诺贝尔物理学奖与长度基准的历史沿革

从2005年诺贝尔物理学奖出发,考察了已往和长度基准有关的诺贝尔物理学奖,从物理学史的角度．探讨了长度基准的历史沿革及其意义．     

加强物理实验改革培养学生创新能力

本文阐述了物理实验在培养创新能力方面的重要作用,针对物理实验存在的问题提出了改革措施,从而达到培养学生创新能力的目的。     

精品课程教材《高分子物理实验》建设的体会——三个及时融入

中国科学技术大学"高分子物理实验"课程是2006年安徽省精品课程,作者结合教学研究和精品课程建设经验,总结出了"三个及时融入"的教材建设理念,本文结合实例对该理念的具体含义进行了阐述.     

热图法测量激光强度时空分布的重构理论研究

为了把量热法应用于远场激光强度时空分布测量,研究了基于热像仪靶面温度测量反演入射激光强度时空分布的重构理论。针对背光面两种不同边界条件(对流-辐射热流边界和恒定温度边界)推导出了由靶面温度分布反演激光束时空分布的重构表达式。获得的分析表达式对广泛的材料具有适用性。通过引入广义参量F0=α/L2,分别就F0》1和F0《1情况给出了重构近似表达式,并对满足F0》1条件的回推算法进行了数值模拟验证。数值结果表明,两种背光面边界条件下回推得到的激光束时空分布与原始激光束达到了很好的一致,但存在一与靶材傅里叶数相关的最小起始回推时间τ0。成果可用于强激光远场参量测量设备的研制。     

蒙特卡罗模拟四极阱中原子的参变激发

在中性原子的磁囚禁实验中,磁阱线圈的电流噪声会激发磁阱中的原子运动,势必对原子团的温度和寿命产生不可忽视的影响。对于非简谐阱,这种激发具有能量选择特性,它又取决于电流噪声的频谱分布。选择了实验中常用的四极阱为研究对象,用直接模拟蒙特卡罗方法来模拟四极阱中原子运动的参变激发现象,得到了原子温度与原子数损失随激发频率的变化关系,并进一步计算了两个共振峰处原子温度随调制时间和调制深度的变化曲线。此外,还研究了弹性碰撞速率对参变激发过程中原子温度上升的影响。这些结果对四极阱参变激发的实验有较好的参考价值。     

Single top partner production in the tZ channel at eγ collision in the littlest Higgs model with T-parity

Introducing the top partner is a common way to cancel the largest quadratically divergent contribution to the Higgs mass induced by the top quark. In this work, we study single top partner production in the tZ channel at eγ collision in the littlest Higgs model with T-parity(LHT). Since it is well known that polarized beams can enhance the cross section, we analyze the signal via polarized electron beams,and photon beams. we have selected two decay modes for comparison, based on the leptonic or the hadronic decays of the W and Z from the top partner. We then construct a detailed detector simulation, and choose a set of cuts to enhance signal significance. For mode A(B), the capacity for exclusion in this process at s~(1/2)=3TeV is comparable to the current experimental limits with L=1000(500) fb~(-1). If the integrated luminosity can be increased to 3000 fb~(-1), the top partner mass+mTcan be excluded up to 1350(1440) GeV at 2σ level. We also considered the initial state radiation effect, and find that this effect reduces the excluding ability of the eγ collision on the the top partner mass by approximately 10 GeV. Moreover, the ability to exclude the LHT parameter space at eγ collision complements the existing research.     

塞曼效应仿真实验平台

塞曼效应实验是学生了解原子具有磁矩和空间取向量子化现象的重要实验,至今塞曼效应仍是研究能级结构的重要方法之一.为了能够让学生更加清楚地了解塞曼效应实验的基本原理和操作规程,针对教学中的重点和难点,运用flash软件制作出塞曼效应仿真实验.该程序可全程高度仿真实验过程,具有界面友好、易于操作、无需安装等优点.为实验教学提供了一种新的辅助方式.     

Experimental review of the ϒ(1S, 2S, 3S) physics at e+e− colliders and the LHC

The three lowest-lying \mathrm{\Upsilon } states, i.e., \mathrm{\Upsilon }(1S), \mathrm{\Upsilon }(2S), and \mathrm{\Upsilon }(3S), composed of bb¯ pairs and below the BB ¯ threshold, provide a good platform for the researches of hadronic physics and physics beyond the Standard Model. They can be produced directly in e⁺e⁻ colliding experiments, such as CLEO, Babar, and Belle, with low continuum backgrounds. In these experiments, many measurements of the exclusive \mathrm{\Upsilon }(1S) and \mathrm{\Upsilon }(2S) decays into light hadrons, which shed light on the “80% rule” for the Okubo–Zweig–Iizuka suppressed decays in the bottomonium sector, were carried out. Meanwhile, many studies of the charmonium and bottomonium productions in \mathrm{\Upsilon }(1S, 2S, 3S) decays were performed, to distinguish different Quantum Chromodynamics (QCD) models. Besides, exotic states and new physics were also extensively explored in \mathrm{\Upsilon }(1S, 2S, 3S) decays at CLEO, BaBar, and Belle. The \mathrm{\Upsilon }(1S, 2S, 3S) states can also be produced in pp collisions and in collisions involving heavy ions. The precision measurements of their cross sections and polarizations at the large hadron collider (LHC), especially in the CMS, ATLAS, and LHCb experiments, help to understandΥproduction mechanisms in pp collisions. The observation of the sequentialΥsuppression in heavy ion collisions at CMS, LHCb, and ALICE is of great importance for verifying the quark–gluon plasma predicted by QCD. In this article, we review the experimental results on \mathrm{\Upsilon }(1S, 2S, 3S) at e⁺e⁻ colliders and the LHC, and summarize their prospects at Belle II and the LHC.     

Seed priming with cold plasma improved seedling performance,secondary metabolism,and expression of deacetylvindoline O-acetyltransferase gene in Catharanthus roseus

The plasma-primed seeds of Catharanthus roseus were cultured in a hormone-free culture medium under sterile conditions. Plasma of 30 or 60 s improved root length (mean = 41.4%) and biomass (mean = 47%), whereas plasma of 90 s delayed plant growth. The plasma treatments enhanced concentrations of photosynthetic pigments and soluble phenols. Plasma of 90 s increased the proline level. With a similar trend, plasma priming induced activities of phenylalanine ammonia-lyase, catalase (about twofold) and peroxidase (31%) enzymes. Plasma also upregulated the expressions of deacetylvindoline O-acetyltransferase gene by an average of 7.8 times. Similarly, the plasma-treated seedlings contained higher concentrations of alkaloids (mean = 72%). Here, molecular evidence is provided on the plasma-associated modifications in secondary metabolism.     

Charge‐Induced Unzipping of Isolated Proteins to a Defined Secondary Structure

Here we present a combined experimental and theoretical study on the secondary structure of isolated proteins as a function of charge state. In infrared spectra of the proteins ubiquitin and cytochrome c, amide I (C=O stretch) and amide II (N–H bend) bands can be found at positions that are typical for condensed‐phase proteins. For high charge states a new band appears, substantially red‐shifted from the amide II band observed at lower charge states. The observations are interpreted in terms of Coulomb‐driven transitions in secondary structures from mostly helical to extended C₅‐type hydrogen‐bonded structures. Support for this interpretation comes from simple energy considerations as well as from quantum chemical calculations on model peptides. This transition in secondary structure is most likely universal for isolated proteins that occur in mass spectrometric experiments.