bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduction of nitrogen oxide by carbon monoxide over pure and platinum-doped LaMnO3 perovskites. Effect of oxygen on the reaction
Authors: Bartoň Jaroslav
Published: February 2010

The reduction of NO by CO has been studied using pure and platinum-doped LaMnO3 perovskites as catalysts. The reaction products always include nitrogen monoxide, whose amount varies with temperature. The reaction kinetics for the two catalysts are different and have been described by different rate laws. Considerable differences have also been found in the apparent activation energies: in the presence of Pt it is about half that for the reaction catalyzed by pure LaMnO3. Both the catalysts exhibit good catalytic properties, but the platinum-doped LaMnO3 shows a higher catalytic activity. The presence of oxygen in the inlet mixture affects considerably the kinetics of the reaction catalyzed by platinum-doped LaMnO3. The conversion of NO passes through a maximum at an oxygen/carbon monoxide molar ratio, m, of 1.8. At m > 1.8, CO is oxidized preferentially by oxygen rather than by NO.
Numerical studies of feed cycling in a CSTR
Authors: Klusáček Karel , Silveston Peter Lewis , Hudgins Robert Ross
Published: February 2010

A numerical study of feed composition cycling (periodic operation) of stoichiometrically simple reactions described by Langmuir-Hinshelwood or Eley-Rideal kinetics reveal that although time-average production rates may be higher than the corresponding steady-state ones at the same time-average feed composition, they do not exceed the maximum steady-state rates at a given space velocity. This behaviour is explained by the dynamics of surface concentrations of adsorbed species during a cycle. Although these findings support other numerical studies, they are at variance with experimental observations. Thus, there is a need to develop more sophisticated kinetic models for the prediction of dynamic behaviour of heterogeneous catalytic systems.
Proximity effects in 29Si, 13C, and 1H NMR spectra of ortho substituted phenoxytrimethylsilanes
Authors: Schraml Jan , Chvalovský Václav , Jancke Harald , Koehler Peter , Larin Mikhail F. , Pestunovich Vadim A. , Voronkov Mikhail G.
Published: February 2010

NMR Spectra of eight ortho substituted phenoxytrimethylsilanes, 2-X-C6H4-OSi(CH3)3 (X = Cl, Br, OCH3, NH2, NO2, OSi(CH3)3, CH3, and H), are reported. In contrast to analogous ortho substituted methoxybenzenes the 13C chemical shifts of C-2 and C-6 aromatic carbons do not exhibit consistent trends indicating different conformational preferences in the trimethylsiloxybenzenes. Under the influence of the ortho substituents the nuclei of OSi(CH3)3 group (29Si, 13C, and 1H) are deshielded; compounds with X = CH3 (and H) appear anomalous in this respect. It is argued that this proximity effect is not due to an interaction involving terminal methyl groups but involves the oxygen atom of the OSi(CH3)3 group; it is most likely due to an interaction with unshared electrons of the ortho substituent.
The structure of 1,2,4,4,6-pentaphenyl-1,4-dihydropyridine
Authors: Vojtěchovský Jaroslav , Hašek Jindřich , Ječný Jiří , Huml Karel
Published: February 2010

Title compound is triclinic, Mr = 461.60; P1, a = 9.158(1), b = 16.062(3), c = 19.472(3) Å, α = 110.69(1)°, β = 89.70(1)°, γ = 103.17(1)°, V = 2 600(1) Å3, Z = 4, Do = 1.15(3), Dc = 1.179(1) Mg m-3, λ(CuKα) = 1.5418 Å, μ = 0.509 mm-1, F(000) = 976 K, R = 0.040 for 8 059 unique observed reflections. Both symmetrically independent molecules show a different geometry of the 1,4-dihydropyridine ring: either the boat conformation with apexes C(sp3), N and boat angles 14.7(3)° and 10.3(2)° respectively, or the planar conformation. The conformation has been compared with similar dihydropyridines obtained from Cambridge Structural Database.
Protoberberine alkaloids from the bark of Enantia chlorantha
Authors: Jalander Lars , Sjöholm Rainer , Virtanen Pauli
Published: February 2010

Four protoberberine alkaloids, palmatine (Ia), jatrorrhizine (Ib), columbamine (Ic) and pseudocolumbamine (Id), were isolated from the bark of Enantia chlorantha and characterized. The corresponding acetylated tetrahydro derivatives (IIa-IId) were also identified.
Reversed-phase high performance liquid chromatographic behaviour of homologous series
Authors: Rittich Bohuslav , Rudolfová Štěpánka , Jandera Pavel
Published: February 2010

The retention model for reversed-phase high-performance liquid chromatography (RP-HPLC) based on interaction indices was applied to separation of the homologous series members. The validity of the equations describing relationship between retention (log k) and the number of methylene groups in alkyl chain (Cn) and composition of mobile phase (φ) by using statistical methods was verified. The regression coefficients of a quadratic term for relationship log k vs Cn and log k vs φ can be neglected. The regression coefficient of interaction term Cnφ is statistically significant.
Internal diffusion in the extruded catalyst particle with tetralobe cross section
Authors: Hanika Jiří
Published: February 2010

The problem of internal diffusion in the catalyst particle of geometrical cross profile in the tetralobe shape is solved numerically for the case of the 1st order reaction taking place under isothermal conditions. The calculated values of the effectiveness factor of internal diffusion for an infinite long particle prove favourable effect of the catalyst particle shaping on its activity in comparison with the cylindrical extrudates.
Kritische Reynolds-Zahlen für gas und flüssigkeit bei der zweiphasenströmung durch füllkörper and packungskolonnen
Authors: Grabbert Gert , Jiřičný Vladimír , Staněk Vladimír
Published: February 2010

Obwohl für den Impuls-, Stoff- und Wärmetransport das Strömungsregime von fundamentaler Bedeutung ist, fehlen in der Literatur für Zweiphasenströmungen durch Schüttungen und Packungen jegliche Angaben zu diesem wichtigen Sachverhalt. Auf der Grundlage theoretischer Überlegungen und experimenteller Ergebnisse aus der Literatur wird in der vorliegenden Arbeit versucht, die kritischen Reynolds-Zahlen für die Gasströmung und die Flüssigkeitsströmung vorauszuberechnen.
Design of continuous flow immobilized bacterial cells reactor for production of L-malic acid
Authors: Fialová Marie , Zahradník Jindřich , Kučerová Hana
Published: February 2010

An experimental study was carried out, aimed at establishing an engineering data base for the optimum design of a pilot-plant fixed bed reactor for continuous biotransformation of natrium fumarate to L-malic acid catalysed by immobilized bacterial cells. Cells Corynebacterium sp. immobilized in calcium alginate were used for experiments. Effective reaction kinetics including the effect of transport phenomena in the bed was determined and conditions of the safe conversion data scale up were defined. Regarding the requirements of continuous production, long-term stability of the biocatalytic system was tested at operation conditions corresponding to constant degree of substrate conversion at the reactor outlet. Quantitative evidence on changes of the effective reaction kinetics (i.e. on the decrease of the effective rate constant value) over the three-months production period was obtained from this experimental run. Decisive design parameters of a pilot-plant reactor were calculated for estimated production of 20 t of L-malic acid per 90 days period (maximum time of economic biocatalyst utilization).
Photoinitiated addition of 1,3-dioxolanes to chlorotrifluoroethylene
Authors: Dědek Václav , Fikar Jiří
Published: February 2010

Article without abstract
Topological aspects of chemical reactivity. On physical meaning of the similarity index
Authors: Ponec Robert , Strnad Martin
Published: February 2010

The paper analyzes and discusses the detailed physical meaning of the similarity indices of the first and second orders which were introduced originally as characteristics expressing, in the sense of the least-motion principle, the extent of the electron reorganization connected with the transformation of reactants into products within a given reaction.
Conformational structure of the antiarrhythmic mexiletine, its cation and hydrochloride
Authors: Remko Milan , Mackov Martin
Published: February 2010

The PCILO and MNDO quantum chemical methods were applied to the conformational analysis of antiarrhythmic mexiletine 1-(2,6-dimethylphenoxy)-2-aminopropane, its cation and hydrochloride. The stable conformations, proton affinity, and the hydrogen bonding energy of the mexiletine ion pair were determined.
The effect of cation concentration on the nitrogen splitting constant of nitroxide free radicals
Authors: Hussain Hamza A.
Published: February 2010

Nitroxide free radicals prepared from diethylamine, piperidine and pyrrolidine by oxidation with hydrogen peroxide were studied by ESR spectroscopy. The changes in the 14N splitting constant (aN) caused by the addition of KBr or tetraethylammonium bromide were measured in dependence on the concentration of the ions. For diethylamine nitroxide and piperidine nitroxide, the results are discussed in terms of two equilibria: the one, involving the anion, is associated with a gain or loss of hydrogen bonds to the nitroxide oxygen atom, the other is associated with the formation of solvent shared units involving the cation, which results in changes in the hydrogen bonding strenght. The large increase in the aN value in the case of pyrrolidine nitroxide is explained in terms of an interaction from one side of the positively charged N atom; the increase in aN in the case of diethylamine and piperidine nitroxides is explained in terms of interactions with both sides of the positively charged N atom.
Reduction of nitrogen oxide by ammonia. Oxidation state of V2O5/Al2O3 catalysts and reaction mechanism
Authors: Čížek Milan
Published: February 2010

When the (NO + NH3 + O2) reaction is carried out over V2O5/Al2O3, the catalysts are partially reduced, and prereduced catalysts are oxidized by the reaction mixture at a slower rate than by an O2 + N2 mixture. The degree of catalyst reduction in the (NO + NH3 + O2) reaction depends on the gas phase composition and particularly on the vanadium loading of the catalyst. The initial oxidation state of catalyst has an effect on the catalyst activity for the reaction. Rate-determining reduction and oxidation steps of the so-called reduction-oxidation mechanism are proposed on the basis of a comparison of the reduction and oxidation of the catalyst by the reaction components.
Pycnometric determination of densities and excess volumes of binary mixtures containing at least one associating component
Authors: Chýlková Kamila , Malijevská Ivona
Published: February 2010

Densities at 20 °C and molar excess volumes calculated from them are reported in the work for the mixtures of the substances: propionic acid-n-heptane, propionic acid-benzene, trifluoroacetic acid-benzene, propionic acid-cyclohexane, acetic acid-cyclohexane, acetic acid-trifluoroacetic acid, acetic acid-propionic acid, and propionic acid-trifluoroacetic acid. For the last system mentioned, a strange dependence of excess volume on composition was found which is noted for three local extremes. The dependences of excess volume on composition are correlated by the Redlich-Kister polynomial.
Concentration boundary layer under general steady-flow conditions
Authors: Wein Ondřej
Published: February 2010

An explicit formula is given for the overall mass-transfer coefficient between a steady liquid stream and a small active part of a solid surface in the stream. This is a generalization of the well-known Lighthill formula to the form applicable for any velocity field and any shape of the active surface. Its use is demonstrated for the circular electrodiffusion probes under various kinematic conditions.
Induction period of crystallization of zinc chloride solutions in ethylene glycol
Authors: Sláma Ivo , Malá Jarmila
Published: February 2010

The dependence of the induction period of crystallization on the supercooling was examined for the ZnCl2-ethylene glycol system at mole fractions of the salt from 0 to 0.07, and treated in terms of the TTT (Time-Temperature-Transformation) diagram. The critical induction period of crystallization increases substantially on the addition of ZnCl2 to ethylene glycol. The thermal stability of supercooled liquids is discussed in terms of the shape and position of the TTT curves.
Qualitative analysis of the vapour-phase equilibrium composition in the systems Si-Cl and Si-Cl-H by matrix-isolation IR spectroscopy
Authors: Leitner Jindřich , Mikulec Jan , Černý Čestmír
Published: February 2010

The vapour phase in the systems Si-Cl and Si-Cl-H in equilibrium with solid silicon has been analyzed quantitatively by matrix-isolation IR spectroscopy. At 1 300 K, the analysis revealed SiCl4, SiCl3 and SiCl2 in the system Si-Cl, and HCl, SiCl4, SiCl3, SiCl2, SiHCl3 and SiH2Cl2 in the system Si-Cl-H. No SiHCl, a compound which according to equilibrium calculations represents one of the dominant components, could be detected.
Synthesis and 1H and 13C NMR spectra of sulfur derivatives of pyrazine derived from amidation product of 2-chloropyrazine and 6-chloro-2-pyrazinecarbonitrile. Tuberculostatic activity
Authors: Dlabal Karel , Palát Karel , Lyčka Antonín , Odlerová Želmíra
Published: February 2010

Homolytic amidations of 2-chloropyrazine and 6-chloropyrazine-2-carbonitrile have been carried out to obtain products which have been used to prepare sulfur derivatives of pyrazine as potential tuberculostatic agents. The 1H and 13C NMR spectra of the products have been measured and interpreted, and the antituberculotic activity has been evaluated.
Epimeric 17-hydroxy derivatives of 14β-androst-5-en-3β-yl acetate
Authors: Černý Ivan , Pouzar Vladimír , Buděšínský Miloš , Drašar Pavel , Havel Miroslav
Published: February 2010

A new, six-step synthesis of 3β-hydroxy-14β-androst-5-en-17-one (IX) starting from 3β-hydroxyandrost-5-en-17-one has been elaborated. Reduction of acetate X with sodium borohydride afforded 17α-hydroxy-14β-androst-5-en-3β-yl acetate (XI). The corresponding 17β-derivative XIV was obtained by epimerization of 17α-O-tosyl derivative XIII with sodium nitrite in hexamethylphosphoramide. The 13C and 1H NMR spectra of 14β-androstane derivatives are discussed.
Synthesis of 5'-O-phosphonomethyl derivatives of pyrimidine 2'-deoxynucleosides
Authors: Krečmerová Marcela , Hřebabecký Hubert , Holý Antonín
Published: February 2010

Reaction of sodium salt of 3-N,3'-O-bis(benzyloxymethyl)-2'-deoxyuridine (X) and 3-N,3'-O-bis(benzyloxymethyl)-2'-deoxythymidine (XI) with diethyl p-toluenesulfonyloxymethanephosphonate in dimethylformamide afforded diesters of the respective 5'-O-phosphonomethyl derivatives XII and XVII. Diethyl esters of 5'-O-phosphonomethyl-2'-deoxynucleosides XV and XIX, obtained after hydrogenolytic removal of the benzyloxymethyl groups, were converted into free 2'-deoxy-5'-O-phosphonomethyluridine (XVI) and a mixture of anomeric 1-(2-deoxy-5-O-phosphonomethyl-β-D-erythro-pentofuranosyl)thymines (XXIIIa, XXIIIb), respectively. Analogously, 2'-deoxy-5'-O-phosphonomethylcytidine (XXXIV) was prepared from 4-N-benzoyl-2'-deoxy-3'-O-(tetrahydro-2H-pyran-2-yl) cytidine (XXX) via diethyl ester of 2'-deoxy-5'-O-phosphonomethylcytidine (XXXIII). This compound reacted with bromotrimethylsilane to give compound XXXIV without anomerization and nucleoside bond cleavage. Condensation of the protected nucleosides X and XI with dibenzyl p-toluenesulfonyloxymethanephosphonate afforded dibenzyl esters of the corresponding 5'-O-phosphonomethyl derivatives XIII and XVIII. The free 5'-O-phosphonomethyl derivatives XVI and XXIIIa were obtained from XIII and XVIII by catalytic hydrogenation.
Synthesis and evaluation of antigenic properties of peptides of the HIV-1 protein gp 41
Authors: Bespalova Zhanna D. , Pekelis Boris L. , Deigin Vladislav I. , Yarova Elena P. , Saks Tatyana P. , Ovchinikov Mikhail V. , Efremov Evgenii E. , Sepetov Nikolai F. , Korotkov Andrei M. , Molokoedov Alexander S.
Published: February 2010

Scheme is described for the synthesis of 19- and 21-member peptides which constitute a part of the domain (sequence 584-609) from the conservative region of the transmembrane protein gp 41 HIV-1. The synthesis was carried out using standard methods of peptide chemistry in solution. The peptides were built from fragments which were synthesized by means of stepwise joining of amino acid residues starting from the C-terminus, using activated esters. The "complex F" or DCC + HONB methods were employed for condensation of the fragments. Alpha amino groups were protected by means of Z- and Boc- protecting groups. The tert. butyl group was used for the protection of functional side chains. The sulfhydryl group of cysteine was blocked with S-acetamidomethyl group and salt formation or benzyl esters were used for protection of the carbonyl group. During the synthesis, it was necessary to solve problems connected with racemization of Asp and Glu residues in the course of condensation of fragments, as well as formation of a beta-peptide at the position of aspartic acid. HPLC and NMR methods were utilized extensively for the separation and characterization of the structure of the synthesized compounds. The final peptides were tested in enzyme immunoassay. ELISA tests proved that the peptides can be employed as antigenic components for the diagnosis of HIV-1.
New trityl-activated esters for peptide synthesis
Authors: Cordopatis Paul , Manessi-Zoupa Evy , Theodoropoulos Dimitrios
Published: February 2010

Article without abstract
Similarity approach to chemical reactivity. Specificity of multibond processes
Authors: Ponec Robert , Strnad Martin
Published: February 2010

The recently suggested approach to analysis of chemical reactivity in terms of the similarity index has been generalized by introduction of similarity indices of higher orders. Using an example of concrete application of the third order similarity index some specific features accompanying the process of electron reorganization in the so-called multibond reactions have been analyzed and discussed.
Three-dimensional structures of substituted diphenyl sulfides
Authors: Schneider Bohdan , Rejholec Václav , Kuchař Miroslav
Published: February 2010

Three-dimensional crystal structures of a diphenyl sulfide skeleton from various compounds were confronted with computed conformational map. Diphenyl sulfide fragments, 31 in total, were retrieved from the Cambridge Structural Database and four fragments were taken from our measurements. Due to the symmetry of the fragment, the number of analyzed fragments rose to 140. The main features of geometrical behaviour of the fragment can be summarized as follows: If an endocyclic torsion angle of a phenyl ring deviates from 0 °C, the adjacent torsion angle is deformed in opposite direction by the same value keeping thus the phenyl ring planar. Repulsion of phenyl rings enlarges a C-S-C bonding angle in all fragments and bends aside the phenyl ring from a symmetrical attachment which has torsion around a S-C bond near 0°. Torsion angles around the S-C bonds correlate with each other keeping approximately perpendicular orientation of the phenyl rings. The correspondence between experimental values of torsion angles and low energy regions of the molecular mechanics conformational map suggests that possible gas-phase and crystal conformations of the diphenyl sulfide molecule are the same. Ab initio calculations fully confirmed results of molecular mechanics and - along with the crystal conformations - justify further usage of molecular mechanics in computational modelling of diphenyl sulfides.
The polarographic and voltammetric determination of 4-aminoazobenzene
Authors: Barek Jiří , Kvapilová Helena , Mejstřík Viktor , Petira Oldřich , Zima Jiří
Published: February 2010

The polarographic reduction of genotoxic 4-aminoazobenzene was studied, a mechanism was proposed and conditions were found for the analytical determination using Tast polarography in the range 1 . 10-4 - 2 . 10-6 mol l-1 and differential pulse polarography in the range 1 . 10-4 - 2 . 10-7 mol l-1. The sensitivity can be further increased by using fast scan differential pulse voltammetry at a hanging mercury drop electrode combined with adsorptive accumulation of the test substance on the surface of the working electrode, permitting the determination to be carried out in the range 1 . 10-7 - 2 . 10-10 mol l-1. The anodic oxidation of 4-aminoazobenzene was also studied at a glassy carbon solid electrode and conditions were found for its analytical utilization in the range 1 . 10-4 - 2 . 10-6 mol l-1 using classical or differential pulse voltammetry at a rotating disk electrode.
The synthesis and X-ray structure of 3,7-diiododibenzosuberone. Synthesis of 3,7-diiodoamitriptyline
Authors: Lešetický Ladislav , Smrček Stanislav , Sváta Vladimír , Podlahová Jana , Podlaha Jaroslav , Císařová Ivana
Published: February 2010

The preparation of iodinated tricyclic antidepressive drug amitriptyline as the substrate for isotopic exchange labelling is described. Direct iodination of 10,11-dihydro-5H-dibenzo[a,d]-cycloheptene-5-one leads mainly to 3,7-diiododerivative (III). Its structure was confirmed by means of single crystal X-ray diffraction analysis: monoclinic, P21/c; a = 13.315(2), b = 7.852(1), c = 13.584(2) Å, β = 103.67(2)°, Z = 4, R = 0.064 for 2 474 observed independent reflections. Iodinated ketone was transformed to 3,7-diiodo-5-(3-N,N-dimethylaminopropylidene)-10,11-dihydro-5H-dibenzo[a,d]-cycloheptene (diiodoamitriptyline), by the reaction with dimethylaminopropylmagnesiumchloride and dehydration of the resulting alcohol. The product was isolated as hydrogen oxalate salt.
Preparation of both enantiomers of (1R*, 2S*)-1-cyclohexyl-1,2-propanediol from the commercial Neuberg's ketol
Authors: Červinka Otakar , Stružka Vladimír
Published: February 2010

Both the optically pure enantiomers of (1R*, 2S*)-1-cyclohexyl-1,2-propanediol (II) were prepared from commercial (R)-(-)-1-phenyl-1-hydroxy-2-propanone (I; Neuberg's ketol). (1R, 2S)-(+)-1-Cyclohexyl-1,2-propanediol ((+)-II) was obtained in 19% total yield, its (1S, 2R)-enantiomer ((-)-II) in 8% yield. Both diols, as well as their precursors, enantiomeric (1R*, 2S*)-1-phenyl-1,2-propanediols (IIIa), are suitable chiral synthons.
Synthesis of compounds related to 2,6-dialkylphenylhydrazines
Authors: Krutošíková Alžbeta , Dandárová Miloslava , Konečný Václav
Published: February 2010

2,6-Dialkylphenylhydrazines were the starting materials for the synthesis of 2,3-dichloro- and 2,3-dibromo-4-(2',6'-dialkylphenylhydrazino)butenoic acids Ia-If and 3-(2',6'-dialkylphenylhydrazinocarbonyl)propionic acids IIIa-IIIc. Compounds IIIa-IIIc cyclized to give 2-(2,6-dialkylphenyl)-2,3-dihydropyridazine-3,6-diones Va-Vc. Chloro-, bromo- and dichloromaleic anhydride reacted with the starting hydrazines to furnish N-(2',6'-dialkylphenylamino)maleimides IVa-IVi. N-((2,2,2-Trichloro-1-formylamino)ethyl)-2,6-dialkylphenylhydrazines VIa-VIc, obtained from the starting hydrazines and N-(1,2,2,2-tetrachloroethyl)formamide together with other products were tested as pesticides.
Potential nootropic agents: Synthesis of some (2-oxo-1-pyrrolidinyl)acetamides and some related compounds
Authors: Valenta Vladimír , Holubek Jiří , Svátek Emil , Valchář Martin , Krejčí Ivan , Protiva Miroslav
Published: February 2010

Ethyl (2-oxo-1-pyrrolidinyl)acetate was transformed by ester exchange to the 2-dimethylaminoethyl ester VI which was converted to the choline iodide ester VII. The mixed anhydride of (2-oxo-1-pyrrolidinyl)acetic acid and monoethyl carbonate was reacted with ethyl aminoacetate to give the ester VIII which was transformed on the one hand to the amide IX, and to the 2-dimethylaminoethyl ester X on the other. Reaction of the latter with methyl iodide afforded a further choline iodide ester XI. Reactions of (2-oxo-1-pyrrolidinyl)acetyl chloride with 4-chloroaniline and 3-aminopyridine gave the amides XII and XIV. The anilide XIII was obtained from 2-(2-oxo-1-pyrrolidinyl)butyric acid and 4-chloroaniline by means of dicyclohexylcarbodiimide. The benzo analogue (XV) of piracetam (I) was synthesized from oxindole via the ester XVI. The anilide XII (V⁄FB-16 536) was found to potentiate significantly the anticonvulsant effect of diazepam in mice, to prolong the survival time of mice under conditions of nitrogen anoxia, and to prolong significantly the duration of the "gasping reflex" in mice.
Fluorescence studies on P1,P3-dinucleoside triphosphates related to mRNA cap: Acidity and intramolecular stacking
Authors: Wieczorek Zbigniew , Darżynkiewicz Edward , Stępiński Janusz , Lönnberg Harri
Published: February 2010

The fluorescence intensity of several P1,P3-dinucleoside triphosphates related to mRNA cap-structure has been measured as a function of pH and temperature. The extent of intramolecular stacking has been estimated by comparing the intensities obtained with dinucleoside triphosphates to those of the corresponding monomers. The pKa values of 7-alkylguanine moieties in both dimeric and monomeric compounds have been determined by fluorescence and absorption spectroscopy.
Regiospecific cleavage of RNA by RNase H from E. coli in the presence of a complementary oligonucleotide with inserted alternating 2'-O-methylcytidine residues
Authors: Metelev Valerii G. , Krynetskaya Natalya F. , Purmal Andrei A. , Shabarova Zoya A. , Točík Zdeněk , Arnold Luboš , Smrt Jiří
Published: February 2010

Undecanucleotide dA-dC-dC-dA-Cm-Cm-dG-Cm-dG-Cm-dT (Cm = 2'-O-methylcytidine) was prepared and used as a probe for splitting of 5S rRNA fragment by RNase H (E. coli). It was found that substitution of 2'-deoxycytidine of d(ACCACCGCGCT) by 2'-O-methylcytidine in positions 5, 6, 8 and 10 provided regiospecific splitting of RNA fragment by RNase H in the presence of modified probe between U25 and C26.
Synthesis of N-substituted 3-isopropyl-1H-2,1,3-benzothiadiazin-(4)-3H-one 2,2-dioxide derivatives
Authors: Prousek Josef
Published: February 2010

Article without abstract
Studies on polyazaindenes synthesis of several new condensed pyridazine derivatives
Authors: Deeb Ali , Said Said Ali
Published: February 2010

Article without abstract
Catalysts and biocatalysts anchored to inorganic supports
Authors: Čapka Martin
Published: February 2010

The review deals with transition metal complexes and enzymes chemically bonded to inorganic supports by means of silyl-substituted anchoring ligands. The synthesis of these functionalization agents, the effect of immobilization procedure, the length of spacer, the texture of support and the structure of anchoring ligand are mentioned. Conclusions bases on kinetic studies of the efficiency and selectivity of immobilized catalysts in hydrogenation, hydrosilylation, isomerization, polymerization and enzymatic reactions are discussed. Proposed mechanisms of the action of these catalysts are supported by the results of IR, NMR, ESCA and ESR studies. The attention is paid to the leaching and deactivation of catalysts, to the other types of immobilized catalysts such as those anchored via polymer ligands or via ligands in molten phase as well as to the effect of support texture and particle shape, to prepare the catalysts with limited nonspecific sorption and long lifetime.
The crystal, molecular structure and EPR spectrum of dipotassium bis[(μ-isothiocyanato-N,S)-(N-salicylidene-(R)-phenylalaninato)(N-salicylidene-(S)-phenylalaninato)]dicuprate(II)
Authors: Sivý Július , Pavelčík František , Krätsmár-Šmogrovič Juraj , Žemlička Milan , Seressová Valéria
Published: February 2010

The title compound crystallizes in the triclinic system with a space group of P1 (No. 2); a = 0.8283(4), b = 0.9477(6), c = 1.2271(5) nm; α = 74.251(41), β = 82.351(34), γ = 70.475(40)°, V = 0.87282(74) nm3, Z = 1, F(000) = 432, μ = 1.624 mm-1, room temperature. The structure was refined to R = 0.0571 (Rw = 0.0568) for 1 920 observed reflections. The Cu(II) adopts a distorted square-pyramidal coordination. The base of the coordination polyhedron is formed by O(1), N(1), O(2) donor atoms of the terdentate Schiff-base dianion (sal-(R)-phe or sal-(S)-phe) and N(2) atom of the additional NCS- ligand. The axial site (apical position) of the pyramid is occupied by a weakly bonded S-atom; Cu-S = 0.2995(1) nm, originating from the -NCS- bridging ligands. Two units, [Cu(sal-(R)-phe)(NCS)]- and the corresponding (S)-form, are thus joined into centrosymmetric dicuprate complex anion; [Cu2(μ-isothiocyanato-N,S)2(sal-(R)-phe)(sal-(S)-phe)]2-. The Q-band EPR spectrum of this complex (powdered sample, room temperature) exhibits orthorhombic g components: gz = 2.234, gy = 2.059 and gx = 2.039 which can be interpreted as molecular ones (G = 4.9).
Effect of the structure of cellulose acetate membranes on their permeability, electrical conductivity and rejection
Authors: Schwarz Hans-Hartmut , Kůdela Vlastimil , Richau Klaus
Published: February 2010

Ultrafiltration cellulose acetate membrane can be transformed by annealing into reverse osmosis membranes (RO type). Annealing brings about changes in structural properties of the membranes, accompanied by changes in their permeability behaviour and electrical properties. Correlations between structure parameters and electrochemical properties are shown for the temperature range 20-90 °C. Relations have been derived which explain the role played by the dc electrical conductivity in the characterization of rejection ability of the membranes in the reverse osmosis, i.e. rRO = (1 + exp (A-B))-1, where exp A and exp B are statistically significant correlation functions of electrical conductivity and salt permeation, or of electrical conductivity and water flux through the membrane, respectively.
Quartz microstructures and c-axis preferred orientations in high-grade gneisses and mylonites around the Morin anorthosite (Grenville Province)
Authors: Zhao Xiao-ou , Ji Shaocheng , Martignole Jacques
Published: February 2010

Quartz in deformed rocks from two large, high-grade shear zones around the Morin anorthosite (Morin terrane, Grenville Province) displays distinctive microstructures, as well as c-axis preferred orientations. In the west-dipping Morin shear zone, east of the Morin anorthosite, four distinct quartz microstructures (types 1–4) are identified, based on deformation features and grain size. The c-axis orientations are characterized by a single maximum near the stretching lineation and two maxima in type 1 microstructure, and by an asymmetrical, single girdle in type 2 microstructure. Quartz c axes show crossed-girdle pattern in type 3 microstructure. Both quartz microstructures and c-axis preferred orientations suggest that crystal–plastic slip and dynamic recrystallization are the dominant deformation mechanisms. The asymmetry of c-axis orientations with respect to the mylonitic foliation, as well as the substructures developed in quartz, indicates a dextral sense of shear in the Morin shear zone. Type 4 microstructure, which developed in some gneisses and granulites, is interpreted to record influence of postdeformation annealing by which quartz c-axis orientations were partially modified. In the north-northeast-trending, subvertical Labelle shear zone that separates the Morin terrane from the Mont-Laurier terrane, metamorphic assemblages and structural elements suggest that an early, sinistral strike-slip deformation occurred under granulite-facies conditions. This was overprinted by a late downdip movement of the Mont-Laurier terrane under retrogressive conditions. Quartz in felsic gneisses from this zone shows two types of microstructures: one is similar to type 4 from the Morin shear zone, the other is named type 5. Quartz c-axis orientations are complex and less systematic, due to overprinting by two episodes of deformation and possible annealing. These complexities limit the utility of quartz microstructures and c-axis data in the structural analysis of the Labelle shear zone.
Headwall retreat of ground-ice slumps, Banks Island, Northwest Territories
Authors: Lewkowicz Antoni G.
Published: February 2010

The relationship between ice-face ablation and headwall retreat is described for three ground-ice slumps in the Sand Hills moraine, southwest Banks Island. Retreat exceeds ablation by a geometric factor that depends on the slope of the ice and the gradient of the surrounding terrain. Amounts of retreat predicted from ice-ablation calculations compare favourably with field measurements, except at the start of thermokarst activity in the spring or when the ground ice remains covered by debris for long periods.Long-term headwall retreat for slumps in southern Banks Island with different orientations and ice contents can be estimated using a model based on meteorological information. The model predicts headwall recession of 11 m/a for a ground-ice slump facing south and 8.8–9.3 m/a for one facing north, with inputs of a 35 °ice face, a ground slope of 5°, and a volumetric latent heat of 270 MJ/m3. These predictions are close to the maximum rates of retreat over a 10 year period as measured from air photographs.
Some mechanical aspects of pingo growth and failure, western Arctic coast, Canada
Authors: Mackay J. Ross
Published: February 2010

Many closed-system pingos are underlain by sub-pingo water lenses, and the same is probably true of numerous open-system pingos. In the early growth stage the bending of the frozen overburden of a pingo by a sub-pingo water lens can be compared to the bending of a thin elastic plate. Although the assumptions of elastic plate theory do not apply fully to a growing pingo, because time-dependent plastic and creep deformation are involved, the application of elastic plate theory nevertheless helps to explain the peripheral normal faulting and spring flow of pingos, summit failure, the ease with which elongated pingos appear to collapse, and the changing roles played by the radius and overburden thickness of pingos from early growth to the cessation of growth.
Recent glacier advances in the Premier Range, British Columbia
Authors: Luckman B. H. , Harding K. A. , Hamilton J. P.
Published: February 2010

Aerial photography (1948–1985) and field investigations are used to reconstruct recent ice-front fluctuations for 27 glaciers (size range 0.63–17.9 km2) in the Premier Range, British Columbia. Rapid rates of frontal recession between ca. 1930 and the mid-fifties were followed by glacier readvance at many sites, culminating in the 1973–1976 period, when 90% of the monitored ice fronts were either advancing (68%) or stable. Maximum downvalley advance was about 0.5 km (median ~90 m), and 14 glaciers formed new terminal or lateral moraine ridges between 1970 and 1985. Nine of these postdate 1976; one is dated to the 1980–1981 winter using tree rings. The glacial advance is attributed to significant mass-balance changes inferred from periods of increased winter precipitation (ca. 1951–1976) and low summer temperatures (1954–1968) measured at Valemount. Warmer summers and reduced winter precipitation after 1976 account for the slight recession of ice fronts from maximum downvalley positions in the last few years.
Geochronology of the Buchans, Roberts Arm, and Victoria Lake groups and Mansfield Cove Complex, Newfoundland
Authors: Dunning G. R. , Kean B. F. , Thurlow J. G. , Swinden H. S.
Published: February 2010

Volcanic groups of the Central Mobile Belt of the Newfoundland Appalachians have previously been subdivided into "early" and "late" arc sequences, separated in time by a quiescent Caradocian stage defined in some areas by fossil-bearing black shales.New U–Pb zircon ages of [Formula: see text] and 473 ± 2 Ma for rhyolites of the Buchans and Roberts Arm groups, respectively, show them to be correlative early Ordovician sequences. These ages serve to refute both the previous Rb–Sr whole-rock isochron ages of 447 Ma and the idea that these groups were "late arc" sequences. These new ages corroborate evidence from late Arenig – early Llanvirn conodonts in the Buchans Group and calibrate this fossil occurrence.A new U–Pb zircon age of 479 ± 3 Ma from plagiogranite of the Mansfield Cove Complex immediately west of the Roberts Arm Group shows that this plutonic body is only slightly older than the adjacent volcanic rocks and not Hadrynian as previously supposed. Local field relationships suggest this body may represent part of a disrupted ophiolite. It is coeval with the ophiolitic Annieopsquotch Complex along a strike to the south and may form part of a belt of rocks derived from early Ordovician ocean floor that is discontinuously exposed along the western boundary of the Buchans – Roberts Arm Belt.Zircons from rhyolite at the northeast termination of the Tulks Hill volcanics, part of the extensive Victoria Lake Group, give an age of [Formula: see text]. This dated sequence contains limestone previously dated as Llanvirn–Llandeilo by conodonts. This part of the group is therefore younger than the Buchans Group, and the designations "early" and "late" arc are not appropriate. The thrusting that juxtaposed these groups is no longer constrained to be of Silurian age but could have been middle to late Ordovician. Precambrian zircons included in the Victoria Lake Group rhyolite could have been incorporated from associated sedimentary rocks and suggest that the group may have formed in a tectonic setting transitional between oceanic and continental and received detritus from several sources.
Allochthonous slope sequence at Lobster Cove Head: evidence for a complex Middle Ordovician platform margin in western Newfoundland
Authors: James Noel P. , Botsford Jack W. , Williams S. Henry
Published: February 2010

The upper part of an intact sequence of Lower to Middle Ordovician deep-water sediments, which now form a large, disrupted raft within the Rocky Harbour Mélange at Lobster Cove Head, is interpreted as having been deposited downslope from a drowned carbonate platform margin. The entire 50 m thick section is Arenig (late Canadian or Ibexian to early Whiterock) in age; graptolite biostratigraphy demonstrates a correlation with upper parts of the Cow Head Group to the north. The basal part of the section is a proximal facies of the Cow Head Group (Shallow Bay Formation, Factory Cove Member, Beds 9, 10, and part of Bed 11). The upper part of the section consists of interbedded dolostone and shale and is unlike any other sequence in the Cow Head Group. This upper sedimentary sequence is defined as the Lobster Cove Head Member of the Shallow Bay Formation, Cow Head Group. Contact between the two sedimentary packages is also marked by a faunal break and coincides with emplacement of megaconglomerate Bed 12 at Cow Head.This break marks the change from a uniform to complex carbonate platform margin configuration and is here interpreted as the result of synsedimentary faulting. The margin upslope from Cow Head remained in shallow water during the final stages of Cow Head Group deposition, whereas that upslope from Lobster Cove Head was drowned and shed little sediment into deep water. The synsedimentary faulting, which led to rapid subsidence and platform-margin drowning upslope from Lobster Cove Head and possibly the deposition of megaconglomerate Bed 12 at Cow Head, coincides with the onset of the Taconic Orogeny in western Newfoundland.
U–Pb zircon, monazite, and sphene ages for granitic orthogneiss of the Barkerville terrane, east-central British Columbia
Authors: Mortensen J. K. , Montgomery J. R. , Fillipone J.
Published: February 2010

Granitic orthogneiss forms an important component of the Barkerville terrane of southeastern British Columbia. Rb–Sr whole-rock ages for the orthogneisses are ambiguous and range from Late Proterozoic to mid-Paleozoic, with large associated errors. U–Pb dating of zircon, monazite, and sphene has been employed in an attempt to establish precise crystallization ages for two of the orthogneiss bodies. U–Pb systematics for zircons from both bodies show the combined effects of inheritance of zircon cores and postcrystallization Pb loss. This complexity precludes a precise estimate of the age of emplacement of the granitic protoliths of the gneiss. The data do, however, constrain possible emplacement ages for the bodies to between 335 and 375 Ma (Late Devonian – mid-Mississippian).A U–Pb age of 174 ± 4 Ma for metamorphic sphene from one of the orthogneiss bodies is interpreted as dating the end of the second phase of deformation in the area. Two nearly concordant U–Pb ages of 114 and 117 Ma for monazite from the second body remain problematical. These data suggest either that the monazite grew during a relatively young shearing and (or) metamorphic event that locally affected the Barkerville terrane or that the closure temperatue for the U–Pb system in monazite is lower than had previously been inferred, or both.
La dispersion clastique des débris rocheux dans les eskers et le till adjacent de la région de Chapais–Chibougamau (Québec) au Wisconsinien supérieur
Authors: Levasseur Denis , Prichonnet Gilbert
Published: February 2010

Petrographie counts of more than 84 500 debris along eskers and in the adjacent till were used to study the dispersion of rock debris derived from local marker outcrops (Opemiska Pluton and Chibougamau Formation) and from distant indicator rocks of Mistassini Basin (Albanel Formation dolomites and Papaskwasati quartzitic sandstones). The frequency distributions are compared for the following granulometric classes:0.8–1.6 cm (fine gravels), 1.6–5.0 cm (small pebbles), 5.0–15.0 cm (large pebbles), and 15.0–45.0 cm (blocks).In the till, the minor content of debris derived from the Chibougamau Formation, downstream from the Waconichi Lake source-area, suggests that glacial erosion in this area was insignificant. Nevertheless, meltwaters transported erratic clasts of this formation for distances of more than 55 km. But the currents that deposited the sediments of the big eskers, which represent a succession of subaquatic outwash deposits, were restrained by the existing Ojibway Glacial Lake. The apparent greater displacement of debris in these eskers, as compared to that in the neighbouring till, is the result of an abundant incorporation of intraglacial materials in the tunnels. Rock debris from the Albanel and Papaskwasati formations were dispersed over distances of more than 250 km.The lack of a significant increase of fine debris at the expense of larger fragments suggests that there was limited crushing at the glacier base, or else limited disintegration in the meltwater currents. The decrease in the frequency of a petrographie marker is mainly controlled by the progressive sedimentation of fragments derived from the indicator outcrop, and by the rate of incorporation of nonmarker debris. Thus, the nature of the eroded rocks, and the size of the marker debris acquired at the source, are determining factors influencing the clastic dispersion. The variable rate of incorporation of rocks issued directly from the dispersion area are in large part responsible for the irregularities in the curves representing the concentration of marker debris. [Journal Translation]
The taxonomic status of Leptopterygius Huene, 1922 (Reptilia: Ichthyosauria)
Authors: McGowan Chris
Published: February 2010

Leptopterygius Huene, 1922, was erected for Leptopterygius tenuirostris, a fairly common long-snouted ichthyosaur from the English lower Liassic. Huene also referred eight other species to Leptopterygius, but these had little in common with L. tenuirostris, or with each another. These eight species have since been rejected, synonymized, or referred to other genera. Other species have also been referred to the genus since 1922, Leptopterygius having become something of a catchall for species not readily referred elsewhere. This unsatisfactory taxonomic situation is exacerbated by the recognition that the name Leptopterygius is preoccupied. A replacement name, Leptonectes, is proposed to replace Leptopterygius. Two species are referred to the new genus, L. tenuirostris (Conybeare, 1822), the type species, and Leptopterygius solei McGowan, 1993. The diagnostic features of the genus include the slenderness of the rostrum and mandible, and the wide distal expansion of the humeus, with its preaxial facet. The genus ranges from the uppermost Triassic to the Lower Jurassic.
Crustal structure across the Nain – Makkovik boundary on the continental shelf off Labrador from seismic refraction data
Authors: Reid Ian
Published: February 2010

A detailed seismic refraction profile was shot along the continental shelf off Labrador, across the boundary between the Archean Nain Province to the north and the Proterozoic Makkovik orogenic zone to the south. A large air-gun source was used, with five ocean-bottom seismometers as receivers. The data were analysed by forward modelling of traveltimes and amplitudes and provided a well-determined seismic velocity structure of the crust along the profile. Within the Nain province, thin postrift sediments are underlain by crust with a P-wave velocity of 6.1 km/s, which increases with depth and reaches 6.6 km/s at about 8 km. Moho is at around 28 km, and there is no evidence for a high-velocity (>7 km/s) lower crust. The P- and S-wave velocity structure is consistent with a gneissic composition for the Archean upper crust, and with granulites becoming gradually more mafic with depth for the intermediate and lower crust. In the Makkovik zone, the sediments are thicker, and a basement layer of P-wave velocity 5.5–5.7 km/s is present, probably due to reworking of the crust and the presence of Early Proterozoic volcanics and metasediments. Upper crustal velocities are lower than in the Nain Province. The crustal thickness, at 23 km, is less, possibly due in part to greater crustal stretching during the Mesozoic rifting of the Labrador Sea. The crustal structure across the Nain–Makkovik boundary is similar to that across the corresponding Archean–Ketilidian boundary off southwest Greenland.
Structural evolution of sulphide tectonites and their host rocks, Stratmat mine, New Brunswick
Authors: Park Adrian F.
Published: February 2010

The sulphide orebodies at the Stratmat mine in New Brunswick are treated as tectonites, because their primary characteristics have been so modified by deformation, recrystallization, and vein injection that most of their original features have been obscured. Pb–Zn–Cu sulphide orebodies at the Stratmat mine consist of sulphide and sulphide–silicate tectonites, gneisses, schists, phyllites, and slates produced by the mixing of two sulphide precursors and silicate host rocks by polyphase deformation, much of which relates to progressive non-coaxial deformation. Quartz-vein injection during and after this period of deformation, and the intermixing of nonsulphide lithotypes, led to dilution of the initial ore composition. Both the deformation of the orebodies and fluid migration, manifested by vein injection, reflect processes that were operative in a major shear zone. No indisputable primary characteristics of the orebodies are preserved, although a number of tectonic and (or) tectonically modified features mimic depositional features, e.g., quartz mylonites resemble "cherts," festoon veinlets resemble dismembered stockwork veins, sulphide mylonites resemble rock with an original fine-grain size and "extra" fold phases that could be mistaken for soft sediment folds.