Polishing of quartz by rapid etching in ammonium bifluoride

The etch rate and surface roughness of polished and lapped AT-cut quartz subjected to hot (90, 110, and 130 degrees C), concentrated (50, 65, 80 wt %) ammonium bi-fluoride have been investigated. Having used principal component analysis to verify experimental solidity and analyze data, we claim with confidence that this parameter space does not, as elsewhere stated, allow for a polishing effect or even a preserving setting. Etch rates were found to correlate well, and possibly logarithmically, with temperature except for the hottest etching applied to lapped material. Roughness as a function of temperature and concentration behaved well for the lapped material, but lacked systematic variation in the case of the polished material. At the lowest temperature, concentration had no effect on etch rate or roughness. Future efforts are targeted at temperatures and concentrations closer to the solubility limit.     

Invited article: Electric solar wind sail: toward test missions

The electric solar wind sail (E-sail) is a space propulsion concept that uses the natural solar wind dynamic pressure for producing spacecraft thrust. In its baseline form, the E-sail consists of a number of long, thin, conducting, and centrifugally stretched tethers, which are kept in a high positive potential by an onboard electron gun. The concept gains its efficiency from the fact that the effective sail area, i.e., the potential structure of the tethers, can be millions of times larger than the physical area of the thin tethers wires, which offsets the fact that the dynamic pressure of the solar wind is very weak. Indeed, according to the most recent published estimates, an E-sail of 1 N thrust and 100 kg mass could be built in the rather near future, providing a revolutionary level of propulsive performance (specific acceleration) for travel in the solar system. Here we give a review of the ongoing technical development work of the E-sail, covering tether construction, overall mechanical design alternatives, guidance and navigation strategies, and dynamical and orbital simulations.     

The ventricular conduction system - ultrastructure and function

The ultrastructure and function of the ventricular conducting system in animals are briefly reviewed. As the ventricular conducting cells are resistant to anoxia, an adequate ultrastructural preservation has been obtained in human autopsy material. In a case of cardiomyopathy, abnormalities in the conducting cells are related to current theories of abberant cardiac rhythm. We propose that further knowledge of the human conduction system can be obtained by extended studies of this kind.     

A study of the combined effects of kinetic parameters and flow models on conversions for second order reactions

The present paper is a study of the interplay between kinetic parameters and different flow patterns and its effect on fractional conversions for second order reactions with arbitrary stoichiometry and arbitrary ratios between the initial concentrations of the reactants. The models studied are the normal, segregated and maximum-mixed axial dispersion and tanks-in-series models. The calculations required have been performed with the aid of digital simulation and the results are presented in diagrams making possible the determination of the fractional conversion for ten different models. When plotted as a function of a reaction rate group the absolute value of the difference between the conversions for the normal and segregated models always attains its highest value for the limiting model represented by complete backmixing, while this difference is zero for the opposite limiting model, i.e. plug flow. In the case of maximum-mixed and normal models this difference attains its highest value between plug flow and complete backmixing, but the exact value is dependent on other parameter values. The diagrams indicate that it is more important to choose the proper model for certain parameter combinations than for others: the maximum difference between the conversions for different models is about 8%; the lowest is zero.     

Employment discrimination: Authority figures' demographic preferences and followers' affective organizational commitment.

The authors used theories of organizational commitment and obedience to authority to explain employment discrimination. In Study 1, employees participated in an experimental simulation of their work. An organizational authority's demographic preferences led to employment discrimination. As expected, affective organizational commitment moderated this effect, such that it was stronger for more committed employees. In Study 2, another sample of employees completed a survey that included an employment discrimination scenario. A model of linkages from affective organizational commitment to submissiveness to organizational authorities to employment discrimination fit the data well, after controlling for prejudicial attitudes and authoritarianism. Submissiveness to organizational authorities mediated the relationship between affective organizational commitment and employment discrimination. The authors discuss the importance of studying employment discrimination as an organizational and not just an intergroup phenomenon. (PsycINFO Database Record (c) 2010 APA, all rights reserved)