Two-stage Sampling on Additive Model for Quantitative Sensitive Question Survey and Its Application

Objective To explore scientific sampling methods and corresponding formulas for quantitative sensitive question survey on two-stage random sampling. To provide scientific data for the prevention and control of high risk AIDS population in Beijing. Methods Additive model for quantitative sensitive question survey, two-stage random sampling, properties of variance and mean were used. Results Formulas for the esti¬mation of the population proportions and its variance on additive model for quantitative sensitive question survey were deduced. The survey methods and formulas were employed successfully in the survey of the age of the first time when MSM having sex with men and the result was 21.9747. Conclusion The methods and corresponding formulas for two-stage sampling on additive model for quantitative sensitive question survey are feasible. Key words: Sensitive questions; Additive model for randomized response technique; Two-stage sampling; MS

Willingness to Accept HIV Pre-Exposure Prophylaxis among Chinese Men Who Have Sex with Men

OBJECTIVE: We investigated the awareness and acceptability of pre-exposure prophylaxis (PrEP) among men who have sex with men (MSM) and potential predicting factors. METHODS: This study was conducted among MSM in Beijing, China. Study participants, randomly selected from an MSM cohort, completed a structured questionnaire, and provided their blood samples to test for HIV infection and syphilis. Univariate logistic regression analyses were performed to evaluate the factors associated with willingness to accept (WTA) PrEP. Factors independently associated with willingness to accept were identified by entering variables into stepwise logistic regression analysis. RESULTS: A total of 152 MSM completed the survey; 11.2% had ever heard of PrEP and 67.8% were willing to accept it. Univariate analysis showed that age, years of education, consistent condom use in the past 6 months, heterosexual behavior in the past 6 months, having ever heard of PrEP and the side effects of antiretroviral drugs, and worry about antiretroviral drugs cost were significantly associated with willingness to accept PrEP. In the multivariate logistic regression model, only consistent condom use in the past 6 months (odds ratio [OR]: 0.31; 95% confidence interval [CI]: 0.13-0.70) and having ever heard of the side effects of antiretroviral drugs (OR: 0.30; 95% CI: 0.14-0.67) were independently associated with willingness to accept PrEP. CONCLUSIONS: The awareness of PrEP in the MSM population was low. Sexual behavioral characteristics and knowledge about ART drugs may have effects on willingness to accept PrEP. Comprehensive prevention strategies should be recommended in the MSM community

Earnings Management and Investment Decisions：From the Perspectives of Accrual-Based and Real Earnings Management

【中文摘要】本文以2004～2013年度中国A股主板非金融类上市公司为研究对象，从应计盈余管理和真实盈余管理的视角，着重考察真实活动盈余管理和应计项目盈余管理对企业投资决策的影响作用。研究结果揭示，经理人真实活动盈余管理会促使企业在当期，甚至下一期进行更多的过度投资活动；而应计项目盈余管理缓解了企业投资不足的问题。进一步的研究还发现，企业会计期末的异常销售行为和延迟可操控性费用记入当期这两种真实活动盈余管理对投资过度具有显著的影响。本文的研究结论在一定程度上说明，在中国资本市场的背景下真实活动盈余管理直接促使企业管理层做出投资过度的决策；而应计项目盈余管理则通过影响企业外部信息环境间接缓解了企业投资不足的问题。该研究结论扩展人们关于真实活动盈余管理对企业投资决策影响的认识，丰富真实活动盈余管理的经济后果方面的文献，也提供关于真实活动盈余管理对企业预期经营业绩带来负面影响的另外一种解释。 【Abstract】Based on a sample of listed Chinese companies from 2004 to 2013, this study investigates whether real earnings management activities may influence investment decisions.The result suggests that real earnings management may result in enterprises’ overinvestments.Specifically, this paper finds that the increased abnormal sales and the deferred discretionary expense may lead to overinvestment decisions. On the other hand, accrual-based earnings management may reduce enterprises’ under-investments. In sum, we argue that different ways of earnings management may have different impacts on enterprises’ investment decision process. Hence, this study sheds light on the economic consequences of real earnings management.国家自然科学基金项目“制度环境、公司治理与投资效率”（71262018）的阶段性成果。 云南财经大学科学研究基金项目“产权性质、盈余管理策略与非效率投资”和云南省创新团队“云南省公司治理研究”项目的资助

Quasi-Amorphous Metallic Nickel Nanopowder as an Efficient and Durable Electrocatalyst for Alkaline Hydrogen Evolution

Nickel is regarded as the best alternative metal electrocatalyst to platinum for hydrogen evolution reaction (HER). Success in developing a quasi-amorphous metallic nickel (QAMN) nanopowder catalyst using a two-step chemical route for efficient and durable HER in alkaline solution is reported. It is found that the QAMN electrocatalyst exhibits essentially zero overpotential at the cathodic onset while delivering 10 mA cm(-2) at an overpotential of only 240 mV; both performances are far better than what was reported previously using prior metallic nickel catalysts. Taking into account increased surface area, further enhanced activity is attributed to the superior intrinsic activity. Meanwhile, the QAMN catalyst shows excellent stability in accelerated and interrupted polarization in alkaline solution for tens of hours. This study provides a new chemical means to prepare amorphous metallic materials for more efficient catalysis

Achievement of visible-light-driven Z-scheme overall water splitting using barium-modified Ta3N5 as a H-2-evolving photocatalyst

Ta3N5 is one of the most promising photocatalyst candidates for solar water splitting, but it still remains challenging to achieve overall water splitting via Ta3N5-based photocatalysts regardless of whether it uses a one step or two step method. Here we will address the relatively poor photocatalytic proton reduction of Ta3N5 with an effort for the promotion of charge separation via barium modification. Onepot nitridation of barium nitrate-impregnated Ta2O5 precursor was adopted here for the synthesis of Ta3N5 accompanied with the creation of a Ta3N5/BaTaO2N heterostructure and surface passivation. Due to the synergetic effect of the improved interfacial charge separation and the decreased defect density, the photocatalytic H-2 evolution rate of barium-modified Ta3N5 is effectively promoted. Encouraged by this, a visible-light-driven Z-scheme overall water splitting system was successfully constructed by using the barium-modified Ta3N5 as a H-2-evolving photocatalyst, together with a PtOx/WO3 and IO3-/I- pair as an O-2-evolving photocatalyst and a redox mediator, respectively

Synergistic Effects for Enhanced Catalysis in a Dual Single-Atom Catalyst

Synergistic effects have been discussed extensively in bimetallic heterogeneous catalysis, but it remains unclear how the effects function at the atomic scale. Here, we report a dual single-atom catalyst (DSAC) Ir1Mo1/TiO2 displaying much greater catalytic chemoselectivity (>96%, at 100% conversion) than comparable single-atom catalysts (SACs) Ir1/TiO2 (38%, at 87% conversion) and Mo1/TiO2 (no activity) for the hydrogenation of 4-nitrostyrene (4-NS) to 4-vinylaniline (4-VA). Activation of the TiO2-supported bimetallic carbonyl cluster Ir2Mo2(CO)10(η5 - C5H5)2 in an Ar atmosphere affords the DSAC Ir1Mo1/TiO2. Characterization of the dual single-atom structure confirms that it consists of well-dispersed Ir single atoms (Ir1) and Mo single atoms (Mo1) on TiO2. Density functional theory studies reveal that Ir1 sites effect H2 activation while Mo1 sites are responsible for 4-NS adsorption, with synergistic cooperation between the two sets of single atoms contributing to the better catalytic performance for the hydrogenation of 4-NS. This work provides a deep understanding of synergistic effects in dual single-atom catalysis.We thank the National Natural Science Foundation of China (grant nos. 21703235 and 21688102), the Strategic Priority Research Program of Chinese Academy of Sciences (grant no. XDB17000000), National Key R&D Program of China (2019YFC1905300), Projects of International Cooperation and Exchanges NSFC (21961142006), and International Postdoctoral Exchange Fellowship Program for the financial support

Hydrogenation of Nitroarenes by Onsite-Generated Surface Hydroxyl from Water

Directly using water as a hydrogen source for hydrogenation of nitroarenes to anilines (HNA) without using H2 is an ideal reduction reaction route but is limited by unfavorable thermodynamics. Herein, we report a high-efficiency and durable H2O-based HNA process achieved by using in situ-generated hydroxyl species from water as a hydrogen donor and low-cost CO as an oxygen acceptor over a molybdenum carbide-supported gold catalyst (Au/α-MoC1–x). It affords nitroarene conversion of over 99% with aniline selectivity of over 99% and excellent functional group tolerance at 25 °C and remains stable after 10 cycles, outperforming the traditional H2-involved route. Spectroscopic and theoretical studies reveal the key role of Au/α-MoC1–x boundaries, at which not only hydroxyl species are generated as a soft reductant on α-MoC1–x but also the nitro group is selectively hydrogenated to anilines with other unsaturated groups intact, and residual O* is removed by adsorbed CO on the atomically thin Au layer. This process provides a durable H2O-based route for aniline production at room temperature

Methyl radical chemistry in non-oxidative methane activation over metal single sites.

Molybdenum supported on zeolites has been extensively studied as a catalyst for methane dehydroaromatization. Despite significant progress, the actual intermediates and particularly the first C-C bond formation have not yet been elucidated. Herein we report evolution of methyl radicals during non-oxidative methane activation over molybdenum single sites, which leads selectively to value-added chemicals. Operando X-ray absorption spectroscopy and online synchrotron vacuum ultraviolet photoionization mass spectroscopy in combination with electron microscopy and density functional theory calculations reveal the essential role of molybdenum single sites in the generation of methyl radicals and that the formation rate of methyl radicals is linearly correlated with the number of molybdenum single sites. Methyl radicals transform to ethane in the gas phase, which readily dehydrogenates to ethylene in the absence of zeolites. This is essentially similar to the reaction pathway over the previously reported SiO2 lattice-confined single site iron catalyst. However, the availability of a zeolite, either in a physical mixture or as a support, directs the subsequent reaction pathway towards aromatization within the zeolite confined pores, resulting in benzene as the dominant hydrocarbon product. The findings reveal that methyl radical chemistry could be a general feature for metal single site catalysis regardless of the support (either zeolites MCM-22 and ZSM-5 or SiO2) whereas the reaction over aggregated molybdenum carbide nanoparticles likely facilitates carbon deposition through surface C-C coupling. These findings allow furthering the fundamental insights into non-oxidative methane conversion to value-added chemicals