Search results for "electromagnetism"
showing 10 items of 276 documents
A secondary mode of action of the herbicide lenacil: Modification of K+ permeability of Acer pseudoplatanus cells
1984
Abstract The action of lenacil on plasmalemma permeability to K+, transmembrane electric potential difference (PD) calculated from the tetraphenylphosphonium distribution, proton extrusion and intracellular pH of Acer pseudoplatanus cells calculated from the 5,5-dimethyloxazolidine,4-dione distribution, was studied and compared with the action of fusicoccin (FC) and diethylstilbestrol (DES). The three compounds temporarily stimulated the rate of 86Rb+ uptake with a half-maximum effect at 5.0 μM for 3-cyclohexyl-6, 7-dihdro-1H-cyclopentapyrimidine-2,4(3H,5H)-dione (lenacil). Lenacil and FC had no action on transmembrane electric potential difference, whereas DES decreased it. Lenacil inhibit…
Modelling chemical composition in electric systems - implications to the dynamics of dye-sensitised solar cells
2010
International audience; Classical electromagnetism provides limited means to model electric generators. To extend the classical theory in this respect, additional information on microscopic processes is required. In semiconductor devices and electrochemical generators such information may be obtained by modelling chemical composition. Here we use this approach for the modelling of dye-sensitised solar cells. We simulate the steady-state current-voltage characteristics of such a cell, as well as its transient response. Dynamic simulations show optoelectronic hysteresis in these cells under transient light pulse illumination.
Usefulness of Caco-2/HT29-MTX and Caco-2/HT29-MTX/Raji B Coculture Models To Predict Intestinal and Colonic Permeability Compared to Caco-2 Monocultu…
2017
The Caco-2 cellular monolayer is a widely accepted in vitro model to predict human permeability but suffering from several and critical limitations. Therefore, some alternative cell cultures to mimic the human intestinal epithelium, as closely as possible, have been developed to achieve more physiological conditions, as the Caco-2/HT29-MTX coculture and the triple Caco-2/HT29-MTX/Raji B models. In this work the permeability of 12 model drugs of different Biopharmaceutical Classification System (BCS) characteristics, in the coculture and triple coculture models was assessed. Additionally, the utility of both models to classify compounds according to the BCS criteria was scrutinized. The obta…
Evaluation of the Ocular Tolerance of Three Tacrolimus Topical Pharmaceutical Preparations by Bovine Corneal Opacity and Permeability Test.
2015
Tacrolimus ocular preparations are commonly employed in autoimmune or inflammatory ocular disorders. However, currently there are not yet approved ocular formulations. Tacrolimus ocular side effects have been reported in clinical use, so the evaluation of different pharmaceutical preparations is mandatory. In this study, the local corneal tolerance and safety profile of three common tacrolimus 0.03% pharmaceutical preparations were evaluated.Corneal irritation and permeability of tacrolimus preparations were evaluated with the bovine corneal opacity and permeability (BCOP) test. Complementary corneal hematoxylin/eosin and immunohistochemistry staining for tight junctions and adherent juncti…
Fabricación de fibras de cristal fotónico y grabación de redes de Bragg
2010
Los trabajos y experimentos desarrollados en esta tesis han ido dirigidos fundamentalmente a la fabricación de fibras de cristal fotónico y a la grabación de redes de Bragg en éstas. Este proyecto se ha desarrollado en dos partes. La primera parte consiste en conocer las características y propiedades de las redes de Bragg grabadas en fibras ópticas. Describe cuáles son las técnicas empleadas para la fabricación de redes de Bragg y explica el método utilizado en la grabación de redes en este trabajo, enfatizando la técnica de apodización de redes de Bragg que se implementó como mejora en el sistema de grabación previamente existente. Se describen algunas de las aplicaciones desarrolladas en …
El concepto de fuerza electromotriz en cursos introductorios de física en la universidad: dificultades de aprendizaje y la presentación del concepto …
2012
La persistencia de concepciones alternativas en los estudiantes, incluso de niveles universitarios y entre profesores son dificultades de la práctica docente sin resolver que ponen en evidencia la necesidad de investigar en las dificultades de comprensión de unos y otros, para orientar la búsqueda de estrategias que disminuyan la incidencia de tales concepciones. Esta investigación contribuye a poner en evidencia que algunas concepciones alternativas (interpretaciones de los estudiantes que están en conflicto con el concepto formal como es entendido por un físico experto) acerca del concepto de fuerza electromotriz, enmarcado en la teoría electromagnética son comunes entre estudiantes quien…
Generación y Validación de algoritmos para la obtención de la temperatura de la superficie terrestre utilizando técnicas de Teledetección en el infra…
2014
La temperatura de superficie terrestre, LST (por sus siglas en inglés), es uno de los principales parámetros en el estudio de balance energético y de masa entre la atmosfera y el suelo, en particular, en la estimación de la evapotranspiración y el estrés hídrico que pueda sufrir la vegetación (Hall et al, 1992; Sellers, et al., 1995; Anderson, et al., 1997; Sánchez, et al. 2008). Además, la LST es necesaria como dato inicial en modelos de predicción meteorológica (Barton, et al. 1989; Gouturbe, et al. 1993), evaluación de daños provocados por las heladas (Caselles y Sobrino 1989), y detección de incendios forestales (Calle, et al. 2005), entre otros muchos. La LST puede considerarse también…
On the carrier of inertia
2018
A change in momentum will inevitably perturb the all-embracing vacuum, whose reaction we understand as inertia. Since the vacuum's physical properties relate to light, we propose that the vacuum embodies photons, but in pairs without net electromagnetic fields. In this physical form the free space houses energy in balance with the energy of matter in the whole Universe. Likewise, we reason that a local gravitational potential is the vacuum in a local balance with energy that is bound to a body. Since a body couples to the same vacuum universally and locally, we understand that inertial and gravitational masses are identical. By the same token, we infer that gravity and electromagnetism shar…
Elektrophysiologische Untersuchung zum Einsatz von Streptolysin O und Natrium-Hyaluronat zur Permeabilitätsmodulation der Membran des runden Fensters…
2003
Background: The round window membrane (RWM) acts like a barrier for topically applied substances into the middle ear preventing diffusion into the perilymphatic fluid compartment. Material and Method: In an animal model, modulation of the permeability of the RWM was attempted using Streptolysin-O (SLO) in various concentrations and sodium hyaluronate. Thereafter, the effect of intratympanically applied Lidocain 2% on hearing threshold measured by auditory brainstem response was tested for Lidocain 2 % and Lidocain 2 % in combination with SLO or sodium hyaluronate. Results: The results show that both, SLO and sodium hyaluronate, influence the effect of Lidocain 2 % on hearing thresholds as a…
Enhancing effect of alpha-hydroxyacids on "in vitro" permeation across the human skin of compounds with different lipophilicity.
2005
The percutaneous penetration-enhancing effects of glycolic acid, lactic acid and sodium lauryl sulphate through the human epidermis was investigated using 5-fluorouracil as a hydrophilic model permeant and three compounds belonging to the phenylalcohols: 2-phenyl-ethanol, 4-phenyl-butanol and 5-phenyl-pentanol. The lipophilicity values of the compounds ranged from log Poct -0.95 to 2.89. The effect of the enhancer concentration was also studied. Skin pretreatment with aqueous solutions of the three enhancers did not increase the permeability coefficient of the most lipophilic compound (log Poct = 2.89). For the other compounds assayed, the increase in the permeability coefficients depended …