Phase Increases (phase + increase)

Distribution by Scientific Domains


Selected Abstracts


Intravenous heroin self-administration decreases GABA efflux in the ventral pallidum: an in vivo microdialysis study in rats

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2004
Stéphanie Caillé
Abstract Several lines of evidence suggest that opiate-induced disinhibition of the ventral pallidum participates in the mediation of opiate reward, though direct in vivo evidence to support this hypothesis has been lacking. The present experiment tested this hypothesis by investigating alterations in ventral pallidal amino acid efflux using in vivo microdialysis during ongoing intravenous heroin self-administration in rats. Concentrations of the inhibitory amino acid GABA in ventral pallidal dialysates were significantly reduced within the first 10 min of heroin self-administration (0.02 mg per infusion; FR-1), and remained ,,65% of presession baseline levels for the remainder of the 3-h self-administration session. Dialysate glutamate levels were unaltered during the first hour of heroin intake but significantly increased to a stable level of ,,120% presession values during the subsequent 2 h of self-administration. Thus, heroin self-administration is associated with both decreased GABA efflux and a late phase increase in glutamate efflux in the ventral pallidum. These observations are consistent with the hypothesis that heroin self-administration results in a disinhibition and/or excitation of the ventral pallidum. [source]


Preparation and microstructure characterization of ball-milled ZrO2 powder by the Rietveld method: monoclinic to cubic phase transformation without any additive

JOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 5 2002
S. Bid
The phase transformation kinetics of high-energy ball-milled monoclinic ZrO2 have been studied in detail by Rietveld powder structure refinement analysis. In the present study, no stabilizing compound was required to obtain the cubic phase. The fine-grain powder was milled in a planetary ball mill for up to several hours at different BPMRs (ball to powder mass ratios): 10:1, 20:1, 35:1 and 40:1. During the process of ball milling, the monoclinic phase is gradually transformed to the cubic phase. The relative phase abundances of the respective phases, the particle sizes, the r.m.s. strains, the lattice parameter changes, etc., have been estimated from Rietveld analysis of X-ray powder diffraction data. It has been found that a higher BPMR exerts more influence on rapid phase transformation. In the m - to c -ZrO2 phase transformation, no formation of an intermediate tetragonal ZrO2 phase has been found. The small change in the lattice volume of m -ZrO2, which is very close to the lattice volume of c -ZrO2, caused by ball milling may be attributed to this phase change. The formation of the c phase is noticed, in general, after just 1,h of ball milling, and the particle size of the m phase is reduced to a large extent at the first stage of milling and remains almost unchanged with increasing milling time. However, the particle size of the c phase increases with increasing milling time for the samples milled with higher BPMRs (35:1 and 40:1), suggesting that quenching caused by a high impact energy followed by an annealing effect may play a vital role, which is further manifested in the agglomeration of small particles. [source]


Behavior of an organic solvent drop during the supercritical extraction of emulsions

AICHE JOURNAL, Issue 5 2010
Facundo Mattea
Abstract The behavior of a drop of dichloromethane in water in contact with CO2 at high pressure has been investigated with the purpose of analyzing the phenomena that takes place during the supercritical fluid extraction of emulsions process. Experiments have been performed with and without a solute (,-carotene) and a surfactant (n -octenylsuccinic anhydride-modified starch) dissolved in the drop, and the evolution of the drop volume as well as of the interfacial tension between the drop and the aqueous phase has been measured. Additionally, a mathematical model has been developed that allows describing the mass transfer. Results show that the drop undergoes swelling and shrinking processes due to diffusion of CO2 into the drop and dichloromethane out of the drop. CO2 concentration in the drop can be as high as 0.9 (molar fraction). Emulsion drops behave as miniature gas antisolvent precipitators and many particles are formed inside the drop. The interfacial tension between the drop and the aqueous phase increases during the process, therefore destabilizing the emulsion. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source]


Axial liquid mixing in high-pressure bubble columns

AICHE JOURNAL, Issue 8 2003
G. Q. Yang
Axial dispersion coefficients of the liquid phase in bubble columns at high pressure are investigated using the thermal dispersion technique. Water and hydrocarbon liquids are used as the liquid phase. The system pressure varies up to 10.3 MPa and the superficial gas velocity varies up to 0.4 cm/s, which covers both the homogeneous bubbling and churn-turbulent flow regimes. Experimental results show that flow regime, system pressure, liquid properties, liquid-phase motion, and column size are the main factors affecting liquid mixing. The axial dispersion coefficient of the liquid phase increases with an increase in gas velocity and decreases with increasing pressure. The effects of gas velocity and pressure on liquid mixing can be explained based on the combined mechanism of global liquid internal circulation and local turbulent fluctuations. The axial liquid dispersion coefficient also increases with increasing liquid velocity due to enhanced liquid-phase turbulence. The scale-up effect on liquid mixing reduces as the pressure increases. [source]


Enhancement of Tc(0) by Substitution of Gallium in the Bismuth-Based High- Tc Superconducting Material

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2008
Muhammad Javed Iqbal
We report the enhancement of the zero resistivity Tc(0) by 5.5 K i.e. from 104 to 109.5 K by substitution of gallium 1.34% of copper in the bismuth 2223 compound. A series of Ga-containing compounds Bi2Pb0.4Sr2Ca2Cu3,xGaxOy (x=0.00, 0.02, 0.04, 0.06, and 0.08) are synthesized by the solid-state reaction method. The samples are characterized by measurements of their dc electrical resistivity and ac magnetic susceptibility and by the powder X-ray diffraction analysis. It is noted that the high- Tc (2223) phase increases from 57.55% in an undoped sample to 92.99% in samples containing a low concentration of gallium i.e. x,0.04. [source]


Radial Liquid Dispersion and Bubble Distribution in Three-Phase Circulating Fluidized Beds

THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2003
Yong Kang
Abstract The liquid dispersion and bubble distribution in the radial direction have been investigated in the riser of a three-phase circulating fluidized bed whose diameter is 0.102m and 3.5m in height. Effects of gas and liquid velocities and solid circulation rate have been determined. It has been found that the radial distribution of bubbles is related closely to the liquid dispersion in the radial direction. The size and rising velocity of bubbles tend to increase as the radial position approaches to the center of the riser. The bubble size increases with increasing UG, but it decreases with increasing UL or GS in all radial positions. The radial dispersion coefficient of the liquid phase increases with increasing UG or GS, however, it tends to decrease with increasing UL. The value of Dr has been well correlated in terms of dimensionless groups based on the isotropic turbulence model. La dispersion liquide et la distribution de bulles dans la direction radiale ont été étudiées dans la colonne montante d'un lit fluidisé circulant triphasique de 0,102 m de diamètre et 3,5 m de hauteur. On a déterminé les effets des vitesses de gaz et de liquide et la vitesse de circulation des solides. On a trouvé que la distribution radiale des bulles était étroitement liée à la dispersion liquide dans la direction radiale. La taille des bulles et leur vitesse de montée tendent à augmenter lorsque la position radiale se rapproche du centre de la colonne. La taille des bulles augmente avec l'augmentation de UG, mais elle diminue avec l'augmentation de UL ou de GS dans toutes les positions radiales. Le coefficient de dispersion radiale de la phase liquide augmente avec l'augmentation de UG ou de Gs, mais celui-ci tend à diminuer avec l'augmentation de UL. La valeur de Dr est bien corrélée par des nombres adimensionnels basés sur le modèle de turbulence isotrope. [source]


Origin of migmatites by deformation-enhanced melt infiltration of orthogneiss: a new model based on quantitative microstructural analysis

JOURNAL OF METAMORPHIC GEOLOGY, Issue 1 2008
P. HASALOVÁ
Abstract A detailed field study reveals a gradual transition from high-grade solid-state banded orthogneiss via stromatic migmatite and schlieren migmatite to irregular, foliation-parallel bodies of nebulitic migmatite within the eastern part of the Gföhl Unit (Moldanubian domain, Bohemian Massif). The orthogneiss to nebulitic migmatite sequence is characterized by progressive destruction of well-equilibrated banded microstructure by crystallization of new interstitial phases (Kfs, Pl and Qtz) along feldspar boundaries and by resorption of relict feldspar and biotite. The grain size of all felsic phases decreases continuously, whereas the population density of new phases increases. The new phases preferentially nucleate along high-energy like,like boundaries causing the development of a regular distribution of individual phases. This evolutionary trend is accompanied by a decrease in grain shape preferred orientation of all felsic phases. To explain these data, a new petrogenetic model is proposed for the origin of felsic migmatites by melt infiltration from an external source into banded orthogneiss during deformation. In this model, infiltrating melt passes pervasively along grain boundaries through the whole-rock volume and changes completely its macro- and microscopic appearance. It is suggested that the individual migmatite types represent different degrees of equilibration between the host rock and migrating melt during exhumation. The melt topology mimicked by feldspar in banded orthogneiss forms elongate pockets oriented at a high angle to the compositional banding, indicating that the melt distribution was controlled by the deformation of the solid framework. The microstructure exhibits features compatible with a combination of dislocation creep and grain boundary sliding deformation mechanisms. The migmatite microstructures developed by granular flow accompanied by melt-enhanced diffusion and/or melt flow. However, an AMS study and quartz microfabrics suggest that the amount of melt present did not exceed a critical threshold during the deformation to allow free movements of grains. [source]


Removal of the PsaF Polypeptide Biases Electron Transfer in Favor of the PsaB Branch of Cofactors in Triton X-100 Photosystem I Complexes from Synechococcus sp.

PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 6 2008
PCC 700
Continuous wave (CW) and transient electron paramagnetic resonance studies have implied that when PsaF is removed genetically, the double reduction of A1A is facile, the lifetime of A1A, is shorter and the ratio of fast to slow kinetic phases increases in PS I complexes isolated with Triton X-100 (Van der Est, A., A. I. Valieva, Y. E. Kandrashkin, G. Shen, D. A. Bryant and J. H. Golbeck [2004] Biochemistry43, 1264,1275). Changes in the lifetimes of A1A, and A1B, are characteristic of mutants involving the quinone binding sites, but changes in the relative amplitudes of A1A, and A1B, are characteristic of mutants involving the primary electron acceptors, A0A and A0B. Here, we measured the fast and slow phases of electron transfer from A1B, and A1A, to FX in psaF and psaE psaF null mutants using time-resolved CW and pump-probe optical absorption spectroscopy. The lifetime of the fast kinetic phase was found to be unaltered, but the lifetime of the slow kinetic phase was shorter in the psaF null mutant and even more so in the psaE psaF null mutant. Concomitantly, the amplitude of the fast kinetic phase increased by a factor of 1.8 and 2.0 in the psaF and psaE psaF null mutants, respectively, at the expense of the slow kinetic phase. The change in ratio of the fast to slow kinetic phases is explained as either a redirection of electron transfer through A1B at the expense of A1A, or a shortening of the lifetime of A1A, to become identical to that of A1B,. The constant lifetime and the characteristics of the near-UV spectrum of the fast kinetic phase favor the former explanation. A unified hypothesis is presented of a displacement of the A-jk(1) ,-helix and switchback loop, which would weaken the H-bond from Leu722 to A1A, accounting for the acceleration of the slow kinetic phase, as well as weaken the H-bond from Tyr696 to A0A, accounting for the bias of electron transfer in favor of the PsaB branch of cofactors. [source]