bluuebunny/crossref_metadata_2025 huggingface dataset:
Telocytes in trachea and lungs
Authors: Zheng Y. , Li H. , Manole C. G. , Sun A. , Ge J. , Wang X.
Published: August 2011

We show the existence of a novel type of interstitial cell—telocytes (TC) in mouse trachea and lungs. We used cell cultures, vital stainings, as well as scanning electron microscopy (SEM), transmission electron microscopy (TEM) and immunohistochemistry (IHC). Phase contrast microscopy on cultured cells showed cells with unequivocally characteristic morphology of typical TC (cells with telopodes—Tp). SEM revealed typical TC with two to three Tp—very long and branched cell prolongations. Tp consist of an alternation of thin segments (podomers) and thick segments (podoms). The latter accommodate mitochondria (as shown by Janus Green and MitoTracker), rough endoplasmic reticulum and caveolae. TEM showed characteristic podomers and podoms as well as close relationships with nerve endings and blood capillaries. IHC revealed positive expression of TC for c‐kit, vimentin and CD34. In conclusion, this study shows the presence in trachea and lungs of a peculiar type of cells, which fulfils the criteria for TC.
Selective hydroxylation of alkanes by an extracellular fungal peroxygenase
Authors: Peter Sebastian , Kinne Matthias , Wang Xiaoshi , Ullrich René , Kayser Gernot , Groves John T. , Hofrichter Martin
Published: August 2011

Fungal peroxygenases are novel extracellular heme‐thiolate biocatalysts that are capable of catalyzing the selective monooxygenation of diverse organic compounds, using only H2O2 as a cosubstrate. Little is known about the physiological role or the catalytic mechanism of these enzymes. We have found that the peroxygenase secreted by Agrocybe aegerita catalyzes the H2O2‐dependent hydroxylation of linear alkanes at the 2‐position and 3‐position with high efficiency, as well as the regioselective monooxygenation of branched and cyclic alkanes. Experiments with n‐heptane and n‐octane showed that the hydroxylation proceeded with complete stereoselectivity for the (R)‐enantiomer of the corresponding 3‐alcohol. Investigations with a number of model substrates provided information about the route of alkane hydroxylation: (a) the hydroxylation of cyclohexane mediated by H218O2 resulted in complete incorporation of 18O into the hydroxyl group of the product cyclohexanol; (b) the hydroxylation of n‐hexane‐1,1,1,2,2,3,3‐D7 showed a large intramolecular deuterium isotope effect [(kH/kD)obs] of 16.0 ± 1.0 for 2‐hexanol and 8.9 ± 0.9 for 3‐hexanol; and (c) the hydroxylation of the radical clock norcarane led to an estimated radical lifetime of 9.4 ps and an oxygen rebound rate of 1.06 × 1011 s−1. These results point to a hydrogen abstraction and oxygen rebound mechanism for alkane hydroxylation. The peroxygenase appeared to lack activity on long‐chain alkanes (> C16) and highly branched alkanes (e.g. tetramethylpentane), but otherwise exhibited a broad substrate range. It may accordingly have a role in the bioconversion of natural and anthropogenic alkane‐containing structures (including alkyl chains of complex biomaterials) in soils, plant litter, and wood.
The Impact of Immigration on the Development of Adolescent Schizophrenia
Authors: Ampadu Esther
Published: August 2011

PROBLEM:  Impact of immigration on the development of adolescent schizophrenia.

METHODS:  The review of literature used Academic Search Premier, CINHAL, PsychINFO, PubMed, and MEDLINE databases to examine reasons given to immigration as a risk factor to adolescent schizophrenia.

FINDINGS:  There is not a single factor or a group of related factors that could explain why the incidence of schizophrenia among immigrants is higher compared with natives of the host county.

CONCLUSION:  Further inquiry into this phenomenon is needed to understand factors that increase the risk of schizophrenia among immigrant children and to help plan and implement strategies for prevention.
Acute and sustained actions of hyperglycaemia on endothelial and glomerular barrier permeability
Authors: Swärd P. , Rippe B.
Published: August 2011

Microalbuminuria is an established marker of systemic endothelial dysfunction, which for patients with diabetes signals an increased risk of both diabetic nephropathy and cardiovascular complications. A better understanding of the pathogenesis of microalbuminuria is important in the quest of finding new approaches to treat patients with diabetes. Direct acute effects of episodes of hyperglycaemia (HG) could have implications for the microalbuminuria seen in early diabetes before renal structural alterations have started, especially in those patients with poor glycaemic control. This review summarizes the literature evidence that acute or sustained HG may lead to an increased vascular or glomerular permeability. Special focus is on glomerular barrier permeability. There is evidence in the literature that HG increases systemic capillary and glomerular barrier permeability within 20–30 min in vivo in rats and mice. Furthermore, exposure of monolayers of cultured endothelial cells to HG has been shown to increase monolayer permeability rapidly and transiently (during 60–100 min). Instant cellular changes following F‐actin cytoskeleton rearrangements, which could be abrogated by Rho‐kinase (ROCK) inhibition, are implicated. Data in this review also suggest that activation of protein kinase C, the polyol pathway, and an increased release of reactive oxygen species (ROS) and cytokines could contribute to the increase in barrier permeability induced by HG. Recent in vitro data from cultured podocyte monolayers also designates a role of insulin in acute podocyte F‐actin remodelling, underpinning the complexity of the mechanisms leading to glomerular and endothelial barrier alterations in diabetes mellitus.
Cold Storage of Six Marine Benthic Diatoms Native to the Mexico Pacific Coast
Authors: Núñez‐Zarco Estrella , Sánchez‐Saavedra M. Del Pilar
Published: August 2011

Cultures of six benthic diatoms were maintained in the dark to measure their viability and biochemical composition after 8 wk of storage at low temperature (4 C) in darkness by refrigeration. Cell density, growth rate, and viability for each benthic diatom changed significantly after storage. Significant differences were observed with regard to cell size (length and width) of Nitzschia laevis, Navicula sp., and Amphora tenerrima as a result of storage. In general, the proximal composition of the benthic diatom cultures changed after week 1 of storage and decreased after week 4 of storage for all the diatoms. These results demonstrate that under 1–4 wk of storage these diatoms maintain their viability and had changes in their proximal composition in species‐specific responses. Storage of preserved live microalgae cells is an alternative technique that can be used to reduce the need for continuous maintenance of live cultures and can provide live feed stock for aquaculture applications.
Does Looking at the Positive Mean Feeling Good? Age and Individual Differences Matter
Authors: Isaacowitz Derek M. , Noh Soo Rim
Published: August 2011

In this paper, we link age differences in gaze patterns toward emotional stimuli to later mood outcomes. While one might think that looking at more positive emotional material leads to better moods, and looking at more negative material leads to worse moods, it turns out that links between emotional looking and mood depend on age as well as individual differences. Though older people can feel good by looking more at positive material, in some cases young adults actually feel better by engaging visually with the negative. These age effects are further moderated by attentional abilities. Such findings suggest that different age groups may use looking differently, and this may reflect their preferences for using distinct emotion regulatory strategies. This work also serves as a reminder that regulatory efforts are not always successful at improving mood.
Primary pleural chloroma: A rare location with fatal prognosis
Authors: Elsayed Hany , Gosney John
Published: August 2011

We report an extremely unique histologically proven case of an isolated primary pleural granulocytic sarcoma (chloroma) in a 44‐year‐old woman who had sustained complete remission for 14 years after being treated for a Hodgkin's lymphoma. There was no history of myelogenous leukemia, which typically precedes chloroma. The prognosis was dismal as the patient died 2 weeks after diagnosis.
Simulation and Validation of Mach Number Effects on Secondary Flow in a Transonic Turbine Cascade Using a Multigrid, k–ε Solver
Authors: Koiro M. , Lakshminarayana B.
Published: August 2011

An existing three-dimensional Navier–Stokes flow solver with an explicit Runge–Kutta algorithm and a low-Reynolds-number k–ε turbulence model has been modified in order to simulate turbomachinery flows in a more efficient manner. The solver has been made to converge more rapidly through use of the multigrid technique. Stability problems associated with the use of multigrid in conjunction with two-equation turbulence models are addressed and techniques to alleviate instability are investigated. Validation for the new code was performed with a transonic turbine cascade tested by Perdichizzi. In the fully three-dimensional turbulent cascade, real convergence (i.e., CPU time) was improved nearly two times the original code. Robustness was enhanced with the full multigrid initialization procedure. The same test case was then used to perform a series of simulations that investigated the effect of different exit Mach numbers on secondary flow features. This permitted an in-depth study into the mechanisms of secondary flow formation and secondary losses at high Mach numbers. In this cascade, it was found that secondary losses and secondary flow deviation, which are fairly constant in incompressible flows with similar geometries, underwent a large reduction in the compressible flow range. The structure of the trailing edge shock system and the reduced end wall boundary layer at supersonic exit conditions were shown to be very significant in reducing the amount of secondary flow and losses.
Computational Prediction of Heat Transfer to Gas Turbine Nozzle Guide Vanes With Roughened Surfaces
Authors: Guo S. M. , Jones T. V. , Lock G. D. , Dancer S. N.
Published: August 2011

The local Mach number and heat transfer coefficient over the aerofoil surfaces and endwalls of a transonic gas turbine nozzle guide vane have been calculated. The computations were performed by solving the time-averaged Navier–Stokes equations using a fully three-dimensional computational code (CFDS), which is well established at Rolls-Royce. A model to predict the effects of roughness has been incorporated into CFDS and heat transfer levels have been calculated for both hydraulically smooth and transitionally rough surfaces. The roughness influences the calculations in two ways; first the mixing length at a certain height above the surface is increased; second the wall function used to reconcile the wall condition with the first grid point above the wall is also altered. The first involves a relatively straightforward shift of the origin in the van Driest damping function description, the second requires an integration of the momentum equation across the wall layer. A similar treatment applies to the energy equation. The calculations are compared with experimental contours of heat transfer coefficient obtained using both thin-film gages and the transient liquid crystal technique. Measurements were performed using both hydraulically smooth and roughened surfaces, and at engine-representative Mach and Reynolds numbers. The heat transfer results are discussed and interpreted in terms of surface-shear flow visualization using oil and dye techniques.
CrdS and CrdA Comprise a Two-Component System That Is Cooperatively Regulated by the Che3 Chemosensory System in Myxococcus xanthus
Authors: Willett Jonathan W. , Kirby John R.
Published: August 2011

Myxococcus xanthus
serves as a model organism for development and complex signal transduction. Regulation of developmental aggregation and sporulation is controlled, in part, by the Che3 chemosensory system. The Che3 pathway consists of homologs to two methyl-accepting chemotaxis proteins (MCPs), CheA, CheW, CheB, and CheR but not CheY. Instead, the output for Che3 is the NtrC homolog CrdA, which functions to regulate developmental gene expression. In this paper we have identified an additional kinase, CrdS, which directly regulates the phosphorylation state of CrdA. Both epistasis and
in vitro
phosphotransfer assays indicate that CrdS functions as part of the Che3 pathway and, in addition to CheA3, serves to regulate CrdA phosphorylation in
M. xanthus
. We provide kinetic data for CrdS autophosphorylation and demonstrate specificity for phosphotransfer from CrdS to CrdA. We further demonstrate that CheA3 destabilizes phosphorylated CrdA (CrdA~P), indicating that CheA3 likely acts as a phosphatase. Both CrdS and CheA3 control developmental progression by regulating the phosphorylation state of CrdA~P in the cell. These results support a model in which a classical two-component system and a chemosensory system act synergistically to control the activity of the response regulator CrdA.

IMPORTANCE
While phosphorylation-mediated signal transduction is well understood in prototypical chemotaxis and two-component systems (TCS), chemosensory regulation of alternative cellular functions (ACF) has not been clearly defined. The Che3 system in
Myxococcus xanthus
is a member of the ACF class of chemosensory systems and regulates development via the transcription factor CrdA (
c
hemosensory
r
egulator of
d
evelopment) (K. Wuichet and I. B. Zhulin, Sci. Signal. 3:ra50, 2010; J. R. Kirby and D. R. Zusman, Proc. Natl. Acad. Sci. U. S. A. 100:2008–2013, 2003). We have identified and characterized a homolog of NtrB, designated CrdS, capable of specifically phosphorylating the NtrC homolog CrdA in
M. xanthus
. Additionally, we demonstrate that the CrdSA two-component system is negatively regulated by CheA3, the central processor within the Che3 system of
M. xanthus
. To our knowledge, this study provides the first example of an ACF chemosensory system regulating a prototypical two-component system and extends our understanding of complex regulation of developmental signaling pathways.
Comments on the papers by J. Balej and coworkers on the mechanism of the formation of peroxomonosulphuric acid and the effect of this acid during the electrolytic preparation of peroxodisulphates
Authors: Smit W.
Published: August 2011

Article without abstract
Anionic cis-trans isomerization of dialkyl perfluoro(4-methyl-2-pentene)dioates. A non-classical equilibrium dependence
Authors: Paleta Oldřich , Svoboda Jiří , Dědek Václav
Published: August 2011

cis-trans-Isomerization of diethyl, diisopropyl, dibutyl and dicyclohexyl perfluoro(4-methyl-2-pentene)dioates (I-IV) was studied in solutions, containing solid potassium fluoride, in the range 20-150°C. The dependence of the cis-trans equilibrium on temperature for the compounds I-IV is within the experimental error identical with that found for the dimethyl ester, i.e. it exhibits and extreme at 40-45°C. This non-classical dependence cannot be described by the van't Hoff equation. The phenomenon is discussed in connection with the so-called cis-effect of fluorine substituents on a double bond.
Flow of liquid in a cylindrical vessel with a turbine impeller and radial baffles
Authors: Fořt Ivan , Obeid Ahmed , Březina Vítězslav
Published: August 2011

The study describes a theoretical model of flow pattern of a newtonian liquid in a flat-bottomed cylindrical vessel with radial baffles at wall agitated by a standard six-blade disc turbine impeller, under turbulent flow. The model, comprising the description of the field of main mean velocity components and of Stokes stream function in the system, is identified by experimental determination of velocity field by means of Pilot direction tubes and hot-film anemometer. The resulting analytical description of the flow pattern in the vessel corresponds well to that found experimentally. Knowing three parameters derived from the velocity profile of the stream streaking from the impeller, the description depends only on the system geometry.
Interaction between horse liver alcohol dehydrogenase and aporphine alkaloids
Authors: Walterová Daniela , Kovář Jan , Preininger Vladimír , Šimánek Vilím
Published: August 2011

The interaction between horse liver alcohol dehydrogenase (ADH) and aporphine alkaloids has been studied by kinetic and fluorescence methods. The aporphine alkaloids inhibit ADH. The inhibitory effect depends on the position and type of the substituents in the aporphine nucleus. Aporheine shows the strongest binding to the enzyme, and that irrespective of the configuration of the molecule. The dissociation constant of the complex enzyme-aporpheine is 20-25μmol l-1. The results indicate that the aporphine alkaloids bind to the active center of alcohol dehydrogenase with stechiometry 1 : 1.
Estimation of P-V-T behaviour of gas mixtures
Authors: Měřičková Vladimíra , Novák Josef P. , Pick Jiří
Published: August 2011

A review of methods is presented which allow to determine the P-V-T behaviour of gas mixtures. This review is based on the computations performed for about 2 200 P-V-T-X data of 12 binary mixtures. The method of combination of the equation-of-state constants, the Joffe method and the modified Bartlett rule proved to be the most suitable.
Preparation and 1H NMR study of soluble alkoxy, alkyl and arylamido derivatives of sodium tetraamidoaluminate
Authors: Kříž Otomar , Mareš František , Čásenský Bohuslav
Published: August 2011

Sodium tetraamidoaluminate reacts with alcohols and aromatic amines under formation of sodium alkoxyimidoaluminates or amido(arylamido)aluminates, respectively. The corresponding sodium amido(alkylamido)aluminates were prepared from sodium tetraamidoaluminate and sodium tetrakis(alkylamido)aluminates in 1,2-dimethoxyethane or pyridine solution. 1H NMR spectra and in some cases also the cryoscopic molecular weights of the prepared compounds were measured.
Effect of various modifying elements on the catalytic properties of vanadium-phosphorus catalysts in oxidation of butane
Authors: Brutovský Milan , Gerej Štefan
Published: August 2011

The flow-through method was applied to a study of the catalytic properties of vanadium-phosphorus catalysts (V: P = 1 : 1.2) prepared by the method of interaction of H3PO4 with V2O2 solution in HCl to which a Li, Ba, Mn, Fe, Co, Ni, Cu, Zn, Pd, Cd, Sn, or Ce salt was added as a modifying substance. The catalysts were ordered in a sequence according to the selectivity found in oxidation of butane. Catalysts with modifying elements whose ions possess an incomplete outer electron shell exhibit higher selectivity and yields of maleic anhydride than those in which the introduced ions possess a complete outer electron shell.
The crystal and molecular structure of copper(II) bis-(ethylenediamine)nitrate selenocyanate
Authors: Vrábel Viktor , Garaj Ján
Published: August 2011

The crystal structure of [Cuen2(NO3)]SeCN was solved by the single-crystal X-ray structural analysis method. The compound crystallizes in the monoclinic system with space group Pc. The unit cell has dimensions: a = 0.9254(3), b = 1.4018(3), c = 0.9722(5) nm, β = 99.20(3)°. The structure was refined by the least squares method to a final value of R = 6.8% for 1965 observed reflections. The crystal structure consits of polymeric cation chain [Cuen2(NO3)]+ and of free uncoordinated SeCN- anions. The nitrate ion NO-3 forms a bridging unit between two [Cuen3]2+ cations. The coordination polyhedron around the Cu(II) atom is a deformed octahedron, formed of two ethylendiamine molecules and two oxygen atoms of the NO-3 ions, bonded to divalent copper in the axial direction along the long coordinates. The crystal structure contains selenocyanate which is not bonded through a covalent bond to the central atom, but there are intermolecular contacts with its immediate surroundings.
Temperature control in a chemical reactor through variable area of the heat transfer surface. Experimental verification
Authors: Horák Josef , Jiráček František , Ježová Libuše
Published: August 2011

A possibility has been tested in the paper of the feed back control of temperature of the reaction mixture in a batch reactor with an exothermic reaction through the variable area of the cooling surface. The measurement were carried out in a laboratory reactor with a retractable cooler which was being immersed into the reaction mixture. The speed of motion of the cooler was sufficiently high permitting the process of immersion to be regarded as practically instantaneous. The aim of the control was to stabilize the set point temperature of the reaction mixture by a two-point controler. In dependence on the rate of response of the system to a change of the section variable either the ideal relay or the relay with hysteresis control algorithmus were used. The results of measurements showed that with the aid of a retractable cooler the temperature could be controlled safely even in those cases, in which the control by the variable flow rate of the coolant was unfeasible. The verification was carried out in the open-loop instable operating point of the reactor.
Conformational analysis of metal chelates. A molecular mechanical study of the relative stability of cobalt(III) 2,3-diaminobutane-N,N,N',N'-tetraacetate complexes
Authors: Pavelčík František , Majer Jaroslav
Published: August 2011

The stereochemistry and relative energy of diastereoisomers of Λ-[Co(DBTA)]- were studied in dependence on the absolute configuration of the ligand using molecular mechanical calculations. The calculated thermodynamic stabilities of the complexes decrease in the order (S, S)-DBTA (R,S)-DBTA (R,R)-DBTA. The destabilization factors are primarily repulsion non-bonding interactions between the axial methyl group and atoms of the acetate ring, R. (S,S)- and (R,R)-DBTA exhibit high diastereoselectivity in octahedral complexes. The large steric strain in the meso-DBTA complex can lead to opening of one chelate ring.
The pyrolysis capillary gas chromatography of some polymeric materials
Authors: Pacáková Věra , Nogatz Marlies , Novák Vladimír
Published: August 2011

The thermal degradation of industrially manufactured polymers based on polyethylene, polypropylene and polystyrene was studied. The pyrolysis was carried out in a tubular quartz pyrolyzer at 510°C and the products were separated on capillary columns coated with squalane and OV-17 and were identified on the basis of their retention indices.
Kinetics of cyclization of 1-phenyl-3-(1,2-dimethyl-3-oxo-1-butenyl)urea and ethyl 2-methyl-3-N-(N'-phenylureido)-2-butenoate
Authors: Kaválek Jaromír , Hruška Jiří , Štěrba Vojeslav
Published: August 2011

1-Phenyl-3-(1,2-dimethyl-3-oxo-1-butenyl)urea (III) has been prepared by reaction of phenyl isocyanate with 4-amino-3-methyl-3-penten-2-one (I). Ethyl 2-methyl-3-N-(N'-phenylureido)-2-butenoate (V) has been prepared by analogous reaction with ethyl 3-amino-2-methyl-2-butenoate (II). Kinetics have been measured of acid and base catalyzed cyclization of III and that of base catalyzed cyclization of V giving 1-phenyl-4,5,6-trimethylpyrimidin-2(1H)-one (IV) and 3-phenyl-5,6-dimethyluracil (VI), respectively. In acid medium the compound V is only hydrolyzed. The base catalyzed cyclization of III is faster than that of V by almost two orders of magnitude.
29Si and 13C NMR spectra of some alkyldiphenylchlorosilanes, alkyldiphenylsilanoles and bis(alkyldiphenylsilyl)chromates
Authors: Lyčka Antonín , Šnobl Dobroslav , Handlíř Karel , Holeček Jaroslav , Nádvorník Milan
Published: August 2011

29Si and 13C NMR spectra of alkyldiphenylchlorosilanes, alkyldiphenylsilanoles, and bis(alkyldiphenylsilyl)chromates (C6H5)2Si(R)X have been studied. The chemical shifts δ(29Si) are most affected by nature of the electronegative substituent X, i.e. Cl, OH or CrO3OSi(R). (C6H5)2. The δ(29Si) shifts due to effects of the substituents R can be correlated successfully with values of the Taft constants σ. Slopes of the correlation dependences have negative signs for all the groups of the studied compounds (increasing electron-acceptor ability of substituent R causes upfield shifts of δ(29Si), and their values decrease with increasing electronegativity of the substituent X (sensitivity of the δ(29Si) shifts due to sustituent R increases with increasing electronegativity of the substituent X). Methyl groups at γ-position of the chain of substituent R cause a diamagnetic shift of δ(29Si) by 0.6 to 3.3 ppm. The δ(13C) shifts depend little on nature of the substituent X. Chemical shifts δ(13C) of carbon atoms at α-, β-, and γ-positions of the substituent R with respect to silicon show a good linear correlation with the δ(13C) shifts of the corresponding carbon atoms in aliphatic hydrocarbons CH3R. Slopes of the correlation dependences of all the groups of studied compounds are close to 1, the intercepts for α- and β-positions are negative because of induction effect. Positive value of the intercepts for γ-positions reflects the influence of sterical γ-effect.
Preparation and properties of β-ketosulphones of 5-nitrofuran series. Study of transfer of electronic effects through sulphone group
Authors: Polakovičová Dana , Jurášek Adolf , Kvasnička Vladimír
Published: August 2011

A series of 2-(5-nitro-2-furyl)-2-oxoethylarylsulphones have been synthesized by reaction of 5-nitro-2-bromoacetylfuran with sodium p-X-benzenesulphinates (where X = H, CH3, OCH3, CH3CONH, NH2, N(CH3)2, Cl, NO2) and used for a study of transfer of electronic effects of the substituent through SO2 group. The found linear dependence between the proton chemical shifts in 1H NMR spectra (and pKa values of the CH2 group) and the Hammett constants of the substituents proves the existence of the transfer through SO2 group. The results of physical measurements were compared with the data obtained by quantum-chemical calculations using the EHT method.
Absolute configuration of (R)-(-)-2-allyl-2-ethyl-3-methoxycarbonylpropionic acid
Authors: Hájíček Josef , Trojánek Jan
Published: August 2011

The absolute configuration pf (R)-(-)-2-allyl-2-ethyl-3-methoxycarbonylpropionic acid (I) was determined on the basis of the conversion of I to dimethyl (S)-(-)-2-ethyl-2-methylsuccinate (X) and (R)-(+)-4-ethyl-4-propyl-4,5-dihydro-6H-canthin-6-one (XIV).
Oscillating heterogeneous reaction with oxalic acid
Authors: Ševčík Peter , Adamčíková Ľubica
Published: August 2011

Catalysed oxidation of oxalic acid with bromate ions at constant flow of nitrogen was investigated. Oscillations of the catalyst and bromine and the stepwise decrease of the concentration of bromate ions were followed by the polarographic method. Optimum conditions for the oscillations are at the stoichiometric ratio of the reactants. Oscillations of the concentration of bromine are enabled by the Ce(III) or Mn(II) catalyst. The oscillating behaviour of oxalic and malonic acids at heterogeneous conditions is compared.
CO2 Laser-induced fluorination of some carbon oxides and sulfides by sulfur hexafluoride
Authors: Pola Josef
Published: August 2011

The cw CO2 laser induced interactions between SF6 and carbon compounds as CO2, C3O2, CO, COS, and CS2 are reported and their mechanism is discussed. The results show SF6 activated by laser radiation to fluorinate carbon compounds of their fragments to yield COF2, SOF2, CF4 and C2F6. The laser-induced processes are shown to possess features different from those of the appropriate thermally induced reactions.
Infrared spectra of 2,4-dinitro and 2,6-dinitroaniline derivatives
Authors: Majer Jaroslav , Kadeřábek Vladimír
Published: August 2011

Infrared absorption spectra of N-substituted derivatives of 2,4-dinitro- and 2,6-dinitroanilines have been measured and interpreted from the point of view of bond and sterical interactions of the substituted amino groups with the both nitro groups.
Post-proline endopeptidase. Partial purification and characterization of the enzyme from pig kidneys
Authors: Hauzer Karel , Servítová Linda , Barth Tomislav , Jošt Karel
Published: August 2011

Post-proline endopeptidase was isolated from pig kidneys and partially purified. The procedure consisted of fractionation with ammonium sulphate, ion exchange chromatography on DEAE-Sephadex A-50, gel filtration on Sephadex G-200 and rechromatography on DEAE-Sephadex A-50. The preparation had 55 times higher specific activity than the crude extract and did not contain any contaminating enzymic activities. The enzyme cleaved a number of proline-containing peptides and was strictly specific in catalyzing the hydrolysis of the peptide bond on the carboxyl side of the proline residue. The optimum pH for the hydrolysis of the synthetic peptides benzyl-oxycarbonylglycyl-prolyl-leucyl-glycinamide and benzyloxycarbonyl-glycyl-proline β-naphtylamide was 7.8-8.0 and, in the case of benzyloxycarbonylglycyl-proline p-nitroanilide, 7.2 to 7.5. For the hydrolysis of the tetrapeptide benzyloxycarbonylglycyl-prolyl-leucyl-glycinamide, the Km value of 75 μ mol l-1 was obtained.
Reactions of 4-aryl-1-methoxynaphtalene-2,3-dicarboxylic acid anhydrides and naphtho(2,3-c)furan-1-(3H)-one derivatives with hydrazines
Authors: Křepelka Jiří , Vančurová Iva , Holubek Jiří
Published: August 2011

Reactions of anhydrides of 4-aryl-1-methoxynaphthalene-2,3-dicarboxylic acids, Ia and Ib, with hydrazine hydrate gave derivatives of benzo(g)phthalazine, IV-VI. Analogous reactions of the compounds Ia and Ib with hydrazines IIIa and IIIb afforded the corresponoding N-aminoimides, VII-X. Derivatives of naphtho(2,3-c)furan-1(3H)-one, IIa-IIc, reacted with hydrazine hydrate with the formation of benzo(f)isoindoline-1(3H)-one derivatives, XI-XIII. In the antineoplastic screening the tested compounds have not proved efficacious.
5-, 6- And 7-substitution derivatives of 7-oxo-7H-benzo(c)fluorene
Authors: Křepelka Jiří , Roubík Jiří , Holubek Jiří , Vančurová Iva
Published: August 2011

Intramolecular ring closure of anhydrides IIa-IIc, under conditions of the Friedel-Crafts reaction, gave 6-carboxy derivatives III-V. Esterification of the acid V by the chloride method led to esters VI and VII. Reaction of the ester VI with hydrazine gave rise to compound XXI, having a pentacyclic structure. Alkylation or acylation of the 5-hydroxy group in compounds Ia-Ic with alkyl halides or acyl chlorides afforded compounds VIII-XIII and XVIII. Compound XI was also formed as a by-product in the Friedel-Crafts reaction of compound Ic with acetyl chloride in 1,2-dichloroethane, in addition to the 6-acetyl derivative XV. An analogous reaction of Ic with dichloracetyl chloride gave compound XIV as a sole product. Substitution reactions on the 7-oxo group in Ic afforded semicarbazone XVI and thiosemicarbazone XVII, and reaction of the compound XVIII with hydroxylamine hydrochloride gave the oxime XIX. The action of N-methylolchloracetamide on Ia in sulphuric acid produced compound XX. The compounds prepared proved to have no antineoplastic effects. In tests for activity against the viruses of vaccinia and encephalomyocarditis they proved to be weaker than Tiloron as control. In assessing the efficacy against influenza virus A2 Singapore compound V exhibited the same effect as Tiloron.
The stripping voltammetric determination of copper with a rotating ring-disk electrode
Authors: Vedral Zbyněk , Beran Přemysl , Opekar František , Štulík Karel
Published: August 2011

The use of a rotating ring-disk electrode in electrochemical stripping analysis was verified. The electrochemical deposition and stripping of copper was studied on an electrode with a glassy carbon disk and platinum ring or with a mercury-covered glassy carbon disk. Copper can be determined down to concentrations of about 10-9 mol l-1 with an error not greater than 5% on a disk with a mercury film and 13% on the carbon electrode. The coverage of the glassy carbon by a monolayer of copper and the energy of interaction between the copper atoms and active sites on the surface of the glassy carbon were found from the areas and positions of the stripping peaks.
Comparison of the reactions of beryllium(II) ions with hydroxytriphenylmethane dyes in the presence of cationic and nonionic tensides. A rapid spectrophotometric method for determining Be(II) ion with eriochromcyanine R in the presence of Septonex
Authors: Burešová Irena , Kubáň Vlastimil , Sommer Lumír
Published: August 2011

Spectrophotometric methods for determining Be(II) with Chromazurol S, Eriochromcyanine R and Eriochromazurol B in the presence of cationic and nonionic tensides were compared using the basic optical and statistical parameters. A rapid and sensitive method was developed for determining Be(II) using the Be(II)-Eriochromcyanine R-Septonex system in 0.1M pyridine or urotropine buffer of pH = 6.0 ± 0.1 with a molar absorption coefficient of 8.3 . 104 mmol-1.cm2 at 590 nm.
Role of histidine in molecule of pea alcohol dehydrogenase
Authors: Čeřovská Noemi , Barthová Jana , Leblová Sylva
Published: August 2011

Alcohol dehydrogenase (E.C.1.1.1.1) from germinating pea seedlings was modified by treatment with diethyl pyrocarbonate. The inactivation rate is proportional to the molar concentration of the modifying agent; the inactivation was almost complete in fifty minutes at a diethyl pyrocarbonate concentration of 5 . 10-6 mol/l. The histidine content calculated from the absorbance difference at 240 nm was 3.43 residues per molecule of native and 4.75 residues per molecule of demetalized enzyme. A correlation of the absorbance difference at 240 nm with a 100% loss of enzymatic activity shows that 1.22 histidine residue is essential for the activity of alcohol dehydrogenase. The dependence of the inactivation rate constant on the pH of the medium indicates that the treatment of pea alcohol dehydrogenase with diethyl pyrocarbonate results in the modification of one group only with a pK of 7.1, well corresponding to the imidazole group of histidine. The enzyme is partially protected against inactivation by NADH at a concentration close to the Michaelis constant for NADH. The treatment of the ethoxyformylated enzyme with hydroxylamine followed by dialysis restored the activity of pea alcohol dehydrogenase by 88%.
Extraction of strontium and barium by nitrobenzene solution of dicarbolide in the presence of polyethylene glycols
Authors: Vaňura Petr , Makrlík Emanuel , Rais Jiří , Kyrš Miroslav
Published: August 2011

Extraction of microamounts of Sr2+ and Ba2+ from 0.2-1.0M-HClO4 by the nitrobenzene solutions of dicarbolide H+[Co(C2B9H11)2]- in the presence of polyethylene glycols (PEG) (Mr = 200, 300, 400) has been investigated. It has been found that the extraction of the protonized polyethylene glycol molecule (H+ + L ##e HL+, where the bar denotes species present in the organic phase) and the extraction of the complex between the extracted ion and polyethylene glycol, i.e., M2+ +L + 2 H+ ##e ML2+ + 2 H+, are the predominant reactions in this system. The respective equilibrium constants have been determined. The hydration numbers of HL+ and ML2+ ions in the organic phase have been obtained from the determination of water content by Karl Fischer titration method. The extraction constants and stability constants in the organic phase increase in the sequence H+ < Sr2+ < Ba2+ and PEG 200 < PEG 300 < PEG 400, while the hydration numbers decrease in the same sequence. Correlations between the hydration numbers and the extraction constants for these cations have been found.
Organic ion exchangers with enhanced catalytic activity
Authors: Prokop Zdeněk , Setínek Karel
Published: August 2011

Several methods aimed at increasing the catalytic activity of the sulphonated styrene-divinylbenzene macroporous ion exchanger Wofatit OK 80 have been tested. The activity of the prepared ion exchanger catalysts has been examined in three reactions of different type which allowed to examine the effect of the methods used in the broader range of conditions. The results obtained show that the catalytic activity of ion exchangers can be increased substantially either by increasing the total number of acid functional groups, or, particularly, by such treatment which makes the maximal number of the present functional groups accessible to reaction components. However, by the chemical procedures used to enhance the activity, the ion exchangers acquire frequently also some properties which affect negatively their application as catalysts.
Liquid-liquid equilibrium. Calculation of equilibrium composition od coexisting phases
Authors: Novák Josef P. , Voňka Petr , Matouš Jaroslav , Růžička Vlastimil
Published: August 2011

A new algorithm is proposed for determining the equilibrium curve on the basis of the knowledge of Gibbs' energy of N-component system. A known equilibrium composition is used during calculation to estimate the next approximation. The method is also modified for chemical-engineering applications when the composition of coexisting phases to a given overall composition is sought (flash calculations).
2-Acylated derivatives of ergoline
Authors: Beneš Jan , Křepelka Jiří
Published: August 2011

Reactions of ergoline derivatives Ia-VIIa with anhydrides of low-molecular-weight aliphatic acids, catalysed by boron trifluoride etherate, gave 2-acylated derivatives Ib-Id, IIb-IId, IIIb-Vb, or 1,2-diacylated derivatives VIb and VIIb. The compound IIb exhibited a hypotensive effect.
Acid base phenomena at the n-TiO2/room temperature molten salt interphase
Authors: Gale R. J. , Nozik A. J. , Cooper J. , Osteryoung R. A.
Published: August 2011

Interphasial properties of the n-TiO2/room temperature AlCl3 : 1-butylpyridinium chloride melt system have been studied by cyclic voltammetry and ac impedance methods. Surface faradaic reactions, dependent on the Lewis acidity of the melt and the semiconductor dopant concentration, are thought to be due to ionizable surface complexes. Theoretical models for flat-band shifts with bulk electrolyte acidity may be complex if the surface coverage is variable or if multiple ligand ionization can occur.
Relations between chromatographic parameters and physical properties of some alkyl tert-butyl ethers
Authors: Šingliar Michal , Macho Vendelín , Kavala Miroslav
Published: August 2011

Retention parameters of alkyl tert-butyl ethers have been measured by gas chromatography using stationary phases of various polarity. The stationary phase polarity influences elution order of a pair alcohol/ether as well as their resolution degree. Dependence of log Vg vs boiling temperature of the ethers is linear within a given homologous series of compounds except for the first two members. The retention times of ethers and alcohols have been found to coincide when using di-n-heptyl phthalate as stationary phase.
The study of the acid catalysed Michael addition to ferrocene derivatives of α,β-unsaturated ketones. Kinetics of cyclization of 1-acetyl-1'-(p-chlorocinnamoyl)ferrocene
Authors: Toma Štefan , Gáplovský Anton
Published: August 2011

Cyclization of 1-acetyl-1'-(p-chlorocinnamoyl)ferrocene catalysed by H2SO4, HCl, CF3COOH and BF3.(C2H5)2O has been studied. Kinetic study of the title reaction catalysed by HCl showed that the rate of cyclization increases with the catalyst concentration. Activation parameters of the cyclization are as follows: ΔH##f = 81.76 kJ mol-1, -ΔS##f = 55.73 J mol-1 K-1. Attempts at acid catalysed addition of several C-nucleophiles to cinnamoylferrocene and acryloylferrocene have been unsuccessful. The effect of the acidity of reaction medium on the electronic spectra of studied ferrocene derivatives is discussed.
Photooxidation effect of cupric complexes on aliphatic alcohols in nonaqueous solutions
Authors: Sýkora Jan , Jakubcová Mária , Cvengrošová Zuzana
Published: August 2011

In the photolysis of copper(II)-chloride-alcohol-acetonitrile systems (cCu = 1 mmol l-1, copper(II)-to-chloride molar ratio 1 : 2 to 1 : 8, 10% (v/v) alcohol), Cu(II) is reduced to Cu(I), and methanol, ethanol, 1-propanol, or 1-butanol is oxidized to the corresponding aldehyde, 2-propanol to acetone. In the case of 1-propanol and 1-butanol, chlorinated aldehydes are formed in addition too. The measured quantum yields of the photoreduction of Cu(II) to Cu(I) lay in the range of ΦCu(I) = 4.5 to 40 mmol einstein-1, the absolute quantum yields of the alcohol oxidation products were 2.3 to 47 mmol einstein-1. The photoactive components are chlorocupric complexes [CuClx](2-x)+ (x = 1-4). The presence of complexes with a higher number of chloroligands in the coordination sphere (x = 3, 4) brings about a decrease in the Cu(II) photoreduction rate. The decrease in the photoreduction rate observed in the presence of dioxygen is explained in terms of re-oxidation of copper(I) by the latter, resulting in an increase in the concentration of the photochemically active cupric complexes. The catalytic aspects of the systems in question are discussed with respect to this effect.
Kinetics of oxidation of ammonia on cobalt catalyst I model of the reactor with catalytically active wall
Authors: Bernauer Bohumil , Šimeček Antonín , Vosolsobě Jan
Published: August 2011

A two dimensional model of a tabular reactor with the catalytically active wall has been proposed in which several exothermic catalytic reactions take place. The derived dimensionless equations enable evaluation of concentration and temperature profiles on the surface of the active component. The resulting nonlinear parabolic equations have been solved by the method of orthogonal collocations.
Application of thermodynamics of systems in a force field to the equilibrium properties of real fluids. Basic relations for pure substances
Authors: Erdös Emerich
Published: August 2011

The real fluid, between the molecules of which intermolecular forces are acting is regarded as an ideal fluid without molecular interaction situated in an external force field. A force potential is assigned to this virtual force field, and it is shown that all the equilibrium properties of real fluids can be expressed in terms of this virtual potential or/and of its derivatives. Equations are given, expressing the common state functions of pure substances as functions of the virtual potential. In addition, it is shown that close relationships do exist between the approach mentioned above and the known fundamental approaches, such as the dynamical and statistical-mechanical one. Therefrom it is evident that the approach proposed here represents an additional alternative for the description of equilibrium properties of fluids which is equivalent to the existing approaches from the formal point of view.
Decomposition of hydrogen peroxide by heterogenized cobalt acetate complexes
Authors: Blažek Václav , Šubčík Leopold , Setínek Karel
Published: August 2011

By mass balance of the acetic acid coordinately bound to cobalt ions exchanged on a sulphonated macroporous styrene-divinylbenzene copolymer, the existence of heterogenized cobalt acetate complexes was confirmed and their amount was determined. It was found that the amount of these complexes depends on crosslinking of the copolymer and on the specific surface of its particles. The dependences found were in good agreement with earlier observed effects of these parameters on the catalytic and sorption activity of macroporous ion exchangers. The catalytic activity of heterogenized cobalt acetate complexes was tested in hydrogen peroxide decomposition at 30 °C. It was found that bromide ions do not exert synergetic effect observed on using these complexes as the catalysts for oxidation with gaseous oxygen.
Oligomerisation of methyloxirane initiated by (C6H5)3C+ AsF6-, (C6H5)3C+ SbCl6- and SbCl5
Authors: Vohlídal Jiří , Pacovská Marta , Dvořák Jiří
Published: August 2011

Reactions of methyloxirane with the title compounds lead to the formation of a mixture of cyclic and linear oligomers with average polymerisation degree ranging from 5 to 10. The oligomers are formed by combination of back-bitting reaction with re-initiation of the transiently desactivated reaction centers followed by monomer transfer. The important role which these reactions play in the overall oligomerisation of methyloxirane is due to the fact that in addition to active centres with the structure of oxonium ions, also carbenium active centres participate significantly in the reaction. In the systems with stable pair anions AsF6-, the irreversible termination of active centres does not take place, in contrast to the latter systems. This termination involves the reaction of the cation of active centre with the pair anion which releases one ligand during this interaction. The results obtained indicate that in the systems initiated by SbCl5 the active centres of amphiion structure can play an important role in initial stages of the reaction.
Purification and a partial characterization of exo-D-galacturonanase of banana
Authors: Heinrichová Kvetoslava
Published: August 2011

Exo-D-galacturonanase (E.C.3.21.67) was obtained from the aqueous extracts of banana peel by salting out with ammonium sulfate and separating the mixture of proteins on a DEAE Sephadex A-50 packed column followed by a gel filtration through Sephadex G-100 and Sephadex G-75. The purified enzyme was stable in acid medium up to 50 °C. The pH optimum for the action of exo-D-galacturonanase depended upon the chain length of the degraded substrate and was found to be 4.4 for di- and tetragalacturonic acids, 4.6 for hexa- and heptagalacturonic acids, and 4.9 for polygalacturonic acid. The chain length of galacturonan affected action of the enzyme. Oligomer of polymerization degree Dp = 6 was the optimal substrate. The enzyme was classified as an exo-D-galacturonanase on the basis of its terminal mode of action, the ability to cleave digalacturonic acid and the decrease of viscosity in relation to the number of cleaved glycosidic bonds.
Study of the mechanism of the oscillating reaction between bromate and phenol
Authors: Tockstein Antonín , Handlířová Marie
Published: August 2011

In the oscillating reaction of bromate with phenol in the medium of 0.4M-H2SO4, the length of the induction period is governed by a kinetic equation for a second-order reaction with a stoichiometry 1 : 1. The concentration of quinones in the reaction mixture increases also according to a kinetic equation for a second-order reaction. The influence of various compounds is discussed, whose additions shorten or prolong the induction period, bring about oscillations in a nonoscillating reaction mixture, or change the frequency of these oscillations. From the comparison of the time dependences of the potential of a platinum and an ion-selective electrodes and of the limiting current of the quinones, a reaction mechanism was proposed.
Utilization of a recyclization reaction for the analysis of the mechanism of enzymic alcohol oxidation
Authors: Kovář Jan , Kučera Igor
Published: August 2011

The kinetics of recyclization reactions catalyzed by horse liver alcohol dehydrogenase in the presence of a coenzyme, p-nitrosodimethylaniline, and various alcohols was studied from theoretical and experimental point of view. It was found that p-nitrosodimethylaniline is an oxidized substrate of the alcohol dehydrogenase suitable for testing basic kinetic parameters of various alcohols, especially for checking the kinetic importance of ternary enzyme-NAD-alcohol complexes.
Electronic absorption, fluorescence and polarisation spectra of β,β'-diamino-9,10-anthraquinones and their interpretation by the method of configuration analysis
Authors: Nepraš Miloš , Titz Miloš , Gaš Bohuslav , Fabian Jürgen
Published: August 2011

On the basis of measurement of absorption frequency-dependent polarisation spectra of fluorescence (APF) and dichroism on oriented polyvinyl alcohol sheets, interpretation has been carried out of electronic absorption spectra of β,β'-diamino-9,10-anthraquinones in the wavelength range 250 to 600 nm. Character of the excited ππ* states has been determined by the method of configuration analysis (PPP-CA).