Research on the fracture behavior of PBX under static tension

The fracture behavior of polymer-bonded explosive(PBX) seriously affects the safety and reliability of weapon system.The effects of interface debonding and initial meso-damage on the fracture behavior of PBX under quasi-static tension are studied using numerical method.A twodimensional representative volume element(RVE) is established based on Voronoi model in which the component contents could be regulated and the particles are randomly distributed.A nonlinear damage model of polymer matrix relative to matrix depth between particles is constructed.The results show that the simulated strain-stress relation is coincident with experiment data.It is found that interface debonding leads to the nucleation and propagation of meso-cracks,and a main crack approximately perpendicular to the loading direction is generated finally.The interface debonding tends to occur in the interface perpendicular to the loading direction.There seems to be a phenomenon that strain softening and hardening alternatively appear around peak stress of stress and strain curve.It is shown that the initial damages of intragranular and interfacial cracks both decrease the modulus and failure stress,and the main crack tends to propagate toward the initial meso-cracks.

Myocardial infarction detected by a smartwatch after transcatheter aortic valve replacement during the COVID-19 pandemic

Dear editor,Transcatheter aortic valve replacement(TAVR)is a safe and effective first-line therapeutic management for patients with severe aortic stenosis.The evidence of multiple randomized clinical trials proves the safety and efficacy of TAVR in patients.[1-2]However,new-onset conduction disorders,atrial fi brillation,and acute coronary syndrome are still common complications after TAVR procedures.Acute life-threatening complications such as myocardial infarction may result in fatal clinical outcomes.The COVID-19 pandemic makes periodic and timely follow-ups for patients after TAVR more diffi cult.An ambulatory electrocardiogram(AECG)monitoring system by a smart wearable device has recently emerged as a tool to monitor cardiac events before and after TAVR.[3]Smartwatches can monitor and record multiple biometric parameters,like heart rate,step counts,sleep cycles,oxygen saturation,and analyze QRS complexes and P waves after triggering incidences。

Pleiotropic Effect of tatC Mutation on Metabolism of Pathogen Yersinia enterocolitica

Objective To analyze the impact of depletion of the twin arginine translocation （TAT） system on virulence and physiology of Yersinia enterocolitica for a better understanding of its pathogenicity. Methods We constructed a △tatC：：Sp^R mutant of Yersinia enterocolitica by P1 phage mediated transduction using Escherichia coli K-12 △tatC：：Sp^R strain as a donor. Results A Pl-mediated genetic material transfer was found between the two species of enterobacteria, indicating a great potential of acquisition of antibiotic resistance in emergency of a new threatening pathogen by genetic material exchanges. Periplasmic trimethylamine N-oxidase reductase activity was detected in the wild type E enterocolitica strain and translocation of this enzyme was completely abolished by the △tatC：：Sp^R mutation. In addition, the △tatC：：Sp^R mutation showed a pleiotropic effect on the metabolism of E enterocolitica. However, the tat mutation did not seem to affect the mobility and virulence of Y. enterocolitica under the conditions used. Conclusion Unlike other pathogenic bacteria studied, the TAT system of E enterocolitica might play an important role in the pathogenic process, which is distinct from other pathogens, such as Pseudomonas aeruginosa and enterohemorrhagic E. coli O 157：H7.

Efficacy of Mild Hypothermia for the Treatment of Patients with Cardiac Arrest

Background： Therapeutic hypothermia has been recommended for the treatment of cardiac arrest patients who remain comatose after the return of spontaneous circulation. The aim of this study was to evaluate the effectiveness and safety of mild hypothermia on patients with cardiac arrest by conducting a meta-analysis. Methods： The relevant trials were searched in Cochrane Library, PubMed, Web of Science, Embase, CNKI and Wan Fang Data from the date of their establishment to October 2014. Thereafter, the studies retrieved were screened based on predeflned inclusion and exclusion criteria. Data were extracted, and the quality of the included studies was evaluated. A meta-analysis was conducted using the Cochrane Collaboration Review Manager 5.2 sottware. Results： Six randomized controlled trials involving 531 cases were included, among which 273 cases were assigned to the treatment group and the other 258 cases to the control group. The meta-analysis indicated that mild hypothermia therapy alter cardiac arrest produced significant differences ill survival rate （relative risk [RR] =1.23, 95% confidence interval [C/]： 1.02-1.48, P = 0.03） and neurological function （RR - 1.33, 95% （.7： 1.08-1.65, P - 0.007） alter 6 months compared with normothermia therapy. However, no significant differences were observed in the survival to the hospital discharge （RR = 1.35, 95% CI： 0.87-2.10, P - 0.1 8）, favorable neurological outcome at hospital discharge （RR = 1.53, 95% CI： 0.95 2.45, P = 0.08） and adverse events. Conclusions： The meta-analysis demonstrated that mild hypothermia can improve the survival rate and neurological function of patients with cardiac arrest after 6 months. On the other hand, regarding the survival to hospital discharge, favorable neurological outcome at hospital discharge, and adverse events, our meta-analysis produced nonsignificant results.

Genetic source tracking of an anthrax outbreak in Shaanxi province,China

Background:Anthrax is an acute zoonotic infectious disease caused by the bacterium known as Bacillus anthracis.From 26 July to 8 August 2015,an outbreak with 20 suspected cutaneous anthrax cases was reported in Ganquan County,Shaanxi province in China.The genetic source tracking analysis of the anthrax outbreak was performed by molecular epidemiological methods in this study.Methods:Three molecular typing methods,namely canonical single nucleotide polymorphisms(canSNP),multiple-locus variable-number tandem repeat analysis(MLVA),and single nucleotide repeat(SNR)analysis,were used to investigate the possible source of transmission and identify the genetic relationship among the strains isolated from human cases and diseased animals during the outbreak.Results:Five strains isolated from diseased mules were clustered together with patients’isolates using canSNP typing and MLVA.The causative B.anthracis lineages in this outbreak belonged to the A.Br.001/002 canSNP subgroup and the MLVA15-31 genotype(the 31 genotype in MLVA15 scheme).Because nine isolates from another four provinces in China were clustered together with outbreak-related strains by the canSNP(A.Br.001/002 subgroup)and MLVA15 method(MLVA15-31 genotype),still another SNR analysis(CL10,CL12,CL33,and CL35)was used to source track the outbreak,and the results suggesting that these patients in the anthrax outbreak were probably infected by the same pathogen clone.Conclusions:It was deduced that the anthrax outbreak occurred in Shaanxi province,China in 2015 was a local occurrence.

Plasma gelsolin level predicts acute kidney injury after cardiopulmonary bypass in infants and young children

Background Acute kidney injury(AKI)after cardiopulmonary bypass(CPB)is a common complication especially in pedi-atric population.Plasma gelsolin(pGSN)is an anti-inflammatory factor through binding with actin and pro-inflammatory cytokines in circulation.Decrease in pGSN has been reported in some pathologic conditions.The purpose of the study was to determine the alterations of pGSN level in infants and young children after CPB and the role of pGSN as a predictor for the morbidity and severity of post-CPB AKI.Methods Sixty-seven infants and young children at age≤3 years old undergoing CPB were prospectively enrolled.PGSN levels were measured during peri-operative period with enzyme-linked immuno-sorbent assay and normalized with plasma total protein concentration.Other clinical characteristics of the patients were also recorded.Results In patients developing AKI,the normalized pGSN(pGSN_(N))levels significantly decreased at 6 h post-operation and remained low for 24 h post-operation as compared to the patients with non-AKI.PGSNN at 6 h post-operation combining with CPB time presents an excellent predictive value for AKI.Conclusions Decreased pGSN_(N)identifies post-CPB AKI in the patients≤3 years old,and is associated with adverse clini-cal outcomes.The findings suggest that circulating GSN in post-CPB patients may have beneficial effects on diminishing inflammatory responses.

Demand for longer quarantine period among common and uncommon COVID-19 infections: a scoping review

Background:As one of the non-pharmacological interventions to control the transmission of COVID-19,determining the quarantine duration is mainly based on the accurate estimates of the incubation period.However,patients with coarse information of the exposure date,as well as infections other than the symptomatic,were not taken into account in previously published studies.Thus,by using the statistical method dealing with the interval-censored data,we assessed the quarantine duration for both common and uncommon infections.The latter type includes the presymptomatic,the asymptomatic and the recurrent test positive patients.Methods:As of 10 December 2020,information on cases have been collected from the English and Chinese databases,including Pubmed,Google scholar,CNKI(China National Knowledge Infrastructure)and Wanfang.Official websites and medias were also searched as data sources.All data were transformed into doubly interval-censored and the accelerated failure time model was applied.By estimating the incubation period and the time-to-event distribution of worldwide COVID-19 patients,we obtain the large percentiles for determining and suggesting the quarantine policies.For symptomatic and presymptomatic COVID-19 patients,the incubation time is the duration from exposure to symptom onset.For the asymptomatic,we substitute the date of first positive result of nucleic acid testing for that of symptom onset.Furthermore,the time from hospital discharge or getting negative test result to the positive recurrence has been calculated for recurrent positive patients.Results:A total of 1920 laboratory confirmed COVID-19 cases were included.Among all uncommon infections,34.1%(n=55)of them developed symptoms or were identified beyond fourteen days.Based on all collected cases,the 95th and 99th percentiles were estimated to be 16.2 days(95%Cl 15.5-17.0)and 22.9 days(21.7-24.3)respectively.Besides,we got similar estimates based on merely symptomatic and presymptomatic infections as 15.1 days(14.4-15.7)and 21.1 days(20.0-22.2).Conclusions:There are a certain number of infected people who require longer quarantine duration.Our findings well support the current practice of the extended active monitoring.To further prevent possible transmissions induced and facilitated by such infectious outliers after the 14-days quarantine,properly prolonging the quarantine duration could be prudent for high-risk scenarios and in regions with insufficient test resources.