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91.
There is ample evidence that human cooperative behaviour towards other individuals is often conditioned on information about previous interactions. This information derives both from personal experience (direct reciprocity) and from experience of others (i.e. reputation; indirect reciprocity). Direct and indirect reciprocity have been studied separately, but humans often have access to both types of information. Here, we experimentally investigate information use in a repeated helping game. When acting as donor, subjects can condition their decisions to help recipients with both types of information at a small cost to access such information. We find that information from direct interactions weighs more heavily in decisions to help, and participants tend to react less forgivingly to negative personal experience than to negative reputation. Moreover, effects of personal experience and reputation interact in decisions to help. If a recipient''s reputation is positive, the personal experience of the donor has a weak effect on the decision to help, and vice versa. Yet if the two types of information indicate conflicting signatures of helpfulness, most decisions to help follow personal experience. To understand the roles of direct and indirect reciprocity in human cooperation, they should be studied in concert, not in isolation.  相似文献   
92.
Following the observation of the presence in mammalian nuclear extracts of a DNA binding activity quite specific for the single-stranded C-rich telomeric motif, we have isolated from the K562 human cell line by affinity chromatography and identified by mass spectrometry a number of proteins able to bind to this sequence. All of them belong to different heterogeneous nuclear ribonucleoprotein subgroups (hnRNP). Whereas many of them, namely hnRNP K, two isoforms of hnRNP I, and the factor JKTBP, appear to bind to this sequence with limited specificity after isolation, an isoform of hnRNP D (alias AUF1) and particularly hnRNP E1 (alias PCBP-1) show a remarkable specificity for the (CCCTAA)n repeated motif. Both have been obtained also as recombinant proteins expressed in Escherichia coli and have been shown to retain their binding specificity toward the C-block repeated sequence. In the light of the current knowledge about these proteins, their possible involvement in telomere functioning is discussed.  相似文献   
93.
Population multiple components is a statistical tool useful for the analysis of time-dependent hybrid data. With a small number of parameters, it is possible to model and to predict the periodic behavior of a population. In this article, we propose two methods to compare among populations rhythmometric parameters obtained by multiple component analysis. The first is a parametric method based in the usual statistical techniques for comparison of mean vectors in multivariate normal populations. The method, through MANOVA analysis, allows comparison of the MESOR and amplitude-acrophase pair of each component among two or more populations. The second is a nonparametric method, based in bootstrap techniques, to compare parameters from two populations. This test allows one to compare the MESOR, the amplitude, and the acrophase of each fitted component, as well as the global amplitude, orthophase, and bathyphase estimated when all fitted components are harmonics of a fundamental period. The idea is to calculate a confidence interval for the difference of the parameters of interest. If this interval does not contain zero, it can be concluded that the parameters from the two models are different with high probability. An estimation of p-value for the corresponding test can also be calculated. Both methods are illustrated with an example, based on clinical data. The nonparametric test can also be applied to paired data, a special situation of great interest in practice. By the use of similar bootstrap techniques, we illustrate how to construct confidence intervals for any rhythmometric parameter estimated from population multiple components models, including the orthophase, bathyphase, and global amplitude. These tests for comparison of parameters among populations are a needed tool when modeling the nonsinusoidal rhythmic behavior of hybrid data by population multiple component analysis.  相似文献   
94.
Many evaluations estimating safe levels of hydrophobic organic chemicals in sediments do not account for confounding factors such as physical habitat quality or covariance among chemicals. Controlled experiments demonstrating cause and effect can be conducted with spiked sediment toxicity tests, but application of this methodology has been limited in part by concerns about chemical bioavailability and challenges in achieving target concentrations. Relevant literature was reviewed to assess the utility of standardizing sediment equilibration times; hydrophobicity, complex sediment characteristics, and temperature were identified as potentially equally important factors. Disequilibrium appears likely following limited equilibration time but should yield conservative toxicity test results relative to aged field sediments. Nominal and measured concentrations in over 20 published studies were compared to assess spiked chemical recovery (i.e., measured concentration/nominal concentration). Recovery varied substantially among studies and was not readily predictable based on spiking or extraction method, chemical properties, or measured sediment characteristics, although unmeasured differences between sediments appeared to be important. Factors affecting specific studies included chemical adsorption to glassware, biodegradation, and volatilization. Pre- and post-toxicity test analyses are recommended to confirm exposure concentrations. Studies with 2,3,7,8-tetrachloro-dibenzo-p-dioxin (2,3,7,8-TCDD) and hexachlorobenzene (HCB) exemplify the utility of verifying results of field studies using spiked sediment tests. Sediments spiked with these chemicals at concentrations greatly exceeding those in associated field studies caused no adverse effects in test organisms, demonstrating that other chemicals co-occurring in test sediment samples caused toxicity initially attributed to 2,3,7,8-TCDD and HCB in the field studies. Another key application of spiked sediment tests has been the investigation of TOC as the primary factor affecting bioavailability of hydrophobic organic chemicals. A review of LC50s for nine chemicals reported in 12 studies shows that comparable LC50s derived in different sediments generally agree within a factor of five when concentrations are normalized to a constant TOC. Additionally, use of spiked sediment toxicity testing to investigate toxicological interactions among chemicals provides a promising approach to improving the ability to predict sediment toxicity in the field.  相似文献   
95.
Briggs W  Ruppert D 《Biometrics》2005,61(3):799-807
Summary Should healthy, middle‐aged women receive precautionary mammograms? Should trauma surgeons use the popular TRISS score to predict the likelihood of patient survival? These are examples of questions confronting us when we decide whether to use a yes/no prediction. In order to trust a prediction we must show that it is more valuable than would be our best guess of the future in the absence of the prediction. Calculating value means identifying our loss should the prediction err and examining the past performance of the prediction with respect to that loss. A statistical test to do this is developed. Predictions that pass this test are said to have skill. Only skillful predictions should be used. Graphical and numerical methods to identify skill will be demonstrated. The usefulness of mammograms is explored.  相似文献   
96.
肖永红  柳丰  贺一原  杨海明 《昆虫学报》2007,50(12):1239-1246
定量评价农药对天敌的影响是IPM研究的重要内容之一,由于对天敌的捕食量缺乏有效的定量测量方法,农药对天敌摄食功能影响仍处于定性水平的研究,误差基数较大。本文采用一种定量的测定方法——荧光物示踪法,以稀土元素铕作为荧光示踪物质,定量地测定了食虫沟瘤蛛在重复接受噻嗪酮喷施后,其存活个体在药后13天内摄食量的变化趋势,且把药后食虫沟瘤蛛的死亡率加以考虑,计算药后整个试验食虫沟瘤蛛群体的摄食量变化。结果表明:任何浓度任何一次施药后2天左右食虫沟瘤蛛存活个体的捕食量均急剧下降;药物浓度较低时,第1次施药对食虫沟瘤蛛的影响最大;药物浓度较高时,食虫沟瘤蛛存活个体药后摄食量恢复周期较长。药后一段时间内整个食虫沟瘤蛛种群的摄食率相当低下,高浓度农药处理的食虫沟瘤蛛组3次施药后13天内的平均种群摄食率只有正常状况下的1/4左右(24.44%),推荐浓度及低于推荐浓度的食虫沟瘤蛛种群摄食率也仅为对照组的1/3左右(38.69%,36.52%)。因此在对水稻虫害防治时,应当尽可能地避免使用化学农药,充分发挥天敌对害虫数量的调控作用;当害虫数量超过经济阈值而必须施药时,也应当掌握农药用药剂量和次数的尺度,以利于食虫沟瘤蛛等稻田天敌的生理恢复和群落重建。  相似文献   
97.
Rapid characterisation of host specificity is important both in biological control of weeds and studies in ecology and evolution. A means for doing this was developed and tested on four species of leaf beetles of interest for biological control of the weed Mimosa pigra (Mimosaceae). We identified the most promising for the more detailed tests necessary to obtain release approval. The impact of time-dependent effects and effects of experience were also investigated as part of this study but were not detected. Short-term host specificity tests on adult feeding accurately predicted the results of longer term trials. The long-term trial showed that survival on a plant species depended on feeding on it. Hence short-term feeding trials can predict the longer term survival of adults on other plant species. Different feeding results were obtained in cut foliage versus entire plants but no consistent pattern was shown: of the two insect species tested, one species ate more of the cut material while the opposite was demonstrated for the second species. Species in order of priority for further consideration as biocontrol agents were Syphrea bibiana, Genaphthona sp., Syphrea sp. and Paria sp. The latter three species were probably not sufficiently specific for release. The tests done here allow the identification of the most likely species upon which to conduct the more laborious and difficult larval developmental tests, saving considerable resources.  相似文献   
98.
目的了解新型抗真菌药物米卡芬净(micafungin,MFG)对分离自中国的念珠菌和曲霉临床株的体外抑菌活性。方法参照CLSI(Clinical and Laboratory Standards Institute,以前为NCCLS)制定的M27-A2和M38-A方案测定86株念珠菌和35株曲霉的最低抑菌浓度(MIC)或最低有效浓度(MEC)。结果MFG对大多数念珠菌属和曲霉属均有较好的抑菌作用。对念珠菌属的MIC90从高到低依次为:氟康唑(FLC)敏感的白念珠菌、热带念珠菌、光滑念珠菌为0.125μg/ml,FLC耐药和剂量依赖敏感株为0.25μg/ml,克柔念珠菌为0.5μg/ml,近平滑念珠菌8μg/ml,季也蒙念珠菌>16μg/ml。MFG对烟曲霉的MEC90为≤0.03μg/ml,对非烟曲霉的曲霉属MEC90为0.06μg/ml。MFG与唑类药物、两性霉素B(AMB)不存在交叉耐药,对FLC耐药的念珠菌、伊曲康唑耐药的曲霉、AMB不敏感的曲霉均有好的抑菌活性。结论MFG对多数念珠菌属和曲霉属(包括对唑类耐药和AMB不敏感的菌株)有较好的体外抑菌作用。  相似文献   
99.
目的: 运动血压反应不足及运动后恢复期血压降低是肥厚型心肌病(HCM)患者常见的异常表现,本研究的目的是分析HCM患者这两类异常血压反应表现的相关因素及其与心肺运动功能的关系。方法: 回顾性研究2018年4月至2020年1月期间在阜外医院功能检测中心行心肺运动试验(CPET)的HCM患者219例。111例行CPET的性别、年龄匹配的正常体检者作为正常对照组。比较正常对照组与HCM组的CPET运动血压反应。将HCM患者分为运动血压反应正常组及运动血压反应不足组,以及运动后血压正常组及运动后恢复期血压降低组,分别比较上述两类运动血压反应异常者的临床情况及CPET功能指标。结果: 与正常对照组相比,HCM患者运动血压反应不足(8.7%比1.8%,P=0.016)及运动后恢复期血压降低(6.8%比0.0%,P=0.003)的发生率显著升高。在HCM患者中,与运动血压反应正常者相比,运动血压反应不足的HCM患者更多合并冠心病(P=0.029)、肺动脉高压(P=0.002)及房颤/房扑(P=0.036);与运动后血压正常者相比,运动后恢复期血压下降的HCM患者静息流出道压差(P=0.017)更高,合并流出道梗阻比例(P=0.015)、合并收缩期二尖瓣前移现象(P=0.022)及左室射血分数(P=0.043)更高。经过Logistic多元回归分析,运动血压反应不足的独立相关因素为冠心病(β=1.519,P=0.013)、肺动脉高压(β=2.292, P=0.000)。而运动后恢复期血压下降仅与左室流出道压差有独立的相关性(β=0.018, P=0.005)。运动血压反应不足的HCM患者峰值摄氧量(P=0.003)、峰值心率(P=0.014)及心率储备(P=0.003)更低,NT末端B型脑钠肽前体(P=0.019)及二氧化碳通气当量斜率(P=0.000)更高。运动后恢复期血压下降与各种心肺功能指标均无相关性。结论: HCM运动血压反应不足及运动后恢复期血压降低的发生率均较正常人群显著升高。HCM患者运动血压反应不足与合并冠心病和肺动脉高压有显著的独立相关性,而运动后血压下降仅与左室流出道压差独立相关。运动血压反应不足的HCM患者心肺运动功能降低,而运动后恢复期血压降低与心肺运动功能无显著相关性。  相似文献   
100.
By incorporating annotation information into the analysis of next-generation sequencing DNA methylation data, we provide an improvement in performance over current testing procedures. Methylation analysis using genome information (MAGI) is applicable for both unreplicated and replicated data, and provides an effective analysis for studies with low sequencing depth. When compared with current tests, the annotation-informed tests provide an increase in statistical power and offer a significance-based interpretation of differential methylation.  相似文献   
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