Polymerization in inverse microemulsion

Homopolymerization of acrylamide as well as that of methyl methacrylate and the copolymerization of acrylamide with methyl methacrylate and/or styrene in inverse microemulsion toluene/water 10: 1 by weight have been studied. Water-soluble ammonium peroxodisulfate, partially water-soluble 2,2′-azobisisobutyronitrile, and oil-soluble dibenzoyl peroxide were used for initiation of these polymerizations at 60°C. Redox initiation system consisting of ammonium peroxodisulfate and tetramethylethylenediamine has been used for an effective initiation of the reactions studied at 30°C. Polymerizations in inverse microemulsions were found start in the interlayer oil macrophase/water microphase. The initial rates of copolymerizations reactions studied depended only on the comonomer mixture composition. The type of the initiator used affected only the exhibited inhibition period.     

Partitioning of plutonium and uranium in aqueous medium using hydroxyurea as reducing agent

A new process for the partitioning of plutonium and uranium during the reprocessing of spent fuel discharged from fast reactor was optimised using hydroxyurea (HU) as a reductant. Stoichiometric ratio of HU required for the reduction of Pu(IV) was studied. The effect of concentration of uranium, plutonium and acidity on the distribution ratio (Kd) of Pu in the presence of HU was studied. The effect of HU in further purification of Pu such as solvent extraction and precipitation of plutonium as oxalate was also studied. The results of the study indicate that Pu and U can be separated from each other using HU as reductant.     

The effective charge number and diffusion coefficient of cationic cytochrome c in aqueous solution.

The diffusion coefficient and the effective charge number of cytochrome c as a function of ionic strength, temperature and pH have been measured. The measurements were carried out using a method based on a convective diffusion process across a porous membrane. The effect of ionic strength was studied in an NaCl solution the concentration of which varied from 0.001 to 1.0 M. The temperature range studied was 10-50 degrees C, and the pH values studied were 4.0, 6.5 and 8.25. The diffusion coefficient is fairly constant as a function of ionic strength and pH, and Walden's rule is valid in the temperature range studied. The effective charge number is practically constant (ca. 2) in the concentration range studied, except in 0.001 M solution, where it is the same as the titrated value. The charge number decreases slightly in the temperature range 10-30 degrees C, but seems to drop suddenly to zero at ca. 40 degrees C. Measurements using heavy water (D2O) as a solvent instead of water did not give zero charge at 40 degrees C for cytochrome c.     

Solvent extraction with organophosphorus extractants in environmental samples: determination of cadmium(II) in natural water

In this work, Cd(II) extraction in natural waters by organophosphorus extractants as organic phase, as well as its back-extraction in an acidic media, has been studied. Cadmium extraction behavior at natural waters’ pH conditions (values in the range 7–8) was studied with two different extractants and co-ions, obtaining the highest extraction efficiency when using 0.1M Cyanex 272 in kerosene as organic phase and 0.1 M NO₃ ^? as co-ion. Once they were selected, the effect on the extraction efficiency of sample pH, buffer concentration, extraction time, Cyanex 272 concentration as well as back-extractant concentration, was studied. The presence of the main inorganic and organic ligands in the sample was also studied, observing that extraction efficiency was affected most significantly when chlorides were present, with a decrease of about 14%, proving negligible for the others. Under the selected conditions, spiked real samples were successfully analyzed.      

Radiation-induced decoloration of oxazine in ethanolic solution

The decoloration yield of oxazine 720 in ethanolic solution was studied as a function of dose rate and concentration of the dye. Linear response for G values to a dose of 1.68 KGy was observed for various dye concentrations. The effect of various organic substances in the radiolysis of the dye was studied and the results were interpreted in terms of scavenging reactions.     

Liquid-Vapor Equilibrium in the Isobutanol-n-Butanol-Butyl Butenyl Ether Ternary System,Azeotropy in Butyl Alcohols-Butyl Butenyl Ether-Water Systems,and Separation of Their Components by Distillation

Liquid-vapor equilibria and azeotropy in isobutanol-n-butanol-butyl butenyl ether ternary system and in isobutanol-butyl butenyl ether and n-butanol-butyl butenyl ether binary systems were studied experimentally and calculated, as well as azeotropy in butyl alcohols-butyl butenyl ether-water systems under atmospheric and reduced pressure. Recovery of commercial butyl alcohols by distillation of alcohol-ether fractions was studied.     

Dynamics of water sorbed in reverse osmosis polyamide membrane

Dynamical motion of water sorbed in reverse osmosis polyamide membrane (ROPM) material is reported as studied by quasielastic neutron scattering (QENS) technique. The ROPM studied here has pore size of 4.4 Å as determined by positron annihilation lifetime spectroscopy. Analysis of the QENS data showed that diffusion behavior of the water within the membrane is describable by random jump diffusion model. A much longer residence time is found as compared to bulk water. Positive shift of the freezing point as observed in differential scanning calorimetry indicates presence of strong attractive interaction corroborating the slower diffusivity as observed in QENS.     

Radiation-induced degradation of 4-chloroaniline in aqueous solution

The radiation-induced decomposition of 4-chloroaniline (4-ClA) was studied under steady-state conditions using aqueous solutions saturated with air, pure oxygen, N₂O, argon and argon in the presence of t-Butanol. Using HPLC-method, the initial G-values of the substrate degradation as well as of a number of radiolytic products were determined. The formation of aminophenols, chlorophenols, aniline and phenol in addition to chloride, ammonia, formaldehyde and mixture of aldehydes as well as carboxylic acids was studied as a function of absorbed dose. Based on the experimental data, probable reaction mechanisms for the degradation of 4-ClA by γ-rays and the formation of the identified products are presented.     

Solvating,manipulating, damaging,and repairing DNA in a computer

This work highlights four different topics in modeling of DNA: (i) the importance of water and ions together with the structure and function of DNA; the hydration structure around the ions appears to be the determining factor in the ion coordination to DNA, as demonstrated in the results of our MD simulations; (ii) how MD simulations can be used to simulate single molecule manipulation experiments as a complement to reveal the structural dynamics of the studied biomolecules; (iii) how damaged DNA can be studied in computer simulations; and (iv) how repair of damaged DNA can be studied theoretically. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Radical Polymerization of Acrylamide in Aqueous-Dimethyl Sulfoxide Solutions in the Presence of Sodium Acetate

The kinetic features of nonisothermal polymerization of acrylamide in aqueous, mixed aqueousdimethyl sulfoxide, and DMSO solutions in the presence of potassium persulfate as initiator and sodium acetate as complexing agent were studied by differential thermal analysis.     

Triplet Photochemistry of Suprofen in Aqueous Environment and in the β-Cyclodextrin Inclusion Complex

The photodecarboxylation of suprofen in the carboxylate form was studied in aqueous medium as a function of the temperature, the concentration and the presence of oxygen by steady-state and time-resolved photochemical techniques. The process is characterized by an activation energy of 9–10 kcal/mol, the precursor state being the lowest triplet which is of π,π* nature. The reactivity of the drug was also studied in the β-cyclodextrin inclusion complex and an additional photoreaction involving the macrocycle as reactive species was observed. Representative NMR and circular dichroism measurements were performed. Singlet molecular oxygen formation was also investigated.     

银杏茶中总黄酮的水溶浸出行为研究

以芦丁为标准品，采用分光光度法，以Al（NO3）3-NaNO2为显色剂，测定了市售银杏茶中总黄酮的含量，并考察了银杏茶在水中浸泡时浸泡温度、浸泡时间、浸泡次数、浸泡溶液的pH值等条件对银杏茶中总黄酮浸出的影响。结果表明，银杏茶中黄酮在水中浸出量受浸泡温度和浸泡溶液DH值的影响比较大。泡茶的溶液应避免使用酸性溶液。还对银杏茶的加工工艺进行了考察研究，发现银杏叶通过微波处理后，其黄酮的浸出量明显高出烘箱烘干的银杏叶的黄酮浸出量。因此，建议在银杏茶的加工工艺中采用微波干燥处理银杏叶。     

Di- and Tetracyano-Substituted Pyrene-Fused Pyrazaacenes: Aggregation in the Solid State

Five di- and tetracyano-substituted pyrene-fused pyrazaacenes were synthesized and studied as potential electron acceptors in the solid state. Single crystals of all compounds were grown and the crystal packing studied by DFT calculations (transfer integrals and reorganization energies) to get insight into possible use for semiconducting charge transport.     

Topological solitons in an inhomogeneous DNA molecule

The dynamics of topological solitons describing the opening of the double helix of a DNA molecule is studied. The estimated actual values of the rigidity of the polynucleotide chains made it possible to develop a more precise DNA model and to show that four types of topological solitons can appear in the DNA double helix. Interactions between solitons are studied, as well as their interaction with the chain inhomogeneities and the stability of solitons with respect to thermal fluctuations. Thermal fluctuations promote propagation of solitons along an inhomogeneous base sequence.     

Solvent effects in u.v. absorption spectra. I. Phenol in cyclohexane ethanol mixtures

The u.v. and i.r. absorption spectra of phenol in a series of solvent systems have been studied and the changes in the spectra, particularly the loss of fine structure in the u.v. spectra, have been qualitatively interpreted in terms of hydrogen bonding effects. The systems studied were chosen to favour either self bonding of the phenol or bonding between the phenol and the minor component of the solvent system. In the latter case the solvent systems were such that the phenol could act either as a proton donor (with an aliphatic ether) or as a donor and acceptor (with ethanol).     

Changes in the pore structure of silica in chemical modification with organic compounds

Changes in the pore structure of silica adsorbents in their chemical modification with organic compounds of various kinds by gas-and liquid-phase processes, as well as those under conditions of high pressure of the reagents, were studied.     

Chromatographische Am-/Cm-Trennung in Schwach Sauren Oxidierenden Medien in der Wässrigen-und dem Chelatbildenden Austauscher Dowex-Al in der Stationären Phase

The separation of Am/Cm was studied in batch and dynamic experiments. It was achieved chromatographicaly on the chelating ion exchanger Dowex-Chelating-Resin-Al making use of the great difference between the complexing ability of trivalent and pentavalent oxidation states. For this purpose, the influence of some variables on the Am/Cm separation factor and on the stability of the adjusted pentavalent state was studied, e.g. the weight of ion exchanger, the time of contact and the pH-values of the solutions. Comparative investigations were carried out on the pentavalent ions of neptunium, plutonium and americium as well as on the hexavalent ions of plutonium and americium, where a significant difference in their behaviours was found.     

Spectrophotometric Study of Interaction in the System Sodium Dodecyl Sulfate-Cetylpyridinium Chloride-Methylene Blue

Complexation of a cationic dye (Methylene Blue) with anionic and cationic surfactants (sodium dodecyl sulfate and cetylpyridinium chloride) was studied spectrophotometrically. The formation constants of complexes formed in the system were estimated. Dispersion of the investigated system was studied as a function of time and cetylpyridinium chloride concentration.     

Electrosurface Properties of Microcrystalline Cellulose of Different Origin in 1 : 1 Electrolyte Solutions

Electrosurface characteristics (the exchange capacity and the electrokinetic potential) of the samples of cotton and wood microcrystalline celluloses (MCC) were studied as functions of the pH and the concentration of background electrolyte (10^–3–1M NaCl). It was found that the MCC samples are negatively charged over the studied pH range (3.5–10.0). The results of measuring exchange capacities were used for calculating constants of surface reactions. The values of dissociation constants of the surface groups allow us to state that the charge of the MCC surface within the studied pH range is mainly determined by the dissociation of carboxyl groups. The surface and electrokinetically mobile charges, concentrations of fixed and mobile ions, as well as Donnan's potentials were calculated for the studied samples.