Diagnosis and Management of Biliary Strictures after Deceased-Donor Liver Transplantation Based on Clinical Practice

Biliary complications are still the main complications for liver transplantation recipients. Biliary strictures comprise the major part of all biliary complications after deceased-donor liver transplantation (LT). Biliary strictures following LT are divided into anastomotic strictures (AS) and non-anastomotic strictures (NAS). A Limitation of current published researches is that most studies aren’t based on clinical practice. The aim of this review is to summarize risk factors, clinical presentation, diagnosis and management in post-LT biliary strictures.

A method to predict rockburst using temporal trend test and its application

Rockbursts have become a significant hazard in underground mining,underscoring the need for a robust early warning model to ensure safety management.This study presents a novel approach for rockburst prediction,integrating the Mann-Kendall trend test(MKT)and multi-indices fusion to enable real-time and quantitative assessment of rockburst hazards.The methodology employed in this study involves the development of a comprehensive precursory index library for rockbursts.The MKT is then applied to analyze the real-time trend of each index,with adherence to rockburst characterization laws serving as the warning criterion.By employing a confusion matrix,the warning effectiveness of each index is assessed,enabling index preference determination.Ultimately,the integrated rockburst hazard index Q is derived through data fusion.The results demonstrate that the proposed model achieves a warning effectiveness of 0.563 for Q,surpassing the performance of any individual index.Moreover,the model’s adaptability and scalability are enhanced through periodic updates driven by actual field monitoring data,making it suitable for complex underground working environments.By providing an efficient and accurate basis for decision-making,the proposed model holds great potential for the prevention and control of rockbursts.It offers a valuable tool for enhancing safety measures in underground mining operations.

Wall temperature effects on the stability of leeward vortices of a blunt inclined cone

Streamwise vortex instability is one of the most potent mechanisms for the transition of the three-dimensional boundary layers.By using the global stability analysis methods,stability characteristics of the leeward vortex over a blunt cone with an angle of attack under a typical wind tunnel condition are studied and are compared to the case with a smaller wall temperature ratio(corresponding to a flight condition).The vortical structure features inward and outward vortices,similar to that in the flight con-dition.Unlike the flight condition,the outward vortices appear stronger than the inward vortices,resulting in stronger outer-mode instabilities.Although the inner mode is heavily stabilized compared to the flight condition,it can still radiate apparent acoustics.The acoustic sources are computed based on Lighthill's acoustic analogy,showing that the entropy term measuring the deviation from the isentropic relation is dominant.While Mack second mode is shown to most likely trigger the transition in the flight condition,it is absent in the wind tunnel condition,and a shear-layer mode turns out to be the most dangerous instead.Moreover,the instability frequencies and growth rates of the wind tunnel case are much smaller than those of the flight case,indicating that wall heating may stabilize the leeward vortices.

Aquaporin 1 overexpression may enhance glioma tumorigenesis by interacting with the transcriptional regulation networks of Foxo4,Maz,and E2F families

Background The glioblastoma has served as a valuable experimental model system for investigating the growth and invasive properties of glioblastoma.Aquaporin-1(AQP1)in facilitating cell migration and potentially contributing to tumor progression.In this study,we analyzed the role of AQP1 overexpression in glioblastoma and elucidated the main mechanisms involved.Methods AQP1 overexpression recombinant vector was introduced into C6 rat glioma cells to construct an AQP1 overexpression C6 cell line,and its effect on cell viability and migration ability was detected by MTT and Transwell.RNA was extracted by Trizol method for gene sequencing and transcriptomics analysis,and the differentially expressed genes(DEGs)were enriched for up-and downregulated genes by Principal component analysis(PCA),and the molecular mechanism of AQP1 overexpression was analyzed in comparison with the control group using the NCBI GEO database.Statistical analysis was performed using Mann-Whitney paired two tailed t test.Results The cell viability of AQP1-transfected cell lines increased by 23%and the mean distance traveled increased by 67%compared with the control group.Quantitative analysis of gene expression showed that there were 12,121 genes with an average transcripts per million(TPM)value greater than 1.DEGs accounted for 13%of the genes expressed,with the highest correlation with upregulated genes being FOXO4 and MAZ,and the highest with down-regulated genes being E2F TFs.Conclusions AQP1 may be implicated in glioma formation by interacting with the transcriptional regulation networks involving the FOXO4,MAZ,and E2F1/2.These findings shed light on the potential significance of AQP1 in glioma pathogenesis and warrant further investigations to unravel the underlying molecular mechanisms.

风雷软件LES开发设计与验证

基于国家数值风洞风雷软件开源框架,设计开发了LES(Large Eddy Simulation)湍流模型,主要包括Fourier谱/有限差分方法 LES求解器和有限体积/有限差分方法 LES求解器。简要介绍了采用的不可压缩流动求解的投影法、Fourier谱/有限差分混合方法、亚格子模型等理论方法,给出设计的软件框架和计算流程,尤其说明采用的松/紧2种耦合模式。通过数值模拟不可压缩槽道湍流、亚临界雷诺数圆柱绕流、NACA0012临界攻角的低频振荡算例,验证求解器的计算精度和复杂湍流模拟能力。基于风雷开源框架设计的开源LES模型,具备高精度数值格式、亚格子模型、湍流统计等通用模块,可为国内学者提供一个LES湍流模拟研究的开放平台。

改进k-ω-γ转捩模式对不同雷诺数下HIAD的转捩预测

高超声速充气式柔性减速器(HIAD)在气动力作用下会变形为波纹状,从而促进流动转捩为湍流,准确预测其转捩位置和壁面热流对热防护系统的设计至关重要。拓展了分离诱导转捩预测性能的改进k-ω-γ模式,同时具备对第1模态、第2模态、横流模态以及流动分离失稳的预测能力。本文将其应用于不同雷诺数下壁面波纹变形的HIAD边界层转捩预测,并与原始k-ω-γ模式的预测结果进行了对比,以评估和验证其对复杂转捩现象的预测性能。在此基础上,细致剖析了改进k-ω-γ模式的转捩预测机制。结果表明,改进k-ω-γ转捩模式可准确预测不同来流雷诺数下HIAD的转捩起始位置、转捩阵面形态和壁面热流分布。波纹壁面波峰处的转捩预测主要由构造的分离间歇因子猝发。而在波谷位置,第1模态、横流模态以及流动分离的贡献都很重要。以上研究显示了改进k-ω-γ模式在复杂外形中的应用潜力,可为多重不稳定耦合作用下的转捩预测方法发展提供参考。

Chemical-vapor-deposition-grown 2D transition metal dichalcogenides:A generalist model for engineering electrocatalytic hydrogen evolution

Two-dimensional(2D)transition metal dichalcogenides(TMDs)have proved to possess exceptional catalytic performance for hydrogen evolution and are considered to be an appropriate substitute for commercial Pt-based catalysts.Experimentally,chemical vapor deposition(CVD)is an extremely important technique for acquiring controllable and high-purity TMDs for electrocatalysis and modern electronic devices.Recently,researchers have made significant achievements in synthesizing TMDs used for electrocatalytic hydrogen evolution by CVD ranging from dynamic mechanism exploration to performance optimization.In this review,we present the recent progress based on electrocatalytic hydrogen evolution implemented by CVDgrowth TMDs nanosheets and unveil the structural–activity correlation.Firstly,in synthesis,diverse factors covering precursor,substrate,temperature settings,and atmosphere will affect the quality and surface morphology of TMDs.Then,we present the current research status of the CVD-grown 2D TMDs for engineering electrocatalytic hydrogen evolution,including intrinsic performance exploring,morphology engineering,composition adjusting,phase engineering,and vertically-oriented structure constructing.Finally,the future prospects and challenges of CVD in 2D TMDs electrocatalysis are provided.

钝度对钝锥/楔熵层稳定性的影响研究

本文利用稳定性理论和数值模拟方法研究头部钝度对高超声速钝锥与钝楔的熵层稳定性的影响.结果表明钝楔的熵层不稳定性相比钝锥更强.随着钝度增加,熵层厚度逐渐变厚,熵层模态的不稳定性频率逐渐减小,但其不稳定区间不断向下游拓宽,表明熵层中的扰动将有更多机会影响边界层的转捩过程.数值模拟实现了熵层模态激发边界层第一模态的过程.

适用于宽速域湍流流动的新型混合对称超松弛隐式时间格式评估

N-S方程的时间离散格式的收敛效率和数值稳定性对工程湍流计算的意义十分重要.通过对原始标量型和矩阵型对称超松弛隐式时间格式的分析,提出了一种基于当地马赫数的混合型对称超松弛隐式时间格式.该格式兼顾了标量型和矩阵型对称超松弛格式的优点,被应用于从低速到高超声速的多个湍流流动的计算.通过计算结果的对比表明,新的混合型对称超松弛格式在较宽速域的湍流流动模拟中,由于其高的计算效率和优异的数值稳定性,表现出了最好的收敛特性.该新型混合对称超松弛格式将有望广泛应用于工程湍流流动的计算.

外场驱动分子极化调控反应物界面及其电催化析氢性能

反应物界面对电催化反应至关重要.然而,由于调控和表征手段的不足,对反应物界面的深入研究仍难以实现.本文中,我们借助单片电催化微纳器件,通过调节背栅电压引入分子极化,实现了对电化学双电层中水合氢离子(H_(3)O^(+))浓度的调控,进而提高了催化剂的电催化析氢性能.以C_(60)/MoS_(2)异质结为例,电学性能测试表明背栅电场促进了电子从C_(60)向MoS_(2)的转移,并导致了C_(60)分子的极化.原位光致发光光谱表征显示,在背栅电场的作用下,极化的C_(60)分子会吸引H_(3)O^(+),使其聚集在MoS_(2)附近.而电催化测试表明,在1.5 V背栅电压下,由于发生了H_(3)O^(+)的富集,C_(60)/MoS_(2)异质结在-0.45 VRHE电位下的析氢电流密度增加了5倍我们提出的调控和监测反应物界面的方法能够促进对多种电催化反应的研究.

Progress in flight tests of hypersonic boundary layer transition

Boundary layer transition(BLT)can cause a sharp rise in heat flux and skin friction,which can seriously affect the flight performance and safety of hypersonic flight vehicles.Therefore,the mechanism,prediction and control of transition have become important issues that must be dealt with for the development of advanced flight vehicles,and it is also a research hotspot of particular interest to major aerospace countries.Compared to other transition research approaches,model flight tests can better present the transition problems under real flight conditions,thus have been carried out extensively over the past 30 years.The United States,Germany,France,Australia,and other countries have carried out transition research based on flight tests,such as the Pegasus wing-glove crossflow transition and the Hypersonic Boundary Layer Transition(HyBOLT)transition control flight test of the United States,the joint research project of the Hypersonic International Flight Research and Experimentation-1(HIFiRE-1)circular cone and the HIFiRE-5 elliptic cone transition flight tests between the United States and Australia,the flight test of compression surface transition of the scramjet forebody(LEA)in France and so on.Although these flight tests suffered various setbacks,they still obtained valuable transition data.Recently,the United States is carrying out the concave-surface transition flight tests of Hypersonic Boundary Layer Transition(BOLT)and BOLT-II.Since its first model flight test mission for verification purpose launched successfully in 2015,several hypersonic BLT flight tests have been conducted by China Aerodynamics Research and Development Center(CARDC).The flight tests have measured valid transition data under flight conditions,obtained the transition front and its dynamical variation on blunt cones at various angles of attack and a lifting body Hypersonic Transition Research Vehicle(HyTRV).The crossflow traveling waves in high-altitude flight were measured for the first time,and our understanding of hypersonic BLT has been greatly improved.

Kinetic comparative study on aerodynamic characteristics of hypersonic reentry vehicle from near-continuous flow to free molecular flow

A scaled model of the X38-like configuration was simulated under hypersonic conditions for the direct simulation Monte Carlo method and the unified gas kinetic scheme.The inflow conditions considered several flow regimes,from the near-continuum through the slip-transitional to the free molecular regime.Flow fields and surface properties were compared in detail between these two methods.Not only the density and temperature contours distribution but also the surface pressure,heat flux,friction distribution,both kinetic methods give fairly consistent results.Aerodynamics of the model were also achieved and compared.The results provided by both methods agreed with each other very well.The effects of the Knudsen number and angle of attack were assessed.It is meaningful to carry out comparative studies and accelerate both methods to further progress.

Assessment and improvement of k-ω-γ model for separation-induced transition prediction

The purpose of this work is to improve the k-ω-γtransition model for separationinduced transition prediction.The fundamental cause of the excessively small separation bubble predicted by k-ω-γmodel is scrutinized from the perspective of model construction.On the basis,three rectifications are conducted to improve the k-ω-γmodel for separation-induced transition.Firstly,a damping function is established via comparing the molecular diffusion timescale with the rapid pressure-strain timescale.The damping function is applied to prevent the effective length scale from incorrect distribution near the leading edge of the separation bubble.Secondly,the pressure gradient parameterλζ,is proposed as an indicator for local susceptibility to the separation instability.Additionally,λζ,-based separation intermittencyγsep is constructed to accelerate the substantial growth of turbulent kinetic energy after flow separation.The improved model appropriate for both low-and high-speed flow has been calibrated against a variety of diverse and challenging experiments,including the subsonic T3L plate,Aerospatial A airfoil,transonic NLR-7301 airfoil and deformed hypersonic inflatable aerodynamic decelerator aeroshell.The improved model is strictly based on local variables and Galilean invariance.Besides,the proposed improvement for k-ω-γmodel can be fairly convenient to incorporate into other existing intermittency-based transition models.

Design and transition characteristics of a standard model for hypersonic boundary layer transition research

To understand fundamental problems in hypersonic laminar-turbulent boundary layer transition for three-dimensional complex vehicles,a new standard model with typical lifting-body features has been proposed,named as hypersonic transition research vehicle(HyTRV).The configuration of HyTRV is fully analytical,and details of the design process are discussed in this study.The transition characteristics for HyTRV are investigated using three combined methods,i.e.,theoretical analyses,numerical simulations,and wind tunnel experiments.Results show that the fully analytic parameterization design of HyTRV can satisfy the model simplification requirements from both numerical simulations and wind tunnel experiments.Meanwhile,the flow field of HyTRV reveals typical transition mechanisms in six relatively separated regions,including the streamwise vortex instability,crossflow instability,secondary instability,and attachment-line instability.Therefore,the proposed HyTRV model is valuable for fundamental researches in hypersonic boundary layer transition.

From primary instabilities to secondary instabilities in Görtler vortex flows

We have studied the transformation process from primary instabilities to secondary instabilities with direct numerical simulations and stability theories(Spatial Biglobal and plane-marching parabolized stability equations)in detail.First Mack mode and second Mack mode are shown to be able to evolve into the sinuous mode and the varicose mode of secondary instability,respectively.Although the characteristics of second Mack mode eventually lose in the downstream due to the synchronization with the continuous spectrum,second Mack mode is found to be able to trigger a sequence of mode resonations which in turn give birth to highly unstable secondary instabilities.In contrast,first Mack mode does not involve in any mode synchronization.Nevertheless,it can still“jump”to a sinuous mode of secondary instability with a much larger growth rate than that of the first Mack mode.Therefore,secondary instabilities of Görtler vortices are highly receptive to the primary instabilities in the upstream,so that one should consider the primary instability in the upstream and the secondary instability in the downstream as a whole in order to get an accurate prediction of the boundary layer transition.

A three-equation transition model with mechanical considerations

A three-equation transition model based on the transition V-model is proposed for subsonic flows in this study. Considering the mechanical approximation of the generation process of the pre-transitional vorticities, the value of laminar Reynolds shear stress related to the mean shear deformation was calculated in the original transition V-model. Then a new transition model, named V-SA model, was proposed, which considered the phenomenological process of transition and presented great results for flows with and without pressure gradient. It is well-known that the baseline Shear Stress Transport(SST) turbulence model shows excellent performance of accuracy and robustness in plentiful flow cases, but it is important to predict boundary layer transition. The current model(V-SST) successfully couples the V-model to the SST turbulence model by introducing the effective turbulent viscosity and additional correction terms into the transport equations. A thorough evaluation of its ability to predict transition features is performed versus the well-documented flat plate of ERCOFTAC, including T3A and T3B without pressure gradient, T3L2 and T3L3 with semi-circular leading edge, the three-dimensional 6:1 prolate-spheroid under two angles of attack, and the NLR-7301 airfoil under different Mach numbers. Numerical results show that the current model has an attractive and superior performance in the simulation of boundary layer transition processes.

Kojic acid and maltol:The“Transformers”in organic synthesis

The deconstructive reorganization strategy for the synthesis of benzene-containing products from the kojic acid-and maltol-derived alkynes has been recently reported.In this strategy,kojic acid and maltol are analogous to the"Transformers",which can transform into benzofurans and benzaldehydes via annulation reactions.Under the synthetic standpoint,this deconstructive reorganization strategy features high atom economy,innate scalability and functional group tolerance.In the near future,we believe that this unique method will be widely investigated a nd other novel transformations of kojic acid and maltol will be discovered.

Wall pressure beneath a transitional hypersonic boundary layer over an inclined straight circular cone

Properties of wall pressure beneath a transitional hypersonic boundary layer over a 7°half-angle blunt cone at angle of attack 6°are studied by Direct Numerical Simulation.The wall pressure has two distinct frequency peaks.The low-frequency peak with f≈10−50 kHz is very likely the unsteady crossflow mode based on its convection direction,i.e.along the axial direction and towards the windward symmetry ray.Highfrequency peaks are roughly proportional to the local boundary layer thickness.Along the trajectories of stationary crossflow vortices,the location of intense high-frequency wall pressure moves from the bottom of trough where the boundary layer is thin to the bottom of shoulder where the boundary layer is thick.By comparing the pressure field with that inside a high-speed transitional swept-wing boundary layer dominated by the z-type secondary crossflow mode,we found that the high-frequency signal originates from the Mack mode and evolves into the secondary crossflow instability.

Application of surrogate models to stability analysis and transition prediction in hypersonic flows

To increase the efficiency and robustness of stability-based transition prediction in flow simulations, simplified methods are introduced to substitute direct stability analyses for rapid disturbance growth prediction. For low-speed boundary layers, these methods are mainly established based on self-similar assumptions, which are not applicable to non-similar boundary layers in hypersonic flows. The objective of this article is to investigate the application of surrogate models to stability analysis of non-similar flows over blunt cones, focused on parameterization of boundary-layer (BL) profiles. Firstly, correlations between BL edge and profile parameters are analyzed, along with self-similar flow parameters and discrete points on BL profiles, which present four groups of BL characteristic parameters. Secondly, using these parameters as inputs, surrogate models are built for disturbance growth prediction over an MF-1 blunt cone. Results show that, surrogate models using four BL edge parameters and a BL shape factor {Ue, Te, ρe, ηe, H12} for stability analysis can achieve comparable accuracy with those using 16 discrete BL profile parameters, which are more precise than those using merely self-similar parameters or BL edge parameters. Thirdly, the established surrogate models are validated by stability analysis and transition prediction over the MF-1 blunt cone in flight experiments at the instants of t = 17 s ~ 22 s. Compared with direct linear stability analyses, the mean relative error of predicted disturbance growth rates by surrogate models is 8.0% and the maximum relative error of N factor envelopes is 6.6%, which indicates feasible applications of surrogate models to stability analysis and transition prediction of non-similar boundary layers in hypersonic flows.

Experimental study of bluntness effects on hypersonic boundary-layer transition over a slender cone using surface mounted pressure sensors

In this work,we studied the bluntness effect on the hypersonic boundary-layer transition over a slender cone at Mach 6 with interchangeable tips in a noisy Ludwieg tube tunnel before the so-called“transition reversal”phenomenon occurs.The evolution of instability waves is characterized using surface flush-mounted pressure sensors deployed along the streamwise direction within unit Reynolds number from 4E+6/m≤Reunit≤10E+6/m,and the bluntness of the cone nose ranges from 0.1 mm to 5 mm.Power spectral density(PSD)of pressure fluctuation indicates that small nose bluntness(ReR≤2000)has little influence on the evolution of instability waves along the hypersonic boundary-layer,whereas with a moderate nose size(2000≤ReR≤5000),the hypersonic boundary layer transition is delayed monotonically as the nose radius increases before the boundary-layer turns into fully laminar without instability waves.The delaying effect can be attributed to the increased entropy-layer swallowing distance with a large tip radius.Instability wave characterization reveals that the second mode instability wave plays a dominant role before the transition reversal happens.The quadratic phase locking of second mode instabilities can be identified by bispectral analysis,and it attenuates as the nose tip radius increases.