bluuebunny/crossref_metadata_2025 huggingface dataset:
Bis(1,10-phenantroline)copper(II) Complexes. Refinement of the Crystal Structure of the Dithiocyanato-bis(1,10-phenanthroline)copper(II) Complex
Authors: Kabešová Mária , Kožíšková Zlatica
Published: June 2004

[Cu(NCS)2(phen)2] possesses the orthorhombic structure Pbcn at room temperature; the elementary cell parameters are a = 1.3029(21), b = 0.9900(15), c = 1.7256(23) nm, Z = 4. The central atom has the pseudooctahedral CuN6 coordination. The thiocyanate ligands are coordinated by the nitrogen atom in the equatorial plane of the coordination polyhedron. Each phenanthroline ligand in the coordination polyhedron coordinates one equatorial and one axial position. All the coordinating ligands possess the cis arrangement in the coordination sphere. The experimental results are correlated with published data of other bis(phenanthroline)copper(II) crystal structures.
Kinetics and Mechanism of Cyclization of N-(2-Methoxycarbonylphenyl)-N-methylsulfonamide to 1-Methyl-(1H)-2,1,3-benzothiadiazine-4(3H)-one-2,2-dioxide
Authors: Kaválek Jaromír , Macháček Vladimír , Sedlák Miloš , Štěrba Vojeslav
Published: June 2004

The cyclization kinetics of N-(2-methoxycarbonylphenyl)-N-methylsulfonamide to 1-methyl-(1H)-2,1,3-benzothiadiazine-4(3H)-one-2,2-dioxide have been studied in glycinamide, morpholine, and butylamine buffers and in solutions of potassium hydroxide. The rate-limiting step consists in splitting off of the proton from the cyclic intermediate formed from the anion of the starting substrate. The value of the Bronsted coefficient β decreases with increasing pKa value of the conjugate acid of buffer. The calculated pKa value of the cyclic intermediate is 9.3.
Reactions of PO(NCS)3 with 4-Hydroxy-1,3-dioxanes. Crystal Structure of rel-(2S,4R,5S,6S)-2,6-Diethyl-5-methyl-4-(N'-benzylthioureido)-1,3-dioxane
Authors: Bernát Juraj , Kniežo Ladislav , Birošová Gabriela , Buděšínský Miloš , Podlaha Jaroslav , Podlahová Jana , Novotný Jiří
Published: June 2004

Substituted 4-hydroxy-1,3-dioxanes II react rapidly with PO(NCS)3 to give 4-isothiocyanato-1,3-dioxanes III. The 1H NMR spectra showed that in the isothiocyanate IIIa the predominant stereoisomer has its NCS group in axial position. The addition of benzylamine to the isothiocyanates IIIa and IIIb gave uniform thioureas IVa and IVb with equatorial alkyl groups at 2 and 6 positions and axial thioureido group at 4 position. On the other hand, the isothiocyanate IIIc reacts with benzylamine to give a mixture of three stereoisomeric thioureas V,VI, and VIII. The structure of VI was proved by means of X-ray diffraction analysis; in crystalline form the molecules of VI are present as H-bonded dimers (N-H...O).
Synthesis and Properties of "Hormonogene" and "Inhibitorogene" Type Oxytocin Analogs
Authors: Pal B. C. , Slaninová Jiřina , Barth Tomislav , Trojnar Jerzy , Lebl Michal
Published: June 2004

Nα-Glycyl, diglycyl and triglycyl [2-D and [2-L-p-ethylphenylalanine]oxytocin analogs were synthesized by the solid phase technology utilizing racemic p-ethylphenylalanine. Analogs containing this amino acid of D-configuration were shown to be weak uterotonic antagonists both in vitro and in vivo tests; the compound containing triglycyl residue in position 1 was shown to have prolonged time course of inhibitory action. Analogs containing the L-amino acid were shown to be inhibitors of uterotonic activity of oxytocin in vitro, but uterotonic agonists with prolonged effect in vivo.
Network Simulation of a Reversible Electron Transfer under Cyclic Voltammetric Conditions
Authors: González-Fernández Carlos F. , García-Hernández Maria T. , Horno José
Published: June 2004

Reversible electron transfer reaction of a freely diffusing species has been studied using the network approach. A network model for this process under cyclic voltammetric conditions has been proposed, and a numerical simulation has been made with the help of the electrical circuit simulation routine PSPICE. A great accuracy in simulated voltammograms has been reached with a personal computer at a moderate cost in computer time.
Sorption of Acetic and Propionic Acids and Propanal on a Molybdenum-Vanadium Oxide Catalyst
Authors: Machek Jaroslav , Handlíř Karel , Švachula Jiří , Tichý Josef
Published: June 2004

It has been found by gas chromatography that the equilibrium adsorption of propanal, propionic and acetic acids on molybdenum-vanadium oxide catalyst can be described by the Langmuir adsorption isotherm. The existence of carboxylates on the catalyst surface has been proved by IR spectroscopy.
Simple Preparation of Methyl 4-Chloromethyl- and Methyl 5-Chloromethyl-2-thiophenecarboxylate
Authors: Kozmík Václav , Paleček Jaroslav
Published: June 2004

Selective reduction of a mixture of methyl 4-chloromethyl-2-thiophenecarboxylate (I) and the 5-chloromethyl isomer II, prepared by chloromethylation of methyl 2-thiophenecarboxylate (III), gave pure 4-chloromethyl derivative I and 5-methyl-2-thiophenecarboxylate (V) which on treatment with sulfuryl chloride was converted into the 5-chloromethyl isomer II.
p-Azobenzenecarboxamidomethyl Esters - New Colored Hydrophobic Carboxyl Protecting Groups in Peptide Synthesis
Authors: Zhuravlev Valentin G. , Mazurov Anatolii A. , Andronati Sergei A.
Published: June 2004

p-Azobenzenecarboxamidomethyl esters (OAbc esters) of several α-amino acids have been synthesized and characterized. Their application in peptide chemistry as a colored alkali labile carboxyl protecting group was demonstrated. The esters are compatible with commonly used protecting groups. They are removed with aqueous potassium carbonate in 15-20 min.
Synthesis and Fungicidal Activity of Isoxazolines Fused to 3,5-Dichloromaleimide
Authors: Konopíková Marta , Fišera Lubor , Prónayová Naďa
Published: June 2004

3-Phenyl-5-(3,5-dichlorophenyl)-3a,4,6,6a-tetrahydropyrrolo[3,4-d]isoxazoles (III, R = H) and 3-phenyl-5-(3,5-dichlorophenyl)-6a-methyl-3a,4,6,6a-tetrahydropyrrolo[3,4-d]isoxazoles (IV, R = CH3) were prepared by 1,3-dipolar cycloaddition of substituted benzonitrile oxides I to N-(3,5-dichlorophenyl)maleimide (I, R = H), or its methyl derivative II (R = CH3). Cycloaddition to compound II (R = CH3) proceeded regiospecifically. Reduction of IVg with NaBH4 was regio- and stereoselective to yield the hydroxylactams VIIg, VIIIg, and IXg. Antifungal activity of several products was worse than that of commercial preparations.
Carcinogenic Non-Aminoazo Dye 1-Phenylazo-2-hydroxynaphthalene (Sudan I) Is Oxidized by Rat Liver Microsomal Cytochrome P-450 to Metabolites Binding to Macromolecules (Nucleic Acids and Proteins)
Authors: Stiborová Marie , Anzenbacher Pavel
Published: June 2004

Carcinogenic non-aminoazo dye 1-phenylazo-2-hydroxynaphthalene (Sudan I) is oxidized by microsomal cytochromes P-450 to reactive metabolite(s) binding to macromolecules (nucleic acids, proteins) in vitro. The extent of binding to macromolecules proceeded in the order: protein > rRNA > tRNA > DNA. The patern of products formed from Sudan I and binding of the reactive metabolites of this compound to macromolecules are dependent on the concentration of Sudan I, NADPH and on the duration of the incubation. The participation of the adducts formed with macromolecules in the initiation of chemical carcinogenesis is discussed.
Synthesis and Reactions of Some Diphenyl Sulfides
Authors: Radwan Shaban M.
Published: June 2004

In view of the wide spectrum of activity associated with many pyrazoline derivatives, substituted thiazoles, oxazoles and diaryl sulfides, we synthesized some new diaryl sulfides carrying the above heterocyclic systems.
Enzymes of Human Herpesviruses
Authors: Kramata Pavel , Votruba Ivan
Published: June 2004

The properties of human herpesvirus-encoded enzymes are reviewed and the importance of sequence analysis of viral genomes as well as the experiments on characteristics of enzymes isolated from infected cell cultures are emphasized. The following enzymes are described in detail: DNA replication complex consisting of DNA polymerase, DNA helicase-primase, single-stranded DNA binding protein and origin binding protein, further thymidine kinase, ribonucleotide reductase, deoxyuridine triphosphatase as well as uracil-DNA-glycosylase, deoxyribonuclease and protein kinase. The importance of these enzymes from the point of view of antiviral chemotherapy is discussed.
The Photovoltaic Properties of a Lithiated TiO2 Electrode
Authors: Vondrák Jiří , Jakubec Ivo , Bludská Jana
Published: June 2004

Titanium electrodes coated by TiO2 (anatas) were prepared by decomposition of peroxotitanic compounds. Their photoelectric behavior in 1 M LiClO4/PC (propylene carbonate) was investigated. The photoeffect was emphasized by the process of electrolytic incorporation and removal of lithium. The effective threshold energy was 1.5 to 1.6 eV, thus indicating donor dissociation being the basic photochemical process.
Extraction of Ce, Pm, Eu, Tm and Sc Using Di-n-butylhydrogenphosphate in 1,1,2,2-Tetrachlorodifluoroethane
Authors: Sládek Petr , Navrátil Oldřich , Linhart Petr
Published: June 2004

A study was carried out of the extraction of Ce, Pm, Eu, Tm and Sc from aqueous HNO3 medium into an organic phase 1,1,2,2-tetrachlorodifluoroethane (CFC-112, Ledon-112) using di-n-butylhydrogenphosphate (HDBP) as extracting reagent. The organic solvent was studied from the point of view of some of its interesting properties that can be utilized in practical applications of liquid extraction. Especially the dependence of the extraction of selected lanthanoids on the HDBP concentration and pH was studied and constants K2 and KD(HA) were found for this reagent in CFC-112 and mixtures of this solvent with benzene.
Investigation of the Synthesis of Verbenyl Compounds, Effective Attractants of Cockroach Species, by Acyloxylation of α-Pinene
Authors: Vinczer Peter , Kajtár-Peredy Mária , Juvancz Zoltan , Novak Lajos , Szántay Csaba
Published: June 2004

The synthesis of verbenyl acetate (Ia) and propionate (Ib) was investigated by acyloxylation of α-pinene with lead(IV) acetate (LTA), lead(IV) propionate (LTP), mercury(II) acetate (MA) and iodosobenzene diacetate (IBDA) in neutral and acidic medium. The neutral medium is better for the formation of Ia and Ib, because the acidic medium helps the opening of cyclobutane ring of α-pinene. These methods can be used for large scale preparation of insect attractants to cockroach species (Blatella germanica, Blatella orientalis and Periplaneta americana).
Studies with Polyfunctionally Substituted Heterocycles: Novel Syntheses of Pyrido[4,3-d]pyridazines and of Pyrido[3,4-d]pyridazines
Authors: Manhi Fatma M. , Zayed Salem E. , Ali Fatma A. , Elnagdi Mohamed Hilmy
Published: June 2004

As a part of our programme aimed at developing efficient syntheses of polyfunctionally substituted azines and condensed azines, we have in the past reported efficient syntheses of compounds I-III. In conjunction of this work we report results of our further studies aimed at exploring the synthetic potentialities of I-III.
Amides of 5-Nitro-3-furanecarboxylic Acid
Authors: Štetinová Jarmila , Dandárová Miloslava , Leško Ján , Kalamárová Lida
Published: June 2004

β-Substituted furane derivatives such as N-(4-R-phenyl)-5-nitro-3-furanecarboxamides (Ia-Ij) have been prepared by the reaction of 5-nitro-3-furanoyl chloride with 4-R-anilines (R = H, CH3, OCH3, N(CH3)2, Cl, Br, NHCOCH3, CN, COOCH3, NO2): The structure of the compounds synthesized has been confirmed by their IR, UV, 1H NMR and mass spectra.
Viscosity of Diluted Aqueous K2CO3/KHCO3 Solutions
Authors: Palatý Zdeněk
Published: June 2004

The applicability of the equation derived for calculating the dynamic viscosity of ternary non-electrolyte mixtures, to the correlation of viscosity data of the H2O- K2CO3/KHCO3 system is verified in this work. It was found out that the values of dynamic viscosity obtained experimentally are in good agreement with the viscosity values calculated from this equation. The equation constants - interaction coefficients - were determined from the measurements of dynamic viscosity on mixing the basic solutions of K2CO3 and KHCO3 of known concentration. The correlation equation makes it possible to calculate viscosity of the K2CO3/KHCO3 solutions in the K2CO3 and KHCO3 concentration range from 0 to about 2.0 kmol m-3.
Equilibrium Sorptions in Heterogeneous Ion Exchange Membranes
Authors: Bleha Miroslav , Šumberová Věra
Published: June 2004

The equilibrium sorption of uni-univalent electrolytes (NaCl, KCl) in heterogeneous cation exchange membranes with various contents of the ion exchange component and in ion exchange membranes Ralex was investigated. Using experimental data which express the concentration dependence of equilibrium sorption, validity of the Donnan relation for the systems under investigation was tested and values of the Glueckauf inhomogeneity factor for Ralex membranes were determined. Determination of the equilibrium sorption allows the effect of the total content of internal water and of the ion-exchange capacity on the distribution coefficients of the electrolyte to be determined.
Reactions of Triformylmethane with Adamantane Derivatives Containing Primary Amino Group
Authors: Burkhard Jiří , Arnold Zdeněk
Published: June 2004

Six new compounds were obtained by condensation of triformylmethane with some aminoadamantane derivatives. The study also includes 7-amino-1,3,5-triazaadamantane.
Kinetic Studies of [4n+2]π-Thermal Cyclodimerization of 1-(3-Pyridazinyl)-3-oxidopyridinium Betaines
Authors: Iskander Madlene L. , El-Abbady Samia A. , Shalaby Alyaa A. , Moustafa Ahmed H.
Published: June 2004

The reactivity of the base induced cyclodimerization of 1-(6-arylpyridazin-3-yl)-3-oxidopyridinium chlorides in a pericyclic process have been investigated kinetically at λ 380 nm. The reaction was found to be second order with respect to the liberated betaine and zero order with respect to the base. On the other hand dedimerization (monomer formation) was found to be first order. It was shown that dimerization is favoured at low temperature, whereas dedimerization process is favoured at relatively high temperature (ca 70 °C). Solvent effects on the reaction rate have been found to follow the order ethanol > chloroform ≈ 1,2-dichloroethane. Complete dissociation was accomplished only in 1,2-dichloroethane at ca 70 °C. The thermodynamic activation parameters have been calculated by a standard method. Thus, ∆G# has been found to be independent on substituents and solvents. The high negative values of ∆S# supports the cyclic transition state which is in favour with the concerted mechanism. MO calculations using SCF-PPP approximation method indicated low HOMO-LUMO energy gap of the investigated betaines.
Selective Adsorption of Strontium on Activated Charcoal from Electrolytic Aqueous Solutions
Authors: Qadeer Riaz , Hanif Javed , Saleem Muhammad , Afzal Muhammad
Published: June 2004

The adsorption of strontium on activated charcoal has been studied as a function of shaking time, pH, concentration of adsorbate and temperature. Wavelength dispersive X-ray fluorescence spectrometer was used for measuring strontium concentration. The adsorption of strontium obeys Freundlich and Langmuir isotherms. Quantities ∆H0 and ∆S0 were calculated from the slope and intercept of plot ln KD vs 1/T. The influence of different cations and anions on strontium adsorption has been examined. The adsorption of other metal ions on activated charcoal has been studied under specific conditions to check its selectivity. Consequently, strontium was removed from Rh, Pr, Rb and Cs. More than 95% adsorbed strontium on activated charcoal can be recovered with 65 ml 3M HNO3 solution.
Conductance and Viscometric Studies of Some Tetraalkylammonium and Sodium Salts in Acetonitrile-Dimethyl Sulfoxide Mixtures at 35 °C
Authors: Chauhan Mohinder S. , Sharma Kishore C. , Gupta Sanjay , Chauhan Suvarcha , Syal Vijay K.
Published: June 2004

Molar conductances and viscosities of Bu4NBPh4, NaBPh4 and R4NBr (R ethyl, propyl and butyl) at 35 °C in acetonitrile (AN), dimethylsulfoxide (DMSO) and their binary mixtures have been reported. The conductivity data has been analysed by the Shedlovsky conductance equation and viscosity data by the Jones-Dole equation. Resolution of limiting molar conductivity (Λ0) and viscosity B coefficient of electrolytes into their ionic components have been achieved by the reference salt method. Viscosity A coefficients have been compared with theoretical Aη coefficients. Derived conductance and viscosity parameters have been discussed in terms of the ion-solvent interaction.
Sorption of Lead and Cadmium on Ostsorb P and Ostsorb SA-5 Cellulose Sorbents
Authors: Svoboda Ladislav , Čáňová Leona
Published: June 2004

The effect of pH and ionic strength on the exchange capacity of sorbents based on modified bead cellulose was examined for the sorption of Pb2+ and Cd2+ ions. Ion exchange of these cations in aqueous solutions is nonselective on Ostsorb SA-5, which is cellulose containing functional groups based on H-acid. The medium acidic Ostsorb P cation exchanger with functional groups formed by the phosphoric acid fragment, on the other hand, sorbs lead, and to a lesser extent also cadmium, also at high ionic strengths of the medium even at low pH values.
Contribution to the Research and Development of Radiation Chambers in Steam Reforming. Problem-Oriented Application of a Fuzzy Expert System
Authors: Stehlík Petr , Babinec František
Published: June 2004

An application of a fuzzy expert system intended for estimating some parameters of steam reforming can also be one of the examples of an ever increasing utilization of expert systems in practice. The present contribution deals with the method making use of a verified mathematical model for simulating thermal chemical processes in reforming furnace radiation chamber in order to create knowledge base. This base includes linguistic values of selected independent and dependent variable quantities. Examples given illustrate an evaluation of dependent variable quantities (methane conversion into carbon dioxide and monoxide, reaction tube service life) by means of the said expert system based on queries.
A Kinetic Method for Determination of the Biosynthetic Activity of Glutamine Synthetase
Authors: Mikeš Vladimír
Published: June 2004

In the present paper a rapid and simple kinetic method for determination of the biosynthetic activity of glutamine synthetase is described based upon the decomposition of ATP, accompanied with acidification of the slightly buffered medium which can be measured by means of a pH indicator. The method can be used for determination of the enzyme activity in whole permeabilized cells, crude cell extracts, as well as for kinetic studies and studies of the effects of inhibitors on the purified glutamine synthetase.
Degrees of Dissociation and Hydration Numbers of Twenty Six Strong Electrolytes in Aqueous Solutions at 25 °C
Authors: Heyrovská Rajalakshmi
Published: June 2004

This paper brings further results on the degrees of dissociation (α) and hydration numbers (nh) of strong electrolytes in aqueous solutions at 25 °C, evaluated for the first time from osmotic coefficients (ϕ). Presented here are also the equations for the non-ideality parameters, ϕ and γ± (the mean molal ionic activity coefficient), in terms of α and nh.
Heats of Solution of Some Sodium and Potassium Salts in Water and in Water-Methanol Mixtures
Authors: Benko Ján , Vollárová Oľga
Published: June 2004

The enthalpies of solution ∆Hs0 were determined for NaSCN, KSCN, NaBrO3, KBrO3, NaClO3, KClO3, NaIO4, KMnO4, KNO2 and NaNO2 in water-methanol mixtures. The transfer functions ∆Ht0 of the salts and anions were calculated based on the extrathermodynamic TPTB assumption. The ∆Ht0 values of the anion obtained from the sodium and potassium salts were compared. The differences observed, particularly at higher concentrations of the cosolvent, are discussed with respect to the interactions between the solvent molecules and the solute-solvent interactions.
The Polarographic Determination of 1-[4'-(Phenylazo)phenyl]-3,3-dimethyltriazene
Authors: Barek Jiří , Dřevínková Dana , Zima Jiří , Fogg Arnold
Published: June 2004

A study has been made of the polarographic behaviour of genotoxic 1-[4'-(phenylazo)phenyl]-3,3-dimethyltriazene in mixed water-methanol medium. A mechanism has been proposed for its polarographic reduction and optimal conditions have been found for its determination by tast polarography in the concentration range 1 . 10-4 - 2 . 10-6 mol l-1 and using differential pulse polarography in the concentration range 1 . 10-4 - 2 . 10-7 mol l-1.
Determination of Organic Bases by Ion-Pair Extraction Polarography Using Orange II as Counter Ion
Authors: Koula Václav , Kučová Daria , Gasparič Jiří
Published: June 2004

The combination of ion-pair extraction and differential pulse polarography is shown to be a method suitable for the determination of 10-7 mol l-1 concentrations of organic bases of quaternary ammonium compounds. Orange II (4-[2-hydroxy-1-naphtyl]azobenzenesulfonic acid) was found to be an appropriate polarographically active counter-ion. The proposed method was used for the determination of tetrapentylammonium bromide (as model compound), Septonex ([1-(ethoxycarbonyl)-pentadecyl]trimethylammonium bromide) and codeine.
Nature and Stability of Oxide Films Formed on Niobium in Acid Bromide Solution
Authors: Gad Allah Ahmed G. , Bekheet Ali M. , El-Egamy Said S. , El-Basiouny Mohamed S.
Published: June 2004

The formation and stability of the anodic oxide films formed on niobium in acid bromide solutions were studied using polarization and impedance measurements. The charging curves in all concentrations display the same general trend. The steady-state potential was found to depend on HBr concentration. The efficiency of oxide building is diminished owing to preferential adsorption of Br- ions on the oxide surface acting as depolarizer for the main anodic process. The dissolution behaviour of the anodized oxide niobium films is duplex in nature. The outer layer becomes more liable to dissolution with increasing film thickness or formation voltage. Also, the properties of the surface oxide film are greatly influenced by HBr concentration.
Polysaccharides from the Flowers of Malva silvestris L., ssp. mauritiana (L.) THELL.: The Structure of D-Glucan
Authors: Capek Peter
Published: June 2004

The neutral polysaccharide α-D-glucan was isolated from the flowers of Malva silvestris L., ssp. mauritiana (L.) THELL. using a combination of ion exchange and gel chromatography. It was homogeneous under the conditions of free electrophoresis of average molecular weight Mn 25260. The chemical and spectroscopic investigations indicated a linear structure of the polysaccharide in which the α-D-glucopyranose units were linked predominantly by 1→6 glycosidic bonds, while some saccharides were the place of branching in position C-3.
Effect of Piperidine Addition in Sulfidation of CoMo/Al2O3 Catalysts on Their Activity and Selectivity in Thiophene Hydrodesulfurization
Authors: Vladov Chavdar D. , Petrov Lachezar A. , Dung Cao Anh , Ytua Bles
Published: June 2004

The effect of piperidine on a commercial Co/Mo/Al2O3 catalyst upon its sulfidation and during thiophene hydrodesulfurization has been studied. The experiments were carried out under atmospheric pressure. Upon sulfidation of the catalyst in the presence of nitrogen-containing compound, a reversible deactivation of hydrodesulfurization active sites and/or an irreversible deactivation of the hydrogenation and isomerization active sites were observed.
Aromatization of C2-C6 Aliphatic Hydrocarbons on Copper-Containing ZSM-5 Zeolites
Authors: Popova Zdravka , Aristirova Katia , Dimitrov Christo
Published: June 2004

The aromatization of a wide range of model aliphatic and cycloaliphatic hydrocarbons (ethene, ethane, propene, n-hexane, 1-hexene, methylcyclopentane, cyclohexane, cyclohexene) on copper-containing NaZSM-5 and HZSM-5 zeolites has been investigated. It was established that the degree of aromatization is related to carbenium ion formation and depends on the acid strength and copper content of zeolite. Experiments with copper-containing samples reduced prior to use indicated the possibility to enhance the selectivity to aromatization. The change of the state of Cu2+ ions during catalytic experiments confirmed the assumption about participation of Cu0 simultaneously with the Bronsted acid centers in the dehydrogenation/hydrogenation steps.
Surface Reactivity of Rh Clusters on ZrO2 Modified by Mn, Fe and Mo
Authors: Marengo Sergio , Miessner Hans , Trunschke Annette , Martinengo Secondo , Zanderighi Luciano
Published: June 2004

The reactivity of Rh clusters supported on ZrO2 and on ZrO2 modified by chemisorption of Mn, Fe, Mo carbonyls has been studied by various surface techniques such as TPD, TPR, FTIR, and by model reactions: Boudouard reaction, ethylene hydroformylation and CO/H2 reaction. Four CO adsorbed species have been identified and the main effect of the modifiers is to change the distribution of the various CO moieties present on the surface, as shown by TPR and reactivity data. Mn promotes methanol formation, Fe oxygenated compounds and chain growth, Mo increases the CO reactivity, mainly to oxygenates.
Hydrogenation of Fatty Acid Esters. II. Kinetics of Hydrogenation of Methyl (Z)- and (E)-9-Octadecenoate Catalyzed by a Ziegler Nickel Catalyst
Authors: Krupičková Jana , Včelák Jaroslav , Hetflejš Jiří
Published: June 2004

Kinetics of the title reactions has been studied, using nickel(II) 2,4-pentanedionate/triethylaluminium system as a model catalyst. Initial rate measurements showed that in both cases the hydrogenation is first order in hydrogen, zero order in the octadecanoate and a fractional order (close to one) in the catalyst. Both hydrogenations have similar activation energies (30.2 ± 2.3 kJ mol-1 and 28.9 ± 2.6 kJ mol-1 for the (Z)- and (E)-9-octadecenoate, respectively). Based on these data and the results of competition experiments, two models have been proposed to describe isomerization of the octadecenoates (either direct or via an intermediate).
Mild Colorimetric Detection of Sialic Acid
Authors: Yang Youjun , Lewis Patrick T. , Escobedo Jorge O. , Luce Nadia N. St. , Treleaven W. Dale , Cook Robert L. , Strongin Robert M.
Published: June 2004

As part of a broader program focusing on the detection of colorless biomolecules in the visible region, a simple and mild procedure for the visual detection of the most abundant sialic acid at room temperature and neutral pH is reported. The role of the interaction of the sialic acid amide with boron in a readily synthesized boronic acid-based receptor is an important feature of the signaling mechanism. Selectivity of reaction can be tuned by the judicious choice of solvents. This study embodies a departure from many of the author's earlier efforts in sugar solutions that are not heated, affording relatively more selective and milder detection.
Synthesis of New Calix[4]arene-Based Ionophores
Authors: Arduini Arturo , Bozzoli Marcella , Massera Chiara , Pochini Andrea , Secchi Andrea , Ugozzoli Franco
Published: June 2004

A synthesis of new calix[4]arene-based ionophores is reported. These ligands are characterized by the presence of two types of coordination sites on their lower rim: one crowning unit of different length, linking two proximal calix[4]arene phenolic oxygens, and two esters or amide groups acting as additional hard binding sites. The choice of the proper reaction conditions, such as the base counterion and the solvent polarity, during the functionalization of the macrocycle lower rim, allows to modulate the stereochemistry of the final ligands. In this way the ligands in cone and 1,2-alternate conformations were obtained in good yields. Complexation properties of these new compounds towards alkali and alkaline-earth cations were studied by means of liquid-liquid extraction experiments. The X-ray solid state structure of the p-tert-butylcalix[4]arene-N,N-diethylacetamide-crown-5 (6a) complex with strontium picrate shows the effective cooperativity among the two type of coordination site in the binding event.
Synthesis of Fluorescent Molecular Sensory System for Endocrine Disruptors Based on Dansylthiacalix[6]arenes
Authors: Toda Masaya , Kondo Yoshihiko , Niimi Tomohiro , Higuchi Yutaka , Endo Ken , Hamada Fumio
Published: June 2004

Flexible fluorescent hosts, mono-, di- and tridansyl-modified tert-butylthiacalix[6]arenes (TC[6]A-1, TC[6]A-2 and TC[6]A-3, respectively) and didansyl-tert-butylcalix[6]arene (C[6]A-2) have been synthesized in order to investigate their fluorescent chemosensor functionality, which detects endocrine disruptors. The hosts, TC[6]A-1, TC[6]A-2, TC[6]A-3 and C[6]A-2 exhibit pure monomer fluorescence spectra, of which the spectra shows a decrease fluorescence intensity in the presence of guests. The extent of fluorescence variation of TC[6]A-1, TC[6]A-2, TC[6]A-3 and C[6]A-2 upon a guest addition was recognized as the manifestation of sensing ability of the hosts. A sensing parameter (∆I/I0) was used to describe the sensing ability of four hosts. Host TC[6]A-2 was able to detect 2,4-dichlorophenoxyacetic acid with high sensitivity. The guest-induced variations in the fluorescence intensities and MM2-minimized structures of the hosts suggest that the appended moieties of the hosts act as a hydrophobic cap and a probe showing the host to form a 1:1 host- guest complex.
Phialocephala sphaeroides sp. nov., a new species among the dark septate endophytes from a boreal wetland in Canada
Authors: Wilson B J , Addy H D , Tsuneda A , Hambleton S , Currah R S
Published: June 2004

Dark septate root endophytic fungi from plants growing on either side of an abrupt wetlandupland ecotone included isolates of Phialocephala fortinii Wang & Wilcox, Leptodontidium orchidicola Sigler & Currah, Hetero conium chaetospira (Grove) Ellis, and a hitherto undescribed fungus resembling P. fortinii. Six isolates of this species were recovered and were distinctive in (i) producing an orangetan diffusible pigment in culture, (ii) causing a yellow colour shift on casamino acids medium containing bromocresol purple, (iii) having the ability to liquefy gelatin, and microscopically, (iv) forming hyaline conidia from phialides arranged in large spherical heads after prolonged incubation at 5 °C. First-formed or primary conidia are bullet shaped, 11.5 µm × 23 µm; subsequent conidia are spherical and 11.5 µm in diameter. Small subunit and internal transcribed spacer region sequence comparisons with P. fortinii and other Phialocephala species supported placing these six unique strains in a new species, Phialocephala sphaeroides B.J. Wilson sp. nov. Phylogenetic analyses also suggest that P. sphaeroides is affiliated with mollisioid taxa in the Dermateaceae. In contrast with P. fortinii, which was isolated on both sides of the ecotone, P. sphaeroides was obtained only from plants in the highly acidic, Sphagnum-dominated wetland habitat and not from the same species in the less acidic, aspen-dominated upland site.Key words: inoperculate discomycetes, phialidic anamorph, Helotiales, root endophytes, Loramycetaceae, Dermateaceae, Mollisia.
Weekly xylem production in trembling aspen (Populus tremuloides) in response to artificial defoliation
Authors: Jones Brin , Tardif Jacques , Westwood Richard
Published: June 2004

The present study investigated the effect of artificial defoliation on weekly radial xylem production in trembling aspen (Populus tremuloides Michx.). It was hypothesized that defoliated trees would show reduced xylem and vessel production and thinner secondary walls in fibres. Two adjacent natural forest sites were selected within Winnipeg, Manitoba. Microcores were extracted weekly from the stems of 30 aspen trees from May to October 2002. Ten aspen trees were defoliated using pole pruners between 22 June and 6 July. Measurements included weekly xylem increment, annual vessel characteristics, and late growing season fibre dimensions. No significant difference in overall ring width was observed; however, trees from both groups showed a significant reduction in ring width in 2002. The ratio of radial growth in 2002 / radial growth in 2001 was significantly less in defoliated trees, suggesting a higher reduction in radial growth due to defoliation. Sigmoidal regression models suggested early growth cessation in defoliated trees. No significant differences in vessel characteristics were observed between groups; however, the diameter and lumen width of fibres was significantly reduced in defoliated trees. It is speculated that a shorter radial growing season may have led to a reduced cell elongation period. An early cessation of the radial growing season associated with a reallocation of carbohydrates to produce a second flush of leaves could explain the reduced size of fibres from defoliated trees.Key words: wood anatomy, diffuse porous, image analysis, radial growth, cell dimension, dendrochronology.
Early stages of initiation of two types of leaves in Thuja occidentalis (eastern white cedar)
Authors: Lacroix Christian , Barabé Denis , Jeune Bernard
Published: June 2004

The developmental morphology of shoots of Thuja occidentalis L. (eastern white cedar) was investigated using scanning electron microscopy to determine the pattern of initiation of two types of leaves characteristic of higher (third and above) order branches. The shoots of eastern white cedar are bilateral in symmetry and bear leaves in an orthogonal decussate phyllotactic pattern. The shoot system is further characterized by the presence of two alternating and morphologically different pairs of leaves that constitute the basic repeating pattern of the shoot apical meristem (SAM). At maturity the dimorphism between leaf types is marked. Leaves in one plane are wide and flat in comparison with narrower and cup-shaped leaves growing in a plane perpendicular to the other leaf type. The early stages of development of each of the two types of leaves were compared using scanning electron microscopy. During the earliest visible stages of initiation (primordial crest), cup-shaped and flat leaves are very similar in morphology. As individual leaf primordia become more easily delimited as structures by the presence of a furrow between the SAM and the leaf, they differ in terms of width. As they develop further and begin to cover the SAM, the two leaf types are distinguishable morphologically (flat vs. cup shaped). Quantitative parameters such as diameter of the SAM, angle of insertion of individual leaves, and size of leaf primordia (in both a tangential and perpendicular plane) were measured on three categories of leaves: stage 1, earliest visible stage of initiation; stage 2, delineation of leaf primordium from SAM by furrowing; stage 3, leaf primordium partially covering SAM. These measurements corroborate our morphological observations, which show that during early stages of development, flat and cup-shaped leaves are morphologically similar and they diverge in their pattern of development postinitiation, especially as far as leaf width and thickness are concerned. Our results also suggest that the size and shape of the apex goes through a "repeating" cycle and is related to the type of primordium that will be initiated.Key words: Thuja occidentalis, eastern white cedar, leaf development, shoot apical meristem, phyllotaxy, leaf dimorphism.
Arbuscular mycorrhizae from semiarid regions of Namibia
Authors: Uhlmann Elisabeth , Görke Claudia , Petersen Andreas , Oberwinkler Franz
Published: June 2004

Arbuscular mycorrhizae from four sites in semiarid parts of Namibia were studied. In addition to areas with different rainfall, different land management systems are compared. High numbers of morphological species with a patchy distribution were recorded. Arbuscular mycorrhizal fungal (AMF) sequences derived from grass roots are less diverse than the community of spores found in adjacent soil, indicating different AMF communities in grass roots during the vegetation period or different AMF communities in the roots of trees and herbs. The AMF community does not appear to be influenced by land management systems, but rather by vegetation cover or rainfall regime.Key words: Namibia, arbuscular mycorrhizae, molecular identification.
A temporal and morphological framework for flower development inAntirrhinum majus
Authors: Vincent Coral A , Coen Enrico S
Published: June 2004

The entire course of flower development in Antirrhinum majus L., from initiation to maturity, is described in terms of regular time intervals. Floral meristem and bud morphology was determined by scanning electron microscopy for a sequence of 58 plastochrons. These can be grouped to define 15 stages or 7 phases of development, providing a temporal framework for gene expression and key morphological events, such as the formation of the complex corolla. The time course is also used to estimate overall growth rates of sepals and petals. Sepals initially grow at a constant rate, but growth rate gradually declines at later stages and sepal growth eventually arrests before flower development is complete. Petals initially grow at a similar rate to that of early sepals, but this growth rate is maintained for a longer period, accounting for the larger size of mature petals relative to sepals. Comparisons with Arabidopsis indicate that the duration of growth also makes an important contribution to variation in flower size.Key words: Antirrhinum, flower development, meristems, zygomorphy, developmental timing, petal.
PROCEDURES FOR LOGIC AND ARITHMETIC OPERATIONS WITH DNA MOLECULES
Authors: FUJIWARA AKIHIRO , MATSUMOTO KEN'ICHI , CHEN WEI
Published: June 2004

In this paper, we consider procedures for logic and arithmetic operations with DNA molecules. We first show a DNA representation of n binary numbers of m bits, and propose a procedure to assign the same values for the representation. The representation enables addressing feature, and the procedure is applicable to n binary numbers of m bits in O(1) steps in parallel. Next, we propose a procedure for logic operations. The procedure enables any boolean operation whose input and output are defined by a truth table, and executes different kinds of boolean operations simultaneously for any pair of n binary numbers of m bits in O(1) lab steps using O(mn) DNA strands. Finally, we propose a procedure for additions of pairs of two binary numbers. The procedure executes O(n) additions of two m-bit binary numbers in O(1) steps using O(mn) DNA strands.
THE FIRST APPROXIMATED DISTRIBUTED ALGORITHM FOR THE MINIMUM DEGREE SPANNING TREE PROBLEM ON GENERAL GRAPHS
Authors: BLIN LÉLIA , BUTELLE FRANCK
Published: June 2004

In this paper we present the first distributed algorithm on general graphs for the Minimum Degree Spanning Tree problem. The problem is NP-hard in sequential. Our algorithm give a Spanning Tree of a degree at most 1 from the optimal.

The resulting distributed algorithm is asynchronous, it works for named asynchronous arbitrary networks and achieves O(|V|) time complexity and O(|V||E|) message complexity.
SEARCHES FOR SINGLE-TOP-QUARK PRODUCTION WITH THE CDF DETECTOR AT FERMILAB
Authors: CIOBANU CATALIN I. , JUNK THOMAS R.
Published: June 2004

In the proton–antiproton collisions at Fermilab, individual top quarks are expected to be produced by an electroweak mechanism referred to as single-top-quark production. In this paper we review the CDF results of the search for single-top-quarks, along with the prospects for the current collider run.
GENERATING FUNCTIONS FOR THE NUMBERS OF PYRAMID AND STAIRCASE POLYHEDRA
Authors: CHEN MALL , LIN KEH YING
Published: June 2004

We have derived the five-variable generating functions for the numbers of pyramid and staircase polyhedra on the cubic lattice with given values of width, depth, height, area and volume.
Acute effects of testosterone on intracellular Ca2+kinetics in rat coronary endothelial cells are exerted via aromatization to estrogens
Authors: Sierra-Ramírez Alfredo , Morato Tomás , Campos Rafael , Rubio Iván , Calzada Claudia , Méndez Enrique , Ceballos Guillermo
Published: June 2004

The objective of this work was to evaluate the effects of testosterone (T) and 17β-estradiol (E2) on coronary microvascular endothelial cells (CMECs) of male and female rats. To analyze the short-term effects of such sex steroid hormones on intracellular Ca2+concentration ([Ca2+]i) kinetics, we used the chelating agent fura-2 acetoxymethyl ester. We also explored the possibility of testosterone aromatization by using selective inhibitors of the aromatase enzyme cytochrome P-450 aromatase ( P450arom), aminoglutethimide (4 μM), and 4-hydroxyandrostenedione (4 μM). The presence of P450aromwas investigated by immunocytochemical and immunoblot assays using peptide-generated polyclonal antibodies raised against a 20-amino acid synthetic fragment of rat P450aromand by in situ hybridization to locate the aromatase mRNA in such cells. The activity of P450aromwas demonstrated by the stereospecific loss of the tritium atom of [1β-3H]androstenedione. Our results indicate that both T and E2induced a rapid increase in [Ca2+]i. The fact that the effects of E2and T were carried out within milliseconds suggests that they were exerted at the membrane level and not through intracellular receptors. The possibility of involvement of PLC-β in these effects is suggested because U-73122 (a PLC inhibitor) blocked the effects of both T and E2. Immunocytochemical assays indicated the expression of androgenic and estrogenic receptors in these cells. The effects of T were blocked by the selective aromatase inhibitors. We also demonstrated membrane association of P450arom, expression of the ovary-specific mRNA after in situ hybridization, and E2formation resulting from a significant activity of P450aromin CMECs. There were no gender-based differences.
Dual functional roles of Tie-2/angiopoietin in TNF-α-mediated angiogenesis
Authors: Chen Jian-Xiong , Chen Ying , DeBusk Laura , Lin Wenyu , Lin Pengnain Charles
Published: June 2004

Inflammation and angiogenesis are associated with pathological disorders. TNF-α is a major inflammatory cytokine that also regulates angiogenesis. TNF-α has been shown to regulate Tie-2 and angiopoietin (Ang) expression, but the functional significance is less clear. In this study, we showed that TNF-α induced a weak angiogenic response in a mouse cornea assay. Systemic overexpression of Ang-1 or Ang-2 dramatically increased corneal angiogenesis induced by TNF-α. In the absence of TNF-α, neither Ang-1 nor Ang-2 promoted corneal angiogenesis. Low doses (0–25 ng/ml) of TNF-α increased vascular branch formation of cultured endothelial cells. Overexpression of Ang-1 or Ang-2 enhanced the effects of TNF-α. These data suggest that Tie-2 signaling synergistically amplifies and participates in TNF-α-mediated angiogenesis. In addition, high doses (≥50 ng/ml) of TNF-α induced apoptosis in endothelial cells, but addition of Ang-1 or Ang-2 significantly reduced cell death. Enhanced endothelial cell survival was correlated with Akt phosphorylation. Collectively, our data reveal dual functional roles of Tie-2: low doses enhance TNF-α-induced angiogenesis, and high doses attenuate TNF-α-induced cell death. The study provides evidence supporting a role for Tie-2 in inflammatory angiogenesis.
Oxygen delivery and consumption in the microcirculation after extreme hemodilution with perfluorocarbons
Authors: Cabrales Pedro , Tsai Amy G. , Frangos John A. , Briceño Juan C. , Intaglietta Marcos
Published: June 2004

The oxygen transport capacity of fluorocarbons was investigated in the hamster chamber window model microcirculation to determine the rate at which oxygen is delivered to the tissue in conditions of extreme hemodilution [hematocrit (Hct) 11%]. Hydroxyethlyl starch (HES 200; 200 kDa molecular mass) was used as a plasma expander for two isovolemic hemodilutions performed with 10% HES 200 until a Hct of 65%. A third step reduced the Hct to 75% of baseline and was performed with either HES 200 or a 60% perfluorocarbon (PFC) emulsion. Comparisons of HES 200-only-hemodiluted animals versus 4.2 g/kg PFC emulsion-hemodiluted animals were made at 21% and 100% normobaric oxygen ventilation. It was found that systemic and microvascular oxygen delivery was 25% and 400% higher in the PFC animals compared with HES 200 animals, respectively, showing that PFCs deliver oxygen to the tissue when combined with hyperoxic ventilation in the present experiments, with no evidence of vasoconstriction or impaired microvascular function. Oxygen ventilation (100%) led to a positive base excess for the PFC group (5.5 ± 2.5 mmol/l) versus a negative balance (−0.8 ± 1.4 mmol/l) for the HES 200 group, suggesting that microvascular findings corresponded to systemic events.
Multiple Large Inputs to Principal Cells in the Mouse Medial Nucleus of the Trapezoid Body
Authors: Bergsman Jeremy B. , De Camilli Pietro , McCormick David A.
Published: June 2004

The calyx of Held is a giant nerve terminal that forms a synapse directly onto the principal cells of the medial nucleus of the trapezoid body (MNTB) in the mammalian auditory brain stem. This central synapse, which is involved in sound localization, has become widely used for studying synaptic transmission. Anatomical studies of this nucleus have indicated that each principal cell is innervated by only one calyx. Here we use previously established electrophysiological criteria of excitatory postsynaptic current amplitude, kinetics, and transmitter type, as well as other characteristics commonly reported for this synapse, to examine the input properties of principal neurons. Our findings indicate that some principal cells receive more than one strong excitatory input. These inputs meet previously established electrophysiological criteria for identification as calyceal nerve terminals. Implications for the execution and analysis of experiments to avoid errors due to such multiple inputs are discussed.
Stromal Cell-Derived Factor (SDF) 1-3′A Polymorphism May Play a Role in Resistance to HIV-1 Infection in Seronegative High-Risk Thais
Authors: Tiensiwakul Pornthep
Published: June 2004

Objective: It is known that a 32-bp-deleted CCR5 mutant (CCR5-Δ32) plays a critical role in resistance to human immunodeficiency virus type 1 (HIV-1) infection. We became aware of a number of seronegative patients at high risk of HIV-1 infections. Since CCR-Δ32 is not found in Thais, we examined the role of stromal cell-derived factor (SDF) 1-3′A polymorphism in resistance to HIV-1 in seronegative Thai prostitutes at high risk. Methods: We determined CCR5-Δ32 by PCR, SDF1-3′A by RFLP, and plasma SDF-1 level by sandwich ELISA. Results: We did not find any CCR-Δ32 mutant in 432 subjects. In our SDF1-3′A genotyping, we found allelic frequencies of 0.406, 0.199, and 0.289 in HIV-1-seronegative prostitutes at high risk, HIV-1-seropositive patients, and normal blood donors, respectively. There was a significant difference in the allelic frequencies of SDF1-3′A between HIV-1-seronegative prostitutes at high risk and HIV-1-seropositive patients (p < 0.005). Striking differences were seen in homozygotes (SDF1-3A/3A); 20.3% in HIV-1-seronegative patients at high risk compared with 2.5% in HIV-1-seropositive patients. In addition, we showed that the plasma SDF1 level in the HIV-1-seronegative prostitutes at high risk was twice that found in normal blood donors (p = 0.005), and even higher than that of HIV-1-seropositive patients (p = 0.002). Conclusions: The finding is relevant as regards the fact that SDF1-3′A polymorphism induces an increase of SDF1 chemokine production, in which it competes with HIV-1 in binding to CXCR4 receptor, and in turn inhibits HIV-1 infection. The SDF1-3′A-mediated resistant mechanism in Thais differs from that of CCR5-Δ32-mediated resistance in Caucasians. This study provides the first evidence for SDF-3′A polymorphism in resistance to HIV-1 infection in Thais, and may represent the resistant mechanism in the extremely rare CCR5-Δ32 mutant of other ethnic groups such as Africans and Japanese.