4,254 research outputs found
Investigation of conductive thermal control coatings by a contactless method in vacuo
A technique for determining the conductance per unit area of thermal control coatings for electrostatically clean spacecraft is described. In order to simulate orbital conditions more closely, current-density-voltage (j-V) curves are obtained by a contactless method in which the paint on an aluminum substrate is the anode of a vacuum diode configuration with a tungsten filament cathode. Conductances per unit area which satisfy the International Sun Earth Explorer (ISEE) requirement were observed on black paints containing carbon and in white and green paints filled with zinc oxide which were fired in order to induce defect conductivity. Because of surface effects and the nonhomogeneous nature of paints, large discrepancies were found between measurements with the contactless method and measurements employing metallic contacts, particularly at low current densities. Therefore, measurements with metallic contacts are considered to be of questionable value in deciding the suitability of coatings for electrostatic charge control
Probing the Goldstone equivalence theorem in Heavy Weak Doublet Decays
This paper investigates the decays from heavy higgsino-like weak-doublets
into Z, h bosons and missing particles. When pair-produced at the LHC, the
subsequent Z, h to 2l, 2b decays in the doublet decay cascade can yield 4l, 2l
2b, and 4b + MET + jets final states. Mutual observation of any two of these
channels would provide information on the the associated doublets' decay
branching fractions into a Z or h, thereby probing the Goldstone equivalence
relation, shedding additional light on the Higgs sector of beyond the Standard
Model theories, and facilitating the discrimination of various contending
models, in turn. We compare the Z/h decay ratio expected in the Minimal
Supersymmetric model, the Next-to Minimal Supersymmetric model and a minimal
singlet-doublet dark matter model. Additionally, we conduct a full Monte Carlo
analysis of the prospects for detecting the targeted final states during 14 TeV
running of the LHC in the context of a representative NMSSM benchmark model.Comment: As accepted to PRD; 15 pages, 12 figures, 5 table
The Architecture and Landscape of Slavery in Fredericksburg, Virginia
The African Americans who endured institutional enslavement played a critical role in the history of Fredericksburg from its 18th-century founding to its Civil War era turmoil. Only recently have historians, archaeologists, and architectural historians brought scholarly and more public attention to bear on the people who comprised over a third of the city’s population as well as its main labor force. Surprisingly little archaeological work on slave-related sites and structures has occurred. This research relies on a combination of architectural and documentary evidence to visualize slavery’s built environment in Fredericksburg as well as the demographic and cultural parameters that framed slaves’ lives. A series of contextual predictions for slave-related sites and households are advanced that hopefully archaeologists will test with future excavations. Such efforts would allow archaeologists to better characterize Fredericksburg’s bonded African Americans as active consumers, agents of change, and members of their own vibrant community
The Water Table and Soil Moisture Response Following the Removal of Conifers from an Encroached Meadow
Montane meadows play a key role in the physical and biologic processes of coniferous forests in the western United States. However, due to climate change, over grazing, and fire suppression, conifer encroachment into meadows has accelerated. In some western regions, nearly half of all meadow habitat has been loss due to conifer encroachment. To combat this issue, encroaching conifers can be removed in an attempt to increase meadow habitat and function. While multiple studies have assessed changes in soil structure and vegetation composition, few studies directly investigate changes in hydrology following meadow conifer removal projects. The goal of this study is to determine if the removal of conifers from an encroached meadow (Marian Meadow) has an effect on soil moisture and groundwater depth such that meadow hydrologic conditions are promoted. This goal will be accomplished by the following objectives: 1) develop a water budget incorporating groundwater depth, soil moisture, and climate measurements to quantify the hydrologic processes prior to and after conifer removal, 2) conduct a statistical analysis of the project meadow’s wet season water table depth prior to and after conifer removal, 3) conduct a statistical analysis of the meadow’s soil moisture prior to and after conifer removal. Marian Meadow is located in Plumas County, CA at an elevation of 4,900 feet. This 45-acre meadow enhancement project is part of a 2,046-acre timber harvest plan implemented by the Collins Pine Company. Soil moisture and water table depth sensors were installed in Marian Meadow and a control meadow in September 2013. The soil moisture sensors were installed at one and three foot depths. Soil moisture and water table depth measurements used in this study span from September 2013 through June 2016. The removal of encroaching conifers from Marian Meadow occurred in July 2015. Evapotranspiration was estimated using the Priestly Taylor equation. Electrical Resistivity Tomography (ERT) was used to determine maximum water table depths. A groundwater recession curve equation was used to model water table depths between water table depth sensor measurements and ERT measurements. Standard least squared linear regression and ANCOVA was used to determine any statistical significant difference in soil moisture and water table depths prior to and after conifer removal. The water balance indicated that the majority of Marian Meadow and the control meadow’s water storage can be attributed to precipitation and not upland sources. This hydrologic characteristic is common in dry meadows. The statistical analysis indicated that measured water table depths increased on average by 0.58 feet following conifer removal. Relative to the control meadow, soil moisture in Marian Meadow initially decreased following conifer removal. However, from November 2015 through June 2016 soil moisture increased. On average soil moisture increased by 4% following conifer removal. Also, growing season (April through September) water table depths indicated that meadow vegetation communities could be supported in Marian Meadow following conifer removal. The removal of conifers from an encroached meadow appears to promote soil moisture and water table depth conditions indicative of a meadow and meadow plant community types
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