RESUMEN
The time-dependent transport through a nanoscale device consisting of a single spin-degenerate orbital with on-site Coulomb interaction, coupled to two leads, is investigated. Various gate and bias voltage time dependences are considered. The key and new point lies in the proposed way to avoid the difficulties of the usual heavy computation when dealing with two-time Green's functions within the Keldysh formalism. The time-dependent retarded dot Green's functions are evaluated, in an efficient manner within a non-canonical Hubbard I approximation. Calculations of the time-dependent current are then presented in the wide-band limit for different parameter sets. A comparison between the method and the Hartree-Fock approximation is performed as well. It is shown that the latter cannot account reliably for dynamical aspects of transport phenomena.
Asunto(s)
Transporte de Electrón , Electrones , Nanocables/química , Puntos Cuánticos , Teoría Cuántica , Simulación por Computador , Modelos Químicos , Factores de TiempoRESUMEN
Proliferative vitreoretinopathy (PVR), the most serious complication causing retinal detachment surgery to fail, is one of the leading causes of vision-loss in developed countries. The pharmaceutical treatment of this disease, located in the posterior segment of the eye, is problematic because it is difficult to achieve effective drug levels in the vitreous and the retina through conventional forms of administration (topical or systemic). Intravitreal injections can deliver drugs to the retina without the side-effects associated with systemic administration. However, because PVR is a long-term complication and the half-life of most drugs in the vitreous cavity is short, repeated injections are needed but this can cause complications. Recent advances in ocular drug delivery methods and the development of novel bioactive compounds could lead to new ways for the treatment of PVR. This review will summarize recent literature concerning intraocular drug delivery of biopharmaceutical agents for the treatment and prevention of PVR.
Asunto(s)
Antiinflamatorios/administración & dosificación , Antimetabolitos Antineoplásicos/administración & dosificación , Sistemas de Liberación de Medicamentos/métodos , Aceites de Silicona , Vitreorretinopatía Proliferativa/tratamiento farmacológico , Animales , Antiinflamatorios/uso terapéutico , Antimetabolitos Antineoplásicos/uso terapéutico , Coloides , Preparaciones de Acción Retardada , Implantes de Medicamentos , Humanos , Inyecciones , Liposomas , Microesferas , Soluciones Oftálmicas , Conejos , Cuerpo VítreoRESUMEN
A method for checking the purity of N-acyl aminonaphthalene disulphonic acid derivatives was required for a systematic study of the anti-human immunodeficiency virus activity of these agents. We describe the use of thin-layer chromatography and flame ionization detection for the separation of these compounds, which are difficult to analyse by conventional methods. All the samples were prepared in methanol solutions (1 microliter) containing 5 micrograms of aminonaphthalene derivative. These samples were applied to each type SIII Chromarod by a single injection and developed with pure methanol or a methanol-chloroform-ammonium hydroxide (35:55:10, v/v/v) solvent system.
Asunto(s)
Antivirales/análisis , VIH/efectos de los fármacos , Naftalenos/análisis , Ácidos Sulfónicos/análisis , Antivirales/farmacología , Cromatografía en Capa Delgada , Ionización de Llama , Naftalenos/farmacología , Ácidos Sulfónicos/farmacologíaRESUMEN
Tartrate resistant acid phosphatase (TRAP) is considered as an enzyme marker for osteoclasts and their precursors. A cytomorphometric study of the osteoclastic population was made after TRAP staining on transiliac bone biopsies from 10 human volunteers, and the diameter of each TRAP positive profile was determined with an automatic image analyser. The frequency distribution of the cell diameter followed a lognormal law. TRAP positive cells along bone trabeculae belong to a homogeneous osteoclastic population.
Asunto(s)
Osteoclastos/citología , Fosfatasa Ácida/análisis , Adulto , Histocitoquímica , Humanos , Masculino , Osteoclastos/enzimología , Tartratos/farmacologíaRESUMEN
The effect of seminal fluid upon human spermatozoa was analyzed using in vitro chromatin decondensation and automated image analysis. A number of specimen portions processed after incubation in seminal fluid showed different total mean areas as compared to the corresponding portions processed immediately. Comparison of the results obtained with and without delay showed that the incubation in seminal fluid promoted decondensation in some cases, but retarded it in others. Thus, the seminal fluid stabilized the chromatin condensation in some spermatozoa, but not all. The stabilization may be due to the influence of prostatic zinc.
Asunto(s)
Núcleo Celular/ultraestructura , Procesamiento de Imagen Asistido por Computador/métodos , Espermatozoides/ultraestructura , Núcleo Celular/fisiología , Cromatina/fisiología , Cromatina/ultraestructura , Humanos , Masculino , Vesículas Seminales/fisiología , Espermatozoides/fisiologíaRESUMEN
The authors subjected 14 human sperm samples to decondensation in vitro. They analyzed the images of a total of 9,681 objects as a function of time of decondensation. The discussion bears on the heterogeneity of the process of chromatin decondensation in human spermatozoa, on the influence of the zinc/fructose ratio in the seminal fluid and on the role of the period during which the spermatozoa are left in contact with the fluid.
Asunto(s)
Núcleo Celular/ultraestructura , Espermatozoides/ultraestructura , Núcleo Celular/metabolismo , Cromatina/metabolismo , Humanos , Técnicas In Vitro , Cinética , Masculino , Semen/metabolismo , Espermatozoides/metabolismo , Zinc/metabolismoRESUMEN
Between the first stage: differentiation of the human spermatozoa from spermatid in testicle, and the second one: formation of male pronucleus in ovum, the nucleus of spermatozoa undergoes a chromatin condensation and a chromatin decondensation mechanism. Besides it is possible to get this decondensation mechanism in vitro by putting spermatozoa into specific solution with the purpose of carry out an image analysis. The aim of this study was to manage a quantitative analysis of the in vitro nuclear chromatin decondensation of human spermatozoa with an image analyzer of T.A.S. "texture analysis system".