BACKGROUND Frontline nurses in Wuhan directly fighting severe acute respiratory syndrome coronavirus-2 diseases are at a high risk of infection and are extremely susceptible to psychological stress,especially due to t...BACKGROUND Frontline nurses in Wuhan directly fighting severe acute respiratory syndrome coronavirus-2 diseases are at a high risk of infection and are extremely susceptible to psychological stress,especially due to the global coronavirus disease 2019(COVID-19)pandemic.The psychological after-effects of this public health emergency on frontline nurses will last for years.AIM To assess factors influencing post-traumatic stress disorder(PTSD)among frontline nurses in Wuhan 6 mo after the COVID-19 pandemic began.METHODS A total of 757 frontline nurses from five hospitals in Wuhan,China,participated in an online survey from July 27 to August 13,2020.This cross-sectional online study used a demographic information questionnaire,the PTSD Checklist for the Diagnostic and Statistical Manual of Mental Disorders,the Connor-Davidson Resilience Scale,and the Patient Health Questionnaire-4.The chisquare test and logistic regression were used to analyze the association of demographics,COVID-19-related variables,and PTSD.Logistic regression was also conducted to investigate which variables were associated with PTSD outcomes.RESULTS A total of 13.5%,24.3%,and 21.4%of the frontline nurses showed symptoms of PTSD,depression,and anxiety,respectively.The multivariate logistic regression analysis showed that the following factors were strongly associated with PTSD:Having a relative,friend,or colleague who died of COVID-19;experiencing stigma;or having psychological assistance needs,depressive symptoms or anxiety.Showing resilience and receiving praise after the COVID-19 outbreak were protective factors.CONCLUSION Frontline nurses still experienced PTSD(13.5%)six months after the COVID-19 outbreak began.Peer support,social support,official recognition,reward mechanisms,exercise,better sleep,and timely provision of information(such as vaccine research progress)by the government via social media,and adequate protective supplies could mitigate the level of PTSD among nurses responding to COVID-19.Stigmatization,depression,and anxiety might be associated with a greater risk of PTSD among nurses.展开更多
The white dwarf(WD)+helium(He)star binary channel plays an important role in the single degenerate scenario for the progenitors of type Ia supernovae(SNe Ia).Previous studies on the WD+main sequence star evolution hav...The white dwarf(WD)+helium(He)star binary channel plays an important role in the single degenerate scenario for the progenitors of type Ia supernovae(SNe Ia).Previous studies on the WD+main sequence star evolution have shown that the magnetic fields of WDs may significantly influence their accretion and nuclear burning processes.In this work we focus on the evolution of magnetized WD+He star binaries with detailed stellar evolution and binary population synthesis(BPS)calculations.In the case of magnetized WDs,the magnetic fields may disrupt the inner regions of the accretion disk,funnel the accretion flow onto the polar caps and even confine helium burning within the caps.We find that,for WDs with sufficiently strong magnetic fields,the parameter space of the potential SN Ia progenitor systems shrinks toward shorter orbital periods and lower donor masses compared with that in the non-magnetized WD case.The reason is that the magnetic confinement usually works with relatively high mass transfer rates,which can trigger strong wind mass loss from the WD,thus limiting the He-rich mass accumulation efficiency.The surviving companion stars are likely of low-mass at the moment of the SN explosions,which can be regarded as a possible explanation for the non-detection of surviving companions after the SNe or inside the SN remnants.However,the corresponding birthrate of Galactic SNe Ia in our high-magnetic models is estimated to be~(0.08–0.13)×10^(-3)yr^(-1)(~0.17–0.28×10^(-3)yr^(-1)for the non-magnetic models),significantly lower than the observed Galactic SN Ia birthrate.展开更多
BACKGROUND Increasing attention has been paid to acute myocardial infarction(AMI)in young female patients for whom secondary factors should be considered during the diagnostic process.Anti-phospholipid syndrome(APS),a...BACKGROUND Increasing attention has been paid to acute myocardial infarction(AMI)in young female patients for whom secondary factors should be considered during the diagnostic process.Anti-phospholipid syndrome(APS),a rare autoimmune disease that is most common in young female patients,is reportedly related to AMI.To date,coronary interventions,particularly stenting,remains controversial in this special clinical scenario.CASE SUMMARY A 26-year-old female patient was admitted to hospital for acute chest pain,palpitations,and dyspnea.She had a past medical history of APS and pulmonary embolism.Coronary angiography showed acute occlusion of the proximal left anterior descending artery.After repeated thrombus aspirations,residual thrombus and mild stenosis were found in the proximal left anterior descending artery.Optical coherence tomography(OCT)was done,which confirmed the non-atherosclerosis coronary thrombosis and an intact intima in this patient.Deferring or avoiding stenting based on follow-up intracoronary findings with intensified antithrombotic treatment was chosen.One week later,coronary angiography and OCT confirmed an intact intima with no injury and no residual thrombus.The 3-mo telephone follow-up reported a good prognosis.CONCLUSION APS can cause acute non-atherosclerosis coronary thrombosis which presents as an AMI in young female patients.Intracoronary OCT findings can guide interventional strategies in this special clinical scenario.展开更多
Southern rice black-streaked dwarf virus (SRBSDV) is a novel Fijivirus prevalent in rice in southern and central China,and northern Vietnam. Its genome has 10 segments of double-stranded RNA named S1 to S10 according ...Southern rice black-streaked dwarf virus (SRBSDV) is a novel Fijivirus prevalent in rice in southern and central China,and northern Vietnam. Its genome has 10 segments of double-stranded RNA named S1 to S10 according to their size. An isolate of SRBSDV,JNi4,was obtained from naturally infected maize plants from Ji'ning,Shandong province,in the 2008 maize season. Segments S7 to S10 of JNi4 share nucleotide identities of 72.6%-73.1%,72.3%-73%,73.9%-74.5% and 77.3%-79%,respectively,with corresponding segments of Rice black-streaked dwarf virus isolates,and identities of 99.7%,99.1%-99.7%,98.9%-99.5%,and 98.6%-99.2% with those of SRBSDV isolates HN and GD. JNi4 forms a separate branch with GD and HN in the phylogenetic trees constructed with genomic sequences of S7 to S10. These results confirm the proposed taxonomic status of SRBSDV as a distinct species of the genus Fijivirus and indicate that JNi4 is an isolate of SRBSDV. Shandong is so far the northernmost region where SRBSDV is found in China.展开更多
The disturbance of flat and V-shaped sandwich reactive armor configurations to shaped-charge jet is studied by a numerical approach. The disturbing and cutting effects of the two reactive armor configurations to the j...The disturbance of flat and V-shaped sandwich reactive armor configurations to shaped-charge jet is studied by a numerical approach. The disturbing and cutting effects of the two reactive armor configurations to the jet are successfully captured. The predicted disturbance characteristics and patterns are in fairly good agreement with the X-ray photographic observations. The residual depth of penetration into a semiinfinitive homogeneous steel target behind the reactive armor is computed for a series of jet/armor parameters. For the flat configuration, it is demonstrated that the residual penetration depth is not significantly reduced for a normal impact while it is reduced up to 75% for an oblique impact. In comparison, the V-shaped configuration reduces the penetration depth of the jet to 90%, and it is observed that the penetration depth is not sensitive to the V-shaped angle.展开更多
AIM:To test the pathogenicity of pseudorabies virus(PRV)variant HN1201 and compare its pathogenicity with a classical PRV Fa strain.METHODS:The pathogenicity of the newly-emerging PRV variant HN1201 was evaluated by d...AIM:To test the pathogenicity of pseudorabies virus(PRV)variant HN1201 and compare its pathogenicity with a classical PRV Fa strain.METHODS:The pathogenicity of the newly-emerging PRV variant HN1201 was evaluated by different inoculating routes,virus loads,and ages of pigs.The classical PRV Fa strain was then used to compare with HN1201 to determine pathogenicity.Clinical symptoms after virus infection were recorded daily and average daily body weight was used to measure the growth performance of pigs.At necropsy,gross pathology and histopathology were used to evaluate the severity of tissue damage caused by virus infection.RESULTS:The results showed that the efficient infection method of RPV HN1201 was via intranasal inoculation at 107 TCID50,and that the virus has high pathogenicity to 35-to 127-d old pigs.Compared with Fa strain,pigs infected with HN1201 showed more severe clinical symptoms and pathological lesions.Immunochemistry results revealed HN1201 had more abundant antigen distribution in extensive organs.CONCLUSION:All of the above results suggest that PRV variant HN1201 was more pathogenic to pigs than the classical Fa strain.展开更多
We employ the supernova fallback disk model to simulate the spin evolution of isolated young neutron stars(NSs). We consider the submergence of the NS magnetic fields during the supercritical accretion stage and its s...We employ the supernova fallback disk model to simulate the spin evolution of isolated young neutron stars(NSs). We consider the submergence of the NS magnetic fields during the supercritical accretion stage and its succeeding reemergence. It is shown that the evolution of the spin periods and the magnetic fields in this model is able to account for the relatively weak magnetic fields of central compact objects and the measured braking indices of young pulsars. For a range of initial parameters, evolutionary links can be established among various kinds of NS sub-populations including magnetars, central compact objects and young pulsars. Thus, the diversity of young NSs could be unified in the framework of the supernova fallback accretion model.展开更多
BACKGROUND Upper gastrointestinal bleeding(UGIB) after an acute myocardial infarction(AMI) is not an uncommon complication. Acute UGIB caused by Mallory-Weiss syndrome(MWS) is usually a dire situation with massive ble...BACKGROUND Upper gastrointestinal bleeding(UGIB) after an acute myocardial infarction(AMI) is not an uncommon complication. Acute UGIB caused by Mallory-Weiss syndrome(MWS) is usually a dire situation with massive bleeding and hemodynamic instability. Acute UGIB caused by MWS after an AMI has not been previously reported.CASE SUMMARY A 57-year-old man with acute inferior wall ST elevation myocardial infarction underwent a primary coronary intervention of the acutely occluded right coronary artery. Six hours after the intervention, the patient had a severe UGIB,followed by vomiting. His hemoglobin level dropped from 15.3 g/d L to 9.7 g/d L. In addition to blood transfusion and a gastric acid inhibition treatment,early endoscopy was employed and MWS was diagnosed. Bleeding was stopped by endoscopic placement of titanium clips.CONCLUSION Bleeding complications after stent implantation can pose a dilemma. MWS is a rare but severe cause of acute UGIB after an AMI that requires an early endoscopic diagnosis and a hemoclip intervention to stop bleeding.展开更多
Magnetars form a special population of neutron stars with strong magnetic fields and long spin periods. About 30 magnetars and magnetar candidates known currently are probably isolated, but the possibility that magnet...Magnetars form a special population of neutron stars with strong magnetic fields and long spin periods. About 30 magnetars and magnetar candidates known currently are probably isolated, but the possibility that magnetars are in binaries has not been excluded. In this work, we perform spin evolution of neutron stars with different magnetic fields in wind-fed high-mass X-ray binaries and compare the spin period distribution with observations, aiming to find magnetars in binaries. Our simulation shows that some of the neutron stars, which have long spin periods or are in widely-separated systems, need strong magnetic fields to explain their spin evolution. This implies that there are probably magnetars in high-mass X-ray binaries. Moreover, this can further provide a theoretical basis for some unclear astronomical phenomena, such as the possible origin of periodic fast radio bursts from magnetars in binary systems.展开更多
The distribution of the mass of white dwarfs(WDs)is one of the fundamental questions in the field of cataclysmic variables(CVs).In this work,we make a systematical investigation on the WD masses in two subclass of CVs...The distribution of the mass of white dwarfs(WDs)is one of the fundamental questions in the field of cataclysmic variables(CVs).In this work,we make a systematical investigation on the WD masses in two subclass of CVs:intermediate polars(IPs)and non-magnetic CVs in the solar vicinity based on the fiux ratios of Fe XXVI-Lyαto Fe XXV-Heαemission lines(I_(7.0)/I_(6.7))from archival XMM-Newton and Suzaku observations.We first verify the(semi-empirical)relations between I_(7.0)/I_(6.7),the maximum emission temperature(T_(max))and the WD mass(M_(WD))with the mkcfiow model based on the apec description and the latest Atom DB.We then introduce a new spectral model to measure M_(WD)directly based on the above relations.A comparison shows that the derived M_(WD)is consistent with dynamically measured ones.Finally,we obtain the average WD masses of 58 CVs(including 36IPs and 22 non-magnetic CVs),which is the largest X-ray selected sample.The average WD masses are<M_(WD,IP)>=0.81±0.21 M☉and<M_(WD,DN)>=0.81±0.21M☉ for IPs and non-magnetic CVs,respectively.These results are consistent with previous works.展开更多
X-ray emission is an important indicator of stellar activity.In this paper,we study stellar Xray activity using the XMM-Newton and LAMOST data for different types of stars.We provide a sample including 1259 X-ray-emit...X-ray emission is an important indicator of stellar activity.In this paper,we study stellar Xray activity using the XMM-Newton and LAMOST data for different types of stars.We provide a sample including 1259 X-ray-emitting stars,of which 1090 have accurate stellar parameter estimations.Our sample size is much larger than those used in previous works.We find a bimodal distribution of the X-ray to optical flux ratio(log(fX/fV)) for G and K stars.We interpret that this bimodality is due to two subpopulations with different coronal heating rates.Furthermore,using the full widths at half maxima calculated from Hα and Hβ lines,we show that these stars in the inactive peaks have smaller rotational velocities.This is consistent with the magnetic dynamo theory that presumes stars with low rotational velocities have low levels of stellar activity.We also examine the correlation between log(fX/fV) and luminosity of the excess emission in the Hα line,and find a tight relation between the coronal and chromospheric activity indicators.展开更多
Most astrophysical accretion disks are likely to be warped.In X-ray binaries,the spin evolution of an accreting neutron star is critically dependent on the interaction between the neutron star magnetic field and the a...Most astrophysical accretion disks are likely to be warped.In X-ray binaries,the spin evolution of an accreting neutron star is critically dependent on the interaction between the neutron star magnetic field and the accretion disk.There have been extensive investigations on the accretion torque exerted by a coplanar disk that is magnetically threaded by the magnetic field lines from the neutron stars,but relevant works on warped/tilted accretion disks are still lacking.In this paper we develop a simplified twocomponent model,in which the disk is comprised of an inner coplanar part and an outer,tilted part.Based on standard assumption on the formation and evolution of the toroidal magnetic field component,we derive the dimensionless torque and show that a warped/titled disk is more likely to spin up the neutron star compared with a coplanar disk.We also discuss the possible influence of various initial parameters on the torque.展开更多
We adopt the tidal truncation model proposed by Negueruela and Okazaki for Be/X-ray binaries to investigate the influence of intermediate-mass black holes (IMBHs) on Be-star disks. We show that the viscous decretion...We adopt the tidal truncation model proposed by Negueruela and Okazaki for Be/X-ray binaries to investigate the influence of intermediate-mass black holes (IMBHs) on Be-star disks. We show that the viscous decretion disks around Be stars are generally truncated ineffectively under the tidal force of IMBHs. Combining this with observations of Be/X-ray binaries, we suggest that Be/IMBH X-ray binaries may appear as recurrent luminous X-ray transients with quasi-periodic X-ray outbursts.展开更多
Several X-ray binaries(XRBs)have been identified to be associated with supernova remnants(SNRs).Because of the short lifetimes of SNRs,this leaves them to be the youngest known XRBs.This small group of binaries provid...Several X-ray binaries(XRBs)have been identified to be associated with supernova remnants(SNRs).Because of the short lifetimes of SNRs,this leaves them to be the youngest known XRBs.This small group of binaries provides valuable information on the formation of compact stars under the framework of massive binary evolution.In this paper we review the observational characteristics of these youngest XRBs and discuss their possible implications on the initial conditions of compact stars and their interaction with the companion stars.展开更多
Abstract The binding energy parameter A plays a vital role in common envelope evolution. Though it is well known that A takes different values for stars with different masses and varies during stellar evolution, it ha...Abstract The binding energy parameter A plays a vital role in common envelope evolution. Though it is well known that A takes different values for stars with different masses and varies during stellar evolution, it has been erroneously adopted as a constant in most population synthesis calculations. We have system- atically calculated the values of A for stars of masses 1 - 60 M by use of an updated stellar evolution code, taking into account the contribution from both gravitational energy and internal energy to the binding energy of the envelope. We adopt the criterion for the core-envelope boundary advocated by Ivanova. A new kind of A with an enthalpy prescription is also investigated. We present fitting formulae for the calculated values of various kinds of A, which can be used in future population synthesis studies.展开更多
We perform numerical calculations to simulate the evolution of low-mass X-ray binary systems. For the accreting compact object we consider the initial mass of 1.4, 10, 20, 100, 200, 500 and 1000 Mo, corresponding to n...We perform numerical calculations to simulate the evolution of low-mass X-ray binary systems. For the accreting compact object we consider the initial mass of 1.4, 10, 20, 100, 200, 500 and 1000 Mo, corresponding to neutron stars (NSs), stellar- mass black holes (BHs) and intermediate-mass BHs. Mass transfer in these binaries is driven by nuclear evolution of the donors and/or orbital angular momentum loss due to magnetic braking and gravitational wave radiation. For the different systems, we determine their bifurcation periods Pbif that separate the formation of converging systems from the diverging ones, and show that Pbif changes from ~ 1 d to ≥ 3 d for a 1 Mo donor star, with increasing initial accretor mass from 1.4 to 1000 Mo. This means that the dominant mechanism of orbital angular momentum loss changes from magnetic braking to gravitational radiation. As an illustration we compare the evolution of binaries consisting of a secondary star of 1 Mo at a fixed initial period of 2 d. In the case of the NS or stellar-mass BH accretor, the system evolves to a well-detached He white dwarf-neutron star/black hole pair, but it evolves to an ultra- compact binary if the compact object is an intermediate-mass BH. Thus the binary evolution heavily depends upon the mass of the compact object. However, we show that the final orbital period-white dwarf mass relation found for NS low-mass X-ray binaries is fairly insensitive to the initial mass of the accreting star, even if it is an intermediate-mass BH.展开更多
There is accumulating evidence for mass ejection in low-mass X-ray binaries (LMXBs) driven by radio pulsar activity during X-ray quiescence. We consider the condition for mass ejection by comparing the radiation pre...There is accumulating evidence for mass ejection in low-mass X-ray binaries (LMXBs) driven by radio pulsar activity during X-ray quiescence. We consider the condition for mass ejection by comparing the radiation pressure from a millisecond pulsar, and the gas pressure at the inner Lagrange point or at the surrounding accretion disk. We calculate the critical spin period of the pulsar below which mass ejection is allowed. Combining with the evolution of the mass transfer rate, we present constraints on the orbital periods of the systems. We show that mass ejection could happen in both wide and compact LMXBs. It may be caused by transient accretion due to thermal instability in the accretion disks in the former, and irradiation-driven mass-transfer cycles in the latter.展开更多
Locust(Locusta migratoria)has a single striated muscle myosin heavy chain(Mhc)gene,which contains 5 clusters of alternative exclusive exons and 1 differently included penultimate exon.The alternative exons of Mhc gene...Locust(Locusta migratoria)has a single striated muscle myosin heavy chain(Mhc)gene,which contains 5 clusters of alternative exclusive exons and 1 differently included penultimate exon.The alternative exons of Mhc gene encode 4 distinct regions in the myosin motor domain,that is,the N-terminal SH3-like domain,one lip of the nucleotide-binding pocket,the relay,and the converter.Here,we investigated the role of the alternative regions on the motor function of locust muscle myosin.Using Sf9-baculovirus protein expression system,we expressed and purified 5 isoforms of the locust muscle myosin heavy meromyosin(HMM),including the major isoform in the thorax dorsal longitudinal flight muscle(FL1)and 4 isoforms expressed in the abdominal intersegmental muscle(AB1 to AB4).Among these 5 HMMs,FL1-HMM displayed the highest level of actin-activated adenosine triphosphatase(ATPase)activity(hereafter referred as ATPase activity).To identify the alternative region(s)responsible for the elevated ATPase activity of FL1-HMM,we produced a number of chimeras of FL1-HMM and AB4-HMM.Substitution with the relay of AB4-HMM(encoded by exon-14c)substantially decreased the ATPase activity of FL1-HMM,and conversely,the relay of FL1-HMM(encoded by exon-14a)enhanced the ATPase activity of AB4-HMM.Mutagenesis showed that the exon-14a-encoded residues Gly474 and Asn509 are responsible for the elevated ATPase activity of FL1-HMM.Those results indicate that the alternative relay encoded by exon-14a/c play a key role in regulating the ATPase activity of FL1-HMM and AB4-HMM.展开更多
The near-Earth(within~100 pc)supernova explosions in the past several million years can cause the global deposition of radioactive elements(e.g.,60Fe)on Earth.The remnants of such supernovae are too old to be easily i...The near-Earth(within~100 pc)supernova explosions in the past several million years can cause the global deposition of radioactive elements(e.g.,60Fe)on Earth.The remnants of such supernovae are too old to be easily identified.It is therefore of great interest to search for million-year-old near-Earth neutron stars or black holes,the products of supernovae.However,neutron stars and black holes are challenging to find even in our Solar neighbourhood if they are not radio pulsars or X-ray/γ-ray emitters.Here we report the discovery of one of the nearest(127.7±0.3 pc)neutron star candidates in a detached single-lined spectroscopic binary LAMOST J235456.73+335625.9(hereafter J2354).Utilizing the time-resolved ground-based spectroscopy and space photometry,we find that J2354 hosts an unseen compact object with M_(inv)being 1.4-1.6 M_(⊙).The follow-up Swift ultraviolet(UV)and X-ray observations suggest that the UV and X-ray emission is produced by the visible star rather than the compact object.Hence,J2354 probably harbours a neutron star rather than a hot ultramassive white dwarf.Two-hour exceptionally sensitive radio follow-up observations with Five-hundred-meter Aperture Spherical radio Telescope fail to reveal any pulsating radio signals at the 6σflux upper limit of 12.5μJy.Therefore,the neutron star candidate in J2354 can only be revealed via our time-resolved observations.Interestingly,the distance between J2354 and our Earth can be as close as~50 pc around 2.5 million years(Myrs)ago,as revealed by the Gaia kinematics.Our discovery demonstrates a promising way to unveil the hidden near-Earth neutron stars in binaries by exploring the optical time domain,thereby facilitating understanding of the metal-enrichment history in our Solar neighbourhood.展开更多
基金Supported by Anhui Provincial Department of Education College Outstanding Talent Cultivation Funding Project,No.gxgwfx2019032the Teaching Quality and Teaching Reform Project of Anhui Provincial Department of Education,No.2020jyxm2090+1 种基金Anhui Wuhu Novel Coronavirus Pneumonia Epidemic Prevention and Control Science and Technology Emergency Project,No.2020rkx1-5Wannan Medical College Teaching Quality and Teaching Reform Project,No.2019jyxm20.
文摘BACKGROUND Frontline nurses in Wuhan directly fighting severe acute respiratory syndrome coronavirus-2 diseases are at a high risk of infection and are extremely susceptible to psychological stress,especially due to the global coronavirus disease 2019(COVID-19)pandemic.The psychological after-effects of this public health emergency on frontline nurses will last for years.AIM To assess factors influencing post-traumatic stress disorder(PTSD)among frontline nurses in Wuhan 6 mo after the COVID-19 pandemic began.METHODS A total of 757 frontline nurses from five hospitals in Wuhan,China,participated in an online survey from July 27 to August 13,2020.This cross-sectional online study used a demographic information questionnaire,the PTSD Checklist for the Diagnostic and Statistical Manual of Mental Disorders,the Connor-Davidson Resilience Scale,and the Patient Health Questionnaire-4.The chisquare test and logistic regression were used to analyze the association of demographics,COVID-19-related variables,and PTSD.Logistic regression was also conducted to investigate which variables were associated with PTSD outcomes.RESULTS A total of 13.5%,24.3%,and 21.4%of the frontline nurses showed symptoms of PTSD,depression,and anxiety,respectively.The multivariate logistic regression analysis showed that the following factors were strongly associated with PTSD:Having a relative,friend,or colleague who died of COVID-19;experiencing stigma;or having psychological assistance needs,depressive symptoms or anxiety.Showing resilience and receiving praise after the COVID-19 outbreak were protective factors.CONCLUSION Frontline nurses still experienced PTSD(13.5%)six months after the COVID-19 outbreak began.Peer support,social support,official recognition,reward mechanisms,exercise,better sleep,and timely provision of information(such as vaccine research progress)by the government via social media,and adequate protective supplies could mitigate the level of PTSD among nurses responding to COVID-19.Stigmatization,depression,and anxiety might be associated with a greater risk of PTSD among nurses.
基金supported by the Natural Science Foundation of China(Grant Nos.11773015,12121003,12041301)Project U1838201 supported by NSFC and CAS。
文摘The white dwarf(WD)+helium(He)star binary channel plays an important role in the single degenerate scenario for the progenitors of type Ia supernovae(SNe Ia).Previous studies on the WD+main sequence star evolution have shown that the magnetic fields of WDs may significantly influence their accretion and nuclear burning processes.In this work we focus on the evolution of magnetized WD+He star binaries with detailed stellar evolution and binary population synthesis(BPS)calculations.In the case of magnetized WDs,the magnetic fields may disrupt the inner regions of the accretion disk,funnel the accretion flow onto the polar caps and even confine helium burning within the caps.We find that,for WDs with sufficiently strong magnetic fields,the parameter space of the potential SN Ia progenitor systems shrinks toward shorter orbital periods and lower donor masses compared with that in the non-magnetized WD case.The reason is that the magnetic confinement usually works with relatively high mass transfer rates,which can trigger strong wind mass loss from the WD,thus limiting the He-rich mass accumulation efficiency.The surviving companion stars are likely of low-mass at the moment of the SN explosions,which can be regarded as a possible explanation for the non-detection of surviving companions after the SNe or inside the SN remnants.However,the corresponding birthrate of Galactic SNe Ia in our high-magnetic models is estimated to be~(0.08–0.13)×10^(-3)yr^(-1)(~0.17–0.28×10^(-3)yr^(-1)for the non-magnetic models),significantly lower than the observed Galactic SN Ia birthrate.
文摘BACKGROUND Increasing attention has been paid to acute myocardial infarction(AMI)in young female patients for whom secondary factors should be considered during the diagnostic process.Anti-phospholipid syndrome(APS),a rare autoimmune disease that is most common in young female patients,is reportedly related to AMI.To date,coronary interventions,particularly stenting,remains controversial in this special clinical scenario.CASE SUMMARY A 26-year-old female patient was admitted to hospital for acute chest pain,palpitations,and dyspnea.She had a past medical history of APS and pulmonary embolism.Coronary angiography showed acute occlusion of the proximal left anterior descending artery.After repeated thrombus aspirations,residual thrombus and mild stenosis were found in the proximal left anterior descending artery.Optical coherence tomography(OCT)was done,which confirmed the non-atherosclerosis coronary thrombosis and an intact intima in this patient.Deferring or avoiding stenting based on follow-up intracoronary findings with intensified antithrombotic treatment was chosen.One week later,coronary angiography and OCT confirmed an intact intima with no injury and no residual thrombus.The 3-mo telephone follow-up reported a good prognosis.CONCLUSION APS can cause acute non-atherosclerosis coronary thrombosis which presents as an AMI in young female patients.Intracoronary OCT findings can guide interventional strategies in this special clinical scenario.
基金The authors are grateful for the financial supports from the Jiangsu Provincial Science and Technology Plan Project,China(BE2018753/KJ185629)the National Natural Science Foundation of China(51571118)the 2020 Extracurricular Academic Research Fund for College Students of Nanjing University of Science and Technology,China.Zong-han XIE acknowledges the support of the Australian Research Council Discovery Projects.
基金National Natural Science Foundation of China (30971895, 31011130031)Special Research Funds for the Doctoral Program of Higher Education (20080434006)+2 种基金Grants from Ministry of Science and Technology (2009ZX08003-014B)Shandong province(2009GG10009021)Modern maize industrial system of Shandong province
文摘Southern rice black-streaked dwarf virus (SRBSDV) is a novel Fijivirus prevalent in rice in southern and central China,and northern Vietnam. Its genome has 10 segments of double-stranded RNA named S1 to S10 according to their size. An isolate of SRBSDV,JNi4,was obtained from naturally infected maize plants from Ji'ning,Shandong province,in the 2008 maize season. Segments S7 to S10 of JNi4 share nucleotide identities of 72.6%-73.1%,72.3%-73%,73.9%-74.5% and 77.3%-79%,respectively,with corresponding segments of Rice black-streaked dwarf virus isolates,and identities of 99.7%,99.1%-99.7%,98.9%-99.5%,and 98.6%-99.2% with those of SRBSDV isolates HN and GD. JNi4 forms a separate branch with GD and HN in the phylogenetic trees constructed with genomic sequences of S7 to S10. These results confirm the proposed taxonomic status of SRBSDV as a distinct species of the genus Fijivirus and indicate that JNi4 is an isolate of SRBSDV. Shandong is so far the northernmost region where SRBSDV is found in China.
文摘The disturbance of flat and V-shaped sandwich reactive armor configurations to shaped-charge jet is studied by a numerical approach. The disturbing and cutting effects of the two reactive armor configurations to the jet are successfully captured. The predicted disturbance characteristics and patterns are in fairly good agreement with the X-ray photographic observations. The residual depth of penetration into a semiinfinitive homogeneous steel target behind the reactive armor is computed for a series of jet/armor parameters. For the flat configuration, it is demonstrated that the residual penetration depth is not significantly reduced for a normal impact while it is reduced up to 75% for an oblique impact. In comparison, the V-shaped configuration reduces the penetration depth of the jet to 90%, and it is observed that the penetration depth is not sensitive to the V-shaped angle.
基金Supported by Major Science and Technology Program in Henan Province,No.131100110200
文摘AIM:To test the pathogenicity of pseudorabies virus(PRV)variant HN1201 and compare its pathogenicity with a classical PRV Fa strain.METHODS:The pathogenicity of the newly-emerging PRV variant HN1201 was evaluated by different inoculating routes,virus loads,and ages of pigs.The classical PRV Fa strain was then used to compare with HN1201 to determine pathogenicity.Clinical symptoms after virus infection were recorded daily and average daily body weight was used to measure the growth performance of pigs.At necropsy,gross pathology and histopathology were used to evaluate the severity of tissue damage caused by virus infection.RESULTS:The results showed that the efficient infection method of RPV HN1201 was via intranasal inoculation at 107 TCID50,and that the virus has high pathogenicity to 35-to 127-d old pigs.Compared with Fa strain,pigs infected with HN1201 showed more severe clinical symptoms and pathological lesions.Immunochemistry results revealed HN1201 had more abundant antigen distribution in extensive organs.CONCLUSION:All of the above results suggest that PRV variant HN1201 was more pathogenic to pigs than the classical Fa strain.
基金supported by theNational Key Research and Development Program ofChina (2016YFA0400803)the National Natural Science Foundation of China (NSFC) (Grant Nos. 11333004,11773015 and 11573016)+1 种基金Project U1838201 supported by NSFC and CASthe Program for Innovative Research Team (in Science and Technology) at the University of Henan Province
文摘We employ the supernova fallback disk model to simulate the spin evolution of isolated young neutron stars(NSs). We consider the submergence of the NS magnetic fields during the supercritical accretion stage and its succeeding reemergence. It is shown that the evolution of the spin periods and the magnetic fields in this model is able to account for the relatively weak magnetic fields of central compact objects and the measured braking indices of young pulsars. For a range of initial parameters, evolutionary links can be established among various kinds of NS sub-populations including magnetars, central compact objects and young pulsars. Thus, the diversity of young NSs could be unified in the framework of the supernova fallback accretion model.
基金Supported by National Natural Science Foundation of China,No.81570360Beijing Lisheng Cardiovascular Grant,No.LHJJ201612425
文摘BACKGROUND Upper gastrointestinal bleeding(UGIB) after an acute myocardial infarction(AMI) is not an uncommon complication. Acute UGIB caused by Mallory-Weiss syndrome(MWS) is usually a dire situation with massive bleeding and hemodynamic instability. Acute UGIB caused by MWS after an AMI has not been previously reported.CASE SUMMARY A 57-year-old man with acute inferior wall ST elevation myocardial infarction underwent a primary coronary intervention of the acutely occluded right coronary artery. Six hours after the intervention, the patient had a severe UGIB,followed by vomiting. His hemoglobin level dropped from 15.3 g/d L to 9.7 g/d L. In addition to blood transfusion and a gastric acid inhibition treatment,early endoscopy was employed and MWS was diagnosed. Bleeding was stopped by endoscopic placement of titanium clips.CONCLUSION Bleeding complications after stent implantation can pose a dilemma. MWS is a rare but severe cause of acute UGIB after an AMI that requires an early endoscopic diagnosis and a hemoclip intervention to stop bleeding.
基金Supported by the National Natural Science Foundation of China。
文摘Magnetars form a special population of neutron stars with strong magnetic fields and long spin periods. About 30 magnetars and magnetar candidates known currently are probably isolated, but the possibility that magnetars are in binaries has not been excluded. In this work, we perform spin evolution of neutron stars with different magnetic fields in wind-fed high-mass X-ray binaries and compare the spin period distribution with observations, aiming to find magnetars in binaries. Our simulation shows that some of the neutron stars, which have long spin periods or are in widely-separated systems, need strong magnetic fields to explain their spin evolution. This implies that there are probably magnetars in high-mass X-ray binaries. Moreover, this can further provide a theoretical basis for some unclear astronomical phenomena, such as the possible origin of periodic fast radio bursts from magnetars in binary systems.
基金supported by the National Natural Science Foundation of China through Grant 11873029the National Key Research and Development Program of China(2016YFA0400803 and 2017YFA0402703)。
文摘The distribution of the mass of white dwarfs(WDs)is one of the fundamental questions in the field of cataclysmic variables(CVs).In this work,we make a systematical investigation on the WD masses in two subclass of CVs:intermediate polars(IPs)and non-magnetic CVs in the solar vicinity based on the fiux ratios of Fe XXVI-Lyαto Fe XXV-Heαemission lines(I_(7.0)/I_(6.7))from archival XMM-Newton and Suzaku observations.We first verify the(semi-empirical)relations between I_(7.0)/I_(6.7),the maximum emission temperature(T_(max))and the WD mass(M_(WD))with the mkcfiow model based on the apec description and the latest Atom DB.We then introduce a new spectral model to measure M_(WD)directly based on the above relations.A comparison shows that the derived M_(WD)is consistent with dynamically measured ones.Finally,we obtain the average WD masses of 58 CVs(including 36IPs and 22 non-magnetic CVs),which is the largest X-ray selected sample.The average WD masses are<M_(WD,IP)>=0.81±0.21 M☉and<M_(WD,DN)>=0.81±0.21M☉ for IPs and non-magnetic CVs,respectively.These results are consistent with previous works.
基金Funding for the project has been provided by the National Development and Reform Commissionsupport from the National Science Foundation of China (NSFC, Nos. 11273028, 11333004, 11603035, 11603038 and 11503054)
文摘X-ray emission is an important indicator of stellar activity.In this paper,we study stellar Xray activity using the XMM-Newton and LAMOST data for different types of stars.We provide a sample including 1259 X-ray-emitting stars,of which 1090 have accurate stellar parameter estimations.Our sample size is much larger than those used in previous works.We find a bimodal distribution of the X-ray to optical flux ratio(log(fX/fV)) for G and K stars.We interpret that this bimodality is due to two subpopulations with different coronal heating rates.Furthermore,using the full widths at half maxima calculated from Hα and Hβ lines,we show that these stars in the inactive peaks have smaller rotational velocities.This is consistent with the magnetic dynamo theory that presumes stars with low rotational velocities have low levels of stellar activity.We also examine the correlation between log(fX/fV) and luminosity of the excess emission in the Hα line,and find a tight relation between the coronal and chromospheric activity indicators.
基金supported by the National Key Research and Development Program of China(2016YFA0400803)the National Natural Science Foundation of China under grant No.11773015Project U1838201 supported by NSFC and CAS。
文摘Most astrophysical accretion disks are likely to be warped.In X-ray binaries,the spin evolution of an accreting neutron star is critically dependent on the interaction between the neutron star magnetic field and the accretion disk.There have been extensive investigations on the accretion torque exerted by a coplanar disk that is magnetically threaded by the magnetic field lines from the neutron stars,but relevant works on warped/tilted accretion disks are still lacking.In this paper we develop a simplified twocomponent model,in which the disk is comprised of an inner coplanar part and an outer,tilted part.Based on standard assumption on the formation and evolution of the toroidal magnetic field component,we derive the dimensionless torque and show that a warped/titled disk is more likely to spin up the neutron star compared with a coplanar disk.We also discuss the possible influence of various initial parameters on the torque.
基金supported by the National Natural Science Foundation of China (Grant No. 10873008)the National Basic Research Program of China (973 Program 2009CB824800)
文摘We adopt the tidal truncation model proposed by Negueruela and Okazaki for Be/X-ray binaries to investigate the influence of intermediate-mass black holes (IMBHs) on Be-star disks. We show that the viscous decretion disks around Be stars are generally truncated ineffectively under the tidal force of IMBHs. Combining this with observations of Be/X-ray binaries, we suggest that Be/IMBH X-ray binaries may appear as recurrent luminous X-ray transients with quasi-periodic X-ray outbursts.
基金supported by the National Key Research and Development Program of China(2016YFA0400803)the National Natural Science Foundation of China under grant No.11773015Project U1838201 supported by NSFC and CAS。
文摘Several X-ray binaries(XRBs)have been identified to be associated with supernova remnants(SNRs).Because of the short lifetimes of SNRs,this leaves them to be the youngest known XRBs.This small group of binaries provides valuable information on the formation of compact stars under the framework of massive binary evolution.In this paper we review the observational characteristics of these youngest XRBs and discuss their possible implications on the initial conditions of compact stars and their interaction with the companion stars.
基金funded by the National Natural Science Foundation of China(Grant Nos.11133001 and 11333004)the Strategic Priority Research Program of CAS(Grant No.XDB09000000)
文摘Abstract The binding energy parameter A plays a vital role in common envelope evolution. Though it is well known that A takes different values for stars with different masses and varies during stellar evolution, it has been erroneously adopted as a constant in most population synthesis calculations. We have system- atically calculated the values of A for stars of masses 1 - 60 M by use of an updated stellar evolution code, taking into account the contribution from both gravitational energy and internal energy to the binding energy of the envelope. We adopt the criterion for the core-envelope boundary advocated by Ivanova. A new kind of A with an enthalpy prescription is also investigated. We present fitting formulae for the calculated values of various kinds of A, which can be used in future population synthesis studies.
基金Supported by the National Natural Science Foundation of Chinasupported by the Natural Science Foundation of China (Grant No. 11133001)+1 种基金the National Basic Research Program of China (973 Program, 2009CB824800)the Qinglan project of Jiangsu Province
文摘We perform numerical calculations to simulate the evolution of low-mass X-ray binary systems. For the accreting compact object we consider the initial mass of 1.4, 10, 20, 100, 200, 500 and 1000 Mo, corresponding to neutron stars (NSs), stellar- mass black holes (BHs) and intermediate-mass BHs. Mass transfer in these binaries is driven by nuclear evolution of the donors and/or orbital angular momentum loss due to magnetic braking and gravitational wave radiation. For the different systems, we determine their bifurcation periods Pbif that separate the formation of converging systems from the diverging ones, and show that Pbif changes from ~ 1 d to ≥ 3 d for a 1 Mo donor star, with increasing initial accretor mass from 1.4 to 1000 Mo. This means that the dominant mechanism of orbital angular momentum loss changes from magnetic braking to gravitational radiation. As an illustration we compare the evolution of binaries consisting of a secondary star of 1 Mo at a fixed initial period of 2 d. In the case of the NS or stellar-mass BH accretor, the system evolves to a well-detached He white dwarf-neutron star/black hole pair, but it evolves to an ultra- compact binary if the compact object is an intermediate-mass BH. Thus the binary evolution heavily depends upon the mass of the compact object. However, we show that the final orbital period-white dwarf mass relation found for NS low-mass X-ray binaries is fairly insensitive to the initial mass of the accreting star, even if it is an intermediate-mass BH.
基金supported by the Natural Science Foundation of China(Grant No.10873008)the Ministry of Science and the National Basic Research Program of China(973 ProgramGrant No.2009CB824800)
文摘There is accumulating evidence for mass ejection in low-mass X-ray binaries (LMXBs) driven by radio pulsar activity during X-ray quiescence. We consider the condition for mass ejection by comparing the radiation pressure from a millisecond pulsar, and the gas pressure at the inner Lagrange point or at the surrounding accretion disk. We calculate the critical spin period of the pulsar below which mass ejection is allowed. Combining with the evolution of the mass transfer rate, we present constraints on the orbital periods of the systems. We show that mass ejection could happen in both wide and compact LMXBs. It may be caused by transient accretion due to thermal instability in the accretion disks in the former, and irradiation-driven mass-transfer cycles in the latter.
基金supported by the National Natural Science Foundation of China(31672359 and 31970657)State Key Laboratory of Integrated Management of Pest Insects and Rodents(Grant No.IPM1601).
文摘Locust(Locusta migratoria)has a single striated muscle myosin heavy chain(Mhc)gene,which contains 5 clusters of alternative exclusive exons and 1 differently included penultimate exon.The alternative exons of Mhc gene encode 4 distinct regions in the myosin motor domain,that is,the N-terminal SH3-like domain,one lip of the nucleotide-binding pocket,the relay,and the converter.Here,we investigated the role of the alternative regions on the motor function of locust muscle myosin.Using Sf9-baculovirus protein expression system,we expressed and purified 5 isoforms of the locust muscle myosin heavy meromyosin(HMM),including the major isoform in the thorax dorsal longitudinal flight muscle(FL1)and 4 isoforms expressed in the abdominal intersegmental muscle(AB1 to AB4).Among these 5 HMMs,FL1-HMM displayed the highest level of actin-activated adenosine triphosphatase(ATPase)activity(hereafter referred as ATPase activity).To identify the alternative region(s)responsible for the elevated ATPase activity of FL1-HMM,we produced a number of chimeras of FL1-HMM and AB4-HMM.Substitution with the relay of AB4-HMM(encoded by exon-14c)substantially decreased the ATPase activity of FL1-HMM,and conversely,the relay of FL1-HMM(encoded by exon-14a)enhanced the ATPase activity of AB4-HMM.Mutagenesis showed that the exon-14a-encoded residues Gly474 and Asn509 are responsible for the elevated ATPase activity of FL1-HMM.Those results indicate that the alternative relay encoded by exon-14a/c play a key role in regulating the ATPase activity of FL1-HMM and AB4-HMM.
基金supported by the National Key R&D Program of China(Grant No.2021YFA1600401)the National Natural Science Foundation of China(NSFC)(Grant Nos.11925301+10 种基金12033006)supported by the NSFC(Grant Nos.11973002,and 12322303)supported by the NSFC(Grant No.12103041)supported by the NSFC(Grant Nos.11988101,and 11933004)supported by the NSFC(Grant No.U2031117)supported by the NSFC(Grant No.12033004)supported by the NSFC(Grant No.12273029)supported by the NSFC(Grant No.12221003)supported by the NSFC(Grant No.11933008)supported by the NSFC(Grant No.12090044)supported by the NSFC(Grant Nos.12041301,and 12121003)。
文摘The near-Earth(within~100 pc)supernova explosions in the past several million years can cause the global deposition of radioactive elements(e.g.,60Fe)on Earth.The remnants of such supernovae are too old to be easily identified.It is therefore of great interest to search for million-year-old near-Earth neutron stars or black holes,the products of supernovae.However,neutron stars and black holes are challenging to find even in our Solar neighbourhood if they are not radio pulsars or X-ray/γ-ray emitters.Here we report the discovery of one of the nearest(127.7±0.3 pc)neutron star candidates in a detached single-lined spectroscopic binary LAMOST J235456.73+335625.9(hereafter J2354).Utilizing the time-resolved ground-based spectroscopy and space photometry,we find that J2354 hosts an unseen compact object with M_(inv)being 1.4-1.6 M_(⊙).The follow-up Swift ultraviolet(UV)and X-ray observations suggest that the UV and X-ray emission is produced by the visible star rather than the compact object.Hence,J2354 probably harbours a neutron star rather than a hot ultramassive white dwarf.Two-hour exceptionally sensitive radio follow-up observations with Five-hundred-meter Aperture Spherical radio Telescope fail to reveal any pulsating radio signals at the 6σflux upper limit of 12.5μJy.Therefore,the neutron star candidate in J2354 can only be revealed via our time-resolved observations.Interestingly,the distance between J2354 and our Earth can be as close as~50 pc around 2.5 million years(Myrs)ago,as revealed by the Gaia kinematics.Our discovery demonstrates a promising way to unveil the hidden near-Earth neutron stars in binaries by exploring the optical time domain,thereby facilitating understanding of the metal-enrichment history in our Solar neighbourhood.