Infra-red and electronic absorption spectra of 2-bromopyrimidine

The electronic absorption spectrum of 2-bromopyrimidine in the u.v. region has been recorded in vapour phase and in solution phase in different solvents. Only one system has been observed in vapour phase and it has been identified as π* ← n transition. In solution phase two systems have been identified. The system on the longer wavelength side has been identified as corresponding to the one observed in vapour phase while the other one has been assigned to a π* ← π transition. The infrared spectrum of this molecule has also been recorded and analysed. Help of these i.r. data has been taken to analyse the u.v. spectrum of 2-bromopyrimidine, considering the molecule as belonging to C_2υ point group.     

Radioimmunoassay of human placental lactogen

A sensitive and specific radioimmunossay procedure (RIA) has been developed for the measurement of Human Placental Lactogen (HPL). Pure HPL has been labelled with¹²⁵I and a specific activity of 100 μCi/μgm of HPL has been attained. Dextran-coated charcoal has been employed to separate the bound from the free hormone in radioimmuno-assay. The sensitivity of this technique has been found to be 0.2 ng of HPL. Intraassay and inter assay variations have been found to be less than 10%. This procedure has been adopted to establish the normal range of HPL in pregnant women at different periods of gestation, and to evaluate risk pregnancies.     

The influence of the concentration and size of silver nanoparticles on the conductivity of ring-shaped deposits resulting from evaporation of colloidal solution droplets

The conductivity of ring-shaped deposits formed at the periphery of evaporating droplets of silver nanoparticle colloidal solutions has been studied. The dependence of the resistance of the ring-shaped deposits on nanoparticle size has been shown to exhibit a percolation transition. The specific conductivity of the deposits has been estimated in relation to their geometric shapes. The conductivity has been established to nonmonotonically depend on nanoparticle sizes. It has been noted that, in rather strong fields, the conductivity of the composite layers dramatically increases after some induction period. The X-ray spectra of silver have been revealed to alter for samples the conductivity of which has increased under the action of an external electric field.     

Effect of chemical structure and crystallinity on sorption,diffusion and chemical stability of polyurethaneacetals

The diffusion of water in non-isocyanate polyurethaneacetals (PUA) of various kinds and compositions has been studied. The direct relationship between the composition of polymers, their degree of crystallinity, morphology and diffusional characteristics has been demonstrated. It has been shown that by changing the polymer composition one can obtain hydrated polymer systems of every type, hydrophobic, hydrophilic and moderately hydrophilic. The kinetics of hydrolytic degradation of PUA in HCl solutions (pH = 0·1) between 20 and 75°C has been investigated. Hydrolysis of acetal bonds has been found to occur in the amorphous phase of a polymer sample, which is mostly formed by the fragments of urethane glycol.The influence of morphology on PUA diffusional characteristics and their stability to hydrolysis has been determined.It has been shown that the physico-chemical properties of PUA can be regulated without the introduction of new compounds.     

Hydrogen and higher shell contributions in Zn2+, Ni2+, and Co2+ aqueous solutions: an X-ray absorption fine structure and molecular dynamics study

A detailed investigation of the hydration structure of Zn2+, Ni2+, and Co2+ in water solutions has been carried out combining X-ray absorption fine structure (EXAFS) spectroscopy and Molecular Dynamics (MD) simulations. The first quantitative analysis of EXAFS from hydrogen atoms in 3d transition metal ions in aqueous solutions has been carried out and the ion-hydrogen interactions have been found to provide a detectable contribution to the EXAFS spectra. An accurate determination of the structural parameters associated with the first hydration shell has been performed and compared with previous experimental results. No evidence of significant contributions from the second hydration shell to the EXAFS signal has been found for these solutions, while the inclusion of the hydrogen signal has been found to be important in performing a quantitative analysis of the experimental data. The high-frequency contribution present in the EXAFS spectra has been found to be due to multiple scattering (MS) effects inside the ion-oxygen first coordination shell. MD has been used to generate three-body distribution functions from which a reliable analysis of the MS contributions to the EXAFS spectra of these systems has been carried out.     

超声幅照下ABS塑料表面的粗化研究

由于外层镀有金属的塑料制品兼有塑料及金属材料的优点,因而是一类具有广泛用途的新型复合材料。其中以金属化的ＡＢＳ塑料的应用最为广泛。＊＊Ｓ塑料金属化的方法很多,其中以电镀法最受重视ｌ‘］。为保证金属镀层与塑料表面具有良好结合力,使塑料表面形成四坑、微孔等均匀微观粗糙状态的粗化工艺是相当关键的步骤之一ｐ‘。现国内外广泛采用铬一硫酸混合液的化学粗化法,但该法对环境污染较大。随着环保要求的日益高涨,其它粗化法越来越受到人们的重视［’］。本文探索了利用超声波的空化效应来粗化ＡＢＳ塑料表面、为ＡＢＳ塑料的电…     

Interaction between polyelectrolyte gels and surfactants of opposite charge

Investigations dealing with fundamental aspects of the interaction between covalently cross-linked polyelectrolyte gels and oppositely charged surfactants are reviewed. For reference, a brief summary of results from recent studies of associative phase separation in linear polyelectrolyte/surfactant mixtures is also included. It is found that great progress has been made in several sub-areas since the first reports appeared in the early 1990's. The frequently observed surfactant-induced volume transition has been studied in detail. Its relation to associative phase separation in solutions and the important role of polyion-mediated micelle–micelle attractions have been clarified. Phase separation in gels, in particular core/shell structures, has been studied in great detail. The importance of network mediated elastic forces between two phases coexisting in the same gel has been demonstrated and some of their consequences have been clarified. Hydrophobic interactions between polyion and micelle have been found to have strong effects on both binding and swelling isotherms. The effect of salt, which has been found to sometimes disfavor, sometimes promote surfactant binding, is quite well understood. The microstructure of gels in the collapsed state has been studied in great detail and is often found to be highly ordered, resembling liquid crystalline phases common to surfactant/water systems. The kinetics of surfactant binding and the associated volume change has been investigated to some extent. Progress has been made for gels displaying phase separation during the volume transition.     

Enantiorecognition of profens by capillary electrophoresis using a novel chiral selector eremomycin

The evaluation of a macrocyclic glycopeptide antibiotic, eremomycin, as a chiral selector in capillary electrophoresis (CE) has been performed. The stability of eremomycin in solution and capillary electrolyte, as well as its optical and electrophoretic properties have been discussed. The effect of experimental parameters influencing the enantioseparation of several profens has been studied. Excellent enantioseparation of profens has been achieved and migration order has been validated. Comparison of enantioseparations of profens in CE by using eremomycin-mediated electrolytes and in HPLC with eremomycin immobilized on silica has revealed similar trends for both methods.     

Ionization probability of the hydrogen atom suddenly released from confinement

The problem of the stability of a confined atom when it is extracted from the confining cavity has been investigated, modeled by a spherical hard wall potential. The ionization probability when the atom is released from confinement has been obtained. The dependence of the ionization probability on the confinement radius and on the quantum numbers of the initial confined state has been studied. The probability density function of the ionization energy of the ejected electron has been obtained for the different cases considered. The oscillatory structure of this distribution function, with a principal maximum located in the neighborhood of the energy of the initial state and minima very close to zero has been elucidated. The sudden approximation has been applied and the analytic continuation method has been used to calculate the different stationary states.     

Electron microtomography: A new method for studying the spatial structure of catalysts

The spatial arrangement of active component (Pt) particles on the surface of a support (Sibunit globule) has been studied by bright-field electron tomography. A tomographic attachment for a standard specimen holder and tomographic grids have been designed. The tomographic procedure has been refined, and adequate tilt series alignment and tomographic reconstruction algorithms have been chosen. The 3D distribution of the active component in the catalyst grain has been studied: particles hidden in micropores have been directly observed, and the size of the pores connecting internal cavities with the exterior has been estimated.     

Gas-liquid partition chromatography : Column behavior and its reproduction criteria for favorable column behavior

The distribution of a solute in a gas-liquid Chromatographic column has been discussed from the probability view point and its analogy to the Bernoulli trial system has been shown. It has been shown that the reproduction of column behavior is possible by reproducing the probability. The criterion for the optimum column temperature has also been discussed. Recommendations have been made for determining the optimum column conditions and its reproduction.     

Synergism in the extraction of scandium

Synergism in the extraction of scandium by a mixture of di-2-ethylhexyl phosphoric acid and a β-diketone has been studied. The nature of the extracted species has been investigated. The effect of temperature on extraction has been studied and synergism has been explained on the basis of thermodynamic parameters of the extraction process.     

Kinetic studies of 2-methoxyethanol and 2-ethoxyethanol by pentavalent vanadium in aqueous sulphuric acid medium

Summary The kinetics of oxidation of 2-methoxyethanol and 2ethoxyethanol by vanadium (V) in aqueous sulphuric acid medium has been studied. The order of reaction with respect to the oxidant and substrate has been found to.be unity. The energy of activation has also been calculated graphically. A probable mechanism has been proposed.     

Kinetics and mechanism of oxidation of cyclopentanone by N-bromosuccinimide

N-bromosuccinimide oxidation of cyclopentanone in acidic media in presence of mercuric acetate has been made. A zero order dependance to N-bromosuccinimide and a first order dependence to cyclopentanone and hydrogen ion concentration has been observed. Ionic strength, mercuric acetate and succinimide has negligible effect while methanol addition has a positive effect. Various rate parameters have been computed and 1,2-cyclopentanedione identified as the end product. A suitable mechanism in confirmity with the above observations has been proposed.With 2 Figures     

Synthesis and alkylation of 2-mercapto-4-quinazolone and the fungicidal activities of the compounds obtained

A convenient method of obtaining 2-mercapto-4-quinazolone has been developed and the alkylation of its ambidentate anions has been studied. It has been found that they exhibit a dual reactivity in alkylation reactions. It has been shown that alkylated 2-mercapto-4-quinazolones possess a moderate fungicidal activity.     

Polyelectrolyte Configuration of Low Molecular Weight Sodium Amylose Xanthate in Aqueous and Salt Solutions

The polyelectrolyte chain configuration of low molecular weight sodium amylose xanthate (NaAX) in aqueous and salt solutions has been studied by viscometry and light scattering. The viscometric results in aqueous solution have been found to be in accordance with the Fuoss's modified equation. The intrinsic viscosities of NaAX in salt solutions from 0.00125 to 0.25 M NaCl have been determined and the expansion factor a at each ionic strength has been determined. The dependence of a on ionic strength has been studied according to the theories of Hermans and Overbeek, Flory, etc. But though qualitative agreement between experimental and theoretical results has been found, quantitative agreement was far from expectations. The frictional coefficient per monomer unit | has been calculated from the relationship of Kirkwood and Riseman. The NaAX macromolecule has been found to have the polydispersed random coil chain configuration in 0.25 M NaCl. Some macromolecular configurational parameters such as effective bond length b, Kuhn-Kuhn equivalent chain length A_m, and steric factor α has been determined.     

Chelate formation of ammonium aurintricarboxy-late with bivalent copper : Physico-chemical investigation of the composition,structure and stability

The formation of a coloured chelate, having λmax at 540 mμ, between cupric ions and ammonium aurintricarboxylate has been reported. It has been concluded that only one complex having metal : reagent ratio of 1:2 is formed in solution. The method adopted for investigation has been the continuous variation method, using spectrophotometric and electrical conductance measurements. It has been observed that there is an increase in acidity on mixing the reactants, which shows that hydrogen ions are liberated as a result of chelation It has been suggested that chelation occurs between the phenolic oxygen and the adjacent carboxylic oxygen.A method has been presented for the calculation of formation constant from spectrophotometric data and the value of K in the case of the chelate investigated has been calculated to be 6.45.10⁸. The free energy of formation works out to be —14.6 kcal at 25°C.     

Continual stochastic description of systems with chemical reactions in the presence of a long-range interaction and concentration dependence of the electrical conductivity of electrolytes

It has been shown that recombination-dissociation processes influence the relaxation correction to the concentration dependence of the conductivity of electrolytes. A theoretical treatment has been carried out in the framework of the continual stochastic formalism of birth-and-death processes with a long-range interaction. Evaluations of the observed effects have been given and the possibility of their experimental measurement has been discussed. The question of the concentration dependence of the Hall effect has also been considered.     

A fluorimetric and circular dichroism study of hemoglobin--effect of pH and anionic amphiphiles

In this work, bovine hemoglobin (Hb) has been studied mainly by the fluorescence method. pH has been found to exert a profound effect on Hb structure. This has been confirmed by fluorescence and circular dichroism (CD) studies. The pH-induced change in quaternary structure of Hb indirectly affects its secondary structure. This in turn affects ligand binding to Hb at various pH. The binding of two amphiphiles, a bile salt and a surfactant, have been investigated. The pH-induced structural modification of Hb has been confirmed by studies with the well-known denaturant urea and the polarity probe ANS, which has been used as an extrinsic fluorophore.     

Indirect atomic absorption spectrophotometric determination of arsenic

Arsenic has been determined indirectly by atomic absorption spectroscopy by estimating molybdenum in a solution of arsenomolybdic acid in methyl isobutyl ketone. Interference from other ions has been eliminated by prior extraction of arsenic as the diethyldithiocarbamate in diethyl ether. Arsenic has been determined in the presence of phosphate, silicate and germanium (IV). The method has also been used for the determination of arsenic in organic material.