Fractional Talbot effect in a Selfoc gradient-index lens

The fractional Talbot effect is demonstrated inside a standard 0.25-pitch Selfoc gradient-index lens under uniform illumination. Comparisons with theoretical expressions of positions and magnification of fractional Talbot images are given.

Talbot effect interpreted by number theory

An interpretation of the Talbot effect in a tapered gradient-index medium by number theory as the output/input relationship between the integer and the noninteger difference of position and the slope of rays is presented. Unit cell and transverse magnification for Talbot images are evaluated, and two criteria for angular magnification are defined. The study is particularized to a finite set of diffracted rays.

Validation of a UV spectrophotometric method for the determination of melatonine in solid dosage forms

The aim of the work described in this paper was to provide a fast, easy, inexpensive, precise, and accurate method for the determination of melatonine in solid pharmaceutical dosage forms. The developed method is based on a UV first-derivative spectrophotometric determination, which exhibits excellent linearity in aqueous solutions (r2 = 0.996) for analyte concentrations of 1.5-4.5 mg/dL within a pH range of 5-9. Neither excipients present in the formulation nor indole adulterants, such as tryptophan (up to 5%), interfere with the assay. A study of variation parameters showed that sonication temperature was the main factor for successful determination. At temperatures of <45 degrees C, the sample dissolved completely, and accurate spectrophotometric measurements were obtained. A study was conducted of all the parameters established by the United States Pharmacopeia, 23rd Rev., to validate an analytical method for a solid pharmaceutical form, i.e., linearity, range, accuracy, precision, and specificity. All the parameters were in accordance with the acceptance criteria of the Comité de Guías Oficiales de Validación de la Dirección General de Control de Insumos para la Salud de Méjico. In addition, robustness and content uniformity tests were performed to substantiate the usefulness of the method.

Nonparaxial diffraction-limited propagation of light in a graded-index planar medium with a hyperbolic secant refractive-index profile

Nonparaxial diffraction-limited propagation of light with amplitude distribution in hyperbolic functions through an inhomogeneous planar medium with a hyperbolic secant refractive-index profile is studied by means of the stationary phase method. The irradiance distribution at geometrical shadow, edge of shadow, and a geometrically illuminated region is analyzed for a particular case.

Coupling of planar waveguides with hyperbolic secant refractive-index profiles by butt joining: beam-size controller design

An analysis of the butt-joining coupling between two inhomogeneous planar optical waveguides with hyperbolic secant refractive-index profiles is made from the point of view of geometrical optics. Furthermore, the design of a new device to contract or expand a collimated beam is presented, and a relationship between sizes of the input and output beams is obtained.

[Effect of insulin-like growth factor I on HLA-DR antigen expression in cultured human thyrocytes: a component of the autoimmune process?]

The aim of this study was to determine whether IGF-1 and INS are able to induce HLA-DR antigen expression (AgHLA-DR) in cultured human thyrocytes. Cytotoxicity assay in thyroid epithelial cells (cultured for 7 days to avoid spontaneous antigen expression) from 14 patients operated due to different thyroidal diseases, was used to assess HLA-DR expression. AgHLA-DR was reinduced adding IFN-delta, IGF-1 or INS to the culture media, alone, combined or associated with TSH or TBII. Both IGF-1 and INS induced HLA-DR expression in a similar way as IFN-delta did, and the response was enhanced with their combination, suggesting that they have different sites of action. Their association with TSH or TBII further augmented the response. To determine if IGF-1 acts via lymphocyte IFN-delta secretion, peripheral lymphocytes from 5 normal subjects were cultured with and without IGF-1 and the supernatant was used as stimulator, observing a stimulation similar to that induced by IFN-delta. This finding supports the hypothesis that IGF-1 acts stimulating a specific tyrosine kinase protein (p56 1ck) which is located in T lymphocyte receptors. According to our results we can conclude that, at least in vitro, both IGF-1 and INS play a role in the immune process, probably exerting a paracrine effect on autoimmunity, acting as perpetuating factors.

[Spontaneous expression of class II (HLA-DR) molecules in thyroid pathology]

The spontaneous expression of Class II molecules (HLA-DR) was studied in cultured thyrocytes obtained from patients with Graves Disease (n = 7), Hashimoto's Thyroiditis (n = 5), euthyroid nodular goiter, (n = 12), papillary carcinoma (n = 5), and laryngeal carcinoma (3 normal thyroid glands). If nodular goiters and papillary carcinoma are of autoimmune origin, as Graves Disease and Hashimoto's Thyroiditis, they should spontaneously express HLA-DR antigen on their cell surface as this has been considered one of the initial steps of autoimmunity. The study was performed using the cytotoxicity assay. Immediately after the thyroid glands were obtained, thyrocytes were labelled with 51-Cr and incubated overnight; the cells were destroyed by adding monoclonal antiHLA-DR antibody and rabbit complement. The cytotoxicity index (CI% + SD) which reflects 51-Cr release from lyzed cells was used to measure antigen expression. While Graves Disease's and Hashimoto's Disease's thyrocytes expressed HLA-DR in high proportion, normal thyrocytes and thyroid cells from other diseases did so in minimal proportion (28.12 +/- 10.71 vs 2.26 +/- 2.32, p < 0.001). These findings strongly suggest that nodular goiters and papillary carcinoma are not of autoimmune origin since they are unable to express HLA-DR on their cell surface. It is postulated that HLA-DR expression is the result of the influence of T lymphocytes previously sensitized to thyroid antigens.