Reconstructing the abundance of Dounreay hot particles on an adjacent public beach in Northern Scotland

Following the discovery of a number of hot particles in the offshore environment of Dounreay on the North Coast of Scotland in 1997, the Dounreay site operator was required to introduce rapid and extensive beach monitoring. Since the introduction of vehicular based beach monitoring in 1999 there have been two further generations of beach monitoring equipment, developed to satisfy regulatory requirements for particle detection and in response to the recommendations of the Dounreay Particles Advisory Group (DPAG). This paper reports the results of DPAG's review of beach monitoring capabilities, evaluating the factors influencing detection capability, assessing the likely monthly particle abundance and whether there has been any real change in particle arrivals with time. The incorporation of real time kinematic GPS has enabled changes in beach elevation to be mapped, and thus allowed the assessment of whether particles detected have recently arrived or may have been buried undisturbed for extended periods of time. The results focus on Sandside Beach from which, between 1984 and December 2009, 150 particles have been recovered. This is by far the largest number of particles found on a Caithness Beach with the exception of the Foreshore of the Dounreay site. The results suggested that there is no evidence for a change in the rate of particle arrivals and DPAG estimated that there is a 1 in 20 million chance of encountering a relevant particle via contact with the skin on Sandside Beach.     

Effect of low temperature upon vitality of Saccharomyces cerevisiae phospholipid mutants

The phospholipid metabolism of Saccharomyces cerevisiae plays a central role in its adaptation to low temperatures. In order to detect the key genes in this adaptation, various phospholipid mutants from the EUROSCARF collection of Saccharomyces cerevisiae BY4742 were tested to ascertain whether the suppression of some genes could improve the fermentation vitality of the cells at low temperature. The cell vitality and phospholipid composition of these mutants were analysed. Some knockouts improved (hmn1Δ) or impaired (cho2Δ and psd1Δ) their vitality at low temperature (13 °C) but were not affected at optimum temperature (25 °C). A common trait of the mutants that had some defect in vitality was a lower concentration of phosphatidylcholine and/or phosphatidylethanolamine. The supplementation with choline allowed them to recover viability, probably by synthesis through the Kennedy pathway. Hmn1Δ showed a lower concentration of phosphatidylcholine, which explains the dominant role of the de novo pathway in cellular phosphatidylethanolamine and phosphatidylcholine vs the Kennedy pathway. The absence of such genes as CRD1 or OPI3 produced important changes in phospholipid composition. Cardiolipin was not detected in crd1Δ but phosphatidylglycerol circumvents most of the functions assigned to CL. The considerable reduction in PC diminished the cell vitality of opi3Δ at both temperatures, although the decrease at 13 °C was more marked. Copyright © 2012 John Wiley & Sons, Ltd.     

On a Thomas-Fermi Model of “Hollow” Atom

Abstract

A Thomas-Fermi model of a spherical shell of positive charge is investigated, under various boundary conditions. The electron distribution and the ionization charge are given particular attention.     

改善比较器瞬态响应的肖特基二极管

在先进的IC比较器中,可编程滞后量消除了以OV为中心的差分输入电压噪声(参考文献1),并且如果比较器的差分输入电压很低,或者随时间变化的速度很慢,则可以改善它的响应.例如,Analog Devices公司的ADCMP609比较器使你能用一个电阻把它的滞后量设定在0至160 mV之间,该电阻连在HYS(即"滞后量")引脚和地之间.但上述电压范围对于某些应用也许太窄.凭借图1中的电路你可以利用两个施加给非逆变输入端的基准电压来加宽滞后量范围.     

Porous anodic alumina formed by anodization of aluminum alloy (AA1050) and high purity aluminum

A two-step anodization process performed at 0 °C was used to prepare highly ordered porous anodic alumina on the AA1050 alloy and high purity aluminum foil. The anodizing of both substrates was carried out in 0.3 M sulfuric acid and 0.3 M oxalic acid baths at 25 V and 40 V, respectively. The effect of the extended duration of the second anodizing step on pore order degree and structural features of AAO membranes was studied. The presence of alloying elements affects not only the rate of oxide growth but also the microstructure of the anodic film. It was found that pore circularity and regularity of pore arrangement in AAO membranes formed on the AA1050 alloy were always worse than those observed on the pure Al substrate. The structural features, such as pore diameter, interpore distance, wall thickness, barrier layer thickness, porosity and pore density of porous anodic alumina formed on AA1050 are a little different from those obtained for high purity Al. The extended time of the second anodizing step, up to 16 h does not affect significantly the regularity of pore order and all structural features of AAO membranes, independently of the anodizing electrolyte.     

Effect of ionic liquids and surfactants on zinc oxide nanoparticle activity in crosslinking of acrylonitrile butadiene elastomer

The goal of this work was to study the influence of several ionic liquids and cationic surfactants on zinc oxide nanoparticle activity in sulfur vulcanization of acrylonitrile butadiene elastomer (NBR). In this article, we discuss the effect of ionic liquids and surfactants on the cure characteristics, crosslink density, and distribution in the elastomer network as well as on mechanical properties of the acrylonitrile butadiene rubber. Ionic liquids (alkylimidazolium salts) and cationic surfactants (alkylammonium bromides) decrease the vulcanization time of rubber compounds. Their application results in the increase of vulcanizate crosslink density as well as of the heterogeneity of elastomer network. The influence of ionic liquids on the acrylonitrile butadiene elastomer properties depends on the anion present in the molecule and on the length of alkyl chains attached to the imidazolium ring. The most active ionic liquids seem to be the ones with the 1‐butyl‐3‐methylimidazolium cation or the BF₄^‐ anion. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Wetting properties of glycerol on silicon,native SiO2, and bulk SiO2 by scanning polarization force microscopy

Scanning polarization force microscopy, a relatively new non-contact scanning probe microscopy technique, was applied in order to investigate the properties of liquid surfaces (droplets), such as: topography, microscopic contact angle θ, surface potential energy P(e), spreading coefficient S, and disjoining pressure П. Investigations were carried out on glycerol droplets deposited on surfaces of bare silicon, silicon covered with native oxide, and bulk silicon oxide. Contact angle values were determined from directly measured topography profiles of micro- and nanodroplets. Values of surface potential energy, spreading coefficient, and disjoining pressure were calculated based on a model of the dependence of contact angle on droplet height. The results of these experiments offer valuable insights into the mechanisms of wetting phenomena at the microscopic scale.