Synthesis of monodisperse spiro-bridged ladder-type oligo-p-phenylenes

Monodisperse spiro-bridged ladder-type oligo-p-phenylenes, which have very rigid backbones, exhibited intensive emissions with very small Stocks shifts, displayed very good color stability upon thermo-oxidation, and were synthesized by Suzuki cross-coupling, oxidation, and BF3.ether-catalyzed cyclization reactions.     

Calculations of Freezing Point Depression,Boiling Point Elevation,Vapor Pressure and Enthalpies of Vaporization of Electrolyte Solutions by a Modified Three-Characteristic Parameter Correlation Model

A method was proposed for calculating the thermodynamic properties, freezing point depression, boiling point elevation, vapor pressure and enthalpy of vaporization for single solute electrolyte solutions, including aqueous and nonaqueous solutions, based on a modified three-characteristic-parameter correlation model. When compared with the corresponding literature values, the calculated results show that this method gives a very good approximation, especially for 1-1 electrolytes. Although the method is not very suitable for some solutions with very high ionic strength, it is still a very useful technique when experimental data is scarce.     

中成药质量稳定性的原子吸收光谱鉴别分析

对全国各地用原子吸收光谱仪测定10批次大活络丸中12种无机元素及建立的指纹图谱,尝试用成分数据分析法、向量相似法和模糊聚类法建立全国无机元素的指纹图谱和中药质量控制标准方法,获得较满意的结果。研究表明,建立无机元素指纹图谱控制中成药中无机元素的质量,具有很好的实用性和可操作性,用于全国各地不同厂家生产的大活络丸无机元素的质量控制是切实可行的。     

Initial guess of the solution of dynamic optimization of chemical processes

Numerical methods and software packages for solving dynamic optimization or optimal control problems require a suitable initial estimation of the solution. This paper focuses on problems that arise in chemical processes described by complex dynamics. We present a very simple method, based on Pontryagin’s Minimum Principle, to obtain an initial guess for the solution. Our method presents numerous advantages: it is very easy to programme, it allows a wide range of problems to be addressed, the computation time is very short, the initial guess is very close to the solution and is attracted to a global minimum.     

Determination of Arsenic in Antimony Trioxide by Hydride Generation Atomic Fluorescence Spectrometer

Antimony trioxide is a very useful industrial product. There is a method of GB1467-78 to determine the impure Arsenic in it. It's very difficult to extract many times. We know that the large amount of Antimony interferes with the determination of Arsenic very seriously. Because of the different decomposition rate between hydrogen arsenide and antimonous hydride in the solution of KMn04, we can let the products of hydrogen arsenide and antimonous hydride pass through the solution of KMn04 to eliminate the antimony's interference mostly. This method is very fast and easy.     

Rapid screening for chiral separations by short-end injection capillary electrophoresis using highly sulfated cyclodextrins as chiral selectors

Two series of amino acid derivatives and phenylamines were used to evaluate the potential of highly sulfated cyclodextrins (HS-CDs) for the screening for chiral separations by capillary electrophoresis (CE). HS-CDs showed to be very versatile and to exhibit very high enantioselectivity. The use of short-end injection allowed to reduce dramatically the analysis time. From the results obtained, a scheme for the rapid screening of enantiomeric molecules was developed and applied to various chiral drugs. Results are very satisfying as almost all compounds (62 out of 67) could be baseline-resolved. Usually, less than three experiments were necessary to obtain very good separation.     

PMMA—b—PTHF／PTHF共混体系中共聚物结晶能力的增强

结晶嵌段共聚物具有一般均聚物所没有的许多特殊结晶行为。虽然,人们很早就已开始对聚氧化乙烯/聚苯乙烯诸类嵌段共聚物的结晶行为进行研究,但对这类体系相分离规律及结晶行为的认识仍很不够。这主要是因为已研究的体系非常有限,此外,大都为对体系非平衡态结构的研究。所以,尽管Whitmore和Noolandi最近提出了结晶嵌段共聚物及其共混物的平衡形态理论,但缺乏实验数据与之比较。     

New Phenomena in Radical Polymerization

G. Smets, Louvain, Belqium: Gentlemen, as Professor Vogl already said, Professor Zubov willpresent today the paper which should have been presented by our colleague, Professor Kabanov. Each of us knows very well the very active research directed by Professor Kabanov at the Lomonosov University of Moscow. We do regret very sincerely his absence. May I now ask, please, Professor Zubov to take the chair.     

Asymmetric multicomponent copper catalyzed synthesis of chiral propargylamines

A three-component stereoselective reaction between an aldehyde, an amine and phenylacetylene to afford optically active propargyl amines in good yields was developed. The reaction is catalysed by copper complexes of enantiomerically pure bis-imines. The best results were obtained with imines readily prepared in very high yields from the commercially available binaphtyl diamine.

A very simple experimental procedure at room temperature allowed to obtain optically active propargyl amines in very good yields and enantioselectivity up to 75%. The extremely simple methodology and the mild reaction conditions, as well as the possibility of a modular approach for developing new and more efficient bis-imine-based chiral ligands make the present methodology very attractive.     

Studies on structurally simple αβ-butenolides. IV. behaviour of protoanemonin as electrophile towards alcohols and thiols

Protoanemonin, reacts in different ways with thiolate and alkoxide anions. Thus, while the very soft nucleophile benzenethiolate attacks exclusively the olefinic carbons of 1, alkoxides always attack the carbonyl group in the first step of the reaction. In intermediate cases, when neither very hard nor very soft nucleophiles are used, regioselectivity is not observed. Mechanisms are discussed to explain this differential reactivity.     

Determination of uranium in presence of plutonium using differential spectrophotometry

The use of beams of heavy ions such as carbon, neon and argon for radiation therapy has the advantage that they have a very sharp Bragg maximum. When the Bragg peak coincide with the tumour location, it is possible to deposit the bulk of the energy of the ion in the region occupied by the malignancy. However, the concentration of ions and free radicals will be very high in the Bragg peak region which has not received the attention it deserves. So mutual recombination of these species will be very high. It is therefore necessary to assess the extent of these radical-radical recombinations at very high LET values. Spur diffusion model calculations have been made for high energy argon ions using water as a medium. For comparison, calculations have been done for proton tracks. It has been shown that in the Bragg peak region of argon ions even very high concentrations of scavengers have very little effect on radical-radical interactions. The implication is that when LET values are very high, practically all the radicals undegro recombination with each other. In order to explain the observed lethality of high LET radiation, it is suggested that the hydrogen peroxide formed also contribute to the killing of cells. In addition, the decomposition of H₂O₂ will contribute oxygen. This may be one of the reasons why high LET radiation shows strong lethality to hypoxic cells.     

交流示波极谱滴定的研究(ⅩⅢ)——有机碱及有机酸盐类药物在水溶液中的中和滴定

本文用交流示波极谱中和滴定技术,在水溶液中直接滴定有机碱和有机酸的盐类药物,简便、快速、准确。     

利用水引发固相反应方法合成氮化铝纳米粉

以AlCl3和Li3N为前驱物,利用过量Li3N与水反应大量放热现象,引发两种前驱物之间的固相反应合成了AlN纳米粉．X射线衍射分析、红外吸收光谱、透射电子显微镜以及X射线光电子能谱测试结果表明,利用这种新的合成方法制备的氮化铝主要是六方相,而且颗粒细小．另外,这种方法反应迅速、操作过程简便,有利于降低制备成本和扩大制备规模．     

一种4β-氨基鬼臼毒素的合成新方法

报道了一种在室温条件下和在四氢呋喃水溶液中用Zn/HCO2NH4还原4β-叠氮鬼臼毒素制备抗癌药物中间体4β-氨基鬼臼毒素的新方法. 此方法具有产率高(96%)、不需要用贵金属(如钯或钐)催化和无水条件、操作方便等优点. 最佳的反应条件为: 底物、Zn和HCO2NH4的物质的量之比为1∶2∶4, 反应溶剂为85%四氢呋喃水溶液, 反应时间为5 h.     

Capillary columns with very thick coatings

It has become common practice with capillary columns to call film thicknesses of 0.1 – 0.3 μm regular or standard, whereas 0.3 – 1.0 μm is considered to denote thick films. Consequently, films with thickness beyond 1μm (we have explored the range up to 8.0 μm) may be termed very thick. Increasing film thickness, at least to about 5 μm, brings important additionl advantages primarily in terms of loading capacity. Columns with very thick coatings may replace the traditional SCOT columns thanks to at least equivalent loading capacity combined with higher separation efficiency, and better stability characteristics. Additional advantages are increased retention, essential for the analysis of very volatile substances, and increased elution temperature, providing a basis for direct water injection. We observe that TZ (the separation number) drops to roughly 50% when the film thickness is increased by a factor of 300 from 0.025 to 8.0 μm, provided TZ is measured with a standard flow of hydrogen. The reduction is only 30% when the thick-film colums are run with individual optimization with nitrogen as a carrier gas. In contrast to standard columns, very thickly coated columns show slightly increased separation efficiency with nitrogen at drastically reduced flow rate. The HETP increases very slightly in the indicated range of flim thickness. This contradicts widespread theoretical expectations, which probably account for the fact that very thick coatings have so far been neglected. Since the preparation of very thick coatings involves some deviations from the standard procedure, complete and detailed instructions are given.     

Signal-pair correlation analysis of single-molecule trajectories

There you go: How to get kinetic information from trajectories of single biomolecules? A method based on correlating signal ranges (here for a three-state DNA hairpin with F = folded, I = intermediate, and U = unfolded state) is reported and shows how to get the kinetic scheme and the corresponding rates, even for states with low occupancy or very short lifetime, states which overlap because of noise, and systems with very similar or very different rates.     

Electron microscope study of low molecular weight fractions of linear polyethylene

Electron microscope studies are reported for crystals of linear polyethylene formed in dilute solution from very sharp low molecular weight fractions. Emphasis is placed on molecular weights in the range of 1.1 × 10³ to 15.1 × 10³. The dependence of the crystal habit on the crystallization temperature is very similar to that which has been found for the higher molecular weight species. However, the demarcation temperature for the crystallization of the different morphological forms is very molecular weight-dependent. The conditions under which interfacial dislocation networks form can be clearly defined. The molecular weight must be less than 3000, so that these structures are restricted to very small chain lengths. However, not all crystallization conditions within this allowable molecular weight range yield such dislocations. The formation of interfacial dislocation networks are shown to occur only under very special circumstances. Their occurrence clearly cannot be offered as evidence, as has been done in the past, for a regular, chain-folded interfacial structure.     

A novel protocol for the preparation of uniform polymer microspheres with high yields through step polymerization of isophorone diisocyanate

Uniform polymer microspheres with neat surface are of high interests. Precipitation polymerization of vinylic monomers remains a very limited process owing to very low monomer concentration allowed. Here, a fully novel protocol for the production of uniform polymeric microspheres is presented. Using one single monomer, isophorone diisocyanate, highly monodisperse polyurea microspheres were achieved with very high yield in a very short time period via precipitation polymerization in water–acetone mixed solvent. Results demonstrated that the ratio of water–acetone and polymerization temperature played important roles in the process. The size of the microspheres was readily adjustable by varying monomer concentration, water/acetone ratio or polymerization temperature. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

The binding of 4He and 3He to a hydrogen molecule: a computational study for pH2 and oH2

One bound state for the very weakly interacting complex of H(2) with one He atom is computed using a recently obtained, very accurate potential energy surface [A. I. Boothroyd and P. G. Martin, J. Chem. Phys. 119, 3187 (2003)] and employing a discrete variable representation expansion. The spatial features of this very diffused, "halo" state are analyzed and discussed for various isotopic variants of the title system.     

Conformational analysis by energy embedding

The distance geometry approach to conformational calculation has been shown to be very effective at producing large molecular structures satisfying many given, long-range constraints on the interatomic distances. I now present a significant extension of the method that handles strictly geometric constraints as well as before while also locating conformers of very low energy. The main feature of the algorithm is a projection of the molecule from a low energy conformation in a high dimensional space to three dimensions in such a way as to perturb the energy as little as possible. Tests of the method on very small systems with simple energy functions completely explored by independent means show that the global minimum of energy is sometimes attained. In every case the final energy is very low, and geometric constraints are completely satisfied.