Electronic Curves Crossing in Methyl Iodide by Spin--Orbit Ab Initio Calculation

An ab initio investigation of electronic curve crossing in a methyl iodide molecule is carried out using spin-orbit multiconfigurational quasidegenerate perturbation theory. The one-dimensional rigid potential curves and optimized effective curves of low-lying states, including spin-orbit coupling and relativistic effects, are calculated. The spin-orbit electronic curve crossing between ^3Qo＋ and ^1Q1, and the shadow minimum in potential energy curve of ^3Qo＋ at large internuclear distance are found in both sets of the curves according to the present calcu- lations. The crossing position is in the range of Re-1 = 0.2370 3：0.0001 nm. Comparisons with other reports are presented.     

Cs^＋-K^＋ Exchange in Z-Cut KTiOPO4 Crystal Covered with Chromium Masking Layer

Cs^＋-K^＋ ion exchanges are performed on z-cut KTiOPO4 crystals with chromium coating covered. The temperature of ion exchange is 430℃, and the time range from 15min to 30min. The dark mode spectra of the samples are measured by the prism coupling method. The channel structures on the samples are observed by a microscope and the near field pattern of the channel waveguides are measured by the end-fire coupling method. The refractive index of the samples increases and the increments at surface are modulated due to the existence of Cr film. In the region covered by Cr film, the refractive index of the samples at the surface increases dramatically in a shallow layer. The results of energy dispersive x-ray spectra indicate that in the region covered with Cr film, Cr ions participate in the ion exchange process, and enhance the refractive index. The results may provide a possibility that achieves index enhancement and Cr doping synchronically.     

Difference of Oxide Hetero-structure Junctions with Semiconductor Electronic Devices

Charge carrier injection is performed in Pr0.7Ca0.3MnO3 （PCMO） hetero-structure junctions, exhibiting the stability without electric fields and dramatic changes in both resistance and interface barriers, which are entirely different from behaviour of semiconductor devices. The disappearance and reversion of interface barriers suggest that the adjustable resistance switching of such hetero-strueture oxide devices should associate with motion of charge carriers across interfaces. The results suggest that injected carriers should be still staying in devices and result in changes of properties, which lead to a carrier self-trapping and releasing picture in a strongly correlated electronic framework. Observations in PCMO and oxygen deficient CeO2-δ devices show that oxides as functional materials could be used in mieroeleetronics with some novel properties, in which the interface is very important.     

Relationship of Polaron Exchange with Ferromagnetic and Insulator--Metal Transitions in Doped Manganites

We report the experiment results and data analyses based on a polaron exchange model for La0.7Ca0.3MnO3 and Pr0.7（Sr1-xCax）0.3MnO3 epitaxial thin films. In the polaron exchange model with an energy balance condition, critical temperature of Tc for stable ferromagnetic （FM） ordering should depend on △E as kBTc = E0 exp（-△E/kBTc）, where A E denotes the potential barrier for the exchange polarons to overcome. Using the small polaron hopping model, the resistivity peak temperature Tp is a function of the hopping energy Ehop. The dependence of Tp on Ehop is similar to the dependence of Tc on AE, which reveals that the polaron exchange relates to FM and insulator-metal transitions. The result indicates that the polaron exchange model is a simple way for describing the FM ordering, and is very helpful for understanding of complex doped manganites.     

现代分析仪器在高中化学教学中的应用*——以“防晒霜的防晒效果实验探究”为例

从高中化学原子、分子等抽象性的知识教学出发,以防晒霜的防晒效果实验探究为例,探讨了现代分析仪器在高中化学教学中的应用。通过利用现代分析仪器紫外可见分光光度计,结合紫外线变色球实验探究防晒霜的防晒效果,分析并认识防晒霜中化学防晒的机理。结果表明,防晒霜的厚度越大、SPF越高,防晒霜的防晒效果越好,并且防晒霜的防晒效果可以持续一段时间,但是不同类型的防晒产品存在一定差异。在化学教学中渗透现代分析仪器的应用,为学生进一步了解化学学科在改变学习方式、拓宽学科知识领域、推动自身全面与可持续发展方面打下坚实的基础。     

二次生长法NaA沸石分子筛膜的合成与表征——推荐一个研究型综合实验

介绍一个研究型综合实验——二次生长法NaA沸石分子筛膜的合成与表征。实验预先利用热浸渍法在α-Al_2O_3多孔载体管外表面引入NaA沸石分子筛晶种,再通过二次生长法合成NaA沸石分子筛膜。用扫描电子显微镜和X射线衍射仪表征载体管和NaA沸石分子筛及膜的形貌和结构,并利用渗透蒸发乙醇脱水膜分离装置测试膜的分离性能。通过本实验使学生了解膜分离技术这一科学前沿领域,激发学生对科学研究的兴趣,培养学生的科研探究能力。本实验涵盖合成、表征及性能测试,知识要点多、学科覆盖面广,有利于提升学生的实践操作能力、创新意识和综合运用知识的能力。     

加速溶剂萃取/气相色谱-三重四极杆串联质谱法测定纺织品中24种多环芳烃

建立了加速溶剂萃取/气相色谱-三重四极杆串联质谱(ASE/GC-MS/MS)同时测定纺织品中24种多环芳烃(PAHs)的方法。样品经丙酮加速溶剂萃取,旋蒸浓缩后采用DB-35色谱柱程序升温分离,选择多反应监测模式(MRM)采集,外标法定量。结果表明,在一定浓度范围内多环芳烃的峰面积与质量浓度呈良好的线性关系,相关系数(r~2)均大于0.994,方法检出限为0.000 3~0.03 mg/kg,方法定量下限为0.001~0.10 mg/kg,加标回收率为80.3%~103%,相对标准偏差(RSD)为1.3%~9.2%。该方法灵敏、准确可靠,能满足纺织品中24种多环芳烃的测试要求。     

化工专业综合性实验“分离乙醇水溶液”的探究

化工专业综合性实验对于培养学生的创新精神和工程实践能力至关重要。以分离乙醇水溶液为例,将气液相平衡测定实验和萃取精馏过程模拟相结合形成综合性实验,涉及到了三元体系的气液相平衡测定方法、实验数据采用不同热力学模型的回归及评价、萃取精馏过程模拟、各因素对分离效果的影响评价等。加深了学生对理论知识的理解,使学生对萃取精馏工业应用有了一定的认识,提高了学生的实验操作水平和工程实践能力,为应用型人才的培养提供了有力保障。     

氢氧化铝表面的硬脂酸改性及溶解动力学研究

抗酸类药物大都为复方制剂,目前正朝着复合消炎、成膜缓释方向发展[1].氢氧化铝作为大多数抗酸剂的基本成分,其临床药理学的研究早已完成[2,3],但有关氢氧化铝在体内和离体环境下的溶解动力学研究未见报道.研究氢氧化铝及改性氢氧化铝在类胃酸环境中的溶解动力学特征,对研发以氢氧化铝为基体或载体的复合型胃药剂型有一定理论意义.     

面包酵母催化不对称还原2,5-己二酮

选用10种面包酵母,研究其对2,5-己二酮的不对称还原特性。筛选出一种酵母S.c No.6,对底物2,5-己二酮有较高的转化活性和对映体选择性。初始底物浓度20 mmol.L-1,经酵母转化48h,2,5-己二醇得率为84.0%,e.e.值94.8%。采用气相色谱-质谱联用技术确认酵母培养液中存在中间产物5-羟基-2-己酮,并推测酵母不对称还原2,5-己二酮的反应分两步进行,首先生成中间产物(S)-5-羟基-2-己酮,而后二次加氢生成(2S,5S)-2,5-己二醇。