N-乙基壳聚糖的针状结晶

在N 乙基壳聚糖的甲酸溶液浇铸膜中观察到高分子少有的针状晶体 .从球晶经后结晶得到的针状晶体为长条矩形 ,典型尺寸为～ 5 0 μm× 2～ 5 μm× 1～ 2 μm ,高分子链平行于晶体长轴 .针状晶体首先出现在球晶的核心处 ,继而出现在球晶微纤每个树枝状分叉处 ,最后才遍布球晶各处 .针状晶体可以看成是高分子伸直链结晶的一种 .浇铸膜吸潮实际上形成了超浓溶液 (浓度 >80wt% ) ,从而分子链可以运动而后结晶成针状晶体     

聚偏氟乙烯取向薄膜的结晶形态

本文用小角激光散射法研究了聚偏氟乙烯薄膜在拉伸取向过程中晶体形态及结构的变化。拉伸使球晶形变为椭球,同时伴随着局部熔融与重结晶过程,散射图案由原来的四叶瓣发展为八叶瓣。红外测量及X-射线衍射分析表明,拉伸引起分子链构象改变,使晶型发生了转变。     

强红外激光场作用下固体甲酸铀酰的光解反应研究

关于在强红外激光场作用下多原子分子在气相介质中的多光子吸收(MPA)和解离(MPD)巳经进行过大量的研究.但是,在固相介质中这方面的研究尚属少见.迄今为止,只有Ambartzumyan等报道的TEA-CO_2激光使冻结在隔离基体上(isolated-matrix)的SF_6分子发生选择性的光解反应,以及Karlov等用类似的方法对BCl_3分子的光解反应研究.最近我们研究了一系列固体甲酸铀酰化合物的红外光谱,发现其中UO_2~(2+)基团的反对称振动频率v_a均在912—952cm~(-1)范围,与TEA-CO_2激光支线频率相符.本文研究TEA-CO_2激光作用下,单结晶水甲酸铀酰和碱式甲酸铀酰化合物发生光解反应的共同特性,并根据实验结果,初步提出了该光解反应的可能机理,即在强红外激光场下,这些化合物可以吸收多个光子而达到具有较高能量的振动激发态,在具有还原性的甲酸根离子作用下发生光解反应.     

青蒿素和类似过氧化合物的过氧基团振动频率的确认

青蒿素(arteannuin)是中药青蒿中抗疟的有效成分,它是一种含有过氧基团的新型倍半萜内酯,在红外光谱中的强吸收谱带831,881,1115cm~(-1)为过氧基团的特征振动频率.Philpotts等对870cm~(-1)附近的强红外吸收谱带为过氧基团振动频率曾提出疑点,特别是叔过氧基团化合物,它在800～900cm~(-1)范围内产生的强谱带归属于一C—O—基团的振动.而且过氧基团两侧取代基结构不同也将影响谱带的改变,拉电子基团会导致振动频率的波数增大,而推电子基团则使频率向低波数位移.本文用激光拉曼光谱并辅以红外光谱进行研究,比较了700～900cm~(-1)各谱带的谱型,相对强度和退偏振比等数据,并排除了倍半萜环振     

胆甾相液晶螺旋方向的光调控

光响应胆甾相液晶是一类在光刺激下通过改变液晶分子排列调控光学特性的智能“软”光子晶体材料,其分子自组装形成周期性螺旋结构,选择性地反射与自身螺旋方向相同的圆偏振光。近年来,利用光刺激诱导胆甾相液晶在左手螺旋和右手螺旋之间发生螺旋翻转的研究引起了广泛关注。胆甾相液晶的螺旋翻转能够改变反射光的圆偏振特性,有望拓展光子晶体材料在可调节滤光器、防伪与加密技术、圆偏振激光器、三维显示等领域的潜在应用。本综述重点关注光响应胆甾相液晶螺旋翻转的研究进展;总结了调控胆甾相液晶螺旋方向的两种主要策略：(1)直接引入螺旋性可逆转变的光响应手性分子开关,(2)利用光响应手性分子开关和与之螺旋性相反的手性掺杂剂之间的手性竞争;分析了分子空间构型转变对调控螺旋翻转程度的影响;并讨论了不同材料体系面临的挑战以及未来的发展方向。     

在低频振动场中注塑成型iPP试样的结构与性能研究

利用自行研制的低频振动注塑成型装置进行等规聚丙烯(iPP)试样的结构与性能研究.实验中对常规注射和振动注射成型的试样力学性能和微观形态进行了对比实验.采用低频振动注塑成型工艺实现了IPP试样的自增强,在190℃下进行注射,强度由常规试样的41.3 MPa最大提高到振动试样的48.4 MPa(振幅PA=59.4 MPa,振频FR=0.7 Hz),强度提高了17.2%;SEM显示常规试样芯层结构主要由球晶构成,振动注射使球晶在流动方向上变形、取向,晶粒尺寸得到细化;DSC表明振动注射促进熔融峰向高温漂移,晶体结晶更加完善,结晶度最大提高了12.1%;WAXD显示低频大振幅振动注塑有利于γ晶型的生成,γ晶型有利于试样实现自增强.     

从Badger和Gordy经验公式定性探讨红外光谱(IR)与分子结构的关系

应用分子结构理论将诱导、共轭、氢键、环、场等效应转换为对振动键的价键数。电负性、核间距(N、x、d)的影响,从而将多原子分子简化为双原子分子模式。应用Badger-Cordy经验公式(1)系统分析了由C,H,O,N组成的多原子分子中各类键伸缩振动IR特征吸收峰的区域范围。(2)定性地阐明了分子结构与红外光谱的关系,探索了解析红外光谱的简易方法。     

硅酸镓镧族非线性光学晶体

中红外非线性光学晶体可以实现中红外激光频率转换、拓展激光波长,在民用和军用领域中有至关重要的应用价值。其中,硅酸镓镧族晶体具有透过范围宽、激光损伤阈值高、晶体质量好等优势,引起了国内外同行的广泛关注。在这篇综述中,我们基于现有的实验数据,研究和分析了三种重要的硅酸镓镧族晶体La_3Ga_5Si O_(14)(LGS)、La_3Ga_(5.5)Nb_(0.5)O_(14)(LGN)、La_3Ga_(5.5)Ta_(0.5)O_(14)(LGT)的综合性能,详细总结了它们在电光调Q开关和中红外光参量振荡以及差频激光输出方面的应用。最后,本文还讨论了今后硅酸镓镧族中红外非线性光学晶体的重点发展方向。     

红外激光泵浦掺稀土固体材料直接输出蓝绿激光

介绍利用红外或红色激光泵浦掺稀土固体材料直接输出蓝绿激光的途径和研究进展：较为详细地介绍了红外激光泵浦掺稀土非线性激光晶体通过自变频过程，以及红外激光泵浦掺稀土固体块状，光纤和微珠材料通过频率上转换过程实现蓝绿激光输出的研究结果，并与其它输出蓝绿波段激光的器件和方法进行比较，着重对比分析了YAl3(BO3)4,GdAl3(BO3)4,Ca4YO(BO3)3和Ca4GdO(BO3)等典型的非线性激光基质晶体以及氟化物光纤等典型的上转换激光介质材料，对该领域目前面临的主要问题和发展方向进行了探讨。     

分子角动量定向布居的制备探测和它的碰撞弛豫

利用受激Raman泵浦,使线性分子C2H2选择性地制备振动态角动量定向布居参数A0(1)达到0.7～0.8。并测定了角动量定向布居碰撞诱导的弛豫速率常数。采用园偏振的紫外激光诱导荧光方法,可表征分子角动量定向布居的制备和它的碰撞弛豫过程。     

HEPT类化合物的QSAR研究

为定量结构／活性相关性研究提取了量子化学参数,拓扑指数Am,分子连接性指数^mxt及疏水性常数,同时应用正交变换和最佳变量子集算法（Leaps-and-Bonds)进行了变量压缩和选择,进而实施了多元回归分析,并由此结果进行了HEPT类化合物（1－[(2-hydroxyethoxy)methyl]-6-(phenylthio)-thymine derivatives)的结构／活性关系的理论解释,进行了人工神经网络法对于该类化合物的活性预测,其结构明显好于多元回归法。     

Effect of the pH of the medium on the chemical shifts in the PMR spectra and on the distribution of the π-electron density

The dependence of the chemical shifts of the ring protons on the pH of the medium for a number of 4-hydroxyquinoline derivatives was studied by means of PMR spectroscopy. The dipolar and uncharged hydroxy forms exist in equilibrium in aqueous solutions. The effect of intramolecular hydrogen bonding on the character of the dependence of the chemical shift on the pH of the medium in the case of 3-piperidinomethyl-4-hydroxyisoquinoline was investigated. The possibility of the separate protonation of the ring nitrogen and the side-chain nitrogen in 3-piperidinomethyl-4-hydroxyisoquinoline was established. The distribution of the -electron density in 4-hydroxyisoquinoline is in good agreement with its chemical behavior.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1546–1549, November, 1971     

Effect of the pH of the medium on the chemical shifts in the PMR spectra and on the distribution of the π-electron density

The dependence of the chemical shift of the ring protons on the pH of the medium for a number of 3-hydroxyquinoline derivatives was studied by PMR spectroscopy. The regions of ionization of the molecules, which correspond to the ranges of acidic, neutral, and alkaline media, were found. In D₂O, 3-hydroxyquinoline is present only in the uncharged hydroxy form. The presence of intramolecular hydrogen bonding in 4-dimethylaminomethyl-3-hydroxyquinoline has a substantial effect on the character of the dependence of the chemical shift on the pH of the medium; the existence of separate protonation of the nitrogen atoms of the ring and the side chain of 4-dimethylaminomethyl-3-hydroxyquinoline was established. The distribution of the -electron density in the 3-hydroxyquinoline molecule is in good agreement with its chemical behavior during electrophilic substitution.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1540–1545, November, 1971.     

液滴荧光传感与计算机联用技术在微量分析中的应用

通过在LS55型荧光-磷光-发光分光光度计上加装液滴产生及调节附件,采用计算机采集与分析处理数据,成功地研制了双通道液滴光化学传感装置.利用葡聚糖凝胶对复合维生素B中不同组分的选择性吸附来达到分离与同时检测的目的,并将其用于复合维生素B药片的分析,取得了满意的结果.     

On the theory underlying the Car-Parrinello method and the role of the fictitious mass parameter

The theory underlying the Car-Parrinello extended-Lagrangian approach to ab initio molecular dynamics (CPMD) is reviewed and reexamined using "heavy" ice as a test system. It is emphasized that the adiabatic decoupling in CPMD is not a decoupling of electronic orbitals from the ions but only a decoupling of a subset of the orbital vibrational modes from the rest of the necessarily coupled system of orbitals and ions. Recent work [J. Chem. Phys. 116, 14 (2002)] has pointed out that, due to the orbital-ion coupling that remains once adiabatic decoupling has been achieved, a large value of the fictitious mass mu can lead to systematic errors in the computed forces in CPMD. These errors are further investigated in the present work with a focus on those parts of these errors that are not corrected simply by rescaling the masses of the ions. It is suggested that any comparison of the efficiencies of Born-Oppenheimer molecular dynamics (BOMD) and CPMD should be performed at a similar level of accuracy. If accuracy is judged according to the average magnitude of the systematic errors in the computed forces, the efficiency of BOMD compares more favorably to that of CPMD than previous comparisons have suggested.