bluuebunny/crossref_metadata_2025 huggingface dataset:
Fluid and Structure Interaction in Cochlea’s Similar Geometry
Authors: Hamadiche Mahmoud
Published: March 2011

A non linear mathematical model addressing the passive mechanism of the cochlea is proposed in this work. In this respect, the interaction between the basilar membrane seen as an elastic solid and fluids in both scala vestibuli and tympani is developed. Via the fluid/solid interface, a full fluid/solid interaction is taking into account. Furthermore a significant improvement of the existing models has been made in both fluid flow modelling and solid modelling. In the present paper, the flow is three dimensional and the solid is non homogeneous two dimensional membrane where the material parameters depend only on the axial distance. The problem formulation leads to a system of non linear partial differential equations. Solution of the linearized system of partial differential equations of the proposed approach is presented. The numerical results obvious a lower and upper limits of the cochlea resonance frequency versus the material parameters of the basilar membrane. It is shown that a monochromatic acoustic wave energises only a portion of the basilar membrane and the location of the excited portion depends on the frequency of the incident acoustic wave. Those results explain the ability of the cochlea in deciphering the frequency of sound with high resolution in striking similarity with the known experimental results. The mathematical model shows that the excited strip of the basilar membrane by a monochromatic acoustic wave is very small when a transverse wave exists in the basilar membrane. Thus, a transverse wave improves highly the resolution of the cochlea in deciphering the high frequency of the incident acoustic wave.
A CFD Study of Flow Past a Rotating Cylinder to Re = 1000
Authors: Du Lue Derek , Dalton Charles
Published: March 2011

In this paper, we examine, computationally, a uniform flow past a rotating circular cylinder. The objective is to determine the effect the rotation has on the lift and drag acting on the cylinder, on the vortex structures and on the vortex-shedding frequency. A streakline calculation illustrates the effect the rotation has on the vortex-structure in the wake. A combination of finite-difference and spectral methods is used to calculate the three-dimensional incompressible unsteady Navier-Stokes equations in primitive variable form in nonorthogonal curvilinear coordinates. A second-order accurate in time fractional-step method is used to decouple pressure and velocity components. High-order compact-difference schemes are used to avoid the problem of the so-called checker-board behavior. The calculated lift coefficient (CL), drag coefficient (CD) and pressure coefficient (CP) of the flows at a Reynolds number of 200 and α = 1 to 5 (α is the nondimensional ratio of the rotating speed-to-free stream speed) agreed very well with results in the literature. However, streak line patterns were not presented in these earlier studies. We also have drag and lift results at Re = 1000 for the same range of α values. These results are found to follow the same trends as at Re = 200. These results have a practical application in offshore drilling.
Fully Coupled Fluid-Structure Interaction Simulations of Vocal Fold Vibration
Authors: Zhang Lucy T. , Wang Xingshi
Published: March 2011

The human vocal folds are modeled and simulated using a fully coupled fluid-structure interaction method. This numerical approach is efficient in simulating fluid and deformable structure interactions. The two domains are fully coupled using an interpolation scheme without expensive mesh updating or re-meshing. The method has been validated through rigorous convergence and accuracy tests. The response of the fluid affects the elastic structure deformation and vice versa. The goal of this study is to utilize this numerical tool to examine the entire fluid-structure system and predict the motion and vocal folds by providing constant inlet and outlet pressure. The input parameters and material properties, i.e. elastic and density of the vocal folds used in the model are physiological. In our numerical results, the glottal jet can be clearly identified; the corresponding pressure field distribution and velocity field are presented.
A Study on Pairs of Stream-Wise Flexible Circular Cylinders in Cross Flow
Authors: Nakamura Tomomichi , Kondo Hironobu
Published: March 2011

The importance of the in-flow oscillation of a single cylinder in cross-flow has been in the spotlight since the accident in a FBR-type reactor. In-flow oscillations can also be observed in heat exchanger tube arrays. Previous reports show some interesting phenomena on the oscillation of cylinder arrays. In this paper, detailed observations on the effect of the pitch ratio for pairs of cylinders, in parallel and in tandem, is highlighted in the range of low flow velocities, where each cylinder can move only in a given direction. The motion of the cylinders is measured by attached strain gages and by a high-speed digital video camera.
A Numerical Study of the Aeroacoustic Interaction of a Cavity With a Confined Flow: Effect of Edge Geometry in Corrugated Pipes
Authors: Nakibog˘lu Gu¨nes¸ , Hirschberg Avraham
Published: March 2011

In the present work a numerical study is carried out to investigate the aeroacoustic interaction of a 2D cavity with a confined flow. Incompressible flow simulations are performed with imposed incoming velocity perturbations. Equivalent time averaged acoustic source power is calculated through enthalpy differences using the theory of Vortex Sound. Information required for the estimation of acoustic source strength in high Reynolds number flows are acquired from relatively low Reynolds number, Re = O (103) simulations. This is done by an extrapolation method in which the effect of friction is estimated by considering a reference flow in a straight channel. The proposed methodology is employed to explain the whistling phenomenon observed in corrugated pipes, which can be considered as rows of acoustically coupled cavities. The method successfully predicts the Strouhal number ranges where acoustic energy production and absorption occur. The method can also explain the effect of edge geometry on sound production, which is known to be important in corrugated pipes. In accordance with the earlier experimental study, round upstream - sharp downstream edge case leads to higher sound production levels than sharp upstream - round downstream case.
Numerical Simulation of the Flow Around a Surface-Mounted Finite Square Cylinder
Authors: Einian Maryam , Bergstrom Donald J. , Sumner David
Published: March 2011

Large eddy simulation (LES) was used to study the unsteady turbulent flow over a surface-mounted square cylinder of finite height, for cylinder aspect ratios of AR = 3 and 5, at a Reynolds number of Re = 500. Employing a semi-implicit fractional step method for momentum and a pressure correction scheme for mass conservation, a collocated finite-volume code was used to solve the Navier-Stokes equations in three dimensions. A multi-grid scheme was employed to accelerate the pressure solver. The cylinder geometry was created on a Cartesian mesh using internal boundary conditions. The motivation for the study was to better understand the complex wake structure of the finite cylinder and the influence of the aspect ratio. The numerical results were consistent with the observations from experiments documented in the literature. For the case of AR = 3, the wake was dominated by downwash effects, where as for more slender cylinder, AR = 5, some upwash effects were noticeable closer to the ground plane.
Large-Amplitude Oscillations of a Finite-Thickness Cantilevered Flexible Plate in Viscous Channel Flow
Authors: Elliott Novak S. J. , Lucey Anthony D. , Heil Matthias
Published: March 2011

The broad aim of the present work is to elucidate mechanisms of obstructive breathing disorders (snoring, sleep apnea) in which flow-induced instabilities of the soft palate feature. We use the well-established analogue system model wherein a two-dimensional flexible plate (soft palate) is mounted downstream of a rigid surface that separates upper and lower plane channel (oral and nasal tracts) flows that interact with the plate motion and then combine into a single plane channel (pharynx) flow. For this system, we take the next step towards biomechanical realism by modeling finite-amplitude motions of the flexible plate and incorporating finite thickness in its structure. The structural model makes use of a geometrically nonlinear formulation of the solid mechanics. Viscous flow is modeled at Reynolds numbers giving unsteady laminar flow. The fully-coupled fluid-structure interaction (FSI) model is developed using the open-source finite-element library oomph–lib. We first show the effects of finite amplitude and finite thickness on the in-vacuo modes of the plate through a validation study of the structural mechanics. Thereafter, we use the FSI model to illustrate both stable and unstable motions of the plate. Overall, this paper demonstrates the versatility of the new modeling approach and its suitability for characterizing the dependence of the plate’s stability on the system parameters.
Analysis of Induced Vibrations in Fully-Developed Turbulent Pipe Flow Using a Coupled LES and FEA Approach
Authors: Shurtz Thomas , Maynes Daniel , Blotter Jonathan
Published: March 2011

This paper presents an approach using numerical simulations that have been used to characterize pipe vibration resulting from fully developed turbulent flow in a straight pipe. The vibration levels as indicated by; pipe surface displacement, velocity, and acceleration are characterized in terms of the influences of geometric and material properties of the pipe, and the effects of varying flow velocity, fluid density and viscosity have considered Reynold’s numbers ranging from 9.1×104 – 1.14×106. A large eddy simulation fluid model was coupled with a finite element structural model to simulate the fluid structure interaction using both one-way and two-way coupled techniques. The one-way technique passes the spatially and temporally varying wall pressure from a completed flow solution with fixed wall boundaries to the structural model. The structural model is then solved for wall displacements. The two-way technique involves the additional passing of wall displacement back to the fluid model which is then resolved given the new boundary location. The structural and fluid models are thus continually updated until convergence is reached at each time step. The results indicate a strong nearly quadratic dependence of pipe wall displacement on fluid average velocity. This relationship has also been verified in experimental investigations of pipe vibration. The results also indicate the pipe vibration has a power law type dependence on several variables. Dependencies on investigated variables are non-dimensionalized and assembled to develop a functional relationship that characterizes turbulence induced pipe vibration.
Performance of a Tethered Point Wave-Energy Absorber in Regular and Irregular Waves
Authors: Bachynski Erin E. , Young Yin Lu , Yeung Ronald W.
Published: March 2011

The importance of the mooring system on the dynamic response of a point-absorber type ocean-wave energy converter (WEC) is investigated using a frequency-domain approach. In order to ensure the safety of WECs, careful consideration of the response and resonance frequencies in all motions must be evaluated, including the effects of the mooring system. In this study, a WEC floater with a closed, flat bottom is modeled as a rigid vertical cylinder tethered by elastic mooring lines. The WEC hydrodynamic added mass and damping are obtained using established potential-flow methods, with additional damping provided by the energy-extraction system. The results show that the response of the WEC, and the corresponding power takeoff, varies with the diameter-to-draft (D/T) ratio, mooring system stiffness, and mass distribution. For a given wave climate in Northern California, near San Francisco, the heave energy extraction is found to be best for a shallow WEC with a soft mooring system, compared to other systems that were examined. This result assumes a physical limit (cap) on the motion which is related to the significant wave height to draft ratio. Shallow draft designs, however, may experience excessive pitch motions and relatively larger viscous damping. In order to mitigate the pitch response, the pitch radius of gyration should be small and the center of mass should be low.
An Experimental Study of the Near-Wake Structure of a Cylinder Undergoing Combined Translational and Rotational Oscillatory Motions
Authors: Nazarinia Mehdi , Thompson Mark C. , Sheridan John , Lo Jacono David
Published: March 2011

The experimental research reported here uses particle image velocimetry to extend the study of Nazarinia et al. [1], recording detailed vorticity fields in the near-wake of a circular cylinder undergoing combined translational and rotational oscillatory motions. The focus of the present study is to examine the effect of the ratio between the translational and rotational velocities of the cylinder on the synchronization of the near-wake structures. The frequencies are fixed close to that of the natural frequency of vortex shedding. The results are presented for a fixed amplitude of rotational oscillation of 1 radian and a range of ratios between the translational and rotational velocities (VR) = [0.25, 0.5, 1.0, 1.5]. In particular, it was found that varying the VR value changed the near-wake structure. The results show that at lower values of VR = 0.25, for all of the phase differences examined, the vortices are shed in a single-row 2S mode aligned in the medial plane with a slight offset from the centerline and also synchronized with the combined oscillatory motion. As VR increases the vortex shedding mode changes from a 2S single-row to a 2S double-row structure and eventually back to the single-row (at VR = 0.5). Increasing VR further resulted in the appearance of unlocked-on regimes over the range of negative phase angles and a transition from 2S to P + S mode at the in-phase case There was transition back to the 2S with a further decrease of Φ. For a higher VR the range of desynchronization increased.
Effect of Bifurcation on Pulse Wave Propagation in Human Arteries
Authors: Kawai Yusuke , Kaneko Shigehiko
Published: March 2011

In recent years, arteriosclerotic cardiovascular disease becomes a serious problem in the developed countries. The degree of the arteriosclerosis should be examined routinely and invasively, and the measurement of pulse wave is considered as an effective estimation method. Nowadays, pulse wave is widely used in clinical practice as a noninvasive method of examining circulatory kinetics, but the mechanism in the process of the systolic wave generated at heart and propagating to the peripheral artery remains to be elucidated. In this research, to investigate the effect of bifurcation on pulse wave propagation, numerical simulations by a dynamic model of arteries and in vitro experiments were conducted. A one-dimensional model of arteries is coupled by partial differential equations describing mass and momentum conservation with the tube law that relates the local cross-sectional area to the local radial pressure difference. In the case of a bifurcated artery model, the governing equations were solved by introducing the momentum caused by the reactive force at bifurcation into the equation of momentum conservation. The momentum by the reactive force at bifurcation was supposed to be proportional to the momentum flowing into the bifurcation, and the proportionality coefficient was derived from experiments. Then, the proposed one-dimensional model was validated by a comparison to experimental data. In the experimental setup, elastic tubes with different values of Young’s modulus were tested to simulate human arteries. From the numerical and experimental results, it turns out that the characteristic waveforms of the pressure and velocity obtained from experiments are also captured by the numerical calculations.
Buckling of Human Aorta Related to Dissection due to Flow-Pressure Conditions
Authors: Karagiozis Kostas , Amabili Marco , Mongrain Rosaire , Cartier Raymond , Pai¨doussis Michael P.
Published: March 2011

Human aortas are subjected to large mechanical stresses and loads due to blood flow pressurization and through contact with the surrounding tissue and muscle. It is essential that the aorta does not lose stability for proper functioning. The present work investigates the buckling of human aorta relating it to dissection by means of an analytical model. A full bifurcation analysis is used employing a nonlinear model to investigate the nonlinear stability of the aorta conveying blood flow. The artery is modeled as a shell by means of Donnell’s nonlinear shell theory retaining in-plane inertia, while the fluid is modelled by a Newtonian inviscid flow theory but taking into account viscous stresses via the time-averaged Navier-Stokes equation. The three shell displacements are expanded using trigonometric series that satisfy the boundary conditions exactly. A parametric study is undertaken to determine the effect of aorta length, thickness, Young’s modulus, and transmural pressure on the nonlinear stability of the aorta. As a first attempt to study dissection, a quasi-steady approach is taken, in which the flow is not pulsatile but steady. The effect of increasing flow velocity is studied, particularly where the system loses stability, exhibiting static collapse. Regions of large mechanical stresses on the artery surface are identified for collapsed arteries indicating possible ways for dissection to be initiated.
Dynamics of Flow Around a Cylinder Oscillating In-Line for Low Reynolds Numbers
Authors: Baranyi L. , Huynh K. , Mureithi N. W.
Published: March 2011

This study builds on an earlier study of low-Reynolds number flow about a cylinder forced to oscillate in-line with the main flow, which found vortex switches at some oscillation amplitude values. Here we extend the Reynolds number domain to Re = 60–350, utilize a computational domain characterized by R2/R1 = 360, and do computations at two frequency ratios of f/St0 = 0.8 and 0.9. Computations were carried out using a thoroughly tested finite-difference code. Some results were compared with those obtained by Ansys CFX, and good agreement was found. When plotted against oscillation amplitude, rms and time-mean values of force coefficients revealed a shift toward lower amplitude with higher Re. Findings for the effect of frequency ratio are similar. Where vortex switches occurred, a pre- and post-jump analysis is carried out. POD analysis of the cylinder wake flow field is employed to reveal the detailed wake dynamics as the forcing parameters are varied. The analysis provides further details on the transition of the dominant wake modes in response to the symmetry breaking bifurcation underlying the vortex switches observed in the simulations.
Wake-Induced Vibration of a Pair of Circular Cylinders and Its Dependency on Reynolds Number
Authors: Assi Gustavo R. S. , Bearman Peter W. , Meneghini Julio R.
Published: March 2011

This paper investigates the wake-induced vibration (WIV) of the downstream cylinder of a pair as far as its dependency of Reynolds number is concerned. Experiments have been conducted in a circulating water channel with a rigid cylinder elastically mounted to respond with oscillations in the cross-flow direction. Various sets of coil springs were employed to vary the reduced velocity of the system maintaining constant the Reynolds number. Experiments performed with a cylinder mounted without springs provided the idealised case of reduced velocity equal to infinity. We conclude that the amplitude of the WIV response has a strong dependency on Reynolds number even within the small range between Re = 2 × 103 and 2.5 × 104. If the reduced velocity parameter is isolated — by making it equal to infinity, for instance — the Re-dependency still dominates over the behaviour of the response.
Ubiquitination of K-Ras Enhances Activation and Facilitates Binding to Select Downstream Effectors
Authors: Sasaki Atsuo T. , Carracedo Arkaitz , Locasale Jason W. , Anastasiou Dimitrios , Takeuchi Koh , Kahoud Emily Rose , Haviv Sasson , Asara John M. , Pandolfi Pier Paolo , Cantley Lewis C.
Published: March 2011

Cancers in which K-Ras activation drives tumor growth could be targeted by treatments blocking K-Ras ubiquitination.
Bones Promote Male Fertility
Authors: Ray L. Bryan
Published: March 2011

Osteocalcin, a peptide hormone produced in bone cells, controls production of the steroid hormone testosterone in the testes.
Death by Lysosome
Authors: Gough Nancy R.
Published: March 2011

A Stat3-regulated pathway leads to lysosomal membrane permeabilization and reduced inhibition of cathepsin activity to promote mammary gland involution.
Immunotherapy with a Combination of Intravenous Immune Globulin and P4 Peptide Rescues Mice from Postinfluenza Pneumococcal Pneumonia
Authors: Weeks Jenni N. , Boyd Kelli L. , Rajam Gowrisankar , Ades Edwin W. , McCullers Jonathan A.
Published: March 2011

Alternate therapies are needed for treatment of secondary bacterial pneumonia following influenza. The immunomodulatory peptide P4 has shown promise in mouse models of primary pneumococcal infection. Mice infected with influenza virus and then challenged with
Streptococcus pneumoniae
were treated with a combination of P4 peptide and intravenous immune globulin. Survival was improved from 20% to 80% in treated mice relative to controls. Clinical cure correlated with increased clearance of bacteria and decreased lung consolidation. Greater trafficking of professional phagocytic cells to the site of pneumococcal infection coupled with enhanced opsonophagocytosis as manifest by decreased surface display of Fcγ receptors (FcγR) on neutrophils and macrophages were associated with P4 peptide treatment. This suggests that the mechanism of action for improved clearance of bacteria engendered by P4 is through improved uptake by phagocytes mediated by IgG Fc-Fcγ receptor interactions following antibody-mediated opsonophagocytosis of bacteria. Antibody-based therapies, when coupled with immune modulators, such as P4 peptide, may be an effective tool together with antibiotics in our armamentarium against severe pneumonia.
Nitric Oxide-Mediated Intracellular Growth Restriction of Pathogenic Rhodococcus equi Can Be Prevented by Iron
Authors: von Bargen Kristine , Wohlmann Jens , Taylor Gregory Alan , Utermöhlen Olaf , Haas Albert
Published: March 2011

Rhodococcus equiis an intracellular pathogen which causes pneumonia in young horses and in immunocompromised humans.R. equiarrests phagosome maturation in macrophages at a prephagolysosome stage and grows inside a privileged compartment. Here, we show that, in murine macrophages activated with gamma interferon and lipopolysaccharide,R. equidoes not multiply but stays viable for at least 24 h. Whereas infection control of other intracellular pathogens by activated macrophages is executed by enhanced phagosome acidification or phagolysosome formation, by autophagy or by the interferon-inducible GTPase Irgm1, none of these mechanisms seems to controlR. equiinfection. Growth control by macrophage activation is fully mimicked by treatment of resting macrophages with nitric oxide donors, and inhibition of bacterial multiplication by either activation or nitric oxide donors is annihilated by cotreatment of infected macrophages with ferrous sulfate. Transcriptional analysis of theR. equiiron-regulated geneiupTdemonstrates that intracellularR. equiencounters iron stress in activated, but not in resting, macrophages and that this stress is relieved by extracellular addition of ferrous sulfate. Our results suggest that nitric oxide is central to the restriction of bacterial access to iron in activated macrophages.
Modulation of Early β-Defensin-2 Production as a Mechanism Developed by Type I Toxoplasma gondii To Evade Human Intestinal Immunity
Authors: Morampudi Vijay , Braun Michel Y. , D'Souza Sushila
Published: March 2011

We investigated the early innate immune responses induced in human intestinal epithelial cells (IEC) by the three definedToxoplasma gondiigenotype strains. Transcriptome analysis revealed that among differentially expressed genes, β-defensins distinguished the most IEC infected by fast- or slow-replicatingT. gondiigenotypes. Although β-defensin 1 and 3 genes were not expressed in host cells at early time points postinfection, the slow-replicating type II and III parasites induced high levels of β-defensin 2 gene expression. Notably, no β-defensin 2 gene expression occurred early after infection with the fast-replicating type I parasite. However, activation of this gene in IEC by poly(I:C) treatment prior to infection substantially decreased parasite viability, and pretreatment of parasites with synthetic β-defensin 2 significantly reduced their infectivity of IEC. These findings strongly support the modulation of early β-defensin 2 expression as a mechanism used by type IT. gondiiparasites to mediate immune evasion.
(E-Z) Isomerization of unsaturated nitriles
Authors: Procházka Miloš , Záruba Arno
Published: March 2011

Equilibrium data of the title isomerization of X-CH=CH-CN nitriles (X = Cl, CN, OR, SR) have been measured, and the respective ΔG values have been compared with the energy difference calculated by the CNDO/2 method.
Potential antidepressants: Some N-substituted derivatives of (E)-11-(3-methylaminopropylidene)-6,11-dihydrodibenzo[b,e]thiepin
Authors: Rajšner Miroslav , Metyš Jan , Holubek Jiří , Protiva Miroslav
Published: March 2011

Alkylation reactions of (E)-11-(3-methylaminopropylidene)-6,11-dihydrodibenzo[b,e]thiepin (II) with alkyl bromide, propargyl bromide, 2-chloroethanol, 1-chloropropan-2-ol and 3-chloropropanol gave the N-substituted derivatives III - VII. Acylation of amino alcohols V - VII with acetyl chloride and decanoyl choride resulted in the esters VIII - XI. 6,11-Dihydrodibenzo[b,ethiepin-11-carboxylic acid was transformed via the acid chloride to the amide XIV. Out of the compounds prepared, only the amino alcohols V- VII and the ester VIII revealed in pharmacological tests the activity similar to that of tricyclic antidepressants; their activity is lower than that of prothiadene (I). The decanoates IX - XI are devoid of antireserpine activity; the attempt at finding long-acting depot antidepressant agents in this way was thus unsuccessful. The amide XIV has mild anticonvulsant activity.
An experimental set-up for the identification of parameters of the trickle flow in a packed bed
Authors: Staněk Vladimír , Čársky Milan
Published: March 2011

An experimental technique has been developed to identify parameters of the trickle flow of liquid under the counter-current flow of gas. The technique has been based on measurement of the response in the outlet stream to a periodic concentration perturbation of the inlet liquid stream. A two-chamber distributor for liquid has been developed effecting a virtually ideal rectangular concentration pulse uniformly across the whole column inlet. The nearly perfect shape of the inlet pulse permitted us to replace the measurement of the inlet concentration by a two-level indication of the instantaneous function of the distributor. An experimental device has been developed for sampling the outlet stream of liquid. The device permits samples to be taken of feasibly small volume and yet large enough to eliminate the stochastic nature of individual rivulets draining from the bed. The function of both devices was tested by measurement of the frequency dependences of the amplitude ratio and the phase lag between the outlet and the inlet stream.
Thiol and disulphide derivatives of cellulose
Authors: Gemeiner Peter , Beneš Milan
Published: March 2011

The acid catalyzed etherification of cellulose with 1-chloro-2,3-epoxypropane yielded 3-chloro-2-hydroxypropylcellulose (SCl ≤ 0.67); the latter, by a known sequence of reactions through the thiosulphate derivative and after its reduction, gave 2-hydroxy-3-mercaptopropylcellulose (up to 0.43 mmol SH/g). Mercaptodeoxycellulose (up to 0.53 mmol SH/g) was prepared from the less reactive chlorodeoxycellulose by an analogous sequence of reactions. Bead mercaptodeoxycellulose is more advantageous obtained by using tosylate of bead cellulose; this procedure is also more advantageous than the preparation of bead 2-hydroxy-3-mercaptopropylcellulose. Disulphide derivatives of cellulose were prepard (a) by a quantitative reaction of thiol derivatives with 2,2'-dipyridyl disulphide and (b) by a reversible crosslinking of cellulose or carboxymethylcellulose with bifunctional disulphides. Disulphide derivatives of cellulose prepared by procedure (b) give after reduction thiol derivatives (up to 0.185 mmol SH/g), and further by employing procedure (a) yield 2-pyridyl disulphide derivatives.
Some 2-substitution derivatives of 5-(4-oxo-6-hydroxy-3,4-dihydro-5-pyrimidinyl)pentanoic acid
Authors: Křepelka Jiří , Beneš Jan , Pouzar Vladimír , Vachek Jaroslav , Holubek Jiří
Published: March 2011

Condensation of triethyl ester of 1,1,5-pentanetricarboxylic acid (XI) with substituted guanidines XXII - XXIX gave acids II - IX, which were converted into esters XI - XIX. The acid II and the ester XI were obtained as mixtures of positional isomers. Analogously, condensation of the triester XXI with dicyanodiamide gave rise to acid X, whose nitrile group, under conditions of esterification of a carboxyl group, produced iminoether XX. In pharmacological tests for antineoplastic activity the compounds prepared exhibited weaker efficacy than 5-(2-amino-6-hydroxy-4-oxo-3,4-dihydro-5-pyrimidinyl)pentanoic acid (I), employed as standard.
Interactions of 2-furylethylenes with thiol enzymes
Authors: Šturdík Ernest , Drobnica Ľudovít , Baláž Štefan
Published: March 2011

Furylethylenes are inhibitors of glyceraldehyde 3-phosphate dehydrogenase (GAPDH; EC 1.2.1.12), glucose 6-phosphate dehydrogenase (EC 1.1.1.49), glutathione reductase (GR; EC 1.6.4.2), and, in part, also malate dehydrogenase (EC 1.1.1.37). These four enzymes served as model thiolproteins employing the SH groups of the embodied cysteine for catalytic activity. The inhibition degree of the afore-mentioned enzymes is proportional to the reactivity of furylethylenes towards thiols. The inhibition of GAPDH and GR with 1-(5-nitro-2-furyl)-2-nitro-2-methoxycarbonylethylene (I) was characterized by inhibition constants Ki and also, its type was estimated. A direct chemical modification of SH groups of cysteine residues was found in GAPDH, a fact that could be closely connected with the inactivation of the enzyme.
Reactions of 2-furylethylenes with thiols in vivo
Authors: Šturdík Ernest , Drobnica Ľudovít , Baláž Štefan
Published: March 2011

The reaction of furylethylenes with thiols proceeds also in vivo. This have been proved with Ehrlich ascitic carcinoma cells and yeast under steady-state conditions by determination of SH groups employing the Ellman reagent. 1-(5-Nitro-2-furyl)-2-nitroethylene caused a considerable decrease of intracellular thiols content proportional to the amount used. A correlation between the degree of modification of SH groups in vivo and the reactivity towards thiols estimated under the in vivo conditions was found. The ability of furylethylenes to react with SH groups is decisive for their biologic activity.
The effects of preparation and some physico-chemical parameters on the properties of styrene catalyst - based on iron(III) oxide.
Authors: Pospíšil Milan , Spěváček Jiří , Kryška Jindřich
Published: March 2011

Hydrated iron(III) oxides were obtained by discontinuous precipitation of an iron(II) sulfate solution with aqueous ammonium - saturated with carbon dioxide to different CO2/NH3 ratios. An additional thermal treatment of these oxides, under different conditions, provided genetic sequences of intermediates and their final products - catalysts on a Fe2O3/K2O basis, with different promoters. The catalysts were studied by means of the microstructural; analysis, thermogravimetry, DTA, IR spectroscopy and further tested by the dehydrogenation of ethylbenzene to styrene. It was observed that by changing the CO2/NH3 ratio in the precipitation of the initial solutions one can influence some of the properties, as well as, the morphology and thermal stability of the initial intermediates of the preparation of the catalysts. The above mentioned properties become practically unified with the increasing number of the heat treatment operations, with all the investigated catalysts - with the exception of the catalysts' behaviour during their reduction with hydrogen. The presence of iron oxides in various valency states and the different phase composition of the catalysts during their reduction affect the final activity and selectivity of the catalyst in the reaction under the study.
The flow rate and the hold-up of solids under the counter-current flow of liquid phase in a vibrating plate column
Authors: Klašková Eva , Rod Vladimír
Published: March 2011

Flow rates and mean hold-ups of solids have been measured under the counter-current flow of water in a 50 mm in diameter vibrating perforated plate column. Experimental data have been described by a mathematical model expressing the specific flow rate of solids in dependence on the hold-up, terminal velocity of the particles, porosity of the plate, specific flow rate of the continuous phase and the frequency and amplitude of plate vibrations. It has been found that for systems exhibiting low particle terminal velocity the pumping effect of the plates may increase the flow rate of the dispersed phase to a value corresponding to the flow in the empty column.
Adaptive nonisothermal computer control of a batch reactor
Authors: Jiráček František , Horák Josef
Published: March 2011

The adaptive temperature control method of reaction mixture in a batch reactor with strongly exothermic reaction is verified experimentally. The utility degree of cooling capacity of the reactor is kept on the required value by use of a two-position controller which is changing the flow rate of heat carrier into the cooler. The method is based on continuous identification of properties of the system in actual time by use of the Hewlett-Packard 3 052 A computer centre. During the experiments temperature of mixture in the reactor and temperature of heat carrier in the cooler were measured. From the obtained data and their time derivatives reactivity of the mixture, heat transfer coefficient and utility degree of cooling capacity of the reactor were evaluated. In the experiments were studied the effects of cooler inertia and of additive noise in the temperature measurement on safety and quality of control. Experimental results have proved that the method is applicable to control of reaction temperature even under conditions when properties of the system are changing significantly e.g. reactivity of the mixture and dynamic properties of the manipulated variable and when pseudostationary states of the reactor are unstable in the open control loop. They simultaneously point to a significant effect of noise on system identification.
Effect of cetyltrimethylammonium bromide on the electrochemiluminiscence and electrooxidation of luminol
Authors: Lasovský Jan , Grambal František
Published: March 2011

The electrooxidation of luminol in alkaline solutions in the presence of cetyltrimethylammonium bromide (I) was studied by linear sweep voltammetry on fixed and vibrating platinum electrodes. The presence of I in low concentrations (below the critical micellar concentration) brings about aggregation of the luminol, which is manifested by an increase in the anodic peak height and its shift towards lower potentials. In micellar solutions the peak height decreases owing to the slower diffusion of the bulkier micelles, the shift to lower potentials being preserved. The light-voltage curves correspond with the voltammetric curves, exhibiting identical shifts of the peak potentials in dependence on the concentration of the surfactant.
Molecular geometry of ribofuranoses obtained from semi-empirical MO calculations
Authors: Krechl Jiří , Kuthan Josef
Published: March 2011

Molecular geometry of ribofuranoses I - VIII has been optimized with respect to all degrees of freedom on the basis of CNDO/2 wave functions. The results obtained are confronted with previous results of partial optimizations.
Preparation of Pt/activated carbon and Pt/alumina catalysts by impregnation with platinum complexes
Authors: Machek Vladimír , Růžička Vlastimil , Šourková Marie , Kunz Jiří , Janáček Leoš
Published: March 2011

Activated carbon and alumina catalysts were prepared by impregnation with solutions of platinum compounds differing substantially in the nature of their interaction with the supports: chloroplatinic acid (dissolved in water or acetone), tetraammineplatinum dichloride, and tetrakis (triphenylphosphine)platinum complex. The relations between the course of impregnation, distribution of platinum across the catalyst grain, and the activity of the catalyst in liquid phase hydrogenations were studied. Lower adsorption rates and amounts of the platinum compound adsorbed on the support bring about a more uniform platinum distribution across the grain. Catalysts with a uniform distribution exhibit higher activities than those with nonuniform distribution. The highest activity was achieved with Pt/alumina catalysts prepared from triphenylphosphine platinum comlex thermally treated in oxygen atmosphere prior to the reduction.
Infrared spectra and substituent effects in 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones
Authors: Perjéssy Alexander , Hrnčiar Pavol , Šraga Ján
Published: March 2011

The wave numbers of the fundamental C=O and C=C stretching vibrations, as well as that of the first overtone of C=O stretching vibration of 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones and 1,3-cycloheptanedione were measured in tetrachloromethane and chloroform. The spectral data were correlated with σ+ constants of substituents attached to phenyl group and with wave number shifts of the C=O stretching vibration of substituted acetophenones. The slope of the linear dependence ν vs ν+ of the C=C stretching vibration of the ethylenic group was found to be more than two times higher than that of the analogous correlation of the C=O stretching vibration. Positive values of anharmonicity for asymmetric C=O stretching vibration can be considered as an evidence of the vibrational coupling in a cyclic 1,3-dicarbonyl system similarly, as with derivatives of 1,3-indanedione. The relationship between the wave numbers of the symmetric and asymmetric C=O stretching vibrations indicates that the effect of structure upon both vibrations is symmetric. The vibrational coupling in 1,3-cycloheptanediones and the application of Seth-Paul-Van-Duyse equation is discussed in relation to analogous results obtained for other cyclic 1,3-dicarbonyl compounds.
Sythesis and mass spectra of aroylbenzamidoximes
Authors: Varella Evangelia A. , Micromastoras Evangelos D. , Alexandrou Nicholas E. , Exner Otto
Published: March 2011

The synthesis of several O-aroylbenzamidoximes I and of some N-aroyl(II) as well as of bis(aroyl)benzamidoximes (III) is described and their fragmentation pattern in the mass spectra is discussed. O- and N-Aroylbenzamidoximes are distinguished on the basis of their mass spectra since the O-derivatives afford the ion corresponding to the acid [ArCOOH]+. whereas the N-derivatives the ion corresponding to the amide [ArCO+NH].
Antiaminic agents derived from thieno[2,3-c]-2-benzothiepin: 4-(1-Methyl-4-piperidylidene)-4,9-dihydrothieno[2,3-c]-2-benzothiepin and some related compounds
Authors: Polívka Zdeněk , Rajšner Miroslav , Metyš Jan , Holubek Jiří , Svátek Emil , Ryska Miroslav , Protiva Miroslav
Published: March 2011

In the reaction of thieno[2,3c]-2-benzothiepin-4(9H)-one (VI) with 1-methyl-4-piperidylmagnesium chloride 7-(1-methyl-4-piperidyl)thieno[2,3-c]-2-benzothiepin-4(9H)-one (VIII) is formed in addition to the expected amino alcohol VII. The title compound I was obtained by the acid catalyzed dehydration of the pure alcohol VII. Compound I (pipethiadene) has outstanding antihistamine, antiserotonin, antireserpine and anticataleptic activity and was recommended to clinical trials as a potential antimigraine agent. For pharmacokinetic and metabolic studies there were prepared the NC2H3 analogue of pipethiadene IV and further, as potential metabolites, the demethyl analogue III, S-oxide X, demethyl S-oxide XI, N-oxide XIII and N,S-dioxide XIV. The Witting reaction of the ketone VI with 3-dimethylaminopropylidenetriphenylphosphorane resulted in a mixture of geometric isomers of 4-(3-dimethylamino-propylidene)-4,9-dihydrothieno[2,3-c]-2-benzothiepin with the strongly predominating Z-isomer XVI which was isolated from the mixture by crystallization of the hydrogen maleate. The mixture with the predominating Z-isomer XVI was converted by the treatment with 80% sulfuric acid and dilution with water to a mixture with the predominating E-isomer XV (dithiadene) which was isolated by crystallization of the hydrogen sulfate. Some further new thieno[2,3-c]-2-benzothiepin derivatives were synthesized as potential intermediates.
N-substituted aminomethyl 4-cyclopentylphenyl ketones and 2-amino-1-(4-cyclopentylphenyl)ethanol: Synthesis and pharmacological screening
Authors: Vejdělek Zdeněk , Protiva Miroslav
Published: March 2011

The non-characterized bromo derivative Ia, obtained by bromination of 4-cyclopentylacetophenone, afforded by substitution reactions with diethylamine, benzylmethylamine, benzylisopropylamine, piperidine, morpholine, 1-methylpiperazine and 1-(2-hydroxyethyl)piperazine the amino ketones IIa-VIIIa which were reduced with lithium aluminium hydride to the aminoalcohols IIb-VIIIb. Compounds IIIb and IVb were debenzylated by catalytic hydrogenation on palladium to the secondary amines IXb and Xb. The compounds prepared have central stimulant effects in higher doses which appears also in the rotarod test and in the evaluation of spontaneous motility. They have mostly a mild spasmolytic effect of the anticholinergic type, some of them bring about local anesthetic and diuretic effects. The adrenolytic and hypotensive effects were found only with single compounds.
Kinetics and mechanism of the azo coupling reaction of 1-aminonaphthalene-4-sulfonic acid
Authors: Demian Barbu A. , Exner Otto , Sallo Aurora
Published: March 2011

Kinetics of the azo coupling reaction of 1-aminonaphthalene-4-sulfonic acid with nine substituted benzenediazonium chlorides was investigated at four temperatures. The results were processed in terms of the isokinetic relationship and of an isoparametric relationship with temperature and σ constant as independent variables. There is a great similarity to the coupling reaction of 1-hydroxynaphthalene-4-sulfonic acid; all the results are consistent with a cyclic transition state implying variable association of a water molecule.
Absorption in vertical stream tubes with swirl bodies
Authors: Winkler Kurt , Kaštánek František , Storz Freimut , Kratochvíl Jan , Havlíček Antonín
Published: March 2011

The absorption of oxygen from air into water has been measured in vertical tubes with swirl bodies in the inlet part. The tubes were of 70 mm I.D. and of height H with diameter ratio H/D ≦ 22. The two-phase flow was directed upward. Superficial gas velocity was ωG = 10 to 35 m s-1 and specific liquid load QLE = 13 to 80 m3m-2h-1. Values of the liquid-side mass transfer coefficient were determined as ratios of experimental values of volumetric mass transfer coefficient and specific interfacial areas, which were measured earlier. Murphree efficiencies were obtained with experimentally determined Peclet numbers considering the real mixing conditions of the liquid phase.
13C and 1H NMR spectra of all methyl O-benzoyl-β-D-xylopyranosides. nonadditivity of acylation effects on 13C chemical shifts in deutoriochloroform solutions
Authors: Petráková Eva , Schraml Jan
Published: March 2011

All methyl O-benzoyl-β-D-xylopyranosides have been prepared and their 1H and 13C NMR spectra measured in deuteriochloroform solutions. The 1H NMR spectra were analysed to the first order and assigned with the aid of homonuclear decoupling. The 13C chemical shifts were assigned through heteronuclear selective decouling experiments. Some of the 13C chemical shifts observed in di- and tri-O-benzoyl derivatives differ considerably from those calculated according to the direct additivity rule from the shifts in the mono derivatives. It is shown that the nonadditivity is due to a conformational heterogeneity of the series of investigated compounds dissolved in deuteriochloroform. The heterogeneity is evidenced by the vicinal 1H-1H coupling constants and by 13 chemical shifts of C(1) methoxyl carbon atoms.
8-Chloro and 8-methylthio derivatives of 10-piperazino-10,11-dihydrodibenzo[b,f]thiepins; New compounds and new procedures
Authors: Jílek Jiří , Pomykáček Josef , Prošek Zdeněk , Holubek Jiří , Svátek Emil , Metyšová Jiřina , Dlabač Antonín , Protiva Miroslav
Published: March 2011

The resolution of racemic clorothepin (Ia) was repeated and the water-soluble methanesulfonates of (S)(+)-clorothepin and (R)(-)-clorothepin were prepared which were used in recent studies of the stereoselectivity of action of this neuroleptic agent. Alkylation of the secondary amine VIa with 2-chloroethyl decanoate resulted in noroxyclothepin decanoate IVa whose basically catalyzed ethanolysis afforded smoothly the amino alcohol IIa. Reactions of amines VIa and VIb with 1,2-butene oxide gave the amino alcohols VIIab. Alkylation of the amine VIa with 5-bromopentan-2-one and the following reduction of the amino ketone IXa formed gave the amino alcohol VIIIa. Amino alcohols IIa and IIIb were transformed by treatment with thionyl chloride to the chloroalkylamines Xa and XIb which were used for the synthesis of mandelates XIIa, XIIIb and benzilates XIVa, XVb derived from noroxyclothepin IIa and oxyprothepin IIIb. A substitution reaction of 2,11-dichloro-10,11-dihydrodibenzo[b,f]thiepin with 1,4-diazabicyclo[4,3,0]nonane led to the clorothepin analogue XVI. From 2-chlorodibenzo[b,f]thiepin-10(11H)-one XVII via the 11-bromo derivative XVIII the amino ketone XIX was prepared. While its reduction with sodium borohydride gave the cis-amino alcohol XXI, the reduction with diborane gave the trans-amino alcohol XXII. The pharmacological properties of the new piperazine derivatives are described; some of them showed a high degree of neuroleptic activity of various profile.
The synthesis and the mass spectra of 28,29,30-trinoroleanane derivatives with a double bond in the ring E or D
Authors: Protiva Jiří , Křeček Václav , Křečková Josefa , Klinotová Eva , Vystrčil Alois
Published: March 2011

A series of 28,29,30-trinor-18α-oleanane derivatives with two double bonds - 17(22) and 20(29) - was prepared. The position of the 17(22) double bond was demonstrated by partial hydrogenation of the diene on tris-triphenylphosphinerhodium chloride and by comparison of the product with an authentic sample. The mass spectra of the series of dienes I-IV and monoenes VI-X are discussed.
Optimization of molecular geometry of meta-substituted benzoic acids and their anions by gradient CNDO/2 method
Authors: Böhm Stanislav , Kuthan Josef
Published: March 2011

32 conformers of meta-substituted benzoic acids I and the corresponding anions II have been optimized with respect to all geometrical degrees of freedom by the title semiempirical MO approach. The calculated geometry characteristics are compared with some published data obtained by means of X-ray diffraction.