1,953 research outputs found
Self-assembled granular walkers
Mechanisms of locomotion in microscopic systems are of great interest not
only for technological applications, but also for the sake of understanding,
and potentially harnessing, processes far from thermal equilibrium.
Down-scaling is a particular challenge, and has led to a number of interesting
concepts including thermal ratchet systems and asymmetric swimmers. Here we
present a system which is particularly intriguing, as it is self-assembling and
uses a robust mechanism which can be implemented in various settings. It
consists of small spheres of different size which adhere to each other, and are
subject to an oscillating (zero average) external force eld. An inherent
nonlinearity in the mutual force network leads to force rectication and hence
to locomotion. We present a model that accounts for the observed behaviour and
demonstrates the wide applicability and potential scalability of the concept.Comment: 17 pages, 4 figure
Corrosion behaviour of nitrided ferritic stainless steels for use in solid oxide fuel cell devices
Plasma nitriding was applied to ferritic stainless steel substrates to improve their performances as interconnects for solid oxide fuel cell devices. The samples underwent electrical conductivity test and SEM/EDS, TEM/EDS, environmental-SEM analyses. The first stages of corrosion were recorded in-situ with the e-SEM. Nitriding is effective in limiting the undesired chromium evaporation from the steel substrates and accelerates the corrosion kinetics, but its influence of the electrical conductivity is ambiguous. No intergranular corrosion is found in the steel substrate after long time operation. Nitriding helps commercially competitive porous coating to improve chromium retention properties of metal interconnects
How to erase surface plasmon fringes
We report the realization of a dual surface plasmon polariton (SPP)
microscope based on leakage radiation (LR) analysis. The microscope can either
image SPP propagation in the direct space or tin the Fourier space. This
particularity allows in turn manipulation of the LR image for a clear
separation of different interfering SPP contributions present close to optical
nanoelements.Comment: Appl. Phys. Lett. 89, 091117 (2006
Inhibition of ornithine decarboxylase activity by follicle stimulating hormone in primary culture of rat Sertoli cells
The effect of follicle stimulating hormone on the activity of ornithine decarboxylase (ODC) was determined in primary culture of rat Sertoli cells. Three different FSH preparations (NIH oFSH-S-15, S-16, and eFSH) inhibited ODC activity in rat Sertoli cells under different media conditions. The inhibition was both time- and dose-dependent. The mechanism of the FSH inhibitory effect was studied using dibutyryl cyclic adenosine monophosphate (dbcAMP), 1-methyl-3-isobutylxanthine (MIX), forskolin, and isoproterenol. All of these agents, known to elevate cellular cAMP levels, inhibited ODC activity in cultured rat Sertoli cells. The combined effect of each of these substances plus FSH was either greater than, or equal to, that of FSH alone, and was not additive. Dibutyryl cyclic guanosine monophosphate had no effect on the ODC activity. These findings suggest that FSH inhibition of ODC activity in the rat Sertoli cell may be mediated by cAMP
Volume Rendering with Advanced GPU Scheduling Strategies
Modern GPUs are powerful enough to enable interactive display of high-quality volume data even despite the fact that many volume rendering methods do not present a natural fit for current GPU hardware. However, there still is a vast amount of computational power that remains unused due to the inefficient use of the available hardware. In this work, we demonstrate how advanced scheduling methods can be employed to implement volume rendering algorithms in a way that better utilizes the GPU by example of three different state-of-the-art volume rendering techniques
A Variational Loop Shrinking Analogy for Handle and Tunnel Detection and {Reeb} Graph Construction on Surfaces
The humble loop shrinking property played a central role in the inception of modern topology but it has been eclipsed by more abstract algebraic formalism. This is particularly true in the context of detecting relevant non-contractible loops on surfaces where elaborate homological and/or graph theoretical constructs are favored in algorithmic solutions. In this work, we devise a variational analogy to the loop shrinking property and show that it yields a simple, intuitive, yet powerful solution allowing a streamlined treatment of the problem of handle and tunnel loop detection. Our formalization tracks the evolution of a diffusion front randomly initiated on a single location on the surface. Capitalizing on a diffuse interface representation combined with a set of rules for concurrent front interactions, we develop a dynamic data structure for tracking the evolution on the surface encoded as a sparse matrix which serves for performing both diffusion numerics and loop detection and acts as the workhorse of our fully parallel implementation. The substantiated results suggest our approach outperforms state of the art and robustly copes with highly detailed geometric models. As a byproduct, our approach can be used to construct Reeb graphs by diffusion thus avoiding commonly encountered issues when using Morse functions
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