Dissertations / Theses on the topic 'Atomic Force Microscopy imaging'
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Grimble, Ralph Ashley. "Atomic force microscopy : atomic resolution imaging and force-distance spectroscopy." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312277.
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LAU, JOAN M. "IMAGING MEMBRANE PROTEINS USING ATOMIC FORCE MICROSCOPY TECHNIQUES." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1022192720.
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Muys, James Johan. "Cellular Analysis by Atomic Force Microscopy." Thesis, University of Canterbury. Electrical and Computer Engineering, 2006. http://hdl.handle.net/10092/1158.
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Exocytosis is a fundamental cellular process where membrane-bound secretory granules from within the cell fuse with the plasma membrane to form fusion pore openings through which they expel their contents. This mechanism occurs constitutively in all eukaryotic cells and is responsible for the regulation of numerous bodily functions. Despite intensive study on exocytosis the fusion pore is poorly understood. In this research micro-fabrication techniques were integrated with biology to facilitate the study of fusion pores from cells in the anterior pituitary using the atomic force microscope (AFM). In one method cells were chemically fixed to reveal a diverse range of pore morphologies, which were characterised according to generic descriptions and compared to those in literature. The various pore topographies potentially illustrates different fusion mechanisms or artifacts caused from the impact of chemicals and solvents in distorting dynamic cellular events. Studies were performed to investigate changes in fusion pores in response to stimuli along with techniques designed to image membrane topography with nanometre resolution. To circumvent some deficiencies in traditional chemical fixation methodologies, a Bioimprint replication process was designed to create molecular imprints of cells using imprinting and soft moulding techniques with photo and thermal activated elastomers. Motivation for the transfer of cellular ultrastructure was to enable the non-destructive analysis of cells using the AFM while avoiding the need for chemical fixation. Cell replicas produced accurate images of membrane topology and contained certain fusion pore types similar to those in chemically fixed cells. However, replicas were often dehydrated and overall experiments testing stimuli responses were inconclusive. In a preliminary investigation, a soft replication moulding technique using a PDMS-elastomer was tested on human endometrial cancer cells with the aim of highlighting malignant mutations. Finally, a Biochip comprised of a series of interdigitated microelectrodes was used to position single-cells within an array of cavities using positive and negative dielectrophoresis (DEP). Selective sites either between or on the electrode were exposed as cavities designed to trap and incubate pituitary and cancer cells for analysis by atomic force microscopy (AFMy). Results achieved trapping of pituitary and cancer cells within cavities and demonstrated that positive DEP could be used as a force to effectively position living cells. AFM images of replicas created from cells trapped within cavities illustrated the advantage of integrating the Biochip with Bioimprint for cellular analysis.
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Jeong, Younkoo. "HIGH SPEED ATOMIC FORCE MICROSCOPY." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236701109.
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Alkassem, Hasan. "Imaging antimicrobial peptides in action by atomic force microscopy." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10043141/.
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Antimicrobial resistance is a challenge facing the world in the twenty-first century with an estimated 10 million deaths by 2050 if no actions are taken. Microbial resistance to drugs is a natural consequence when bacteria develop and adapt genetically to face new challenges including antibiotics. Currently, this development occurs at a higher rate than drug discovery. Hence there is a need for a new generation of antibiotics that kill pathogenic bacteria. Nature itself provides inspiration for such new antibiotics. For example, our immune system secretes antimicrobial peptides (AMPs), which have been successful agents in killing pathogens with no reported bacterial resistance. Compared with conventional antibiotics, these peptides are larger and more sophisticated biological molecules, which disturb the bacterial membrane, leading to cell lysis. It is currently costly to extract AMPs from natural resources to be used for fighting infections. Alternatively, synthetic AMPs that mimic natural ones could provide a sustainable cheap weapon against such thread. This also provides a unique opportunity to understand the structure–function relationships of such molecules to optimise these effective, non-toxic antimicrobial properties. Our collaborators at National Physical Laboratory have designed and synthesised new AMPs from their essential building blocks (amino acids). This thesis describes the use of atomic force microscopy (AFM) as a nanoscale imaging technique for characterising and imaging membrane poration mechanisms of four new AMP systems. Two of these systems are helical peptides, explained in chapter 3. The third system, explained chapter 4, is a triskelion with three arms of antimicrobial β-sheet peptide that co-assemble to form a hollow antimicrobial capsules. The latter has two possible functions: gene delivery and bactericidal effects. The fourth system, explained in chapter 5, contains two peptide monomers that are designed to co-assemble and form antimicrobial hollow capsids, inspired by the natural viral capsids. Finally, chapter 6 is a plan for taking these AMPs a step closer to commercialisation, including a business plan for one potential application.
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Hernandez, Sergio Santos. "Dynamic atomic force microscopy and applications in biomolecular imaging." Thesis, University of Leeds, 2011. http://etheses.whiterose.ac.uk/1910/.
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The Atomic Force Microscope (AFM) is a key member of the Scanning Probe Microscope (SPM) family. Its versatility allows it to image and manipulate nanoscale features with high precision, making it one of the main instruments in nanotechnology for surface characterization. The aim of this thesis is to improve robustness, reproducibility, resolution and data interpretation in ambient conditions for dynamic AFM of heterogeneous samples. The AFM is particularly notorious for lack of reproducibility with apparent height and width being the two main measured parameters where accuracy is sought. Here i) the origins of reproducibility, or lack thereof, have been investigated experimentally via a systematic approach to imaging for the whole range of parameter space and relative humidity, ii) smooth and step-like transitions have been investigated both experimentally and with simulations, iii) a method to mechanically stabilise the tip radius and calculate the effective area of interaction in the dynamic mode has been developed and used to predict the number of eV dissipated per atom per cycle, iv) a method to predict the tip radius in situ has been developed, v) three types of dynamic behaviour have been categorised and distinguished (Type I, II and III) allowing to both predict the tip radius and noise patterns, vi) a general interpretation of a mechanism behind height reconstruction and vii) a novel high resolution and low wear imaging technique (SASS) have been developed, modelled, implemented and interpreted with the help of simulations. The most general outcome of this work is that the tip radius has to be well characterised since it plays a major role in any AFM experiment. The investigation is general for nano-mechanical forced oscillators in ambient conditions and the calculations will lead to mapping of local chemistry and mechanics at higher resolution.
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Forchheimer, Daniel. "Imaging materials with intermodulation : Studies in multifrequency atomic force microscopy." Doctoral thesis, KTH, Nanostrukturfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-159689.
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The Atomic Force Microscope (AFM) is a tool for imaging surfaces at the microand nano meter scale. The microscope senses the force acting between a surfaceand a tip positioned at the end of a micro-cantilever, forming an image of the surface topography. Image contrast however, arises not only from surface topography, but also from variation in material composition. Improved material contrast, and improved interpretation of that contrast are two issues central to the further development of AFM. This thesis studies dynamic AFM where the cantilever is driven at multiple frequencies simultaneously. Due to the nonlinear dependence of the tip-surface force on the tip’s position, the cantilever will oscillate not only at the driven frequencies, but also at harmonics and at mixing frequencies of the drives, so-called intermodulation products. A mode of AFM called Intermodulation AFM (ImAFM) is primarily studied, which aims to make use of intermodulation products centered around the resonance frequency of the cantilever. With proper excitation many intermodulation products are generated near resonance where they can be measured with large signal-to-noise ratio. ImAFM is performed on samples containing two distinct domains of different material composition and a contrast metric is introduced to quantitatively evaluate images obtained at each response frequency. Although force sensitivity is highest on resonance, we found that weak intermodulation response off resonance can show larger material contrast. This result shows that the intermodulation images can be used to improve discrimination of materials. We develop a method to obtain material parameters from multifrequency AFM spectra by fitting a tip-surface force model. Together with ImAFM, this method allows high resolution imaging of material parameters. The method is very generalas it is not limited to a specific force model or particular mode of multifrequency AFM. Several models are discussed and applied to different samples. The parameter images have a direct physical interpretation and, if the model is appropriate, they can be used to relate the measurement to material properties such as the Young’s modulus. Force reconstruction is tested with simulations and on measured data. We use the reconstructed force to define the location of the surface so that we can address the issue of separating topographic contrast and material contrast.Svepkraftmikroskop (eller atomkraftmikroskop från engelskans atomic forcemicroscope, AFM) är ett instrument för att avbilda ytor på mikro- och nanometer skalan. Mikroskopet känner av kraften som verkar mellan en yta och en spetsplacerad längst ut på ett mikrometerstort fjäderblad och kan därigenom skapa en topografisk bild av ytans form. Bildkontrast uppstår dock inte bara från ytans form utan även från variation i material. Förbättrad materialkontrast och förbättrad tolkning av denna kontrast är två centrala mål i vidareutvecklingen av AFM. Denna avhandling berör dynamisk AFM där fjädern drivs med flera frekvensersamtidigt. På grund av det ickelinjära förhållandet i yt-spets-kraften som funktion av spetsens position så kommer fjädern inte bara att svänga på de drivna frekvenserna utan också på övertoner och blandfrekvenser, så kallade intermodulationsprodukter. Vi undersöker primärt Intermodulation AFM (ImAFM) som ämnar att utnyttja intermodulationsprodukter nära fjäderns resonansfrekvens. Med en lämplig drivsignal genereras många intermodulationsprodukter nära resonansen, där de kan mätas med bra signal till brus förhållande. ImAFM utförs på ytor bestående av två distinkta domäner av olika material ochen kontrastmetrik introduceras för att kvantitativt utvärdera bilderna som skapas vid varje frekvens. Trots att känsligheten för kraftmätningen är högst på resonans-frekvensen, så fann vi att svaga intermodulationsprodukter bortanför resonansen kan visa hög materialkontrast. Detta resultat visar att intermodulationsbilderna kan användas för att bättre särskilja olika material. Vi har utvecklat en metod för att rekonstruera yt-spets-kraften från multifrekventa AFM spektra genom modellanpassning i frekvensrymden. Tillsammans med ImAFM leder detta till högupplösta bilder av materialparametrar. Metoden är generell och är applicerbar för olika kraftmodeller och AFM-varianter. Parametrarna har en direkt fysikalisk tolkning och, om lämpliga modeller används, kan egenskaper så som materialets elasticitetsmodul mätas. Metoden har testats på simulerat såvälsom experimentellt data, och den har också används för att särskilja topografisk kontrast från materialkontrast.
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Burns, Jonathan. "High resolution atomic force microscopy imaging of living bacterial surfaces." Thesis, University of Sheffield, 2017. http://etheses.whiterose.ac.uk/19929/.
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Khan, Z. "Imaging biomolecules using frequency modulation atomic force microscopy in liquids." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1399519/.
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Atomic force microscopy is an advanced imaging technique for viewing biological structures and dynamic biological mechanisms at the nanometre scale. This thesis describes a high-resolution atomic force microscope designed for imaging biological samples in physiological solution. This microscope includes a highly sensitive interferometric cantilever detector, along with a home-built frequency/phase and amplitude detector. The initial chapters of this thesis begin with a description of the experimental set-up, as well as various tests carried out to characterise the fast frequency detector. Following this is a description of the interferometric cantilever detector, which possess a noise floor at a mere 5 fm/√Hz, making it particularly suited for detecting cantilevers in liquids. Results chapters then go on to demonstrate the capability of this instrument to image at nanometre and atomic-scale resolution. Images of the atomic structure of muscovite mica in buffer solution are presented. Images of chaperonin protein GroEL were also acquired, which contain features of the protein's apical domain. Most importantly, for the first time AFM was used to track the pore-formation of pore forming protein pneumolysin in buffer solution. Supported lipid bilayers were prepared and images were captured of the proteins oligomerising on their surface. The initial stage of pore-formation was investigated by comparing the height of pneumolysin before and after pores were formed. Details of the monomers making up the structure of the protein were also imaged, as well as pores created within the supported lipid bilayers.
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Tien, Szu-Chi. "High-speed nano-precision positioning : theory and application to AFM imaging of soft samples /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/7089.
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Rodriguez, Raúl D. "Dynamic atomic force microscopy on hematite nanoparticules : beyond topographic measurements." Paris 6, 2008. http://www.theses.fr/2008PA066505.
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In this thesis, atomic force microscopy studies in Tapping Mode have been performed on a system composed of hematite nanoparticles deposed on either a MoS2 (molybdenite) or SiO2 (silice) substrate. The nature of nanoparticles facets was determined combining both atomic force microscopy and transmission electron microscopy. Later on, this nanoparticles and substrates were used as a model system to deduce material properties of a SiO2 surface using force spectroscopy. From the determination of interactions between the AFM tip and the SiO2 surface, the Hamaker constant was deduced. Contact interactions as a function of humidity were evidenced which confirmed the hydrophobic character of hematite nanoparticlesDans cette thèse, des études de microscopie à force atomique en mode tapping ont été effectuées sur un système de nano-particules d'hématites sur substrat de MoS2 (molybdénite) ou de SiO2 (silice). La nature des facettes des nano-particules a été déterminée en combinant à la microscopie à force atomique la microscopie électronique en transmission. Ensuite ces nano-particules et leurs substrats ont été utilisées comme système modèle pour sonder comment interroger les propriétés de surface par spectroscopie et microscopie à force atomique, au-delà de la simple information de topographie, à partir de la détermination des interactions entre la pointe d'AFM et la surface des échantillons. Les interactions de Van der Waals à longue distance et la constante de Hamaker ont été déterminées. Les interactions de contact en présence et en absence d'humidité ont été mises en évidence, menant, entre autres, à la détermination du caractère hydrophobe des nano-particules
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Vuong, Ngoc Quang. "Imaging the Nicotinic Acetylcholine Receptor in Reconstituted Membranes by Atomic Force Microscopy." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28592.
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Several recent studies have suggested that the nicotinic acetylcholine receptor (nAChR) segregates lipids into domains in reconstituted bilayers. These studies, however, lack direct evidence (e.g., microscopic images) to show domain formation. Atomic force microscopy (AFM) has been used extensively to image both lipid domains and proteins in membranes, but has not been applied extensively to reconstituted membrane proteins due to the lack of available protocols for preparing suitable planar bilayers on AFM supports. The aim of the work presented in this thesis was to image the nAChR in planar reconstituted membranes by AFM. I developed a novel method for reconstituting the nAChR in POPC (POPC-nAChR) to generate vesicles with high lipid-to-protein (L:P) ratios (i.e., greater than 100:1 w/w). Freeze-thaw cycles are required to improve vesicle homogeneity. The high L:P vesicles must also be isolated from protein-free vesicles using sucrose density gradients. Finally, the preparation of planar bilayers from the high L:P ratio proteoliposomes requires an appropriate sample load and incubation time on a defined area of mica surface (the solid AFM support) and an appropriate level of calcium. AFM images of a POPC-nAChR bilayers show a number of features that protrude out of the bilayer with an average height of 3 nm and diameter of 4 -- 9 nm, which is appropriate for the dimensions of the cytoplasmic side of the nAChR. My results thus represent the first AFM images of the nAChR in a reconstituted membrane environment. Now that the key parameters governing nAChR reconstitution and planar bilayer preparation for AFM imaging are understood, they will undoubtedly be useful for reconstituting and imaging the nAChR in more complex bilayers.
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Lu, Qingyou. "Magnetic force microscopy of colossal magneto-resistive materials and superconductors /." Digital version:, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992856.
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Fan, Tai-Hsi. "Fluid mechanics and bio-transport phenomena in imaging of biological membranes using AFM-integrated microelectrode." Diss., Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04062004-164638/unrestricted/fan%5Ftai-shi%5F200312%5Fphd.pdf.
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Callaghan, Fergal Dominique. "Magnetic force microscope for imaging fluxlines in superconductors." Thesis, Queen's University Belfast, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287399.
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Farnham, Rodrigo Bouchardet. "Processing and inpainting of sparse data as applied to atomic force microscopy imaging." California State University, Long Beach, 2013.
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Gao, D. "Modeling of adsorption and atomic force microscopy imaging of molecules on insulating surfaces." Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1468925/.
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The study of atoms and molecules on bulk insulating surfaces is of critical importance to many fields of surface science including lubrication, and molecular electronics. I studied these systems by using a variety of theoretical methods to predict adsorption geometry, diffusion pathways, and film structure, and to interpret noncontact atomic force microscopy (NCAFM) data. I began by using molecular dynamics (MD) simulations to predict that Pd atoms deposited onto MgO(100) exhibit some transient mobility. They were initially able to move across the surface, but were eventually captured at an adsorption site when enough energy had been dissipated. Similarly, deposited molecules may also be able move around and find nucleation sites such as step edges or kinks before becoming stabilized on surface terraces at low temperature. I then moved on to study the properties of single molecules on oxide surfaces. I combined my theoretical calculations with experimental data to compare adsorption sites and geometries of Co-Salen molecules on NaCl(100) and NiO(100). I used density functional theory calculations (DFT) to show that minor differences in commensurability between the molecule and the surface can qualitatively change adsorption. Both surfaces are bulk insulators with simple cubic crystal structures, however, a much higher adsorption energy and distortion of the molecule on NiO(100) produced a significant vertical dipole moment. Single molecules adsorbed onto insulators can be directly imaged with chemical resolution using metal coated NCAFM tips. However, accurate interpretation of the results is needed. I studied metallic tips using DFT calculations and developed a point dipole model to represent the Cr coated tips used experimentally. I then fit the position and magnitude of the point dipole in this model directly to experimental scan-lines and was able to produce virtual AFM (VAFM) images and scan-lines that were in quantitative agreement with experiment. This method simultaneously reduced the complexity of interpretation of experimental data and the computational cost of producing VAFM images. Finally, I studied larger systems using a hybrid quantum mechanics/molecular mechanics (QM/MM) and parametrized classical force fields using genetic algorithm (GA) methods. This allowed me to study CDB, a large organic molecule, on KCl(100). Static DFT calculations and classical MD simulations using these force fields showed that adsorbed CDB molecules are mobile at room temperature and stabilized at step edges due to increased adsorption energy. These results provide insight into the processes and mechanisms that govern deposition, adsorption, and diffusion of atoms and molecules on insulating surfaces and can help guide the design of functional molecules and films.
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Singjai, Pisith. "Improved meso-scale and atom-scale imaging for atomic force microscopy study of corrosion." Thesis, University of Surrey, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324162.
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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.
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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.
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Prempraneerach, Pradya 1975. "Color imaging segmentation for automatic alignment of Atomic Force Microscope." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/89326.
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Roy, Chowdhury Susovan. "Single-Molecule Force Manipulation and Nanoscopic Imaging of Protein Structure-Dynamics-Function Relationship." Bowling Green State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu162707900722617.
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Budde, Michael [Verfasser]. "Single molecule force spectroscopic investigation of the siloxane bond in polydimethylsiloxane and atomic force microscopy Imaging of nucleosomal arrays / Michael Budde." Ulm : Universität Ulm. Fakultät für Naturwissenschaften, 2015. http://d-nb.info/1076083897/34.
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Marutschke, Christoph Peter [Verfasser]. "Three-dimensional imaging of the solid-liquid interface with high-resolution atomic force microscopy / Christoph Peter Marutschke." Mainz : Universitätsbibliothek Mainz, 2016. http://d-nb.info/1121241832/34.
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Oral, Hasan Giray. "Modeling time-resolved interaction force mode AFM imaging." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43691.
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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.
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Al-Hammood, Orooba [Verfasser]. "Nano-indentation and Nano-scale imaging using atomic force microscopy: from single cell to single molecule / Orooba Al-Hammood." Bielefeld : Universitätsbibliothek Bielefeld, 2021. http://d-nb.info/1235664252/34.
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Klash, Abdalah. "Imaging and quantifying the different crystalline structures of polypropylene with the atomic force microscope." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1070.
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Wu, Ying. "Inversion-based feedforward-feedback control theory and implementation to high-speed atomic force microscope imaging /." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3396982.
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Bippes, Christian Alexander. "Investigation of biological macromolecules using atomic force microscope-based techniques." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-23734.
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The atomic force microscope (AFM) provides a powerful instrument for investigating and manipulating biological samples down to the subnanometer scale. In contrast to other microscopy methods, AFM does not require labeling, staining, nor fixation of samples and allows the specimen to be fully hydrated in buffer solution during the experiments. Moreover, AFM clearly compares in resolution to other techniques.
In general, the AFM can be operated in an imaging or a force spectroscopy mode. In the present work, advantage was taken of this versatility to investigate single biomolecules and biomolecular assemblies.
A novel approach to investigate the visco-elastic behavior of biomolecules under force was established, using dextran as an example. While a molecule tethered between a solid support and the cantilever tip was stretched at a constant velocity, the thermally driven oscillation of the cantilever was recorded. Analysis of the cantilever Brownian noise provided information about the visco-elastic properties of dextran that corresponded well to parameters obtained by alternative methods. However, the approach presented here was easier to implement and less time-consuming than previously used methods.
A computer controlled force-clamp system was set up, circumventing the need for custom built analogue electronics. A commercial PicoForce AFM was extended by two computers which hosted data acquisition hardware. While the first computer recorded data, the second computer drove the AFM bypassing the manufacturer's microscope control software. To do so, a software-based proportional-integral-differential (PID) controller was implemented on the second computer. It allowed the force applied to a molecule to be held constant over time. After tuning of the PID controller, response times obtained using that force-clamp setup were comparable to those of the recently reported analogue systems. The performance of the setup was demonstrated by force-clamp unfolding of a pentameric Ig25 construct and the membrane protein NhaA. In the latter case, short-lived unfolding intermediates that were populated for less than 10 ms, could be revealed.
Conventional single-molecule dynamic force spectroscopy was used to unfold the serine:threonine antiporter SteT from Bacillus subtilis, an integral membrane protein. Unfolding force patterns revealed the unfolding barriers stabilizing structural segments of SteT. Ligand binding did not induce new unfolding barriers suggesting that weak interactions with multiple structural segments were involved. In contrast, ligand binding caused changes in the energy landscape of all structural segments, thus turning the protein from a brittle, rigid into a more stable, structurally flexible conformation. Functionally, rigidity in the ligand-free state was thought to facilitate specific ligand binding, while flexibility and increased stability were required for conformational changes associated with substrate translocation. These results support the working model for transmembrane transport proteins that provide alternate access of the binding site to either face of the membrane.
Finally, high-resolution imaging was exploited to visualize the extracellular surface of Cx26 gap junction hemichannels (connexons). AFM topographs reveal pH-dependent structural changes of the extracellular connexon surface in presence of HEPES, an aminosulfonate compound. At low pH (< 6.5), connexons showed a narrow and shallow channel entrance, which represented the closed pore. Increasing pH values resulted in a gradual opening of the pore, which was reflected by increasing channel entrance widths and depths. At pH > 7.6 the pore was fully opened and the pore diameter and depth did not increase further. Importantly, coinciding with pore gating a slight rotation of the subunits was observed. In the absence of aminosulfonate compounds, such as HEPES, acidification did not affect pore diameters and depths, retaining the open state. Thus, the intracellular concentration of taurine, a naturally abundant aminosulfonate compound, might be used to tune gap junction sensitivity at low pH.
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Bergstrom, Torbjorn S. "Investigation of measurement artifacts introduced by horizontal scanning surface profiling instruments." Link to electronic thesis, 2002. http://www.wpi.edu/Pubs/ETD/Available/etd-0108102-131441.
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Oestreicher, Zachery Walter John. "Magnetotactic Bacteria: Isolation, Imaging, and Biomineralization." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1354146141.
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Berthold, Tobias. "Advanced nanoscale characterization concepts for copper interconnection technologies." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/456236.
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En tecnologías de interconexión de cobre, las propiedades de cobre (Cu) y especialmente su oxidación, dificultan su implementación en comparación con materiales estándar como el aluminio o el oro. Como Cu es susceptible de oxidación, incluso a temperatura ambiente, la caracterización de superficies de Cu es un aspecto importante para el desarrollo del proceso.
En esta tesis, se ha desarrollado un nuevo método para investigar la oxidación de superficies del Cu en la nanoescala utilizando técnicas combinadas de caracterización. Se obtuvieron valores característicos de la diferencia de potencial de contacto (CPD) para los diferentes estados del óxido de cobre. Se utilizaron técnicas de microscopia como PF-KPFM que permitieron distinguir entre los diferentes tipos de óxido de Cu con resolución nanométrica y correlacionar los estados de oxidación a las características de la topografía local.
Además, se introdujeron capas de pasivación en el rango nanométrico para alcanzar condiciones superficiales estables y fiables sin limitar los procesos de interconexión. Para la realización de medidas precisas mediante microscopía de fuerzas atómicas (AFM) de variaciones superficiales de recubrimientos protectores orgánicos muy suaves, la punta de la sonda AFM debe funcionar en un medio líquido. El modelo numérico presentado es capaz de proporcionar predicciones precisas de la resistencia de las fuerzas presentes en aplicaciones AFM en medios fluidos. Se ha demostrado que palancas triangulares presentan fuerzas de arrastre inferiores. Se pudo demostrar la influencia de diferentes líquidos como agua ultrapura o una mezcla de etanol y agua, así como la variación de la temperatura inducida de la fuerza de arrastre.
Los estudios realizados demostraron que monocapas finas autoensambladas orgánicas (SAM) actúan como barrera efectiva para proteger al cobre de la corrosión. El modelo numérico mejoró las medidas de AFM en medios líquidos y permitió la caracterización a escala nanométrica de capas SAM con CH3 para proteger la superficie del Cu. Técnicas como TR-TUNA y dCFM permitieron la correlación de alta hidrofobicidad con corrientes túnel de bajo nivel en escala nanométrica manteniendo la integridad intacta de la película y viceversa. Alta corriente y baja hidrofobicidad podrían estar relacionados con la desintegración de la capa local SAM y la oxidación local de la superficie de Cu a 100°C. Una temperatura de 150°C conduce finalmente a una descomposición completa de la capa de SAM.
También se analizó el efecto protector del platino (Pt) y del carbono (C) de superficies de Cu combinado técnicas no destructivas de microscopia electrónica de barrido (SEM) y PF-KPFM. Se observó que una película de C proporciona un efecto protector mucho mejor que una capa de Pt. No se observó degradación progresiva relevante de la capa de C hasta una temperatura de 200 ° C con espesores por debajo de 3 nm. Por el contrario, superficies de Cu protegidas con capas de 10 nm de Pt muestran ya a una temperatura de 150 ° C granos de óxido de Cu localmente crecidos.
También se ha analizado la bola de aire de Cu de libre formación (FAB) utilizando técnicas de caracterización basadas en SEM. Cambios topográficos de FABs de varios diámetros podrían deberse a la oxidación de capas con espesores inferiores a 55 nm. Los resultados mostraron que la oxidación de FABs se produce solamente en la superficie. Una estructura de grano más fina y un tamaño de grano más pequeño se pueden conseguir con descargas de voltajes bajos. Por el contrario, se detectó una baja densidad de dislocación en las fronteras para voltajes más altos. La transferencia de calor hasta el cable y el enfriamiento convectivo por aire circundante podría explicar las conclusiones introducidas con respecto a la oxidación y la densidad de dislocación.For the implementation of a direct copper-copper interconnection technology, the different properties of copper (Cu), especially the oxidation behavior, impede the easy transition to Cu compared to standard materials such as aluminum or gold. Since Cu is subject to oxidation, even at room temperature, the characterization of the Cu surface is an important aspect for the process development. A novel method to research the oxidation behavior of the Cu surface in the nanoscale was developed by using combined characterization techniques. Characteristic values of the Contact Potential Difference (CPD) were obtained for the copper oxide states. By this means, Peakforce Kelvin Probe Force Microscopy (PF-KPFM) enabled to distinguish between the different types of Cu oxide with nanometer resolution and to correlate the oxidation states to local topography features. Beside the nanoscale characterization of the Cu surface, novel passivation layer in the nanometer range were introduced to achieve reliable and stable surface conditions without limiting the ability for interconnection processes. For advanced atomic force microscopy (AFM) investigations of chemical surface modifications or very soft organic protective coatings, the AFM probe tip needs to be operated in a liquid environment. The presented numerical model is able to provide accurate predictions of the drag forces present in AFM fluid imaging applications. It could be shown that triangular cantilevers provide significant lower drag forces. The influence of different liquids such as ultrapure water or an ethanol-water mixture as well as the temperature induced variation of the drag force could be demonstrated. Studies showed that thin organic Self-Assembled Monolayer (SAM) act as effective barrier to protect Cu from corrosion. The numerical model improved the AFM fluid measurements and enabled the nanoscale characterization of the CH3-terminated SAM film protecting the Cu surface. Torsional Resonance Tunneling AFM (TR-TUNA) and dynamic Chemical Force Microscopy (dCFM) enabled the correlation of high hydrophobicity and low tunneling current on nanometer scale with intact film integrity and vice versa. Compared with additional analyses, high current and low hydrophobicity could be assigned to local SAM film disintegration and local oxidation of the Cu surface at 100 °C. 150 °C finally leads to a complete decomposition of the SAM film. In addition to SAM films, the protective effect of platinum (Pt) and carbon (C) based films deposited onto Cu surfaces was reported by combined non-destructive Scanning Electron Microscopy (SEM) techniques and PF-KPFM. A C film provides a much better protective effect than a Pt layer. Besides very local sporadically distributed Cu oxide grains, a gradual degradation of the C film was not observable for a temperature up to 200 °C and layer thicknesses down to 3 nm. In contrast, the 10 nm Pt protected Cu surface exhibits already at a temperature of 150 °C locally grown Cu oxide grains. The C film passivated Cu surface has the potential of being a key technique for a reliable Cu-Cu wire bonding. Beside the research of the Cu pad surface, the Cu free air ball (FAB) formation in the ambient environment was investigated by using SEM based characterization techniques. Topographic changes of FABs with various diameters could be assigned to different oxidation layers which were well below a thickness of 55 nm. Element mappings of cross sectioned FABs showed that the oxidation occurs only on the surface. A finer grain structure and a lower grain size could be achieved by lower discharge voltages. In contrast, a lower dislocation density at the borders could be detected for higher EFO voltages. The heat transfer up to the wire and the convective cooling by the surrounding air could explain the introduced conclusions regarding the oxidation and the dislocation density.
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Conneely, Michael. "High-speed imaging of holographically trapped microbubble ensembles stimulated by clinically relevant pulsed ultrasound." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/37b78423-14a9-4d5a-bdf1-e2a3562c66f0.
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The development of ultrasound contrast agents, or microbubbles, over the past 40 years has increased the possibilities for diagnostic imaging, although, more recently they have been proposed as a new vehicle for delivery of drugs and genes. However, there yet remains a considerable lack of fundamental understanding of microbubble behaviour under ultrasound excitation which has restricted their translation to therapeutic use. This project focussed on three key areas relating to the generation, observation, and bioeffects of microbubbles and the ultrasound used in their excitation. The experimental endeavour involved first, a full characterisation of the performance of a rotating mirror high-speed camera (Cordin 550-62) that was previously used by our group [and others] to investigate microbubble dynamics. Specifically, the investigation begins with an assessment of the frame-rate reporting accuracy of the system, a key aspect to the robustness of quantitative measurements extracted from recorded image sequences. This is then followed by the demonstration of a novel method of analysis for examining the image formation process in this type of camera, which facilitates a sensor-by-sensor assessment of performance that was not previously realised. Consolidating with previous work from within the group, this new analysis method was used to clarify previous data, and in the process suggested the presence of a temporal anomaly embedded within recorded images. In addition, the analysis also revealed empirical evidence for the mechanisms leading to this anomaly. Following on, a holographic optical tweezer system was developed for the purpose of exercising precise spatial control over microbubbles within their experimental environment. By positioning microbubbles in specific arrangements, interesting behaviours that were not previously achieved experimentally in the context of shelled microbubbles, were observed. Furthermore, by careful positioning of microbubbles within the imaging plane, it was possible to exploit the temporal anomaly present in the camera to greatly improve the integrity of data recorded, and to also operate in an enhanced imaging mode. Group aspirations to accelerate the development of therapeutic microbubbles had previously generated some early work on the in-house generation of bespoke bubble populations using microfluidic lab-on-a-chip techniques. In order to facilitate further development in this area, a finite-element computational model was herein developed to aid next generation chip design. Finally, in a slightly different context, considering not only the mechanical effect a microbubble may effect in a therapeutic treatment, a single biological cell assay was developed in order to probe any mechanical effects that were induced by the excitation ultrasound itself. Capitalising on the precise force control possible with atomic force spectroscopy, the elastic moduli of cells pre- and post-ultrasound insonation (sans microbubbles) were recorded. These new developments have extended the group capability and expertise in the areas of high-speed imaging, experimental observations of microbubble dynamics and with microfluidic generation of microbubbles. Additionally, the insights garnered have both served to consolidate the group's previous and as yet unpublished data, opening the way for circulation with absolute confidence in the integrity of that data.
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Saxena, Shubham. "Nanolithography on thin films using heated atomic force microscope cantilevers." Thesis, Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-08302006-223629/.
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Liu, Zhen. "Reconstruction and Control of Tip Position and Dynamic Sensing of Interaction Force for Micro-Cantilever to Enable High Speed and High Resolution Dynamic Atomic Force Microscopy." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1483629656167247.
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Wang, Congzhou. "INTEGRATED NANOSCALE IMAGING AND SPATIAL RECOGNITION OF BIOMOLECULES ON SURFACES." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/4067.
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Biomolecules on cell surfaces play critical roles in diverse biological and physiological processes. However, conventional bulk scale techniques are unable to clarify the density and distribution of specific biomolecules in situ on single, living cell surfaces at the micro or nanoscale. In this work, a single cell analysis technique based on Atomic Force Microscopy (AFM) is developed to spatially identify biomolecules and characterize nanomechanical properties on single cell surfaces. The unique advantage of these AFM-based techniques lies in the ability to operate in situ (in a non-destructive fashion) and in real time, under physiological conditions or controlled micro-environments.
First, AFM-based force spectroscopy was developed to study the fundamental biophysics of the heparin/thrombin interaction at the molecular level. Based on force spectroscopy, a force recognition mapping strategy was developed and optimized to spatially detect single protein targets on non-biological surfaces. This platform was then translated to the study of complex living cell surfaces. Specific carbohydrate compositions and changes in their distribution, as well as elasticity change were obtained by monitoring Bacillus cells sporulation process.
The AFM-based force mapping technique was applied to different cellular systems to develop a cell surface biomolecule library. Nanoscale imaging combined with carbohydrate mapping was used to evaluate inactivation methods and growth temperatures effects on Yersinia pestis surface. A strategy to image cells in real time was coupled with hydrophobicity mapping technique to monitor the effect of antimicrobials (antimicrobial polymer and copper) on Escherichia coli and study their killing mechanisms. The single spore hydrophobicity mapping was used to localize the exosporium structure and potentially reconstruct culture media. The descriptions of cell surface DNA on single human epithelial cells potentially form a novel tool for forensic identification.
Overall, these nanoscale tools to detect and assess changes in cell behavior and function over time, either as a result of natural state changes or when perturbed, will further our understanding of fundamental biological processes and lead to novel, robust methods for the analysis of individual cells. Real time analysis of cells can be used for the development of lab-on-chip type assays for drug design and testing or to test the efficacy of antimicrobials.
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Moreno, Villavicencio Maiglid Andreina. "Development of 3D high-resolution imaging of complex devices by the correlation of ToF-SIMS and AFM." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSEI122.
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La miniaturisation continue et la complexité des dispositifs poussent les techniques existantes de nano-caractérisation à leurs limites. De ce fait, la combinaison de ces techniques apparait être une solution attrayante pour continuer à fournir une caractérisation précise et exacte. Dans le but de dépasser les verrous existants pour l’imagerie chimique 3D haute résolution à l’échelle nanométrique, nous avons concentré nos recherches sur la création d’un protocole combinant la spectrométrie de masse à ions secondaires de temps de vol (ToF-SIMS) avec la microscopie à force atomique (AFM). Ceci permet entre autre de corréler la composition et la visualisation en 3 dimensions avec des cartographies de topographie ou d’autres propriétés locales fournies par l’AFM. Trois principaux résultats sont obtenus grâce à cette méthodologie : la correction d’un ensemble de données ToF-SIMS pour une visualisation 3D sans artefacts, la cartographie du taux de pulvérisation locale permettant de mettre en évidence les effets liés à la rugosité et la présence d’interfaces verticales et la superposition des informations avancées ToF-SIMS et AFM. Quatre applications de la méthodologie combinée ToF-SIMS et AFM sont abordées dans cette thèse. La procédure de correction des données ToF-SIMS en 3D a été appliquée sur une structure hétérogène GaAs / SiO2. Les artefacts liés à la pulvérisation, notamment l’effet d’ombrage, ont été étudiés par le biais des cartographies de taux de pulvérisation sur des échantillons avec nano-motifs structurés et non structuré. Enfin, nous avons exploré la combinaison de l’analyse ToF-SIMS avec trois modes avancées de microscopie AFM : piézoélectrique (PFM), capacité (SCM) et conducteur (SSRM). Une première étude a notamment permis d’observer l’évolution et la modification chimique suite à l’application d’une contrainte électrique sur deux film mince piézoélectriques. Une deuxième étude s’est focalisée sur l’impact de l’implantation Ga lors de la préparation d’échantillons par FIB pour voir comment limiter l’effet de l’amorphisation sur la mesure électrique. Les aspects techniques de la méthodologie seront abordés pour chacune de ces applications et les perspectives de cette combinaison seront discutésThe continuous miniaturization and complexity of devices have pushed existing nano-characterization techniques to their limits. The correlation of techniques has then become an attractive solution to keep providing precise and accurate characterization. With the aim of overcoming the existing barriers for the 3D high-resolution imaging at the nanoscale, we have focused our research on creating a protocol to combine time-of-flight secondary ion mass spectrometry (ToF-SIMS) with atomic force microscopy (AFM). This combination permits the correlation of the composition in 3-dimensions with the maps of topography and other local properties provided by the AFM. Three main results are achieved through this methodology: a topography-corrected 3D ToF-SIMS data set, maps of local sputter rate where the effect of roughness and vertical interfaces are seen and overlays of the ToF-SIMS and AFM advanced information. The application fields of the ToF-SIMS and AFM combined methodology can be larger than expected. Indeed, four different applications are discussed in this thesis. The procedure to obtain the topography-corrected 3D data sets was applied on a GaAs / SiO2 patterned structure whose initial topography and composition with materials of different sputter rates create a distortion in the classical 3D chemical visualization. The protocol to generate sputter rate maps was used on samples with structured and non-structured nano-areas in order to study the possible ToF-SIMS sputtering artefacts, especially the geometric shadowing effect. Finally, we have explored the combination of ToF-SIMS analysis with three AFM advanced modes: piezoresponse force microcopy (PFM), scanning capacitance microscopy (SCM) and scanning spreading resistance microscopy (SSRM). Specifically, two main applications were studied: the chemical modification during electrical stress of a piezoelectic thin film and the recovery of initial electrical characteristics of a sample subjected to Ga implantation during FIB preparation. Technical aspects of the methodology will be discussed for each application and the perspectives of this combination will be given
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Zhao, Yue. "Self-Assembled Lipid Tubules: Structures, Mechanical Properties, and Applications." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2204.
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Self-assembled lipid tubules are particularly attractive for inorganic synthesis and drug delivery because they have hollow cylindrical shapes and relatively rigid mechanical properties. In this thesis work, we have synthesized lipid tubules of 1,2-bis(tricosa-10,12-dinoyl)-sn-glycero-3-phosphocholine (DC8,9PC) by self-assembly and polymerization in solutions. We demonstrate for the first time that both uniform and modulated molecular tilt orderings exist in the tubule walls, which have been predicted by current theories, and therefore provide valuable supporting evidences for self-assembly mechanisms of chiral molecules. Two novel methods are developed for studying the axial and radial deformations of DC8,9PC lipid tubules. Mechanical properties of DC8,9PC tubules are systematically studied in terms of persistence length, bending rigidity, strain energy, axial and radial elastic moduli, and critical force for collapse. Mechanisms of recovery and surface stiffening are discussed. Due to the high aspect ratio of lipid tubules, the hierarchical assembly of lipid tubules into ordered arrays and desired architectures is critical in developing their applications. Two efficient methods for fabricating ordered arrays of lipid tubules on solid substrates have been developed. Ordered arrays of hybrid silica-lipid tubes are synthesized by tubule array-templated sol-gel reactions. Ordered arrays of optical anisotropic fibers with tunable shapes and refractive indexes are fabricated. This thesis work provides a paradigm for molecularly engineered structures.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Materials Science & Engr PhD
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Zuttion, Francesca. "Effet inhibiteur des glycoclusters dans l'adhésion bactérienne des Pseudomonas aeruginosa caractérisé par microscopie à force atomique : de la molécule à la cellule." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEC031/document.
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La bactérie Pseudomonas aeruginosa (PA) est un pathogène responsable de 20%-30% des infections nosocomiales en milieu hospitalier. Pour les individus sains, elle ne présente pas de réel danger, mais pour les personnes atteintes par la mucoviscidose et les patients immunodéprimés, elle est la cause principale de mortalité et des infections pulmonaires. PA a développé des souches multi-résistantes aux antibiotiques et des nouvelles approches thérapeutiques plus efficaces sont donc nécessaires. Elle se fixe à la surface des cellules-hôtes par une interaction entre des protéines (lectines) présentes sur sa membrane et des sucres présents sur la membrane cellulaire. L’interaction lectine-sucre joue un rôle important dans l’adhésion de la bactérie puis dans la fabrication d’un biofilm pathogène.Une nouvelle approche thérapeutique consiste à créer des molécules synthétiques (glycomimes) de plus grande affinité que les sucres présents sur les cellules. Pour cela, plus de 150 glycomimes ont été synthétisés et examinés afin de trouver le meilleur candidat pour empêche le processus d'infection de bactéries. Certains d'entre eux ont été choisis et étudiés par la Microscopie à Force Atomique (AFM). Cette thèse est consacrée à l’étude des interactions lectine-glycomime et aussi cellule-bactérie par AFM. L’imagerie combinée avec la modélisation permet de comprendre le rôle du glycomime sur la géométrie des complexes créés et la spectroscopie permet de mesurer les forces d’interaction présentes lors de l’adhésion, au niveau moléculaire et cellulaire. Une réduction de l’adhésion bactérienne a été observée après l’introduction du glycomime, confirmant son rôle d’inhibiteur et la validité de toute la démarche. L’objectif ultime est l’identification des meilleurs glycomimes à introduire afin de développer de nouveaux médicamentsPseudomonas aeruginosa (PA) is a human opportunistic pathogen responsible for 20% -30% of nosocomial infections in French hospitals. For healthy people, it presents no real danger, but for people with cystic fibrosis disease and immune-compromised patients, it is the leading cause of mortality and lung infections. PA has developed antibiotic multi-resistant strains and new and more effective therapeutic approaches are needed. It binds to the surface of the host cells by an interaction between proteins (lectins) present on the membrane and sugars of the host-cell membrane. The lectin-sugar interaction plays an important role in adherence of the bacteria and in the manufacture of a pathogenic biofilm.A new therapeutic approach is to create synthetic molecules (glycoclusters) of greater affinity than the natural sugars present on the cells. To this aim, more than 150 glycoclusters have been synthetized and screened to find the best candidate to inhibit the bacteria infection process. Some of them have been selected and studied by Atomic Force Microscopy (AFM). In particular, this thesis is devoted to study the lectin-glycocluster and cell-bacteria interactions by AFM. The combination of AFM imaging with molecular dynamic simulations let understanding the role of the geometry of the glycoclusters on the complex formation, while AFM spectroscopy accesses the lectin-glycocluster interaction forces at the molecular and cellular levels. The reduction of bacterial adhesion has been observed upon the addition of the glycocluster. This confirms the anti-adhesive properties of the glycocluster and validates the procedure. The ultimate goal is the identification of the best glycoclusters in order to develop new drugs
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Curry, Nathan. "Development and application of correlative STED and AFM to investigate neuronal cells." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274579.
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Over the past three decades in cellular neuroscience there has been a shift towards the view of the 'tripartite synapse', where, astrocytes -- as well as the pre-synapse and post-synapse -- are involved in synaptic signalling. The migration of astrocytes to form branched networks in the brain is, therefore, of great interest in understanding brain development and neuronal function. Migration is a complex interplay between cytoskeletal reorganisation and cell mechanical stiffness. In order to improve understanding of this process, correlative measurements of cytoskeletal organisation and mechanical stiffness are required. To investigate astrocyte migration a technique combining atomic force microscopy (AFM) with stimulated emission depletion (STED) microscopy was developed. First a custom STED microscope was developed. To facilitate the design of this system the theoretical performance of a range of STED techniques (cw-STED, time-gated STED, pulsed STED and RESOLFT) were compared, identifying that pulsed STED theoretically has the highest photon efficiency. A pulsed STED microscope, which uses adaptive optics, was then designed, developed and characterised. The microscope was found to achieve resolutions below 50 nm. The STED microscope was combined with a commercial AFM to study live cells. Using the recently developed SiR-actin and SiR-tubulin dyes and AFM probes optimised for live cell mechanical property studies, images of the actin and tubulin cytoskeleton were correlated with AFM topography and mechanical stiffness measurements. It was found that, in astrocytes, actin contributes significantly both to astrocyte stiffness and topography. Investigations of migrating cells showed differences in actin organisation and mechanical stiffness between the basis and leading edge of migration. A further study was performed, investigating the effects of the gap-junction protein connexin30, which is expressed during the early stages of brain development, on migration. This protein was found to inhibit the actin reorganisation and mechanical stiffness changes observed in basal conditions. Overall the combination of mechanosensitive AFM measurements with advanced microscopy, such as super-resolution, on live cells is a promising approach which will enable a range of investigations, for instance when studying cell structural remodeling during brain development or tumorigenesis.
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Valencia, Carolina Elisa Guillen. "Sistema de análise de imagens SEBS por microscopia de força atômica." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-05062014-092420/.
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Neste trabalho, se pretende caracterizar a morfologia de filmes finos poliméricos por meio de técnicas de processamento de imagens, utilizando principalmente a geometria computacional e técnicas de classificação de padrões. Os objetivos principais foram quantificar as grandezas geométricas das estruturas observadas nos filmes finos e descrever padrões de superfície formados nestes filmes. Foram estudadas imagens obtidas por microscopia de força atômica (AFM) de amostras de filmes finos SEBS [poliestireno-poli(etileno-co-butileno)-poliestireno], depositados sobre um substrato de mica por técnicas de imersão. Os filmes finos SEBS são considerados de grande interesse devido à formação de estruturas auto-organizadas na escala nanométrica. A caracterização e a obtenção da morfometria dos filmes são de relevância neste trabalho, pois contribuem para o entendimento da dinâmica de formação destes padrões nas nanoestruturas estudadas. Foram analisadas diferentes morfologias, como forma de gotículas com anéis concêntricos e forma de tiras e pontos regularmente espaçados. Os resultados obtidos permitem caracterizar os padrões observados.In this work, we intend to characterize the morphology of polymer thin films by techniques of image processing, mainly using computational geometry and pattern classification. The main objectives were to quantify the geometrical structures observed in thin films and describe surface patterns formed in these films. Were studied images obtained by atomic force microscopy (AFM) of SEBS [polystyrene-poly(ethylene-co-butylene)-polystyrene] thin films samples, deposited on a mica substrate by dip-coating technique . SEBS thin film polymers have great interest due to the formation of self-organized structures on the nanometer scale. The characterization and obtaining measurements of the morphology of the thin films are of relevance in this work, because they contribute to the understanding of the formation dynamics of these patterns in nanostructures studied. We analyzed different morphologies, such as droplets form with concentric rings and stripe and regularly spaced points forms. The results allow to characterize the observed patterns.
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Pendery, Joel S. "Nanoscale Patterning and Imaging of Liquid Crystals and Colloids at Surfaces." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1396623443.
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Rodrigues, Carlos Alberto. "Aplicações de processamento e análise avançada de imagens para a caracterização de imagens de microscopia de força atômica." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-19102011-102450/.
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Esta tese aborda a aplicação de técnicas avançadas de processamento e análise de imagens em problemas originais envolvendo imagens de microscopia de força atômica. Para isso, foi desenvolvida uma série de algoritmos para a caracterização e o entendimento do processo de formação de novos materiais poliméricos com perspectivas de inúmeras aplicações tecnológicas. As análises envolveram a determinação da orientação da morfologia de substratos para alinhamento de cristais líquidos, contagem e estimativa dos raios de domínios em filmes automontados POMA/PVS, análise do aumento da fotoluminescência em filmes PPV e estudos da curvatura espontânea de macromoléculas de polímeros. Dentre os algoritmos principais podemos citar a determinação da inclinação dos autovalores da matriz de covariância das coordenadas dos pontos da forma, aplicação da técnica dos máximos regionais e diagramas de Voronoi, filtros passabanda 2D através da transformada de Fourier e extração da curvatura multiescala. A implementação destes algoritmos envolveu algoritmos básicos de análise de imagens tais como esqueletização, dilatações exatas e extração do contorno de formas. A principal contribuição deste trabalho foi a implementação do software denominado SPIA (Scanning Probe Image Analysis) que possui ferramentas para análise e processamento de imagens incluindo todas as que foram utilizadas no decorrer deste trabalho além de outras ferramentas. Este software foi desenvolvido em ambiente Delphi sob o paradigma da orientação a objetos para plataformas Windows NT/9X/2000/XP. Possui uma interface amigável e semelhante a outros softwares dedicados a processamento de imagens. Todas as técnicas aplicadas foram testadas extensivamente e os resultados que corroboram sua eficiência são mostrados ao longo da teseThis thesis address the application of advanced techniques of processing and analysisof images in original problems involving images of atomic force microscopy. For this, a series of algorithms for characterization and understanding of process of formation of new polymeric materials was developed and implemented, with perspectives of many technological applications. The analysis was applied to the determination of orientation of the morphology of substrates for alignment of liquid crystals, counting and estimative of radiuses of granules in layer-by-layer polymer films, analysis of enhancement of photoluminescence in PPV cast films, as well as the study of curvature spontaneous of macromolecules. The principal algorithms included are determination of inclination of eigenvectors of matrix of covariance of coordinates of points of shape,application of regional maxima technique and Voronoi diagrams, passband filters 2D through Fourier Transform and curvature multiscale. The implementation of these algorithms involved a series of image analysis algorithms such as squeletonization, exact dilations and extracting of contour of shapes. The principal contribution of this work was to develop a software called SPIA (Scanning Probe Image Analysis) that includes tools for analysis of processing of images including that were used in this work. This software was developed in Delphi under object orientation paradigm to Windows NT/9X/2000/XP. It has a friendly interface similar to other image processing softwares. All this techniques were tested extensively and the results that corroborate the robustness of the algorithms are included throughout the thesis
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Obeid, Sameh. "Analyse quantitative et qualitative sur puce de vésicules extracellulaires en milieux complexes au sein d'une plateforme nanobioanalytique." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCD009/document.
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Les vésicules extracellulaires (VEs) sont des nanovésicules circulantes (30 à 100nm de diamètre) libérées dans l'espace extracellulaire par la plupart des cellules humaines, suite à leur activation ou à leur apoptose. Les VEs se divisent en 3 grandes catégories ; les exosomes (Exo), les microparticules (MPs) et les corps apoptotiques (cAPO). Les VEs sont présentes à l'état physiologique dans les différents fluides biologiques du corps humain et jouent un rôle majeur dans différents processus physio-pathologiques. De nos jours, plusieurs techniques, certaines en routine, sont utilisées pour étudier les VEs. Cependant, aucune d'entre elles ne permet de déterminer à la fois leur concentration, leur taille et leurs caractéristiques biochimiques. Un consensus existe sur la nécessité de combiner des techniques pour disposer enfin d'une caractérisation fine et complète des VEs. Il est d'un intérêt majeur de développer des plateformes analytiques dédiées à ces VEs en vue d'améliorer la qualification des échantillons biologiques et de découvrir de nouveaux biomarqueurs de pathologies humaines ou de bio-indicateurs de suivi thérapeutique.Notre projet consiste à développer une plateforme NanoBioAnalytique (NBA) combinant trois techniques : l'imagerie par Résonance des Plasmons de Surface (SPRi), la Microscopie à Force Atomique (AFM) et la Spectrométrie de Masse (MS). L'enjeu est de développer une interface biopuce-instruments qui permettra d'effectuer des investigations multiphysiques et multiéchelles apportant, en une stratégie globale, les informations plus complètes sur les différentes populations de VEs.[...]Ces travaux ont montré la capacité de notre plateforme à détecter sélectivement, et simultanément, différentes sous-populations des VEs co-existantes dans un échantillon complexe tel que du plasma, en s'appuyant sur l'expression différentielle des marqueurs protéiques membranaires. Les taux de capture se sont avérés être directement corrélés à la concentration des vésicules dans l'échantillon injecté. L'analyse AFM a permis de déterminer la distribution en taille de différentes sous-populations de VEs et permettre une analyse différentielle de la distribution en taille sur la gamme 20 nm - 1000 nm. Enfin, des études protéomiques "sur-puce" ont été également engagées afin de caractériser la composition en protéines des VEs libérées sous différentes conditions. Cette analyse a permis d'établir des premiers profils protéomiques différentiels des VEs dans les échantillons étudiés.La plateforme NBA est une méthode efficace pour caractériser et quantifier les VEs, sans marquage et avec une grande sensibilité, sur une large gamme dynamique (environ 10(7) à 10(12) particules/mL) cohérente avec celle existante en fluide physiologique et sur une plage de taille couvrant 2 décades. Elle s'inscrit parmi les approches les plus prometteuses pour l'investigation des VEs en complément de la cytométrie en flux. La grande adaptabilité de cette méthode d'analyse des VEs ouvre de larges perspectives de déploiement dans les secteurs de la Santé, de l'Environnement et de l'Agro-alimentaireExtracellular vesicles (EVs) are small vesicles (30 to 1000 nm) released from different cell types, upon activation or apoptosis, and present in most body fluids (Blood, Urine….). Based on the current state of knowledge of their biogenesis and biochemical properties, EVs can be devided into three distinct populations: exosomes (EXO), microparticles (MPs) and apoptotic bodies (APOb). EVs have been found to play important biological roles and are also biomarkers of different pathologies. […] The first step consists of the injection of the samples containing EVs onto the biochip surface. This step is accomplished by SPR technique that allows label-free monitoring of EVs immunocapture onto the surface of a biochip presenting different specific bioreceptors. Following the capture of EVs, a nanometrological investigation of the biochip surface by AFM is engaged to characterize the physical properties of captured vesicles (size, morphology, etc..). Owning a nanometrical resolution, AFM can discriminate between individual EVs and vesicles or protein aggregates, leading to an accurate characterization of individual vesicles. The coupling of SPR technique with AFM was adapted to offer a representative global view of each array of bioreceptors and to measure the size of thousands of individual EVs. A proteomic investigation was also engaged to characterize the proteomic compositions of the different subpopulations of EVs. Such an investigation could contribute to the understanding of EVs biogenesis, biology and pathophysiology. To evaluate the potential of our platform to detect, quantify and characterize nanoparticles, two calibration particles, which cover the lower and upper size range of EVs, were chosen: (i) virus-like particles of 50 nm of diameter, also called CP50, and (ii) protein-functionnalized synthetic beads of 920 nm of diameter, called CP920. The capture tests in SPR showed a specific capture of these two calibration particles with their specific bioreceptors, immobilized onto the biochip surface, regardless the complexity of the media in which they were diluted. Also, a positive correlation was obtained between the capture level, measured by SPR, and the particle 9
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Neumann, Martin. "Time-resolved imaging of the micro-mechanical behavior of elastomeric polypropylene." Doctoral thesis, Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-182113.
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Ziel dieser Arbeit ist es, eine Verbindung zwischen der Mikrostruktur teilkristalliner Polymere und derer mechanischen Eigenschaften auf der Mikro- und Nanometerskala aufzubauen. Dazu wurden Methoden der Rasterkraftmikroskopie verwendet um sowohl orts- als auch zeitaufgelöst Kristallisations-, Deformations- und Diffusionsprozesse in der Mikrostruktur von elastomerem Polypropylen (ePP) abzubilden. Die mechanischen Eigenschaften wurden simultan mit Mikrozugversuchen bestimmt. So konnte beispielsweise ein Zusammenhang zwischen abnehmender Kristall-Kristall-Distanz und einem Ansteigen des Elastizitätsmoduls während der Kristallisation nachgewiesen werden. Weiterhin war es möglich die Veränderung der nano-mechanischen Eigenschaften während der Kristallisation einzelner kristalliner Lamellen in deren direkter Umgebung mit MUSIC-mode Rasterkraftmikroskopie zu untersuchen. Laterale Querexpansion (auxetisches Verhalten) konnte bei uniaxialen Zugversuchen für die Kreuzschraffur-Struktur elastomeren Polypropylens auf der Größenskala einiger Mikrometer nachgewiesen werden. Zusätzlich wurde eine Orientierungsabhängigkeit dieses Effekts beobachtet. Außerdem wurde die Diffusion einzelner Kristalle in der Mikrostruktur von ePP beobachtet. Die Heterogenität dieser Diffusion lässt auf eine kristallin-amorph Grenzschicht um alle Kristalle schließen.
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Bernaud, Julien. "Propriétés physiques de capsides virales étudiées à l'échelle du virus unique par microscopie à force atomique : exemples du rétrovirus VIH-1 et du parvovirus AAV." Thesis, Lyon, École normale supérieure, 2015. http://www.theses.fr/2015ENSL1028/document.
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Les virus sont des parasites biologiques de taille nanométrique. Détournant la machinerie cellulaire de la cellule infectée, ils mettent en place une stratégie de réplication permettant la production de nouveaux virus. Un virus est constitué d’une capside protéique protégeant le génome viral, long polymère d’ADN ou ARN, et possède dans certains cas une enveloppe lipidique. Des travaux récents suggèrent que les propriétés physiques des virus sont importantes pour comprendre certaines étapes du cycle viral. Dans le but de relier le comportement biologique des virus à leurs propriétés physiques, nous avons utilisé une approche combinant l’imagerie AFM et des mesures mécaniques à l’échelle nanométrique, en lien avec la modélisation physique des capsides virales. Nous avons développé des outils d’analyse automatisée des images et courbes de forces obtenues pour quantifier les propriétés physiques de capsides virales et l’effet du microenvironnement. Nous avons étudié deux virus très différents : le rétrovirus VIH-1, responsable du SIDA et le vecteur AAV, utilisé en thérapie génique. Ce travail a permis la caractérisation des propriétés morphologiques et mécaniques de pseudo-particules virales et de cores du VIH-1, à l’échelle du virus unique et sur des populations de centaines de virus. En nous intéressant à l’effet de la nature de l’ARN encapsidé dans les particules virales in cellulo, nous avons montré un rôle structurant pour l’ARN viral du VIH-1 et en particulier son signal d’encapsidation psi. Enfin, nous avons initié l’étude de l’effet de la retro-transcription (conversion du génome viral ARN en ADN) au sein du core VIH-1 sur la stabilité de celui-ci. L’étude du parvovirus AAV existant sous forme de plusieurs variants naturels (sérotypes) nous a permis de comparer les propriétés physiques des capsides à l’équilibre thermodynamique et hors d’équilibre. En faisant varier le microenvironnement (température et pH), nous avons sondé son influence sur la stabilité des capsides AAV. Nous avons pu montrer en particulier que la capside AAV8 est plus rigide que AAV9 alors que sa stabilité thermique est réduite, en relation avec des propriétés biologiques différentes pour ces deux sérotypes. En outre, la rigidité des capsides AAV8 diminue dans un environnement acide imitant l’endosome tardif, et ceci se traduit par une plus grande stabilité thermique. Enfin, nous avons quantifié l’effet de la longueur et de la nature du génome sur la stabilité des capsides AAVViruses are nanometer size biological parasite, which highjack the cellular machinery of the infected cells to replicate and thereby produce new viruses. A virus consists of a protein capsid, protecting the viral genome, a long polymer of DNA or RNA, and in some cases is surrounded by a lipid envelope. Recent work suggests that the physical properties of viruses are important in order to understand the viral cycle. In order to link the biological behavior of the virus to their physical properties, we used an approach combining AFM imaging and mechanical measurements at the nanometer scale, in connection with the physical modeling of viral capsids. We have developed automated image and force curves analysis tools to quantify the physical properties of viral capsids and the effect of the microenvironment. We have focused on two very different viruses: the HIV-1 retrovirus, responsible for AIDS and the AAV vector used in gene therapy. This work has led to the characterization of the morphological and mechanical properties of virus-like particles and cores of HIV-1 at the single virus level and on populations of hundreds of viruses. Focusing on the effect of the nature of the RNA encapsidated inside the viral particles in cellulo, we have highlighted the structural control of the viral RNA, and more precisely the psi packaging signal, on both HIV-1 VLPs and cores. Finally, we have initiated the study of the effect of reverse transcription (conversion of viral genomic RNA into DNA) within the cores HIV-1 on its stability. The study of parvovirus AAV existing form of several natural variants (serotypes) allowed us to compare the capsid physical properties at thermodynamic equilibrium and out of equilibrium. By varying the microenvironment (temperature and pH), we probed its influence on the stability of the AAV capsid. We have shown in particular that the AAV8 virus is stiffer than AAV9 while thermal stability is reduced, in relation to different biological properties for these two serotypes. In addition, the rigidity of AAV8 capsids decreases in an acidic environment mimicking the late endosome transport, and this results in a higher thermal stability. Finally, we quantified the effect of the length and nature of the confined genome on the thermal stability of AAV capsids
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Faes, Romain. "Nanotubes de carbonne ultracourts pour la bioimagerie." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0035/document.
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Les travaux de recherche effectués lors de cette thèse portent sur l’obtention de nanotubes de carbone ultracourts et leur biofonctionnalisation pour une utilisation comme biomarqueur proche infrarouge. Des dispersions de nanotubes de carbone en milieux aqueux ont été formulées à l’aide de différents tensioactifs. Un traitement chimique oxydant préalable et/ou l’application d’ultrasons aux nanotubes ont permis de réduire leur longueur de façon significative, la sélection des plus courts étant effectuée par ultracentrifugation en gradient de densité. Les différentes fractions sélectionnées à l’issu de ce processus ont été caractérisées par spectroscopie Raman et spectroscopie d’absorption ainsi que par microscopie à force atomique. Il est ainsi montré la sélection de nanotubes d’une longueur inférieure à 20 nm. Nous montrons également leur fonctionnalisation à l’aide d’anticorps monoclonaux et leur visualisation par imagerie photothermique hétérodyne. Des résultats prometteurs ont été obtenus avec la fixation spécifique de nanotubes de carbone ultracourts sur des cellules. Ces travaux ouvrent de nombreuses perspectives en bioimagerie et en particulier l’étude de la plasticité synaptique au sein de neurones vivantsThis thesis reports the achievement of ultrashort carbon nanotubes and their biofunctionalization for applications as near-infrared biomarker. Dispersions of carbon nanotubes in aqueous media have been formulated with various surfactants. Oxidizing chemical treatments combined with the application of ultrasounds allowed significant shortening of the carbon nanotubes. Sorting and selection of the shortest nanotubes was done by density gradient ultracentrifugation. The different fractions selected at the end of this process have been characterized by Raman spectroscopy, UV-vis absorption spectroscopy and atomic force microscopy. Selection of nanotubes of a length below 20 nm is demonstrated. We also show functionalization by antibodies and the visualization of ultrashort functionalized nanotubes by photothermal heterodyne imaging. Promising results were obtained with the specific binding of ultrashort carbon nanotubes to cells. This work open route towards bioimaging applications and in particular towards the study of the synapsis plasticity within alive neurons
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Carnally, Stewart Antoni Michael. "Carbon nanotube atomic force microscopy." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491631.
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This thesis concerns the manufacture of carbon nanotube atomic force microscope (NTAFM) probes and their employment in the high-resolution imaging of biological macromolecules. Attention was focused initially on synthesis of carbon nanotubes and the refinement of the growth processes to obtain nanotubes of controlled dimensions. These growth processes were subsequently used to grow nanotubes directly onto AFM tips, followed by attempts at controlling the dimensions of these directly-grown nanotubes. Individually fabricated NTAFM probes are also described, along with attempts to optimise the strength of the AFM probe-nanotube interaction through the use of various hydrophobic coatings. NTAFM probes produced by both techniques, but predominantly through individually assembled probes using hydrophobic coatings, were used to image a range of natural and synthetic nucleic acid molecules and investigate the influence of the use of a nanotube probe on the dimensions observed.
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Duan, Junbo. "Restauration et séparation de signaux polynômiaux par morceaux. Application à la microscopie de force atomique." Thesis, Nancy 1, 2010. http://www.theses.fr/2010NAN10082/document.
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Cette thèse s'inscrit dans le domaine des problèmes inverses en traitement du signal. Elle est consacrée à la conception d'algorithmes de restauration et de séparation de signaux parcimonieux et à leur application à l'approximation de courbes de forces en microscopie de force atomique (AFM), où la notion de parcimonie est liée au nombre de points de discontinuité dans le signal (sauts, changements de pente, changements de courbure). Du point de vue méthodologique, des algorithmes sous-optimaux sont proposés pour le problème de l'approximation parcimonieuse basée sur la pseudo-norme l0 : l'algorithme Single Best Replacement (SBR) est un algorithme itératif de type « ajout-retrait » inspiré d'algorithmes existants pour la restauration de signaux Bernoulli-Gaussiens. L'algorithme Continuation Single Best Replacement (CSBR) est un algorithme permettant de fournir des approximations à des degrés de parcimonie variables. Nous proposons aussi un algorithme de séparation de sources parcimonieuses à partir de mélanges avec retards, basé sur l'application préalable de l'algorithme CSBR sur chacun des mélanges, puis sur une procédure d'appariement des pics présents dans les différents mélanges. La microscopie de force atomique est une technologie récente permettant de mesurer des forces d'interaction entre nano-objets. L'analyse de courbes de forces repose sur des modèles paramétriques par morceaux. Nous proposons un algorithme permettant de détecter les régions d'intérêt (les morceaux) où chaque modèle s'applique puis d'estimer par moindres carrés les paramètres physiques (élasticité, force d'adhésion, topographie, etc.) dans chaque région. Nous proposons finalement une autre approche qui modélise une courbe de force comme un mélange de signaux sources parcimonieux retardées. La recherche des signaux sources dans une image force-volume s'effectue à partir d'un grand nombre de mélanges car il y autant de mélanges que de pixels dans l'imageThis thesis handles several inverse problems occurring in sparse signal processing. The main contributions include the conception of algorithms dedicated to the restoration and the separation of sparse signals, and their application to force curve approximation in Atomic Force Microscopy (AFM), where the notion of sparsity is related to the number of discontinuity points in the signal (jumps, change of slope, change of curvature).In the signal processing viewpoint, we propose sub-optimal algorithms dedicated to the sparse signal approximation problem based on the l0 pseudo-norm : the Single Best Replacement algorithm (SBR) is an iterative "forward-backward" algorithm inspired from existing Bernoulli-Gaussian signal restoration algorithms. The Continuation Single Best Replacement algorithm (CSBR) is an extension providing approximations at various sparsity levels. We also address the problem of sparse source separation from delayed mixtures. The proposed algorithm is based on the prior application of CSBR on every mixture followed by a matching procedure which attributes a label for each peak occurring in each mixture.Atomic Force Microscopy (AFM) is a recent technology enabling to measure interaction forces between nano-objects. The force-curve analysis relies on piecewise parametric models. We address the detection of the regions of interest (the pieces) where each model holds and the subsequent estimation of physical parameters (elasticity, adhesion forces, topography, etc.) in each region by least-squares optimization. We finally propose an alternative approach in which a force curve is modeled as a mixture of delayed sparse sources. The research of the source signals and the delays from a force-volume image is done based on a large number of mixtures since there are as many mixtures as the number of image pixels
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Konopinski, D. I. "Forensic applications of atomic force microscopy." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1402411/.
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The first project undertaken was to develop a currently non-existent forensic technique -- data recovery from damaged SIM cards. SIM cards hold data valuable to a forensic investigator within non-volatile EEPROM/flash memory arrays. This data has been proven to be able to withstand temperatures up to 500°C, surviving such scenarios as house fires or criminal evidence disposal. A successful forensically-sound sample extraction, mounting and backside processing methodology was developed to expose the underside of a microcontroller circuit's floating gate transistor tunnel oxide, allowing probing via AFM-based electrical scanning probe techniques. Scanning Kelvin probe microscopy has thus far proved capable of detecting the presence of stored charge within the floating gates beneath the thin tunnel oxide layer, to the point of generating statistical distributions reflecting the threshold voltage states of the transistors. The second project covered the novel forensic application of AFM as a complimentary technique to SEM examination of quartz grain surface textures. The analysis and interpretation of soil/sediment samples can provide indications of their provenance, and enable exclusionary comparisons to be made between samples pertinent to a forensic investigation. Multiple grains from four distinct sample sets were examined with the AFM, and various statistical figures of merit were derived. Canonical discriminant analysis was used to assess the discriminatory abilities of these statistical variables to better characterise the use of AFM results for grain classification. The final functions correctly classified 65.3% of original grouped cases, with the first 3 discriminant functions used in the analysis (Wilks' Lambda=0.336, p=0.000<0.01). This degree of discrimination shows a great deal of promise for the AFM as a quantitative corroborative technique to traditional SEM grain surface examination.
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Acosta, Mejia Juan Camilo. "Atomic force microscopy based micro/nanomanipulation." Paris 6, 2011. http://www.theses.fr/2011PA066691.
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A l’échelle nanoscopique, un problème scientifique fondamental réside dans la difficulté de manipuler de façon interactive et répétable un nano-objet. Cette difficulté est un frein majeur pour des applications comme les nanotransistors, les nanosystèmes ou les futurs NEMS (Nano Electro Mechanical System). Ces dispositifs émergents sont ainsi ralentis dans leur cadre expérimental. Cette thèse s’inscrit dans la continuité des recherches développées au sein de l’équipe de microrobotique de l'ISIR. Elle se focalise sur l'exploitation de capteurs d'effort pour la manipulation contrôlée à plusieurs doigts actifs. Le microscope à force atomique est utilisé pour ses propriétés de capteur d'effort. Dans un premier temps, un préhenseur composé de deux doigts indépendants avec mesures des forces d'interaction a été conçue. Avec ce système original, des micromanipulations en trois dimensions de microsphères ont été réalisée avec succès dans l'air, en mesurant de façon continue les efforts d'interaction. Ce système a aussi été utilisé pour saisir et déposer des nanofils afin de former des nanocroix, ces dernières étant des nanostructures émergentes pour la fabrication, par jonctions, de nanotransistors. Par la suite, des oscillateurs en quartz ont été utilisés pour la caractérisation de nanostructures, avec retour d'effort dynamique. Le comportement non-linéaire en raideur de nanohélices lors de l'élongation a été caractérisé pour la première fois sur la totalité de la plage. Enfin, des sondes en quartz de haute fréquence ont été exploitées pour augmenter la vitesse d'acquisition d'images de l'AFM. De cette manière, la tâche de manipulation et d'imagerie en parallèle sous AFM a été optimisée et de nombreuses applications sont maintenant envisagées