bluuebunny/crossref_metadata_2025 huggingface dataset:
Perception of longitudinal components in piano string vibrations
Authors: Bank Balázs , Lehtonen Heidi-Maria
Published: September 2010

This paper investigates the audibility of longitudinal components in piano string vibrations with listening tests. The recorded fortissimo sounds of two grand and one upright pianos have been resynthesized with and without longitudinal components and used in ABX type listening tests. Results suggest that the longitudinal components are audible up to note C5. However, a second test seeking the importance of the difference shows that the effect of longitudinal components for the range A3−C5 is subtle. This means that modeling the phenomenon up to around note A3 only is acceptable for sound synthesis applications.
A micro-machined piezoelectric flexural-mode hydrophone with air backing: A hydrostatic pressure-balancing mechanism for integrity preservation
Authors: Choi Sungjoon , Lee Haksue , Moon Wonkyu
Published: September 2010

Although an air-backed thin plate is an effective sound receiver structure, it is easily damaged via pressure unbalance caused by external hydrostatic pressure. To overcome this difficulty, a simple pressure-balancing module is proposed. Despite its small size and relative simplicity, with proper design and operation, micro-channel structure provides a solution to the pressure-balancing problem. If the channel size is sufficiently small, the gas-liquid interface may move back and forth without breach by the hydrostatic pressure since the surface tension can retain the interface surface continuously. One input port of the device is opened to an intermediate liquid, while the other port is connected to the air-backing chamber. As the hydrostatic pressure increases, the liquid in the micro-channel compresses the air, and the pressure in the backing chamber is then equalized to match the external hydrostatic pressure. To validate the performance of the proposed mechanism, a micro-channel prototype is designed and integrated with the piezoelectric micro-machined flexural sensor developed in our previous work. The working principle of the mechanism is experimentally verified. In addition, the effect of hydrostatic pressure on receiving sensitivity is evaluated and compared with predicted behavior.
The interplay between active hair bundle motility and electromotility in the cochlea
Authors: Ó Maoiléidigh Dáibhid , Jülicher Frank
Published: September 2010

The cochlear amplifier is a nonlinear active process providing the mammalian ear with its extraordinary sensitivity, large dynamic range and sharp frequency tuning. While there is much evidence that amplification results from active force generation by mechanosensory hair cells, there is debate about the cellular processes behind nonlinear amplification. Outer hair cell electromotility has been suggested to underlie the cochlear amplifier. However, it has been shown in frog and turtle that spontaneous movements of hair bundles endow them with a nonlinear response with increased sensitivity that could be the basis of amplification. The present work shows that the properties of the cochlear amplifier could be understood as resulting from the combination of both hair bundle motility and electromotility in an integrated system that couples these processes through the geometric arrangement of hair cells embedded in the cochlear partition. In this scenario, the cochlear partition can become a dynamic oscillator which in the vicinity of a Hopf bifurcation exhibits all the key properties of the cochlear amplifier. The oscillatory behavior and the nonlinearity are provided by active hair bundles. Electromotility is largely linear but produces an additional feedback that allows hair bundle movements to couple to basilar membrane vibrations.
Expansions of reflected-transmitted signals to estimate the slow wave strength in fluid-saturated porous layers
Authors: Franklin H. , Derible S. , Popa Cristina
Published: September 2010

A method for estimating the strength of the slow wave in the modes propagating in porous layers is presented. It is based upon expansions on transition terms which are linear combinations of the reflection and transmission coefficients. Suitable forms of these coefficients are needed and it is shown how they can be obtained. Both open pore and sealed pore boundary conditions are investigated. It is shown that the zeroth-order and the first-order terms of the expansions suffice to describe accurately the modes and to estimate the strength of the slow wave. Approximations of the absorption coefficient by the porous layer can be deduced. Angles of incidence above and below the critical angle of the shear wave are considered. Comparisons between theory and experiments for the two types of boundary conditions are presented at normal incidence for the transition terms.
Diffusive benefits of cylinders in front of a Schroeder diffuser
Authors: Pogson M. A. , Whittaker D. M. , Gehring G. A. , Cox T. J. , Hughes R. J. , Angus J. A. S.
Published: September 2010

A numerical investigation is performed into the diffusive effects of cylinders positioned in front of a Schroeder diffuser. A regular line of cylinders is shown to offer notable improvements to diffusion from a periodic Schroeder device, provided lateral cylinder spacing is incommensurable with the Schroeder period width. Further investigation considers angular dependence and low frequency results in greater detail, as well as the effects on narrowband and modulated Schroeder devices. An optimization procedure is subsequently performed to investigate the effects of an irregular cylinder arrangement, which provides further diffusive benefits.
Different models of the active cochlea, and how to implement them in the state-space formalism
Authors: Sisto Renata , Moleti Arturo , Paternoster Nicolo , Botti Teresa , Bertaccini Daniele
Published: September 2010

The state-space formalism [Elliott S. J., et al. (2007). J. Acoust. Soc. Am. 122, 2759–2771] allows one to discretize cochlear models in a straightforward matrix form and to modify the main physical properties of the cochlear model by changing the position and functional form of a few matrix elements. Feed-forward and feed-backward properties can be obtained by simply introducing off-diagonal terms in the matrixes expressing the coupling between the dynamical variables and the additional active pressure on the basilar membrane. Some theoretical issues related to different cochlear modeling choices, their implementation in a state-space scheme, and their physical consequences on the cochlear phenomenology, as predicted by numerical simulations, are discussed. Different schematizations of the active term describing the behavior of the outer hair cell’s feedback mechanism, including nonlinear and nonlocal dependences on either pressure or basilar membrane displacement, are also discussed, showing their effect on some measurable cochlear properties.
Hertzian impact: Experimental study of the force pulse and resulting stress waves
Authors: McLaskey Gregory C. , Glaser Steven D.
Published: September 2010

Ball impact has long been used as a repeatable source of stress waves in solids. The amplitude and frequency content of the waves are a function of the force-time history, or force pulse, that the ball imposes on the massive body. In this study, Glaser-type conical piezoelectric sensors are used to measure vibrations induced by a ball colliding with a massive plate. These measurements are compared with theoretical estimates derived from a marriage of Hertz theory and elastic wave propagation. The match between experiment and theory is so close that it not only facilitates the absolute calibration the sensors but it also allows the limits of Hertz theory to be probed. Glass, ruby and hardened steel balls 0.4 to 2.5 mm in diameter were dropped onto steel, glass, aluminum, and polymethylmethacrylate plates at a wide range of approach velocities, delivering frequencies up to 1.5 MHz into these materials. Effects of surface properties and yielding of the plate material were analyzed via the resulting stress waves and simultaneous measurements of the ball’s coefficient of restitution. The sensors are sensitive to surface normal displacements down to about ±1 pm in the frequency range of 20 kHz to over 1 MHz.
Talker-listener accent interactions in speech-in-noise recognition: Effects of prosodic manipulation as a function of language experience
Authors: Pinet Melanie , Iverson Paul
Published: September 2010

Previous work has shown that accents affect speech recognition accuracy in noise, with intelligibility being modulated by the similarity between the talkers' and listeners' accents, particularly in the case where they have different L1s. The present study examined the contribution of prosody to recognizing native (L1) and non-native (L2) speech in noise, and how this is affected by the listener's L2 experience. A group of monolingual English listeners and two groups of French listeners with varying L2 English experience were presented with English sentences produced by L1 and L2 (French) speakers. The stimuli were digitally processed to exchange the pitch and segment durations between recordings of the same sentences produced by different speakers (e.g., imposing a French-accented prosody onto recordings made from English speakers). The results revealed that English listeners were more accurate at recognizing L1 English with English prosody, the French inexperienced listeners were more accurate at recognizing French-accented speech with French prosody, and the French experienced listeners varied in the cues that they used depending on the noise level, showing more flexibility of processing. The use of prosodic cues in noise thus appears to be modulated by language experience and varies according to listening context.
Extracting binaural information from simultaneous targets and distractors: Effects of amplitude modulation and asynchronous envelopes
Authors: Stellmack Mark A. , Byrne Andrew J. , Viemeister Neal F.
Published: September 2010

When different components of a stimulus carry different binaural information, processing of binaural information in a target component is often affected. The present experiments examine whether such interference is affected by amplitude modulation and the relative phase of modulation of the target and distractors. In all experiments, listeners attempted to discriminate interaural time differences of a target stimulus in the presence of distractor stimuli with ITD=0. In Experiment 1, modulation of the distractors but not the target reduced interference between components. In Experiment 2, synthesized musical notes exhibited little binaural interference when there were slight asynchronies between different streams of notes (31 or 62 ms). The remaining experiments suggested that the reduction in binaural interference in the previous experiments was due neither to the complex spectra of the synthesized notes nor to greater detectability of the target in the presence of modulated distractors. These data suggest that this interference is reduced when components are modulated in ways that result in the target appearing briefly in isolation, not because of segregation cues. These data also suggest that modulation and asynchronies between modulators that might be encountered in real-world listening situations are adequate to reduce binaural interference to inconsequential levels.
Phonetic tone signals phonological quantity and word structure
Authors: Vainio Martti , Järvikivi Juhani , Aalto Daniel , Suni Antti
Published: September 2010

Many languages exploit suprasegmental devices in signaling word meaning. Tone languages exploit fundamental frequency whereas quantity languages rely on segmental durations to distinguish otherwise similar words. Traditionally, duration and tone have been taken as mutually exclusive. However, some evidence suggests that, in addition to durational cues, phonological quantity is associated with and co-signaled by changes in fundamental frequency in quantity languages such as Finnish, Estonian, and Serbo-Croat. The results from the present experiment show that the structure of disyllabic word stems in Finnish are indeed signaled tonally and that the phonological length of the stressed syllable is further tonally distinguished within the disyllabic sequence. The results further indicate that the observed association of tone and duration in perception is systematically exploited in speech production in Finnish.
Double panel with skyhook active damping control units for control of sound radiation
Authors: Gardonio Paolo , Alujević Neven
Published: September 2010

This paper presents an experimental study on decentralized velocity feedback control on a double panel consisting of an external aluminum panel and a honeycomb trim panel. The decentralized feedback loops are formed by a 3×3 array of coil-magnet electrodynamic actuators that react off the trim panel and a lightweight stiff frame structure located in the air gap between the two panels. Microelectromechanical systems (MEMS) accelerometers are located on the opposite side of the trim panel in correspondence to the electrodynamic actuators. The grid structure is designed to provide an inertial reference to the actuators. In this way the velocity feedback control loops produce skyhook active damping on the double panel, which minimizes the vibrational response and sound radiation of the trim panel at low audio frequencies. Two configurations are considered where the grid structure is either weakly coupled or strongly coupled to the external panel. Both stability and control performance of the two configurations are analyzed experimentally. The study shows that the control configuration with the weakly coupled grid structure enables the implementation of larger stable feedback control gains, which lead to reductions of the sound radiated by the trim panel between 10 and 30 dB for the first seven resonance peaks.
Ototoxicity risk assessment combining distortion product otoacoustic emissions with a cisplatin dose model
Authors: Dille Marilyn F. , McMillan Garnett P. , Reavis Kelly M. , Jacobs Peter , Fausti Stephen A. , Konrad-Martin Dawn
Published: September 2010

An objective method for identifying ototoxic hearing loss among patients receiving cisplatin is necessary since the ability of patients to take a behavioral test may change over the course of treatment. Data from 56 monitoring visits by 19 Veterans taking cisplatin were used to identify combinations of distortion-product otoacoustic emission (DPOAE) metrics and ototoxicity risk factors that best identified ototoxic hearing loss. Models were tested that incorporated DPOAE metrics generated statistically using partial least-squares analysis. Models were also tested that incorporated a priori DPOAE change criteria, such as a minimum DPOAE level shift of 6 dB. Receiver Operating Characteristic analysis was used to compare the accuracy of these models. The best performing model incorporated weighted combinations of pre-treatment hearing, cumulative cisplatin dose and DPOAE metrics that were determined using partial least-squares and evaluated over a quarter octave range near each subjects’ high frequency DPOAE limit. Using this model and the DPOAE recording methods described herein, the chance of ototoxic hearing change can be determined at any given observed change in DPOAE level. This approach appears to provide an accurate and rapid ototoxicity risk assessment (ORA) that once validated can be used clinically.
The time course of cochlear gain reduction measured using a more efficient psychophysical technique
Authors: Roverud Elin , Strickland Elizabeth A.
Published: September 2010

In a previous study it was shown that an on-frequency precursor intended to activate the medial olivocochlear reflex (MOCR) at the signal frequency reduces the gain estimated from growth-of-masking (GOM) functions. This is called the temporal effect (TE). In Expt. 1 a shorter method of measuring this change in gain is established. GOM functions were measured with an on- and off-frequency precursor presented before the masker and signal, and used to estimate Input/Output functions. The change in gain estimated in this way was very similar to that estimated from comparing two points measured with a single fixed masker level on the lower legs of the GOM functions. In Expt. 2, the TE was measured as a function of precursor duration and signal delay. For short precursor durations and short delays the TE increased (buildup) or remained constant as delay increased, then decreased. The TE also increased with precursor duration for the shortest delay. The results were fitted with a model based on the time course of the MOCR. The model fitted the data well, and predicted the buildup. This buildup is not consistent with exponential decay predicted by neural adaptation or persistence of excitation.
A quantitative model of epitaxial layers growth from the gas phase with a simultaneous participation of diffusion, adsorption, and chemical reaction
Authors: Erdös Emerich , Laitner Jiří , Stejskal Josef , Klíma Přemysl
Published: September 2010

For a quantitative description of the epitaxial growth rate of gallium arsenide, a model has been proposed including two rate controlling steps, namely one step of physical nature and the other one of chemical nature. As the step of physical nature, the diffusion of gaseous components between the gas phase and the epitaxial layer surface has been considered, and from the steps of chemical nature the adsorption of gaseous components on the epitaxial layer surface and a heterogenous surface reaction have been taken into account. According to the kind of the chemical rate controlling step, five mechanisms have been proposed, where a one - centre model was used in all cases, i.e. the idea that the rate controlling step takes place under participation of one active centre. For all the mechanisms considered, the pertaining rate equations have been derived, which were confronted with the experimentally found dependences of the growth rate on partial pressures of components in the feed. The results are discussed both from the view point of plausibility of individual mechanisms and from the point of view of their applicability and of the next research direction.
Polarographic determination of azobenzene
Authors: Barek Jiří , Hrnčíř Roman
Published: September 2010

Conditions were found for the determination of azobenzene by means of DC, AC, TAST, DP, and FSDP polarography and linear sweep voltammetry on a hanging mercury drop electrode in the medium of aqueous methanol, which ensures a sufficient solubility of azobenzene. In the latter two methods, the detection limit was around 10-8 mol/l; a still lower value could be attained by preliminary accumulation of azobenzene, i.e. adsorption on the electrode surface.
Potential noncataleptic neuroleptic agents; 2,6-Dichloro-, 2,7-dichloro- and 2,8-dichloro-10-piperazino-10,11-dihydrodibenzo[b,f]thiepins
Authors: Protiva Miroslav , Dlabač Antonín , Valchář Martin , Wildt Stanislav , Červená Irena , Šedivý Zdeněk
Published: September 2010

Substitution reactions of 2,6,10-trichloro-, 2,7,10-trichloro- and 2,8,10-trichloro-10,11-dihydrodibenzo[b,f]thiepin (Vabc) with 1-(2-hydroxyethyl)piperazine, 1-methylpiperazine and 1-benzylpiperazine gave the title compounds IIabc, IIIab and IVab. The new chloro compounds Va and Vb were obtained in 6 steps starting from reactions of 2,5-dichloroacetophenone with 2-chlorothiophenol or 3-chlorothiophenol. Compounds IIabc are 6-chloro, 7-chloro and 8-chloro derivatives of the noncataleptic neuroleptic agent docloxythepin (I). They are almost devoid of cataleptic activity and do not inhibit the apomorphine stereotypies in rats. Compounds IIab have a clozapine-like affinity to dopaminergic receptors in the rat brain striatum; the affinity of IIc is much higher. On the other hand only compounds IIb and IIIa prove a significant antidopaminergic activity in vivo (increase significantly the homovanillic acid level in the rat brain striatum).
Topological aspects of chemical reactivity. A simple method for estimating the activation energies in pericyclic reactions
Authors: Ponec Robert
Published: September 2010

A simple topological model allowing to estimate the activation energies in thermally initiated pericyclic reactions is proposed. The formalism of the model is closely connected with the recently formulated overlap determinant method. Due to its simplicity the proposed model is especially convenient for the semiquantitative estimate of the reactivity, e.g. in computer designed synthesis where even the simplest quantum chemical procedures are still too time consuming.
Adsorption with mobile precursors - determination of the kinetic order
Authors: Pavlíček Jan
Published: September 2010

A method is proposed which makes possible a more reliable determination of the adsorption order from the dependence of coverage on exposition in the case of adsorption with mobile precursors. It is pointed out that the evaluation of experiments carried out at a single temperature may lead to erroneous conclusions. The method is also advantegeous for the more exact determination of the limiting coverage and the slope of the tangent at the origin of coordinates.
The effect of Co and Ni in hydrodesulphurization of benzo[b]thiophene on Mo and W catalysts
Authors: Peter Rudolf , Zdražil Miroslav
Published: September 2010

Hydrodesulphurization of benzo[b]thiophene (BT) on sulphided Mo, W, Co-Mo, Co-W, Ni-Mo, and Ni-W catalysts has been studied at total pressure 2.1 MPa and temperature 543 K. The catalysts were laboratory preparations with alumina or active carbon as a support and also commercial samples. The formation of intermidate 2,3-dihydrobenzo[b]thiophene (DHBT) was observed with all catalysts. On non-promoted catalysts, large quantities of it were formed; partial equilibrium BT-DHBT-H2 was attained already at low desulphurization conversions. On promoted catalysts (Co-W, Co-Mo, Ni-W, Ni-Mo) the amount of DHBT formed was small; the partial equilibrium BT-DHBT-H2 was not attained even at high desulphurization conversions. The data were correlated by kinetic equations derived from consecutive reaction scheme assuming steady state conditions for adsorbed species. The separation of individual reaction steps was not possible and only formal kinetic constants were obtained. It was concluded that the effect of Co or Ni in the reaction sequence is localized in the steps between partially hydrogenated BT on the surface and gaseous hydrogen sulphide and hydrocarbons.
Preparation of secondary alcohols of high optical purity
Authors: Červinka Otakar , Fábryová Anna , Sablukova Irina
Published: September 2010

Partially resolved enantiomers of optically active alcohols I-V, obtained by enantioselective reduction of the corresponding ketones with lithium aluminium hydride in the presence of (-)-quinine, were converted into crystalline 3,5-dinitrobenzoates or phenylcarbamates. The esters of the nearly optically pure enantiomers were separated by crystallization from the generally more soluble esters of the racemates. Optical purity of the hydrolytically liberated alcohols was determined by 1H NMR spectroscopy in the presence of chiral shifting agents.
Kinetic scheme of oscillation reaction of three and four particles
Authors: Tockstein Antonín
Published: September 2010

The paper deals with four schemes, each of three out of the particles X, A, Y, C, consisting of two coupled autocatalytic blocks of the type Q→X→A→Y→C. The schemes showing relative stability of the Y particle or its dimer can exhibit a limit cycle, the other have always a stable stationary point. The scheme of four particles X, A, Y, C or dimers of particles X, Y can exhibit an unstable stationary point with the limit cycle. For the individual cases conditions were derived for the rate constants sufficient for formation of the limit cycle, and they are discussed from the point of view of available experimental data on the reaction of bromate with phenol and aniline.
New highly efficient coulometric cell with homogenous potential distribution on the working electrode
Authors: Németh Michal , Mocák Ján
Published: September 2010

A highly efficient coulometric cell was designed and constructed, ensuring a constant potential over the whole surface of the working electrode and suitable for very rapid electrolysis. It consists of concentric cylindrical Teflon parts; also the working and auxiliary electrodes are cylindrical and concentric. Electrolysis can be carried out under anaerobic conditions. Functioning of the cell was tested on the oxidation of hexacyanoferrate(II) and chlorpromazine and reduction of hexacyanoferrate(III). The new cell is suitable for routine quantitative analyses and in studying the mechanism and kinetics of moderately rapid chemical reactions.
Interactions of tungsten hexachloride with esters of carboxylic acids
Authors: Balcar Hynek , Dosedlová Alena , Matyska Bohumír
Published: September 2010

The interactions of tungsten chlorides and oxychlorides with methyl 10-undecenoate, methyl palmitate and methyl acetate, respectively, have been investigated by UV-VIS, IR and EPR spectroscopic methods. The primary complex formed by coordination of the carbonyl group to WCl6 is converted successively to an analogical, very stable complex WOCl4.ester under the simultaneous formation of acyl chloride and methyl chloride. In the case of methyl undecenoate, the coordination reaction is accompanied by a partial reduction of WCl6 to WCl5. The latter reacts with the ester in excess to give a complex characterized by a broad EPR single line at g = 1.767 (ΔH = 7.8 mT). At higher ester-to-tungsten molar ratios, this complex undergoes deeper reduction to products containing tungsten in a lower oxidation state, and competitively, a parallel oxygen abstraction reaction yielding WOCl3, acyl chloride and methyl chloride. The participation of these reactions in the formation of active WCl6-based catalysts for methathesis of unsaturated esters is discussed.
Chemistry of compounds with the 1-carba-closo-dodecaborane(12) framework
Authors: Jelínek Tomáš , Plešek Jaromír , Heřmánek Stanislav , Štíbr Bohumil
Published: September 2010

Synthesis of various compounds containing the 1-carba-closo-dodecaborane cage is reported. The isolated derivatives include zwitterionic 1-L-1-CB11H11 (l = H3N and (CH3)2S) and 12-L-1-CB11H11 (L = (CH3)2S and CH3SCH2SCH3) compounds along with C-substituted derivatives of the general formula [1-X-CB11H11]- (X = HOOC, HO, CH3O, HS and CH3S). Direct halogenation of [1-CB11H12}- produces [7,8,9,10,12-Cl5-1-CB11H7]-, [7,8,9,10,11,12-X6-1-CB11H6]- (X = Cl, Br), [12-I-CB11H11]- and [7,12-I2-1-CB11H10]- substituted species. Constitution of all products was established by 1H, 11B, IR and mass spectrometry and is supported by some chemical reactions of the compounds.
Complex nickel compounds with Schiff bases derived from diacetylmonoxime
Authors: Březina František , Šindelář Zdeněk
Published: September 2010

Schiff bases derived from diacetylmonoxime and ethylenediamine or diethylenetriamine give Ni(HDEM)ClO4, Ni(HDEM) (ClO4)Br, Ni(H2DTM)Br2.2 H2O and Ni(H2DTM)Br4 complex compounds. H2DTM splits in solution in the presence of triethylamine, owing to which Ni(DAO) (dien)Cl complex could be isolated. The possibility of Employing the above Schiff bases for the preparation of compounds involving nickel in a higher valency state is discussed.
1H and 13C NMR study of some substituted 2-furyl- and 2-thienylethylene derivatives
Authors: Dandárová Miloslava , Végh Daniel , Kováč Jaroslav , Goljer Igor , Prónayová Nadežda , Špirková Katarína
Published: September 2010

The 1H and 13C NMR spectral data of 1-(5-nitro-2-furyl)-2-X-2-Y-ethylenes and some their thienyl analogues are presented. Geometrical arrangement of the trisubstituted ethylenes was adduced from vicinal coupling constants 3J(C, H) for the carbon atom at the functional group attached to the double bond and the ethylene proton. The orientation of the heterocyclic ring towards the double bond of the side chain was determined from the 1H NMR data. The preferred s-cis or s-trans conformations of 5-nitro-2-furylethylene derivatives is substituent at the double bond dependent; all thiophene derivatives under study were found in the s-trans conformation.
Simulation of mechanically stirred two-phase liquid-gas flow
Authors: Fořt Ivan , Rogalewicz Vladimír , Richter Miroslav
Published: September 2010

The study describes simulation of the motion of bubbles in gas, dispersed by a mechanical impeller in a turbulent low-viscosity liquid flow. The model employs the Monte Carlo method and it is based both on the knowledge of the mean velocity field of mixed liquid (mean motion) and of the spatial distribution of turbulence intensity ( fluctuating motion) in the investigated system - a cylindrical tank with radial baffles at the wall and with a standard (Rushton) turbine impeller in the vessel axis. Motion of the liquid is then superimposed with that of the bubbles in a still environment (ascending motion). The computation of the simulation includes determination of the spatial distribution of the gas holds-up (volumetric concentrations) in the agitated charge as well as of the total gas hold-up system depending on the impeller size and its frequency of revolutions, on the volumetric gas flow rate and the physical properties of gas and liquid. As model parameters, both liquid velocity field and normal gas bubbles distribution characteristics are considered, assuming that the bubbles in the system do not coalesce.
Reaction of hydroxydiamantanes with chloroethylenes in sulfuric acid
Authors: Vodička Luděk , Burkhard Jiří , Janků Josef
Published: September 2010

Reaction of hydroxydiamantanes with 1,1-dichloroethylene in concentrated sulfuric acid leads to complex reaction mixtures, containing predominantly diamantylacetic and diamantanebisacetic acids. The same reaction with trichloroethylene affords diamantylchloroacetic and diamantanebischloroacetic acids. In all these products the substituents are bonded to the apical and secondary carbon atoms of the diamantane skeleton. For steric reason, acids with carboxyl in the medial position are not formed.
Determination of zero components in the composition of a system
Authors: Coufal Oldřich
Published: September 2010

A method is proposed for determing components whose concentration in a system of chemically reacting components is zero without necessity of computing the composition of the entire system. Theoretical considerations are applied to the case of the equilibrium composition of combustion products of hydrocarbons with air and an ionization additive, K2CO3.
Theoretical analysis of counter-current absorption of a poorly soluble gas based on the PDE-AD model
Authors: Moravec Pavel , Staněk Vladimír
Published: September 2010

Expression have been derived in the paper for all four possible transfer functions between the inlet and the outlet gas and liquid steams under the counter-current absorption of a poorly soluble gas in a packed bed column. The transfer functions have been derived for the axially dispersed model with stagnant zone in the liquid phase and the axially dispersed model for the gas phase with interfacial transport of a gaseous component (PDE - AD). calculations with practical values of parameters suggest that only two of these transfer functions are applicable for experimental data evaluation.
Analysis of mechanism of the catalytic effect of hydrogen on the decay of alkyl macroradicals in polyethylene
Authors: Bartoš Josef
Published: September 2010

The suggested one-step and two-step mechanism of decay of alkyl macroradicals in polyethylene are analyzed in detail at the activation energy level. For the one-step mechanism, the BEBO method is modified for reactions proceeding via a three-particle state. For the two-step mechanism, a three-process kinetic model is used; the contributions to the total energy barrier are calculated by the original BEBO method for two-particle transition states and by a molecular model for the diffusion of simple penetrants in polymers. The results indicate that the catalytic effect of hydrogen on the migration of the alkyls in the amorphous phase proceeds by the two-step mechanism.
Synthesis of some monoterpenols via cyclopropylcarbinyl rearrangement
Authors: Moiseenkov Alexander M. , Czeskis Boris A.
Published: September 2010

Condensation of appropriately substituted aldehydes and Grignard reagents leads to cyclopropyl alcohols V - VIII chromatographically separated in all cases into individual diastereoisomers. Perchloric acid catalyzed cyclopropylcarbinyl rearrangement of V - VIII (as a mixture of diastereoisomers or individual isomers) gives unsaturated monoterpenols IX - XII with high regio- and stereospecifity.
Diffusion coefficients of potassium chromate and dichromate in water at 25 °C
Authors: Vacek Václav , Rod Vladimír
Published: September 2010

The concentration dependences of diffusion coefficients of potassium chromate and dichromate in water at 25 °C were measured by using the Taylor technique of the concentration pulse dispersion in laminar flow of liquid. The results were compared with hitherto published mutually inconsistent data for potassium and sodium chromates and dichromates.
Synthesis of N-(1-phenyl-2-propyl)-2,5-diphenylpentylamine and some related compounds as potential neurotropic and cardiovascular drugs
Authors: Vejdělek Zdeněk , Němec Jiří , Protiva Miroslav
Published: September 2010

Heating of 2,5-diphenylvaleric acid with 2-phenylethylamine, 1-phenyl-2-propylamine, 1-phenyl-2-butylamine (IX), 1-(4-methoxyphenyl)-2-propylamine, 1-(4-methoxyphenyl)-2-butylamine (X) and 1-(4-dimethylaminophenyl)-2-propylamine to 200-210 °C resulted in the amides IIb-VIIb which were reduced with lithium aluminium hydride in boiling dibutyl ether to give the amines IIa, IIIa, and Va - VIIa. A similar two-step sequence starting from 4-phenyl-4-(phenylthio)-butyric acid and the amine IX gave compound VIIIa. The salts of the title amines revealed some central stimulating, antireserpine, thiopental potentiating, anticonvulsant, and antiarrhythmic effects. 1-(4-Dimethylaminophenyl)-2-butylamine (XI), prepared in this connection, proved anoretic activity.
Effect of the ionizing radiation on the kinetics of the reduction by hydrogen of NiO-Fe2O3 mixed oxides of various genesis
Authors: Pospíšil Milan , Topinka Jan
Published: September 2010

The kinetics of the reduction by hydrogen of two series of NiO-Fe2O3 mixed oxides of different composition was studied in the temperature range 320 - 410 °C using thermogravimetry. Both series were prepared from different precursors that were thermally decomposed at different temperatures. The oxidizing ability of the surface ( the content of chemisorbed oxygen) is the only parameter from all physico-chemical properties studied that changed significantly during the pre-irridation of the system by 60Co gamma radiation (dose 505 kGy), by fast neutrons from the 252Cf source (dose Dn = 110 Gy) and by accelerated electrons (3 MeV, dose 500 kGy). A positive radiation effect was observed in the first case while the irritation by neutrons and electrons resulted in a negative effect. The magnitude of the effect depends on the composition and genesis of the system and it decreases in the sequence γ, e-, n. The radiation induced changes in the reduction kinetics of mixed oxides change their magnitude and sign in dependence on the composition and genesis. Not only the increase by an order of magnitude of the rate of the initial phase of the reduction which was ascribed to the partial reduction of hematite to magnetite but also the acceleration of the second step (reduction of Fe3O4 to Fe) was observed after the exposure to photons or fast neutrons. The radiation changes induced by electrons are limited only to the surface of the irradiated solid and they affect only the first step of the reduction. The maximum positive effect was observed in the region of high excess of hematite and its magnitude decreases with the increasing content of nickel oxide. The radiation effects decrease with the increasing temperature of the reduction and at about 400 °C the effect of irradiation is completely annealed.
Syntheses of some 4-dialkylaminoalkylamino derivatives of 2,3-dimethyl-2H- and 3,9-dimethyl-9H-pyrazolo[3,4-b]quinoline
Authors: Rádl Stanislav , Zikán Viktor
Published: September 2010

Reactions of 4-chloro-2,3-dimethyl-2H-pyrazolo[3,4-b]quinoline and 4-chloro-6-methoxy-2,3-dimethyl-2H-pyrazolo[3,4-b]quinoline with 3-dimethylaminopropylamine and/or 2-dimethylaminoethylamine afforded 4-(3-dimethylaminopropylamino)-2,3-dimethyl-2H-pyrazolo[3,4-b]quinoline (IIa), its 6-methoxy derivative (IIc), 4-(2-diethylaminoethylamino)-2,3-dimethyl-2H-pyrazolo[3,4-b]quinoline (IIb) and its 6-methoxy derivative (IId). Reaction of 4,9-dihydro-3,9-dimethyl-4-oxo-1H-pyrazolo[3,4-b]quinoline with thionyl chloride gave an intermediate, whose reaction with 3-dimethylaminopropylamine afforded 4-(3-dimethylaminopropylamino)-3,9-dimethyl-9H-pyrazolo[3,4-b]quinoline (III). The compounds were tested in vivo in mice for efficacy against the A2-Hongkong influenza virus and the encephalomyocarditis virus.
Mechanism of action of heavy metals, S-triazine herbicides and nitrates on alcohol dehydrogenase from rape
Authors: Stiborová Marie , Leblová Sylva
Published: September 2010

Heavy metals (Pb2+, Cu2+, Cd2+, and Zn2+) inhibited alcohol dehydrogenase (ADH) of rape (EC 1.1.1.1.); Pb2+ and Cd2+ ions affected the imidazole ring of histidine, Cu2+ and Zn2+ ions interacted with the sulphydryl groups of cysteine in the molecule of the enzyme. The coenzyme protected ADH from inactivation by Pb2+ and Cd2+, but did not protect it from Cu2+ and Zn2+. Ethanol in a ternary complex ADH-NAD+ -ethanol was a strong protecting agent from Pb2+ and Cd2+ ions. Nitrates inhibited rape ADH toward any substrate. Sulphates and fluorides had no effect. The S-triazine herbicides studied proved strong inhibitors of rape ADH (their Ki's corresponded to concentrations of the order 10-4 mol 1-1), occupying the binding site for the coenzyme. The herbicides interacted with the metallic component of the enzyme, to which the nicotinamide part of the coenzyme is bound.
Calculation of potential and concentration gradients in trickle-bed electrodes producing hydrogen peroxide
Authors: Špalek Otomar
Published: September 2010

A mathematical model for describing the trickle-bed electrode has been developed and used to calculate the potential distribution along the current flow and the hydrogen peroxide concentration profile along the electrolyte flow (normal to the direction of current). Polarization curves and dependences of the current yield of hydrogen peroxide and the peroxide losses due to the processes occurring (reduction, decomposition, and transport into the anode chamber) on the current density have also been calculated. A comparison is made between calculated and measured dependences of the current yield of hydrogen peroxide on the current density.
The change in the standard Gibbs energy during the formation of the acid selenites of the alkali metals
Authors: Mička Zdeněk , Ebert Miroslav
Published: September 2010

The heterogeneous M2SeO3-H2SeO3-H2O systems (M = Li, Na, K, Rb, Cs) were studied at 298 K using the Filippov eutonic method, yielding the values of the change in the standard Gibbs energy of reactions leading to the formation of the acid selenites of these metals. It follows from the ΔG0 values that the stability of hydrogenselenites and trihydrogenbis(selenites) increases from lithium to cesium and also, except for cesium salts, on transition from MHSeO3 to MH3(SeO3)2.
Vibrational energies of H3+ and Li3+ based on the diatomics-in-molecules potentials
Authors: Vojtík Jan , Špirko Vladimír , Jensen Per
Published: September 2010

The present publication reports variational calculations of the vibrational energy levels for H3+, D3+, 6Li3+, and 7Li3+, starting from potential energy surfaces generated by the DIM scheme. The vibrational energies obtained agree semiquantitatively with those based on the best ab initio potentials available. The results seem to indicate that an analogous approach might be useful in describing the vibrational motion of heavier alkali cluster cations A3+.
Conformational structure of the local anaesthetic lidocaine, its cation, and hydrofluoride
Authors: Remko Milan
Published: September 2010

The PCILO quantum chemical method was applied to the conformational analysis of the local anaesthetic lidocaine (2-diethylaminoacet-2',6'-dimethylanilide), its cation and hydrofluoride. The stable conformations, proton affinity, and the hydrogen bonding energy of the lidocaine ion pair were determined. The results are compared with published data and discussed in terms of the present theories of the mechanism accounting for the activity of these drugs.
Synthese von bis(norcara-2,4,2',4'-tetraenyliden) ueber eine carbendimerisierung
Authors: Pilidis Georgios
Published: September 2010

Aus 7,7-Dibrom-3,4-isopropylidenbicyclo[4.1.0]heptan-3,4-diol (VI) und Methyllithium in Ether, sowohl bei -50 °C als auch unter Ruckflussbedingungen entsteht das Carben, das sofort dimerisiert. Aus diesem Dimeren lasst sich in wenigen Reaktionsschritten das Bis(norcara-2,4,2',4'-tetraenyliden) (VII) synthetisieren. Die 1H-NMR- und 13C-NMR-Spectren des Dimeren und der Titelverbindung VII werden diskutiert.
The crystal structure of dibutyl-bis(pentamethylenedithiocarbamato)tin(IV)
Authors: Lokaj Jan , Kellö Eleonóra , Kettmann Viktor , Vrábel Viktor , Rattay Vladimír
Published: September 2010

The crystal and molecular structure of SnBu2(pmdtc)2 has been solved by X-ray diffraction methods and refined by a block-diagonal least-squares procedure to R = 0.083 for 895 observed reflections. Monoclinic, space group C2, a = 19.893(6), b = 7.773(8), c = 12.947(8) . 10-10 m, β = 129.07(5)°, Z = 2, C20H38N2S4Sn. Measured and calculated densities are Dm = 1.38(2), Dc = 1.36 Mg m-3. Sn atom, placed on the twofold axes, is coordinated with four S atoms in the distances Sn-S 2.966(6) and 2.476(3) . 10-10 m. Coordination polyhedron is a strongly distorted octahedron. Ligand S2CN is planar.
Chelates of molybdenum(VI) with citrate and malate
Authors: Bartušek Miloš , Havel Josef , Matula Dalibor
Published: September 2010

The interaction of MoO42- ions with citrate and malate, respectively, has been studied by potentiometric neutralization titrations in aqueous solutions at pH 4-7. The equilibrium constants of chelate formation have been determined for MoO2(OH)(citH-1)3-, MoO2(citH-1)2-, MoO2(OH)(malH-1)2-, and MoO2(malH-1)24-. The way of bonding of the citrate and malate ligands to the central Mo(VI) atom is discussed.
Improved separation of C12-C22 fatty acid phenacyl esters by reversed phase column liquid chromatography
Authors: Haniš Tomáš , Smrž Miroslav , Klír Pavel , Macek Karel , Deyl Zdeněk
Published: September 2010

Phenacyl esters of C12-C22 fatty acids were separated on Separon SGX C18 column, using a gradient elution with methanol-acetonitrile-water. The proposed gradient showed better resolution of the critical pairs C18:3-C14:0, C16:1-C20:4, and C16:0-C18:1 than the gradient elution with methanol-water or acetonitrile-water, or than the isocratic elution with methanol-acetonitrile-water. The optimum volume concentration (83%) of the sum of both methanol and acetonitrile was maintained constant for 35 min; in this period the acetonitrile concentration decreased linearly from the initial 42-60% to 0% while the methanol concentration increased from the initial 41-23% to 83% at the same rate. After 35 min the elution was completed with a methanol-water gradient. The whole analysis can be performed within 63 min at a flow rate 1 ml/min.
Investigation on mechanochemical dehydration of γ-FeOOH
Authors: Klissurski Dimiter , Blaskov Vladimír , Šubrt Jan , Bechině Karel
Published: September 2010

The process of mechanochemical dehydration of γ-FeOOH has been investigated. It has been established that grinding of γ-FeOOH leads to its direct transformation into α-Fe2O3. The IR spectroscopy and X-ray phase analyses did not detect γ-Fe2O3 in the dehydration products. During dehydration, α-Fe2O3 with a defective magnetic structure is formed. The smallest size of the hematite particles obtained is 10 nm. The difference between mechanochemical and controlled thermal dehydration of γ-FeOOH is discussed.
5-Substituted and 5,7-disubstituted 5,7-dihydrodibenzo[c,e]thiepins and the corresponding S-oxygenated compounds: Alkylamines, carboxylic acids, and carboxamides; synthesis and pharmacological screening
Authors: Šindelář Karel , Holubek Jiří , Ryska Miroslav , Koruna Ivan , Protiva Miroslav
Published: September 2010

Reaction of 5,7-dihydrodibenzo[c,e]thiepin (I) with n-butyllithium resulted in the partial sulfur extrusion and in the formation of the 9,10-dihydrophenanthrene-9-thiolate anion (B). Its further transformations (by hydrolysis, aminoalkylation and spontaneous dehydrogenation) led to phenanthrene-9-thiol (IX), the corresponding disulfide X, and the S-(2-dimethylaminoethyl) derivatives XI and XIV. Reactions of 5-chloro-5,7-dihydrodibenzo[c,e]thiepin (II) with the corresponding Grignard reagents were only a poor source of the amines III and IV. Reaction of the sulfoxide XVIII with n-butyllithium or with sodium hydride and the following treatment with 2-dimethylaminoethyl chloride gave the amine XIX in a low yield. Only the sulfone X was found more useful for preparing the 5- and 5,7-substituted derivatives. Treatment with n-butyllithium and following carbonation afforded mixtures of the monocarboxylic acid XXI and dicarboxylic acid XXVIII. Via acid chlorides they were transformed to the methylamides XXII and XXIX, and to the dimethylamides XXIII and XXX. The amide XXIII was reduced to the 5-(dimethylaminomethyl) compound XXV. Lithiation of the sulfone XX or treatment with sodium hydride, and the following action of 2-dimethylaminoethyl chloride and 3-dimethylaminopropyl chloride gave the amines XXVI, XXVII, and XXXI. Only the phenanthrene derivatives XI and XIV, and the amino sulfone XXVII showed clear indications of thymoleptic activity as potential antidepressants.
Synthesis of cyclohexylaliphatic acids and their pharmacological properties
Authors: Kuchař Miroslav , Brunová Bohumila , Grimová Jaroslava , Vaněček Stanislav , Holubek Jiří
Published: September 2010

A series of substituted cyclohexylacetic acids I has been obtained by hydrogenation of the unsaturated analogues II and III. Esters of these analogues were prepared by the Horner-Wittig reaction of the corresponding cyclohexanones IV and/or 2-cyclohexenones V with triethyl phosphonoacetate. These esters were obtained in two isomeric forms (Z and E), differing in the double bond in the exo-position. The derivatives with a substituent in the 2-position exhibited a partial shift of the double bond to the cyclohexane ring; this shift was especially marked in the 2-phenyl derivative. With the acids I-III, activation of fibrinolysis was assessed by the hanging clot method; the anti-inflammatory effect was assessed by inhibition of two experimental model inflammations. The regression equation relating fibrinolytic capacity to lipophilicity was a quadratic one, the logarithm of optimum lipophilicity being log Popt = 5.55. A qualitative assessment of the anti-inflammatory effect in relation to lipophilicity suggests that log Popt is probably higher than with arylaliphatic acids. These acids seem to have an active site different from that of the acids I-III.
MULTIFRACTAL MEASURES OF TIME SERIES: f(α) SURFACES
Authors: MARTINO WILLIAM , FRAME MICHAEL
Published: September 2010

Binning the data points of a time series and associating a contraction map with each bin gives rise to a driven IFS representation of the time series. Varying the bins changes the driven IFS, sometimes in complex ways difficult to parse. From the transition matrix for any particular binning we can plot an f(α) curve. Assembling these curves as the bins change gives a surface, which we call the f(α) surface. We use properties of this surface to investigate time series from iterating logistic and tent maps, and also time series of financial data.