bluuebunny/crossref_metadata_2025 huggingface dataset:
Room volume classification from room impulse response using statistical pattern recognition and feature selection
Authors: Shabtai Noam R. , Zigel Yaniv , Rafaely Boaz
Published: September 2010

Classification of the room volume from the room impulse response (RIR) can be useful in acoustic scene analysis applications, using RIR that is provided directly, or estimated from audio recordings. Current methods for estimating the room volume from the RIR require the source-to-receiver distance, and may be sensitive to differences in absorption. A room volume classification method is presented that does not require the source-to-receiver distance, and which is potentially robust to differences in absorption. Room volume features are defined that are related to the room volume and may be extracted from the RIR. Gaussian mixture models are trained to model room volume classes. Room volume is classified according to a maximum likelihood criterion that is normalized with a background model. Feature selection is performed with different classification error criteria. Both simulated and measured RIRs were examined, achieving an equal error rate of 0.1% and 19.1%, respectively.
Auditory feedback control of voice fundamental frequency in school children
Authors: Liu Peng , Chen Zhaocong , Larson Charles R. , Huang Dongfeng , Liu Hanjun
Published: September 2010

The present study was intended to address how the online control of voice fundamental frequency (F0) during vocalization develops from school children to young adults. Nineteen school children (7–12 years old) and twenty-one young adults (19–27 years old) participated in this experiment. They were asked to sustain a vowel sound /u/ while their voice pitch feedback was randomly shifted (±50, ±100, ±200, and ±500 cents) and fed back to them instantaneously over headphones. Results showed that school children produced significantly larger but slower compensatory responses to voice pitch feedback perturbations than young adults. Response latencies became longer with the increase in pitch perturbation magnitude, but no systematic changes were found as a function of stimulus direction. In addition, the number of responses “following” the stimulus direction across different stimulus magnitudes for school children was greater than for young adults. These findings demonstrate developmental changes of vocal responses to pitch feedback perturbations during vocalization from school children to young adults, and suggest that vocal responses can serve as an objective index of the maturation of the audio-vocal system.
Vowel identification by younger and older listeners: Relative effectiveness of vowel edges and vowel centers
Authors: Donaldson Gail S. , Talmage Elizabeth K. , Rogers Catherine L.
Published: September 2010

Young normal-hearing (YNH) and older normal-hearing (ONH) listeners identified vowels in naturally produced /bVb/ syllables and in modified syllables that consisted of variable portions of the vowel edges (silent-center [SC] stimuli) or vowel center (center-only [CO] stimuli). Listeners achieved high levels of performance for all but the shortest stimuli, indicating that they were able to access vowel cues throughout the syllable. ONH listeners performed similarly to YNH listeners for most stimuli, but performed more poorly for the shortest CO stimuli. SC and CO stimuli were equally effective in supporting vowel identification except when acoustic information was limited to 20 ms.
Three-dimensional source tracking in an uncertain environment via Bayesian marginalization
Authors: Tollefsen Dag , Dosso Stan E.
Published: September 2010

This paper develops a non-linear Bayesian marginalization approach for three-dimensional source tracking in shallow water with uncertain environmental properties. The algorithm integrates the posterior probability density via a combination of Metropolis-Hastings sampling over environmental and bearing model parameters and Gibbs sampling over source range/depth, with track constraints on source velocity applied. Marginal distributions for source range/depth and source bearing are derived, with source position uncertainties estimated from the distributions. The Viterbi algorithm is applied to obtain the most probable three-dimensional track. The approach is applied to experimental narrowband data recorded on a bottom-moored horizontal line array in the Barents Sea.
Gene-Associated AMPK
Authors: Gough Nancy R.
Published: September 2010

The energy sensor AMPK localizes to chromatin and phosphorylates histone H2B to facilitate gene transcription and cellular adaptation to stress.
Receptor Tyrosine Kinase Transmembrane Domain Interactions: Potential Target for “Interceptor” Therapy
Authors: Najumudeen Arafath Kaja
Published: September 2010

Disrupting intermolecular interactions between transmembrane domains is a potential method for attenuating signaling through receptor tyrosine kinases.
Infrared spectra of compounds with the methoxymethyl protecting group
Authors: Vašíčková Soňa , Pouzar Vladimír , Černý Ivan , Drašar Pavel , Havel Miroslav
Published: September 2010

Infrared spectra of a series of compounds containing the CH3OCH2O- (MOM-O-) group have been studied. All the spectra exhibit three characteristic strong absorption bands due to coupled stretching vibrations of C-O-C-O-C grouping in the region 1 200 - 1 000 cm-1.
6-Substituted and 2-chloro-6-substituted 10-piperazino-10,11-dihydrodibenzo[b,f]thiepins as potential antidepressants; Synthesis and pharmacology
Authors: Červená Irena , Holubek Jiří , Svátek Emil , Metyšová Jiřina , Valchář Martin , Dlabač Antonín , Wildt Stanislav , Protiva Miroslav
Published: September 2010

6-Substituted and 2-chloro-6-substituted 10-chloro-10,11-dihydrodibenzo[b,f]thiepins XIIIa - f were reacted with 1-(ethoxycarbonyl)piperazine and the carbamates IIIa - f obtained were hydrolyzed to the title compounds Ia -f. The new chlorides XIIIa - c were obtained from 2-(2-aryl-thiophenyl)acetic acids VIIIa - c via ketones XIa - c and alcohols XIIa - c. Reactions of the chlorides XIIIa and XIIIc with 1-methylpiperazine afforded compounds IIa and IIc. All compounds I are devoid of antireserpine and cataleptic activity; they are neither typical antidepressants nor neuroleptics.
Raman scattering from adenine, uracil and their derivatives adsorbed at a silver electrode
Authors: Brabec Viktor , Niki Katsumi
Published: September 2010

Adsorption at a silver electrode of adenine, uracil and their monomeric nucleosides and nucleotides from neutral solutions of KCl was studied by means of Raman spectroscopy and the measurement of the double-layer capacitance. It was found that all compounds investigated except uridine 5'-monophosphate were strongly adsorbed at a positively charged electrode. Analysis of the surface Raman spectra was performed with the aim of obtaining qualitative information on the orientation and configuration of nucleic acid components in the adsorbed state. The results of this analysis were compatible with the conclusions on adsorption of these compounds drawn on the basis of previous measurements with the mercury electrode.
Quaternary salts of N,N-dimethylaminoethyl esters of pivalic and 2-methyl-3-methoxypropionic acid and their hydrolysis
Authors: Ševčík Stanislav , Přádný Martin
Published: September 2010

The synthesis and kinetics of quaternization of model compounds of poly(N,N-dimethylaminoethyl methacrylate) in water-alcoholic solutions brought about by methyl iodide and the alkaline hydrolysis of products in water have been investigated. N,N-Dimethylaminoethyl pivalate was selected as a model of the structural unit of the reported polymer; N,N-dimethylaminoethyl-2-methyl-3-methoxypropionate was the model of the terminal unit of the anionically prepared polymer.
Transformations of substituted 5-aminopyrimidines under conditions of the diazotization
Authors: Nemeryuk Michal P. , Sedov Andrej L. , Safonova Tamara S. , Černý Antonín , Křepelka Jiří
Published: September 2010

Reaction of nitrous acid with 4-substituted and 4,6-substituted 5-aminopyrimidines Ia-In produces 4-substituted and 4,5-disubstituted 1,2,3-triazoles IIa-IIv,resp. Under similar conditions, 2,5-diaminopyrimidines XIIa-XIId give N(7)-oxides of 2-amino-4-aralkylthiopyrimido[5,4-d]-1,2,3-triazines XIIIa-XIIId, and 5-amino-4-chloropyrimidines In and X give 2-diazocyanoacetamides XIa and XIb resp. Also described are syntheses of 5-formylaminopyrimidines XVa-XVg from glycine ethyl ester via sodium salt XVI.
Effect of the ionizing radiation on the catalytic activity of the BASF K-3-10 catalyst in the low-temperature conversion of carbon monoxide by water vapour. Catalytic activity of the pre-irradiated catalyst
Authors: Motl Alois
Published: September 2010

The catalytic activity of the BASF K-3-10 catalyst with regard to the low-temperature conversion of carbon monoxide by water vapour and its changes after irradiation of the contact area by gamma or beta radiation or by fast neutrons has been investigated. The irradiated samples exhibit a moderately or even substantially higher catalytic activity in comparison with the non-irradiated catalyst, the change being dependent on the absorbed dose; moreover, the effective activation energy of the reaction increases, too. Important differences in the action of different types of the ionizing radiation used have been observed and their probable explanation is offered. In course of these experiments the catalysts were analyzed and the specific surface of the catalyst was measured at various stages of their history. It has been found that at all stages the specific surfaces of the irradiated catalyst are equal to the respective specific surfaces of the non-irradiated contacts.
Modeling of hydrolysis mechanism of 3-hydroxytriazenes in strongly acidic medium
Authors: Pytela Oldřich , Vala Václav , Ludwig Miroslav , Večeřa Miroslav
Published: September 2010

Four derivatives of 3-hydroxy1-phenyl-3-alkyltriazene have been synthesized and their hydrolytic stability has been measured in sulphuric acid medium (0.2-16 mol l-1). The rate constant has been found to increase with increasing concentration of sulphuric acid at first, but, on the contrary, at higher concentrations it decreases. Twelve kinetic schemes of acid catalysis have been suggested and evaluated, and a probable mechanism of decomposition has been suggested which involves nitrenium ion as an intermediate.
Chemical actinometry in the UV range based on the photohydrolysis of 3,4-dimethoxynitrobenzene
Authors: Pavlíčková Libuše , Kuzmič Petr , Souček Milan
Published: September 2010

Photochemical hydrolysis of 3,4-dimethoxynitrobenzene in aqueous potassium hydroxide leading to the formation of 2-methoxy-5-nitrophenolate anion is routinely used for the determination of UV light intensity. The quantum efficiency of the actinometric system is independent on the excitation wavelength ( 254, 313, 365 nm) and reaches the value of 0.116 ± 0.002 in 0.5 M-KOH. The light intensity determination is based purely on UV/VIS spectral absorption data. A photokinetic model is presented for the reaction which is generally applicable for any photochemical system with the involvement of inner filtration due to products and partial light absorption. The evaluation of primary spectral data is performed by numerical integration of the photokinetic equation.
Preparation of 6-amino-6-deoxy-D-altronic acid and their derivatives
Authors: Kefurt Karel , Čapek Karel , Kefurtová Zdeňka , Jarý Jiří
Published: September 2010

Methyl 6-azido-3,5-di-O-benzoyl-6-deoxy-α- and -β-D-glucofuranosides (IIIandIV), obtained by methanolysis of 1,2-O-isopropylidene derivative II were converted via 2-O-methanesulfonyl esters V and VI to methyl 2,3-anhydro-6-azido-6-deoxy-α- and -β-D-mannofuranosides (VII or VIII, respectively). Epoxide VII when submitted to alkaline hydrolysis gave methyl 6-azido-6-deoxy-α-D-altrofuranoside (IX) exclusively, while epoxide VIII afforded a mixture of methyl 6-azido-6-deoxy-β-D-furanosides of altro (X) and gluco(XI) configuration in a 5 : 4 ratio. Altrofuranosides IX and X were converted to 6-azido-6-deoxy-D-altrose (XII) the oxidation of which with bromine and catalytic reduction with hydrogen afforded amorphous amino acid XIV, characterized as its tetraacetyllactam XVI. The structural changes of the compounds from individual steps of the synthesis were checked by IR and 1H NMR spectra which are discussed.
Absolute configurations of some heterocyclic acids
Authors: Červinka Otakar , Bajanzulyn Ojuunčimeg , Fábryová Anna , Šačkus Algirdas
Published: September 2010

Employing the method of asymmetric transformation, the absolute configurations of heterocyclic acids III, IV, Va, and VIIa have been determined. The acids Va and VIIa were chemically correlated with alcohols of known absolute configurations.
Synthesis of 13,13,13a,15,15-pentamethyl-6H,7H,13H,13aH,15H-1,4-diazepino[1,7a :4,5a']diindole and the structure of its perchlorate
Authors: Šačkus Algirdas , Smrček Stanislav , Trška Petr , Červinka Otakar
Published: September 2010

Condensation of 2,3,3-trimethyl-3H-indole (I) with 1,2-dibromoethane gave base V, affording perchlorate III. In strongly acid solutions both the base and its perchlorate got converted into disalt IV.
Furan-related N-onium salts as synthons for preparation of 3-furylbenzoindolizines
Authors: Štetinová Jarmila , Jurášek Adolf , Kováč Jaroslav , Dandárová Miloslava , Šafář Peter
Published: September 2010

Substituted 3-furylbenzoindolizines V-X were prepared via 1,3-dipolar cycloaddition of yields generated from the furan-related N-onium salts I-IV to dimethyl butinedioate, ethyl 3-(5-nitro-2-furyl)-2-propeonate, 1-phenyl-3-(5-nitro-2-furyl)-2-propenone, and 1-phenyl-2-nitroethylene. Structure of the compounds synthesized was confirmed by spectral data.
The synthesis of 5,6-cyclopropanocholestanes with oxygen functions in positions 3 and 7
Authors: Kohout Ladislav
Published: September 2010

The Simmons-Smith methylenation of the double bond in 3β-acetoxycholest-5-en-7-ols takes place selectively under formation of an adduct the configuration of which is determined by the configuration of the 7-hydroxyl group: 7β-alcohol IV gave 5β,6β-cyclopropane derivative VI, 7α-alcohol V gave 5α,6α-cyclopropane derivative VIII. On photochemically initiated cyclization of 3β-acetoxy-B-homo-5-en-7a-one (XIII) we obtained the product with an α-cyclopropane ring exclusively, i.e. 3β-acetoxy-5,6α-cyclopropano-5α-cholestan-7-one (XII).
9-(Aminoalkyl)-8-hydroxyadenines: Preparation, mechanism of formation and use in affinity chromatography of S-adenosyl-L-homocysteine hydrolase
Authors: Holý Antonín , Kohoutová Jitka , Merta Aleš , Votruba Ivan
Published: September 2010

Bromine reacts with 9-(2-hydroxyethyl)- (Va), 9-(3-hydroxypropyl)- (Vb), 9-(2-hydroxypropyl)- (Vc), 9-(2,3-dihydroxypropyl)- (Vd), 9-(1,3-dihydroxy-2-propyl)- (Ve), 9-threo-(2,3-dihydroxybutyl)- (Vf) and 9-threo-(2,3,4-trihydroxybutyl)adenine (Vg) to give 8-bromoadenine derivatives (Vl). Reaction of compounds Vl with ammonia results in intramolecular cyclization to five- and six-membered cyclic esters which are regiospecifically opened to afford the respective 2-amino-alkyl-8-hydroxyadenines (VIIa, b) and 3-aminoalkyl-8-hydroxyadenines (VIIc-VIIf). Binding of compounds VII to CH-Sepharose 4B led to the polymeric material XIII capable of binding S-adenosyl-L-homocysteine hydrolase. Compounds XIII derived from the amino derivatives VIIa, b, d are of affinity support character and liberate the enzyme only on elution with dilute adenosine solution.
Preparation of C(18)-empiric 20,29,30-trinorlupane derivatives. 1H, 13C NMR and mass spectra
Authors: Křeček Václav , Protiva Jiří , Buděšínský Miloš , Klinotová Eva , Vystrčil Alois
Published: September 2010

Reaction of amide I with nitrous acid gave the olefins II, III and IV. On allylic oxidation of olefin IV α,β-unsaturated ketone V is formed from which olefins VIII and IX were prepared by a sequence of further reactions. Addition of hydrogen to the double bond of olefin IV and α,β-unsaturated ketone V takes place on catalytic hydrogenation from the β-side and leads to derivatives with cis-annellated rings D/E. This made the preparation of hydrocarbons VI and VII epimeric on C(18) possible, which represent reference compounds for the study of the effect of substituents on the chemical shifts of the methyl groups and the saturated carbon atoms of 18αH and 18βH-lupane derivatives. The configuration of the hydroxyl group in epimers XI and XII were derived from 1H NMR spectra. Deuteration of olefins III, IV and IX gave deuteriohydrocarbons XVI to XVIII. The 1H, 13C NMR and mass spectra of the substances prepared are discussed.
Preparation and properties of epoxided Separon-based ion exchangers with bonded 8-hydroxyquinoline
Authors: Janák Karel , Janák Jaroslav
Published: September 2010

The direct fixation of copper(II) 5-(4-hydroxyphenylazo)-8-quinolinate and the indirect fixation of 8-hydroxyquinoline to Separon H 40Emax and Separon H 1000 Emax were compared from the point of view of the practical sorption capacities of the resulting ion exchangers. For the ion exchanger obtained by indirect fixation of the reagent to Separon H 40 Emax, the rate of Cu2+ ions, and the stability were determined and compared with those of a G-gel-based ion exchanger.
13C NMR spectra of 1-aryl-ferrocenylethylenes
Authors: Solčániová Eva , Toma Štefan , Liptaj Tibor
Published: September 2010

13C NMR spectra of 18 ferrocene analogues of trans stilbenes (1-aryl-2-ferrocenylethylenes) were measured. It was found that bridge group weakens the transfer of the substituent electron effects into ferrocene nucleus, especially distinctly into 3',4'positions of cyclopentadienyl ring. The transfer of substituent effects into β-position of the bridge -CH=CH- is greater in derivatives studied by us than in stilbenes. Synthesis of 1-(4-dimethylaminophenyl)-2-ferrocenylethylene is described.
Asymmetric reduction of p-alkylacetophenones
Authors: Červinka Otakar , Fábryová Anna , Brožová Ivana , Holík Miroslav
Published: September 2010

Asymmetric reduction of p-alkylacetophenones Ia-VIIa with lithium aluminium hydride in the presence of (-)-quinine affords optically active alcohols Ib-VIIb of the (R)-(+) configuration in optical yields of about 50%.
Preparation of 2α,3α-dihydroxy-7-oxa-6-oxo-23,24-dinor-B-homo-5α-cholanic acid, its esters and amides as brassinolide analogues
Authors: Černý Václav , Strnad Miroslav , Kamínek Miroslav
Published: September 2010

Synthesis of brassinosteroids IIb, d, g, i, k, m, o and evaluation of their growth-promoting activity is reported. The acid IIb shows high activity in both the bean first and second internode assay.
Fluorinated tricyclic neuroleptics with prolonged action: 7-Fluoro-11-[4-(2-hydroxyethyl)piperazino]-2-isopropyl-10,11-dihydrodibenzo[b,f]thiepin
Authors: Protiva Miroslav , Jílek Jiří , Rajšner Miroslav , Pomykáček Josef , Ryska Miroslav , Holubek Jiří , Svátek Emil , Metyšová Jiřina
Published: September 2010

Substitution reaction of 11-chloro-7-fluoro-2-isopropyl-10,11-dihydrodibenzo[b,f,]thiepin with 1-(2-hydroxyethyl)piperazine gave the title compound I which proved a very potent and longacting oral neuroleptic agent (isofloxythepin). Its resolution by means of dibenzoyl-(+)- and -(-)-tartaric acid led to (-)- and (+)-enantiomer out of which the former represents the neuroleptically active component. In the synthetic sequence leading to I, preparation of two key intermediates was re-elaborated using new partial sequences: 4-fluoro-2-iodobenzoic acid (XIII) from 4-fluoro-2-nitroaniline (V) via the nitrile VI and the acids VIII and XII, and [4-fluoro-2-(4-iso-propylphenylthio)phenyl]acetic acid (XVIII) from XIII via XIV and the compounds XV-XVII. The sulfoxides and N-oxides XIX-XXII were prepared as potential metabolites of isofloxythepin (I).
Synthesis of 16-(4-iodophenyl)hexadecanoic acid
Authors: Protiva Jiří , Pecka Jaroslav , Klinotová Eva , Procházka Miloš
Published: September 2010

16-(4-Iodophenyl)hexadecanoic acid was prepared in six steps by two methods: from 6-(2-thienyl) hexanoic acid and 6-phenylhexanoyl chloride or by alkylation, or acylation, of 2-thienylthiophene. Mass and 1H NMR spectra of some prepared compounds are discussed. The synthesis is suitable for preparation of radioactively labelled acids used as myocardial imaging agents.
New method of preparation of 5-(N,N-dimethylamino)-2-furylethylenes via furan vinamidinium salts
Authors: Gracza Tibor , Arnold Zdeněk , Kováč Jaroslav
Published: September 2010

Reaction of the vinamidinium system in 5-(N,N-dimethylamino)-2-furfurylidene-N,N-dimethyliminium bromide (I) and its 4-formyl derivatives II and III with methylene compounds has been utilized for the preparation of furylethylenes.
Structure of isosilerolide, relative and absolute configuration of silerolide and lasolide - Sesquiterpenic lactones of new stereoisomeric type of eudesmanolides
Authors: Holub Miroslav , Buděšínský Miloš , Smítalová Zdenka , Šaman David , Rychłewska Urszula
Published: September 2010

On the basis of spectroscopic, particularly 1H NMR data, isosilerolide was assigned structure I, including the absolute configuration. The structure was confirmed by X-ray diffraction. Isosilerolide represents a new stereoisomeric type of natural eudesmanolides, characterized as 5βH, 6αH, 7αH, 10αCH3-eudesman-6,12-olide. As shown by the chemical correlation of isosilerolide (I) with silerolide (III) and lasolide (X), the latter two natural lactones belong to this stereoisomeric group of eudesmanolides. Analysis of models and 1H NMR data shows that structures of some eudesman-6,12-olides, published by other authors, should be corrected.
Participation of the oxygen-containing substituent in alkaline saponification of 3,4a-disubstituted 4,4-dimethyl-5,6β-epoxy-A-homo-5β-cholestane derivatives
Authors: Velgová Helena
Published: September 2010

Alkaline saponification of the 3-acetoxy group in 3,4a-disubstituted 4,4-dimethyl-5,6β-epoxy-A-homo-5βcholestane derivatives I-VI was studied. It was found that the 3α- and 4aα-hydroxy groups participated in the cleavage of the 5β,6β-epoxide ring in the derivatives II-IV: the 5(O)n participation by the 3α-hydroxy group (the derivatives III and IV) led to formation of the transannular 3α,5α-epoxides XII and XIV whereas the participation by the 4aα-hydroxy group (the derivatives II and IV) gave rise to the 4aα,5α-epoxides IX and XV. The 5(O)n participation by the 3α-hydroxy group predominated over the preparation by the 4aα-hydroxy group. In the case of the 4a-keto epoxides V and VI the retroaldol-aldol type isomerization led to formation of 3β-hydroxy-4,4-dimethyl-5,6β-epoxy-A-homo-5β-cholestan-4a-one as the main component of the equilibration mixtures.
Influence of solvents on electrochemical reduction potentials of chlorosilanes
Authors: Duchek Petr , Ponec Robert , Chvalovský Václav
Published: September 2010

The reduction potentials of 1,1-dichloro- and 1-chloro-1-methylsilacyclobutane and their acyclic analogues were measured by cyclic voltammetry in the medium of anisole and dimethylformamide. The obtained values which reflect the simultaneous effect of angular strain and possible interactions of the depolarizer with the solvent were correlated with the result of quantum chemical calculations.
On chemical form of H+ ion in aqueous solutions
Authors: Čeleda Jiří
Published: September 2010

Using the method of the addition of another salt worked out and verified in the previous work, it has been concluded from experimental densities of aqueous NaCl + HCl solutions that even in highly diluted solutions, H+ ion exists as integral H3O+ species which is bonded to the ice-like structure of surrounding water only by relatively weak hydrogen bonds. This bonding does not prevent the outer hydration sheath from fully participating in hydration equilibria of other ions present in solution. The hypothesis about the stable H9O4+ complex could not be maintained.
Capillary isotachophoresis of piperidinoethylethers of the alkoxyphenylcarbamic acids
Authors: Chmela Zdeněk , Čižmárik Jozef , Stránský Zdeněk
Published: September 2010

Conditions for the separation and determination of N-[2-(alkoxyphenylcarbamoyloxy)-ethyl]-piperidinium chlorides ( analogues of heptacaine) by the capillary isotachophoresis have been studied. For the successful separation of lower alkoxy derivatives the acetate buffer solution, pHL = 4.75, was found to be a suitable leading electrolyte (K+ as the leading ion) and β-alanine a suitable terminator. The separation can be achieved even in the acid medium with H+ as the leading ion and with a voluminous terminating cation. For instance, pseudoaconitine or N-[2-(2-heptyloxyphenylcarbamoyloxy)-ethyl]-benzylpiperidinium chloride were found to be acceptable. The steric hindrance of the solvation, characteristic for 2-alkoxy isomers, makes their separation from 3- or 4-alkoxy isomers possible, with the exception of methoxy derivatives.
Preparation and infrared and 13C, 17O, and 119Sn NMR spectra of some substituted di- and tri(1-butyl)tin phenoxyacetates and phenylthioacetates
Authors: Holeček Jaroslav , Handlíř Karel , Lyčka Antonín , Chattopadhyay T. K. , Majee B. , Kumar A. K.
Published: September 2010

The paper describes preparation and basic physical and chemical properties of a group of substituted di- and tri(1-butyl)tin(IV) phenoxyacetates and phenylthioacetates of the general formula (RxC6H5-xECH2CO2)nSn(1-C4H9)4-n, where R = H, 2-Cl, 4-Cl, 2-CH3, and 2-OCH3, E means oxygen or sulphur atoms, n = 1 or 2, and x = 1 or 2. From IR spectral data, 13C, 17O, and 119Sn NMR spectra, and from other physico-chemical methods, conclusions are drawn about structure of the compounds in solid state and in solutions of coordinating (hexamethylphosphoric triamide) and non-coordinating solvents (chloroform, carbon tetrachloride, carbon disulphide, benzene). In solid state the tri(1-butyl)tin(IV) compounds form polymeric chains with bidentate bridge carboxylic groups. In non-coordinating solvents these compounds are present as isolated pseudotetrahedral molecules, whereas in hexamethylphosphoric triamide they form complexes with one solvent molecule, the central tin atom exhibiting the trans-trigonally bipyramidal coordination. The di(1-butyl)tin(IV) compounds form, both in solid state and in non-coordinating solvents, monomeric particles containing bidentate chelate carboxylic groups. In hexamethylphosphoric triamide they form complexes with octahedral coordination around the tin atom containing monodentate carboxylic groups and the butyl groups are trans position. In none of the cases studied evidence was obtained for interaction of the oxygen or sulphur atoms of C6H5ECH2 group with the tin atom.
Some derivatives of 5-(2-amino-6-hydroxy-4-oxo-3,4-dihydro-5-pyrimidinyl)pentanoic acid
Authors: Křepelka Jiří , Černý Antonín , Kotva Rudolf , Vachek Jaroslav , Mělka Milan
Published: September 2010

Using the chloride method esters II - X, amides XI - XIV, and condensates with amino acid esters XV - XVII were prepared from 5-(2-amino-6-hydroxy-4-oxo-3,4-dihydro-5-pyrimidinyl)pentanoic acid (I); the amides XIII and XIV were also prepared by aminolysis of ester II. The derivative of glycine, XVIII, was obtained on saponification of ester XV, also obtained by condensation of triethyl ester of N-(6,6-dicarboxyhexanol)glycine (XXIII) with guanidine hydrochloride in a medium containing sodium ethylate. Hydrazinolysis of ethyl ester XXIV gave hydrazine XIX. Disubstituted ureas XX - XXI were obtained on reaction of esters VI and XXIV with 2-chloroethyl isocyanate; saponification of the ester function in the urea derivative XX led to the free acid XXII. Reaction of acid I with an excess of diazomethane gave a mixture of compounds in which compound XXV (a product of esterification and O-methylation) and XXVI( a product of esterification, O-methylation, and N-methylation) predominated. None of the substances prepared displayed a clear ant-tumour activity. Some of the substances tested affected the weight of experimental tumours (XV, XVI, XX, XXV) or protracted the survival time of experimental animals (XXVI, XX). Substance XX had the broadest spectrum of activity.
Binding of lead and copper(II) ions to starch and amylose 2,3-dicarboxy derivatives
Authors: Kohn Rudolf , Tihlárik Karol
Published: September 2010

The binding of Pb2+ and Cu2+ ions to starch and amylose 2,3-dicarboxy derivatives of degrees of oxidation DO = 0.09-0.74 was investigated. The interaction of the metal cations with the carboxy groups of the derivatives was evaluated in terms of the counter-ion activity, determined with ion specific electrodes. The binding is very strong; at DO ≥ 0.34, lead ions are bound quantitatively ( degree of association β = 0.999), copper ions are also bound to a great extent (β = 0.94-0.97). The complexation of copper with the ligands at ionic strength I = 0.15 mol 1-1 was treated in terms of multiple equilibria theory. Different complexes were found in dependence on the concentration ratios of the reactants; at a high excess of COO- groups with respect to Cu2+ ions, the latter are strongly bound and the number of COO- groups binding a Cu2+ cation is greater than 2, whereas at a sufficiently high concentration of Cu2+ ions the number of COO- groups binding a Cu2+ cation approaches the stoichiometric value of 2.
Comments on the physical meaning of the minimum energy path
Authors: Pick Štěpán , Friedrich Břetislav
Published: September 2010

The relation between the minimum energy path and the classical equations of motion is found, and conditions implying trajectories along gradient lines are analyzed. Attention is drawn to possible statistical features of the minimum energy path.
Equilibria in the transport epitaxial formation of indium phosphide and arsenide
Authors: Braun Ivo , Klíma Přemysl , Stejskal Josef , Černý Čestmír , Voňka Petr , Holub Robert
Published: September 2010

From the data available in literature, equilibria were calculated of the reactions which come into consideration in the preparation of indium phosphide and indium arsenide. In the first case it was supposed that indium phosphide was formed as a pure solid substance, that indium might exist either as a pure liquid, or as a gas and that the remaining 16 components in the equilibrium mixture were in the ideal gaseous state. In the second case, the formation of pure solid indium arsenide and the existence of 18 other substances in the equilibrium mixture, also in the ideal gaseous state, were supposed. The results of these theoretical calculations for indium phosphide were compared with the experimental deposition temperatures and reasonable agreement has been found.
Non-Newtonian oscillatory boundary layer, a numerical approach
Authors: Wein Ondřej , Sobolík Václav
Published: September 2010

Differential schemes have been constructed by using the integro-differential formulation of the equation of motion in stresses. The problem of periodic flow of the purely-viscous non-Newtonian liquid on a harmonically oscillating plate has been solved numerically for extremally high values of the Reynolds number. The velocity and stress fields as well as estimates of the flow enhancement E are given for the quasi-oscillatory regime, Fr → ∞, for the pseudoplastic liquid with the extremally low flow index, n = 0.15.
Synthesis of 2-amino-5-β-D-ribofuranosyl-1,3,4-thiadiazole and 2-amino-β-D-ribofuranosyl-1,3,4-oxadiazole
Authors: Hřebabecký Hubert
Published: September 2010

Benzoylated 2-amino-5-ribosylthiadiazole III and 2-amino-5-oxadiazole IV were synthesized by cyclization of allonoylthiosemicarbazide I and allonoylsemicarbazide II with phosphorus pentoxide in nitromethane. The oxadiazole IV was alternatively prepared by heating compound I with lead(II)oxide in acetonitrile. Free ribosylthiadiazole V and ribosyloxadiazole VI were obtained by methanolysis of III and IV.
Liquid-liquid equilibrium. Computation of liquid-liquid equilibrium in terms of an equation of state
Authors: Novák Josef P. , Růžička Vlastimil , Matouš Jaroslav , Pick Jiří
Published: September 2010

An algorithm for calculating the boiling point pressure at a chosen temperature and composition was used for computing liquid-liquid equilibrium. A lot of attention is paid to the determination of the first approximation which is specified in terms of the conditions of thermodynamic stability. The conditions of thermodynamic stability make as well possible to localize the lower and upper critical end points (LCEP and UCEP. The Redlich-Kwong-Soave equation of state was applied in calculations, and it was found out that this equation with zero interaction parameters predicts well the lower and upper critical end temperatures in the systems methane-n-hexane, ethane-n-eicosane and ethane-n-docosane.
Orientation dependent concentration potentials of asymmetrical cellulose acetate membranes
Authors: Kůdela Vlastimil , Richau Klaus , Ryba Olen , Schwarz Hans-Hartmuth
Published: September 2010

Orientation dependent (asymmetrical) membrane potentials were observed on both reverse osmosis and ultrafiltration cellulose acetate and polymer sulfone membranes in contact with electrolyte solutions. It was shown that this phenomenon can be observed only on asymmetrical membranes with a gradient of fixed charge molality in the active layer (skin), provided that the activity of the more concentrated solution is comparable with or higher than the fixed charge molality in the active layer. This holds also for partly hydrolyzed reverse osmosis membranes. The origin of the orientation dependence of the membrane potential can be explained by means of an analysis of Donnan potentials in given conditions. Diffusion potentials cannot play the decisive role. The asymmetry of osmotic fluxes observed only on reverse osmosis (annealed) membranes does not contribute to the orientation dependence of the membrane potential, because the asymmetrical dilution effect is compensated by the arising streaming potential.
Partially acetylated sucrose. Structures of hepta-O-acetylsucroses formed by deacetylation of octa-O-acetylsucrose
Authors: Čapek Karel , Vodrážková-Medonosová Monika , Moravcová Jitka , Sedmera Petr
Published: September 2010

Formation of hepta-O-acetylsucroses I, II, XI, and XII, having a free hydroxyl group on the fructose moiety, in deacetylation of octa-O-acetylsucrose on aluminum oxide impregnated by potassium carbonate was proved by preparative chromatography on silica gel and by liquid chromatography. Their structures were inferred from the 1H and 13C NMR spectra, from NMR and mass spectra of their mono-methanesulfonyl derivatives VI - IX, or using comparison with authentic samples. Methanolic solutions of hepta-O-acetylsucroses I and II, a mixture of hepta-O-acetylsucroses XI and XII, and octa-O-acetylsucrose were deacetylated on aluminum oxide impregnated by potassium carbonate ant the time dependence of the reaction mixture composition was studied by liquid chromatography. Kinetic measurements show that deacetylation is first order reaction with respect to the starting compounds. With octa-O-acetylsucrose, the most reactive group is that at position 4', so that formation of 1',2,3,3',4,6,6'-hepta-O-acetylsucrose (II) is preferred. Both this compound and 1',2,3,4,4',6,6'-hepta-O-acetylsucrose (XII) are deacetylated to 1',2,3,4,6,6'-hexa-O-acetylsucrose (V). From 2,3,3',4,4',6,6'-hepta-O-acetylsucrose (XI), the 2,3,4,4',6,6'-hexa-O-acetylsucrose (IV) results. Other hexa-O-acetylsucroses, formed by deacetylation of hepta-O-acetylsucroses I and II, are deacetylated to penta-O-acetylsucroses faster than the hexa-O-acetylsucrose V and their proportion in the mixture after deacetylation of octa-O-acetylsucrose is very low. No migration of the O-acetyl group from the position 4' to the position 6' or vice versa occurs during the deacetylation.
N-(piperazinoacyl) and N-(piperazinoalkyl) derivatives of 4-cyclopentylaniline and related compounds: Synthesis and pharmacological screening
Authors: Vejdělek Zdeněk , Protiva Miroslav
Published: September 2010

Five N-(4-cyclopentylphenyl)haloalkanecarboxamides were reacted with 1-methylpiperazine and 1-(2-hydroxyethyl)piperazine to give the corresponding N-(4-cyclopentylphenyl)piperazinoalkanecarboxamides Iab -Vab. Their reduction with lithium aluminium hydride afforded the triamines VIIab - XIab. Acylation of the N-(4-methylpiperazino)alkyl-4-cyclopentylanilines Xa and XIa with propionyl chloride resulted in the propionanilides XIVa and XVa, whereas a similar reaction of the N-(4-(2-hydroxyethyl)piperazino)alkyl-4-cyclopentylanilines VIIb and IXb - XIb produced the propionoxypropionanilides XIIc - XVc. Ethanolysis of these compounds afforded corresponding hydroxypropionanilides XIIb - XVb. Many of the basic amides showed local anaesthetic and papaverine-like antispasmodic activity. The propionanilides XIIb, XIVc, and XVa proved interesting analgesic effects in the peritoneal test in mice.
Polarographic behaviour of petroleum components in aqueous solutions: A study using DPP and convective adsorption accumulation
Authors: Kalvoda Robert , Novotný Ladislav
Published: September 2010

Tensametric behaviour of solutions of petroleum and its fractions in aqueous base electrolytes was studied by differential pulse polarographic method (DPP) using a stationary mercury drop electrode with adsorptive accumulation. The results indicate that water pollution with petroleum can be determined by DPP, the sensitivity of the determination depending on the quality of the pollutant and on the composition of the base electrolyte. Well utilizable calibration curves were obtained with Diesel oil at concentrations from 30-50 μl/l to 0.5 mg/l and with Saratov petroleum from 0.1-0.2 mg/l to 3.3 mg/l. Use of adsorptive accumulation led to a marked increase of the sensitivity of the analysis.
Polarographic behaviour of petroleum components in aqueous solutions: Application of electrocapillary measurements and convective adsorption accumulation
Authors: Novotný Ladislav , Kalvoda Robert
Published: September 2010

Electrocapillary investigations by the drop time method revealed a rather strong surface activity of aqueous petroleum solutions and some petroleum fractions in solutions of base electrolytes at the dropping mercury electrode, depending on the quality of the surfactant. The highest surface activity and sensitivity of analytical determination was found between -0.4 and -0.6 V (S.C.E.). The detection limit of the electrocapillary method was 10-20 μg/l for Diesel oil and up to 5 times higher for petroleum samples. The sensitivity of the measurements at lowest concentrations was increased by convective adsorption accumulation at the surface of the growing drop.
Furo[2,3-d]thiazoles
Authors: Uher Michal , Leško Ján , Tóth Ivan
Published: September 2010

Carbonyl isothiocyanates react with 5-amino-2-furancarboxylates to give the corresponding acylthioureas which cyclize to condensed derivatives related to furo[2,3-d]thiazoles. Structure of these substances was corroborated by IR, mass, 1H and 13C{1H}NMR spectral means.
(-)-Strempeliopine, stereoselective total synthesis and the determination of absolute configuration
Authors: Hájíček Josef , Trojánek Jan
Published: September 2010

A synthesis of (±)-strempeliopine (II) is described, the key step of which is the stereoselective reductive rearrangement of 18-methylene-1,2-dehydroaspidospermidine (XI). The absolute configuration of the natural (-)-base II was determined as (2S, 7R, 20R, 21R) on the basis of its synthesis from (+)-18-methylenevincadifformine (XVII) the configuration of which was derived from a comparison of circular dichroism properties of bases with a β-anilinoacrylate chromophore. The biogenesis of the alkaloids of the schizozygane type is discussed.
On alkaloids from the aerial parts of three Eschscholtzia species
Authors: Slavík Jiří , Slavíková Leonora
Published: September 2010

In the aerial parts of Eschscholtzia californica CHAM., E. douglasii (HOOK. etARN.) WALP. and E. glauca GREENE the main alkaloidal component is the quaternary base californidine. Eschscholtzine, allocryptopine, and protopine belong among the dominant tertiary alkaloids, which are accompanied by a small amount of N-methyllaurotetanine and the quaternary benzophenanthridines (sanguinarine, chelerythrine, chelirubine, chelilutine, and macarpine). The pavinane alkaloids isonorargemonine, caryachine, norargemonine, and bisnorargemonine and the aporphine alkaloids corydine and isocorydine were isolated from the aerial part of the E. douglasii species for the first time. These alkaloids were also detected in E. californica and E. glauca. Corytuberine was also isolated from all three species. From the fraction of Quaternary alkaloids after conversion to iodides, in addition to californidine, escholamidine iodide was isolated from E. californica and E. douglasii species. From E. douglasii N-methylcaryachinium iodide and from E. glauca magnoflorine iodide were also isolated. The presence of a small amount of the mentioned quaternary alkaloids, as well as traces of escholamine were also detectable in all three species.
Hydrogen peroxide decomposition on a two-component NiO-Fe2O3 catalyst
Authors: Múčka Viliam
Published: September 2010

Some physical and catalytic properties of the two-component nickel oxide-ferric oxide catalysts were studied using samples with different content of both components, covering the whole concentration range from 0 to 100% of one of the components. It was proved that these properties depend strongly on the preparation procedure of the catalyst of the desired composition and on the catalyst composition for the given preparation procedure; moreover, it was proved that the phase composition of the contact catalyst is not decisive for the catalytic activity of the given system. It seems probable that the valence state of the catalyst metal ions and their ability to form the reaction catalytic centers are the rate-determining factors. The results obtained lead at the same time to the assumption that these parameters change substantially with the catalyst composition. No changes of the catalytic activity were observed for catalysts irradiated by fast neutrons or accelerated electrons.
Heterocyclic ethers derived from 6,11-dihydrodibenzo[b,e]thiepin-11-ols and 4,9-dihydrothieno[2,3-c]-2-benzothiepin-4-ol; A new series of potential antidepressants and antihistamine agents
Authors: Polívka Zdeněk , Metyš Jan , Protiva Miroslav
Published: September 2010

Reactions of 11-chloro-6,11-dihydrodibenzo[b,e]thiepin and methanesulfonates of 6,11-dihydrodibenzo[b,e]thiepin-11-ol (I), its 2-methyl derivative II and 4,9-dihydrothieno[2,3-c]-2-benzothiepin-4-ol (III) with 1-methylpiperidin-4-ol, 1-methylperhydroazepin-4-ol (XIX), and tropine gave the ethers V-X. Their methanesulfonates were pharmacologically tested and showed antireserpine, anticataleptic, and antihistamine activities of various degree. The most active compounds were the ethers V and VI.
Kinetics of the aflatoxin B1-sodium hypochlorite reaction and its application to the study of aflatoxin B1-bovine albumin binding
Authors: Picó Guillermo A. , Picconi María A. , Gatti Carlos A.
Published: September 2010

The course of the aflatoxin B1-sodium hypochlorite reaction was followed by fluorescence emission at 450 nm. The formation of intermediate compounds with a higher fluorescence quantum yield than that of aflatoxin B1 was observed. This formation fitted a second order kinetics, and the measurement of the initial formation rate was used to calculate the concentration of the aflatoxin in solution. Bovine albumin exerted a protective effect on aflatoxin B1 against the sodium hypochlorite action, which was related to the hydrophobic nature of the aflatoxin B1-albumin binding. This effect was used to give a further insight of aflatoxin B1-albumin interaction.
Determination of subnanogram amounts of sulfur dioxide and sulfites by pneumatopotentiometry
Authors: Langmaier Jan , Opekar František
Published: September 2010

Gold porous membrane electrode has been used for the potentiometric determination of small amounts of sulfur dioxide absorbed in the solutions of sodium tetrachloromercurate or sodium hydroxide. Sulfur dioxide is released by the reaction with an acid into a stream of nitrogen and led to the electrode immersed into the solution of iodine monochloride. Part of SO2 penetrates through the membrane pores into the solution where it is oxidized. The electrode redox potential change is a measure of the SO2 concentration in the absorption solution. In the solution of 1 . 10-5 M[ICl2]- in 0.02 M-HClO4 the limit of quantitation was found to be 0.07 ng SO2 . ml-1. The relative standard deviations of 1.4% and 2.5% were found for the determinations of 10 ng and 0.5 ng of SO2, respectively. Higher concentrations of H2S interfere only in the hydroxide solution. About 10 samples can be analyzed per one hour.
The effect of origin and physico-chemical properties on the kinetics of reduction of mixed NiO-Fe2O3 oxides with hydrogen
Authors: Pospíšil Milan , Topinka Jan
Published: September 2010

We investigated the effect of origin and some physico-chemical parameters on the kinetics of reduction with hydrogen of two series of mixed NiO-Fe2O3 oxides differing by their composition, the character of their precursors (mixed crystalline nitrates and coprecipitated hydroxides) and their decomposition temperature.This effect manifested itself by different magnitudes of specific surfaces of the mixed oxides and coherent regions of present phases as well as by different oxidizing abilities of the surface and differences in morphology and phase composition of corresponding samples in both series investigated. Nonlinear or nonmonotonous composition dependences of physico-chemical parameters investigated point to a mutual influence of individual components, which is also a function of the system origin and which modifies its reactivity during its reduction with hydrogen. The kinetics of the reduction was studied thermogravimetrically at 320-410 °C. The reduction of oxides of the hydroxide origin is catalytically accelerated by primarily reduced nickel, whereas in corresponding samples of the nitrate series, the total NiO is bound to the spinel phase and the reduction is delayed. Experimental IR spectra, the effect of preliminary annealing and DTA of the mixed oxides point to an inhibitory effect of water, which is constitutionally bound in trace admixtures of the goethite phase, on the kinetics of reduction of samples in the hydroxide series.
The 119Sn and 15N NMR spectral study of the chelate formation in the triphenyltin(IV) oxinate
Authors: Holeček Jaroslav , Lyčka Antonín , Wagener Roland
Published: September 2010

The 119Sn and 15N NMR spectra of triphenyltin(IV) oxinate and (therewith isoelectronic compound) 1-naphthoxide have been measured in the media of a non-coordinating solvent - deuteriochloroform - and two coordinating solvents - pyridine and hexamethylphosphoramide - in the temperature region from 240 to 370 K. The values of parameters of the 119Sn and 15N NMR spectra and their temperature dependences and comparison of the parameters of the 119Sn NMR spectra of the two isoelectronic compounds indicate that, in the non-coordinating solvent (deuteriochloroform), the triphenyltin(IV) oxinate forms a chelate complex with bidentate function of the oxinate ligand and with cis-trigonally bipyramidal geometry around the penta-coordinated central tin atom, whereas the triphenyltin(IV) 1-naphthoxide forms a simple compound with pseudo-tetrahedral arrangement of the substituents around the tetra-coordinated central tin atom. In both coordinating solvents chemical reactions take place which produce complexes of triphenyltin(IV) compounds with one molecule of the solvent and with trans-trigonally bipyramidal structure around the penta-coordinated central tin atom. The temperature dependences of δ(119Sn) chemical shifts have been used for estimation of the basic thermodynamic parameters of formation of these complexes which confirm that the formation of the complexes with coordinating solvents is - in the case of triphenyltin(IV) oxinate - connected with an exchange equilibrium consuming the original cis-chelate complex (the coordination number 5 of the central atom does not change), whereas with the 1-naphthoxide the reaction consists in a simple formation of the complex with an increase in the coordination number of the central atom (from 4 to 5).