Computational modeling of cadmium sulfide deposition in the CdS/CdTe solar cell manufacturing process

2013 Spring.Includes bibliographical references.A thin film CdS/CdTe solar cell manufacturing line has been developed in the Photovoltaic Materials Engineering Lab at Colorado State University. This system incorporates multiple stations using NiCr embedded heaters in graphite crucibles to successively sublimate layers of different photovoltaic materials onto glass substrates. Times, temperatures and chemical compositions of these layers can be varied or excluded according to the desired characteristics of the 3" x 3" solar cell sample. Though the tool allows for flexibility and variability of materials, the uniformity of material deposition remains one of the largest sources of performance variability between samples. Computational Fluid Dynamics (CFD) programs have been used previously to predict the thermal performance of the embedded heaters and to ensure thermal uniformity in each of the heated deposition pockets. The thermal modeling used in the designing of these sources has been proven to be within 2.5% of the experimentally measured temperatures in laboratory and industrial applications. Building off of the thermal modeling effort, CFD models were created to model the sublimation, vapor transport and film deposition that occurs within the CdS source. Fluid models of the CdS source were created to accurately reflect the current deposition technique with the intent of predicting future deposition uniformity during the evaluation process for new source designs. The developed model was able to accurately predict film growth in an untested source in which the uniformity of the film deposition was increased by over 70%. These models were created using ANSYS Fluent, and utilized Arrhenius reaction rate equations to describe the sublimation and condensation reactions. Modeling results showed a strong correlation with the experimental data

Multiple Mediations in Zora Neale Hurston's Mules and Men

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67224/2/10.1177_0308275X9301300404.pd

Abstracts and classification of graduate studies, submitted at Boston University, on the slow learning child

Thesis (M.A.)--Boston Universit

A Logical Model Provides Insights into T Cell Receptor Signaling

Cellular decisions are determined by complex molecular interaction networks. Large-scale signaling networks are currently being reconstructed, but the kinetic parameters and quantitative data that would allow for dynamic modeling are still scarce. Therefore, computational studies based upon the structure of these networks are of great interest. Here, a methodology relying on a logical formalism is applied to the functional analysis of the complex signaling network governing the activation of T cells via the T cell receptor, the CD4/CD8 co-receptors, and the accessory signaling receptor CD28. Our large-scale Boolean model, which comprises 94 nodes and 123 interactions and is based upon well-established qualitative knowledge from primary T cells, reveals important structural features (e.g., feedback loops and network-wide dependencies) and recapitulates the global behavior of this network for an array of published data on T cell activation in wild-type and knock-out conditions. More importantly, the model predicted unexpected signaling events after antibody-mediated perturbation of CD28 and after genetic knockout of the kinase Fyn that were subsequently experimentally validated. Finally, we show that the logical model reveals key elements and potential failure modes in network functioning and provides candidates for missing links. In summary, our large-scale logical model for T cell activation proved to be a promising in silico tool, and it inspires immunologists to ask new questions. We think that it holds valuable potential in foreseeing the effects of drugs and network modifications

Feasibility of a large cohort study in sub-Saharan Africa assessed through a four-country study

Background: Large prospective epidemiologic studies are vital in determining disease etiology and forming national health policy. Yet, such studies do not exist in sub-Saharan Africa (SSA) notwithstanding the growing burden of chronic diseases. Objective: We explored the feasibility of establishing a large-scale multicountry prospective study at five sites in four sub-Saharan countries. Design: Based on country-specific considerations of feasibility, Nigeria enrolled health care professionals, South Africa and Tanzania enrolled teachers, and Uganda enrolled village residents at one rural and one periurban site each. All sites used a 6-month follow-up period but different approaches for data collection, namely standardized questionnaires filled out by participants or face-to-face interviews. Results: We enrolled 1415 participants from five sites (range 200–489) with a median age of 41 years. Approximately half had access to clean-burning cooking fuel and 70% to piped drinking water, yet 92% had access to a mobile phone. The prevalence of chronic diseases was 49% among 45- to 54-year-olds and was dominated by hypertension (21.7% overall) – ranging from 4.5 to 31.2% across sites – and a serious injury in the past 12 months (12.4% overall). About 80% of participants indicated willingness to provide blood samples. At 6-month follow-up, 68% completed a questionnaire (45 to 96% across sites) with evidence that mobile phones were particularly useful. Conclusions: Our pilot study indicates that a large-scale prospective study in SSA is feasible, and the burden of chronic disease in SSA may already be substantial necessitating urgent etiologic research and primary prevention

Homicide and geographic access to gun dealers in the United States

<p>Abstract</p> <p>Background</p> <p>Firearms are the most commonly used weapon to commit homicide in the U.S. Virtually all firearms enter the public marketplace through a federal firearms licensee (FFL): a store or individual licensed by the federal government to sell firearms. Whether FFLs contribute to gun-related homicide in areas where they are located, in which case FFLs may be a homicide risk factor that can be modified, is not known.</p> <p>Methods</p> <p>Annual county-level data (1993–1999) on gun homicide rates and rates of FFLs per capita were analyzed using negative binomial regression controlling for socio-demographic characteristics. Models were run to evaluate whether the relation between rates of FFLs and rates of gun homicide varied over the study period and across counties according to their level of urbanism (defined by four groupings, as below). Also, rates of FFLs were compared against FS/S – which is the proportion of suicides committed by firearm and is thought to be a good proxy for firearm availability in a region – to help evaluate how well the FFL variable is serving as a way to proxy firearm availability in each of the county types of interest.</p> <p>Results</p> <p>In major cities, gun homicide rates were higher where FFLs were more prevalent (rate ratio [RR] = 1.70, 95% CI 1.03–2.81). This association increased (p < 0.01) from 1993 (RR = 1.69) to 1999 (RR = 12.72), due likely to federal reforms that eliminated low-volume dealers, making FFL prevalence a more accurate exposure measure over time. No association was found in small towns. In other cities and in suburbs, gun homicide rates were significantly lower where FFLs were more prevalent, with associations that did not change over the years of the study period. FFL prevalence was correlated strongly (positively) with FS/S in major cities only, suggesting that the findings for how FFL prevalence relates to gun homicide may be valid for the findings pertaining to major cities but not to counties of other types.</p> <p>Conclusion</p> <p>Modification of FFLs through federal, state, and local regulation may be a feasible intervention to reduce gun homicide in major cities.</p