Nuclear Magnetic Resonance Studies of Silicon Carbide Polytypes

The ²⁹Si MAS NMR spectra of the 2H, 4H, 6H, and 3C polytypes of silicon carbide are presented. An attempt is made to correlate differences in the chemical shifts with local atomic environment. The results of the analysis of the spectra of pure polytypes are used as a basic for the interpretation of the spectra of mixed polytypes and a discussion of the crystallinity and impurity levels of different samples. Carbon-13 chemical shifts obtained from spectra of the same polytypes are also tabulated.     

Stability of everyday memory in age-associated memory impairment: A longitudinal study.

Everyday memory performance was examined longitudinally in 2 groups of Ss meeting the diagnostic criteria for age-associated memory impairment (AAMI). One group of 157 participants in a drug trial for reversing memory loss in AAMI was tested over multiple sessions. The other group of 75 persons did not participate in a drug trial and thus was tested only twice. Both groups were retested for longitudinal follow-up about 4 yrs after initial session. Follow-up test performance remained fairly stable relative to initial performance in both groups. The drug study group showed large practice effects during the course of the drug studies, but these effects subsided after the drug studies' end. Implications regarding memory decline in the normal elderly and neuropsychological measurement issues are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of surface treatment on the photoelectrochemical behaviour of Y-Ba-Cu-O thin films

Y-Ba-Cu-O films with different surface treatments have been studied by photoelectrochemical and XPS measurements. The influence of etching by bromine in ethanol of these films has been followed by means of the electrochemical oxidation of ferrocene in an aprotic electrolyte. From the dependence of dark and photocurrent on etching time it is concluded that Y-Ba-Cu-O thin films on LaAlO₃ are covered by a 1, 1nm thick nonstoichiometric surface layer. The cathodic polarization of Y-Ba-Cu-O at -0,9 V vs. Ag/AgCl in acetonitrile/0,1 M lithium perchlorate leads to the formation of a lithium-containing, oxygen-enriched surface layer. The photoelectrochemical response of the reduced films is similar to that of cuprous oxide and passive layers on copper.     

'Multifrequency' location and clustering of sequence patterns from proteins

In previous work, we have shown that a set of characteristics, defined as (code frequency) pairs, can be derived from a protein family by the use of a signal-processing method. This method enables the location and extraction of sequence patterns by taking into account each (code frequency) pair individually. In the present paper, we propose to extend this method in order to detect and visualize patterns by taking into account several pairs simultaneously. Two 'multifrequency' methods are described. The first one is based on a rewriting of the sequences with new symbols which summarize the frequency information. The second method is based on a clustering of the patterns associated with each pair. Both methods lead to the definition of significant consensus sequences. Some results obtained with calcium-binding proteins and serine proteases are also discussed.     

Machine translation of non-literary texts: Some Canadian experiences

A survey was carried out of past and current Canadian experiences with machine-aided translation (MAT) systems of non-literary texts in one government institution and three industrial settings. Each organization requires a great deal of translation and had conducted several experiments in the use of MAT. The survey supports positive conclusions about the prospects for expanded use of computers in translation.The authors express their thanks to all those who helped in the preparation of this paper. We are particularly grateful to the staff of the translation departments of the organizations mentioned in the paper for their kind cooperation and their willingness to answer our questions: Chantal Delorme ofIBM Canada, Lorraine Desmarais and Mr. Plamondon of Bell Canada, Pierre Tellier of the Department of the Secretary of State, Maria Russo and Raymond Lapointe of the Xerox Corporation. Furthermore we thank Prof. Graeme Hirst for helpful discussion.