Impacts of agri-food e-commerce on traditional wholesale industry:Evidence from China

Rapidly expanding studies investigate the effects of e-commerce on company operations in the retail market.However,the interaction between agri-food e-commerce(AEC)and the traditional agri-food wholesale industry(AWI)has not received enough attention in the existing literature.Based on the provincial panel data from 2013 to 2020 in China,this paper examines the effect of AEC on AWI,comprising three dimensions:digitalization(DIGITAL),agrifood e-commerce infrastructure and supporting services(AECI),and agri-food e-commerce economy(AECE).First,AWI and AEC are measured using an entropy-based combination of indicators.The results indicate that for China as a whole,AWI has remained practically unchanged,whereas AEC exhibits a significant rising trend.Second,the findings of the fixed-effect regression reveal that DIGITAL and AECE tend to raise AWI,whereas AECI negatively affects AWI.Third,threshold regression results indicate that AECI tends to diminish AWI with three-stage inhibitory intensity,which manifests as a first increase and then a drop in the inhibition degree.These results suggest that with the introduction of e-commerce for agricultural product circulation,digital development will have catfish effects that tend to stimulate the vitality of the conventional wholesale industry and promote technical progress.Furthermore,the traditional wholesale industry benefits financially from e-commerce even while it diverts part of the traditional wholesale circulation for agricultural products.

Critical Opalescence and Its Impact on the Jet Quenching Parameter q

Jet quenching parameter q is essential for characterizing the interaction strength between jet partons and nuclear matter.Based on the quark-meson model,we develop a new framework for calculating q at finite chemical potentials,in which q is related to the spectral function of the chiral order parameter.

Understanding the spatial representativeness of air quality monitoring network and its application to PM_(2.5)in the China's Mainland

Air pollution has seriously endangered human health and the natural ecosystem during the last decades.Air quality monitoring stations(AQMS)have played a critical role in providing valuable data sets for recording regional air pollutants.The spatial representativeness of AQMS is a critical parameter when choosing the location of stations and assessing effects on the population to long-term exposure to air pollution.In this paper,we proposed a methodological framework for assessing the spatial representativeness of the regional air quality monitoring network and applied it to ground-based PM_(2.5)observation in the mainland of China.Weighted multidimensional Euclidean distance between each pixel and the stations was used to determine the representativeness of the existing monitoring network.In addition,the K-means clustering method was adopted to improve the spatial representativeness of the existing AQMS.The results showed that there were obvious differences among the representative area of 1820 stations in the mainland of China.The monitoring stations could well represent the PM_(2.5)spatial distribution of the entire region,and the effectively represented area(i.e.the area where the Euclidean distance between the pixels and the stations was lower than the average value)accounted for 67.32%of the total area and covered 93.12%of the population.Forty additional stations were identified in the Northwest,North China,and Northeast regions,which could improve the spatial representativeness by 14.31%.

Conjugate addition‐enantioselective protonation to forge tertiary stereocentresαto azaarenes via cooperative hydrogen atom transfer and chiral hydrogen‐bonding catalysis

Cooperative hydrogen atom transfer and chiral hydrogen‐bonding catalysis as a new platform for the asymmetric synthesis of azaarene derivatives is reported.By using a tetrabutylammonium decatungstate as the photocatalyst and a chiral phosphoric acid as the hydrogen‐bonding catalyst,transformations of a variety of commercially available hydrocarbons and silanes with diverseα‐branched 2‐vinylazaarenes could efficiently experience a tandem radical conjugate addition and enantioselective protonation process,providing a convenient and fully atom economical approach to access a range of valuable enantioenrichedα‐tertiary azaarenes in high yields with good to excellent enantioselectivities(up to 93%ee).Through the direct use of tert‐butyl methylcarbamate as the feedstock,this method enables a highly practical and concise synthesis of the enantiomerically pure medicinal molecule pheniramine(Avil).

Enantioselective intermolecular[2+2]photocycloadditions of vinylazaarenes with triplet-state electron-deficient olefins

The development of catalytic asymmetric radical reactions is an attractive but formidable task.The high reactivity of radicals enables the use of readily accessible feedstocks and mild reaction conditions,but it leads to substantial difficulty for chiral catalysts to provide sufficient enantiocontrol.Moreover,a racemic background process is often inevitable,further deteriorating enantioselectivity.In this regard,an effective protocol has been established for enantioselective intermolecular[2+2]photocycloadditions to overcome the challenges,which is capitalising on the ground-state preassociations of chiral catalysts with photoactivated substrates.Here,we report the viability of substrate-differentiating synergistic catalysis for this important reaction.In this new platform,energy transfer occurs between DPZ as a photosensitizer and enones or(E)-2-substituted vinylazaarenes for producing triplet-state species,and chiral phosphoric acid interacts with ground-state 2-vinylazaarenes via hydrogen bonding for subsequent enantiofacial cycloaddition.Although all active species are dispersed in the reaction system,valuable enantioenriched mono-and di-azaarene-functionalized cyclobutanes are obtained efficiently and selectively.In addition to constructing all-carbon quaternary stereocentres,flexible modulation of azaaryl groups and other substituents on the cyclobutane ring is also operative.

Simulation of Fatigue Stiffness Degradation in Prestressed Concrete Beams under Cyclic Loading

In order to investigate and research the fatigue cracking of prestressed concrete fatigue properties and loading and stiffness degeneration process,cyclic loading tests were carried out on six prestressed concrete beams and the stiffness degradation under fatigue was investigated. A simulation model of stiffness degradation is proposed based on the stiffness analysis of the fatigue-damaged section. The elastic modulus of damaged concrete and the effective residual area of steel were introduced as well as an adjusted three-stage concrete fatigue damage evolution model. The strip method was used to analyze concrete damage due to changing stress along the depth of the beam section. The simulation and test results were compared and a method of predicting fatigue deflection was presented based on the simulation model. The predicted results were compared with that of the neural network method. It is in good agreement for the simulation results with the test results. It is only less than5% error for the simulation model which can reveal the two-stage degradation of prestressed concrete beams under cyclic loading. It is more precise for the simulation prediction method under proper conditions.

Quenching and flow of charm and bottom quarks via semi-leptonic decay of D and B mesons in Pb+Pb collisions at the LHC

Heavy flavor particles provide important probes of the microscopic structure and thermodynamic properties of the quark-gluon plasma(QGP)produced in high-energy nucleus-nucleus collisions.We studied the energy loss and flow of charm and bottom quarks inside the QGP via the nuclear modification factor(R_(AA))and elliptic flow coefficient(v_(2))of their decayed leptons in heavy-ion collisions at the LHC.The dynamical evolution of the QGP was performed using the CLVisc(3+1)-dimensional viscous hydrodynamics model;the evolution of heavy quarks inside the QGP was simulated with our improved Langevin model that considers both collisional and radiative energy loss of heavy quarks;the hadronization of heavy quarks was simulated via our hybrid coalescence-fragmentation model;and the semi-leptonic decay of D and B mesons was simulated via PYTHIA.Using the same spatial diffusion coefficient for charm and bottom quarks,we obtained smaller R_(AA) and larger v_(2) of charm decayed leptons than bottom decayed leptons,indicating stronger energy loss of charm quarks than bottom quarks inside the QGP within our current model setup.

Interactions between heavy quarks and tilted QGP fireballs in 200 A GeV Au+Au collisions

Heavy quark observables are applied to probe the initial energy density distribution with violation of longitudinal boost invariance produced in relativistic heavy-ion collisions.Using an improved Langevin model coupled to a(3+1)-dimensional viscous hydrodynamic model,we study the nuclear modification factor(R_(AA)) and directed flow(v_(1)) and elliptic flow(v_(2)) coefficients of heavy mesons and their decayed electrons at an RHIC energy.We find that the counter-clockwise tilt of nuclear matter in the reaction plane results in a positive(negative) heavy flavor vi in the backward(forward) rapidity region,whose magnitude increases with the heavy quark transverse momentum.The difference in the heavy flavor R_(AA) between different angular regions is also proposed as a complementary tool to characterize the asymmetry of the medium profile.Our model results are consistent with currently available data at the RHIC and provide predictions that can be tested by future measurements.

Effects of the formation time of parton shower on jet quenching in heavy-ion collisions

Jet quenching has successfully served as a hard probe to study the properties of Quark-Gluon Plasma(QGP).As a multi-particle system,jets require time to develop from a highly virtual parton to a group of partons close to mass shells.In this study,we present a systematical analysis on the effects of this formation time on jet quenching in relativistic nuclear collisions.Jets from initial hard scatterings were simulated with Pythia,and their interactions with QGP were described using a Linear Boltzmann Transport(LBT) model that incorporates both elastic and inelastic scatterings between jet partons and the thermal medium.Three different estimations of the jet formation time were implemented and compared,including instantaneous formation,formation from single splitting,and formation from sequential splittings,before which no jet-medium interaction was assumed.We found that deferring the jet-medium interaction with a longer formation time not only affects the overall magnitude of the nuclear modification factor of jets but also its dependence on the jet transverse momentum.

急性缺血性脑卒中患者认知功能的影响因素分析

目的:探究急性缺血性脑卒中(AIS)患者认知功能现况并分析其影响因素。方法:收集2021年12月至2022年11月就诊于安徽医科大学第一附属医院神经内科的192例急性缺血性脑卒中患者的一般资料,采用长沙版蒙特利尔认知功能评估量表、匹兹堡睡眠质量指数量表和日常生活活动能力量表对全部AIS患者进行评估,探究睡眠质量和日常生活活动能力是否为认知功能的影响因素。结果:192名AIS患者认知功能得分为(22.89±3.77)分,匹兹堡睡眠质量指数得分为(7.20±4.21)分。相关性分析显示,AIS患者的认知功能与匹兹堡睡眠质量、睡眠时间、睡眠效率以及日间功能障碍程度呈负相关(P<0.05),与日常生活活动能力呈正相关(P<0.05)。多因素分析显示,文化程度及日常生活活动能力是AIS患者认知功能的影响因素(P<0.05)。结论:AIS患者总体认知功能下降发生率较高,且认知功能受文化程度以及日常生活活动能力的影响。

Fine-Grained Bulk NiTi Shape Memory Alloy Fabricated by Rapid Solidifcation Process and Its Mechanical Properties and Damping Performance

A near-equiatomic NiTi shape memory alloy was fabricated by rapid solidification process through vacuum arc melting followed by vacuum suction casting in water-cooled thick copper mold. The rapidly solidified （or suction cast） NiTi alloy shows much finer grains and homogenous microstructure, in particular a uniform distribution of various fine precipitates, compared to the conventional cast one. The resultant alloy also exhibits the homogenous Ni distribution in the matrix of the alloy, allowing the martensitic transformation to take place throughout the NiTi alloy matrix simultaneously and resulting in sharper transformation peaks compared to the conventional cast alloy. Moreover, the suction cast NiTJ alloy shows a significant improvement over the conventional cast one, in terms of possessing higher deformation recovery rates and displaying the increased compressive strength and damping capacity by 4% and 20%, respectively.

Kilometers Long Graphene-Coated Optical Fibers for Fast Thermal Sensing

The combination of optical fiber with graphene has greatly expanded the application regimes of fiber optics,from dynamic optical control and ultrafast pulse generation to high precision sensing.However,limited by fabrication,previous graphene-fiber samples are typically limited in the micrometer to centimeter scale,which cannot take the inherent advantage of optical fibers—longdistance optical transmission.Here,we demonstrate kilometers long graphene-coated optical fiber(GCF)based on industrial graphene nanosheets and coating technique.The GCF shows unusually high thermal diffusivity of 24.99 mm^(2) s^(-1) in the axial direction,measured by a thermal imager directly.This enables rapid thermooptical response both in optical fiber Bragg grating sensors at one point(18-fold faster than conventional fiber)and in long-distance distributed fiber sensing systems based on backward Rayleigh scattering in optical fiber(15-fold faster than conventional fiber).This work realizes the industrial-level graphene-fiber production and provides a novel platform for two-dimensional material-based optical fiber sensing applications.

Sustainability of SARS-CoV-2 Induced Humoral Immune Responses in COVID-19 Patients from Hospitalization to Convalescence Over Six Months

Understanding the persistence of antibody in convalescent COVID-19 patients may help to answer the current major concerns such as the risk of reinfection,the protection period of vaccination and the possibility of building an active herd immunity.This retrospective cohort study included 172 COVID-19 patients who were hospitalized in Wuhan.A total of404 serum samples were obtained over six months from hospitalization to convalescence.Antibodies in the specimens were quantitatively analyzed by the capture chemiluminescence immunoassays(CLIA).All patients were positive for the anti-SARS-Co V-2 Ig M/Ig G at the onset of COVID-19 symptoms,and the Ig G antibody persisted in all the patients during the convalescence.However,only approximately 25%of patients can detect the Ig M antibodies,Ig M against N protein(NIg M)and receptor binding domain of S protein(RBD-Ig M)at the 27 th week.The titers of Ig M,N-Ig M and RBD-Ig M reduced to 16.7%,17.6%and 15.2%of their peak values respectively.In contrast,the titers of Ig G,N-Ig G and RBD-Ig G peaked at 4–5 th week and reduced to 85.9%,62.6%and 87.2%of their peak values respectively at the end of observation.Dynamic behavior of antibodies and their correlation in age,gender and severity groups were investigated.In general,the COVID-19 antibody was sustained at high levels for over six months in most of the convalescent patients.Only a few patients with antibody reducing to an undetectable level which needs further attention.The humoral immune response against SARS-Co V-2 infection in COVID-19 patients exhibits a typical dynamic of acquired immunity.

Distinct gut microbiota and health outcomes in asymptomatic infection,viral nucleic acid test re-positive,and convalescent COVID-19 cases

Gut microbiota composition is suggested to associate with coronavirus disease 2019(COVID-19)severity,but the impact of gut microbiota on health outcomes is largely unclear.We recruited 81 individuals from Wuhan,China,including 13 asymptomatic infection cases(Group A),24 COVID-19 convalescents with adverse outcomes(Group C),31 severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)re-positive cases(Group D),and 13 non-COVID-19 healthy controls(Group H).The microbial features of Groups A and D were similar and exhibited higher gut microbial diversity and more abundant short-chain fatty acid(SCFA)-producing species than Group C.Group C was enriched with opportunistic pathogens and virulence factors related to adhesion and toxin production.The abundance of SCFA-producing species was negatively correlated,while Escherichia coli was positively correlated with adverse outcomes.All three groups(A,C,and D)were enriched with the mucusdegrading species Akkermansia muciniphila,but decreased with Bacteroides-encoded carbohydrate-active enzymes.The pathways of vitamin B6 metabolic and folate biosynthesis were decreased,while selenocompound metabolism was increased in the three groups.Specifically,the secondary bile acid(BA)metabolic pathway was enriched in Group A.Antibiotic resistance genes were common among the three groups.Conclusively,the gut microbiota was related to the health outcomes of COVID-19.Dietary supplementations(SCFAs,BA,selenium,folate,vitamin B6)may be beneficial to COVID-19 patients.

Physics perspectives of heavy-ion collisions at very high energy

Heavy-ion collisions at very high colliding energies are expected to produce a quark-gluon plasma(QGP) at the highest temperature obtainable in a laboratory setting. Experimental studies of these reactions can provide an unprecedented range of information on properties of the QGP at high temperatures. We report theoretical investigations of the physics perspectives of heavy-ion collisions at a future high-energy collider. These include initial parton production, collective expansion of the dense medium, jet quenching,heavy-quark transport, dissociation and regeneration of quarkonia, photon and dilepton production. We illustrate the potential of future experimental studies of the initial particle production and formation of QGP at the highest temperature to provide constraints on properties of strongly interaction matter.

Heavy flavor quenching and flow:the roles of initial condition,pre-equilibrium evolution,and in-medium interaction

Within an advanced Langevin-hydrodynamics framework coupled to a hybrid fragmentation-coalescence hadronization model,we study heavy flavor quenching and flow in relativistic heavy-ion collisions.We investigate how the initial heavy quark spectrum,the in-medium energy loss and hadronization mechanisms of heavy quarks,the evolution profile of the pre-equilibrium stage,the medium flow,and the temperature dependence of heavy quark diffusion coefficients influence the suppression and elliptic flow of heavy mesons at the RHIC and the LHC.Our results show that the different modeling of initial conditions,pre-equilibrium evolution,and in-medium interactions can individually yield uncertainties of approximately 10-40% in D meson suppression and flow at a low transverse momentum.We also find that proper combinations of collisional versus radiative energy loss,coalescence versus fragmentation in hadronization,and the inclusion of medium flow are the most important factors for describing the suppression and elliptic flow of heavy mesons.