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One Phase (one + phase)
Selected AbstractsRole of GABAA inhibition in modulation of pyramidal tract neuron activity during postural correctionsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2007Zinaida A. Tamarova Abstract In a previous study we demonstrated that the activity of pyramidal tract neurons (PTNs) of the motor cortex is modulated in relation to postural corrections evoked by periodical tilts of the animal. The modulation included an increase in activity in one phase of the tilt cycle and a decrease in the other phase. It is known that the motor cortex contains a large population of inhibitory GABAergic neurons. How do these neurons participate in periodic modulation of PTNs? The goal of this study was to investigate the role of GABAA inhibitory neurons of the motor cortex in the modulation of postural-related PTN activity. Using extracellular electrodes with attached micropipettes, we recorded the activity of PTNs in cats maintaining balance on a tilting platform both before and after iontophoretic application of the GABAA receptor antagonists gabazine or bicuculline. The tilt-related activity of 93% of PTNs was affected by GABAA receptor antagonists. In 88% of cells, peak activity increased by 75 ± 50% (mean ± SD). In contrast, the trough activity changed by a much smaller value and almost as many neurons showed a decrease as showed an increase. In 73% of the neurons, the phase position of the peak activity did not change or changed by no more than 0.1 of a cycle. We conclude that the GABAergic system of the motor cortex reduces the posture-related responses of PTNs but has little role in determining their response timing. [source] A thermodynamic approach to the instantaneous non-active powerEUROPEAN TRANSACTIONS ON ELECTRICAL POWER, Issue 6 2001A. P. Morando, Article first published online: 22 MAR 200 Having schematically run through the transition from single-phase to three-phase relationships, the energy balance is formalised using Park vector notation. The imaginary power notation emerges. Leading back, in the sinusoidal case, to the usual reactive power, it generalises its specific contents in the case of variable states, explaining in particular a typical aspect of three-phase networks: the energy bouncing from one phase to another. This aspect can be seen as an index of power quality. At last, these same considerations are obtained by means of Lagrangian and thermodynamic approaches that lend a deeper meaning to the energy related quantities. [source] Numerical aspects of an algorithm for the Eulerian simulation of two-phase flowsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 10-11 2003Paulo J. Oliveira Abstract It is often the case that the numerical simulation of two phase flows leads to a number of difficulties associated with the solution algorithms utilized. Those difficulties manifest themselves as an impossibility to converge the iterative solution process, typical of the finite-volume pressure-correction methods, and are particularly persistent in cases with phase segregation (complete, or almost complete, separation of one phase from the other) and with fine meshes. A number of effective measures to overcome such problems are here proposed and tested, encompassing: (1) modification of the momentum equations formulation in a way that avoids singularity as volume fractions (,) tend to zero; (2) bounding of the volume fractions during the iterative algorithm in a way that enforces the physical limits, ,0 and 1; (3) symmetric treatment of some terms in the equations, and consistent formulation of cell-face fluxes in order to prevent numerical-induced oscillations. Copyright © 2003 John Wiley & Sons, Ltd. [source] Hydrothermal Synthesis and Spark Plasma Sintering of (K, Na)NbO3 Lead-Free PiezoceramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 8 2009Nan Liu A facile hydrothermal route was adopted for synthesis of lead-free piezoceramics (K, Na)NbO3 powders. The influences of temperature and KOH/NaOH concentration on the resultant powders were investigated. Although two similar perovskite phases appeared when K/Na ratio tended toward 1:1, the two-phase coexistence tendency was weakened by increasing hydrothermal reaction temperature, and consequently only one phase could be obtained after spark plasma sintering. Reasonably good ferroelectric and piezoelectric properties were obtained for the samples after postannealing, whose piezoelectric constant (d33) reached 135 pC/N. The optimal remnant polarization (Pr) and mechanical quality factor (Qm) were 26.2 ,C/cm2 and 164, respectively, which were both twice as much as those of the samples using powders prepared from solid-state reaction. [source] Microwave Plasma Synthesis of Nanostructured ,-Al2O3 PowdersJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2003L. Fu Nanostructured Al2O3 powders have been synthesized by combustion of aluminum powder in a microwave oxygen plasma, and characterized by X-ray diffraction and electron microscopy. The main phase is ,-Al2O3, with a small amount of ,-Al2O3. The particles are truncated octahedral in shape, with mean particle sizes of 21,24 nm. The effect of reaction chamber pressure on the phase composition and the particle size was studied. The ,-alumina content increases and the mean particle size decreases with decreasing pressure. No ,-Al2O3 appears in the final particles. Electron microscopy studies find that a particle may contain more than one phase. [source] Instabilities in two-fluid magnetized media with inter-component driftMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2002P. V. Tytarenko Abstract We analyse the stability of a magnetized medium consisting of a neutral fluid and a fluid of charged particles, coupled to each other through a drag force and exposed to differential body forces (for example, as the result of radiation forces on one phase). We consider a uniform equilibrium and simple model input physics, but do not arbitrarily restrict the relative orientations of the magnetic field, slip velocity and wavevector of the disturbance. We find several instabilities and classify these in terms of wave resonances. We briefly apply our results to the structure of SiO maser regions appearing in the winds from late-type stars. [source] Seasonal and spatial patterns of population density in the marine macroalga Mazzaella splendens (Gigartinales, Rhodophyta)PHYCOLOGICAL RESEARCH, Issue 1 2006Leonard James Dyck SUMMARY Insight into demographic processes that operate at larger spatial scales can be achieved through studying local populations when a particular species of interest is examined over time, by many investigators, in a variety of locations. On the west coast of North America, Mazzaella splendens (Setchell et Gardner) Fredericq is such a species of interest. A synthesis of local demographic studies of M. splendens from the late 1960s to the present reveals a pattern that is potentially common to the larger natural populations. This is the pattern: population density is high in summer and low in winter for both alternate free-living life history phases of M. splendens. The magnitude of this seasonal change decreases in increasingly wave-exposed habitats. In wave-sheltered habitats there is a seasonal alternation from summer haploid to winter diploid dominance. This alternation gradually changes to constant diploid dominance as wave exposure in the habitat increases. Changes in population density are primarily a function of appearances and disappearances of perennating basal crusts (genets), as modules are produced or lost, rather than differential module production by genets of one phase over those of the other. To test the generality of this pattern, we examined seasonal changes in density, in local populations of M. splendens, in both a wave-sheltered and a wave-exposed habitat at Second Beach, Barkley Sound. Greater seasonal fluctuation in population density at wave-sheltered, compared to wave-exposed habitats is supported as a pattern potentially common to the natural populations of M. splendens. A change from summer haploid dominance in wave-sheltered areas to summer diploid dominance in wave-exposed areas is similarly supported. All changes in population density were the result of appearances and disappearances of genets rather than differential module production by haploid versus diploid basal crusts, also consistent with previous observations. A seasonal alternation in phase dominance, however, was absent from the wave-sheltered site at Second Beach, Barkley Sound for 3 consecutive years. Seasonal alternation in phase dominance of M. splendens appears dependent on local conditions and is not common to all natural populations. [source] AFM study of crystalline cellulose in the cell walls of strawPOLYMER INTERNATIONAL, Issue 1 2006Wan Li Abstract Crystalline cellulose in the cell walls of straw was studied by atomic force microscopy (AFM). The samples were first treated and then observed by AFM under dimethylsulfoxide (DMSO). The crystalline regions were located and two allomorphs of crystalline cellulose, triclinic I, and monoclinic I, phases, were identified. In most crystalline regions, the I, and I, phases are intimately associated, with the I, phase more abundant than the I, phase. In some small domains only one phase with long-range order was observed. It was demonstrated that in these one-phase domains, I, phase crystals always have their (010) plane lying parallel to the cell wall surface and I, phase crystals with (110) plane lying parallel. Copyright © 2005 Society of Chemical Industry [source] The response of the coupled tropical ocean,atmosphere to westerly wind burstsTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 579 2002Alexey V. Fedorov Abstract Two different perspectives on El Niño are dominant in the literature: it is viewed either as one phase of a continual southern oscillation (SO), or alternatively as the transient response to the sudden onset of westerly wind bursts (WWBs). Occasionally those bursts do indeed have a substantial effect on the SO,the unusual strength of El Niño of 1997/98 appears to be related to a sequence of bursts,but frequently the bursts have little or no impact. What processes cause some bursts to be important, while others remain insignificant? The question is addressed by using a simple coupled tropical ocean,atmosphere model that simulates a continual, possibly attenuating, oscillation to study the response to WWBs. The results show that the impact of WWBs depends crucially on two factors: (i) the background state of the system as described by the mean depth of the thermocline and intensity of the mean winds, and (ii) the timing of the bursts with respect to the phase of the SO. Changes in the background conditions alter the sensitivity of the system, so that the impact of the bursts on El Niño may be larger during some decades than others. Changes in the timing of WWBs affect the magnitude and other characteristics of the SO by modifying the energetics of the ocean,atmosphere interactions. A reasonable analogy is a swinging pendulum subject to modest blows at random times,those blows can either magnify or diminish the amplitude, depending on their timing. It is demonstrated that a WWB can increase the strength of El Niño significantly, if it occurs 6 to 10 months before the peak of warming, or can reduce the intensity of the subsequent El Niño, if it occurs during the cold phase of the continual SO. Copyright © 2002 Royal Meteorological Society. [source] Two polymorphs of lysozyme nitrate: temperature dependence of their solubilityACTA CRYSTALLOGRAPHICA SECTION D, Issue 10-1 2002L. Legrand Two crystallographic forms of lysozyme nitrate are known, namely monoclinic and triclinic. Having previously determined the temperature dependence of the solubility of the monoclinic form (0.2 M NaNO3 solutions at pH = 4.5) [Legrand et al. (2001). J. Crystal Growth232, 244-249], we focus here on the solubility of the triclinic form. The temperature dependence of the solubility of this crystallographic form has been measured with a static light device developed in our laboratory. This device allows to observe of the dissolution of one phase and/or the occurrence of a new one by varying the temperature with a sweep rate as low as 0.6 degree/hour. The new solubility data are complemented with crystallographic data of the triclinic form for the sake of completeness. The faces of a triclinic crystal are indexed. The crystallisation enthalpy of the triclinic form is deduced from these new results. These new solubility data allow us now to discuss (1) the publishedprotocols used to obtain the monoclinic and triclinic forms of lysozyme nitrate and (2) the phase transformation. 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