Unveiling the Initial Conditions of Open Star Cluster Formation

Open clusters(OCs)are infrequent survivors of embedded clusters gestated in molecular clouds.Up to now,little is known about the initial conditions for the formation of OCs.Here,we studied this issue using high-precision astrometric parameters provided by Gaia data release 3.The statistics show that the peculiar motion velocities of OCs vary slightly from infancy to old age,providing a remarkable opportunity to use OCs to trace their progenitors.Adopting a dynamical method,we derived the masses of the progenitor clumps where OCs were born,which have statistical characteristics comparable to previously known results for clumps observed in the Galaxy.Moreover,the masses of the progenitor clumps of OCs indicate they should be capable of gestating massive O-type stars.In fact,after inspecting the observed OCs and O-type stars,we found that there are many O-type stars in OCs.The destructive stellar feedback from O-type stars may disintegrate the vast majority of embedded clusters,and only those sufficiently dense ones can survive as OCs.

广泛耐药革兰阴性菌感染的实验诊断、抗菌治疗及医院感染控制:中国专家共识

广泛耐药革兰阴性杆菌(XDR-GNB),是指除1~2类抗菌药物(主要指多黏菌素和替加环素)外,几乎对所有类别抗菌药物均不敏感的革兰阴性杆菌。XDR-GNB常见于肠杆菌科细菌、鲍曼不动杆菌、铜绿假单胞菌和嗜麦芽窄食单胞菌等。近年来,中国XDR-GNB的发生率呈不断上升趋势,由于缺乏有效的治疗药物,XDR-GNB感染成为公共卫生安全的一大威胁。我国有关感染的临床、微生物学及临床药理学专家们就XDR-GNB感染的实验室诊断、临床诊疗和医院感染控制等问题深入讨论,形成此共识。其中细菌药敏试验的抗菌药物品种及结果判定标准遵循美国临床和实验室标准化协会(CLSI)、欧洲抗菌药物敏感性试验委员会(EUCAST)或美国食品与药物监督管理局(FDA)的指南。研究提示长疗程使用广谱抗菌药物是引发XDR-GNB感染最重要的危险因素。根据现有的临床研究和实验室数据,共识提供治疗各种XDRGNB感染的联合用药推荐方案,其中常用的抗菌药物有替加环素、多黏菌素、碳青霉烯类、氨基糖苷类和磷霉素等。同时建议实行严格的感染控制措施,包括手卫生、接触隔离、主动筛查、环境消毒、去定植和抗菌药物应用管理等遏制XDRGNB感染的传播。

Methods for a blind analysis of isobar data collected by the STAR collaboration

In 2018,the STAR collaboration collected data from^(96)_(44)Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr at√^(S)NN=200 Ge V to search for the presence of the chiral magnetic effect in collisions of nuclei.The isobar collision species alternated frequently between 9644 Ru+^(96)_(44)Ru and^(96)_(40)Zr+^(96)_(40)Zr.In order to conduct blind analyses of studies related to the chiral magnetic effect in these isobar data,STAR developed a three-step blind analysis procedure.Analysts are initially provided a"reference sample"of data,comprised of a mix of events from the two species,the order of which respects time-dependent changes in run conditions.After tuning analysis codes and performing time-dependent quality assurance on the reference sample,analysts are provided a species-blind sample suitable for calculating efficiencies and corrections for individual≈30-min data-taking runs.For this sample,species-specific information is disguised,but individual output files contain data from a single isobar species.Only run-by-run corrections and code alteration subsequent to these corrections are allowed at this stage.Following these modifications,the"frozen"code is passed over the fully un-blind data,completing the blind analysis.As a check of the feasibility of the blind analysis procedure,analysts completed a"mock data challenge,"analyzing data from Au+Au collisions at√^(S)NN=27 Ge V,collected in 2018.The Au+Au data were prepared in the same manner intended for the isobar blind data.The details of the blind analysis procedure and results from the mock data challenge are presented.

STUDY ON THE VARIATION MECHANISM OF CARBON CONTENT OF LIQUID IRON IN MELTING GASIFIER

This paper studied the changing principles of carbon content in direct reduction iron (DRI) and liquid iron in the COREX melting gasifier. Under the normal working conditions of experimental equipment, liquid nitrogen was poured into the melting gasifier from its tuyere to cool down quickly. And then seven cross sections were made to study the carburization reaction and its characteristics of the solid iron and the liquid iron, and also the reaction of carbon between the slag and the metal. According to the results, the influences of the thickness of the semi-coke layer and the temperature on the carbon content of liquid iron in the COREX melting gasifier were confirmed.

STCF conceptual design report (Volume 1): Physics & detector

The superτ-charm facility(STCF)is an electron–positron collider proposed by the Chinese particle physics community.It is designed to operate in a center-of-mass energy range from 2 to 7 GeV with a peak luminosity of 0.5×10^(35) cm^(–2)·s^(–1) or higher.The STCF will produce a data sample about a factor of 100 larger than that of the presentτ-charm factory—the BEPCII,providing a unique platform for exploring the asymmetry of matter-antimatter(charge-parity violation),in-depth studies of the internal structure of hadrons and the nature of non-perturbative strong interactions,as well as searching for exotic hadrons and physics beyond the Standard Model.The STCF project in China is under development with an extensive R&D program.This document presents the physics opportunities at the STCF,describes conceptual designs of the STCF detector system,and discusses future plans for detector R&D and physics case studies.

Measurements of dihadron correlations relative to the event plane in Au+Au collisions at√^(S)NN=200 GeV

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 extens-ive systematic studies of the dihadron correlations as a function ofФ_(s),trigger and associated particle pT,and the pseudo-rapidity range△_(η),should provide stringent inputs to help understand the underlying physics mechanisms of jet-medium interactions in high energy nuclear collisions.

Acceleration of 60 MeV proton beams in the commissioning experiment of the SULF-10 PW laser

We report the experimental results of the commissioning phase in the 10 PW laser beamline of the Shanghai Superintense Ultrafast Laser Facility(SULF).The peak power reaches 2.4 PW on target without the last amplifying during the experiment.The laser energy of 72±9 J is directed to a focal spot of approximately 6μm diameter(full width at half maximum)in 30 fs pulse duration,yielding a focused peak intensity around 2.0×10^(21)W/cm^(2).The first laser-proton acceleration experiment is performed using plain copper and plastic targets.High-energy proton beams with maximum cut-off energy up to 62.5 MeV are achieved using copper foils at the optimum target thickness of 4μm via target normal sheath acceleration.For plastic targets of tens of nanometers thick,the proton cut-off energy is approximately 20 MeV,showing ring-like or flamented density distributions.These experimental results reflect the capabilities of the SULF-10 PW beamline,for example,both ultrahigh intensity and relatively good beam contrast.Further optimization for these key parameters is underway,where peak laser intensities of 10^(22)-10^(23)w/cm^(2)are anticipated to support various experiments on extreme field physics.

Mapping non-laminar proton acceleration in laser-driven target normal sheath field

We report on experimental observation of non-laminar proton acceleration modulated by a strong magnetic field in laser irradiating micrometer aluminum targets.The results illustrate the coexistence of ring-like and filamentation structures.We implement the knife edge method into the radiochromic film detector to map the accelerated beams,measuring a source size of 30-110μm for protons of more than 5 MeV.The diagnosis reveals that the ring-like profile originates from low-energy protons far off the axis whereas the filamentation is from the near-axis high-energy protons,exhibiting non-laminar features.Particle-in-cell simulations reproduced the experimental results,showing that the short-term magnetic turbulence via Weibel instability and the long-term quasi-static annular magnetic field by the streaming electric current account for the measured beam profile.Our work provides direct mapping of laser-driven proton sources in the space-energy domain and reveals the non-laminar beam evolution at featured time scales.

Measurement of away-side broadening with self-subtraction of flow in Au+Au collisions at √sNN=200 GeV

High transverse momentum(pT)particle production is suppressed owing to the parton(jet)energy loss in the hot dense medium created in relativistic heavy-ion collisions.Redistribution of energy at low-to-modest pT has been difficult to measure,owing to large anisotropic backgrounds.We report a data-driven method for background evaluation and subtraction,exploiting the away-side pseudorapidity gaps,to measure the jetlike correlation shape in Au+Au collisions at √sNN=200 GeV in the STAR experiment.The correlation shapes,for trigger particles pT>3GeV/c and various associated particle pT ranges within 0.5<pT<10GeV/c,are consistent with Gaussians,and their widths increase with centrality.The results indicate jet broadening in the medium created in central heavy-ion collisions.