44,533 research outputs found
Microparticle impact sensor measures energy directly
Construction of a capacitor sensor consisting of a dielectric layer between two conductive surface layers and connected across a potential source through a sensing resistor permits measurement of energy of impinging particles without degradation of sensitivity. A measurable response is produced without penetration of the dielectric layer
Massive scalar fields in the early Universe
We discuss the role of gravitational excitons/radions in different
cosmological scenarios. Gravitational excitons are massive moduli fields which
describe conformal excitations of the internal spaces and which, due to their
Planck-scale suppressed coupling to matter fields, are WIMPs. It is
demonstrated that, depending on the concrete scenario, observational
cosmological data set strong restrictions on the allowed masses and initial
oscillation amplitudes of these particles.Comment: 6 pages, Latex2e, talk presented at the 1st International Workshop on
Astronomy and Relativistic Astrophysics, 12-16 October, 2003, (IWARA2003),
Olinda-PE, Brazi
Material growth and characterization directed toward improving III-V heterojunction solar cells
In addition to the existing materials growth laboratory, the photolithographic facility and the device testing facility were completed. The majority of equipment for data acquisition, solar cell testing, materials growth and device characterization were received and are being put into operation. In the research part of the program, GaAs and GaA1As layers were grown reproducibly on GaAs substrates. These grown layers were characterized as to surface morphology, thickness and thickness uniformity. The liquid phase epitaxial growth process was used to fabricate p-n junctions in Ga(1-x)A1(x)As. Sequential deposition of two alloy layers was accomplished and detailed analysis of the effect of substrate quality and dopant on the GaA1As layer quality is presented. Finally, solar cell structures were formed by growing a thin p-GaA1As layer upon an epitaxial n-GaA1As layer. The energy gap corresponding to the long wavelength cutoff of the spectral response characteristic was 1.51-1.63 eV. Theoretical calculations of the spectral response were matched to the measured response
CARETS: A prototype regional environmental information system. Volume 7: Land use information and air quality planning
The author has identified the following significant results. The pilot air quality system provided data for updating information on the sources of point and area emissions of SO2 and particulate matter affecting the Norfolk-Portsmouth area of Virginia for 1971-72 winter and the annual 1972 period. During the 1971-72 winter, estimated SO2 amounts over an area with a SW-NE axis in the central section of Norfolk exceeded both primary and secondary levels
The role of topology and mechanics in uniaxially growing cell networks
In biological systems, the growth of cells, tissues, and organs is influenced
by mechanical cues. Locally, cell growth leads to a mechanically heterogeneous
environment as cells pull and push their neighbors in a cell network. Despite
this local heterogeneity, at the tissue level, the cell network is remarkably
robust, as it is not easily perturbed by changes in the mechanical environment
or the network connectivity. Through a network model, we relate global tissue
structure (i.e. the cell network topology) and local growth mechanisms (growth
laws) to the overall tissue response. Within this framework, we investigate the
two main mechanical growth laws that have been proposed: stress-driven or
strain-driven growth. We show that in order to create a robust and stable
tissue environment, networks with predominantly series connections are
naturally driven by stress-driven growth, whereas networks with predominantly
parallel connections are associated with strain-driven growth
Sustainability Strategies in U.S. Agribusiness: Understanding Key Drivers, Objectives, and Actions
sustainability, triple bottom line, strategy, stakeholders, supply chain, Agribusiness, Demand and Price Analysis, Environmental Economics and Policy, Production Economics, Productivity Analysis, Risk and Uncertainty,
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