This study presents finely resolved radar signatures of multiple cyclonic vortices associated with an EF2 tornadic supercell that occurred in Guangzhou on 16 June 2022 and discusses how the mesocyclone formed on the l...This study presents finely resolved radar signatures of multiple cyclonic vortices associated with an EF2 tornadic supercell that occurred in Guangzhou on 16 June 2022 and discusses how the mesocyclone formed on the lee side of mountain.A nearby X-band phased-array radar provides evidence that the mesocyclone was shallow,with a depth generally confined to less than 3 km.The mesocyclonic feature was observed to initiate from near-ground level,driven by the interaction between intensifying cold pool surges and shallow lee-side ambient flows.It was first recognized shortly after the presence of near-ground cyclonic convergence signatures over the leading edges of cold pool outflows.Over the subsequent 17 min,the mesocyclone developed upward,reaching a maximum height of 3 km,and produced a tornado 8min later.Nearly coinciding with the time of tornadogenesis,a noticeable separation of the low-level tornado cyclone from the midlevel mesocyclone was observed.This shift in the vertically oriented vortex tube was likely caused by modifications to the low-level flow due to the complex hilly terrain or by occlusions associated with rear-flank downdrafts.After tornadogenesis,high-resolution X-PAR observations revealed that the lowest-level mesocyclonic signature contracted into a gate-to-gate tornadic vortex signature(TVS)at the tip of hook echoes.Compared to conventional S-band operational weather radars,rapid-scan X-PAR observations indicate that a core diameter threshold of 1.5–2 km could be employed to identify a cyclonically sheared radial velocity couplet as a TVS,potentially extending the lead time for Doppler-based tornado warnings.展开更多
This study employs the self-organizing map method to investigate the upper-tropospheric outflow patterns of tropical cyclones(TCs)over the western North Pacific from 1979 to 2019,using the 200 hPa horizontal wind fiel...This study employs the self-organizing map method to investigate the upper-tropospheric outflow patterns of tropical cyclones(TCs)over the western North Pacific from 1979 to 2019,using the 200 hPa horizontal wind fields from the ERA5 reanalysis datasets.According to the number and orientation of TC outflow channels,as well as the wind speed,the outflow patterns are classified into five categories:southwestward single-channel pattern S1(26.1%);northwestward single-channel pattern S2(23.6%);northeastward single-channel pattern S3(23.6%);double-channel outflow pattern D(20.8%);and high latitude outflow pattern H(6.0%).Composite analysis shows that the orientations of the TC outflow channels are aligned with the direction of the environmental vertical wind shear and closely related to the distribution of the environmental inertial instability,upper-level divergence,and inner-core convective activities.TC intensity and intensity changes for different outflow patterns are also significantly different.Patterns S1 and S2 usually appear in the development phase and are thus prone to TC intensification,while patterns S3 and H usually occur in the weakening phase and are thus prone to TC weakening.The double-channel pattern(D)has the largest mean intensity and accounts for more than 60%of super-typhoon samples.展开更多
Landslide dams,as frequent natural hazards,pose significant risks to human lives,property,and ecological environments.The grading characteristics and density of dam materials play a crucial role in determining the sta...Landslide dams,as frequent natural hazards,pose significant risks to human lives,property,and ecological environments.The grading characteristics and density of dam materials play a crucial role in determining the stability of landslide dams and the potential for dam breaches.To explore the failure mechanisms and evolutionary processes of landslide dams with varying soil properties,this study conducted a series of flume experiments,considering different grain compositions and material densities.The results demonstrated that grading characteristics significantly influence landslide dam stability,affecting failure patterns,breach processes,and final breach morphologies.Fine-graded materials exhibited a sequence of surface erosion,head-cut erosion,and subsequent surface erosion during the breach process,while well-graded materials typically experienced head-cut erosion followed by surface erosion.In coarse-graded dams,the high permeability of coarse particles allowed the dam to remain stable,as inflows matched outflows.The dam breach model experiments also showed that increasing material density effectively delayed the breach and reduced peak breach flow discharge.Furthermore,higher fine particle content led to a reduction in the residual dam height and the base slope of the final breach profile,although the relationship between peak breach discharge and the content of fine and coarse particles was nonlinear.To better understand breach morphology evolution under different soil characteristics and hydraulic conditions,three key points were identified—erosion point,control point,and scouring point.This study,by examining the evolution of failure patterns,breach processes,and breach flow discharges under various grading and density conditions,offers valuable insights into the mechanisms behind landslide dam failures.展开更多
How gamma-ray bursts(GRBs),the most powerful and spectacular explosions known in the universe since the Big Bang,fuel their high-energy radiations?What kind of physical reactions can trigger and sustain such violent,e...How gamma-ray bursts(GRBs),the most powerful and spectacular explosions known in the universe since the Big Bang,fuel their high-energy radiations?What kind of physical reactions can trigger and sustain such violent,energetic outflow?This has captivated astronomers.Over the past decades,thousands of GRBs have been observed;however,the origin and the product of the burst-the central celestial body,or the“central engine”,is still pending for identification.展开更多
Glaucoma,a visual thief,is characterized by elevated intraocular pressure(IOP)and the loss of retinal ganglion cells(RGCs).Selecting suitable animals for preclinical models is of great significance in research on the ...Glaucoma,a visual thief,is characterized by elevated intraocular pressure(IOP)and the loss of retinal ganglion cells(RGCs).Selecting suitable animals for preclinical models is of great significance in research on the prevention,early screening,and effective treatments of glaucoma.Rabbit eyeballs possess similar vascularity and aqueous humor outflow pathways to those of humans.Thus,they are among the earliest in vivo models used in glaucoma research.Over the years,rabbit models have made substantial contributions to understanding glaucomatous pathophysiology,surgical adaptations,biomedical device development,and drug development for reducing IOP,protecting RGCs,and inhibiting fibrosis.Compared to other animals,rabbits fit better with surgical operations and cost less.This review summarizes the merits and demerits of different ways to produce glaucomatous rabbit models,such as intracameral injection,vortex vein obstruction,Trendelenburg position,laser photo-coagulation,glucocorticoid induction,limbal buckling induction,retinal ischemia–reperfusion models,and spontaneous models.We analyzed their mechanisms in the hope of providing more references for experimental design and promoting the understanding of glaucoma treatment strategies.展开更多
BACKGROUND Hepatic venous outflow obstruction(HVOO)is a rare but serious complication of liver transplantation,particularly in piggyback liver transplantation techniques where the inferior vena cava(IVC)is preserved.C...BACKGROUND Hepatic venous outflow obstruction(HVOO)is a rare but serious complication of liver transplantation,particularly in piggyback liver transplantation techniques where the inferior vena cava(IVC)is preserved.CASE SUMMARY A transplanted liver patient underwent retransplantation due to hepatic artery thrombosis and subsequently developed HVOO caused by graft compression of the IVC.A novel approach using a retrohepatic tissue expander effectively relieved the IVC compression,restored venous outflow,and stabilized hemodynamics.We discuss this case in the context of current treatment options and advances in HVOO management,from endovascular interventions such as balloon dilation and stenting to innovative surgical solutions such as graft repositioning and retrohepatic implants.CONCLUSION This case shows how important personalized treatments are for managing HVOO and how tissue expanders can be an adjustable and less invasive option.展开更多
SN 2014av is a type Ibn supernova(SN)characterized by the interaction between the SN ejecta and a helium-rich circumstellar medium(CSM).We use the^(56)Ni model,the ejecta-CSM interaction(CSI)model,and the CSI plus^(56...SN 2014av is a type Ibn supernova(SN)characterized by the interaction between the SN ejecta and a helium-rich circumstellar medium(CSM).We use the^(56)Ni model,the ejecta-CSM interaction(CSI)model,and the CSI plus^(56)Ni model to fit the multiband light curves(LCs)of SN 2014av.For the CSI and CSI plus^(56)Ni models,we assume that the CSM is a constant density shell(“shell”)or a steady-state stellar wind(“wind”)with density∝r-2.We find that both the^(56)Ni and CSI models fail to fit the multiband LCs of SN 2014av,while the CSI plus^(56)Ni model can account for the LCs.In the last scenario,the LCs around the peaks were mainly powered by the CSI,while the flattening of the LCs was mainly powered by the radioactive decay of^(56)Ni.For the wind case,the derived mass-loss rate of the progenitor is≈20.5-205.5 M_(⊙)yr^(-1),whose lower limit is significantly larger than the upper limit of normal stellar winds,and comparable the upper limit of hyper-winds.Hence,we suggest that the wind case is disfavored.For the shell case,the best-fitting values of the ejecta,^(56)Ni,and the CSM are2.29 M_(⊙),0.09 M_(⊙),and 5.00 M_(⊙),respectively.Provided the velocity of the CSM shell is 100-1000 km s^(-1),we infer that the shell might be expelled≈0.49-5.20 yr before the SN exploded.展开更多
BACKGROUND Living donor liver transplantation(LDLT)is a crucial alternative to deceased donor transplantation,especially in regions with limited access to cadaveric organs.Right lobe graft implantation into the inferi...BACKGROUND Living donor liver transplantation(LDLT)is a crucial alternative to deceased donor transplantation,especially in regions with limited access to cadaveric organs.Right lobe graft implantation into the inferior vena cava(IVC)requires advanced surgical techniques to optimize outcomes and reduce complications.AIM To compare two venous anastomosis techniques—direct polytetrafluoroethylene(PTFE)grafting of V5-V8 veins to the IVC vs triangulation to the right hepatic vein(RHV)—in terms of graft viability and postoperative outcomes.METHODS A retrospective analysis was conducted on 96 patients who underwent LDLT with right lobe grafts between 2014 and 2023.Patients were divided into three groups:(1)No venous outflow reconstruction;(2)PTFE graft direct anastomosis to the IVC;and(3)PTFE graft anastomosis using triangulation to the RHV.Perioperative and postoperative outcomes,including bile duct complications,alanine aminotransferase/aspartate aminotransferase levels,and graft perfusion,were compared across groups.RESULTS Group 3(triangulation to RHV)showed significantly improved venous outflow,fewer complications,and faster normalization of liver function tests.Bile duct complications were highest in group 1(12.8%)and lowest in group 3(7%).Doppler ultrasonography revealed better graft perfusion in group 3 compared to groups 1 and 2.CONCLUSION Triangulation to the RHV improves graft viability,reduces biliary complications,and enhances early postoperative outcomes compared to direct PTFE grafting to the IVC.展开更多
In this paper,we present results from a semi-analytical model that investigates the launching of cold,nonrelativistic jets from a wide radial extent of stationary and axisymmetric magnetized accretion disks.Specifical...In this paper,we present results from a semi-analytical model that investigates the launching of cold,nonrelativistic jets from a wide radial extent of stationary and axisymmetric magnetized accretion disks.Specifically,we examine the effects of magnetization on the disk-jet system in configurations where the magnetic field is near equipartition with the thermal pressure at the disk midplane.In this study,the magnetic strength parameterμis explicitly expressed as a function of the magnetic diffusivity parameter(μ-1/√αm).This formulation provides a more direct link between the magnetic field configuration and the diffusive processes within the accretion disk.By establishing this relationship,we better constrain the role of magnetization in jet launching and explore how variations inμinfluence the overall disk-jet dynamics.We focus on three representative cases whereμtakes the values 0.5,0.7,and 0.9.We solve the stiff ordinary differential equations of the semi-analytical MHD model using the Seulex subroutine of Hairer&Wanner,which employs the Taylor method with adaptive mesh refinement.The resulting solutions are compared with those obtained by Zanni et al.,Tzeferacos et al.,and Stepanovs&Fendt.展开更多
Using the stellar evolution code MESA,we mimic the negative jet feedback mechanism in common envelope evolution(CEE)of low-mass main sequence stars,M_(2)?0.1-0.2M_(☉),spiraling inward inside the envelopes of asymptot...Using the stellar evolution code MESA,we mimic the negative jet feedback mechanism in common envelope evolution(CEE)of low-mass main sequence stars,M_(2)?0.1-0.2M_(☉),spiraling inward inside the envelopes of asymptotic giant branch or red giant branch stars and find that the jets reduced the envelope density,and therefore the jets'power,by a factor ofχ≈0.5(M_(2)/0.1M_(☉))^(-1).We mimic the energy that the jets deposit into the envelope by depositing energy into the outer envelope,a process that inflates the envelope,therefore reducing the density in the vicinity of the main sequence star,the accretion rate,and the jets'power.In deriving this expression for the negative jet feedback coefficientχ,we assume that the actual mass accretion rate is a fractionξ≈0.2-0.5 of the classical Bondi-Hoyle-Lyttleton mass accretion rate and that the jets carry a fractionη≈0.25-0.5 of the accretion energy onto the main sequence star.Our study is another step in establishing the major role of jets in the onset and early phase of CEE,a possible grazing envelope evolution phase,and in transient events,such as luminous red novae,which these processes can power.展开更多
In the current paper,we present a study of the spatial distribution of luminous blue variables(LBVs)and various LBV candidates(c LBVs)with respect to OB associations in the galaxy M33.The identification of blue star g...In the current paper,we present a study of the spatial distribution of luminous blue variables(LBVs)and various LBV candidates(c LBVs)with respect to OB associations in the galaxy M33.The identification of blue star groups was based on the LGGS data and was carried out by two clustering algorithms with initial parameters determined during simulations of random stellar fields.We have found that the distribution of distances to the nearest OB association obtained for the LBV/c LBV sample is close to that for massive stars with Minit>20 M⊙and WolfRayet stars.This result is in good agreement with the standard assumption that LBVs represent an intermediate stage in the evolution of the most massive stars.However,some objects from the LBV/cLBV sample,particularly Fe II-emission stars,demonstrated severe isolation compared to other massive stars,which,together with certain features of their spectra,implicitly indicates that the nature of these objects and other LBVs/cLBVs may differ radically.展开更多
I examine images of 50 planetary nebulae(PNe)with observable post-common envelope evolution(CEE)binary central stars and find that jets are about 40%more common than dense equatorial outflows.Because,in some cases,ene...I examine images of 50 planetary nebulae(PNe)with observable post-common envelope evolution(CEE)binary central stars and find that jets are about 40%more common than dense equatorial outflows.Because,in some cases,energetic jets can compress an equatorial outflow and because fast jets might disperse early in the PN evolution and avoid detection,the CEE process is likelier to launch jets than to eject a dense equatorial outflow by a larger factor than 1.4.In most cases,the companion,mainly a main sequence star,launches the jets as it accretes mass from the envelope of the giant star.By CEE jets,I also refer to jets launched shortly before the onset of the CEE,likely a grazing envelope evolution phase,and shortly after the CEE.The jets and the accretion of mass by the companion before,during,and after the CEE affect envelope mass removal and the final orbital separation.Most numerical simulations of the CEE ignore jets,and those that include jets omit other processes.Despite the considerable progress in the last decade with tens of hydrodynamical simulations of the CEE,we are still far from correctly simulating the CEE.Including jets in simulations of the CEE requires heavy computer resources,but it must be the next step.展开更多
In order to investigate the CH4 and CO2 fluxes across the water-gas interface and identify their controlling factors, four diel field campaigns and one monthly sampling campaign during June 2010-May 2011 were carried ...In order to investigate the CH4 and CO2 fluxes across the water-gas interface and identify their controlling factors, four diel field campaigns and one monthly sampling campaign during June 2010-May 2011 were carried out at a site near the Three Gorges Dam, China. The averaged CH4 and CO2 fluxes across the air-water interface from the site were much less than those reported from reservoirs in tropic and temperate regions, and from the natural river channels of the Yangtze River. CH4 Fluxes at the site were very low compared to most other reservoirs or natural lakes. One of the most important reasons may be due to the oxidation of CH4 in the water column owing to the great water depth and high DO in water in the Three Gorges Reservoir. The averaged monthly CH4 and CO2 fluxes at the site during the observation year were 0.05 mg/（m^2·hr） and 104.43 mg/（m^2·hr） respectively with the maximum occurred in July 2010. The monthly CO2 fluxes during the observation year were positively correlated to the surface water temperature, and negatively correlated to the air pressure and the surface water pH. The CO2 flux showed a positive correlation with DOC to some extent, although not significantly, which indicated that allochthonous organic C was a major source of CO2 and biogeochemical processes in this reservoir were C-limited. The significantly positive correlation between the reservoir outflow and the seasonal gas flux indicate the disturbance condition of the water body dominated the seasonal gas emission.展开更多
A squall line on 14 June 2009 in the provinces of Jiangsu and Anhui was well simulated using the Advanced Regional Prediction System （ARPS） model. Based on high resolution spatial and temporal data, a detailed analy...A squall line on 14 June 2009 in the provinces of Jiangsu and Anhui was well simulated using the Advanced Regional Prediction System （ARPS） model. Based on high resolution spatial and temporal data, a detailed analysis of the structural features and propagation mechanisms of the squall line was conducted. The dynamic and thermodynamic structural charac- teristics and their causes were analyzed in detail. Unbalanced flows were found to play a key role in initiating gravity waves during the squall line＇s development. The spread and development of the gravity waves were sustained by convection in the wave-CISK process. The squall line＇s propagation and development mainly relied on the combined effect of gravity waves at the midlevel and cold outflow along the gust front. New cells were continuously forced by the cold pool outflow and were enhanced and lifted by the intense upward motion. At a particular phase, the new cells merged with the updraft of the gravity waves, leading to an intense updraft that strengthened the squall line.展开更多
Hypertrophic cardiomyopathy(HCM),the most variable cardiac disease in terms of phenotypic presentation and clinical outcome,represents the most common inherited cardiomyopathic process with an autosomal dominant trait...Hypertrophic cardiomyopathy(HCM),the most variable cardiac disease in terms of phenotypic presentation and clinical outcome,represents the most common inherited cardiomyopathic process with an autosomal dominant trait of inheritance.To date,more than 1400 mutations of myofilament proteins associated with the disease have been identified,most of them "private" ones.This striking allelic and locus heterogeneity of the disease certainly complicates the establishment of phenotype-genotype correlations.Additionally,topics pertaining to patients' everyday lives,such as sudden cardiac death(SCD)risk stratification and prevention,along with disease prognosis,are grossly related to the genetic variation of HCM.This review incorporates contemporary research findings and addresses major aspects of HCM,including preclinical diagnosis,genetic analysis,left ventricular outflow tract obstruction and SCD.More specifically,the spectrum of genetic analysis,the selection of the best method for obstruction alleviation and the need for a unique and accuratefactor for SCD risk stratification are only some of the controversial HCM issues discussed.Additionally,future perspectives concerning HCM and myocardial ischemia,as well as atrial fibrillation,are discussed.Rather than enumerating clinical studies and guidelines,challenging problems concerning the disease are critically appraised by this review,highlighting current speculations and recommending future directions.展开更多
Liquid distributor is a very import intemal for distillation columns. Pre-distributor is usually set on the top of distributor for initial distribution. Fluid flow in pre-distributor is a complex system of variable ma...Liquid distributor is a very import intemal for distillation columns. Pre-distributor is usually set on the top of distributor for initial distribution. Fluid flow in pre-distributor is a complex system of variable mass flow with many orifices and sub-branches. Consequently, the two phase modeling of pre-distributors was carried out andthe homogeneous model with free surface model was applied. The numerical method was validated by comparing with experimental data. Using the simulated results for different pre-distributors, the impacts of inflow rate, location and orientation uoon the outflow distribution were investigated. Furthermore, influences of the outflow distribution for pre-distributor on liquid uniformity in trough were also analyzed, The conclusions can De aaoptea for me structural design of liquid distributor and pre-distributor of large scale.展开更多
Aim： To explore the interaction between bladder compliance （BC） and bladder outflow obstruction （BOO） in men with benign prostatic hyperplasia （BPH） using cross-sectional and longitudinal studies. Methods： A t...Aim： To explore the interaction between bladder compliance （BC） and bladder outflow obstruction （BOO） in men with benign prostatic hyperplasia （BPH） using cross-sectional and longitudinal studies. Methods： A total of 181 men with BPH were recruited, and 100 of them were followed for one year. Cystometry was performed in a standing or a sitting position with 30 mL/min infusion. BC was manually corrected and defined. Obstruction coefficient （OCO）, linear passive urethral resistance relation and international continence society （ICS） nomogram were used to diagnose BOO. The obstructed parameters were compared between the reduced BC group and the non-reduced group. BC was compared between the first investigation at the beginning of study and the second investigation at the end of study during the one-year follow-up period. Results： The group with reduced BC had increased OCO and linear passive urethral resistance relation. BC was significantly lower in the obstructed group （55.7 mL/cm water） than that in unobstructed and equivocal one （74.9 mL/cm water, P 〈 0.01）. BC gradually reduced with the increased obstructed grade. There was a significantly weak negative correlation between BC and OCO （r = - 0.132, P 〈 0.01）. Over the one-year follow-up period in the longitudinal study, BC for all men changed from 54.4 to 48.8 mL/cm water （P 〉 0.05）, and BC for the group with BOO fell from 58.4 ± 70.1 to 46.5 ± 38.7 mL/cm water （P 〉 0.05）. Conclusion： In men with BPH, a significant systematic decrease occurred in BC in the obstructed group and a significant systematic increase with urethral resistance occurred in the low BC group. A longitudinal study of the tendency of BC reduction in a group with BOO is necessary in the future.展开更多
Hepatic vena cava syndrome(HVCS) also known as membranous obstruction of inferior vena cava reported mainly from Asia and Africa is an important cause of hepatic venous outflow obstruction(HVOO) that is complicated by...Hepatic vena cava syndrome(HVCS) also known as membranous obstruction of inferior vena cava reported mainly from Asia and Africa is an important cause of hepatic venous outflow obstruction(HVOO) that is complicated by high incidence of liver cirrhosis(LC) and moderate to high incidence of hepatocellular carcinoma(HCC). In the past the disease was considered congenital and was included under Budd-Chiari syndrome(BCS). HVCS is a chronic disease common in developing countries, the onset of which is related to poor hygienic living condition. The initial lesion in the disease is a bacterial infection induced localized thrombophlebitis in hepatic portion of inferior vena cava at the site where hepatic veins open which on resolution transforms into stenosis, membrane or thick obstruction,and is followed by development of cavo-caval collateral anastomosis. The disease is characterized by long asymptomatic period and recurrent acute exacerbations(AE) precipitated by clinical or subclinical bacterial infection. AE is managed with prolonged oral antibiotic. Development of LC and HCC in HVCS is related to the severity and frequency of AEs and not to the duration of the disease or the type or severity of the caval obstruction. HVOO that develops during severe acute stage or AE is a pre-cirrhotic condition. Primary BCS on the other hand is a rare disease related to prothrombotic disorders reported mainly among Caucasians that clinically manifest as acute, subacute disease or as fulminant hepatic failure; and is managed with life-long anticoagulation, portosystemic shunt/endovascular angioplasty and stent or liver transplantation. As epidemiology, etiology and natural history of HVCS are different from classical BCS, it is here, recognized as a separate disease entity, a third primary cause of HVOO after sinusoidal obstruction syndrome and BCS. Understanding of the natural history has made early diagnosis of HVCS possible. This paper describes epidemiology, natural history and diagnosis of HVCS and discusses the pathogenesis of LC in the disease and mentions distinctive clinical features of HVCS related LC.展开更多
基金supported by the National Key R&D Program of China(2022YFC3004101)the National Natural Science Foundation of China(Grant No.42275006)+2 种基金the Guangdong Basic and Applied Basic Research Foundation(Grant No.2022A1515011814)the China Meteorological Administration Tornado Key Laboratory(Grant No.TKL202302)the Science and Technology Research Project of Guangdong Meteorological Service(Grant No.GRMC2023Q35)。
文摘This study presents finely resolved radar signatures of multiple cyclonic vortices associated with an EF2 tornadic supercell that occurred in Guangzhou on 16 June 2022 and discusses how the mesocyclone formed on the lee side of mountain.A nearby X-band phased-array radar provides evidence that the mesocyclone was shallow,with a depth generally confined to less than 3 km.The mesocyclonic feature was observed to initiate from near-ground level,driven by the interaction between intensifying cold pool surges and shallow lee-side ambient flows.It was first recognized shortly after the presence of near-ground cyclonic convergence signatures over the leading edges of cold pool outflows.Over the subsequent 17 min,the mesocyclone developed upward,reaching a maximum height of 3 km,and produced a tornado 8min later.Nearly coinciding with the time of tornadogenesis,a noticeable separation of the low-level tornado cyclone from the midlevel mesocyclone was observed.This shift in the vertically oriented vortex tube was likely caused by modifications to the low-level flow due to the complex hilly terrain or by occlusions associated with rear-flank downdrafts.After tornadogenesis,high-resolution X-PAR observations revealed that the lowest-level mesocyclonic signature contracted into a gate-to-gate tornadic vortex signature(TVS)at the tip of hook echoes.Compared to conventional S-band operational weather radars,rapid-scan X-PAR observations indicate that a core diameter threshold of 1.5–2 km could be employed to identify a cyclonically sheared radial velocity couplet as a TVS,potentially extending the lead time for Doppler-based tornado warnings.
基金supported by the National Natural Science Foundation of China[grant numbers 42192553 and 61827091]。
文摘This study employs the self-organizing map method to investigate the upper-tropospheric outflow patterns of tropical cyclones(TCs)over the western North Pacific from 1979 to 2019,using the 200 hPa horizontal wind fields from the ERA5 reanalysis datasets.According to the number and orientation of TC outflow channels,as well as the wind speed,the outflow patterns are classified into five categories:southwestward single-channel pattern S1(26.1%);northwestward single-channel pattern S2(23.6%);northeastward single-channel pattern S3(23.6%);double-channel outflow pattern D(20.8%);and high latitude outflow pattern H(6.0%).Composite analysis shows that the orientations of the TC outflow channels are aligned with the direction of the environmental vertical wind shear and closely related to the distribution of the environmental inertial instability,upper-level divergence,and inner-core convective activities.TC intensity and intensity changes for different outflow patterns are also significantly different.Patterns S1 and S2 usually appear in the development phase and are thus prone to TC intensification,while patterns S3 and H usually occur in the weakening phase and are thus prone to TC weakening.The double-channel pattern(D)has the largest mean intensity and accounts for more than 60%of super-typhoon samples.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.U22A20602,U2040221,and 42207228)the Sichuan Science and Technology Program(2022NSFSC1060)the Fundamental Research Funds for Central Public Research Institutes(Grant No.Y324006)。
文摘Landslide dams,as frequent natural hazards,pose significant risks to human lives,property,and ecological environments.The grading characteristics and density of dam materials play a crucial role in determining the stability of landslide dams and the potential for dam breaches.To explore the failure mechanisms and evolutionary processes of landslide dams with varying soil properties,this study conducted a series of flume experiments,considering different grain compositions and material densities.The results demonstrated that grading characteristics significantly influence landslide dam stability,affecting failure patterns,breach processes,and final breach morphologies.Fine-graded materials exhibited a sequence of surface erosion,head-cut erosion,and subsequent surface erosion during the breach process,while well-graded materials typically experienced head-cut erosion followed by surface erosion.In coarse-graded dams,the high permeability of coarse particles allowed the dam to remain stable,as inflows matched outflows.The dam breach model experiments also showed that increasing material density effectively delayed the breach and reduced peak breach flow discharge.Furthermore,higher fine particle content led to a reduction in the residual dam height and the base slope of the final breach profile,although the relationship between peak breach discharge and the content of fine and coarse particles was nonlinear.To better understand breach morphology evolution under different soil characteristics and hydraulic conditions,three key points were identified—erosion point,control point,and scouring point.This study,by examining the evolution of failure patterns,breach processes,and breach flow discharges under various grading and density conditions,offers valuable insights into the mechanisms behind landslide dam failures.
文摘How gamma-ray bursts(GRBs),the most powerful and spectacular explosions known in the universe since the Big Bang,fuel their high-energy radiations?What kind of physical reactions can trigger and sustain such violent,energetic outflow?This has captivated astronomers.Over the past decades,thousands of GRBs have been observed;however,the origin and the product of the burst-the central celestial body,or the“central engine”,is still pending for identification.
基金The 64th batch of China Postdoctoral Science Foundation,Grant/Award Number:2018M640754National Natural Science Foundation of China,Grant/Award Number:81860870The“Wang Heng xin Scientific Research Fund”project of Hunan University of Chinese Medicine,Grant/Award Number:2023HX007。
文摘Glaucoma,a visual thief,is characterized by elevated intraocular pressure(IOP)and the loss of retinal ganglion cells(RGCs).Selecting suitable animals for preclinical models is of great significance in research on the prevention,early screening,and effective treatments of glaucoma.Rabbit eyeballs possess similar vascularity and aqueous humor outflow pathways to those of humans.Thus,they are among the earliest in vivo models used in glaucoma research.Over the years,rabbit models have made substantial contributions to understanding glaucomatous pathophysiology,surgical adaptations,biomedical device development,and drug development for reducing IOP,protecting RGCs,and inhibiting fibrosis.Compared to other animals,rabbits fit better with surgical operations and cost less.This review summarizes the merits and demerits of different ways to produce glaucomatous rabbit models,such as intracameral injection,vortex vein obstruction,Trendelenburg position,laser photo-coagulation,glucocorticoid induction,limbal buckling induction,retinal ischemia–reperfusion models,and spontaneous models.We analyzed their mechanisms in the hope of providing more references for experimental design and promoting the understanding of glaucoma treatment strategies.
文摘BACKGROUND Hepatic venous outflow obstruction(HVOO)is a rare but serious complication of liver transplantation,particularly in piggyback liver transplantation techniques where the inferior vena cava(IVC)is preserved.CASE SUMMARY A transplanted liver patient underwent retransplantation due to hepatic artery thrombosis and subsequently developed HVOO caused by graft compression of the IVC.A novel approach using a retrohepatic tissue expander effectively relieved the IVC compression,restored venous outflow,and stabilized hemodynamics.We discuss this case in the context of current treatment options and advances in HVOO management,from endovascular interventions such as balloon dilation and stenting to innovative surgical solutions such as graft repositioning and retrohepatic implants.CONCLUSION This case shows how important personalized treatments are for managing HVOO and how tissue expanders can be an adjustable and less invasive option.
基金supported by the National Key R&D Program(2024YFA1611700)the National Natural Science Foundation of China(grant Nos.12133003,12494571 and 11963001)supported by the Guangxi Talent Program(“Highland of Innovation Talents”)and Program of Bagui Scholars(LHJ)。
文摘SN 2014av is a type Ibn supernova(SN)characterized by the interaction between the SN ejecta and a helium-rich circumstellar medium(CSM).We use the^(56)Ni model,the ejecta-CSM interaction(CSI)model,and the CSI plus^(56)Ni model to fit the multiband light curves(LCs)of SN 2014av.For the CSI and CSI plus^(56)Ni models,we assume that the CSM is a constant density shell(“shell”)or a steady-state stellar wind(“wind”)with density∝r-2.We find that both the^(56)Ni and CSI models fail to fit the multiband LCs of SN 2014av,while the CSI plus^(56)Ni model can account for the LCs.In the last scenario,the LCs around the peaks were mainly powered by the CSI,while the flattening of the LCs was mainly powered by the radioactive decay of^(56)Ni.For the wind case,the derived mass-loss rate of the progenitor is≈20.5-205.5 M_(⊙)yr^(-1),whose lower limit is significantly larger than the upper limit of normal stellar winds,and comparable the upper limit of hyper-winds.Hence,we suggest that the wind case is disfavored.For the shell case,the best-fitting values of the ejecta,^(56)Ni,and the CSM are2.29 M_(⊙),0.09 M_(⊙),and 5.00 M_(⊙),respectively.Provided the velocity of the CSM shell is 100-1000 km s^(-1),we infer that the shell might be expelled≈0.49-5.20 yr before the SN exploded.
文摘BACKGROUND Living donor liver transplantation(LDLT)is a crucial alternative to deceased donor transplantation,especially in regions with limited access to cadaveric organs.Right lobe graft implantation into the inferior vena cava(IVC)requires advanced surgical techniques to optimize outcomes and reduce complications.AIM To compare two venous anastomosis techniques—direct polytetrafluoroethylene(PTFE)grafting of V5-V8 veins to the IVC vs triangulation to the right hepatic vein(RHV)—in terms of graft viability and postoperative outcomes.METHODS A retrospective analysis was conducted on 96 patients who underwent LDLT with right lobe grafts between 2014 and 2023.Patients were divided into three groups:(1)No venous outflow reconstruction;(2)PTFE graft direct anastomosis to the IVC;and(3)PTFE graft anastomosis using triangulation to the RHV.Perioperative and postoperative outcomes,including bile duct complications,alanine aminotransferase/aspartate aminotransferase levels,and graft perfusion,were compared across groups.RESULTS Group 3(triangulation to RHV)showed significantly improved venous outflow,fewer complications,and faster normalization of liver function tests.Bile duct complications were highest in group 1(12.8%)and lowest in group 3(7%).Doppler ultrasonography revealed better graft perfusion in group 3 compared to groups 1 and 2.CONCLUSION Triangulation to the RHV improves graft viability,reduces biliary complications,and enhances early postoperative outcomes compared to direct PTFE grafting to the IVC.
文摘In this paper,we present results from a semi-analytical model that investigates the launching of cold,nonrelativistic jets from a wide radial extent of stationary and axisymmetric magnetized accretion disks.Specifically,we examine the effects of magnetization on the disk-jet system in configurations where the magnetic field is near equipartition with the thermal pressure at the disk midplane.In this study,the magnetic strength parameterμis explicitly expressed as a function of the magnetic diffusivity parameter(μ-1/√αm).This formulation provides a more direct link between the magnetic field configuration and the diffusive processes within the accretion disk.By establishing this relationship,we better constrain the role of magnetization in jet launching and explore how variations inμinfluence the overall disk-jet dynamics.We focus on three representative cases whereμtakes the values 0.5,0.7,and 0.9.We solve the stiff ordinary differential equations of the semi-analytical MHD model using the Seulex subroutine of Hairer&Wanner,which employs the Taylor method with adaptive mesh refinement.The resulting solutions are compared with those obtained by Zanni et al.,Tzeferacos et al.,and Stepanovs&Fendt.
文摘Using the stellar evolution code MESA,we mimic the negative jet feedback mechanism in common envelope evolution(CEE)of low-mass main sequence stars,M_(2)?0.1-0.2M_(☉),spiraling inward inside the envelopes of asymptotic giant branch or red giant branch stars and find that the jets reduced the envelope density,and therefore the jets'power,by a factor ofχ≈0.5(M_(2)/0.1M_(☉))^(-1).We mimic the energy that the jets deposit into the envelope by depositing energy into the outer envelope,a process that inflates the envelope,therefore reducing the density in the vicinity of the main sequence star,the accretion rate,and the jets'power.In deriving this expression for the negative jet feedback coefficientχ,we assume that the actual mass accretion rate is a fractionξ≈0.2-0.5 of the classical Bondi-Hoyle-Lyttleton mass accretion rate and that the jets carry a fractionη≈0.25-0.5 of the accretion energy onto the main sequence star.Our study is another step in establishing the major role of jets in the onset and early phase of CEE,a possible grazing envelope evolution phase,and in transient events,such as luminous red novae,which these processes can power.
文摘In the current paper,we present a study of the spatial distribution of luminous blue variables(LBVs)and various LBV candidates(c LBVs)with respect to OB associations in the galaxy M33.The identification of blue star groups was based on the LGGS data and was carried out by two clustering algorithms with initial parameters determined during simulations of random stellar fields.We have found that the distribution of distances to the nearest OB association obtained for the LBV/c LBV sample is close to that for massive stars with Minit>20 M⊙and WolfRayet stars.This result is in good agreement with the standard assumption that LBVs represent an intermediate stage in the evolution of the most massive stars.However,some objects from the LBV/cLBV sample,particularly Fe II-emission stars,demonstrated severe isolation compared to other massive stars,which,together with certain features of their spectra,implicitly indicates that the nature of these objects and other LBVs/cLBVs may differ radically.
文摘I examine images of 50 planetary nebulae(PNe)with observable post-common envelope evolution(CEE)binary central stars and find that jets are about 40%more common than dense equatorial outflows.Because,in some cases,energetic jets can compress an equatorial outflow and because fast jets might disperse early in the PN evolution and avoid detection,the CEE process is likelier to launch jets than to eject a dense equatorial outflow by a larger factor than 1.4.In most cases,the companion,mainly a main sequence star,launches the jets as it accretes mass from the envelope of the giant star.By CEE jets,I also refer to jets launched shortly before the onset of the CEE,likely a grazing envelope evolution phase,and shortly after the CEE.The jets and the accretion of mass by the companion before,during,and after the CEE affect envelope mass removal and the final orbital separation.Most numerical simulations of the CEE ignore jets,and those that include jets omit other processes.Despite the considerable progress in the last decade with tens of hydrodynamical simulations of the CEE,we are still far from correctly simulating the CEE.Including jets in simulations of the CEE requires heavy computer resources,but it must be the next step.
基金supported by National Science Foundation of China (No.41273110,51079163)the National Basic Research Program (973) of China(No.2010CB955904)State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences
文摘In order to investigate the CH4 and CO2 fluxes across the water-gas interface and identify their controlling factors, four diel field campaigns and one monthly sampling campaign during June 2010-May 2011 were carried out at a site near the Three Gorges Dam, China. The averaged CH4 and CO2 fluxes across the air-water interface from the site were much less than those reported from reservoirs in tropic and temperate regions, and from the natural river channels of the Yangtze River. CH4 Fluxes at the site were very low compared to most other reservoirs or natural lakes. One of the most important reasons may be due to the oxidation of CH4 in the water column owing to the great water depth and high DO in water in the Three Gorges Reservoir. The averaged monthly CH4 and CO2 fluxes at the site during the observation year were 0.05 mg/（m^2·hr） and 104.43 mg/（m^2·hr） respectively with the maximum occurred in July 2010. The monthly CO2 fluxes during the observation year were positively correlated to the surface water temperature, and negatively correlated to the air pressure and the surface water pH. The CO2 flux showed a positive correlation with DOC to some extent, although not significantly, which indicated that allochthonous organic C was a major source of CO2 and biogeochemical processes in this reservoir were C-limited. The significantly positive correlation between the reservoir outflow and the seasonal gas flux indicate the disturbance condition of the water body dominated the seasonal gas emission.
基金supported by the National Basic Research Program of China (Grant No. 2013CB 430105)the Key Program of the Chinese Academy of Sciences (Grant No. KZZD-EW-05)+1 种基金the project of CAMS (Chinese Academy of Meteorological Sciences) (Grant No. 2011LASWB15)the National Natural Sciences Foundation of China (Grant No. 41175060)
文摘A squall line on 14 June 2009 in the provinces of Jiangsu and Anhui was well simulated using the Advanced Regional Prediction System （ARPS） model. Based on high resolution spatial and temporal data, a detailed analysis of the structural features and propagation mechanisms of the squall line was conducted. The dynamic and thermodynamic structural charac- teristics and their causes were analyzed in detail. Unbalanced flows were found to play a key role in initiating gravity waves during the squall line＇s development. The spread and development of the gravity waves were sustained by convection in the wave-CISK process. The squall line＇s propagation and development mainly relied on the combined effect of gravity waves at the midlevel and cold outflow along the gust front. New cells were continuously forced by the cold pool outflow and were enhanced and lifted by the intense upward motion. At a particular phase, the new cells merged with the updraft of the gravity waves, leading to an intense updraft that strengthened the squall line.
文摘Hypertrophic cardiomyopathy(HCM),the most variable cardiac disease in terms of phenotypic presentation and clinical outcome,represents the most common inherited cardiomyopathic process with an autosomal dominant trait of inheritance.To date,more than 1400 mutations of myofilament proteins associated with the disease have been identified,most of them "private" ones.This striking allelic and locus heterogeneity of the disease certainly complicates the establishment of phenotype-genotype correlations.Additionally,topics pertaining to patients' everyday lives,such as sudden cardiac death(SCD)risk stratification and prevention,along with disease prognosis,are grossly related to the genetic variation of HCM.This review incorporates contemporary research findings and addresses major aspects of HCM,including preclinical diagnosis,genetic analysis,left ventricular outflow tract obstruction and SCD.More specifically,the spectrum of genetic analysis,the selection of the best method for obstruction alleviation and the need for a unique and accuratefactor for SCD risk stratification are only some of the controversial HCM issues discussed.Additionally,future perspectives concerning HCM and myocardial ischemia,as well as atrial fibrillation,are discussed.Rather than enumerating clinical studies and guidelines,challenging problems concerning the disease are critically appraised by this review,highlighting current speculations and recommending future directions.
基金Supported by the National Key Basic Research and Development Program of China (2009CB219905, 2009CB219907)the Program for Changjiang Scholars and Innovative Research Teams in Universities (IRT0936)
文摘Liquid distributor is a very import intemal for distillation columns. Pre-distributor is usually set on the top of distributor for initial distribution. Fluid flow in pre-distributor is a complex system of variable mass flow with many orifices and sub-branches. Consequently, the two phase modeling of pre-distributors was carried out andthe homogeneous model with free surface model was applied. The numerical method was validated by comparing with experimental data. Using the simulated results for different pre-distributors, the impacts of inflow rate, location and orientation uoon the outflow distribution were investigated. Furthermore, influences of the outflow distribution for pre-distributor on liquid uniformity in trough were also analyzed, The conclusions can De aaoptea for me structural design of liquid distributor and pre-distributor of large scale.
文摘Aim： To explore the interaction between bladder compliance （BC） and bladder outflow obstruction （BOO） in men with benign prostatic hyperplasia （BPH） using cross-sectional and longitudinal studies. Methods： A total of 181 men with BPH were recruited, and 100 of them were followed for one year. Cystometry was performed in a standing or a sitting position with 30 mL/min infusion. BC was manually corrected and defined. Obstruction coefficient （OCO）, linear passive urethral resistance relation and international continence society （ICS） nomogram were used to diagnose BOO. The obstructed parameters were compared between the reduced BC group and the non-reduced group. BC was compared between the first investigation at the beginning of study and the second investigation at the end of study during the one-year follow-up period. Results： The group with reduced BC had increased OCO and linear passive urethral resistance relation. BC was significantly lower in the obstructed group （55.7 mL/cm water） than that in unobstructed and equivocal one （74.9 mL/cm water, P 〈 0.01）. BC gradually reduced with the increased obstructed grade. There was a significantly weak negative correlation between BC and OCO （r = - 0.132, P 〈 0.01）. Over the one-year follow-up period in the longitudinal study, BC for all men changed from 54.4 to 48.8 mL/cm water （P 〉 0.05）, and BC for the group with BOO fell from 58.4 ± 70.1 to 46.5 ± 38.7 mL/cm water （P 〉 0.05）. Conclusion： In men with BPH, a significant systematic decrease occurred in BC in the obstructed group and a significant systematic increase with urethral resistance occurred in the low BC group. A longitudinal study of the tendency of BC reduction in a group with BOO is necessary in the future.
文摘Hepatic vena cava syndrome(HVCS) also known as membranous obstruction of inferior vena cava reported mainly from Asia and Africa is an important cause of hepatic venous outflow obstruction(HVOO) that is complicated by high incidence of liver cirrhosis(LC) and moderate to high incidence of hepatocellular carcinoma(HCC). In the past the disease was considered congenital and was included under Budd-Chiari syndrome(BCS). HVCS is a chronic disease common in developing countries, the onset of which is related to poor hygienic living condition. The initial lesion in the disease is a bacterial infection induced localized thrombophlebitis in hepatic portion of inferior vena cava at the site where hepatic veins open which on resolution transforms into stenosis, membrane or thick obstruction,and is followed by development of cavo-caval collateral anastomosis. The disease is characterized by long asymptomatic period and recurrent acute exacerbations(AE) precipitated by clinical or subclinical bacterial infection. AE is managed with prolonged oral antibiotic. Development of LC and HCC in HVCS is related to the severity and frequency of AEs and not to the duration of the disease or the type or severity of the caval obstruction. HVOO that develops during severe acute stage or AE is a pre-cirrhotic condition. Primary BCS on the other hand is a rare disease related to prothrombotic disorders reported mainly among Caucasians that clinically manifest as acute, subacute disease or as fulminant hepatic failure; and is managed with life-long anticoagulation, portosystemic shunt/endovascular angioplasty and stent or liver transplantation. As epidemiology, etiology and natural history of HVCS are different from classical BCS, it is here, recognized as a separate disease entity, a third primary cause of HVOO after sinusoidal obstruction syndrome and BCS. Understanding of the natural history has made early diagnosis of HVCS possible. This paper describes epidemiology, natural history and diagnosis of HVCS and discusses the pathogenesis of LC in the disease and mentions distinctive clinical features of HVCS related LC.
