7,131 research outputs found
Archaeological and Paleo-osteological Investigations at the Cold Morning Site, New Hanover County, North Carolina
A miscellaneous report by the Research Laboratories of Archaeology, University of North Carolina at Chapel Hill. These reports discuss the findings of archaeological survey, testing, and excavations undertaken by the RLA between 1973 and 1985. SENSITIVE CONTENT: This report contains photographs of human remains
Anti-self-dual Maxwell solutions on hyperk\"ahler manifold and N=2 supersymmetric Ashtekar gravity
Anti-self-dual (ASD) Maxwell solutions on 4-dimensional hyperk\"ahler
manifolds are constructed. The N=2 supersymmetric half-flat equations are
derived in the context of the Ashtekar formulation of N=2 supergravity. These
equations show that the ASD Maxwell solutions have a direct connection with the
solutions of the reduced N=2 supersymmetric ASD Yang-Mills equations with a
special choice of gauge group. Two examples of the Maxwell solutions are
presented.Comment: 9 page
Solid-phase crystallization of Si films in contact with Al layers
Low-temperature (400–540 °C) crystallization of amorphous and polycrystalline Si films deposited on SiO2 and covered with an evaporated Al layer has been studied using SEM, TEM, electron diffraction, electron channeling, and MeV 4He + backscattering. Silicon deposited by evaporation and chemical vapor deposition (CVD) at 640 °C (both amorphous) was found to crystallize into islands of polycrystalline aggregates. Silicon deposited by CVD at 900 °C (polycrystalline with ~2000-Å grains) produced relatively large (~10 µm) single-crystal islands. In both cases island size increased with annealing time, and the rate of crystallization increased with temperature. Crystallization rates were observed to be the same for both sources of amorphous Si, while 900 °C CVD Si was noticeably slower, consistent with the postulate that the driving force for the reaction is the free-energy difference between initial and final states. The crystallization rate for 900 °C CVD Si decreased when the Al layer thickness was reduced to a value less than the initial Si grain size. The inclusion of a native oxide layer between the deposited Si and Al layers greatly retarded the crystallization process
Swainson\u27s Thrushes Do Not Show Strong Wing Selectivity Prior to Crossing the Gulf of Mexico
During long-distance fall migrations, nocturnally migrating Swainson’s Thrushes often stop on the northern Gulf of Mexico coast before flying across the Gulf. To minimize energetic costs, trans-Gulf migrants should stop over when they encounter crosswinds or headwinds, and depart with supportive tailwinds. However, time constrained migrants should be less selective, balancing costs of headwinds with benefits of continuing their migrations. To test the hypotheses that birds select supportive winds and that selectivity is mediated by seasonal time constraints, we examined whether local winds affected Swainson’s Thrushes’ arrival and departure at Ft. Morgan, Alabama, USA at annual, seasonal, and nightly time scales. Additionally, migrants could benefit from forecasting future wind conditions, crossing on nights when winds are consistently supportive across the Gulf, thereby avoiding the potentially lethal consequences of depleting their energetic reserves over water. To test whether birds forecast, we developed a movement model, calculated to what extent departure winds were predictive of future Gulf winds, and tested whether birds responded to predictability. Swainson’s Thrushes were only slightly selective and did not appear to forecast. By following the simple rule of avoiding only the strongest headwinds at departure, Swainson’s Thrushes could survive the 1500 km flight between Alabama and Veracruz, Mexico
Space-Time Supersymmetry of Extended Fermionic Strings in Dimensions
The fermionic string theory is revisited in light of its recently
proposed equivalence to the non-compact fermionic string model. The
issues of space-time Lorentz covariance and supersymmetry for the BRST
quantized strings living in uncompactified dimensions are
discussed. The equivalent local quantum supersymmetric field theory appears to
be the most transparent way to represent the space-time symmetries of the
extended fermionic strings and their interactions. Our considerations support
the Siegel's ideas about the presence of Lorentz symmetry as well as
at least one self-dual space-time supersymmetry in the theory of the
fermionic strings, though we do not have a compelling reason to argue about the
necessity of the {\it maximal} space-time supersymmetry. The world-sheet
arguments about the absence of all string massive modes in the physical
spectrum, and the vanishing of all string-loop amplitudes in the Polyakov
approach, are given on the basis of general consistency of the theory.Comment: 29 pages, LaTeX, ITP-UH-1/9
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