The application of parabolic trough technology under Jordanian climate

Parabolic trough solar thermal power plants are a proven technology in the utility scale since mid of the eighties. Between 1984 and 1991 nine power plants with an overall capacity of 354 MW have been installed in the Mojave Desert in California. Since, these power plants can be equipped with a thermal storage or a fossil back-up they offer a fully dispatchable electricity generation capacity. This technology will be a very interesting near term option for countries with high solar irradiation levels and small resources of fossil fuels like Jordan.This paper, discusses the use of parabolic trough solar thermal power plants for electricity production under Jordanian climate for two different sites (Amman, and Ma'an). An analysis of the daily power output, direct normal irradiation and the efficiency for the two sites has been carried out. The results showed that Ma'an site would be preferred than Amman site, so that it is recommended to erect the Parabolic Trough Concentrator (PTC) plant in the southern region of Jordan.Also this study aims to encourage the Jordanian government and the private sector to implement the solar thermal power plants for future expansion of power sector due to the increasing electricity demand and environmental degradation.     

Optimization of band structure and quantum-size-effect tuning for two-photon absorption enhancement in quantum dots

The two-photon absorption, 2PA, cross sections of PbS quantum dots, QDs, are theoretically and experimentally investigated and are shown to be enhanced with increasing quantum confinement. This is in contrast to our previous results for CdSe and CdTe QDs where the reduced density of states dominated and resulted in a decrease in 2PA with a decrease in QD size. Qualitatively this trend can be understood by the highly symmetric distribution of conduction and valence band states in PbS that results in an accumulation of allowed 2PA transitions in certain spectral regions. We also measure the frequency nondegenerate 2PA cross sections that are up to five times larger than for the degenerate case. We use a k·p four-band envelope function formalism to model the increasing trend of the two-photon cross sections due to quantum confinement and also due to resonance enhancement in the nondegenerate case.     

A mixture-model approach to linking ADHD to adolescent onset of illicit drug use.

Prior research findings have been mixed as to whether attention-deficit/hyperactivity disorder (ADHD) is related to illicit drug use independent of conduct problems (CP). With the current study, the authors add to this literature by investigating the association between trajectories of ADHD symptoms across childhood and adolescence and onset of illicit drug use, with and without controlling for CP. In a longitudinal panel study of a community sample of 754 girls and boys recruited in kindergarten, this research question was examined with a combination of growth mixture modeling (to model parent-reported ADHD symptom trajectories) and survival analysis (to model youth-reported initiation of illicit drug use). Results revealed a 3-class model of ADHD trajectories, with 1 class exhibiting no or minimal symptoms throughout childhood and adolescence, another class showing a convex shape (an increase, then a decrease in symptoms) across time, and a third class showing a concave shape (a decrease, then a slight increase in symptoms) over time. The concave-trajectory class demonstrated significantly earlier onset of illicit drug use than the minimal-problem class, with the convex-trajectory class falling between (but not significantly different from either of the other two classes). These results did not change when the authors added CP to the model as a covariate. Implications of findings for theory and practice are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modified angström exponent for the characterization of submicrometer aerosols

The classical Angstr?m exponent is an operationally robust optical parameter that contains size information on all optically active aerosols in the field of view of a sunphotometer. Assuming that the optical effects of a typical (radius) size distribution can be approximated by separate submicrometer and supermicrometer components, we show that one can exploit the spectral curvature information in the measured optical depth to permit a direct estimation of a fine-mode (submicrometer) Angstr?m exponent (alpha(f)) as well as the optical fraction of fine-mode particles (eta). Simple expressions that enable the estimation of these parameters are presented and tested by use of simulations and measurements.     

Interaction of Salmonella typhi strains with cultured human monocyte-derived macrophages

Human monocyte-derived macrophages (MDM) provided this laboratory with a tool to develop a primary-cell assay for evaluating the relative virulence of newly constructed Salmonella typhi carrier strains. In this study, the interaction with and survival within MDM were compared for delta aroA143-attenuated strains, wild-type virulent strains, and the current oral-vaccine strain, Ty21a.     

Design Families and Design Individuals

This paper discusses design families and design individuals. Phase space is introduced to complement state space. Phase transition as a generic method of generating design families is proposed and then demonstrated through an example of simple designs with one component. Based on phase transition in the biological world, a development model for complex designs (with multi-components) is established, by which different phase transitions for changing complex design families are analysed and simulated. Two concepts are drawn from the biological analogy: through gene mutation and regulation the individuals of complex design systems can be varied and searched within their state space; and by changing the interpretation process of genes, the families of such systems can be explored within their phase space.