Objectives:One of the most notable challenges in endoscopic procedures is maintaining correct orientation.Mental rotation exercise(MRE)has been suggested as a potential aid for improving orientation.However,there is a...Objectives:One of the most notable challenges in endoscopic procedures is maintaining correct orientation.Mental rotation exercise(MRE)has been suggested as a potential aid for improving orientation.However,there is a lack of research on designing MREs with varying difficultylevels for training purposes.Furthermore,few studies provide solid evidence linking MRE difficultylevels with cognitive load measurements.This study aims to address this gap by investigating the correlation between the MRE difficultylevels and participants’cognitive load,as measured by pupil dilation.Method:We recruited 33 participants to perform MREs on a computer equipped with a screen-mounted eye-tracker.The test consisted of 15 MREs,with the first10 relatively easy(traditional cube)and the next 5 more complex(invented molecule).The participants’eye movements during MREs were recorded.The participants’MRE scores and pupil dilation were obtained and compared between two MRE difficultylevels.Results:The participants who performed traditional cube MREs achieved significantlybetter MRE scores(0.77±0.11 vs.0.58±0.03,p<0.001)and lower pupil dilation(0.27±0.04 pixels vs.0.47±0.09 pixels,p<0.001)than did those who performed the invented molecule MREs.Moreover,there were significant negative correlations(r=0.62,p=0.015)between pupil dilation and MRE scores.Conclusions:The results revealed a significantnegative correlation between MRE scores and pupil dilation.The more challenging MRE questions led to worse MRE scores but increased pupil dilation.The MRE difficultylevels can be evaluated not only by the degrees or dimensions with which the objects were rotated but also by the participants’MRE scores and pupil dilation.The results of this study provide a basis for training orientation skills in endoscopy using MREs.By incorporating MREs with varying difficultylevels,customized training programs can be developed to enhance camera navigation in endoscopic and laparoscopic procedures.展开更多
In a second-order r-mode theory, Sa and Tome found that the r-mode oscillation in neutron stars （NSs） could induce stellar differential rotation, which naturally leads to a saturated state of the oscillation. Based ...In a second-order r-mode theory, Sa and Tome found that the r-mode oscillation in neutron stars （NSs） could induce stellar differential rotation, which naturally leads to a saturated state of the oscillation. Based on a consideration of the coupling of the r-modes and the stellar spin and thermal evolution, we carefully investigate the influences of the differential rotation on the long-term evolution of isolated NSs and NSs in low-mass X-ray binaries, where the viscous damping of the r-modes and its resultant effects are taken into account. The numerical results show that, for both kinds of NSs, the differential rotation can significantly prolong the duration of the r-modes. As a result, the stars can keep nearly a constant temperature and constant angular velocity for over a thousand years. Moreover, the persistent radiation of a quasi-monochromatic gravitational wave would also be predicted due to the long-term steady r-mode oscillation and stellar rotation. This increases the detectability of gravitational waves from both young isolated and old accreting NSs.展开更多
In our previous work, we developed a model to study the effects of rotation and/or tidal distortions on anharmonic radial oscillations and hence on the radial velocity curves of the polytropic models of pulsating vari...In our previous work, we developed a model to study the effects of rotation and/or tidal distortions on anharmonic radial oscillations and hence on the radial velocity curves of the polytropic models of pulsating variable stars.We considered the first three modes(fundamental and the next two higher modes) for the polytropic models of index 1.5 and 3.0 in that work.In the present paper, we are further extending our previous work to study the effect of the interaction of various modes on anharmonic radial oscillations and hence on radial velocity curves of the rotationally and/or tidally distorted polytropic models of pulsating variable stars.For this purpose, we have considered the following cases:(i) fundamental mode(ii) fundamental and the first mode,(iii) fundamental and the next two modes and finally(iv) fundamental and the next three higher modes of pulsation in our study.The objective of this paper is also to investigate whether the interaction of various modes affects the results of our previous study or not.The results of this study show that the interaction of the fundamental mode with higher modes appreciably changes the shape of the radial velocity curve of rotationally distorted and rotationally and tidally distorted polytropic models of pulsating variable stars.展开更多
Anharmonic oscillations of rotating stars have been studied by various authors in literature to explain the observed features of certain variable stars. However, there is no study available in literature that has disc...Anharmonic oscillations of rotating stars have been studied by various authors in literature to explain the observed features of certain variable stars. However, there is no study available in literature that has discussed the combined effect of rotation and tidal distortions on the anharmonic oscillations of stars. In this paper, we have created a model to determine the effect of rotation and tidal distortions on the anharmonic radial oscillations associated with various polytropic models of pulsating variable stars. For this study we have used the theory of Rosseland to obtain the anharmonic pulsation equation for rotationally and tidally distorted polytropic models of pulsating variable stars. The main objective of this study is to investigate the effect of rotation and tidal distortions on the shapes of the radial velocity curves for rotationally and tidally distorted polytropic models of pulsating variable stars. The results of the present study show that the rotational effects cause more deviations in the shapes of radial velocity curves of pulsating variable stars as compared to tidal effects.展开更多
We investigate the rotation profile of solar-like stars with magnetic fields. A diffu- sion coefficient of magnetic angular momentum transport is deduced. Rotating stellar models with different mass incorporating the ...We investigate the rotation profile of solar-like stars with magnetic fields. A diffu- sion coefficient of magnetic angular momentum transport is deduced. Rotating stellar models with different mass incorporating the coefficient are computed to give the rotation profiles. The total angular momentum of a solar model with only hydrodynamic instabilities is about 13 times larger than that of the Sun at the age of the Sun, and this model can not reproduce quasi-solid rotation in the radiative region. However, the solar model with magnetic fields not only can reproduce an almost uniform rotation in the radiative region, but also a total angular momentum that is consistent with the helioseismic result at the 3 tr level at the age of the Sun. The rotation of solar-like stars with magnetic fields is almost uniform in the radiative region, but for models of 1.2-1.5 MG, there is an obvious transition region between the convective core and the radiative region, where angular velocity has a sharp radial gradient, which is different from the rotation profile of the Sun and of massive stars with magnetic fields. The change of angular velocity in the transition region increases with increasing age and mass.展开更多
We monitored 16 X-ray selected young solar-type stars for light variation and found appreciable periodic light variability with amplitudes of a few hundredths of a magni- tude in nine of the objects. Using the method ...We monitored 16 X-ray selected young solar-type stars for light variation and found appreciable periodic light variability with amplitudes of a few hundredths of a magni- tude in nine of the objects. Using the method of Phase Dispersion Minimization （PDM） and Fourier analysis （software PERIOD04）, the rotation periods of these stars were determined from the photometric data. The rotation periods of all nine stars are shorter than about 3 days. It is suggested that, as with the Pleiades cluster, small amplitude light variations are quite common among young solar-type stars with rotation periods around 3 days or less. This gives further evidence for the spin up of solar-type stars predicted by models of angular momentum evolution of pre-main sequence stars.展开更多
The availability of astrometfic data and radial velocities of carbon stars near the Galactic plane enables us to investigate the kinematics of the Milky Way, especially the rotation curve. The recently published Third...The availability of astrometfic data and radial velocities of carbon stars near the Galactic plane enables us to investigate the kinematics of the Milky Way, especially the rotation curve. The recently published Third U. S. Naval Observatory CCD Astrograph Catalog （UCAC3） provides the opportunity to test this problem using three-dimensional velocity in order to obtain more reliable rotation curves. We intend to study the Galactic rotation curve up to 15 kpc using the radial velocities and proper motions of carbon stars. The motivation for using UCAC3 is to provide high precision proper motions which have hardly been used in determining the rotation velocity of tracers. Seventy-four carbon stars and carbon-rich Mira variables toward the anti-center direction （90° 〈 l 〈 270°, ｜b｜ 〈 6°） are picked up from the literature then matched with UCAC3 carbon star candidates to obtain their proper motions. A rigorous geometrical method is employed to compute the rotation velocity of each object. Taking carbon stars as tracers, we find a flat rotation curve of 210 ± 12 kms^-1 assuming R0 = 8.0kpc for the galactocentric distance and V0 = 220kms^-1 for the rotation velocity of the Sun. Due to the uncertainties of distances, the rotation velocities are more dispersed if tangential velocities enter the calculation, compared to those derived from radial velocities only. However, the whole rotation curve shows coherence with previous results. Increasing observation and study of carbon stars would be desirable in order to provide more homogeneous data for the kinematical study of the Galactic disk.展开更多
In the present paper, the establishment of a systematic multi-barycenter mechanics is based on the multi-particle mechanics. The new theory perfects the basic theoretical system of classical mechanics, which finds the...In the present paper, the establishment of a systematic multi-barycenter mechanics is based on the multi-particle mechanics. The new theory perfects the basic theoretical system of classical mechanics, which finds the law of mutual interaction between particle groups, reveals the limitations of Newton’s third law, discovers the principle of the intrinsic relationship between gravity and tidal force, reasonably interprets the origin and change laws for the rotation angular momentum of galaxies and stars and so on. By applying new theory, the multi-body problem can be transformed into a special two-body problem and for which an approximate solution method is proposed, the motion law of each particle can be roughly obtained.展开更多
The tidal interactions of planets affect the stellar evolutionary status and the constraint of their physical parameters by gyrochronology.In this work,we incorporate the tidal interaction and magnetic braking of the ...The tidal interactions of planets affect the stellar evolutionary status and the constraint of their physical parameters by gyrochronology.In this work,we incorporate the tidal interaction and magnetic braking of the stellar wind into MESA and calculate a large grid of 25,000 models,covering planets with masses of 0.1–13.0MJ with different orbital distances that orbit late-type stars of different metallicities.We also explore the effect of different stellar initial rotations on the tidal interactions.Our results show that in the case of tidal inward migration,the stellar rotation periods are always lower than that of the star without planet before the planet is engulfed and the difference in the rotation period of its host star always increases with time.After the planet is engulfed,the stellar rotation periods are still lower than that of star without planet,but the difference of periods can be quickly eliminated if the star has a thick convective envelope(smaller mass and larger metallicity),regardless of the mass of the planet and the initial rotation period of the star.In the case of stars with thinner convective envelopes(larger mass and smaller metallicity),the stars will be spun up and remain the faster rotation in a long time.Meanwhile,the planet is easily swallowed and the period differences are large if the initial rotation period of its host star is higher.Finally,we also study the evolution of WASP-19 and estimate the range of tidal quality parameter Q_(*)^(')=(4.6±0.9)×10^(6)and the initial semimajor axis as(0.035±0.004)au.展开更多
We present a spectroscopic and photometric study of HIP 12653 to investigate its magnetic cycle and differential rotation.Using HARPS archival spectra matched with MARCS-AMBRE theoretical templates,we derive the stell...We present a spectroscopic and photometric study of HIP 12653 to investigate its magnetic cycle and differential rotation.Using HARPS archival spectra matched with MARCS-AMBRE theoretical templates,we derive the stellar parameters(Teff,logg,FeH,and vsini)of the target.The S-index,an activity indicator based on the emission of the CaⅡH&K lines,is fitted to determine the magnetic cycle and rotation periods.We refine the magnetic cycle period to 5799.20±0.88 days and suggest the existence of a secondary,shorter cycle of674.6922±0.0098 days,making HIP 12653 the youngest star known to exhibit such a short activity cycle.During the minimum activity phase,a rotation period of 4.8 days is estimated.This is notably different from the 7 day period obtained when measurements during minimum activity are excluded,suggesting that these two periods are rotation periods at different latitudes.To explore this hypothesis,we introduce a novel light curve fitting method that incorporates multiple harmonics to model different spot configurations.Applied to synthetic light curves,the method recovers at least two rotation periods close to the true input values(within three times their uncertainties)in 92.1%of cases.The inferred rotation shear shows a median deviation of 0.0011±0.0003 and a standard deviation of 0.0177±0.0002 from the true value.Applying this approach to TESS photometric data from 2018 to2023,we detect three distinct rotation periods—4.8 days,5.7 days,and 7.7 days,(along with a signal at 3.75 days interpreted as its first harmonic)—consistent with spots located at different latitudes.Assuming a solar-like differential rotation,we estimate an inclination of 34.0°±1.8°and a rotational shear ofα=0.38±0.01.These results confirm the 4.8 day period and demonstrate that differential rotation can be constrained by tracking rotation period changes across different phases of the magnetic cycle.展开更多
Recent studies have increasingly identified extended main sequence turn-off(e MSTO)phenomena in Galactic open clusters,yet the number of such clusters with sufficient spectroscopic information for member stars remains...Recent studies have increasingly identified extended main sequence turn-off(e MSTO)phenomena in Galactic open clusters,yet the number of such clusters with sufficient spectroscopic information for member stars remains limited.Unlike most studies that rely on fitting isochrones based on color–magnitude diagram(CMD)morphology to account for varying rotational velocities,our approach leverages LAMOST spectral data to compute actual rotational velocity distributions for confirmed cluster members,along with parameters such as metallicity,differential extinction,and rotational inclination,to utilize PARSEC isochrones for fitting the cluster CMDs.We systematically surveyed all known Galactic open clusters and selected 12 clusters where rotational velocity distributions could be reliably calculated for detailed fitting.Our results successfully reproduced the eMSTO phenomenon observed in these clusters.For the majority of clusters,considering only differential extinction and variations in rotational velocity adequately explains the position and morphology of the MSTO.For some intermediate-age clusters,incorporating rotational inclination additionally accounts for the broadening of the MSTO.This study underscores the importance of spectroscopic data in understanding eMSTO phenomena and provides a probable explanation for interpreting the combined effects of differential extinction,rotation,and inclination on the CMDs of Galactic open clusters.展开更多
1.Introduction.Cold Spray(CS)is a highly advanced solid-state metal depo-sition process that was first developed in the 1980s.This innovative technique involves the high-speed(300-1200 m/s)impact deposition of micron-...1.Introduction.Cold Spray(CS)is a highly advanced solid-state metal depo-sition process that was first developed in the 1980s.This innovative technique involves the high-speed(300-1200 m/s)impact deposition of micron-sized particles(5-50μm)to fabricate coatings[1-3].CS has been extensively used in a variety of coating applications,such as aerospace,automotive,energy,medical,marine,and others,to provide protection against high temperatures,corrosion,erosion,oxidation,and chemicals[4,5].Nowadays,the technical interest in CS is twofold:(i)as a repair process for damaged components,and(ii)as a solid-state additive manufacturing process.Compared to other fusion-based additive manufacturing(AM)technologies,Cold Spray Additive Manufacturing(CSAM)is a new member of the AM family that can enable the fabrication of deposits without undergoing melting.The chemical composition has been largely preserved from the powder to the deposit due to the minimal oxidation.The significant advantages of CSAM over other additive manufacturing processes include a high production rate,unlimited deposition size,high flexibility,and suitability for repairing damaged parts.展开更多
Global food production faces enormous challenges in increasing yields while promoting environmental sustainability.A field experiments in the ecotone between the Yangtze River Basin and the HuangHuai-Hai Plain evaluat...Global food production faces enormous challenges in increasing yields while promoting environmental sustainability.A field experiments in the ecotone between the Yangtze River Basin and the HuangHuai-Hai Plain evaluated the effects of changing preceding crop rotation cycles(wheat and rapeseed)on long-term wheat-rice(W)and rapeseed-rice(R)rotation systems.A comprehensive evaluation of crop rotation systems was conducted using life cycle assessment,considering productivity,economic benefits,carbon footprint(CF),and soil health.Compared with fallow-rice rotation(F),alternating rapeseed and wheat rotations increased equivalent yield by 60.4%-82.2%,reduced CF by 0.3%-5.7%,and improved soil health by 0.3%-47.5%.Additionally,adding rapeseed to rotations increased soil nutrient content and raised soil organic carbon stocks by 31.3%-40.5%.The 3R rotation(3-year rapeseed-rice and 1-year wheat-rice)boosted rice yield by 82.2%and annual economic benefits by 84.4%,offering an effective model for optimizing long-term R rotations.Similarly,the 2W rotation(2-year wheat-rice and 1-year rapeseed rice)enhanced rice yield by 70.0% and annual economic benefits by 65.9%,providing a successful example for optimizing long-term W rotations.The 3R rapeseed-based rotation and the 2W wheatbased rotation demonstrated good environmental sustainability.These rotation systems have broad potential in sustainable intensive farming,especially in China and similar regions.展开更多
Management of patients with acute hemorrhage requires addressing the source of bleeding,replenishing blood volume,and addressing any coagulopathy that may be present.Assessing coagulopathy and predicting blood require...Management of patients with acute hemorrhage requires addressing the source of bleeding,replenishing blood volume,and addressing any coagulopathy that may be present.Assessing coagulopathy and predicting blood requirements in real-time in patients experiencing ongoing bleeding can pose substantial challenges.In these patients,transfusion concepts based on ratios do not effectively address coagulopathy or reduce mortality.Moreover,ratio-based concepts do not stop bleeding;instead,they just give physicians more time to identify the bleeding source and plan management strategies.In clinical practice,standard laboratory coagulation tests(SLCT)are frequently used to assess various aspects of blood clotting.However,these tests may not always offer a comprehensive under-standing of clinically significant coagulopathy and the severity of blood loss.Furthermore,the SLCT have a considerable turnaround time,which may not be ideal for making prompt clinical decisions.In recent years,there has been a growing interest in point-of-care viscoelastic assays like rotational thromboelast-ometry,which provide real-time,dynamic information about clot formation and dissolution.展开更多
With the advancement of astronomical observation technology,people have a deeper understanding of the formation and evolution of galaxies,but many details of our own Milky Way and other external galaxies are still unk...With the advancement of astronomical observation technology,people have a deeper understanding of the formation and evolution of galaxies,but many details of our own Milky Way and other external galaxies are still unknown.Therefore,by studying the formation and orbital transformation mechanism of satellites,planets and stars,the author puts forward a new theory on the formation and evolution of stars and galaxies,thus revealing the hierarchical structure of galaxies and the formation and evolution laws of main sequence stars,red giants,white dwarfs,black dwarfs,supernovae,neutron stars,black holes and quasars.Some special phenomena in the course of star formation and evolution,such as sunspots,flares,fast radio bursts and gamma-ray bursts,have also been revealed.展开更多
Electrical energy can be harvested from the rotational kinetic energy of moving bodies,consisting of both mechanical and kinetic energy as a potential power source through electromagnetic induction,similar to wind ene...Electrical energy can be harvested from the rotational kinetic energy of moving bodies,consisting of both mechanical and kinetic energy as a potential power source through electromagnetic induction,similar to wind energy applications.In industries,rotational bodies are commonly present in operations,yet this kinetic energy remains untapped.This research explores the energy generation characteristics of two rotational body types,disk-shaped and cylinder-shaped under specific experimental setups.The hardware setup included a direct current(DC)motor driver,power supply,DC generator,mechanical support,and load resistance,while the software setup involved automation testing tools and data logging.Electromagnetic induction was used to harvest energy,and experiments were conducted at room temperature(25℃)with controlled variables like speed and friction.Results showed the disk-shaped body exhibited higher energy efficiency than the cylinder-shaped body,largely due to lower mechanical losses.The disk required only two bearings,while the cylinder required four,resulting in lower bearing losses for the disk.Additionally,the disk experienced only air friction,whereas the cylinder encountered friction from a soft,uneven rubber material,increasing surface contact losses.Under a 40 W resistive load,the disk demonstrated a 17.1%energy loss due to mechanical friction,achieving up to 15.55 J of recycled energy.Conversely,the cylinder body experienced a 48.05%energy loss,delivering only 51.95%of energy to the load.These insights suggest significant potential for designing efficient energy recycling systems in industrial settings,particularly in manufacturing and processing industries where rotational machinery is prevalent.Despite its lower energy density,this system could be beneficially integrated with energy storage solutions,enhancing sustainability in industrial practices.展开更多
The emission of anomalous X-ray pulsars(AXPs)and soft gamma-ray repeaters(SGRs)is believed to be powered by the dissipation of their strong magnetic fields,which coined the name“magnetar”.By combining timing and ene...The emission of anomalous X-ray pulsars(AXPs)and soft gamma-ray repeaters(SGRs)is believed to be powered by the dissipation of their strong magnetic fields,which coined the name“magnetar”.By combining timing and energy observational results,the magnetar model can be easily appreciated.From a timing perspective,the magnetic field strengths of AXPs and SGRs,which are calculated under the assumption of dipole radiation,are extremely strong.From an energy perspective,the X-ray/soft gamma-ray luminosities of AXPs and SGRs are larger than their rotational energy loss rates(i.e.,L_(x>E_(rot)).It is thus reasonable to assume that the high-energy radiation comes from magnetic energy decay,and the magnetar model has been extensively discussed(or accepted).However,we argue that:(ⅰ)Calculating magnetic fields by assuming that rotational energy loss is dominated by dipole radiation(i.e.,E_(rot)■E_(μ))may be controversial,and we suggest that the energies carried by outflowing particles should also be considered.(ⅱ)The fact that X-ray luminosity is greater than the rotational energy loss rate does not necessarily mean that the emission energy comes from the magnetic field decaying,which requires further observational testing.Furthermore,some observational facts conflict with the“magnetar”model,such as observations of anti-magnetars,high magnetic field pulsars,and radio and X-ray observations of AXPs/SGRs.Therefore,we propose a crusted strange star model as an alternative,which can explain many more observational facts of AXPs/SGRs.展开更多
We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chi...We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chiral anomaly of QCD and the spontaneously broken symmetry are invoked to explain the non-conservation of the axion current. From the coupling form factors, the axion emissivities ϵacan be derived, from which fluxes can be determined. We predict a photon flux, which may be detectable by Fermi LAT, and limits on the QCD mass ma. In this model, axions decay to gamma rays in a 2-photon vertex. We may determine the expected fluxes from the theoretical emissivity. The sensitivity curve from the Fermi Large Area Telescope (Fermi LAT) would allow axion mass constraints for neutron stars as low as ma≤10−14eV 95% C.L. Axions could thus be detectable in gamma rays for neutron stars as distant as 100 kpc. A signal from LIGO GWS 170817 could be placed from the NS-NS merger, which gives an upper limit of ma≤10−10eV.展开更多
Internal rotation of conjugated organic backbone seriously impaired room temperature phosphorescence(RTP),leading to rare realization of ultra-long afterglows with RTP lifetimes over 2 s in non-bibulous polymers.Herei...Internal rotation of conjugated organic backbone seriously impaired room temperature phosphorescence(RTP),leading to rare realization of ultra-long afterglows with RTP lifetimes over 2 s in non-bibulous polymers.Herein,N-(bromophenyl)carbazoles are cyclized to lock up phenyl-carbazol internal rotation in advance and the fused nitrogen hetero-cyclic compounds are doped into poly(methyl methacrylate)(PMMA).The results show that locking up the molecular internal rotation can achieve ultra-long RTP polymers with lifetimes over 2 s,in contrast,the unlocked molecules hardly emit RTP in PMMA.The high-lying triplet excitons can transfer the energy to low-lying organic fluorescent dyes,and the persistent multicolor afterglows including white emission can be readily modulated.This work discloses an effective and extendable dopant molecular strategy for developing high-performance ultra-long organic RTP polymers.展开更多
With a one-dimensional stellar evolution model,we find that massive main sequence stars can accrete mass at very high mass accretion rates without expanding much if they lose a significant fraction of this mass from t...With a one-dimensional stellar evolution model,we find that massive main sequence stars can accrete mass at very high mass accretion rates without expanding much if they lose a significant fraction of this mass from their outer layers simultaneously with mass accretion.We assume the accretion process is via an accretion disk that launches powerful jets from its inner zones.These jets remove the outer high-entropy layers of the mass-accreting star.This process operates in a negative feedback cycle,as the jets remove more envelope mass when the star expands.With the one-dimensional model,we mimic the mass removal by jets by alternating mass addition and mass removal phases.For the simulated models of 30M☉and 60M☉,the star does not expand much if we remove more than about half of the added mass in not-too-short episodes.This holds even if we deposit the energy the jets do not carry into the envelope.As the star does not expand much,its gravitational potential well stays deep,and the jets are energetic.These results are relevant to bright transient events of binary systems powered by accretion and the launching of jets,e.g.,intermediate luminosity optical transients,including some luminous red novae,the grazing envelope evolution,and the 1837–1856 Great Eruption of Eta Carinae.展开更多
文摘Objectives:One of the most notable challenges in endoscopic procedures is maintaining correct orientation.Mental rotation exercise(MRE)has been suggested as a potential aid for improving orientation.However,there is a lack of research on designing MREs with varying difficultylevels for training purposes.Furthermore,few studies provide solid evidence linking MRE difficultylevels with cognitive load measurements.This study aims to address this gap by investigating the correlation between the MRE difficultylevels and participants’cognitive load,as measured by pupil dilation.Method:We recruited 33 participants to perform MREs on a computer equipped with a screen-mounted eye-tracker.The test consisted of 15 MREs,with the first10 relatively easy(traditional cube)and the next 5 more complex(invented molecule).The participants’eye movements during MREs were recorded.The participants’MRE scores and pupil dilation were obtained and compared between two MRE difficultylevels.Results:The participants who performed traditional cube MREs achieved significantlybetter MRE scores(0.77±0.11 vs.0.58±0.03,p<0.001)and lower pupil dilation(0.27±0.04 pixels vs.0.47±0.09 pixels,p<0.001)than did those who performed the invented molecule MREs.Moreover,there were significant negative correlations(r=0.62,p=0.015)between pupil dilation and MRE scores.Conclusions:The results revealed a significantnegative correlation between MRE scores and pupil dilation.The more challenging MRE questions led to worse MRE scores but increased pupil dilation.The MRE difficultylevels can be evaluated not only by the degrees or dimensions with which the objects were rotated but also by the participants’MRE scores and pupil dilation.The results of this study provide a basis for training orientation skills in endoscopy using MREs.By incorporating MREs with varying difficultylevels,customized training programs can be developed to enhance camera navigation in endoscopic and laparoscopic procedures.
基金Supported by the National Natural Science Foundation of China(Grant Nos.10603002 and 10773004)
文摘In a second-order r-mode theory, Sa and Tome found that the r-mode oscillation in neutron stars （NSs） could induce stellar differential rotation, which naturally leads to a saturated state of the oscillation. Based on a consideration of the coupling of the r-modes and the stellar spin and thermal evolution, we carefully investigate the influences of the differential rotation on the long-term evolution of isolated NSs and NSs in low-mass X-ray binaries, where the viscous damping of the r-modes and its resultant effects are taken into account. The numerical results show that, for both kinds of NSs, the differential rotation can significantly prolong the duration of the r-modes. As a result, the stars can keep nearly a constant temperature and constant angular velocity for over a thousand years. Moreover, the persistent radiation of a quasi-monochromatic gravitational wave would also be predicted due to the long-term steady r-mode oscillation and stellar rotation. This increases the detectability of gravitational waves from both young isolated and old accreting NSs.
基金the Council of Scientific and Industrial Research (CSIR) for the financial support
文摘In our previous work, we developed a model to study the effects of rotation and/or tidal distortions on anharmonic radial oscillations and hence on the radial velocity curves of the polytropic models of pulsating variable stars.We considered the first three modes(fundamental and the next two higher modes) for the polytropic models of index 1.5 and 3.0 in that work.In the present paper, we are further extending our previous work to study the effect of the interaction of various modes on anharmonic radial oscillations and hence on radial velocity curves of the rotationally and/or tidally distorted polytropic models of pulsating variable stars.For this purpose, we have considered the following cases:(i) fundamental mode(ii) fundamental and the first mode,(iii) fundamental and the next two modes and finally(iv) fundamental and the next three higher modes of pulsation in our study.The objective of this paper is also to investigate whether the interaction of various modes affects the results of our previous study or not.The results of this study show that the interaction of the fundamental mode with higher modes appreciably changes the shape of the radial velocity curve of rotationally distorted and rotationally and tidally distorted polytropic models of pulsating variable stars.
文摘Anharmonic oscillations of rotating stars have been studied by various authors in literature to explain the observed features of certain variable stars. However, there is no study available in literature that has discussed the combined effect of rotation and tidal distortions on the anharmonic oscillations of stars. In this paper, we have created a model to determine the effect of rotation and tidal distortions on the anharmonic radial oscillations associated with various polytropic models of pulsating variable stars. For this study we have used the theory of Rosseland to obtain the anharmonic pulsation equation for rotationally and tidally distorted polytropic models of pulsating variable stars. The main objective of this study is to investigate the effect of rotation and tidal distortions on the shapes of the radial velocity curves for rotationally and tidally distorted polytropic models of pulsating variable stars. The results of the present study show that the rotational effects cause more deviations in the shapes of radial velocity curves of pulsating variable stars as compared to tidal effects.
基金Supported by the National Natural Science Foundation of China though Grants 10173021, 10433030,10773003 and 10778601supported by the Ministry of Science and Technology of the People’s Republic of China through Grant 2007CB815406
文摘We investigate the rotation profile of solar-like stars with magnetic fields. A diffu- sion coefficient of magnetic angular momentum transport is deduced. Rotating stellar models with different mass incorporating the coefficient are computed to give the rotation profiles. The total angular momentum of a solar model with only hydrodynamic instabilities is about 13 times larger than that of the Sun at the age of the Sun, and this model can not reproduce quasi-solid rotation in the radiative region. However, the solar model with magnetic fields not only can reproduce an almost uniform rotation in the radiative region, but also a total angular momentum that is consistent with the helioseismic result at the 3 tr level at the age of the Sun. The rotation of solar-like stars with magnetic fields is almost uniform in the radiative region, but for models of 1.2-1.5 MG, there is an obvious transition region between the convective core and the radiative region, where angular velocity has a sharp radial gradient, which is different from the rotation profile of the Sun and of massive stars with magnetic fields. The change of angular velocity in the transition region increases with increasing age and mass.
基金the National Natural Science Foundation of China.
文摘We monitored 16 X-ray selected young solar-type stars for light variation and found appreciable periodic light variability with amplitudes of a few hundredths of a magni- tude in nine of the objects. Using the method of Phase Dispersion Minimization （PDM） and Fourier analysis （software PERIOD04）, the rotation periods of these stars were determined from the photometric data. The rotation periods of all nine stars are shorter than about 3 days. It is suggested that, as with the Pleiades cluster, small amplitude light variations are quite common among young solar-type stars with rotation periods around 3 days or less. This gives further evidence for the spin up of solar-type stars predicted by models of angular momentum evolution of pre-main sequence stars.
基金funded by the National Natural Science Foundation of China(NSFC) (Grant Nos 10673005 and 10973009)
文摘The availability of astrometfic data and radial velocities of carbon stars near the Galactic plane enables us to investigate the kinematics of the Milky Way, especially the rotation curve. The recently published Third U. S. Naval Observatory CCD Astrograph Catalog （UCAC3） provides the opportunity to test this problem using three-dimensional velocity in order to obtain more reliable rotation curves. We intend to study the Galactic rotation curve up to 15 kpc using the radial velocities and proper motions of carbon stars. The motivation for using UCAC3 is to provide high precision proper motions which have hardly been used in determining the rotation velocity of tracers. Seventy-four carbon stars and carbon-rich Mira variables toward the anti-center direction （90° 〈 l 〈 270°, ｜b｜ 〈 6°） are picked up from the literature then matched with UCAC3 carbon star candidates to obtain their proper motions. A rigorous geometrical method is employed to compute the rotation velocity of each object. Taking carbon stars as tracers, we find a flat rotation curve of 210 ± 12 kms^-1 assuming R0 = 8.0kpc for the galactocentric distance and V0 = 220kms^-1 for the rotation velocity of the Sun. Due to the uncertainties of distances, the rotation velocities are more dispersed if tangential velocities enter the calculation, compared to those derived from radial velocities only. However, the whole rotation curve shows coherence with previous results. Increasing observation and study of carbon stars would be desirable in order to provide more homogeneous data for the kinematical study of the Galactic disk.
文摘In the present paper, the establishment of a systematic multi-barycenter mechanics is based on the multi-particle mechanics. The new theory perfects the basic theoretical system of classical mechanics, which finds the law of mutual interaction between particle groups, reveals the limitations of Newton’s third law, discovers the principle of the intrinsic relationship between gravity and tidal force, reasonably interprets the origin and change laws for the rotation angular momentum of galaxies and stars and so on. By applying new theory, the multi-body problem can be transformed into a special two-body problem and for which an approximate solution method is proposed, the motion law of each particle can be roughly obtained.
基金supported by the Strategic Priority Research Program of Chinese Academy of Sciences, grant No. XDB41000000the National Natural Science Foundation of China (No. 11973082)the National Key R&D Program of China, grant Nos. 2021YFA1600400/2021YFA1600402.
文摘The tidal interactions of planets affect the stellar evolutionary status and the constraint of their physical parameters by gyrochronology.In this work,we incorporate the tidal interaction and magnetic braking of the stellar wind into MESA and calculate a large grid of 25,000 models,covering planets with masses of 0.1–13.0MJ with different orbital distances that orbit late-type stars of different metallicities.We also explore the effect of different stellar initial rotations on the tidal interactions.Our results show that in the case of tidal inward migration,the stellar rotation periods are always lower than that of the star without planet before the planet is engulfed and the difference in the rotation period of its host star always increases with time.After the planet is engulfed,the stellar rotation periods are still lower than that of star without planet,but the difference of periods can be quickly eliminated if the star has a thick convective envelope(smaller mass and larger metallicity),regardless of the mass of the planet and the initial rotation period of the star.In the case of stars with thinner convective envelopes(larger mass and smaller metallicity),the stars will be spun up and remain the faster rotation in a long time.Meanwhile,the planet is easily swallowed and the period differences are large if the initial rotation period of its host star is higher.Finally,we also study the evolution of WASP-19 and estimate the range of tidal quality parameter Q_(*)^(')=(4.6±0.9)×10^(6)and the initial semimajor axis as(0.035±0.004)au.
基金Funding for the TESS mission is provided by the NASA Explorer Program。
文摘We present a spectroscopic and photometric study of HIP 12653 to investigate its magnetic cycle and differential rotation.Using HARPS archival spectra matched with MARCS-AMBRE theoretical templates,we derive the stellar parameters(Teff,logg,FeH,and vsini)of the target.The S-index,an activity indicator based on the emission of the CaⅡH&K lines,is fitted to determine the magnetic cycle and rotation periods.We refine the magnetic cycle period to 5799.20±0.88 days and suggest the existence of a secondary,shorter cycle of674.6922±0.0098 days,making HIP 12653 the youngest star known to exhibit such a short activity cycle.During the minimum activity phase,a rotation period of 4.8 days is estimated.This is notably different from the 7 day period obtained when measurements during minimum activity are excluded,suggesting that these two periods are rotation periods at different latitudes.To explore this hypothesis,we introduce a novel light curve fitting method that incorporates multiple harmonics to model different spot configurations.Applied to synthetic light curves,the method recovers at least two rotation periods close to the true input values(within three times their uncertainties)in 92.1%of cases.The inferred rotation shear shows a median deviation of 0.0011±0.0003 and a standard deviation of 0.0177±0.0002 from the true value.Applying this approach to TESS photometric data from 2018 to2023,we detect three distinct rotation periods—4.8 days,5.7 days,and 7.7 days,(along with a signal at 3.75 days interpreted as its first harmonic)—consistent with spots located at different latitudes.Assuming a solar-like differential rotation,we estimate an inclination of 34.0°±1.8°and a rotational shear ofα=0.38±0.01.These results confirm the 4.8 day period and demonstrate that differential rotation can be constrained by tracking rotation period changes across different phases of the magnetic cycle.
基金supported by the National Natural Science Foundation of China,No.12261141689。
文摘Recent studies have increasingly identified extended main sequence turn-off(e MSTO)phenomena in Galactic open clusters,yet the number of such clusters with sufficient spectroscopic information for member stars remains limited.Unlike most studies that rely on fitting isochrones based on color–magnitude diagram(CMD)morphology to account for varying rotational velocities,our approach leverages LAMOST spectral data to compute actual rotational velocity distributions for confirmed cluster members,along with parameters such as metallicity,differential extinction,and rotational inclination,to utilize PARSEC isochrones for fitting the cluster CMDs.We systematically surveyed all known Galactic open clusters and selected 12 clusters where rotational velocity distributions could be reliably calculated for detailed fitting.Our results successfully reproduced the eMSTO phenomenon observed in these clusters.For the majority of clusters,considering only differential extinction and variations in rotational velocity adequately explains the position and morphology of the MSTO.For some intermediate-age clusters,incorporating rotational inclination additionally accounts for the broadening of the MSTO.This study underscores the importance of spectroscopic data in understanding eMSTO phenomena and provides a probable explanation for interpreting the combined effects of differential extinction,rotation,and inclination on the CMDs of Galactic open clusters.
基金supported by the National Natural Science Foundation of China(No.52061135101 and 52001078)the German Research Foundation(DFG,No.448318292)+3 种基金the Technology Innovation Guidance Special Foundation of Shaanxi Province(No.2023GXLH-085)the Fundamental Research Funds for the Central Universities(No.D5000240161)the Project of Key areas of innovation team in Shaanxi Province(No.2024RS-CXTD-20)The author Yingchun Xie thanks the support from the National Key R&D Program(No.2023YFE0108000).
文摘1.Introduction.Cold Spray(CS)is a highly advanced solid-state metal depo-sition process that was first developed in the 1980s.This innovative technique involves the high-speed(300-1200 m/s)impact deposition of micron-sized particles(5-50μm)to fabricate coatings[1-3].CS has been extensively used in a variety of coating applications,such as aerospace,automotive,energy,medical,marine,and others,to provide protection against high temperatures,corrosion,erosion,oxidation,and chemicals[4,5].Nowadays,the technical interest in CS is twofold:(i)as a repair process for damaged components,and(ii)as a solid-state additive manufacturing process.Compared to other fusion-based additive manufacturing(AM)technologies,Cold Spray Additive Manufacturing(CSAM)is a new member of the AM family that can enable the fabrication of deposits without undergoing melting.The chemical composition has been largely preserved from the powder to the deposit due to the minimal oxidation.The significant advantages of CSAM over other additive manufacturing processes include a high production rate,unlimited deposition size,high flexibility,and suitability for repairing damaged parts.
基金supported by the National Natural Science Foundation of China(31971855)the Agricultural Science and Technology Innovation Project of the Chinese Academy of Agricultural Science(CAAS-ASTIP-2021-OCRI)+2 种基金the Hubei Provincial Natural Science Foundation of China(2024AFB442)the Wuhan Knowledge Innovation Special Program(2023020201020400)the China Agriculture Research System(CARS-12)。
文摘Global food production faces enormous challenges in increasing yields while promoting environmental sustainability.A field experiments in the ecotone between the Yangtze River Basin and the HuangHuai-Hai Plain evaluated the effects of changing preceding crop rotation cycles(wheat and rapeseed)on long-term wheat-rice(W)and rapeseed-rice(R)rotation systems.A comprehensive evaluation of crop rotation systems was conducted using life cycle assessment,considering productivity,economic benefits,carbon footprint(CF),and soil health.Compared with fallow-rice rotation(F),alternating rapeseed and wheat rotations increased equivalent yield by 60.4%-82.2%,reduced CF by 0.3%-5.7%,and improved soil health by 0.3%-47.5%.Additionally,adding rapeseed to rotations increased soil nutrient content and raised soil organic carbon stocks by 31.3%-40.5%.The 3R rotation(3-year rapeseed-rice and 1-year wheat-rice)boosted rice yield by 82.2%and annual economic benefits by 84.4%,offering an effective model for optimizing long-term R rotations.Similarly,the 2W rotation(2-year wheat-rice and 1-year rapeseed rice)enhanced rice yield by 70.0% and annual economic benefits by 65.9%,providing a successful example for optimizing long-term W rotations.The 3R rapeseed-based rotation and the 2W wheatbased rotation demonstrated good environmental sustainability.These rotation systems have broad potential in sustainable intensive farming,especially in China and similar regions.
文摘Management of patients with acute hemorrhage requires addressing the source of bleeding,replenishing blood volume,and addressing any coagulopathy that may be present.Assessing coagulopathy and predicting blood requirements in real-time in patients experiencing ongoing bleeding can pose substantial challenges.In these patients,transfusion concepts based on ratios do not effectively address coagulopathy or reduce mortality.Moreover,ratio-based concepts do not stop bleeding;instead,they just give physicians more time to identify the bleeding source and plan management strategies.In clinical practice,standard laboratory coagulation tests(SLCT)are frequently used to assess various aspects of blood clotting.However,these tests may not always offer a comprehensive under-standing of clinically significant coagulopathy and the severity of blood loss.Furthermore,the SLCT have a considerable turnaround time,which may not be ideal for making prompt clinical decisions.In recent years,there has been a growing interest in point-of-care viscoelastic assays like rotational thromboelast-ometry,which provide real-time,dynamic information about clot formation and dissolution.
文摘With the advancement of astronomical observation technology,people have a deeper understanding of the formation and evolution of galaxies,but many details of our own Milky Way and other external galaxies are still unknown.Therefore,by studying the formation and orbital transformation mechanism of satellites,planets and stars,the author puts forward a new theory on the formation and evolution of stars and galaxies,thus revealing the hierarchical structure of galaxies and the formation and evolution laws of main sequence stars,red giants,white dwarfs,black dwarfs,supernovae,neutron stars,black holes and quasars.Some special phenomena in the course of star formation and evolution,such as sunspots,flares,fast radio bursts and gamma-ray bursts,have also been revealed.
基金The APC was funded by Research Management Center, Multimedia University, Malaysia.
文摘Electrical energy can be harvested from the rotational kinetic energy of moving bodies,consisting of both mechanical and kinetic energy as a potential power source through electromagnetic induction,similar to wind energy applications.In industries,rotational bodies are commonly present in operations,yet this kinetic energy remains untapped.This research explores the energy generation characteristics of two rotational body types,disk-shaped and cylinder-shaped under specific experimental setups.The hardware setup included a direct current(DC)motor driver,power supply,DC generator,mechanical support,and load resistance,while the software setup involved automation testing tools and data logging.Electromagnetic induction was used to harvest energy,and experiments were conducted at room temperature(25℃)with controlled variables like speed and friction.Results showed the disk-shaped body exhibited higher energy efficiency than the cylinder-shaped body,largely due to lower mechanical losses.The disk required only two bearings,while the cylinder required four,resulting in lower bearing losses for the disk.Additionally,the disk experienced only air friction,whereas the cylinder encountered friction from a soft,uneven rubber material,increasing surface contact losses.Under a 40 W resistive load,the disk demonstrated a 17.1%energy loss due to mechanical friction,achieving up to 15.55 J of recycled energy.Conversely,the cylinder body experienced a 48.05%energy loss,delivering only 51.95%of energy to the load.These insights suggest significant potential for designing efficient energy recycling systems in industrial settings,particularly in manufacturing and processing industries where rotational machinery is prevalent.Despite its lower energy density,this system could be beneficially integrated with energy storage solutions,enhancing sustainability in industrial practices.
基金supported by the National Natural Science Foundation of China(12273008,12025303,12403046)the National SKA Program of China(2022SKA0130104)+3 种基金the Natural Science and Technology Foundation of Guizhou Province(QiankehejichuMS[2025]266,[2023]024,ZK[2022]304)the Foundation of Guizhou Provincial Education Department(KY(2020)003)the Academic New Seedling Fund Project of Guizhou Normal University([2022]B18)the Major Science and Technology Program of Xinjiang Uygur Autonomous Region(2022A03013-4).
文摘The emission of anomalous X-ray pulsars(AXPs)and soft gamma-ray repeaters(SGRs)is believed to be powered by the dissipation of their strong magnetic fields,which coined the name“magnetar”.By combining timing and energy observational results,the magnetar model can be easily appreciated.From a timing perspective,the magnetic field strengths of AXPs and SGRs,which are calculated under the assumption of dipole radiation,are extremely strong.From an energy perspective,the X-ray/soft gamma-ray luminosities of AXPs and SGRs are larger than their rotational energy loss rates(i.e.,L_(x>E_(rot)).It is thus reasonable to assume that the high-energy radiation comes from magnetic energy decay,and the magnetar model has been extensively discussed(or accepted).However,we argue that:(ⅰ)Calculating magnetic fields by assuming that rotational energy loss is dominated by dipole radiation(i.e.,E_(rot)■E_(μ))may be controversial,and we suggest that the energies carried by outflowing particles should also be considered.(ⅱ)The fact that X-ray luminosity is greater than the rotational energy loss rate does not necessarily mean that the emission energy comes from the magnetic field decaying,which requires further observational testing.Furthermore,some observational facts conflict with the“magnetar”model,such as observations of anti-magnetars,high magnetic field pulsars,and radio and X-ray observations of AXPs/SGRs.Therefore,we propose a crusted strange star model as an alternative,which can explain many more observational facts of AXPs/SGRs.
文摘We present a theoretical model for detecting axions from neutron stars in a QCD phase of quark matter. The axions would be produced from a quark-antiquark pair uu¯or dd¯, in loop(s) involving gluons. The chiral anomaly of QCD and the spontaneously broken symmetry are invoked to explain the non-conservation of the axion current. From the coupling form factors, the axion emissivities ϵacan be derived, from which fluxes can be determined. We predict a photon flux, which may be detectable by Fermi LAT, and limits on the QCD mass ma. In this model, axions decay to gamma rays in a 2-photon vertex. We may determine the expected fluxes from the theoretical emissivity. The sensitivity curve from the Fermi Large Area Telescope (Fermi LAT) would allow axion mass constraints for neutron stars as low as ma≤10−14eV 95% C.L. Axions could thus be detectable in gamma rays for neutron stars as distant as 100 kpc. A signal from LIGO GWS 170817 could be placed from the NS-NS merger, which gives an upper limit of ma≤10−10eV.
文摘Internal rotation of conjugated organic backbone seriously impaired room temperature phosphorescence(RTP),leading to rare realization of ultra-long afterglows with RTP lifetimes over 2 s in non-bibulous polymers.Herein,N-(bromophenyl)carbazoles are cyclized to lock up phenyl-carbazol internal rotation in advance and the fused nitrogen hetero-cyclic compounds are doped into poly(methyl methacrylate)(PMMA).The results show that locking up the molecular internal rotation can achieve ultra-long RTP polymers with lifetimes over 2 s,in contrast,the unlocked molecules hardly emit RTP in PMMA.The high-lying triplet excitons can transfer the energy to low-lying organic fluorescent dyes,and the persistent multicolor afterglows including white emission can be readily modulated.This work discloses an effective and extendable dopant molecular strategy for developing high-performance ultra-long organic RTP polymers.
基金A grant from the Pazy Foundation supported this research.
文摘With a one-dimensional stellar evolution model,we find that massive main sequence stars can accrete mass at very high mass accretion rates without expanding much if they lose a significant fraction of this mass from their outer layers simultaneously with mass accretion.We assume the accretion process is via an accretion disk that launches powerful jets from its inner zones.These jets remove the outer high-entropy layers of the mass-accreting star.This process operates in a negative feedback cycle,as the jets remove more envelope mass when the star expands.With the one-dimensional model,we mimic the mass removal by jets by alternating mass addition and mass removal phases.For the simulated models of 30M☉and 60M☉,the star does not expand much if we remove more than about half of the added mass in not-too-short episodes.This holds even if we deposit the energy the jets do not carry into the envelope.As the star does not expand much,its gravitational potential well stays deep,and the jets are energetic.These results are relevant to bright transient events of binary systems powered by accretion and the launching of jets,e.g.,intermediate luminosity optical transients,including some luminous red novae,the grazing envelope evolution,and the 1837–1856 Great Eruption of Eta Carinae.
