Insights into the crucial role of a Zn promoter for methanol dehydrogenation to methyl formate over Cu(111) catalysts.

Zn-doped Cu(111) alloy (Cu3Zn(111)) and Cu(111) surfaces were built using density functional theory (DFT) calculations to investigate the role of the Zn promoter in the methyl formate (MF) synthesis by the direct dehydrogenation of methanol. The rate determining step (RDS) of the MF synthesis is the dehydrogenation of CH3O to CH2O on both the Cu3Zn(111) alloy and the Cu(111) surfaces. Nevertheless, the energy barrier of the RDS is 119.4 kJ mol-1 on the Cu3Zn(111) alloy surface, lower than that on the Cu(111) surface. Compared with the favorable CH3O-CH2O coupling on the Cu(111) surface, the CH3O-CHO coupling is kinetically favorable on the Cu3Zn(111) alloy surface. Moreover, the formation of the by-product CO is effectively suppressed over the Cu3Zn(111) alloy surface. In addition, the results of the d-band center show that the addition of the Zn promoter increases the electron density of copper atoms, which accounts for the reduction in the energy barrier for the CH2O formation and inhibition of the CO formation.

The improved activity of Co3O4 nanorods using silver in the catalytic oxidation of toluene.

Co3O4 nanorods with diameters of ~0.15 µm and lengths of ~1 µm were prepared using a hydrothermal method via the assembly of microcrystals and tested in the catalytic oxidation of toluene. The catalytic performance of Co3O4 nanorods was improved by the addition of Ag at various concentrations, and the 7% Ag/Co3O4 catalyst achieves a toluene conversion of 90% at 256 °C with a space velocity of 78,000 mL g-1 h-1, which is much lower than that of the pristine Co3O4 (269 °C). The addition of Ag promoted the activation of the surface oxygen species and the formation of more oxygen vacancies, improving the relative low-temperature reducibility of Co3O4, which is favorable for toluene oxidation. Moreover, the 7% Ag/Co3O4 catalyst showed an excellent stability for toluene oxidation at 250 and 260 °C for 50 h under the same conditions.

Fabrication of Few-Layer Graphene-Supported Copper Catalysts Using a Lithium-Promoted Thermal Exfoliation Method for Methanol Oxidative Carbonylation.

Exfoliation of graphene oxide (GO) via thermal expansion is regarded as the most promising approach to obtain few-layer graphene (FLG) in bulk. Herein, we introduce an efficient strategy for improving the exfoliation process by adding a tiny amount of lithium nitrate in the precursors, which significantly enhances the removal of oxygen-containing functional groups and produces 1-2 layer graphene. FLG-supported highly dispersed Cu nanoparticles (NPs, ≈4.2 nm) can be further synthesized through exfoliating the mixture of GO, lithium nitrate, and copper(II) nitrate, which displayed superior catalytic activity and stability in the synthesis of dimethyl carbonate (DMC) using liquid methanol oxidative carbonylation. The characterization results demonstrate that during the thermal expansion process, lithium nitrate was decomposed to Li2O and immediately reacted with CO2 released by the decomposition of GO to form stable Li2CO3, which promotes efficient charge transfer and produces Cuδ+ (0 < δ < 1) species in the Cu/Li-PGO catalyst. Density functional theory calculations prove that the presence of Cuδ+ markedly facilitates CO adsorption over the resulting catalyst and causes a decrease of the energy barrier of the rate-limiting step for DMC formation (CO insertion). These findings give a theoretical explanation of the enhanced catalytic performance of the Cu/Li-PGO catalyst. The present work provides a simple and practical avenue to the exfoliation of graphene and the dispersions of metal NPs on graphene sheets.

Association between recreational drug use and sexual practices among people who inject drugs in Southwest China: a cross-sectional study.

OBJECTIVE: To describe the differences in sexual practices among individuals with various drug administration patterns. SETTING: A detoxification centre in Southwest China, a part of the Chinese national sentential surveillance network for hepatitis C virus (HCV), HIV and syphilis infections, was recruited. PARTICIPANTS: A total of 610 newly enrolled injection drug users (IDUs) from detoxification centre were included during 2015. PRIMARY AND SECONDARY OUTCOME MEASURES: Self-reported sexual activities, drug-related practices and laboratory-confirmed HCV, HIV and syphilis infection status were collected. RESULTS: Of the 610 IDU, 295 (48.4%) used heroin only, 277 (45.4%) poly-drug users reported the mixed use of synthetic drugs (SDs) with heroin and 38 (6.2%) used SDs only. The average daily drug injection frequency for poly-drug users (3.3±1.2 times) was the highest, followed by heroin-only (2.2±0.8 times) and SD-only users (1.2±0.4 time). SD-only drug users reported the highest proportion (86.8%) of engaging in sexual activities in the previous month, with more than half (54.5%) reporting any condomless sex. A higher frequency of daily injecting in heroin-only users was significantly correlated with the less likelihood of sex, condomless sex in the past month, having sex with fixed partners, condomless commercial sex in the previous 12 months (all p<0.01). In poly-drug users, who injected drugs two times per day was associated with the highest proportion of people who engaged in sex and commercial sex (p<0.05). For SD-only users, increased drug use was not associated with reducing sexual risk (p>0.05). Different patterns of HCV, HIV and syphilis infections prevalence rates were shown among the IDU depending on the roles and length of exposure. CONCLUSIONS: The daily drug injecting frequency of heroin-only and poly-drug users was negatively associated with sexual activities, but SD-only users kept a high frequent engagement in sex. The interventions for relevant diseases should adapt to characteristics of IDU.

Epidemics of HIV, HCV and syphilis infection among synthetic drugs only users, heroin-only users and poly-drug users in Southwest China.

The number of poly-drug users who mix use heroin and synthetic drugs (SD) is increasing worldwide. The objective of this study is to measure the risk factors for being infected with hepatitis C (HCV), human immunodeficiency virus (HIV) and syphilis among SD-only users, heroin-only users and poly-drug users. A cross-sectional study was conducted in 2015 from a national HIV surveillance site in Southwest China, 447 poly-drug, 526 SD-only and 318 heroin-only users were recruited. Poly-drug users have higher drug-use frequency, higher rates of drug-sharing and unsafe sexual acts than other users (p < 0.05). About a third (36.7%) of poly-drug users experienced sexual arousal due to drug effects, which is higher than the rate among other drug users. Poly-drug users had the highest prevalence of HIV (10.5%) and syphilis (3.6%), but heroin-only users had the highest prevalence of HCV (66.0%) (all p < 0.05) among three groups. Logistic regression shows among poly-drug users, having sex following drug consumption and using drugs ≥1/day were the major risk factors for both HIV (Adjusted odds ratio (AOR) = 2.4, 95% CI [1.8-3.4]; 2.3, [1.6-3.1]) and syphilis infection (AOR = 4.1, [2.1-6.9]; 3.9, [1.8-5.4]). Elevated risk of both HIV and syphilis infection have been established among poly-drug users.

Fabrication of Yolk-Shell Cu@C Nanocomposites as High-Performance Catalysts in Oxidative Carbonylation of Methanol to Dimethyl Carbonate.

A facile way was developed to fabricate yolk-shell composites with tunable Cu cores encapsulated within hollow carbon spheres (Cu@C) with an average diameter about 210 nm and cavity size about 80 nm. During pyrolysis, the confined nanospace of hollow cavity ensures that the nucleation-and-growth process of Cu nanocrystals take place exclusively inside the cavities. The size of Cu cores can be easily tuned from 30 to 55 nm by varying the copper salt concentration. By deliberately creating shell porosity through KOH chemical activation, at an optimized KOH/HCS mass ratio of 1/4, the catalytic performance for the oxidative carbonylation of methanol to dimethyl carbonate (DMC) of the activated sample is enhanced remarkably with TOF up to 8.6 h-1 at methanol conversion of 17.1%. The activated yolk-shell catalyst shows promising catalytic properties involving the reusability with slight loss of catalytic activity and negligible leaching of activated components even after seven recycles, which is beneficial to the implementation of clean production for the eco-friendly chemical DMC thoroughly.

Introduction of carbon nano-tubes into the phosphor to restrain the saturation behavior in low voltage cathodoluminescence.

To restrain the saturation behavior in low voltage cathodoluminescence, a small amount of carbon nano-tubes (CNT) was introduced into the phosphor to form CNT-introduced phosphor material. In the specific working conditions in low voltage cathodoluminescence, the field enhancement effect is initiated in the CNT-introduced phosphor material, and the local electric fields surrounding the top of each CNT is much stronger than the background electric field. The CNTs, with enhanced local electric fields surrounding their tops, play a key role in removing the electrons in the phosphor material, in which the CNTs act as convenient channels for electrons to be removed in cathodoluminescence. By introducing a small amount of CNTs into the phosphor, the saturation behavior in low voltage cathodoluminescence is effectively restrained, which has a similar effect as improving the conductivity of the phosphor material. The field enhancement effect in the CNT-introduced phosphor material may be activated and become more effective when the applied current density in cathodoluminescence is increased, thus the dynamic performance of the CNT-introduced phosphor material is favorable in low voltage cathodoluminescence.

Investigation on the conductivity-dependent performance in low voltage cathodoluminescence.

With the increase of applied current density in low voltage cathodoluminescence, the exciting power tends to saturate, causing the saturation of electron-hole generation rate in the phosphor layer. Moreover, ground-state depletion could emerge for the activators owing to the increased exciting power and decreased average penetration depth of incident electrons in the phosphor layer, causing the decrease of the energy transfer probability of e-h pairs exciting ground-state activators. In addition, the radiative transition probability of excited activators could be decreased due to the increase of temperature. In view of these key factors, the efficiency decrease in cathodoluminescence is the inevitable result. To restrain the efficiency decrease so as to improve the performance in low voltage cathodoluminescence, the conductivity of the phosphor material was improved. By introducing a conductive component, which improves the conductivity of the phosphor material, the performance in low voltage cathodoluminescence was effectively improved.

[An ambispective cohort study of the natural history of HIV infection among former unsafe commercial blood and plasma donors].

OBJECTIVE: Discussing the natural history and the influencing factors of HIV infection among former commercial blood and plasma donors engaged in unsafe blood donation practices in China. METHODS: Using ambispective cohort study, with data obtained from ten counties (districts) from six provinces in the National AIDS Control Demonstration Area. HIV/AIDS cases were found and confirmed prior to July 24, 2006 being former commercial blood. Plasma donors were selected and data regarding infection, incidence, death, and influencing factors was collected. Analysis was performed using SPSS 12.0 statistical analysis software. RESULTS: (1) In 7551 cases of HIV infection, there were 6533 typical progressors (86.52%, 4757 cases of AIDS), 108 rapid progressors (1.43%), 910 long-term non-progressors (12.05%) with 4865 cases progressed to AIDS (64.43%). The median incubation period for HIV progression to AIDS was nine years (95% CI:8.96-9.04). (2) According to data, from a total of 1157 AIDS cases without ARV therapy (23.78% of total AIDS cases), there were 283 confirmed AIDS-related deaths, of which the median survival time was 6 months (95% CI:4-7) and the two and three year fatality rates were 95% and 99%, respectively. (3) The duration of HIV incubation period was irrespective to gender and age at the time of HIV infection (P > 0.05). Length of survival for untreated AIDS showed correlation to gender (P < 0.05) but no correlation with culture, marital status or age at the time of diagnosis of AIDS (P > 0.05). CONCLUSION: Compared with the UNAIDS theory regarding slow disease progressors among adults, our study showed a longer AIDS incubation period and shorter outlook for untreated survival, but a similar incubation period for other routes of HIV infection.

[The effects of triptolide inhibition of mouse lymphocytes activated in vitro].

OBJECTIVE: To study the effects of triptolidel on murine T lymphocytes activated. METHODS: We isolated and cultured the mouse lymphocytes from lymph nodes of mice in vitro. The lymphocytes were pre-treated triptolide for 1 h prior to activation with ConA. After 6 hours stimulation, determined IL-2 and IFN mRNA expression by RT-PCR. CD69 expression of mouse CD3+ T cell was determined by multi-color flow cytometric analysis after 6 hours stimulation, and CD25 expression of mouse CD3+ T cell was determined by multi-color flow cytometric analysis after 24 hours stimulation. RESULTS: TRD could inhibit IL-2 and IFN-gamma mRNA expression. It also inhibited CD69 and CD25 expression of mouse CD3+ T cell. CONCLUSION: the immunosuppressive mechanism of TRD may be related to the inhibitory effects on IL-2 and IFN-gamma mRNA expression and the inhibition of CD69 and CD25 expression.