Singularities explained: Response to Klein.

Klein [Klein, A. S. (2006). Separating transducer nonlinearities and multiplicative noise in contrast discrimination. Vision Research, 46, 4279-4293] questions the existence of intrinsic singularities in two-alternative force-choice (2AFC) Signal Detection Theory (SDT) models, suggesting that the singularities found in Katkov et al. [Katkov, M., Tsodyks, M., & Sagi, D. (2006a). Singularities in the inverse modeling of 2AFC contrast discrimination data. Vision Research, 46, 259-266; Katkov, M., Tsodyks, M., & Sagi, D. (2006b). Analysis of two-alternative force-choice Signal Detection Theory model. Journal of Mathematical Psychology, 50, 411-420] are due to discarding higher order terms in the Taylor expansion of d' and/or limited to steep psychometric functions. Here we provide some simple intuitive examples that illustrate the results described in Katkov et al. (2006a, 2006b). We show, for the constant noise model, that singularities exist when exact values of d' are computed and that the singularities are not limited to steep psychometric functions. In these cases the disambiguation of the different models requires millions of trials.     

维纳滤波器在数字化X射线影像中的应用

介绍了一种简单有效的维纳滤波器设计过程,并采用该过程对数字化X射线影像进行滤波,试验表明:维纳滤波器能在去除图像噪声的同时较好地保留图像细节,具有实际应用价值。     

临床护士锐器伤调查与预防

目的探讨护士预防锐器伤的对策。方法对某所综合性医院193名护士在2004年1月~2005年6月发生的锐器伤进行问卷调查。结果46.1%护士发生锐器伤,人均1.6次;发生锐器伤的锐器主要是注射器针头(36.7%),其次是玻璃(32.4%);护士主要在掰安瓿(29.5%)、使用后处理锐器(22.3%)、安装调整针头(15.8%)、医护配合传递锐器(10.1%)等环节容易发生锐器伤;有79.1%护士发生锐器伤时未戴手套。结论护士面临锐器伤职业危险,各方应当采取对策,预防和控制锐器伤。     

头发、血浆、红细胞中铅对评价职业性接触水平的作用

[目的]探讨发铅、血浆和红细胞中铅对评价职业性铅接触水平的作用。[方法]用原子吸收分光光度计测定接触铅组与不接触铅对照组工人的血浆、红细胞及发中铅、铁、铜、镁、钙含量，测量数据用SAS软件处理。[结果]用0．25mol／L的HCl处理发样，能有效去除发表面的铅污染。接触组与对照组血浆铅无显著差异，而红细胞铅、发铅差异显著，血中其他元素含量无显著差异。[结论]去除表面污染的发铅和红细胞铅可作为铅接触指标。血浆铅则无意义。     

Prevalence of occupational allergy due to live fish bait

BACKGROUND: Larvae of insects and worms, used as live fish bait (LFB), are a common source of allergy in anglers and occupationally exposed workers, but the prevalence and predictors have not yet been investigated. OBJECTIVE: This study assessed the prevalence and associated factors of occupational allergy in workers exposed to LFB. METHODS: We assessed the prevalence of sensitization to LFB and work-related symptoms (WRS) in 76 workers occupationally exposed to it. All workers completed a case history questionnaire and underwent skin prick tests (SPT) for common aeroallergens and bluebottle (Calliphora vomitoria), bee moth (Galleria mellonella), mealworm (Tenebrio molitor), and gusano rojo (Cilecomadia moorei). Specific IgE were tested in 64 subjects. Two-thirds of the workers had a high level of LFB exposure. RESULTS: Sensitization to LFB was found in 24 workers (31.6%). Seven subjects (9.2%) reported WRS (asthma in 3, rhinoconjunctivitis in 5, and contact urticaria in 1), and 5 were positive for SPT and serum IgE to one or more LFB extracts. One was also exposed to LFB while fishing. Sensitization to LFB extracts and WRS were strongly associated (Odds Ratio = 6.6, P < 0.05). The 7 subjects with WRS had been exposed longer than asymptomatic subjects with positive skin tests to LFB (P < 0.05). No differences in sex, age, smoking habit, duration or level of exposure, and atopy were detected in symptomatic or in sensitized subjects, compared with normal workers. CONCLUSION: Sensitization to LFB and WRS are relatively frequent in occupationally exposed workers. No associated factors of occupational allergy to LFB could be detected.     

Signal-to-noise ratio effects in quantitative cerebral perfusion using dynamic susceptibility contrast agents.

Theoretical and simulation evidence is presented in support of the idea that the optimal manner of determining blood flow from MR perfusion studies is not necessarily obtained by setting experimental conditions to maximize either the arterial input or the measured tissue concentration level for a particular echo time (TE). The noise power in the contrast concentration curve is associated with its peak because of the nonlinear relationship between the contrast concentration and MR signal intensity curves. The optimum signal-to-noise ratio (SNR), SNR(C), for a particular contrast concentration curve can be obtained when the experimental concentration level and TE are adjusted to produce an MR intensity curve whose signal loss is 63% of the precontrast MR signal intensity. It is demonstrated that the stability of the singular valued decomposition (SVD) deconvolution approach to determine blood flow parameters is increased when the tissue curve maximum signal loss is in the range of 40-80%. The accuracy and stability of the SVD-determined blood flow parameters are affected by deviations from these optimum conditions in a manner that depends on the mean transit time (MTT) associated with the residue function. It is recommended that the experimental TE value be set so that neither the tissue nor the arterial curves are placed a region of rapidly deteriorating SNR(C).     

广东省放射工作人员健康状况调查

目的　了解长期小剂量电离辐射对放射工作人员健康的影响 ,为保障其工作者的健康和改进防护措施提供依据。方法　通过职业流行病学现况调查的方法 ,按照广东省放射工作人员职业健康体检规范要求 ,对 2 0 0 2年广东省999例放射工作人员的职业健康状况进行分析。结果　随着工龄增加 ,放射工作人员眼科检查的异常率增加。血液常规检查和细胞遗传学指标 (外周血淋巴细胞微核率 )及眼晶状体混浊率 ,部分组间指标差异有统计学意义。男性微核率的异常率 >15年组是 <5年组的 5 2倍 ,是 5～ 15年组的 1 4倍 ,女性微核率异常率 >15年组是 <5年组的 3 3倍 ,是 5～15年组的 2 5倍。结论　加强放射卫生监督管理 ,重点保护暴露工龄较长的放射工作人员 ,以减低放射对该人群的影响     

Localized pleural plaques and lung cancer.

In a mass chest radiography survey conducted in 1971 for 7,986 residents of three Finnish communities, 604 subjects (7.6%) with pleural plaques but not other asbestos-related radiographic signs were identified. The same number of referents, each individually matched to each plaque carrier on sex, birth year, and community, was selected from among persons in the same source population with no pleural plaques. The two groups were followed for investigation of incidence of lung cancer during 1972-1989. Twenty-eight of those with plaques and 25 referents contracted lung cancer (crude conditional RR = 1.1; CL95 = 0.7, 1.9). The application of the proportional hazards model, with adjustment for sex, age, and residence, resulted in a hazard ratio of 1.1 (CL = 0.6, 1.8). The risk ratio estimate may be biased; hence, the result is inconclusive in regard to the predictive assessment of lung cancer risk among carriers of pleural plaques.     

五型病毒性肝炎的暴露因素与临床表现的比较

比较急性病毒性肝炎患者感染打危险因素，同时比较五型肝炎的症状和体征。连续收集急性病毒性肝炎患者血清２９３份，用ＥＬＩＳＡ法检测了五型肝炎病毒的病原学指标，并进行了流赞美同学调查。暴露因素：丙肝的肠道外暴露外明显多于甲肝；甲肝和戊肝有较高的“甲肝”患者接触史；乙肝，丙肝和丁肝有高的“乙肝”接触史，与甲肝，戊肝相比差异显著。