Kinetic Condition Research Articles

Kinetics of micellar catalysis on oxidation of p-anisaldehyde to p-anisic acid in aqueous medium at room temperature

Oxidation of p-anisaldehyde by chromic acid produces p-anisic acid under kinetic condition [p-anisaldehyde]T≫[Cr(VI)]T. This oxidation reaction is performed also in presence of micellar catalysts in aqueous media at room temperature. The progress of the reaction is monitored spectrophotometrically by following the decay of Cr(VI) at 450nm wavelength. The product is confirmed by 1H NMR spectroscopy. Anionic surfactant sodium dodecyl sulfate (SDS) accelerated the reaction almost three-fold compared to uncatalyzed path, whereas cationic surfactant N-cetylpyridinium chloride (CPC) and neutral surfactant triton-X-100 (TX-100) inhibited the reaction.

Suitable combination of promoter and micellar catalyst for kilo fold rate acceleration on propanol to propionaldehyde conversion in aqueous media

Oxidation of propanol by chromic acid produces propionaldehyde under kinetic condition [propanol]T≫[Cr(VI)]T. This oxidation reaction is performed also in presence of micellar catalysts (anionic, cationic and neutral) and hetero-aromatic nitrogen bases promoters (picolinic acid, 2,2′-bipyridine, 1,10-phenanthroline) in aqueous media. The product is confirmed by 2,4-DNP test and 1H NMR spectroscopy. Anionic surfactant sodium dodecyl sulphate (SDS), neutral surfactant triton X-100 (TX-100) accelerated the reaction both in presence and absence of promoters whereas cationic surfactant N-cetyl pyridinium chloride (CPC) inhibited the reaction. Combination of SDS and bipy is found to be the most efficient for this oxidation.

Pore development and combustion behavior of gasified semi-char in a drop tube furnace

A fly ash sample was collected en-suite from an industrial circulating fluidized bed (CFB) gasifier. The fly ash is herein referred to as semi-char (partially burnt char) as it still contained a high amount of carbon. CFB gasification involves long sample residence times and the resulting residual chars are expected to be different from conventional chars from processes such as pulverized coal gasification or chars prepared under laboratory furnaces where usually, residence times are relatively much shorter.In this study, the semi-char was burned in a flat flame reactor (FFR) under oxygen conditions. The semi-char reactivity, pore development and microstructure were then used to characterize its combustion behavior.The ‘raw’ semi-char, before the FFR oxygen reactions was porous with a dominant meso–macro pore structure which is associated with its formation path in the CFB gasifier. A linear monotonic decrease with conversion in both internal surface area and pore volume was then observed while pore size increased slightly with conversion.Pore structure and reactivity data were used to determine the effectiveness factor at various stages of conversion of the semi-char. Effectiveness factor values reveal the semi-char reactions to be close to kinetic controlled condition.

J053025 Enskog-Vlasov方程式による気液界面の気体論境界条件に関する数値シミュレーション(〔J053-02〕マイクロ・ナノスケールの熱流体現象(2))

The aim of the present study is to investigate the kinetic boundary condition (KBC) at a vapor-liquid interface in net evaporation/condensation states by using the Enskog-Vlasov equation. Our target system is a steady evaporation and condensation state between two liquid slabs with different temperatures. The results show that we can realize the simulation of steady evaporation and condensation phenomena between the two-liquid slabs with different temperature. Also, the normal and tangential temperatures including the kinetic boundary condition is not only the function of molecular energy flux but also the function of molecular collision mass flux in net condensation interface.

Microfluidic synthesis of atto-liter scale double emulsions toward ultrafine hollow silica spheres with hierarchical pore networks

A facile PDMS-glass hybrid microfluidic device is developed for generating uniform submicrometer-scale double emulsion droplets with unprecedented simplicity and controllability. Compared with planar flow-focusing geometries, our three-dimensional flow-focusing geometry is advantageous for stably producing femto- to atto-liter droplets without the retraction problem of the dispersed phase fluid. In addition, this microfluidic platform can withstand the use of strong organic solvents (e.g. tetrahydrofuran (THF) and toluene) as a dispersed phase without deforming PDMS devices because the dispersed phase containing organic solvents does not directly contact the PDMS wall. In particular, monodisperse double emulsions are generated spontaneously via the internal phase separation of single emulsions driven by the diffusion of a co-solvent (tetrahydrofuran) in microfluidic devices. Finally, we demonstrated that the double emulsions can be used as morphological templates of ultrafine spherical silica capsules with controlled hierarchical pore networks via the evaporation-induced self-assembly (EISA) method. During EISA, triblock copolymers (Pluronic F127) act as a surfactant barrier separating the internal droplet from the continuous oil phase, resulting in the 'inverse' morphology (i.e. hydrophobic polymer-in-water-in-oil emulsions). Depending on the precursor composition and kinetic condition, various structural and morphological features, such as mesoporous hollow silica spheres with a single central core, multi-cores, or a combination of these with robust controllability can be seen. Electron microscopy (SEM, STEM, HR-TEM), small angle X-ray scattering (SAXS), and N(2) adsorption-desorption confirm the well-controlled hierarchical pore structure of the resulting particles.

Motor function evaluation of hydrocephalus children

Abstract Objectives: To evaluate the kinetic functional condition of children with hydrocephalus; to identify the condition of the muscle tone; to verify the static and dynamic functional activities; and to verify the association between tone changes and functional activities. Method: A cross-sectional, descriptive, exploratory and field study, using qualitative and quantitative approach, performed at the University Hospital in Aracaju city, from August 2009 to March 2010. Results: From 50 evaluated children, 30 (60%) had hypertonia; 10 (20%) were hypotonic; and 10 (20%) did not show muscle tone alteration. The age average was considerably lesser in hypertonic children and higher in hypotonic and without tone alteration children. The average of carried through surgeries was more expressive in hypertonic children. Motor sequels had been present in 92% of the sample. The static functional activities, as well as dynamic functional activities, were lower in hypertonic children (p < 0,0001) and higher in hypotonic and normal tone children. Conclusions: Muscle tone exacerbation is more present in hydrocephalus children and motor function is impaired, being the neuropsychomotor development delayed more evident in spastic children group and less pronounced in children with normal muscle tone.

Chiral Condensate and Mott–Anderson Freeze-Out

We present the idea of a Mott–Anderson freeze-out that suggests a key role of the localization of the hadron wave functions when traversing the hadronization transition. The extension of hadron wave functions in dense matter is governed by the behavior of the chiral quark condensate such that its melting at finite temperatures and chemical potentials entails an increase of the size of hadrons and thus their geometrical strong interaction cross sections. It is demonstrated within a schematic resonance gas model, that a kinetic freeze-out condition reveals a correlation with the reduction of the chiral condensate in the phase diagram up to 50% of its vacuum value. Generalizing the description of the chiral condensate by taking into account a full hadron resonance gas such correlation gets distorted. We discuss, that this may be due to our approximations in calculating the chiral condensate which disregard both, in-medium effects on hadron masses and hadron–hadron interactions. The latter, in particular due to quark exchange reactions, could lead to a delocalization of the hadron wave functions in accordance with the picture of a Mott–Anderson transition.

The effects of TPA023, a GABAAα2,3 subtype-selective partial agonist, on essential tremor in comparison to alcohol

Essential tremor (ET) is a relatively frequent neurological disorder that responds in some patients to gamma-aminobutyric acid A (GABA(A)) agonists such as the benzodiazepines. Partial subtype-selective GABA(A) agonists may have an improved side effect profile compared to non-selective GABA(A) agonists. However, it is unknown which GABA(A) subtypes are involved in the therapeutic effects of benzodiazepines in ET. The effects of 2 mg TPA023, a GABA(A) α2,3 subtype-selective partial agonist, on ET were compared to the effects of a stable alcohol level (0.6 g/L) and placebo in nine patients with ET. Tremor evaluation included laboratory accelerometry and a performance-based scale. Additional measurements were performed to evaluate other effects on the central nervous system (CNS). Alcohol significantly diminished tremor symptoms in the postural and kinetic condition, as assessed by laboratory accelerometry, but the performance-based rating scale was unaffected. Tremor was also reduced after TPA023 treatment in the kinetic condition, albeit not significantly. Additionally, TPA023 decreased saccadic peak velocity, while alcohol decreased subjective feelings of alertness. This study showed that alcohol reduced maximum tremor power, as assessed by laboratory accelerometry, unlike TPA023, which decreased tremor symptoms to some extent but not significantly. This study showed that treatment with an α2,3 subunit-selective GABA(A) partial agonist was less effective than a stable level of alcohol in reducing ET symptoms. These results provide no support for a therapeutic role of TPA023 in the suppression of ET symptoms.

Mass flow measurement through rectangular microchannel from hydrodynamic to near free molecular regimes

The mass flow rate through microchannels with rectangular cross section is measured for a wide Knudsen number range (0.0025-26.2) in isothermal steady conditions. The experimental technique called ‘Constant Volume Method’ is used for the measurements. This method consists of measuring the small pressure variations in the tanks upstream and downstream of the microchannel. The measurements of the mass flow rate are carried out for three gases (Helium, Nitrogen and Argon). The microchannel internal surfaces are covered with a thin gold coat of mean roughness characterized by Ra = 0.87nm (RMS). The continuum approach (Navier-Stokes equations), associated to the first order velocity slip boundary condition, was used in the slip regime (Knudsen number varies from 0.0025 to 0.1). The experimental velocity slip and the accommodation coefficients based on the Maxwell kinetic boundary condition were deduced. In the transitio-nal and near free molecular regimes the linearized kinetic BGK model was used to calculate numerically the mass flow rate. From the comparison of the numerical and measured values of the mass flow rate the accommodation coefficient was also obtained.

Analytical solution of axi-symmetrical lattice Boltzmann model for cylindrical Couette flows

Analytical solution for the axi-symmetrical lattice Boltzmann model is obtained for the low-Mach number cylindrical Couette flows. In the hydrodynamic limit, the present solution is in excellent agreement with the result of the Navier–Stokes equation. Since the kinetic boundary condition is used, the present analytical solution using nine discrete velocities can describe flows with the Knudsen number up to 0.1. Meanwhile, the comparison with the simulation data obtained by the direct simulation Monte Carlo method shows that higher-order lattice Boltzmann models with more discrete velocities are needed for highly rarefied flows.

Effect of Electromagnetic Stirring on Microstructure of <i>In Situ</i> Synthesized (Al<sub>2</sub>O<sub>3</sub>+Al<sub>3</sub>Zr)<sub>P</sub>/Al Composites

(Al2O3+Al3Zr)P/Al composites were in situ synthesized from Al-Zr(CO3)2 system. In the process of in situ reaction, electromagnetic stirring (EMS) is employed to improve the conditions of reaction between reactants powder and melt. The results indicate that the Lorenz force improves the kinetic condition and accelerates the nucleation of endogenetic particulates. The optimized electromagnetic density is 0.025T. Scanning electronic microscope (SEM) observation demonstrates that the sizes of reinforced particulates are controlled at 1~2 μm. Moreover, the particulates are well distributed in Al matrix.

Making the best use of our previous results as a clue for interpreting kinetics of scintigraphic agents

Up to now, we have performed scintigraphy with 201-thallium chloride (201-TlCl) and 99m-Tc-hexakis-2-methoxy-isobutyl-isonitrile (99m-Tc-MIBI) for malignant tumors and lymphoscintigraphy with 99m-Tc-rhenium-colloid (99m-Tc-Re) and 99m-Tc-human-serum-albumin-diethylene-triamine-penta-acetic-acid (99m-Tc-HSA-D) for lymph node metastasis. In this article, we re-evaluated scintigraphic images retrospectively with a hope that the results might be a clue, even if it is small, for dentists to try to improve the accuracy of diagnosis of malignant tumors. From scintigraphy, we obtained the tumor retention index as a factor to estimate the uptake of radioactive agents in tumor cells. Moreover, we estimated transport proteins of Na + /K + -ATPase and permeability-glycoprotein (P-gp) expressed on the cell membrane that might regulate the kinetic condition of radioactive agents. Among the tumor retention index, the transport protein and the histopathologic finding of tumors, there were relatively well correlations. The tumor retention index showed a difference clearly between malignant tumor and benign tumor. The transport protein revealed a distinct expression in accordance with the malignancy of tumor, and the uptake clearly depended upon the expression of transport protein. Moreover, the lymph node metastasis was detected well by lymphoscintigraphy with 99m-Tc-Re and 99m-Tc-HSA-D.

Effects of Static Magnetic Field on Electrolyte Solutions under Kinetic Condition

Electrolyte solutions were exposed for different time to weak static magnetic field (MF) generated from a stack of magnets (B = 15 mT) at the flow rate of 1.4 mL/s. The conductivity was measured as a function of time following the application of MF. It was found that the changes in conductivity depend on the kind of electrolyte and the magnetic exposure time and are related to the thermodynamic function of hydration.

Phase field approximation of a kinetic moving-boundary problem modelling dissolution and precipitation

We present a phase field model which approximates a one-phase Stefan-like problem with a kinetic condition at the moving boundary, and which models a dissolution and precipitation reaction. The concentration of dissolved particles is variable on one side of the free boundary and jumps across the free boundary to a fixed value given by the constant concentration of the particles in the precipitate. Using a formal asymptotic analysis we show that the phase field model approximates the appropriate sharp interface limit. The existence and uniqueness of solutions to the phase field model is studied. By numerical experiments the approximating behaviour of the phase field model is investigated.

Microstructure, billet surface quality and tensile property of (Al 2O 3 + Al 3Zr) p/Al composites in situ synthesized with electromagnetic field

The aluminum matrix composites reinforced by Al 2O 3 and Al 3Zr particulates were fabricated via in situ chemical reaction between Al–15 wt.% Zr(CO 3) 2 systems. In the process of in situ reaction, a low frequency electromagnetic field (EMF) is employed to improve the conditions of reaction between reactants powder and melt. The optimized electromagnetic density of low frequency EMF is 0.025 T. During the direct chill casting process of composites melt, the custom-designed electromagnetic fields are introduced to control the microstructures and improve the billet surface quality. XRD analysis shows that Al 2O 3 and Al 3Zr reinforcement phases have been obtained. The Lorenz force improves the kinetic condition and accelerates the nucleation of endogenetic particulates. Microstructure analysis by SEM indicates that the average size of particulates and grain size of matrix are refined to 0.5–1 μm and 20–40 μm, respectively. The surface quality of round billet is greatly improved by the high frequency EMF. The results of tensile properties test show that the tensile strength of composites in situ fabricated with EMF is 254.6 MPa, which is increased by about 104 MPa and 69.4% compared with those of composites in situ fabricated without EMF.

Viscous Compressible Slip Flows. Part 2 : Meshless Solver for Rotating Slip Flows

The Part 1 presented kinetic treatment of the slip flow and described kinetic flux vector splitting. The Part 2 of the paper presents the kinetic theory based approach for solving rotating slip flows. The paper describes numerical flow modeling of slip and rarefied flows. It also presents the meshless solver which makes use of least squares and Kinetic Flux Vector Splitting (KFVS) scheme and its Variance Reduction form (VRKFVS). The kinetic slip flow boundary condition is added with the Burnett terms which are quadratic in Knudsen number. The solver is able to capture slip flow features and typical features of the strongly rotating flows characterized by steep density gradient, supersonic flows, thin boundary layers towards the peripheral region with a rarefied central core.

A Boundary Integral Method for Computing the Dynamics of an Epitaxial Island

In this paper, we present a boundary integral method for computing the quasi-steady evolution of an epitaxial island. The problem consists of an adatom diffusion equation (with desorption) on terrace and a kinetic boundary condition at the step (island boundary). The normal velocity for step motion is determined by a two-sided flux. The integral formulation of the problem involves both double- and single-layer potentials due to the kinetic boundary condition. Numerical tests on a growing/shrinking circular or a slightly perturbed circular island are in excellent agreement with the linear analysis, demonstrating that the method is stable, efficient, and spectrally accurate in space. Nonlinear simulations for the growth of perturbed circular islands show that sharp tips and flat edges will form during growth instead of the usual dense branching morphology seen throughout physical and biological systems driven out of equilibrium. In particular, Bales–Zangwill instability is manifested in the form of wave-like fronts (meandering instability) around the tip regions. The numerical techniques presented here can be applied generally to a class of free/moving boundary problems in physical and biological science.

Linking optical and electrical small amplitude perturbation techniques for dynamic performance characterization of dye solar cells

This paper unifies the analytical models used widely but thus far mostly separately for electrical and optical small amplitude perturbation measurements of nanostructured electrochemical dye solar cells (DSC): electrochemical impedance spectroscopy (EIS), intensity-modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS). The models are linked by expressing the kinetic boundary condition used for solving the time-dependent continuity equation of electrons in IMPS and IMVS analysis in terms of the series and parallel impedance components found in the complete equivalent circuit impedance model of DSC. As a result, analytical expressions are derived for potentiostatic IMPS and galvanostatic IMVS transfer functions of complete DSCs that are applicable at any operating point along the solar cell current-voltage (IV) curve. In agreement with the theory, impedance spectrum calculated as a ratio of IMVS and IMPS transfer functions measured near the maximum power point matches exactly with the impedance spectrum measured directly with EIS. Consequently, both IMPS-IMVS and EIS yield equal estimates for the electron diffusion length. The role of the chemical capacitance of the nanostructured semiconductor photoelectrode in the interpretation of the so-called RC attenuation of the IMPS response is clarified, as well as the capacitive frequency dispersion in IMPS and IMVS.

J054031 音波共鳴法による水の蒸発係数測定([J05403]マイクロ・ナノスケールの熱流体現象(3))

We propose a new method for measurement of the evaporation coefficient using sound resonance experiment based on a theory of molecular gas dynamics. The evaporation coefficient is one of the parameters contained in the kinetic boundary condition. The evaporation coefficient of water is determined from the pressure amplitude of resonant sound wave in a cylindrical space bounded by a sound source and a vapor-liquid interface. By comparing the pressure amplitude with a linear theory based on molecular gas dynamics, we prove that the evaporation coefficient of water is about 1.0 around 300K.

Effects of static magnetic field on water at kinetic condition

Water was exposed for different times to weak static magnetic field (MF) generated from a stack of magnets ( B = 15 mT) or from a single permanent magnet ( B = 0.27 T) at flow conditions. The water conductivity and the amount of evaporated water were measured as a function of time following the application of MF. It was found that the MF decreases the water conductivity, which is inversely proportional to the flow rate, and increases the amount of evaporated water, even after the water's distillation. The effects are due to the hydrogen bond network strengthening and the perturbation of gas/liquid interface from the air nanobubbles in the water.