This paper is part of a series on the Azimuthally Symmetric Theory of Gravitation （ASTG）. This theory is built on Laplace-Poisson＇s well known equation and it has been shown that the ASTG is capable of explaining, ...This paper is part of a series on the Azimuthally Symmetric Theory of Gravitation （ASTG）. This theory is built on Laplace-Poisson＇s well known equation and it has been shown that the ASTG is capable of explaining, from a purely classical physics standpoint, the precession of the perihelion of solar planets as a consequence of the azimuthal symmetry emerging from the spin of the Sun. This symmetry has and must have an influence on the emergent gravitational field. We show herein that the emergent equations from the ASTG, under some critical conditions determined by the spin, do possess repulsive gravitational fields in the polar regions of the gravitating body in question. This places the ASTG on an interesting pedestal to infer the origins of outflows as a repulsive gravitational phenomenon. Outflows are a ubiquitous phenomenon found in star forming systems and their true origin is a question yet to be settled. Given the current thinking on their origin, the direction that the present paper takes is nothing short of an asymptotic break from conventional wisdom; at the very least, it is a complete paradigm shift because gravitation is not at all associated with this process, but rather it is thought to be an all-attractive force that only tries to squash matter together onto a single point. Additionally, we show that the emergent Azimuthally Symmetric Gravitational Field from the ASTG strongly suggests a solution to the supposed Radiation Problem that is thought to be faced by massive stars in their process of formation. That is, at ,- 8-10M⊙, radiation from the nascent star is expected to halt the accretion of matter. We show that in-falling material will fall onto the equatorial disk and from there, this material will be channeled onto the forming star via the equatorial plane, thus accretion of mass continues well past the value of - 8-10M⊙, albeit via the disk. Along the equatorial plane, the net force （with the radiation force included） on any material there-on right up to the surface of the star is directed toward the forming star, hence accretion of mass by the nascent star is un-hampered.展开更多
This paper considers fluid mixing driven by inflows connected to a circular shallow lake using a numerical framework consisting of a shallow water hydrodynamic model and a passive particle-tracking model.With the flow...This paper considers fluid mixing driven by inflows connected to a circular shallow lake using a numerical framework consisting of a shallow water hydrodynamic model and a passive particle-tracking model.With the flow field driven by alternate inflows predicted by a shallow water model,particle trajectories are traced out using a particle tracking model.The horizontal fluid mixing dynamics are then interpreted using dynamics system analysis approaches including finite-time Lyapunov exponent(FTLE)and Lagrangian coherent structure(LCS).From the simulation results,it is confirmed that periodic inflows are able to create a weak dynamic system in an idealised circular lake,with the particle dynamics controlled by a single dimensionless parameter associated with the inflow duration.The mixing and transport property of the lake changes from regular to chaotic as the value of the dimensionless parameter increases until global chaotic particle dynamics is achieved.By further analysing the advection of particles injected continuously to the inflows(freshwater),the fate of“freshwater”particles in a“polluted”lake is tracked and revealed.The results provide useful guidance for engineering applications,i.e.,transferring freshwater from rivers to improve the water quality in polluted water bodies such as lakes.The presented approach will be able to facilitate the design of‘optimised’schemes for such engineering implementation.展开更多
Mapping observations in12CO J = 1 - 0 lines were made towards S39 and IRAS 06306 + 0232 with the 13.7 m radio telescope at Qinghai Station of Purple Mountain Observatory. The results showed that both of them have bipo...Mapping observations in12CO J = 1 - 0 lines were made towards S39 and IRAS 06306 + 0232 with the 13.7 m radio telescope at Qinghai Station of Purple Mountain Observatory. The results showed that both of them have bipolar outflows. We have calculated the outflow parameters. The outflows have significantly more mass and higher mass loss rate than those from low mass YSOs. We also find that although the bolometric luminosities of the associated sources are large, the radiation pressure of wind is not sufficient to drive the observed outflows. There exist several stars of different evolve states in S39. It suggests that the star formation in S39 is in sequence, not in eruption.展开更多
Under the support of the National Natural Science Foundation of China,the research team led by Prof.Wang TingGui(王挺贵)and Prof.Liu GuiLin(刘桂琳)at the CAS Key Laboratory for Research in Galaxies and Cosmology,Depar...Under the support of the National Natural Science Foundation of China,the research team led by Prof.Wang TingGui(王挺贵)and Prof.Liu GuiLin(刘桂琳)at the CAS Key Laboratory for Research in Galaxies and Cosmology,Department of Astronomy,University of Science and Technology of China(USTC),recently reported their novel method to measure the spatial scale of quasar outflows.展开更多
By mapping the12COJ = 1—0 lines in IRAS 05391-0217, 06114 + 1745 and 06291 + 0421, three new high-velocity bipolar molecular outflows are found. Parameters of these outflows are derived, which suggest that they are m...By mapping the12COJ = 1—0 lines in IRAS 05391-0217, 06114 + 1745 and 06291 + 0421, three new high-velocity bipolar molecular outflows are found. Parameters of these outflows are derived, which suggest that they are massive and energetic outflows with total kinetic energies of about 1038 J and mass loss rates about 10-5 M/a. The driving sources are identified by analyzing the positions, intensities and color temperatures of the associated infrared sources. These outflows are most likely driven by single sources which correspond to massive young stellar objects. In these regions H2O masers have been detected located near the embedded infrared sources, which indicates that their exciting mechanism may be correlated with that of the CO outflows. The relationship between the parameters of outflows and central sources shows that high-velocity outflow and thermal radiation of a star are two basic correlated but different features in the evolution of young stars.展开更多
Water stored in reservoirs has a lot of crucial function,including generating hydropower,supporting water supply,and relieving lasting droughts.During floods,water deliveries from reservoirs must be acceptable,so as t...Water stored in reservoirs has a lot of crucial function,including generating hydropower,supporting water supply,and relieving lasting droughts.During floods,water deliveries from reservoirs must be acceptable,so as to guarantee that the gross volume of water is at a safe level and any release from reservoirs will not trigger flooding downstream.This study aims to develop a well-versed assessment method for managing reservoirs and pre-releasing water outflows by using the machine learning technology.As a new and exciting AI area,this technology is regarded as the most valuable,time-saving,supervised and cost-effective approach.In this study,two data-driven forecasting models,i.e.,Regression Tree(RT)and Support Vector Machine(SVM),were employed for approximately 30 years’hydrological records,so as to simulate reservoir outflows.The SVM and RT models were applied to the data,accurately predicting the fluctuations in the water outflows of a Bhakra reservoir.Different input combinations were used to determine the most effective release.For cross-validation,the number of folds varied.It is found that quadratic SVM for 10 folds with seven different parameters would give the minimum RMSE,maximum R2,and minimum MAE;therefore,it can be considered as the best model for the dataset used in this study.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
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 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
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
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
基金supported by the Republic of South Africa's National Research Foundation
文摘This paper is part of a series on the Azimuthally Symmetric Theory of Gravitation （ASTG）. This theory is built on Laplace-Poisson＇s well known equation and it has been shown that the ASTG is capable of explaining, from a purely classical physics standpoint, the precession of the perihelion of solar planets as a consequence of the azimuthal symmetry emerging from the spin of the Sun. This symmetry has and must have an influence on the emergent gravitational field. We show herein that the emergent equations from the ASTG, under some critical conditions determined by the spin, do possess repulsive gravitational fields in the polar regions of the gravitating body in question. This places the ASTG on an interesting pedestal to infer the origins of outflows as a repulsive gravitational phenomenon. Outflows are a ubiquitous phenomenon found in star forming systems and their true origin is a question yet to be settled. Given the current thinking on their origin, the direction that the present paper takes is nothing short of an asymptotic break from conventional wisdom; at the very least, it is a complete paradigm shift because gravitation is not at all associated with this process, but rather it is thought to be an all-attractive force that only tries to squash matter together onto a single point. Additionally, we show that the emergent Azimuthally Symmetric Gravitational Field from the ASTG strongly suggests a solution to the supposed Radiation Problem that is thought to be faced by massive stars in their process of formation. That is, at ,- 8-10M⊙, radiation from the nascent star is expected to halt the accretion of matter. We show that in-falling material will fall onto the equatorial disk and from there, this material will be channeled onto the forming star via the equatorial plane, thus accretion of mass continues well past the value of - 8-10M⊙, albeit via the disk. Along the equatorial plane, the net force （with the radiation force included） on any material there-on right up to the surface of the star is directed toward the forming star, hence accretion of mass by the nascent star is un-hampered.
基金Project supported by the National Natural Science Foundation of China(Grant No.11371117).
文摘This paper considers fluid mixing driven by inflows connected to a circular shallow lake using a numerical framework consisting of a shallow water hydrodynamic model and a passive particle-tracking model.With the flow field driven by alternate inflows predicted by a shallow water model,particle trajectories are traced out using a particle tracking model.The horizontal fluid mixing dynamics are then interpreted using dynamics system analysis approaches including finite-time Lyapunov exponent(FTLE)and Lagrangian coherent structure(LCS).From the simulation results,it is confirmed that periodic inflows are able to create a weak dynamic system in an idealised circular lake,with the particle dynamics controlled by a single dimensionless parameter associated with the inflow duration.The mixing and transport property of the lake changes from regular to chaotic as the value of the dimensionless parameter increases until global chaotic particle dynamics is achieved.By further analysing the advection of particles injected continuously to the inflows(freshwater),the fate of“freshwater”particles in a“polluted”lake is tracked and revealed.The results provide useful guidance for engineering applications,i.e.,transferring freshwater from rivers to improve the water quality in polluted water bodies such as lakes.The presented approach will be able to facilitate the design of‘optimised’schemes for such engineering implementation.
基金This work was supported by NKBRSF, the National Natural Science Foundation of China (Grant Nos. 10133020, 10128306 & 19773002) the United Astronomy Laboratory of CAS.
文摘Mapping observations in12CO J = 1 - 0 lines were made towards S39 and IRAS 06306 + 0232 with the 13.7 m radio telescope at Qinghai Station of Purple Mountain Observatory. The results showed that both of them have bipolar outflows. We have calculated the outflow parameters. The outflows have significantly more mass and higher mass loss rate than those from low mass YSOs. We also find that although the bolometric luminosities of the associated sources are large, the radiation pressure of wind is not sufficient to drive the observed outflows. There exist several stars of different evolve states in S39. It suggests that the star formation in S39 is in sequence, not in eruption.
文摘Under the support of the National Natural Science Foundation of China,the research team led by Prof.Wang TingGui(王挺贵)and Prof.Liu GuiLin(刘桂琳)at the CAS Key Laboratory for Research in Galaxies and Cosmology,Department of Astronomy,University of Science and Technology of China(USTC),recently reported their novel method to measure the spatial scale of quasar outflows.
基金Project supported by the National Natural Science Foundation of China (Gran No. 19773002)the United Radio Astronomy Lab. of Chinese Academy of Sciences.
文摘By mapping the12COJ = 1—0 lines in IRAS 05391-0217, 06114 + 1745 and 06291 + 0421, three new high-velocity bipolar molecular outflows are found. Parameters of these outflows are derived, which suggest that they are massive and energetic outflows with total kinetic energies of about 1038 J and mass loss rates about 10-5 M/a. The driving sources are identified by analyzing the positions, intensities and color temperatures of the associated infrared sources. These outflows are most likely driven by single sources which correspond to massive young stellar objects. In these regions H2O masers have been detected located near the embedded infrared sources, which indicates that their exciting mechanism may be correlated with that of the CO outflows. The relationship between the parameters of outflows and central sources shows that high-velocity outflow and thermal radiation of a star are two basic correlated but different features in the evolution of young stars.
文摘Water stored in reservoirs has a lot of crucial function,including generating hydropower,supporting water supply,and relieving lasting droughts.During floods,water deliveries from reservoirs must be acceptable,so as to guarantee that the gross volume of water is at a safe level and any release from reservoirs will not trigger flooding downstream.This study aims to develop a well-versed assessment method for managing reservoirs and pre-releasing water outflows by using the machine learning technology.As a new and exciting AI area,this technology is regarded as the most valuable,time-saving,supervised and cost-effective approach.In this study,two data-driven forecasting models,i.e.,Regression Tree(RT)and Support Vector Machine(SVM),were employed for approximately 30 years’hydrological records,so as to simulate reservoir outflows.The SVM and RT models were applied to the data,accurately predicting the fluctuations in the water outflows of a Bhakra reservoir.Different input combinations were used to determine the most effective release.For cross-validation,the number of folds varied.It is found that quadratic SVM for 10 folds with seven different parameters would give the minimum RMSE,maximum R2,and minimum MAE;therefore,it can be considered as the best model for the dataset used in this study.
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.
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.
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.
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.
