Electrical conductivity of cellular Si/SiC ceramic composites prepared from plant precursors

Electrical conductivity (sigma_dc) of the cellular Si/SiC ceramic composites has been measured over a temperature range 25-1073 K while the thermoelectric power (S) has been measured over 25-300 K. Remarkably, these cellular compounds developed through biomimetic route - where the ceramic system grows within a plant bio-template retaining the structural intricacies of the native templates - are found to exhibit excellent mechanical, thermal, and electrical properties quite comparable to or even better than those of the systems prepared through conventional ceramic route. The electrical conductivity measured parallel (sigma||) and perpendicular (sigma+) to the growth axes of the native plants, depicts nearly temperature-independent anisotropy (sigma+/sigma||) of the order \~2 while the thermoelectric power is nearly isotropic. The charge conduction across the entire temperature range is found to follow closely the variable range hopping (VRH) mechanism. The conductivity anisotropy appears to be driven primarily by the unique microcellular morphology of the bio-templates which can be exploited in many electrical applications.Comment: 22 pages including 6 figures; pdf only; submitted to J. Appl. Phy

Special features of the 9^9Be→\to2He fragmentation in emulsion at an energy of 1.2~A~GeV

The results of investigations of the relativistic $^9$Be nucleus fragmentation in emulsion which entails the production of two He fragments of an energy of 1.2~A~GeV are presented. The results of the angular measurements of the $^9$Be$\to$2He events are analyzed. The $^9$Be$\to^8$Be+n fragmentation channel involving the $^8$Be decay from the ground (0$^+$) and the first excited (2$^+$) states to two $\alpha$ particles is observed to be predominant.Comment: 10 pages, 6 figures, conference: Conference on Physics of Fundamental Interactions, Moscow, Russia, 5-9 Dec 2005 (Author's translation

Targeted JAM-C deletion in germ cells by Spo11-controlled Cre recombinase

Meiosis is a crucial process for the production of functional gametes. However, the biological significance of many genes expressed during the meiotic phase remains poorly understood, mainly because of the lethal phenotypes of the knockout mice. Functional analysis of such genes using the conditional knockout approach is hindered by the lack of suitable Cre transgenic lines. We describe here the generation of transgenic mice expressing Cre recombinase under the control of the meiotic Spo11 gene. Using LacZ-R26(loxP) and EYFP-R26(loxP) reporter mice, we show the specific expression and activity of Cre during meiosis in males and females. Spo11(Cre) mice were then crossed with floxed Nbs1 and JAM-C mice to produce conditional knockouts. A strong reduction of Nbs1 and JAM-C protein levels was found in the testis. Although Nbs1-deleted mice developed minor gonadal abnormalities, JAM-C-knockout mice showed a spermiogenetic arrest, as previously described for the null mice. These results provide strong evidence that Spo11(Cre) transgenic mice represent a powerful tool for deleting genes of interest specifically in meiotic and/or in postmeiotic germ cells

FeP Nanocatalyst with Preferential [010] Orientation Boosts the Hydrogen Evolution Reaction in Polymer-Electrolyte Membrane Electrolyzer

The development of nonprecious metal electrocatalysts for polymer-electrolyte membrane (PEM) water electrolysis is a milestone for the technology, which currently relies on rare and expensive platinum-group metals. Half-cell measurements have shown iron phosphide materials to be promising alternative hydrogen evolution electrocatalysts, but their realistic performance in flow-through devices remains unexplored. To fill this gap, we report herein the activity and durability of FeP nanocatalyst under application-relevant conditions. Our facile synthesis route proceeds via impregnation of an iron complex on conductive carbon support followed by phosphorization, giving rise to highly crystalline nanoparticles with predominantly exposed [010] facets, which accounts for the high electrocatalytic activity. The performance of FeP gas diffusion electrodes toward hydrogen evolution was examined under application-relevant conditions in a single cell PEM water electrolysis at 22 °C. The FeP cathode exhibited a current density of 0.2 A cm–2 at 2.06 V, corresponding to a difference of merely 0.07 W cm–2 in power input as compared to state-of-the-art Pt cathode, while outperforming other nonprecious cathodes operated at similar temperature. Quantitative product analysis of our PEM device excluded the presence of side reactions and provided strong experimental evidence that our cell operates with 84–100% Faradaic efficiencies and with 4.1 kWh Nm–3 energy consumption. The FeP cathodes exhibited stable performance of over 100 h at constant operation, while their suitability with the intermittency of renewable sources was demonstrated upon 36 h operation at variable power inputs. Overall, the performance as well as our preliminary cost analysis reveal the high potential of FeP for practical applications.</p

Propagation of Magnetic Fields from Electrical Domestic Appliances

The article presents a research into propagation of magnetic fields from electrical domestic devices. A safe distance at which magnetic induction does not exceed the background level is determined for each type of devices. It is proved that there are two stages of increasing magnetic induction as the distance from the source increases. At the first stage magnetic induction rises and electromagnetic field is formed. At the second stage exponential decrease of magnetic field induction takes place. Mathematical regularities of propagation of magnetic field from electrical domestic devices are experimentally educed

A Fixed-Parameter Algorithm for the Max-Cut Problem on Embedded 1-Planar Graphs

We propose a fixed-parameter tractable algorithm for the \textsc{Max-Cut} problem on embedded 1-planar graphs parameterized by the crossing number $k$ of the given embedding. A graph is called 1-planar if it can be drawn in the plane with at most one crossing per edge. Our algorithm recursively reduces a 1-planar graph to at most $3^k$ planar graphs, using edge removal and node contraction. The \textsc{Max-Cut} problem is then solved on the planar graphs using established polynomial-time algorithms. We show that a maximum cut in the given 1-planar graph can be derived from the solutions for the planar graphs. Our algorithm computes a maximum cut in an embedded 1-planar graph with $n$ nodes and $k$ edge crossings in time $\mathcal{O}(3^k \cdot n^{3/2} \log n)$.Comment: conference version from IWOCA 201

Topology of "white" stars in relativistic fragmentation of light nuclei

In the present paper, experimental observations of the multifragmentation processes of light relativistic nuclei carried out by means of emulsions are reviewed. Events of the type of "white" stars in which the dissociation of relativistic nuclei is not accompanied by the production of mesons and the target-nucleus fragments are considered. A distinctive feature of the charge topology in the dissociation of the Ne, Mg, Si, and S nuclei is an almost total suppression of the binary splitting of nuclei to fragments with charges higher than 2. The growth of the nuclear fragmentation degree is revealed in an increase in the multiplicity of singly and doubly charged fragments with decreasing charge of the non-excited part of the fragmenting nucleus. The processes of dissociation of stable Li, Be, B, C, N, and O isotopes to charged fragments were used to study special features of the formation of systems consisting of the lightest $\alpha$, d, and t nuclei. Clustering in form of the $^3$He nucleus can be detected in "white" stars via the dissociation of neutron-deficient Be, B, C, and N isotopes.Comment: 20 pages, 3 figures, 9 tables, conference: Conference on Physics of Fundamental Interactions, Moscow, Russia, 1-5 Mar 2004.(Author's translation

Dynamics of railway freight vehicles

This paper summarises the historical development of railway freight vehicles and how vehicle designers have tackled the difficult challenges of producing running gear which can accommodate the very high tare to laden mass of typical freight wagons whilst maintaining stable running at the maximum required speed and good curving performance. The most common current freight bogies are described in detail and recent improvements in techniques used to simulate the dynamic behaviour of railway vehicles are summarised and examples of how these have been used to improve freight vehicle dynamic behaviour are included. A number of recent developments and innovative components and sub systems are outlined and finally two new developments are presented in more detail: the LEILA bogie and the SUSTRAIL bogie