Criticality of QCD in a holographic QCD model with critical end point

The thermodynamics of strongly interacting matter near the critical end point are investigated in a holographic QCD model, which can describe the QCD phase diagram in T-μ plane qualitatively. Critical exponents along different axes(α,β,γ,δ) are extracted numerically. It is given that α≈0,β≈0.54,γ≈1.04, and δ≈2.97,which is similar to the three-dimensional Ising mean-field approximation and previous holographic QCD model calculations. We also discuss the possibilities to go beyond the mean field approximation by including the full back-reaction of the chiral dynamics in the holographic framework.     

超高效液相色谱-串联质谱法快速测定农产品中残留的种衣剂农药

应用超高效液相色谱-串联质谱(UPLC-MS/MS)联用技术,建立了高灵敏、快速地同时检测农产品中8种种衣剂农药残留量的方法。样品经甲醇-水(体积比为1∶1)提取后,无需经过任何净化过程;以梯度流动相洗脱、经Acquity UPLC C18超高效液相色谱柱分离;电喷雾正离子(ESI+)采集模式、多反应监测模式(MRM)对定量离子和定性离子进行MS/MS测定。8种种衣剂农药在0.001～0.20 mg/L范围内线性关系良好(r≥0.997)。添加浓度为0.006～1.2 mg/kg时,回收率为60%～110%,相对标准偏差小于10%;方法的检出限为0.0005～0.002 mg/kg。该方法仅需约2 min的检测时间,而且灵敏、准确,适合于水果、蔬菜、粮谷等农产品中种衣剂农药残留量的快速、高灵敏地检测分析。     

纳米复合水凝胶的研究进展

传统水凝胶存在机械性能差、响应速度慢等缺点,限制了它作为新材料的应用前景。纳米材料具有独特的微观尺度结构和性质,在电子学、光学、机械学、生物学等领域展现出巨大的潜力。将无机纳米材料添加入水凝胶中不但有可能提高水凝胶的机械强度,同时还能赋予凝胶特殊的新性能,如电响应性能、紫外吸收性能、磁敏感性能等。因而纳米复合水凝胶成为近期的研究热点。本文综述了纳米复合水凝胶的增强理论、典型制备方法及其功能化研究进展。     

具有变系数的二阶中立型差分方程

研究一类具有变系数的二阶中立型时滞差分方程 △τ^2[x（t）-c（t）x（t-τ）]=p（t）x（t-σ），t≥t0〉0 的解的振动性，给出了该类方程一切有界解振动的几个充分条件．     

Restriction on the form of the quark anomalous magnetic moment from lattice QCD results

The quark anomalous magnetic moment(AMM) is dynamically generated through spontaneous chiral symmetry breaking. It has been revealed that, even though its exact form is still unknown, the quark AMM is essential to exploring quark matter properties and QCD phase structure under external magnetic fields. In this study, we take three different forms of the quark AMM and investigate its influence on the chiral phase transition under a magnetic field. In general, a negative(positive) quark AMM acts a...     

大范围市场系统的稳定性分析

本文利用 L iapunov泛函的加权研究具时间滞后效应的大范围市场系统的稳定性 ,得到系统的均衡价格为一致渐近稳定的充分条件 ,它们推广或改进了文献 [1,4 ,5 ]的相应结果     

电感耦合等离子体原子发射光谱法测定硅锰合金中磷

建立了电感耦合等离子体-原子发射光谱法(ICP-AES)测定硅锰合金中磷的方法.进行了样品分解试验,并考察了基体、共存元素对磷测定的影响,选择P214.914 nm为分析谱线.方法的检出限为0.003％,R2=0.9998,RSD小于2％,回收率为96.9％％～101.6％％.方法用于国际能力验证样品分析,结果满意,与...     

Electric and magnetic screenings of gluons in a model with a dimension-2 gluon condensate

Electric and magnetic screenings of thermal gluons are studied using the background expansion method in a gluodynamic model with a gauge invariant dimension-2 gluon condensate at zero momentum. At low temperature, the electric and magnetic gluons are degenerate. With the increase of temperature, it is found that the electric and magnetic gluons start to split at a certain temperature T₀ . The electric screening mass changes rapidly with temperature when T >T₀ , and the Polyakov loop expectation value rises sharply around T₀ from zero in the vacuum to a value around 0.8 at a high temperature. This suggests that the color electric deconfinement phase transition is driven by electric gluons. It is also observed that the magnetic screening mass remains almost the same as its vacuum value, which manifests that the magnetic gluons remain confined. Both the screening masses and the Polyakov loop results are qualitatively in agreement with the Lattice calculations.     

离子液凝胶的研究进展

离子液凝胶结合了离子液体的稳定、不挥发、良好导电性以及普通凝胶的环境响应性智能特点,因而不但可用于制作新型太阳能电池、锂电池、超级电容器、人工肌肉和电致变色装置,还可作为功能膜材料用于催化反应和气体分离,以及作为生物传感器用于检测葡萄糖、多巴胺等生物分子.本文综述了近年来离子液凝胶主要的制备方法及其在电化学、热学、环境响应等方面的性能,展望了这些材料作为光电材料、功能膜材料和生物传感器的潜在巨大前景.     

美国高中化学教材以及化学教学特点

通过对美国著名的Saint John's Preparatory High School(圣约翰预备高中)和Apollo High School(阿波罗高中)化学教学实地听课与调查发现,美国高中化学教材以及化学教学有其鲜明的特点。美国高中化学教材有2/3是化学理论知识,1/3是化学应用性知识,教材内容紧密结合学科前沿技术与应用。美国高中化学教学的特点是:注重让学生用自己的方法解决问题,建构证据;知识的讲授注重强调知识之间的理解与联系,适当教授相关的学习策略;教学注重直观与模型建构等。