Shear Thickening and Scaling of the Elastic Modulus in a Fractal Colloidal System with Attractive Interactions

Dilute oil dispersions of fractal carbon black particles with attractive Van der Waals interactions display continuous shear thickening followed by shear thinning at high shear rates. The shear thickening transition occurs at $\dot\gamma_{c}\approx 10^{2}-10^{3}s^{-1}$ and is driven by hydrodynamic breakup of clusters. Pre-shearing dispersions at shear rates $\dot\gamma>\dot\gamma_{c}$ produces enhanced-modulus gels where $G' \sim \sigma_{pre-shear}^{1.5-2}$ and is directly proportional to the residual stress in the gel measured at a fixed sample age. The observed data can be accounted for using a simple scaling model for the breakup of fractal clusters under shear stress.Comment: 5 pages, 5 figures; v2: treating low shear rate date separately; edited title; reworked figure

Biosensing platform combining label-free and labelled analysis using Bloch surface waves

Bloch surface waves (BSW) propagating at the boundary of truncated photonic crystals (1D-PC) have emerged as an attractive approach for label-free sensing in plasmon-like sensor configurations. Due to the very low losses in such dielectric thin film stacks, BSW feature very low angular resonance widths compared to the surface plasmon resonance (SPR) case. Besides label-free operation, the large field enhancement and the absence of quenching allow utilizing BSW coupled fluorescence detection to additionally sense the presence of fluorescent labels. This approach can be adapted to the case of angularly resolved resonance detection, thus giving rise to a combined label-free / labelled biosensor platform. It features a parallel analysis of multiple spots arranged as a one-dimensional array inside a microfluidic channel of a disposable chip. Application of such a combined biosensing approach to the detection of the Angiopoietin-2 cancer biomarker in buffer solutions is reported

Facing the challenge of liquid phase crystallizing silicon on textured glass substrates

A major limitation in current liquid phase crystallized LPC silicon thin film record solar cells are optical losses caused by their planar glass silicon interface. In this study, silicon is grown on nanoimprinted periodically as well as on randomly textured glass substrates and successfully implemented into state of the art LPC silicon thin film solar cell stacks. By systematically varying every layer the whole sample stack is optimized regarding its anti reflection ability. Compared to an optimized planar reference device, a reduction of reflection losses by 3.5 absolute on the random and by 9.4 absolute on the periodic texture has been achieved in the wavelength range of interes

Growth hormone modulates hippocampal excitatory synaptic transmission and plasticity in old rats

Cataloged from PDF version of article.Alterations in the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate receptor (AMPA-R) and N-methyl-D-aspartate receptor (NMDA-R) have been documented in aged animals and may contribute to changes in hippocampal-dependent memory. Growth hormone (GH) regulates AMPA-R and NMDA-R-dependent excitatory transmission and decreases with age. Chronic GH treatment mitigates age-related cognitive decline. An in vitro CA1 hippocampal slice preparation was used to compare hippocampal excitatory transmission and plasticity in old animals treated for 6–8 months with either saline or GH. Our findings indicate that GH treatment restores NMDA-Rdependent basal synaptic transmission in old rats to young adult levels and enhances both AMPA-R-dependent basal synaptic transmission and long-term potentiation. These alterations in synaptic function occurred in the absence of changes in presynaptic function, as measured by paired-pulse ratios, the total protein levels of AMPA-R and NMDA-R subunits or in plasma or hippocampal levels of insulin-like growth factor-I. These data suggest a direct role for GH in altering age-related changes in excitatory transmission and provide a possible cellular mechanism through which GH changes the course of cognitive decline. © 2012 Elsevier Inc. All rights reserved

On the calculation of equilibrium thermodynamic properties and the establishment of statistical-thermodynamically-consistent finite bound-state partition functions in nonideal multi-component plasma mixtures within the chemical model

The problem of the calculation of equilibrium thermodynamic properties and the establishment of statistical-thermodynamically-consistent finite bound-state partition functions in nonideal multi-component plasma systems is revised within the chemical picture. The present exploration accompanied by the introduction of a generalized accurate formulation, in terms of the solution of the inverse problem, clears ambiguities and gives a better understanding of the problem on top of pointing out weaknesses and inaccuracies/inconsistencies buried in widely used models in the literature.Comment: 22 pages, 4 figure

On reminder effects, drop-outs and dominance: evidence from an online experiment on charitable giving

We present the results of an experiment that (a) shows the usefulness of screening out drop-outs and (b) tests whether different methods of payment and reminder intervals affect charitable giving. Following a lab session, participants could make online donations to charity for a total duration of three months. Our procedure justifying the exclusion of drop-outs consists in requiring participants to collect payments in person flexibly and as known in advance and as highlighted to them later. Our interpretation is that participants who failed to collect their positive payments under these circumstances are likely not to satisfy dominance. If we restrict the sample to subjects who did not drop out, but not otherwise, reminders significantly increase the overall amount of charitable giving. We also find that weekly reminders are no more effective than monthly reminders in increasing charitable giving, and that, in our three months duration experiment, standing orders do not increase giving relative to one-off donations

Restructuring of colloidal aggregates in shear flow: Coupling interparticle contact models with Stokesian dynamics

A method to couple interparticle contact models with Stokesian dynamics (SD) is introduced to simulate colloidal aggregates under flow conditions. The contact model mimics both the elastic and plastic behavior of the cohesive connections between particles within clusters. Owing to this, clusters can maintain their structures under low stress while restructuring or even breakage may occur under sufficiently high stress conditions. SD is an efficient method to deal with the long-ranged and many-body nature of hydrodynamic interactions for low Reynolds number flows. By using such a coupled model, the restructuring of colloidal aggregates under stepwise increasing shear flows was studied. Irreversible compaction occurs due to the increase of hydrodynamic stress on clusters. Results show that the greater part of the fractal clusters are compacted to rod-shaped packed structures, while the others show isotropic compaction.Comment: A simulation movie be found at http://www-levich.engr.ccny.cuny.edu/~seto/sites/colloidal_aggregates_shearflow.htm

Smooth anti reflective three dimensional textures for liquid phase crystallized silicon thin film solar cells on glass

Recently, liquid phase crystallization of thin silicon films has emerged as a candidate for thin film photovoltaics. On 10 amp; 956;m thin absorbers, wafer equivalent morphologies and open circuit voltages were reached, leading to 13.2 record efficiency. However, short circuit current densities are still limited, mainly due to optical losses at the glass silicon interface. While nano structures at this interface have been shown to efficiently reduce reflection, up to now these textures caused a deterioration of electronic silicon material quality. Therefore, optical gains were mitigated due to recombination losses. Here, the SMooth Anti Reflective Three dimensional SMART texture is introduced to overcome this trade off. By smoothing nanoimprinted SiOx nano pillar arrays with spin coated TiOx layers, light in coupling into laser crystallized silicon solar cells is significantly improved as successfully demonstrated in three dimensional simulations and in experiment. At the same time, electronic silicon material quality is equivalent to that of planar references, allowing to reach Voc values above 630 mV. Furthermore, the short circuit current density could be increased from 21.0 mA cm amp; 8722;2 for planar reference cells to 24.5 mA cm amp; 8722;2 on SMART textures, a relative increase of 18 . External quantum efficiency measurements yield an increase for wavelengths up to 700 nm compared to a state of the art solar cell with 11.9 efficiency, corresponding to a jsc, EQE gain of 2.8 mA cm amp; 8722;