bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxydation von Zitronensaure mit Mangan(III)-sulfat
Authors: Barek Jiří , Berka Antonín , Pokorná Alena
Published: October 2011

Wie nachgewiesen wurde, wird die Zitronensaure mit Mangan(III)-sulfat nach der Gleichung (COOH-CH2)2C(OH)COOH + 14 Mn3+ + 5 H2O → 2 HOOCH + 4 CO2 + 14 Mn2+ + 14 H+ oxydiert. Es wurde die Kinetik untersucht, der Mechanismus dieser Reaktion vorgeschlagen und die optimalen Bedingungen fur die indirekte Zitronensaurebestimmung gefunden, die auf deren Oxydation mit Mangan(III)-sulfat im Uberschuss und auf der potentiometrischen Rucktitration des nichtverbrauchten Reagens mit Eisen(II)-sulfat beruht.
Synthesis of 2,2,4-trisubstituted 2H-1,3-oxazetes from acyl isothiocyanates
Authors: Kristian Pavol , Kutschy Peter , Dzurilla Milan
Published: October 2011

Reaction of acyl isothiocyanates with amines, methanol or methanethiol afforded addition products which on treatment with lithium hydride in dimethylformamide and subsequent alkylation with methyl iodide, cyclized immediately to give 2,2,4-trisubstituted 2H-1,3-oxazetes which represent a new type of heterocycles. Under identical conditions, N-phenyl-N'-cinnamoylthioureas and N-phenyl-N'-3-(2-furyl)-acryloylthioureas afforded S-methyl N-acylmonothiocarbamates whereas N-phenyl-N'-acetylthiourea gave N-phenyl-N'-acetyl-S-methylisothiourea. The structure of the obtained compounds was confirmed by their IR, 1H NMR and mass spectra.
Esters of adenosine 5'-phosphate with lipoid hydroxy compounds (adenosine nucleolipids) and their effects on the activity of enzymes of cyclic AMP system
Authors: Hynie Sixtus , Smrt Jiří
Published: October 2011

Esters of adenosine 5'-phosphate with lipoid hydroxy compounds exhibit strong inhibitory effect on adenylate cyclase activity. The activities of cyclic AMP phosphodiesterase and protein kinase are moderately inhibited.
Calculation of the difference between molar heat capacity of liquid and ideal gas from the temperature dependence of heat of vaporization
Authors: Majer Vladimír , Svoboda Václav , Pick Jiří
Published: October 2011

A method was developed for calculating the difference ΔcP between molar heat capacity of liquid cP1 and of ideal gas cPgo from the temperature dependence of heat of vaporization. By an a priori analysis the maximum error of the calculation procedure was determined. The exploitation of the method was demonstrated on a group of 20 saturated hydrocarbons. Besides these ΔcP values, the data on cP1 and cPgo were calculated in the regions where no experimental data are available, by combining ΔcP with the experimental values of molar heat capacities.
Photolysis of quinonediazides in cyclohexane formation of coloured adduct, heavy atom effect
Authors: Řehák Viktor , Poskočil Jaroslav , Dvořáček Ivo
Published: October 2011

Photolysis of 1,2-naphthoquinone-1-diazide and 9,10-phenathrenequinonediazide in cyclohexane gives coloured products decomposing on further irradiation. Formation of the products and their concentration depends on the way of irradiation (short, continuous) and on the presence of 1-propanol in the solution. The products are presumed to be adducts of ketene with the starting quinonediazides. Rate constants of their formation have been determined. Influence of solvent containing a heavy atom (1-bromopropane, iodoethane) on quantum yield of the photolysis and influence of oxygen have been investigated.
Study of reaction of substituted nitrophenyl acetates and benzoates with nucleophiles
Authors: Macháček Vladimír , Marečková Sylvie , Štěrba Vojeslav
Published: October 2011

Reaction of 2-substituted 4,6-dinitrophenyl acetates and benzoates with methoxide, 4-bromophenoxide and acetate anions and with anion of methyl cyanoacetate has been studied in methanol at 25 °C, and the respective rate constants have been determined along with the rate constant ratios of nucleophilic attacks at carbonyl carbon (CCO) and C1 carbon of the aromatic ring (CAr). Content of the 2-substituted 4,6-dinitrophenols formed by nucleophilic attack at CCO increases in the product with increasing hardness of the nucleophiles in the series methyl cyanoacetate anion < 4-bromophenoxide anion < methoxide anion. The substituents polar effects are decisive for the attack at CAr, whereas both polar and steric effect operate in the attack at CCO. Methoxide anion attacks the CCO of 2,4-dinitrophenyl ester even faster than the CCO of 2,4,6-trinitrophenyl ester.
Study of solvolysis mechanism of some ureas derived from 2-benzoxazolone
Authors: Štohandl Jiří , Večeřa Miroslav
Published: October 2011

6-Nitro-, 6-chloro-, 6-bromo- and 6-amino-2-benzoxazolones I have been prepared and aminolyzed with piperidine and butylamine into the respective 2-hydroxy-4-nitro-, 4-chloro-, 4-bromo- and 4-aminophenylureas II, III. pKa values of hydroxyl group of these ureas have been determined. The aminolysis and hydroxylaminolysis mechanism of the mentioned 2-benzoxazolones is discussed on the basis of kinetic data. Reaction of the 6-substituted-2-benzoxazolones with methyl, phenyl and p-toluenesulphonyl isocyanates and N,N-dimethylchloroformamide has been used for preparation of the respective ureas V to VII of the type of 3-alkylcarbamoyl- or arylcarbamoyl-2-benzoxazolone. Hydrolysis mechanism of these ureas possessing a good leaving (3-benzoxazolone) group in alkaline medium and behaviour of anions of ureas VI in alkaline medium are discussed.
Phase equilibria in binary systems containing acetaldehyde
Authors: Suška Josef
Published: October 2011

The vapour-liquid equilibrium in binary acetaldehyde-diethyl ether, acetaldehyde-ethanol and acetaldehyde-water systems was measured at the pressure of 101.32 kPa. The experimental data were correlated by the two- and three-constant Redlich-Kister equation.
Crystal size distribution of benzoic acid at its crystallization from the bulk of vapour phase
Authors: Vítovec Jaroslav , Smolík Jiří , Kugler Josef
Published: October 2011

Crystal size and their distribution were measured in the crystallizer with gas-permeable walls, at crystallization of benzoic acid vapours from the bulk of vapour phase in the mixture with nitrogen in dependence on concentration (in range from 1.1 to 23 vol.%), temperature (401 to 473 K) and velocity of mixture (0.5 to 6.6 cm/s). At small cooling rate of the mixture the vapours of benzoic acid are condensing in the form of droplets which at continuing cooling solidify. At cooling of the mixture by water dispersion create the needle-shaped crystals. The effect of concentration, temperature and velocity is not profound obviously because by evaporation of water is the mixture rapidly cooled and supersaturated. This results in creation of a large amount of crystal nuclei and thus also of small crystals.
Growth of crystals not obeying the McCabe ΔL-law
Authors: Nývlt Jaroslav
Published: October 2011

On basis of the film model of crystal growth the relation L = L0 (1 + az) has been derived which describes the dependence of the linear growth rate on crystal size as a function of the dimensionless residence time of crystals z. For the perfectly stirred (MSMPR) crystallizer were then derived relations for the reduced population density of crystals nucleation rate, mean crystal size and distribution of crystal sizes. For very small values of the parameter a all derived relations give numerical values close to those satisfying the McCabe ΔL-law.
Primary structure of peptides which form the disulfide bonds of chicken pepsin
Authors: Keilová Helena , Baudyš Miroslav , Kostka Vladimír
Published: October 2011

The molecule of chicken pepsin is cross-linked by three disulfide bonds. The structures of the half-cystine peptides which form these bonds were determined by the analysis of different enzymic digests of the enzyme. The order of the disulfide bonds in the molecule was elucidated with regard to sequential homologies between chicken pepsin and other acid proteases. The three disulfide bonds of chicken pepsin, numbered from the N-terminus of pepsin, are: 1st bond Ile-Tyr-Cys-(Lys-Ser-Ser-Ala)-Cys-Ser-Asn-His-Lys; 2nd bond Val-Ala-Cys-Cys-(Thr-Phe)-Gln-Ala; 3rd bond Asp-Leu-Gly-Val-Ser-Ser-Asp-Gly-Glu-Ile-Ser-Cys-(Asp-Asp-Ile-Ser-Lys-Leu-Pro-Asp)-Cys-(Ser-Gly-Asp-Glu-Asn-Leu-Val)-Met.
Aldol condensation of butyraldehyde in the liquid phase catalysed by aluminium, iron and chromium sesquioxides
Authors: Nondek Lubomír , Málek Jaroslav
Published: October 2011

Aldol condensation of butyraldehyde catalysed by aluminium, iron and chromium sesquioxides has been studied in the liquid phase at temperatures from 160 °C to 210 °C, using a plug-flow stainless steel reactor. Relationships between the activity of the catalysts, surface concentrations of basic sites and the butyric acid concentration in butyraldehyde were determined. The catalytic activity depended both on the surface concentration of basic sites and on their basicity; the latter increased in the sequence Fe2O3 ##i Cr2O3 < Al2O3.
Some 3-cyano-4,6-diaryl-2-pyridones with luminiscent properties
Authors: Kuthan Josef , Nesvadba Petr , Popl Milan , Fähnrich Jan
Published: October 2011

Fluorescence spectra of methanolic solutions of the 2-pyridone derivatives I to XI have been measured at laboratory temperature and interpreted. Influence of the substituents R1 and R2, the 3-cyano group, and that of methylation on quantum yield of the fluorescence has been followed. Preparation of the studied compounds I to XI has been described, and methylation of the compound I has been studied in detail.
Synthesis of uracils substituted in the position 5 or 5,6 with alkyl or cycloalkyl groups and their UV spectra
Authors: Bašnák Ivan , Farkaš Jiří
Published: October 2011

Lithium diisopropylamide used as a base in the Claisen condensation of alkylacetates and cycloalkylacetates with ethyl formate or acetate gave substantially higher yields of β-oxo esters than sodium hydride or sodium bis(trimethylsilyl)amide. Reaction of the obtained β-oxo esters with thiourea in an alkaline medium afforded 5- or 5,6-disubstituted 2-thiouracils Ib-XIIb which on subsequent reaction with chloroacetic acid were transformed into the uracil derivatives Ia-XIIa. The UV spectra of uracils substituted in the positions 5 or 6 with cyclopropane ring exhibit in the 265 nm region bathochromic shifts of 1 to 6.5 nm as compared with the correspondingly substituted alkyl derivatives. A qualitative correlation of these shifts with the electron deficit on the carbon atom bonded to the cyclopropane ring was attempted.
Tryptic splitting of vasopressin analogues containing homologues of lysine or arginine in position 8
Authors: Dimeli Anastasia , Barth Tomislav
Published: October 2011

Vasopressin analogues containing an amino acid with a shorter side chain in position 8 of the peptide chain were more resistant to tryptic splitting of the peptide bond formed by the basic amino acid and terminal glycine amide. In the lysine vasopressin series, analogues with ornithine or lower homologues of lysine in position 8 were not hydrolyzed. In the arginine vasopressin series, the analogue containing 3-guanidino-2-aminopropionic acid in position 8 was completely resistant to the action of trypsin. The vasopressin analogue with norarginine in position 8 was split at a lower rate than natural arginine vasopressin.
Electronic spectra of salts of dithiocarbamic acids
Authors: Oktavec Drahomír , Štefanec Jozef , Síleš Bohumil , Konečný Václav , Garaj Ján
Published: October 2011

The report gives synthesis and UV spectra of a series of alkali and ammonium salts of the dithiocarbamic acids derived from dimethyl-, diethyl-, dipropyl-, dibutyl-, dipentyl-, dihexyl-, diheptyl-, dioctyl-, diisopropyl-, diisobutyl-, methylisopropylamine, piperidine, morpholine, piperazine and pyrrolidine. The absorption bands due to transitions localized in the groups CSS (λmax ~ 260 nm) and NCS (λmax ~ 280 nm) show a red shift with increasing length of the alkyl chain. Increasing polarity of solvent causes, with some of the compounds, a small red shift of λmax of the band due to CSS group, but it causes a considerable blue shift of λmax of the band due to NCS group in all the studied compounds. The absorption band near 207 nm is ascribed to the carbon disulphide produced by decomposition of the dithiocarbamates.
Alkylation reactions of 5-nitrofurfuryl derivatives as C-acids
Authors: Prousek Josef , Jurášek Adolf , Kováč Jaroslav
Published: October 2011

5-Nitrofurfuryl bromide (I) and 4-nitrobenzyl bromide (VI) were investigated as possible alkylation reagents in reaction with 5-nitrofurfuryl trichloromethyl sulfone (IV) and 5-nitrofurfuryl phenyl sulfone (V). 1,2-Bis(5-nitro-2-furyl)ethylene (III) was formed from I in an alkaline medium and 1,2-bis(5-nitro-2-furyl)ethane (X) in the presence of furfuryl mercaptan. Products of this reaction were identified by IR, UV, 1H NMR and mass spectrometries.
Synthesis of new dibenzo[b,e]thiepin derivatives related to the antidepressant agent prothiadene
Authors: Rajšner Miroslav , Bártl Václav , Šindelář Karel , Svátek Emil , Holubek Jiří , Metyš Jan , Protiva Miroslav
Published: October 2011

A reaction of dibenzo[b,e]thiepin-11(6H)-one with cyclopropylmagnesium bromide afforded the carbinol VII giving by treatment with hydrogen bromide the bromo derivative IV. Application of the Gabriel synthesis led to the primary amine III postulated earlier to be a metabolite of the antidepressant agent prothiadene (I). Demethylation of 2-methoxy-11-(3-dimethylaminopropylidene)-6,11-dihydrodibenzo[b,e]thiepin (X) with boron tribromide or hydrobromic acid gave mixtures of geometric isomers of the phenol IX from which either the trans- or cis-form could be isolated; trans-IX is another potential metabolite of prothiadene (I). Attempts at preparing prothiadene N-oxide yielded as the main product the nitrogen-free diene XI which was apparently formed by a Cope elimination. The analogous sulfone XII was obtained as a by-product of the preparation of prothiadene S,S-dioxide (XV). Treatment of dibenzo[b,e]thiepin-11(6H)-one with methoxymethylmagnesium chloride opened the access to the aldehyde XVI which was further used for the preparation of the nitrile XVIII, alcohol XIX, carboxylic acid XX and acrylic acid XXI.
Synthesis and properties of oxytocin analogues acting as irreversible inhibitors of the uterotonic response to oxytocin
Authors: Lebl Michal , Bojanovska Vera , Barth Tomislav , Jošt Karel
Published: October 2011

A series of compounds containing reactive groups of different chemical character was synthetized from [4-glutamic acid]deamino-1-carba-oxytocin or from [2-O-methyltyrosine, 4-glutamic acid]deamino-1-carba-oxytocin. The analogues acted as specific irreversible inhibitors of the uterotonic response to oxytocin. Active esters of the initial compounds were the most effective inhibitors.
Kinetics and mechanism of hydrolysis of substituted phenyl N-(4-methylphenyl)sulphonylcarbamates. Solvolysis of 3-nitrophenyl N-(4-methylphenyl)-sulphonylcarbamate in mixtures water-1,4-dioxane and water-tert-butyl alcohol and its decomposition to neutral molecules in non-aqueous media
Authors: Moravcová Jitka , Večeřa Miroslav
Published: October 2011

pH Dependence of hydrolysis rate of the substituted phenyl N-(4-methylphenyl)sulphonylcarbamates has been followed in aqueous medium. The activation parameters and the Hammet reaction constant (ρ = 2.4) have been determined at pH 11.3. For hydrolysis of 3-nitrophenyl N-(4-methylphenyl)sulphonylcarbamate (pK about 3.5) no general base catalysis has been found. The hydrolysis mechanism is discussed. Perturbation of the water structure by organic solvents (1,4-dioxane and tert-butyl alcohol) has been used for differentiation of ElcB and Bac2 mechanisms, 2,4-dinitrophenyl acetate being used for comparison. The decomposition rates of 3-nitrophenyl N(4-methylphenyl)sulphonylcarbamate have been determined in six organic solvents. Mechanism of spontaneous splitting of the carbamate molecule in non-aqueous media is discussed.
Reactions of asymmetric carbodiimides with azoimide
Authors: Světlík Jan , Hrušovský Igor , Martvoň Augustin
Published: October 2011

Reaction of asymmetric aliphatic-aromatic and diaryl carbodiimides with HN3 leads to 1,5-disubstituted tetrazoles. Carbodiimides of general formula C6H5-N=C=N-R (R = alkyl) from an adduct at C=N bond exclusively at a less basic nitrogen, i.e. near phenyl whereas those with R = aryl afford a 1 : 1 mixture of products. 1H-NMR spectroscopy revealed an aminotetrazole-iminotetrazoline tautomerism of the prepared 1=phenyl-5-alkylaminotetrazoles, which undergo isomerization to 1-alkyl-5-anilinotetrazoles.
Third-order energy using CNDO/2 and INDO Hamiltonian approximations in the modified PCILO method
Authors: Boča Roman
Published: October 2011

The perturbative configuration interaction using strictly localized molecular orbitals, called the modified PCILO method has been applied in this communication for the calculations of the energy terms of 15 small molecules up to the third order of the perturbation theory. For this method the use of the Rayleigh-Schrodinger many-body perturbation theory with the Moller-Plesset type of the Hamiltonian partitioning is characteristic. On the CNDO/2 and INDO level of approximations the strictly localized molecular orbitals have been constructed by solving the modified 2 x 2 Roothaan's equations. From the zeroth order ground-state wave function the charge distributions, dipole moments and carbon 13-proton nuclear spin-spin coupling constants have been calculated. Results show that the chemical formula, represented with the zeroth order of the perturbation theory, is a good order of the approximation for the study of the molecule. For diatomic molecules the equilibrium interatomic distances and harmonic force constants have been calculated up to the third order of the perturbation theory. The second order of the perturbation theory provides results which are very near to the MO-LCAO-SCF calculations. The main advantage of the PCILO method lies in much saving of the computing time.
Pumping effect of impellers with flat inclined blades
Authors: Medek Jaroslav , Fořt Ivan
Published: October 2011

Hydrodynamic analysis of the flow around the blade of an impeller agitating a low-viscosity Newtonian liquid in a cylindrical baffled vessel has been employed to assess the influence of blade inclination on impeller pumping capacity. Volumetric flow rate of an impeller with flat inclined blades is understood as the sum of its axial and radial components. From the relations obtained, the ratio of individual volumetric flow rates depending on blade inclination can be calculated using a single universal parameter. Experimental results consist of the flow rate criteria values in dependence on blade inclination, for impellers with various blade numbers, in the range of Reynolds numbers Re Σ 1. 104; 1.5 . 105.
[1-β-Mercaptopropionic acid, 8-α-amino-β-glycylaminopropionic acid]vasopressin. A vasopressin analog with an isopeptide structure in its molecule
Authors: Zaoral Milan , Krchňák Viktor , Škopková Jana , Machová Alena
Published: October 2011

[1-β-Mercaptopropionic acid, 8-α-amino-β-glycylaminopropionic acid]vasopressin (II) was prepared by solid-phase peptide synthesis. II has an antidiuretic effect of considerable magnitude (435 I.U./mg) and specificity.
A new method of preparation of α-amino derivatives of furan
Authors: Považanec František , Kováč Jaroslav , Hesek Dušan
Published: October 2011

The reaction of 5-nitro-2-furfuryl nitrate with sodium azide and malononitrile or methyl cyanoacetate was studied. Products of this treatment are 5-amino-2-furfurylidenemalonodinitrile and methyl 3-(5-amino-2-furyl)-2-cyanoacrylate.
Practical synthesis of 2'(3')-O-aminoacyl derivatives of CpA
Authors: Smrt Jiří , Jonák Jiří
Published: October 2011

N-Tert-butyloxycarbonyl-L-phenylalanine reacts with 1 equivalent of 1,1'-carbonyldiimidazole and 5'-O-dimethoxytrityl-2'-tetrahydropyranyl-N4-dimethylaminomethylenecytidylyl-(3' 5')-N6-dimethylaminomethyleneadenosine (I) and affords 2'(3')-O-(N-tert-butyloxycarbonyl)-L-phenylalanyl derivative II. The compound II gives by the action of formic acid in aqueous 1-butanol the 2'-O-tetrahydropyranylcytidylyl-(3' 5')-2'(3)-O-(tert-butyloxycarbonyl)-L-phenylalanyladenosine (III), which affords cytidyl-(3' 5')-2'(3')-O-L-phenylalanyladenosine (IV) by treatment with 95% aqueous trifluoroacetic acid.
Reaction of p-nitroso-N,N-dimethylaniline with 2,2'-azobisisobutyronitrile. Kinetics and mechanism
Authors: Berdinskii Valerii L. , Kholvad Vladimir , Kende Imre , Pershin Aleksander D.
Published: October 2011

Abstract in Russian
The effect of particle size on the reactivity of active sodium carbonate towards sulfur dioxide
Authors: Mocek Karel , Lippert Erich , Husek Dušan , Erdös Emerich
Published: October 2011

The effect of particle size (0.33-1.0 mm) of the sodium carbonate on the reactivity of the active sodium carbonate prepared therefrom towards the sulfur dioxide was studied in a fixedbed integral reactor at a temperature of 150 °C. The found dependence of the reaction rate on the particle size exhibits an unexpected course; at sizes of about 0.65 mm, a distinct minimum appears. The reaction rate decreases approximately ten times in the first branch of this dependence. The controlling factor of the reactivity of sodium carbonate, however, remains to be the method of preparing the active form.
FEM and FIM study of the work function of stepped metal surfaces
Authors: Knor Zlatko
Published: October 2011

A comparison between FEM and FIM images of the tungsten surface shows that stepped (high-index) planes influence emitted electrons in two ways; a) if monoatomic steps whose edges form the crystal face under question are wider than about three atoms, the surface behaves as a patchy surface formed by flat areas of the steps; b) if steps are narrower than the above mentioned limit, the emitted electrons feel the field of the crystal plane determined by step edges (the work function acquires low values corresponding to atomically rough surface).
Structure, energy characteristics, and electronic spectra of two isoelectronic radicals, HCN2 and H2C2N: A theoretical study
Authors: Slanina Zdeněk , Grabowski Zbigniew R.
Published: October 2011

The molecular structure of the title radicals was investigated by means of the CNDO/2 and MINDO/2 methods. Calculations suggest that both radicals might exist in two isomeric forms (cyclic and open). Thermodynamic characteristics of the H2C2N isomerization were calculated. Electronic spectra of both radicals were obtained using limited configuration interaction treatment based on the Del Bene and Jaffe SCF method. Calculation and observation agree satisfactorily for the HCN2 radical. A comment is made on the role of isomerism when electronic spectra are studied theoretically.
Thermodynamic properties of pure hard sphere, spherocylinder and dumbell fluids
Authors: Nezbeda Ivo , Pavlíček Jan , Labík Stanislav
Published: October 2011

A universal equation of state for the fluid of hard bodies of an arbitrary shape is proposed. New Monte Carlo data of the hard sphere system are published and the existing pseudoexperimental data for hard spheres, spherocylindres and dumbells are critically reviewed.
Kinetics of oxidation of cis-bis(ethylenediamine)isothiocyanatonitrocobalt(III) ion with peroxodisulphate
Authors: Holba Vladislav , Volárová Olga
Published: October 2011

The oxidation kinetics of cis-bis(ethylenediamine)isothiocyanonitrocobalt(III) ion with peroxodisulphate was investigated in the medium of 0.01 M-HClO4 in dependence on the ionic strength and temperature and the reaction products were identified. Extrapolated values of thermodynamic activation parameters were determined from the temperature dependence of the rate constants extrapolated to zero ionic strength. The distance of the closest approach was estimated for the reacting ions by evaluating the primary salt effect. To elucidate the mechanism, the influence of the cyclic polyether 18-crown-6 on the reaction rate was followed.
Mechanism of OH-initiated atmospheric oxidation of diethyl phthalate
Authors: Bao Yuan , Sun Xiaoyan , Sun Xiaomin , Hu Jingtian
Published: October 2011

Diethyl phthalate (1,2-benzenedicarboxylic acid diethyl ester, DEP) is one of a group of widely used plasticizers, which can lead to serious environmental problems. Because of manufacturing and application, DEP can be released into the atmosphere where it can undergo transport and chemical transformation. To assess the atmospheric behavior of pollutants, it is critical to know their atmospheric reactions. In this paper, the reaction mechanism and possible oxidation products for the OH-initiated atmospheric reaction of DEP were theoretically investigated by using the density functional theory (DFT) method. The geometries and frequencies of the reactants, intermediates, transition states, and products were calculated at the MPWB1K/6–31+G(d,p) level, and the energetic parameters were further refined by the MPWB1K/6–311+G(3df,2p) method. The present study shows that H abstractions from the CH3 and CH2 groups, as well as OH addition to the benzene ring, are energetically favorable reaction pathways for the reaction of DEP with OH radicals. Detailed degradation products are provided.
Effective Usage of Computational Trust Models in Rational Environments
Authors: Vu Le-Hung , Aberer Karl
Published: October 2011

Computational reputation-based trust models using statistical learning have been intensively studied for distributed systems where peers behave maliciously. However practical applications of such models in environments with both malicious and rational behaviors are still very little understood. In this article, we study the relation between their accuracy measures and their ability to enforce cooperation among participants and discourage selfish behaviors. We provide theoretical results that show the conditions under which cooperation emerges when using computational trust models with a given accuracy, and how cooperation can still be sustained while reducing the cost and accuracy of those models.

Specifically, we propose a peer selection protocol that uses a computational trust model as a dishonesty detector to filter out unfair ratings. We prove that such a model with reasonable misclassification error bound in identifying malicious ratings can effectively build trust and cooperation in the system, considering rationality of participants. These results reveal two interesting observations. First, the key to the success of a reputation system in a rational environment is not a sophisticated trust-learning mechanism, but an effective identity-management scheme to prevent whitewashing behaviors. Second, given an appropriate identity-management mechanism, a reputation-based trust model with a moderate accuracy bound can be used to effectively enforce cooperation in systems with both rational and malicious participants. As a result, in heterogeneous environments where peers use different algorithms to detect misbehavior of potential partners, cooperation may still emerge. We verify and extend these theoretical results to a variety of settings involving honest, malicious, and strategic players through extensive simulation. These results will enable a much more targeted, cost-effective and realistic design for decentralized trust management systems, such as needed for peer-to-peer, electronic commerce, or community systems.
Approximation Schemes for Steiner Forest on Planar Graphs and Graphs of Bounded Treewidth
Authors: Bateni Mohammadhossein , Hajiaghayi Mohammadtaghi , Marx Dániel
Published: October 2011

We give the first
polynomial-time approximation scheme
(PTAS) for the
Steiner forest
problem on planar graphs and, more generally, on graphs of bounded genus. As a first step, we show how to build a
Steiner forest spanner
for such graphs. The crux of the process is a clustering procedure called
prize-collecting clustering
that breaks down the input instance into separate subinstances which are easier to handle; moreover, the terminals in different subinstances are far from each other. Each subinstance has a relatively inexpensive Steiner tree connecting all its terminals, and the subinstances can be solved (almost) separately. Another building block is a PTAS for
Steiner forest
on graphs of bounded treewidth. Surprisingly,
Steiner forest
is NP-hard even on graphs of treewidth 3. Therefore, our PTAS for bounded-treewidth graphs needs a nontrivial combination of approximation arguments and dynamic programming on the tree decomposition. We further show that
Steiner forest
can be solved in polynomial time for series-parallel graphs (graphs of treewidth at most two) by a novel combination of dynamic programming and minimum cut computations, completing our thorough complexity study of
Steiner forest
in the range of bounded-treewidth graphs, planar graphs, and bounded-genus graphs.
Endogenous ouabain regulates cell viability
Authors: Dvela Moran , Rosen Haim , Ben-Ami Hagit Cohen , Lichtstein David
Published: October 2011

The endogenous cardiac steroid-like compounds, endogenous ouabain (EO) in particular, are present in the human circulation and are considered putative ligands of the inhibitory binding site of the plasma membrane Na+-K+-ATPase. A vast amount of data shows that, when added to cell cultures, these steroids promote the growth of cardiac, vascular, and epithelial cells. However, the involvement of the endogenous compounds in the regulation of cell viability and proliferation has never been addressed experimentally. In this study, we show that EO is present in mammalian sera and cerebral spinal fluid, as well as in commercial bovine and horse sera. The lowering of serum EO concentration by the addition of specific anti-ouabain antibodies caused a decrease in the viability of several cultured cell lines. Among these, neuronal NT2 cells were mostly affected, whereas no reduction in viability was seen in rat neuroendocrine PC12 and monkey kidney COS-7 cells. The anti-ouabain antibody-induced reduction in NT2 cell viability was significantly attenuated by the addition of ouabain and was not observed in cells growing in serum-free media. Furthermore, the addition to the medium of low concentrations (nM) of the cardenolide ouabain, but not of the bufadienolide bufalin, increased NT2 and PC12 cell viability and proliferation. In addition, at these concentrations both ouabain and bufalin caused the activation of ERK1/2 in the NT2 cells. The specific ERK1/2 inhibitor U0126 inhibited both the ouabain-induced activation of the enzyme and the increase in cell viability. Furthermore, anti-ouabain antibodies attenuated serum-stimulated ERK1/2 activity in NT2 but not in PC12 cells. Cumulatively, our results suggest that EO plays a significant role in the regulation of cell viability. In addition, our findings support the notion that activation of the ERK1/2 signaling pathway is obligatory but not sufficient for the induction of cell viability by EO.
Increased NHE3 abundance and transport activity in renal proximal tubule of rats with heart failure
Authors: Inoue Bruna H. , dos Santos Leonardo , Pessoa Thaissa D. , Antonio Ednei L. , Pacheco Bruna P. M. , Savignano Fernanda A. , Carraro-Lacroix Luciene R. , Tucci Paulo J. F. , Malnic Gerhard , Girardi Adriana C. C.
Published: October 2011

Heart failure (HF) is associated with a reduced effective circulating volume that drives sodium and water retention and extracellular volume expansion. We therefore hypothesized that Na+/H+exchanger isoform 3 (NHE3), the major apical transcellular pathway for sodium reabsorption in the proximal tubule, is upregulated in an experimental model of HF. HF was induced in male rats by left ventricle radiofrequency ablation. Sham-operated rats (sham) were used as controls. At 6 wk after surgery, HF rats exhibited cardiac dysfunction with a dramatic increase in left ventricular end-diastolic pressure. By means of stationary in vivo microperfusion and pH-dependent sodium uptake, we demonstrated that NHE3 transport activity was significantly higher in the proximal tubule of HF compared with sham rats. Increased NHE3 activity was paralleled by increased renal cortical NHE3 expression at both protein and mRNA levels. In addition, the baseline PKA-dependent NHE3 phosphorylation at serine 552 was reduced in renal cortical membranes of rats with HF. Collectively, these results suggest that NHE3 is upregulated in the proximal tubule of HF rats by transcriptional, translational, and posttranslational mechanisms. Enhanced NHE3-mediated sodium reabsorption in the proximal tubule may contribute to extracellular volume expansion and edema, the hallmark feature of HF. Moreover, our study emphasizes the importance of undertaking a cardiorenal approach to contain progression of cardiac disease.
Sex hormones induce a gender-related difference in renal expression of a novel prostaglandin transporter, OAT-PG, influencing basal PGE2concentration
Authors: Hatano Ryo , Onoe Kimitaka , Obara Masaya , Matsubara Mitsunobu , Kanai Yoshikatsu , Muto Shigeaki , Asano Shinji
Published: October 2011

Based on the nucleotide sequence of a mouse prostaglandin-specific transporter (mOAT-PG), we identified a rat homolog (rOAT-PG) which shares 80% identity with mOAT-PG in a deduced amino acid sequence. rOAT-PG transports PGE2and colocalizes with 15-hydroxyprostaglandin dehydrogenase (15-PGDH), a metabolic enzyme for PGs, in proximal tubules, suggesting that rOAT-PG is involved in PGE2clearance to regulate its physiological function in the renal cortex. We found that the expression level of rOAT-PG in the renal cortex was much higher in male rats than in female rats whereas there was no gender difference in the expression level of cyclooxygenase-2, a key enzyme producing PGE2, and 15-PGDH in the renal cortex. Tissue PGE2concentration in the renal cortex was lower in male rats than in female rats, suggesting that renocortical PGE2concentration is primarily determined by the expression level of OAT-PG, which is regulated differently between male and female rats. Castration of male rat led to a remarkable reduction in OAT-PG expression and a significant increase in renocortical PGE2concentration. These alterations were recovered by testosterone supplementation. These results suggest that OAT-PG is involved in local PGE2clearance in the renal cortex. Although the physiological importance of the gender difference in local PGE2clearance is still unclear, these findings might be a key to clarifying the physiological roles of PGE2in the kidney.
Angiotensin II Type II Receptor Deficiency Accelerates the Development of Nephropathy in Type I Diabetes via Oxidative Stress and ACE2
Authors: Chang Shiao-Ying , Chen Yun-Wen , Chenier Isabelle , Tran Stella Le Minh , Zhang Shao-Ling
Published: October 2011

Since the functional role(s) of angiotensin II (Ang II) type II receptor (AT2R) in type I diabetes is unknown, we hypothesized that AT2R is involved in decreasing the effects of type I diabetes on the kidneys. We induced diabetes with low-dose streptozotocin (STZ) in both AT2R knockout (AT2RKO) and wild-type (WT) male mice aged 12 weeks and followed them for 4 weeks. Three subgroups nondiabetic, diabetic, and insulin-treated diabetic (Rx insulin implant) were studied. Systolic blood pressure (SBP), physiological parameters, glomerular filtration rate (GFR), renal morphology, gene expression, and apoptosis were assessed. After 4 weeks of diabetes, compared to WT controls, AT2RKO mice clearly developed features of early diabetic nephropathy (DN), such as renal hypertrophy, tubular apoptosis, and progressive extracellular matrix (ECM) protein accumulation as well as increased GFR. AT2RKO mice presented hypertension unaffected by diabetes. Renal oxidative stress (measured as heme oxygenase 1 (HO-1) gene expression and reactive oxygen species (ROS) generation) and intrarenal renin angiotensin system components, such as angiotensinogen (Agt), AT1R, and angiotensin-converting enzyme (ACE) gene expression, were augmented whereas angiotensin-converting enzyme2 (ACE2) gene expression was decreased in renal proximal tubules (RPTs) of AT2RKO mice. The renal changes noted above were significantly enhanced in diabetic AT2RKO mice but partially attenuated in insulin-treated diabetic WT and AT2RKO mice. In conclusion, AT2R deficiency accelerates the development of DN, which appears to be mediated, at least in part, via heightened oxidative stress and ACE/ACE2 ratio in RPTs.
Weak Convergence of the Projection Type Ishikawa Iteration Scheme for Two Asymptotically Nonexpansive Nonself‐Mappings
Authors: Thianwan Tanakit
Published: October 2011

We study weak convergence of the projection type Ishikawa iteration scheme
for two asymptotically nonexpansive nonself‐mappings in a real uniformly convex Banach
space E which has a Fréchet differentiable norm or its dual E* has the Kadec‐Klee property. Moreover, weak convergence of projection type Ishikawa iterates of two asymptotically
nonexpansive nonself‐mappings without any condition on the rate of convergence associated with the two maps in a uniformly convex Banach space is established. Weak convergence theorem without making use of any of the Opial′s condition, Kadec‐Klee property, or Fréchet differentiable norm is proved. Some results have been obtained which generalize and unify many important known results in recent literature.
A Self-Similar Flow behind a Magnetogasdynamic Shock Wave Generated by a Moving Piston in a Gravitating Gas with Variable Density: Isothermal Flow
Authors: Nath G. , Sinha A. K.
Published: October 2011

The propagation of a cylindrical (or spherical) shock wave in an ideal gas with azimuthal magnetic field and with or without self-gravitational effects is investigated. The shock wave is driven out by a piston moving with time according to power law. The initial density and the initial magnetic field of the ambient medium are assumed to be varying and obeying power laws. Solutions are obtained, when the flow between the shock and the piston is isothermal. The gas is assumed to have infinite electrical conductivity. The shock wave moves with variable velocity, and the total energy of the wave is nonconstant. The effects of variation of the piston velocity exponent (i.e., variation of the initial density exponent), the initial magnetic field exponent, the gravitational parameter, and the Alfven-Mach number on the flow field are obtained. It is investigated that the self-gravitation reduces the effects of the magnetic field. A comparison is also made between gravitating and nongravitating cases.
Ultrasound Biomicroscopy in Small Animal Research: Applications in Molecular and Preclinical Imaging
Authors: Greco A. , Mancini M. , Gargiulo S. , Gramanzini M. , Claudio P. P. , Brunetti A. , Salvatore M.
Published: October 2011

Ultrasound biomicroscopy (UBM) is a noninvasive multimodality technique that allows high-resolution imaging in mice. It is affordable, widely available, and portable. When it is coupled to Doppler ultrasound with color and power Doppler, it can be used to quantify blood flow and to image microcirculation as well as the response of tumor blood supply to cancer therapy. Target contrast ultrasound combines ultrasound with novel molecular targeted contrast agent to assess biological processes at molecular level. UBM is useful to investigate the growth and differentiation of tumors as well as to detect early molecular expression of cancer-related biomarkersin vivoand to monitor the effects of cancer therapies. It can be also used to visualize the embryological development of mice in uterus or to examine their cardiovascular development. The availability of real-time imaging of mice anatomy allows performing aspiration procedures under ultrasound guidance as well as the microinjection of cells, viruses, or other agents into precise locations. This paper will describe some basic principles of high-resolution imaging equipment, and the most important applications in molecular and preclinical imaging in small animal research.
Walnut Allergy in Peanut-Allergic Patients: Significance of Sequential Epitopes of Walnut Homologous to Linear Epitopes of Ara h 1, 2 and 3 in Relation to Clinical Reactivity
Authors: Rosenfeld Leonard , Shreffler Wayne , Bardina Ludmilla , Niggemann Bodo , Wahn Ulrich , Sampson Hugh A. , Beyer Kirsten
Published: October 2011

Background: Peanut allergy is a frequent and potentially life-threatening food allergy. Despite the large taxonomic distance between the plants, peanut-allergic patients often react to tree nuts such as walnuts. While the allergens of peanut and walnut have a high degree of homology in their amino-acid sequences, it is unknown whether this similarity is responsible for the observed co-reactivity. Therefore, we analyzed the binding of specific IgE antibodies to sequential epitopes of peanut and walnut in peanut-allergic patients with and without walnut allergy. Methods: The IgE binding to previously described sequential epitopes of peanut and the homologous regions of walnut was assessed in 32 peanut-allergic patients using a peptide microarray technology. Twelve patients had a clinically relevant walnut allergy and 20 were tolerant to walnut. Inhibition assays with peanut peptides and corresponding walnut sequences were performed to show specific binding to sequential epitopes. Results: No differences in the recognition of sequential epitopes could be found between peanut-allergic patients with or without walnut allergy. Only a few patients showed IgE binding to walnut sequences that corresponded to sequential epitopes of peanut. In the inhibition assays, no relevant cross-reacting IgE antibodies could be detected for the peptides analyzed. Conclusion: Our results indicate that although they share a rather high degree of homology with the corresponding regions of walnut allergens, the sequence stretches previously identified as sequential IgE binding epitopes of Ara h 1, Ara h 2 and Ara h 3 have no IgE binding equivalents in walnut allergens.
Imaging Geographic Atrophy in Age-Related Macular Degeneration
Authors: Göbel Arno P. , Fleckenstein Monika , Schmitz-Valckenberg Steffen , Brinkmann Christian K. , Holz Frank G.
Published: October 2011

Advances in retinal imaging technology have largely contributed to the understanding of the natural history, prognostic markers and disease mechanisms of geographic atrophy (GA) due to age-related macular degeneration. There is still no therapy available to halt or slow the disease process. In order to evaluate potential therapeutic effects in interventional trials, there is a need for precise quantification of the GA progression rate. Fundus autofluorescence imaging allows for accurate identification and segmentation of atrophic areas and currently represents the gold standard for evaluating progressive GA enlargement. By means of high-resolution spectral-domain optical coherence tomography, distinct microstructural alterations related to GA can be visualized.
Preventive Scleral Buckling and Silicone Oil Tamponade Are Important for Posttraumatic Endophthalmitis Successfully Managed with Vitrectomy
Authors: Lin Haotian , Ling Shiqi , Liu Zhaochuan , Zhong Xiaojian , Chen Weirong
Published: October 2011

Aims: Posttraumatic endophthalmitis (PTE) managed with pars plana vitrectomy (PPV) and a variety of other methods often resulted in retinal detachment (RD), which deteriorates postoperative visual acuity (VA). We investigated initial ocular conditions, surgical management and outcomes of PTE patients and analyzed their relationship in order to find the necessary management for different patients’ conditions. Methods: Retrospective study. Medical records of 62 consecutive patients who were diagnosed with PTE and managed with PPV were retrospectively analyzed. The included patients were divided into two groups depending on their initial VA, with light perception (LP) as borderline: group A (12 cases; VA = LP) and group B (50 cases; VA > LP). Specific variables related to surgical outcomes were analyzed, including: initial VA; intraocular foreign body; location and length of the wound; microbiologic test; cataract extraction; scleral buckling; silicon oil tamponade; gas tamponade, and retinal restoration. Data were statistically analyzed by the χ2 test, by univariate analysis for predictors and by multivariate logistic regression analysis. Results: RD happened in 19 (30.6%) of the 62 cases included. There were 6 cases (50%) in group A and 13 cases (26%) in group B which resulted in RD. Statistical analysis demonstrated that none of the related factors were correlated to the occurrence of RD (all factors: p > 0.05) in group A, but in group B, scleral buckling (with: 2/22, 9%; without: 11/28, 39%; p < 0.05) and silicone oil tamponade (with: 0/6; without: 13/44, 30%; p < 0.05) were statistically significantly correlated to the occurrence of RD. Conclusions: Preventive scleral buckling and silicone oil tamponade are important for patients with good initial VA (VA > LP) to be successfully managed by PPV.
In Vivo Implantation of Tissue‐Engineered Human Nasal Septal Neocartilage Constructs
Authors: Chang Angela A. , Reuther Marsha S. , Briggs Kristen K. , Schumacher Barbara L. , Williams Gregory M. , Corr Maripat , Sah Robert L. , Watson Deborah
Published: October 2011

Objective

To determine the in vivo biocompatibility of septal neocartilage constructs developed in vitro by an alginate intermediate step.

Study Design

Prospective, animal model.

Setting

Research laboratory.

Subjects and Methods

A murine model was used to examine the maturation of neocartilage constructs in vivo. Chondrocytes collected from patients undergoing septoplasty were expanded in monolayer and suspended in alginate beads for 3‐dimensional culture in media containing human serum and growth factors. After in vitro incubation for 5 weeks, the constructs were implanted in the dorsum of athymic mice for 30 and 60 days (n = 9). After the mice were sacrificed, the constructs were recovered for assessment of their morphological, histochemical, biochemical, and biomechanical properties.

Results

The mice survived and tolerated the implants well. Infection and extrusion were not observed. Neocartilage constructs maintained their general shape and size and demonstrated cell viability after implantation. The implanted constructs were firm and opaque, sharing closer semblance to native septal tissue relative to the gelatinous, translucent preimplant constructs. Histochemical staining with hematoxylin and eosin (H&E) revealed that the constructs exhibited distinct morphologies characteristic of native tissue, which were not observed in preimplant constructs. DNA and type II collagen increased with duration of implantation, whereas type I collagen and glycoaminoglycans (GAG) decreased. Mechanical testing of a 60‐day implanted construct demonstrated characteristics similar to native human septal cartilage.

Conclusions

Neocartilage constructs are viable in an in vivo murine model. The histologic, biochemical, and biomechanical features of implanted constructs closely resemble native septal tissue when compared with preimplant constructs.