8,046 research outputs found
Excavations at San Juan Capistrano, 41BX5, Bexar County, Texas
In February 1986, test excavations were conducted outside the north wall of Mission San Juan Capistrano (41 BX 5). This testing was done to determine any potential impact of proposed City Water Board trenching activities on buried structural features. Although no structural remains were found, midden deposits were encountered. This report discusses the artifacts and the identified depositional strata of the midden
Spectral Type and Radial Velocity Variations in Three SRC Variables
SRC variables are M supergiants, precursors to Type II supernovae, that vary
in brightness with moderately regular periods of order 100-1000 days. Although
identified as pulsating stars that obey their own period-luminosity relation,
few have been examined in enough detail to follow the temperature and spectral
changes that they undergo during their long cycles. The present study examines
such changes for several SRC variables revealed by CCD spectra obtained at the
Dominion Astrophysical Observatory (DAO) during 2005-2009, as well as by
archival spectra from the DAO (and elsewhere) for some stars from the 1960s to
1980s, and Cambridge radial velocity spectrometer measures for Betelgeuse.
Described here is our classification procedure and information on the spectral
type and radial velocity changes in three of the stars. The results provide
insights into the pulsation mechanism in M supergiants.Comment: To appear in the Odessa Variable Stars 2010 conference proceedings
(see http://uavso.org.ua/?page=vs2010), edited by I. Andronov and V. Kovtyuk
Strains for studying Spore killer elements in four Neurospora species
This note gives a comprehensive list of stocks useful for working with Spore killer elements, including reference strains for use as testers, genetically marked derivatives, and strains sensitive and resistant to killing by Sk-1K, Sk-2K, and . Geographical site of origin is indicted for the various killer alleles. Many of the strains are newly deposited in FGSC. Some are listed also under other categories. Updated versions of the list will appear in future FGSC Stock Lists (Part IV, Special Purpose Stocks)
Salt balance analysis
December 1983.Bibliography: page 79.Project no. A-051-COLO, agreement no. 14-34-0001-1106, 14-34-0001-2106; partially funded by the U.S. Dept. of the Interior, as authorized by the Water Research and Development Act of 1978
Anomalous coupling between topological defects and curvature
We investigate a counterintuitive geometric interaction between defects and
curvature in thin layers of superfluids, superconductors and liquid crystals
deposited on curved surfaces. Each defect feels a geometric potential whose
functional form is determined only by the shape of the surface, but whose sign
and strength depend on the transformation properties of the order parameter.
For superfluids and superconductors, the strength of this interaction is
proportional to the square of the charge and causes all defects to be repelled
(attracted) by regions of positive (negative) Gaussian curvature. For liquid
crystals in the one elastic constant approximation, charges between 0 and
are attracted by regions of positive curvature while all other charges
are repelled.Comment: 5 pages, 4 figures, minor changes, accepted for publication in Phys.
Rev. Let
The PL calibration for Milky Way Cepheids and its implications for the distance scale
The rationale behind recent calibrations of the Cepheid PL relation using the
Wesenheit formulation is reviewed and reanalyzed, and it is shown that recent
conclusions regarding a possible change in slope of the PL relation for
short-period and long-period Cepheids are tied to a pathological distribution
of HST calibrators within the instability strip. A recalibration of the
period-luminosity relation is obtained using Galactic Cepheids in open clusters
and groups, the resulting relationship, described by log L/L_sun =
2.415(+-0.035) + 1.148(+-0.044)log P, exhibiting only the moderate scatter
expected from color spread within the instability strip. The relationship is
confirmed by Cepheids with HST parallaxes, although without the need for
Lutz-Kelker corrections, and in general by Cepheids with revised Hipparcos
parallaxes, albeit with concerns about the cited precisions of the latter. A
Wesenheit formulation of Wv = -2.259(+-0.083) - 4.185(+-0.103)log P for
Galactic Cepheids is tested successfully using Cepheids in the inner regions of
the galaxy NGC 4258, confirming the independent geometrical distance
established for the galaxy from OH masers. Differences between the extinction
properties of interstellar and extragalactic dust may yet play an important
role in the further calibration of the Cepheid PL relation and its application
to the extragalactic distance scale.Comment: Accepted for Publication (Astrophysics & Space Science
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A Market-based Bandwidth Charging Framework
The increasing demand for high-bandwidth applications such as video-on-demand and grid computing is reviving interest in bandwidth reservation schemes. Earlier attempts did not catch on for a number of reasons, notably lack of interest on the part of the bandwidth providers. This, in turn, was partially caused by the lack of an efficient way of charging for bandwidth. Thus, the viability of bandwidth reservation depends on the existence of an efficient market where bandwidth-related transactions can take place. For this market to be effective, it must be efficient for both the provider (seller) and the user (buyer) of the bandwidth. This implies that: (a) the buyer must have a wide choice of providers that operate in a competitive environment, (b) the seller must be assured that a QoS transaction will be paid by the customer, and (c) the QoS transaction establishment must have low overheads so that it may be used by individual customers without a significant burden to the provider. In order to satisfy these requirements, we propose a framework that allows customers to purchase bandwidth using an open market where providers advertise links and capacities and customers bid for these services. The model is close to that of a commodities market that offers both advance bookings (futures) and a spot market. We explore the mechanisms that can support such a model
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