bluuebunny/crossref_metadata_2025 huggingface dataset:
1,3-Dipolar cycloaddition of C-benzoyl-N-phenylnitrone to oxanorbornadiene and oxanorbornene derivatives; endo-exo and site selectivity
Authors: Fišera Lubor , Kováč Jaroslav , Patúš Juraj , Pavlovič Dušan
Published: March 2011

C-Benzoyl-N-phenylnitrone (Ia) and C,N-diphenylnitrone (Ib) react with 2,3-dimethoxycarbonyl-7-oxabicyclo[2,2,1]heptadiene (II) to give endo- and exo-adducts at both the substituted double bonds. The endo-exo and site selectivity of 1,3-dipolar cycloaddition is discussed. Cycloadditions of the nitrones Ia and Ib to 5,6-dimethoxycarbonyl-7-oxabicyclo[2,2,1]heptene and 2,3-dimethoxycarbonyl-7-oxabicyclo[2,2,1]-2-heptene are also described.
Basic amides of 2,4,5-trichlorophenoxyacetic, 2,4,6-trimethylphenoxyacetic and 4-bromo-3,5-dimethylphenoxyacetic acid and some related compounds; Synthesis and pharmacological screening
Authors: Valenta Vladimír , Němec Jiří , Protiva Miroslav
Published: March 2011

Reactions of methyl esters II of 2,4,5-trichlorophenoxyacetic (Ia), 2,4,6-trimethylphenoxyacetic (Ib) and 4-bromo-3,5-dimethylphenoxyacetic acid (Ic) with 2-diethylaminoethylamine, 2-morpholinoethylamine, 3-morpholinopropylamine, 1-methylpiperazine, 3-(4-methylpiperazino)propylamine, 3-[4-(2-tolyl)piperazino]propylamine and 1,4-bis(3-aminopropyl)piperazine in boiling ethanol gave the basic amides Va-XIc which were isolated as hydrochlorides. Reactions of the acid chlorides IVa and IVb with 1,4-bis(2-hydroxyethyl)piperazine and 1,4-bis(3-hydroxypropyl)piperazine in dimethylformamide resulted directly in dihydrochlorides of diesters XIIab and XIIIab. The compounds prepared have only weak CNS effects (mostly of the depressant type); they have local anaesthetic, mild hypotensive (some of them adrenolytic), antiarrhythmic and peripheral vasodilating activities.
Physico-chemical properties of the ternary system urea-ammonium nitrate-water. Density
Authors: Bartovská Ludmila , Hejtmánková Jiřina , Šišková Marie , Jäger Lubomír
Published: March 2011

Density of the ternary system urea-ammonium nitrate-water was measured in the range of overall concentrations 0-75 mass % at temperatures of 0, 20, 30 and 40 °C. The experimental data are compared with the values calculated from the relation obtained by combining the temperature dependences of densities of the binary systems urea-water and ammonium nitrate-water.
Radioimmunoanalytical determination of the specific activity of [125I]L-thyroxine
Authors: Talán Peter , Mucha Juraj
Published: March 2011

The possibility to determine directly the specific activity of [125I]L-thyroxine by the usual radioimmunoanalytical procedure using the data required for the determination of the calibration graph is demonstrated in this study. This approach, which is from the point of view of the mathematical formalism similar to the double substoichiometric isotopic dilution, can be used - due to its simplicity and sufficient precision in certain cases - for the determination of the specific activity of radioindicators used in the radioimmunoanalysis, particularly for the univalent (from the point of view of immunochemistry) haptenes. The method is limited by the index of heterogeneity of the used antiserum.
Epimerization of esters of stereoisomeric 8-ergolinecarboxylic acids on carbon C(8)
Authors: Beneš Jan , Černý Antonín , Miller Vladimír , Kudrnáč Stanislav
Published: March 2011

Esters of 8β-ergolinecarboxylic acids, I-XI, exposed to strong bases, such as lithium diisopropylamide, in polar aprotic solvents gave enolates, which were decomposed by suitable proton donors to a mixture of epimers. This contained, apart from the starting 8β-esters, the corresponding 8α-esters, Ia-IVa and VIa-XIa (65-80%) and Va (about 16%). Exposure of 8α-ester XIIa to these conditions produced epimerization on C(8) (about 54%) and, to a small extent, isomerization on C(10), affording ester I (c. 1%) and Ia (c. 5%).
The crystal and molecular structure of calcium (S,S)-ethylenediamine-N,N'-disuccinatoferrate octahydrate
Authors: Pavelčík František , Kettmann Viktor
Published: March 2011

Crystals of Ca[Fe((S,S)-EDDS)]2.8 H2O are monoclinic with lattice parameters of a = 1.0284, b = 0.8403, c = 2.1273 nm, β = 116.04°. The space group is Pc, Z = 2. The structure was solved by the heavy atom method and refined by the least squares method to give R = 0.057. The crystals consist of [Fe(III) ((S,S)-EDDS)]- anions, hydrated Ca2+ cations and molecules of water of crystallization. The iron atoms are coordinated by two nitrogen atoms and four oxygen atom of the carboxyl groups of the hexadentate ligand. The coordination polyhedron of the iron atom forms a deformed octahedron. The absolute configuration of the complex is (O,C-6-13-A) for the (S,S) absolute ligand configuration.
Substituent effect in electrochemical and ferricyanide oxidations of para-substituted 1-benzyl-3-carbamoyl-1,4-dihydropyridines
Authors: Pavlíková-Raclová Františka , Kuthan Josef
Published: March 2011

Half-wave potentials E1/2 of electrochemical oxidation of the title 1,4-dihydropyridine derivatives with the substituents N(CH3)2, OCH3, CH3, H, F, Cl, COOCH3, and CN have been measured on platinum rotating disc electrode in aqueous and anhydrous dimethylformamide, and apparent rate constants k2 of their oxidation with potassium ferricyanide have been measured in water at 298 K. The two quantities (E1/2 and k2) have been correlated both mutually and with empirical σp constants of the substituents. The found correlation relations have been discussed with respect to mechanism of the two transformations investigated.
Dissociation constants of m- and p-substituted phenylthioureas and ureas in water and in methanol
Authors: Kaválek Jaromír , Štěrba Vojeslav , El Bahaie Said
Published: March 2011

Dissociation constants of nine m- and p-substituted phenylthioureas, 4-nitrophenylurea, and 1-(4-nitrophenyl)-3,3-dimethylurea have been measured in water and in methanol. The pKa values in methanol are higher than those in water by about 4 units. The Hammett ρ constant has the values 2.6 and 2.35 in water and in methanol, respectively. The pKa difference between 4-nitrophenylurea and 4-nitrophenylthiourea is 2.85 in methanol and 3.25 in water.
Simulation of chemical processes with uncertain parameters
Authors: Dohnal Mirko , Ulmanová Marie
Published: March 2011

An integral part of the simulation problem are numerical values of parameters or constants of industrial units. Either these quantities need not be known accurately or it is not possible to control them at the set up value. The result of simulation cannot be then accurate. It is necessary to determine the region in which the flow rates of components through branches could change when the parameters and constants change. For these purposes is applicable the Monte Carlo method. But it is very time-consuming. Here, algorithms are proposed which with the use of the algebraic norm approximately determine the looked-for set of flow rate uncertainty. These algorithms can be applied for solution of a number of practical problems related with optimum sizing of units, sensitivity studies etc. An example is given of a cooling cascade cycle.
1,3-Dipolar cycloadditions of C-benzoyl-N-phenylnitrone indole derivatives
Authors: Fišera Lubor , Mesko Peter , Leško Ján , Dandárová Miloslava , Kováč Jaroslav , Goljer Igor
Published: March 2011

Reaction of the title nitrone I with indole derivatives IIa,b gives the 1,3-addition product IIIa,b, its hydrogenated derivative IVa,b and dehydrogenation products VIa,b and VIIa,b from transient product of 1,3-dipolar cycloaddition (V). Indole itself only gives cycloaddition products VIc and VIIc. Carbazole derivative VIII does not react due to sterical reasons. The reaction course is discussed on the basis of PMO theory. Structure of the products has been proved by 1H and 13C NMR, IR, UV, and mass spectra.
Preparation of isomeric 3-aminopropylamino derivatives of 9-(RS)-(2,3-dihydroxypropyl)adenine
Authors: Holý Antonín
Published: March 2011

Treatment of 9-(RS)-(2,3-dihydroxypropyl)adenine (III) with bromine in water afforded the 8-bromo derivative IV which on reaction with acetone was converted into the 1,3-dioxolane derivative VI. Reaction of compound VI with 1,3-diaminopropane, followed by acid hydrolysis, gave 9-(RS)-(2,3-dihydroxypropyl)-8-(3-aminopropylamino)adenine (VIII). Compound IV reacts with 1,3-diaminopropane under formation of a mixture of compound VIII and isomeric 9-(RS)-[3(2)-(3-aminopropylamino)-2(3)-hydroxypropyl]-8-hydroxyadenines (IX, X). 9-(RS)-(2,3-Dihydroxypropyl)-8-hydroxyadenine (XVII) was prepared by reaction of compound VI with sodium benzoxide in dimethylformamide and subsequent acid hydrolysis. Its tosylation, followed by reaction of the obtained 3'-O-p-toluenesulfonyl derivative XVIII with 1,3-diaminopropane, furnished also the compound IX. In an analogous way, 9-(RS)-[3-(3-aminopropylamino)-2-hydroxypropyl]adenine (XXI) was prepared from 3'-O-p-toluenesulfonyl derivative of compound III (XX).
Graph theory approach
Authors: Kvasnička Vladimír
Published: March 2011

A graph-theory formalism of the organic chemistry is suggested. The molecular system is considered as a multigraph with loops, the vertices are evaluated by their mapping onto the vocabulary of vertex labels (e.g. atomic symbols). A multiedge of multiplicity t corresponds to a t-tuple (single, double, triple, etc) bond. The chemical reaction of molecular systems is treated by the transformation of graphs. The suggested graph-theory approach allows to formalize many notions and concepts that are naturally emerging in the computer simulation of organic chemistry.
TPD-MS study of carbonation and hydration of Yb2O3(C)
Authors: Bernal S. , García R. , López J. M. , Rodríguez-Izquierdo J. M.
Published: March 2011

A TPD-MS study of the behaviour of Yb2O3(C) against atmospheric environment has been carried out. Contrary to suggestions in the literature, the results show that after prolonged atmospheric exposure (3 years) bulk hydration and carbonation of ytterbia take place. If this sample, previously regenerated by calcination in helium flow at 870 K, is exposed to the atmosphere up to 80 hours, only surface reactions seem to occur. The present study, in which several CO2 and H2O treatments have been included, suggests that over Yb2O3, the hydration and carbonation reactions are related to each other, the amount and thermal stability of adsorbed CO2 being determined by the surface water content. The discussion of the results is based on a surface model of Yb2O3.
7-Oxo-7H-benzimidazo[2,1-a]benz[d,e]isoquinoline-9-sulphonyl chloride as a new fluorescence reagent for identification and determination of aliphatic amines
Authors: Tocksteinová Dagmar , Novák Antonín , Horáková Hana , Nepraš Miloš , Churáček Jaroslav
Published: March 2011

Absorption and fluorescence properties have been studied of a new fluorescence reagent - 7-oxo-7H-benzimidazo[2,1-a]benz[d,e]isoquinoline-9-sulphonyl chloride and the corresponding sulphonamides derived from aliphatic amines. The fluorescence intensity is temperature-independent in the range 0-35 °C and depends linearly on concentration of the sulphonamides in the range 6 . 10-9 to 1 . 10-6 mol l-1. TLC separation of the sulphonamides is good, the yields of elution being 95%, which allows application of the procedure to determination of the amines.
Density estimates of binary aqueous solutions
Authors: Söhnel Otakar , Novotný Petr , Šolc Zdeněk
Published: March 2011

Two methods are given for assessment of density of binary aqueous solutions of electrolytes; one is based on partial molar volume of the dissolved electrolyte at infinite dilution, and the other is based on additivity of apparent molar volumes at a given concentration. The density estimates of aqueous solutions by means of the two methods are compared with experimental values for some electrolytes of the type 1-1 to 4 and 2-2. In all cases the estimates agree with experimental densities up to concentrations of the saturated solutions.
Dissociation constants of monosubstituted diphenylamines and an optimized construction of acidity function
Authors: Pytela Oldřich , Vetešník Pavel
Published: March 2011

Eleven monosubstituted diphenylamines have been synthetized, and concentration ratio of the protonated and free bases has been measured in aqueous sulphuric acid in the concentration range 1.0 . 10-3 to 9.0 mol l-1. An algorithm has been suggested and used for determination of optimized values of pK and H'' acidity function within sulphuric acid concentration range 0.05 to 9.0 mol l-1. The results have been compared with literature data and discussed in terms of theory of acidity functions and linear free energy relationships.
Preparation of 2-amino-2,4-dideoxy-D-lyxo-hexopyranose (4-deoxy-D-mannosamine) from 1,6-anhydro-β-D-glucopyranose
Authors: Černý Ivan , Trnka Tomáš , Černý Miloslav
Published: March 2011

1,6-Anhydro-4-deoxy-2-O-p-toluenesulfonyl-β-D-xylo-hexopyranose (III), obtainable by a four-step synthesis from 1,6-anhydro-β-D-glucopyranose, was converted to 3-O-(N-benzylcarbamoyl) derivative V on reaction with benzyl isocyanate. The cyclization of V with sodium hydride in dimethylformamide gave a derivative of oxazolidin-2-one, VII, which on alkaline hydrolysis and hydrogenolysis gave the hydrochloride of 2-amino-1,6-anhydro-2,4-dideoxy-β-D-lyxo-hexopyranose (XI). When 1,6-anhydro derivative XI was treated with hydrochloric acid the hydrochloride of 2-amino-2,4-dideoxy-D-lyxo-hexopyranose (XIV) was obtained. Corresponding N-acetyl derivative XVI is suitable for studies of enzymatic synthesis of N-acetylneuraminic acid.
Interfacial heat and mass transfer in the turbulent flow and its experimental verification
Authors: Vašák František , Kolář Václav , Brož Zdeněk
Published: March 2011

Various methods have been discussed of experimental measurement of interfacial mass transfer under the turbulent flow in a tube at high values of the Schmidt number. Difficulties and shortcomings have been discussed of the determination of the mass transfer coefficient k∞+, i.e. the quantity necessary for experimental verification of theoretical models. Necessity has been stressed of devising special experiments to further elucidate the mechanism of interfacial heat and mass transfer in the turbulent flow.
Preparation of some 8-oxa derivatives of 2,4-dienoic acid esters
Authors: Streinz Ludvík , Romaňuk Miroslav
Published: March 2011

The method of preparation of the esters of 8-oxa-2,4-dienoic acids is described, utilizing 3-methyl-4-oxa-6-heptynal (III) as the key intermediate which was prepared on addition of 2-propyn-1-ol to 2-butenal.
4,4-Dimethyl-A-homoandrostane epoxides
Authors: Velgová Helena
Published: March 2011

The configuration of the oxygen-containing substituent in the position 3 of some 4,4-dimethyl-A-homo-4a-androstene derivatives was determined and their epimeric 4a,5-epoxides were prepared. The acid catalysed opening of the 4a,5-epoxide ring in epoxides XV and XXIX with the trans-orientation of the substituent in the position 3 and the epoxide ring afforded the products of 5(0)n participation of the 3-substituent, i.e. 3,5-transannular epoxides XVII and XXX. 3,5-Transannular epoxides XXII, XXXIV and XXXVI were prepared as substances with a potential biological activity.
Pyrolysis of primary and hydrogenated kerosenes
Authors: Bajus Martin , Baxa Jozef , Maťaš Michal
Published: March 2011

Pyrolysis of primary, hydrotreated and hydrogenated kerosene and hydrogenated fraction 160-280 after separation of alkanes was studied in a stainless steel tubular reactor at 800 °C in the presence f steam. Pyrolysis of hydrogenated feedstocks leads to an increased conversion into low molecular olefins and alkanes. The presence of 0.05% of elemental sulphur increases the conversion of primary kerosene into gaseous pyrolysis products. The formation of carbon monoxide is inhibited by the passivation of the reactor wall with hydrogen sulphide. The effect of elemental sulphur on the formation of coke was investigated in the pyrolysis of kerosene in a stainless steel tubular reactor at 800 and 810 °C without steam. In comparison with the pyrolysis of primary kerosene, hydrogenated materials are more inclined to form coke. In the presence of 0.05% sulphur coking decreases.
Synthesis of 1,2,4-triazine-3,5(2H,4H)-diones containing electronegative substituents in position 6
Authors: Farkaš Jiří
Published: March 2011

Reaction of fluorine with 1,2,4-triazine-3,5(2H,4H)-dione (I) in acetic acid afforded the 6-fluoro derivative II in low yield. The 6-nitro compound III was prepared by oxidation of the 6-amino derivative of compound I with hydrogen peroxide in trifluoroacetic acid. Synthesis of the 6-cyano compound IV was accomplished by treatment of the 6-bromo derivative with cuprous cyanide in N,N,N',N'-tetramethylurea. The effect of substituents on the carbonyl frequencies for 6-substituted derivatives of I was studied.
Diethyl ether sorption on titanium trichloride and its correlation with catalytic activity in the polymerization of propene
Authors: Pololáník Luboš , Mejzlík Jiří , Hamřík Oldřich , Blatný Jan
Published: March 2011

A series of samples exhibiting different catalytic activity and sorption properties was obtained by grinding two basic types of titanium trichloride (TiCl3.1/3 AlCl3 and TiCl3). The samples with co-crystallized AlCl3 can sorb, under otherwise identical conditions, by an order of magnitude more diethyl ether than those of pure TiCl3. The amount of sorbed ether increases with its partial pressure and decreases when elevating the temperature of sorption. There is a correlation between the quantity of ether sorbed on TiCl3 and the catalytic activity of the latter in the propene polymerization. This correlation is, however, different for both examined catalyst types.
Kinetics of acid-catalyzed hydrolysis of fluorinated propanoates
Authors: Paleta Oldřich , Kvíčala Jaroslav , Dědek Václav
Published: March 2011

Rates of hydrolysis, kH+, of methyl 2-chloro-2,3,3,3-tetrafluoro-(III), 2,3-dichloro-2,3,3-trifluoro-(IV), 2,2,3-trichloro-3,3-difluoro-(V), 2,3,3,3-tetrafluoro-(VI) and 3-chloro-2,3,3-trifluoropropanoate (VII) were measured in 0.5M-HCl in aqueous methanol (80% vol; 76% wt) at 40, 50 and 60 °C. The relative rate constants, krel (50 °C), (for the propanoate III, kH+ = 4.3 . 10-5 l mol-1 s-1; krel = 100) are 311, 100, 38, 9.4, 44 and 15 for the esters II, III, IV, V, VI and VII, respectively (experimental error ±9%). It was found that krel = αβ where α and β are the following factors for groups in the position 2 and 3: CClF 10, CHF 4.2, CCl2 2.8, CF3 10 and CClF2 3.6. The rate constants obey the isokinetic relationship. For the ester III the dependence of log kobs on logarithm of hydrogen chloride concentration is linear at concentrations 0.08-2.4 mol l-1 which, together with high activation entropy ΔS≠ for the esters III-VII (-167 to -217 J mol-1 K-1), shows that the hydrolysis proceeds by an AAC2 mechanism.
Photochemical reactions of phenanthrenequinone and duroquinone with substituted 2(3H)-oxazolones
Authors: Sekretár Stanislav , Kopecký Jan , Martvoň Augustin
Published: March 2011

9,10-Phenanthrenequinone forms α-oxo-oxetane (VIII) when irradiated with 3-acetyl-2(3H)-oxazolone, and it gives adducts X-XII with 3,4,5-trisubstituted 2(3H)-oxazolones IV-VI. Duroquinone forms spirooxetanes XIII and XIV on photocycloaddition with IV and V.
Immobilization of chymotrypsin (E.C.3.4.21.1), subtilisin (E.C.3.4.21.14) and neutral proteinase from Bacillus subtilis by covalent binding to benzoquinone-activated pearl cellulose
Authors: Škachová Helena , Kučera Jiří
Published: March 2011

Chymotrypsin (E.C.3.4.21.1), subtilisin (E.C.3.4.21.14), and a neutral proteinase from Bacillus subtilis were immobilized by covalent binding to benzoquinone-activated pearl cellulose. The yield of the immobilized protein was 55% in the case of chymotrypsin and 50% in the case of subtilisin and neutral proteinase from B. subtilis. The determination of activation energy at a low substrate concentration showed that the enzyme activity is limited by diffusion under these conditions. The activity yields are generally very good yet the activity of the enzymes immobilized is relatively low, most likely because of the presence of benzoquinone, as shown in experiments with the immobilization of chymotrypsin by the same technique on supports with different hydrophilicity.
The crystal and molecular structure of bis(ethylenediamine) copper(II) selenocyanate
Authors: Vrábel Viktor , Lokaj Jan , Garaj Ján
Published: March 2011

The crystal structure of [Cu(en)2](SeCN)2 was solved by the heavy atom method and refined by the least squares method using the full matrix and anisotropic thermal parameters to a value of R = 0.063 for 660 observed reflections. The crystals are triclinic , with a space group of P1 and lattice parameters of a = 6.660(2), b = 9.360(2), c = 7.754(2) . 10-10 m, α = 129.22(2), β = 109.87(2) and γ = 92.38(2)°, Z = 1. The structure consists of discrete molecules that are centrosymmetric. The Cu(II) atom occupies a special position at the centre of symmetry and is coordinated by 4 nitrogen atoms from two bidentate ethylenediamine molecules: C-N 1.999(8) and 2.033(8) . 10-10 m and angle N1-Cu-N2, 84.1(3)°. The selenium atom in the SeCN group completes this square planar arrangement to form a deformed octahedron along the longer Cu...Se distance of 3.263(2) . 10-10 m. The ethylenediamine molecule has a non-symmetrical gauche arrangement with the carbon atoms C1 and C2 + 0.542 and -0.095 . 10-10 m above and below the N1-Cu-N2 coordination plane, respectively.
Inelastic mean free paths of photoelectrons from polymer surfaces determined by the XPS method
Authors: Lukáš Jaromír , Ježek Břetislav
Published: March 2011

Inelastic mean free paths were determined for a number of polymeric materials by using the X-ray photoelectron spectroscopy method. Some of the results obtained are confronted with other reported data; the majority have not been published yet.
N-Deacetyl-N-3-oxobutyrylcolchicine, an alkaloid from Colchicum autumnale L. seeds
Authors: Šantavý František , Sedmera Petr , Vokoun Jindřich , Dvoráčková Svatava , Šimánek Vilím
Published: March 2011

The structure of N-deacetyl-N-3-oxobutyrylcolchicine (V), based on spectroscopic measurements, was proposed for a minor alkaloid isolated from seeds of Colchicum autumnale L.
Reactive polymeric carriers obtained by suspension polymerization of hydroxyethyl methacrylate sulphonates
Authors: Beneš Milan J. , Peška Jan
Published: March 2011

Reaction of monomeric 2-hydroxyethyl methacrylate with sulphochlorides, such as e.g. toluenesulphonyl chloride, gives rise to asymmetrical ethylene esters which can be polymerized to beads possessing alkylating properties. In this procedure, a single precursor can be used to prepare a large variety of polymeric sorbents, catalysts, and the like.
New synthesis of 2-(4-nitrophenyl)-1-(5-nitro-2-furyl)ethylene and 2-(4-ethoxycarbonylphenyl)-1-(5-nitro-2-furyl)ethylene
Authors: Hrabovský Ján , Kováč Jaroslav
Published: March 2011

(E)-2-Ar-1-(5-nitro-2-furyl)ethylenes (where Ar is O2N-C6H4- or H5C2OOC-C6H4-) were prepared by reaction of aryldiazonium salts with 3-(5-nitro-2-furyl)-2-propenoic acid or 2-bromo-1-(5-nitro-2-furyl)ethylene. Photochemical modification of the Meerwein reaction was also checked.
Binding of zinc cations to pectin and its oligomeric fragments
Authors: Malovíková Anna , Kohn Rudolf
Published: March 2011

The activity of Zn2+ ions bound to carboxyl groups of pectin of esterification degree E 0 to 90% and to oligomeric potassium galacturonates of polymerization degree 1 to 7 was estimated by the metallochromic indicator (tetramethylmurexide) method. The zinc ions are stoichiometrically bound to pectin, one Zn2+ cation to two free carboxyl groups. The stability constant K of zinc pectinates strongly decreases with the increasing esterification degree in a relationship close to a linear logarithmic function, log K = f(E) similarly, as with the binding of Ca2+ ions to pectin. Pectin reveals a little higher selectivity to Zn2+ ions when considering this couple of cations. The zinc ions are bound to the monomeric D-galacturonic acid to a very low extent in contrast to some toxic cations as e.g. Pb2+, Cu2+, and Cd2+. A continuous increase of the degree of association of Zn2+ ions with carboxyl groups of oligomers takes place with the increasing polymerization degree. The validity of the increment additivity of terminal and inner uronic acid units to the final activity of zinc counterions bound to these oligomers was proved. The results are discussed from the standpoint of application of pectin as an active component of prophylactic diets against poisoning with cations of toxic metals with respect to the excretion of Zn2+ ions from the human body. Findings concerning the interaction of Zn2+ ions with pectin in dependence on its esterification degree (E) constitute a theoretical basis for a potential application of pectin as a useful ligand of Zn2+ ions in medical treatment of zinc deficiency in the human body.
Kinetics of the reaction between hexamethylenediisocyanate and 1-pentanol
Authors: Hudeček Slavko , Bohdanecký Miloslav , Hudečková Ivana , Špaček Pavel , Čefelín Pavel
Published: March 2011

The reaction between hexamethylenediisocyanate and 1-pentanol in toluene was studied by means of reversed-phase liquid chromatography. By employing this method, it was possible to determine all components of the reaction mixture including both products, i.e. N-(6-isocyanate hexyl)pentylcarbamate and N,N'-bis(pentyloxycarbonyl)hexamethylenediamine. Relations for the calculation of kinetic constants were derived assuming a competitive consecutive second-order reaction. It was demonstrated that the reaction involved in this case is indeed a second-order reaction, and the rate constants of the first and second consecutive reactions were determined.
Solvent effect - Classification of parameters describing influence of solvents
Authors: Svoboda Petr , Pytela Oldřich , Večeřa Miroslav
Published: March 2011

On the basis of factor analysis of data matrices containing 35 empirical and non-empirical parameters for 85 solvents (or a limited matrix of 20 parameters for 51 solvents), an orthogonal set of parameters with normed normal distribution has been suggested which characterizes influence of the solvents on chemical processes. A four-parameter equation has been suggested for description of the solvent effect in the form A = A0 + aAP + bBP + eEP + pPP, where AP, BP, EP, PP are newly introduced parameters expressing individual types of interactions between solvent and solute. A comparison has been carried out of these parameters with those defined earlier. The new set of parameters was tested with 22 examples taken from literature. The correlations obtained show higher or comparable agreement as compared with those carried out earlier. Values of the regression coefficients make it possible to discuss the reaction mechanisms from the point of view of solvent effects.
A new heterocyclic ring closure in ferricyanide oxidation of 2,4,6-triphenylpyridinium salts
Authors: Nesvadba Petr , Štrop Petr , Kuthan Josef
Published: March 2011

The quaternary pyridinium salts Ia-Ic react with alkaline solution of potassium ferricyanide to give the condensed heterocyclic derivatives IIIa, b, IV, whereas the salts Id-If give the pyrrole derivatives IIa-IIc under the same conditions. The diaza heterocycle IIIa reacts with methyl iodide to give methoiodide V, whereas by action of bromine it produces two monobromo derivatives VIa, b. The pyrrole derivatives IIa, b give monobromo derivatives IId, e on bromination. A probable mechanism of formation of the heterocyclic derivatives is discussed.
Synthetic oligopeptides as polymer precursors
Authors: Masař Bohumil , Čefelín Pavel
Published: March 2011

By reacting N-carboxyanhydrides of L-phenylalanine, DL-phenylalanine, L-leucine or of a mixture of DL-phenylalanine and L-leucine with hexamethylenediamine (15-20 mol.% related to monomer) in absolute benzene at 25 °C, which was followed by an additional treatment with hexamethylenediamine (60 °C, 4 h), oligopeptides were prepared with the average functionality (Fn) 1.72-1.96 with respect to primary amino groups. The reaction between these oligopeptides and poly(oxyethylene) terminated with isocyanate groups (Fn 1.69-1.94) in anhydrous chloroform at 25 °C leads to copolymers of the type A-B and A-B-A with a minority content of copolymers (A-B)m for m ≥ 2. The low efficiency of the coupling reaction is attributed to the formation of an important amount of monofunctional oligopeptide in the preparation reaction.
Choice of electrolyte for electrochemical machining from the point of view of intergranular corrosion
Authors: Novák Petr , Roušar Ivo , Číhal Vladimír
Published: March 2011

In a study of electrochemical drilling, the influence of the electrolyte composition on intergranular corrosion of various nickel alloys and of hardenable stainless steel was investigated. The nickel-base alloys did not undergo intergranular corrosion in a solution of 15% NaNO3 + 20% NaClO3 + 65% H2O, but they did so in solutions of NaNO3 alone and in solutions containing NaCl. Stainless steel did not corrode in any of the electrolyte solutions used.
Kinematic viscosities of acetone, vinyl acetate, crotonaldehyde, acetic acid, acetic anhydride and their binary and ternary mixtures
Authors: Škubla Pavol , Waradzin Walter
Published: March 2011

Kinematic viscosities of acetone, vinyl acetate, crotonaldehyde, acetic acid, acetic anhydride, their binary mixtures and two ternary mixtures (acetone-vinyl acetate-acetic acid and vinyl acetate-acetic acid-acetic anhydride) were measured. The values of coefficients of the Linke, McAllister, and Chandramouli-Laddha equations were calculated. The temperature dependence of the coefficients of last two equations can be expressed in terms of a function in exponential form, coefficients of which are tabulated.
Wittig-Reaktion von Triphenylphosphonio-alkyliden mit substituierten Benzaldehyden: Hammett-Beziehung und teilweise Reversibilität der Addukt-bildung
Authors: Pískala Alois , Rehan Abdul Hamid , Schlosser Manfred
Published: March 2011

Bei Abwesenheit löslicher Lithium-Salze vereinigen sich Triphenylphosphonio-methylid und -ethylid bereits bei -75 °C mit Aldehyden. Elektronenanziehende Liganden beschleunigen, elektronenspendende Liganden verzögern die Anlagerung der Ylide an die substituierten Benzaldehyde. Die Addukte (Oxaphosphetane) zerfallen erst oberhalb -30 °C zu Olefin und Triphenylphosphinoxid. Wird vor dem Zerfall ein zweiter Aldehyd oder ein zweites Ylid zugesetzt, so findet ein teilweiser Austausch der Komponenten statt.
Heterocycles with a pyrido[3,2-e]-1,3-selenazine and pyrido[3,4-e]-1,3-selenazine ring systems
Authors: Kristian Pavol , Koščík Dušan , Gonda Jozef
Published: March 2011

2-Chloronicotinoyl isoselenocyanate (IIa) and 2,6-dimethyl-4-chloronicotinoyl isoselenocyanate (IIb) react with arylamines to give 2-arylimino-4-oxopyrido[3,2-e]-1,3-selenazines IV and 2-arylimino-5,7-dimethyl-4-oxopyrido[3,4-e]-1,3-selenazines V. A reaction of IIa,b with sodium hydrogen sulfide and hydroselenide afford the respective 2-thio- and 2-seleno-4-oxopyrido-1,3-selenazines VI and VII. Structure of these new types of heterocycles was corroborated by spectral (IR, UV, 1H NMR, 13C NMR, and mass) means.
DIRAC EQUATION FOR A COULOMB SCALAR, VECTOR AND TENSOR INTERACTION
Authors: ZARRINKAMAR S. , HASSANABADI H. , RAJABI A. A.
Published: March 2011

There is now motivating experimental evidence for relativistic symmetries in nuclei and hadrons, namely pseudospin and spin symmetry limits of the Dirac equation besides the old theoretical backgrounds. The most fundamental ingredients in such studies are definitely the wave functions and energy eigenvalues. Here, having in mind the importance of the Coulomb term as well as the degeneracy-removing role of tensor interaction, we obtain the exact solutions to the problem for Coulomb scalar, vector and tensor terms in both spin and pseudospin symmetry limits. We see that, contrary to many other common cumbersome techniques, the problem is simply solved via the methodology of supersymmetric quantum mechanics.
CARBONATED APATITE COATING ON CHITOSAN WITH GRADIENT DISTRIBUTION VIA IONS ASSEMBLY
Authors: LI BAOQIANG , HUANG YANQUAN , WANG YONGLIANG , JIA DECHANG
Published: March 2011

Carbonated apatite (CHA) coating on chitosan with gradient distribution was achieved by ions assembly at ambient condition in a short period time. Chitosan hydrogel can directly chelate with calcium via amino groups without inducing carboxyl or hydroxyl group previously. The complexation of chitosan with calcium ions subsequently absorbed phosphate ions via electrostatic interaction. Calcium phosphate ( CaP ) minerals dispersed in chitosan with the thickness of 0.5 mm is exactly CHA with Ca/P molar ratio of 2.01. The transformation route of CaP salts in chitosan hydrogel started from amorphous calcium phosphate with Ca/P molar ratio of 1.19 after ions assembly, and ended at CHA with help of alkali treatment. The content of calcium and phosphorous element decreased with increasing the depth toward the core according to the energy dispersive spectrometer (EDS) results. The gradient distribution of CHA in chitosan and Vickers hardness of chitosan with CHA coating were similar to the distribution of hydroxyapatite in bone and hardness of weight-bearing bovine bone, respectively.
STRETCHING FLOWS WITH GENERAL SLIP BOUNDARY CONDITION
Authors: SAJID M. , ALI N. , ABBAS Z. , JAVED T.
Published: March 2011

General slip boundary condition is used to solve the viscous incompressible flows induced by a stretching sheet. These flow problems corresponds to the planar and axisymmetric stretching. A similarity solution is developed by shooting method using Runge–Kutta algorithm. The results are graphically displayed and discussed under the influence of slip parameter and critical shear rate. The comparison of stretching flow problem subject to Navier's boundary condition in the planar case is made with the available numerical results in the literature.
A visitor's guide in an active museum
Authors: Kuflik Tsvi , Stock Oliviero , Zancanaro Massimo , Gorfinkel Ariel , Jbara Sadek , Kats Shahar , Sheidin Julia , Kashtan Nadav
Published: March 2011

Technology can play a crucial role in supporting museum visitors and enhancing their overall museum visit experiences. Visitors coming to a museum do not want to be overloaded with information, but to receive the relevant information, learn, and have an overall interesting experience. To serve this goal, a user-friendly and flexible system is needed. The design of such a system poses several challenges that need to be addressed in parallel. The user interface should be intuitive and let the visitors focus on the exhibits, not on the technology. Content and delivery must provide relevant information and at the same time allow visitors to get the level of detail and the perspectives in which they are interested. Personalization may play a key role in providing relevant information to individuals. Yet, since visitors tend to visit the museum in small groups, technology should also contribute to and facilitate during-the-visit communication or post-visit group interaction. The PIL project applied at the Hecht museum extended the research results of the PEACH project and tried to address all of these considerations. Evaluation involving users substantiated several aspects of the design.
DECHO—a framework for the digital exploration of cultural heritage objects
Authors: Aliaga Daniel G. , Bertino Elisa , Valtolina Stefano
Published: March 2011

We present a framework for the digital exploration of cultural heritage objects. Today computing and information technology is pervasive and ubiquitous and has boosted at unprecedented levels, information diffusion and productivity. Such technology is today a ripe context for succinctly gathering knowledge by combining in innovative ways powerful visualization tactics, rapid access to a significant amount of relevant information, domain-specific knowledge, and rich and pervasive tools to sort, group, and slice the information and knowledge in different ways. To this end, we present a complete framework that is easy to use, does not require expensive custom equipment, and has been designed for helping archaeology researchers and educators reconstruct and analyze the historical context of cultural heritage objects. Our main inspiration is that archaeology today would benefit significantly from having spur-of-the-moment access to information from a variety of heterogeneous data sources and being able to have multiple participants visually observe factual and visual data in an intuitive and natural setting. While we present a framework geared towards archaeology, in the long term we envision reusing it in a variety of fields.

Our framework includes data acquisition, data management, and data visualization components. The data acquisition component enables the fast, easy, and accurate addition of 3D object models and factual data, including narrations. The data management component includes a novel semantic database system that provides an intuitive view of the available contents in terms of an ontology, supports the addition of narrations, integrates data stored by other databases, and supports object retrieval, browsing, and knowledge navigation. The data visualization component provides visual feedback, which is a crucial part of an exploratory endeavor. It provides the ability to alter the appearance of archaeological objects, complete fragments of 3D object models, and several compelling forms of digital inspection and information visualization. All algorithms exploit knowledge from the database and from the obtained 3D models. Visuals can be applied on top of the physical object or on a 3D model shown in a traditional display, controllable via a Web page interface.
Evaluation of work product defects during corrective & enhancive software evolution
Authors: Hale David P. , Hale Joanne E. , Smith Randy K.
Published: March 2011

Information systems portfolio management assumes that software will evolve to maintain alignment with operational needs, a goal that must be met through effective ongoing maintenance. Thus, a primary goal of software maintainers is to ensure that production code is updated without the introduction of defects. However, there is a dearth of research that examines the work product defects that occur as these applications evolve.

The goal of this study is to characterize software evolution lifecycle work product defects and factors that may increase or reduce their occurrence. The study takes place within a global consulting organization conducting ongoing software maintenance for a Fortune 100 telecommunications firm by a project team assessed at Capability Maturity Model Integration (CMMI) Level 3. This study reports on 991 work product reviews conducted across the evolution activities of the ISO/IEC 12207 Software Development Life Cycle Processes.

After controlling for team and expertise differences, the study's major finding is that corrective evolution projects inject a greater number of work product defects than enhancive evolution projects. This result does not arise from the schedule compression often associated with corrective evolution. Rather, it is concluded that the increase in work product defects is associated with the increased complexity of analysis-stage problem diagnosis found in corrective evolution projects. The analysis is augmented by additional covariates including the number of work product reviewers, preparation time of reviewers, and size of the project.
Applications of graph algorithms in GIS
Authors: Vanhove Stéphanie , Fack Veerle
Published: March 2011

This paper describes ongoing PhD research on applications of graph algorithms in Geographical Information Systems. Many GIS problems can be translated into a graph problem, especially in the domain of routing in road networks. Our research aims to evaluate and develop efficient methods for different variants of the routing problem.

Standard existing shortest path algorithms are not always suited for use in road networks, e.g. in a realistic situation forbidden turns and turn penalties need to be taken into account. An experimental evaluation of different methods for this purpose is presented.

Another interesting problem is the generation of alternative routes. This can be modelled as a
k
shortest paths problem, where a ranking of
k
paths is desired rather than only the shortest path itself. A new heuristic approach for generating alternative routes is presented and evaluated.
Voluntary participation in an active learning exercise leads to a better understanding of physiology
Authors: Carvalho Helena , West Crystal A.
Published: March 2011

Students learn best when they are focused and thinking about the subject at hand. To teach physiology, we must offer opportunities for students to actively participate in class. This approach aids in focusing their attention on the topic and thus generating genuine interest in the mechanisms involved. This study was conducted to determine if offering voluntary active learning exercises would improve student understanding and application of the material covered. To compare performance, an anonymous cardiorespiratory evaluation was distributed to two groups of students during the fall (control, n = 168) and spring (treatment, n = 176) semesters. Students in both groups were taught by traditional methods, and students in the treatment group had the option to voluntary participate in two additional active learning exercises: 1) a small group discussion, where students would discuss a physiology topic with their Teaching Assistant before running BIOPAC software for the laboratory exercise and 2) a free response question, where students anonymously responded to one short essay question after the laboratory exercise. In these formative assessments, students received feedback about their present state of learning from the discussion with their peers and also from the instructor comments regarding perceived misconceptions. As a result of the participation in these activities, students in the treatment group had a better overall performance [ χ2 (degree of freedom = 1) = 31.2, P < 0.001] on the evaluation (treatment group: 62% of responses correct and control group: 49%) with an observed difference of 13% (95% confidence interval: 8, 17). In conclusion, this study presents sufficient evidence that when the opportunity presents itself, students become active participants in the learning process, which translates into an improvement in their understanding and application of physiological concepts.
Evaluation of maximal O2 uptake with undergraduate students at the University of La Reunion
Authors: Tarnus Evelyne , Catan Aurélie , Verkindt Chantal , Bourdon Emmanuel
Published: March 2011

The maximal rate of O2 consumption (V̇o2max) constitutes one of the oldest fitness indexes established for the measure of cardiorespiratory fitness and aerobic performance. Procedures have been developed in which V̇o2max is estimated from physiological responses during submaximal exercise. Generally, V̇o2max is estimated using the classical renowned Astrand-Ryhming test. In young adults, poor fitness and low aerobic performance are often associated with a sedentary lifestyle, which is a well-described factor for the development of obesity and its related disorders such as cardiovascular diseases and type 2 diabetes. In the Indian Ocean, the inhabitants of La Reunion Island, a French overseas department, exhibit an increasing prevalence of obesity and type 2 diabetes. At the University of La Reunion, a new laboratory course involving students was designed to teach the indirect evaluation of their V̇o2max from the classical Astrand-Ryhming test and using a cycle ergometer as the exercise mode. Inverse and significant correlations were established between the students' fat mass percentages and their V̇o2max and between their waist-to-hip ratio and V̇o2max as well. Results from the international physical activity questionnaire showed that most participants in this laboratory were sedentary students. Therefore, this laboratory makes the students practice and understand the use of a classical test to estimate their V̇o2max. It also alerts them to the correlation between a sedentary lifestyle and higher body fat content. This exercise allowed students to use a scientific method to engage the problem of sedentary lifestyle, which is a real world issue.
Learning outcomes and student-perceived value of clay modeling and cat dissection in undergraduate human anatomy and physiology
Authors: DeHoff Mary Ellen , Clark Krista L. , Meganathan Karthikeyan
Published: March 2011

Alternatives and/or supplements to animal dissection are being explored by educators of human anatomy at different academic levels. Clay modeling is one such alternative that provides a kinesthetic, three-dimensional, constructive, and sensory approach to learning human anatomy. The present study compared two laboratory techniques, clay modeling of human anatomy and dissection of preserved cat specimens, in the instruction of muscles, peripheral nerves, and blood vessels. Specifically, we examined the effect of each technique on student performance on low-order and high-order questions related to each body system as well as the student-perceived value of each technique. Students who modeled anatomic structures in clay scored significantly higher on low-order questions related to peripheral nerves; scores were comparable between groups for high-order questions on peripheral nerves and for questions on muscles and blood vessels. Likert-scale surveys were used to measure student responses to statements about each laboratory technique. A significantly greater percentage of students in the clay modeling group “agreed” or “strongly agreed” with positive statements about their respective technique. These results indicate that clay modeling and cat dissection are equally effective in achieving student learning outcomes for certain systems in undergraduate human anatomy. Furthermore, clay modeling appears to be the preferred technique based on students' subjective perceptions of value to their learning experience.
Ways of coping as predictors of satisfaction with curriculum and academic success in medical school
Authors: Alimoglu Mustafa Kemal , Gurpinar Erol , Mamakli Sumer , Aktekin Mehmet
Published: March 2011

The purpose of the present study was to determine the coping strategies of medical students and to investigate the effects of coping strategies on student satisfaction and academic achievement with different instruction methods. A total of 152 medical students was followed throughout the first 2 yr of medical education between 2008 and 2010. Students completed a sociodemographic questionnaire and revised form of the Ways of Coping questionnaire both at the beginning of the first year and at the end of the second year. These forms provided data about the characteristics and main coping strategies (problem focused or emotion focused) of the students and revealed the change over time. At the end of the second year, participants also completed a satisfaction questionnaire asking their satisfaction with lectures, problem-based learning, and practicals. The authors used block, problem-based learning, and practical exam scores of the students attained in the past 2 yr as academic achievement indicators. No sociodemographic variable was related to coping strategy. The majority of students (80.9%) adopted problem-focused coping. A shift occurred in the main coping strategies of some students in both sides. Problem-focused coping scores decreased over time. Problem-focused coping positively correlated with satisfaction with practicals and practical exam scores, whereas emotion-focused coping showed the same correlation negatively. The main coping strategy also predicted satisfaction and exam success in practicals. In conclusion, a main coping strategy may be helpful to predict student satisfaction and academic achievement with some student-centered instruction methods. Determining undesired coping strategies may provide an opportunity for intervention to prevent relevant dissatisfaction and failure.