The effect of thermal history and strain rate on the mechanical properties of diethylenetriamine-cured bisphenol-A-diglycidyl ether epoxies

The tensile mechanical properties of diethylenetriamine (DETA)-cured bisphenol-A-diglycidyl ether (DGEBA) epoxies prepared from 9, 11 and 13 phr DETA are reported as a function of thermal history, strain-rate and test temperature. These epoxies exhibit macroscopic yield stresses and >10% ultimate elongations. The mechanical properties of these epoxies exhibit a free-volume dependence as a function of thermal history. Annealing below T_g causes an increase in the macroscopic yield stress and a decrease in the ultimate elongation, whereas quenching from above T_g lowers the yield stress and increases the elongation. These mechanical property modifications are shown to be reversible with reversible thermal–anneal cycles. The activation volumes associated with Eyring's theory for stress-activated viscous flow for the DGEBA-DETA epoxies are within the range of values (9–12 nm³) reported for noncrosslinked polymers. These observations suggest that the DGEBA-DETA epoxies are not as highly crosslinked as would be expected from normal addition reactions of epoxide groups with primary and secondary amines. The formation of lower crosslink density networks is discussed in terms of potential chemical reactions.     

Hypnotic analgesia: A preliminary investigation of quantitated hemispheric electroencephalographic and attentional correlates.

The effects of hypnotically induced analgesia were studied in 6 undergraduate Ss rated as moderately hypnotizable and 5 Ss rated as highly hypnotizable. Subjective pain reports and EEG activation were recorded during 1-min periods of cold-pressor stimulation. Both groups reported decreased pain during hypnosis, but the decrease was greater for the highly hypnotizable group. During hypnotic analgesia, immersion of either the right or the left hand in ice water was correlated with contralateral EEG activation for moderately hypnotizable but not for highly hypnotizable Ss. Lack of contralateral shift was correlated for the whole sample and within groups with success on an attentional task related by previous research to hypnotizability as well as with reports of reduced pain. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Incidence of hiatus hernia and gastro-oesophageal reflux in 1030 prospective barium meal examinations in adult Nigerians

A prospective study to determine the incidence of hiatus hernia and gastro-oesophageal reflux in 1030 consecutive symptomatic adult Nigerian patients undergoing barium meal examination is reported. The results show a very low incidence of hiatus hernia (0-39%) and an equally low incidence of gastro-oesophageal reflux (2-2%) when compared with similar studies in Europe and America. There was a high incidence of duodenal ulcer (23-3%) and a low incidence of gastric ulcer (1-8%), the duodenal/gastric ulcer ratio of 12-1:1 being much higher than in Europe.     

An adaptive finite element method for transient compressible flows

An adaptive finite element method for the solution of time dependent strongly compressible flows in two dimensions is described. The computational domain is represented by an unstructured assembly of linear triangular elements and the mesh adaptation is achieved by local regeneration of the grid, using an error estimation procedure coupled to an automatic triangular mesh generator. Problems involving shock propagation are solved to illustrate the numerical performance of the proposed approach.     

The overjustification effect: A developmental test of self-perception interpretations.

Examined the self-perception explanations of the overjustification effect and their underlying assumptions about cognitive structures based on the operation of multiple-sufficient-causal schemata (MSCS). Two studies were carried out that initially identified the Ss as belonging to the additive, transitional, or discounting stage of MSCS according to the procedure of M. C. Smith (see record 1974-22388-001). A total of 94 5-, 8-, and 11-yr-old schoolchildren were selected as Ss. Half of the Ss were given a tangible reward for an interesting task in the usual overjustification paradigm. The results of both studies indicate that the rewarded groups showed a decline in intrinsic interest that was independent of the Ss' level of functioning on the schema. The author examines objections to the present research strategy and assesses the educational implications of the outcomes. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

采用金属镓层氮化技术在石英衬底上生长多晶GaN

随着多晶GaN材料发光研究的不断深入 ,大面积、价格低廉的多晶GaN基光电器件的研制已成为工业生产中一个重要的研究领域。石英玻璃以其自身特有的优势 ,成为生长多晶GaN材料的较为理想的衬底。本文采用一种新的金属镓层氮化技术 ,使用无定形石英作衬底 ,在常压下制备出多晶GaN。经分析测试表明 ,生长出的多晶GaN为六方结构且质量较好 ,并观察到针状的表面结构     

Improvements in controlled-environment facilities for testing domestic air-to-water heat pumps

A control system is described, based on a microcomputer, which maintains constant temperature and relative humidity in a controlled-environment laboratory used for research on air-to-water heat pumps. The performance of the control system is measured under both steady-state and changing conditions, and optimum values of the control constants are deduced. The temperature can be maintained at the set value to within 0–1°C, and the relative humidity to within 1 per cent, under steady-state conditions. The effects of transients, such as the starting or stopping of the heat pump under test, or the deliberate changing of the controlled conditions, are studied in detail. In addition, a system is described for controlling the temperature of the condenser cooling water, which can be held to within 0–1°C of the set value.