High channel density dual operation mode MOS-controlled thyristorwith superior current saturation capability

A 1200-V dual operation mode MCT with low on state voltage drop, high turn-off current and superior current saturation capability has been developed. The dual operation mode MCT overcomes the tradeoff between the on-state voltage drop and the current saturation capability of the conventional IGBT operation by working in a thyristor mode in the on state and in an IGBT mode during the switching transient. This letter reports the device development and demonstrates how the dual operation mode MCT can be beneficial in switching circuit applications     

Factors controlling crack velocity in 7000 series aluminium alloys during fatigue in an aggressive environment

Results obtained for the corrosion fatigue of the aluminium-zinc-magnesium alloy 7017-T651 in seawater at frequencies from 0.1 to 70 Hz are examined on the basis of existing models for predicting crack growth rates. The enhanced growth rates in seawater, compared with dry air, are not compatible with the simple superposition model that may be applied to 7079-T651, unless some secondary process produces several orders of magnitude increase over the stress corrosion rates observed under static loading. The changes in fracture mode observed at certain critical crack velocities, and their dependence upon the square root of the reciprocal of the frequency of loading, are shown to be consistent with an environment-enhanced crack growth rate involving diffusion of hydrogen ahead of the crack tip during each fatigue cycle. Examination of the reported frequency dependence of crack growth rates during corrosion fatigue in steels and other aluminium alloys indicates a need for further work to identify the rate-determining steps for crack propagation during corrosion fatigue. Theories proposed to date are found to be inadequate.     

Assessment and psychological management of recurrent headache disorders.

This article updates earlier reviews of recurrent headache disorders published in 1982 and 1992, selectively reviewing research published since 1990. Current issues in assessment (headache diagnosis, psychophysiology, comorbid psychopathology, quality-of-life assessment, and new assessment technologies) and psychological treatment (efficacy, therapeutic mechanisms, treatment delivery, and integration with drug therapy) are addressed. The author emphasizes the need to adapt psychological treatments to the severity of the headache disorder and to developments in drug therapy. Opportunities for the integration of biological, medical, and psychological science are highlighted. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The energetics of shortening amphibian cardiac muscle

An isolated amphibian cardiac muscle preparation, toad ventricular strip, was used to examine the energetics of shortening. Simultaneous measurements of force and length changes and the associated heat production were made. Both the isometric heat/stress and the enthalpy (heat+work)/load relationships were similar to those previously reported in mammalian cardiac muscle. The activation metabolism was higher in this preparation and, like its mammalian counterpart, was length dependent. The heat production measured in an isometric contraction was approximately 50% higher than that observed at the same stress level in rodent mammalian cardiac muscle. This did not affect the maximum isotonic mechanical efficiency (work divided by enthalpy) of the preparation which, at an afterload of 20% of the maximum stress was 18.1 +/- 1.7% (n = 8). There was no evidence for a shortening heat component in this preparation during isotonic contractions. It appears therefore that the energetics of shortening amphibian cardiac muscle closely resemble the energetics of mammalian cardiac tissue.     

The development of a clinical skills centre

Guidelines produced by the General Medical Council of Great Britain have emphasised the importance of the development of the skills and attitudes appropriate for a junior doctor. Medical schools are in the process of reforming their curricula accordingly. The development of these skills is made increasingly difficult by changes such as short admissions to hospital, increased care in the community, and reduced resources. This article outlines the development of a clinical skills centre as a multidisciplinary unit to improve clinical skills teaching with the aid of up-to-date technology and educational practices. By sharing our experience we aim to provide a practical guide for the development of such units in other medical and nursing colleges.     

Deciphering the biology of Mycobacterium tuberculosis from the complete genome sequence

Countless millions of people have died from tuberculosis, a chronic infectious disease caused by the tubercle bacillus. The complete genome sequence of the best-characterized strain of Mycobacterium tuberculosis, H37Rv, has been determined and analysed in order to improve our understanding of the biology of this slow-growing pathogen and to help the conception of new prophylactic and therapeutic interventions. The genome comprises 4,411,529 base pairs, contains around 4,000 genes, and has a very high guanine + cytosine content that is reflected in the biased amino-acid content of the proteins. M. tuberculosis differs radically from other bacteria in that a very large portion of its coding capacity is devoted to the production of enzymes involved in lipogenesis and lipolysis, and to two new families of glycine-rich proteins with a repetitive structure that may represent a source of antigenic variation.     

The Selective Oxidation of Methanol to Formaldehyde on Iron Molybdate Catalysts and on Component Oxides

The reaction of methanol with an industrial iron molybdate catalyst, and with Fe₂O₃ and with MoO₃, has been investigated with a pulsed flow reactor and temperature-programmed desorption (TPD). The molybdena-based samples show only formaldehyde in TPD as the carbon-containing product, arising from the decomposition of a surface methoxy species. In contrast, haematite yields no formaldehyde, only CO₂ and H₂, which evolve coincidently at 290 °C, and indicates the presence of a formate intermediate on the surface. In turn, the reactor work shows high selectivity to formaldehyde for the molybdate materials and zero for haematite. The iron molybdate sample is more active than the molybdena, conversion beginning at 150 °C for the former and 270 °C for the latter. These data are discussed in terms of a global mechanism for the reaction and a tentative reaction enthalpy profile is proposed. The main differences between the iron and molybdenum samples arise from the stronger binding of oxygen in the former and the higher concentration of cation sites.     

Coping and the self-control of chronic tension headache.

Assigned 39 community residents, mean age 35.2 yrs, with chronic tension headache to 1 of 2 self-control treatment groups, a headache discussion group, or a symptom-monitoring control group. Ss in the 2 self-control treatment groups and in the headache discussion group were provided similar rationales for treatment and were taught to monitor their cognitive responses to stress-eliciting situations. Ss in the 2 self-control treatment groups were also taught either cognitive or both cognitive and relaxation coping skills for controlling tension headache. Ss in the headache discussion group were not provided with specific skills for controlling their headaches but were led in a discussion of the historical roots of their symptoms. Both the self-control treatments and the headache discussion procedure produced substantial reductions in headache that were maintained at a 6-wk follow-up. The symptom-monitoring control group showed no change in headache symptoms. These findings provide additional evidence of the effectiveness of cognitively oriented therapeutic procedures for the treatment of tension headache but raise questions concerning the active ingredients of these treatments. (41 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)