Effect of the Chameleon Scalar Field on Brane Cosmological Evolution

We have investigated a brane world model in which the gravitational field in the bulk is described both by a metric tensor and a minimally coupled scalar field. This scalar field is taken to be a chameleon with an appropriate potential function. The scalar field interacts with matter and there is an energy transfer between the two components. We find a late-time asymptotic solution which exhibits late-time accelerating expansion. We also show that the Universe recently crosses the phantom barrier without recourse to any exotic matter. We provide some thermodynamic arguments which constrain both the direction of energy transfer and dynamics of the extra dimension.Comment: 9 pages, 4 figures. To appear in Physics Letters

Synthesis and Characterization of Tungstite (WO3.H2O) Nanoleaves and Nanoribbons

An environmentally benign method capable of producing large quantities of materials was used to synthesize tungstite (WO3.H2O) leaf-shaped nanoplatelets (LNPs) and nanoribbons (NRs). These materials were simply obtained by aging of colloidal solutions prepared by adding hydrochloric acid (HCl) to dilute sodium tungstate solutions (Na2WO4.2H2O) at a temperature of 5-10oC. The aging medium and the pH of the precursor solutions were also investigated. Crystallization and growth occurred by Ostwald ripening during the aging of the colloidal solutions at ambient temperature for 24 to 48hrs. When dispersed in water, the LNPs and NRs take many days to settle, which is a clear advantage for some applications (e.g., photocatalysis). The materials were characterized using scanning and transmission electron microscopy, Raman and UV/Vis spectroscopies. The current versus voltage characteristics of the tungstite NRs showed that the material behaved as a Schottky diode with a breakdown electric field of 3.0x105V.m-1. They can also be heat treated at relatively low temperatures (300oC) to form tungsten oxide (WO3) NRs and be used as photoanodes for photoelectrochemical water splitting.Comment: 12 pages, 5 figure

Health concerns of Iranian adolescents: Protocol for a mixed methods study

Background: Adolescents have particular health and developmental needs that suggest they should neither be treated as older children nor younger adults. Objectives: The aim of this paper is to report the protocol for a mixed methods study that set out to investigate the health concerns of Iranian adolescents and their sources of health information with the goal of identifying suitable strategies to address their health concerns. Materials and Methods: This mixed methods study consists of an explanatory sequential design to be conducted in two phases. The first phase was a population-based cross-sectional survey of 915, 14-18 year old adolescents who were selected by stratified cluster random sampling method from the 22 main municipal sectors of Tehran, Iran. They completed a series of self-administered questionnaires which were analyzed using quantitative approaches. The second phase was a qualitative study in which adolescents were selected using purposeful sampling for individual in-depth semi-structured interviews on the basis of the quantitative findings from the first phase. These data, together with a literature review and data obtained through nominal group technique, would then be used to in the development of strategies to reduce adolescents' health concerns. Results: The findings of this mixed methods sequential explanatory study are expected to provide unique information about the health concerns of Iranian adolescents and their sources of information, which to date have received little attention. Conclusions: These data will provide a rich source of information that can be used by intervention programs, health professionals and policy makers in addressing the health concerns of adolescents, with the goal of facilitating a successful passage to adult life. © 2014, Iranian Red Crescent Medical Journal

Motivasi Indonesia Mengakuisisi Ladang Minyak Di Aljazair Pada Tahun 2013

This study describes the acquisition of Indonesia to the oil fields in Algiers in 2013. Themain factor is the motivation to acquire oilfields Indonesia is Indonesias economic and politicalinterests.The data was obtained from books, and from the internet. This research analyzed byusing the theory of decision making.This study explains that Indonesian policy acquired oil fields in Algeria to meet the needsof the oil in Indonesia. the existence of good relations between Indinesia and Algiers, and thechallenges of oil exploration in Indonesia.Keyword: acquisition, motivation, national interest