Preparation and characterization of crosslinked proton conducting membranes based on chitosan and PSSA-MA copolymer

Proton conducting crosslinked complex membranes were prepared by blending of a cationic polyelectrolyte, i.e. chitosan (CS) and an anionic polyelectrolyte, i.e. poly(4-styrenesulfonic acid-co-maleic acid) (PSSA-MA). In particular, the dual function of PSSA-MA as a crosslinker and a proton conductor is described. The esterification reaction between –OH of CS and –COOH of PSSA-MA and the complex formation of NH₃⁺ of CS and SO₃^? of PSSA-MA were confirmed using FT-IR spectroscopy. The ion exchange capacity (IEC) of membranes continuously increased with PSSA-MA concentrations, resulting from the increase of ionic groups. However, the membranes exhibited the minimum values of proton conductivity and water uptake at 50–67 wt.% of PSSA-MA due to the effect of crosslinking and complex formation. In addition, a maximum of Young's modulus was achieved at 50 wt.% of PSSA-MA, as revealed by universal testing machine (UTM). Thermogravimetric analysis (TGA) showed that the thermal stability of membranes increased with increasing PSSA-MA concentrations and was the highest at 50 wt.% of PSSA-MA.     

Effect of ethylene carbonate concentration on the conductivity of carbonate-based electrolytes with LiPF6 for Li-ion batteries

A four-probe pouch-type cell was used to study the influence of carbonate-based electrolyte composition on the total conductivity of polyolefin separator impregnated with electrolyte through the electrochemical impedance spectroscopy. A frequency dispersion of separator with electrolyte is found to be dependent on the volume ratio of ethylene carbonate and ethyl methyl carbonate in an electrolyte solution. The origin of high- and low-frequency relaxation processes obtained from the impedance spectra is discussed. A correlation between the direct current resistance of separator with electrolyte and dissociation degree of electrolyte salt is found.     

An efficient synthesis of dihydrofuranyl spirooxindoles from isatin-derived propargylic alcohols and 1,3-dicarbonyls

Various dihydrofuranyl spirooxindoles have been synthesized via montmorillonite K-10-catalyzed propargylation of 1,3-dicarbonyl compounds with isatin-derived propargylic alcohols and subsequent base-mediated 5-exo-dig cyclization.     

Heat Capacities of Three Isomeric Chlorobenzenes and of Three Isomeric Chlorophenols

Isobaric heat capacities C _p in the liquid and in the solid phase of 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,2,4-trichlorobenzene, 3-chlorophenol and 4-chlorophenol and in the liquid phase of 2-chlorophenol were measured by commercial Setaram heat conduction and power compensated calorimeters. Results obtained cover the following temperature range (depending on the compound and state of aggregation): 1,2-dichlorobenzene 208 to 323 K,1,3-dichlorobenzene 183 to 323 K, 1,2,4-trichlorobenzene 133 to 323 K, 2-chlorophenol from293 to 353 K, 3-chlorophenol and 4-chlorophenol from 133 to 353 K. The heat capacity data obtained in this work were merged with available experimental data from literature, critically assessed and sets of recommended data were developed by correlating selected data as a function of temperature. Temperature and enthalpy of fusion of two isomeric chlorophenols and of 1,2,4-trichlorobenzene were also determined. This revised version was published online in August 2006 with corrections to the Cover Date.     

Utilization of radiochemical and mass-spectrometric analysis of the spent fuel of the A-1 power plant for non-destructive burn-up determination

During the burning-up fuel in a nuclear reactor, changes in the isotopic composition of the fuel as well as in the reactor power generation take place. To explain these effects, destructive radiochemical analyses of the spent fuel were carried out. The results obtained have been used for the calibration of non-destructive burn-up determination and for the evaluation of simple computer codes. The main results of the codes as well as the methods applied for the separation of radionuclides studied are presented.     

Osmylated macroporous resins: safe,highly efficient and recyclable catalysts for asymmetric aminohydroxylation of olefins

Osmylated macroporous resins displayed excellent catalytic performances in the asymmetric aminohydroxylation of olefins and, moreover, these resins were easily recovered and reused without any significant decrease in catalytic efficiencies.     

32P-postlabelling and mass spectrometric methods for analysis of bulky, polyaromatic carcinogen-DNA adducts in humans.

There has been significant recent progress toward the development of human carcinogen-DNA adduct biomonitoring methods. 32P-Postlabelling is a technique which has found wide application in human studies. 32P-Postlabelling involves enzymatic preparation and labelling of DNA samples, followed by chromatographic separation of carcinogen-nucleotide adducts from unadducted nucleotides. Thin-layer ion-exchange and high-performance liquid chromatography (HPLC) have been utilized. This paper critically reviews 32P-postlabelling methods for analysis of bulky, polyaromatic carcinogen-DNA adducts and details a strategy to optimize this technique for monitoring human samples. Development of a human carcinogen biomonitoring method requires that the biomarker meet certain criteria: that the biomarker be responsive to exposures known to increase human cancer risk, to reductions in those exposures, and to the influence of metabolic differences. In addition, reliable samples must be available by non-invasive means. The ability of 32P-postlabelling to meet these criteria is traced in the literature and discussed. Identification of specific carcinogen-DNA adducts is a difficult task due to the low (femtomole) levels in human target tissues. Because co-chromatography in thin-layer chromatography (TLC) is generally not considered to be proof of chemical identity, both synchronous fluorescence and HPLC in conjunction with 32P-postlabelling and TLC are used to confirm the identity of specific carcinogen-DNA adducts in human samples. Mass spectrometry is a highly specific method, the sensitivity of which has been improved to the point which may allow its use to confirm the identity of carcinogen-DNA adducts isolated by 32P-postlabelling and other methods. The literature relating to the use of mass spectral techniques in carcinogen-DNA adduct analysis is reviewed.     

Investigation of sulfhydryl groups in cabbage phospholipase D by combination of derivatization methods and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

All eight cysteine residues in 92 kDa cabbage phospholipase D (PLD), deduced from the cDNA sequence, were shown to have free sulfhydryl groups by analysis using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) of tryptic peptides of PLD derivatized with p-chloromercurybenzoate, iodoacetic acid, and N-ethylmaleimide, as well as of underivatized PLD. Assignment of sulfhydryl groups by any one method was not conclusive. However, complementary information derived from tryptic peptides derivatized with different reagents made full assignment of sulfhydryl groups possible.     

Coordination chemistry of polyoxomolybdates: The versatile behavior of amidoximes

The reactions of 2-thienylamidoxime and 2-thienylmethylamidoxime with [MoO₂(acae)₂] or x-(NBu₄ [Mo₈O₂₆]. in alcohols or acetonitrile, yield a number of compounds with different nuclearities and various molybdenum cores, such as the compact {Mo₄O₁₀(OMe)₂}²⁺ the cyclic {Mo₄O₁₂}, and the open {Mo₁₁On_211-1}²⁺ (n= 2 or 4) cores. Addition of NH₂OH to the reaction mixtures results in the formation of nitrosyl complexes containing either the Mo(NO)³ or the Mo(NO) ₂ ² units. The amidoxime component may be present either as RC(NH₂)NHO. RC(NHi2), RC(NH)NHO or RC(NH)NO²: ligands, or as hydrogen-bonded RC(NH₂)NOH molecules. The crystal structures of [MoO(acac)RIC'(NH₂)NO] {R^JC(NH)NO}](1), [Mo(NO)(acae)₂ {R^IC(NH₂)NO}] (4), (NBu₄)₂[Mo₄O₁₀(OMe)₂{R^IC(NH) NO}₂] (12a),(NBu₄)₂(H₃O)[Mo₅O₁₃(OMe)₄(NO)].2R¹C(NH₂)NOH(13b) and [R¹C(NH₂)₂)]₃[Mo₅O₁₃(OEt)₄(NO)] (14) (R¹=2-thienyl) are reported. The cryslallographic data for these compounds are as follows:1, mono-clinic. P2₁ a.a=24.547(4)A. b=8.188(4)A. c=9.607(3)A, ß=96.18(3)^c, R=0.046. R₁₀=0.050: 4. monoclinic, P2₁c.a=8.265(2)A, b=9.381(2)A,_c=24.770(4)A, c = 24.7701(4) A, ß=93.99(2). R=0.039. R=0.042;12a, monoclinic, C2/c, a= 19.570(5)A. b=16.883(4)A, c = 19.82(l)A. ß= 114.36(5)°, R=0.064,R.=0.074;13b monoclinic;. P2₁ c.a=18.197(5)A, b=15.857(14) A, c = 23.075(17) A, =93.20(3). R=O.050. R_w=0.057;14, trictinic PI, a = 9.871(3),b= 14.138(3).c= 14.781(8)A. =92.67(2)^c =99.36(1)° =90.52(2)°. R = 0.044. R_w = 0.049. Particular attention is focused on the various coordination modes that the different ligand forms adopt: µ- O, ²N,O, ₂N',O, µ-N: ²O. and ₃- N:N:₂O.