Semaphorin 3d Signaling in Cardiovascular Development

Development of the heart is an intricate and complex process. Crucial to this process is vascular patterning and the signals that properly guide developing vessels. Consequences of improper patterning can be severe, including life-threatening congenital heart defects. In this dissertation, I investigate the role of the secreted guidance molecule semaphorin 3d (Sema3d) in cardiovascular patterning during development, and attempt to dissect the molecular mechanisms involved in Sema3d signaling. Using loss-of-function genetic experiments in mice, I model multiple forms of congenital heart defects such as total anomalous pulmonary venous connections, transposition of the great arteries, and congenital abnormalities of the coronary vessels. These mouse models are powerful tools, which I use to investigate the etiology and morphogenesis of these disorders. Critical to understanding these congenital defects in these models is precisely deciphering the cellular and molecular mechanisms involved. I show how Sema3d affects the motility, migration, and adhesion of endothelial cells through a process of cytoskeletal reorganization, and I identify multiple molecules in the Sema3d signaling pathway, including a novel holoreceptor comprised of the receptor tyrosine kinase ErbB2 and semaphorin receptor neuropilin 1. Elucidating the precise mechanisms of normal vascular development along with pathologic processes is a necessary step towards future interventions and possible therapeutics

Theory and simulation of electronic and optical properties of charged defects in two-dimensional semiconductors

Charged defects are frequently observed in quasi two-dimensional (2D) semiconductors such as monolayer transition-metal dichalcogenides (TMDCs) and few-layer black phosphorus (BP), and can have a significant effect on the performance of such materials in transport and optical applications. To aid the development of nanoscale devices fabricated using 2D materials, a detailed understanding of charged defects in these systems is needed. In this thesis, isolated charged defects are modelled in 2D semiconductors using the tight-binding approach which allows the use of large supercells which are required to capture the bound states that arise. The screened defect potential is described through an external potential determined via first-principles random-phase approximation. The binding energies and wavefunctions of bound states induced by charged defects in monolayer forms of MoS$_2$, WS$_2$, and BP as well as bilayer BP, were studied and the effect of varying the defect charge, defect height and the dielectric constant of possible substrates was investigated. It was found that for shallow defects in TMDCs, the binding energies of bound states can be mostly understood using effective mass theory. However, the presence of multiple low-energy valleys in the conduction and valence bands with different effective masses results in an interplay and competition between defect levels originating from different valleys. This results in resonant states that hybridise with the continuum bands, which has implications for transport, and results in the optical conductivity exhibiting excitonic resonances at energies below the optical band gap. Applying a similar analysis to monolayer BP, it was found that the substrate dielectric constant presents a promising means of control over both the donor and acceptor binding energies. In both monolayer and bilayer BP, it was found that the large difference between the armchair and zigzag effective masses of holes and electrons results in highly anisotropic wavefunctions of the defect states.Open Acces

Infant Mortality Trends and Differentials in Iran

This paper is about trends and differentials in infant mortality in Iran. There is very little known about the topic of infant mortality in Iran. The dearth of knowledge about infant mortality in Iran is mainly due to lack of data. There is no reliable vital registration data as a large number of infant deaths in rural areas and small towns go without registration. Under such situation the best source for studying infant mortality is retrospective data from demographic surveys. In this paper I analyze data from Iran Fertility Survey of 1976-77 to examine the levels, trends, and differentials in infant mortality since 1947 . A declining trend in infant mortality is observed since the 1950\u27s and a remarkable decline is reported by 1992 . However, they are consistent regional and rural-urban, socioeconomic, and demographic differences in the rate of infant mortality . The paper presents and discusses results from logistical regression analysis of the determinants of infant mortality and their implications for future infant mortality decline in Iran

A Study of Pattern and variation of Alcohol and Drug Abuse in A Predominantly Black College

Introduction In recent years college enrollment has been considered as a high risk activity as measured by the increase in the illegal drug and alcohol abuse on campuses around the country. While there is general knowledge about high rate of alcohol and drug abuse across campuses, there is not much known about variation in terms of geographic location, ethnic composition, andregional/cultural background. This study is about pattern and variation of alcohol abuse in a predominantly black university. Since the student body includes a relatively large size of students from other ethnic groups, the setting provides for exploring ethnic/racial differences in alcohol and drug abuse among students

How to find out what’s really going on: understanding impact through participatory process evaluation

This article considers the contribution participatory process evaluation can make to impact assessment, using a case study of a study carried out to evaluate how a Kenyan nutrition education program had brought about change in the nutritional status of children and in their and their parents’ understanding and practices. Using Bhola’s three dimensions of impact—“impact by design”, “impact by interaction”, and “impact by emergence”—focuses not just on what changes as an intended result of an intervention, but on how change happens and how positive changes can be sustained. The principal focus of the article is methodological and as such it describes in some detail the development of a sequence of participatory visualization and discussion methods and their application with a range of stakeholders, from program staff in the headquarters of the implementing agency, to local government officials, front-line program workers, and beneficiaries. It suggests that the use of a participatory approach can enable researchers and evaluators to gain a fuller picture of incidental and unintended outcomes arising from interventions, making participatory process evaluation a valuable complement to other impact assessment methodologies