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1.
J Phys Condens Matter ; 30(24): 244003, 2018 Jun 20.
Artículo en Inglés | MEDLINE | ID: mdl-29708503

RESUMEN

We show on in-plane magnetized thin films that magnetization can be switched efficiently by 180 degrees using large amplitude Rayleigh waves travelling along the hard or easy magnetic axis. Large characteristic filament-like domains are formed in the latter case. Micromagnetic simulations clearly confirm that this multi-domain configuration is compatible with a resonant precessional mechanism. The reversed domains are in both geometries several hundreds of [Formula: see text], much larger than has been shown using spin transfer torque- or field-driven precessional switching. We show that surface acoustic waves can travel at least 1 mm before addressing a given area, and can interfere to create magnetic stripes that can be positioned with a sub-micronic precision.

2.
J Phys Condens Matter ; 25(34): 346001, 2013 Aug 28.
Artículo en Inglés | MEDLINE | ID: mdl-23883527

RESUMEN

The magnetic anisotropy of the ferromagnetic semiconductor (Ga, Mn) (As, P) is studied in a material-specific microscopic k ⋅p approach. We calculate the electronic energy band structure of (Ga, Mn) (As, P) quaternary ferromagnetic alloys using a 40-band k ⋅p model and taking into account the s, p-d exchange interaction and the strain of the (Ga, Mn) (As, P) layer on a GaAs substrate. We determine the variations of the carrier effective masses in the strained (Ga, Mn) (As, P)/GaAs system. The magnetic anisotropy constants obtained from our simulations using a mean-field model are compared with the experimental ones determined by ferromagnetic resonance spectroscopy on a set of samples with constant manganese concentration and varying phosphorus concentration. An excellent quantitative agreement between experiment and theory is found for the uniaxial out-of-plane and cubic in-plane anisotropy parameters.

3.
Anal Bioanal Chem ; 405(10): 3117-23, 2013 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-23354583

RESUMEN

A cloud point extraction coupled with high performance liquid chromatography (HPLC/UV) method was developed for the determination of Δ(9)-tetrahydrocannabinol (THC) in micellar phase. The nonionic surfactant "Dowfax 20B102" was used to extract and pre-concentrate THC from cannabis resin, prior to its determination with a HPLC-UV system (diode array detector) with isocratic elution. The parameters and variables affecting the extraction were investigated. Under optimum conditions (1 wt.% Dowfax 20B102, 1 wt.% Na2SO4, T = 318 K, t = 30 min), this method yielded a quite satisfactory recovery rate (~81 %). The limit of detection was 0.04 µg mL(-1), and the relative standard deviation was less than 2 %. Compared with conventional solid-liquid extraction, this new method avoids the use of volatile organic solvents, therefore is environmentally safer.


Asunto(s)
Cannabis/química , Fraccionamiento Químico/métodos , Cromatografía Líquida de Alta Presión/métodos , Dronabinol/aislamiento & purificación , Extractos Vegetales/aislamiento & purificación , Resinas de Plantas/química , Dronabinol/análisis , Extractos Vegetales/análisis
4.
J Hazard Mater ; 205-206: 171-8, 2012 Feb 29.
Artículo en Inglés | MEDLINE | ID: mdl-22260753

RESUMEN

The two aqueous phases extraction process is widely used in environmental clean up of industrial effluents and fine chemical products for their reuse. This process can be made by cloud point of polyethoxylated alcohols and micellar solubilization phenomenon. It is commonly called "coacervate extraction" and is used, in our case, for humic acid extraction from aqueous solution at 100mg/L. The surfactants used are alcohol polyethoxylate and alkylphenol polyethoxylate. Phase diagrams of binary water/surfactant and pseudo-binary are plotted. The extraction results are expressed by the following responses: percentage of solute extracted, E (%), residual concentrations of solute and surfactant in dilute phase (X(s,w), and X(t,w) respectively) and volume fraction of coacervate at equilibrium (ϕ). For each parameter, the experimental results are fitted to empirical equations in three dimensions. The aim of this study is to find out the best compromise between E and ϕC. The comparison between experimental and calculated values allows models validation. Sodium sulfate, cetyltrimethylammonium bromide (CTAB) addition and pH effect are also studied. Finally, the possibility of recycling the surfactant has been proved.


Asunto(s)
Restauración y Remediación Ambiental/métodos , Sustancias Húmicas/análisis , Tensoactivos/química , Contaminantes del Agua/aislamiento & purificación , Glicoles de Etileno/análisis , Glicoles de Etileno/química , Concentración de Iones de Hidrógeno , Fenoles/análisis , Fenoles/química , Reciclaje , Tensoactivos/análisis , Temperatura , Contaminantes del Agua/química
5.
Phys Rev Lett ; 96(8): 087002, 2006 Mar 03.
Artículo en Inglés | MEDLINE | ID: mdl-16606216

RESUMEN

The phase transition between the intermediate and normal states in type-I superconducting films is investigated using magneto-optical imaging. Magnetic hysteresis with different transition fields for collapse and nucleation of superconducting domains is found. This is accompanied by topological hysteresis characterized by the collapse of circular domains and the appearance of lamellar domains. Magnetic hysteresis is shown to arise from supercooled and superheated states. Domain-shape instability resulting from long-range magnetic interaction accounts well for topological hysteresis.

6.
J Colloid Interface Sci ; 299(1): 472-85, 2006 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-16530211

RESUMEN

The influence of mass transfer on the drainage behaviour of the thin liquid film between two drops immersed in another liquid colliding at constant approach velocity has been studied experimentally. The liquid-liquid system used is glycerol in silicone oil. The transferred solute is acetone and the volume concentration difference across the interface ranges from 1 to 5%. The film thickness evolution has been measured using a laser interferometry technique. The direction of mass transfer (from the drops towards the film phase and inversely) has been investigated and the results compared to the case with no mass transfer. When the solute transfers from the drops towards the continuous phase, the drainage rate is significantly higher than in the case with no mass transfer. This result is interpreted as a consequence of the mass transfer induced surface mobility in the film region (the so-called Marangoni effect) due to localized surface tension differences. This effect has been demonstrated by the visualization of the flow patterns in the drops and in the film phase (using a particle tracer technique). In this case, the slope of the film height as a function of time seems to be independent of the approach velocity condition imposed on the drop and appears to be controlled by the interfacial tension gradient. In the opposite case, when the solute transfers from the continuous phase towards the drops, the film drainage rate is lowered with respect to the case of no mass transfer, goes to zero or even changes its sign depending on the mass transfer intensity. The results also show that in the range of solute concentration studied, the effect of mass transfer on the film drainage process takes place at large distances compared to the scales at which lubrication theory is valid.

7.
Pharmazie ; 59(9): 727-8, 2004 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-15497760

RESUMEN

Extraction of valerenic acids (valerenic, acetoxyvalerenic and hydroxyvalerenic) from dry ground rhizomes of valerian (Valeriana officinalis L.) was studied. The effect of ethanol concentration in the solvent, extraction temperature and drug particle size on extraction kinetics were investigated and the optimum values of these process parameters were determined for the case of intensively stirred two-phase dispersion. It was found that increased processing temperature favors extraction kinetics, but provokes moderate degradation of valerenic acids.


Asunto(s)
Indenos/química , Sesquiterpenos/química , Valeriana/química , Etanol , Indenos/aislamiento & purificación , Cinética , Tamaño de la Partícula , Extractos Vegetales/química , Raíces de Plantas/química , Sesquiterpenos/aislamiento & purificación , Solventes , Temperatura
8.
Phys Rev Lett ; 92(14): 147001, 2004 Apr 09.
Artículo en Inglés | MEDLINE | ID: mdl-15089565

RESUMEN

Normal state bubble patterns in type I superconducting indium and lead slabs are studied by the high resolution magneto-optical imaging technique. The size of bubbles is found to be independent of the long-range interaction between the normal state domains. Under bubble diameter and slab thickness proper scaling, the results gather onto a single master curve. We calculate the equilibrium diameter of an isolated bubble resulting from the competition between the Biot-and-Savart interaction of the Meissner current encircling the bubble and the superconductor-normal interface energy. A good quantitative agreement with the master curve is found over two decades of the magnetic Bond number. The isolation of each bubble in the superconductor and the interface energy are shown to preclude any continuous size variation of the bubbles after their formation, contrary to the prediction of mean-field models.

9.
Ultrason Sonochem ; 7(4): 187-92, 2000 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-11062874

RESUMEN

The use of ultrasound in various processes of the chemical industry has been a subject of research and development for many years. As regards in emulsification, apart from formulation variables, power is the most important parameter. Efficiency of emulsification processes may be followed and evaluated by measuring particle size distribution, which mainly governs the kinetic stability of such dispersions. Unfortunately, this kind of measurement must be performed at high dilution (low volume fraction of dispersed phase). The present work is devoted to the on-line study of ultrasound emulsification by means of a newly developed apparatus based on multiple light scattering, which allows us to determine average droplet diameter and its variations directly on concentrated media. The model system was an oil (kerosene)-in-water emulsion stabilized by a polyethoxylated sorbitan monostearate.

10.
J Colloid Interface Sci ; 229(1): 274-285, 2000 Sep 01.
Artículo en Inglés | MEDLINE | ID: mdl-10942569

RESUMEN

Experiments and modeling of the drainage of the thin liquid film between two deformable spherical drops approaching each other at constant velocity in another liquid are being presented. Two numerical models based on the lubrication theory have been developed considering the cases of immobile or mobile drop interfaces. The absolute film thickness and the thinning rate have been measured using laser interferometry for a wide range of capillary numbers. In all studied cases, the model with immobile interfaces was found to give the best predictions of the experimental time evolution of the film thickness and radial expansion. These results made it possible to derive a typical time scale of the drainage process. Copyright 2000 Academic Press.

11.
Ultrason Sonochem ; 6(1-2): 75-83, 1999 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-11233941

RESUMEN

The aim of this work is to compare the oil-in-water emulsions produced by mechanical agitation (Ultra-Turrax, 10,000 rpm, P = 170 W) or power ultrasound (ultrasound horn, 20 kHz, 130 W) using the same model system: water/kerosene/polyethoxylated (20 EO) sorbitan monostearate. The following parameters were varied: emulsification time, surfactant concentration, consumed power and volume fraction of oil. With ultrasound, the drop size (Sauter diameter, d32) is much smaller than that given by mechanical agitation under the same conditions, which makes insonated emulsions more stable. For a given drop size (d32), less surfactant is required.

12.
Ultrason Sonochem ; 5(2): 63-8, 1998 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-11270338

RESUMEN

In order to propose standard methods for the local measurement of the effects of power ultrasound inside a reactor, we compare three methods: a chemical dosimeter (Weissler reaction), a thermal sensor (embedded thermocouple) and an electrochemical probe (developed in our laboratory). The same emission device, i.e. the resonant tube (Sonitube-Sodeva), was used for all these methods. Similar trends were observed using various measurements: ultrasound effects vary significantly along the tube axis (due to standing waves in the resonant tubular emitter), but only slightly from the tube axis to the wall. More reliable and reproducible results were obtained with the thermal and electrochemical probes than with the chemical dosimeter.

13.
Ultrason Sonochem ; 4(3): 235-43, 1997 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-11232780

RESUMEN

Ultrasound is used in different domains, and in sonochemistry particularly, for different purposes and in various flow configurations: monophasic, two-phase and polyphasic reactors. In order to optimize and to design sonochemical reactors, it is important to describe the ultrasonic intensity space and time distribution. In addition, it is important to study the different parameters influencing the intensity profiles of the ultrasonic wave. In this work, a thermoelectric probe has been used to measure the ultrasonic intensity. This procedure has shown that the ultrasound propagation is influenced by the presence of cavitation bubbles, the flow regime and the presence of solid particles.

14.
J Colloid Interface Sci ; 191(1): 22-9, 1997 Jul 01.
Artículo en Inglés | MEDLINE | ID: mdl-9241200

RESUMEN

A new model is proposed for the calculation of the interfacial tension between an organic solvent and concentrated aqueous solutions of electrolytes. The interfacial tension is derived from the isothermal Gibbs equation. The increase or decrease of interfacial tension with concentrations are modeled using a Langmuir-type adsorption equation and the strong non-ideality of the mixtures is taken into account through the Mikulin equation. The model parameters are first determined with binary water-electrolyte solutions and are kept constant in the case of mixtures. The model has been applied to chloride solutions-chloride salts of various metals and hydrochloric acid-and compared with experimental data obtained by using the pendant drop technique and a Wilhelmy tensiometer. In all cases investigated, good agreement is observed, even in the case of stiff variations of interfacial tension with the electrolyte concentration and also at high concentrations of electrolytes.

16.
Phys Rev Lett ; 74(9): 1645-1648, 1995 Feb 27.
Artículo en Inglés | MEDLINE | ID: mdl-10059081
17.
Eur Respir J ; 6(5): 748-9, 1993 May.
Artículo en Inglés | MEDLINE | ID: mdl-8519387

RESUMEN

We report a case of spontaneous interlobar pneumothorax, an uncommon condition. The diagnosis was suspected from the frontal chest X-ray, which showed an incompletely circumscribed air-containing space, with a fluid level. The diagnosis was confirmed by the lateral projections of standard X-ray and tomography, and by thoracic computed tomography (CT). Such air-fluid levels should not be confused with pneumatocele, cystic or cavitary diseases.


Asunto(s)
Asma/complicaciones , Neumotórax/etiología , Bronquiectasia/complicaciones , Humanos , Masculino , Persona de Mediana Edad , Neumotórax/diagnóstico por imagen , Recurrencia , Tomografía Computarizada por Rayos X
18.
Presse Med ; 22(10): 480-6, 1993 Mar 20.
Artículo en Francés | MEDLINE | ID: mdl-8511069

RESUMEN

Respiratory tract viruses have been held responsible for the genesis and aggravation of asthma in both children and adults. The relationship between asthma and viruses is looser in adults than in children, but it has been demonstrated that viral infections can generate a peripheral obstructive disorder on the one hand, and a transient non-specific bronchial hyperreactivity in healthy subjects on the other hand. Current data are insufficient to define clearly the alterations induced by viral infections and responsible for bronchial inflammation and non-specific bronchial hyperreactivity. Numerous studies have concluded to a complex mechanism involving bronchial epithelium lesions, imbalance of the autonomic nervous system in bronchial tone regulation, occurrence of immediate hypersensitivity reaction with facilitation of its delayed component, and cytokines produced during viral infection.


Asunto(s)
Asma/microbiología , Virosis/complicaciones , Adolescente , Adulto , Anciano , Asma/etiología , Hiperreactividad Bronquial/etiología , Niño , Preescolar , Humanos , Inmunoglobulina E/inmunología , Lactante , Virus de la Influenza A/aislamiento & purificación , Vacunas contra la Influenza/efectos adversos , Gripe Humana/microbiología , Mastocitos/metabolismo , Persona de Mediana Edad
19.
Rev Prat ; 42(19): 2447-51, 1992 Dec 01.
Artículo en Francés | MEDLINE | ID: mdl-1296320

RESUMEN

The diagnosis of occupational asthma requires the integration of a multiplicity of data; the history, cutaneous skin tests, biological tests, respiratory function tests and non-specific tests of bronchial hyperreactivity and specific bronchial provocation test. The history search for the presence of an atopic state, the occurrence of similar disorders in members of the same firm and also the timing of symptoms in relation to the occupational activities. Cutaneous tests are particularly helpful in IgE-mediated asthma in relation to the inhalation of animal or vegetable materials of glycoprotein origin. For haptens, the need for their prior coupling to a protein carrier causes problems which have not been entirely resolved. Laboratory tests run into the same snags. Respiratory function and non-specific bronchial provocation tests, confirm the diagnosis of asthma and enable the medium and long term prognostic to be assessed. Specific bronchial provocation tests are the most appropriate tests to establish an aetiological diagnosis in occupational asthma. Different technical methods are possible: quantitative administration of allergen aerosols, realistic tests, and tests using exposure chambers to achieve true test doses. The products responsible for occupational asthma are multiple. The different substances are characterised in a simplified manner: first animal matter (mammalian and arthropod allergens), secondly substances of vegetable origin (roots, leaves, flowers, grain and flour, wood and its derivates) and finally chemical products. The chemical products are primarily from the pharmaceutical and metal industries and above all from the plastics industry.


Asunto(s)
Asma , Enfermedades Profesionales , Alérgenos , Asma/diagnóstico , Asma/fisiopatología , Asma/terapia , Exposición a Riesgos Ambientales , Humanos , Enfermedades Profesionales/diagnóstico , Enfermedades Profesionales/fisiopatología , Enfermedades Profesionales/terapia
20.
Phys Rev B Condens Matter ; 46(8): 4644-4650, 1992 Aug 15.
Artículo en Inglés | MEDLINE | ID: mdl-10004221
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