一种神秘的基本粒子--中微子

有一种粒子,与电子一样是构成物质世界的基本粒子,然而由于其特殊性和神秘性,大众对其的了解微乎其微,但是它却非常重要,而且是近几十年来科学家们研究的“宠儿”和最“前沿”。这种粒子叫做中微子。中微子是一种跟电子一样的基本粒子,只是由于电子太普及太普遍了,大众都知道它,而中微子由于其特殊性,大众缺乏对它的深入了解。实际上在当今的科学界,中微子却是被研究得异常“活跃”和重要的粒子,可以说是近几十年来粒子物理方向最火热的研究方向之一。并且中微子也是大量充斥在我们的身边,以接近光速在运动,但是我们看不见摸不着也感觉不到它。今天我们就来揭开中微子的神秘面纱。

The direct and gut microbiota-mediated effects of dietary bile acids on the improvement of gut barriers in largemouth bass(Micropterus salmoides)

Fish gut barrier damage under intensive culture model is a significant concern for aquaculture industry.This study aimed to investigate the effects of bile acids(BAs)on gut barriers in Micropterus salmoides.A germ-free(GF)zebrafish model was employed to elucidate the effects of the direct stimulation of BAs and the indirect regulations mediated by the gut microbiota on gut barrier functions.Four diets were formulated with BAs supplemented at 0,150,300 and 450 mg/kg,and these 4 diets were defined as control,BA150,BA300 and BA450,respectively.After 5 weeks of feeding experiment,the survival rate of fish fed with BA300 diet was increased(P<0.05).Histological analysis revealed an improvement of gut structural integrity in the BA150 and BA300 groups.Compared with the control group,the expression of genes related to chemical barrier(mucin,lysozyme and complement 1)and physical barrier(occludin and claudin-4)was increased in the BA150 and BA300 groups(P<0.05),and the expression of genes related to immunological barrier(interleukin[IL]-6,tumor growth factorβ,IL-10,macrophage galactosetype lectin and immunoglobulin M[Ig M])was significantly increased in the BA300 group(P<0.05),but the expression of genes related to chemical barrier(hepcidin)and immunological barrier(IL-1β,tumor necrosis factor-a,IL-6 and arginase)was significantly decreased in the BA450 group(P<0.05).Gut microbiota composition analysis revealed that the abundance of Firmicutes was augmented prominently in the BA150 and BA300 groups(P<0.05),while that of Actinobacteriota and Proteobacteria showed a downward trend in the BA150 and BA300 groups(P>0.05).The results of the gut microbiota transferring experiment demonstrated an upregulation of gut barrier-related genes,including immunoglobulin Z/T(Ig Z/T),IL-6,IL-1βand IL-10,by the gut microbiota transferred from the BA300 group compared with the control(P<0.05).Feeding the BA300 diet directly to GF zebrafish resulted in enhanced expression of Ig M,Ig Z/T,lysozyme,occludin-2,IL-6 and IL-10(P<0.05).In conclusion,BAs can improve the gut barriers of fish through both direct and indirect effects mediated by the gut microbiota.

JUNO sensitivity on proton decay p→νK^(+)searches

The Jiangmen Underground Neutrino Observatory(JUNO)is a large liquid scintillator detector designed to explore many topics in fundamental physics.In this study,the potential of searching for proton decay in the p→νK^(+)mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification.Moreover,the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals.Based on these advantages,the detection efficiency for the proton decay via p→νK^(+)is 36.9%±4.9%with a background level of 0.2±0.05(syst)±0.2(stat)events after 10 years of data collection.The estimated sensitivity based on 200 kton-years of exposure is 9.6×1033 years,which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies.

远程教育培养乡村振兴本土人才的先行探索——以教育部“一村一名大学生计划”为例

国家开放大学2004年启动实施的'一村一名大学生计划'是应用现代远程开放教育形式就地培养乡村振兴本土人才的先行探索。计划实施14年来,积累了丰富的培养乡村本土人才的经验,为我国新农村建设培养了一大批有文化、懂技术、会经营的农民创业致富带头人和政治素质高、有管理能力的农村基层干部,在带动地域经济发展、加强农村基层组织建设、推动乡风文明等方面发挥了积极作用,同时也向世界展现了培养乡村本土人才的中国经验、中国方案。新时期,为深入推进乡村振兴战略,需要吸收借鉴项目实施的先行经验,通过加大办学支持、加强顶层设计、着力均衡发展、强化人才培养的针对性、扩展社会参与等方面推动项目持续发展,以更好培育乡村振兴本土人才,强化乡村振兴人才支撑。

高等继续教育专业社会适应性评估指标体系构建研究——以国家开放大学为例

顺应经济社会发展和成人学习者需求日趋多元等趋势,高等继续教育领域正在探索包括学科专业建设等在内多层面的"社会适应性"变革。本研究从专业与社会发展的关系出发,对专业社会适应性的概念及评估指标体系的功能做出界定,并从社会发展、学习者需求、学校定位、学科专业自身发展规律等影响专业发展的内外部因素着手,在充分借鉴并参考分析普通本科及高职院校专业适应性相关评估指标的基础上,综合考量高等继续教育专业的特殊性,初步构建了专业社会适应性评估指标体系的基本雏形。之后通过词频分析法及德尔菲法对指标进行确认与修正,利用层次分析法确定评估指标的权重,并结合问卷调查结果对指标进行了信度、效度和相关性检验,最终形成相对科学、合理的专业社会适应性评估指标体系。该体系主要从匹配度、支持度、认可度三个层面来构建,以期指导高等继续教育专业合理发展,促进专业结构优化布局,提高人才培养的适切度,同时为高等继续教育专业设置及专业评估提供参考。

Sub-percent precision measurement of neutrino oscillation parameters with JUNO

JUNO is a multi-purpose neutrino observatory under construction in the south of China.This publication presents new sensitivity estimates for the measurement of the △m_(31)^(2),△m_(21)^(2),sin^(2)θ_(12),and sin^(2)θ_(13) oscillation parameters using reactor antineutrinos,which is one of the primary physics goals of the experiment.The sensitivities are obtained using the best knowledge available to date on the location and overburden of the experimental site,the nuclear reactors in the surrounding area and beyond,the detector response uncertainties,and the reactor antineutrino spectral shape constraints expected from the TAO satellite detector.It is found that the △m_(21)^(2) and sin^(2)θ_(12) oscillation parameters will be determined to 0.5%precision or better in six years of data collection.In the same period,the △m_(31)^(2) parameter will be determined to about 0.2%precision for each mass ordering hypothesis.The new precision represents approximately an order of magnitude improvement over existing constraints for these three parameters.

Feasibility and physics potential of detecting ^(8)B solar neutrinos at JUNO

The Jiangmen Underground Neutrino Observatory(JUNO)features a 20 kt multi-purpose underground liquid scintillator sphere as its main detector.Some of JUNO's features make it an excellent location for^8B solar neutrino measurements,such as its low-energy threshold,high energy resolution compared with water Cherenkov detectors,and much larger target mass compared with previous liquid scintillator detectors.In this paper,we present a comprehensive assessment of JUNO's potential for detecting^8B solar neutrinos via the neutrino-electron elastic scattering process.A reduced 2 MeV threshold for the recoil electron energy is found to be achievable,assuming that the intrinsic radioactive background^(238)U and^(232)Th in the liquid scintillator can be controlled to 10^(-17)g/g.With ten years of data acquisition,approximately 60,000 signal and 30,000 background events are expected.This large sample will enable an examination of the distortion of the recoil electron spectrum that is dominated by the neutrino flavor transformation in the dense solar matter,which will shed new light on the inconsistency between the measured electron spectra and the predictions of the standard three-flavor neutrino oscillation framework.IfDelta m^(2)_(21)=4.8times10^(-5);(7.5times10^(-5))eV^(2),JUNO can provide evidence of neutrino oscillation in the Earth at approximately the 3sigma(2sigma)level by measuring the non-zero signal rate variation with respect to the solar zenith angle.Moreover,JUNO can simultaneously measureDelta m^2_(21)using^8B solar neutrinos to a precision of 20% or better,depending on the central value,and to sub-percent precision using reactor antineutrinos.A comparison of these two measurements from the same detector will help understand the current mild inconsistency between the value of Delta m^2_(21)reported by solar neutrino experiments and the KamLAND experiment.

Studies of detector cells for a hadronic calorimeter based on plastic scintillators

In this paper,we study variations of a plastic scintillator tile coupled to silicon photomultiplier via a dome-shaped cavity originally developed in the CALICE collaboration.Four kinds of plastic scintillator detector cells with different sizes based on the structure were studied for applications in analog readout highly granular hadronic calorimeter(AHCAL)in future circular electron positron collider(CEPC)project.The responses to cosmic rays of the detector cells could reach 33.89 p.e./MIPs(minimum ionizing particles).The good results of both response uniformity and MIP detection efficiency(above 95%)show that the detector cells with larger sizes(40×40×3 and 50×50×3 mm^(3))could provide an option for AHCAL detector cells of CEPC detectors.