Exploring Interfacial Phenomena in Photovoltaic Materials Structures Using First-Principles Calculations and Beyond.

Photovoltaics are a large part of the global strategy to reduce carbon dioxide emissions. The strict processing requirements of silicon are viewed as economic barriers to larger scale deployment of solar energy. Many of these materials have photocurrents limited by dissociation of bound excited states. The separation between the photo-excited electron and the hole at the interface between the donor and acceptor material is at the core of the functional response of an organic photovoltaic (OPV) device. We therefore examine the effects of interfacial electrostatics in a semi-classical manner on these excited states for both an organic interface and a hybrid organic-inorganic interface. We use boron subphtalocyanine chloride and C60 as our organic interface wherein we also simulate the effects of thermal motion on the excited state energetics using ab initio molecular dynamics. For our hybrid interface, we use pentacene and silicon for which the applicability of our model depends on surface termination. We develop a semi-classical model for the description of dissociation between electron and hole, which takes into account the difference of dielectric constants of the materials juxtaposed at the interface, as well as the potentially polar nature of the interfacial termination. Particularly this latter effect can be exploited for device performance optimization. Using ab intio modeling, we explore possible modifications of boron subphthalocyanine chloride derivatives to control the dipole associated with these molecules and their photonic properties. We substitute the axial boron and chlorine atoms for other trivalent and halogen atoms in our derivatives. We explore boron subphthalocyanine chloride derivatives as possible organic photovoltaic materials. Possible crystal structures are predicted and their electronic and photonic properties for the proposed derivatives. We further refine the semi-classical model, leading to a quantum mechanical model based on the effective mass Schrödinger equation, which utilizes a self-consistent approach for the calculation of excited states. This model reveals that at hybrid organic/inorganic interfaces, excited electron-hole configurations transition from a regime where both reside in the donor phase to a regime where they are separated across the interface, which is controlled by the attraction between electron and hole and the band edge offset.PHDMaterials Science and EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120725/1/mjwaters_1.pd

Investigating Potential Mechanisms of Obesity by Metabolomics

Obesity is a serious health problem with an increased risk of several common diseases including diabetes, cardiovascular disease, and cancer. Metabolomics is an emerging analytical technique for systemic determination of metabolite profiles, which is useful for understanding the biochemical changes in obesity or related diseases both in individual organs and at the organism level. Increasingly, this technology has been applied to the study of obesity, complementing transcriptomics and/or proteomics analyses. Indeed, the alterations of metabolites in biofluids/tissues are direct indicators of variations in physiology or pathology. In this paper, we will examine the obesity-related alterations in significant metabolites that have been identified by metabolomics as well as their metabolic pathway associations. Issues concerning the screening of biologically significant metabolites related to obesity will also be discussed

A critical examination of property valuation variance in Dubai

This research investigates the extent and possible causes of property valuation variance in Dubai (United Arab Emirates). It complements the wide body of academic research examining valuation in new global markets. A literature review was undertaken and two questionnaire surveys circulated to local commercial property valuers. The surveys revealed that valuers in Dubai are on par with variance observed in other international case studies. The surveys found the main cause of variance to be a result of information efficiency; including sparse transactional evidence; wide yield assumptions; and a lack of standardisation in key areas of the valuation process. Individual client behavioural influences were also pertinent in the cause of valuation variance. An exam-based analysis of postgraduate real estate valuation students also highlighted a number of critical observations relating to variance and valuation methodology. The research, through an industry focus group, recommends a range of solutions to manage variance. Greater market transparency through the pooling of property data and more detail within transactional evidence would ensure more consistent valuation advice. It is expected with an improvement in temporal data the local valuation profession will be better informed and client pressure exerted when finalising the valuation figure will subside. This new research is a useful starting point to expand the range of global studies in property valuation. In addition, the findings undoubtedly assist in improving valuation practices in Dubai and wider GCC/Middle Eastern markets

Host reticulocytes provide metabolic reservoirs that can be exploited by malaria parasites

Human malaria parasites proliferate in different erythroid cell types during infection. Whilst Plasmodium vivax exhibits a strong preference for immature reticulocytes, the more pathogenic P. falciparum primarily infects mature erythrocytes. In order to assess if these two cell types offer different growth conditions and relate them to parasite preference, we compared the metabolomes of human and rodent reticulocytes with those of their mature erythrocyte counterparts. Reticulocytes were found to have a more complex, enriched metabolic profile than mature erythrocytes and a higher level of metabolic overlap between reticulocyte resident parasite stages and their host cell. This redundancy was assessed by generating a panel of mutants of the rodent malaria parasite P. berghei with defects in intermediary carbon metabolism (ICM) and pyrimidine biosynthesis known to be important for P. falciparum growth and survival in vitro in mature erythrocytes. P. berghei ICM mutants (pbpepc-, phosphoenolpyruvate carboxylase and pbmdh-, malate dehydrogenase) multiplied in reticulocytes and committed to sexual development like wild type parasites. However, P. berghei pyrimidine biosynthesis mutants (pboprt-, orotate phosphoribosyltransferase and pbompdc-, orotidine 5′-monophosphate decarboxylase) were restricted to growth in the youngest forms of reticulocytes and had a severe slow growth phenotype in part resulting from reduced merozoite production. The pbpepc-, pboprt- and pbompdc- mutants retained virulence in mice implying that malaria parasites can partially salvage pyrimidines but failed to complete differentiation to various stages in mosquitoes. These findings suggest that species-specific differences in Plasmodium host cell tropism result in marked differences in the necessity for parasite intrinsic metabolism. These data have implications for drug design when targeting mature erythrocyte or reticulocyte resident parasites

Crystallization and preliminary x-ray diffraction analysis of the unliganded human growth hormone receptor

The crystal structure of the extracellular domain of growth hormone receptor complexed to its ligand, growth hormone, has been known since 1992. However, no information exists for the unliganded form of the receptor. The human growth hormone receptor's extracellular ligand-binding domain, encompassing amino-acid residues 1 - 238, has been expressed in Escherichia coli, purified by anion ion-exchange chromatography and crystallized in its unliganded state by the hanging-drop vapour-diffusion method in 100 mM HEPES pH 7.0 containing 27.5%(w/v) PEG 5000 monomethyl ether and 200 mM ammonium sulfate as the co-precipitants. The crystals belong to the othorhombic space group C222(1), have unit-cell parameters a = 99.7, b = 112.2, c = 93.2 Angstrom and diffract to 2.5 Angstrom resolution using synchrotron radiation. The crystal structure will shed light on the nature of any conformation changes that occur upon ligand binding and will provide information to develop potential low-molecular-weight agonists/antagonists to treat clinical diseases in which the growth hormone receptor is implicated