Weighted estimation of the dependence function for an extreme-value distribution

Bivariate extreme-value distributions have been used in modeling extremes in environmental sciences and risk management. An important issue is estimating the dependence function, such as the Pickands dependence function. Some estimators for the Pickands dependence function have been studied by assuming that the marginals are known. Recently, Genest and Segers [Ann. Statist. 37 (2009) 2990-3022] derived the asymptotic distributions of those proposed estimators with marginal distributions replaced by the empirical distributions. In this article, we propose a class of weighted estimators including those of Genest and Segers (2009) as special cases. We propose a jackknife empirical likelihood method for constructing confidence intervals for the Pickands dependence function, which avoids estimating the complicated asymptotic variance. A simulation study demonstrates the effectiveness of our proposed jackknife empirical likelihood method.Comment: Published in at http://dx.doi.org/10.3150/11-BEJ409 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Controlled release of paclitaxel from a self-assembling peptide hydrogel formed in situ and antitumor study in vitro

Background: A nanoscale injectable in situ-forming hydrogel drug delivery system was developed in this study. The system was based on a self-assembling peptide RADA16 solution, which can spontaneously form a hydrogel rapidly under physiological conditions. We used the RADA16 hydrogel for the controlled release of paclitaxel (PTX), a hydrophobic antitumor drug. Methods: The RADA16-PTX suspension was prepared simply by magnetic stirring, followed by atomic force microscopy, circular dichroism analysis, dynamic light scattering, rheological analysis, an in vitro release assay, and a cell viability test. Results: The results indicated that RADA16 and PTX can interact with each other and that the amphiphilic peptide was able to stabilize hydrophobic drugs in aqueous solution. The particle size of PTX was markedly decreased in the RADA16 solution compared with its size in water. The RADA16-PTX suspension could form a hydrogel in culture medium, and the elasticity of the hydrogel showed a positive correlation with peptide concentration. In vitro release measurements indicated that hydrogels with a higher peptide concentration had a longer half-release time. The RADA16-PTX hydrogel could effectively inhibit the growth of the breast cancer cell line, MDA-MB-435S, in vitro, and hydrogels with higher peptide concentrations were more effective at inhibiting tumor cell proliferation. The RADA16-PTX hydrogel was effective at controlling the release of PTX and inhibiting tumor cell growth in vitro. Conclusion: Self-assembling peptide hydrogels may work well as a system for drug delivery

Adicción al teléfono móvil y ansiedad social entre adolescentes chinos: papel mediador de los problemas interpersonales

Objectives:Mobile phone addiction (MPA) has frequently report-ed to be correlated with psychological disorders such as depression, stress and anxiety among young population. However, the extent to which these factors are correlated with MPA and the potential mechanism underlying those relationships are conclusive. This study aimed to investigate the as-sociation between MPA level and social anxiety among Chinese adolescents, and examined the mediation effect of interpersonal problems between them. Methods: A sample of 1027 school-based students selected by a stratified-cluster random sampling method responded to questionnaires regarding MPA Index, Social Interaction Anxiousness Scale, Interpersonal Problems Inventory, and demographic variables. Spearman correlation and multiple linear regression analyses were performed to investigate the extent of the association between MPA and social anxiety, and Sobel test and bootstrapping sampling confirmed the mediating role ofinterpersonal problems.Results: Of all students in our study, 5.9% were MPA, and MPA score was positively correlated with social anxiety after controlled for de-mographic variables in the adjusted model. Multiple mediation regression analysis revealed that the interpersonal problem was a significant partial mediator between MPA and social anxiety. Conclusion:The MPA adolescents were a subgroup population who need to pay more attention to prevent social anxiety. Improving interpersonal problems might be aneffec-tive approach to deal with MPA-induced social anxiety in adolescents.Objetivos: Con frecuencia se ha informado que la adicción al teléfono móvil (MPA) está correlacionada con trastornos psicológicos como la depresión, el estrés y la ansiedad entre la población joven. Sin embargo, el grado en que estos factores se correlacionan con el AMP y el mecanismo potencial subyacente a esas relaciones son concluyentes. Este estudio tuvo como objetivo investigar la asociación entre el nivel de AMP y la ansiedad social entre adolescentes chinos y examinó el efecto de mediación de los problemas interpersonales entre ellos. Métodos: Una muestra de 1027 estudiantes escolares seleccionados mediante un método de muestreo aleatorio por conglomerados estratificados respondió a cuestionarios sobre el índice MPA, la escala de ansiedad por interacción social, el inventario de problemas interpersonales y variables demográficas. Se realizaron análisis de correlación de Spearman y de regresión lineal múltiple para investigar el alcance de la asociación entre la AMP y la ansiedad social, y la prueba de Sobel y el muestreo de arranque confirmaron el papel mediador de los problemas interpersonales. Resultados: De todos los estudiantes de nuestro estudio, el 5,9% tenían AMP, y la puntuación de AMP se correlacionó positivamente con la ansiedad social después de controlar las variables demográficas en el modelo ajustado. El análisis de regresión de mediación múltiple reveló que el problema interpersonal era un mediador parcial significativo entre la AMP y la ansiedad social. Conclusión: Los adolescentes del AMP fueron un subgrupo de población que necesita prestar más atención para prevenir la ansiedad social. Mejorar los problemas interpersonales podría ser un enfoque eficaz para abordar la ansiedad social inducida por el AMP en los adolescentes

Fermentation of pretreated corncob hemicellulose hydrolysate to ethanol by Candida shehatae and Saccharomyces cerevisiae

To investigate the effect of unknown fermentation inhibitors in corncob hemicellulose acid hydrolysate processed by pretreatment and detoxification on fermentation, corncob hemicellulose acid hydrolysate and artificially prepared hydrolysate were fermented in parallel by Candida shehatae YHFK-2. The results show that fermentability of corncob hemicellulose acid hydrolysate was better than that of the artificially prepared hydrolysate and scale-up of C. shehatae YHFK-2 fermentation was done, which showed that ethanol production in the fermenter was obviously much more than that in flasks. In addition, C. shehatae YHFK-2 and Saccharomyces cerevisiae W5 were used for mixed fermentation of corncob hemicellulose acid hydrolysate, which was done for exploring the possibility of efficiently increasing ethanol production.Key words: Ethanol, corncob hemicellulose acid hydrolysate, fermentation property, stability, mixed fermentation