1,665 research outputs found
Ions modulate stress-induced nano-texture in supported fluid lipid bilayers.
Most plasma membranes comprise a large number of different molecules including lipids and proteins. In the standard fluid mosaic model, the membrane function is effected by proteins whereas lipids are largely passive and serve solely in the membrane cohesion. Here we show, using supported 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayers in different saline solutions, that ions can locally induce ordering of the lipid molecules within the otherwise fluid bilayer when the latter is supported. This nanoordering exhibits a characteristic length scale of âŒ20 nm, and manifests itself clearly when mechanical stress is applied to the membrane. Atomic force microscopy (AFM) measurements in aqueous solutions containing NaCl, KCl, CaCl2, and Tris buffer show that the magnitude of the effect is strongly ion-specific, with Ca2+ and Tris, respectively, promoting and reducing stress-induced nanotexturing of the membrane. The AFM results are complemented by fluorescence recovery after photobleaching experiments, which reveal an inverse correlation between the tendency for molecular nanoordering and the diffusion coefficient within the bilayer. Control AFM experiments on other lipids and at different temperatures support the hypothesis that the nanotexturing is induced by reversible, localized gel-like solidification of the membrane. These results suggest that supported fluid phospholipid bilayers are not homogenous at the nanoscale, but specific ions are able to locally alter molecular organization and mobility, and spatially modulate the membraneâs properties on a length scale of âŒ20 nm. To illustrate this point, AFM was used to follow the adsorption of the membrane-penetrating antimicrobial peptide Temporin L in different solutions. The results confirm that the peptides do not absorb randomly, but follow the ion-induced spatial modulation of the membrane. Our results suggest that ionic effects have a significant impact for passively modulating the local properties of biological membranes, when in contact with a support such as the cytoskeleton
Ions modulate stress-induced nano-texture in supported fluid lipid bilayers
Most plasma membranes comprise a large number of different molecules including lipids and proteins. In the standard fluid mosaic model, the membrane function is effected by proteins whereas lipids are largely passive and serve solely in the membrane cohesion. Here we show, using supported 1,2-dioleoyl-sn-glycero-3-phosphocholine lipid bilayers in different saline solutions, that ions can locally induce ordering of the lipid molecules within the otherwise fluid bilayer when the latter is supported. This nanoordering exhibits a characteristic length scale of âŒ20 nm, and manifests itself clearly when mechanical stress is applied to the membrane. Atomic force microscopy (AFM) measurements in aqueous solutions containing NaCl, KCl, CaCl2, and Tris buffer show that the magnitude of the effect is strongly ion-specific, with Ca2+ and Tris, respectively, promoting and reducing stress-induced nanotexturing of the membrane. The AFM results are complemented by fluorescence recovery after photobleaching experiments, which reveal an inverse correlation between the tendency for molecular nanoordering and the diffusion coefficient within the bilayer. Control AFM experiments on other lipids and at different temperatures support the hypothesis that the nanotexturing is induced by reversible, localized gel-like solidification of the membrane. These results suggest that supported fluid phospholipid bilayers are not homogenous at the nanoscale, but specific ions are able to locally alter molecular organization and mobility, and spatially modulate the membraneâs properties on a length scale of âŒ20 nm. To illustrate this point, AFM was used to follow the adsorption of the membrane-penetrating antimicrobial peptide Temporin L in different solutions. The results confirm that the peptides do not absorb randomly, but follow the ion-induced spatial modulation of the membrane. Our results suggest that ionic effects have a significant impact for passively modulating the local properties of biological membranes, when in contact with a support such as the cytoskeleton
Evolution of Complexity in Out-of-Equilibrium Systems by Time-Resolved or Space-Resolved Synchrotron Radiation Techniques
Out-of-equilibrium phenomena are attracting high interest in physics,
materials science, chemistry and life sciences. In this state, the study of
structural fluctuations at different length scales in time and space are
necessary to achieve significant advances in the understanding of
structure-functionality relationship. The visualization of patterns arising
from spatiotemporal fluctuations is nowadays possible thanks to new advances in
X-ray instrumentation development that combine high resolution both in space
and in time. We present novel experimental approaches using high brilliance
synchrotron radiation sources, fast detectors and focusing optics, joint with
advanced data analysis based on automated statistical, mathematical and imaging
processing tools. This approach has been used to investigate structural
fluctuations in out-of-equilibrium systems in the novel field of inhomogeneous
quantum complex matter at the crossing point of technology, physics and
biology. In particular, we discuss how nanoscale complexity controls the
emergence of high temperature superconductivity (HTS), myelin functionality and
formation of hybrid organic-inorganic nanostructures. The emergent complex
geometries, opening novel venues to quantum technology and to development of
quantum physics of living systems, are discussedComment: 18 pages, 7 figure
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An investigation on design and analysis of micro-structured surfaces with application to friction reduction
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel UniversityDrag reduction in wall-bounded flows can be achieved by the passive flow control
technique using riblets and surface grooves aligned in the mean direction of an
overlying turbulent flow. They were inspired by the skin of fast sharks covered
with small longitudinal ribs on their skin surfaces. Although it was found that the
drag reduction depends on the ribletsâ geometrical characteristics, their physical
mechanisms have not yet been fully understood in the scientific terms.
Regarding riblets sizing, it has been critically explained in the literature how riblets with vanishing size interact with the turbulent flow and produce a change in the drag proportional to their size. Their shapes are focused upon because these are
most significant from a technological perspective, and also less well understood.
Different riblet shapes have been designed, some with complicated geometries, but
except for the simple ones, such as U and V grooves, there has not been enough
study regarding shape features. Therefore, special effort is undertaken to the design
of an innovative type of ribleted surface, e.g. the Serrate-Semi-Circular shape, and
its effect on the skin friction and drag reduction. In this work, the possible physical mechanisms of riblets for turbulent drag reduction have been explored. The modelling and experiments concerning the
relationship between the riblets features and the turbulent boundary layer structure
have also been reviewed. Moreover, numerical simulations on riblets with different shapes and sizes are presented and studied in detail. An accurate treatment based on k-Δ turbulence model was adopted to investigate the flow alteration and the consequent drag
reduction on ribleted surfaces. The interaction of the overlying turbulent flow with riblets and its impact on their drag reduction properties are further investigated. In addition, the experimental facilities, instrumentation (e.g. hotwires) and measurement techniques (e.g. time-averaged turbulence structure) have been
employed to experimentally investigate the boundary layer velocity profiles and
skin friction for smooth and micro-structured surfaces (the proposed riblet shape, respectively and the presented new design of riblets with serration inside provides 7% drag reduction. The results do not show significant reduction in momentum
transfer near the surface by riblets, in particular, around the outer region of the
turbulent boundary layer. Conclusions with respect to the holistic investigation on the drag reduction with Serrate-Semi-Circular riblets have been drawn based on the research objectives as achieved. Recommendations for future work have been put forward particularly for further future research in the research area.Brunel University and KIMM (Korea Institute of Machinery and Materials
Photorealistic Texturing for Modern Video Games
Simulating realism has become a standard for many games in the industry. While real-time rendering requires considerable rendering resources, texturing defines the physical parameters of the surfaces with a lower computer power.
The objective of this thesis was to study the evolution of Texture Mapping and define a workflow for approaching a photorealism with modern instruments for video game production. All the textures were created with the usage of Agisoft Photoscan, Substance Designer & Paintrer, Abode Photoshop and Pixologic Zbrush.
With the aid of both the theory and practical approaches, this thesis explores the questions of how the textures are used and which applications can help to build them for a better result. Each workflow is introduced with the main points of their purposes as the authorâs suggestion, which can be used as a guideline for many companies, including Ringtail Studios OĂ.
In conclusion, the thesis summarizes the outcome of the textures and their workflow. The results are successfully established by the author with attendance to introduce methods for the material production
CREATING CONVINCING AND DRAMATIC LIGHT TRANSITIONS FOR COMPUTER ANIMATION
Lighting and atmospheric changes are complex phenomena that exist in nature; therefore replicating them using computer graphics can be quite challenging. Subtle changes in light conditions can greatly affect the mood or perception of the viewer and has been an important component of film making. With ever increasing technology and computing resources, filmmakers continue to strive to produce such complex effects that enhance their storytelling. Light transition (e.g.; day to night), continuously moving light sources, and dramatic change in seasons have been the focus of experimentation for many films. Most studios have therefore developed their own pipeline to create such effects. This thesis describes some simple and efficient observations and techniques to create such convincing lighting transitions
Interactive Extraction of High-Frequency Aesthetically-Coherent Colormaps
Color transfer functions (i.e. colormaps) exhibiting a high frequency luminosity component have proven to be useful in the visualization of data where feature detection or iso-contours recognition is essential. Having these colormaps also display a wide range of color and an aesthetically pleasing composition holds the potential to further aid image understanding and analysis. However producing such colormaps in an efficient manner with current colormap creation tools is difficult. We hereby demonstrate an interactive technique for extracting colormaps from artwork and pictures. We show how the rich and careful color design and dynamic luminance range of an existing image can be gracefully captured in a colormap and be utilized effectively in the exploration of complex datasets
Low Energy Electron Point Projection Microscopy of Suspended Graphene, the Ultimate "Microscope Slide"
Point Projection Microscopy (PPM) is used to image suspended graphene using
low-energy electrons (100-200eV). Because of the low energies used, the
graphene is neither damaged or contaminated by the electron beam. The
transparency of graphene is measured to be 74%, equivalent to electron
transmission through a sheet as thick as twice the covalent radius of
sp^2-bonded carbon. Also observed is rippling in the structure of the suspended
graphene, with a wavelength of approximately 26 nm. The interference of the
electron beam due to the diffraction off the edge of a graphene knife edge is
observed and used to calculate a virtual source size of 4.7 +/- 0.6 Angstroms
for the electron emitter. It is demonstrated that graphene can be used as both
anode and substrate in PPM in order to avoid distortions due to strong field
gradients around nano-scale objects. Graphene can be used to image objects
suspended on the sheet using PPM, and in the future, electron holography
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