On a new variational principle in general relativity and the energy of the gravitational field

A new variational principle based on the affine connection in space-time is proposed. This leads to a new formulation of general relativity. The gravitational field is a field of inertial frames in space-time. The metricg appears as a momentum canonically conjugate to the gravitational field. In the case of simple matter fields, e.g., scalar fields, electromagnetic fields, Proca fields, or hydrodynamical matter, the new formulation is equivalent to the traditional one. A new formulation of conservation laws is proposed.     

Studies on use of differential thermal and thermogravimetric techniques for checking compositions of some drug formulations

The suitability of the differential thermal and thermogravimetric techniques for the determination of compositions of solid and soft drug formulations has been studied. A total of 117 pharmaceutical preparations have been examined, including powders, dusting powders, capsules, granulates, tablets, tablets for sucking, effervescent tablets, dragees, suppositories and ointments. Both techniques have been shown to be applicable for identification of pharmaceutical preparations. A specification has been made of thermal processes which can be employed for assaying the main components of the preparations. A rough estimate of the relative errors has been given.

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Zusammenfassung Die Eignung der differentialthermoanalytischen und thermogravimetrischen Methoden zur Bestimmung der Zusammensetzung fester und weicher ArzeneiprÄparate wurde studiert. Eine Gesamtzahl von 117 pharmazeutischen PrÄparaten, einschliesslich Pulver, Streupulver, Kapseln, Granulate, Tabletten, Saugtabletten, Brausetabletten, Dragees, Suppositorien und Salben wurde untersucht. Beide Methoden erwiesen sich als anwendbar zur Identifizierung pharmazeutischer PrÄparate. Eine Spezifizierung der zur Bestimmung der Hauptkomponenten der PrÄparate geeigneten thermischen Prozesse wurde durchgeführt. Eine grobe SchÄtzung der relativen Fehler wurde gegeben.

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Résumé On a étudié l'utilité des techniques ATD et TG pour déterminer la composition des préparations pharmaceutiques solides et molles. On a soumis à l'examen un total de 117 préparations pharmaceutiques comprenant des poudres, des talcs, des capsules, des granulats, des tablettes, des tablettes à sucer, des tablettes effervescentes, des dragées, des suppositoires et des onguents. Les deux techniques se sont montrées applicables à l'identification des préparations pharmaceutiques. On a effectué une spécification des processus thermiques qui se prÊtent au dosage des composants essentiels des préparations. On a donné une évaluation approximative des erreurs relatives.

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The chemistry of thujone. IX. Thujone as a chiral synthon for the synthesis of optically active steroid analogues. The vinylpicoline route

The thujone-derived enone 1 , upon base-catalyzed reaction with 2-methyl-6-vinylpyridine is converted to the pyridine analogue 5 (Scheme 1). Catalytic reduction of the latter to 6 generates two new centers of chirality which eventually become C(8) and C(14) in the ultimate synthetic steroid analogue 12 . An X-ray analysis of 6 establishes the structure and absolute configuration so as to determine its suitability in subsequent synthetic studies. The acetal derivative 7 , via Birch reduction, hydrolysis, and internal aldol cyclization, is converted into the cyclohexenone analogue 10 (Scheme 2). This ‘one-pot’ process affords an efficient conversion of the pyridine ring into a cyclohexenone system required for A-ring construction of the steroid skeleton. Finally, conversion of 10 , via the unsaturated diketone 11 , provides the chiral steroid analogue 12 .     

Physicochemical properties and hds activity of CoMo?P?Al2O3 catalysts

Porous structure, acidity and hds activity of the CoMo–P–Al₂O₃ catalysts have been studied. Phosphorus was introduced jointly with molybdenum. This method of phosphorus incorporation gave substantial diminution of surface area, moderate changes of acidity and decrease in hds activity for the catalysts with P₂O₅ content higher than 5 wt.%.

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, CoMo–P–Al₂O₃. . , P₂O₅ 5 .%.

     

Attractive halogen–halogen interactions: F3CCl⋯FH and F3CCl⋯FCH3 dimers

The F₃CCl?FH and F₃CCl?FCH₃ dimers, which feature the halogen–halogen contacts, are investigated at MP2/6–311++G(d,p) and MP2/aug–cc–pVDZ levels of approximation. The binding energies of these complexes are found to be comparable to those of the weak hydrogen bonds. In both complexes the Cl?F are found to be significantly shorter than the sum of the corresponding van der Waals radii. The C–Cl?F contacts are also found to exhibit certain deviation from linearity. However, the energy differences between linear and bent structures are very small and primarily accounted for by electrostatic interactions between remote parts of the dimer. This indicates a high conformational flexibility of the halogen–halogen contacts and may help to explain the diversity of structural features in crystals formed by halogen-containing molecules. In both dimers the halogen–halogen interaction leads to certain shortening of the C–Cl electron accepting bond. This is accompanied by a small increase of the C–Cl stretching frequency. Hence, the two investigated dimers can possibly be classified as the blue-shifting halogen–halogen contacts.     

Monomer basis-set truncation effects in calculations of interaction energies: A model study

Supermolecular interaction energies are analyzed in terms of the symmetry-adapted perturbation theory and operators defining the inaccuracy of the monomer wave functions. The basis set truncation effects are shown to be of first order in the monomer inaccuracy operators. On the contrary, the usual counterpoise correction schemes are of second order in these operators. Recognition of this difference is used to suggest an approach to corrections for basis-set truncation effects. Also earlier claims--that dimer-centered basis sets may lead to interaction energies free of basis-set superposition effects--are shown to be misleading. According to the present study the basis-set truncation contributions, evaluated by means of the symmetry-adapted perturbation theory with monomer-centered basis sets, provide physically and mathematically justified corrections to supermolecular results for interaction energies.     

Fluorescence probes based on 9‐acridyl derivatives of aromatic amines for monitoring free‐radical polymerization

The series of 9‐acridyl derivatives of aromatic amines have been investigated as fluorescent probes for monitoring the progress of free‐radical polymerization. This study on the changes in the fluorescence intensity and spectroscopic shift of specific compounds was carried out during thermally initiated polymerization of methyl methacrylate and photoinitiated polymerization of 2‐ethyl‐2‐(hydroxymethyl)‐1,3‐propanediol triacrylate‐1‐methyl‐2‐pyrrolidonone mixture. The purpose of this investigation was to find a relationship between the changes in the shape and intensity of fluorescent probes and the degree of monomer conversion into a polymer. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3481–3488, 2002     

The effects of substituent size and molecular weight on the liquid crystalline properties of poly(2-alkyl-1,4-phenylene terephthalate)s

A series of low molecular weight, thermotropic poly(2-alkyl-1,4-phenylene terephthalate)s was prepared by the solution polycondensation reaction of terephthaloyl chloride and alkylhydroquinones containing n-alkyl substituents of increasing size from methyl to dodecyl. Samples of the low molecular weight polymers so obtained were also further polycondensed in the solid state to obtain high molecular weight polymers. The liquid crystalline phase behaviors and textures were determined, and the effects of polymer structure and molecular weight on these properties are discussed. All of the polymers obtained formed thermotropic, nematic mesophases, which were less stable for the lower molecular weight polymers, as expected, than were the mesophases formed by the higher molecular weight polymers. © 1994 John Wiley & Sons, Inc.     

Tautomerism of xanthine: The second-order MØller-Plesset study

Four 9H and four 7H tautomers of DNA base xanthine were studied by the ab initio LCAO-MO method at the MP2/6-311G^**//HF/6-31G^** and MP2/6-31G^**//HF/6-31G^** approximations. All calculated structures are minima at the HF/6-31G^** potential energy surface with the dioxo 7H tautomer (A1) being the global minimum. The second most stable tautomer, dioxo-9H (B1) is by 9 kcal/mol less stable. For the A1 B1 transition the calculated MP2 energy gap corresponds to the equilibrium constant of 2 × 10^–7. Therefore, only the major tautomeric form A1 is predicted to be detectable in the gas phase. The 7H and 9H groups of tautomers are discussed separately. Within both groups, the dioxo form (A1-7H, B1-9H) is the most stable one and is succeeded by the 2-dihydroxy (A2, B2) form. However, while the energy difference between A1 and A2 is 10 kcal/mol, the energy difference between B1 a B2 is only 2 kcal/mol. The effect of polar environment was estimated by the SCRF method, using a spherical cavity, at the HF/6-31G^** level. These calculations did not change the gas phase stability order of the tautomers. However, the energy difference between A1 and B1 decreased from 9 kcal/mol at the HF/6-31G^** level to 4 kcal/mol at the SCRF HF/6-31G^** level.