bluuebunny/crossref_metadata_2025 huggingface dataset:
Salivaricin 9, a new lantibiotic produced by Streptococcus salivarius
Authors: Wescombe P. A. , Upton M. , Renault P. , Wirawan R. E. , Power D. , Burton J. P. , Chilcott C. N. , Tagg J. R.
Published: February 2011

Salivaricin 9 (Sal9) is a 2560 Da lantibiotic having just 46 % amino acid identity with its closest known homologue, the Streptococcus pyogenes lantibiotic SA-FF22. The Sal9 locus (designated siv) in Streptococcus salivarius strain 9 was partially sequenced and localized to an approximately 170 kb megaplasmid, which also harbours the locus for the lantibiotic salivaricin A4. The entire locus was fully characterized in the draft genome sequence of S. salivarius strain JIM8780 and shown to consist of eight genes, having the following putative functions: sivK, sensor kinase; sivR, response regulator; sivA, Sal9 precursor peptide; sivM, lantibiotic modification enzyme; sivT, ABC transporter involved in the export of Sal9 and concomitant cleavage of its leader peptide; and sivFEG, encoding lantibiotic self-immunity. Intriguingly, in contrast to strain 9, the siv locus was chromosomally located in strain JIM8780 – the first lantibiotic locus shown not to be exclusively plasmid-associated in S. salivarius. Sal9-containing extracts specifically induced lantibiotic production in both strain 9 and strain JIM8780, indicating that Sal9 functions as a signal peptide for upregulation of its own biosynthesis. Screening representative strains of three streptococcal species (S. salivarius, S. pyogenes and S. mitis) for sivA indicated that it was present only in S. salivarius, with 12 of 28 tested S. salivarius positive. Since Sal9 was inhibitory to all tested S. pyogenes strains it appears to have potential as an important component of the bacteriocin armoury of S. salivarius probiotics intended to control S. pyogenes infections of the human oral cavity.
Influence of the combination and phase variation status of the haemoglobin receptors HmbR and HpuAB on meningococcal virulence
Authors: Tauseef Isfahan , Harrison Odile B. , Wooldridge Karl G. , Feavers Ian M. , Neal Keith R. , Gray Stephen J. , Kriz Paula , Turner David P. J. , Ala’Aldeen Dlawer A. A. , Maiden Martin C. J. , Bayliss Christopher D. , Shaw J. G.
Published: February 2011

Neisseria meningitidiscan utilize haem, haemoglobin and haemoglobin–haptoglobin complexes as sources of iron via two TonB-dependent phase variable haemoglobin receptors, HmbR and HpuAB. HmbR is over-represented in disease isolates, suggesting a link between haemoglobin acquisition and meningococcal disease. This study compared the distribution of HpuAB and phase variation (PV) status of both receptors in disease and carriage isolates. Meningococcal disease (n = 214) and carriage (n = 305) isolates representative of multiple clonal complexes (CCs) were investigated for the distribution, polyG tract lengths and ON/OFF status of both haemoglobin receptors, and for the deletion mechanism for HpuAB. Strains with both receptors or onlyhmbRwere present at similar frequencies among meningococcal disease isolates as compared with carriage isolates. However, >90 % of isolates from the three CCs CC5, CC8 and CC11 with the highest disease to carriage ratios contained both receptors. Strains with anhpuAB-only phenotype were under-represented among disease isolates, suggesting selection against this receptor during systemic disease, possibly due to the receptor having a high level of immunogenicity or being inefficient in acquisition of iron during systemic spread. Absence ofhpuABresulted from either complete deletion or replacement by an insertion element. In an examination of PV status, one or both receptors were found in an ON state in 91 % of disease and 71 % of carriage isolates. We suggest that expression of a haemoglobin receptor, either HmbR or HpuAB, is of major importance for systemic spread of meningococci, and that the presence of both receptors contributes to virulence in some strains.
Increased level of intragenomic 16S rRNA gene heterogeneity in commensal strains closely related to Haemophilus influenzae
Authors: Nørskov-Lauritsen Niels
Published: February 2011

The 16S rRNA gene sequence of strains closely related to, but excluded from, Haemophilus influenzae was investigated and a conspicuously high number of polymorphic nucleotide positions due to intragenomic 16S rRNA gene heterogeneity was observed. The average frequency of 16S rRNA gene polymorphic nucleotide positions in 31 variant strains was 7.0×10−3, which is approximately ten times the level observed in validated strains of H. influenzae. Sixty-seven polymorphic nucleotide positions in seven strains most likely originated from the simultaneous presence of two distinct types of helix 18 as a consequence of prior recombinatorial events. The increased level of 16S rRNA gene polymorphism in commensal taxa excluded from the pathogenic species H. influenzae is unexplained. The heterogeneity imposes difficulties on rRNA gene-based classification and systematics.
Biome representational in silico karyotyping
Authors: Muthappan Valliammai , Lee Aaron Y. , Lamprecht Tamara L. , Akileswaran Lakshmi , Dintzis Suzanne M. , Lee Choli , Magrini Vincent , Mardis Elaine R. , Shendure Jay , Van Gelder Russell N.
Published: February 2011

Metagenomic characterization of complex biomes remains challenging. Here we describe a modification of digital karyotyping—biome representational in silico karyotyping (BRISK)—as a general technique for analyzing a defined representation of all DNA present in a sample. BRISK utilizes a Type IIB DNA restriction enzyme to create a defined representation of 27-mer DNAs in a sample. Massively parallel sequencing of this representation allows for construction of high-resolution karyotypes and identification of multiple species within a biome. Application to normal human tissue demonstrated linear recovery of tags by chromosome. We apply this technique to the biome of the oral mucosa and find that greater than 25% of recovered DNA is nonhuman. DNA from 41 microbial species could be identified from oral mucosa of two subjects. Of recovered nonhuman sequences, fewer than 30% are currently annotated. We characterized seven prevalent unknown sequences by chromosome walking and find these represent novel microbial sequences including two likely derived from novel phage genomes. Application of BRISK to archival tissue from a nasopharyngeal carcinoma resulted in identification of Epstein-Barr virus infection. These results suggest that BRISK is a powerful technique for the analysis of complex microbiomes and potentially for pathogen discovery.
Degenerations and limit Frobenius structures in rigid cohomology
Authors: Lauder Alan G. B.
Published: February 2011

We introduce a ‘limiting Frobenius structure’ attached to any degeneration of projective varieties over a finite field of characteristicpwhich satisfies ap-adic lifting assumption. Our limiting Frobenius structure is shown to be effectively computable in an appropriate sense for a degeneration of projective hypersurfaces. We conjecture that the limiting Frobenius structure relates to the rigid cohomology of a semistable limit of the degeneration through an analogue of the Clemens–Schmidt exact sequence. Our construction is illustrated, and conjecture supported, by a selection of explicit examples.
Postbuckling of Shear Deformable Geodesically Stiffened Anisotropic Laminated Cylindrical Shell Under External Pressure
Authors: Li Zhi-Min , Lin Zhong-Qin , Chen Guan-Long
Published: February 2011

A boundary layer theory for buckling and postbuckling of anisotropic laminated thin shells is extended to shear deformable stiffened anisotropic laminated shells. A postbuckling behavior is investigated for a shear deformable anisotropic laminated cylindrical shell with geodesical stiffener of finite length subjected to lateral or hydrostatic pressure. The material of each layer of the shell is assumed to be linearly elastic, anisotropic, and fiber-reinforced. The governing equations are based on a higher-order shear deformation shell theory with von Kármán–Donnell-type of kinematic nonlinearity and including the extension/twist, extension/flexural, and flexural/twist couplings. The nonlinear prebuckling deformations and initial geometric imperfections of the shell are both taken into account. A singular perturbation technique is employed to determine the buckling pressure and postbuckling equilibrium paths. The numerical illustrations concern the postbuckling response of perfect and imperfect, moderately thick, geodesically stiffened shells, axial and ring stiffened shells, and unstiffened shells with different values of shell parameters and stacking sequence. The results confirm that there exists a circumferential stress along with an associate shear stress when the shell is subjected to lateral pressure. The postbuckling equilibrium path is stable for the moderately long shell under external pressure and the shell structure is virtually imperfection-insensitive.
Correlation of Gaseous Mass Leak Rates Through Micro- and Nanoporous Gaskets
Authors: Grine Lotfi , Bouzid Abdel-Hakim
Published: February 2011

The present work deals with the theoretical and experimental studies of gaseous flow through tight gaskets. The paper presents an innovative approach to accurately predict and correlate leak rates of several gases through nanoporous gaskets. The new approach is based on the calculation of the gasket porosity parameters (D and N) using a model based on a first order slip flow regime. The model assumes the flow to be continuum but employs a slip boundary condition on the leak path wall. Experimental measured gas flow rates were performed on gaskets with a microscopic flow rate range and isothermal steady conditions. The flow rate is accurately measured using multigas mass spectrometers. The gasket porosity parameters used in the developed leakage rate formula were experimentally obtained for a reference gas (helium) for each stress level. In the presence of the statistical properties of a porous gasket, the leak rates for different gases can be predicted with reasonable accuracy. It was found that the approach that considers the slip flow with the first order combined to the molecular flow covers the prediction of flow rates at the microscopy level and down to 10−8 mg/s very well. Tightness hardening is the result of the saturation of the gasket combined porosity parameters or the equivalent thickness of the void layer.
Incorporation, Release, and Effectiveness of Dexamethasone in Poly(Lactic-Co-Glycolic Acid) Nanoparticles for Inner Ear Drug Delivery
Authors: Wang Youdan , Gao Xinsheng , Kuriyavar Satish , Bourne David , Grady Brian , Chen Kejian , Dormer Kenneth , Kopke Richard D.
Published: February 2011

Poly (D,L-lactide-co-glycolide) (PLGA) particles have been widely used as drug delivery carriers for a variety of payloads. Three forms of dexamethasone (DEX), namely, acetate, base, and phosphate, were incorporated into a PLGA matrix. First, we compared the drug loading efficiency and release kinetics of drug-loaded PLGA particles. Dexamethasone acetate (DEX-Ac) loaded particles exhibited a higher loading efficiency and a more linear release profile of drug as compared with the other forms of DEX particles. Also, we coincorporated oleic acid-coated superparamagnetic iron oxide nanoparticles (SPION) with DEX-Ac into PLGA submicron particles. No differences in size, zeta potential, drug loading, or release kinetics were found between particles prepared with and without SPION. Additionally, particles were applied to an in vitro cochlear, organotypic culture. DEX-Ac PLGA nanoparticles showed a protective effect against 4-hydroxynonenal induced hair cell damage. These results suggest a promising method for inner ear magnetic targeted treatment.
FLane: An Adaptive Fuzzy Logic Lane Tracking System for Driver Assistance
Authors: Reina Giulio , Milella Annalisa
Published: February 2011

In the last few years, driver assistance systems are increasingly being investigated in the automotive field to provide a higher degree of safety and comfort. Lane position determination plays a critical role toward the development of autonomous and computer-aided driving. This paper presents an accurate and robust method for detecting road markings with applications to autonomous vehicles and driver support. Much like other lane detection systems, ours is based on computer vision and Hough transform. The proposed approach, however, is unique in that it uses fuzzy reasoning to combine adaptively geometrical and intensity information of the scene in order to handle varying driving and environmental conditions. Since our system uses fuzzy logic operations for lane detection and tracking, we call it “FLane.” This paper also presents a method for building the initial lane model in real time, during vehicle motion, and without any a priori information. Details of the main components of the FLane system are presented along with experimental results obtained in the field under different lighting and road conditions.
Stability and Interpretation of Autoregressive Models of Terrain Topology
Authors: Wagner Shannon , Ferris John B.
Published: February 2011

Terrain topology is the principal source of vertical excitation into the vehicle system and must be accurately represented in order to correctly predict the vehicle response. It is desirable to evaluate vehicle models over a wide range of terrain, but it is computationally impractical to simulate long distances of every terrain type. A method to characterize terrain topology is developed in this work so that terrain can be grouped into meaningful sets with similar physical characteristics. Specifically, measured terrain profiles are considered realizations of an underlying stochastic process; an autoregressive model provides the mathematical framework to describe this process. The autocorrelation of the spatial derivative of the terrain profile is examined to determine the form of the model. The required order for the model is determined from the partial autocorrelation of the spatial derivative of the terrain profile. The stability of the model is evaluated and enforced by transforming the autoregressive difference equation into an infinite impulse response filter representation. Finally, the method is applied to a set of U.S. highway profile data and an optimal model order is determined for this application.
Closed-Form Solution to Controller Design for Human-Robot Interaction
Authors: Lacevic Bakir , Rocco Paolo
Published: February 2011

This paper deals with controller design for gentle physical human-robot interaction. Two objectives are set up. The first is to establish an analytical framework in order to justify the good features of state of the art controller, recently designed by numerical search of parameter space. The second is to investigate the possibilities to improve the performance of such controller. Our method ensures “prescribed” admittance behavior of the robot, similar to natural admittance controller design but with both more realistic model of the robot and more realistic target admittance. Joining natural admittance approach with the concept of complementary stability allows reaping the benefits of both. Limited knowledge about the environment via structured uncertainty allows a very simple worst-case analysis using elementary tools such as Routh–Hurwitz stability criterion. Consequent relation within the parameters determines an allowed region in the parameter space, where the contact stability is guaranteed. Not surprisingly, on one border of this region, the system behaves exactly the same as when the state of the art controller is employed. In addition, unexpected stability regions are discovered, suggesting theoretical performance improvements.
Mobility Criteria of Planar Single-Loop N-Bar Chains With Prismatic Joints
Authors: Xue Changyu , Ting Kwun-Lon , Wang Jun
Published: February 2011

This paper presents the extension of the N-bar rotatability laws to N-bar chains containing prismatic joints. The extension is based on the principle that a prismatic joint may be regarded as a revolute joint located at infinity in the direction normal to the sliding path. The effects of long and short links, full rotatability, linkage classification, and formation of branches and sub-branches are discussed. The extension provides a consistent method to understand all aspects of linkage rotatability disregarding the existence of prismatic joints. The results are demonstrated by several examples.
Nonsingular Spherically Constrained Clemens Linkage Wrist
Authors: Milenkovic Paul
Published: February 2011

The parallel connection of a revolute-spherical-revolute Clemens linkage with a revolute-universal joint (RU) spherical linkage realizes a two-axis spherical pointing device suitable for use in a robot wrist. The design is derived from a Clemens linkage constant-velocity coupling having a spherical constraint. A novel transverse orientation of the RU linkage facilitates control of the pointing direction through actuation of a pair of revolute joints at the base of the device, a capability not otherwise required when this type of mechanism is employed as a constant-velocity coupling. As the mechanism is confined to spherical space, spherical trigonometry and related geometric reasoning may be employed in the analysis of mobility and actuation. The analysis derives the forward and inverse kinematic relations, showing that the mechanism allows a full 180 deg of deflection of the pointer from the center before encountering a singularity.
Tomography of Reaction-Diffusion Microemulsions Reveals Three-Dimensional Turing Patterns
Authors: Bánsági Tamás , Vanag Vladimir K. , Epstein Irving R.
Published: February 2011

Tomography reveals three-dimensional Turing patterns created by the Belousov-Zhabotinsky reaction running in a microemulsion.
The World’s Technological Capacity to Store, Communicate, and Compute Information
Authors: Hilbert Martin , López Priscila
Published: February 2011

An inventory of the world’s technological capacity from 1986 to 2007 reveals the evolution from analog to digital technologies.
Different B Cell Populations Mediate Early and Late Memory During an Endogenous Immune Response
Authors: Pape Kathryn A. , Taylor Justin J. , Maul Robert W. , Gearhart Patricia J. , Jenkins Marc K.
Published: February 2011

A cell enrichment technique reveals the dynamics of the endogenous memory B cell response.
Decomposition of hydrogen peroxide on cerium dioxide-nickel oxide two-component catalysts and the effect of ionizing radiation on them
Authors: Múčka Viliam
Published: February 2011

Some physical and catalytic properties of cerium dioxide-nickel oxide two-component catalysts have been studied over the entire composition region, employing the decomposition of hydrogen peroxide in aqueous solution as a model catalytic process. The two oxides have been found to affect each other, particularly for NiO contents of 9.1 and 96.7 mol%; the mutual influencing, the nature of which in the conditions applied remains unaffected by heat treatment of the sample or by its exposition to ionizing radiation, is manifested by the nonmonotonic dependences of the oxidation power and of the specific activity of the catalysts on their composition. This can be interpreted in terms of the concept of bivalent catalytic centres, assuming that for nickel oxide the centres consist of Ni2+-Ni3+ ion pairs, for cerium dioxide they consist of Ce3+-Ce4+ ion pairs, and that in the region of the mutual influencing , Ni2+-Ce4+ ion pairs play a major role. Within the scope of this concept, the increase in the oxidation power of all the catalysts in question and a simultaneously decrease in the specific activity of the pure nickeloxide exposed to ionizing radiation can be explained in terms of the ionization effect.
Response in the catalytic properties to presulphidation for promoted and nonpromoted molybdenum hydrorefining catalysts
Authors: Hillerová Eva , López Rafael , Maternová Jindřiška , Peter Rudolf , Zdražil Miroslav
Published: February 2011

The sensitivity of nonpromoted molybdenum catalysts to presulphidation was examined on the adsorption of hydrocarbons and pyridine, hydrodesulphurization of thiophene and benzothiophene, and cracking and dehydrogenation of isopropylbenezene. Published data of other authors concerning the hydrodesulphurization of thiophene and benzothiophene and hydrogenation of cyclohexene were also evaluated. In all cases except the dehydrogenation of isopropylbenzene, the change in the adsorption properties and catalysts activity brought about by the presulphidation were lower for the nonpromoted catalysts than for the promoted ones, thus indicating that cobalt is directly involved in the active surface of CoMo/Al2O3 catalysts.
Determination of trace amounts of heavy metals in foodstuffs by anodic stripping voltammetry. Optimization of apparatus parameters
Authors: Aliakbar Alireza , Popl Milan
Published: February 2011

The use of differential pulse anodic stripping voltammetry in the determination of heavy metals (Cd, Pb, Cu, As) in foodstuffs was studied. Preconcentrating from solutions and dissolution took place on a thin film mercury electrode. A factorial experiment served to determine the effects of variable parameters of the apparatus, a polarographic analyzer: pulse amplitude, pulse period, and potential scan of the working electrode during dissolution. The first two parameters are significant but the scan rate is not. The apparatus parameters were optimized further by the method of response surface fitting near optimum.
13C, 15N, and 19F NMR spectra of 4-fluoro-(3´ or 4´-substituted) azobenzenes
Authors: Lyčka Antonín , Kaválek Jaromír
Published: February 2011

The 13C and 19F NMR spectra of fifteen 4-fluoro-(3´ or 4´-substituted (azobenzenes have been measured. The δ(19F) values correlate with the corresponding σm,p constants (δ(19F) = 3.60σm,p-30.78). The 15N NMR spectra have been measured of six compounds, and additivity of the 15N substitution chemical shifts has been proved. The measured coupling constants are 6J(19F15N) = 2.1 Hz and 7J(19F13C) = 0.7 Hz.
Hydroboration of 1-(3-butenyl)piperidine and 1-(4-pentenyl)piperidine
Authors: Kafka Stanislav , Ferles Miloslav
Published: February 2011

Hydroboration of 1-(3-butenyl)- (Ia and 1-(4-pentenyl)piperidine (Ib) with triethylamineborane followed by hydrolysis and oxidation afforded the appropriate alcohols IIIc and IIIf resp. The spirocyclic amine-borane IIa,b isolated from the hydroboration products were transformed by hydrochloric acid into the hydrochlorides of piperidinealkylboronic acids IVa,b which were oxidized in an alkaline medium with hydrogen peroxide to the primary alcohols IIIc,f. Diethyl ester V was prepared by ethanolysis of IIa.
Some 1-substitution derivatives of 4-aryl-2,3-dihalogeno-1-naphthols
Authors: Křepelka Jiří , Vlčková Drahuše , Mělka Milan
Published: February 2011

Alkylation of derivatives of 4-aryl-1-naphthols (I-V) by 2,3-epoxypropyl chloride in methanolic sodium hydroxide gave epoxy derivatives VI, VIII, IX, XI and XII, apart from products of cleavage of the oxirane ring, VII and X. Analogous alkylation of compounds I, IV and V by 2-(N,N-diethylamino)ethyl chloride hydrochloride in a two-phase medium afforded basic ethers XIII to XV. The cleavage of the oxirane ring in compound VI by the action of primary and secondary amines, piperidine and substituted piperazines led to compounds XVI-XXIV. Reaction of thionyl chloride with compounds XXI, XXII and XXIV gave chloro derivatives XXV-XXVII.Exposure of compound XXII to 4-methylbenzenesulfonyl chloride produced compound XXVIII, retaining the secondary alcoholic group. In an antineoplastic screening in vivo none of the compounds prepared had an appreciable activity. Compound XVII, being an analogue of propranolol, was used in the test of isoproterenolic tachycardia, and showed a beta-lytic effect comparable with that of propranol.
Quantitative relations between structure and activation of fibrinolysis in selected series of arylaliphatic acids
Authors: Kuchař Miroslav , Brunová Bohumila , Rejholc Václav , Jelínková Magda , Holubek Jiří , Němeček Oldřich
Published: February 2011

The paper describes the reaction of arylacetones IX with triethyl phosphonoacetate, producing esters of 4-aryl-3-methyl-2-butenoic acid, X, and 4-aryl-3-methyl-3-butenoic acid, X'. Their hydrolysis gave a mixture of the isomeric acids I and I', whose composition was investigated by 1H NMR spectra. Also prepared were 3-methyl-3-phenyl-2-propenoic acids, II, 2-aryl-2-hydroxypropanoic acids, IV, and substituted α-benzyloxyphenylacetic acids, V. These acids, along with aryloxoaliphatic acids III, were investigated for efficacy in activation of fibrinolysis. The lipophilicites of the acids studied were determined either through the partition coefficients (acids Ia and IIa), using a system n-octanol-water (pH 3.5) or by partition chromatography. The experimental values of log Pwere compared with those calculated from the fragmental constants f and the parameters π. With the acids V the decrease in lipophilicity was similar to that observed with arylalkoxyaliphatic acids. With the acids, I, I' and II the fibrinolytic capacity was linearly proportional to lipophilicity. Although we evaluated fibrinolytic capacity of mixtures of the acids I and I', the linear relation was in agreement with that derived previously for a group of arylaliphatic acids. The presence of a functional group on the connecting chain in the acids III and IV had a negative effect on the fibrinolytic capacity. The decrease in fibrinolytic capacity might be due the functional groups being capable of forming hydrogen bonds.
The tyrosyl and tryptophyl residues of orosomucoid studied by difference and derivative spectrophotometry
Authors: Kálal Petr , Kalous Vítěz
Published: February 2011

The accessibility of the tyrosyl and tryptophyl residues in orosomucoid (an acid α1-glycoprotein) was studied by the methods of temperature-perturbation difference spectrophotometry spectrophotometry and derivative spectrophotometry. It has been found that four residues of tyrosine and one residue of tryptophan are on the surface of the molecule, exposed to the solution. The method of derivative spectrophotometry has been modified to be applicable to proteins containing both tyrosine and tryptophan.
Numerical simulation of a catalytic reaction dynamics in a kinetic region
Authors: Klusáček Karel
Published: February 2011

The method of numerical simulation of a catalytic system dynamics with lumped parameters is reported. Appropriate balance equations have been derived and suitable calculation procedures are discussed. Numerical example of simulation of the catalytic methanol dehydration dynamics is presented and calculated relaxation curves are compared with experimental data obtained earlier.
Preparation and capillary gas chromatography of polymethyl- and ethylmethylbiphenyls and polymethyldiphenylmethanes
Authors: Novrocík Jan , Novrocíková Marta , Foniok Jaroslav
Published: February 2011

Trimethyl-, tetramethyl-, and ethylmethylbiphenyls with the alkyl groups at one aromatic ring have been prepared by the Gomberg reaction and identified by capillary gas chromatography. The products are either chemical individua or mixtures of up to three isomers depending on choice of the aromatic hydrocarbon. The ethylmethylbiphenyls have been prepared as mixed standards only. Most aromatic hydrocarbons used in the Gomberg reaction have been prepared by combination of rectification and sulphonation procedures. The HMO method has been used for calculation of the values of the radical superdelocalizabilities at individual centres of the 1,2,4- and 1,2,3-trimethylbenzene molecules which have been compared with product composition of the Gomberg reactions of these hydrocarbons. Reactivities of the aromatic substrates used in the Gomberg reaction have been compared by the competition technique. Capillary gas chromatography using three columns wetted with non-polar , medium, and polar stationary phases has been used to determine the Kovats indexes of the hydrocarbons prepared and parameters of the linear dependences IApiez.L = k.Istat.phase(2) + q (with the corresponding correlation coefficients). From the elution data of the isomeric methyl- and ethylbiphenyls the increments have been derived for methyl and ethyl groups, and possibility of prediction and assessment of the Kováts indexes of polyalkybiphenyls and dimethyldiphenylmethanes is discussed.
Reactions of 2-(benzimidazol-2-yl)acetonitrile and its N-ethoxycarbonyl derivative with some azol-3-diazonium salts
Authors: Slouka Jan , Bekárek Vojtěch
Published: February 2011

Coupling of 2-(1-ethoxycarbonyl-benzimidazol-2-yl)acetonitrile (II) with 5-methylpyrazol-3-diazonium (IIIa) or indazol-3-diazonium salt (IIIb) does not give the corresponding derivatives VIIa, VIIb of pyrazolo[3,2-c]-1,2,4-triazine but, instead, gives the corresponding 2-(3-azolyl)-1-oxo-1,2-dihydro-1,2,4-triazino-[4,5-a]benzimidazole-4-carbonitriles VIIIa, VIIIb. Coupling of 2-(benzimidazol-2-yl)acetonitrile (I) with the diazonium salt IIIa gives 7-amino-6-(benzimidazol-2-yl)-2-methylpyrazolo[3,2-c]-1,2,4-triazine (VIa) which, on reaction with ethyl chloroformate, undergoes cyclization to 2-methyl-12,13-dihydropyrazolo[3",2":3',4']-1,2,4-triazino[5',6':6,5]-pyrimido[3,4-a]benzimidazol-12-one (IXa). The compound VIa and 1-amino-2-(benzimidazol-2-yl)-1,2,4-triazono[4,3-b]indazole (VIb) are also formed by recyclization of the compounds VIIIa and VIIIb, respectively, in boiling aqueous pyridine.
The synthesis and reactivity of 5-nitro-2-furylacetylene
Authors: Végh Daniel , Kováč Jaroslav
Published: February 2011

This paper describes the preparation of 5-nitro-2-furylacetylene (I), the starting material for the synthesis of 1-iodo-2-(5-nitro-2-furyl)ethylene (II), 3-(5-nitro-2-furyl)propinoic acid (III) and 1,2-bis-(5-nitro-2-furyl)-acetylene (IX), substances possessing antibacterial properties.
Synthesis of 2-(S-aryloxycarbonylthio)ethyl isothiocyanates - Analogues of natural mustard oils
Authors: Kristian Pavol , Gonda Jozef
Published: February 2011

A simple reaction of 2-aryloxythiazolines with thiophosgene leads to formation of 2-(S-aryloxycarbonylthio)ethyl isothiocyanates. The starting thiazolines can easily be obtained from 2-bromoethyl isothiocyanates and phenolates. The structure of the products synthesized was evidenced by spectral methods.
New preparation of steroidal 3-hemisuccinates
Authors: Drašar Pavel , Černý Ivan , Pouzar Vladimír , Havel Miroslav
Published: February 2011

3-Hemisuccinates (3-(3-carboxypropanoates)) XI-XV, derived from cholesterol (I), (20R)-3β-hydroxy-21-norchola-5,22-dien-24 20-olide (II), estrone (III), (20E)-21-methoxycarbonyl-3β-hydroxypregna-5,20-diene (IV) and digitoxigenine (V), were prepared via the mixed succinates of the alcohols I-V and trichloroethanol (3-[4-(2,2,2-trichloroethoxy)-4-oxobutanoates] VI-X). The usual acylation of II and IV with succinic anhydride in pyridine failed.
7-O-Alkyl derivatives of daunomycinone
Authors: Přikrylová Věra , Sedmera Petr , Jizba Josef V. , Vokoun Jindřich , Lipavská Helena , Podojil Miloslav , Vaněk Zdenko
Published: February 2011

Reaction of daunomycinone (I) with alcohols and p-toluenesulfonic acid produces a mixture (~3 : 1) of its (7S)- and (7R)-O-alkyl derivatives II-IX. According to the 1H NMR evidence, the alicyclic ring exists in the 9H8 conformation in (7R)-O-alkyl derivatives, on the contrary to (7S)-epimers and 7-epi-daunomycinone that adopt the 8H9 conformation.
A kinetic study of the inhibiting effect of benzotriazole on the reaction of copper songle crystal in sodium hydroxide aqueous solution
Authors: Miadoková Milica , Šiška Jozef
Published: February 2011

The effect of benzotriazole on the reaction of copper single crystal in aqueous solution of NaOH has been studied by kinetic methods. The mechanism of the inhibiting effect is interpreted in terms of adsorption of benzotriazole anions on the pure metal as well as on its oxides, Cu2O and CuO. The efficiency of inhibition depends on the crystallographic orientation, increasing in the order I100 < I110 < I111.
Evaluation of variations of backmixing in bubble column type fermentors in dependence on the axial coordinate
Authors: Havlík Ivo , Janík Petr , Votruba Jaroslav
Published: February 2011

Analysis of experimental data from a batch column has shown the coefficient of backmixing to increase in dependence on the distance from the column bottom. Limiting values may differ by up to an order of magnitude. Original method has been worked out, based on the method of moments, to process experimental data obtained as a response of the column to a tracer impulse.
Hydrolysis of amidochloro-cyclo-triphosphazenes
Authors: Kouřil Milan , Mezník Lubomír , Dostál Karel
Published: February 2011

It was found by 31P NMR spectroscopy and paper chromatography that amidochloro-cyclo-triphosphazenes N3P3Cl4(NH2)2 and N3P3Cl5NH2 undergo hydrolysis in acidic, neutral, and alkaline medium with preservation of their cyclic skeleton to give triphosphazane anions (NHPO2)33-. As found spectroscopically, the hydrolysis of N3P3Cl4(NH2)2 in acidic medium leads initially to formation of an intermediate of the composition N3P3(OH)4(NH2)2, which speaks for the preferential hydrolytic cleavage of P-Cl bonds compared to exogenic P-NH2 bonds in the molecule of this compoud.
Photochemical reduction of potassium chromate solubilized with 18-crown-6 in chloroform
Authors: Muchová Jana , Holba Vladislav
Published: February 2011

The cyclic polyether 18-crown-6 was used as solubilizer to obtain a solution of potassium chromate in chloroform. While perfectly steady in darkness, the solution decomposes under the action of light. The decomposition reaction was monitored by measuring the decrease in the absorbance of chromate ions, and the rate constants, the temperature coefficient of the rate constant, and the quantum yield were determined. The mechanism of the reaction is discussed.
Analysis of the experimental binding data obtained in the radioimmunoanalysis of thyroxine
Authors: Talán Peter , Mucha Juraj
Published: February 2011

The antithyroxine antiserum parameters, namely the association constant and the so-called binding capacity, have been determined in the radioimmunoanalysis of thyroxine using the Scatchard transformation with modified input parameters. Limitations of this method are demonstrated and a new transformation of the radioimmunoanalytical results is proposed, which takes into consideration the relation between the concentrations of antigen and the binding sites of the antibody. The applicability of the Scatchard relation can be decided using this transformation.
Topological aspects of chemical reactivity
Authors: Ponec Robert
Published: February 2011

A simple formalism is proposed allowing to characterise the nature of chemical reactions. In comparison with existing techniques the presented method does not require to perform either quantum chemical calculations or to use the group theory. This makes the method convenient not only for pedagogical purposes but also as a routine tool for organic chemists.
Stochastic model of nonideal mixer. Boundary conditions in batch system
Authors: Kudrna Vladimír , Hasal Pavel , Vlček Jiří
Published: February 2011

The earlier proposed general approach for description of the non-ideal mixer is coupled with corresponding boundary conditions for the closed system. Some simplifications in this procedure result in relations which are in agreement with experimental data.
13C NMR study of hydrolyzed poly(acrylonitrile)
Authors: Loevy Jan , Janout Václav , Hrudková Hana
Published: February 2011

A method for the determination of chain microstructure of hydrolyzed poly(acrylonitrile) (PAN) and of copolymers of acrylonitrile with acrylamide by means of 13C NMR spectroscopy is described. Besides the overall composition of poly(acrylonitrile-co-acrylamide), this method permits the population of all acrylamide-centered compositional triads to be determined; it is then possible to follow the values of the rate constants of nitrile group hydrolysis in dependence on its neighbours. Under certain circumstances the knowledge of the mentioned triads permits also the copolymerization parameters for copolymerization of acrylonitrile with acrylamide to be determined. It was confirmed that acid-catalyzed hydrolysis of PAN in concentrated nitric acid yields acrylonitrile-acrylamide block copolymers.
1,3-Dipolar cycloadditions of N-(5-nitro-2-furfuryl)isoquinolinium bromide in the synthesis of benzoindolizines
Authors: Štetinová Jarmila , Kováč Jaroslav , Považanec František , Dandárová Miloslava , Pajchortová Alžbeta
Published: February 2011

Substituted 3-(5-nitro-2-furyl)benzo[g]indolizines III-XII were synthesized by a 1,3-dipolar cycloaddition of the ylide II formed in situ from N-(5-nitro-2-furfuryl)isoquinolinium bromide (I) and dimethyl butinedioate, diethyl butenedioate, 1-nitro-2-phenylethylene, ethyl 2-propenoate, ethyl 3-(5-nitro-2-furyl)-2-propenoate, 1,3-diphenyl-2-propenone, 1,3-diphenyl-2-propinone, 2-propenenitrile, 1-phenyl-3-(5-nitro-2-furyl)-2-propenone, and methyl 2-cyano-3-(4-nitrophenyl)-2-propenoate. Structure of these products was verified by spectral evidence.
Oxidation of 1,2,3,4,6-substituted pyridinium salts with ferricyanide
Authors: Nesvadba Petr , Kuthan Josef
Published: February 2011

Quaternary pyridinium salts IIa-IId are oxidized with alkaline solution of potassium ferricyanide to give a mixture of pyrrole derivatives Ia-Ib and IVa-IVd. The quaternary salt IIe under the same conditions affords a mixture of compounds IVe and V whereas IId gives only the pyrrole derivative IVd. The reaction mechanism is discussed and spectral characteristics of the products are interpreted.
Synthesis and characterization of methylphosphinediacetic acid
Authors: Podlahová Jana , Hartl František
Published: February 2011

Methylphosphinediacetic acid, a novel carboxyphosphine ligand, was obtained as the hydrochloride after reacting methyldichlorophosphine with ethyl bromozinc acetate, subjecting the ester formed to basic hydrolysis, and treating the disodium salt with excess hydrochloric acid. The substance was characterized by its analytical and spectral data. The protonation of the anion demonstrated that the methyl group, with low electronic and steric demands, induces a pronounced increase in the basicity of the phosphorus atom as compared with hitherto examined phosphineacetic acids: the first proton bonds exclusively to the phosphorus (pK = 6.19), whereas protonation of the carboxyl groups only occurs in acid solutions (pK = 2.76 and 1.2, respectively); hence, the free acid has the zwitterion structure.
Mechanism of 1-phenyl-1,4-dihydropyridine formation in reaction of 1-phenylpyridinum chloride with alkali metal alkoxides
Authors: Kuthan Josef , Krechl Jiří , Bělohradský Martin , Trška Petr
Published: February 2011

Quaternary salt Ia reacts with sodium and lithium alkoxides to give 1-phenyl-1,4-dihydropyridine (IIIa) together with unsaturated aldehyde IVa. The reaction mechanism for formation of compound IVa from the primarily arising 2-alkoxy-1-phenyl-1,2-dihydropyridines is suggested on the basis of products IIIb and IVb, arising from the 3,4,5-trideuterio precursor Ib.
Potential hypnotics and anxiolytics: Synthesis of 2-bromo-4-(2-chlorophenyl)-9-[4-(2-methoxyethyl)piperazino]-6H-thieno[3,2,4-triazolo[4,3-a]-1,4-diazepine and of some related compounds
Authors: Polívka Zdeněk , Holubek Jiří , Svátek Emil , Metyš Jan , Protiva Miroslav
Published: February 2011

The synthesis of 2,9-dibromo-4-(2-chlorophenyl)-6H-thieno[3,2-f]-1,2,4-triazolo[4,3-a]-1,4,diazepine (XX) has been carried out. The substitution reactions of XX with 1-(2-methoxyethyl) piperazine, 1-(3-methoxypropyl)piperazine, 1-(2-ethoxyethyl)piperazine and 1-(2-methylthiothyl)-piperazine afforded the title compound XXIV and its analogues XXV-XXVII. N-Alkylations of 2-bromo-4-(2-chlorophenyl)-9-piperazino-6H-thieno[3,2-f]-1,2,4-triazolo[4,3-a]-1,4-diazepine (XXIII) with 2-phenoxyethyl bromide and 2-phenylthioethyl bromide gave compounds XXVIII and XXIX. Cyclization of 5-(2-chlorophenyl)-2-hydrazino-3H-thieno[2,3-e]-1,4-diazepine(XVIIIa) by treatment with triethyl orthoformate resulted in 4-(2-chlorophenyl)-6H-thieno[3,2-f]-1,2,4-triazolo[4,3-a]-1,4-diazepine (XIX) which could be brominated only to the 9-bromo derivative XXI; attempts at further bromination to position 2 were unsuccessful. Some contribution to the syntheses of etizolam (I) and its dechloro analogue V in the stage of intermediates are being described. Compounds XXIV-XXIX were pharmacologically tested from the point of view of discoordinating and anticonvulsant activities; they proved less active than the analogous 8-chloro-6-(2-chlorophenyl)-1-piperazino-4H-striazolo[4,3-a]-1,4-benzodiazepines.
9α-Hydroxyparthenolide from Zoegea baldschuanica C. WINKL. and its absolute configuration
Authors: Buděšínský Miloš , Šaman David , Nowak Gerard , Drożdż Bohdan , Holub Miroslav
Published: February 2011

From the aerial parts of Zoegea baldschuanica C. WINKL. was isolated 9α-hydroxyparthenolide (I), whose absolute configuration was established on the basis of CD spectra. 1 H NMR data for I, parthenolide (VI) and the derivatives III and IV are discussed.
Synthesis and properties of oxytocin analogues modified in the tripeptide side chain
Authors: Procházka Zdenko , Lebl Michal , Barth Tomislav , Hlaváček Jan , Trka Antonín , Buděšínský Miloš , Jošt Karel
Published: February 2011

Two oxytocin analogues were synthesized by fragment condensation (6 + 3) in the presence of dicyclohexylcarbodiimide and 1-hydroxybenzotriazole. In one of the analogues, proline in the position 7 and leucine in the position 8 were substituted by 2-[1-(2-oxo-3-aminopyrrolidinyl)]-4-methylpentanoic acid, in the other proline was replaced by 1-aminocyclopropane-1-carboxylic acid. Biological activities of the first analogue were strongly reduced and dissociation of the uterotonic and galoctogogic activities was observed with both the analogues. The structure of 2-(3-tert-butyloxycarbonylaminopyrrolidin-2-on-1-yl)-4-methylpentanoylglycine and its amide was confirmed by mass and 1 H NMR spectroscopy.
Calculation of bulk and surface electronic properties of diamond-like semiconductors
Authors: Gadiyak G. V. , Karpushin A.A. , Morokov Yu. N. , Tomášek Mojmír
Published: February 2011

Local density of states (LDS) calculations have been performed by the recursion method for a model diamond-like semiconductor. LDS have been obtained for the following situations: the bulk, the vacancy and bivacancy in the bulk, the ideal (100) and (111) surfaces and the steps on these surfaces. Numerical results have been compared with experimental data for silicon. The calculated LDS show a one to one correspondence between the number of broken bonds on the investigated atom and the type of localized states near that atom. This supports the idea about the chemical nature of surface states, since the presence of steps on a strictly oriented surface leads to the appearance in the total density of surface states of additional peaks corresponding to another crystal surface.
Decomposition of peroxobenzoic acid in benzene catalyzed by transition metal 2,4-pentanedionates
Authors: Lederer Pavel , Mácová Eva , Vepřek-Šiška Josef
Published: February 2011

The decomposition of peroxobenzoic acid in benzene was studied, and catalytic effects of Fe(III), Mn(III), Co(II), Co(III), and Cr(III) on the reaction rate and the composition of the reaction mixture were investigated. An analogous experiment carried out in perdeuterobenzene and determination of the distribution of deuterium in the reaction products provided evidence for the participation of the solvent in peroxobenzoic acid decomposition.
Stereochemistry of [carbonato-bis((S)-prolinato)]cobaltate(III) anion
Authors: Hájek Bohumil , Sýkorová Dagmar , Chyba Jiří
Published: February 2011

The λ-C1-cis(N), δ-C1-cis(N), λ-C2-cis(N) and δ-C2-cis(N) isomers of the complex K[Co((S)-Pro)2CO3] were chromatographically separated and characterized by their electronic absorption spectra and CD spectra.
Comparison of characteristics of thymidylate synthesis isolated from eukaryotic and prokaryotic cells
Authors: Slavíková Věra , Slavík Karel , Motyčka Karel , Přistoupilová Kamila , Holý Petr
Published: February 2011

The preparations of thymidylate synthase (TDS) from calf thymus, Gardner mouse lymphosarcoma and E. coli were investigated by affinity chromatography based on the formation of a ternary complex of the enzyme with tetrahydromethotrexate and deoxyuridine-5'-monophosphate (dUMP). The E. coli enzyme was a homogeneous protein of mol.wt. 70 000 and it was shown by reductive denaturation to contain one single chain of mol.wt. 35 000. The preparation isolated from the Gardner lymphosarcoma was a homogeneous protein of mol.wt. 72 000 containing a single subunit of mol.wt. 36 000. The enzyme from both sources yielded after treatment with 5-fluorodeoxyuridine-5'-monophosphate (FdUMP) and N5-10-methylenetetrahydrofolate a negatively charged complex which was separated electrophoretically. Three proteins of mol.wt 35 000 (component 1), 70 000 (component 2), and more than 250 000 (component 3), were isolated by affinity chromatography from calf thymus and separated by electrophoresis and gel filtration. Component 2 only was enzymatically active and yielded a complex when treated with 5-fluorodeoxyuridine-5'-monophosphate and N5-10-methylenetetrahydrofolate. Components 1 and 3 were enzymatically inactive yet were immunologically related. The antiserum against component 3 precipitated in addition to component 3 also the active enzyme (component 2) and component 1. The antiserum against the active enzyme precipitated proteins 1 and 3. All three components were found to contain one chain of mol.wt. 35 000 after reductive denaturation. Components 1 and 2 contained this chain only whereas other, heavier chains were found in component 3.
Hydrolysis of uranium monocarbide
Authors: Hájek Bohumil , Karen Pavel , Brožek Vlastimil
Published: February 2011

The substoichiometric uranium monocarbide UC0.95 was hydrolyzed in acid medium at 80 °C. The composition of the products of hydrolysis corresponds to published data, but it correlates better with the stoichiometric composition of the hydrolyzable carbids. The mechanisms of the hydrolysis reaction are discussed and a modified radical mechanism is suggested based on the concept of initiation of the radical process by H. radicals formed owing to the nonstoichiometry of the substance. A relation is proposed for calculating the content of free hydrogen in the hydrolysis products of carbides of metal nature, for which a radical mechanism of their reaction with water can be assumed. Some effects occurring during the hydrolysis of uranium carbide, as described in literature, are explained in terms of the concept suggested, and the results obtained by the authors for carbides of manganese (Mn7C3) and for rare earth elements are discussed.
Alternative synthesis of 4-methyl-2H-1,2,6-thiadiazin-3(6H)-one 1,1-dioxide, a structural analogue of thymine
Authors: Ledvina Miroslav , Farkaš Jiří
Published: February 2011

N-Alkylsulfamides react with methyl 3-methoxy-2-methyl-2-propenoate (XI) in aqueous hydrochloric acid under formation of methyl 3-(N' -alkylsulfamido)-2-methyl-2-propenoates (VIIa to VIIc). Attempted base-catalyzed cyclization of the ester VIIb was unsuccessful. The 2-benzyl derivative IV and the 6-benzyl derivative V were prepared by reaction of iodotrimethylsilane with the acid VIII and the amide IX, respectively. Hydrogenolytic removal of the benzyl groups in the 2- and 6-benzyl derivatives IV and V afforded the title compound III.
A new type of A-homo-B-norcholestane derivatives
Authors: Kasal Alexander
Published: February 2011

5-Bromo-6β-chloro-5α-cholestan-3β-ol (I) undergoes solvolysis to yield products of Westphalen rearrangement one of them (XXIX) undergoing further rearrangement to the A-homo-B-nor-system V. The reaction course was established by the use of suitably labeled substrates. The structures of the products and positions of the labels were determined by chemical transformations and physicochemical methods (1H, 13C NMR spectra).