Mechanochemical reactions on poly (vinyl chloride)

This paper is concerned with molecular phenomena appearing during deformation of poly(vinyl chloride) under tensile stress conditions. By using indirect techniques (reactions with radical acceptors, with vinylic monomers, electron microscopy) the formation of free radicals, appearing as a consequence of splitting of chemical bonds, is evidenced. The amount of reacted radical acceptor or monomer was proved to be related to solution concentration and to the duration of mechanical stress.     

Reactivity of acrylic monomers

Summary The copolymerization of N,N-diethylacrylamide (M_l) with methyl acrylate (M₂) was investigated and reactivity ratiosr ₁= 0.41 andr ₂ = 0.52 obtained. Also the distribution of diad fractions was calculated and the results were interpreted in terms of the product of reactivity ratios. The tendency of the two monomers to alternate was explained on the basis of differences in polatities between the double bonds, this explanation being supported both by the values ofe parameter and NMR spectroscopy data. A copolymerization mechanism was suggested.With 5 figures and 2 tables     

Fixed points and powers of self-maps of -spaces

We give a new proof of the following result due to Duan: Let be any self-map of a finite connected -space. Then has a fixed point if . Our proof is based on an approach due to Steve Halperin, whereby the Lefschetz number of a self-map is expressed in terms of the eigenvalues of the induced homomorphism of rational homotopy groups. This allows us to give a considerably shorter proof which avoids most of the technicalities of the original proof.

     

Current trends in lead discovery: Are we looking for the appropriate properties?

The new drug discovery paradigm is based on high-throughputtechnologies, both with respect to synthesis and screening. Theprogression HTS hits lead series candidatedrug marketed drugappears to indicate that the probability of reaching launched status isone in a million. This has shifted the focus from good qualitycandidate drugs to good quality leads. We examined the current trendsin lead discovery by comparing MW (molecular weight), LogP(octanol/water partition coefficient, estimated by Kowwin [17])and LogSw (intrinsic water solubility, estimated by Wskowwin [18])for the following categories: 62 leads and 75 drugs [11];compounds in the development phase (I, II, III and launched), asindexed in MDDR; and compounds indexed in medicinal chemistry journals[ref. 20], categorized according to their biological activity.Comparing the distribution of the above properties, the 62 leadstructures show the lowest median with respect to MW (smaller) and LogP(less hydrophobic), and the highest median with respect to LogSw (moresoluble). By contrast, over 50% of the medicinal chemistry compoundswith activities above 1 nanomolar have MW > 425, LogP > 4.25 andLogSw < -4.75, indicating that the reported active compounds arelarger, more hydrophobic and less soluble when compared to time-testedquality leads. In the MDDR set, a progressive constraint to reduce MWand LogP, and to increase LogSw, can be observed when examining trendsin the developmental sequence: phase I, II, III and launched drugs.These trends indicate that other properties besides binding affinity,e.g., solubility and hydrophobicity, need to be considered whenchoosing the appropriate leads.     

The antioxidant response induced by Lonicera caerulaea berry extracts in animals bearing experimental solid tumors

Lonicera caerulea is a species of bush native to the Kamchatka Peninsula (Russian Far East) whose berries have been extensively studied due to their potential high antioxidant activity. The aim of our work was to investigate the in vivo effects of the antioxidant action of Lonicera caerulea berry extracts on the dynamics of experimentally-induced tumors. Our data showed that aqueous Lonicera caerulaea extracts reduced the tumor volume when administered continuously during the tumor growth and development stages, but augmented the tumor growth when the administration of extracts started three weeks before tumor grafting. Prolonged administration of Lonicera caerulaea berry extracts induced the antioxidant defense mechanism in the tumor tissues, while surprisingly amplifying the peripheral oxidative stress.     

Esterification of palmitic acid with epichlorohydrin on anion exchange resin catalyst

The esterification reaction of palmitic acid with epichlorohydrin catalyzed by an anionic macroporous resin was studied. Purolite A-500 resin proved to be a very effective catalyst in the synthesis of 3-chloro-2-hydroxypropyl palmitate. The effects of certain parameters such as speed of agitation, catalyst particle size, catalyst loading, temperature, initial molar ratio between reactants on the rate of reaction were studied. It was found that the overall rate is intrinsically kinetically controlled. The structure of synthesized ester was confirmed by FTIR and ¹H NMR analyses.      

Spectroellipsometric Characterization of Multilayer Sol-Gel Fe2O3 Films

Multilayer Fe₂O₃ films were deposited by the sol-gel method on glass substrates using three successive deposition procedures. The films were thermally treated for 1 h at 300°C.The optical and microstructural properties of these films were investigated by spectroscopic ellipsometry (SE) in the 500–1000 nm range. The optical gap was found by fitting the dispersion of the film refractive index (n) with the Wemple-DiDomenico (WDD) formula.The ellipsometric measurements showed also that the Fe₂O₃ films are anisotropic. The birefringence values (n) of the sol-gel films (0.05–0.08) are smaller than the large values of the Fe₂O₃ (which are around 0.28) but increase with the crystalization of the films. AFM mesurements showed that the films treated at 300°C start to crystallize.     

溴化四丁基铵-碘化钾-水体系中Bi(Ⅲ)与Zr(Ⅳ)、Ce(Ⅲ)、U(Ⅵ)和Mg(Ⅱ)的浮选分离

在水溶液中,Bi(Ⅲ)与溴化四丁基铵和KI形成不溶于水的三元缔合物BiI-4·TBAB+,此三元缔合物沉淀浮于盐水相上层形成界面清晰的液-固两相。当溶液中溴化四丁基铵和KI的浓度分别为5.0×10-4mol/L和3.0×10-3mol/L,pH=3时,Bi(Ⅲ)可与Zr(Ⅳ)、Ce(Ⅲ)、U(Ⅵ)和Mg(Ⅱ)定量分离,Bi(Ⅲ)的浮选率达到100%。对合成水样中Bi(Ⅲ)的分离和测定,效果良好。该方法具有选择性高,操作简便和不污染环境等特点,在微量铋的分离和富集分析中有一定的实用价值。