Thermodynamics of solute transfer between chloroform and water

The apparent enthalpies, free energies and entropies of transfer from water saturated chloroform to chloroform saturated aqueous buffer (pH 7) were determined for five primary alcohols and six other organic nonelectrolytes using an isoperibol flow microcalorimeter. A linear relationship between the enthalpies and free energies of transfer is found for the homologous series of alcohols indicating that the occurrence of enthalpy-entropy compensation in solute transfer is not restricted to solvent systems of low mutual solubility. The apparent thermodynamics of transfer from chloroform to aqueous buffer were compared with those from 2,2,4-trimethylpentane to aqueous buffer and were rationalized in terms of solvation interactions.     

Interaction between carbon dioxide and naphthalene: A molecular modeling approach

The formation of a charge-transfer complex between carbon dioxide and naphthalene was studied using a molecular modeling program, with the aim of studying the solubility of naphthalene in supercritical carbon dioxide. The orbitals involved in the formation of the complex were studied using MINDO/3 as the semi-empirical method. A solvent cage was constructed, and the maximum number of carbon dioxide molecules to surround naphthalene was found to be 20. The heat of interaction of the complex was obtained using MINDO/3. © 1994 by John Wiley & Sons, Inc.     

Speciation of protein-bound trace elements by gel electrophoresis and atomic spectrometry

The metabolism of trace elements, in particular their binding to proteins in biological systems is of great importance in biochemical, toxicological, and pharmacological studies. As a result there has been a sustained interest over the last two decades in the speciation of protein-bound metals. Various analytical approaches have been employed, combining efficient separation of metalloproteins by liquid chromatography or electrophoresis with high-sensitivity elemental detection. Slab-gel electrophoresis (GE) is a key platform for high-resolution protein separation, and has been combined with autoradiography and various atomic spectrometric techniques for in-gel determination of protein-bound metals. Recently, the combination of GE with state-of-the-art inductively coupled plasma-mass spectrometry (ICP-MS), particularly when linked to laser ablation (LA) for direct gel interrogation, has opened up new opportunities for rapid characterization of metalloproteins. The use of GE and atomic spectrometry for the speciation of protein-bound trace elements is reviewed in this paper. Technical requirements for gel electrophoresis/atomic spectrometric measurement are considered in terms of method compatibilities, detection capability and potential usefulness. The literature is also surveyed to illustrate current status and future trends.     

Temperature dependent self-diffusion coefficient measurements of glycerol by the pulsed N.M.R. technique

A review of the coupled Hartree-Fock method for calculation of second-order one-electron properties is given with special reference to force constants and static electric and magnetic properties. A comprehensive analysis of the computational problems is attempted and we present the logic of a computer programme. A number of results obtained for the H₂O molecule are reported in part II of this work.     

Development and validation of a sensitive method for simultaneous determination of rosuvastatin and N‐desmethyl rosuvastatin in human plasma using liquid chromatography/negative electrospray ionization/tandem mass spectrometry

A sensitive and specific liquid chromatography tandem mass spectrometric method was developed and validated for the simultaneous determination of rosuvastatin (ROS) and N‐desmethyl rosuvastatin (NOR‐ROS) in human plasma using deuterium‐labeled internal standards. The plasma samples were prepared using liquid–liquid extraction with diethyl ether. Chromatographic separation was accomplished on an Xterra MS C₁₈ column. The mobile phase consisted of a gradient mixture of 15 µmol/L ammonium acetate in water and in methanol, maintained at a flow rate of 0.4 mL/min. Mass spectrometric detection was carried out in negative electrospray ionization mode and monitored by quantification and qualification transitions for each analyte. Using 300 μL plasma samples, the lower limits of quantification of ROS and NOR‐ROS were 0.05 and 0.02 µg/L respectively. The linearity of ROS and NOR‐ROS ranged from 0.05 to 42 and 0.02 to 14 µg/L respectively. The relative standard deviations of ROS and NOR‐ROS were <13 and 9%, respectively, while the deviations from expected values were within ?4.7–9.8 and ?5.2–4.6%, respectively. The present method offered high sensitivity and was successfully applied to a 24 h pharmacokinetic study of ROS and NOR‐ROS in healthy subjects receiving a single dose of 10 mg ROS. Copyright © 2013 John Wiley & Sons, Ltd.     

New binary codes from extended Goppa codes

An efficient construction of extended length Goppa codes is presented. The construction yields four new binary codes [153, 71, 25], [151, 70, 25], [160, 70, 27], and [158, 69, 27]. The minimum distances are larger than those of the best previously known linear codes of the same length and dimension.     

Studies on the thermoelectric microdetermination of molecular weight

Summary The conditions required in the thermoelectric microdetermination of molecular weight have been investigated, and determinations using the modified procedure resulted in a standard deviation of 1.9% in the range 100–700.

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Zusammenfassung Die bei der thermoelektrisehen Mikrobestimmung des Molekulargewichtes einzuhaltenden Bedingungen wurden untersucht. Bestimmungen nach dem modifizierten Verfahren zeigten in dem Gebiet zwischen 100 und 700 eine Standardabweichung von 1,9%.

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Résumé On a étudié les conditions exigées pour la microdétermination thermoélectrique du poids moléculaire. En apportant des modifications au procédé, les résultats obtenus présentent un écart-type de 1,9% dans le domaine 100–700.

     

Tuning the optical and electronic properties of 4,8-disubstituted benzobisoxazoles via alkyne substitution

In an effort to design new electron-deficient building blocks for the synthesis of conjugated materials, a series of new trans-benzobisoxazoles bearing halogen or alkynyl substituents at the 4,8-positions was synthesized. Additionally, the impact of these modifications on the optical and electronic properties was investigated. Theoretical calculations predicted that the incorporation of various alkynes can be used to tune the energy levels and band gaps of these small molecules. The targeted 4,8-disubstituted benzobisoxazoles were easily prepared in good yields using a two-step reaction sequence: Lewis acid catalyzed orthoester cyclization followed by Sonogashira cross-coupling. The experimentally determined HOMO values for these 4,8-disubstituted benzobisoxazoles ranged from -4.97 to -6.20 eV and showed reasonable correlation to the theoretically predicted values, with a percent deviation that ranged from 2.4-12.8%. However, the deviation between actual and predicted HOMO values was reduced to less than 3.5% when the theoretical values were extrapolated to the long-chain limit and compared to copolymers containing the 4,8-disubstituted benzobisoxazoles. Collectively, these results indicate that these 4,8-disubstituted trans-benzobisoxazoles can be used for the synthesis of new conjugated materials with electronic properties that are variable and predictable.     

Free energy and electrical resistivity of molten alloys

The free energies of mixing for molten indium-antimony, cadmium-antimony, indium-bismuth, lead-bismuth and tin-bismuth were calculated from the variation of electrical resistivity with composition employing the model of Takeuchi and Endo. Resistivities measured in this laboratory with an electrodeless technique for In-Sb alloys, together with published values for Cd-Sb, In-Bi, Pb-Bi and Sn-Bi alloys were used in the calculations.

Evaluation of the resistivity data gave the composition dependence of the derivatives of the chemical potentials of the constituents and the integral molar free energies of mixing. No assumptions regarding ideal entropy were made to obtain these free energy values although a statistically random mixture of ions is presumed in the scattering model.

Conclusions drawn from a comparison between the calculated free energy values and published thermodynamic data for these systems are discussed in terms of departures from regularity and the variations in the effective free electron concentration.