Non-smoothness of event horizons of Robinson-Trautman black holes

It is shown that generic small data Robinson-Trautman space-times cannot beC ¹²³ extended beyond the r=2m Schwarzschild-like event horizon. This implies that an observer living in such a space-time can determine by local measurements whether or not he has crossed the event-horizon of the black-hole.     

Thes-f model with Coulomb repulsion: Thermodynamics of two atomic cluster. Spin 1/2

A cluster of two atoms described by thes-f model with Coulomb repulsion has been considered. The interaction between localized 4f electrons (S=1/2) is taken in the molecular field approximation. The thermodynamic quantities like magnetization, specific heat and correlation functions n , n , S ^z n , S ^z n , S ^z (n –n ), n n and S ⁺ a ⁺ a as functions of temperature are presented for different band fillingN=0, 0.5, 1, 1.5, 2. The dependence of Curie temperature onN is calculated. The phase diagram forN=1 (T=0K) shows the possibility of existence of two phases: paramagnetic and ferromagnetic.The Curie temperature and the specific heat as functions ofN exhibit similar trends as found in experiments on doped magnetic semiconductors.     

Multilayer adsorption of alcohols from benzene/n-heptane mixtures on silica gel

An equation for multilayer adsorption from multicomponent liquid mixtures on solid surfaces¹ has been examined. For this purpose experimental adsorption data for four alcohols from benzene/n-heptane mixture on silica gel have been measured. Average number of the adsorbed layers, heterogeneity parameter and capacity of the surface phase have been evaluated by using the equation mentioned above.

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Mehrschichten-Adsorption von Alkoholen aus Benzol/n-Heptan-Mischung an Silica Gel

Zusammenfassung Eine Gleichung für Mehrschichten-Adsorption an festen Oberflächen¹ aus Mehrkomponentenlösungen wurde getestet. Zu diesem Zweck wurden experimentelle Daten für die Adsorption von vier Alkoholen aus Benzol/n-Heptan-Mischung an Silica Gel herangezogen. Der Mittelwert für die Anzahl der Adsorptionsschichten, der Heterogenitätsparameter und die Kapazität der Oberflächenphase wurde aus dieser Gleichung berechnet.

     

Thermolytic carbonates for potential 5'-hydroxyl protection of deoxyribonucleosides

Thermolytic groups structurally related to well-studied heat-sensitive phosphate/thiophosphate protecting groups have been evaluated for 5'-hydroxyl protection of deoxyribonucleosides as carbonates and for potential use in solid-phase oligonucleotide synthesis. The spatial arrangement of selected functional groups forming an asymmetric nucleosidic 5'-O-carbonic acid ester has been designed to enable heat-induced cyclodecarbonation reactions, which would result in the release of carbon dioxide and the generation of a nucleosidic 5'-hydroxyl group. The nucleosidic 5'-O-carbonates 3-8, 10-15, and 19-21 were prepared and were isolated in yields ranging from 45 to 83%. Thermolytic deprotection of these carbonates is preferably performed in aqueous organic solvent at 90 degrees C under near neutral conditions. The rates of carbonate deprotection are dependent on the nucleophilicity of the functional group involved in the postulated cyclodecarbonation reaction and on solvent polarity. Deprotection kinetics increase according to the following order: 4 < 5 < 10 < 6 < 12 < 7 < 13 < 8 < 14 congruent with 19-21 and CCl4 < dioxane < MeCN < t-BuOH < MeCN:phosphate buffer (3:1 v/v, pH 7.0) < EtOH:phosphate buffer (1:1 v/v, pH 7.0). Complete thermolytic deprotection of carbonates 7, 8, 13, and 14 is achieved within 20 min to 2 h under optimal conditions in phosphate buffer-MeCN. The 2-(2-pyridyl)amino-1-phenylethyl and 2-[N-methyl-N-(2-pyridyl)]aminoethyl groups are particularly promising for 5'-hydroxyl protection of deoxyribonucleosides as thermolytic carbonates.     

Diastereoselective addition of vinylmagnesium halides to variously N-mono- and N,N-diprotected l-alaninals

Diastereoselective C₂-elongation processes of N-mono- 1a-c and N,N-diprotected 1d-fl-alaninals, using vinylmagnesium bromide and chloride, are described. A substantial difference between effects of the N-protecting groups replacing either one or two amino protons was observed.     

Interaction potentials of the RG-I anions, neutrals, and cations (RG = He, Ne, Ar)

Interaction potentials of the iodine atom, atomic cation, and anion with light rare-gas atoms from He to Ar are calculated within the unified ab initio approach using the unrestricted coupled-cluster with singles and doubles and perturbative treatment of triples correlation treatment, relativistic small-core pseudopotential, and an extended basis set. Ab initio points are fit to a flexible analytical function. The calculated potentials are compared with available literature data, assessed in the I(-)-and I+-ion mobility calculations and the Ar-I(-)-anion zero electron kinetic-energy spectra simulations, and analyzed using the correlation rules. The results indicate a high precision of the reported potentials.     

Construction of a thermoanalyzer for DTA-TD-TMAG-T measurements on metals up to 1100 °C

A thermoanalyzer is described for the simultaneous testing of metals and alloys by three methods: differential thermal analysis (DTA), thermal dilatometry (TD) and thermomagnetometry (TMAG). One reference specimen is used as a standard for each of the above kinds of analysis. Measurements can be performed in vacuum or in a static or dynamic atmosphere of gases at any pressure between normal and 5× 10^–5 Torr. The temperature of the sample can be changed linearly in the range 20–1100 °C. DTA and TD are performed classically, whereas TMAG is based on the temperature and magnetic field-dependences of the reversible magnetic susceptibility of the sample. Some analysis results are presented.

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Zusammenfassung Es wird ein Thermoanalysator zur simultanen Untersuchung von Metallen und Legierungen durch drei Methoden beschrieben: Differentialthermoanalyse (DTA), Thermodilatometrie (TD) und Thermomagnetometrie (TMAG). Für alle drei Verfahren wurde die gleiche Referenzsubstanz als Standard benutzt. Messungen können im Vakuum oder is statischer bzw. bewegter Atmosphäre von Gasen beliebigen Druckes zwischen Normaldruck und 5·10^–5 Torr durchgeführt werden. Die Temperatur der Probe kann zwischen 20 und 1100 °C linear variiert werden. Während DTA und TG die herkömmlichen Verfahren zu Grunde liegen, basiert TMAG auf der Temperatur- und Magnetfeldabhängigkeit der reversiblen magnetischen Suszeptibilität der Probe. Einige Analysenergebnisse wurden dargestellt.

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: (), () (). . , 5·10^–5 . 20–1100°. , . .

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Presented at the 4th European Symposium on Thermal Analysis and Calorimetry, Jena, GDR, August 1987.     

Synthesis and photoinduced isomerization ofansa{·5,·5′-[1,1′-(1-silacyclopent-3-ene-1,1-diyl)bis(indenyl)]} dichlorozirconium The crystal structure of itsmeso form

ansa{·⁵,·⁵′-[1,1′-(1-silacyclopent-3-ene-1,1-diyl)bis(indenyl)]} dichlorozirconium (1a,b) was synthesized. The crystal structure ofmeso-[(1,4-CH₂CH=CHCH₂)Si(C₉H₆)₂ZrCl₂] (1b) was established by X-ray diffraction analysis. Photoinduced interconversion of the racemic (1a) andmeso forms was studied under various conditions. The photostationary state (rac: meso=55∶45) was established rapidly when solutions ofansa-zirconocene were irradiated with visible light. Deceased Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2351–2356, November, 1998.     

Development of hollow fiber‐supported liquid‐phase microextraction and HPLC‐DAD method for the determination of pyrethroid metabolites in human and rat urine

A simple hollow fiber liquid‐phase microextraction method for the determination of synthetic pyrethroid metabolites, 3‐phenoxybenzoic acid and 4‐hydroxy‐3‐phenoxybenzoic acid, in human and rat urine was developed and validated. A polypropylene hollow fiber tightly fitted onto a Nylon rod and impregnated with organic solvent served as a disposable extraction device. Desorption of analytes was carried out in NaOH solution, analyzed further by gradient HPLC and diode array detection method. Important factors were identified using Taguchi OA16 (4⁵) orthogonal array design and further optimized using univariate approach. The optimum method performance was observed when 1 mL of urine hydrolyzed with 0.2 mL of concentrated HCl was further supplemented with 100 mg of NaCl and extracted for 120 min into dihexyl ether immobilized in the pores of the hollow fiber. Metabolites were desorbed into 0.1 mL of 0.1 M NaOH for another 120 min. Limits of detection and quantitation of 15 and 50 ng/mL were obtained for both analytes. Relative standard deviations of 1.6–12.6% over the linear range (50–10,000 ng/mL, r > 0.9906) were observed. Intra‐ and inter‐day accuracies of the method ranged from 98.3 to 109.5% and from 93.3 to 110.9%, respectively. The optimized method was applied to the analysis of real urine samples collected from rats exposed orally to cypermethrin. Copyright © 2013 John Wiley & Sons, Ltd.