bluuebunny/crossref_metadata_2025 huggingface dataset:
Chiral Organic Ion Pair Catalysts Assembled Through a Hydrogen-Bonding Network
Authors: Uraguchi Daisuke , Ueki Yusuke , Ooi Takashi
Published: August 2009

Catalytic Assembly

Most asymmetric catalysts employed in organic chemistry are assembled through binding of chiral ligands to one or more metal ions.

Uraguchi
et al.

(p.
120
, published online 27 August) show that a highly selective catalyst can assemble through hydrogen bonding from a small collection of small molecules in the absence of metals. In the solid state, the catalyst comprises a central chiral phosphonium cation bound to two phenol molecules, which in turn bind a charge-compensating phenoxide ion. In solution, an oxazolone derivative appears to be able to bind in place of the phenoxide, spurring its stereoselective addition to a broad range of esters.
Nitrous Oxide (N
2
O): The Dominant Ozone-Depleting Substance Emitted in the 21st Century
Authors: Ravishankara A. R. , Daniel John S. , Portmann Robert W.
Published: August 2009

Unwelcome Dominance

Stratospheric ozone is depleted by many different chemicals; most prominently, chlorofluorocarbons (CFCs) responsible for causing the Antarctic ozone hole. Nitrous oxide is also an ozone-depleting substance that has natural sources in addition to anthropogenic ones. Moreover, unlike CFCs, its use and emission are not regulated by the Montreal Protocol, which has helped to reverse the rate of growth of the ozone hole. Surprisingly,

Ravishankara
et al.

(p.
123
, published online 27 August; see the Perspective by

Wuebbles

) now show that nitrous oxide is the single greatest ozone-depleting substance that, if its emissions are not controlled, is expected to remain the dominant ozone-depleting substance throughout the 21st century. Reducing nitrous oxide emissions would thus enhance the rate of recovery of the ozone hole and reduce the anthropogenic forcing of climate.
Much Hype and Many Errors
The Link
Uncovering Our Earliest Ancestor

by Colin Tudge, with Josh Young

Little, Brown, New York, 2009. 304 pp. $25.99, C$28.99. ISBN 9780316070089.
Authors: Kay Richard F.
Published: August 2009

This account of
Darwinius masillae
, its discovery, and its importance was rushed into print as part of the hype surrounding the public announcement of the work.
Mycotic Keratitis Due to
Aspergillus nomius
Authors: Manikandan Palanisamy , Varga János , Kocsubé Sándor , Samson Robert A. , Anita Raghavan , Revathi Rajaraman , Dóczi Ilona , Németh Tibor Mihály , Narendran Venkatapathy , Vágvölgyi Csaba , Manoharan Chockaiya , Kredics László
Published: August 2009

We report the first known case of fungal keratitis caused by
Aspergillus nomius.
Ocular injury was known as a predisposing factor. The patient was treated with natamycin and econazole eye drops, itraconazole eye ointment, and oral ketoconazole. A therapeutic penetrating keratoplasty was performed 16 days after presentation. A sequence-based approach was used to assign the isolate to a species.
Broth Microdilution Method To Detect Extended-Spectrum β-Lactamases and AmpC β-Lactamases in
Enterobacteriaceae
Isolates by Use of Clavulanic Acid and Boronic Acid as Inhibitors
Authors: Jeong Seok Hoon , Song Wonkeun , Kim Jae-Seok , Kim Han-Sung , Lee Kyu Man
Published: August 2009

This study was designed to evaluate the performance of the broth microdilution (BMD) method to detect production of extended-spectrum β-lactamases (ESBLs) and AmpC β-lactamases in
Enterobacteriaceae
by using clavulanic acid (CA) and boronic acid (BA) as ESBL and AmpC β-lactamase inhibitors, respectively. A total of 100 clinical isolates of
Enterobacteriaceae
were analyzed. Mueller-Hinton broth containing serial twofold dilutions of cefotaxime (CTX), ceftazidime (CAZ), aztreonam (ATM), or cefepime (FEP) with or without either or both CA and BA was prepared. An eightfold or greater decrease in the MIC of CTX, CAZ, ATM, or FEP in the presence of CA and BA was considered a positive result for ESBL and plasmid-mediated AmpC β-lactamase (PABL), respectively. In tests with CA, expanded-spectrum β-lactams containing BA (CTX-BA, CAZ-BA, ATM-BA, and FEP-BA) showed higher positive rates in detecting ESBL producers than those without BA. The combination of CTX- and CAZ-based BMD tests with CA and BA showed sensitivity and specificity of 100% for the detection of ESBLs and PABLs. The BMD testing could be applicable for routine use in commercially available semiautomated systems for the detection of ESBLs and PABLs in
Enterobacteriaceae
.
Blocking Hepatitis C Virus Infection with Recombinant Form of Envelope Protein 2 Ectodomain
Authors: Whidby Jillian , Mateu Guaniri , Scarborough Hannah , Demeler Borries , Grakoui Arash , Marcotrigiano Joseph
Published: August 2009

More than 120 million people worldwide are chronically infected with hepatitis C virus (HCV), making HCV infection the leading cause of liver transplantation in developed countries. Treatment is limited, and efficacy depends upon the infecting strain and the initial viral load. The HCV envelope glycoproteins (E1 and E2) are involved in receptor binding, virus-cell fusion, and entry into the host cell. HCV infection proceeds by endosomal acidification, suggesting that fusion of the viral envelope with cellular membranes is a pH-triggered event. E2 consists of an amino-terminal ectodomain, an amphipathic helix that forms a stem region, and a carboxy-terminal membrane-associating segment. We have devised a novel expression system for the production of a secreted form of E2 ectodomain (eE2) from mammalian cells and performed a comprehensive biochemical and biophysical characterization. eE2 is properly folded, as determined by binding to human CD81, blocking of infection of cell culture-derived HCV, and recognition by antibodies from patients chronically infected with different genotypes of HCV. The glycosylation pattern, number of disulfide bonds, oligomerization state, and secondary structure of eE2 have been characterized using mass spectrometry, size exclusion chromatography, circular dichroism, and analytical ultracentrifugation. These results advance the understanding of E2 and may assist in the design of an HCV vaccine and entry inhibitor.
Human Immunodeficiency Virus Type 1 Envelope gp120-Induced Partial T-Cell Receptor Signaling Creates an F-Actin-Depleted Zone in the Virological Synapse
Authors: Vasiliver-Shamis Gaia , Cho Michael W. , Hioe Catarina E. , Dustin Michael L.
Published: August 2009

Cell-to-cell transmission of human immunodeficiency virus type 1 (HIV-1) occurs via a virological synapse (VS), a tight cell-cell junction formed between HIV-infected cells and target cells in which the HIV-1-infected cell polarizes and releases virions toward the noninfected target cell in a gp120- and intercellular adhesion molecule 1 (ICAM-1)-dependent process. The response of the target cell has been less studied. We utilized supported planar bilayers presenting gp120 and ICAM-1 as a reductionist model for the infected-cell membrane and investigated its effect on the target CD4 T cell. This study shows that HIV-1 gp120 interaction with its receptors is initially organized into microclusters that undergo F-actin-dependent consolidation into a central supramolecular activation complex (cSMAC). Src kinases are active in both gp120 microclusters and in the VS cSMAC. The early T-cell receptor (TCR) signaling machinery is partially activated at the VS, and signaling does not propagate to trigger Ca2+elevation or increase CD69 expression. However, these partial TCR signals act locally to create an F-actin-depleted zone. We propose a model in which the F-actin-depleted zone formed within the target CD4 T cell enhances the reception of virions by releasing the physical barrier for HIV-1 entry and facilitating postentry events.
Competitive chemical reactions in DC polarography: Influence of fast protonation equilibria on CE and ECE mechanisms
Authors: Muñoz Eulogia , Avila José L. , Ruiz Juan J. , Camacho Luis
Published: August 2009

We carried out a DC polarographic study of the limiting current for CE and ECE processes with chemical stages subject to potential catalytic effects and in direct competition with protonation reactions in quasi-equilibrium. The aforesaid competition may result in the appearance of maxima in the limiting current vs pH plots for CE mechanisms. We established the conditions required for the rise of such maxima, and developed methods for the calculation of kinetic parameters. The competition did not result in any maxima in the above-mentioned plots for ECE mechanisms; however, we established criteria for their potential identification.
In situ observation using a scanning tunneling microscope of a local morphological light-induced transformation of n-molybdenumdisulfide in contact with acetonitrile containing a small amount of water
Authors: Sakamaki Kenji , Hinokuma Kohichiroh , Fujishima Akira
Published: August 2009

A scanning tunneling microscope (STM) under photoelectrochemical control was used to expand the understanding of nanometer scale in situ photoelectrochemical processes at an n-MoS2/acetonitrile interface. A local morphological light-induced transformation occurred around a MoS2(0001) surface depression. This morphological transformation was attributed to the n-MoS2 photoelectrochemical reaction which was controlled by a small amount of water contained in the acetonitrile. After visible light illumination (276 s), photoelectrochemical reactions under anodic polarization transformed the original depression into a "right-angled triangular" type depression.
Catalytic effects in the electrochemical reactions involving nickel and cysteine. Voltammetric studies
Authors: Banica Florinel Gabriel , Diacu Elena
Published: August 2009

The electrode reactions in the nickel-cysteine system at pH-values around 7 were studied by cyclic voltammetry on the hanging mercury drop electrode. The following processes are induced by cysteine:1) the catalytic reduction of the nickel ion; 2) the anodic dissolution of the nickel amalgam by a catalytic mechanism; 3) the catalytic evolution of hydrogen. Some analogies with the behaviour of the nickel center in hydrogenase are suggested.
Ion-selective electrode and enzyme sensors for flow-type environmental analysis
Authors: Thomas J. D. R.
Published: August 2009

Illustrative examples from researches in the author’s laboratories are given of potentiometric ion-selective electrodes (ISEs) and catalytic membrane amperometric electrodes suitable for environmental analysis. The uses of sulphide ISEs are demonstrated for monitoring the activities of sulphate-reducing bacteria, in effluent analysis for sulphide, and in process/effluent analysis for sulphide, thiols and polysulphides. Diquat and paraquat ISEs are discussed in relation to their optimisation in terms of appropriate crown ether and ion-pairing agents, together with prospects of their uses. Catalytic membrane systems for use in electrochemical analysis may be based on metal oxide catalysts or enzymes. The best of the new metal oxide catalysts for hydrogen peroxide analysis in association with an oxygen electrode is based on manganese dioxide and offers an alternative to lead dioxide and catalase. An alternative membrane system for use with a platinum electrode is peroxidase in association with a mediator in order to permit a low potential approach for hydrogen peroxide sensing. Hydrogen peroxide is a product of many oxidase catalysed reactions and its electrochemical detection permits the analysis of a wide range of substrates, illustrated here for glucose in various food products and hypoxanthine in the spoilage of fish meats.
Polarographic determination of alkaline earths with azo dyes
Authors: Kopanskaya L. S. , Meryan V. T. , Smelov V. A.
Published: August 2009

Magnesium and calcium can be determined in an alkaline medium as complexes with azo dyes by square-wave polarography on the dropping mercury electrode or by linear sweep voltammetry on the hanging mercury drop. The linear dependence of current on magnesium concentration in the presence of IREA magnezone is valid within half an order; in the presence of calcone in a wider range. The lower limit of determination is 2.10-7 mol 1-1. The dependence of current on calcium concentration in the presence of calcion is linear within the interval of 5.10-7 to 4.10-6 mol 1-1 in the voltammetric determination with accumulation.
Discharge of chemical and electrochemical manganese dioxides in nonaqueous electrolytes
Authors: Ilchev Nikolai , Manev Vesselin , Banov Branimir , Momchilov Anton
Published: August 2009

The rate of lithium ion insertion in different types of manganese dioxide, depending on their pretreatment temperature, was investigated. To obtain maximum utilization at heavy discharge drains, the optimum thermal pretreatment temperature for different chemical and electrochemical manganese dioxides (CMD and EMD) was determined. For most types of MnO2 samples this temperature is 300 °C. The manganese dioxides studied display a correlation between their specific surface area and specific capacity by weight. The specific capacity by volume of different CMD and EMD samples was compared in lithium button cells. Their specific electrochemical characteristics were studied at high discharge rates in a wide temperature range. Owing to its high utilization CMD Faradiser M appears to be an excellent cathode material, especially at heavy discharge drains and low temperatures.
Galvanostatic study of the kinetics of lithium deposition on platinum electrode in dimethylformamide
Authors: Xu Dafeng , Cai Shengmin , Wu Xizun , Zhang Wenzhi
Published: August 2009

The deposition of lithium in dimethylformamide (DMF) has been studied by means of galvanostatic measurements. The overpotential was recorded during constant current pulses of so short a duration that only a few monolayers per pulse were deposited. The experiments were carried out under conditions of minimum contamination of the metal surface. The deposition process of Li in DMF is irreversible, the electron transfer being the rate-determining step. A mechanism of Li electrodeposition in DMF was proposed.
A selective INEPT experiment for the assignment of NMR lines of low-gyromagnetic ratio nuclei through long-range couplings
Authors: Blechta Vratislav , Schraml Jan
Published: August 2009

A selective variant of the standard INEPT experiment is suggested. The selectivity is achieved by replacing the refocusing proton pulses of the standard INEPT pulse sequence with selective (DANTE) 180° pulses. Since this approach eliminates the undesirable influences of homo- and heteronuclear couplings, the sensitivity of the method is high. In the case of assigning 29Si NMR lines of trimethylsilylated compounds the pulse sequence can be further simplified and a pair of refocusing pulses can be eliminated from the refocusing period. Advantages of the simplified method are demonstrated.
Mass transport to a vibrating electrode
Authors: Kimla Arnošt , Míčka Jiří , Olyšar Karel
Published: August 2009

The present work is concerned with the concentration field near an electrode located on a vibrating plate. A mathematical model is proposed to describe the hydrodynamic behaviour of a steaming electrolyte solution and of the resulting concentration distribution at the vibrating plate. The results of numerical calculations were used to derive an empirical formula for the concentration gradient as function of dimensionless parameters. The influence of the electrode width and of the width of the vibrating plate on the value of the diffusion flux was also determined.
Reduction of Eu(III) on rotating disc Pt and Cu electrodes
Authors: Loučka Tomáš , Němec Jaroslav
Published: August 2009

The reduction of Eu(III) on rotating disc Pt and Cu electrodes was studied in the medium of chlorides containing some other rare earth elements. The rate constants of the electrode reaction Eu3+ ⇆ Eu2+ were determined and compared with the values obtained earlier by cyclic voltammetry.
Transient convective diffusion to a uniformly accessible surface under aparent slip conditions
Authors: Wein Ondřej
Published: August 2009

Analytical solutions are given to a class of unsteady one-dimensional convective-diffusion problems assuming power-law velocity profiles close to the transport-active surface.
Carbon-13 substituent-induced chemical shifts in benzene derivatives: Substituted anilines
Authors: Buděšínský Miloš , Johnels Dan , Edlund Ulf , Exner Otto
Published: August 2009

Carbon-13 NMR spectra are reported for 59 meta- and para-substituted anilines in deuterochloroform or in its mixture with hexadeuterodimethyl sulphoxide. The substituent-induced chemical shifts (SCS) of ring carbon atoms in position 4 correlate well with dual substituent parameters (DSP). In the remaining positions correlations are not satisfactory with any kind of known substituent constants. There is, however, a close resemblance between SCS in the same position of meta- and para-substituted anilines and even in other series of aromatic compounds.
Dimeric pyrroline alkaloids from Lilium candium L.
Authors: Haladová Mária , Eisenreichová Eva , Bučková Anna , Tomko Jozef , Uhrín Dušan , Ubik Karel
Published: August 2009

Dimeric compounds 5,5’-oxydi(3-methyl-3-pyrrolin-2-one) and 5-hydroxy-3-methyl-1-(3’-methyl-2’-oxo-3’-pyrrolin-2-one were isolated from bulbs of Lilium candidum L., family Liliaceae. Structure of these compounds has been confirmed by spectral measurements. The ether link between two substituted pyrroline rings represents a new type of dimeric alkaloids.
Kinetics and mechanism of the reaction between oxidized cytochrome c and ascorbic acid
Authors: Perez-Benito Joaquin F. , Arias Conchita
Published: August 2009

The reaction between horse-heart cytochrome c and ascorbic acid has been investigated in the pH range 5.5 – 7.1 and at 10.0 – 25.0 °C. The rate shows a first-order dependence on the concentration of cytochrome c, it increases in a non-linear way as the concentration of ascorbic acid increases, it increases markedly with increasing pH and, provided that the ionic strength of the medium is high enough, it fulfills the Arrhenius equation. The apparent activation energy increases as the pH of the solution increases. The results have been explained by means of a mechanism that includes the existence of an equilibrium between two forms (acidic and basic) of oxidized cytochrome c: cyt-H+ -Fe3+ + OH- cyt -Fe3+ + H2O, whose equilibrium constant is (6.7 ± 1.4). 108 at 25.0 °C, the acidic form being more reducible than the basic one. It is suggested that there is a linkage of hydrogenascorbate ion to both forms of cytochrome c previous to the redox reactions. Two possibilities for the oxidant-reductant linkage (binding and adsorption) are discussed in detail.
Dipole moment of the charge transfer complex 1-ethyl-4-methoxy carbonyl pyridinium iodide
Authors: Mohammad Mahboob , Khan Athar Yaseen , Iqbal Rashid , Khan Intisar Ahmed , Mahmood Tariq
Published: August 2009

Dipole moment of a biologically important model compound: Charge transfer complex 1-ethyl-4-methoxy carbonyl pyridinium iodide was determined experimentally. A three component method was employed for this purpose, which is especially useful for determining the dipole moment of a salt insoluble in nonpolar solvents. The experimental dipole moment of this compound, hitherto unmeasured, was found to be (37.7 ± 1.0) . 10-30 C m against the theoretical (contact) ion pair value of 46.4 . 10-30 C m.
Comparison of MgO-supported Ni-Mo hydrodesulfurization catalysts prepared by impregnation and by precipitation-adsorption in emulsion
Authors: Koloušek Vladimír , Pálka Pavel , Hillerová Eva , Zdražil Miroslav
Published: August 2009

Magnesia-supported Ni-Mo sulfide catalysts were prepared by several versions of aqueous impregnation method and by the unconventional method of precipitation-adsorption of sulfides in emulsion water-toluene. The activity of catalysts was tested in hydrodesulfurization of thiophene at pressure of 1.6 Mpa. The samples of Ni-Mo/MgO prepared by impregnation exhibited only 15 – 30% of the activity of Ni-Mo/Al2O3 catalysts Shell 324; the principle obstacle was found to be chemical and hydrothermal instability of MgO with high surface area. The activity of samples prepared by precipitation-adsorption was not much lower than that of the impregnated catalysts; this was taken as an indirect evidence of the acid-base interaction between sulfides and MgO surface. It was concluded that the course of low activity of Ni-Mo/MgO catalysts was textural and not chemical; surface area of Ni-Mo active phase in MgO-supported catalysts was supposed to be lower than in Al2O3-supported catalysts.
The voltammetric determination of 4-nitrobiphenyl
Authors: Barek Jiří , Malik Gulamustafa , Zima Jiří
Published: August 2009

Optimum conditions were found for the determination of 4-nitrobiphenyl by fast scan differential pulse voltammetry at a hanging mercury drop electrode in the concentration range 1 . 10-5 to 2 . 10-7 mol l-1. A further increase in sensitivity was attained by adsorptive accumulation of this substance on the surface of the working electrode, permitting determination in the concentration range (2 – 10) . 10-8 mol l-1 with one minute accumulation of the substance in unstirred solution or (2 – 10) . 10-9 mol l-1 with three-minute accumulation in stirred solution. Linear scan voltammetry can be used to determine 4-nitrobiphenyl in the concentration range (2 – 10) . 10-9 mol l-1 with five-minute accumulation in stirred solution, with the advantage of a smoother baseline and smaller interference from substances that yield only tensametric peaks.
Design and scale-up of Venturi-tube gas distributors for bubble column reactors
Authors: Zahradník Jindřich , Rylek Milan
Published: August 2009

General principles of ejector distributors performance are surveyed and demonstrated for two particular cases of Venturi tubes commonly employed for gas dispersion in tower reactors with forced liquid circulation. Design recommendations for the two types of Venturi-tube gas distributors are presented and a general method is outlined for ejector distributors scale-up, based on the decisive effect of energy dissipation rate on the distributors performance. As an illustration, the specific case of Venturi-tube gas distributor design for an industrial reactor for catalytic hydrogenation of rape-seed oil is treated in detail. The procedure included design of a small-scale laboratory reactor for kinetic experiments at real process conditions (scale-down step) and subsequent ejector distributor scale up to dimensions corresponding to the industrial reactor (vessel diameter 1.6 m, effective reactor volume ~ 5 m3). Comparison with other modes of gas dispersion proved superiority of Venturi-tube distributors both on the laboratory- and industrial-scale level, regarding the overall rate of reaction process achieved and/or catalyst load requirements.
Polyhedral platinadicarbaborane chemistry. The molecular structure and some NMR properties of [9,9-(PPh3)2-arachno-9,5,6-PtC2B7H11]
Authors: Štíbr Bohumil , Baše Karel , Jelínek Tomáš , Fontaine Xavier L. R. , Kennedy John D. , Thornton-Pett Mark
Published: August 2009

The reaction of [Pt(PPh3)4] with [arachno-4,5-C2B7H13] in benzene solution at room temperature yields the arachno ten-vertex platinadicarborane [9,9-( PPh3)2-arachno-9,5,6-PtC2B7H11] as white air-stable needles (80%). Crystals are monoclinic, space group P21/n, with a = 1 433.9(3), b = 1 495.9(3), c = 1 852.5(4) pm, β = 105.89(2)°, and Z = 4. From 5 193 observed [I < 2σ(I)] data, the final R(RW) were 0.0376(0.0374) (406 variables). The structure is based on an arachno {B10H142-}-type ten-vertex {PtC2B7} skeleton with the Pt and two C atoms respectively in the 9,5 and 6 positions in the open face. The assigned 11B and 1H NMR chemical shifts have been measured and are briefly compared to those of the [arachno-4,5-C2B7H13] substrate.
An ESR study of UV-irradiated solutions of tetramethylammonium mercaptoundecahydro-closo-dodecaborate(2-) at 77 K
Authors: Stopka Pavel , Štrouf Oldřich
Published: August 2009

The superoxide anion-radicals O2·- are generated by the ultraviolet irradiation of air- or oxygen-saturated aqueous solutions of tetramethylammonium mercaptoundecahydro-closo-dodecaborate(2-) at 77 K. The superoxide anion-radicals are formed from the oxygen molecule coordinated on the mercaptoundecahydro-closo-dodecaborate dianion. In the absence of this dianion no O2·- are generated. By the irradiation in the presence of hydrogen peroxide the formation of the superoxide anion-radicals is more intensive than in the presence of oxygen only. Simultaneously with O2·- generation the corresponding thiol radicals are formed. These radicals give the disulfide compound [B12H11S]24-. A possible role of sulfur-centered radicals in the autoxidation transformations of the mercaptoundecahydro-closo-dodecaborate dianion is discussed.
Interfacial bahaviour of indolecarboxylic acids and structural parameters
Authors: Benedetti Luca , Fontanesi Claudio , Camurri Giulio , Battistuzzi Gavioli Giovanna
Published: August 2009

The adsorption at the mercury/aqueous solution interface of the 3-, 4-, 5-indolecarboxylic acids in their anionic form has been characterized. The thermodynamic analysis has shown that the process is mainly determined by the interaction of the planar aromatic system with the mercury surface and well described by a Frumkin type isotherm. From the experimental values of the electrosorption valency (γN) and using the model proposed by Schultze a relation between the partial charge transfer (λ) and the repulsive Frumkin interaction parameter has been found. At least, the interfacial activity of the aromatic anions is also discussed on the basis of localized (charge densities) and delocalized (frontier MO energies) theoretical parameters.
Determination of europium by AAS with electrothermal atomization
Authors: Komárek Josef , Gánóczy Mojmír
Published: August 2009

A WETA all-tungsten atomizer and a tungsten probe in conjunction with a graphite atomizer were used for the electrothermal atomization of europium. The life of the tungsten probe was extended by combining it with a pyrolytically coated graphite tube fitted with tantalum lining and using argon-hydrogen atmosphere. The sensitivity of europium determination in the tungsten atomizer was increased by adding La3+ in a concentration of 0.02 g l-1.
A comparison of spectrophotometric methods for the determination of uranium
Authors: Jančář Luděk , Jančářová Irena , Havel Josef
Published: August 2009

Some spectrometric and extraction photometric methods for the determination of uranium were compared using pure solutions, a model sample and samples of surface waters and waste waters; the characteristics examined included sensitivity, accuracy, repeatability, time demands and tediousness. Among the most sensitive methods are those based on the use of triphenylmethane dyes in the presence of surfactants; uranium is separated from associate ions by extraction into tri-n-octylamine in an organic solvent and subsequently re-extracted into an aqueous phase. The results compare well with those attained by using methods given in the Czechoslovak State Standard and in the standard of the Czechoslovak Uranium Industry corporation.
The liquid chromatography of cholesterol esters
Authors: Svoboda Ladislav , Krejčová Alena
Published: August 2009

The retention characteristics were found for cholesterol and 19 of its esters with saturated and unsaturated carboxylic acids containing 1 to 22 carbon atoms using high performance liquid chromatography in the normal and reversed-phase systems. HPLC on silica gel in a mobile phase consisting of heptane and 2-propanol or ethyl acetate is especially suitable for analysis of the esters of the lower acids, while chromatography on an octadecyl silica gel sorbent in a water-tetrahydrofuran or acetonitrile-dichlormethane mobile phase can bee successfully used for the separation of esters with acids containing 10–22 carbon atoms, that can differ in the presence of double bonds in the acyl or through cis-trans isomerism.
Application of capillary GC-MS to analyses of wastes from chemical plants. Identification of N-arylphthalimides in naphthalenic pitches
Authors: Čermák Jiří , Sebránek Miloslav , Nývltová Zora , Jirman Josef
Published: August 2009

A number of interesting nitrogen compounds have been identified in naphthalenic pitches and their extracts, viz. N-phenyl, N-methylphenyl, and N-(dimethylphenyl)phthalimides. Their structure has been derived from mass spectral analysis and confirmed by comparison with MS and elution data of the authentic standards prepared. Also discussed are the MS, NMR and chromatographic data of N-arylphthalimides and corresponding N-arylphthalisoimides.
Contribution to the research and development of radiation chambers in steam reforming. Influence of selected parameters on main characteristic quantities
Authors: Stehlík Petr
Published: August 2009

By means of a mathematical model simulating thermal chemical processes taking place in primary reformer radiation chamber, the influence of selected parameters on main characteristic quantities in steam reforming process was investigated. The parameters were divided into inlet parameters on flue gas side, inlet parameters on reaction mixture side and those of radiation chamber geometry. As main characteristic quantities outlet temperature of reaction mixture, maximum temperature of reaction tubes outer surface, outlet temperature of flue gases, absorbed heat, methane conversion into carbon dioxide and carbon monoxide as well as temperature distance from equilibrium were chosen.
Thermodynamic analysis of the deposition of (Ga, Al)As epitaxial layers prepared by the MOCVD technique
Authors: Leitner Jindřich , Voňka Petr , Mikulec Jan , Stejskal Josef , Klíma Přemysl
Published: August 2009

Based on a detailed thermodynamic analysis of the Ga-Al-As-C-H system, starting conditions were determined under with the reaction of trimethylgallium, trimethylaluminium and arsine in hydrogen results in the formation of a single condensed phase, viz. solid (Ga, Al)As. At initial ratios BV/AIII < 1, liquid Ga-Al-As and solid Al4C3 are also formed. At high initial concentrations of the AIII-element alkyl derivatives, solid graphite also emerges, particularly at elevated temperatures and reduced pressures. The calculated composition of the solid (Ga, Al)As is compared with experimental data.
Hydrogen bonds in derivatives of N-substituted N’-benzoyl- and N’-(2-chlorobenzoyl)thiourea
Authors: Hritzová Oľga , Koščík Dušan
Published: August 2009

Intramolecular hydrogen bonds of the N-H···O=C type have been detected in the derivatives of N-substituted N’-benzoyl- and N’-(2-chlorobenzoyl)thiourea on the basis of IR spectral studies. The title compounds can exist in two tautomeric forms.
Sesquiterpene lactones in mongolian Saussurea lipshitzii
Authors: Todorova Milka N. , Ognyanov Iliya V. , Shatar Sanduin
Published: August 2009

Five known guaianolides were isolated from the areal part of Saussurea lipshitzii(Asteraceae) collected in South Gobi, Mongolia: cynaropicrin (I), janerin (II), chlorojanerin (III), 15-deschloro-15-acetoxychlorojanerin (IV), and 15-deschloro-15-hydroxychlorojanerin (V). The correlation between I-V and the β-configuration of the C-4/C-15 bond in II-V was shown by biomimetic chemical transformations, suggesting compound I as the possible common precursor. (
Changes in DNA conformation and types of mutation induced in CHO dhfr gene by N-2-acetylaminofluorene and N-2-aminofluorene
Authors: Grunberger Dezider , Carothers Adelaide M.
Published: August 2009

Article without abstract
The conformation of some trimethylsilylesters by spectroscopic methods
Authors: Al-Azzawi Souad F. , Jakoubková Marie
Published: August 2009

The doublet structure of v(C=O) bands in the IR absorption spectra of some trimethylsilylesters of carboxylic acids XCOOY [X = CCl3, CCl2H, CClH2, C(CH3)3, CH2Si(CH3)3] indicates conformational heterogeneity. The conformations of these esters were studied by analyzing the changes in IR spectra caused by solvent and temperature effects.
Electrochemical investigation of ternary complexes of Cd(II) with some amino acids (α-alanine and β-alanine) and citrate anions
Authors: Killa Hamada M. , Mabrouk El-Sayed M. , Ghoneim Mohamed M.
Published: August 2009

The ternary complexes of Cd(II) with citrate anions as a primary ligand and amino acids (α-alanine and β-alanine) as a secondary ligand have been investigated using differential pulse polarography. Formation of three mixed complexes, [Cd(amino acid)(citrate)2] and [Cd(amino acid)2(citrate)] is observed in each case. The stability constants and the mixing constants of the ternary system have been calculated, as well as the stabilization constants. The electrochemical reduction was reversible and diffusion controlled. The various equilibria involved in the ternary systems are also given.
Determination of 2,3,7,8-tetrachlorodibenzo-p-dioxin in soil in the presence of large excess of chlorinated hydrocarbons
Authors: Kočan Anton , Zemek Alexandr , Popl Milan
Published: August 2009

The paper describes a method of 2,3,7,8-TCDD determination in soils heavily contaminated with organic compounds ( the soil from areas of plants producing pesticides, chlorophenols, etc.). The procedure is based on a sample extraction with a hexane-acetone mixture, cleaning of the extract by washing with potassium hydroxide and sulfuric acid solution and by liquid chromatography on a multilayer modified silica column and aluminia columns, and on GC/MS determination using a labelled internal standard (13C-2,3,7,8-TCDD). The determination limit is 10 ppt and the average recovery 55%.
Modelling of gaseous phase in bubble columns
Authors: Vašáková Jana , Čermák Jan
Published: August 2009

An axial dispersion model of a bubble column was verified by an experimental method based on pseudo-random binary signals of maximum length. The diameter of the column was 0.292 m and the height of the dispersion layer was 1.33 m. Water formed a stagnant liquid layer and a mixture of air with up to 5 vol.% of CO2 formed a streaming gas phase. The model was evaluated from the response of the bubble column to pseudo-random binary signals and from impulse characteristics calculated from this response by the correlation method. The use of the axial dispersion model with mass transfer was evaluated in dependence on the driving force.
Effect of precipitation and aging on porous structure of aluminium hydroxide. I. Statistical treatment of experimental data
Authors: Roček Josef , Weiss Jindřich , Jirátová Květuše
Published: August 2009

The analysis of variance (ANOVA) was used to test the effect of changes of temperature and pH of precipitation, the time of aging and the addition of surfactants on the porous structure of dried aluminium hydroxide (containing sulphate ions). Changes in precipitation temperature effect the structure of samples, the most pronounced effect being observed in the region of large and small pores. The less distinct effect is exerted by pH of precipitation which affects especially small pores. The time of aging up to 48 h has little effect; it affects the volume of large and medium pores. The addition of surfactants during precipitation and washing leads to the increase of large and medium pores volume. Surfactants eliminate relatively efficiently the effect of aging time. Cationic and nonionic surfactants act similarly, but with different intensity, affecting the porous structure of aluminium hydroxide.
Metal complexes of nitrogen-oxygen donor ligands as potential drugs
Authors: Ibrahim Said A. , El-Gyar Sahar A. , El-Gahami Mohamed A.
Published: August 2009

Twelve new complexes of Cu(II), Ni(II), Co(II) and Cd(II) with 5-phenyl, 5-p-tolyl and 5-aminothioacetimide-azo-8-hydroxyquinoline have been synthesized. The ligands act as bidentate (NO) chelating agents forming the bis-chelate complexes. Analytical, conductivity, spectral and thermal data are consistent with six coordinated structure in the case of Cu(II), Ni(II), Co(II) and four coordinate structure in the case of the analogues Cd(II). It is identified that the metal chelates possess enhanced antibacterial and antifungal activities relative to the free ligands.
3β,11α,17-Trihydroxy-5-pregnen-20-one 11-hemisuccinate as a haptene for RIA of "17α-hydroxypregnenolone"
Authors: Kasal Alexander , Pokorná Jenny , Zajíček Jaroslav
Published: August 2009

6β,17-Dihydroxy-3α,5-cyclo-5α-pregnan-20-one (VII) and 17-hydroxy-6β-methoxy-3α,5-cyclo-5α-pregnan-20-one (IX) were hydroxylated into the position 11α using Rhizopus nigricans fungi culture, and then selectively converted into haptene XIII for the RIA determination of 3β,17-dihydroxypregn-5-en-20-one (IV).
Conformational studies of Angiotensin II and analogues in dimethyl sulfoxide by 1H NMR: Lability and intramolecular interactions of the tyrosine hydroxyl and histidine imidazole NH protons
Authors: Matsoukas John , Bigam Glen , Yamdagni Raghav , Moore Graham J.
Published: August 2009

1H NMR studies in dimethyl sulfoxide illustrate that the tyrosine hydroxyl proton and the histidine imidazole NH proton in [Sar1]ANGII and analogues are labile at neutral pH but not at acid pH. This is attributable to intramolecular interactions of these groups with negatively charged groups. Methylation or elimination of the Tyr hydroxyl in [Sar1]ANGII and analogues, invokes a small but consistent deshielding effect on the His C-2 and C-4 protons, suggesting an interaction between the Tyr hydroxyl and the His ring. Nuclear Overhauser Effect (NOE) enhancement experiments in {Sar1]ANGII and the Sarmesin analogue [Des1, Tyr(Me)4]ANGII, support the Tyr/His interaction and confirm the presence of a trans His-Pro peptide bond.
The enthalpy of vaporization and the liquid surface curvature
Authors: Svoboda Václav
Published: August 2009

The effect of liquid surface curvature on enthalpy of vaporization is investigated. The limits are found at which this effect begins to manifest itself both for the concave and convex surface.
Preparation of solid superacid catalysts by chemical modification of oxides. II.
Authors: Hochmann Tomáš , Setínek Karel
Published: August 2009

Acid properties of the oxides Al2O3, SiO2, TiO2, SnO2, Sb2O3, ZrO2 and ZrSiO4 were modified by the action of Lewis acids. The acids ( AlCl3, TiCl4, PCl5, SbF5 and P2O5) were deposited on the oxides by sublimation at 150, 250 and 350°C. The strength and number of acid centres of the prepared catalysts and their catalytic activity in hydrocarbon reactions were determined.
Polarographic and voltammetric determination of N,N’-dinitrosopiperazine
Authors: Barek Jiří , Švagrová Ivana , Zima Jiří
Published: August 2009

Polarographic reduction of the genotoxic N,N’-dinitrosopiperazine was studied and its mechanism was suggested. Optimum conditions were established for the determination of this substance by tast polarography over the concentration region of 1 . 10-3 to 1 . 10-6 mol l-1 and by differential pulse polarography on the conventional dropping mercury electrode or by fast scan differential pulse voltammetry and linear sweep voltammetry on a hanging mercury drop electrode over the concentration region of 1 . 10-3 to 1 . 10-7 mol l-1. Attempts at increasing further the sensitivity via adsorptive accumulation of the analyte on the surface of the hanging mercury drop failed. The methods are applicable to the testing of the chemical efficiency of destruction of the title chemical carcinogen based on its oxidation with potassium permanganate in acid solution.
Preferential elimination of hydrogen fluoride from fluorohalo compounds
Authors: Hudlický Miloš
Published: August 2009

Examples of base-promoted eliminations of hydrogen fluoride in preference to other hydrogen halides from vicinal fluorohalo compounds are quoted, and an explanation of the fairly rare preferential elimination of poorer halogen leaving group is offered.
Photolyses and pyrolyses of triterpenoid nitrites
Authors: Sejbal Jan , Klinot Jiří , Buděšínský Miloš
Published: August 2009

Derivatives of 19β,28-epoxy-18α-oleanane and lupane with nitrosyloxy group in positions 1α, 2β, 3α, 3β and 28 (II, V, VIII, X and XXVII, respectively) were subjected to photolysis in solution and in the crystalline state, as well as to pyrolysis. In most cases the products identified were alcohols, ketones, olefins and seco derivatives. Photolysis of 2β-nitrile V in benzene afforded the known 24- and 25-oximino derivatives XV and XVII, photolysis of 1α-nitrite II in the crystalline state led to the little stable form XIX of N-hydroxylactam XXI which in solution was easily converted into the derivative of O-acyl-N-alkylhydroxylamine XXII. Photolysis of crystalline 3β,28-lupanediyl 3-acetate, 28-nitrite XXVII gave 28-norolefins XXX and XXXI and 13β,28-epoxy derivative XXXII.
Strong uterotonic inhibitors – analogs of 1-deamino-8-D-homoarginine-vasopressin with p-substituted phenylalanine in position 2
Authors: Žertová Miroslava , Procházka Zdenko , Barth Tomislav , Slaninová Jiřina , Škopková Jana , Bláha Ivo , Lebl Michal
Published: August 2009

Solid phase methodology on benzhydrylamine or p-methylbenzhydrylamine resin was used for the synthesis of five analogs of deamino-vasopressin with non-coded amino acids. D-homoarginine, in position 8 and p-substituted D- or L-phenylalanine in position 2. Besides the mother analog, [Mpr1, D-Har8]vasopressin (I), [Mpr1, L-Phe(p-Me)2, D-Har8]vasopressin (II), [Mpr1, D-Phe(p-Me)2,D-Har8]vasopressin (III), [Mpr1, L-Phe(p-Et)2, D-Har8]vasopressin (IV) and [Mpr1, D-Phe(p-Et)2, D-Har8]vasopressin (V) were synthesized. All analogs have very low antidiuretic and pressor activities. Analogs containing p-methylphenylalanine of L-configuration and p-ethylphenylalanine of both D- and L-configuration are pressor inhibitors. All analogs substituted in position 2 were found to act as the uterotonic inhibitors, the most potent being [Mpr1, D-Phe(p-Et)2, D-Har8]vasopressin (V) with pA2 = 8.30.
Constructive enumeration of acyclic molecules
Authors: Kvasnička Vladimír , Pospíchal Jiří
Published: August 2009

Simple combinatorial theory of constructive enumeration of rooted trees and trees is suggested. As a byproduct of this approach very simple recursive formulae for numerical (i.e. nonconstructive) enumeration are obtained. The method may be simply generalized for (rooted) trees with edges evaluated by multiplicities and vertices evaluated by alphabetic – atomic symbols. In the process of constructive enumeration the (rooted) trees are represented by unambiguous linear code composed of valences of vertices, edge multiplicities, and atomic symbols assigned to vertices. The elaborated theory may serve as a simple algorithmic background of computer programs for contsructive enumeration of acyclic molecular structures containing heteroatoms and multiple bonds.
Standardization of dilute solutions of EDTA by photometric titration with standard tetraamminecopper(II) titrant
Authors: Mach Vladimír , Kotrlý Stanislav , Říha Václav
Published: August 2009

Direct photometric titration (without an added indicator) using a standard ammoniacal solution of copper(II) prepared from pure copper metal asa primary standard is recommended as a reliable method for the standardization of Na2H2(edta) in 10-3 -5 . 10-4M solutions. The technique of photometric microtitration (720 nm, 50 mm cell) with an increased precision of transmittance reading (s ~10-2%, n > 7) and in optimum medium of pH 4.7 ± 0.4 (acetate buffer) can yield precise results in assays of EDTA (sr ⪬ 10-1%, n = 6-9).
Oxidation of hydrogen sulfide over Fe2O3/Al2O3 catalyst: Influence of support texture and Fe2O3 precursor
Authors: Novák Michal , Zdražil Miroslav
Published: August 2009

Activity and selectivity in hydrogen sulfide oxidation by oxygen on a Fe2O3/α-Al2O3 catalyst was studied at 200°C and atmospheric pressure. Reaction products were sulfur and sulfur dioxide. Two factors influencing catalytic activity were studied: support porous structure and the type of Fe2O3 precursor. The porous structure influenced substantially catalytic activity; mesopores were more active than macropores. The catalysts prepared from Fe(NO3)3 and iron(III) acetylacetonate exhibited comparable activity, the lower activity was found for the catalyst prepared from Fe2(SO4)3. The selectivity to sulfur formation was higher on catalysts containing greater amount of macropores and the value of it changed in the interval 0-85% depending on the type of catalyst.
Heterocyclic quinones: Synthesis of some new heterocyclic quinones from 6-chloroquinoline-5,8-dione hydrochloride
Authors: Yanni Amal S.
Published: August 2009

Interaction of 6-chloroquinoline-5,8-dione hydrochloride with amides and/or thioamides in ethylene glycol afforded oxazolo[5,4-g]quinoline-4,9-dione (III) and thiazolo[5,4-g]quinoline-4,9-dione (V). Using semicarbazide and/or thiosemicarbazide in the above reaction, oxadiazino-, and thiadiazino[6,5-g]quinoline-5,10-diones (VI, VII), respectively, were obtained. Their bactericidal activities have been determined.
Palladium-catalyzed cross-coupling reaction of organostannanes with nucleoside halides
Authors: Hassan Mohamed Ezeldin
Published: August 2009

A general reaction is described for the synthesis of C-5 substituted nucleosides through the coupling of organostannanes with nucleoside-palladium intermediate derived in situ from 5-iodouridine (or 5-iodo-2’-deoxyuridine) and [PdCl2(PPh3)2]. The reaction was used for the synthesis of C-5 aryl, heteroaryl, vinyl, allyl and alkyl substituted nucleosides.
Synthesis and biological activity in GPI test of scyliorhinin I and its analogues modified in position 8 by Leu, Sar and Pro residues
Authors: Rolka Krzysztof , Kupryszewski Gotfryd , Janas Piotr , Myszor Jarosław , Herman Zbigniew S.
Published: August 2009

Three analogues of scyliorhinin I with Gly in position 8 substituted with Leu, Sar and Pro residues, were synthesized by the solid-phase method. The agonistic activity was determined on isolated guinea pig ileum. Analogues with Sar and Pro in position 8 appeared to be significantly more active than scyliorhinin I and the analogues with Leu in this position. For all analogues the Hill cooperativity coefficient is much lower than one suggesting that the interaction of these peptides with tachykinin receptor(s) in not a one-step reaction.
The crystal structure of o-(1,2-dicarba-closo-dodecaborane-1-yl)methyl-cholesterol
Authors: Šubrtová Věra , Petříček Václav , Malý Karel
Published: August 2009

The structure of C2B10H11.CH2C27H45O was determined by X-ray diffraction. This compound crystallizes in the orthorhombic system with the P212121 space group. The unit cell parameters are a = 994.0(4), b = 3 231.0(7), c = 1 039.6(2) pm, V = 3 338 . 106 pm3, Z = 4, calculated density Dc = 1.080Mg m-3. Mr = 542.9, linear absorption coefficient μ(MoK α) = 0.54 cm-1 F(000) = 1 184. Intensities were measured at room temperature, radiation used λ(MoK α) = 71.073 pm. Final R = 0.063 for 2 099 observed independent reflections. The studied molecule is built from ortho-carborane icosahedron connected with the cholesterol through the methylene CH2 group bonded to the icosahedral carbon atom C(B1) (C-C= 151.0(7) pm) and to the oxygen atom of the cholesterol (C-O = 138.3(7) pm). Valence angle C(B1)-C-O = 108(2)°, torsion angle C(B1)-C-O-C(3) = 164(4)°.
Effect of grain size on the vapour phase hydration of monoclinic and triclinic modifications of tricalcium silicate; role of high temperature activation
Authors: Hanafi S. , El-Shafei G. M. S. , Abd El-Hamid B.
Published: August 2009

The hydration of tricalcium silicate (C3S) with three grain sizes of monoclinic (M) and triclinic (T) modifications and on their thermally activated samples were investigated by exposure to water vapour at 80°C for 60 days. The products were investigated by XRD, TG and N2 adsorption. The smaller the particle size the greater was the hydration for both dried and activated samples from (M). In the activated samples a hydrate with 2θ values of 38.4°, 44.6° and 48.6° could be identified. Hydration increased with particle size for the unactivated (T) samples but after activation the intermediate size exhibited enhanced hydration. Thermal treatment at 950°C of (T) samples increased the surface active centers on the expense of those in the bulk. Changes produced in surface texture upon activation and/or hydration are discussed.