Determination of air-loop volume and radon partition coefficient for measuring radon in water sample

A simple method for the direct determination of the air-loop volume in a RAD7 system as well as the radon partition coefficient was developed allowing for an accurate measurement of the radon activity in any type of water. The air-loop volume may be measured directly using an external radon source and an empty bottle with a precisely measured volume. The partition coefficient and activity of radon in the water sample may then be determined via the RAD7 using the determined air-loop volume. Activity ratios instead of absolute activities were used to measure the air-loop volume and the radon partition coefficient. In order to verify this approach, we measured the radon partition coefficient in deionized water in the temperature range of 10–30 °C and compared the values to those calculated from the well-known Weigel equation. The results were within 5 % variance throughout the temperature range. We also applied the approach for measurement of the radon partition coefficient in synthetic saline water (0–75 ppt salinity) as well as tap water. The radon activity of the tap water sample was determined by this method as well as the standard RAD-H₂O and BigBottle RAD-H₂O. The results have shown good agreement between this method and the standard methods.     

Validated HPLC Method for Simultaneous Quantitation of Bergenin,Arbutin, and Gallic Acid in Leaves of Different Bergenia Species

Bergenia species (Saxifragaceae) are important sources of herbal medicines in Asia, mainly in Russia. Various plant parts are valued for their antibacterial, anti-inflammatory, antioxidant sand adaptogenic effect, and used for the dissolution of kidney and bladder stones. In this study a rapid reversed phase liquid chromatography (RP-HPLC) method has been developed for rapid screening and identifying of the main active components in leaf samples of Bergenia accessions. The main goal of this study was to develop an efficient method for the simultaneous identification and detection of arbutin, bergenin and gallic acid from Bergenia leaf samples, which were extracted with a methanolic solvent mixture [methanol:water = 1:1 (v/v)]. Chromatographic separations were performed on a reversed phase Luna C18(2)-HST HPLC column. This chromatographic system provided increased speed and efficiency for separations, without the need for ultra-high pressures. Reversed phase HPLC coupled with diode array detector method was used for the analysis. The method was validated using ICH guidelines. The level of gallic acid was significantly higher in Bergenia crassifolia samples compared to Bergenia cordifolia. However, the samples of the two Bergenia species did not differ substantially regarding the concentrations of arbutin and bergenin. The novel method proved to be fast and allowed sufficient separation and quantification of arbutin, bergenin and gallic acid, the most important bioactive compounds of Bergenia leaves; thus facilitating rapid screening and quality assessment of Bergenia samples of various botanical and geographical origins.     

Approximate （m,n）-Cauchy-Jensen Additive Mappings in C^＊-algebras

Concerning the stability problem of functional equations, we introduce a general (m, n)-Cauchy-Jensen functional equation and establish new theorems about the Hyers-Ulam stability of general (m, n)-Cauchy-Jensen additive mappings in C*-algebras, which generalize the results obtained for Cauchy-Jensen type additive mappings.     

Anion-exchange chromatography of organic acids in magnesium acetate medium

Magnesium acetate solution is a useful eluant in the separations of dibasic organic acids by anion-exchange chromatography. The following acids were separated: oxalic, tartronic, malic, glucaric, galactaric, tartaric and maleic acids. The eluate was analyzed automatically using chromic acid oxidation.     

Unambiguous identification of Möbius aromaticity for meso-aryl-substituted [28]hexaphyrins(1.1.1.1.1.1)

meso-Aryl-substituted [28]hexaphyrins(1.1.1.1.1.1) have been examined by (1)H, (13)C, and (19)F NMR spectroscopies, UV-vis absorption spectroscopy, magnetic circular dichroism spectroscopy, and single-crystal X-ray diffraction analysis. All of these data consistently indicate that [28]hexaphyrins(1.1.1.1.1.1) in solution at 25 degrees C exist largely as an equilibrium among several rapidly interconverting twisted M?bius conformations with distinct aromaticities, with a small contribution from a planar rectangular conformation with antiaromatic character at slightly higher energy. In the solid state, [28]hexaphyrins(1.1.1.1.1.1) take either planar or M?bius-twisted conformations, depending upon the meso-aryl substituents and crystallization conditions, indicating a small energy difference between the two conformers. Importantly, when the temperature is decreased to -100 degrees C in THF, these rapid interconversions among M?bius conformations are frozen, allowing the detection of a single [28]hexaphyrin(1.1.1.1.1.1) species having a M?bius conformation. Detailed analyses of the solid-state M?bius structures of compounds 2b, 2c, and 2f showed that singly twisted structures are achieved without serious strain and that cyclic pi-conjugation is well-preserved, as needed for exhibiting strong diatropic ring currents. Actually, the harmonic-oscillator model for aromaticity (HOMA) values of these structures are significantly large (0.85, 0.69, and 0.71, respectively), confirming the first demonstration of stable M?bius aromatic systems consisting of free-base expanded porphyrins without the assistance of metal coordination.     

Kinetic studies on the addition of phenol to S-phenyl-S-vinyl-N-p-tosylsulfilimine derivatives

The rate constants of nucleophilic addition of phenyl to vinylsulfilimine(VSI) and its derivatives were determined by an ultraviolet spectrophotometer at 25°C, and the rate equations which can be applied over a wide pH range were obtained. On the basis of the pH-rate profile, product analysis, general base catalysis, and the substituent effect, a plausible mechanism of this addition reaction was proposed: Below pH 3.0, the reaction proceeded via the addition of a neutral molecule to the carbon-carbon double bond after protonation at the nitrogen atom of the sulfilimine. Above pH 10.0, the addition of a phenoxide ion to the carbon-carbon double bond was rate controlling. However, in the pH range of 3.0 to 10.0, these two reactions occurred competitively.     

Phases containing tungsten in Cu(1) positions

A tetragonal (123) phase of composition CdBa₂Cu₂WO₈ with the complete and selective substitution of tungsten atoms for copper in the Cu(1) positions is synthesized from CdWO₄ and BaCuO₂ at 800°C in flowing oxygen. The percentage of the (123) phase in the sample is at least 90%; the unit cell parameters are a = b = 0.4151(3) nm, c = 1.2537(8) nm. The X-ray diffraction pattern shows a superstructure with all three of the unit cell parameters being doubled.     

Synthesis, structure, and magnetic properties of valence ambiguous dinuclear antiferromagnetically coupled cobalt and ferromagnetically coupled iron complexes containing the chloranilate(2-) and the significantly stronger coupling chloranilate(*3-) radical trianion

Dinuclear [(TPyA)MII(CA2-)MII(TPyA)]2+ [TPyA=tris(2-pyridylmethyl)amine; CA2-=chloranilate dianion; M=Co (1(2+)), Fe (2(2+))] complexes have been prepared by the reaction of M(BF4)(2).6H2O, TPyA, H2CA, and triethylamine in MeOH solution. Their reduced forms [(TPyA)MII(CA*3-)MII(TPyA)]+ [M=Co(1+), Fe (2+)] have been synthesized by using cobaltocene, and oxidized forms of 1, [(TPyA)CoIII(CAn)CoIII(TPyA)]z+ [z=3, n=3- (1(3+)); z=4, n=2- (1(4+))], have been obtained by using FcBF4 and ThianBF4 (Fc=ferrocenium; Thian=thianthrinium), respectively. The dinuclear compound bridged chloranilates (CA2- or CA*3-) were isolated and characterized by X-ray crystallography, electrochemistry, magnetism, and EPR spectroscopy. Unlike the other redox products, valence ambiguous 13+ forms via a complex redox-induced valence electron rearrangement whereby the one-electron oxidation of the [CoIICA2-CoII]2+ core forms [CoIIICA*3-CoIII]3+, not the expected simple 1-e- transfer mixed-valent [CoIICA2-CoIII]3+ core. The M ions in 1 and 2 have a distorted octahedral geometry by coordination with four nitrogens of a TPyA, two oxygens of a chloranilate. Due to the interdimer offset face-to-face pi-pi and/or herringbone interactions, all complexes show extended 1-D and/or 2-D supramolecular structures. The existence of CA*3- in 1(3+) is confirmed from both solid-state magnetic and solution EPR data. Co-based 1n+ exhibit antiferromagnetic interactions [1(2+): g=2.24, J/kB=-0.65 K (-0.45 cm-1); 1+: g=2.36, J/kB=-75 K (52 cm-1)], while Fe-based 2n+ exhibit ferromagnetic interactions [2(2+): g=2.08, J/kB=1.0 K (0.70 cm-1); 2+: g=2.03, J/kB=28 K (19 cm-1)] [H=-2JS1.S2 for 12+ and 2(2+); H=-2J(S1.S2+S2.S3) for 1+ and 2+]. Thus, due to direct spin exchange CA*3- is a much strong spin coupling linkage than the superexchange spin-coupling pathway provided by CA2-.     

A study of cryostructuring of polymer systems. 43. Characteristics of microstructure of chitosan-containing complex and composite poly(vinyl alcohol) cryogels

The microstructure of complex and composite poly(vinyl alcohol) (PVA) cryogels containing water-soluble chitosan hydrochloride (ChHC) of dispersed particles of water-insoluble chitosan base (Ch), respectively, has been studied by optical microscopy and attenuated total reflection FTIR spectroscopy. The macroporous morphology of cryogels has been studied using preparations in the form of thin (~10 μm) sections and discs 1 mm thick. The introduction of non-gelling additives (NaCl and ChHC) into an initial PVA solution causes significant changes in the size and shapes of macropores in the complex cryogels formed by freezing–defrosting, as compared with the pores in the samples obtained under the same conditions without additives. The reasons for the changes are the process of phase segregation and the influence of low- and high-molecular-weight electrolytes on crystallization of ice, which plays the role of a porogen upon cryotropic gelation of aqueous PVA solutions. As a result of an alkaline treatment of the complex cryogels, which transforms ChHC into Ch, microcoagulation of chitosan yields discrete, almost spherical, particles with sizes of about 1–5 μm. IR spectral studies have shown that concentration gradients of the gelling and nongelling polymers arise along the thickness of the gel discs, with PVA concentration prevailing near the lower surface and ChHC or Ch concentration dominating near the upper surface of the disc.