Estimation of Multinomial Probabilities under a Model Constraint

In this paper estimation of the probabilities of a multinomial distribution has been studied. The five estimators considered are: unrestricted estimator (UE), restricted estimator (RE) (under model ), preliminary test estimator (PTE) based on a test of the model , shrinkage estimator (SE) and the positive-rule shrinkage estimator (PRSE). Asymptotic distributions of these estimators are given under Pitman alternatives and the asymptotic risk under a quadratic loss has been evaluated. The relative performance of the five estimators is then studied with respect to their asymptotic distributional risks (ADR). It is seen that neither of the preliminary test and shrinkage estimators dominates the other, though each fares well relative to the other estimators. However, the positive rule estimator is recommended for use for dimension 3 or more while the PTE is recommended for dimension less than 3.     

A self-powered and sensitive terahertz photodetection based on PdSe2

With the rapid development of terahertz technology, terahertz detectors are expected to play a key role in diverse areas such as homeland security and imaging, materials diagnostics, biology, medical sciences, and communication. Whereas self-powered, rapid response, and room temperature terahertz photodetectors are confronted with huge challenges. Here, we report a novel rapid response and self-powered terahertz photothermoelectronic (PTE) photodetector based on a low-dimensional material: palladium selenide (PdSe₂). An order of magnitude performance enhancement was observed in photodetection based on PdSe₂/graphene heterojunction that resulted from the integration of graphene and enhanced the Seebeck effect. Under 0.1-THz and 0.3-THz irradiations, the device displays a stable and repeatable photoresponse at room temperature without bias. Furthermore, rapid rise (5.0 μs) and decay (5.4 μs) times are recorded under 0.1-THz irradiation. Our results demonstrate the promising prospect of the detector based on PdSe₂ in terms of air-stable, suitable sensitivity and speed, which may have great application in terahertz detection.     

Stripping voltammetry at micro-interface arrays: A review

In this article, a comprehensive overview of the most recent developments in the field of stripping voltammetry at regular micro-interfaces (both solid–liquid and liquid–liquid interfaces) is presented. This review will report on the most conventional arrays of metallic micro-electrodes but also on the rapidly growing field of electrochemistry at arrays of micro-interfaces between two immiscible electrolyte solutions (μITIES). The main fabrication methods, together with some design considerations and diffusion phenomena at such interfaces are discussed. Main applications of micro-interface arrays are presented including heavy metals detection at micro-electrode arrays and detection of organic molecules (amino acids, vitamins, peptides and drugs) at the μITIES. Stripping analysis at micro-interface arrays is suitable for the detection of analytes in several real media including water, soil extracts and biological fluids (blood and saliva) with high specificity, sensitivity (detection limits of nM, ppb level) and reliability. Stripping analysis at μITIES and micro-electrode arrays are two complementary approaches that have the advantages of being cost effective, simple to use and easily adaptable to field measurement.     

Hydrochloric Acid Catalysis of N-Bromosuccinimide (NBS) Mediated Nuclear Aromatic Brominations in Acetone

Nuclear bromination of activated aromatic substrates can be achieved quickly and in high yields using N-bromosuccinimide (NBS) in acetone with 1 M HCl catalysis.     

一般、个人教学效能感与中学教师心理健康关系的分离

目的:通过对一般教学效能感(GTE)、个人教学效能感(PTE)与教师焦虑、压力、职业倦怠关系的考察增进对影响当前教师心理健康的因素的理解。方法:经过因素分析将中文教学效能感量表、TES(教师效能感量表)相结合以保证GTE、PTE测量的信、效度。以OSTES(俄亥俄州教师效能感量表)做校标,进一步检验PTE的效度。用状态-特质焦虑问卷、教师工作压力问卷、教师职业倦怠问卷测量教师心理健康状态。474名来自贵州、山东两省15所中学的老师完成了测试。结果:GTE与PTE相关系数-0.02,是相互独立的心理变量。GTE与状态、特质焦虑、教师压力、职业倦怠相关系数-0.31、-0.35、-0.46、-0.51,都有极其显著的统计意义。而PTE与它们的相关系数从-0.04到-0.13,没有显著统计意义或有但非常微弱。典型相关分析的结果也验证了这些发现。多元方差分析表明GTE和PTE对教师心理健康变量的影响有交互作用。结论:本研究的结果说明当前环境因素对教师心理健康状态的影响远大于个人教学能力因素。低GTE水平提示低心理健康水平并掩盖PTE和心理健康的相关。