bluuebunny/crossref_metadata_2025 huggingface dataset:
Coxsackievirus B3 Infection Activates the Unfolded Protein Response and Induces Apoptosis through Downregulation of p58
IPK
and Activation of CHOP and SREBP1
Authors: Zhang Huifang M. , Ye Xin , Su Yue , Yuan Ji , Liu Zhen , Stein David A. , Yang Decheng
Published: June 2010

Cardiomyocyte apoptosis is a hallmark of coxsackievirus B3 (CVB3)-induced myocarditis. We used cardiomyocytes and HeLa cells to explore the cellular response to CVB3 infection, with a focus on pathways leading to apoptosis. CVB3 infection triggered endoplasmic reticulum (ER) stress and differentially regulated the three arms of the unfolded protein response (UPR) initiated by the proximal ER stress sensors ATF6a (activating transcription factor 6a), IRE1-XBP1 (X box binding protein 1), and PERK (PKR-like ER protein kinase). Upon CVB3 infection, glucose-regulated protein 78 expression was upregulated, and in turn ATF6a and XBP1 were activated via protein cleavage and mRNA splicing, respectively. UPR activity was further confirmed by the enhanced expression of UPR target genes ERdj4 and EDEM1. Surprisingly, another UPR-associated gene, p58
IPK
, which often is upregulated during infections with other types of viruses, was downregulated at both mRNA and protein levels after CVB3 infection. These findings were observed similarly for uninfected Tet-On HeLa cells induced to overexpress ATF6a or XBP1. In exploring potential connections between the three UPR pathways, we found that the ATF6a-induced downregulation of p58
IPK
was associated with the activation of PKR (PERK) and the phosphorylation of eIF2α, suggesting that p58
IPK
, a negative regulator of PERK and PKR, mediates cross-talk between the ATF6a/IRE1-XBP1 and PERK arms. Finally, we found that CVB3 infection eventually produced the induction of the proapoptoic transcription factor CHOP and the activation of SREBP1 and caspase-12. Taken together, these data suggest that CVB3 infection activates UPR pathways and induces ER stress-mediated apoptosis through the suppression of P58
IPK
and induction/activation of CHOP, SREBP1, and caspase-12.
Ion solvation in mixed solvents. An ab initio study
Authors: Kyselka Petr , Havlas Zdeněk , Sláma Ivo
Published: June 2010

The paper is concerned with the solvation of Li+, Be2+, Na+, Mg2+, and Al3+ ions in the mixed solvents acetonitrile···water, dimethyl sulphoxide···water, and dimethylformamide···water. The complexes acetonitrile···ion···acetonitrile are also studied. The ab initio quantum chemical method with the minimal STO-3G basis set was used to calculate the equilibrium distances, solvation energies, three-particle energy contributions, charge distributions, and overlap populations for the above systems. Optimum structures of the 1 : 1 : 1 complexes were determined on the basis of the results obtained.
The polarographic and voltammetric determination of 1-phenyl-5-hydroxy-3-carbamoylpyrazol-4-azo-(4'-ethoxycarbonylbenzene)
Authors: Barek Jiří , Civišová Dagmar
Published: June 2010

The polarographic reduction of the title azodye has been studied, a mechanism has been proposed for this process and conditions have been found for the determination of this substance by TAST polarography, with a detection limit of 7 . 10-7 mol l-1, differential pulse polarography at a dropping mercury electrode with a detection limit of 3.5 . 10-7 mol l-1, fast scan differential pulse voltammetry at a static mercury drop electrode with a detection limit of 6.9 . 10-9 mol l-1 and voltammetry with linearly increasing voltage at a hanging mercury drop with a detection limit of 1.6 . 10-9 mol l-1.
Preparation and properties of green rust type substances
Authors: Vinš Jaroslav , Šubrt Jan , Zapletal Vladimír , Hanousek František
Published: June 2010

A method has been worked out for the reproducible preparation of Green Rust substances involving SO42-, Cl-, Br-, and I- anions. The chemical composition of the substances prepared has been followed in dependence on the synthesis conditions. The powder X-ray and electron diffraction patterns and infrared and Moessbauer spectra have been measured and discussed.
Mechanism of base-catalyzed cyclization of ethyl N-(substituted aminocarbonyl)glycinates
Authors: Mindl Jaromír , Štěrba Vojeslav
Published: June 2010

The cyclization rate constants have been measured of substituted ethyl N-(phenylaminocarbonyl)-, N-(alkylaminocarbonyl)-, and N-(phenylaminothiocarbonyl)glycinates RNHCXNHCH2CO2.C2H5 (X = O, S). Logarithms of these constants increase with decreasing basicity of the amines down to the value of pKa(RNH2) = 5.5. The rate-limiting step of the reaction is formation of the tetrahedral intermediate. With ethyl N-(phenylaminocarbonyl)glycinates (whose pKa(RNH2) values are higher) this dependence, on the contrary, slightly decreases, and the acid-catalyzed splitting off of ethoxy group from the cyclic intermediate becomes rate-limiting. The cyclization rate of a series of ethyl N-(phenylaminothiocarbonyl)glycinates is practically independent of the pKa(RNH2) values, the change in the rate-limiting step would take place at pH about 9.
Synthesis of bis-sulphonium salts of naphthalene derivatives
Authors: Antoun S.
Published: June 2010

Bis-sulphonium salts of naphthalene derivatives have been synthesized in good yields via the reaction of dimethyl sulphide with primary naphthyl halides under mild conditions.
Interaction at interfaces and induction of surface free energy components
Authors: Kloubek Jan
Published: June 2010

A set of published data on surface free energy (γ1, γ2) and interfacial energy (γ12) for interfaces mercury-organic liquid, mercury-water, and water-organic liquid (125 pairs altogether) has been critically evaluated. It has been found that the Antonow rule does not hold, that the Neumann equation is suitable for determining the work of adhesion, if γ1 and γ2 are not too different, and that the Fowkes equation can be used to assess the type of interaction at the interface. A hypothesis has been suggested which states that, besides the interaction between dispersion components of the surface free energies of the adjoining phases and the interaction between the non-dispersion components of the same type in bulk, a non-dispersion component of one phase may interact by inducing a component of the same type in the other phase near the interface. Relations concerning the mechanism of interaction at the interface have been derived. Also, the relation between the Girifalco-Good, Neumann and complemented Fowkes equation has been evaluated. For the particular liquids the dispersion portion of their surface free energies and the interaction mechanism at their interface with water and mercury have been estimated. For water, e.g. the polar component of the surface free energy (14.7 mJ m-2) and the hydrogen-bond component (36.3 mJ m-2) have been determined. The introduction of the induced component of the surface free energy is shown, as an example, for water-aromatic hydrocarbons and water-alcohols systems.
Neue konstruktion eines ringschergerätes
Authors: Schünemann Ulrich , Höhne Detlef , Šmíd Jiří , Neumann Jürgen
Published: June 2010

Die neue Konstruktion eines Ringschergerätes für Schüttgüter und Pulver zeichnet sich durch einen neuartigen Scherdeckel ab, der eine gleichzeitige und voneinander unabhängige Messung des wirklichen Normaldrucks in der Materialprobe und der Scherspannungskomponente ermöglicht. Die Funktion des Gerätes wird durch Ergebnisse von Messungen des Fliessortes von Quarzmehl (mit Teilchen < 90 μm) belegt.
Diels-Alder reaction of acryloylferrocene with 1-phenyl-1,3-butadiene catalysed by homoionic forms of montmorillonite
Authors: Toma Štefan , Elečko Pavol , Gažová Jarmila , Solčániová Eva
Published: June 2010

Diels-Alder addition of acryloylferrocene to 1-phenyl-1,3-butadiene catalysed by homoionic forms of montmorillonite proceeds with higher selectivity and yields than does the reaction catalysed with aluminium trichloride. The catalytic activity of Mn+-montmorillonites decreases in the sequence: Al3+, Cr3+, Co2+, Fe3+, and Cu2+.
Oxidation of 3β,28-lupanediol diacetate and lupane with peroxyacetic acid
Authors: Sejbal Jan , Klinot Jiří , Vystrčil Alois
Published: June 2010

Lupane triterpenoids are attacked by peroxyacetic acid in position 19. 3β,28-Lupanediol diacetate (I) affords the 18β,19β-epoxy derivative III and the 19β-hydroxy derivative V, lupane (II) gives 18β,19β-epoxylupane (IV); however, the yields are low. Structure of the products III and IV was confirmed by independent preparation from the 20(29)-unsaturated compounds IX and X.
Effect of heavy metal ions on barley ribulose-1,5-bisphosphate carboxylase
Authors: Stiborová Marie , Doubravová Marta , Březinová Alena , Friedrich Aleš
Published: June 2010

Heavy metal ions (Cu2+, Cd2+, Pb2+, and Zn2+) in concentrations of 10-4 mol l-1 inhibit barley ribulose-1,5-bisphosphate carboxylase (RuBPC) (EC 4.1.1.39). The enzyme is inhibited most strongly by Cd2+ and Cu2+ and only very little by Zn2+-ions. Cu2+ and Zn2+-ions in concentrations of the order of 10-6 mol l-1 stimulate the RuBPC activity. The reaction of metal ions with the protein molecule of the enzyme is time dependent. The activation of the enzyme by Cu2+ and Zn2+-ions is the highest after 10 min incubation. Cd2+-ions in concentrations of 10-6 mol l-1 lead to a time dependent irreversible inhibition of the enzyme.
Topological aspects of chemical reactivity. On the similarity of molecular structures
Authors: Ponec Robert
Published: June 2010

A topological similarity index is introduced, allowing to characterize quantitatively the extent of reorganization of electron density in the course of chemical reactions. The possible application of this new index for the description and the classification of chemical reactions is discussed on the basis of certain analogy of similarity criteria with the so-called least-motion principle.
Leakage of solids through the perforated distributor
Authors: Veselý Václav , Čársky Milan , Pata Jaroslav , Hartman Miloslav
Published: June 2010

Experiments were conducted to explore the effect of free area, orifice diameter and grid thickness on the rate of backflow of particles (leakage, weeping) through the multi-orifice distributor. Air was used as a fluidizing medium. Two sieved fractions of glass beads and ash particles of different shape and density were employed in the experiments. The measured rates of backflow were fitted by an empirical correlation with an accuracy of ±30%.
Modelling of impregnation of γ-alumina with cobalt and molybdenum salts. CoCl2-(NH4)2MoO4-γ-Al2O3 (aluminate type) system
Authors: Hanika Jiří , Janoušek Vladimír , Sporka Karel
Published: June 2010

Adsorption data for the impregnation of alumina with an aqueous solution of cobalt dichloride and ammonium molybdate were treated in terms of the Langmuir adsorption isotherm and compared with a mathematical model set up to describe the kinetics of simultaneous impregnation of a support by two components. The effective diffusion coefficients of the two components at 25 °C in a cylindrical particle of alumina were obtained. The validity of the model used was verified qualitatively by comparing the numerical results with the experimental time dependent concentration profiles of the active components in a catalyst particle, measured by electron microanalysis technique.
Structural investigations of substituted methylenemalonaldehydes by X-ray crystallography and NMR spectroscopy
Authors: Pakkanen Tapani A. , Nevalainen Vesa , Král Vladimír , Laatikainen Reino , Arnold Zdeněk
Published: June 2010

Crystal and molecular structure of three substituted methylenemalonaldehydes I-III was studied. The spatial arrangement of the monosubstituted derivative I differs significantly from that of the disubstituted methylenemalonaldehydes II and III, not only in the solid state conformation of the malonaldehyde fragment but also in the length of the ethylenic C=C double bond and in its distorsion. The structures found in crystal are compared with conformations in solutions determined by NMR spectroscopy.
New approach to steroidal hemisuccinates and glycosides
Authors: Pouzar Vladimír , Černý Ivan , Drašar Pavel , Havel Miroslav
Published: June 2010

New synthesis of hemisuccinate and β-D-glucopyranoside of (20E)-21-ethoxycarbonyl-5,20-pregnadien-3β-ol (XVIII and XXVI) is described, consisting in the preparation of a protected hemisuccinate (XV) or glucoside (XXIII) intermediate, into which the unsaturated ester grouping in the side-chain is incorporated only in the final stage of the synthesis. The primary hydroxyl at C(20) was protected by tert-butyldimethylsilyl, trityl or nitrate groups, the succinate was blocked with 2-(trimethylsilyl)ethyl or 2,2,2-trichloroethyl groups and the glucosides were used in the form of peracetyl derivatives.
Transfer of trisbipyridine transition metal complexes across the water-dichloroethane interface
Authors: Hanzlík Josef , Hovorka Jan , Camus Anna Maria
Published: June 2010

Transfer of trisbipyridine transition metal complexes [M(bpy)3]2+ (bpy = bipyridine) across the water-1,2-dichloroethane interface can be classified as a simple transfer of a divalent cation in case that the central atom M = Fe, Ni, Ru or Os, while for M = Co, Cu or Zn the charge transfer is accompanied by considerable chemical changes, such as the ligand dissociation and the solvolysis. Thermodynamic and transport parameters characterizing the transfer of [M(bpy)3]2+ ions from water to 1,2-dichloroethane have been determined from voltammetric measurements.
Potentiostatically controlled transient diffusion on solid electrodes with rough surface
Authors: Wein Ondřej , Assaf Fawzi Hassan
Published: June 2010

Transient limiting diffusion currents were measured under potentiostatic conditions on several platinum electrodes for various solutions of sucrose with profoundly different diffusivities of a depolarizer. Systematic increase of the current densities against a Cottrellian (penetration) asymptote is correlated with parameters of roughness description.
Symmetrical isomers of arachno-5,5'-X-(6,9-C2B8H13)2 (X = O and OSO2O) compounds
Authors: Štíbr Bohumil , Plešek Jaromír , Jelínek Tomáš , Heřmánek Stanislav , Solntsev Konstantin A. , Kuznetsov Nicolai T.
Published: June 2010

Treatment of the [6,9-C2B8H10]Na2 salt with concentrated sulphuric acid produces two compounds of the general formula σ, ρ'-5,5'-X-(6,9-C2B8H13)2, where X = O or OSO2O, the constitution of which was established on the basis of their NMR data.
Radiotracer technique in adsorption study, part II. Adsorption of phosphate ions on chromium metal powder
Authors: Mishra Shuddhodan P. , Singh Tej Bahadur
Published: June 2010

The adsorption of phosphate ions on chromium metal powder from aqueous solutions of sodium dihydrogen phosphate labelled with 32P has been studied as a function of concentrative (10-3 to 10-6 mol l-1), temperature (303-323 K), and pH (3.5-10.6) of the adsorptive solution. The time for the equilibrium establishment was found to be about 4 hours and it is dependent on the solution acidity. The smooth and continuous growth of phosphate adsorption follows the first order kinetics and the rate constants are found to be of the order of 10-3 min-1. The results show that the adsorption in the system under study obeys the Freundlich isotherm. The increase in temperature from 303 K to 323 K does not effect the process markedly. The adsorption kinetics of phosphate ions is highly dependent on pH of the adsorptive solution. On the basis of the present data the nature and mechanism of the adsorption are discussed.
Synthesis of 1,3-diazaspiro[5,5]undecanes and 1-thia-3-azaspiro[5,5]undec-2-enes by reaction of 2-cyanocyclohexylideneacetyl isothiocyanate with amines and sodium hydrogen sulfide
Authors: Dzurilla Milan , Forgáč Ondrej , Kutschy Peter , Kristian Pavol , Koščík Dušan , Imrich Ján
Published: June 2010

2-Cyanocyclohexylideneacetyl isothiocyanate (II) reacts with sodium hydrogen sulfide to give 1-thia-3-azaspiro[5,5]undecane. Reaction of II with secondary amines afforded 1-thia-3-azaspiro[5,5]undec-2-enes whereas primary aromatic amines gave 1,3-diazaspiro[5,5]undecanes under the same conditions. Both types of reactions proceed via substituted thioureas which were isolated pure only in the case of 4-methylaniline and 4-methoxyaniline. They were cyclized in alkaline medium to the corresponding diazaspiro derivatives. The structure of the synthesized compounds was confirmed by their elemental analyses and IR, 1H NMR, 13C NMR and mass spectroscopy.
Reactions of α,β-unsaturated ketones with arylacetonitriles
Authors: Al-Arab Mohammad M. , Issa Ali M.
Published: June 2010

1,3-Diaryl-2-propene-1-ones I react with arylacetonitriles II in the presence of sodium ethoxide at room temperature to give a single diastereomer of the corresponding 2,3-diaryl-4-aroylbutyronitriles III. The structures of the reaction products were established by infrared, nuclear magnetic resonance, and mass spectral data as well as elemental analysis. The diastereomeric purity was determined by NMR measurements using lanthanide shift reagents. The observed resonances did not show any resolved diastereomeric proton signals.
Reaction of 3-keto and 2-ketotriterpenoids with 3-chloroperoxybenzoic acid in aliphatic alcohols. A new method of preparation of α-hydroxy ketones
Authors: Sejbal Jan , Klinot Jiří , Vystrčil Alois
Published: June 2010

19β,28-Epoxy-18α-oleanan-3-one (I), 19β,28-epoxy-24-nor-18α-oleanan-3-one (XIV) and 3-lupanone (XVII) are hydroxylated with 3-chloroperoxybenzoic acid in the presence of methanol or ethanol and 0.01-0.1% of sulfuric acid in position 2α. Hydroxy ketones VII, XV, and XVI are formed, respectively. The reaction is sensitive to the concentration of sulfuric acid; beyond this concentration range predominantly various 3,4-seco derivatives are formed (for example VI, IX, X, XVIII). 2-Oxo derivative IV is hydroxylated in a similar manner, giving rise to 3α-hydroxy-2-ketone VIII, while 1-oxo derivative XIII does not react. A reaction path is proposed for the hydroxylation, comprising the enol form or the enol ether as an intermediate.
Frictional resistance of spheres rotating in power-law non-Newtonian fluids
Authors: Mitschka Pavel
Published: June 2010

Frictional resistance coefficients have been calculated for the rotation of spheres in non-Newtonian power-law fluids under laminar boundary-layer conditions using the approximate method of integral momentum balances. The values obtained agree satisfactorily with the available experimental data and the published theoretical solution.
Particle size distribution of agglomerated crystal product from a continuous crystallizer
Authors: Hostomský Jiří
Published: June 2010

Relationships have been derived for the particle size distribution in a continuous crystallizer operating in a steady-state regime, where agglomeration of the primarily generated crystalline particles takes place. The derivation was made for a constant kinetic coefficient of agglomeration (independent of the particle size) and for a negligible particle growth rate. The relatioships are used to interpret the particle size distribution of calcium carbonate precipitated from 0.2 mol dm-3 solutions of calcium chloride and sodium carbonate in a laboratory continuous crystallizer. Anomalous shapes of the size distributions of small particles frequently observed in continuous crystallizers are discussed in terms of the agglomeration phenomenon.
Kinetics and mechanism of solvolysis of substituted phenyl N-phenylbenzimidoesters
Authors: Kaválek Jaromír , Hejtmánková Ludmila , Štěrba Vojeslav
Published: June 2010

Kinetics of hydrochloric acid-catalyzed solvolysis of substituted phenyl and methyl N-phenylbenzimidoesters have been studied in methanol, 50 vol. % aqueous methanol, and 50 vol. % aqueous tetrahydrofurane, and the composition of the reaction products has been determined. The rate-limiting step consists in addition of water or methanol to the protonated substrate. The reaction of methyl N-phenylbenzimidoester with both water and methanol and that of substituted phenyl N-phenylbenzimidoesters with methanol produce aniline, the ester (or orthoester) and the corresponding phenol. The reaction of substituted phenyl N-phenylbenzimidoesters with water gives both the neutral tetrahedral intermediate (which is decomposed into phenol and anilide) and the protonated intermediate (which produces aniline and the ester). At the same proton concentration the phenol content increases with increasing value of the σ constant of the substituent.
Stereoselectivity of cycloadditions of arylnitrile oxides to 5-alkoxy-2(5H)-furanone
Authors: Fišera Lubor , Oravec Peter
Published: June 2010

1,3-Dipolar cycloaddition of arylnitrile oxides to 5-alkoxy-2(5H)-furanones (II) and 5-hydroxy-2(5H)-furanone leads regiospecifically to 4-oxo-3a,4,6,6a-tetrahydrofuro[3,4-d]isoxazole derivatives IIIa-IIIj. The alkoxy derivatives give exclusively products of exo-configuration (III), whereas the hydroxy compound affords a 52 : 48 mixture of both diastereoisomers IIIj and IVj. Reaction of III with ammonia furnished diastereoisomeric tetrahydropyrrolo[3,4-d]isoxazoles V and VI, reaction with hydrazines led to hexahydroisoxazolo[4,5-d]pyridazin-7-one derivatives VII.
4-Aryl-3-(dimethylaminomethyl)thiacyclohexan-4-ols including the thia analogue of tramadol; Synthesis and analgetic activity
Authors: Urban Jiří , Svátek Emil , Ryska Miroslav , Metyš Jan , Wildt Stanislav , Protiva Miroslav
Published: June 2010

Mannich reaction of thiacyclohexan-4-one with dimethylamine and paraformaldehyde afforded 3-(dimethylaminomethyl)thiacyclohexan-4-one (XIV) which was subjected to reactions with a series of arylmagnesium bromides. The products were mixtures of trans- and cis-amino alcohols III-XII from which the predominating trans-components were mostly obtained by crystallization of hydrochlorides or chromatography of bases. The tramadol (I) analogue, i.e. the 3-methoxy compound V, was prepared in the form of both racemates and their relative configuration was confirmed by the IR spectra. Compound V was demethylated to the 3-hydroxyphenyl analogue XIII, transformed to the bis-onium salt XVI, partially N-demethylated to the N-monodemethyl analogue XVII, and oxidized to the sulfoxide XX and to the sulfone N-oxide XXI. Some of the amino alcohols (III-V, VIII, IX, XIII) showed clear analgetic activity in the writhing syndrome inhibition test in mice; the 3-methoxy and 3-hydroxy compounds (V and XIII) were the most active ones, the latter being slightly more active than tramadol (I).
Circular dichroism and infrared study of β-turn formation in repeat peptides of elastin
Authors: Rahman S. Abdel , Elsafty M. , Hattaba A.
Published: June 2010

The conformation of elastin-like peptides Boc-Ala-Pro-Gly-Val-APEGM, Boc-Ala-Pro-Gly-Val-Gly-Val-APEGM, Boc-Ala-Pro-Gly-Val-Ala-Pro-Gly-Val-Gly-Val-APEGM, Boc-Ala-Pro-Gly-Val-Gly-Val-Ala-Pro-Gly-Val-Gly-Val-APEGM were examined in solution using circular dichroism at 30 °C, 50 °C, and 70 °C and in solid state by IR at room temperature. The studies show that the β-turn is a significant conformational feature for peptides under investigation in solution at 30 °C and 50 °C, but at 70 °C the tetra, hexa, and decapeptides show the CD feature characteristic of the β-structure while the dodecapeptide spectra show the presence of β-turn which indicates the stability of the β-turn at this chain length. The IR spectra show that in the solid state at room temperature all investigated peptides assume essentially a β-turn except the tetrapeptide which present evidence of antiparallel β-structure. The β-turn contribution in the IR spectra increases with the increase of the chain length of the peptide.
Topological aspects of chemical reactivity. On the possible use of similarity index in characterizing the transition state structure in concerted pericyclic reactions
Authors: Ponec Robert
Published: June 2010

The use of the topological similarity index as a simple means for classification and characterization of the structure of the transition states in concerted pericyclic reactions is discussed. The suggested formulation makes it possible to bring a quantitative aspects into the empirical Dewar's classification of transition states in terms of aromaticity and/or antiaromaticity.
Mathematical modelling of remote detection of molecular air pollutants
Authors: Zrcek František , Horák Milan
Published: June 2010

A model of remote detection of molecular air pollutants is devised based on the lidar equation. The various kinds of interaction of radiation with matter, viz. absorption, induced fluorescence, and Raman scattering, are taken into account; detection of either scattered or reflected signal is considered. The reflection is assumed to be either axial, using a retroreflector, or omnidirectional from a field target. Based on this model, an algorithm was set up for simulation of the different variants of the experiment, making allowance for a generally variable concentration of the compound along the optical pathway of the light beam. The basic atmospheric processes, viz. radiation absorption by the backround, heat emission, turbulence, and the effect of atmospheric aerosols, are treated, and the last of them is found to play the major role. Aerosols are looked upon as a source of the Mie scattering and they are described by distribution equations with respect to the particle size and the complex refractive index. The variable concentration of the aerosol along the optical pathway and the simultaneous effect of a higher numberof aerosol types are included.
Theoretical and experimental investigation of the function of the wall flow deflecting ring. A mathematical model for the case of a large number of deflecting rings
Authors: Semkov Krumm , Kolev Nikolai , Staněk Vladimír , Moravec Pavel
Published: June 2010

Solution of the mathematical model has been developed of the distribution of liquid in a random packed bed in the presence of the wall flow deflecting rings. The solution was obtained in the form of a recurrent analytical formula. The formula permits, by repetitive calculation, profiles to be obtained of the densities of irrigation in a bed equipped with an arbitrary number of the wall flow deflecting rings. A comparison of experimental profiles of the density of irrigation with theoretical profiles showed considerable discrepancies between the two profiles. A new optimization of the parameters of the model, taking also the width of the wall flow deflecting ring as an adjustable parameter, showed a good agreement provided that the optimum width of the deflecting ring is about 1·5 times its real physical dimension. This finding can be explained by interaction of the function of the deflecting ring with the packing elements immediately adherring to the ring. This explanation may be partially supported by the visual observation showing the liquid to be deflected by the elements of the packing contacting the deflecting ring instead of the ring alone.
Theoretical and experimental investigation of the function of the wall flow deflecting ring. A generalized mathematical model for the case of a large number of deflecting rings
Authors: Semkov Krumm , Kolev Nikolai , Staněk Vladimír , Moravec Pavel
Published: June 2010

Based on the probability theory considerations a probability density distribution function has been derived for the radius on which the liquid, upon hiting the wall flow deflectiong ring, or an element of packing resting on it, is deflected and proceeds descending in a trickle bed column. The obtained probability density distribution function has been used in turn in the model describing the distribution of liquid in columns equipped with the wall flow deflecting rings. The ultimate goal is a reliable theory for optimization of the size and spacing of the wall flow deflecting rings in packed bed columns.
Δ-Sym-cis and Δ-unsym-cis-carbonato-(2S,2'S)-2,2'-ethylene-bis(2-amino-3-methylbutanoato)cabaltate(III) isomers
Authors: Jursík František , Abdel-Moez Samir
Published: June 2010

The tetradentate ligand (2S,2'S)-2,2'-ethylene-bis(2-amino-3-methylbutanoato) (eddval) is coordinated in the [Co(eddval)CO3]- anion to give 88% of Δ-sym-cis and 12% of Δ-unsym-cis isomers. The stereospecific formation of the Δ-sym-cis isomer is explained by steric crowding in the Λ-sym-cis isomer. The predominance of the sym-cis isomer indicates that the synthesis is also influenced by kinetic effects. These are particularly pronounced in the case of the Δ-unsym-cis isomer which for steric reasons is thermodynamically less stable than the Λ-unsym-cis isomer. The secondary nitrogen atoms in the Δ-sym-cis isomer are of the R configuration whereas in the Δ-unsym-cis isomer they have configuration R and S. The absolute configuration of the isomers has been determined from their absorption, CD, 1H and 13C NMR spectra. Acid hydrolysis of Δ-sym-cis-[Co(eddval)CO3]- proceeds with retention of configuration to give the Δ-[Co(eddval)(H2O)2]+ isomer.
Analysis of oligosaccharides. 29Si and 13C NMR spectra of pertrimethylsilylated oligosaccharides derived from xylopyranose
Authors: Petráková Eva , Schraml Jan , Hirsch Ján , Kvíčalová Magdalena , Zelený Jan , Chvalovský Václav
Published: June 2010

29Si and 13C chemical shifts are reported for a series of 30 pertrimethylsilylated oligosaccharides containing xylopyranosyl unit. The number of lines in 29Si NMR spectra is in all cases in agreement with the number of hydroxyl groups present in the parent compound prior to trimethylsilylation. The results demonstrate the usefulness of 29Si NMR spectroscopy for the analysis of oligosaccharides and other polyfunctional compounds. The validity of direct additivity of 13C chemical shifts is tested on some model trisaccharides.
Acylation of ω-phenylalkanoylferrocenes by cinnamoyl and phenylpropiolyl chlorides
Authors: Toma Štefan , Sališová Marta
Published: June 2010

In Friedel-Crafts acylation of ω-phenylalkanoylferrocenes, the site of electrophilic attack depends on the reagent used. The acylation with cinnamoyl chloride yields preferentially the products of substitution of the unsubstituted cyclopentadienyl ring of ferrocene. The acylation with phenylpropionyl chloride affords the products of acylation of the benzene ring of the starting compound. The different behaviour of both acylating agents is discussed.
Determination of the hydrocracking and hydroisomerization activities of catalysts containing zeolites Y and ZSM-5 for high boiling hydrocarbons conversion
Authors: Grzechowiak Jolanta R. , Masalska Aleksandra
Published: June 2010

Hydrocracking, hydroisomerization activities and selectivities were investigated using silica-alumina, silica-alumina-Y, and silica-alumina-ZSM-5 catalysts. The results show that white oil cracking activity of H-ZSM-5-containing catalyst is much higher than the cracking activity of H-Y. The work has shown that it is possible to carry out hydrocracking process at temperature 593-613 K and space velocity 2-3 h-1 (pressure 5·1 MPa, H2 : CH = 500 Nm3 m-3 h-1) using H-ZSM-5 containing catalysts. In such conditions, 76-84 wt. % of liquid product from white oil was obtained. After removing the low boiling fraction (below the initial boiling point of the feed), the lowering of the freezing point from 252 to 235 K was noticed.
Synthesis of peptide and glycopeptide fragments of bacterial cell walls
Authors: Ježek Jan , Straka Radovan , Krchňák Viktor , Ryba Miloš , Rotta Jiří , Mayer Peter , Zaoral Milan
Published: June 2010

Peptides, ranging from tetrapeptide I, II to octadecapeptide XXI and from N-acetylmuramyl-hexapeptide XXIII to tris(N-acetylmuramyl)-octadecapeptide XXVII, were prepared using synthesis in solution as well as solid-phase synthesis. H-L-Ala-D-iGln-L-Lys-D-Ala-(L-Ala)2-OMe (VIII) and its lysine-acetylated analogue X were pyrogenic and the former (VIII) exhibited weak immunoadjuvant activity. The immunoadjuvant activity of tris(N-acetylmuramyl)-octadecapeptide XXVII was comparable with that of MDP and the compound was not pyrogenic.
The prediction of valence force constants and vibration frequencies for XY6 (Oh) molecules, using the effective nuclear charge model
Authors: Fernández-Goméz Manuel , López-Gonzáles Juan J. , Martínez-Sánchez Manuel
Published: June 2010

Ohwada's effective nuclear charge model has been extended to the calculation of valence force constants for XY6 (Oh) molecules. To achieve this the potential energy function has had to be expressed in terms of independent force constants for which it has been necessary to eliminate the gem- and tree-redundancies that exist between the displacement coordinates. The vibration frequencies predicted by the use of these constants agree well in general with experimental observations.
Extraction of silver and mercury with tetraphenyl imidothiodiphosphate
Authors: Navrátil Oldřich , Herrmann Eckhard , Slezák Petr
Published: June 2010

The extraction of complexes of silver and mercury with tetraphenyl imidothiodiphosphate (HA) from HNO3 and HCl solutions, respectively, into benzene was studied. The extraction from dilute aqueous solutions establishes within 10 min. The composition and stability of the complexes extracted, AgA(HA) and HgA2, were derived from the dependences of the distribution ratios of the respective metals on the acidity of the aqueous phase and analytical concentration of reagent. Using HClO4 solutions as the aqueous phase, silver is extracted by a double extraction mechanism, an appreciable fraction of the metal passing into benzene also in the absence of HA. Based on the distribution of HA between the aqueous phase and benzene, its distribution and dimerization constants were established; the dissociation constant of the reagent was determined potentiometrically.
Smoothing of a stationary random signal in a continuous mixer
Authors: Hasal Pavel , Vyhlídková Jitka , Kudrna Vladimír
Published: June 2010

The paper presents results of the first stage of experimental verification of the theoretical concept published in the two first preceding communications concerning the flow of liquid in a continuous nonideal mixer and, namely, the smoothing effect of such a mixer on a passing stationary random concentration signal. In a sufficiently wide range of experimental conditions it has been proven that stochastic fluctuations of the distribution of the residence time of liquid in the mixer do not contribute significantly to the variance of the outlet random signal of the mixer. Further, a good agreement has been proven between the experimental data and the model relationship for the smoothing effect of the mixer based on the application of the gamma distribution of the residence time.
Photoreaction of N-butyl 3,4-dimethoxy-6-nitrobenzamide with butylamine. A model study for lysine-directed photoaffinity labelling
Authors: Kuzmič Petr , Pavlíčková Libuše , Souček Milan
Published: June 2010

Ultraviolet irradiation of the title compound I in the presence of butylamine gave predominantly products of nucleophilic photosubstitution by the amine, i.e., nitroanilines IIa and IIb. Besides, small amounts of products of hydrolysis (phenol III) and reductive coupling (azoxybenzene IV) were also formed. Comparison of the overall photolysis rate of I with that of 3,4-dimethoxy-1-nitrobenzene (V) indicates a minor loss of reactivity, most probably due to some deviation from coplanarity of the activating nitro group and the aromatic ring.
Configuration of natural 9-hydroxyfuroeremophilane, its 9-hydroxy epimer and furanopetasin: NMR and CD studies
Authors: Novotný Ladislav , Buděšínský Miloš , Jizba Josef , Harmatha Juraj , Lukeš Vít , Lindner Wolfgang , Grosser Rolf , Snatzke Günther
Published: June 2010

The conformation and configuration analysis of cis- and trans-furoeremophilanes with hydroxy group in position 9, using 1H NMR and CD spectra, is discussed. Some steroid derivatives were used as models for CD study. A combination of both spectral methods gives complementary results. For natural 9-hydroxyfuroeremophilane the configuration 9β-OH was unequivocally proved and the originally proposed structure of furanopetasin corrected to VII.
Preparation of (20E)-21-methoxycarbonyl-5,14,20-pregnatrien-3β-ol derivatives
Authors: Pouzar Vladimír , Černý Ivan , Drašar Pavel , Havel Miroslav
Published: June 2010

(20E)-21-Methoxycarbonyl-5,14,20-pregnatrien-3β-yl hydrogen butanedioate (XII) and (20E)-21-ethoxycarbonyl-5,14,20-pregnatrien-3β-yl hydrogen butanedioate (XIV) were prepared in nine steps from 3β-acetoxy-5,14-pregnadien-20-one (I). In the key intermediate, 20-(bis(4-methoxyphenyl)phenylmethoxy)-21-nor-5,14-pregnadien-3β-yl 2-(trimethylsilyl)ethyl butanedioate (VIII), the hydroxyl in position 20 was protected with 4,4'-dimethoxytrityl group and the succinate moiety with 2-(trimethylsilyl)ethyl group.
Model of vortex flow of charge in a vessel with turbine impeller
Authors: Hošťálek Miloslav , Fořt Ivan
Published: June 2010

A theoretical model is described of the mean two-dimensional flow of homogeneous charge in a flat-bottomed cylindrical tank with radial baffles and six-blade turbine disc impeller. The model starts from the concept of vorticity transport in the bulk of vortex liquid flow through the mechanism of eddy diffusion characterized by a constant value of turbulent (eddy) viscosity. The result of solution of the equation which is analogous to the Stokes simplification of equations of motion for creeping flow is the description of field of the stream function and of the axial and radial velocity components of mean flow in the whole charge. The results of modelling are compared with the experimental and theoretical data published by different authors, a good qualitative and quantitative agreement being stated. Advantage of the model proposed is a very simple schematization of the system volume necessary to introduce the boundary conditions (only the parts above the impeller plane of symmetry and below it are distinguished), the explicit character of the model with respect to the model parameters (model lucidity, low demands on the capacity of computer), and, in the end, the possibility to modify the given model by changing boundary conditions even for another agitating set-up with radially-axial character of flow.
The crystallochemistry of tetracyanocomplexes. The crystal and molecular structure of Cd(NH3)2Ni(CN)4.0·5 H2O
Authors: Kappenstein Charles , Černák Juraj
Published: June 2010

Cd(NH3)2Ni(CN)4.0·5 H2O is orthorhombic, Imma, with parameters a = 0·7622(4), b = 1·4992(13), c = 0·8961(6) nm, Z = 4, d(exp) = 2·07(4), d(calc.) = 2·066 Mg m-3. The structure, which was refined by the least squares method to R = 0·038 for 1 508 independent reflections, is isostructural with Ni(NH3)2Ni(CN)4.0·5 H2O and consists of infinite layers of the [Cd(NC)4Ni] type. Two water molecules in the unit cell occupy 4 equivalent positions between the layers. The shortest intermolecular distances 0·3023(2) (H2O···Ni) and 0·3371(1) nm (H2O···NH3) indicate zeolitic character of the water molecule.
Stereochemistry of organic ions in the gas phase: A review
Authors: Tureček František
Published: June 2010

The stereochemistry of organic ions in the gas phase can be regarded from two different points of view: (i) stereoselectivity in ion formation and (ii) stereospecifity of ion fragmentations. Fast ionization by electron or photon impact shows little stereoselection. Differences in the ionization energies and cross sections between stereoisomers are generally small, save for a few exceptions. Proton or larger ion transfer, as employed in chemical ionization mass spectrometry, gives more possibilities for stereoselection. Bi- or polyfunctional molecules can capture the proton in a hydrogen-bond stabilized [M + H]+ ion, which is feasible only with a favourable spatial orientation of the chelating groups. Adduct ions [M + R]+ can also be formed stereoselectively. The use of a chiral ionizing medium adds a new dimension, since enantiomers can be distinguished, or even independently identified. The stereochemistry of even-electron cations in the gas-phase is most pronounced with polyfunctional species. The stereochemical behaviour is ruled by two reactivity principles, i.e. the geometry-dependent stabilization of [M + H]+ ions by chelation, and the anchimeric assistance by neighbouring groups in elimination of small molecules (water, ammonia, alcohols, acetic acid, etc.). The stereochemistry of odd-electron cations seems to be governed by three principles, i.e. the thermochemistry of decompositions proceeding with simple-bond cleavage, stereoelectronic effects on bond dissociations in the presence of a control orbital, and long-range interactions resulting in transfer of a hydrogen atom or a larger group. All these three reaction classes have limited areas of application. The stereochemistry of even-electron anions has been developing rapidly. The reactivity of gas-phase anions finds numerous analogies in their chemistry in solution, e.g. hydride transfer reactions and nucleophilic substitution. The applications of mass spectrometry to configurational assignment and structure elucidation remain restricted to selected classes of organic compounds.
Assignment of 29Si NMR lines and determination of 29Si-13C coupling constants in pertrimethylsilylated lignin-related phenol-carboxylic acids by selective heteronuclear INADEQUATE method
Authors: Schraml Jan , Past Jaan , Puskar Jüri , Pehk Tõnis , Lippmaa Endel , Brežný Robert
Published: June 2010

Selective heteronuclear (Si-C) INADEQUATE method has been successfully used to assign all 29Si chemical shifts in six pertrimethylsilylated lignin model compounds. Empirical assignment of the lines in the region δ = 23-25 to trimethylsilyl esters of carboxylic compounds has been confirmed. Selectivity of the method permits unambiguous assignment to trimethylsiloxy groups which differ by their position on the benzene ring only. The assignment is possible despite that 29Si-13C two-bond coupling constants (2·1-3·0 Hz) are of comparable magnitude with the three-bond coupling constants (1-2·3 Hz). The chemical shifts of trimethylsiloxy groups on the benzene ring are sensitive to substituent effect to such an extent that their assignment cannot rely on an empirical rule but requires experimental method such as the one used here.
An anomalous effect of methyl group on acidity of acylthioureas
Authors: Kaválek Jaromír , Jirman Josef , Macháček Vladimír , Štěrba Vojeslav
Published: June 2010

Dissociation constants and methanolysis rate constants have been measured of 1-acetyl- and 1-benzoylthioureas and their N-methyl derivatives. Replacement of hydrogen atom at N(1) (next to the acyl group) by methyl group increases the acidity of the benzoyl derivative by one order, that of the acetyl derivative by as much as two orders of magnitude. Replacement of both hydrogens at N(3) by methyl groups lowers the methanolysis rate constant by more than two orders, whereas the replacement of hydrogen atom at N(1) by methyl group increases the methanolysis rate by the factor of 30.
Reaction of adamantanone, diamantanone, and their derivatives with thionyl chloride
Authors: Janků Josef , Burkhard Jiří , Vodička Luděk
Published: June 2010

In reaction of adamantanone, diamantanone, and their chloro or oxo derivatives with thionyl chloride the oxo group is replaced with two chlorine atoms under formation of geminal dichloro derivatives. The presence of a chlorine atom or an oxo group in both ketones reduces the reaction rate. The reaction rate decreases with decreasing distance between the substituent and the carbonyl group. Ketones with chlorine atom in α- or β-axial position do not react with thionyl chloride. The reaction is accelerated by hydrogen chloride whereas in the presence of pyridine no reaction was observed.
Power input of aerated agitator system of high-speed fermenter
Authors: Seichter Pavel
Published: June 2010

A correlation complying a simple model idea about function of an agitator in aerated high hold-up system has been found on basis of power input measurement of four fermenter agitators.
Polymer sulfoxides based on poly(vinyl alcohol) as effective catalysts of nucleophilic substitution reactions
Authors: Hrudková Hana , Čefelín Pavel , Janout Václav
Published: June 2010

Using the addition of alcohols to ethyl vinyl sulfoxide, a number of 2-alkoxyethyl ethyl sulfoxides were prepared, containing the following alkyls: methyl, ethyl, isopropyl, benzyl, and cyclohexyl. With a 10 mole % excess of alcohol the extent of the reaction was 70-95%. By a polymeranalogous reaction with poly(vinyl alcohol) and poly(ethylene-co-vinyl alcohol), copolymers poly[1-hydroxyethylene (74 mole %)-co-1-(2-ethylsulfinylethoxy)ethylene (26 mole %)] and poly[ethylene (62 mole %)-co-1-hydroxyethylene (35 mole %)-co-1-(2-ethylsulfinylethoxy)ethylene (3 mole %)] were prepared; the reaction with polymer alcohols requires the use of excess ethyl vinyl sulfoxide. These polymer sulfoxides were tested as catalysts of nucleophilic substitution reactions, using reactions of 1-bromooctane with sodium phenoxide, sodium iodide and potassium thiocyanate. They are more effective catalysts than polymer sulfoxides based on crosslinked poly(styrene) under the conditions of a two-phase (S-L) and three-phase (L-S-L) catalysis.
Solvolysis kinetics and mechanism of substituted 3-acetyl-1,3-diphenyltriazenes in acid medium; Kinetic acidity function
Authors: Pytela Oldřich , Kaska Martin , Ludwig Miroslav , Večeřa Miroslav
Published: June 2010

The decomposition kinetics has been measured of fourteen 3-acetyl-1,3-bis(subst. phenyl)triazenes in 40% (v/v) ethanol and sulphuric acid. The kinetic acidity function and catalytic rate constants have been determined from the rate constants observed. Mechanism has been suggested for the general acid-catalyzed solvolysis from comparison of the course of the kinetic acidity function and H0 function and from the reaction constant of the Hammett equation.
Oxidation of p–xylene to terephthalic acid in benzoic acid and methyl ester of p–toluic acid
Authors: Hronec Milan , Masarovič František , Cvengrošová Zuzana , Ilavský Ján
Published: June 2010

The oxidation of p-xylene to terephthalic acid has been studied at 130 to 190 °C, using benzoic acid and methyl ester of p-toluic acid as the solvent. It was found that the solvent affects strongly the activity of the cobalt catalyst which effect is dependent on the presence of bromide and pyridine ligands. In the methyl ester of p-toluic acid as the solvent, cobalt-bromide catalysts induce also hydrolysis of the methyl ester which proceeds parallelly to the oxidation of p-xylene. The activating effect of bromide and pyridine ligands results from their effect on the rate of the reaction of peroxy radicals with the catalyst in the propagation step and from their effect on the rate of consecutive oxidation of p-toluic acid to terephthalic acid.
Synthesis and mass spectra of piperidine and piperazine N-oxyl radicals
Authors: Kaliská Viera , Toma Štefan , Leško Ján
Published: June 2010

It has been found that ultrasound could accelerate the synthesis of piperidine and piperazine N-oxyl radicals. These radicals were investigated for their utilization as spin probes for checking the properties of liquid crystals. Electron impact mass spectra of the N-oxyl radicals were recorded and their fundamental fragmentation pattern was proposed.
A bistable kinetic system with oscillations on the thermodynamic and flow-through branches
Authors: Tockstein Antonín
Published: June 2010

A model of a flow-through perfectly stirred reactor comprising three consecutive competitive reactions with parallel reactions of some intermediates and exhibiting bistable behaviour and possessing regions with an oscillatory character on the thermodynamic branch is treated. The stationary concentration vs parameter dependence is of the fourth degree and the characteristic equation, of the fifth degree.