bluuebunny/crossref_metadata_2025 huggingface dataset:
Connecting species richness, abundance and body size in deep‐sea gastropods
Authors: McClain Craig R.
Published: June 2004

Aim  This paper examines species richness, abundance, and body size in deep‐sea gastropods and how they vary over depth, which is a strong correlate of nutrient input. Previous studies have documented the empirical relationships among these properties in terrestrial and coastal ecosystems, but a full understanding of how these patterns arise has yet to be obtained. Examining the relationships among macroecological variables is a logical progression in deep‐sea ecology, where patterns of body size, diversity, and abundance have been quantified separately but not linked together.

Location  196–5042 m depth in the western North Atlantic.

Method  Individuals analysed represent all Vetigastropoda and Caenogastropoda (Class Gastropoda) with intact shells, excluding Ptenoglossa, collected by the Woods Hole Benthic Sampling Program (3424 individuals representing 80 species). Biovolume was measured for every individual separately (i.e. allowing the same species to occupy multiple size classes) and divided into log2 body size bins. Analyses were conducted for all gastropods together and separated into orders and depth regions (representing different nutrient inputs). A kernel smoothing technique, Kolmogorov‐Smirnov test of fit, and OLS and RMA were used to characterize the patterns.

Results  Overall, the relationship between the number of individuals and species is right skewed. There is also a positive linear relationship between the number of individuals and the number of species, which is independent of body size. Variation among these relationships is seen among the three depth regions. At depths inferred to correspond with intermediate nutrient input levels, species are accumulated faster given the number of individuals and shift from a right‐skewed to a log‐normal distribution.

Conclusion  A strong link between body size, abundance, and species richness appears to be ubiquitous over a variety of taxa and environments, including the deep sea. However, the nature of these relationships is affected by the productivity regime and scale at which they are examined.
Ecological niches as stable distributional constraints on mammal species, with implications for Pleistocene extinctions and climate change projections for biodiversity
Authors: Martínez‐Meyer Enrique , Townsend Peterson A. , Hargrove William W.
Published: June 2004

Aim Theoretical work suggests that species’ ecological niches should remain relatively constant over long‐term ecological time periods, but empirical tests are few. We present longitudinal studies of 23 extant mammal species, modelling ecological niches and predicting geographical distributions reciprocally between the Last Glacial Maximum and present to test this evolutionary conservatism.

Location This study covered distributional shifts in mammal species across the lower 48 states of the United States.

Methods We used a machine‐learning tool for modelling species’ ecological niches, based on known occurrences and electronic maps summarizing ecological dimensions, to assess the ability of ecological niches as modelled in one time period to predict the geographical distribution of the species in another period, and vice versa.

Results High intertemporal predictivity between niche models and species’ occurrences indicate that niche conservatism is widespread among the taxa studied, particularly when statistical power is considered as a reason for failure of reciprocal predictions. Niche projections to the present for 8 mammal taxa that became extinct at the end of the Pleistocene generally increased in area, and thus do not support the hypothesis of niche collapse as a major driving force in their extinction.

Main conclusions Ecological niches represent long‐term stable constraints on the distributional potential of species; indeed, this study suggests that mammal species have tracked consistent climate profiles throughout the drastic climate change events that marked the end of the Pleistocene glaciations. Many current modelling efforts focusing on anticipating climate change effects on species’ potential geographical distributions will be bolstered by this result — in essence, the first longitudinal demonstration of niche conservatism.
Scale and macroecological patterns in seed dispersal mutualisms
Authors: Burns K. C.
Published: June 2004

Although some studies of seed dispersal mutualisms have documented adaptive relationships between fruits and frugivores, others have shown that adaptive patterns are constrained by phylogenetic, historical or climatic effects. Variable results among studies have thwarted attempts to find a paradigm to unite the field and direct research. Two recent studies in Global Ecology and Biogeography exemplify this dichotomy. One paper reported adaptive relationships between abundances of birds and fruits, while the other study found that bird‐fruit abundance patterns were constrained by climatic effects. Almost paradoxically, both studies were conducted at the same locale. However, they focused on different spatio‐temporal scales. These results are surprisingly consistent with several other recent studies that have taken a macroecological approach. They also indicate that mutualistic relationships between fruits and frugivores are scale dependent. When viewed together, recent work suggests that the conflicting results of previous studies may result from spatio‐temporal variability of mutualistic relationships. This paper briefly reviews the emerging field of seed dispersal macroecology. A growing appreciation for scale appears to be leading the field in a new direction.
Cleavages, competition and coalition‐building: Agrarian parties and the European question in Western and East Central Europe
Authors: BATORY AGNES , SITTER NICK
Published: June 2004

Abstract.  The central argument in this article is that Europeanisation of party politics – the translation of issues related to European integration into domestic party politics – is driven by the dynamics of long‐ and short‐term party strategy. Variations in the patterns of Euroscepticism found in agrarian parties across Europe is therefore explained in terms of three central variables: the agrarian parties’ long‐term policy goals linked to identity and interest; their position in the party systems and the mainstream left‐ and right‐wing parties’ stance on European integration; and their long‐ and short‐term electoral strategies and office‐related incentives.
Culture and Characterization of Human Hepatocytes Obtained after Graft Reduction for Liver Transplantation: A Reliable Source of Cells for a Bioartificial Liver
Authors: Barbich Mariana , Lorenti Alicia , Hidalgo Alejandra , Ielpi Marcelo , De Santibáñez Martín , De Santibáñez Eduardo , Morales Vanina , Marín María C. , Callero Maria F. , Argibay Pablo F.
Published: June 2004

Abstract:  This article describes results obtained when human liver cells obtained from reduced grafts are cultured in a chemically defined medium. Remnants of livers after reduction for pediatric transplantation were processed by a multiple cannulation system through the existing vasculature, which allowed the homogeneous perfusion of collagenase. The graft weight ranged between 55 and 1000 g (median value: 145.6 g). The yield ranged between 0.13 × 106 and 38 × 106 cells/g of tissue (median value 14.73 × 106 cells/g), and the viability was 61.17 ± 27.43%. The total number of cells ranged between 57.6 × 106 and 12 150 × 106 cells (median value: 740 × 106 cells). Cells were cultured for 30 days. Albumin synthesis was observed during the first 2 weeks, with a peak value at day 6 (27.85 ± 1.77 µg/mL). Urea production was detected during the first week (peak value at day 6: 17.12 ± 2.11 mg/dL). Light microscopy showed the presence of cells in a monolayer. Biliary pigments were observed at day 20. By immunohistochemistry, positive cells for albumin, for hepatocyte marker, cytokeratin 19, CD 34, CD 68, and for alpha actin for smooth muscle, were observed. Our results showed that hepatocytes obtained from reduced liver grafts are easily cultured and are able to maintain viability and functionality in vitro. This alternative source of human cells maintained under controlled culture conditions may play an important role in the development of a bioartificial liver.
Large Bore Catheters with Surface Treatments versus Untreated Catheters for Vascular Access in Hemodialysis
Authors: Bambauer Rolf , Latza Reinhard , Bambauer Silke , Tobin Eric
Published: June 2004

Abstract:  Infection, thrombosis, and stenosis are among the most frequent complications associated with blood‐contacting catheters. Complications resulting from infection remain a major problem for hemodialysis catheters, with significant numbers of catheters being removed due to catheter‐related sepsis. Numerous strategies have been employed to reduce the occurrence of infection and im‐prove long‐term outcomes, with varying degrees of success. The most important is the careful and sterile handling by the attending staff of the catheters during hemodialysis treatments to minimize or stop a microbial colonization of the skin and the catheter. Another approach is coating the external surface of the catheters with substances which are antibacterial like silver and/or substances with low thrombogenicity like silicone. This investigation reviews results of animal and clinical experiments conducted to assess the efficacy and biocompatibility of silver and silicone coated dialysis catheters. It is concluded that silver coatings can reduce bacterial colonization and occurrence of infection associated with these devices. The catheters employing ion implantation of silicone rubber showed low thrombogenicity. Results of the studies indicate that ion beam based processes can be used to improve thrombus and infection resistance of blood contacting catheters. A new development is the microdomain structured surface (PUR‐SMA coated catheters). Preliminary results with these catheters are very encouraging.
The Impact of Pump Speed and Inlet Cannulation Site on Left Ventricular Unloading with a Rotary Blood Pump
Authors: Vandenberghe Stijn , Nishida Takahiro , Segers Patrick , Meyns Bart , Verdonck Pascal
Published: June 2004

Abstract: Background:  Ventricular assist devices are gaining ground in the therapeutic treatment of chronic heart failure. These devices are sometimes used as a bridge to recovery by unloading the left ventricle (LV) and restoring its function. It is therefore important to preserve the heart muscle and apply less invasive implantation methods.

Methods:  In this study ventricular unloading was achieved in 7 healthy sheep with a rotary blood pump at different pump flow levels. Ventricular cannulation via the left atrium (LA) and through the mitral valve was compared to atrial cannulation. The unloading of the heart was assessed with LV pressure‐volume loops, derived energetic parameters, and an estimate of LV wall stress.

Results:  No significant difference between the cannulations was found for any flow or pressure. LA cannulation, however, resulted in significantly lower stroke volumes and stroke work for all pump flow levels. Irrespective of cannulation site, LV volumes and energetic parameters showed a significant decrease with increasing pump flow.

Conclusion:  LV assist with a rotary blood pump can provide sufficient unloading with atrial cannulation.
The Board of Directors in Family Firms: One Size Fits All?
Authors: Corbetta Guido , Salvato Carlo A.
Published: June 2004

Boards of directors are governance bodies that serve important functions for organizations, ranging from monitoring management on behalf of different shareholders to providing resources. Board roles and characteristics vary widely among national cultures and, within each country, among different company types. Despite such variety, research on family business boards has been dominated by prescriptions and by the lack of an explicit recognition of family firm types characterized by different governance requirements. We argue that a contingency approach to defining board structure, activity, and roles offers useful guidance in understanding board contributions to family business performance. We develop a theory to show how board characteristics are a reflection of a family firm's power, experience, and culture makeup. This theory provides insight into descriptions of existing board choices and prescriptions for family firms interested in starting or adapting their board of directors.
Family Business Succession: Suggestions for Future Research
Authors: Brockhaus Robert H.
Published: June 2004

Management succession is a significant moment in a family business's life and an issue that requires analysis from the perspectives of family, management, and ownership systems in order to understand adequately the perspectives of the different stakeholders. In an effort to help improve the quality of the research methodology on this subject, past family business research methodology will be reviewed and critiqued, and some specific recommendations will be presented that can enhance the quality and value of family business research.
Ternary Corrections in the Liquid-Liquid Equilibria Computation for Three-Component Systems Containing Components of Mixed Solvent N-Methylpyrrolidone-Ethylene Glycol
Authors: Graczová Elena , Surový Július , Bafrncová Soňa
Published: June 2004

Presented are the liquid-liquid (L-L) equilibrium data for three-component heterogeneous systems toluene-N-methylpyrrolidone-ethylene glycol, heptane-N-methylpyrrolidone-ethylene glycol and heptane-toluene-ethylene glycol at 50 °C. Equations for the excess Gibbs energy (NRTL. Novák modification of Wilson equation and Redlich-Kister 4th order expansion) extended by ternary universal contribution were employed for correlating the L-L equilibrium data. The binary equation parameters were independently evaluated from the binary equilibrium data. The presented ternary data served for evaluation of parameters of the universal ternary contribution.
Use of the Internal and External Standard Techniques in Determinations of Amino Acids by Ion Exchange Chromatography
Authors: Rittich Bohuslav , Standara Stanislav
Published: June 2004

Influence of internal standard technique on precision of amino acid determination was studied. The law of propagation of errors and the information theory was applied in this paper. From the results it follows that the internal standard technique did not inevitably improve the precision of the determination. In the case of multicomponent sample, the external standard technique improved the accuracy only if calibration curve was used.
Structure of Another Phase of (1-Phenyl-3-(2-[(2-aminoethyl)amino]ethylimino)-1-buten-1-olato-O,N,N',N")palladium(II) Perchlorate
Authors: Kratochvíl Bohumil , Ondráček Jan , Novotný Jiří , Macíček Josef , Haber Václav
Published: June 2004

The structure of the β-phase of (1-phenyl-3-(2-[(2-aminoethyl)amino]-ethylimino)-1-buten-1-olato-O,N,N',N") palladium(II) perchlorate, β-[Pd(baden)]ClO4, was solved by the heavy atom method and refined anisotropically to R = 0.035 for 11 226 unique observed reflections. The title compound is orthorhombic, a = 14.152(2), b = 12.507(1), c = 20.012(2) Å, Pca21, Z = 8. The structure contains two symmetrically independent molecules both formed by two five-membered and two six-membered rings (one of them is phenyl) and disordered perchlorate anion. The crystal packing is predominantly given by electrostatic interactions accompanied by weak hydrogen bonding among nitrogens and perhlorate oxygens. No structural significant differences between α- and β-phases were found.
An Anomalous Course of the Darzens Reaction Catalyzed with Magnesium Methoxide
Authors: Svoboda Jiří , Nič Miloslav , Paleček Jaroslav
Published: June 2004

The reaction of benzaldehyde with methyl chloroacetate catalyzed with magnesium methoxide gave beside the expected methyl 2,3-epoxy-3-phenylpropanoate (I) also comparable amounts of methyl 2-hydroxy-3-methoxy-3-phenylpropanoate (II). The condensation was accompanied by a competing disproportionation of benzaldehyde giving methyl benzoate and benzyl alcohol. The course of the condensation reaction is discussed.
Cyclization Reactions of 2-(6-Azauracil-5-yl)benzoic Acid and Some Its Derivatives
Authors: Hejsek Miloslav , Slouka Jan , Bekárek Vojtěch , Lyčka Antonín
Published: June 2004

2-(6-Azauracil-5-yl)benzoic acid (Ib) and its thio analogue Ia give new heterocyclic compounds, 1,2-dihydro-1,2,4-triazino[5,6-c]isocoumarin-3-one (IVb) and analogous 3-thione IVa, respectively, on treatment with N,N'-dicyclohexylcarbodiimide. A series of substituted 1,2,4-triazino[5,6-c]isoquinolines V-XVI have been prepared from these compounds and from other functional derivatives (II, III) of the acids I.
The Reaction of Dimethyl N-(1,2,4-Triazol-5-yl)iminodithiocarbonates with Dinucleophiles
Authors: Pongó László , Dvortsák Péter , Reiter József
Published: June 2004

A series of N-(3-methylthio-1,2,4-triazol-5-yl) substituted carbamimidothioates (III), 2-iminoazolidines (IV, X = O, S, NH, n = 2), 2-iminohexahydro-1,3-oxazines (IV, X = O, n = 3), 2-iminohexahydropyrimidines (IV, X = NH, n = 3), and N,N'-alkylenebis(carbamimidothioates) (V) was prepared from dimethyl N-(3-methylthio-1,2,4-triazol-5-yl)iminodithiocarbonates (I). N-substituted azolidines IV, X = O, S, NH, n = 2, such as acetyl, methyl, (ethoxycarbonyl)methyl, 1-(ethoxycarbonyl)ethyl, 2-chloroethylcarbamoyl, 2-cyano-2-(ethoxycarbonyl)ethenyl, and 2,2-dicyanoethenyl, were also prepared. The structure of isomers and tautomers of several compounds was determined using 1H NMR, 13C NMR, and UV data.
Geiparvarin Regioisomers
Authors: Rampa Angela , Valenti Piero , Da Re Paolo , Chicca Milvia , Gasperini Simonetta , Colombo Giuseppe
Published: June 2004

The synthesis and the cytotoxicity of Geiparvarin (7-[(E)-3-(4,5-dihydro-5,5-dimethyl-4-oxo-2-furanyl)-2-butenyloxy]-coumarin) regioisomers are reported.
Potentiometric Investigation of Mixed-Ligand Complexes of Co(II), Ni(II) and Zn(II) Ions with Thiosalicylic Acid and Ethylenediamine
Authors: Masłowska Joanna , Szmich Józef
Published: June 2004

Formation of mixed-ligand complexes of Co(II), Ni(II) and Zn(II) ions with thiosalicylic acid (H2SR) and ethylenediamine (en) in aqueous ethanol (50 vol.%) was investigated by the potentiometric method at 298, 313 and 328 K at the ionic strength of 0.1 (NaClO4). The thermodynamic functions ∆G0, ∆H0 and ∆S0 have been evaluated at these temperatures.
Hydration of Complexes of Some Univalent Cations with Polyethylene Glycol Ligands in Nitrobenzene Saturated with Water
Authors: Makrlík Emanuel
Published: June 2004

The hydration numbers of the complexes ML+ formed by some univalent cations (M+ = Li+, Na+, NH4+, K+, Rb+ and Cs+) and polyethylene glycol ligands (L = PEG 200, PEG 300 and PEG 400) in nitrobenzene saturated with water were determined. The highest differences between the hydration numbers of the cations M+ and the complexes ML+ were found in the systems with the Na+ cation.
Addition of Tetrachloromethane to 1,5-Hexadiene
Authors: Kotora Martin , Hájek Milan
Published: June 2004

The 2 : 1 adduct as the final product of the addition of tetrachloromethane to 1,5-hexadiene catalyzed by copper(I)-butylamine complex was obtained in high yield (96%) under mild reaction conditions. Predominant 1 : 1 adduct formation was observed in the presence of a palladium catalyst or dibenzoyl peroxide initiator.
Oxidation of Ethanol on Sn-Mo Oxide Catalysts
Authors: Wassel Magdy A. , Allahaverdova Nalla K. , Alkhazov Tofki G.
Published: June 2004

To determine the acidic and basic properties of the title catalysts, the adsorption of NH3 and SO2 was compared using pulse method. It was found that this characteristics undergoes changes when the Sn-Mo catalyst is treated with aqueous potassium hydroxide solutions of different concentrations. The catalyst treated with the more concentrated KOH solution possesses mainly properties of a base. When studying the oxidation of ethanol it has been found that the αCO2/αaldehyde conversion ratio increases with the time of contact of the mixture with the catalyst while the αCO2/α acid ratio is not affected. The study of two alcohols deuterated either in OH group (C2H5OD) or in the alkyl group ((C2D5OH) has shown that the substitution of C-H for C-D bond enhances the stability of the primary oxidation product, deuterated ethanal, so that it is not transformed further to acetic acid.
Oxidation of Ethanol to Ethyl Acetate on Sb-Mo Oxide Catalysts
Authors: Wassel Magdy A. , Allahaverdova Naila K. , Adyamov Keykavus Y.
Published: June 2004

The catalytic activity of three Sb-Mo oxide catalysts in the title reaction has been investigated. The catalyst Sb2Mo10O31 showed the highest and the catalyst Sb2MoO6 the lowest activity. The distances between surfaces and intensities for the Sb-Mo-O catalysts Sb4Mo10O31, Sb2Mo10O31 and Sb2MoO6 were obtained by diffractometric measurements.
Preparation and Properties of (1,2-Diaminocyclohexane)dichloroplatinum(II) Complexes Containing cis or trans 1,2-Diaminocyclohexane
Authors: Valigura Dušan , Vančová Vlasta , Ondrejovič Gregor , Kováčová Jolana , Kiss František
Published: June 2004

The preparation and properties of (1,2-diaminocyclohexane)dichloroplatinum(II) complexes containing cis and trans 1,2-diaminocyclohexane were studied, and the separation of the isomers from their mixture was investigated. Separation in the form of the nickel(II) complexes was chosen with regard to its efficiency and to the possibility of obtaining directly the corresponding 1,2-diaminocyclohexane hydrochloride. Good quality products were obtained in a yield of more than 90% by reacting 1,2-diaminocyclohexane dihydrochloride with K2[PtCl4] in aqueous solution, pH ca 10, in dark at room temperature.
Preparation, Characterization and Stereochemistry of Mixed Anhydrides of O-Alkylbenzohydroximic Acid
Authors: Lakhanpal Sunita , Rao G. C. , Misra Bhupendra Nath
Published: June 2004

A number of stable isoimides have been prepared by acylation and sulfonylation of O-benzylbenzohydroxamic acid and O-butylbenzohydroxamic acid by anisoyl chloride, benzoyl chloride, phenoxyacetyl chloride, p-toluenesulfonyl chloride, benzenesulfonyl chloride and p-nitrobenzenesulfonyl chloride in the presence of pyridine. Spectral investigations indicate that the products have the mixed anhydride structure with (Z)-configuration. Corresponding (E)-isomers and isomeric N-acetylated products if formed, could not be isolated. An attempt has been made to study 1,3-rearrangement of the mixed anhydrides by thermal method.
Electrophilic 3,5-Substitution of 2,4,4,6-Tetraphenyl-4H-pyran and Some of Its 1-Heteroanalogues
Authors: Schwarz Marián , Šebek Pavel , Kuthan Josef
Published: June 2004

The reaction of dibromine with the heterocycles I-IV gives corresponding 3,5-dibromo derivatives, while the less selective reactions with dichlorine afforded 3,5-dichloro derivative XII only in the case of 4H-thiopyran IV and trichloro derivative of the probable formula XIII in the case of 1,4-dihydropyridine II. Dichloro derivative IX was obtained on reaction of phosphorus pentachloride with substrate I. Nitration of compounds I-IV gives 3,5-dinitroderivatives XV-XVIII, but mononitro derivatives XIX and XX were also obtained. Iodination of compounds II-IV with di-iodine was unsuccessful.
Preparation of Some Pyrazole Derivatives by Extrusion of Elemental Sulfur from 1,3,4-Thiadiazines
Authors: Rádl Stanislav
Published: June 2004

In connection with our research of pyrazolo[3,4-b]quinolines we were also interested in the preparation of various pyrazole intermediates. In some cases we found a method useful based on extrusion of elemental sulfur from intermediate 1,3,4-thiadiazines. This short contribution describes the preparation of some new 3-anilino-4-pyrazolecarboxylic acid derivatives using this method.
Kinetic Aspects of the Crystallization of SAPO-5 Molecular Sieves
Authors: Kornatowski Jan , Kanz-Reuschel Beate , Finger Gerd , Baur Werner H. , Bülow Martin , Unger Klaus K.
Published: June 2004

The kinetics of hydrothermal crystallization of microporous silicoaluminophosphate SAPO-5 have been studied as a function of water content using the templates tripropylamine (TPA) and triethylamine (TEA). The investigation included the formation of the SAPO-5 phase, its growth in large single crystals, and the size distribution of the crystals. An attempt to fit the experimental data to kinetic models of crystallization is presented. The systems studied have been found to be very similar except for the nucleation stage which is mainly responsible for both the dimensions of the resulting crystals and for the purity of the SAPO-5 phase.
Reductive Amination of Diethylene Glycol to Morpholine over Supported Nickel Catalysts: Zeolites as Catalyst Admixtures
Authors: Jirátová Květa , Šnajdaufová Hana , Morávková Lenka , Kubelková Ludmila
Published: June 2004

The effect of HZSM-5, H-silicalite and amorphous silica admixtures on the surface properties of nickel catalysts as well as on their activities, selectivities and stabilities in the reductive amination of diethylene glycol was studied. It was found that, in comparison with amorphous silica, zeolites do not positively affect the catalytic properties of nickel catalysts. In addition, the acidity of the zeolites, the dispersity of the nickel phase, changes in the chemical composition during the reaction and adsorption of the reaction components or intermediates on the surface and consequent blocking of the zeolite surface played a role.
Role of Mechanical Treatment in Preparation of Multicomponent Bismuth Molybdate Catalyst for Propylene Ammoxidation
Authors: Wassel Magdy A. , Khamamedova Alla K. , Adyamov Keikavus Y.
Published: June 2004

The multicomponent catalyst Mo12Bi1Fe3Co4.5Ni2.5K0.1P0.5Ox/SiO2 (50% w/w) for propylene ammoxidation was prepared by mechanical treatment of the initial components and compared with the catalyst obtained by co-precipitation. Data on its catalytic activity, selectivity and texture (surface area and porosity) are reported. X-Ray study of the samples subjected to mechanical treatment for different times (from 0.5 to 12 h) showed that the treatment leads to changes in phase composition of the catalyst which become more pronounced on prolonged grinding time. The increase of grinding time results also in reduction of the surface area and porosity of the catalysts. Notwithstanding, data obtained demonstrate that mechanical treatment exerts favourable effect on the activity of Fe-Bi-Mo oxide catalysts.
Effect of Nickel and Phosphorus in Hydrodesulfurization of Thiophene and Hydrodenitrogenation of Pyridine over Alumina-Supported Molybdenum Catalysts
Authors: Damyanova Sonia , Spojakina Alla , Vít Zdeněk
Published: June 2004

The effect of nickel and phosphorus on activity of alumina-supported molybdenum catalysts in simultaneous hydrodesulfurization (HDS) of thiophene and hydrodenitrogenation (HDN) of pyridine was studied. The introduction of nickel into molybdenum-containing catalysts promotes strongly HDS of the alumina-supported nickel-molybdenum catalyst while the increase in HDN activity is less pronounced. The synergistic effect in pyridine HDN is explained as the consequence of synergism in HDS. The weak promoting effect of phosphorus was observed for NiMo/Al2O3 catalyst containing 1 wt% of phosphorus. Above this concentration, both HDS and HDN activities decrease again. HDS activity of P-modified NiMo/Al2O3 samples was similar to that of the commercial NiMo/Al2O3 Shell catalyst. However, the HDN selectivity in pyridine reaction was higher for commercial catalyst which is explained by exceptionally higher dispersion of nickel on this catalyst.
EPR Study of Nitroxyl Radicals of Substituted 5-Anilinotriazoles, 5-Anilinotetrazoles, and 2-Anilinobenzimidazoles
Authors: Omelka Ladislav , Meske Michael , Cholvad Vladimír , Světlík Jan , Schulz Manfred
Published: June 2004

Substituted 5-anilinotriazoles V, 5-anilinotetrazoles VI and 2-anilinobenzimidazoles VII were oxidized by RO2• radicals to the corresponding nitroxyls VIII-X in a non-polar medium. The nitroxyls were characterized by the distribution of spin density into both benzene and N-heterocyclic rings. The influence of substitutents at various positions on the values of aNNO splitting constant was evaluated. The EPR spectral parameters of nitroxyls VIII-X were compared with those for the diphenylnitroxyl radical IV.
1-Ethoxycarbonylquinolizinium Salts Condensation of β-Ketoenol Ethers with 2-Pyridylacetates
Authors: Szychowski Jerzy , Leniewski Andrzej , Wróbel Jerzy T. , Glinka Tomasz
Published: June 2004

A general route to some 1-ethoxycarbonylquinolizinium bromides has been worked out. The method allows to conduct the condensation between β-ketoenol ethers and substituted 2-pyridylacetates in homogenous conditions in the presence of trifluoroacetic acid in an aprotic solvent. The substitution at C-6 in 2-pyridylacetates completely changes the reaction course affording 3,6-disubstituted 2-pyrones.
Synthesis of 5,7-Dioxo-6-halogenophenyl-6,7-dihydro-5H-dibenzo[a,c]cycloheptene Derivatives
Authors: Nedev Hinyu N. , Stoyanov Neiko M. , Minchev Stoyan , Aleksiev Boris V.
Published: June 2004

The condensation of diphenic anhydride with o-, m- and p- halogenosubstituted phenylacetic acids gave the respective enolacetates Ia-Ie. The alkaline hydrolysis of these compounds yields the diketones IIa-IIe. After testing blood cloting agents in vivo, the last compounds showed indications of anticoagulants.
The Antifungal Activity of Some Aliphatic and Aromatic Acids
Authors: Rittich Bohuslav , Pirochtová Marta , Hřib Jiří , Jurtíková Kamila , Doležal Petr
Published: June 2004

The present paper deals with the relationship between biological activities of some aliphatic and aromatic acids and their physico-chemical parameters expressing the influence of hydrophobic factors. The test strain in the biotest of growth inhibition was the fungus Fusarium moniliforme CCMF-180 and Penicillium expansum CCMF-576. Significant relationship between antifungal activities of un-ionized form of aliphatic acids and their capacity factors (log k'0) extrapolated to pure water, partition coefficients determined in 1-octanol-water system (log Poct) and the first order of molecular connectivity indices (1χ) were calculated. The ionized form of aliphatic acids were antifungally active too. For benzoic acids significant relationships between antifungal activities and capacity factors of anionic form (log k'ia) were calculated.
Hydrophobic Core and Surface Charges of Human β2-Microglobulin Probed by CD Measurements
Authors: Vučić Milanka , Bray Paul , Zloh Mire , Vučelić Dušan
Published: June 2004

The roles of hydrophobic bonding and charge electrostatics in the stabilization of human β2-microglobulin have been probed by variations in solution conditions and monitored by circular dichroism in the near and far UV regions. Sodium perchlorate initially gives a decrease in intensity of the positive 234 nm peak in the near UV followed by a shift of this peak to negative ellipticity at high perchlorate concentration. These 234 nm changes indicate a new environment for a tyrosyl chromophore(s). A conformational rearrangement of the β-sheet sandwich must occur since all six tyrosines of human β2-microglobulin are located in the two β-sheets of this sandwich. A slight decrease in intensity for the 200 nm positive peak in the far UV indicates a less close packing of the β-sheets at high perchlorate. In other experiments, enthalpy and entropy values have been calculated from thermal unfolding studies at 50 and 180 mM NaCl for pH values 6.0 and 8.0. Larger enthalpy values are obtained at higher NaCl concentration consistent with salt shielding of predominantly unfavorable charge interactions. These enthalpy differences are relatively large suggesting that charge electrostatics are energetically significant in stabilization of human β2-microglobulin.
Synthesis of 1-Arylazo-3-acetyl-1H-cinnolin-4-one Derivatives
Authors: Abbady Mohamed S. , Gaber Abd El-Aal M.
Published: June 2004

The biological activity of azocinnoline derivatives especially in the chemotherapy of Trypanosomiasis was already reported. Considering the foregoing and in continuation of our previous work, 3-acetyl-1H-cinnolin-4-one (I) has been well exploited as a coupling component.
Distribution of the Lifetimes of Energized Polyatomic Molecules in the Harmonic Model
Authors: Šolc Milan
Published: June 2004

In the harmonic model of unimolecular reactions of polyatomic molecules, the decay of a molecule is defined as the passage of an internal coordinate (given by the superposition of normal vibrations) over a critical value. A numerical study of the behaviour of the superposition of harmonic vibrations with frequencies linearly independent in the field of rationals has shown that the distribution of time gaps between upzeros of the superposition over the critical value is not exponential. For molecules with uniform density of phases, however, the lifetime distribution is close to an exponential one.
A Method for Estimation of Kinetic Parameters; A Simple First-Order Reaction and Two Parallel First-Order Reactions Producing a Common Product
Authors: Wu Xizun , Zhang Wenzhi , Cai Shengmin , Han Degang
Published: June 2004

A method is proposed for the treatment of data from a kinetic system of a simple first-order reaction and two parallel first-order reactions, producing a common product. It is based on the solving of a contrary proposition for an ordinary differential equation.
BET Adsorption Isotherm and Surface Heterogeneity
Authors: Cascarini de Torre Lydia Ethel , Bottani Eduardo Jorge
Published: June 2004

The BET adsorption isotherm is modified in order to take account of surface heterogeneity. The adsorption isotherm is obtained following the statistical mechanics formalism, proposed by Steele, and the effect of surface heterogeneity is limited to the first layer. A Gaussian adsorption energies distribution function is used to describe surface heterogeneity. The variations of the C parameter, multilayer formation and the inversion of adsorption isotherms are analysed.
Kinetics of Autocatalytic Oxidation of Mn(II) Ions by Periodate in Relation to Manganese Oscillations
Authors: Sodnomdordž Gongoryn , Melicharčík Milan , Treindl Ľudovít
Published: June 2004

The kinetics of the autocatalytic oxidation of Mn(II) ions by periodate was investigated in unbuffered phosphoric acid solutions and in buffered solutions; the process was studied in a bath reactor in relation to the chemical oscillations in a continuously flow stirred tank reactor (CSTR), which are based on the chemistry of manganese. The rate constants k1 and k'2 corresponding to the noncatalyzed and catalyzed reaction course were determined by the Schwartz method. While MnO4- ions are the reaction product in the unbuffered phosphoric acid medium, in a CH3COOH-NaOH buffer the Mn2+ ions are only oxidized to Mn(IV). For this case, a reaction pathway is discussed where the key step encompasses dimerization of MnO(OH)+ ions followed by the formation of (MnO2)col colloids, stabilized by adsorption of H2PO4- ions on their surface. This reaction pathway is also of importance with respect to the new manganese oscillator which is based on the autocatalytic oxidation of Mn(II) ions by periodate in a CSTR.
Relative Reactivities of 1,1,1-Trichloroethane and 1,1,1-Trichlorotrifluoroethane in Competitive Addition Reactions
Authors: Adámek František , Hájek Milan , Janoušek Zbyněk
Published: June 2004

Relative reactivity of CH3CCl3 and CF3CCl3 measured in competitive addition reactions with 1-hexene in the presence of free radical initiators or Cu, Pd and Ru complexes was found to depend on the type of catalyst. The unusual course of the reaction has been found in the additions catalyzed with copper(I)-amine complexes where CH3CCl3 in competition with CF3CCl3 was completely unreactive. The results have been explained in terms of the change of reaction mechanism and compared with classical free radical initiation.
Molar Refractivities of Solutions of the Eutectic Silver Nitrate-Thalium Nitrate Mixture in Water and Dimethyl Sulfoxide
Authors: Kodejš Zdeněk , Špalková Hana , Sacchetto Guiseppe A.
Published: June 2004

Refractive indices of the (Ag0.516, Tl0.484)NO3-H2O and (Ag0.516, Tl0.484)NO3-DMSO solutions have been measured at 90 °C over the whole composition range extending from the molecular solvents to the molten electrolyte. The molar refractivities of the melts were calculated from the refractive indices and a set of density values interpolated at the same temperature. Both systems were found to exhibit deviations from the ideal additive behaviour. The molar refractivities of the electrolyte (eutectic mixture AgNO3-TlNO3) and the solvent were calculated and their composition dependence and the deviations from the additivity are compared and discussed. The molar refractivity was found to be a complex, a less indicative, and a less sensitive indicator of the types and strength of ion-solvent interactions in these melts than the molar volume.
Feedback Reactor with Continuous Injection of One Reaction Component with Potentiometric Indication
Authors: Skopal František
Published: June 2004

The time dependence of the volume of one reactant solution injected into the other was derived. The injection is feedback-controlled to hold the reaction mixture potential constant. The theoretical relations were tested in a feedback reactor on two second-order reactions.
Heterogeneous Electron Transfer Rate Constants for the Second Reduction Process of Some Dinitroaromatics
Authors: Mohammad Mahboob , Khan Athar Yaseen , Qureshi Romana , Ashraf Naila , Begum Waheeda
Published: June 2004

Standard heterogeneous electron transfer rate constants k0 for the second reduction process of 1,2-, 1,3- and 1,4-dinitrobenzenes were evaluated by the Gileadi method. The temperature dependences of k0 were investigated using Marcus' and other expression for ∆G*. However, it was found that to explain the values of k0 and its variation with temperature, it might be prudent to take into consideration the dielectric constant near the site of the reactant (the anion radical) and the product (the dianion).
Synthesis and Antibacterial Activity of Certain Quinoline Derivatives
Authors: Abd-Alla Mohamed A. , Ahmed Abdel-Hamid N. , El-Zohry Maher F. , Omar Farghaly A.
Published: June 2004

Some aryl or heterocyclic mercaptans reacted with 8-quinolyl chloroacetate II or 8-quinolinoxyacetyl chloride IV to give the corresponding 8-quinolyl-α-mercaptoacetate V or 8-quinolyloxy thioacetate VI, respectively. The mercaptans V were oxidized to the corresponding sulfones VII. Some of these compounds were tested for their antimicrobial activities in comparison with tetracycline reference compound.
Synthesis of Some New Chloro Derivatives of Quinazolino[4,3-b]quinazolin-5-one and Tetrazolo[5,4-c]quinazoline
Authors: Abdel-Megeed Mohamed F. , Yassin Salah M. , Saleh Mohamed A.
Published: June 2004

Introducing of chlorine into biologically versatile heterocyclic rings might led to the improvement of their pharmacological activity. Therefore compounds IIa-IIr and IIIa-IIIf were prepared with the aim to combine the pesticidal qualities of heterocyclic nuclei.
Nitriles in Heterocyclic Synthesis: A New Synthesis of Some 4H-Naphthopyrans, 2H-Benzothiopyrans and Their Fused Derivatives
Authors: Harb Abdel-Fattah A. , El-Maghraby Awatef M. , Metwally Saoud A.
Published: June 2004

α,β-Unsaturated nitriles are versatile reagents and their chemistry has received considerable attention. The reactivity of cinnamonitriles I toward active methylene reagents has been extensively utilised for synthesis of pyranes.
Synthesis of 3-(5-Alkyl-4-acetyl(ethoxycarbonyl))-2-propenoates from Derivatives of 3-Phenoxy-2-furylmethylene
Authors: Marchalín Štefan , Mlynárik Vladimír , Staňová Anna , Ilavský Dušan
Published: June 2004

3-(2-Furyl)propenoates IV-VIII were obtained by treatment of 5-phenoxy-2-furylmethylene derivatives I-III with alcoholic hydrogen chloride in one step. The probable transition mechanism of synthons I-III into the 2,4,5-trisubstituted furans is presented. The geometric isomers E-IV, Z-V and Z-VI, isolated in pure form, were transformed into the corresponding acids E-IX, Z-IX and E-X by base-catalyzed hydrolysis. Acid hydrolysis of the 1,3-diketone I afforded (4Z,6Z)-6-acetyl-7-hydroxy-2,4,6-octatrien-4-olide (XI). Structure of the products was verified by spectral (IR, UV, NMR and mass) methods.
Biologically Important Physicochemical Properties of Some Cephalosporins
Authors: Škvareninová Katarína , Baláž Štefan , Šturdík Ernest , Veverka Miroslav , Adamcová Jana , Olexová Jana
Published: June 2004

In the series of cephalosporin derivatives, consisting of eight 7-(R1-CH2-CO-NH)cephalosporanic acids and of seven analogical compounds with 3-acetoxymethyl replaced by 3-CH3, physicochemical properties, which are expected to play a role in their antibacterial effects (the transport rate parameters and partition coefficients in the systems 1-octanol-water and 1-octanol-buffer, dissociation constants of the 4-carboxyl group, reactivity towards L-glutathione imitating the nucleophilic groups of the cell components and hydrolysis rate parameters), were determined. Linear dependences were observed between the partition coefficients and the π-constants of the varying substituents as well as between reactivity towards SH-groups of L-glutathione and OH-groups. The relationship between the transport rate parameters and partition coefficients, both measured in buffered as well as non-buffered system, was described by a common non-linear equation.
The Uses of Ethyl Cyanobromoacetate in Heterocyclic Synthesis: Novel Synthesis of Thiophene, Pyrazolo[3,4d]thiazole and Thieno[2,3d]pyridazine Derivatives
Authors: Mohareb Rafat Milad , El-Kousy Salah , El-Torgoman Abdel Monem
Published: June 2004

The reaction of active methylene reagents Ia-Ie with phenyl isothiocyanate in basic N,N-dimethylformamide solution followed by cyclization with ethyl cyanobromoacetate II affords the acyclic thioether derivatives IVa-IVe. The use of IVa-IVe in heterocyclic synthesis was described.
Enthalpy of Hydrogen Absorption in Palladium Deposited on Al2O3 and TiO2 Supports
Authors: Paseka Ivo
Published: June 2004

The potentials of the Pd/TiO2 and Pd/Al2O3 catalysts were measured during saturation with hydrogen and during oxidation of the absorbed hydrogen with Ce(IV) in the medium of 0.5M-H2SO4. From the potential values attained in the coexistence region of the α- and β-hydride phases the enthalpy of hydrogen absorption, ∆Hab in Pd deposited on various supports was evaluated. With standard supports Degussa, ∆Hab approaches the value measured on Pt black; a marked decrease of the absorption enthalpy was observed on the support TiO2 of domestic provenience.
Liquid Chromatography of Diethyldithiocarbamate Complexes of Cadmium, Lead, Chromium, Cobalt and Mercury
Authors: Svoboda Ladislav , Prokeš Petr
Published: June 2004

The conditions of chromatographical analysis have been studied and the elution data have been determined of diethyldithiocarbamate complexes of cadmium, lead, chromium, cobalt, and mercury using an octadecylsilica gel column and mobile phases water-methanol containing sodium diethyldithiocarbamate. The method is based on a direct injection of aqueous solution of the metal ions into the column and detection of the separated complexes by means of a UV detector in the wavelengths interval of 254-365 nm.
Effect of Errors in Temperature Measurement on the Accuracy of Composition of the Liquid-Vapour Phases and Their Impact on the Calculated Number of Theoretical Stages of Rectification Columns
Authors: Dojčanský Ján , Bafrncová Soňa , Surový Július
Published: June 2004

The effect of random and systematic errors in the determination of the equilibrium temperature on the phase composition in isobaric L-G equilibria was simulated on five binary systems with different size and relative volatility. The impact of the inaccuracies on the calculated number of theoretical stages of a continuously operating rectification column is discussed with respect to the different operating conditions of the separatory process.
The Effect of Interparticle Heat and Mass Transfer on the Behaviour of Catalytic Adiabatic Reactors with Endothermic Reactions. I. The Reactor Model
Authors: Horák Josef , Červenková Simona
Published: June 2004

The effect of gas-particle heat and mass transfer on the reaction rate and the catalyst temperature in an adiabatic reactor with strongly endothermic reaction was studied using a mathematical model. It was found that subcooling of the catalyst surface against the reaction mixture is the prevailing phenomenon affecting the effectiveness factor and the longitudinal profile of the reaction rate.
Preparation and Structural Characterization of Cyanatocopper(II) Complexes with Substituted Piperidines
Authors: Mašlejová Anna , Hvastijová Mária , Kohout Jiří
Published: June 2004

Coordination geometry of the newly prepared complex compounds of [Cu(NCO)2L2] type (L is piperidine, 2-methylpiperidine, 4-methylpiperidine and 2,6-dimethylpiperidine) was investigated at room temperature utilizing the results of infrared, electronic and ESR spectra and magnetic moments. All complexes show a tetragonal arrangement with small axial interaction depending on steric properties of the piperidine ligand given.
Coupling Kinetics of Benzenediazonium Ions with 2,6-Dioxo-3-(p-substituted phenylhydrazono)-1,2,3,6-tetrahydropyridine-4-carboxylic Acid
Authors: Horáčková Jaroslava , Štěrba Vojeslav
Published: June 2004

The kinetics have been measured of the reactions of 4-nitro-, 4-chloro-, and 4-methoxybenzenediazonium ions with substituted phenylazo derivatives of citrazinic acid in buffer solutions, and the pKa values of the corresponding monoazo and bisazo compounds have been estimated. The reactions of 4-nitrobenzenediazonium ion with 4-chloro- and 4-methoxyphenylazo derivatives and of 4-chlorobenzenediazonium ion with 4-methoxyphenylazo derivative were accompanied by a partial replacement of the substituted phenylazo group by the 4-nitro- and 4-chlorophenylazo groups, respectively. The reactions of 4-chloro- and 4-methoxybenzenediazonium ions are subject to general base catalysis, the rate-limiting step consisting in the splitting off of the proton from the tetrahedral intermediate; with 4-nitrobenzenediazonium ion the reaction rate is limited by the formation of the tetrahedral intermediate.
Preparation of New Organic Luminophores Based on 3,5-Diacetylpyridines
Authors: Lhoták Pavel , Kurfürst Antonín
Published: June 2004

The reaction of acetylacetone or sodium salt of oxymethyleneacetone with corresponding aldehydes has been used to prepare 3,5-diacetyl-1,4-dihydropyridines III which have been oxidized to diacetylpyridines VII. These compounds have been transformed by an acid-catalyzed reaction with benzaldehyde into the chalcones VIII which have been utilized for the Kröhnke synthesis of luminophoric terpyridines I and II.
Acylation of the N-Terminus of B2 Bradykinin Antagonists with Bulky Substituents Dramatically Increases Potency
Authors: Lammek Bernard , Ito Yasushi , Gavras Irene , Gavras Haralambos
Published: June 2004

While studying structural factors which can influence B2 antagonistic activity we designed and synthesized five new bradykinin (BK) antagonists. Two of them, namely Aaa[D-Arg0, Hyp3, D-Phe7, Leu8]BK and Aca[D-Arg0, Hyp3, D-Phe7, Leu8]BK are among the most potent B2-antagonists of exogeneous BK described to date. The remaining three analogs are also potent B2-antagonists. None of the new compounds contain Thi at position 5 and 8, a change that markedly reduces their cost. The new antagonists have obvious potential as valuable pharmacological tools in the investigation of the role of endogenous BK in cardiovascular regulation.