Synthesis of a Compact Tetralattice Heat Exchanger using Solid Freeform Fabrication and Comparison Testing Against a Tube Heat Exchanger

The challenge for Solid Freeform Fabrication (SFF) lies in fabricating complex parts that are not possible by conventional manufacturing means. The goal was to apply SFF techniques to complex geometry heat exchangers. The heat exchanger structure is modeled after the covalently bonded carbon atoms of a diamond. The tetrahedron diamond lattice, or Tetralattice, is a repeating lattice unit that forms a network of channels to form the heat exchanger. Electroforming methods creating Tetralattice were applied to synthesize an air-oil compact heat exchanger. After production, the heat exchanger was tested and compared with an industry standard heat exchanger for performance evaluation.Mechanical Engineerin

Genetic Interaction Maps in Escherichia coli Reveal Functional Crosstalk among Cell Envelope Biogenesis Pathways

As the interface between a microbe and its environment, the bacterial cell envelope has broad biological and clinical significance. While numerous biosynthesis genes and pathways have been identified and studied in isolation, how these intersect functionally to ensure envelope integrity during adaptive responses to environmental challenge remains unclear. To this end, we performed high-density synthetic genetic screens to generate quantitative functional association maps encompassing virtually the entire cell envelope biosynthetic machinery of Escherichia coli under both auxotrophic (rich medium) and prototrophic (minimal medium) culture conditions. The differential patterns of genetic interactions detected among >235,000 digenic mutant combinations tested reveal unexpected condition-specific functional crosstalk and genetic backup mechanisms that ensure stress-resistant envelope assembly and maintenance. These networks also provide insights into the global systems connectivity and dynamic functional reorganization of a universal bacterial structure that is both broadly conserved among eubacteria (including pathogens) and an important target

Modeling Shielding Designs for the Safe Operation of Neutron Generators

Boise State University recently procured Thermo Fisher Scientific P385 neutron generators to test novel sensors and materials for next generation nuclear reactors. In order to safely operate the neutron generators without exposing personnel to excess radiation, the Nuclear Regulatory Commission (NRC) requires a dosimetry study before installation. This study sought to design shielding that was not prohibitively large or expensive and which reduces dosage rates to allow 100 annual hours of operation within the NRC dose limits. Monte-Carlo N-Particle Transport code (MCNP) was used to model the generator and surrounding room. A variety of materials and geometries were investigated to determine the most efficient neutron attenuator as well as gamma ray shields. Borated polyethylene and graphite were found to be the most effective shielding while an exterior lining of lead proved necessary to decrease gamma radiation. In order to reduce cost and volume of shielding around the generator, an additional ‘labyrinth’ of conventional bricks was modeled within the room. The size of the room was also adjusted to determine the minimum space required for safe operation. Shielding materials and dimensions were optimized to meet the NRC’s safe dose requirements

Medical care usage and self-rated mental health

<p>Abstract</p> <p>Background</p> <p>Population studies frequently employ a single item dependent variable for overall health. Self-rated mental health has been the focus of attention less often. The purpose of this project was to investigate the relationship between use of medical care and poor mental health in an elderly population.</p> <p>Methods</p> <p>This study involved a cross-sectional telephone survey of persons over 65 years of age in West Texas, a sparsely-populated 108-county region. Independent variables included number of medical visits, race/ethnicity, age, gender and ability to pay for care. Mental health was measured by asking subjects how often they felt downhearted or blue.</p> <p>Results</p> <p>Multiple logistic regression analysis revealed that more medical visits were made by persons who were downhearted or blue. Females, persons who had difficulty paying for care, Hispanic respondents, and older persons were more likely to report poor mental health.</p> <p>Conclusions</p> <p>Elderly persons in this region who use more medical care are at greater risk of being in poor mental health. Public health agencies that are planning population-based approaches to improving mental health should consider targeting persons who are high users of medical care as well as those of limited means, women, persons of Hispanic ethnicity, and people who are of greater age.</p

Bandgap Engineering of Quantum Semiconductor Microstructures

International audienc