Electrical Conductance Studies in Aqueous Solutions with Ascorbate Ions

Conductivity measurements in dilute aqueous solutions of L-ascorbic acid, sodium-L-ascorbate, magnesium-L-ascorbate, calcium-L-ascorbate and ferrous-L-ascorbate were performed in the (288.15 to 323.15) K temperature range. The limiting molar conductances of the ascorbic anion, λ^∘(HAsc⁻, T), and the dissociation constants of ascorbic acid, K(T), were derived by the use of the Debye-Hückel equation for the activity coefficients and the Onsager and Quint and Viallard conductivity equations.     

InclusiveK *+(890),K *+(1430) and\bar K^{ * - } (890) production inK + p interactions at 32 GeV/c

We present final results on inclusive production ofK ^*+(890),K ^*+(1430) andK ^*?(890) in \(\bar K^ + p\) interactions at 32 GeV/c, based on a statistics of ～27 events/μb. Total cross sections,p _T -andx-dependence of inclusive distributions are compared with experiments at other energies and with the Lund fragmentation model. Spin density matrix elements of theK ^*+(890) are also discussed. The results suggest that “recombination” of both initial state valence quarks \(\bar s\) andu of theK ⁺ intoK ^*+(890), responsible in the Lund model for ～45% of theK ^*+(890) cross section, is strongly suppressed.     

Electrical Conductance Studies in Aqueous Solutions of Glutaric Acid,Disodium Glutarate and Sodium Hydrogen Glutarate

Conductivity measurements of glutaric acid and disodium glutarate in dilute aqueous solutions were performed in the 288.15 to 323.15 K temperature range. The limiting equivalent conductances of glutarate anions, λ ^o(HGlut⁻,T) and λ ^o(1/2Glut²⁻,T), and the dissociation constants of glutaric acid, K ₁(T) and K ₂(T), were derived by the use of the Onsager and the Quint and Viallard conductivity equations. The applied molecular model was successfully confirmed by analyzing the conductivities of sodium hydrogen glutarate at 298.15 K.     

Oxidation of Tetrahydrofuran and 1,4-Butanediol with Nitric Acid

Preparation of succinic acid by oxidation of tetrahydrofuran and 1,4-butanediol with nitric acid was studied.     

Electron acceptors of the fluorene series. 10.(1) novel acceptors containing butylsulfanyl, butylsulfinyl, and butylsulfonyl substituents: synthesis, cyclic voltammetry, charge-transfer complexation with anthracene in solution, and X-ray crystal structures of two tetrathiafulvalene complexes

2,4,5,7-Tetranitro-9-fluorenone (1b) reacts readily with n-butanethiol in dipolar aprotic solvents with selective substitution of nitro groups by butylsulfanyl groups in positions 2 and 7 (2, 3); the 2,5-isomer 4 was formed only as a minor product (<1%). Condensation of fluorenones 2-4 with malononitrile yielded 9-dicyanomethylene derivatives 5-7, which showed strong intramolecular charge transfer (lambda approximately 510-560 nm) and were found to sensitize the photoconductivity of carbazole-containing polymer films. Oxidation of sulfides 2-4 gave sulfoxide 8 or sulfones 9-11, which then were converted into their corresponding dicyanomethylene derivatives 12-15. All these novel acceptors showed three reversible single-electron reduction waves (cyclic voltammetry) yielding radical anion, dianion, and radical trianion; moreover, acceptors 13-15 showed also a fourth reduction wave, representing reversible tetraanion formation. Substitution of the oxygen of the carbonyl group in the fluorenones by a dicyanomethylene group increased the thermodynamic stability (K(SEM) growth) of the radical anion; K(SEM) ranged from 3 x 10(5) to 3 x 10(9) M(-1). CV measurements characterize compounds 3, 4 (EA = 1. 86-1.89 eV) as poor acceptors, 2, 6-11 (EA = 2.13-2.31 eV) as moderate acceptors, and 5, 12-15 (EA = 2.53-2.66 eV) as strong electron acceptors. Charge-transfer complex (CTC) formation between acceptors 9, 10, 13, 14, and anthracene as a donor was monitored by the appearance of additional low-energy bands in the visible region (CTC bands) of their electron absorption spectra. Increasing the EA of the acceptors from 9-fluorenones to the corresponding 9-dicyanomethylenefluorenes increases the complexation constants K(CTC) by 2.5-3 times, while sulfonyl substituents present substantial steric hindrance for complexation (as compared to the nitro group), decreasing K(CTC) values. Two CTCs for acceptors 14 and 17 with tetrathiafulvalene (TTF) were obtained, and their structures were solved by single-crystal X-ray diffractometry, giving the stoichometries 14:TTF, 2:3, and 17:TTF:PhCl, 1:1:0.5. In the former complex the packing motif is a mixed.DDAD'A. stack; in the latter complex the D and A moieties form unusually close CT pairs, which pack in a herringbone motif.     

Electrical Conductance and Volumetric Studies in Aqueous Solutions of DL-Pyroglutamic Acid

Conductivity measurements of DL-pyroglutamic acid and sodium pyroglutamate in dilute aqueous solutions were performed in the 288.15–323.15 K temperature range. The limiting molar conductances of pyroglutamate anion, λ^o(pGlu⁻, T) and the dissociation constants of pyroglutamic acid, K(T) were derived from the Onsager, and the Quint and Viallard conductivity equations. Densities of aqueous solutions with molalities lower than 0.5 mol-kg⁻¹ were determined at 5 K intervals from T = 288.15 K to 333.15 K. Densities served to evaluate the apparent molar volumes, V_2,φ(m, T), the cubic expansion coefficients, α (m,T) and the changes of the isobaric heat capacities with respect to pressure, (∂ C_P/∂ P)_T,m. They were correlated qualitatively with the changes in the structure of water when pyroglumatic acid is dissolved in it.     

Detonation nanodiamonds as catalysts of steam reforming of ethanol

Physicochemical properties and catalytic performance of detonation nanodiamonds were studied. Original samples of nanodiamonds and nanodiamonds modified by hydrogen, oxygen, and nitric acid with hydrogen peroxide and infrared-treated were investigated. The catalyst structure and morphology were examined by transmission electron microscopy and IR spectroscopy. All the investigated catalysts were active in the steam reforming of ethanol. The correlation of catalytic properties with composition and structure of the described systems is discussed. The specific surface area of nanodiamonds is changed insignificantly upon modification.     

The effects of sample preparation methods on the variability of the electrospray ionization response for model drug compounds

A post-column infusion system was developed in order to analyze suppression of electrospray ionization (ESI) tandem mass spectrometry response in the presence of endogenous plasma interferences. By enabling direct detection of these interfering components, this experimental system was used to analyze the ability of several common extraction procedures to remove endogenous plasma components that cause changes in the ESI response of model drug substances. Methyl-t-butyl ether (MTBE) liquid-liquid, Oasis and Empore solid-phase, and acetonitrile (ACN) protein precipitation sample preparation methods were tested using the post-column infusion system. In all cases, ACN protein precipitation samples showed the greatest amount of ESI response suppression while liquid-liquid extracts demonstrated the least. In addition, the three test compounds, phenacetin, caffeine, and a representative Merck compound, demonstrated that ESI response suppression is compound dependent. Suppression was greatest with caffeine, the most polar analyte, and the smallest for the Merck compound, the least polar analyte. Copyright 1999 John Wiley & Sons, Ltd.     

Investigation of a Contamination Film Formed by the Electron Beam Irradiation

Technical Physics - In the study of materials on electron probe devices in the field of action of the electron beam, a contaminating hydrocarbon film is formed, which affects the experimental...