Littérature scientifique sur le sujet « Colloidal Probes »
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Articles de revues sur le sujet "Colloidal Probes"
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Singh, Gurvinder, Kristen E. Bremmell, Hans J. Griesser et Peter Kingshott. « Colloid-probe AFM studies of the interaction forces of proteins adsorbed on colloidal crystals ». Soft Matter 11, no 16 (2015) : 3188–97. http://dx.doi.org/10.1039/c4sm02669a.
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Witt, Hannes, Filip Savić, Sarah Verbeek, Jörn Dietz, Gesa Tarantola, Marieelen Oelkers, Burkhard Geil et Andreas Janshoff. « Membrane fusion studied by colloidal probes ». European Biophysics Journal 50, no 2 (18 février 2021) : 223–37. http://dx.doi.org/10.1007/s00249-020-01490-5.
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AbstractMembrane-coated colloidal probes combine the benefits of solid-supported membranes with a more complex three-dimensional geometry. This combination makes them a powerful model system that enables the visualization of dynamic biological processes with high throughput and minimal reliance on fluorescent labels. Here, we want to review recent applications of colloidal probes for the study of membrane fusion. After discussing the advantages and disadvantages of some classical vesicle-based fusion assays, we introduce an assay using optical detection of fusion between membrane-coated glass microspheres in a quasi two-dimensional assembly. Then, we discuss free energy considerations of membrane fusion between supported bilayers, and show how colloidal probes can be combined with atomic force microscopy or optical tweezers to access the fusion process with even greater detail.
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Duncan, Gregg A., D. Howard Fairbrother et Michael A. Bevan. « Diffusing colloidal probes of cell surfaces ». Soft Matter 12, no 21 (2016) : 4731–38. http://dx.doi.org/10.1039/c5sm02637g.
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Beesley, J. E. « Colloidal gold probes for parasite antigens ». Parasitology Today 1, no 5 (novembre 1985) : 145–46. http://dx.doi.org/10.1016/0169-4758(85)90061-4.
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Duncan, Gregg A., et Michael A. Bevan. « Diffusing Colloidal Probes of Cell Surfaces ». Biophysical Journal 108, no 2 (janvier 2015) : 485a. http://dx.doi.org/10.1016/j.bpj.2014.11.2654.
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Dolata, Benjamin E., et Roseanna N. Zia. « Non-equilibrium pair interactions in colloidal dispersions ». Journal of Fluid Mechanics 836 (12 décembre 2017) : 694–739. http://dx.doi.org/10.1017/jfm.2017.789.
Texte intégralRésumé :
We study non-equilibrium pair interactions between microscopic particles moving through a model shear-thinning fluid. Prior efforts to model pair interactions in non-Newtonian fluids have largely focused on constitutive models derived from polymer-chain kinetic theories focusing on conformational degrees of freedom, but neglecting the details of microstructural evolution beyond a single polymer length scale. To elucidate the role of strong structural distortion in mediating pair interactions in Brownian suspensions, we formulate and solve a Smoluchowski equation describing the detailed evolution of the particle configuration between and around a pair of microscopic probes driven at fixed velocity by an external force through a colloidal dispersion. To facilitate analysis, we choose a model system of Brownian hard spheres that do not interact hydrodynamically; while simple, this ‘freely draining’ model permits insight into connections between microstructure and rheology. The flow induces a non-equilibrium particle density gradient that gives rise to both viscous drag and an interactive force between the probes. The drag force acts to slow the centre-of-mass velocity of the pair, while the interactive force arising from osmotic pressure gradients can lead to attraction or repulsion, as well as deterministic reorientation of the probes relative to the external force. The degree to which the microstructure is distorted, and the shape of that distortion, depend on the arrangement of the probes relative to one another and their orientation to the driving force. It also depends on the magnitude of probe velocity relative to the Brownian velocity of the suspension. When only thermal fluctuations set probe velocity, the equilibrium depletion attraction is recovered. For weak forcing, long-ranged interactions mediated via the bath-particle flux give rise to entropic forces on the probes. The linear response is a viscous drag that slows forward motion; only the weakly nonlinear response can produce relative motion–attraction, repulsion or reorientation of the probes. We derive entropic coupling tensors, similar in ethos to pair hydrodynamic tensors, to describe this behaviour. The structural symmetry that permits this analogy is lost when forcing becomes strong, revealing instabilities in system behaviour. Far from equilibrium, the interactive force depends explicitly on the initial probe separation, orientation and strength of forcing; widely spaced probes interact through the distorted microstructure, whereas the behaviour of closely spaced probes is largely set by excluded-volume effects. In this regime, a pair of closely spaced probes sedimenting side-by-side tend to attract and reorient to permit alignment of their line-of-centres with the flow, while widely spaced probes fall without reorienting. Our results show qualitative agreement with experimental observations and provide a potential connection to the observed column instability in shear-thinning fluids.
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Webster, Paul. « Preparation of Protein a Gold ». Microscopy Today 5, no 5 (juin 1997) : 12–13. http://dx.doi.org/10.1017/s1551929500061563.
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Colloidal gold has been used for centuries in the preparation of stained glass for windows and fine glassware. In recent years, colloidal gold particles have become a useful tool in microscopy for staining tissues and sections. Colloidal gold particles are especially useful for biological electron microscopy, Some of the reasons why are listed below.*Homogeneous preparations of particles varying in size from 3μm to 20μm can be easily prepared.*Colloidal gold suspensions are inexpensive to prepare. Most proteins can be easily coupled to colloidal gold particles.*Most proteins can be easily coupled to colloidal gold particles.*Proteins coupled to gold particles do not appear to lose their biological activity.*The colloidal gold particles can be easily seen in the electron microscope.*Colloidal gold does not naturally occur in biological material. Therefore, if you see it, it is because you put it there.*Colloidal gold probes can be used for light microscopy, The larger gold particles can be directly observed by the light microscope. Small particles are detected by silver enhancement or epipolarized illumination.*The same probes can be used for both LM and TEM imrnunocytochemistry.
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Eichmann, Shannon L., Gulsum Meric, Julia C. Swavola et Michael A. Bevan. « Diffusing Colloidal Probes of Protein–Carbohydrate Interactions ». Langmuir 29, no 7 (4 février 2013) : 2299–310. http://dx.doi.org/10.1021/la304355t.
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Daboss, Sven, Peter Knittel, Christoph E. Nebel et Christine Kranz. « Multifunctional Boron‐Doped Diamond Colloidal AFM Probes ». Small 15, no 48 (2 juillet 2019) : 1902099. http://dx.doi.org/10.1002/smll.201902099.
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Cao, Cuong, et Sang Jun Sim. « Preparation of Highly Stable Oligo(ethylene glycol) Derivatives-Functionalized Gold Nanoparticles and Their Application in LSPR-Based Detection of PSA/ACT Complex ». Journal of Nanoscience and Nanotechnology 7, no 11 (1 novembre 2007) : 3754–57. http://dx.doi.org/10.1166/jnn.2007.009.
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A sandwich immunoassay for PSA/ACT complex detection based on gold nanoparticle aggregation using two probes was developed. The functionalized colloidal gold nanoparticles (AuNPs) showed highly stable not only in the presence of high ionic strength but also in a wide pH range. The functionalized AuNPs were tagged with PSA/ACT complex monoclonal antibody and goat PSA polyclonal antibody and served as the probes to induce aggregation of the colloidal particles. As a result, PSA/ACT complex was detected at concentrations as low as 1 ng/ml. This is the first time that a new aggregation sandwich-immunoassay technique using two gold probes has been used, and the results are generally applicable to other LSPR-based immunoassays.
Thèses sur le sujet "Colloidal Probes"
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Suárez, García Salvio. « Colloidal coordination polymer nanostructures : novel thermochromic and bioimaging probes ». Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/669764.
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Los polímeros de coordinación y su diseño racional permiten la formación de materiales nanoestructurados con una amplia variedad de propiedades. Las múltiples combinaciones entre iones metálicos y ligandos orgánicos como precursores de materiales autoensamblados, han fascinado a los científicos durante décadas. La aplicación de la química de coordinación a nanoescala se considera uno de los enfoques más versátiles para el desarrollo de nuevos materiales nanoestructurados debido a las infinitas posibilidades para alcanzar propiedades sin precedentes. Además, el desarrollo de sistemas metal-orgánicos ha despertado en una gran cantidad de ejemplos para su uso en una amplia gama de aplicaciones.
En esta Tesis hemos estado particularmente interesados en el ajuste controlado de las propiedades de los materiales nanoestructurados basados en polímeros de coordinación que se obtuvieron a través de diferentes rutas sintéticas. El método de síntesis, la selección adecuada de precursores y el estudio de las propiedades finales han centrado el trabajo realizado. Además, la formación de suspensiones coloidales estables en agua se estableció como un requisito principal para su potencial aplicación. Para eso, fue necesaria una sinergia multidisciplinaria con el objetivo de buscar la aplicación final de los nuevos materiales nanoestructurados desarrollados. El logro de este objetivo fue posible gracias a un diseño adecuado de la estrategia seguida junto con la caracterización completa de las nanoestructuras preparadas.
En una primera parte de esta Tesis, la nanoestructuración de sistemas conmutables basados en Fe(II) con comportamiento de entrecruzamiento de espín (SCO por sus siglas en inglés) se logró siguiendo dos estrategias diferentes. Por un lado, se aplicó una metodología descendente (top-down) basada en la exfoliación en fase líquida para el aislamiento de láminas 2D de cristales multilaminares. Por otro lado, a través de un enfoque ascendente (bottom-up), la síntesis de nuevas nanopartículas fue posible modulando la difusión de la reacción utilizando metodologías basadas en microfluidica. En ambos casos, los materiales nanoestructurados se integraron en matrices poliméricas para evaluar su aplicación potencial como películas termocrómicas para su prueba de concepto. En la segunda parte de la Tesis, se estableció una nueva familia de polímeros de coordinación a nanoescala (NCP por sus siglas en inglés) basados en Fe(III), Gd(III), Mn(II), In(III) y Cu(II) a través de su síntesis racional usando una reacción en un sola etapa. Las nanopartículas obtenidas se validaron mediante pruebas preclínicas in vivo que muestran un rendimiento interesante como posibles agentes teranósticos para la obtención de imágenes (resonancia magnética, tomografía por emisión de positrones y tomografía computarizada por emisión de fotón único) y pretratamiento potencial de glioblastoma y enfermedades pulmonares.Coordination polymers and its rational design let the formation of nanostructured materials with a broad variety of properties. The multiple combinations between metal ions and organic ligands as precursors of self-assembled materials have fascinated scientists for decades. The application of coordination chemistry at the nanoscale is considered one of the most versatile approaches for the development of new nanostructured materials due to the infinite possibilities for reaching unprecedented properties. Furthermore, the development of metal-organic systems has aroused in a plethora of examples for their use in a wide range of applications. In this Thesis we have been particularly interested in the fine tune of the properties of nanostructured materials based on coordination polymers whose were obtained through different synthetic routes. The method of synthesis, the properly selection of precursors and the study of the final properties has centred the work carried out. Additionally, the formation of water-stable colloidal suspensions was stablished as a main requirement for their potential application. For that, a multidisciplinary synergy was necessary with the aim to pursue the final application of the novel nanostructured materials developed. Achieving this objective was possible thanks to a properly design of the strategy followed together with complete characterization of the nanostructures prepared. In a first part of this Thesis, the nanostructuration of Fe(II)-based switchable systems with spin crossover behaviour was achieved by following two different strategies. On the one hand, a top-down methodology based on liquid-phase exfoliation was applied for the isolation of 2D flakes from the bulk crystal. On the other hand, through a bottom-up approach, the synthesis of novel nanoparticles was possible by modulating the reaction diffusion using microfluidic based methodologies. In both cases, the nanostructured materials were integrated in polymeric matrices to evaluate their potential application as proof-of-concept thermochromic films. In the second part of the Thesis, a novel family of nanoscale coordination polymers (NCPs) based on Fe(III), Gd(III), Mn(II), In(III) and Cu(II) was stablished through its rational synthesis by using one-pot reaction. The nanoparticles obtained were validated by pre-clinical in vivo tests showing interesting performance as potential theranostic agents for imaging (Magnetic resonance imaging, positron emission tomography and single-photon emission computed tomography) and potential pre-treatment of glioblastoma and lung diseases.
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Baker, Bryan Alexander. « Employing double-stranded DNA probes on colloidal substrates for competitive hybridization events ». Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33922.
Texte intégralRésumé :
The study of the DNA has found application beyond our understanding of its cellular function and into a variety of materials assembly and nucleic acid detection systems. The current research investigates double-stranded DNA probes in both a colloidal particle assembly and fluorescent assay format utilizing competitive hybridization events. In both contexts, the affinity of the dsProbes is tuned by the sequence design parameters of duplex length and complementarity. These systems were incubated with nucleic acid targets of interest and, based on the mechanism of competitive hybridization, were responsive to the presence of a high affinity competitive target. In the case of the particle assemblies, incubation with the competitive target resulted in observable disassembly of particle structures. In the case of fluorescently labeled dsProbes, incubation with competitive targets resulted in a quantifiable loss of fluorescence as determined by flow cytometry. Utilizing the fluorescently labeled dsProbe system, the kinetics of competitive hybridization was characterized for nucleic acid targets of varying specificity and strand context. The results indicate promise for the development of the competitive hybridization approach in nucleic acid detection systems providing advantages over current single-stranded probe designs. By utilizing a fluorescently labeled dsProbe approach, it is unnecessary to chemically modify the target of interest to impart a signaling mechanism. Additionally, as the process of competitive hybridization of dsProbes with targets of interest is an affinity driven process, discrimination of targets based on specificity is decoupled from standard measures such as elevated temperature protocols, an important step in translating nucleic acid technologies from the controlled laboratory environment to field applications.
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Huang, Hao Ph D. Massachusetts Institute of Technology. « Colloidal semiconductor nanocrystals as nanoscale emissive probes in light emitting diodes and cell biology ». Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/43760.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2008.Vita.
Includes bibliographical references.
This thesis employs colloidal semiconductor nanocrystals (NCs) as nanoscale emissive probes to investigate the physics of light emitting diodes (LEDs), as well as to unveil properties of cells that conventional imaging techniques cannot reveal. On the LED side, in particular, Chapter 2 utilizes individual NCs to alter layered organic LED structures at nanometer scale, resulting in spectrally resolved electroluminescence from single colloidal CdSe/ZnS (core/shell) NCs at room temperature. Chapter 3 takes NCs as emissive probes in layered organic LEDs, and shows that the photoluminescence of single NCs is bias dependent which helps elucidate the interactions between NCs and organic semiconductors, knowledge useful for designing efficient NC organic optoelectronics. Instead of using a planar LED geometry, Chapter 4 presents a technique for making nanoscale gap LEDs which allow the spectrally coincidental photoluminescence and electroluminescence from NCs. The work investigates the interactions between NCs and different metal gaps, and suggests electromigrating leads made of different metals as a promising route to fabricating nanoscale gaps with workfunction offsets for optoelectronic devices. On the cell biology side, we develop a three-dimensional sub-diffraction limited single fluorophore imaging method for proteins labeled with NCs. Chapter 5 applies the method to measure the endothelial glycocalyx thickness in vitro for the first time, by labeling different proteins with NCs of different emission wavelengths. Taking a step further, Chapter 6 utilizes the NC based imaging method to investigate the flow induced dynamics of endothelial glycocalyx, and measures the shear modulus of glycocalyx.
by Hao Huang.
Ph.D.
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Pussak, Daniel [Verfasser]. « Synthesis and Functionalization of Soft Colloidal Probes based on Poly(ethylene glycol) as Carbohydrate Biosensors / Daniel Pussak ». Berlin : Freie Universität Berlin, 2014. http://d-nb.info/1058360906/34.
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Wu, Hung-Jen. « Direct measurements of ensemble particle and surface interactions on homogeneous and patterned substrates ». Texas A&M University, 2005. http://hdl.handle.net/1969.1/3747.
Texte intégralRésumé :
In this dissertation, we describe a novel method that we call Diffusing Colloidal
Probe Microscopy (DCPM), which integrates Total Internal Reflection Microscopy
(TIRM) and Video Microscopy (VM) methods to monitor three dimensional trajectories
in colloidal ensembles levitated above macroscopic surfaces. TIRM and VM are well
established optical microscopy techniques for measuring normal and lateral colloidal
excursions near macroscopic planar surfaces. The interactions between particle-particle
and particle-substrate in colloidal interfacial systems are interpreted by statistical
analyses from distributions of colloidal particles; dynamic properties of colloidal
assembly are also determined from particle trajectories.
Our studies show that DCPM is able to detect many particle-surface interactions
simultaneously and provides an ensemble average measurement of particle-surface
interactions on a homogeneous surface to allow direct comparison of distributed and
average properties. A benefit of ensemble averaging of many particles is the diminished
need for time averaging, which can produce orders of magnitude faster measurement
times at higher interfacial particle concentrations. The statistical analyses (Ornstein-
Zernike and three dimensional Monte Carlo analyses) are used to obtain particle-particle
interactions from lateral distribution functions and to understand the role of nonuniformities
in interfacial colloidal systems. An inconsistent finding is the observation of
an anomalous long range particle-particle attraction and recovery of the expected DLVO
particle-wall interactions for all concentrations examined. The possible influence of
charge heterogeneity and particle size polydispersity on measured distribution functions
is discussed in regard to inconsistent particle-wall and particle-particle potentials. In the final part of this research, the ability of DCPM is demonstrated to map potential energy
landscapes on patterned surfaces by monitoring interactions between diffusing colloidal
probes with Au pattern features. Absolute separation is obtained from theoretical fits to
measured potential energy profiles and direct measurement by sticking silica colloids to
Au surfaces via electrophoretic deposition. Initial results indicate that, as colloidal probe
and pattern feature dimensions become comparable, measured potential energy profiles
suffer some distortion due to the increased probability of probes interacting with
surfaces at the edges of adjacent pattern features. Measurements of lateral diffusion via
analysis of mean square displacements also indicated lateral diffusion coefficients in
excellent agreement with rigorous theoretical predictions.
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CHIGHIZOLA, MATTEO. « INVESTIGATION OF CELL-MICROENVIRONMENT INTERACTIONS BY ATOMIC FORCE MICROSCOPY TECHNIQUES ». Doctoral thesis, Università degli Studi di Milano, 2021. http://hdl.handle.net/2434/819943.
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The role of forces is fundamental in a wide variety of biological processes, such as cell adhesion, migration, proliferation and differentiation. The ability of cells to perceive the nanotopographical features of the surrounding microenvironment (i.e. the extracellular matrix, ECM), called mechanotransduction, is mediated by specific trans-membrane proteins, called integrins, clustered together in Integrin Adhesion Complexes (IAC). Unraveling which mechanical and nanoscale morphological properties of the ECM determine the IAC composition and tune specific cellular response, is particularly challenging.
Works have shown that biocompatible nanostructured thin films, grown by assembling zirconia nanoparticles (ns-ZrO2) on a substrate by Supersonic Cluster Beam Deposition technique, possess a morphological disorder on nanometer scale with structural features that mimic topographical properties of the ECM. Experiments performed with the neuron-like cell line PC12 demonstrated a link between the nanotopography of the ns-ZrO2 films and mechanotransductive events, which eventually foster neuronal differentiation.
During my three years of PhD, I have developed novel approach based on Atomic Force Microscopy (AFM) to quantify cell sensing of nanotopographical features of the microenvironment, represented by ns-ZrO2 films reproducing the nanostructured surface of the ECM. Using custom ns-ZrO2–coated colloidal probes, we have carried out a quantitative analysis of adhesion strength and distribution of IACs by AFM-based adhesive force spectroscopy.
We deposited ns-ZrO2 on custom AFM colloidal probes5. Bringing these nanostructured colloidal probes into contact with the body of living PC12 cells, it was possible to measure the strength, number and distribution of the IAC bonds by AFM force spectroscopy6, for different morphological properties of the interface. Furthermore, I used these functionalized probes to characterize the role of the surface pericellular layer, known as the Glycocalyx, in relation to the cell capability to react to external stimuli.
Eventually, along with my personal research project, I had the opportunity to participate to two external collaboration with the Istituto Nazionale dei Tumori and with Istitute of Nuclear Physiscs from the Polish academy of Science. These collaborations aimed to exploit the knowledge in the mechanobiolgy field to study the mechanical implications of cells and tissues in cancer development and survival.
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Muthukumar, Shankarapandian. « Spectral multiplexing using quantum dot tagged microspheres with diffusing colloidal probe microscopy ». [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1245.
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ARESTI, MAURO. « Ultrafast Optical Spectroscopy Techniques applied to colloidal nanocrystals ». Doctoral thesis, Università degli Studi di Cagliari, 2014. http://hdl.handle.net/11584/266450.
Texte intégralRésumé :
In this thesis I will describe my experimental work based on ultrafast optical spectroscopy techniques applied to colloidal nanocrystals.
Colloidal semiconductor nanocrystals in recent years have attracted a lot of attention in particular in optoelectronic applications, because they present
unique optical, electronic and charge carrier transport properties that can be easily modified via colloidal chemical synthesis.
In the first chapter of this thesis, I will introduce the basic concepts of nanocrystals and their optical properties, I will consider some simple models
to explain the physical properties of semiconductor nanocrystals. I will briefly describe the colloidal chemical synthesis of these nanocrystals and how we
can change the optical properties by simply acting on the colloidal chemical synthesis.
In the second chapter I will describe the basic concepts of ultra fast optical spectroscopy techniques used in my experimental work. I will describe the basic principles and the experimental set-up of the two main techniques that I
used: time-resolved photoluminescence spectroscopy (TR-PL) and transient absorption spectroscopy or also called Pump Probe. These two techniques allow to investigate in a very precise way the main optical properties and dynamics of charge carriers in nanocrystals.
In the third chapter I will describe my experimental work based on timeresolved photoluminescence spectroscopy applied to CdSe=CdS core=shell nanocrystals. These nanocrystals are a reference nanocrystals and their optical
properties are extensively investigated, however, some aspects are not fully understood, for example, the instability or blinking of the light emission
under constant illumination in these nanocrystals is still an unsolved problem that limits the real applications. The particular spectroscopic technique that I have used variable pulse rate photoluminescence spectroscopy revealed
the causes of this issue, and will give us a solution to resolve it.
In the fourth chapter I will discuss novel nanostructures of CdSe=CdS multi branched shape, in this case octapod shaped nanocrystals consist of eight arms made of CdS grown on a CdSe core, these present a large crosssection for light absorption and efficient charge separation ideally suited for applications of photocatalysis. The optical spectroscopy technique used to investigate the properties of these nanocrystals are the transient absorption
spectroscopy.
In the fifth chapter I will discuss experimental work on Bi2S3 semiconductor nanocrystals and I will describe related optical techniques used to study the optical and electronic properties. This nanocrystal has excellent
properties of optical absorption of solar radiation and can be used for the realization of solar cells. Another important property of Bi2S3 is its nontoxicity
that will allow in the future to achieve efficient solar cells and easy disposal and simultaneously not damaging to the environment.
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Roy, Thomas Robert. « Plasma Potential Measurements in a Colloid Thruster Plume ». Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-042705-114729/.
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Bleier, Blake J. « Droplet-Based Approaches to Probe Complex Behavior in Colloidal Fluids with High Composition Resolution ». Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1173.
Texte intégralRésumé :
In this work, microfluidic and millifluidic droplets are utilized to study and control complex fluid behavior with high composition resolution. Different techniques are used on two length scales to create unique approaches towards the same goal of merging droplet-based experiments with classical colloidal characterization experiments. First, a microfluidic dehydrating droplet device is characterized and a procedure established by concentrating a phase separating organic-inorganic system on chip and using geometric calculations to determine composition. The device is then expanded to a more complex, particle-polymer system to investigate suspension stability and interparticle behavior. A model system containing silica particles and PEO polymer is found to transition from a bridging flocculation mechanism to polymer-coated particle jamming based on the mass ratio of polymer to particle. Lastly, a phase separating particle-polymer system consisting of polystyrene particles and hydroxyethyl cellulose is concentrated on-chip. Interparticle interactions are controlled by varying particle size, polymer size, and polymer type and the effects on phase behavior are examined. Droplet experiments are scaled-up to millifluidic droplets and concentration gradients are used to produce high composition resolution in place of time, used in the dehydrating microfluidic experiments. A novel, millifluidic containment device is created to study aggregation and sedimentation in droplets containing carbon black and OLOA surfactant suspended in dodecane. A slow increase in stabilization behavior is observed as opposed to the previously observed sharp “on-off” effect. The droplet production technique is then improved to achieve more complex composition paths and the device is expanded for a small angle neutron scattering (SANS) application. SANS is performed on flowing droplets with varying concentration to map interparticle interactions and phase behavior of complex particulate systems. Feasibility of device is demonstrated and preliminary model systems of silica particles and polymer, salt, and surfactant are analyzed and characterized.
Livres sur le sujet "Colloidal Probes"
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The Langevin and generalised Langevin approach to the dynamics of atomic, polymeric and colloidal systems. Amsterdam : Elsevier, 2005.
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Furst, Eric M., et Todd M. Squires. Laser tweezer microrheology. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199655205.003.0009.
Texte intégralRésumé :
To many, the idea that light can be used to hold and manipulate matter is probably quite foreign. The photon is a seemingly evanescent particle; its interactions with matter are weak. But while it has no rest mass, a photon carries momentum. Optical traps have become important tools used to measure forces on nanometer to micrometer length scale. Laser tweezers can be used to drive (or hold) microrheological probes. Optical trapping forces are reviewed and optical trap designs discussed, incluing the use of fixed and moving reference frame optical traps. Proper calibration of optical traps especially in the material under test is discussed. Linear and non-linear measurements using laser tweezers are presented, including shear thinning of colloidal dispersions when probes are translated through a suspension. The operating regime of laser tweezer microrheology is presented.
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Furst, Eric M., et Todd M. Squires. Introduction. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199655205.003.0001.
Texte intégralRésumé :
General concepts of rheology and microrheology are presented, including basic concepts of the microrheology measurement, the characteristics of soft materials, rheological functions and principles of conventional rheometric measurements, as well as several common rheological properties that will be encountered throughout the text. Microrheology encompasses a set of rheometric methods or techniques with unique capabilities|a part of the experimental toolbox for characterizing the rheological properties of materials to aid their understanding, or help in the design of new materials. There are limitations to microrheology that are important to understand from the outset. Colloidal particles are central to all microrheology measurements. Basic concepts of colloid science, including typical probe chemistries, colloidal stability, characterization, and preparation are presented.
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Furst, Eric M., et Todd M. Squires. Magnetic bead microrheology. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199655205.003.0008.
Texte intégralRésumé :
Magnetism is a convenient force for actively pulling colloidal particles in a material. Many materials of interest in a microrheology experiment have a negligible magnetic susceptibility, and so embedded magnetic particles can be subject to relatively strong forces by fields imposed from outside of the sample. These are usually generated by electromagnets, but can also include the use of permanent magnets, or a combination of both. Such “magnetic tweezers” are used as sensitive force probes, capable of generating forces ranging from femtonewtons to nanonewtons. Magnetic forces and magnetic materials are reviewed and magnetic tweezer designs discussed. Linear and non-linear measurements using magnetic tweezers are presented, including studies yield stress and shear thinning. The operating regime of magnetic tweezer microrheology is presented, which enables microrheology experiments to access stiffer materials.
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Furst, Eric M., et Todd M. Squires. Particle motion. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199655205.003.0002.
Texte intégralRésumé :
The movement of colloidal particles in simple and complex fluids and viscoelastic solids is central to the microrheology endeavor. All microrheology experiments measure the resistance of a probe particle forced to move within a material, whether that probe is forced externally or simply allowed to fluctuate thermally. This chapter lays a foundation of the fundamental mechanics of micrometer-dimension particles in fluids and soft solids. In an active microrheology experiment, a colloid of radius a is driven externally with a specifed force F (e.g.magnetic, optical, or gravitational), and moves with a velocity V that is measured. Of particular importance is the role of the Correspondence Principle, but other key concepts, including mobility and resistance, hydrodynamic interactions, and both fluid and particle inertia, are discussed. In passive microrheology experiments, on the other hand, the position of a thermally-uctuating probe is tracked and analyzed to determine its diffusivity.
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Furst, Eric M., et Todd M. Squires. Microrheology. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199655205.001.0001.
Texte intégralRésumé :
We present a comprehensive overview of microrheology, emphasizing the underlying theory, practical aspects of its implementation, and current applications to rheological studies in academic and industrial laboratories. Key methods and techniques are examined, including important considerations to be made with respect to the materials most amenable to microrheological characterization and pitfalls to avoid in measurements and analysis. The fundamental principles of all microrheology experiments are presented, including the nature of colloidal probes and their movement in fluids, soft solids, and viscoelastic materials. Microrheology is divided into two general areas, depending on whether the probe is driven into motion by thermal forces (passive), or by an external force (active). We present the theory and practice of passive microrheology, including an in-depth examination of the Generalized Stokes-Einstein Relation (GSER). We carefully treat the assumptions that must be made for these techniques to work, and what happens when the underlying assumptions are violated. Experimental methods covered in detail include particle tracking microrheology, tracer particle microrheology using dynamic light scattering and diffusing wave spectroscopy, and laser tracking microrheology. Second, we discuss the theory and practice of active microrheology, focusing specifically on the potential and limitations of extending microrheology to measurements of non-linear rheological properties, like yielding and shear-thinning. Practical aspects of magnetic and optical tweezer measurements are preseted. Finally, we highlight important applications of microrheology, including measurements of gelation, degradation, high-throughput rheology, protein solution viscosities, and polymer dynamics.
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Snook, Ian. Langevin and Generalised Langevin Approach to the Dynamics of Atomic, Polymeric and Colloidal Systems. Elsevier Science & Technology Books, 2006.
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Kovzun, I. G., V. A. Prokopenko, A. V. Panko, O. A. Tsyganovich, V. O. Oliinyk, O. M. Nikipelova et Z. R. Ulberg. Nanochemical, nanostructural and biocolloidal aspects of transformations in dispersions of iron-aluminosilicate minerals. PH "Akademperiodyka", 2020. http://dx.doi.org/10.15407/akademperiodyka.416.188.
Texte intégralRésumé :
It was considered the modern ideas of colloidal and biocolloidal nanoscience concerning complex transformational processes in widespread dispersions of iron-aluminosilicates. It was shown for the fi rst time that they infl uence on catastrophic phenomena in marine turbiditic-pelitic sediments and soils consisting of iron-aluminosilicates. Th e fundamental study results of nano- and microstructure transformations of disperse ironaluminosilicate compositions are presented. And it was established the possibilities of their application in: constructing of protective structures; balneology and medicine; metallurgy; development of the problem of saving the ecological balance in the sea hydrosphere; developing the new branch of science — biocolloidal marine geoecology.
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Snook, Ian. The Langevin and Generalised Langevin Approach to the Dynamics of Atomic, Polymeric and Colloidal Systems. Elsevier Science, 2007.
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Furst, Eric M., et Todd M. Squires. Light scattering microrheology. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199655205.003.0005.
Texte intégralRésumé :
The fundamentals and best practices of passive microrheology using dynamic light scattering and diffusing wave spectroscopy are discussed. The principles of light scattering are introduced and applied in both the single and multiple scattering regimes, including derivations of the light and field autocorrelation functions. Applications to high-frequency microrheology and polymer dynamics are presented, including inertial corrections. Methods to treat gels and other non-ergodic samples, including multi-speckle and optical mixing designs are discussed. Dynamic light scattering (DLS) is a well established method for measuring the motion of colloids, proteins and macromolecules. Light scattering has several advantages for microrheology, especially given the availability of commercial instruments, the relatively large sample volumes that average over many probes, and the sensitivity of the measurement to small particle displacements, which can extend the range of length and timescales probed beyond those typically accessed by the methods of multiple particle tracking and bulk rheology.
Chapitres de livres sur le sujet "Colloidal Probes"
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Hughes, David A., et Julian E. Beesley. « Preparation of Colloidal Gold Probes ». Dans Immunochemical Protocols, 275–82. Totowa, NJ : Humana Press, 1998. http://dx.doi.org/10.1007/978-1-59259-257-9_29.
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Hughes, David. « Preparation of Colloidal Gold Probes ». Dans Immunochemical Protocols, 155–72. Totowa, NJ : Humana Press, 2005. http://dx.doi.org/10.1385/1-59259-873-0:155.
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Municio, A. M., S. Abarca, J. L. Carrascosa, R. Garcia, I. Diaz-Laviada, M. J. Ainaga, M. T. Portoles, R. Pagani, C. Risco et M. A. Bosch. « Immunocytochemical Localization of Bacterial Lipopolysaccharide with Colloidal-Gold Probes in Different Target Cells ». Dans Endotoxin, 199–202. Boston, MA : Springer US, 1990. http://dx.doi.org/10.1007/978-1-4757-5140-6_17.
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De Mey, J., et M. Moeremans. « The Preparation of Colloidal Gold Probes and Their Use as Marker in Electron Microscopy ». Dans Advanced Techniques in Biological Electron Microscopy III, 229–71. Berlin, Heidelberg : Springer Berlin Heidelberg, 1986. http://dx.doi.org/10.1007/978-3-642-71135-0_6.
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Van de Plas, Peter F. E. M., et Jan L. M. Leunissen. « Colloidal Gold as a Marker in Molecular Biology : The Use of Ultra-Small Gold Probes ». Dans Nonradioactive Labeling and Detection of Biomolecules, 116–26. Berlin, Heidelberg : Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-662-00144-8_7.
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Jana, Nikhil Ranjan. « Plasmonic Property of Gold Nanorod for Optical Probe ». Dans Colloidal Gold Nanorods, 63–74. Boca Raton : CRC Press, 2022. http://dx.doi.org/10.1201/9781003245339-5.
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Friedman, Avner. « Mass transport in colloidal dispersions ». Dans Mathematics in Industrial Problems, 12–22. New York, NY : Springer New York, 1995. http://dx.doi.org/10.1007/978-1-4613-8454-0_2.
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Zeng, Yan, Sebastian Schön, Adrian Carl et Regine von Klitzing. « Colloidal Particles in Thin Liquid Films ». Dans Colloid Process Engineering, 3–19. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-15129-8_1.
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Bürger, Vincent, Eva Schlauch, Volker Becker, Ryohei Seto, Marek Behr et Heiko Briesen. « Simulating the Restructuring of Colloidal Aggregates ». Dans Colloid Process Engineering, 145–73. Cham : Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-15129-8_7.
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Stappers, Linda, et Jan Fransaer. « Colloidal Probe AFM Measurements of the Electrophoretic Force ». Dans Electrophoretic Deposition : Fundamentals and Applications II, 1–6. Stafa : Trans Tech Publications Ltd., 2006. http://dx.doi.org/10.4028/0-87849-998-9.1.
Texte intégralActes de conférences sur le sujet "Colloidal Probes"
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Wang, Hao, Zhaolin Xue, Kholud Dardir et Laura Fabris. « Bioconjugation strategies toward efficient intracellular nanoparticle probes ». Dans Colloidal Nanoparticles for Biomedical Applications XVI, sous la direction de Marek Osiński et Antonios G. Kanaras. SPIE, 2021. http://dx.doi.org/10.1117/12.2583250.
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Raymo, Francisco, Yang Zhang, Adrienne S. Brown, James N. Wilson, Kevin M. Collins, Ek Raj Thapaliya et Pravat Dhakal. « Bright and compact macromolecular probes for bioimaging applications ». Dans Colloidal Nanoparticles for Biomedical Applications XIII, sous la direction de Xing-Jie Liang, Wolfgang J. Parak et Marek Osiński. SPIE, 2018. http://dx.doi.org/10.1117/12.2287852.
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Yodh, Arjun G. « Speckle Fluctuations and Their Use as Probes of Dense Random Media ». Dans Photon Correlation and Scattering. Washington, D.C. : Optica Publishing Group, 1992. http://dx.doi.org/10.1364/pcs.1992.mb1.
Texte intégralRésumé :
There is a rich variety of systems in nature which are essentially dense aggregations of particle-like structures whose positions vary randomly in space and time. Unfortunately because the particles often scatter light strongly, progress in our understanding of fluctuating, random media has been limited to very dilute systems. Recently, a number of researchers have developed and applied a new spectroscopy to study the properties of colloidal suspensions which multiply scatter light [1]. This method, called diffusing-wave spectroscopy (DWS), exploits the diffusive nature of light transport in strongly scattering media to relate temporal intensity fluctuations of the scattered light to average particle motion. In contrast to traditional quasi-elastic light scattering methods, DWS probes particle motion in dense, strongly scattering colloids and over length scales much shorter than the wavelength of light (<10Å).
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Yang, Seung Ho, et Stephen M. Hsu. « Effect of Colloidal Probe Random Surface Features on Adhesion ». Dans World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63701.
Texte intégralRésumé :
We have uncovered the fact that colloidal probes often have random surface features which when not properly accounted for, can significantly affect the magnitudes of the measured adhesive forces using atomic force microscopes (AFM). Colloidal probes have been used to measure the pull-off forces between the probe and surfaces. We prepared a series of colloidal probes by attaching glass spheres (radii of 3.3 μm to 17.4 μm) to the end of AFM cantilevers. Adhesive force between the probes and a silicon wafer surface was measured using an AFM under various loads from 6 nN to 100 nN in dry air. Results showed that the values of the pull-off forces did not correlate with the radii of the probes. Direct imaging of the glass sphere surface using a sharp tip revealed substantial random surface features which altered the size of real contact areas. We extracted the load-bearing areas from the topography data and used them to normalize the adhesion data. The measured adhesive force, after being normalized, was found to be independent of the load and the sphere radii, in agreement with prevailing contact mechanics theory.
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Urban, Ben E., Purnima Neogi, Yasuhisa Fujita et Arup Neogi. « Colloidal ZnO nanoparticles for nonlinear optical probes and selective cell destruction ». Dans SPIE BiOS, sous la direction de Wolfgang J. Parak, Marek Osinski et Kenji Yamamoto. SPIE, 2013. http://dx.doi.org/10.1117/12.2005938.
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Varenberg, Michael, Izhak Etsion et Grigory Halperin. « Nanoscale Fretting Study by Scanning Probe Microscopy (Keynote) ». Dans World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63233.
Texte intégralRésumé :
Nanoscale fretting can be studied by using scanning probe microscopy (SPM) and a newly proposed “slip index” which provides unified approach to fretting on different scales. Various relevant issues such as production of colloidal probes and SPM calibration will be presented. Partial and gross slip nanoscale fretting tests with displacement amplitude from 5 to 500 nm and normal load from 15 to 28 μN will be described. Experiments show a substantial increase of the friction at the transition from partial to gross slip and a significant difference of damaged surfaces in the two fretting regimes.
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Lawandy, N. M., et R. MacDonald. « Optical Debye effect ». Dans OSA Annual Meeting. Washington, D.C. : Optica Publishing Group, 1990. http://dx.doi.org/10.1364/oam.1990.wv6.
Texte intégralRésumé :
The interaction of acoustic waves with charged colloids results in electrical signals. This phenomena, known as the Debye effect, results due to the instantaneous separation between the charged colloidal particle and its surrounding double layer. The separation results in a macroscopic polarization within the medium, which creates a voltage difference. This work demonstrates that radiation pressure forces can be used to impulsively move the colloid, resulting in a dipolar electric field. Experiments were performed using 100 ps, 1.06-µm pulses and 80 ps, 532-nm pulses incident on aqueous colloidal suspensions of charged latex spheres. Experiments were performed on random colloidal suspensions as well as high density crystals ordered in an fcc lattice. The dependence of the effect on sphere size and pulse intensity are presented. The effect exhibits the expected polarity when opposite sides of the sample are illuminated. Using electro-optic sampling, the dynamics of the double layer response can be directly probed on a picosecond time scale.
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Estry, D. W., et J. C. Mattson. « DIRECT BINDING OF FIBRINOGEN-GOLD PROBES DOES NOT DISCLOSE THE ENTIRE POPULATION OF BOUND FIBRINOGEN ON ADHERENT PLATELETS ». Dans XIth International Congress on Thrombosis and Haemostasis. Schattauer GmbH, 1987. http://dx.doi.org/10.1055/s-0038-1643526.
Texte intégralRésumé :
The binding characteristics of fibrinogen to adherent platelets were determined using both direct protein-gold labeling and an immunogold procedure. The binding of colloidal gold-fibrinogen was studied in whole mounts of contact activated, gel filtered platelets by transmission electron microscopy. There was a transition from minimal binding of fibrinogen in dendritic platelets to marked zonal binding in fully spread platelets. The pattern of direct fibrinogen binding in fully spread platelets appeared to orient itself with the underlying filamentous cytoskeleton, a pattern that is consistant with that previously reported by us and others. In contrast, when bound fibrinogen was assayed using a rabbit anti-fibrinogen antibody, the pattern of bound fibrinogen was diffuse and strong labeling was present in both early dendritic forms as well as late fully spread platelets. To further confirm these observations the direct labeling technique was combined with the immunogold labeling procedure using two different sized gold probes. Platelets previously incubated with fibrinogen-gold (20 nm) were fixed, incubated with rabbit anti-human fibrinogen and then with gold conjugated goat anti-rabbit IgG (10 nm). The morphologic organization of the direct label was unchanged. However, the immunogold technique demonstrated a diffuse binding pattern over the entire cytoplasmic veil including areas previously unlabeled by the direct technique. This suggested that in addition to fibrinogen receptors identified by direct labeling, there are other receptors that either already contain bound fibrinogen, compete for released fibrinogen more affectively, or represent membrane bound granule fibrinogen that is exposed rather than released and rebound and is therefore identified only by the immunogold labeling procedure.
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Yang, Seung Ho, et Stephen M. Hsu. « Nanoscale Surface Force Measurement ». Dans World Tribology Congress III. ASMEDC, 2005. http://dx.doi.org/10.1115/wtc2005-63702.
Texte intégralRésumé :
At nanoscale, surface forces often dominate or exert significant influence on contact interfaces. Adhesion and stiction in micro- and nanodevices are important technological challenges in nanotechnology and they are closely linked to our ability to control the surface forces. Yet our understanding of surface forces in nanoscale contacts is lacking, especially the interplay between surface roughness, material properties, contact geometry and the environment. Traditional means of measuring surface forces use a macrocontact with atomically flat mica surfaces and the forces measured by laser interferometry. Semiconductor and insulator materials cannot be measured by this technique. We have developed a preliminary AFM-based technique using colloidal probes capable of directly measure the surface forces at nanoscale. The difficulties are surface roughness control, force sensitivity of the cantilevers, the control of snapon, and the size of the probe tip. We have demonstrated that all these issues can be controlled to a large extent and reasonable surface forces can be measured between a probe tip and a flat surface down to a nanometer distance to the surface.
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Amme, M., H. Lang et M. Sto¨ckl. « Different Pathways of Secondary Phase Formation Induced by Colloidal and Dissolved Silica During the Dissolution of UO2 Nuclear Fuel in Leaching Tests ». Dans ASME 2003 9th International Conference on Radioactive Waste Management and Environmental Remediation. ASMEDC, 2003. http://dx.doi.org/10.1115/icem2003-4504.
Texte intégralRésumé :
We investigated the different dissolution behaviour of UO2 nuclear fuel material in waters containing silica in two different physical and chemical forms (dissolved ions and as SiO2 colloids, respectively) at elevated temperatures (95 °C in autoclaves). It was investigated if SiO2 colloids can act as carrier material for U ions during a interface geochemical dissolution process, a process that might possibly enhance the mobilization of uranium. Herefore, leaching / dissolution tests were conducted in batch reactors, using both dissolved Si (sodium metasilicate solution), as well as synthetic SiO2 colloids (100 nm diameter). Solid materials were examined with scanning electron microscopy (SEM-EDX) after the tests and ICP-OES was used for analysis of concentrations of U and Si in solutions. Thermodynamic calculations were applied for modelling the surface charges of the solid materials. Results show that a treatment with colloidal SiO2 has different effects on the surfaces than a leaching in dissolved silicate solutions. In the presence of colloids, well-crystallized secondary phases containing U and Si (most obviously uranyl silicates) were found on the surfaces, which were attacked by the treatment. This was not the case when dissolved Si was used. SiO2 colloids were partly found to remain on the surfaces after 1000 h at 95 °C. Dissolved U concentrations decreased with increasing Si content in the systems, especially so when colloidal Si was used. Ultrafiltration showed that the greatest part of the dissolved U was associated with Si colloids. A surface charge model suggests that the different effects are due to the development of electrostatic interactions between the UO2 and SiO2 surfaces.
Rapports d'organisations sur le sujet "Colloidal Probes"
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Asenath-Smith, Emily, Emma Ambrogi, Eftihia Barnes et Jonathon Brame. CuO enhances the photocatalytic activity of Fe₂O₃ through synergistic reactive oxygen species interactions. Engineer Research and Development Center (U.S.), septembre 2021. http://dx.doi.org/10.21079/11681/42131.
Texte intégralRésumé :
Iron oxide (α-Fe₂O₃, hematite) colloids were synthesized under hydrothermal conditions and investigated as catalysts for the photodegradation of an organic dye under broad-spectrum illumination. To enhance photocatalytic performance, Fe₂O₃ was combined with other transition-metal oxide (TMO) colloids (e.g., CuO and ZnO), which are sensitive to different regions of the solar spectrum (far visible and ultraviolet, respectively), using a ternary blending approach for compositional mixtures. For a variety of ZnO/Fe₂O₃/CuO mole ratios, the pseudo-first-order rate constant for methyl orange degradation was at least double the sum of the individual Fe₂O₃ and CuO rate constants, indicating there is an underlying synergy governing the photocatalysis reaction with these combinations of TMOs. A full compositional study was carried out to map the interactions between the three TMOs. Additional experiments probed the identity and role of reactive oxygen species and elucidated the mechanism by which CuO enhanced Fe₂O₃ photodegradation while ZnO did not. The increased photocatalytic performance of Fe2O3 in the presence of CuO was associated with hydroxyl radical ROS, consistent with heterogeneous photo-Fenton mechanisms, which are not accessible by ZnO. These results imply that low-cost photocatalytic materials can be engineered for high performance under solar illumination by selective pairing of TMOs with compatible ROS.
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Huang, Cihang, Yen-Fang Su et Na Lu. Self-Healing Cementitious Composites (SHCC) with Ultrahigh Ductility for Pavement and Bridge Construction. Purdue University, 2021. http://dx.doi.org/10.5703/1288284317403.
Texte intégralRésumé :
Cracks and their formations in concrete structures have been a common and long-lived problem, mainly due to the intrinsic brittleness of the concrete. Concrete structures, such as rigid pavement and bridge decks, are prone to deformations and deteriorations caused by shrinkage, temperature fluctuation, and traffic load, which can affect their service life. Rehabilitation of concrete structures is expensive and challenging—not only from maintenance viewpoints but also because they cannot be used for services during maintenance. It is critical to significantly improve the ductility of concrete to overcome such issues and to enable better infrastructure quality. To this end, the self-healing cementitious composites (SHCC) investigated in this work could be a promising solution to the aforementioned problems. In this project, the team has designed a series of cementitious composites to investigate their mechanical performances and self-healing abilities. Firstly, various types of fibers were investigated for improving ductility of the designed SHCC. To enhance the self-healing of SHCC, we proposed and examined that the combination of the internal curing method with SHCC mixture design can further improve self-healing performance. Three types of internal curing agents were used on the SHCC mixture design, and their self-healing efficiency was evaluated by multiple destructive and non-destructive tests. Results indicated a significant improvement in the self-healing capacity with the incorporation of internal curing agents such as zeolite and lightweight aggregate. To control the fiber distribution and workability of the SHCC, the mix design was further adjusted by controlling rheology using different types of viscosity modifiers. The team also explored the feasibility of the incorporation of colloidal nano-silica into the mix design of SHCC. Results suggest that optimum amounts of nano-silica have positive influence on self-healing efficiency and mechanical properties of the SHCC. Better hydration was also achieved by adding the nano-silica. The bonding strength of the SHCC with conventional concrete was also improved. At last, a standardized mixing procedure for the large scale SHCC was drafted and proposed.
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Nechypurenko, Pavlo P., Viktoriia G. Stoliarenko, Tetiana V. Starova, Tetiana V. Selivanova, Oksana M. Markova, Yevhenii O. Modlo et Ekaterina O. Shmeltser. Development and implementation of educational resources in chemistry with elements of augmented reality. [б. в.], février 2020. http://dx.doi.org/10.31812/123456789/3751.
Texte intégralRésumé :
The purpose of this article is an analysis of opportunities and description of the experience of developing and implementing augmented reality technologies to support the teaching of chemistry in higher education institutions of Ukraine. The article is aimed at solving problems: generalization and analysis of the results of scientific research concerning the advantages of using the augmented reality in the teaching of chemistry, the characteristics of modern means of creating objects of augmented reality; discussion of practical achievements in the development and implementation of teaching materials on chemistry using the technologies of the augmented reality in the educational process. The object of research is augmented reality, and the subject - the use of augmented reality in the teaching of chemistry. As a result of the study, it was found that technologies of augmented reality have enormous potential for increasing the efficiency of independent work of students in the study of chemistry, providing distance and continuous education. Often, the technologies of the augmented reality in chemistry teaching are used for 3D visualization of the structure of atoms, molecules, crystalline lattices, etc., but this range can be expanded considerably when creating its own educational products with the use of AR-technologies. The study provides an opportunity to draw conclusions about the presence of technologies in the added reality of a significant number of benefits, in particular, accessibility through mobile devices; availability of free, accessible and easy-to-use software for creating augmented-reality objects and high efficiency in using them as a means of visibility. The development and implementation of teaching materials with the use of AR-technologies in chemistry teaching at the Kryvyi Rih State Pedagogical University has been started in the following areas: creation of a database of chemical dishes, creation of a virtual chemical laboratory for qualitative chemical analysis, creation of a set of methodical materials for the course “Physical and colloidal chemistry”.
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Wicker, Louise, Ilan Shomer et Uzi Merin. Membrane Processing of Citrus Extracts : Effects on Pectinesterase Activity and Cloud Stability. United States Department of Agriculture, octobre 1993. http://dx.doi.org/10.32747/1993.7568754.bard.
Texte intégralRésumé :
The U.S. team studied the role of cations and pH on thermolabile (TL-PE) and thermostable (TS-PE), permeation in ultrafiltration (UF) membranes, affinity to ion exchange membranes, mechanism of cation and pH activation, and effect on PE stability. An optimum pH and cation concentration exists for activity and UF permeation, which is specific for each cation type. Incomplete release of PE from a pectin complex resulted in low PE binding to cationic and anionic membranes. Incubation of PE at low pH increases the surface hydrophobicity, especially TL-PE, but the secondary structure of TL-PE is not greatly affected. The Israeli team showed that stable cloud colloidal constituents flocculate following the conversion of soluble to insoluble biopolymers. First, formation of pectic acid by pectinesterase activity is followed by the formation of calcium pectate gel. This process initiates a myriad of poorly defined reactions that result in juice clarification. Second, protein coagulation by heat resulted in flocculation of proteinacous bound cloud constituents, particularly after enzymatic pectin degradation. Pectinesterase activity is proposed to be an indirect cause for clarification; whereas binding of cloud constituents is the primary event in clarification by pectate gel and coagulated proteins. Understanding the mechanism of interaction of protein and pectic polymers is key to understanding cloud instability. Based on the above, it was hypothesized that the structure of pectin-protein coagulates plays a key role in cloud instability.
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Shomer, Ilan, Louise Wicker, Uzi Merin et William L. Kerr. Interactions of Cloud Proteins, Pectins and Pectinesterases in Flocculation of Citrus Cloud. United States Department of Agriculture, février 2002. http://dx.doi.org/10.32747/2002.7580669.bard.
Texte intégralRésumé :
The overall objective was to understand the cloud flocculation of citrus juice by characterization of the interactions between proteins and pectins, and to determine the role of PE isozymes in catalyzing this phenomenon. Specific objectives were to: 1. identify/characterize cloud-proteins in relation to their coagulable properties and affinity to pectins; 2. to determine structural changes of PME and other proteins induced by cation/pectin interactions; 3. localize cloud proteins, PME and bound protein/pectates in unheated and pasteurized juices; 4. to create "sensitized" pectins and determine their effect on clarification. The original objectives were not changed but the methods and approach were modified due to specific research requirements. Two i postulates were: 1. there is a specific interaction of cloud proteins with de-esterified regions of ! pectin and this contributes to cloud loss; 2. isozymes of pectin-methyl-esterase (PME) vary in efficiency to create sensitized pectins. The appearance of citrus fruit juice is an important quality factor and is determined by the color and turbidity that .are conferred by the suspended particles, i.e., by the cloud and its homogeneity. Under some circumstances the cloud tend to flocculate and the juice clarifies. The accepted approach to explain the clarification is based on pectin demethoxylation by PME that promotes formation of Ca-pectate. Therefore, the juice includes immediate heat-inactivation upon ~ squeezing. Protein coagulation also promotes cloud instability of citrus fruit extracts. However, the clarification mechanism is not fully understood. Information accumulated from several laboratories indicates that clarification is a more complex process than can be explained by a single mechanism. The increasing trend to consume natural-fresh juice emphasizing the importance of the knowledge to assure homogeneity of fresh juice. The research included complementary directions: Conditions that induce cloud-instability of natural- juice [IL]. Evaluate purification schemes of protein [USA]. Identifications of proteins, pectin and neutral sugars ([IL]; Structure of the cloud components using light and electron microscopy and immuno-labeling of PME, high-methoxyl-pectin (HMP) and low-methoxyl-pectin (LMP); Molecular weight of calcium sensitized pectins [US]; Evaluation of the products of PME activity [US]. Fractions and size distribution and cloud components [IL-US]. The optimal pH activity of PME is 7 and the flocculation pH of the cloud is 3-4. Thus, the c roles of PME, proteins and pectins in the cloud instability, were studied in pH ranges of 2- 7. The experiments led to establish firstly repeatable simulate conditions for cloud instability [IL]. Thermostable PME (TS-PE) known to induce cloud instability, but also thermolabile forms of PME (TL-PE) caused clarification, most likely due to the formation and dissolution of inactive :. PE-pectin complexes and displacement of a protective colloid from the cloud surface [US]. Furthermore, elimination of non-PME protein increases TS-PE activity, indicating that non-PME proteins moderate PME activity [US]. Other experiments Concomitantly with the study of the PME activity but promotes the association of cloud-proteins to pectin. Adjusting of the juice pH to f 7 retains the cloud stability and re-adjusting of the pH to 40% DE reacts to immuno-labeling in the cloud fragments, whereas