The prevalence of asymptomatic cryptococcal antigenemia(ACA)in human immunodeficiency virus(HIV)infected individuals has been observed to be elevated.The prevalence of ACA ranges from 1.3%to 13%,with different rates o...The prevalence of asymptomatic cryptococcal antigenemia(ACA)in human immunodeficiency virus(HIV)infected individuals has been observed to be elevated.The prevalence of ACA ranges from 1.3%to 13%,with different rates of prevalence in various regions of the world.We reviewed studies conducted internationally,and also referred to two established expert consensus guideline documents published in China,and we have concluded that Chinese HIV-infected patients should undergo cryptococcal antigen screening when CD4+T-cell counts fall below 200 cells/μL and that the recommended treatment regimen for these patients follow current World Health Organization guidelines,although it is likely that this recommendation may change in the future.Early screening and optimized preemptive treatment for ACA is likely to help decrease the incidence of cryptococcosis,and is lifesaving.Further studies are warranted to explore issues related to the optimal management of ACA.展开更多
To the Editor:At the end of 2019,an outbreak of novel coronavirus disease 2019(COVID-19),caused by 2019-nCov,causing widespread novel coronavirus disease.This outbreak of COVID-19 occurred during the period of the 202...To the Editor:At the end of 2019,an outbreak of novel coronavirus disease 2019(COVID-19),caused by 2019-nCov,causing widespread novel coronavirus disease.This outbreak of COVID-19 occurred during the period of the 2020 Spring Festival in China,a period known for massive population movements within China.This has resulted in large numbers of infected patients as a consequence of multiple human contact episodes in individual travelers.展开更多
It has been established that star polymers with a large number of arms display both the conventional chain relaxation and a slower interchain relaxation due to the formation of hard cores,which is called the local str...It has been established that star polymers with a large number of arms display both the conventional chain relaxation and a slower interchain relaxation due to the formation of hard cores,which is called the local structural relaxation.Here,we demonstrate that this unique relaxation property of multi-arm stars leads to unusual rheological behaviors.We study the response of star polymer melts with various arm numbers to start-up shear flow via nonequilibrium molecular dynamics simulation.Our simulation results indicate that the stress-strain response of multi-arm star polymer melts differs from that of star polymers with a small number of arms in both quantitative and qualitative manners.While the multi-arm star polymer melts exhibit an overshoot peak in the stress-strain curve both at relatively small and sufficiently large shear rates,two overshoot peaks appear when the flow strength is comparable to the relaxation time of the star polymers.This double stress overshoot is absent in linear polymers and star polymers with a small number of arms and is evidently related to the presence of the local structural relaxation in star polymers with a large number of arms.We present a detailed analysis of the conformational and dynamical properties of star polymer melts under start-up shear to gain a molecular understanding of their stress response.展开更多
We adopt Langevin dynamics to explore the stress-structure relationship of telechelic reversible associating polymer gel during startup shear flow, with shear strengths varying from Wi=12.6 to Wi=12640. At weak shear ...We adopt Langevin dynamics to explore the stress-structure relationship of telechelic reversible associating polymer gel during startup shear flow, with shear strengths varying from Wi=12.6 to Wi=12640. At weak shear flow Wi=12.6, the shear stress proportionally increases with shear strain at short times, followed by a strain hardening behavior and then passes through a maximum(σmax, γmax) and finally decreases until it reaches the steady state. During the evolution of stress, the gel network is only slightly broken and essentially maintains its framework, and the strain hardening behavior originates from the excessive stretching of chains. On the other hand, the stress-strain curve at intermediate shear flow Wi=505.6 shows two differences from that at Wi=12.6, namely, the absence of strain hardening and a dramatic increase of stress at large strains,which is caused by the rupture of gel network at small strains and the network recovery at large strains, respectively. Finally, at very strong shear flow Wi=6319.7, the gel network is immediately broken by shear flow and the stress-strain curve exhibits similar behaviors to those of classical polymeric liquids.展开更多
基金This work was supported by the National Science and Technology Major Project of China During the 13th Five-year Plan Period(No.2018ZX10302104)the Joint Medical Research Project of Chongqing Science and Technology Commission(No.2019ZDXM012)+1 种基金the Youth Scientific Research and Innovation Fund Project of Chongqing Public Health Medical Center(No.2019QNKYXM05)the Capacity Improvement Plan Project of Units appointed by the Chongqing Municipal Health Commission(No.2019NLTS003)。
文摘The prevalence of asymptomatic cryptococcal antigenemia(ACA)in human immunodeficiency virus(HIV)infected individuals has been observed to be elevated.The prevalence of ACA ranges from 1.3%to 13%,with different rates of prevalence in various regions of the world.We reviewed studies conducted internationally,and also referred to two established expert consensus guideline documents published in China,and we have concluded that Chinese HIV-infected patients should undergo cryptococcal antigen screening when CD4+T-cell counts fall below 200 cells/μL and that the recommended treatment regimen for these patients follow current World Health Organization guidelines,although it is likely that this recommendation may change in the future.Early screening and optimized preemptive treatment for ACA is likely to help decrease the incidence of cryptococcosis,and is lifesaving.Further studies are warranted to explore issues related to the optimal management of ACA.
基金This work was supported by the Chongqing Special Research Project for Prevention and Control of Novel Coronavirus Pneumonia(No.cstc2020jscx-fyzx0074)。
文摘To the Editor:At the end of 2019,an outbreak of novel coronavirus disease 2019(COVID-19),caused by 2019-nCov,causing widespread novel coronavirus disease.This outbreak of COVID-19 occurred during the period of the 2020 Spring Festival in China,a period known for massive population movements within China.This has resulted in large numbers of infected patients as a consequence of multiple human contact episodes in individual travelers.
基金financially supported by the National Natural Science Foundation of China(Nos.21873092,21790341 and B040102)。
文摘It has been established that star polymers with a large number of arms display both the conventional chain relaxation and a slower interchain relaxation due to the formation of hard cores,which is called the local structural relaxation.Here,we demonstrate that this unique relaxation property of multi-arm stars leads to unusual rheological behaviors.We study the response of star polymer melts with various arm numbers to start-up shear flow via nonequilibrium molecular dynamics simulation.Our simulation results indicate that the stress-strain response of multi-arm star polymer melts differs from that of star polymers with a small number of arms in both quantitative and qualitative manners.While the multi-arm star polymer melts exhibit an overshoot peak in the stress-strain curve both at relatively small and sufficiently large shear rates,two overshoot peaks appear when the flow strength is comparable to the relaxation time of the star polymers.This double stress overshoot is absent in linear polymers and star polymers with a small number of arms and is evidently related to the presence of the local structural relaxation in star polymers with a large number of arms.We present a detailed analysis of the conformational and dynamical properties of star polymer melts under start-up shear to gain a molecular understanding of their stress response.
基金financially supported by the National Natural Science Foundation of China (Nos. 21873092, 21774127,21790341, 21790342)the Key Research Program of Frontier Sciences+1 种基金CAS (No. QYZDY-SSW-SLH027)the Jilin Provincial science and technology development program (No.20190103115JH)。
文摘We adopt Langevin dynamics to explore the stress-structure relationship of telechelic reversible associating polymer gel during startup shear flow, with shear strengths varying from Wi=12.6 to Wi=12640. At weak shear flow Wi=12.6, the shear stress proportionally increases with shear strain at short times, followed by a strain hardening behavior and then passes through a maximum(σmax, γmax) and finally decreases until it reaches the steady state. During the evolution of stress, the gel network is only slightly broken and essentially maintains its framework, and the strain hardening behavior originates from the excessive stretching of chains. On the other hand, the stress-strain curve at intermediate shear flow Wi=505.6 shows two differences from that at Wi=12.6, namely, the absence of strain hardening and a dramatic increase of stress at large strains,which is caused by the rupture of gel network at small strains and the network recovery at large strains, respectively. Finally, at very strong shear flow Wi=6319.7, the gel network is immediately broken by shear flow and the stress-strain curve exhibits similar behaviors to those of classical polymeric liquids.
