振幅型光栅法人眼调制传递函数测定的理论分析

目的:介绍测量视网膜调制传递函数的方法和光学原理,验证振幅型正弦光栅加零级空间滤波的方法测量视网膜调制传递函数使测量仪器小型化的可行性。方法:目前测量仪器中获得两相干点光源主要是使用平行板法、双道威棱镜法和光栅法3种,从理论上分析比较3种方法的优劣性,并重点分析矩形光栅、振幅型正弦光栅的各级衍射光强分布特点。结果:①平板法和双道威棱镜法可获得两相干点光源,也是在视网膜调制传递函数测量仪中应用比较成熟的技术,其光学原理简单,获得相干点光源的相干性良好,光强稳定。另外,使用双道威棱镜法时,可以用电位带动反射镜的移动来控制两点光源的间距,易于装置的智能化控制,但所设计的仪器外观尺寸较大,移动性较差,不利于测量装置的手持式和小型化发展。②矩形光栅法可以实现仪器的小型化,但由于矩形光栅的衍射图样是单缝衍射图样与多光束干涉图样相互调制的结果,即衍射光强的多光束干涉条纹干扰测量结果。③振幅型正弦光栅的透过率函数可以实现0￣1,以余弦波形式对入射光波产生振幅调制,且衍射光强只有三级谱线(0级和±1级),且±1级谱线的光强分布具有对称性,只要进行零级空间滤波,就可以得到作为视标调制度的两个点光源。结论:振幅型正弦光栅加零级空间滤波可以获得相干性良好相干点光源,并且可以实现测量仪器的小型化。     

The Impact of Increased Availability of Wine in Grocery Stores on Consumption: four case histories

Regression analyses were performed on per capita wine consumption in four states of the U.S.A. where the availability of wines was increased. In three of four states, wine consumption was found to be significantly greater in the years of the changes than one would expect, based on the regression trends of the previous eight to thirteen years. Differences in findings were probably a reflection of differences in the nature and extent of the increased availability among the four stales. Consumption of beer and spirits was also analysed for the years in question, and substitution from beer or spirits to wine was not found. Finally, alternative explanations for the patterns of increases were examined and considered unlikely.     

SUCCESSFUL TREATMENT OF ACUTE DAPSONE INTOXICATION USING CHARCOAL HEMOPERFUSION

Abstract: A 22 year old female was admitted to hospital two hours after ingesting 4 g of dapsone. Over the next 15 h she developed progressive hemolysis and methemoglobinemia. Charcoal hemoper-fusion and sequential dialysis were performed because of the serious risk of fatality following such a massive dose of dapsone. Charcoal hemoperfusion led to rapid clearing of dapsone from the circulation. This resulted in clinical improvement and controlled the progression of hemolysis and methemoglobinemia.     

Increasing dietetic referrals: Perceptions of general practitioners,practice nurses and dietitians

Aim: To examine Australian private practice dietitians' relationships with general practitioners and practice nurses as a factor that influences dietetic referrals. Methods: Semistructured telephone interviews and an online survey were conducted with Australian private practice dietitians (n = 52 and n = 90, respectively) between April and May 2008. Semistructured questionnaires were conducted with general practitioners (n = 11) and practice nurses (n = 12) from the ‘GP Access’ Division of General Practice between March and July 2007. Results: General practitioners' relationships with dietitians were believed to be the primary influencing factor on referral, provided by 81% of survey dietitians and 25% of interview dietitians. The most common means of initially forming relationships with general practitioners were face‐to‐face introduction (48%) and introductory letters (37%). Patient feedback via letter, fax or email was the most popular method of maintaining relationships with general practitioners (77%). Meeting with general practitioners in person was believed to be the most effective activity in building relationships with general practitioners and increasing referral rates (42%). Referral was made easier for general practitioners by providing paper (37%) or electronic (19%) referral forms and contact details (19%). The majority of general practitioners and dietitians believed that the ‘Allied Health Services Under Medicare’ made it easier to refer to a dietitian. Conclusions: Dietetic referrals can be encouraged through good relationships between general practitioners, practice nurses and dietitians. Private practice dietitians would benefit from cultivating relationships with general practitioners and practice nurses through personal contact and providing good patient feedback.     

Beliefs about constipation in old age psychiatry

A questionnaire survey of opinions about the influence of constipation on the mental state of older people was sent to RMN and RGN nursing staff and psychiatrists in the South-East Thames Region. The response rate for trusts was 62.5%, and just over 50% of individuals from participating services returned questionnaires. Constipation was thought to be an important cause of deterioration in patients with dementia by 86.6% of respondents, and although it was the least favourite mechanism, 54.9% felt that reabsorption of toxic substances contributed to this. Of respondents, 86.6% believed that delirium could be caused de novo by constipation. There was little difference between doctors and nurses in their responses. These results from experienced clinicians suggest that further investigation of the role of constipation in deterioration in the elderly with dementia is warranted.