Dihadron azimuthal correlations containing a high transverse momentum(pr)trigger particle are sensit-ive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the tr...Dihadron azimuthal correlations containing a high transverse momentum(pr)trigger particle are sensit-ive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium,ie.jet-quenching.Previous measurements revealed a strong modification to di-hadron azimuthal correlations in Au+Au collisions with respect to ptp and d+Au collisions.The modification in-creases with the collision centrality,suggesting a path-length or energy density dependence to the je-quenching ef-fect.This paper reports STAR measurements of dihadron azimuthal correlations in mid-central(20%-60%)Au+Au collisions at√^(S)NN=200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane,Ф_(s)=|Ф_(t)-ψ_(Ep)|.The azimuthal correlation is studied as a function of both the trigger and associated particle pr.The subtractions of the combinatorial background and anisotropic flow,assuming Zero Yield At Minimum(ZYAM),are described.The correlation results are first discussed with subtraction of the even harmonic(elliptic and quadrangu-lar)flow backgrounds.The away-side correlation is strongly modifed,and the modification varies withФ_(s),with a double-peak structure for out-of-plane trigger particles.The near-side ridge(long range pseudo-rapidity△_(η)correla-tion)appears to drop with increasingФ_(s)while the jet-like component remains approximately constant.The correla-tion functions are further studied with the subtraction of odd harmonic triangular flow background arising from fluc-tuations.It is found that the triangular flow,while responsible for the majority of the amplitudes,is not sufficient to explain theφs-dependence of the ridge or the away-side double-peak structure.The dropping ridge withФ_(s)could be attributed to aФ_(s)-dependent lliptie anisotropy;however,the physics mechanism of the ridge remains an open ques-tion.Even with aФ_(s)-dependent elliptic flow,the away-side correlation structure is robust.These results,with exte展开更多
Metasurfaces offer a unique platform to precisely control optical wavefronts and enable the realization of flat lenses,or metalenses,which have the potential to substantially reduce the size and complexity of imaging ...Metasurfaces offer a unique platform to precisely control optical wavefronts and enable the realization of flat lenses,or metalenses,which have the potential to substantially reduce the size and complexity of imaging systems and to realize new imaging modalities.However,it is a major challenge to create achromatic metalenses that produce a single focal length over a broad wavelength range because of the difficulty in simultaneously engineering phase profiles at distinct wavelengths on a single metasurface.For practical applications,there is a further challenge to create broadband achromatic metalenses that work in the transmission mode for incident light waves with any arbitrary polarization state.We developed a design methodology and created libraries of meta-units—building blocks of metasurfaces—with complex cross-sectional geometries to provide diverse phase dispersions(phase as a function of wavelength),which is crucial for creating broadband achromatic metalenses.We elucidated the fundamental limitations of achromatic metalens performance by deriving mathematical equations that govern the tradeoffs between phase dispersion and achievable lens parameters,including the lens diameter,numerical aperture(NA),and bandwidth of achromatic operation.We experimentally demonstrated several dielectric achromatic metalenses reaching the fundamental limitations.These metalenses work in the transmission mode with polarization-independent focusing efficiencies up to 50%and continuously provide a near-constant focal length over λ=1200–1650 nm.These unprecedented properties represent a major advance compared to the state of the art and a major step toward practical implementations of metalenses.展开更多
Metasurfaces are optically thin metamaterials that promise complete control of the wavefront of light but are primarily used to control only the phase of light.Here,we present an approach,simple in concept and in prac...Metasurfaces are optically thin metamaterials that promise complete control of the wavefront of light but are primarily used to control only the phase of light.Here,we present an approach,simple in concept and in practice,that uses meta-atoms with a varying degree of form birefringence and rotation angles to create high-efficiency dielectric metasurfaces that control both the optical amplitude and phase at one or two frequencies.This opens up applications in computer-generated holography,allowing faithful reproduction of both the phase and amplitude of a target holographic scene without the iterative algorithms required in phase-only holography.We demonstrate all-dielectric metasurface holograms with independent and complete control of the amplitude and phase at up to two optical frequencies simultaneously to generate two-and three-dimensional holographic objects.We show that phaseamplitude metasurfaces enable a few features not attainable in phase-only holography;these include creating artifactfree two-dimensional holographic images,encoding phase and amplitude profiles separately at the object plane,encoding intensity profiles at the metasurface and object planes separately,and controlling the surface textures of three-dimensional holographic objects.展开更多
Nonalcoholic fatty liver disease(NAFLD)is a heterogeneous and complex disease that is imprecisely diagnosed by liver biopsy.NAFLD covers a spectrum that ranges from simple steatosis,nonalcoholic steatohepatitis(NASH)w...Nonalcoholic fatty liver disease(NAFLD)is a heterogeneous and complex disease that is imprecisely diagnosed by liver biopsy.NAFLD covers a spectrum that ranges from simple steatosis,nonalcoholic steatohepatitis(NASH)with varying degrees of fibrosis,to cirrhosis,which is a major risk factor for hepatocellular carcinoma.Lifestyle and eating habit changes during the last century have made NAFLD the most common liver disease linked to obesity,type 2 diabetes mellitus and dyslipidemia,with a global prevalence of 25%.NAFLD arises when the uptake of fatty acids(FA)and triglycerides(TG)from circulation and de novo lipogenesis saturate the rate of FAβ-oxidation and verylow density lipoprotein(VLDL)-TG export.Deranged lipid metabolism is also associated with NAFLD progression from steatosis to NASH,and therefore,alterations in liver and serum lipidomic signatures are good indicators of the disease’s development and progression.This review focuses on the importance of the classification of NAFLD patients into different subtypes,corresponding to the main alteration(s)in the major pathways that regulate FA homeostasis leading,in each case,to the initiation and progression of NASH.This concept also supports the targeted intervention as a key approach to maximize therapeutic efficacy and opens the door to the development of precise NASH treatments.展开更多
In this paper, a finite element model was developed for a turbine blade with thermal barrier coatings to investigate its failure behavior under cyclic thermal loading. Based on temperature and stress fields obtained f...In this paper, a finite element model was developed for a turbine blade with thermal barrier coatings to investigate its failure behavior under cyclic thermal loading. Based on temperature and stress fields obtained from finite element simulations, dangerous regions in ceramic coating were determined in terms of the maximum principal stress criterion. The results show that damage preferentially occurs in the chamfer and rabbet of a turbine blade with thermal barrier coatings and its thermal fatigue life decreases with the increase of thermal stress induced by high service temperature.展开更多
To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer a...To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer analysis and the decoupled thermal-stress calculation method are adopted. Based on the simulation results, it is found that a non-uniform distribution of temperature appears in different positions of the blade surface, which has directly impacted on stress field. The maximum temperature with a value of 1030 ℃ occurs at the leading edge. During the steady stage, the maximum stress of thermally grown oxide （TGO） appears in the middle of the suction side, reaching 3.75 GPa. At the end stage of cooling, the maximum compressive stress of TGO with a value of-3.5 GPa occurs at the leading edge. Thus, it can be predicted that during the steady stage the dangerous regions may locate at the suction side, while the leadine edge mav be more Drone to failure on cooling.展开更多
Clostridium difficile （C.difficile） infection has become one of the major hospital-associated infections in Western countries in the last two decades.However,there is limited information on the status of C.difficile...Clostridium difficile （C.difficile） infection has become one of the major hospital-associated infections in Western countries in the last two decades.However,there is limited information on the status of C.difficile infection in Chinese healthcare settings.Given the large and increasing elderly population and the well-recognized problem of over-prescribing of broad spectrum antibiotics in China,it is critical to understand the epidemiology and potential risk factors that may contribute to C.difficile infection in China.A literature review of available published studies,including those in Chinese language-based journals,was conducted.A review of the currently available literature suggested the presence of C.difficile infections in China,but also suggested that these infections were not particularly endemic.This finding should lead to better designed and greatly expanded studies to provide a more reliable epidemiologically-based conclusion on the actual status of C.difficile infection in China,including the identification of any associated risk factors.Such information is ultimately valuable to develop appropriate strategies to prevent C.difficile infection and the vast negative impact of such infections in China and other developing countries.展开更多
An effective single layered finite element （FE） computational model is proposed to predict the structural behavior of lightweight sandwich panels having two dimensional （2D） prismatic or three dimensional （3D） t...An effective single layered finite element （FE） computational model is proposed to predict the structural behavior of lightweight sandwich panels having two dimensional （2D） prismatic or three dimensional （3D） truss cores. Three different types of cellular core topology are considered： pyramidal truss core （3D）, Kagome truss core （3D） and corrugated core （2D）, representing three kinds of material anisotropy： orthotropic, monoclinic and general anisotropic. A homogenization technique is developed to obtain the homogenized macroscopic stiffness properties of the cellular core. In comparison with the results obtained by using detailed FE model, the single layered computational model can give acceptable predictions for both the static and dynamic behaviors of orthotropic truss core sandwich panels. However, for non-orthotropic 3D truss cores, the predictions are not so well. For both static and dynamic behaviors of a 2D corrugated core sandwich panel, the predictions derived by the single layered computational model is generally acceptable when the size of the unit cell varies within a certain range, with the predictions for moderately strong or strong corrugated cores more accurate than those for weak cores.展开更多
It is well accepted that grain-boundary phases in metallic alloys greatly deteriorate the mechanical properties.In our work,we report on a novel strategy to prepare high strength-ductility β-type(Ti69.71 Nb23.72Zr4.8...It is well accepted that grain-boundary phases in metallic alloys greatly deteriorate the mechanical properties.In our work,we report on a novel strategy to prepare high strength-ductility β-type(Ti69.71 Nb23.72Zr4.83Ta1.74)97Si3(at.%)(TNZTS) alloys by tailoring grain-boundary metastable Si-containing phase.Specifically,the thin shell-shaped metastable S1 phase surrounding the columnar β-Ti grain was intercepted successfully via nonequilibrium rapid solidification achieved by selective laser melting(SLM).Subsequently,the thin shell-shaped metastable(Ti,Nb,Zr)5 Si3(called S1) phase was transformed into globular(Ti,Nb,Zr)2 Si(called S2) phase by the solution heat treatment.Interestingly,the globular S2 phases reinforced TNZTS alloy exhibits ultrahigh yield strength of 978 MPa,ultimate strength of 1010 MPa and large elongation of 10.4 %,overcoming the strength-ductility trade-off of TNZTS alloys by various methods.Especially,the reported yield strength herein is 55 % higher than that of conventionally forged TNZT alloys.Dynamic analysis indicates the globularization process of the metastable S1 phase is controlled by the model of termination migration.The quantitative analysis on strengthening mechanism demonstrates that the increase in yield strength of the heat-treated alloys is mainly ascribed to the strengthening of the precipitated silicide and the dislocations induced by high cooling rate.The obtained results provide some basis guidelines for designing and fabricating β-titanium alloys with excellent mechanical properties,and pave the way for biomedical application of TNZTS alloy by SLM.展开更多
AIM To determine steatosis and fibrosis prevalence in hepatitis C patients after a sustained virological response achieved with direct-acting antivirals.METHODS Transient elastography with controlled attenuation param...AIM To determine steatosis and fibrosis prevalence in hepatitis C patients after a sustained virological response achieved with direct-acting antivirals.METHODS Transient elastography with controlled attenuation parameter(CAP) was used to assess hepatic steatosis post-sustained virological response(SVR);the CAP technology was not available in the United States at study initiation.Liver stiffness/fibrosis was measured before and 47 wk after treatment completion.Patients with genotype 3 and patients with cirrhosis were excluded.RESULTS One hundred and one patients were included in the study.Post-SVR there were decreases from baseline in alanine aminotransferase(ALT)(63.1 to 17.8 U/L),aspartate aminotransferase(51.8 to 21.5 U/L) and fibrosis score(7.4 to 6.1 k Pa)(P < 0.05).Post-SVR,48 patients(47.5%) had steatosis on CAP;of these,6.25% had advanced fibrosis.Patients with steatosis had higher body mass index(29.0 vs 26.1 kg/m2),glucose(107.8 vs 96.6 mg/d L),ALT(20.4 vs 15.3 mg/d L),CAP score(296.3 vs 212.4 d B/m) and fibrosis score(7.0 vs 5.3 k Pa);P < 0.05.Interestingly,compared to baseline,both patients with and without steatosis had change in fibrosis score post-SVR(7.7 k Pa vs 7.0 k Pa and 7.0 k Pa vs 5.3 k Pa);alternatively,(P < 0.05) and therefore patients with steatosis continued to have clinically significant stiffness(≥ 7 k Pa).CONCLUSION Fatty liver is very common in hepatitis C virus(HCV) patients post-SVR.These patients continue to have elevated mean fibrosis score(≥ 7 k Pa) compared to those without fatty liver;some have advanced fibrosis.Long term follow up is needed to assess steatosis and fibrosis in HCV patients post-SVR.展开更多
The full array of the Large High Altitude Air Shower Observatory(LHAASO)has been in operation since July 2021.For its kilometer-square array(KM2A),we optimized the selection criteria for very high and ultrahigh energy...The full array of the Large High Altitude Air Shower Observatory(LHAASO)has been in operation since July 2021.For its kilometer-square array(KM2A),we optimized the selection criteria for very high and ultrahigh energyγ-rays using data collected from August 2021 to August 2022,resulting in an improvement in significance of the detection in the Crab Nebula of approximately 15%,compared with that of previous cuts.With the implementation of these new selection criteria,the angular resolution was also significantly improved by approximately 10%at tens of TeV.Other aspects of the full KM2A array performance,such as the pointing error,were also calibrated using the Crab Nebula.The resulting energy spectrum of the Crab Nebula in the energy range of 10-1000 TeV are well fitted by a log-parabola model,which is consistent with the previous results from LHAASO and other experiments.展开更多
Methionine adenosyltransferases(MATs)are essential enzymes for life as they produce S-adenosylmethionine(SAMe),the biological methyl donor required for a plethora of reactions within the cell.Mammalian systems express...Methionine adenosyltransferases(MATs)are essential enzymes for life as they produce S-adenosylmethionine(SAMe),the biological methyl donor required for a plethora of reactions within the cell.Mammalian systems express two genes,MAT1A and MAT2A,which encode for MATα1 and MATα2,the catalytic subunits of the MAT isoenzymes,respectively.A third gene MAT2B,encodes a regulatory subunit known as MATβwhich controls the activity of MATα2.MAT1A,which is mainly expressed in hepatocytes,maintains the differentiated state of these cells,whilst MAT2A and MAT2B are expressed in extrahepatic tissues as well as non-parenchymal cells of the liver(e.g.,hepatic stellate and Kupffer cells).The biosynthesis of SAMe is impaired in patients with chronic liver disease and liver cancer due to decreased expression and inactivation of MATα1.A switch from MAT1A to MAT2A/MAT2B occurs in multiple liver diseases and during liver growth and dedifferentiation,but this change in the expression pattern of MATs results in reduced hepatic SAMe level.Decades of study have utilized the Mat1a-knockout(KO)mouse that spontaneously develops non-alcoholic steatohepatitis(NASH)and hepatocellular carcinoma(HCC)to elucidate a variety of mechanisms by which MAT proteins dysregulation contributes to liver carcinogenesis.An increasing volume of work indicates that MATs have SAMe-independent functions,distinct interactomes and multiple subcellular localizations.Here we aim to provide an overview of MAT biology including genes,isoenzymes and their regulation to provide the context for understanding consequences of their dysregulation.We will highlight recent breakthroughs in the field and underscore the importance of MAT’s in liver tumorigenesis as well as their potential as targets for cancer therapy.展开更多
The Large High Altitude Air Shower Observatory(LHAASO)has three sub-arrays,KM2A,WCDA,and WFCTA.The flux variations of cosmic ray air showers were studied by analyzing the KM2A data during a thunderstorm on June 10,202...The Large High Altitude Air Shower Observatory(LHAASO)has three sub-arrays,KM2A,WCDA,and WFCTA.The flux variations of cosmic ray air showers were studied by analyzing the KM2A data during a thunderstorm on June 10,2021.The number of shower events that meet the trigger conditions increases significantly in atmospheric electric fields,with a maximum fractional increase of 20%.The variations in trigger rates(increases or decreases)were found to be strongly dependent on the primary zenith angle.The flux of secondary particles increased significantly,following a trend similar to that of shower events.To better understand the observed behavior,Monte Carlo simulations were performed with CORSIKA and G4KM2A(a code based on GEANT4).We found that the experimental data(in saturated negative fields)were in good agreement with the simulations,assuming the presence of a uniform electric field of-700 V/cm with a thickness of 1500 m in the atmosphere above the observation level.Due to the acceleration/deceleration by the atmospheric electric field,the number of secondary particles with energy above the detector threshold was modified,resulting in the changes in shower detection rate.展开更多
The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite elemen...The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite element model has been developed to compute the temperature and stress profile in beam blank continuous casting. The enthalpy method was used in the heat conduction equation. The thermo-mechanical property in the mushy zone was taken into consideration in this calculation. It is shown that at the mold exit the thickness of the shell had its maximum value at the flange tip and its minimum value at the fillet. The temperature had a great fluctuation on the surface of the beam blank in the secondary cooling zone. At the unbending point, the surface temperature of the web was in the brittleness temperature range under the present condition. To ensure the quality, it is necessary to weaken the intensity of secondary cooling. At the mold exit the equivalent stress and strain have higher values at the flange tip and at the web. From the spray 1 to the unbending point, the maximum values of stress and strain gradually moved to the internal section of the flange tip and the web. However, whenever, there were bigger stress and strain values near the flange tip and the web than in the other parts, it must be very easy to generate cracks at those positions. Now, online verification of this simulation has been developed, which has proved to be very useful and efficient to instruct the practical production of beam blank continuous casting.展开更多
Broadband high reflectance in nature is often the result of randomly,three-dimensionally structured materials.This study explores unique optical properties associated with one-dimensional nanostructures discovered in ...Broadband high reflectance in nature is often the result of randomly,three-dimensionally structured materials.This study explores unique optical properties associated with one-dimensional nanostructures discovered in silk cocoon fibers of the comet moth,Argema mittrei.The fibers are populated with a high density of air voids randomly distributed across the fiber cross-section but are invariant along the fiber.These filamentary air voids strongly scatter light in the solar spectrum.A single silk fiber measuring~50μm thick can reflect 66%of incoming solar radiation,and this,together with the fibers’high emissivity of 0.88 in the mid-infrared range,allows the cocoon to act as an efficient radiative-cooling device.Drawing inspiration from these natural radiative-cooling fibers,biomimetic nanostructured fibers based on both regenerated silk fibroin and polyvinylidene difluoride are fabricated through wet spinning.Optical characterization shows that these fibers exhibit exceptional optical properties for radiative-cooling applications:nanostructured regenerated silk fibers provide a solar reflectivity of 0.73 and a thermal emissivity of 0.90,and nanostructured polyvinylidene difluoride fibers provide a solar reflectivity of 0.93 and a thermal emissivity of 0.91.The filamentary air voids lead to highly directional scattering,giving the fibers a highly reflective sheen,but more interestingly,they enable guided optical modes to propagate along the fibers through transverse Anderson localization.This discovery opens up the possibility of using wild silkmoth fibers as a biocompatible and bioresorbable material for optical signal and image transport.展开更多
基金Supported in part by the Offices of NP and HEP within the U.S.DOE Office of Sciencethe U.S.NSF+18 种基金the Sloan Foundationthe DFG cluster of excellence‘Origin and Structure of the Universe’of Germany,CNRS/IN2P3STFC and EPSRC of the United KingdomFAPESP CNPq of Brazil,Ministry of Ed.Sci.of the Russian FederationNNSFCCASMoSTMoE of ChinaGA and MSMT of the Czech RepublicFOM and NWO of the NetherlandsDAEDSTCSIR of IndiaPolish Ministry of Sci.Higher Ed.,Korea Research Foundation,Ministry of Sci.,Ed.Sports of the Rep.Of CroatiaRussian Ministry of Sci.and TechRos-Atom of Russia。
文摘Dihadron azimuthal correlations containing a high transverse momentum(pr)trigger particle are sensit-ive to the properties of the nuclear medium created at RHIC through the strong interactions occurring between the traversing parton and the medium,ie.jet-quenching.Previous measurements revealed a strong modification to di-hadron azimuthal correlations in Au+Au collisions with respect to ptp and d+Au collisions.The modification in-creases with the collision centrality,suggesting a path-length or energy density dependence to the je-quenching ef-fect.This paper reports STAR measurements of dihadron azimuthal correlations in mid-central(20%-60%)Au+Au collisions at√^(S)NN=200 GeV as a function of the trigger particle's azimuthal angle relative to the event plane,Ф_(s)=|Ф_(t)-ψ_(Ep)|.The azimuthal correlation is studied as a function of both the trigger and associated particle pr.The subtractions of the combinatorial background and anisotropic flow,assuming Zero Yield At Minimum(ZYAM),are described.The correlation results are first discussed with subtraction of the even harmonic(elliptic and quadrangu-lar)flow backgrounds.The away-side correlation is strongly modifed,and the modification varies withФ_(s),with a double-peak structure for out-of-plane trigger particles.The near-side ridge(long range pseudo-rapidity△_(η)correla-tion)appears to drop with increasingФ_(s)while the jet-like component remains approximately constant.The correla-tion functions are further studied with the subtraction of odd harmonic triangular flow background arising from fluc-tuations.It is found that the triangular flow,while responsible for the majority of the amplitudes,is not sufficient to explain theφs-dependence of the ridge or the away-side double-peak structure.The dropping ridge withФ_(s)could be attributed to aФ_(s)-dependent lliptie anisotropy;however,the physics mechanism of the ridge remains an open ques-tion.Even with aФ_(s)-dependent elliptic flow,the away-side correlation structure is robust.These results,with exte
基金supported by the Defense Advanced Research Projects Agency(no.D15AP00111 and no.HR0011-17-2-0017)the Air Force Office of Scientific Research(no.FA9550-14-1-0389 and no.FA9550-16-1-0322)+2 种基金the National Science Foundation(no.ECCS-1307948)support from the NSF IGERT program(no.DGE-1069240)supported by the US Department of Energy,Office of Basic Energy Sciences(contract no.DE-SC0012704)。
文摘Metasurfaces offer a unique platform to precisely control optical wavefronts and enable the realization of flat lenses,or metalenses,which have the potential to substantially reduce the size and complexity of imaging systems and to realize new imaging modalities.However,it is a major challenge to create achromatic metalenses that produce a single focal length over a broad wavelength range because of the difficulty in simultaneously engineering phase profiles at distinct wavelengths on a single metasurface.For practical applications,there is a further challenge to create broadband achromatic metalenses that work in the transmission mode for incident light waves with any arbitrary polarization state.We developed a design methodology and created libraries of meta-units—building blocks of metasurfaces—with complex cross-sectional geometries to provide diverse phase dispersions(phase as a function of wavelength),which is crucial for creating broadband achromatic metalenses.We elucidated the fundamental limitations of achromatic metalens performance by deriving mathematical equations that govern the tradeoffs between phase dispersion and achievable lens parameters,including the lens diameter,numerical aperture(NA),and bandwidth of achromatic operation.We experimentally demonstrated several dielectric achromatic metalenses reaching the fundamental limitations.These metalenses work in the transmission mode with polarization-independent focusing efficiencies up to 50%and continuously provide a near-constant focal length over λ=1200–1650 nm.These unprecedented properties represent a major advance compared to the state of the art and a major step toward practical implementations of metalenses.
基金supported by the Defense Advanced Research Projects Agency(grant no.D15AP00111 and HR0011-17-2-0017)the National Science Foundation(grant no.ECCS-1307948 and QII-TAQS-1936359)+2 种基金the Air Force Office of Scientific Research(grant no.FA9550-14-1-0389 and FA9550-16-1-0322)support from the NSF IGERT program(grant no.DGE-1069240)supported by the US Department of Energy,Office of Basic Energy Sciences(contract no.DESC0012704).
文摘Metasurfaces are optically thin metamaterials that promise complete control of the wavefront of light but are primarily used to control only the phase of light.Here,we present an approach,simple in concept and in practice,that uses meta-atoms with a varying degree of form birefringence and rotation angles to create high-efficiency dielectric metasurfaces that control both the optical amplitude and phase at one or two frequencies.This opens up applications in computer-generated holography,allowing faithful reproduction of both the phase and amplitude of a target holographic scene without the iterative algorithms required in phase-only holography.We demonstrate all-dielectric metasurface holograms with independent and complete control of the amplitude and phase at up to two optical frequencies simultaneously to generate two-and three-dimensional holographic objects.We show that phaseamplitude metasurfaces enable a few features not attainable in phase-only holography;these include creating artifactfree two-dimensional holographic images,encoding phase and amplitude profiles separately at the object plane,encoding intensity profiles at the metasurface and object planes separately,and controlling the surface textures of three-dimensional holographic objects.
文摘Nonalcoholic fatty liver disease(NAFLD)is a heterogeneous and complex disease that is imprecisely diagnosed by liver biopsy.NAFLD covers a spectrum that ranges from simple steatosis,nonalcoholic steatohepatitis(NASH)with varying degrees of fibrosis,to cirrhosis,which is a major risk factor for hepatocellular carcinoma.Lifestyle and eating habit changes during the last century have made NAFLD the most common liver disease linked to obesity,type 2 diabetes mellitus and dyslipidemia,with a global prevalence of 25%.NAFLD arises when the uptake of fatty acids(FA)and triglycerides(TG)from circulation and de novo lipogenesis saturate the rate of FAβ-oxidation and verylow density lipoprotein(VLDL)-TG export.Deranged lipid metabolism is also associated with NAFLD progression from steatosis to NASH,and therefore,alterations in liver and serum lipidomic signatures are good indicators of the disease’s development and progression.This review focuses on the importance of the classification of NAFLD patients into different subtypes,corresponding to the main alteration(s)in the major pathways that regulate FA homeostasis leading,in each case,to the initiation and progression of NASH.This concept also supports the targeted intervention as a key approach to maximize therapeutic efficacy and opens the door to the development of precise NASH treatments.
基金supported by the National Natural Science Foundation of China(Nos.11002122,51172192,11272275 and 11002121)the Natural Science Foundation of Hunan Province, China(No.11JJ4003)the Key Project of Scientific Research Conditions in Hunan Province,China(No.2012TT2040)
文摘In this paper, a finite element model was developed for a turbine blade with thermal barrier coatings to investigate its failure behavior under cyclic thermal loading. Based on temperature and stress fields obtained from finite element simulations, dangerous regions in ceramic coating were determined in terms of the maximum principal stress criterion. The results show that damage preferentially occurs in the chamfer and rabbet of a turbine blade with thermal barrier coatings and its thermal fatigue life decreases with the increase of thermal stress induced by high service temperature.
基金supported by the National Natural Science Foundation of China(Grant Nos.51172192,11272275 and 11002122)the Natural Science Foundation of Hunan Province(Grant No.11JJ4003)the Doctoral Scientific Research Foundation of Xiangtan University(Grant Nos.KZ08022,KZ03013 and KF20140303)
文摘To study the temperature distribution and thermal-stress field in different service stages, a two-dimensional model of a turbine blade with thermal barrier coatings is developed, in which the conjugate heat transfer analysis and the decoupled thermal-stress calculation method are adopted. Based on the simulation results, it is found that a non-uniform distribution of temperature appears in different positions of the blade surface, which has directly impacted on stress field. The maximum temperature with a value of 1030 ℃ occurs at the leading edge. During the steady stage, the maximum stress of thermally grown oxide （TGO） appears in the middle of the suction side, reaching 3.75 GPa. At the end stage of cooling, the maximum compressive stress of TGO with a value of-3.5 GPa occurs at the leading edge. Thus, it can be predicted that during the steady stage the dangerous regions may locate at the suction side, while the leadine edge mav be more Drone to failure on cooling.
基金supported by Jiangsu Province’s Key Laboratory inInfectious Diseases
文摘Clostridium difficile （C.difficile） infection has become one of the major hospital-associated infections in Western countries in the last two decades.However,there is limited information on the status of C.difficile infection in Chinese healthcare settings.Given the large and increasing elderly population and the well-recognized problem of over-prescribing of broad spectrum antibiotics in China,it is critical to understand the epidemiology and potential risk factors that may contribute to C.difficile infection in China.A literature review of available published studies,including those in Chinese language-based journals,was conducted.A review of the currently available literature suggested the presence of C.difficile infections in China,but also suggested that these infections were not particularly endemic.This finding should lead to better designed and greatly expanded studies to provide a more reliable epidemiologically-based conclusion on the actual status of C.difficile infection in China,including the identification of any associated risk factors.Such information is ultimately valuable to develop appropriate strategies to prevent C.difficile infection and the vast negative impact of such infections in China and other developing countries.
基金The project supported by the National Basic Research Program of China(2006CB601202)the National Natural Science Foundation of China(10328203,10572111,10572119,10632060)+2 种基金the National 111 Project of China(B06024),the Program for New Century Excellent Talents in University(NCET-04-0958)the 0pen Foundation of State Key Laboratory of Structural Analysis of Industrial EquipmentDoctorate Foundation of Northwestern Polytechnical University.
文摘An effective single layered finite element （FE） computational model is proposed to predict the structural behavior of lightweight sandwich panels having two dimensional （2D） prismatic or three dimensional （3D） truss cores. Three different types of cellular core topology are considered： pyramidal truss core （3D）, Kagome truss core （3D） and corrugated core （2D）, representing three kinds of material anisotropy： orthotropic, monoclinic and general anisotropic. A homogenization technique is developed to obtain the homogenized macroscopic stiffness properties of the cellular core. In comparison with the results obtained by using detailed FE model, the single layered computational model can give acceptable predictions for both the static and dynamic behaviors of orthotropic truss core sandwich panels. However, for non-orthotropic 3D truss cores, the predictions are not so well. For both static and dynamic behaviors of a 2D corrugated core sandwich panel, the predictions derived by the single layered computational model is generally acceptable when the size of the unit cell varies within a certain range, with the predictions for moderately strong or strong corrugated cores more accurate than those for weak cores.
基金supported financially by the National Natural Science Foundation of China (Nos.U19A2085 and 51627805)the Key-Area Research and Development Program of Guangdong Province (No.2020B090923001)+2 种基金the Key Basic and Applied Research Program of Guangdong Province (No.2019B030302010)the Optical Valley Science Research Project,WEHDZ (No.2019001)financial support from the China Postdoctoral Science Foundation (Nos.2019TQ0099 and 2019M662908)。
文摘It is well accepted that grain-boundary phases in metallic alloys greatly deteriorate the mechanical properties.In our work,we report on a novel strategy to prepare high strength-ductility β-type(Ti69.71 Nb23.72Zr4.83Ta1.74)97Si3(at.%)(TNZTS) alloys by tailoring grain-boundary metastable Si-containing phase.Specifically,the thin shell-shaped metastable S1 phase surrounding the columnar β-Ti grain was intercepted successfully via nonequilibrium rapid solidification achieved by selective laser melting(SLM).Subsequently,the thin shell-shaped metastable(Ti,Nb,Zr)5 Si3(called S1) phase was transformed into globular(Ti,Nb,Zr)2 Si(called S2) phase by the solution heat treatment.Interestingly,the globular S2 phases reinforced TNZTS alloy exhibits ultrahigh yield strength of 978 MPa,ultimate strength of 1010 MPa and large elongation of 10.4 %,overcoming the strength-ductility trade-off of TNZTS alloys by various methods.Especially,the reported yield strength herein is 55 % higher than that of conventionally forged TNZT alloys.Dynamic analysis indicates the globularization process of the metastable S1 phase is controlled by the model of termination migration.The quantitative analysis on strengthening mechanism demonstrates that the increase in yield strength of the heat-treated alloys is mainly ascribed to the strengthening of the precipitated silicide and the dislocations induced by high cooling rate.The obtained results provide some basis guidelines for designing and fabricating β-titanium alloys with excellent mechanical properties,and pave the way for biomedical application of TNZTS alloy by SLM.
文摘AIM To determine steatosis and fibrosis prevalence in hepatitis C patients after a sustained virological response achieved with direct-acting antivirals.METHODS Transient elastography with controlled attenuation parameter(CAP) was used to assess hepatic steatosis post-sustained virological response(SVR);the CAP technology was not available in the United States at study initiation.Liver stiffness/fibrosis was measured before and 47 wk after treatment completion.Patients with genotype 3 and patients with cirrhosis were excluded.RESULTS One hundred and one patients were included in the study.Post-SVR there were decreases from baseline in alanine aminotransferase(ALT)(63.1 to 17.8 U/L),aspartate aminotransferase(51.8 to 21.5 U/L) and fibrosis score(7.4 to 6.1 k Pa)(P < 0.05).Post-SVR,48 patients(47.5%) had steatosis on CAP;of these,6.25% had advanced fibrosis.Patients with steatosis had higher body mass index(29.0 vs 26.1 kg/m2),glucose(107.8 vs 96.6 mg/d L),ALT(20.4 vs 15.3 mg/d L),CAP score(296.3 vs 212.4 d B/m) and fibrosis score(7.0 vs 5.3 k Pa);P < 0.05.Interestingly,compared to baseline,both patients with and without steatosis had change in fibrosis score post-SVR(7.7 k Pa vs 7.0 k Pa and 7.0 k Pa vs 5.3 k Pa);alternatively,(P < 0.05) and therefore patients with steatosis continued to have clinically significant stiffness(≥ 7 k Pa).CONCLUSION Fatty liver is very common in hepatitis C virus(HCV) patients post-SVR.These patients continue to have elevated mean fibrosis score(≥ 7 k Pa) compared to those without fatty liver;some have advanced fibrosis.Long term follow up is needed to assess steatosis and fibrosis in HCV patients post-SVR.
基金Supported by the National Key R&D Program of China(2018YFA0404201,2018YFA0404202,2018YFA0404203,2018YFA0404204)the National Natural Science Foundation of China(12022502,12205314,12105301,12261160362,12105294,U1931201)+2 种基金the Youth Innovation Promotion Association CAS(2022010)in Thailand by the National Science and Technology Development Agency(NSTDA)the National Research Council of Thailand(NRCT):High-Potential Research Team Grant Program(N42A650868)。
文摘The full array of the Large High Altitude Air Shower Observatory(LHAASO)has been in operation since July 2021.For its kilometer-square array(KM2A),we optimized the selection criteria for very high and ultrahigh energyγ-rays using data collected from August 2021 to August 2022,resulting in an improvement in significance of the detection in the Crab Nebula of approximately 15%,compared with that of previous cuts.With the implementation of these new selection criteria,the angular resolution was also significantly improved by approximately 10%at tens of TeV.Other aspects of the full KM2A array performance,such as the pointing error,were also calibrated using the Crab Nebula.The resulting energy spectrum of the Crab Nebula in the energy range of 10-1000 TeV are well fitted by a log-parabola model,which is consistent with the previous results from LHAASO and other experiments.
基金National Institutes of Health,NIAAA,No.R01AA026759(Lu)National Institutes of Health,NIDDK,No.R01DK107288(Lu)+4 种基金National Institutes of Health,NCCIH,No.R01AT001576National Institutes of Health,NCI,No.R01CA172086(Lu and Mato)Agencia Estatal de Investigación MINECO,No.SAF 2017-88041-RISCiii PIE14/00031,No.CIBERehdISCiiiSevero Ochoa Excellence Accreditation,No.SEV-2016-0644)(Mato)
文摘Methionine adenosyltransferases(MATs)are essential enzymes for life as they produce S-adenosylmethionine(SAMe),the biological methyl donor required for a plethora of reactions within the cell.Mammalian systems express two genes,MAT1A and MAT2A,which encode for MATα1 and MATα2,the catalytic subunits of the MAT isoenzymes,respectively.A third gene MAT2B,encodes a regulatory subunit known as MATβwhich controls the activity of MATα2.MAT1A,which is mainly expressed in hepatocytes,maintains the differentiated state of these cells,whilst MAT2A and MAT2B are expressed in extrahepatic tissues as well as non-parenchymal cells of the liver(e.g.,hepatic stellate and Kupffer cells).The biosynthesis of SAMe is impaired in patients with chronic liver disease and liver cancer due to decreased expression and inactivation of MATα1.A switch from MAT1A to MAT2A/MAT2B occurs in multiple liver diseases and during liver growth and dedifferentiation,but this change in the expression pattern of MATs results in reduced hepatic SAMe level.Decades of study have utilized the Mat1a-knockout(KO)mouse that spontaneously develops non-alcoholic steatohepatitis(NASH)and hepatocellular carcinoma(HCC)to elucidate a variety of mechanisms by which MAT proteins dysregulation contributes to liver carcinogenesis.An increasing volume of work indicates that MATs have SAMe-independent functions,distinct interactomes and multiple subcellular localizations.Here we aim to provide an overview of MAT biology including genes,isoenzymes and their regulation to provide the context for understanding consequences of their dysregulation.We will highlight recent breakthroughs in the field and underscore the importance of MAT’s in liver tumorigenesis as well as their potential as targets for cancer therapy.
基金Supported in China by National Key R&D program of China(2018YFA0404201,2018YFA0404202,2018YFA0404203,2018YFA0404204)NSFC(U2031101,11475141,12147208)in Thailand by RTA6280002 from Thailand Science Research and Innovation。
文摘The Large High Altitude Air Shower Observatory(LHAASO)has three sub-arrays,KM2A,WCDA,and WFCTA.The flux variations of cosmic ray air showers were studied by analyzing the KM2A data during a thunderstorm on June 10,2021.The number of shower events that meet the trigger conditions increases significantly in atmospheric electric fields,with a maximum fractional increase of 20%.The variations in trigger rates(increases or decreases)were found to be strongly dependent on the primary zenith angle.The flux of secondary particles increased significantly,following a trend similar to that of shower events.To better understand the observed behavior,Monte Carlo simulations were performed with CORSIKA and G4KM2A(a code based on GEANT4).We found that the experimental data(in saturated negative fields)were in good agreement with the simulations,assuming the presence of a uniform electric field of-700 V/cm with a thickness of 1500 m in the atmosphere above the observation level.Due to the acceleration/deceleration by the atmospheric electric field,the number of secondary particles with energy above the detector threshold was modified,resulting in the changes in shower detection rate.
基金supported by the Hebei Provincial Natural Science Foundation of China(No.E2007000591).
文摘The aim of this study was to simulate the solidification process of beam blank continuous casting, and then find the reasons for the typical defects of the beam blank. A two-dimensional transient coupled finite element model has been developed to compute the temperature and stress profile in beam blank continuous casting. The enthalpy method was used in the heat conduction equation. The thermo-mechanical property in the mushy zone was taken into consideration in this calculation. It is shown that at the mold exit the thickness of the shell had its maximum value at the flange tip and its minimum value at the fillet. The temperature had a great fluctuation on the surface of the beam blank in the secondary cooling zone. At the unbending point, the surface temperature of the web was in the brittleness temperature range under the present condition. To ensure the quality, it is necessary to weaken the intensity of secondary cooling. At the mold exit the equivalent stress and strain have higher values at the flange tip and at the web. From the spray 1 to the unbending point, the maximum values of stress and strain gradually moved to the internal section of the flange tip and the web. However, whenever, there were bigger stress and strain values near the flange tip and the web than in the other parts, it must be very easy to generate cracks at those positions. Now, online verification of this simulation has been developed, which has proved to be very useful and efficient to instruct the practical production of beam blank continuous casting.
基金supported by the NSF(grant no.PHY-1411445)the Air Force Office of Scientific Research(grant nos.FA9550-14-1-0389 and FA9550-16-1-0322)supported by the US Department of Energy,Office of Basic Energy Sciences,under contract no.DE-SC0012704.
文摘Broadband high reflectance in nature is often the result of randomly,three-dimensionally structured materials.This study explores unique optical properties associated with one-dimensional nanostructures discovered in silk cocoon fibers of the comet moth,Argema mittrei.The fibers are populated with a high density of air voids randomly distributed across the fiber cross-section but are invariant along the fiber.These filamentary air voids strongly scatter light in the solar spectrum.A single silk fiber measuring~50μm thick can reflect 66%of incoming solar radiation,and this,together with the fibers’high emissivity of 0.88 in the mid-infrared range,allows the cocoon to act as an efficient radiative-cooling device.Drawing inspiration from these natural radiative-cooling fibers,biomimetic nanostructured fibers based on both regenerated silk fibroin and polyvinylidene difluoride are fabricated through wet spinning.Optical characterization shows that these fibers exhibit exceptional optical properties for radiative-cooling applications:nanostructured regenerated silk fibers provide a solar reflectivity of 0.73 and a thermal emissivity of 0.90,and nanostructured polyvinylidene difluoride fibers provide a solar reflectivity of 0.93 and a thermal emissivity of 0.91.The filamentary air voids lead to highly directional scattering,giving the fibers a highly reflective sheen,but more interestingly,they enable guided optical modes to propagate along the fibers through transverse Anderson localization.This discovery opens up the possibility of using wild silkmoth fibers as a biocompatible and bioresorbable material for optical signal and image transport.
