Mode Repulsion and Mode Coupling in Random Lasers

We studied experimentally and theoretically the interaction of lasing modes in random media. In a homogeneously broadened gain medium, cross gain saturation leads to spatial repulsion of lasing modes. In an inhomogeneously broadened gain medium, mode repulsion occurs in the spectral domain. Some lasing modes are coupled through photon hopping or electron absorption and reemission. Under pulsed pumping, weak coupling of two modes leads to synchronization of their lasing action. Strong coupling of two lasing modes results in anti-phased oscillations of their intensities.Comment: 13 pages, 4 figure

Influence of Spatial Correlations on the Lasing Threshold of Random Lasers

The lasing threshold of a random laser is computed numerically from a generic model. It is shown that spatial correlations of the disorder in the medium (i.e., dielectric constant) lead to an increase of the decay rates of the eigenmodes and of the lasing threshold. This is in conflict with predictions that such correlations should lower the threshold. While all results are derived for photonic systems, the computed decay rate distributions also apply to electronic systems

Phenology and ripening of Vitis vinifera L. grape varieties in São Joaquim, southern Brazil: a new South American wine growing region

This study investigated the phenology and the ripening characteristics of Vitis vinifera grapes Cabernet Franc, Merlot, Sangiovese and Syrah in two consecutive vintages (2006 and 2007) in order to evaluate the adaptation of these recently cultivated varieties in São Joaquim, Santa Catarina State, Brazil. The phenological data observed, budburst, blooming, setting, véraison and harvest were monitorated. In order to monitor the ripening levels of pH, total acidity, total soluble solids, maturation Índex, total monomeric anthocyanins, total polyphenols index and color index were analyzed.The results show that the phenological cycle from budburst to harvest occurred within a frame time of 191 and 219 days and the heat summation requirements varied between 1,161 and 1,340 GDD. The summing of the GDD results during the phenological cycle of the grapevines (budburst - harvest) characterizes São Joaquim-SC as "Region I" (< 1,389 GDD), that is, a "cold region" in terms of the Winkler Regions.The climatic parameters influenced the grapevine phenology and the grape ripening. The results showed that these different grape varieties had typical characteristics at maturity and indicated that they have potential for the production of fine wines, suggesting that São Joaquim-SC is suitable for Vitis vinifera grape growing.Se estudio la fenología y las características de maduración de uvas Vitis vinifera Cabernet Franc, Merlot, Sangiovese y Syrah en dos vendimias consecutivas (2006 y 2007), con el fin de evaluar la adaptación de estas variedades cultivadas recientemente en San Joaquim, Santa Catarina (Brasil). Las características fenológicas observadas fueron: brotación, floración, cuajado, envero y vendimia. Se analizaron los niveles de maduración de pH, acidez total, sólidos solubles totales, índice de maduración, el total de antocianos, índice de los polifenoles totales y el índice de color. Los resultados muestran que el ciclo fenológico desde la brotación hasta la vendimia se produjo entre 191 y 219 días y con requerimientos de acumulación de calor de 1.161 y 1.340 grados día. El resumen de los resultados de suma térmica durante el ciclo fenológico de la vid (brotación -cosecha) caracteriza a São Joaquim-SC como "Region I" (<1.389 grados día), es decir, una "zona fría", en términos de las Regiones Winkler. Los parámetros climáticos influyeron en la fenología de la vid y la maduración de la uva. Los resultados mostraron que estas variedades de uva tenían características típicas en la madurez y que ellos tienen un potencial para la producción de vinos finos, lo que sugiere que San Joaquim-SC es adecuado para el crecimiento de uvas Vitis vinifera

Chemical characteristics of grape juices from different cultivar and rootstock combinations.

The objective of this work was to evaluate the influence of different combinations of grape cultivars and rootstocks on chemical characteristics of grape juices. Six treatments were evaluated, consisting of combinations between the Isabel Precoce and BRS Cora grape cultivars and the 'IAC 766', 'IAC 313', and 'IAC 572' rootstocks. Approximately 10 L of juice were obtained per treatment. Analyses of color, total soluble solids content, pH, anthocyanins, total phenolics, total sugars, and quantification and identification of biogenic amines by HPLC were performed. Biogenic amines, such as putrescine, cadaverine, spermidine, and spermine, were found in all evaluated cultivars. By principal component analysis (PCA), treatments can be divided into two groups, according to the cultivar. Juices obtained from 'Isabel Precoce' are characterized by higher levels of total sugar content and soluble solids; however, juices from 'BRS Cora' are positively correlated with phenolic content, anthocyanins, and color and acidity parameters. The differences found by PCA for juices from the Isabel Precoce and BRS Cora cultivars indicate that, regardless of the rootstock used, the most important factor in the chemical characterization of juices is the grape cultivar.2014DOI: 10.1590/S0100-204X201400070000