Background and Aims:Currently,insufficient clinical data are available to address whether low-level viremia(LLV)observed during antiviral treatment will adversely affect the clinical outcome or whether treatment strat...Background and Aims:Currently,insufficient clinical data are available to address whether low-level viremia(LLV)observed during antiviral treatment will adversely affect the clinical outcome or whether treatment strategies should be altered if LLV occurs.This study compared the clinical out-comes of patients with a maintained virological response(MVR)and patients who experienced LLV and their treatment strategies.Methods:A retrospective cohort of 674 patients with chronic hepatitis B virus(HBV)infection who received antiviral treatment for more than 12 months was analyzed for the development of end-stage liver disease and treatment strategies during the follow-up period.End-stage liver disease included decompensated liver cirrhosis and hepatocellular carcinoma(HCC).Results:During a median 42-month follow-up,end-stage liver disease developed more frequently in patients who experienced LLV than in those who experienced MVR(7.73%and 15.85%vs.0.77%and 5.52%at 5 and 10 years,respectively;p=0.000).The trend was consistent after propensity score matching.In the high-risk group of four HCC risk models,LLV patients had a higher risk of HCC development(p<0.05).By Cox proportional hazard model analysis,LLV was an independent risk factor for end-stage liver disease and HCC(hazard ratio[HR]=6.280,confidence interval[CI]=2.081-18.951,p=0.001;HR=5.108,CI=1.392-18.737,respectively;p=0.014).Patients achieved a lower rate of end-stage liver disease by adjusting treatment compared to continuing the original treatment once LLV occurred(p<0.05).Conclusions:LLV is an independent risk factor for end-stage liver disease and HCC,and treatment adjustments can be considered.展开更多
The record-breaking mei-yu in the Yangtze-Huaihe River valley(YHRV)in 2020 was characterized by an early onset,a delayed retreat,a long duration,a wide meridional rainbelt,abundant precipitation,and frequent heavy rai...The record-breaking mei-yu in the Yangtze-Huaihe River valley(YHRV)in 2020 was characterized by an early onset,a delayed retreat,a long duration,a wide meridional rainbelt,abundant precipitation,and frequent heavy rainstorm processes.It is noted that the East Asian monsoon circulation system presented a significant quasi-biweekly oscillation(QBWO)during the mei-yu season of 2020 that was associated with the onset and retreat of mei-yu,a northward shift and stagnation of the rainbelt,and the occurrence and persistence of heavy rainstorm processes.Correspondingly,during the mei-yu season,the monsoon circulation subsystems,including the western Pacific subtropical high(WPSH),the upper-level East Asian westerly jet,and the low-level southwesterly jet,experienced periodic oscillations linked with the QBWO.Most notably,the repeated establishment of a large southerly center,with relatively stable latitude,led to moisture convergence and ascent which was observed to develop repeatedly.This was accompanied by a long-term duration of the mei-yu rainfall in the YHRV and frequent occurrences of rainstorm processes.Moreover,two blocking highs were present in the middle to high latitudes over Eurasia,and a trough along the East Asian coast was also active,which allowed cold air intrusions to move southward through the northwestern and/or northeastern paths.The cold air frequently merged with the warm and moist air from the low latitudes resulting in low-level convergence over the YHRV.The persistent warming in the tropical Indian Ocean is found to be an important external contributor to an EAP/PJ-like teleconnection pattern over East Asia along with an intensified and southerly displaced WPSH,which was observed to be favorable for excessive rainfall over YHRV.展开更多
RIEMS' ability to simulate extreme monsoon rainfall is examined using the 18-month (April 1997 September 1998) integrated results. Model-simulated heavy precipitation over the Yangtze River valley during 11-30 Jun...RIEMS' ability to simulate extreme monsoon rainfall is examined using the 18-month (April 1997 September 1998) integrated results. Model-simulated heavy precipitation over the Yangtze River valley during 11-30 June 1998 is compared with the observation, and the relationships between this heavy rainfall process and the large-scale circulations, such as the westerly jet, low-level jet, and water vapor transport, are analyzed to further understand the mechanisms for simulating heavy monsoon rainfall. The analysis results show that (1) RIEMS can reproduce the pattern of heavy precipitation over the Yangtze River valley during 11-30 June 1998, but it is shifted northwestwards. (2) The simulated West Pacific Subtropical High (WPSH) that controls the East Asia Monsoon evolution is stronger than the observation and is extended westwards, which possibly leads to the north westward shift of the heavy rain belt. (3) The Westerly jet at 200 hPa and the Low-level jet at 850 hPa, both of which are related to the heavy monsoon rainfall, are reasonably reproduced by RIEMS during 11-30 June 1998, although the intensities of the simulated Westerly/Low-level jets are strong and the location of the Westerly jet leans to the southeast, which may be the causes of RIEMS producing too much heavy rainfall in the north of the Yangtze River valley.展开更多
An extremely heavy rainfall event occurred in Zhengzhou,China,on 20 July 2021 and produced an hourly rainfall rate of 201.9 mm,which broke the station record for China's Mainland.Based on radar observations and a ...An extremely heavy rainfall event occurred in Zhengzhou,China,on 20 July 2021 and produced an hourly rainfall rate of 201.9 mm,which broke the station record for China's Mainland.Based on radar observations and a convection-permitting simulation using the WRF-ARW model,this paper investigates the multiscale processes,especially those at the mesoscale,that support the extreme observed hourly rainfall.Results show that the extreme rainfall occurred in an environment characteristic of warm-sector heavy rainfall,with abundant warm moist air transported from the ocean by an abnormally northward-displaced western Pacific subtropical high and Typhoon In-Fa(2021).However,rather than through back building and echo training of convective cells often found in warm-sector heavy rainfall events,this extreme hourly rainfall event was caused by a single,quasi-stationary storm in Zhengzhou.Scale separation analysis reveals that the extreme-rainproducing storm was supported and maintained by the dynamic lifting of low-level converging flows from the north,south,and east of the storm.The low-level northerly flow originated from a mesoscale barrier jet on the eastern slope of the Taihang Mountain due to terrain blocking of large-scale easterly flows,which reached an overall balance with the southerly winds in association with a low-level meso-β-scale vortex located to the west of Zhengzhou.The large-scale easterly inflows that fed the deep convection via transport of thermodynamically unstable air into the storm prevented the eastward propagation of the weak,shallow cold pool.As a result,the convective storm was nearly stationary over Zhengzhou,resulting in record-breaking hourly precipitation.展开更多
Based on the final analyses data （FNL） of the Global Forecasting System of the NCEP and the obser- vational radiosonde data, the evolution mechanism of an eastward-moving low-level vortex over the Tibetan Plateau in...Based on the final analyses data （FNL） of the Global Forecasting System of the NCEP and the obser- vational radiosonde data, the evolution mechanism of an eastward-moving low-level vortex over the Tibetan Plateau in June 2008 was analyzed. The results show that the formation of the vortex was related to the convergence between the northwesterly over the central Tibetan Plateau from the westerly zone and the southerly from the Bay of Bengal at 500 hPa, and also to the divergence associated with the entrance re- gion of the upper westerly jet at 200 hPa. Their dynamic effects were favorable for ascending motion and forming the vortex over the Tibetan Plateau. Furthermore, the effect of the atmospheric heat source （Q1） is discussed based on a transformed potential vorticity （PV） tendency equation. By calculating the PV budgets, we showed that Q1 had a great inffuence on the intensity and moving direction of the vortex. In the developing stage of the vortex, the heating of the vertically integrated Q1 was centered to the east of the vortex center at 500 hPa, increasing PV tendency to the east of the vortex. As a result, the vortex strengthened and moved eastward through the vertically uneven distribution of Q1. In the decaying stage, the horizontally uneven heating of Q1 at 500 hPa weakened the vortex through causing the vortex tubes around the vortex to slant and redistributing the vertical vorticity field.展开更多
Using a new vortex detection and tracing method, a dataset of the Southwest Vortex(SWV) is established based on Japanese 25-year Reanalysis(JRA-25) reanalysis data during 1979–2008. The spatiotemporal features of the...Using a new vortex detection and tracing method, a dataset of the Southwest Vortex(SWV) is established based on Japanese 25-year Reanalysis(JRA-25) reanalysis data during 1979–2008. The spatiotemporal features of the SWV are derived from the dataset. In comparison to other seasons, summer yields the least SWVs, but with the highest probability that they will migrate from their region of origin. SWVs mostly emerge in the southwest of the Sichuan Basin and the southeast of the Tibetan Plateau. Migratory SWVs mainly move along either an eastward or southeastward path. Detailed composite analysis of warm-season SWVs shows that the subtropical high is a key factor in determining the direction of migratory SWVs. Furthermore, the steering wind at 700 hPa dominates the moving direction of migratory SWVs. Potential stability diagnosed by pseudo-equivalent potential temperature ? se is of certain significance for the evolution and movement of SWVs. On the other hand, migratory SWVs possess relatively greater strength than stationary SWVs, due to a stronger low-level jet with enhanced baroclinicity and moisture transport providing more energy to support the growth of SWVs along their paths of movement.展开更多
Low-level viremia(LLV)was defined as persistent or intermittent episodes of detectable hepatitis B virus(HBV)DNA(<2000 IU/mL,detection limit of 10 IU/mL)after 48 weeks of antiviral treatment.Effective antiviral the...Low-level viremia(LLV)was defined as persistent or intermittent episodes of detectable hepatitis B virus(HBV)DNA(<2000 IU/mL,detection limit of 10 IU/mL)after 48 weeks of antiviral treatment.Effective antiviral therapies for chronic hepatitis B(CHB)patients,such as entecavir(ETV),tenofovir disoproxil fumarate(TDF),and tenofovir alafenamide(TAF),have been shown to inhibit the replication of HBV DNA and prevent liver-related complications.However,even with long-term antiviral therapy,there are still a number of patients with persistent or intermittent LLV.At present,the research on LLV to address whether adversely affect the clinical outcome is limited,and the follow-up treatment for these patients is open to question.At the same time,the mechanism of LLV is not clear.In this review,we summarize the incidence of LLV,the association between LLV and long-term outcomes,possible mechanisms,and management strategies in these patient populations.展开更多
The temporal variations during 1948-2010 and vertical structures of the summer Somali and Australia cross-equatorial flows （CEFs） and the implications for the Asian summer monsoon were explored in this study. The st...The temporal variations during 1948-2010 and vertical structures of the summer Somali and Australia cross-equatorial flows （CEFs） and the implications for the Asian summer monsoon were explored in this study. The strongest southerly and northerly CEFs exist at 925 hPa and 150 hPa level, respectively. The low-level Somali （LLS） CEFs were significantly connected with the rainfall in most regions of India （especially the monsoon regions）, except in a small area in southwest India. In comparison to the climatology, the low- level Australia （LLA） CEFs exhibited stronger variations at interannual time scale and are more closely connected to the East Asian summer monsoon circulation than to the LLS CEFs. The East Asian summer monsoon circulation anomalies related to stronger LLA CEFs were associ- ated with less water vapor content and less rainfall in the region between the middle Yellow River and Yangtze River and with more water vapor and more rainfall in southern China. The sea-surface tempera- ture anomalies east of Australia related to summer LLA CEFs emerge in spring and persist into summer, with implications for the seasonal prediction of summer rainfall in East Asia. The connection between the LLA CEFs and East Asian summer monsoon rainfall may be partly due to its linkage with E1 Nino-Southern Oscillation. In addition, both the LLA and LLS CEFs .exhibited interdecadal shifts in the late 1970s and the late 1990s, consistent with the phase shifts of Pacific Decadal Oscillation （PDO）.展开更多
Chronic hepatitis B virus(HBV)infection(CHB)is a public health concern worldwide.Current therapies utilizing nucleos(t)ide analogs(NA)have not resulted in a complete cure for CHB.Furthermore,patients on long-term NA t...Chronic hepatitis B virus(HBV)infection(CHB)is a public health concern worldwide.Current therapies utilizing nucleos(t)ide analogs(NA)have not resulted in a complete cure for CHB.Furthermore,patients on long-term NA treatment often develop low-level viremia(LLV).Persistent LLV,in addition to causing the progression of liver disease or hepatocellular carcinoma,may shed light on the current plight of NA therapy.Here,we review the literature on LLV,NA treatment,and various doses of entecavir to find a strategy for improving the efficacy of this antiviral agent.For LLV patients,three therapeutic options are available,switching to another antiviral monotherapy,interferon-αswitching therapy,and continuing monotherapy.In real-world clinical practice,entecavir overdose has been used in antiviral therapy for CHB patients with NA refractory and persistent LLV,which encouraged us to conduct further in-depth literature survey on dosage and duration related entecavir studies.The studies of pharmacodynamics and pharmacokinetics show that entecavir has the maximal selected index for safety,and has great potential in inhibiting HBV replication,in all of the NAs.In the particular section of the drug approval package published by the United States Food and Drug Administration,entecavir doses 2.5-20 mg/d do not increase adverse events,and entecavir doses higher than 1.0 mg/d might improve the antiviral efficacy.The literature survey led us to two suggestions:(1)Increasing entecavir dose to 1.0 mg/d for the treatment of NA naïve patients with HBV DNA>2×106 IU/mL is feasible and would provide better prognosis;and(2)Further research is needed to assess the long-term toxic effects of higher entecavir doses(2.5 and 5.0 mg/d),which may prove beneficial in treating patients with prior NA treatment,partial virological response,or LLV state.展开更多
Two novel thermal cycles based on Brayton cycle and Rankine cycle are proposed, respectively, which integrate the recovery of low-level waste heat and Liquefied Nature Gas （LNG） cold energy utilization for power gen...Two novel thermal cycles based on Brayton cycle and Rankine cycle are proposed, respectively, which integrate the recovery of low-level waste heat and Liquefied Nature Gas （LNG） cold energy utilization for power generation. Cascade utilization of energy is realized in the two thermal cycles, where low-level waste heat,low-temperature exergy and pressure exergy of LNG are utilized efficiently through the system synthesis. The simulations are carried out using the commercial Aspen Plus 10.2, and the results are analyzed. Compared with the conventional Brayton cycle and Rankine cycle, the two novel cycles bring 60.94% and 60% in exergy efficiency, respectively and 53.08% and 52.31% in thermal efficiency, respectively.展开更多
The diurnal variation of precipitation over the Dabie Mountains(DBM) in eastern China during the 2013 mei-yu season is investigated with forecasts of a regional convection-permitting model. Simulated precipitation is ...The diurnal variation of precipitation over the Dabie Mountains(DBM) in eastern China during the 2013 mei-yu season is investigated with forecasts of a regional convection-permitting model. Simulated precipitation is verified against surface rain-gauge observations. The observed morning precipitation peak on the windward(relative to the prevailing synoptic-scale wind) side of the DBM is reproduced with good spatial and temporal accuracy. The interaction between the DBM and a nocturnal boundary layer low-level jet(BLJ) due to the inertial oscillation mechanism is shown to be responsible for this precipitation peak. The BLJ is aligned with the lower-level southwesterly synoptic-scale flow that carries abundant moisture.The BLJ core is established at around 0200 LST upwind of the mountains. It moves towards the DBM and reaches maximum intensity at about 70 km ahead of the mountains. When the BLJ impinges upon the windward side of the DBM in the early morning, mechanical lifting of moist air leads to condensation and subsequent precipitation.展开更多
An extremely heavy rainfall event lasting from 17 to 22 July 2021 occurred in Henan Province of China, with accumulated precipitation of more than 1000 mm over a 6-day period that exceeded its mean annual precipitatio...An extremely heavy rainfall event lasting from 17 to 22 July 2021 occurred in Henan Province of China, with accumulated precipitation of more than 1000 mm over a 6-day period that exceeded its mean annual precipitation. The present study examines the roles of persistent low-level jets(LLJs) in maintaining the precipitation using surface station observations and reanalysis datasets. The LLJs triggered strong ascending motions and carried moisture mainly from the outflow of Typhoon In-fa(2021). The varying directions of the LLJs well corresponded to the meridional shifts of the rainfall. The precipitation rate reached a maximum during 20-21 July as the LLJs strengthened and expanded vertically into double LLJs, including synoptic-weather-system-related LLJs(SLLJs) at 850–700 hPa and boundary-layer jets(BLJs)at ~950 hPa. The coupling of the SLLJ and BLJ provided strong mid-and low-level convergence on 20 July, whereas the SLLJ produced mid-level divergence at its entrance that coupled with low-level convergence at the terminus of the BLJ on21 July. The formation mechanisms of the two types of LLJs are further examined. The SLLJs and the low-pressure vortex(or inverted trough) varied synchronously as a whole and were affected by the southwestward movement of the WPSH in the rainiest period. The persistent large total pressure gradient force at low levels also maintained the strength of low-level geostrophic winds, thus sustaining the BLJs on the synoptic scale. The results based on a Du-Rotunno 1D model show that the Blackadar and Holton mechanisms jointly governed the BLJ dynamics on the diurnal scale.展开更多
基金the National Science and Technology Major Project of China(2017ZX10202203-007,2017ZX10202203-008 and 2018ZX10302-206-003)the Kuanren Talents Program of the Second Affiliated Hospital of Chongqing Medical University N/A and Guizhou Science and Technology Project QiankeheJC(2016)1086.
文摘Background and Aims:Currently,insufficient clinical data are available to address whether low-level viremia(LLV)observed during antiviral treatment will adversely affect the clinical outcome or whether treatment strategies should be altered if LLV occurs.This study compared the clinical out-comes of patients with a maintained virological response(MVR)and patients who experienced LLV and their treatment strategies.Methods:A retrospective cohort of 674 patients with chronic hepatitis B virus(HBV)infection who received antiviral treatment for more than 12 months was analyzed for the development of end-stage liver disease and treatment strategies during the follow-up period.End-stage liver disease included decompensated liver cirrhosis and hepatocellular carcinoma(HCC).Results:During a median 42-month follow-up,end-stage liver disease developed more frequently in patients who experienced LLV than in those who experienced MVR(7.73%and 15.85%vs.0.77%and 5.52%at 5 and 10 years,respectively;p=0.000).The trend was consistent after propensity score matching.In the high-risk group of four HCC risk models,LLV patients had a higher risk of HCC development(p<0.05).By Cox proportional hazard model analysis,LLV was an independent risk factor for end-stage liver disease and HCC(hazard ratio[HR]=6.280,confidence interval[CI]=2.081-18.951,p=0.001;HR=5.108,CI=1.392-18.737,respectively;p=0.014).Patients achieved a lower rate of end-stage liver disease by adjusting treatment compared to continuing the original treatment once LLV occurred(p<0.05).Conclusions:LLV is an independent risk factor for end-stage liver disease and HCC,and treatment adjustments can be considered.
基金This work was jointly supported by National Key R&D Program of China(2018YFC1505806)Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)+1 种基金National Science Foundation of China(41875100)the China Meteorological Administration Innovation and Development Project(CXFZ2021Z033),and China Three Gorges Corporation(Grant No.0704181).
文摘The record-breaking mei-yu in the Yangtze-Huaihe River valley(YHRV)in 2020 was characterized by an early onset,a delayed retreat,a long duration,a wide meridional rainbelt,abundant precipitation,and frequent heavy rainstorm processes.It is noted that the East Asian monsoon circulation system presented a significant quasi-biweekly oscillation(QBWO)during the mei-yu season of 2020 that was associated with the onset and retreat of mei-yu,a northward shift and stagnation of the rainbelt,and the occurrence and persistence of heavy rainstorm processes.Correspondingly,during the mei-yu season,the monsoon circulation subsystems,including the western Pacific subtropical high(WPSH),the upper-level East Asian westerly jet,and the low-level southwesterly jet,experienced periodic oscillations linked with the QBWO.Most notably,the repeated establishment of a large southerly center,with relatively stable latitude,led to moisture convergence and ascent which was observed to develop repeatedly.This was accompanied by a long-term duration of the mei-yu rainfall in the YHRV and frequent occurrences of rainstorm processes.Moreover,two blocking highs were present in the middle to high latitudes over Eurasia,and a trough along the East Asian coast was also active,which allowed cold air intrusions to move southward through the northwestern and/or northeastern paths.The cold air frequently merged with the warm and moist air from the low latitudes resulting in low-level convergence over the YHRV.The persistent warming in the tropical Indian Ocean is found to be an important external contributor to an EAP/PJ-like teleconnection pattern over East Asia along with an intensified and southerly displaced WPSH,which was observed to be favorable for excessive rainfall over YHRV.
基金supported by the National Key Program for Developing Basic Sciences(G1999043403)the Program for Knowledge Innovation Project,Chinese Academy of Sciences(KZCX3-SW-218).
文摘RIEMS' ability to simulate extreme monsoon rainfall is examined using the 18-month (April 1997 September 1998) integrated results. Model-simulated heavy precipitation over the Yangtze River valley during 11-30 June 1998 is compared with the observation, and the relationships between this heavy rainfall process and the large-scale circulations, such as the westerly jet, low-level jet, and water vapor transport, are analyzed to further understand the mechanisms for simulating heavy monsoon rainfall. The analysis results show that (1) RIEMS can reproduce the pattern of heavy precipitation over the Yangtze River valley during 11-30 June 1998, but it is shifted northwestwards. (2) The simulated West Pacific Subtropical High (WPSH) that controls the East Asia Monsoon evolution is stronger than the observation and is extended westwards, which possibly leads to the north westward shift of the heavy rain belt. (3) The Westerly jet at 200 hPa and the Low-level jet at 850 hPa, both of which are related to the heavy monsoon rainfall, are reasonably reproduced by RIEMS during 11-30 June 1998, although the intensities of the simulated Westerly/Low-level jets are strong and the location of the Westerly jet leans to the southeast, which may be the causes of RIEMS producing too much heavy rainfall in the north of the Yangtze River valley.
基金supported by the National Science Foundation of China(Grant No.42122036)the Second Tibetan Plateau Scientific Expedition and Research(STEP)program(2019QZKK0105)+2 种基金the National Key R&D Programs of China(2018YFC1507300)the National Science Foundation of China(Grant No.91837207)the Beijing Climate Center(QHMS2021008).
文摘An extremely heavy rainfall event occurred in Zhengzhou,China,on 20 July 2021 and produced an hourly rainfall rate of 201.9 mm,which broke the station record for China's Mainland.Based on radar observations and a convection-permitting simulation using the WRF-ARW model,this paper investigates the multiscale processes,especially those at the mesoscale,that support the extreme observed hourly rainfall.Results show that the extreme rainfall occurred in an environment characteristic of warm-sector heavy rainfall,with abundant warm moist air transported from the ocean by an abnormally northward-displaced western Pacific subtropical high and Typhoon In-Fa(2021).However,rather than through back building and echo training of convective cells often found in warm-sector heavy rainfall events,this extreme hourly rainfall event was caused by a single,quasi-stationary storm in Zhengzhou.Scale separation analysis reveals that the extreme-rainproducing storm was supported and maintained by the dynamic lifting of low-level converging flows from the north,south,and east of the storm.The low-level northerly flow originated from a mesoscale barrier jet on the eastern slope of the Taihang Mountain due to terrain blocking of large-scale easterly flows,which reached an overall balance with the southerly winds in association with a low-level meso-β-scale vortex located to the west of Zhengzhou.The large-scale easterly inflows that fed the deep convection via transport of thermodynamically unstable air into the storm prevented the eastward propagation of the weak,shallow cold pool.As a result,the convective storm was nearly stationary over Zhengzhou,resulting in record-breaking hourly precipitation.
基金supported by the National Natural Science Foundation of China (Grant No. 40921003)the National Key Program for Developing Basic Sciences (Grant No. 2004CB418300)the International S&T Cooperation Project of the Ministry of Science and Technology of China under Grant No.2009DFA21430
文摘Based on the final analyses data （FNL） of the Global Forecasting System of the NCEP and the obser- vational radiosonde data, the evolution mechanism of an eastward-moving low-level vortex over the Tibetan Plateau in June 2008 was analyzed. The results show that the formation of the vortex was related to the convergence between the northwesterly over the central Tibetan Plateau from the westerly zone and the southerly from the Bay of Bengal at 500 hPa, and also to the divergence associated with the entrance re- gion of the upper westerly jet at 200 hPa. Their dynamic effects were favorable for ascending motion and forming the vortex over the Tibetan Plateau. Furthermore, the effect of the atmospheric heat source （Q1） is discussed based on a transformed potential vorticity （PV） tendency equation. By calculating the PV budgets, we showed that Q1 had a great inffuence on the intensity and moving direction of the vortex. In the developing stage of the vortex, the heating of the vertically integrated Q1 was centered to the east of the vortex center at 500 hPa, increasing PV tendency to the east of the vortex. As a result, the vortex strengthened and moved eastward through the vertically uneven distribution of Q1. In the decaying stage, the horizontally uneven heating of Q1 at 500 hPa weakened the vortex through causing the vortex tubes around the vortex to slant and redistributing the vertical vorticity field.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41275064 and 41175057)the Public Science and Technology Research Fund Projects of the Ocean (Grant No. 201005019)
文摘Using a new vortex detection and tracing method, a dataset of the Southwest Vortex(SWV) is established based on Japanese 25-year Reanalysis(JRA-25) reanalysis data during 1979–2008. The spatiotemporal features of the SWV are derived from the dataset. In comparison to other seasons, summer yields the least SWVs, but with the highest probability that they will migrate from their region of origin. SWVs mostly emerge in the southwest of the Sichuan Basin and the southeast of the Tibetan Plateau. Migratory SWVs mainly move along either an eastward or southeastward path. Detailed composite analysis of warm-season SWVs shows that the subtropical high is a key factor in determining the direction of migratory SWVs. Furthermore, the steering wind at 700 hPa dominates the moving direction of migratory SWVs. Potential stability diagnosed by pseudo-equivalent potential temperature ? se is of certain significance for the evolution and movement of SWVs. On the other hand, migratory SWVs possess relatively greater strength than stationary SWVs, due to a stronger low-level jet with enhanced baroclinicity and moisture transport providing more energy to support the growth of SWVs along their paths of movement.
基金the National Science and Technology Major Project of China(Nos 2017ZX10202203-007,2017ZX10202203-008,and 2018ZX10302-206-003).
文摘Low-level viremia(LLV)was defined as persistent or intermittent episodes of detectable hepatitis B virus(HBV)DNA(<2000 IU/mL,detection limit of 10 IU/mL)after 48 weeks of antiviral treatment.Effective antiviral therapies for chronic hepatitis B(CHB)patients,such as entecavir(ETV),tenofovir disoproxil fumarate(TDF),and tenofovir alafenamide(TAF),have been shown to inhibit the replication of HBV DNA and prevent liver-related complications.However,even with long-term antiviral therapy,there are still a number of patients with persistent or intermittent LLV.At present,the research on LLV to address whether adversely affect the clinical outcome is limited,and the follow-up treatment for these patients is open to question.At the same time,the mechanism of LLV is not clear.In this review,we summarize the incidence of LLV,the association between LLV and long-term outcomes,possible mechanisms,and management strategies in these patient populations.
基金supported by the National Basic Research Program of China(Grant Nos. 2009CB421406 and 2010CB950304)the Special Fund for the Public Welfare Industry (Meteorology+1 种基金Grant Nos. GYHY201006022 and GYHY200906018)the strategic technological program of the Chinese Academy of Sciences (Grant No. XDA05090405)
文摘The temporal variations during 1948-2010 and vertical structures of the summer Somali and Australia cross-equatorial flows （CEFs） and the implications for the Asian summer monsoon were explored in this study. The strongest southerly and northerly CEFs exist at 925 hPa and 150 hPa level, respectively. The low-level Somali （LLS） CEFs were significantly connected with the rainfall in most regions of India （especially the monsoon regions）, except in a small area in southwest India. In comparison to the climatology, the low- level Australia （LLA） CEFs exhibited stronger variations at interannual time scale and are more closely connected to the East Asian summer monsoon circulation than to the LLS CEFs. The East Asian summer monsoon circulation anomalies related to stronger LLA CEFs were associ- ated with less water vapor content and less rainfall in the region between the middle Yellow River and Yangtze River and with more water vapor and more rainfall in southern China. The sea-surface tempera- ture anomalies east of Australia related to summer LLA CEFs emerge in spring and persist into summer, with implications for the seasonal prediction of summer rainfall in East Asia. The connection between the LLA CEFs and East Asian summer monsoon rainfall may be partly due to its linkage with E1 Nino-Southern Oscillation. In addition, both the LLA and LLS CEFs .exhibited interdecadal shifts in the late 1970s and the late 1990s, consistent with the phase shifts of Pacific Decadal Oscillation （PDO）.
文摘Chronic hepatitis B virus(HBV)infection(CHB)is a public health concern worldwide.Current therapies utilizing nucleos(t)ide analogs(NA)have not resulted in a complete cure for CHB.Furthermore,patients on long-term NA treatment often develop low-level viremia(LLV).Persistent LLV,in addition to causing the progression of liver disease or hepatocellular carcinoma,may shed light on the current plight of NA therapy.Here,we review the literature on LLV,NA treatment,and various doses of entecavir to find a strategy for improving the efficacy of this antiviral agent.For LLV patients,three therapeutic options are available,switching to another antiviral monotherapy,interferon-αswitching therapy,and continuing monotherapy.In real-world clinical practice,entecavir overdose has been used in antiviral therapy for CHB patients with NA refractory and persistent LLV,which encouraged us to conduct further in-depth literature survey on dosage and duration related entecavir studies.The studies of pharmacodynamics and pharmacokinetics show that entecavir has the maximal selected index for safety,and has great potential in inhibiting HBV replication,in all of the NAs.In the particular section of the drug approval package published by the United States Food and Drug Administration,entecavir doses 2.5-20 mg/d do not increase adverse events,and entecavir doses higher than 1.0 mg/d might improve the antiviral efficacy.The literature survey led us to two suggestions:(1)Increasing entecavir dose to 1.0 mg/d for the treatment of NA naïve patients with HBV DNA>2×106 IU/mL is feasible and would provide better prognosis;and(2)Further research is needed to assess the long-term toxic effects of higher entecavir doses(2.5 and 5.0 mg/d),which may prove beneficial in treating patients with prior NA treatment,partial virological response,or LLV state.
基金the Science and Technology Foundation of Shaanxi Province (No.2002K08-G9).
文摘Two novel thermal cycles based on Brayton cycle and Rankine cycle are proposed, respectively, which integrate the recovery of low-level waste heat and Liquefied Nature Gas （LNG） cold energy utilization for power generation. Cascade utilization of energy is realized in the two thermal cycles, where low-level waste heat,low-temperature exergy and pressure exergy of LNG are utilized efficiently through the system synthesis. The simulations are carried out using the commercial Aspen Plus 10.2, and the results are analyzed. Compared with the conventional Brayton cycle and Rankine cycle, the two novel cycles bring 60.94% and 60% in exergy efficiency, respectively and 53.08% and 52.31% in thermal efficiency, respectively.
基金supported by the Special Foundation of the China Meteorological Administration (Grant No.GYHY201506006)supported by the National Science Foundation of China (Grant Nos.41405100,41322032 and 41275031)
文摘The diurnal variation of precipitation over the Dabie Mountains(DBM) in eastern China during the 2013 mei-yu season is investigated with forecasts of a regional convection-permitting model. Simulated precipitation is verified against surface rain-gauge observations. The observed morning precipitation peak on the windward(relative to the prevailing synoptic-scale wind) side of the DBM is reproduced with good spatial and temporal accuracy. The interaction between the DBM and a nocturnal boundary layer low-level jet(BLJ) due to the inertial oscillation mechanism is shown to be responsible for this precipitation peak. The BLJ is aligned with the lower-level southwesterly synoptic-scale flow that carries abundant moisture.The BLJ core is established at around 0200 LST upwind of the mountains. It moves towards the DBM and reaches maximum intensity at about 70 km ahead of the mountains. When the BLJ impinges upon the windward side of the DBM in the early morning, mechanical lifting of moist air leads to condensation and subsequent precipitation.
基金supported by Guangdong Major Project of Basic and Applied Basic Research(2020B0301030004)the National Natural Science Foundation of China(Grant Nos.42122033,41875055,and 42075006)Guangzhou Science and Technology Plan Projects(202002030346 and 202002030196).
文摘An extremely heavy rainfall event lasting from 17 to 22 July 2021 occurred in Henan Province of China, with accumulated precipitation of more than 1000 mm over a 6-day period that exceeded its mean annual precipitation. The present study examines the roles of persistent low-level jets(LLJs) in maintaining the precipitation using surface station observations and reanalysis datasets. The LLJs triggered strong ascending motions and carried moisture mainly from the outflow of Typhoon In-fa(2021). The varying directions of the LLJs well corresponded to the meridional shifts of the rainfall. The precipitation rate reached a maximum during 20-21 July as the LLJs strengthened and expanded vertically into double LLJs, including synoptic-weather-system-related LLJs(SLLJs) at 850–700 hPa and boundary-layer jets(BLJs)at ~950 hPa. The coupling of the SLLJ and BLJ provided strong mid-and low-level convergence on 20 July, whereas the SLLJ produced mid-level divergence at its entrance that coupled with low-level convergence at the terminus of the BLJ on21 July. The formation mechanisms of the two types of LLJs are further examined. The SLLJs and the low-pressure vortex(or inverted trough) varied synchronously as a whole and were affected by the southwestward movement of the WPSH in the rainiest period. The persistent large total pressure gradient force at low levels also maintained the strength of low-level geostrophic winds, thus sustaining the BLJs on the synoptic scale. The results based on a Du-Rotunno 1D model show that the Blackadar and Holton mechanisms jointly governed the BLJ dynamics on the diurnal scale.
