Search results for "PHASE"
showing 10 items of 6344 documents
Análisis de la distancia recorrida en pádel en función del nivel de juego y el número de puntos por partido (Analysis of distance covered in padel ba…
2020
La distancia que recorren los jugadores por partido supone una forma de cuantificar el volumen de carga externa del juego, y su estudio tiene una gran aplicación en la planificación del entrenamiento deportivo. El objetivo de este estudio fue analizar la distancia recorrida en diferentes fases del partido (activa y pasiva) y su relación con el número de puntos disputados y nivel de juego de los deportistas. La muestra estuvo compuesta por 108 jugadores federados de pádel (edad media = 33.81 ± 6.72 años). Se analizaron, a través de observación sistemática con el sistema SAGIT, un total 4406 puntos correspondientes a 27 partidos de pádel. Los partidos fueron divididos en tres niveles de compe…
A fluorescence spectroscopy study of the interaction of monocationic quinine with phospholipid vesicles Effect of the ionic strength and lipid compos…
1997
Abstract The interaction of monocationic quinine with zwitterionic dimyristoyl phosphatidylcholine (DMPC) and mixed negatively-charged dimyristoylphosphatidyl glycerol (DMPG) DMPC small unilamellar vesicles in the liquid-crystalline phase was investigated by steady-state fluorescence spectroscopy at pH 7 and 37°C. The maximum fluorescence emission peak at 383 nm, upon excitation at 335 nm, shifts to lower wavelength and decreases its intensity as the ratio between the total lipid and quinine concentrations increases. This indicates that in the membrane-bound state quinine is in an environment of low polarity, more deeply buried when anionic DMPG is present in the vesicle. For monoprotonated…
Modelling of the ternary system H3PO4/H2O/TBP
2002
Abstract A thermodynamic model is presented for the extraction of phosphoric acid from water by tri-n-butylphosphate (TBP), from aqueous solutions containing 0–6 mol/kg phosphoric acid. The activity coefficient of phosphoric acid was calculated from experimental data using Pitzer’s equation, and those of the components in the organic phase were calculated by Sergievskii–Danus’s relationship. The proposed model gives a satisfactory description of the distribution of phosphoric acid and water, in the considered concentration range, by taking into account the formation of the following species: TBP, TBP·H2O, H3PO4·TBP and (TBP)2·H3PO4·H2O.
Co-adsorption of 1,2-dichloroethane and 1-bromo,2-chloroethane on zeolite ZSM-5 from the liquid and vapour phases, using the Myers-Prausnitz-Dubinin …
2002
Abstract The adsorption/co-adsorption of 1,2-dichloroethane (DCA) and 1-bromo,2-chloroethane (BCA) from the vapour and the liquid phases by zeolite ZSM-5 at ambient temperature is reported, using Dubinin's theory and the recent Myers-Prausnitz-Dubinin (MPD) theory. For adsorption from the liquid phase, the activity coefficients in the adsorbed and the liquid states are the same and no selectivity is observed. This is confirmed by the absence of an excess enthalpy of immersion of ZSM-5 into the mixtures. Adsorption from the vapour phase proceeds in two stages, as indicated by double Dubinin-Astakhov (DA) plots. If one considers only the domain of high relative pressure, co-adsorption is desc…
Phase equilibria in the systems isobutyl alcohol+N,N-dimethylformamide, isobutyl acetate+N,N-dimethylformamide and isobutyl alcohol+isobutyl acetate+…
2005
Abstract Consistent vapor–liquid equilibria (VLE) were determined for the ternary system isobutyl alcohol (IBA) + isobutyl acetate (IBAc) + N,N-dimethylformamide (DMF) and two constituent binary systems at 101.3 kPa. The IBA + DMF system exhibits negative deviation from ideal behaviour and IBAc + DMF system deviates positively from ideal behaviour. The activity coefficients of the solutions were correlated with its composition by the Wilson, NRTL and UNIQUAC models. The ternary system is well predicted from binary interaction parameters.
Phase equilibria involved in extractive distillation of dipropyl ether+1-propyl alcohol using 2-ethoxyethanol as entrainer
2007
Abstract Consistent vapour–liquid equilibrium data at 101.3 kPa have been determined for the ternary system dipropyl ether + 1-propyl alcohol + 2-ethoxyethanol and two constituent binary systems: dipropyl ether + 2-ethoxyethanol and 1-propyl alcohol + 2-ethoxyethanol. The dipropyl ether + 2-ethoxyethanol system shows positive deviations from ideal behaviour and 1-propyl alcohol + 2-ethoxyethanol system exhibits no deviation from ideal behaviour. The activity coefficients and the boiling points were correlated with their compositions by the Wilson, NRTL and UNIQUAC equations. It is shown that the models allow a very good prediction of the phase equilibria of the ternary system using the pert…
Acute effects of cold pack on mechanical properties of the quadriceps muscle in healthy subjects.
2012
Purpose: To examine the effects of local cooling on mechanical properties of the quadriceps muscle in healthy subjects. Subjects: Thirty-nine healthy subjects (27 women, 12 men, mean age 39, range 20e62) volunteered. Methods: A cold gel pack was applied to the quadriceps muscle for 20 min. Properties were quantified by analyzing the frequency (tension), decrement (elasticity) and stiffness of damped oscillations and the compliance of the muscle before, immediately after and after 15-min after cooling. Results: The largest responses immediately after cooling were seen in the oscillation decrement parameter, 7.9 (3.7e12.1) %, and in the compliance parameter, � 7.5 (� 9.8 to � 5.3) %. Response…
Hexagonal-columnar mesophases of acylated azacrowns with enhanced stabilities
1992
A series of discotic liquid crystals based on completely acylated macrocyclic oligoamines (azacrowns) has been synthesized. Discotic mesophases could be very highly stabilized by making use of an increased steric hindrance, caused by supplemental lateral meta-substituents which were introduced into the cinnamic acids used as the acylation agents. Employing this method yields compounds exhibiting hexagonal mesophases over a very broad range of more than 300°. Even if very large macrocycles are used as the core of such disc-shaped compounds, enantiotropic mesophases are achieved. Themeta-substituents as well as the size of the azacrowns were varied and their influence on the mesomorphic behav…
Geometric factors in the adiabatic evolution of classical systems
1992
Abstract The adiabatic evolution of the classical time-dependent generalized harmonic oscillator in one dimension is analyzed in detail. In particular, we define the adiabatic approximation, obtain a new derivation of Hannay's angle requiring no averaging principle and point out the existence of a geometric factor accompanying changes in the adiabatic invariant.
Revealing Anisotropy in a Paul Trap Through Berry Phase
2006
When an ion confined in an anisotropic bidimensional Paul trap is subjected to a laser beam oriented along an arbitrary direction, the interaction between its electronic and vibrational degrees of freedom is described by a time-dependent Hamiltonian model as a consequence of the lack of symmetry. Appropriately choosing the laser frequency, the Hamiltonian model turns out to be sinusoidally oscillating at the difference between the proper frequencies of the center of mass of the ion. Thus, if the anisotropy of the trap is sufficiently small, the evolution of the system can be considered as adiabatic. In the context of this physical situation we have calculated the Berry phase acquired in a c…