Search

Graphitic carbon nitride (g-C3N4) is a promising heterogeneous photocatalyst in the visible range. It can be used, among others, for reductive conversion of the toxic hexavalent chromium occurring in various wastewaters. Its photocatalytic efficiency, however, has to be improved, which can be realized by modification with different dopants or co-catalysts forming heterojunctions. In our work, ruthenium-modified g-C3N4 has been prepared by ultrasonic impregnation of the pristine g-C3N4, which was synthesized from thiourea. The morphology, microstructure, and optical properties of the photocatalysts were characterized by XRD, SEM, FT-IR, TEM, XPS, and DRS. Their compositions were analyzed by EDS and XPS measurements, indicating 0.5% and 1.4% Ru, due to the different penetrating depths. XPS study showed mainly +2 for the oxidation state of Ru. DRS analysis indicated a slight change in both the CB (from −1.14 to −1.22 eV) and the VB (from 1.49 to 1.56 eV) energies of Ru/g-C3N4, compared to those of g-C3N4. The photocatalytic Cr(VI) reduction efficacy increased from 50.1 to 96.8%. Low pH (=2) was preferred for the photocatalytic Cr(VI) reduction due to the favorable surface charge and E(Cr(VI)/Cr(III)) redox potential. Ru modification proved to be promising for improving the photocatalytic performance of g-C3N4.

BackgroundLittle is known about the natural history of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.MethodsWe conducted a prospective study at a quarantine center for coronavirus disease 2019 in Ho Chi Minh City, Vietnam. We enrolled quarantined people with reverse-transcription polymerase chain reaction (RT-PCR)–confirmed SARS-CoV-2 infection, collecting clinical data, travel and contact history, and saliva at enrollment and daily nasopharyngeal/throat swabs (NTSs) for RT-PCR testing. We compared the natural history and transmission potential of asymptomatic and symptomatic individuals.ResultsBetween 10 March and 4 April 2020, 14 000 quarantined people were tested for SARS-CoV-2; 49 were positive. Of these, 30 participated in the study: 13 (43%) never had symptoms and 17 (57%) were symptomatic. Seventeen (57%) participants imported cases. Compared with symptomatic individuals, asymptomatic people were less likely to have detectable SARS-CoV-2 in NTS collected at enrollment (8/13 [62%] vs 17/17 [100%]; P = .02). SARS-CoV-2 RNA was detected in 20 of 27 (74%) available saliva samples (7 of 11 [64%] in the asymptomatic group and 13 of 16 [81%] in the symptomatic group; P = .56). Analysis of RT-PCR positivity probability showed that asymptomatic participants had faster viral clearance than symptomatic participants (P ConclusionsAsymptomatic SARS-CoV-2 infection is common and can be detected by analysis of saliva or NTSs. The NTS viral loads fall faster in asymptomatic individuals, but these individuals appear able to transmit the virus to others.

In this study, iron nanomaterial was synthesized by a reaction between FeCl3 and NaBH4 using microfluidic device as a microreactor which is prepared by photolithography and soft molding processes. Morphology and structure of the as-prepared nanomaterial was characterized by scanning microscope and X-ray diffraction analysis methods. The collected product is zero valent iron material with the morphology is nano-sheet with the thickness is approximatly 50 nm. Hexavalent chromium ion from K2Cr2O7 solution could be removed by the as-prepared iron nanomaterial. The removal of ions Cr(VI) is determined and confirmed by the visible ultraviolet (UV-Vis) absorption spectroscopy which is proportional to the amount of nanomaterial used and is influenced by pH conditions.

The pyridinedicarboxylate-Tb(III) complexes, TbPDC and Tb(PDC)3, as luminescent probes for ATP monitoring have been conveniently prepared and characterized by FT-IR, 1H-NMR, ESI-MS, UV-Vis, excitation, and emission spectroscopy. Interestingly, these two Tb(III) complexes were quenched by ATP by a similar mechanism via π-π stacking interaction between the chelating ligand and adenine moiety. The ability of luminescent probes applied for the determination of ATP in aqueous solution has been investigated. The dynamic ranges for the quantification of ATP are within 10−90 μM and 10−100 μM with detection limits of 7.62 and 11.20 μM for TbPDC and Tb(PDC)3, respectively. The results demonstrated that these luminescent probes would be a potential candidate assay for ATP monitoring in hygiene assessment.

Currently, MnBi magnetic material is promising to be very potential for low-cost high-temperature permanent magnetic applications. The most attractive parameters are the high magnetocrystalline anisotropy energy and its positive thermal coefficient which allow a high coercivity of MnBi magnets working even at 150 – 200 oC. This advantage is paid by the moderate value of magnetization, so the high energy product of MnBi magnets depends on how one can keep a good balance between the remanent magnetization Mr and the coercivity bHc. The paper considers this problem and discusses how to regulate the processing route to keep this balance to enhance the performance of MnBi green powders and MnBi bulk magnets prepared thereof

BackgroundOne hundred days after SARS-CoV-2 was first reported in Vietnam on January 23rd, 270 cases have been confirmed, with no deaths. We describe the control measures used by the Government and their relationship with imported and domestically-acquired case numbers, with the aim of identifying the measures associated with successful SARS-CoV-2 control.MethodsClinical and demographic data on the first 270 SARS-CoV-2 infected cases and the timing and nature of Government control measures, including numbers of tests and quarantined individuals, were captured by Vietnam’s National Steering Committee for COVID-19 response. Apple and Google mobility data provided proxies for population movement. Serial intervals were calculated from 33 infector-infectee pairs and used to estimate the proportion of pre-symptomatic transmission events and time-varying reproduction numbers.FindingsAfter the first confirmed case on January 23rd, the Vietnamese Government initiated mass communications measures, case-contact tracing, mandatory 14-day quarantine, school and university closures, and progressive flight restrictions. A national lockdown was implemented between April 1st and 22nd. Around 200 000 people were quarantined and 266 122 RT-PCR tests conducted. Population mobility decreased progressively before lockdown. 60% (163/270) of cases were imported; 43% (89/208) of resolved infections remained asymptomatic for the duration of infection. 21 developed severe disease, with no deaths. The serial interval was 3.24 days, and 27.5% (95% confidence interval, 15.7%-40.0%) of transmissions occurred pre-symptomatically. Limited transmission amounted to a maximum reproduction number of 1.15 (95% confidence interval, 0.37-2.36). No community transmission has been detected since April 15th.InterpretationVietnam has controlled SARS-CoV-2 spread through the early introduction of mass communication, meticulous contact-tracing with strict quarantine, and international travel restrictions. The value of these interventions is supported by the high proportion of asymptomatic and imported cases, and evidence for substantial pre-symptomatic transmission.FundingThe Vietnam Ministry of Health and Wellcome Trust, UK.Research in contextEvidence before this studyVietnam was one of the first countries outside of China to detect imported and human-to-human transmitted SARS-CoV-2 within its borders. Yet, as of May 1st, a total of only 270 cases have been confirmed, no deaths have occurred, and no community transmission has been detected since April 15th despite intensive screening, tracing and testing. We did a PubMed database search to identify studies investigating COVID-19 response in Vietnam using the terms “Vietnam”, “COVID-19”, and “SARS-CoV-2”. All relevant articles were evaluated. Studies describe cases of COVID-19 and their management, aspects of the government response from newspapers and online government sources, but there are no previous reports using national data to describe and investigate the national epidemic and the impact of control measures cases over time.Added value of this studyWe used data from the National Steering Committee for COVID-19 response to give a comprehensive account of the first 100 days of the SARS-CoV-2 epidemic in Vietnam, including case numbers and their symptomatology, the estimated reproductive number by week, and their relation to the multiple control measures instituted by the Vietnam Government over time. We show two distinctive features of Vietnam’s response. First, the Government took rapid actions to restrict international flights, closed schools and universities, and instituted meticulous case-contact tracing and quarantining from late January, well before these measures were advised by WHO. Second, they placed mass communication, education, and the identification, serial testing, and 14-day quarantine of all direct contacts of cases, regardless of symptom development, at the heart of the response. The value of strict contact-tracing and quarantine is supported by the high proportion of asymptomatic cases (43%) and imported cases (60%), and evidence for substantial pre-symptomatic transmission.Implications of all the available evidenceVietnam has had remarkable success in controlling the emergence of SARS-CoV-2. Our report provides a complete picture of the control of SARS-CoV-2 in Vietnam, with lessons for other Governments seeking to extend national SARS-CoV-2 control or prevent future epidemics. Our findings shows the importance of acting early, before the virus becomes established in the community, and before the case numbers overwhelm systems of case-contact tracing and mass quarantine. They also demonstrate the value of effective mass communication in rapidly educating the public in infection prevention measures and providing real-time information on the state of the epidemic.

A simple and accurate method has been developed for the simultaneous determination of fourpyrrolizidine alkaloids (PAs) including echimidine, senecionine, jacobine and intermidine in foodsupplements of plant origin. The instrumental conditions including the use of TSK-Gel columnfor the separation and an MS/MS detector in positive ESI source, multi-reactive monitoring(MRM) mode for quantitation were optimized. The method has fully validated and meets theperformance requirement of AOAC with good specificity. The linearity varies from 1.0 µg/kg to40 µg/kg, the LOD was of 0.3 µg/kg; the repeatability and recovery range from 3.6% to 7.5% and88.7% to 117%, respectively. The method was applied to determine PAs in 90 food supplementsamples, of which 26 samples (28.8%) contain PAs.