A micro-aerodynamic decelerator based on permeable surfaces of nanofiber mats

This work deals with nonwoven permeable light mats made of submicron-diameter nanofibers. The nanofibers were obtained through electrospinning of polymer solutions. The mats were positioned on light pyramid-shaped frames. These platforms fell freely through the air, apex down, at a constant velocity. The drag of such passive airborne platforms is of significant interest in a number of modern aerodynamics applications including, for example, dispersion of "smart dust" carrying various chemical and thermal sensors, dispersion of seeds, as well as movement of small organisms with bristle appendages. In the present work, drag is measured using the free fall method supplemented by extensive flow visualization. The effects of platform weight, average nanofiber diameter, and porosity of the nonwoven mats on the drag force are studied. The results are compared to data for the corresponding impermeable structures that are covered with plastic wrap. The data are presented in the form of standard dependencies of drag coefficient on the Reynolds number of the structure. It was found that permeable platforms with holes on the order of several microns (which is about ten times the diameter of the nanofibers) are essentially impermeable for airflow.     

Fluorescence of Acridine Orange in inorganic glass matrices

Steady-state, time-resolved and polarization-resolved fluorescence studies of glasses doped with acridine orange with concentrations near 10^–3 M/L are reported. It was found that at this concentration a noticeable part of dye molecules exists in the form of dimers. By means of a polarization-resolved spectroscopic technique the structure of dimers was found to be consistent with the simple exciton theory.     

Neutron multiplicities in inelastic collisions of132Xe with197Au

Neutrons have been detected in coincidence with charged reaction products in inelastic scattering of 7.5 MeV/u¹³²Xe ions from¹⁹⁷Au. The deduced neutron multiplicities associated with the heavy and light fragment, respectively, are roughly proportional to the total kinetic energy loss, and their ratios are close to the Au-Xe mass ratio for allQ-values. These results and the measured neutron energy spectra are consistent with the assumptions of thermal equilibrium between the fragments at scission, and of neutron emission from fully accelerated fragments. For deep inelastic events, the measured absolute multiplicities are smaller than expected from statistical model calculations, but an effect due to pre-equilibrium emission of particles — as suggested by an earlier analysis of the present data [1] — cannot be definitely established.     

14N PNQR investigation of the phase transition in s-triazine

¹⁴N PNQR frequencies, linewidths and spin lattice relaxation times were measured in s-triazine between 77° and 280°K. A second order phase transition was observed at 198.5°K. The temperature dependence and anisotropy of the relaxation times indicate a reorientation of the molecule around its three-fold axis.     

Hidden neuronal correlations in cultured networks

Utilization of a clustering algorithm on neuronal spatiotemporal correlation matrices recorded during a spontaneous activity of in vitro networks revealed the existence of hidden correlations: the sequence of synchronized bursting events (SBEs) is composed of statistically distinguishable subgroups each with its own distinct pattern of interneuron spatiotemporal correlations. These findings hint that each of the SBE subgroups can serve as a template for coding, storage, and retrieval of a specific information.     

CO2 activation by metal−ligand-cooperation mediated by iridium pincer complexes

Abstract

Herein we report the reversible activation of CO₂ by the dearomatized complex [(^tBuPNP*)Ir(COE)] (1) and by the aromatized complex [(^tBuPNP)Ir(C₆H₅)] (2) via metal-ligand cooperation (MLC) (^tBuPN = 2,6-bis-(di-tert-butylphosphinomethyl)pyridine; ^tBuPNP* = deprotonated PNP; COE = cyclooctadiene). The [1,3]-addition of CO₂ to 1 and 2 is reversible at ambient temperature. While the dearomatized complex 1 reacts readily at ambient temperature with CO₂ in THF or benzene, complex 2 reacts with CO₂ upon heating in benzene at 80 °C or at ambient temperature in THF. The novel aromatized complex [(^tBuPNP)IrCl] (10) does not react with CO₂. Based on the reactivity patterns of 1, 2, and 10 with CO₂, we suggest that CO₂ activation via MLC takes place only via the dearomatized species, and that in the case of 2 THF plays a role as a polar solvent in facilitating formation of the dearomatized hydrido phenyl complex intermediate (complex II).     

A Dynamic Alternating Direction of Multipliers for Nonconvex Minimization with Nonlinear Functional Equality Constraints

Journal of Optimization Theory and Applications - This paper studies the minimization of a broad class of nonsmooth nonconvex objective functions subject to nonlinear functional equality...     

Mitochondria-derived reactive oxygen species mediate blue light-induced death of retinal pigment epithelial cells

Throughout the lifetime of an individual, light is focused onto the retina. The resulting photooxidative stress can cause acute or chronic retinal damage. The pathogenesis of age-related macular degeneration (AMD), the leading cause of legal blindness in the developed world, involves oxidative stress and death of the retinal pigment epithelium (RPE) followed by death of the overlying photoreceptors. Evidence suggests that damage due to exposure to light plays a role in AMD and other age-related eye diseases. In this work a system for light-induced damage and death of the RPE, based on the human ARPE-19 cell line, was used. Induction of mitochondria-derived reactive oxygen species (ROS) is shown to play a critical role in the death of cells exposed to short-wavelength blue light (425 +/- 20 nm). ROS and cell death are blocked either by inhibiting the mitochondrial electron transport chain or by mitochondria-specific antioxidants. These results show that mitochondria are an important source of toxic oxygen radicals in blue light-exposed RPE cells and may indicate new approaches for treating AMD using mitochondria-targeted antioxidants.     

Importance of solvent accessibility and contact surfaces in modeling side-chain conformations in proteins

Contact surface area and chemical properties of atoms are used to concurrently predict conformations of multiple amino acid side chains on a fixed protein backbone. The combination of surface complementarity and solvent-accessible surface accounts for van der Waals forces and solvation free energy. The scoring function is particularly suitable for modeling partially buried side chains. Both iterative and stochastic searching approaches are used. Our programs (Sccomp-I and Sccomp-S), with relatively fast execution times, correctly predict chi1 angles for 92-93% of buried residues and 82-84% for all residues, with an RMSD of approximately 1.7 A for side chain heavy atoms. We find that the differential between the atomic solvation parameters and the contact surface parameters (including those between noncomplementary atoms) is positive; i.e., most protein atoms prefer surface contact with other protein atoms rather than with the solvent. This might correspond to the driving force for maximizing packing of the protein. The influence of the crystal packing, completeness of rotamer library and precise positioning of Cbeta atoms on the accuracy of side-chain prediction are examined. The Sccomp-S and Sccomp-I programs can be accessed through the Web (http://sgedg.weizmann.ac.il/sccomp.html) and are available for several platforms.     

The Nakamura Theorem for coalition structures of quota games

This paper considers a model of society $S$ with a finite number of individuals,n, a finite set off alternatives, Ω effective coalitions that must contain ana priori given numberq of individuals. Its purpose is to extend the Nakamura Theorem (1979) to the quota games where individuals are allowed to form groups of sizeq which are smaller than the grand coalition. Our main result determines the upper bound on the number of alternatives which would guarantee, for a given e andq, the existence of a stable coalition structure for any profile of complete transitive preference relations. Our notion of stability, $S$ -equilibrium, introduced by Greenberg-Weber (1993), combines bothfree entry andfree mobility and represents the natural extension of the core to improper or non-superadditive games where coalition structures, and not only the grand coalition, are allowed to form.