Dehydration and ionic conductance quantization in nanopores

There has been tremendous experimental progress in the last decade in identifying the structure and function of biological pores (ion channels) and fabricating synthetic pores. Despite this progress, many questions still remain about the mechanisms and universal features of ionic transport in these systems. In this paper, we examine the use of nanopores to probe ion transport and to construct functional nanoscale devices. Specifically, we focus on the newly predicted phenomenon of quantized ionic conductance in nanopores as a function of the effective pore radius - a prediction that yields a particularly transparent way to probe the contribution of dehydration to ionic transport. We study the role of ionic species in the formation of hydration layers inside and outside of pores. We find that the ion type plays only a minor role in the radial positions of the predicted steps in the ion conductance. However, ions with higher valency form stronger hydration shells, and thus, provide even more pronounced, and therefore, more easily detected, drops in the ionic current. Measuring this phenomenon directly, or from the resulting noise, with synthetic nanopores would provide evidence of the deviation from macroscopic (continuum) dielectric behavior due to microscopic features at the nanoscale and may shed light on the behavior of ions in more complex biological channels.Comment: 13 pages, 10 figure

A Finite-Size Scaling Study of a Model of Globular Proteins

Grand canonical Monte Carlo simulations are used to explore the metastable fluid-fluid coexistence curve of the modified Lennard-Jones model of globular proteins of ten Wolde and Frenkel (Science, v277, 1975 (1997)). Using both mixed-field finite-size scaling and histogram reweighting methods, the joint distribution of density and energy fluctuations is analyzed at coexistence to accurately determine the critical-point parameters. The subcritical coexistence region is explored using the recently developed hyper-parallel tempering Monte Carlo simulation method along with histogram reweighting to obtain the density distributions. The phase diagram for the metastable fluid-fluid coexistence curve is calculated in close proximity to the critical point, a region previously unattained by simulation.Comment: 17 pages, 10 figures, 2 Table

Electron-beam modification of coating-aluminum substrate systems

Multiphase surface alloys with improved strength and tribological characteristics have been synthesized by exposing coating/A7 substrate systems to a pulsed electron beam. Optimum modes of electron-ion-plasma treatment of commercially pure aluminum have been found at which the wear resistance and hardness of the surface layer were observed to increase by a factor of about 7.5 and up to 18, respectively

Influence of Phase Diffuser Dynamics on Scintillations of Laser Radiation in Earth Atmosphere: Long-Distance Propagation

The effect of a random phase diffuser on fluctuations of laser light (scintillations) is studied. Not only spatial but also temporal phase variations introduced by the phase diffuser are analyzed. The explicit dependence of the scintillation index on finite-time phase variations is obtained for long propagation paths. It is shown that for large amplitudes of phase fluctuations, a finite-time effect decreases the ability of phase diffuser to suppress the scintillations.Comment: 15 pages, 4 figure

Saint-Petersburg Academic Fine Art in the Space of Contemporary Creative Industries

В последние десятилетия в Петербурге активно развиваются креативные индустрии, формируются все новые креативные пространства, нацеленные на взаимодействие разных художественных институций и репрезентацию современного искусства. Важно оценить, какую роль играет профессиональное академическое искусство, представленное традиционными школами и отдельными мастерами в развитии новых арт-пространств, появившихся в Северной столице. Как соотносится академическая школа с её традиционными устоями с потребностями посетителей арт-пространств, в чем роль современных художников, занимающихся преобразованием культурного досуга населения Петербурга? В статье предлагается искусствоведческий обзор современной ситуации существования академического искусства в рамках петербургской креативной индустрии, представляющей различные художественные направленияСreative industries have been actively developing during the in recent decades in Saint Petersburg more and more new creative spaces aimed at the interaction of various art institutions and representation of contemporary art have been formed. The study tested the role professional academic art, as represented by traditional schools and individual masters in the development of the new art spaces that have appeared in Saint Petersburg. How does the academic school with its traditional ways relate to the needs of visitors of art spaces, what is the role of contemporary artists engaged in the transformation of the cultural leisure time of visitors of creative spaces? The article offers an art history review of the current situation of academic art within St. Petersburg’s creative industries, representing different artistic movement

Are We There Yet?: The Development of a Corpus Annotated for Social Acts in Multilingual Online Discourse

We present the AAWD and AACD corpora, a collection of discussions drawn from Wikipedia talk pages and small group IRC discussions in English, Russian and Mandarin. Our datasets are annotated with labels capturing two kinds of social acts: alignment moves and authority claims. We describe these social acts, describe our annotation process, highlight challenges we encountered and strategies we employed during annotation, and present some analyses of resulting data set which illustrate the utility of our corpus and identify interactions among social acts and between participant status and social acts and in online discourse

Mössbauer characterization of microbially mediated iron and manganese ores of variable geological ages

A combination of various techniques was applied to investigate the mineralogy of the Neoproterozoic Urucum iron and manganese deposit (Brazil) and Carboniferous and Permian manganese carbonate deposits (China). The examined deposits exhibited signs of microbial mediation from Fe and Mn bacteria and cyanobacteria. The studied samples showed diversity in their composition and particle size. Probes from Urucum deposit revealed that the rocks consist mainly of hematite, showing Mn substitution which reflects the oxidation of Mn on the active surface of Fe-rich biomat. Nanominerals occurring in significant concentration also supported the microbial contribution to the formation of these ores. Representative samples of Neoproterozoic and Permian deposits showed considerable amount of mixed carbonates with variable composition. 57Fe Mössbauer spectroscopy analysis supported by X-ray diffraction and transmission electron microscopy data provided a detailed characterization of Fe-rich mineral phases of the samples, including metal ratio outlooks, particle size dimension and presence and type of impurities. Integrity and high resolution of the methods allowed to determine new features of the samples reflecting important signatures of microbial activity revealing the biogeochemistry of the biomat formation

Protective Effect of Meso-Tetrakis-(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin on the In Vivo Impact of Trimethyltin Chloride on the Antioxidative Defense System

The in vivo effect of trimethyltin chloride (Me(3)SnCl), free base meso-tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)porphyrin (R′(4)PH(2)) and their equimolar mixture, on the enzymatic activity of catalase (CAT), superoxide dismutase (SOD), and on the total content of free sulfhydryl groups has been studied in rat liver and kidney. It was demonstrated that the simultaneous treatment of tested animals with the combination of Me(3)SnCl and R′(4)PH(2) reduced the toxic impact of Me(3)SnCl