Amorphous silicon photovoltaic modules and test devices design, fabrication and testing

In July of 1984, Hughes and JPL initiated a contract for Hughes to design, fabricate and test 10 thin film Amorphous Silicon (a-Si) photovoltaic power modules. These modules were to be 1 ft x 4 ft in size. They were to be preceded by the delivery of 10 a-Si 4 in. square test devices. This effort is very timely since thin film PV development has progressed to the point where intermediate load power applications are on the horizon. It is important to know if current a-Si submodule design and manufacturing processes yield a product that is compatible with the packaging needed to meet a 20 to 30 year life span expectancy. The term submodule is assigned to an interconnected assembly of 28 a-Si cells deposited on a 1 foot square glass superstrate. These assemblies are equipped with electrical terminations, i.e., copper tabs at the four corners of the inverted submodules. It is these submodules that are to be interconnected and packaged into power modules, as opposed to the interconnected individual crystalline cells packaged into todays PV modules. A discussion of the fabrication methods and results follows

THE ECONOMICS OF CONTROLLING INFECTIOUS DISEASES ON DAIRY FARMS

Cost effective disease control on the dairy farm can enhance productivity and subsequently profitability. Previous economic studies on animal disease have focused on production losses and evaluation of disease eradication programs and provided little guidance as to the optimal prevention action. This paper presents a theoretical model on the economics of livestock disease and develops an empirical model to determine the optimal set of control strategies for four production limiting cattle diseases: bovine viral diarrhea (BVD), enzootic bovine leukosis (EBL), Johne's Disease (JD) and neosporosis. Control functions indicating the prevalence of infection with each of the four diseases for each of the ten strategies are estimated. The optimal strategies that minimize total disease cost (direct production losses and control expenditures) are provided for each disease on the basis of farm survey results from the Maritime provinces. The results emphasize the importance of introduction checks before new animals enter the herd and adequate vaccination protection as cost-effective control strategies.Farm Management, Livestock Production/Industries,

Expectations of Field Supervisors in Kenya: Implications for Community-based Human Service Practicums

Community-based learning (CBL), which provides opportunities for undergraduate students to develop disciplinary and work-related knowledge and skills, is increasingly becoming an integral component of higher education. Similar to other countries, there is a widespread belief among employers in Kenya that there is a mismatch between university programs and labour market demands. In order to enhance the employability of graduates, many departments at a Kenyan university have incorporated work-integrated experiential learning opportunities such as practicums in the educational experience for undergraduate students. The aim of this article is to describe the expectations of field supervisors in host organisations participitating in a community-based human services program at a Kenyan University. Fifteen purposively sampled field supervisors participated in individual face-to-face interviews that included questions about their understanding of the department’s expectations of student learning activities during practicums, knowledge of the academic preparation of students in the program and challenges associated with the supervisory role. Six field supervisors exhibited some level of understanding of the expectations of their role in working with practicum students, while nine field supervisors indicated unclear expectations of the students’ practicum experience. Thematic analysis revealed key themes related to: (1) student abilities, learning goals and their contributions to the host organisations, and (2) the academic program of study and academic support available from the university faculty or staff to field supervisors. The results of our study revealed a lack of clarity around practicum expectations for most of the field supervisors interviewed and insufficient preparation of the community-based organisations to host a practicum student. Several recommendations are identified to clarify the expectations of community partner organisations and the staff providing student supervision to ensure benefits for both students and the host organisation. Results from this study can be used to inform the development or improvement of practicum opportunities focused on producing a skilled workforce

Evolutionary aspects in evaluating mutations in the melanocortin 4 receptor

More than 70 missense mutations have been identified in the human melanocortin 4 receptor (MC4R), and many of them have been associated with obesity. In a number of cases, the causal link between mutations in MC4R and obesity is controversially discussed. Here, we mined evolution as an additional source of structural information that may help to evaluate the functional relevance of naturally occurring variations in MC4R. The sequence information of more than 60 MC4R orthologs enabled us to identify residues that are important for maintaining receptor function. More than 90% of all inactivating mutations found in obese patients were located at amino acid positions that are highly conserved during 450 million years of MC4R evolution in vertebrates. However, for a reasonable number of MC4R variants, we found no correlation between structural conservation of the mutated position and the reported functional consequence. By re-evaluating selected mutations in the MC4R, we demonstrate the usefulness of combining functional and evolutionary approaches

Emergent low-symmetry phases and large property enhancements in Ferroelectric KNbO3 bulk crystals

The design of new or enhanced functionality in materials is traditionally viewed as requiring the discovery of new chemical compositions through synthesis. Large property enhancements may however also be hidden within already well-known materials, when their structural symmetry is lowered from equilibrium through a small local strain or field. This work reports on the discovery of enhanced material properties associated with a new metastable phase of monoclinic symmetry within bulk KNbO3. This phase is found to co-exist with the nominal orthorhombic phase at room temperature, and is both induced by and stabilized with local strains generated by a network of ferroelectric domain walls. While the local microstructural shear strain involved is only ~0.017%, the concurrent symmetry reduction results in an optical second harmonic generation response that is over 550% higher at room temperature.Moreover, the meandering walls of the low symmetry domains also exhibit enhanced electrical conductivity on the order of 1 S m-1. This discovery reveals a potential new route to local engineering of significant property enhancements and conductivity through symmetry lowering in bulk ferroelectric crystals

Strangeness and the discovery of quark-gluon plasma

Strangeness flavor yield s and the entropy yield S are the observables of the deconfined quark-gluon state of matter which can be studied in the entire available experimental energy range at AGS, SPS, RHIC, and, in near future, at the LHC energy range. We present here a comprehensive analysis of strange, soft hadron production as function of energy and reaction volume. We discuss the physical properties of the final state and argue how evidence about the primordial QGP emerges.Comment: 16 pages: Invited talk at 5th International Conference on Physics and Astrophysics of Quark Gluon Plasma, February 8 - 12, 2005, Salt Lake City, Kolkata, India, to appear in: Journal of Physics: Conference Serie