Search results for " layer"
showing 10 items of 1022 documents
Bright hot impacts by erupted fragments falling back on the Sun: UV redshifts in stellar accretion
2014
A solar eruption after a flare on 7 Jun 2011 produced EUV-bright impacts of fallbacks far from the eruption site, observed with the Solar Dynamics Observatory. These impacts can be taken as a template for the impact of stellar accretion flows. Broad red-shifted UV lines have been commonly observed in young accreting stars. Here we study the emission from the impacts in the Atmospheric Imaging Assembly's UV channels and compare the inferred velocity distribution to stellar observations. We model the impacts with 2D hydrodynamic simulations. We find that the localised UV 1600A emission and its timing with respect to the EUV emission can be explained by the impact of a cloud of fragments. The …
Stock market dynamics and turbulence: parallel analysis of fluctuation phenomena
1997
Abstract We report analogies and differences between the fluctuations in an economic index and the fluctuations in velocity of a fluid in a fully turbulent state. Specifically, we systematically compare (i) the statistical properties of the S&P 500 cash index recorded during the period January 84–December 89 with (ii) the statistical properties of the velocity of turbulent air measured in the atmospheric surface layer about 6 m above a wheat canopy in the Connecticut Agricultural Research Station. We find non-Gaussian statistics, and intermittency, for both processes (i) and (ii) but the deviation from a Gaussian probability density function are different for stock market dynamics and turbu…
Diffusion and Migration
2003
The sections in this article are Introduction Fundamental Concepts Diffusion–migration Flux Equations Poisson Equation and the LEN Assumption Continuity Equation Ohm's Law and Migrational Transport Numbers Diffusion-conduction Flux Equation Diffusion Boundary Layer Faraday's Law and Integral Transport Numbers Nernst Equation and Concentration Overpotential Steady State Current–voltage Curves of Systems with One Active Species Integration of the Transport Equations Solutions of Homovalent Ions, |zi | =z Binary Electrolyte Solutions Ternary Electrolyte Solutions. The Supporting Electrolyte Weak Binary Electrolyte Steady State Current–overpotential Curves in the Presence of Supporting Electrol…
Three New Triterpene Saponins from Two Species of Carpolobia
2002
Three new acetylated triterpene saponins 1-3 were isolated from the roots of Carpolobia alba and C. lutea. Their structures were established mainly by 2D NMR techniques as 3-O-beta-D-glucopyranosylpresenegenin-28-O-beta-D-galactopyranosyl-(1-->4)-[beta-D-xylopyranosyl-(1-->3)]-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-(3,4-di-O-acetyl)-beta-D-fucopyranosyl ester, 3-O-beta-D-glucopyranosylpresenegenin-28-O-beta-D-galactopyranosyl-(1-->4)-[alpha-L-arabinopyranosyl-(1-->3)]-beta-D-xylopyranosyl-(1-->4)-alpha-L-rhamnopyranosyl-(1-->2)-(3,4-di-O-acetyl)-beta-D-fucopyranosyl ester, and 3-O-beta-D-glucopyranosylpresenegenin-28-O-beta-D-xylopyranosyl-(1-->4)-[beta-D-apiofuranosyl…
Layer-by-Layer Assembly of a Streptavidin–Fibronectin Multilayer on Biotinylated TiOX
2013
The biomodification of surfaces, especially titanium, is an important issue in current biomedical research. Regarding titanium, it is also important to ensure a specific protein modification of its surface because here protein binding that is too random can be observed. Specific nanoscale architectures can be applied to overcome this problem. As recently shown, streptavidin can be used as a coupling agent to immobilize biotinylated fibronectin (bFn) on a TiO(X) surface. Because of the conformation of adsorbed biotinylated fibronectin on a streptavidin monolayer, it is possible to adsorb more streptavidin and biotinylated fibronectin layers. On this basis, an alternating protein multilayer c…
Layer-by-layer assembled protein/polymer hybrid films: nanoconstruction via specific recognition
1998
Abstract In the present study it is shown that streptavidin-containing multilayer films with varying numbers of polyelectrolyte spacer layers can be fabricated reproducibly using optimized deposition conditions. Direct alternation of streptavidin and PLB leads to multilayer systems with an average streptavidin thickness of 5.3 nm which is in good agreement with the dimensions of the protein. When the streptavidin layers are spacered by more polyelectrolyte layers the distance between the protein sheets is increased up to e.g. 6.5 nm in the case of (PLB/PSS/PAH/PSS/PLB) as spacer layer. X-ray reflectivity reveals that streptavidin increases the surface roughness of the films probably due to …
Surface effects, boundary conditions and evolution laws within second strain gradient plasticity
2014
Abstract The principle of the virtual power (PVP) is used in conjunction with the concepts of “energy residual” and “insulation condition” to address second strain gradient plasticity. The energy residual with its typical divergence format is an extra stress power playing the role of basic state variable to describe the gradient effects, whereas the insulation condition constitutes a global energy characterization of the body as part of the body/environment system. The microstructure of a second strain gradient material (but not of a first strain gradient one) is shown to exhibit surface effects with the formation of a thin boundary layer. This boundary layer is in local (and global) equili…
A unifying variational framework for stress gradient and strain gradient elasticity theories
2015
Abstract Stress gradient elasticity and strain gradient elasticity do constitute distinct continuum theories exhibiting mutual complementary features. This is probed by a few variational principles herein presented and discussed, which include: i) For stress gradient elasticity, a (novel) principle of minimum complementary energy and an (improved-form) principle of stationarity of the Hellinger–Reissner type; ii) For strain gradient elasticity, a (known) principle of minimum total potential energy and a (novel) principle of stationarity of the Hu–Washizu type. Additionally, the higher order boundary conditions for stress gradient elasticity, previously derived by the author (Polizzotto, Int…
Radiative and dynamic effects of absorbing aerosol particles over the Pearl River Delta, China
2008
Abstract Results are reported from a ground-based measurement campaign conducted in a highly polluted region in southeast of China in October–November 2004. The experiment focused on absorbing aerosol particles and their effects on the solar radiation field and local meteorology. A Raman lidar in conjunction with Sun photometer data measured profiles of particle extinction; ground-based in situ data of aerosol optical properties were collected by nephelometer and absorption photometer. Exceptionally high values of aerosol optical depth of up to 1.5 were observed. The measurements were input to a radiative transfer model, which simulated high solar radiative forcing values for the aerosol pa…
Enhanced superconductivity in atomically thin TaS2
2016
The ability to exfoliate layered materials down to the single layer limit has presented the opportunity to understand how a gradual reduction in dimensionality affects the properties of bulk materials. Here we use this top–down approach to address the problem of superconductivity in the two-dimensional limit. The transport properties of electronic devices based on 2H tantalum disulfide flakes of different thicknesses are presented. We observe that superconductivity persists down to the thinnest layer investigated (3.5 nm), and interestingly, we find a pronounced enhancement in the critical temperature from 0.5 to 2.2 K as the layers are thinned down. In addition, we propose a tight-binding …