermally activated process, allows the formation of a capillary meniscus at the interface between an atomic force microscope (AFM) probe and a substrate. This capillary meniscus leads to a capillary force that acts as an additional normal load on the tip, and affects the adhesion and friction forces. The Atomic Force Microscopy (AFM) offers interesting opportunities for the measurement of surface properties at the nanometer scale. Nevertheless, in the classical imaging mode, limitations are encountered that lead to a non stationary state. These limitations are overcome by implementing a new AFM mode (called Circular AFM mode). By employing the Circular AFM mode, the evolution of the adhesion force vs. the sliding velocity was investigated in ambient conditions on model hydrophilic and hydrophobic surfaces with different physical-chemical surface properties such as hydrophilicity. For hydrophobic surfaces, the adhesion forces or mainly van der Waals forces showed no velocity dependence, whereas, in the case of hydrophilic surfaces, adhesion forces, mainly due to capillary forces follow three regimes. From a threshold value of the sliding velocity, the adhesion forces start decreasing linearly with the logarithm increase of the sliding velocity and vanish at high sliding velocities. This decrease is also observed on a monoasperity contact between a atomically flat mica surface and a smooth probe, thus eliminating the possibility of the kinetics of the capillary condensation being related to a thermally activated nucleation process as usually assumed. Therefore, we propose a model based on a thermally activated growth process of a capillary meniscus, which perfectly explains the experimental results. Based on these results, we focused on directly investigating with the Circular mode the role of capillary adhesion in friction mechanisms. We investigated the influence of the sliding velocity on the friction coefficient, and a decrease following three regimes, similar to the sliding velocity dependence of the capillary adhesion, was observed for hydrophilic surfaces that possess a roughness higher than 0.1 nm. Whereas, an increase of the friction coefficient was observed on hydrophilic (Mica) or hydrophobic (HOPG) atomically flat surfaces that posses a roughness lower than 0.1 nm. However, in this latter case, the three regimes are not established. Finally, on a rough hydrophobic surface, the friction coefficient was sliding velocity independent. A direct comparison with capillary adhesion behavior with the sliding velocity is expected to give new insights to explain this interplay.

Style APA, Harvard, Vancouver, ISO itp.

7

Hida, H., M. Shikida, K. Fukuzawa, A. Ono, K. Sato, K. Asaumi, Y. Iriye i K. Sato. "Quartz tuning-fork type AFM probe operated in Anti-phase Vibration Mode". IEEE, 2006. http://hdl.handle.net/2237/9554.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

8

Lin, Zhen. "AFM electrical mode development for nanostructure semiconductor study : application on Ge / Si nanostructure". Lyon, INSA, 2010. http://theses.insa-lyon.fr/publication/2010ISAL0135/these.pdf.

Pełny tekst źródła

Streszczenie:

Aujourd'hui, la technologie des semi-conducteurs est confrontée au défi de la réduction ultime de la taille des composants pour augmenter la performance des appareillages électroniques en les miniaturisant. Cette forte réduction d'échelle provoque un développement considérable des techniques de microscopie pour révéler de nouvelles caractéristiques physiques à l'échelle nanométrique. La compréhension de ces nouvelles propriétés à l'échelle du nanomètre est donc de première importance. Dans ce travail, l’utilisation et l’application des techniques de caractérisation des propriétés électriques par microscopie à force atomique à pointes conductrices sont développées vis-à-vis de l’application aux semi-conducteurs. Les modes électriques spécifiques, comprenant la mesure de capacité par microscopie AFM (SCM) et la spectroscopie associée (SCS), la microscopie à force électrostatique (EFM) et la microscopie à sonde locale de Kelvin (KPFM) sont utilisées à température ambiante pour étudier les propriétés électroniques de nanostructures de germanium sur silicium qui ont été fabriquées par un procédé de démouillage. Il ressort que les mesures SCM, SCS, EFM et KPFM sont bien adaptées pour la caractérisation de nanostructures semi-conductrices, en particulier pour l'étude des nanocristaux à l'échelle du nanomètre. Ces travaux de caractérisation par AFM à modes électriques sont d'une importance primordiale dans le développement de dispositifs électroniques, en particulier pour l'application de transistors à mémoire utilisant des nanoilots de Ge / Si
Nowadays, the semiconductor technology is facing a great challenge to increase the device performance while reducing its dimension. This downscaling in microelectronics industry causes a drastic development of microscopy to reveal new physical characteristics at nanoscale. The understanding of these new properties in nanometer scale is of prime importance. In this work, the AFM fundamental working principle and some typical electric property characterization techniques in semiconductor industry were introduced. The electrical AFM modes including scanning capacitance microscopy (SCM) and spectroscopy (SCS), electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KPFM) were developed at room temperature to study the properties of the promising replacement of the conventional poly-silicon floating gate, Germanium nanocrystals local Ge/Si nanostructures, which were fabricated by dewetting process. SCM, SCS, EFM and KPFM were proved to be available methodologies for semiconductor nanostructures characterizations, especially the nanocrystal study in nanometer scale. These characterisation works with developed AFM electrical mode are of prime importance in developing electronic devices application, especially the memory transistors application using Ge/Si nanocrystal

Style APA, Harvard, Vancouver, ISO itp.

9

Sebinelli, Heitor Gobbi. "Estudo de proteolipossomos constituídos de Na,K-ATPase utilizando a técnica de microscopia de força atômica". Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-21092016-140434/.

Pełny tekst źródła

Streszczenie:

A Na, K-ATPase (NKA) é uma proteína de membrana encontrada em organismos eucariotos multicelulares cuja atividade e funções já são amplamente discutidas na literatura. Sua unidade funcional corresponde a um heterodímero formado por duas subunidades , com regiões transmembrana. Espécies multiméricas como dímeros e tetrâmeros dessa enzima também são conhecidos por exercer atividade enzimática. As interações lipídio-proteína são intrínsecas para a NKA, por tal motivo, proteolipossomos constituídos de DPPC e DPPC:DPPE foram preparados por co-solubilização. Como controle, lipossomos de mesma composição foram produzidos por extrusão e/ou sonicação. Para as imagens de AFM, as amostras foram fixadas com glutaraldeído, para proteção mecânica e contra desidratação das vesículas. Para lipossomos de DPPC as imagens topográficas de AFM das vesículas apresentaram formato oval, superfície perfeitamente lisa e diâmetro médio de 151 + 46 nm, enquanto as vesículas de composição DPPC:DPPE, apesar de lisas, tiveram cantos pontiagudos e diâmetro médio de 98 + 28 nm. Imagens de fase de ambas as composições não apresentaram qualquer indicativo de diferenças na composição química, provavelmente devido à natureza de carga neutra dos dois fosfolipídios. As imagens de fase por AFM para os proteolipossomos tanto de DPPC-NKA, quanto DPPC:DPPE-NKA, revelaram resultados inéditos na literatura, onde a inserção da NKA aparece como nítidas regiões transições de fase de composição química distinta quando comparadas com os lipossomos. No entanto, as mudanças de fase são diferentes entre as composições estudadas, aparecendo como manchas escuras circulares para DPPC-NKA e mais visíveis como interstícios brilhantes para composição de DPPC:DPPE-NKA. As vesículas de DPPC-NKA apresentaram diâmetro médio de 390 + 326 nm e, nas imagens de topografia tridimensionais, protusões de 38 a 115 nm correspondentes às regiões de mudanças de fase, que, indicaram o diâmetro dos microdomínios relacionados à proteína. Já nas imagens para DPPC:DPPE-NKA o diâmetro médio dos proteolipossomos foi de 189 + 156 nm, e as protusões apareceram entre os interstícios, variando de 20 a 66 nm. O estudo de DSC dos lipossomos revelou que a concentração de glutaraldeído nas condições das análises de AFM, em torno de 5% (v/v), afetam as características físico-químicas para as composições com DPPE. A AFM foi eficiente para confirmar a reinserção da NKA em proteolipossomos pelas imagens de fase, e, para medir o diâmetro dos microdomínios pelas imagens de topografia.
Na, K-ATPase (NKA) is a membrane protein present in eukaryotic multicellular organisms. Its functions and activity are already widely described in the literature. Its minimal functional structure is a heterodimer of two main subunits , with transmembrane domains. However, dimers and tetramers of the enzyme are also known to have enzymatic activity. Since there are intrinsic lipid-protein interactions, NKA proteoliposomes composed of DPPC and DPPC:DPPE (1:1 molar ratio) were prepared by the co-solubilization method and liposomes of the same compositions were obtained by extrusion and/or sonication to be used as control. The samples to the AFM study were prepared using glutaraldehyde to protect the vesicles from mechanical shocks and dehydration. Liposomes composed of DPPC and DPPC:DPPE (1:1 molar ratio) were prepared by extrusion and sonication, respectively, as control. The topographical images for DPPC liposomes showed vesicles with an oval shape and smoothed surfaces with a mean diameter of 151 + 46 nm. DPPC:DPPE vesicles also presented smoothed surfaces, but with pointed corners and mean diameter of 98 + 28 nm. Phase images for both lipid compositions showed no differences in chemical composition. For DPPC:DPPE samples, this can be explained by the neutral net charge of both lipids. The proteoliposomes observed in the AFM phase images showed darker and large circular spots in the vesicles. These spots represent delays in the phase oscillation of the AFM probe and are associated with different chemical composition. The phase changes showed the reconstitution of the NKA in the proteoliposomes. When compared with topographical images, this spots matched protrusions. The mean diameter of DPPC-NKA proteoliposomes determined by AFM was 390 + 326 nm. In the three-dimensional topographical images of composition, protrusions from 38 to 115 nm near the areas of different phases indicate the diameters of the NKA microdomains. The phase changes for DPPC:DPPE-NKA appeared as bright interstices with the protrusions of the topographical images in between them. The size of these protrusions ranged from 20 to 66 nm and the mean diameter of the proteoliposomes was 189 + 156 nm. The DSC liposomes data showed that the glutaraldehyde concentration used in the AFM analysis affect the physical chemistry properties of the samples with DPPE. AFM proved to be an efficient method to confirm the reconstitution of into proteoliposomes with phase images and to determine the diameter of the protein microdomains with the topographical images.

Style APA, Harvard, Vancouver, ISO itp.

10

Horstmeier, Sebastian [Verfasser]. "Dynamische AFM-Kraftspektroskopie an Desoxyribonukleinsäure im frequenz-modulierten Modus mit konstanter Anregung / Sebastian Horstmeier". Bielefeld : Universitätsbibliothek Bielefeld, 2013. http://d-nb.info/1045878561/34.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

11

El-Rifai, Khalid 1979. "Control of AFMs in contact mode". Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/17597.

Pełny tekst źródła

Streszczenie:

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2003.
Includes bibliographical references (leaves 71-74).
The Atomic Force Microscope (AFM) is a high precision surface characterization tool commonly used in Nano-technology, Bio-technology, semiconductors, MEMS, and life sciences' applications. As most versatile systems, AFM offers little guarantees on achieving repeatable satisfactory operation. This is the case as AFMs are not used to perform a single predictable task. AFM systems are feedback regulators, which rely on photodiode detector (PSD) sensing and piezoelectric actuation. The change in probe-surface contact is a disturbance created by scanning across a surface. This disturbance is to be rejected to maintain probe-surface contact and thus allow proper surface characterization. AFM feedback systems are not only required to maintain a nominal PSD output but also guarantee that the control signal used is representative of the rejected disturbance. This is due to the fact that the image of the scanned surface is created from this control voltage. These characteristics impose severe limitations on the system's operation bandwidth, repeatability, and precision. In this effort, the key characteristics and limitations of AFM operation are analyzed. Challenges due to surface variations, plant dynamics, and contact nonlinearity are presented. The closed loop response of AFM systems in single actuator as well as in dual actuator configurations is evaluated. The emphasis is on the underlying structure corresponding to each configuration and not on a particular system tuning. In this regard, the bounds on achievable performance in each configuration are contrasted for operation within the system's overall objectives.
by Khalid El-Rifai.
S.M.

Style APA, Harvard, Vancouver, ISO itp.

12

Rozmovits, Linda 1959. "A.M. Klein and modernism". Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64004.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

13

Fermé, Eduardo. "On the Logic of Theory Change : Extending the AGM Model". Doctoral thesis, KTH, Filosofi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-29601.

Pełny tekst źródła

Streszczenie:

This thesis consists in six articles and a comprehensive summary. • The pourpose of the summary is to introduce the AGM theory of belief change and to exemplify the diversity and significance of the research that has been inspired by the AGM article in the last 25 years. The research areas associated with AGM was divided in three parts: criticisms, where we discussed some of the more common criticisms of AGM. Extensions where the most common extensions and variations of AGM are presented and applications where we provided an overview of applications and connections with other areas of research. • Article I elaborates on the connection between partial meet contractions [AGM85] and kernel contractions [Han94a] in belief change theory. Also both functions are equivalent in belief sets, there are notequivalent in belief bases. A way to define incision functions (used in kernel contractions) from selection functions (used in partial meet contractions) and vice versa is presented. It is explained under which conditions there are exact correspondences between selection and incision functions so that the same contraction operations can be obtained by using either of them. • Article II proposes an axiomatic characterization for ensconcement-based contraction functions, belief base functions proposed byWilliams and relates this function with other kinds of base contraction functions. • Article III adapts the Fermé and Hansson model of Shielded Contraction [FH01] as well as Hansson et all Credibility-Limited Revision [HFCF01] for belief bases, to join two of the many variations of the AGM model [AGM85], i.e. those in which knowledge is represented through belief bases instead of logic theories, and those in which the object of the epistemic change does not get the priority over the existing information as it is the case in the AGM model. • Article IV introduces revision by comparison a refined method for changing beliefs by specifying constraints on the relative plausibility of propositions. Like the earlier belief revision models, the method proposed is a qualitative one, in the sense that no numbers are needed in order to specify the posterior plausibility of the new information. The method uses reference beliefs in order to determine the degree of entrenchment of the newly accepted piece of information. Two kinds of semantics for this idea are proposed and a logical characterization of the new model is given. • Article V focuses on the extension of AGM that allows change for a belief base by a set of sentences instead of a single sentence. In [FH94], Fuhrmann and Hansson presented an axiomatic for Multiple Contraction and a construction based on the AGM Partial Meet Contraction. This essay proposes for their model another way to construct functions: Multiple Kernel Contraction, that is a modification of Kernel Contraction,proposed by Hansson [Han94a] to construct classical AGM contractions and belief base contractions. • Article VI relates AGM model with the DFT model proposed by Carlos Alchourrón [Alc93]. Alchourrón devoted his last years to the analysis of the notion of defeasible conditionalization. His definition of the defeasible conditional is given in terms of strict implication operator and a modal operator f which is interpreted as a revision function at the language level. This essay points out that this underlying revision function is more general than AGM revision. In addition, a complete characterization of that more general kind of revision that permits to unify models of revision given by other authors is given.
QC 20110211

Style APA, Harvard, Vancouver, ISO itp.

14

Sarker, Md Omar Faruque. "Self-regulated multi-robot task allocation". Thesis, University of South Wales, 2010. https://pure.southwales.ac.uk/en/studentthesis/selfregulated-multirobot-task-allocation(4b92f28f-c712-4e75-955f-97b4e5bf12dd).html.

Pełny tekst źródła

Streszczenie:

To deploy a large group of autonomous robots in dynamic multi-tasking environments, a suitable multi-robot task-allocation (MRTA) solution is required. This must be scalable to variable number of robots and tasks. Recent studies show that biology-inspired self-organized approaches can effectively handle task-allocation in large multi-robot systems. However most existing MRTA approaches have overlooked the role of different communication and sensing strategies found in selfregulated biological societies. This dissertation proposes to solve the MRTA problem using a set of previously published generic rules for division of labour derived from the observation of ant,human and robotic social systems. The concrete form of these rules, the attractive field model (AFM), provides sufficient abstraction to local communication and sensing which is uncommon in existing MRTA solutions. This dissertation validates the effectiveness of AFM to address MRTA using two bio-inspired communication and sensing strategies: "global sensing - no communication" and "local sensing - local communication". The former is realized using a centralized communication system and the latter is emulated under a peer-topeer local communication scheme. They are applied in a manufacturing shop-floor scenario using 16 e-puck robots. A robotic interpretation of AFM is presented that maps the generic parameters of AFM to the properties of a manufacturing shopfloor. A flexible multi-robot control architecture, hybrid event-driven architecture on D-Bus, has been outlined which uses the state-of-the-art D-Bus interprocess communication to integrate heterogeneous software components. Based-on the organization of task-allocation, communication and interaction among robots, a novel taxonomy of MRTA solutions has been proposed to remove the ambiguities found in existing MRTA solutions. Besides, a set of domainindependent metrics, e.g., plasticity, task-specialization and energy usage, has been formalized to compare the performances of the above two strategies. The presented comparisons extend our general understanding of the role of information exchange strategies to achieve the distributed task-allocations among various social groups.

Style APA, Harvard, Vancouver, ISO itp.

15

Khanal, Dipesh. "Toxicological considerations of nanoparticles using two and three dimensional liver models: Holistic approach to nanoparticle characterization and nanotoxicity assessment". Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/18637.

Pełny tekst źródła

Streszczenie:

Nanoparticles became ‘indispensable’ components of cosmetics, food products, biosensor and therapeutics. Daily consumption of nanoparticles exceeds 1 mg/kg of body mass for adults and more importantly 2 mg/kg of body mass for kids (few trillions of nanoparticles per day). There is increasing evidence that nanoparticles contribute to the loss of cell function and may be responsible for increase in auto immune disease, asthma and autism. The impact of nanomaterials on health still remains unexplored. Conventional nanosafety assessment tools have limited capability and resolution, these methods are incapable to provide robust evidence of the nano-biointeractions and the toxicity associated to these engineered nanoparticles precisely. In the current study, we developed a holistic approach to characterize the safety of nanoparticles which had the advantage of high-throughput screening abilities as well as sub nano level resolution. We confirmed the dynamic process of protein corona formation on the nanodiamond particles (NDs) with the tools as nanoIsothermal calorimetry (nanoITC), matrix assisted laser desorption/ionization time of flight spectrometry (MALDI-TOF). In addition, we used nanoscale infrared spectroscopy (AFM-IR) to detect interactions of single nanoparticle with proteins within cells. We demonstrated that NDs induced alterations in the secondary protein structure evidenced by the formation of antiparallel β-sheet and β-turns. For the first time Lorentz contact resonance spectroscopic technique (LCR) was used to investigate the uptake and localization of nanoparticles based on local viscoelasticity. Nanomechanical studies using molecular force probe (MFP) for cells treated with NDs showed concentration-dependent change in the cell stiffness. Since stiffness represents cell functionality these results imply that NDs induce some toxic effects. All the toxicity studies of NDs were conducted using 2D and 3D liver models (High-throughput screening tool). Monolayer cell culture model (Fao cells) and scaffold-free tissue model generated using magnetic levitation were used as 2D and 3D models. Nanotoxicity was assessed using:3D holographic tomographic microscopy and serial block face scanning electron microscopy (uptake and distribution), live cell imaging (cell morphology and migration), viability (live/dead), vitality (CCK-8), tight junction integrity (impedance measurement), 3D ring closure and spheroid dot assay. These in vitro assays showed that NDs induced concentration-dependent toxicity in both 2D & 3D models. In summary, our results highlight that the tools such as 3D ring closure and dot assay along with, nanoITC, MALDI-TOF, LCR, AFM-IR, MFP, not only provide fundamental understanding of interactions of material and biological milieu at nanolevel but also enable precise assessment of nanotoxicity.

Style APA, Harvard, Vancouver, ISO itp.

16

Spitzner, Eike-Christian. "Subsurface and MUSIC-Mode Atomic Force Microscopy". Doctoral thesis, Universitätsbibliothek Chemnitz, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-94864.

Pełny tekst źródła

Streszczenie:

Ziel dieser Arbeit war die Entwicklung neuer Methoden in der Rasterkraftmikroskopie, um die Qualität und Interpretierbarkeit von Oberflächenabbildungen auf der Nanometerskala, vor allem jener sehr weicher Proben, entscheidend zu verbessern. Der für polymere und biologische Materialien standardmäßig verwendete intermittierende Kontaktmodus führt auf weichen Oberflächen zu verfälschten Abbildungen der Topographie und der mechanischen Eigenschaften. In dieser Arbeit wurden Techniken entwickelt, die einerseits zerstörungsfreie, tiefenaufgelöste Rasterkraftmikroskopie und andererseits Einzelmessungen mit variabler Dämpfung im intermittierenden Kontaktmodus ermöglichen. Die laterale Auflösung beider Methoden liegt dabei im Rahmen herkömmlicher Techniken (< 10 nm). Die Tiefenauflösung konnte im Vergleich zu anderen Methoden um eine Größenordnung auf unter 1 nm verbessert werden. Die neuen Methoden wurden auf einer breiten Palette polymerer Materialien angewandt. Die räumliche Struktur oberflächennaher Bereiche eines Blockcopolymerfilms konnte im Vergleich zu herkömmlichen Methoden deutlich genauer abgebildet werden. Gleiches wurde auf elastomerem Polypropylen erreicht. Es konnten weiche, amorphe Deckschichten auf teilkristallinen Polymeren nachgewiesen und vermessen werden, was in der organischen Elektronik eine wichtige Rolle spielen kann. Die innere Struktur selbstangeordneter Nanodrähte aus Oligothiophen-Aggregaten konnte aufgelöst werden und es wurde die Selbstanordnung von Kollagenfibrillen im gequollenen Zustand beobachtet.

Style APA, Harvard, Vancouver, ISO itp.

17

Vecchiola, Aymeric. "Développement d’une imagerie de résistance électrique locale par AFM à pointe conductrice en mode contact intermittent". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112058/document.

Pełny tekst źródła

Streszczenie:

Le microscope à force atomique (AFM) permet de caractériser avec une excellente résolution spatiale les surfaces d’échantillons de différentes natures et peut être mis en œuvre dans des milieux variés. Cette versatilité a favorisé le développement d’un grand nombre de techniques dérivées, destinées à investiguer diverses propriétés physiques locales. Le LGEP a ainsi réalisé un module, le Résiscope, capable de mesurer la résistance électrique locale à la surface d’un échantillon polarisé en continu, sur une gamme de 11 décades. Mise au point en mode contact, où la pointe exerce en permanence une force sur l’échantillon, cette technique fonctionne très bien sur des matériaux durs, mais trouve ses limites sur des échantillons mous ou fragiles puisque dans certaines conditions, la pointe peut altérer leur surface. Pour de tels échantillons, un mode contact intermittent, dans lequel la pointe vient à intervalles réguliers toucher très brièvement la surface, est plus approprié, mais complique la réalisation des mesures électriques. Le but de la thèse consistait à lever cette difficulté en modifiant le Résiscope pour pouvoir l’associer au « Pulsed Force Mode », mode intermittent où la pointe oscille à une fréquence de 100Hz à 2000Hz.Différentes évolutions matérielles et logicielles ont été apportées pour permettre le suivi temporel détaillé du signal de résistance électrique à chaque établissement/rupture de contact (indispensable pour passer en revue les phénomènes liés à l’intermittence), de même que pour pouvoir travailler à des vitesses de balayage acceptables. Pour l’imagerie, les meilleurs contrastes ont été obtenus grâce à une électronique de synchronisation et de traitement prenant en compte les valeurs de résistance électrique à des moments bien précis. Pour tester ce nouveau système, nous avons dans un premier temps comparé les courbes de résistance et de déflexion que nous obtenons par ce mode avec celles considérées classiquement dans le mode approche-retrait. Nous avons ensuite étudié l’influence des principaux paramètres (fréquence et amplitude d’oscillation, force d’appui, type de pointe, etc.) sur les mesures topographiques et électriques, en utilisant le HOPG comme matériau de référence. Ces essais ont notamment permis de mettre en évidence un retard quasi systématique du signal électrique par rapport au signal de déflexion (autre que le temps de mesure propre au Résiscope), dont nous n’avons pu élucider l’origine. Une fois ces connaissances acquises, nous avons étudié deux types d’échantillons organiques, l’un à caractère académique – des monocouches auto-assemblées d’alcanethiols (SAMs), l’autre à finalité plus applicative – des couches minces formées d’un réseau interpénétré de deux constituants (P3HT:PCBM) destinées aux cellules photovoltaïques. Dans les deux cas nous avons montré la pertinence de l’outil Résiscope en mode intermittent pour obtenir des informations qualitatives et quantitatives. Parallèlement à ces travaux sur matériaux fragiles, nous avons mené une étude annexe sur un phénomène de croissance de matière à caractère isolant constaté dans des conditions particulières sur différents matériaux durs, qui a été interprété comme la formation de polymère de friction sous l’effet des nano-glissements répétés associés à la déflexion du levier.Ces travaux ont été réalisés dans le cadre d’une convention CIFRE avec la société Concept Scientifique Instruments, adossée au projet ANR « MELAMIN » (P2N 2011)
The atomic force microscope (AFM) allows to characterize with excellent spatial resolution samples of different types of surfaces and can be implemented in various environments. This versatility has encouraged the development of a large number of derivative technics, intended to investigate various local physical properties. The LGEP thus achieved a module, the Résiscope, capable of measuring the local electrical resistance on the surface of a sample polarized continuously, on a range of 11 decades. Developed in contact mode, where the tip continuously exerts a force on the sample, this technic works well on hard materials, but finds its limits on soft or fragile samples since under certain conditions, the tip can alter the surface. For such samples, an intermittent contact mode, in which the tip comes at regular intervals touch very briefly the surface, is more appropriate, but complicates the achievement of electrical measurements. The aim of this thesis was to overcome this difficulty by changing the Résiscope to be able to join the "Pulsed Force Mode", intermittent mode where the tip oscillates at a frequency of 100Hz to 2000Hz. Different hardware and software changes have been made to permit the detailed temporal monitoring of the electrical resistance signal to each make / break contact (necessary to review the phenomena related to intermittency), as well as to be able to work in acceptable scan speeds. For imaging, the best contrasts were obtained through an electronic timing and treatment taking into account the electrical resistance values at specific times.To test this new system, we have initially compared resistance and deflection curves we get by this mode with those considered classically in the force-distance curves mode. We then investigated the influence of main parameters (frequency and amplitude of oscillation, setpoint, coating of the tips, etc.) on the topographical and electrical measurements, using the HOPG as reference material. These tests resulted to highlight a nearly systematic delay of the electrical signal relative to the deflection signal (other than the Resiscope measure time), which we were not able to elucidate the origin. Once these knowledge acquired, we studied two types of organic samples, one in academic nature - Self-Assembled Monolayers of alkanethiols (SAMs), the other more applicative purpose – formed of thin layers of an interpenetrating network of two components (P3HT:PCBM) for photovoltaic cells. In both cases we have shown the relevance of the Resiscope tool in intermittent mode to obtain qualitative and quantitative information. In addition to these work on fragile materials, we conducted an annex study on a phenomenon of growth material of insulating nature found in special conditions on various hard materials, which has been interpreted as the friction polymer formation as a result of repeatedly nano-sliding associated with the deflection of the cantilever. These investigations were conducted under a CIFRE agreement with the Concept Scientific Instruments company, backed by the ANR MELAMIN» (P2N 2011) project

Style APA, Harvard, Vancouver, ISO itp.

18

Wang, Kathleen F. "Characterizing molecular-scale interactions between antimicrobial peptides and model cell membranes". Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-dissertations/153.

Pełny tekst źródła

Streszczenie:

Due to the escalating challenge of antibiotic resistance in bacteria over the past several decades, interest in the identification and development of antibiotic alternatives has intensified. Antimicrobial peptides (AMPs), which serve as part of the innate immune systems of most eukaryotic organisms, are being researched extensively as potential alternatives. However, the mechanism behind their bactericidal capabilities is not well understood. Previous studies have suggested that AMPs may first attach to the cell membranes, leading to pore formation caused by peptide insertion, lipid removal in the form of peptide-lipid aggregates, or a combination of both mechanisms. In addition to the lack of mechanistic knowledge, a significant hurdle in AMP-based drug development is their potential cytotoxicity to mammalian cells. Understanding AMP interactions with eukaryotic model membranes would allow therapeutics to be tailored for preferential action toward specific classes of bacterial membranes. In this study, we developed novel methods of quartz crystal microbalance with dissipation monitoring (QCM-D) data analysis to determine the fundamental mechanism of action between eukaryotic and bacterial membrane mimics and select membrane-active AMPs. A new technique for creating supported membranes composed entirely of anionic lipids was developed to model Gram-positive bacterial membranes. Atomic force microscopy (AFM) imaging was also used to capture the progression of AMP-induced changes in supported lipid membranes over time and to validate our method of QCM-D analysis. QCM-D and AFM were used to investigate the molecular-scale interactions of four peptides, alamethicin, chrysophsin-3, sheep myeloid antimicrobial peptide (SMAP-29) and indolicidin, with a supported zwitterionic membrane, which served as a model for eukaryotic cell membranes. Since established methods of QCM-D analysis were not sufficient to provide information about these interaction mechanisms, we developed a novel method of using QCM-D overtones to probe molecular events occurring within supported lipid membranes. Also, most previous studies that have used AFM imaging to investigate AMP-membrane interactions have been inconclusive due to AFM limitations and poor image quality. We were able to capture high-resolution AFM images that clearly show the progression of AMP-induced defects in the membrane. Each AMP produced a unique QCM-D signature that clearly distinguished their mechanism of action and provided information on peptide addition to and lipid removal from the membrane. Alamethicin, an alpha-helical peptide, predominantly demonstrated a pore formation mechanism. Chrysophsin-3 and SMAP-29, which are also alpha-helical peptides of varied lengths, inserted into the membrane and adsorbed to the membrane surface. Indolicidin, a shorter peptide that forms a folded, boat-shaped structure, was shown to adsorb and partially insert into the membrane. An investigation of rates at which the peptide actions were initiated revealed that the highest initial interaction rate was demonstrated by SMAP-29, the most cationic peptide in this study. The mechanistic variations in peptide action were related to their fundamental structural properties including length, net charge, hydrophobicity, hydrophobic moment, accessible surface area and the probability of alpha-helical secondary structures. Due to the charges associated with anionic lipids, previous studies have not been successful in forming consistent anionic supported lipid membranes, which were required to mimic Gram-positive bacterial membranes. We developed a new protocol for forming anionic supported lipid membranes and supported vesicle films using a vesicle fusion process. Chrysophsin-3 was shown to favor insertion into the anionic lipid bilayer and did not adsorb to the surface as it did with zwitterionic membranes. When introduced to supported anionic vesicle films, chrysophsin-3 caused some vesicles to rupture, likely through lipid membrane disruption. This study demonstrated that molecular-level interactions between antimicrobial peptides and model cell membranes are largely determined by peptide structure, peptide concentration, and membrane lipid composition. Novel techniques for analyzing QCM-D overtone data were also developed, which could enable the extraction of more molecular orientation and interaction dynamics information from other QCM-D studies. A new method of forming supported anionic membranes was also designed, which may be used to further investigate the behavior of bacterial membranes in future studies. Insight into AMP-membrane interactions and development of AMP structure-activity relationships will facilitate the selection and design of more efficient AMPs for use in therapeutics that could impact the lives of millions of people per year who are threatened by antibiotic-resistant organisms.

Style APA, Harvard, Vancouver, ISO itp.

19

Jarmusik, Keith Edward. "An Improved Model for Interpreting Molecular Scale Electrostatic Interactions". Case Western Reserve University School of Graduate Studies / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=case1275666964.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

20

Chai, Hao. "Statistical inference in high dimensional linear and AFT models". Diss., University of Iowa, 2014. https://ir.uiowa.edu/etd/1303.

Pełny tekst źródła

Streszczenie:

Variable selection procedures for high dimensional data have been proposed and studied by a large amount of literature in the last few years. Most of the previous research focuses on the selection properties as well as the point estimation properties. In this paper, our goal is to construct the confidence intervals for some low-dimensional parameters in the high-dimensional setting. The models we study are the partially penalized linear and accelerated failure time models in the high-dimensional setting. In our model setup, all variables are split into two groups. The first group consists of a relatively small number of variables that are more interesting. The second group consists of a large amount of variables that can be potentially correlated with the response variable. We propose an approach that selects the variables from the second group and produces confidence intervals for the parameters in the first group. We show the sign consistency of the selection procedure and give a bound on the estimation error. Based on this result, we provide the sufficient conditions for the asymptotic normality of the low-dimensional parameters. The high-dimensional selection consistency and the low-dimensional asymptotic normality are developed for both linear and AFT models with high-dimensional data.

Style APA, Harvard, Vancouver, ISO itp.

21

Singh, Amit Kumar. "Caractérisation des Mémoires Non-Volatiles Résistives par Microscopie à Force Atomique en mode Conduction (C-AFM) sous Ultravide". Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAT033.

Pełny tekst źródła

Streszczenie:

Les mémoires sont à la base de tout système électronique avec lequel nous interagissons dans notre vie quotidienne et deviennent de plus en plus important jour après jour à notre époque. Les fonctionnalités et les performances croissantes des produits électroniques tels que les appareils photo numériques, les téléphones cellulaires, les ordinateurs personnels, les disques durs, etc., nécessitent une amélioration continue de ses fonctionnalités. La technologie Flash à grille flottante est la principale technologie NVM utilisée sur le marché actuellement. Néanmoins, la technologie Flash pose de nombreux problèmes rendant tout redimensionnement impossible. Dans ce contexte, de nombreuses autres technologies de mémoire sont en train d'émerger et l'intérêt pour les nouveaux concepts et matériaux allant au-delà de la technologie Flash ne cesse de croître. Des mémoires résistives non volatiles basées sur deux types de dispositifs, dans lesquelles un matériau actif est pris en sandwich entre deux électrodes, ont été étudiées. L'idée principale d'utiliser ce type de structure et de matériau est d'utiliser un mécanisme physique spécifique permettant de le basculer entre deux états résistifs différents pour le stockage d'informations. Par exemple, dans la mémoire à base d’oxydes (OxRAM), un filament conducteur est développé à l’intérieur de la couche d’oxyde, reliant les deux électrodes. En créant et en interrompant ce filament, deux états de résistance différents peuvent être générés. Un autre exemple est la mémoire à changement de phase (PCRAM), dans laquelle un matériau à base de chalcogénure capable de changer de phase entre un état amorphe à haute résistance et un état cristallin à faible résistance est utilisé. Les mémoires OxRAM ont été largement étudiées au cours des dernières années en raison de leurs nombreux avantages, tels qu'une bonne évolutivité en matière de réduction de taille, une longue rétention, une vitesse de lecture et d'écriture rapide et une faible consommation d'énergie. Le principal avantage est leur compatibilité avec la fabrication en back end. Dans les structures MIM pour OxRAM, la formation et la rupture d’un filament conducteur de taille nanométrique sont communément acceptées comme étant le phénomène physique de la commutation, mais un débat est toujours en cours pour comprendre la nature et les caractéristiques du filament conducteur. De plus, de nombreuses études ont été réalisées pour évaluer le potentiel de réduction des dimensions des mémoires OxRAM et PCRAM. Par conséquent, dans cette thèse, nous étudions les mécanismes liés à la commutation résistive à base de filaments conducteurs à l’échelle nanométrique. Pour effectuer la caractérisation électrique, une nouvelle technique utilisant la microscopie à force atomique en mode conduction (C-AFM) sous ultravide est proposée. L’influence du matériau de la pointe AFM (utilisés comme électrode supérieure), du matériau de l’électrode inférieure et l’effet du courant limite dans deux régimes différents (en nA et en µA) sont étudiés. Il ressort de notre travail que dans les mémoires OxRAM à base de HfO2, le filament est créé par diffusion de Ti de l’électrode inférieure à travers l’oxyde. Les résultats sont en bon accord avec ceux obtenus sur des dispositifs et ont pu être reproduits par un modèle. En outre, la transition de phase dans les matériaux pour PCRAM est étudiée pour le GST riche en Ge et le GST-225. Il a été constaté que la transition de phase dans les matériaux à changement de phase est possible à l'échelle nanométrique. Enfin, le champ électrique de seuil observé dans le cas du GST-225 est bien plus proche des valeurs mesurées que celles obtenues avec un CAFM standard
Memories are the fundamental for any electronic system we interact with in our daily life and are getting more and more important day by day in our present era. The growing functionalities and performance of the electronic products such as digital cameras, smart phone, personal computer, solid state hard disk and many more, need continues improvement of its features. Floating gate-based Flash technology is the main NVM technology used extensively in market these days. Nevertheless, Flash technology presents many problems making further scaling impossible. In this context, there are many other memory technologies emerging and interest in new concepts and materials to go beyond the Flash technology is growing. Resistive non-volatile memories based on two terminal devices, in which an active material is sandwiched between two electrodes have been investigated. The main idea of using this kind of structure and material is to use a specific physical mechanism allowing to switch it between two different resistive states for information storage. For example, in oxide based random-access memory (OxRAM), a conductive filament is grown inside the oxide layer, linking the two electrodes. By creation and disruption of this filament, two different resistance states can be generated. Another example is the phase change random-access memory (PCRAM), in which a chalcogenide material with the ability to change its phase between a high resistive amorphous and a low resistive crystalline state is used. Over the last few years OxRAM has been widely investigated due to many advantages like good scalability, long data retention time, fast read & write speed and low power consumption. The main benefit is that it is compatible with Back-end of line fabrication. In MIM structures for OxRAM, forming and disruption of the nanometer sized conductive filament is commonly accepted as the physical phenomenon for the switching, but still a debate is going on to understand the nature and characteristics of the conductive filament. Also, many studies have been done to evaluate the scaling capability of OxRAM and PCRAM. Hence, in this thesis work we studied mechanisms related to the conductive filament based resistive switching at nanoscale. To do the electrical characterization, a new technique using conductive atomic force microscopy (C-AFM) in ultra-high vacuum is proposed. The impact of different AFM tip materials (which is used as top electrode), different bottom electrode materials and the compliance current effect in two different regimes (in nA and in µA) are investigated. It is found that in the case of HfO2 based OxRAM, the filament is formed by Ti diffusion from the bottom electrode through the oxide layer. The results are in good agreement with device characteristics and could be reproduced by modeling. Also, phase transition in phase change materials for PCRAM is investigated for Ge2Sb2Te5 (GST-225) and Ge rich GST. It was found that the phase transition from amorphous to crystalline is possible at nanoscale. Finally, the threshold for GST-225 is observed at values nearer to those observed on devices than former observations with standard C-AFM

Style APA, Harvard, Vancouver, ISO itp.

22

Horne, Jimmy D. "Modeling optical turbulence with coamps during two observation periods at Vandenberg AFB /". Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FHorne.pdf.

Pełny tekst źródła

Streszczenie:

Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, March 2004.
Thesis advisor(s): Douglas Miller. Includes bibliographical references (p. 67-70). Also available online.

Style APA, Harvard, Vancouver, ISO itp.

23

Dressel, Frank. "Sequenz, Energie, Struktur - Untersuchungen zur Beziehung zwischen Primär- und Tertiärstruktur in globulären und Membran-Proteinen". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1222781322751-68621.

Pełny tekst źródła

Streszczenie:

Proteine spielen auf der zellulären Ebene eines Organismus eine fundamentale Rolle. Sie sind quasi die „Maschinen“ der Zelle. Ihre Bedeutung wird nicht zuletzt in ihrem Namen deutlich, welcher 1838 erstmals von J. Berzelius verwendet wurde und „das Erste“, „das Wichtigste“ bedeutet. Proteine sind aus Aminosäuren aufgebaute Moleküle. Unter physiologischen Bedingungen besitzen sie eine definierte dreidimensionale Gestalt, welche für ihre biologische Funktion bestimmend ist. Es wird heutzutage davon ausgegangen, dass diese dreidimensionale, stabile Struktur von Proteinen eindeutig durch die Abfolge der einzelnen Aminosäuren, der Sequenz, bestimmt ist. Diese Abfolge ist für jedes Protein in der Desoxyribonukleinsäure (DNS) gespeichert. Es ist allerdings eines der größten ungelösten Probleme der letzten Jahrzehnte, wie die Beziehung zwischen Sequenz und 3D-Struktur tatsächlich aussieht. Die Beantwortung dieser Fragestellung erfordert interdisziplinäre Ansätze aus Biologie, Informatik und Physik. In dieser Arbeit werden mit Hilfe von Methoden der theoretischen (Bio-) Physik einige der damit verbundenen Aspekte untersucht. Das Hauptaugenmerk liegt dabei auf Wechselwirkungen der einzelnen Aminosäuren eines Proteins untereinander, wofür in dieser Arbeit ein entsprechendes Energiemodell entwickelt wurde. Es werden Grundzustände sowie Energielandschaften untersucht und mit experimentellen Daten verglichen. Die Stärke der Wechselwirkung einzelner Aminosäuren erlaubt zusätzlich Aussagen über die Stabilität von Proteinen bezüglich mechanischer Kräfte. Die vorliegende Arbeit unterteilt sich wie folgt: Kapitel 2 dient der Einleitung und stellt Proteine und ihre Funktionen dar. Kapitel 3 stellt die Modellierung der Proteinstrukturen in zwei verschiedenen Modellen vor, welche in dieser Arbeit entwickelt wurden, um 3D-Strukturen von Proteinen zu beschreiben. Anschließend wird in Kapitel 4 ein Algorithmus zum Auffinden des exakten Energieminimums dargestellt. Kapitel 5 beschäftigt sich mit der Frage, wie eine geeignete diskrete Energiefunktion aus experimentellen Daten gewonnen werden kann. In Kapitel 6 werden erste Ergebnisse dieses Modells dargestellt. Der Frage, ob der experimentell bestimmte Zustand dem energetischen Grundzustand eines Proteins entspricht, wird in Kapitel 7 nachgegangen. Die beiden Kapitel 8 und 9 zeigen die Anwendung des Modells an zwei Proteinen, dem Tryptophan cage protein als dem kleinsten, stabilen Protein und Kinesin, einem Motorprotein, für welches 2007 aufschlussreiche Experimente zur mechanischen Stabilität durchgeführt wurden. Kapitel 10 bis 12 widmen sich Membranproteinen. Dabei beschäftigt sich Kapitel 10 mit der Vorhersage von stabilen Bereichen (sog. Entfaltungsbarrieren) unter externer Krafteinwirkung. Zu Beginn wird eine kurze Einleitung zu Membranproteinen gegeben. Im folgenden Kapitel 11 wird die Entfaltung mit Hilfe des Modells und Monte-Carlo-Techniken simuliert. Mit dem an Membranproteine angepassten Wechselwirkungsmodell ist es möglich, den Einfluss von Mutationen auch ohne explizite strukturelle Informationen vorherzusagen. Dieses Thema wird in Kapitel 12 diskutiert. Die Beziehung zwischen Primär- und Tertiärstruktur eines Proteins wird in Kapitel 13 behandelt. Es wird ein Ansatz skizziert, welcher in der Lage ist, Strukturbeziehungen zwischen Proteinen zu detektieren, die mit herkömmlichen Methoden der Bioinformatik nicht gefunden werden können. Die letzten beiden Kapitel schließlich geben eine Zusammenfassung bzw. einen Ausblick auf künftige Entwicklungen und Anwendungen des Modells.

Style APA, Harvard, Vancouver, ISO itp.

24

PERISSINOTTO, FABIO. "Lipid raft formation and lipid-protein interactions in model membranes". Doctoral thesis, Università degli Studi di Trieste, 2018. http://hdl.handle.net/11368/2919798.

Pełny tekst źródła

Streszczenie:

The biological membranes of eukaryotic organisms contain functional, highly dynamic nano-domains called "lipid rafts" (LRs) which are enriched in cholesterol, sphingolipids and GPI-anchor proteins. They are involved in several biological processes which implicate or are mediated by the plasma membrane. Moreover, LRs seem to have a critical role in the onset of some neurodegenerative diseases such as the Alzheimer’s disease (AD), Parkinson’s disease (PD) and Prion protein disorders. In the last two decades, the complexity of studying such domains in living cells has caused a growing interest in the use and design of artificial membrane models, which mimic the structure and composition of biological membranes. In this context, I promoted the formation and investigated the properties of lipid raft domains in artificial lipid bilayers by exploiting Atomic Force Microscopy (AFM). I compared two different fabrication methods for the production of artificial lipid bilayers, the drop-casting and the direct vesicle fusion techniques. I started from one-component lipid membranes and I progressively moved towards more complex models, as binary and ternary lipid compositions, in order to study the main LRs features in relation to specific biological phenomena, such as protein-lipid interactions involved in particular pathological diseases. The direct vesicle fusion method appeared to be the most suitable approach in term of reproducibility, stability and control of lipid composition. I took advantage from this method for carrying out a morphological characterization of raft-like model membranes composed by phosphocoline (DOPC), sphingomyelin (SM) and cholesterol focusing in particular on lipid phase behavior. Membranes exhibited the coexistence of two lipid phases, the fluid phase made by DOPC, and the solid-ordered phase made by SM and cholesterol, the latter resembling raft-like domains. With selected 3-component lipid systems, I then investigated the distribution of GM1 ganglioside, a LR marker, into my system, demonstrating its preferential localization in the nano-domains and highlighting the feasibility and versatility of model membrane technology. For the first time, I studied the binding of synthetic full-length Prion protein (PrPc), carrying a C-terminal membrane anchor (MA), to LRs domains. The conversion of PrPc into the scrapie isoform PrPsc, which displays high propensity to aggregate leading to cytotoxicity, has been reported to take place into LRs and to be influenced by lipid-anchors. I demonstrated with this study the propensity of this protein to specifically target LR domains of my artificial systems, observing an aggregation process occurring even at low protein concentrations. A comparative analysis with PrPc lacking of MA is however required to assess the role of lipid-anchor into the protein distribution and aggregation. Finally, in the last part of my research I focused on the study of the role of iron ions in the interaction between alpha synuclein (αS) and lipid membranes. αS is the central protein of PD and the presence of amyloid αS fibrils is the main pathological hallmark of the disease. By AFM in combination with attenuated total reflectance infrared (ATR-IR) spectroscopy, I compared the structural behavior of the wild-type (wt) and a mutant form of αS (A53T) in presence of Fe2+ ions and the effect of the iron ions on the interaction with my artificial membrane, and specifically with LRs.

Style APA, Harvard, Vancouver, ISO itp.

25

Oh, Yunje. "Prediction of steady state response in dynamic mode atomic force microscopy and its applications in nano-metrology". The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1135222817.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

26

Parlak, Zehra. "Quantitative imaging of subsurface structures and mechanical properties at nanoscale using atomic force microscope". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/37181.

Pełny tekst źródła

Streszczenie:

This dissertation focuses on quantitative subsurface and mechanical properties imaging potential of AFM probes. Extensive modeling of AFM probes are presented for thorough understanding of capabilities and limitations of current techniques, these models are verified by various experiments, and different methods are developed by utilizing force-sensing integrated read-out active tip (FIRAT), which is an active AFM probe with broad bandwidth. For quantitative subsurface imaging, a 3-D FEA model of AFM tip-sample contact is developed and this model can simulate AFM tip scan on nanoscale-sized buried structures. FIRAT probe, which is active and broadband, is utilized for interaction forces imaging during intermittent contact mode and mechanical characterization capability of this probe is investigated. It is shown that probe dynamics, stiffness, stiffness ambiguity, assumed contact mechanics, and noise are important parameters for the accuracy of mechanical properties imaging. An active tip control mechanism is introduced to limit contact forces during intermittent contact mode. In addition to these, a combined ultrasonic AFM and interaction forces imaging method is developed and modeled to solve the reduced elasticity measurement sensitivity on composite materials. This method is capable of imaging a broader range of elasticity on combination samples such as metal nanoparticles in polymers at nanoscale.

Style APA, Harvard, Vancouver, ISO itp.

27

Luu, Ngoc Mai. "Sondes à nanotubes de carbone mono-paroi pour la microscopie à force atomique : synthèse et imagerie à l'air et en milieu liquide". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0071/document.

Pełny tekst źródła

Streszczenie:

La microscopie à force atomique (AFM) permet d’étudier à l’échelle nanométrique la surface d’échantillons. Elle offre de nombreux avantages par rapport aux microscopes optiques et aux microscopes électroniques, tout en évitant des étapes de préparation particulières : pas de nécessité de congeler, de métalliser ou de teinter l’échantillon ni de travailler sous vide. La résolution de l'imagerie AFM est principalement déterminée par la morphologie de la sonde utilisée et peut atteindre la résolution moléculaire. Toutefois, les sondes en silicium sont très fragiles. De plus, leur forme pyramidale ou conique génère des artefacts sur l’image résultante. Parmi les sondes actuellement en développement, les sondes à nanotubes de carbone mono-paroi offrent de bonnes caractéristiques en termes de qualité d'imagerie et de longévité. Ces sondes sont plus résistantes et de plus petite taille que les sondes traditionnelles.Cette thèse s’intéresse à la fabrication directe de sondes à nanotubes mono-paroi sur des extrémités de pointes AFM commerciales par la méthode de dépôt chimique en phase vapeur assistée par filament chaud dans un réacteur développé au CBMN. En jouant sur les paramètres de synthèse, tels que la quantité de catalyseur ou la température, nous optimisons le protocole de synthèse originel en collaboration avec son auteur Anne-Marie Bonnot afin de l’adapter à notre réacteur. Les nanotubes obtenus sont caractérisés par les microscopies Raman, électronique à balayage et transmission et à force atomique. La caractérisation montre que les nanotubes obtenus ont une structure mono-paroi. Le rendement d’obtention de sondes nanotubes utilisables est de 30%.Les courbes d’approche-retrait d'AFM nous donnent des informations sur la sonde à nanotube utilisée, telles que sa raideur, le nombre de nanotubes en contact avec la surface. Ces courbes nous permettent de sélectionner les paramètres d’imagerie. Deux échantillons sont testés avec les sondes produites : du graphite pyrolytique haute orientation et des origamis d’ADN rectangulaires. Nous réalisons des expériences d’imagerie avec des sondes à nanotube dans l’air en mode dynamique FM et en milieu liquide en mode Peak Force. Les résultats montrent des images à haute résolution de l’origami d’ADN où la période de 5,8 nm est observable. Les sondes à nanotube présentent également une plus longue durée de vie que les pointes AFM en silicium
Atomic force microscopy (AFM) is used to study at nanometer scale samples on surfaces. It offers many advantages over conventional optical microscopes and electron microscopes: no freezing, metal coating, vacuum or dye is needed to prepare the sample. The AFM imaging resolution is mostly determined by the sharpness of the used probe and can reach molecular resolution. However, silicon probes are brittle. Additionally, their pyramidal or conical shape generates artifacts on the resulting image. Among the probes currently under development, single-walled carbon nanotube probes offer good characteristics in terms of imaging quality and longevity. These probes are more resistant and smaller in size than traditional probes.This thesis focuses on the direct fabrication of single-wall nanotube probes at the apex of commercial AFM tips by the hot-filament chemical vapor deposition method in a reactor developed at CBMN. By playing on the synthesis parameters, such as the amount of catalyst or the temperature of synthesis, we optimize the original synthesis protocol in collaboration with its author Anne-Marie Bonnot in order to adapt it to our reactor. The nanotubes obtained are characterized by Raman, scanning electron microscopy and transmission electron microscopy and AFM. The characterization shows that the nanotubes obtained have a single-wall structure. The yield of nanotube probes for AFM is 30%.AFM approach-retract curves give us information about the nanotube probe used, such as its stiffness or the number of nanotubes in contact with the surface. These curves allow us to select the imaging parameters. Two samples are tested with the produced probes: highly oriented pyrolytic graphite and rectangular DNA origamis. We image the samples with nanotube probes in both air with dynamical FM mode and in liquid medium with Peak Force mode. The results show high resolution images of DNA origami where the 5.8 nm period is observable. Nanotube probes also have longer life than silicon AFM tips

Style APA, Harvard, Vancouver, ISO itp.

28

AZİZOĞLU, YAĞIZ. "Micromechanical Numeric Investigation of Fiber Bonds in 3D Network Structures". Thesis, KTH, Hållfasthetslära (Avd.), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-144036.

Pełny tekst źródła

Streszczenie:

In manufacturing of paper and paperboard, optimized fiber usage has crucial importance for process efficiency and profitability. Dry strength of paper is one of the important quality criteria, which can be improved by adding dry strength additive that affect fiber to fiber bonding. This study is using the micromechanical simulations which assist interpretation of the experimental results concerning the effect of strength additives. A finite element model for 3D dry fiber network was constructed to study the effect of bond strength, bond area and the number of bonds numerically on the strength of paper products. In the network, fibers’ geometrical properties such as wall thickness, diameter, length and curl were assigned according to fiber characterization of the pulp and SEM analyses of dry paper cross-section. The numerical network was created by depositing the fibers onto a flat surface which should mimic the handsheet-making procedure. In the FE model, each fiber was represented with a number of quadratic Timoshenko beam elements where fiber to fiber bonds were modelled by beam-to-beam contact. The contact model is represented by cohesive zone model, which needs bond strength and bond stiffness in normal and shear directions. To get a reasonable estimate of the bond stiffness, a detailed finite element model of a fiber bond was used. Additionally, the effect of different fiber and bond geometries on bond stiffness were examined by this model since the previous work [13] indicated that the bond stiffness can have a considerable effect on dry strength of paper. The network simulation results show that the effect of the strength additive comes through improving the bond strength primarily. Furthermore, with the considered sheet structure, both the fiber bond compliance and the number of bonds affect the stiffness of paper. Finally, the results of the analyses indicated that the AFM measurements of the fiber adhesion could not be used directly to relate the corresponding changes in the bond strength. The fiber bond simulation concluded that fiber wall thickness has the most significant effect on the fiber bond compliance. It was also affected by micro-fibril orientation angle, bond orientation and the degree of pressing.

Style APA, Harvard, Vancouver, ISO itp.

29

Buchoux, Julien. "Nanotubes de carbone comme sondes en microscopie à force atomique : nanomécanique et étude à l’interface air-liquide de fluides complexes". Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14221/document.

Pełny tekst źródła

Streszczenie:

La microscopie à force atomique exploite les interactions entre une sonde et un échantillon. Les nanotubes de carbone représentent la sonde idéale, ils sont: fins, robustes, peu réactifs et ont un haut rapport d'aspect. L'utilisation à grande échelle des sondes à nanotubes de carbone passe par l'étude de leur comportement mécanique en contact avec une surface. Nous étudions deux types de sondes: les sondes avec nanotubes multiparois et les sondes avec nanotubes monoparois. Pour les nanotubes multiparois nous avons utilisé trois mode de fonctionnement AFM différents que sont les modes contact, modulation de fréquence et bruit thermique. Les résultats expérimentaux sont comparés à des modèles mécaniques que nous avons développés. Les études des nanotubes monoparois ont été réalisées à partir d'un AFM interférométrique. Ces mesures nous ont permis de déterminer l'énergie d'adhésion par unité de longueur d'un nanotube monoparoi sur des surfaces de graphite et mica.Enfin nous présentons deux applications des sondes AFM avec nanotube multiparoi. La première est un projet de sondes électrochimiques pour lesquelles un nanotube multiparoi sert de nanolocalisateur. La seconde est une étude par AFM d'une interface air-liquide de fluides complexes
Atomic force microscopy exploits interactions between a probe and a sample. Carbon nanotubes represent the ideal probe; they are thin with a high aspect ratio, robustes and few reactive. The widespread use of carbon nanotube probes needs the study of their mechanical behavior in contact with a surface. We study two types of probes: probes with multiwalled nanotubes and probes with singlewalled nanotubes. For multiwalled nanotubes, we used three differents AFM modes that are contact, frequency modulation and thermalnoise. The experimental results are compared with mechanical models that we developed. Studies of singlewalled nanotubes have been produced from an interferometric AFM. These measures have enabled us to determine the adhesion energy per unit length of singlewalled nanotubes on graphite and mica surfaces.Finally we present two applications of AFM probes with multiwall nanotubes. The first is a project of electrochemical sensors for which a multiwall nanotube is used as a nanolocalisator. The second is a study by AFM of air-liquid interface of complex fluids

Style APA, Harvard, Vancouver, ISO itp.

30

Baiti, Risa Nurin. "Characterization of nano-mechanical properties of biological lipid membranes with circular mode atomic force microscopy". Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2403/document.

Pełny tekst źródła

Streszczenie:

Les membranes cellulaires sont impliquées dans de nombreux processus cellulaires : la diffusion des médicaments et des ions, la transduction des signaux, la génération d'énergie, le développement cellulaire (fusion et fission). Les bicouches phospholipides sont les principaux composants des membranes cellulaires, elles constituent une barrière dynamique protégeant les réactions biochimiques cellulaires. La détermination des propriétés biochimiques et mécaniques des bicouches lipidiques et leur évolution avec les conditions environnementales est nécessaire pour étudier la nature des processus cellulaires et l'influence des agents externes (résistance mécanique, perméabilité et réponse biologique). Pour mener de telles caractérisations, des modèles simplifiés de membrane biomimétique, tels que des bicouches lipidiques supportées (SLB), ont été développés. Parmi les techniques de caractérisation disponibles, la microscopie à force atomique (AFM) a été largement utilisée pour étudier l'organisation nanométrique des SLB dans des conditions physiologiques. AFM peut produire des images à la haute résolution et peut également être utilisé pour quantifier la résistance mécanique des SLB au moyen d'expériences de perforation. Pendant 30 ans, AFM a traversé de nombreux développements. Très récemment, le Mode circulaire AFM (CM-AFM) a été développé à l'Université de Technologie de Compiègne. CM-AFM est capable de générer un mouvement de glissement de la pointe AFM sur l'échantillon à une vitesse élevée, constante et continue et de mesurer les forces de frottement latéral rapidement et exactement simultanément avec les forces verticales. Pour la première fois, le CM-AFM sert à caractériser les échantillons biologiques dans des conditions physiologiques, ce qui permet de mesurer simultanément les forces de poinçonnage et de frottement en fonction de la vitesse de glissement. Il offre pour la première fois la capacité de décrire le comportement de friction des SLB en complément de la force de perforation. En raison du besoin important de mesure quantitative, l'optimisation du protocole CM-AFM a été effectuée en premier. Le protocole d'étalonnage du scanner a été établi avec succès pour assurer la précision de la vitesse de glissement. En outre, le protocole d'étalonnage des pointes, basé sur la méthode de Wedge et un échantillon rayé, est également conçu pour déterminer la constante d'étalonnage de la force latérale. Nous avons utilisé CM-AFM pour mesurer les propriétés tribologiques des échantillons solides pour améliorer l'équipement sous milieu liquide. Ensuite, les propriétés mécaniques (forces de poinçonnage et de frottement) des SLB ont été mesurées en fonction de la vitesse de glissement. Les SLB purs et mixtes ont été préparés par la méthode de fusion des vésicules. Différents médias ont également été utilisés pour étudier l'effet des cations monovalents sur les propriétés mécaniques des SLB. Dans tous les cas, la force de frottement augmente linéairement avec la vitesse de glissement, ce qui nous permet de déduire le coefficient visqueux de frottement. Comme prévu, la force de poinçonnage et le coefficient visqueux de frottement sont influencés par la composition des mélanges de lipides, par la nature des cations en milieu liquide et par la longueur des chaînes hydrocarbonées mais pas de manière similaire. L'interprétation de l'évolution du coefficient de force de frottement visqueux avec le système étudié est particulièrement délicate car la force de frottement pourrait être influencée par les propriétés d'interface ou de volume. Cette problématique sera le défi pour les prochaines études. Néanmoins, nos résultats illustrent la puissance de la technique CM-AFM et ouvre de nombreuses possibilités pour caractériser d'autres échantillons biologiques (cellules et tissus) afin de mieux comprendre les mécanismes élémentaires de friction
Cell membranes are involved in many cellular processes: drugs and ions diffusion, signal transduction, energy generation, cell development (fusion and fission). Phospholipid bilayers are the main components of cell membranes, they act as a dynamic barrier protecting cellular biochemical reactions. The determination of biochemical and mechanical properties of lipid bilayers and their evolution with environmental conditions is necessary to study the nature of cellular processes and the influence of external agents (mechanical resistance, permeability, and biological response). To conduct such characterizations, simplified biomimetic membrane models, such as supported lipid bilayers (SLBs), were developed. Among the available characterization techniques, atomic force microscopy (AFM) has been widely used to study the nanoscale organization of SLBs under physiological conditions. AFM can yield high resolution images and it can also be used to quantify the mechanical resistance of SLBs by means of punch through experiments. For 30 years, AFM has been through many developments. Very recently, the Circular Mode AFM (CM-AFM) has been developed at the Université de Technologie de Compiègne. CM-AFM is able to generate a sliding movement of the AFM tip on the sample at high, constant and continuous velocity and to measure the lateral friction forces fast and accurately simultaneously with the vertical forces. For the first time CM-AFM is used to characterize biological samples under physiological conditions, allowing the simultaneous measurement of both the punch-through and the friction forces as a function of the sliding velocity. It offers for the first time the ability to describe the friction behavior of SLBs in complement of the punch-through force. Due to the important need for quantitative measurement, optimization of the CM-AFM protocol has been done first. Protocol of scanner calibration has been successfully established to ensure the accuracy of sliding velocity. Besides, the protocol for tip calibration, based on wedge method and a scratched sample, is also made to determine the lateral force calibration constant. We have employed CM-AFM to measure the tribological properties of solid samples to improve the equipment under liquid medium. Then, the mechanical properties (punchthrough and friction forces) of SLBs were measured as function of the sliding velocity. Pure and mixed SLBs were prepared by the vesicle fusion method. Various media were also used to study the effect of monovalent cations to the mechanical properties of SLBs. In all cases, the friction force increases linearly with the sliding velocity allowing us to deduce the friction viscous coefficient. As expected both the punchthrough force and the friction viscous coefficient are influenced by the composition of lipid mixtures, by the nature of cations in liquid medium, and by the length of hydrocarbon chains but not in a similar fashion. The interpretation of the evolution of the viscous friction force coefficient with the studied system is particularly tricky as the friction force could be influenced by interface or volume properties. This problematic will be the challenge for the next studies. Nevertheless, our results illustrate how powerful the CM-AFM technique is and it opens wide opportunities to characterize other biological samples (cells and tissues) to gain a better understanding of the elementary mechanisms of friction

Style APA, Harvard, Vancouver, ISO itp.

31

Kelly, Joseph. "Advances in the Normal-Normal Hierarchical Model". Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11498.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

32

Cheng, Kun. "Deformable models for adaptive radiotherapy planning". Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/22893.

Pełny tekst źródła

Streszczenie:

Radiotherapy is the most widely used treatment for cancer, with 4 out of 10 cancer patients receiving radiotherapy as part of their treatment. The delineation of gross tumour volume (GTV) is crucial in the treatment of radiotherapy. An automatic contouring system would be beneficial in radiotherapy planning in order to generate objective, accurate and reproducible GTV contours. Image guided radiotherapy (IGRT) acquires patient images just before treatment delivery to allow any necessary positional correction. Consequently, real-time contouring system provides an opportunity to adopt radiotherapy on the treatment day. In this thesis, freely deformable models (FDM) and shape constrained deformable models (SCDMs) were used to automatically delineate the GTV for brain cancer and prostate cancer. Level set method (LSM) is a typical FDM which was used to contour glioma on brain MRI. A series of low level image segmentation methodologies are cascaded to form a case-wise fully automatic initialisation pipeline for the level set function. Dice similarity coefficients (DSCs) were used to evaluate the contours. Results shown a good agreement between clinical contours and LSM contours, in 93% of cases the DSCs was found to be between 60% and 80%. The second significant contribution is a novel development to the active shape model (ASM), a profile feature was selected from pre-computed texture features by minimising the Mahalanobis distance (MD) to obtain the most distinct feature for each landmark, instead of conventional image intensity. A new group-wise registration scheme was applied to solve the correspondence definition within the training data. This ASM model was used to delineated prostate GTV on CT. DSCs for this case was found between 0.75 and 0.91 with the mean DSC 0.81. The last contribution is a fully automatic active appearance model (AAM) which captures image appearance near the GTV boundary. The image appearance of inner GTV was discarded to spare the potential disruption caused by brachytherapy seeds or gold markers. This model outperforms conventional AAM at the prostate base and apex region by involving surround organs. The overall mean DSC for this case is 0.85.

Style APA, Harvard, Vancouver, ISO itp.

33

Darwich, Samer. "Colloidal Gold Nanoparticules : A study of their Drying-Mediated Assembly in Mesoscale Aggregation Patterns and of their AFM Assisted Nanomanipulation on Model Solid Surfaces". Phd thesis, Université de Haute Alsace - Mulhouse, 2011. http://tel.archives-ouvertes.fr/tel-00718640.

Pełny tekst źródła

Streszczenie:

This work deals with the study of the drying-mediated assembly of colloidal gold nanoparticles (Au NPs) in mesoscale aggregation patterns and their manipulation by atomic force microscopy (AFM) on model surfaces. The assembly of NPs in mesoscale and complex aggregation patterns assisted by the wetting and the drying of complex fluids (suspensions of NPs, NPs/biopolymers mixed solutions) on homogeneous and heterogeneous molecular surfaces was studied. This issue is important, both for understanding fundamental processes of self-organization, and for generating new functional mesostructures. The drying of complex fluids often leads to the emergence of highly complex aggregation structures as shown and discussed in this work. The richness and the aesthetics of these complex structures generated by these interfacial phenomena reflect not only the bulk properties of fluids (different sizes and lengths- scales, kinetic changes in state), but more importantly, the coupling between the fluid properties and those of the substrate surface (wetting interactions, confinement, hydrodynamics). In the case of two important heterogeneous fluids which are Au NPs and polysaccharide solutions, these drying-mediated structure formation lead to the genesis of unusually large and highly ramified dendrites aggregation patterns. The growth mechanism and the critical parameters that control the morphogenesis of these complexes structures are addressed in this work. In addition, the aging mechanisms and kinetics of these structures that are metastable and evolve either through direct dislocation via clusters NPs mobility on the surface, or through undulation-induced roughning of the dendrite branches. To better understanding this NPs mobility and thus the dislocation mechanism of the aging, a detailed study based on the manipulation of NPs by atomic force microscopy in tapping mode (AFM) was developed. The threshold dissipated energy to manipulate (move) the NPs can be quantified according to the intrinsic parameters of the particle (size, shape, and chemical nature), the chemical nature and topography of the substrate, and finally the operating and environment conditions. This work enabled us to understand the mechanisms and characterize the critical parameters that may intervene in the dislocation (aging) of NPs-based functional structures, depending on the nature of the environment liquid and the substrate. Finally, this work proposes an approch of evaluation and of monitoring the stability and the aging of these aggregation structures, in particular, those formed from the drying of films and drops of nano-particles solutions (metal nanoparticles, blood: proteins, viruses ...).

Style APA, Harvard, Vancouver, ISO itp.

34

Spadafora, Evan. "Etude par microscopie à force atomique en mode non contact et microscopie à sonde de Kelvin, de matériaux modèles pour le photovoltaïque organique". Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00647312.

Pełny tekst źródła

Streszczenie:

La nanostructure et les propriétés électroniques de matériaux modèles pour le photovoltaïque organique, ont été étudiées en utilisant la Microscopie à Force Atomique en mode non contact sous ultra-vide (NC-AFM) et la Microscopie à sonde de Kelvin (KPFM). En utilisant le mode modulation d'amplitude (AM-KPFM), le potentiel de surface photo- généré dans des mélanges donneur-accepteur présentant une ségrégation de phase optimale a pu être visualisé à l'échelle du nanomètre. Afin de préciser la nature des forces mises en jeu dans le processus d'imagerie KPFM, des oligomères π-conjugués auto-assemblés ont ensuite été étudiés. Une transition entre régimes à longue et à courte portée a ainsi été mise en évidence en combinant l'imagerie en haute résolution aux mesures de spectroscopie en distance. Ces mesures ont également démontré que l'influence des forces électrostatiques à courte portée peut être minimisée en travaillant au seuil du contraste de dissipation. Enfin cette procédure a été utilisée, en combinaison avec les mesures de spectroscopie de photoélectrons UV, pour analyser la fonction de sortie locale d'électrodes transparentes à base de nanotubes de carbone fonctionnalisés.

Style APA, Harvard, Vancouver, ISO itp.

35

Collins, E. C. J. "In vivo models for elucidation of role of MLL-AF9 chromosomal translocations in leukaemia". Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597866.

Pełny tekst źródła

Streszczenie:

Chromosomal translocations involving the MLL and AF9 genes in human acute myeloid leukaemia were investigated using two complementary in vivo models. LoxP sites were introduced into the murine Mll and Af9 genes by homologous recombination in embryonic stem (ES) cells, at positions corresponding to the breakpoints observed in human patients. Generation of de novo inter-chromosomal recombination events was evaluated by transient expression of Cre recombinase in doubly transfected ES cells. The presence and correct expression of the expected fusion gene were verified by polymerase chain reaction and sequence analysis. Subsequently, mouse strains were generated that carried the modified Mll and Af9 alleles. After inter-breeding with a mouse strain ubiquitously expressing a cre transgene, Mll-Af9 fusion genes were detected in tissues of adult animals, indicating that recombination - presumably translocation - had occurred during mouse development. This constitutes the first example of Cre-loxP-dependent inter-chromosomal rearrangement in mammals, and should provide a valuable tool to study translocation fusion genes associated with human cancers as well as potential therapeutic regimes. Furthermore, with a view to elucidation of the role of the AF9 gene, its murine homologue was inactivated by homologous recombination in ES cells and subsequent generation of Af9 null mutant mice. Homozygous gene disruption was lethal shortly after birth, but the mutation was found to have no discernible effect on haematopoiesis as determined by histology and FACS analysis. However, knock-out mice exhibited anomalies of the axial skeleton, indicating a role of Af9 in embryo patterning. Both the cervical and thoracic regions appeared affected by anterior homeotic transformation. Strikingly, mice lacking functional Af9 exhibited a grossly deformed atlas, as well as an extra cervical vertebra, an effect not hitherto observed in any known mouse mutants. This phenotype suggests that the MLL-AF9 oncogene affects key regulators of embryo patterning processes also involved in leukaemogenesis.

Style APA, Harvard, Vancouver, ISO itp.

36

Vogel, Alexander, Jörg Nikolaus, Katrin Weise, Gemma Triola, Herbert Waldmann, Roland Winter, Andreas Herrmann i Daniel Huster. "Interaction of the human N-Ras protein with lipid raft model membranes of varying degrees of complexity". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-191006.

Pełny tekst źródła

Streszczenie:

Ternary lipid mixtures composed of cholesterol, saturated (frequently with sphingosine backbone), and unsaturated phospholipids show stable phase separation and are often used as model systems of lipid rafts. Yet, their ability to reproduce raft properties and function is still debated. We investigated the properties and functional aspects of three lipid raft model systems of varying degrees of biological relevance – PSM/POPC/Chol, DPPC/POPC/Chol, and DPPC/DOPC/Chol – using 2H solidstate nuclear magnetic resonance (NMR) spectroscopy, fluorescence microscopy, and atomic force microscopy. While some minor differences were observed, the general behavior and properties of all three model mixtures were similar to previously investigated influenza envelope lipid membranes, which closely mimic the lipid composition of biological membranes. For the investigation of the functional aspects, we employed the human N-Ras protein, which is posttranslationally modified by two lipid modifications that anchor the protein to the membrane. It was previously shown that N-Ras preferentially resides in liquid-disordered domains and exhibits a time-dependent accumulation in the domain boundaries of influenza envelope lipid membranes. For all three model mixtures, we observed the same membrane partitioning behavior for N-Ras. Therefore, we conclude that even relatively simple models of raft membranes are able to reproduce many of their specific properties and functions.

Style APA, Harvard, Vancouver, ISO itp.

37

Huang, Chia-Pin John. "From the triple helix model (THM) to an actor flow model (AFM) : two case studies on the co-creative evolutionary relationship between universities, industry, the government, and a research institute in Taiwan". Thesis, University of Bath, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.600723.

Pełny tekst źródła

Streszczenie:

The need for collaboration among different institutional actors including, universities, industry and governments, in national innovation systems, has been championed by the creators of the Triple Helix Model (e.g., Etzkowitz and Leydesdorff, 1995). However, these authors played down the importance of research institutes in these interactions during the evolution of innovation. Moreover, although under the THM it is accepted that there are flows of resources between actors, this has yet to be comprehensively conceptualised. To address these issues, in this research the THM is extended to a model that not only includes the role of research institutes, but also allows for examination of the energy flows during successful innovations, involving: human, knowledge. money and physical resources, entitled the Actor Flow Model (AFM). Further, central to this concept of 'flow', an evolutionary perspective ofinc1usionality (Huang, 20 10) is posited as a possible enhancement of the innovative process. This is a new evolutionary perspective conceived by Rayner (2006, 2010), a micro-biologist, who found that the evolution of the mycelia and other natural phenomena are not driven solely by competition, as Darwinists forecast, but by the facilitation of dynamic energy flows and their mutual influencing relationships across space. That is, central to this aspect of the thesis is the notion of interdependency between parties in the innovatory process. This model is then applied to case studies of two inventions in Taiwan that involved collaboration between the four aforementioned actors to show how its constructs offer an improvement on the THM, regarding its explanatory power for successful innovations. The two focal inventions originate from different technological fields: biomedical and optoelectronics. A further element that this thesis shows is that the language used needs to change in order to generate an inc1usional and transformational journey. The language used in this narrative changes with the development of my epistemology.

Style APA, Harvard, Vancouver, ISO itp.

38

Wilson, Diane Easter. "A model curriculum for an associate of science in computer science, based on the ACM model, AACJC and CSAB guidelines". Virtual Press, 1991. http://liblink.bsu.edu/uhtbin/catkey/770947.

Pełny tekst źródła

Streszczenie:

This thesis argues that an AS model in computer science needs to be independent of a BS model because their student populations are distinct. The first two years of a BS model cannot be successfully copied in the AS environment. The AS model curriculum must begin at a different level while also providing competencies comparable to those in the first two years of a BS curriculum.Three questions had to be addressed before an AS model could be formulated. 1) What is an AS in computer science? Specific attention was given to the AA, AAS, BA and BS degrees, along with computer engineering, information systems, systems analysis and data processing majors. 2) How does the student population of the AS differ from other degrees? Compared to their BS counterpart, the AS population is weighted toward female, older, ethnicly diverse, mobile, part-time, remedial students who have additional responsibilities. 3) Lastly, is there a need for standardization? An unequivocable yes was the answer. After exploring these questions a model was presented.The proposed model attempted to address the primary goals of the educational, industrial and accreditation organizations (AACJC, ACM and CSAB). A very explicit description of the model was followed by two implementations.
Department of Computer Science

Style APA, Harvard, Vancouver, ISO itp.

39

Lacroix, Loïc. "Mécanismes de corrosion localisée de l'alliage d'aluminium 2024 : apport de la microscopie à force atomique (AFM) couplée au mode Kelvin (KFM) et des alliages modèles". Phd thesis, Toulouse, INPT, 2008. http://oatao.univ-toulouse.fr/7821/1/lacroix.pdf.

Pełny tekst źródła

Streszczenie:

L'alliage 2024 (Al-Cu-Mg) est, dans le contexte de l'allègement de structure, encore largement utilisé par l'industrie aéronautique. Sa microstructure le rend sensible à la corrosion localisée (corrosion par piqûres, corrosion feuilletante et intergranulaire). Parmi les paramètres microstructuraux, les particules intermétalliques, et notamment les particules de phase S-Al2CuMg, sont dans de nombreux cas un facteur d'endommagement. Ce travail de thèse est donc centré sur leur réactivité ainsi que sur l'apport de techniques locales à cette étude. Dans ce travail, une étude multianalytique a été réalisée. La microscopie à force atomique (AFM pour Atomic Force Microscopy) couplée au mode Kelvin (KFM pour Kelvin Force Microscopy) permettent l'acquisition de la topographie et du potentiel de surface d'un échantillon à l'échelle nanométrique. Le couplage de ces techniques à des analyses chimiques d'extrême surface par SIMS (Secondary Ions Mass Spectroscopy) ainsi que le suivi de la composition des particules lors de leur dissolution (MEB-EDS) ont démontré que l'association AFM-KFM permet le suivi de l'ensemble des phénomènes de dissolution de particules intermétalliques riches en cuivre avec une résolution spatiale de l'ordre de la centaine de nanomètres. En parallèle à ces travaux, l'étude d'alliages et de systèmes modèles par des techniques électrochimiques stationnaires et transitoires telles que la Spectroscopie d'Impédance Electrochimique Locale (SIEL) a été réalisée. Ce travail a permis de montrer la représentativité de ces systèmes pour étudier les phénomènes de microcouplage galvanique entre particules intermétalliques et matrice de l'alliage commercial 2024. La réactivité du couple aluminium/magnésium a été simulée numériquement par la méthode des éléments finis. Les distributions de courant et de potentiel calculées ont été validées par des observations en microscopie optique et électronique.

Style APA, Harvard, Vancouver, ISO itp.

40

Lacroix, Loïc Baret-Blanc Christine Ressier Laurence. "Mécanismes de corrosion localisée de l'alliage d'aluminium 2024 apport de la microscopie à force atomique (AFM) couplée au mode Kelvin (KFM) et des alliages modèles /". Toulouse : INP Toulouse, 2009. http://ethesis.inp-toulouse.fr/archive/00000842.

Pełny tekst źródła

Style APA, Harvard, Vancouver, ISO itp.

41

Amrous, Ania. "Etude d'auto-assemblages moléculaires sur surfaces isolantes par microscopie à force atomique en mode non-contact sous ultravide à température ambiante". Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4368.

Pełny tekst źródła

Streszczenie:

Dans ce rapport de thèse, nous présentons les résultats obtenus avec la croissance d'assemblages supramoléculaires hautement cristallins et stables à température ambiante sur des surfaces isolantes d'halogénures d'alcalins. L'objectif de cette étude est de caractériser structurellement ces réseaux auto-assemblés et de mettre en évidence l'ensemble des forces d'interaction mises en œuvre dans les processus de croissance et de diffusion, en combinant la microscopie à force atomique en mode non contact (nc-AFM) sous ultravide et des calculs théoriques basés sur la théorie de la fonctionnelle de la densité (DFT) et la dynamique moléculaire. Nous montrons comment des paramètres bien définis concernant le choix de la molécule d'une part tels que sa taille, sa forme, sa symétrie, sa flexibilité et sa fonctionnalité, et le choix du substrat d'autre part, influent sur la morphologie de croissance et permettent de contrôler les propriétés de diffusion des molécules en surface et donc la structure supramoléculaire résultante
In this thesis, we report the results obtained with the growth of highly crystalline and stable supramolecular assemblies at room temperature on insulating surfaces of bulk alkali halides single crystals. The objective of this study is to structurally characterize these self-assembled networks and understand all the interaction forces involved in the growth and diffusion processes. This is performed by joint non-contact atomic force microscopy (nc-AFM) experiments in ultrahigh vacuum and theoretical calculations based on density functional theory (DFT) and molecular dynamics. We show how well-defined parameters for the choice of the molecule on the one hand such as size, shape, symmetry, flexibility and functionality, and the choice of the substrate on the other hand, influence the morphology growth and serve to steer the structure and diffusion properties of such systems

Style APA, Harvard, Vancouver, ISO itp.

42

Taccad, Caesar C. "A model of contract administration for the Armed Forces of the Philippines (AFP) modernization program". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA374091.

Pełny tekst źródła

Streszczenie:

Thesis (M.S. in Management) Naval Postgraduate School, December 1999.
"December 1999". Thesis advisor(s): David V. Lamm. David A. Smith. Includes bibliographical references (p. 115-117). Also available online.

Style APA, Harvard, Vancouver, ISO itp.

43

Myklatun, Ahne. "Production and Application of Micronsized Polysaccharide Particles - Studying Perturbation of a Model Mucus Barrier with Total Internal Reflection Fluorescence (TIRF) Microscopy and Atomic Force Microscopy (AFM) Indentation". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13742.

Pełny tekst źródła

Streszczenie:

The overall aim of this project was to produce homogeneously sized polysaccharide microparticles and apply these and similar sized particles as probes for investigation of mucin layers as a model for a biological barrier. Small polysaccharide particles have many applications, e.g. within the medical field of drug delivery. In this study a microfluidic system was developed to produce alginate beads, which can be used in drug delivery systems. Different designs, continuous phases and concentrations were tested in order to find an optimal system. Beads in the size range of 10 µm were produced using a device with T-shaped design and three inlets. An electrostatic bead generator was also used to make alginate beads, however the beads produced were too large to be used in the experiments with the mucin layers.One of the many challenges when working with drug delivery systems is the mucus barrier protecting the epithelial cells. In this study a model mucus barrier was made by immobilizing mucins, the glycoprotein responsible for the physical properties of the barrier. A procedure for fluorescence labelling of polystyrene beads with quantum dots was developed, and penetration of these beads into the model barrier was measured with total internal reflection fluorescence (TIRF) microscopy. In TIRF the excitation field intensity decays exponentially, and the emitted fluorescence intensity from the beads gives an indication of the distance between the beads and the surface. Measurements performed on mucin layers of different concentrations indicate that mucin concentrations above 0,5 mg/ml will result in a layer too thick or too dense to give a intensity signal. At mucin concentration 0,05 mg/ml fluorescence was observable in TIRF, and it was clearly weaker than for the control with a bead directly on a glass surface. This indicates that the beads hover over the surface due to the mucin layers, and show that it is in principle possible to measure the penetration depth of beads into mucin layer using TIRF. To simulate the condition in the lungs of cystic fibrosis (CF) patients, the mucin layers were incubated with alginate. Measurements were performed to see how this affected the penetration of the beads into the layer. A weaker fluorescent signal was obtained for these samples in TIRF, which suggests that there has been interaction between mucin and alginate. It was in addition investigated how different concentrations of G-blocks in the solution affected the penetration into the mucin-alginate layer. These testes were carried out using both TIRF and atomic force microscopy (AFM) nanoindentation experiments. The TIRF measurements were inconclusive, while the nanoindentation experiments showed decreased interaction between mucin-alginate layer and a bead.

Style APA, Harvard, Vancouver, ISO itp.

44

Parkin, John D. "Microcantilevers : calibration of their spring constants and use as ultrasensitive probes of adsorbed mass". Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3608.

Pełny tekst źródła

Streszczenie:

The dynamic properties of several rectangular and V-shaped microcantilevers were investigated. Particular attention was paid to the higher flexural eigenmodes of oscillation. The potential of the higher flexural modes was demonstrated through the use of cantilevers as standalone sensors for adsorbed mass. The mass adsorbed on the surface of a cantilever was in the form of a homogeneous water layer measured as a function of relative humidity. The minimum detectable water layer thicknesses were 13.7 Å, 3.2 Å, 1.1 Å, and 0.7 Å for the first four modes of a rectangular cantilever, clearly demonstrating enhanced accuracy for the higher eigenmodes of oscillation. These thicknesses correspond to minimum detectable masses of 33.5 pg, 7.8 pg, 2.7 pg and 1.7 pg for the first four modes. For quantitative applications the spring constants of each cantilever must be determined. Many methods exist but only a small number can calibrate the higher flexural eigenmodes. A method was developed to simultaneously calibrate all flexural modes of microcantilever sensors. The method was demonstrated for the first four eigenmodes of several rectangular and V-shaped cantilevers with nominal fundamental spring constants in the range of 0.03 to 1.75 N/m. The spring constants were determined with accuracies of 5-10 %. Spring constants of the fundamental mode were generally in agreement with those determined using the Sader method. The method is compatible with existing AFM systems. It relies on a flow of gas from a microchannel and as such poses no risk of damage to the cantilever beam, its tip, or any coating. A related method was developed for the torsional modes of oscillation. Preliminary results are shown for the fundamental mode of a rectangular cantilever. The method can be easily extended to the higher torsional modes, V-shaped cantilevers, and potentially, the flapping modes of the legs of V-shaped microcantilevers.

Style APA, Harvard, Vancouver, ISO itp.

45

Vogel, Alexander, Jörg Nikolaus, Katrin Weise, Gemma Triola, Herbert Waldmann, Roland Winter, Andreas Herrmann i Daniel Huster. "Interaction of the human N-Ras protein with lipid raft model membranes of varying degrees of complexity". de Gruyter, 2014. https://ul.qucosa.de/id/qucosa%3A14050.

Pełny tekst źródła

Streszczenie:

Ternary lipid mixtures composed of cholesterol, saturated (frequently with sphingosine backbone), and unsaturated phospholipids show stable phase separation and are often used as model systems of lipid rafts. Yet, their ability to reproduce raft properties and function is still debated. We investigated the properties and functional aspects of three lipid raft model systems of varying degrees of biological relevance – PSM/POPC/Chol, DPPC/POPC/Chol, and DPPC/DOPC/Chol – using 2H solidstate nuclear magnetic resonance (NMR) spectroscopy, fluorescence microscopy, and atomic force microscopy. While some minor differences were observed, the general behavior and properties of all three model mixtures were similar to previously investigated influenza envelope lipid membranes, which closely mimic the lipid composition of biological membranes. For the investigation of the functional aspects, we employed the human N-Ras protein, which is posttranslationally modified by two lipid modifications that anchor the protein to the membrane. It was previously shown that N-Ras preferentially resides in liquid-disordered domains and exhibits a time-dependent accumulation in the domain boundaries of influenza envelope lipid membranes. For all three model mixtures, we observed the same membrane partitioning behavior for N-Ras. Therefore, we conclude that even relatively simple models of raft membranes are able to reproduce many of their specific properties and functions.

Style APA, Harvard, Vancouver, ISO itp.

46

Demianyk, Bryan C. P. "Development of agent-based models for healthcare: applications and critique". IEEE, 2010. http://hdl.handle.net/1993/31049.

Pełny tekst źródła

Streszczenie:

Agent-based modeling (ABM) is a modeling and simulation paradigm well-suited to social systems where agents interact and have some degree of autonomy. In their most basic sense, ABMs consist of agents (generally, individuals) interacting in an environment according to a set of behavioural rules. The foundational premise and the conceptual depth of ABM is that simple rules of individual behaviour will aggregate to illuminate complex and/or emergent group-level phenomena that are not specifically encoded by the modeler and that cannot be predicted or explained by the agent-level rules. In essence, ABM has the potential to reveal a whole that is greater than the sum of its parts. In this thesis, ABMs have been utilized as a modeling framework for three specific healthcare applications, including: • the development of an ABM of an emergency department within a hospital allowing the modeling of contact-based infectious diseases such as influenza, and simulating various mitigation strategies; • the development of an ABM to model the effectiveness of a real-time location system (RTLS) using radio frequency identification (RFID) in an emergency department, used for patient tracking as one measure of hospital efficiency; and, • the development of an ABM to test strategies for disaster preparedness (high volume, high risk patients) using a fictitious case of zombies in an emergency department. Although each ABM was purposeful and meaningful for its custom application, each ABM also represented an iteration toward the development of a generic ABM framework. Finally, a thorough critique of ABMs and the modifications required to create a more robust framework are provided.
February 2016

Style APA, Harvard, Vancouver, ISO itp.

47

Horne, Jimmy D. Jr. "Modeling optical turbulence with COAMPS during two observation periods at Vandenberg AFB". Thesis, Monterey, California. Naval Postgraduate School, 2004. http://hdl.handle.net/10945/1671.

Pełny tekst źródła

Streszczenie:

Approved for public release, distribution is unlimited
The objective of this thesis is to investigate the forecastability of optical turbulence using the U.S. Navy's Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS). First, a detailed synoptic study was performed over the Eastern Pacific region for observation periods in October 2001 and March 2002 to focus on mesoscale features affecting Vandenberg AFB. Second, a modified version of COAMPS version 2.0.16 model output was evaluated to ensure reasonable modeling of the mesoscale. Next, temperature and dewpoint temperature vertical profiles of COAMPS, modified with the Turbulent Kinetic Energy (TKE) Method, were compared with balloon-launched rawinsondes, initially, then with higher resolution thermosondes. Optical turbulence parameters were then calculated from the data and a comparison between synthetic profiles and thermosonde-derived profiles were qualitatively and quantitatively studied. Then the vertical resolution of the model was increased for selected forecasts to determine the potential for forecast improvement.
Lieutenant Commander, United States Navy

Style APA, Harvard, Vancouver, ISO itp.

48

Hoff, Brice. "Nanostructuration et caractérisation en ultravide de dépôts de molécules sur surfaces isolantes par microscopie à force atomique en mode non-contact et sonde de Kelvin". Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4078/document.

Pełny tekst źródła

Streszczenie:

Grâce à des expériences en ultra-vide avec un AFM en mode non-contact (nc-AFM) et une nano-sonde de Kelvin (KPFM), nous avons pu précisément caractériser plusieurs dépôts de molécules sur différentes surfaces isolantes, dont la surface (001) de monocristaux de NaCl dopés par des ions Cd2+, appelée la surface de Suzuki. Cette surface est nanostructurée de façon à ce que deux régions très distinctes coexistent : des régions de NaCl pures et des régions de Suzuki qui recouvrent partiellement la surface (001) du cristal. Nous montrons que la surface de Suzuki peut être utilisée comme surface nanostructurée dans le but de confiner l'adsorption de nano-objets tels que des molécules organiques ou inorganiques. Après déposition de différentes molécules pentahélicènes fonctionalisées, une large partie de celles-ci reste préférentiellement adsorbée dans les régions de Suzuki. Suite aux observations nc-AFM et KPFM un modèle sera présenté sur les mécanismes d'adsorption et désorption de ces hélicènes, accompagné d'une étude étonnante sur des ilots de molécules fullerènes C60 déposés sur plusieurs surfaces isolantes, et la manipulation de charges dans ces ilots
Thanks to ultra high vacuum experiments using non-contact AFM and Kelvin probe force microscopy (KPFM), we have been able to characterize precisely several depositions of molecules on different surfaces, including the (001) surface of a Cd2+ doped NaCl single crystal called the Suzuki surface. This surface is nanostructured such as two different regions coexist : pure NaCl regions and Suzuki regions covering partially the (001) surface. We show that the Suzuki surface can be used as a nanotemplate in order to confine the adsorption of nano-objects such as organic or inorganic molecules. After deposition of different functionalised pentahelicenes molecules, a large part of those stay preferentially adsorbed on Suzuki regions. Following the nc-AFM and KPFM observations a model will be presented on the mechanism of adsorption and desorption of those helicenes, accompanied with a astonishing study about fullerenes C60 molecules deposed on several surfaces, and the charge manipulation in these islands

Style APA, Harvard, Vancouver, ISO itp.

49

Kotarsky, Ulf. "Hochauflösender mikromechanischer Sensor zur Erfassung von Oberflächenprofilen". Doctoral thesis, Universitätsbibliothek Chemnitz, 2005. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200500132.

Pełny tekst źródła

Streszczenie:

In der vorliegenden Arbeit wird die Entwicklung von ausschließlich elektrostatisch arbeitenden Sensor-Aktor-Arrays zur Oberflächenprofilbestimmung an Mikroteilen beschrieben. Ein wesentliches Merkmal der Strukturen ist ihr großer Eigenzustellbereich von bis zu 20 Mikrometer. Die Auswertung atomarer Kräfte ermöglicht Wegauflösungen im Nanometerbereich. Auf Grund der geringen Abmessungen durch die mikromechanische Fertigung des Sensorelements und der integrierten Sensor-Aktorfunktion sind Anordnungen als Zeilenarray möglich. Die Entwicklung richtet sich auf Strukturen, welche in klassischer Oberflächentechnologie gefertigt werden können. Durchgeführte experimentelle Tests wurden mit Sensoren in Silizium-bulk-Mikromechanik (SCREAM) realisiert. Der Schwerpunkt der Arbeit behandelt die Charakterisierung der Sensorelemente und damit verbundene Layoutverbesserungen, wie das Einbringen von Feldstoppern und die Nutzbarkeit des Sensors zur Profilbestimmung von Oberflächen unter Beachtung industrieller Anforderungen. Vorteile des Einsatzes eines solchen Sensor-Aktor-Arrays liegen in der Miniaturisierung und dem vergleichsweise großen Eigenzustellbereich jedes einzelnen Sensors. Dadurch ist es möglich, technische Oberflächen, welche im Eigenzustellbereich des Sensorarrays liegen, ohne das Nachregeln einer übergeordneten Positioniereinheit im Profil zu bestimmen. Es wird gezeigt, wie die angewandte kapazitive Wirkungsweise des Sensors mit den sehr kleinen Nutzkapazitäten im Beisein von großen Parasitärkapazitäten zur Signalauswertung genutzt werden kann.

Style APA, Harvard, Vancouver, ISO itp.

50

Fanelli, Gabriele. "Facial Features Tracking using Active Appearance Models". Thesis, Linköping University, Department of Electrical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-7658.

Pełny tekst źródła

Streszczenie:

This thesis aims at building a system capable of automatically extracting and parameterizing the position of a face and its features in images acquired from a low-end monocular camera. Such a challenging task is justified by the importance and variety of its possible applications, ranging from face and expression recognition to animation of virtual characters using video depicting real actors. The implementation includes the construction of Active Appearance Models of the human face from training images. The existing face model Candide-3 is used as a starting point, making the translation of the tracking parameters to standard MPEG-4 Facial Animation Parameters easy.

The Inverse Compositional Algorithm is employed to adapt the models to new images, working on a subspace where the appearance is "projected out" and thus focusing only on shape.

The algorithm is tested on a generic model, aiming at tracking different people’s faces, and on a specific model, considering one person only. In the former case, the need for improvements in the robustness of the system is highlighted. By contrast, the latter case gives good results regarding both quality and speed, with real time performance being a feasible goal for future developments.

Style APA, Harvard, Vancouver, ISO itp.

Rozprawy doktorskie na temat „AFM Modes”

Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych