bluuebunny/crossref_metadata_2025 huggingface dataset:
Molar heat capacities and enthalpies of fusion for the system zinc chloride-dimethyl sulphoxide
Authors: Skokánek Mojmír , Sláma Ivo
Published: June 2010

Molar heat capacities and molar enthalpies of phase transitions in the system ZnCl2-DMSO have been investigated over the temperature range 240 to 405 K and the concentration range 11.1 to 40 mole % ZnCl2. The temperatures of fusion and of phase transitions were determined and compared with literature data. Equations were proposed for the description of the temperature dependence of the molar heat capacity in the liquid state. The concentration dependence of the molar heat capacity in the molten state was found to exhibit positive deviations from additivity.
Kinetics and mechanism of spiro adduct formation from and smiles rearrangement of N-methyl-N-(2,4,6-trinitrophenyl)aminoacetanilide. Base-catalyzed transformation of N-(2,4,6-trinitrophenylamino)acetanilide into 2-nitroso-4,6-dinitroaniline
Authors: Macháček Vladimír , Hassanien Makky M. M. , Štěrba Vojeslav
Published: June 2010

The paper deals with kinetics and mechanism of the reaction of N-(2,4,6-trinitrophenyl)aminoacetanilide (IIa) with methoxide ion and with the reaction kinetics and product structure of the reaction of N-methyl-N-(2,4,6-trinitrophenyl)aminoacetanilide (IIb) in methanolic buffers. The main product of the reaction of compound IIa with methoxide is 2-nitroso-4,6-dinitroaniline along with about 3% spiro adduct. The dependence of the experimental rate constant kexp of the reaction with methoxide on the methoxide concentration is similar to that of the reaction of N-(2,4,6-trinitrophenyl)glycine methylamide, however, compound IIa reacts about 2·5 times faster and produces the spiro adduct in an about four times smaller amount. In basic acetate buffers, compound IIb is transformed quantitatively into the spiro adduct. In chloroacetate buffers, the reverse ring opening of the spiro adduct prevails. The ring opening takes two ways: A specific acid catalyzed one and a non-catalyzed one. Corresponding therewith is the non-catalyzed and specific base catalyzed formation of the spiro adduct. In aniline-anilinium chloride buffers, equilibrium is rapidly established between the spiro adduct and 2-methylamino-N-phenyl-N-(2,4,6-trinitrophenyl)acetamide hydrochloride. The mixture of the two compounds is transformed gradually into compound IIb which shows the highest thermodynamic stability in the given medium. At [H+] > 10-3 mol l-1 the thermodynamically most stable species is 2-methylamino-N-phenyl-N-(2,4,6-trinitrophenyl)acetamide hydrochloride.
Preparation of methyl 2,4-diacetamido-2,4,6-trideoxy-α-D-ido-, α-D-talo-, α-D-altro-, and α-D-mannopyranoside
Authors: Čapek Karel , Čapková Jindra , Jarý Jiří , Knirel Yurii A. , Shashkov Alexander S.
Published: June 2010

Title compounds were prepared from methyl 2-O-acetyl-3,4-anhydro-6-deoxy-α-D-galactopyranoside (I). Solvolysis of I afforded methyl 3-O-acetyl-6-deoxy-α-D-gulopyranoside (II) from which in turn was prepared its 2,4-di-O-methanesulfonyl derivative III. The reaction of III with sodium azide undergoes under participation of the O-acetyl group in the position 3 and produces methyl 2,4-diazido-2,4,6-trideoxy-α-D-idopyranoside (V) that after hydrogenation and acetylation yields methyl 2,4-diacetamido-2,4,6-trideoxy-α-D-idopyranoside (VIII). Methyl 2,4-diacetamido-2,4,6-trideoxy-α-D-talopyranoside (XI) was prepared by its mesylation and by solvolysis of the product. Azidolysis of I, followed by hydrogenation and acetylation gave methyl 4-acetamido-4,6-dideoxy-α-D-glucopyranoside (XII). Its subsequent reaction with diethyl azodicarboxylate-triphenylphosphine mixture led to methyl 4-acetamido-2,3-anhydro-4,6-dideoxy-α-D-allopyranoside (XV). Mixture of methyl 4-acetamido-2-azido-2,4,6-trideoxy-α-D-altropyranoside (XVII) and its gluco- isomer XVIII is formed in the reaction of XV with sodium azide. Hydrogenation of XVII yields amino derivative XIX that in turn gives methyl 2,4-diacetamido-2,4,6-trideoxy-α-D-altropyranoside (XXI) by acetylation. Methyl 2,4-diacetamido-2,4,6-trideoxy-α-D-mannopyranoside (XXII) was prepared by its mesylation and solvolysis. All structures were confirmed by 1H and 13C NMR spectra.
New intermediate for rapid synthesis of N-isopropyl-2-amino-1-(4-iodophenyl)propane (N-isopropyl-4-iodoamphetamine), labelled with radioactive iodine
Authors: Protiva Jiří , Křeček Václav , Lešetický Ladislav , Sedmera Petr
Published: June 2010

The triazene derivative of N-isopropyl-2-amino-1-phenylpropane XIV, synthesized in seven steps from 2-amino-1-phenylpropane (II), enables a rapid, simple and regiospecific preparation of N-isopropyl-2-amino-1-(4-iodophenyl)propane (N-isopropyl-4-iodoamphetamine; I), labelled with short-living isotopes of iodine, directly prior to application.
Reaction of 6,11-dihydrodibenzo[b,e]thiepin-11-carbonitrile with 1,2-dibromoethane, a reinvestigation. Formation of 11,12-dihydro-6H-6,12-methanodibenzo[b,f]thiocin-12-carbonitrile
Authors: Šindelář Karel , Buděšínský Miloš , Vaněk Tomáš , Holubek Jiří , Svátek Emil , Matoušová Oluše , Rees Charles Wayne , Protiva Miroslav
Published: June 2010

Reinvestigation of the minor product of reaction of 6,11-dihydrodibenzo[b,e]thiepin-11-carbonitrile (I) with 1,2-dibromoethane in the presence of tetrabutylammonium bromide or benzyltriethylammonium chloride and 50% sodium hydroxide by means of 1H and 13C NMR spectroscopy led to the formula XI named in the title, which was confirmed by X-ray crystallographic analysis. The product of a similar reaction, carried out in dimethyl sulfoxide in the presence of potassium carbonate at 100 °C was identified as the stereoisomeric mixture of 11,11'-ethylenebis(6,11-dihydrodibenzo[b,e]thiepin-11-carbonitriles) (XII) which was separated to the components by preparative HPLC. The title compound XI was oxidized to the sulfoxide XIII and the sulfone XIV, and was transformed by reduction and the following methylation to amines XV and XVI. The reduction of the vinyl nitrile III with lithium aluminium hydride is complicated on the one hand by allylic rearrangement, and with cyanide anion abstraction on the other, the products being (E,Z)-mixture of 3-(6,11-dihydrodibenzo[b,e]thiepin-11-ylidene)propylamines (XVII) and 11-vinyl-6,11-dihydrodibenzo[b,e]thiepin (X). The amine XVI is devoid of thymoleptic activity.
Biotransformation of 2-(4-methoxybenzyl)-1-cyclohexanone by means of Saccharomyces cerevisiae
Authors: Wimmer Zdeněk , Buděšínský Miloš , Macek Tomáš , Svatoš Aleš , Šaman David , Vašíčková Soňa , Romaňuk Miroslav
Published: June 2010

Biotransformation reduction of 2-(4-methoxybenzyl)-1-cyclohexanone was investigated. A method was elaborated for the preparation of some diastereoisomeric alcohols derived from the racemic title ketone and for the determination of the products obtained. The study resulted in the synthesis of cis-(1S,2S)-(+)-2-(4-methoxybenzyl)-1-cyclohexanol and trans-(1S,2R)-(+)-2-(4-methoxybenzyl)-1-cyclohexanol in optical purity of at least 91.6 ± 1.0% and 97.5 ± 1.0%, respectively.
Inhibition of aldehyde reductase I by some isoquinoline alkaloids
Authors: Paulová Hana , Kovář Jan , Plocek Jiří , Slavík Jiří
Published: June 2010

Aldehyde reductase I has been found to be inhibited by certain isoquinoline alkaloids (protoberberines, protopines, benzylisoquinolines, benzyltetrahydroisoquinolines, phthalideisoquinolines, pavinanes) and narceine imide. The sensitivity of this enzyme to the compounds tested was compared with that of alcohol dehydrogenase and/or aldehyde reductase II to them; alcohol dehydrogenase proved more selective in binding the alkaloids. The kinetics of the inhibitory action of berberine and other results suggest that the binding site of aldehyde reductase I for alkaloids is relatively large, has a hydrophobic nature, and probably contains a group with a positive charge. This binding site is probably not identical with the active centre of the nezyme.
Enzyme-catalyzed partial deacetylation of 1,6-anhydro-2,3,4-tri-O-acetyl-β-D-glucopyranose
Authors: Zemek Jiří , Kučár Štefan , Anderle Dušan
Published: June 2010

Various esterases, lipases, and proteases with esterolytic activity were investigated for their power to catalyse deacetylation of 1,6-anhydro-2,3,4-tri-O-acetyl-β-D-glucopyranose. Out of these, chymotrypsin, esterase ex liver, lipase ex pancreas, and lipase ex wheat-germ have been found to be selective catalysts of deacetylation; chymotrypsin and wheat-germ lipase preferably removed the acetyl at C(3), whereas liver esterase and pancreas lipase the acetyl at C(4). Compared to chemical catalysis, whether by methanolic hydrogen chloride or hydrazine hydrate, the locoselectivity of the enzyme-catalysed deacetylation appear to be much better.
Grenzaktivitätskoeffizienten binärer ethylacetat-kohlenwasserstoff-systeme mit der kinetischen mitführung und der differentialebulliometrie
Authors: Wobst Michael , Hradetzky Gerd , Bittrich Hans-Joachim , Dohnal Vladimír
Published: June 2010

Unter bestimmten Bedingungen sind sowohl die kinetische Mitführung als auch die Differentialebulliometrie für Messungen bei der Grenzaktivitätskoeffizienten binarer Systems geeignet. Solche Messungen wurden für 4 binäre Systeme Ethylacetat-Kohlenwasserstoff bei 338,15 K durchgeführt. Die Ergebnisse beider Methoden stimmen sehr gut überein. für die kinetische Mitführung wird der Einfluss des Realverhaltens der Gasphase diskutiert.
Radiation catalytical effects in the pre-irradiated and thermally treated catalyst BASF K-3-10
Authors: Motl Alois
Published: June 2010

The effects of various thermal treatment methods on the radiation catalytical effects, induced by the pre-irradiation of the BASF K-3-10 catalyst by the γ- or β-radiation or by fast neutrons, were investigated. It has been found that the calcination of the irradiated non-reduced catalyst results in a strong decrease or even in total disappearance of the final radiation catalytical effects; however, at the same time the catalytical activity of the unirradiated catalyst was found to increase. The calcination of the catalysts in nitrogen atmosphere after reduction led also to a substantial decrease of the resulting positive radiation catalytical effects and exceeding a certain calcination temperature resulted in the decrease even of the unirradiated catalyst activity. It could be concluded that the calcination in nitrogen of the reduced irradiated samples decreases the radiation catalytical effects less than the calcination on air of the non-reduced irradiated samples. In both cases a different thermal stability of effects induced by different types of the ionizing radiation has been observed and it has been found that it increases in the sequence beta radiation – gamma radiation – fast neutrons. The investigation of the γ radiation dose dependence of the radiation catalytical effect on the catlyst calcinated before irradiation under the access of air showed that the final radiation catalytical effects are lower than those observed in the case of similarly irradiated but non-calcinated samples. At the same time the dose dependence of the effect has the same character in both cases.
Adsorption of oxygen and carbon monoxide on DymCun bimetallic surfaces at room temperature
Authors: Kopešťanský Josef
Published: June 2010

The adsorption of oxygen and carbon monoxide on surfaces of dysprosium, copper, and their bimetallic “alloys” DymCun was studied by work function measurements. In the starting stage of adsorption of oxygen, copper surfaces are more reactive than dysprosium surfaces, and bulk oxide appears in the sub-surface copper layers at room temperature; this was also observed for the bimetallic surfaces, where the starting adsorption of oxygen took place nearly exclusively on copper. With dysprosium, the bulk oxide did not form at room temperature; instead, oxygen was adsorbed on the surface to form a layer consisting of species of two kinds with substantially different dipole moments. Carbon monoxide practically did not adsorb on copper at 25 °C, whereas on dysprosium it exhibited dissociative adsorption. On the bimetallic surfaces (DyCu and DyCu6) the amount of adsorbed CO decreased proportionally to the increasing Cu content of the alloy. Segregation of copper in the surface layer, observed for the bimetallic DymCun “alloys”, resulted in an additional decrease in the amount of adsorbed CO.
Investigation on some operating factors influencing batch cooling crystallization
Authors: Mydlarz Jerzy
Published: June 2010

The influence of batch time as well as the saturation temperature of stock solution on crystal size distribution has been examined. The results show that there is an optimal batch time, tc, for which the mean crystal size of MgSO4.7 H2O has a maximum. For MgSO4.7 H2O and H2C2O4.2 H2O, the mean crystal size of the product increased with increasing saturation temperature of the solution.
Regioselectivity of nucleophilic aromatic photosubstitution in the biphenyl series. Photohydrolysis of some dimethoxynitrobiphenyls
Authors: Urban Ján , Kuzmič Petr , Šaman David , Souček Milan
Published: June 2010

Anaerobic photolysis of dimethoxynitrobiphenyls IIIa-VIa in aqueous alkaline tert-butanol gave products of nucleophilic photosubstitution of methoxyl by hydroxide anion, while the dimethoxybiphenyls Ia and IIa were found unreactive. Regioselectivity of the reaction was examined in view of a possible “extended meta activation” by the nitro group. The most reactive substrate IIIa gives both C-3 and C-4 substitution products with an unsubstantial preference for the latter, which opposes the “extended meta selectivity” rule. All of the other compounds obey the rule, and 3,4-dimethoxy-3'-nitrobiphenyl (IVa) even displayed absolute selectivity by yielding C-3 substituted compound as the only product. 2,5-Dimethoxy substituted compounds underwent photosubstitution which much lower quantum yields than their 3,4-substituted counterparts, most probably due to some steric hindrance of conjugation. Similarly, 3-nitro-substituted biphenyls exhibited much lower overall reactivity than 4-nitro derivatives.
2-Isothiocyanatobenzyltriphenylphosphonium bromides – new type of functionalized heterocumulenes suitable for synthesis of indole derivatives
Authors: Gonda Jozef , Kristian Pavol , Imrich Ján
Published: June 2010

Reaction of 2-bromomethylphenyl isothiocyanates with triphenylphosphine afforded triphenyl-(2-isothiocyanatobenzyl)phosphonium salts. Their reaction with bases liberated the corresponding carbanions which on intramolecular addition to the N=C=S group gave substituted 3-triphenylphosphoniumindolyl-2-thiolates. These compounds did not react in the Wittig reaction but underwent electrophilic reactions on the sulfur atom or on the indol nitrogen atom. According to a detailed analysis of 1H, 13C, 31P NMR and mass spectra, the indole derivatives exist predominantly in the betaine form. X-Ray diffraction analysis of the unsubstituted betaine, 3-triphenylphosphoniumindolyl-2-thiolate, agrees well with the spectral results.
Reactions of 4-chloro-1-nitrobenzene with o-substituted phenylacetonitriles; Synthesis of 8-chloro-1-methyl(and methylthiomethyl)-6-(2-substituted phenyl)-4H-s-triazolo[4,3-a]-1,4-benzodiazepines
Authors: Vejdělek Zdeněk , Holubek Jiří , Ryska Miroslav , Koruna Ivan , Svátek Emil , Buděšínský Miloš , Protiva Miroslav
Published: June 2010

Reactions of 4-chloro-1-nitrobenzene with 2-methyl-, 2-methoxy- and 2-(methylthio)phenylacetonitrile in methanolic potassium hydroxide gave mixtures from which the expected 3-aryl-5-chloro-2,1-benzisoxazoles Ia-c were isolated in addition to the 2H-indoles IIIa and IIIc and acridines VIII and IX. The 2,1-benzisoxazoles were reduced to the 2-aminobenzophenones XIIa-c which were transformed via the phthalimidoacetamido compounds XIIIa-c to 5-aryl-7-chloro-1,3-dihydro-1,4-benzodiazepine-2-ones XVa-c. Treatment with phosphorus pentasulfide led to the thiones XVIa-c which reacted in boiling butanol either with acetohydrazide or with (methylthio)acetohydrazide to give the title compounds XVIIa-c and XVIIIa-c. They showed only weak anticonvulsant, incoordinating and central depressant effects.
Energy effectiveness and working characteristics of different tower reactors for aerated slurry systems
Authors: Vlaev Serafim D. , Zahradník Jindřich
Published: June 2010

Decisive hydrodynamic and mass transfer characteristics of different types of tower reactors (rotating disc reactor, single and multistage sieve-tray bubble columns, tower reactor with ejector gas distributor) as well as the energy effectiveness of their performance were compared with the purpose to establish a quantitative basis for the qualified choice of the proper reactor type according to demands of specific reaction processes. Selected design parameters included gas and solid phase holdup, kLaL, liquid phase residence time distribution, and axial distribution of the solid phase, the experiments were carried out in a wide range of solid phase concentration (0-20 wt. %) and particle sizes (2.3-280 μm). The experimental results proved that due to their favourable suspension characteristics and operation stability the rotating disc reactors can be advantageously used for slow reaction processes with low demands on the intensity of interfacial gas-liquid contact which can be carried out at low gas flow rates. On the other hand the multistage bubble column reactors proved to be superior devices for transport–controlled reaction processes regarding both the achievable rate of interfacial mass transfer and the overall energetic efficiency of phase contacting.
Oxygen transfer in high-speed fermenter under steady cultivation conditions
Authors: Seichter Pavel
Published: June 2010

A method for volume mass transfer coefficient calculation under steady fermentation conditions, including correction of partial oxygen pressure in bubbles, has been developed. Number of continuous cultivations on ethanol and sulphite substrates were evaluated on the basis of the suggested method.
Michael reaction of methylenemalonaldehydes: Synthetic approach to 4H-pyran-5-carboxaldehydes and 2-amino-4H-pyran-5-carboxaldehydes
Authors: Dvořák Dalimil , Šaman David , Hodačová Jana , Král Vladimír , Arnold Zdeněk
Published: June 2010

Base-catalyzed addition of β-dicarbonyl compounds to methylenemalonaldehydes led to tetracarbonyl compounds II which were dehydrated in an acid medium to 4H-pyran-5-carboxaldehydes III. In the addition of compounds containing a nitrile group, the primarily formed addition products were immediately cyclized to give directly 2-amino-4H-pyran-5-carboxaldehydes V.
Metallation of benzene with the system organolithium compound-potassium tert-pentoxide
Authors: Lochmann Lubomír
Published: June 2010

By acting with the system organolithium compound and potassium tert-pentoxide on benzene, phenylpotassium is obtained as the main product, the purity of which is considerably dependent on reaction conditions. The relatively purest phenylpotassium (molar ratio K/Li > 12) can be obtained at a high benzene concentration in the reaction mixture and/or in the presence of diethyl ether. This dependence makes the metallation of benzene differ from a similar metallation of toluene, and it is therefore not possible to suggest general optimal conditions for such a metallation of different substrates yet.
Synthesis and reactivity of methyl ester of 1'-(chloromethyl)ferrocenecarboxylic acid
Authors: Kaluz Štefan , Toma Štefan
Published: June 2010

The reaction of methyl ester of 1'-(hydroxymethyl)ferrocenecarboxylic acid with PCl3 afforded methyl ester of 1'-(chloromethyl)ferrocenecarboxylic acid. The reactivity of the ester with selected O, S, N and C-nucleophiles has been investigated. In all cases the high yields of the products of substitution of the chlorine of chloromethyl group were obtained.
Preparation of 21-methoxycarbonyl-21-methylene-5-pregnen-3β-ol derivatives
Authors: Pouzar Vladimír , Kárászová Lenka , Havel Miroslav
Published: June 2010

Reaction of 3β-methoxymethoxy-21-nor-5-pregnen-20-ol p-toluenesulfonate (II) with sodium dimethyl malonate afforded dimethyl 3β-methoxymethoxy-5-pregnene-21,21-dicarboxylate (III). Partial hydrolysis of III, followed by reaction with formaldehyde and diethylamine, gave methyl 3β-methoxymethoxy-21-methylene-5-pregnene-21-carboxylate (XVI) which was further transformed into hemisuccinate XIX.
E-seco-Acids of pentacyclic triterpenoids. Oxidative cleavage of ring E in 3β-acetoxy-21-oxo-18α,19βH-ursan-28→20β-olide
Authors: Klinotová Eva , Pavlíková Helena , Pressová Martina , Chodounská Hana , Klinot Jiří , Protiva Jiří , Vystrčil Alois
Published: June 2010

Oxidative cleavage of 3β-acetoxy-22-hydroxymethylene-21-oxo-18α,19βH-ursan-28→20β-olide (VII) and 3β-acetoxy-21,22-dioxo-18α,19βH-ursan-28→20β-olide (VIII) afforded primarily the E-seco-acid XII which was converted into acids XVI and XX, isomeric at the C(17) carbon atom. Configuration of these acids has been determined.
Synthesis of potential prodrugs and metabolites of 9-(S)-(3-hydroxy-2-phosphonylmethoxypropyl)adenine
Authors: Rosenberg Ivan , Holý Antonín
Published: June 2010

Reaction of 9-(S)-(3-hydroxy-2-phosphonylmethoxypropyl)adenine (I) with N,N'-dicyclohexylcarbodiimide afforded the cyclic phosphonate II. The same compound was also obtained by controlled alkaline hydrolysis of 3'-O-chloromethanephosphonyl-9-(S)-(2,3-dihydroxypropyl)adenine (III). Methanolysis of compound II or III by sodium methoxide gave methyl ester VII. Isomeric cyclic ester V and methyl ester VIII were obtained from 3'-O-phosphonylmethyl ether IV or 2'-O-chloromethanephosphonyl ester VI by the same reactions. Compound I was transformed into morpholide IX which afforded the P-diphosphoryl derivative X by treatment with inorganic diphosphate. The P-phosphoryl derivative XII was obtained from compound I by successive protection with dimethoxytrityl chloride, activation with diphenyl chlorophosphate, treatment with inorganic phosphate and acid deprotection.
Acidobasicity, reactivity, lipophilicity, and ability of phenylhydrazonopropanedinitriles to disturb the membrane potential
Authors: Šturdík Ernest , Ďurčová Edita , Mikeš Vladimír , Dadák Vladimír , Baláž Štefan , Sulo Pavol , Antalík Marián
Published: June 2010

The ability to disturb the membrane potential of rat liver mitochondria or Paracoccus denitrificans bacteria was quantitatively determined with 21 o-, m-, and p-substituted phenylhydrazonopropanedinitriles. Dependence of this ability on partition coefficients, dissociation constants and nucleophilic reactivity of these derivatives was characterized by equations employed in quantitative structure-activity relationship (QSAR); as found, decisive for investigating the disturbance effect is the lipophilicity of phenylhydrazonopropanedinitriles which determines their ability to pass through biomembranes. Close values of optimal lipophilicities (log P = 3.98 or 3.81) of models under examination indicate the very like lipo-hydrophilic character of both membranes. Of further parameters considered, the more significant is the acidobasicity, determining the ability of these substances to transfer protons through the interface, thereby disturbing the pH-gradient as a substantial component of the membrane potential.
C60(g), C70(g), saturated carbon vapour and increase of cluster populations with temperature: A combined AM1 quantum-chemical and statistical-mechanical study
Authors: Slanina Zdeněk , Rudziński Jerzy M. , Ōsawa Eiji
Published: June 2010

Saturated vapour above graphite and the content of Cn(g) aggregates therein have been studied at various temperatures. The equilibrium constants of C(g) into Cn(g) association have been obtained for: (i) n = 1-5 from the available tabulated thermodynamical data, (ii) C60 and C70 from a quantum-chemical description in terms of the AM1 method as a source of molecular parameters for the construction of partition functions, and (iii) the other aggregates by linear inter- or extrapolation of the data sub (i) and (ii). The content of clusters with n ≥ 2 in the saturated vapour has been shown to increase steeply with temperature. This increase is due to small clusters (n ~ 2-5), whereas the recently proved particular structures C60 and C70 are - according to these calculations – negligibly populated in the saturated vapour at all temperatures studied. At the conditions of saturated vapour the population of C60 always exceeds that of C70 by several orders of magnitude. The relations of these calculations to the recent observations of distinct populations of C60 and C70 are discussed.
Electrolytic dissolution of iron in aqueous citrate solutions
Authors: Žežula Ivan
Published: June 2010

Analysis of polarization curves for electrolytic dissolution of an iron (steel) electrode in citrate solutions of various pH values and concentrations of citrate anions showed that the given medium promotes the electrolytic dissolution by shifting the corrosion potential of iron to more negative values. However, the catalytic formation of an iron(II) hydroxo complex cation in the active dissolution region according to the scheme proposed by Heusler remains the rate-determining step of the dissolution mechanism.
Analysis of substituent and solvent effects on dissociation of N-phenylbenzenesulphonamides
Authors: Ludwig Miroslav , Pytela Oldřich , Javůrková Helena , Večeřa Miroslav
Published: June 2010

The potentiometric titration in water, methanol, dimethyl sulphoxide, dimethylformamide, and acetonitrile has been used for determination of pK values of 13 N-arylbenzenesulphonamides. The validity of the Hammett and Yukawa-Tsuno models using several sets of substituent constants has been evaluated by the test to check adequacy of the regression function and by the factor analysis. It has been found that the substituent effects in solvents must be interpreted with regard to the experimental method used, solvent, set of the substituent constants, as well as the model equation ETR. The dependence of the Hammett reaction constants on the solvent has been analyzed and reveals a preferred stabilization of the conjugated base through hydrogen bonds. Direct conjugation of the reaction centre with the substituent and with different extent of the solvent-dependence with the 4-CN and 4-NO2 derivatives have been observed.
Kinetics of hydrogenation of alkynes and dienes on palladium catalyst
Authors: Červený Libor , Řehůřková Šárka
Published: June 2010

Alkynic and dienic substrates (C6-C10) in hexane and methanol were hydrogenated over a catalyst of 3% Pd on activated carbon at 20 °C and atmospheric pressure. The initial reaction rates were measured for the individual substrates; the hydrogenation rates of the olefinic substances formed were also determined if the hydrogenation was selective. The selectivities in competitive hydrogenations of substrate pairs were established and the relative adsorption coefficients of the substrates were calculated from them. The effect of the substrate structure and the solvent effect on the hydrogenation rate and relative adsorptivity are discussed for the alkynic and dienic substances studied.
Thermal cyclocondensations of 3-N(4- and 5-benzimidazolyl and benztriazolyl)amino derivatives of 2-propenoic acid
Authors: Milata Viktor , Ilavský Dušan
Published: June 2010

The cyclization of 3-N(4- and 5-benzimidazolyl and benztriazolyl)amino-2-cyano- and 2-ethoxycarbonyl-2-propenoate esters Ia, b-IVa, b under the conditions of the Gould-Jacobs reaction leads to angularly ring-fused substituted imidazo or triazolo[4,5-f] (V, VI) and [4,5-h] (VII, VIII) quinolines, respectively. The esters Vb-VIIIb have been transformed into the corresponding chloroderivatives Vc-VIIIc. 3-N(5-Benzimidazolyl and 5-benztriazolyl)amino-2-cyano-2-propenenitriles are cyclized in the presence of aluminium(III) chloride to give the aminoquinolines Vd, VId. The structure of the products has been characterized by their 1H, 13C NMR, IR, and UV spectra.
15N, 13C, and 1H NMR spectra of 1-substituted-2,4,6-trinitrobenzenes
Authors: Lyčka Antonín , Macháček Vladimír , Jirman Josef
Published: June 2010

The 15N, 13C, and 1H NMR spectra of twenty 1-substituted-2,4,6-trinitrobenzenes have been measured in hexadeuteriodimethyl sulphoxide. The δ(15N) chemical shifts of 2-NO2 and 6-NO2 groups are different from those of 4-NO2 group. Except for 1-(4-subst. phenoxy)derivatives, the δ(15N-4) are shifted upfield as compared with δ(15N-2,6). The assignment of signals in the 15N NMR spectra was confirmed in three cases by measurements of selectively 15N-labelled compounds.
Preparation and photochemistry of 3-methoxycarbonyl substituted condensed isoxazolines
Authors: Oremus Vladimír , Fišera Lubor , Timpe Hans-Joachim
Published: June 2010

The 1,3-dipolar cycloaddition of methoxy- and ethoxycarbonylnitriloxide to 2,3- and 2,5-dihydrofuran, 2,3-dihydropyrane, 7-oxabicyclo[2,2,1]-2-heptene, and 1,3-dioxep-5-ene derivatives is described. The condensed isoxazolines Ia, IIIa, Va, Vb are rearranged on irradiation to give the methoxycarbonyl substituted enaminoaldehydes IIa, IVa, VIa, VIb, respectively. The photolysis of VIIc, VIIIa, VIIIc is connected with destruction. The quantum yields of the photorearrangement are higher than those of the phenyl substituted derivatives but lower than those of the corresponding cyano derivatives. The enaminoaldehydes IIa and VIa have been used for preparation of new heterocyclic pyridazino[4,5-d]oxazine (IX) and pyridazino[7,8-d]-2,4,6-dioxazocine (X) systems, respectively.
A versatile synthesis of oligocrown compounds with hydroxyl groups at the hinge
Authors: Bělohradský Martin , Holý Petr , Stibor Ivan , Závada Jiří
Published: June 2010

Oxirane ring-opening reaction of N-(2,3-epoxy-1-propyl) azacrowns Ia-Ic and 4,5-epoxy-2-oxapentylcrowns IIa-IIe with mono- and diamines (including mono- and diazacrowns) afforded array of new di-, tri-, and tetracrown compounds with hydroxyl groups placed at the hinge.
Crown and azacrown ethers with pendant adenine group
Authors: Holý Petr , Bělohradský Martin , Stibor Ivan , Koudelka Juraj , Šaman David , Hodačová Jana , Holý Antonín , Závada Jiří
Published: June 2010

Base-catalyzed oxirane ring-opening reaction of 4,5-epoxy-2-oxapentyl crown ethers Ia-Ie and N-(2,3-epoxy-1-propyl) azacrown ethers IIa-IIc with adenine affords mixtures of corresponding adenin-9-yl, adenin-3-yl and adenin-7-yl derivatives (IIIa-IIIe, IVa-IVe, Va-Ve, VIa-VIc, VIIa-VIIc and VIIIa-VIIIc) respectively, separable by liquid chromatography. Structure of the individual isomers was assigned on basis of 1H, and 13C NMR spectroscopy. Compexation of the prevailing (adenin-9-yl) isomers IIIa-IIIe and VIa-VIc with sodium ion was measured potentiometrically in 99% methanol and the calculated stability constants were compared with corresponding data from related homologous series of crown and azacrown ethers IXa-IXe, Xa-Xe, XIa-XIc and XIIa-XIIc differing in pendant group.
Solvolytic rearrangements in 4β,5-cyclopropano-5β-cholestane-3β,19-diol 3-acetate 19-p-toluenesulphonate
Authors: Joska Jiří , Fajkoš Jan , Tureček František
Published: June 2010

Acetolysis of the tosylate VIII proceeded under participation of the cyclopropane ring at the electron-deficient center formed during the reaction to yield three products all having modified steroid skeletons. They were the diene XXIII, the unsaturated acetate XI, and the saturated 4β,10β-cycloderivative XIII carrying two acetoxy groups in the molecule. For the purpose of spectral studies and structure elucidation the acetolysis has been carried out with the labelled tosylate XXXII the synthesis of which is described and analogous three labelled products were isolated. The structures of these products were established on the basis of spectral and chemical evidence and a mechanism of the rearrangements is proposed.
Synthesis of 4-methoxyphenoxyacetic and 3,4,5-trimethoxyphenoxyacetic acid amides and hydrazides as potential neurotropic and cardiovascular agents
Authors: Valenta Vladimír , Holubek Jiří , Svátek Emil , Protiva Miroslav
Published: June 2010

4-Methoxyphenoxyacetyl chloride, 3,4,5-trimethoxyphenoxyacetic acid and its methyl ester were reacted with 2-phenylethylamine, 1-benzylpiperazine, 1-(2-phenylethyl)piperazine, 1-(1-phenyl-2-propyl)piperazine, isopropylhydrazine, 1-aminopiperidine, and 4-aminomorpholine and afforded the amides and hydrazides Iab-IVab and Vb-VIIIb. 1-Amino-4-methylpiperazine and 1-amino-4-phenylpiperazine were transformed to the hydrazones XV and XVI, and to the quaternary salts XVII and XVIII. Pharmacological screening showed indications of thymoleptic activity with compounds Ia-IIIa, anorectic effect with IIa and IIIb, antiarrhythmic activity with IIIa, XVII, and XVIII, and myorelaxant effect with XVII and XVIII. Antimicrobial and anthelmintic effects were also noted.
The effect of phosphonylmethyl analogs of ribonucleoside 5'-diphosphates on (E. coli) polynucleotide phosphorylase catalyzed reactions
Authors: Holý Antonín , Nishizawa Masahiko , Rosenberg Ivan , Votruba Ivan
Published: June 2010

Ribonucleoside 5'-O-phosphorylphosphonylmethyl ethers (I) are not substrates of Escherichia coli polynucleoside phosphorylase in the presence of either Mg2+- or Mn2+-ions. Compounds I are efficient competitive inhibitors of the polymerization of naturally occurring ribonucleoside 5'-diphosphates (Ki/Km 2 . 10-3 - 10-1). The analogs are not incorporated either into the polymer chain or into its termini during copolymerization with the natural substrate yet the homopolymer obtained shows a larger (by 20-85%) chain length. The presence of short oligonucleotides containing analogs II was not found after the polymerization reaction either. PolyA and polyC phosphorolyses are not affected by the presence of either naturally occurring 5'-diphosphates or of compounds Ib-Id. Adenine analog Ia as the only one significantly stimulates the phosphorolysis reaction catalyzed by E. coli polynucleotide phosphorylase.
MODELING THE EFFECTS OF SCHISTOSOMIASIS ON THE TRANSMISSION DYNAMICS OF HIV/AIDS
Authors: BHUNU C. P. , TCHUENCHE J. M. , GARIRA W. , MAGOMBEDZE G. , MUSHAYABASA S.
Published: June 2010

A schistosomiasis and HIV/AIDS co-infection model is presented as a system of nonlinear ordinary differential equations. Qualitative analysis (properties) of the model are presented. The disease-free equilibrium is shown to be locally asymptotically stable when the associated epidemic threshold known as the basic reproduction number for the model is less than unity. The Centre Manifold theory is used to show that the schistosomiasis only and HIV/AIDS only endemic equilibria are locally asymptotically stable when the associated reproduction numbers are greater than unity. The model is numerically analyzed to assess the effects of schistosomiasis on the dynamics of HIV/AIDS. Analysis of the reproduction numbers and numerical simulations show that an increase of schistosomiasis cases result in an increase of HIV/AIDS cases, suggesting that schistosomiasis control have a positive impact in controlling the transmission dynamics of HIV/AIDS.
ANALYSIS OF AN HIV/AIDS MODEL WITH PUBLIC-HEALTH INFORMATION CAMPAIGNS AND INDIVIDUAL WITHDRAWAL
Authors: NYABADZA FARAI , CHIYAKA CHRISTINAH , MUKANDAVIRE ZINDOGA , HOVE-MUSEKWA SENELANI D.
Published: June 2010

Primary prevention measures designed to alter susceptibility and/or reduce exposure of susceptible individuals to diseases, remain the mainstay in the fight against HIV/AIDS. A model for HIV/AIDS, that investigates the reduction in infection by advocating for sexual behavior change through public-health information campaigns and withdrawal of individuals with AIDS from sexual activity is proposed and analyzed. The contact rate is modeled using an incidence function with saturation that depends on the number of infectives. The dynamics of the model is determined using the model reproduction number [Formula: see text]. Numerical simulations are presented to illustrate the role of some key epidemiological parameters. The results from the study demonstrate that an increase in the rate of dissemination of effective public-health information campaigns results in a decrease in the prevalence of the disease. Similarly, an increase in the fraction of individuals with AIDS who withdraw from sexual activities reduces the burden of the disease.
PERMANENCE AND EXTINCTION OF A NONAUTONOMOUS STAGE-STRUCTURED EPIDEMIC MODEL WITH DISTRIBUTED TIME DELAY
Authors: SAMANTA G. P.
Published: June 2010

In this paper, we have considered a nonautonomous stage-structured epidemic model having two stages of the period of infection according to the progressing process of some infectious diseases (e.g. Chagas' disease, hepatitis C, etc.) with varying total population size and distributed time delay to become infectious. The infected persons in the different stages have different ability of transmitting disease. We have established some sufficient conditions on the permanence and extinction of the disease by using inequality analytical technique. We have obtained the explicit formula of the eventual lower bounds of infected persons. We have introduced some new threshold values R0and R* and further obtained that the disease will be permanent when R0> 1 and the disease will be going to extinct when R* < 1. By Lyapunov functional method, we have also obtained some sufficient conditions for global asymptotic stability of this model. Computer simulations are carried out to explain the analytical findings. The aim of the analysis of this model is to identify the parameters of interest for further study, with a view to informing and assisting policy-maker in targeting prevention and treatment resources for maximum effectiveness.
PROBABILITY OF ENTRAINMENT, SYNAPTIC MODIFICATION AND ENTRAINED PHASE ARE PHASE-DEPENDENT IN STDP
Authors: ZHAO GANG
Published: June 2010

Synaptic conductance can be modified in an activity dependent manner, in which the temporal relationship between pre- and post-synaptic spikes plays a major role. This spike timing dependent plasticity (STDP) has profound implications in neural coding, computation and functionality. Because the STDP learning curve is strongly nonlinear, initial state may have great impacts on the eventual state of the system. However, although this feature is intuitively clear, it has not been explored in detail before. This paper presents a preliminary numerical study in this direction. In a model of two pacemaker neurons and a synapse undergoing STDP, it is found that the probability of entrainment, direction of synaptic modification and entrained phase are all influenced by the initial relative phase. Based on these findings, it is reasonable to propose that the initial-state sensitive feature of STDP may contribute to its role of selective response in oscillatory neural networks.
A RATIO-DEPENDENT PREDATOR-PREY MODEL WITH DELAY AND HARVESTING
Authors: MISRA A. K. , DUBEY B.
Published: June 2010

In this paper a predator-prey model with discrete delay and harvesting of predator is proposed and analyzed by considering ratio-dependent functional response. Conditions of existence of various equilibria and their stability have been discussed. By taking delay as a bifurcation parameter, the system is found to undergo a Hopf bifurcation. Numerical simulations are also performed to illustrate the results.
WEB SERVICE CHOREOGRAPHY CONFORMANCE VERIFICATION THROUGH THE piX-MODEL
Authors: VAN SEGHBROECK GREGORY , VOLCKAERT BRUNO , DE TURCK FILIP , DHOEDT BART , DEMEESTER PIET
Published: June 2010

As the adoption of the Service Oriented Architecture paradigm has dramatically increased over the past few years, proper coordination of loosely coupled services becomes an important issue when building state-of-the-art applications. This coordination is typically organized through orchestration (requiring a central coordinating entity) or through choreographies. While the latter approach allows for a fully distributed coordination, the need also arises for a distributed conformance check, ensuring that each participant of the choreography behaves according to the general choreography.

In this paper, a formalism is presented to ensure this conformance at design time, with possible extensions to deploy time and to runtime conformance checking. This formalism is referred to as the piX-model and it will be shown that the approach taken is inherently less complex, both in time and space, than the conventional π-calculus-based approach, whilst offering the same conformance guarantees. This gain in performance allows for a small design turnaround time, and also opens the avenue to runtime conformance checking by resource constrained devices.
MODELING AND EXPLOITING CONTEXT FOR ADAPTIVE COLLABORATION
Authors: HAAKE JOERG M. , HUSSEIN TIM , JOOP BJÖRN , LUKOSCH STEPHAN , VEIEL DIRK , ZIEGLER JÜRGEN
Published: June 2010

Collaborative work is characterized by frequently changing situations and corresponding demands for tool support and interaction behavior provided by the collaboration environment. Current approaches to address these changing demands include manual tailoring by end-users and automatic adaptation of single user tools or for individual users. Few systems use context as a basis for adapting collaborative work environments, mostly focusing on document recommendation and awareness provision. In this paper, we present, firstly, a generic four layer framework for modeling and exploiting context. Secondly, a generic adaptation process translating user activity into state, deriving context for a given focus, and executing adaptation rules on this context. Thirdly, a collaboration domain model for describing collaboration environments and collaborative situations. Fourthly, examples of exploiting our approach to support context-based adaptation in four typical collaboration situations: co-location, co-access, co-recommendation, and co-dependency.
Shear-induced endothelial cell-cell junction inclination
Authors: Melchior Benoît , Frangos John A.
Published: June 2010

Atheroprone regions of the arterial circulation are characterized by time-varying, reversing, and oscillatory wall shear stress. Several in vivo and in vitro studies have demonstrated that flow reversal (retrograde flow) is atherogenic and proinflammatory. The molecular and structural basis for the sensitivity of the endothelium to flow direction, however, has yet to be determined. It has been hypothesized that the ability to sense flow direction is dependent on the direction of inclination of the interendothelial junction. Immunostaining of the mouse aorta revealed an inclination of the cell-cell junction by 13° in direction of flow in the descending aorta where flow is unidirectional. In contrast, polygonal cells of the inner curvature where flow is disturbed did not have any preferential inclination. Using a membrane specific dye, the angle of inclination of the junction was dynamically monitored using live cell confocal microscopy in confluent human endothelial cell monolayers. Upon application of shear the junctions began inclining within minutes to a final angle of 10° in direction of flow. Retrograde flow led to a reversal of junctional inclination. Flow-induced junctional inclination was shown to be independent of the cytoskeleton or glycocalyx. Additionally, within seconds, retrograde flow led to significantly higher intracellular calcium responses than orthograde flow. Together, these results show for the first time that the endothelial intercellular junction inclination is dynamically responsive to flow direction and confers the ability to endothelial cells to rapidly sense and adapt to flow direction.
Airborne particulate matter selectively activates endoplasmic reticulum stress response in the lung and liver tissues
Authors: Laing Suzette , Wang Guohui , Briazova Tamara , Zhang Chunbin , Wang Aixia , Zheng Ze , Gow Alexander , Chen Alex F. , Rajagopalan Sanjay , Chen Lung Chi , Sun Qinghua , Zhang Kezhong
Published: June 2010

Recent studies have suggested a link between inhaled particulate matter (PM) exposure and increased mortality and morbidity associated with pulmonary and cardiovascular diseases. However, a precise understanding of the biological mechanism underlying PM-associated toxicity and pathogenesis remains elusive. Here, we investigated the impact of PM exposure in intracellular stress signaling pathways with animal models and cultured cells. Inhalation exposure of the mice to environmentally relevant fine particulate matter (aerodynamic diameter < 2.5 μm, PM2.5) induces endoplasmic reticulum (ER) stress and activation of unfolded protein response (UPR) in the lung and liver tissues as well as in the mouse macrophage cell line RAW264.7. Ambient PM2.5 exposure activates double-strand RNA-activated protein kinase-like ER kinase (PERK), leading to phosphorylation of translation initiation factor eIF2α and induction of C/EBP homologous transcription factor CHOP/GADD153. Activation of PERK-mediated UPR pathway relies on the production of reactive oxygen species (ROS) and is critical for PM2.5-induced apoptosis. Furthermore, PM2.5 exposure can activate ER stress sensor IRE1α, but it decreases the activity of IRE1α in splicing the mRNA encoding the UPR trans-activator X-box binding protein 1 (XBP1). Together, our study suggests that PM2.5 exposure differentially activates the UPR branches, leading to ER stress-induced apoptosis through the PERK-eIF2α-CHOP UPR branch. This work provides novel insights into the cellular and molecular basis by which ambient PM2.5 exposure elicits its cytotoxic effects that may be related to air pollution-associated pathogenesis.
Successful implantation of physiologically functional bioengineered mouse internal anal sphincter
Authors: Raghavan Shreya , Miyasaka Eiichi A. , Hashish Mohamed , Somara Sita , Gilmont Robert R. , Teitelbaum Daniel H. , Bitar Khalil N.
Published: June 2010

We have previously developed bioengineered three-dimensional internal anal sphincter (IAS) rings from circular smooth muscle cells isolated from rabbit and human IAS. We provide proof of concept that bioengineered mouse IAS rings are neovascularized upon implantation into mice of the same strain and maintain concentric smooth muscle alignment, phenotype, and IAS functionality. Rings were bioengineered by using smooth muscle cells from the IAS of C57BL/6J mice. Bioengineered mouse IAS rings were implanted subcutaneously on the dorsum of C57BL/6J mice along with a microosmotic pump delivering fibroblast growth factor-2. The mice remained healthy during the period of implantation, showing no external signs of rejection. Mice were killed 28 days postsurgery and implanted IAS rings were harvested. IAS rings showed muscle attachment, neovascularization, healthy color, and no external signs of infection or inflammation. Assessment of force generation on harvested IAS rings showed the following: 1) spontaneous basal tone was generated in the absence of external stimulation; 2) basal tone was relaxed by vasoactive intestinal peptide, nitric oxide donor, and nifedipine; 3) acetylcholine and phorbol dibutyrate elicited rapid-rising, dose-dependent, sustained contractions repeatedly over 30 min without signs of muscle fatigue; and 4) magnitudes of potassium chloride-induced contractions were 100% of peak maximal agonist-induced contractions. Our preliminary results confirm the proof of concept that bioengineered rings are neovascularized upon implantation. Harvested rings maintain smooth muscle alignment and phenotype. Our physiological studies confirm that implanted rings maintain 1) overall IAS physiology and develop basal tone, 2) integrity of membrane ionic characteristics, and 3) integrity of membrane associated intracellular signaling transduction pathways for contraction and relaxation by responding to cholinergic, nitrergic, and VIP-ergic stimulation. IAS smooth muscle tissue could thus be bioengineered for the purpose of implantation to serve as a potential graft therapy for dysfunctional internal anal sphincter in fecal incontinence.