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The history of the AEI (formerly Metrovick) electron microscopes is traced from the very first model in 1935 until the company ceased production of the instrument some 10 years ago. The new concepts incorporated in successive designs are outlined, so as to set them in the context of developments elsewhere.  相似文献   

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Artificial insemination (AI) has a considerable cultural significance in addition to its economic and technical impact. This study is the first to examine the history of its application to pigs, and uses evidence provided directly by both the scientists involved in its development, and some of the farmers who were among the first to use it, in addition to archival and published sources, to show how the scientific studies of the 1950s evolved into a widely available commercial product by the 1980s. It describes the initial scientific work and quantifies the extent to which the technique was used at various points in time, showing that by 1990 nearly one half of UK pig herds were using AI for more than 25% of all services. It traces changes in the techniques employed and argues that these were the result of a multi-dimensional process of contemporaneous change. The various dimensions are identified firstly as authorities, meaning the people and organisations controlling the perception, administration, control, and so on, of the technique; secondly the discourses employed by the authorities; and thirdly the media by which the discourses were disseminated. Finally, it is suggested that this approach might be used more widely to examine the construction of other technologies.  相似文献   

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A national survey of breeding Barn Owls was undertaken between 1995 and 1997 using intensive fieldwork methods within a stratified sample of 1100 2 × 2-km survey squares selected at random from those available. Each year, fieldwork was divided into two sessions: one to locate potential nest-sites (winter session) and one to determine occupancy of these sites (summer session). Fieldworkers spent an average of 30 hours on fieldwork within each survey square. The survey produced national population estimates of 2830 (95% confidence intervals: 1952–3761) breeding pairs for 1995, 3967 (95% CI: 2785–5252) for 1996 and 3951 (95% CI: 2769–5214) for 1997. Analysis taking account of the poor coverage in certain regions of high Barn Owl density in 1995 suggests that a population estimate of 3480 would be more accurate for that year. Regional and temporal variations in estimates were examined and interpreted in relation to Barn Owl productivity and ecology. Validation of fieldwork efficiency was carried out within a random selection of the available survey tetrads, demonstrating that fieldworkers achieved a high degree of survey reliability. This paper provides a baseline population estimate and standardized, repeatable methods, allowing future population changes to be monitored effectively.  相似文献   

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K. J. Williams  J. B. Osbaldeston 《CMAJ》1965,92(21):1117-1124
Before a hospital medical staff can realistically accept responsibility for the professional practices of its members, a principle initially fostered by the American College of Surgeons and adopted by both the Canadian and American accreditation programs, it must have an effectively functioning medical staff organization. The medical advisory committee is the most important committee of the medical staff organization. A representative composition, adherence to sound administrative principles, and recognition of its prime functions of co-ordination, supervision and jurisdiction will permit this committee—and the total medical staff organization—to discharge adequately the very important responsibilities delegated to them by the governing board of the hospital. Properly structured medical staff bylaws with clearly defined terms of reference assist the smooth functioning of the “cabinet” of the medical staff and safeguard the prerogatives of the individual members of the staff.  相似文献   

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In the 1970s, 1% of the UK population consulted with dyspepsia; fiberoptic gastroscopy allowed biopsy specimens under direct vision enabling systematic histopathology. Steer et al described clusters of flagellated bacteria closely apposed to the gastric epithelium associated with chronic active gastritis. The first UK series of Helicobacter pylori following Marshall's 1983 visit to Worcester confirmed the association of H. pylori with gastritis. UK researchers completed much early helicobacter research as there were many UK campylobacteriologists. Steer and Newell proved the Campylobacter-like organisms grown on culture were the same as those seen in the gastric mucosa using antiserum raised by inoculating rabbits with H. pylori from cultures. Wyatt, Rathbone, and others showed a strong correlation between the number of organisms, type and severity of acute gastritis, immunological response, and bacterial adhesion similar to enteropathogenic E coli. Seroprevalence studies indicated H. pylori increased with age. Histopathologists also showed peptic duodenitis was in effect “gastritis in the duodenum” caused by H. pylori, unifying its role in the pathogenesis of both gastritis and duodenal ulceration. These bacteria were initially called Campylobacter pyloridis and then C. pylori. However, electron microscopy suggested that the bacteria were not campylobacters, and this was supported by differences in fatty acid and polyacrylamide electrophoresis profiles. In-vitro tests indicated that H. pylori was susceptible to penicillins, erythromycin, and quinolones, but not trimethoprim or cefsulodin allowing development of selective media for culture. Monotherapy with erythromycin ethylsuccinate was ineffective, and patients treated with bismuth subsalicylate initially responded with clearance of H. pylori and the associated gastritis, but then many relapsed. Thus, pharmacokinetic and treatment studies were important to direct suitable dual and triple treatments. Work optimized serology, and the rapid biopsy urease and urea breath tests. The link between H.pylori and gastric cancer was established in large seroprevalence studies, and H. pylori test and treat for dyspepsia became routine.  相似文献   

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