三苯膦-铂(Ⅱ)络合物的质子核磁共振研究(Ⅰ)

过渡金属离子的d-电子特性,使得它们的络合物可以在很多有机合成反应中起催化作用,含三苯磷配体的反式铂氢络合物就是一种稳定的、广泛应用的催化剂^[1.2.3.4.]。为此,本工作合成了反式-[PtHXL₂],L=PPh₃,X=Cl^-、Br^-、I^-、NO₃^-、NO₂^-、NCS^-六种铂络合物,并测定了其¹H-NMR谱。实验获得该络合物系列中,与铂(Ⅱ)相连的质子在高场具有较大的化学位移,即δ_H=-12~-24ppm和很大的铂-氢偶合常数即J_pt-H=900-1400Hz,以及磷氢偶合常数即J_p-H≈15Hz。此外,还研究了配体对铂-氢的¹H化学位移及铂-氢偶合常数;铂-氢键长对铂-氢的¹H化学位移的影响,并找出了一定的规律性。从而得到了络合物的顺反异构,键合异构及电子密度分布的有关信息。关于铂络合物的核磁共振研究,虽有过报道^[5.6],但配体为三苯膦的反式-[PtH(PPh³)₂]系列络合物NMR研究,尚未见报道。     

在各向异性化学位移和电四极相互作用下固体核磁共振的粉末线形的理论计算和计算机拟合

Peterson等人的随机结构模型法^[1,2](Random Strnctnre Model)只考虑了电四极相互作用对固体核磁共振的粉末线形的影响,本文在此基础上,又考虑了各向异性化学位移相互作用对粉末线形的影响,得出了相应的理论表达式P(v_r)。     

钴超分子络合物中的氢键相互作用—59Co核磁共振研究及分子模拟

钴超分子络合物[12]aneN₄[Co(CN)₆], [18]aneN₆[Co(CN)_6^], [24] aneN₈[Co(CN)₆], [16] aneN₄[Co(CN)₆], [24] aneN₆[Co(CN)₆]以及[32] aneN₈[Co(CN)₆]中, 氢键相互作用的程度与它们在水溶液中的构象密切相关, 从而引起⁵⁹Co的化学位移向高场移动, 并且其四极矩耦合作用也随构象发生了变化. 实验证明, 络合物中的氢键越强, 化学位移越向高场移动, 四极矩耦合作用也越大. 另一方面, 尺寸大的超分子具有较长的分子转动相关时间,也导致⁵⁹Co具有较短的纵向弛豫时间. 简而言之,⁵⁹Co核磁共振不仅在小分子甚至在超分子络合物中都可以用作理想的探针研究分子的次层或弱相互作用.     

取代基效应对二芳基硝酮CH=N(O)桥基1H NMR化学位移的影响

合成一系列取代二芳基硝酮XArCH=N（O）ArY化合物,测定其核磁共振氢谱（¹H NMR）,指认出桥基CH=N（O）上质子的化学位移δH[CH=N（O）],定量研究取代基效应对δH[CH=N（O）]的影响.得到一个4参数定量方程,标准偏差（S）为0.020,较好地表达了δH[CH=N（O）]的变化规律.结果表明,该类化合物的δH[CH=N（O）]主要受4个因素影响：X基团的场/诱导效应[σ_F（X）];Y基团的共轭效应[σ_R（X）];基团X和Y之间的特殊交叉作用（Δσ²）;以及基团X和O^-之间的特殊交叉作用[Δσ²_（X-O^-）].其中,Δσ²_（X-O^-）对δ_{H[CH=N（O）]}变化的贡献超过70%.通过δH[CH=N（O）]与二芳基希夫碱XArCH=NArY桥基CH=N上质子化学位移的δH（CH=N）比较发现,这两类化合物桥基上质子的化学位移之间没有良好的线性关系.因而,在应用NMR谱图解析有机化合物分子结构时,不能简单地用δH（CH=N）的变化去类比δ_{H[CH=N（O）]}的变化.     

8种苯并[h]喹啉的13C NMR归属

报道了8种新的苯并[h]喹啉的¹³C NMR谱.应用¹³C NMR等谱确定了这8种新化合物的分子结构,并对全部谱峰进行了归属,初步探讨了分子结构对¹³C NMR化学位移的影响.     

19F NMR化学位移经验公式的影响因素

化学位移是核磁共振技术的重要参数,目前对¹H NMR、¹³C NMR已提出一系列估算化学位移的经验公式,但¹⁹F NMR化学位移规律研究报道则较少,以δ=B+∑△i+C化学位移通式为基础,分析屏蔽常数对化学位移的作用,并针对¹⁹F原子,分析了氟的电子云密度、立体效应、溶剂效应、氢键、标准、浓度和温度等影响因素,对¹⁹F NMR化学位移经验公式的提出提供理论依据。     

用23Na NMR研究竹红菌乙素光敏损伤对鼠腹水肝癌细胞Na+通透性的影响

用²³Na NMR技术并借助于水溶性位移试剂Dy(PPPi)₂^7-研究了新型光敏剂-竹红菌乙素光敏损伤对鼠腹水肝癌细胞Na⁺通透性的影响。实验结果表明:在乙素光敏作用下,细胞内Na⁺浓度随曝光时间的延长和乙素浓度增高而增加。同时观察到细胞外²³Na_out NMR峰的化学位移(δ值)随光照时间增加而向低场位移。分析表明:化学位移的改变与细胞膜损伤引起细胞内K⁺泄漏和K⁺、Na⁺竞争位移试剂有关。因此,化学位移的改变也可作为光敏损伤的指标。本文还就Na⁺平衡失调与细胞死亡之间的关系进行了讨论。     

西洋参皂甙的核磁共振波谱研究Ⅰ.西洋参叶中Ocotillol型皂甙的结构分析

本文用常规一维¹H、¹³C核磁共振波谱和远程异核化学位移相关谱。异核化学位移相关谱和同核化学位移相关谱技术研究了西洋参叶中首次分离出的一种Ocotillol型皂甙,确认了化学结构,并对其¹³C、¹H NMR谱线进行了归属。     

Ag离子注入非晶SiO2的光学吸收、拉曼谱和透射电镜研究

能量为200keV的Ag离子，以1×10¹⁶，5×10¹⁶，1×10¹⁷ cm^-2的剂量分别注入到非晶SiO₂玻璃，光学吸收谱显示：注入剂量为1×10¹⁶ cm^-2的样品的光吸收谱为洛伦兹曲线，与Mie理论模拟的曲线形状一致；注入剂量较大的5×10¹⁶，1×10¹⁷ cm^-2的谱线共振吸收增强，峰位红移并出现伴峰. 透射电镜观察分析表明，注入剂量不同的样品中形成的纳米颗粒的大小、形状、分布都不同，注入剂量较大的还会产生明显的表面溅射效应，这些因素都会影响共振吸收的峰形、峰位和峰强. 当注入剂量达到1×10¹⁷ cm^-2时，Ag纳米颗粒内部可能还形成了杂质团簇. 关键词： 离子注入 纳米颗粒 共振吸收 红移     

含甲氧基二氮杂萘酮结构类双酚单体的波谱表征

用核磁共振谱和质谱表征了4-（3-甲氧基-4-羟基苯基）-2,3-二氮杂萘-1-酮 (OO-DHPZ) ,对其结构的¹H和¹³Ｃ NMR谱的化学位移作了全归属.     

Imaging of multiphase fluid saturation within a porous material via sodium NMR

We present in this paper a method to monitor multiphase fluid core saturation through measurement of the sodium NMR signal. In a rock core saturated with water and oil, sodium will be present only in the water phase, and therefore can be used to separate the two fluids. Two dimensional sodium images were taken to monitor the movement of brine into oil saturated rock cores. The measured fluid exchange agrees well with expected behavior from traditional core analysis methods. Indications of damage to the rock structure can be seen from the patterns of fluid imbibition.     

光学玻璃研抛用磁流变液的研究

利用智能材料之一的磁流变液 (MRfluids)作为加工工具对光学玻璃进行了精密抛光加工。讨论了适用于光学玻璃抛光的磁流变液的配制机理及磁流变液对光学玻璃抛光效果的影响因素。针对光学玻璃磁流变的抛光原理和特点 ,开发配制了适合于光学玻璃加工用的磁流变液 ,并用该磁流变液对光学玻璃进行了实验加工。结果表明 ,最终得到的光学玻璃表面经过AFM测试 ,得到Ra =1 0 1 5nm。     

The Compressible Viscous Surface-Internal Wave Problem: Stability and Vanishing Surface Tension Limit

This paper concerns the dynamics of two layers of compressible, barotropic, viscous fluid lying atop one another. The lower fluid is bounded below by a rigid bottom, and the upper fluid is bounded above by a trivial fluid of constant pressure. This is a free boundary problem: the interfaces between the fluids and above the upper fluid are free to move. The fluids are acted on by gravity in the bulk, and at the free interfaces we consider both the case of surface tension and the case of no surface forces. We establish a sharp nonlinear global-in-time stability criterion and give the explicit decay rates to the equilibrium. When the upper fluid is heavier than the lower fluid along the equilibrium interface, we characterize the set of surface tension values in which the equilibrium is nonlinearly stable. Remarkably, this set is non-empty, i.e., sufficiently large surface tension can prevent the onset of the Rayleigh-Taylor instability. When the lower fluid is heavier than the upper fluid, we show that the equilibrium is stable for all non-negative surface tensions and we establish the zero surface tension limit.     

油基钻井液条件下油层的NMR判识方法

油基钻井液具有润滑性好、抑制性强等特点,有利于井壁稳定和油气层保护,在非常规油气水平井及深井、超深井中广泛使用．但是,油基钻井液具有较强的荧光背景和全烃基值,岩屑难以洗出本色,地层油与钻井液的基础油融合,给油层的识别和评价带来了严重影响．为此,创新采用高分辨率低场核磁共振技术随钻监测钻井液含油率及含油性的变化．室内实验结果表明,油基钻井液不同于混油钻井液,后者属于水包油体系,钻遇油层后,在钻井液T₂谱上出现新峰;而前者属于油包水体系,钻遇油层后,在钻井液T₂谱上不出现新峰,但可通过含油性的变化识别重质油层,通过含油率的变化识别轻-中质油层,并在S903H井全油基钻井液及极端的地质条件下取得了较好的应用效果,证明了钻井液核磁共振是油基钻井液条件下一项有效的油层识别技术．     

Molecular dynamics simulation of composite nanochannels as nanopumps driven by symmetric temperature gradients

In this Letter, we propose a composite nanochannel system, where half of the channel is of low surface energy, while the other half has a relatively high surface energy. Molecular dynamics simulations show that fluids in such channels can be continuously driven by a symmetric temperature gradient. In the low surface energy part, the fluid moves from high to low temperature, while the fluid migrates from low to high temperature in the high surface energy part. The mechanisms that govern the flow are explained and the conditions required to guarantee the flow and the possible applications are discussed.     

Hydrodynamics and time correlation functions for cellular automata

Hydrodynamic excitations in lattice gas cellular automata are described in terms of equilibrium time correlation functions for the local conserved variables. For large space and time scales the linearized hydrodynamic equations are obtained to Navier-Stokes order. Exact expressions for the associated susceptibilities and transport coefficients are identified in terms of correlation functions. The general form of the time correlation functions for conserved densities in the hydrodynamic limit is given and illustrated by some examples suitable for comparison with computer simulation. The transport coefficients are related to time correlation functions for the conserved fluxes in a way analogous to the Green-Kubo expressions for continuous fluids. The general results are applied for a one-component fluid and several types of binary diffusion. Also discussed are the effects of unphysical slow modes such as staggered particle or momentum densities.     

Sonic velocity in holographic fluids and its applications

Gravity/fluid correspondence acts as an important tool in investigating the strongly correlated fluids.We carefully investigate the holographic fluids at the finite cutoff surface by considering different boundary conditions in the scenario of gravity/fluid correspondence. We find that the sonic velocity of the boundary fluids at the finite cutoff surface is critical in clarifying the superficial similarity between the bulk viscosity and perturbation of the pressure for the holographic fluid, where we set a special boundary condition at the finite cutoff surface to explicitly express this superficial similarity. Moreover, we further take the sonic velocity into account to investigate a case with a more general boundary condition. In this more genaral case, although two parameters in the first order stress tensor of holographic fluid cannot be fixed, one can still extract the information about the transport coefficients by considering the sonic velocity seriously.     

Stability of fluid flow past a membrane

The stability of the flow of a fluid past a solid membrane of infinitesimal thickness is investigated using a linear stability analysis. The system consists of two fluids of thicknesses R and H R and bounded by rigid walls moving with velocities and , and separated by a membrane of infinitesimal thickness which is flat in the unperturbed state. The fluids are described by the Navier-Stokes equations, while the constitutive equation for the membrane incorporates the surface tension, and the effect of curvature elasticity is also examined for a membrane with no surface tension. The stability of the system depends on the dimensionless strain rates and in the two fluids, which are defined as and for a membrane with surface tension , and and for a membrane with zero surface tension and curvature elasticity K. In the absence of fluid inertia, the perturbations are always stable. In the limit , the decay rate of the perturbations is O(k ³ ) smaller than the frequency of the fluctuations. The effect of fluid inertia in this limit is incorporated using a small wave number asymptotic analysis, and it is found that there is a correction of smaller than the leading order frequency due to inertial effects. This correction causes long wave fluctuations to be unstable for certain values of the ratio of strain rates and ratio of thicknesses H. The stability of the system at finite Reynolds number was calculated using numerical techniques for the case where the strain rate in one of the fluids is zero. The stability depends on the Reynolds number for the fluid with the non-zero strain rate, and the parameter , where is the surface tension of the membrane. It is found that the Reynolds number for the transition from stable to unstable modes, , first increases with , undergoes a turning point and a further increase in the results in a decrease in . This indicates that there are unstable perturbations only in a finite domain in the plane, and perturbations are always stable outside this domain. Received: 29 May 1997 / Revised: 9 October 1997 / Accepted: 26 November 1997