17,271 research outputs found
Quanta Without Quantization
The dimensional properties of fields in classical general relativity lead to
a tangent tower structure which gives rise directly to quantum mechanical and
quantum field theory structures without quantization. We derive all of the
fundamental elements of quantum mechanics from the tangent tower structure,
including fundamental commutation relations, a Hilbert space of pure and mixed
states, measurable expectation values, Schroedinger time evolution, collapse of
a state and the probability interpretation. The most central elements of string
theory also follow, including an operator valued mode expansion like that in
string theory as well as the Virasoro algebra with central charges.Comment: 8 pages, Latex, Honorable Mention 1997 GRG Essa
Method and apparatus for stable silicon dioxide layers on silicon grown in silicon nitride ambient
A method and apparatus for thermally growing stable silicon dioxide layers on silicon is disclosed. A previously etched and baked silicon nitride tube placed in a furnace is used to grow the silicon dioxide. First, pure oxygen is allowed to flow through the tube to initially coat the inside surface of the tube with a thin layer of silicon dioxide. After the tube is coated with the thin layer of silicon dioxide, the silicon is oxidized thermally in a normal fashion. If the tube becomes contaminated, the silicon dioxide is etched off thereby exposing clean silicon nitride and then the inside of the tube is recoated with silicon dioxide. As is disclosed, the silicon nitride tube can also be used as the ambient for the pyrolytic decomposition of silane and ammonia to form thin layers of clean silicon nitride
Building a functional, integrated GIS/remote sensing resource analysis and planning system
To be an effective tool for resource analysis and planning, a geographic information system (GIS) needs to be integrated with a digital remote sensing capability. To be truly functional, the paired system must be driven by grass roots local needs. A case study couched in a Soil Conservation District in northern Utah is presented. Agency representatives determined that the most fundamental data sets to be entered into the GIS system analysis system in the first round were: land use/land cover; geomorphic/soil unit data; hydrologic unit data; and digital terrain. The least expensive and best ways to obtain these data were determined. Data were acquired and formatted to enter the state's PRIME/ARC-INFO GIS, and are being interrogated for resource management decisions related to such issues as agricultural preservation, urban expansion, soil erosion control, and dam siting
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Molecular cloning and characterization of B-cadherin, a novel chick cadherin.
Calcium-dependent cell-cell adhesion is mediated in large part by a set of homologous integral membrane glycoproteins termed cadherins. In this report, antibodies to conserved domains in previously described cadherins have been used to isolate cDNAs encoding a novel chick cadherin. The deduced primary structure of this novel molecule, assigned the name B-cadherin, contains 726 amino acid residues which include five extracellular domains characteristic of this class of adhesion molecules, a single putative transmembrane spanning region, and a cytoplasmic tail. In each domain, B-cadherin shares extensive homologies with other cadherins, but is more closely related to E-cadherin, P-cadherin, and L-CAM than to N-cadherin. It is expressed in a wide variety of chick tissues at embryonic day 13. In particular, immunohistochemical staining and in situ hybridization localize B-cadherin protein and mRNA to the epithelial lining of the choroid plexus and to cells in specific layers of the optic tectum in chick brain. Levels of the protein and RNA transcript change dramatically as development proceeds in chick brain. These results suggest that B-cadherin has important functions in neurogenesis, in at least some epithelia, and in embryogenesis
Nickel-cadmium cell life test
Over 6,9000 Low Earth Orbit cycles were accumulated at 30% Depth of Discharge on twelve INTELSAT-design nickel-hydrogen cells. Physical equipment and cells are described. Performance characteristics are seen to be uniform. Further testing is planned to seek a failure mode, and also to investigate the effects of a new additive for nickel-hydrogen cells. Initial results indicate improved performance at higher temperatures and diminished swelling of positive nickel plates
A Methodology for Water Quality Assessment in Developing Regions: A Case Study of China's Yellow River
Due to limited data and scarce financial resources in developing regions, policy decisions for managing water resources must often be made without a full understanding of what potential impacts on water quality may result. This study demonstrates a methodology for utilizing georeferenced statistical data to assess the primary pollution contributions and to model the physical impacts resulting from these contributions. Using socio-economic data on population, agricultural production and industrial output provides a basis for evaluating the potential effects on the current water quality situation and allows a method to assess the influences resulting from changes of these socio-economic patterns. This study focused on evaluating the current conditions in the Yellow River in China. A conceptual model is developed to estimate Biochemical Oxygen Demand (BOD) generation and link these sources with the hydrologic characteristics of the landscape to generate BOD loadings into the main river channel. In-stream fate and transport modeling is then used to estimate the BOD and dissolved oxygen throughout the river
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