38,086 research outputs found
Current status of plague and plague control in the United States
During the first quarter of the 20th century, massive rat-borne plague epidemics occurred in port cities of the United States in conjunction with the last world-wide pandemic which originated in China in 1893. By 1950, plague was found to be firmly established in wild rodent populations in states west of the 100th meridian. Presumably because of improved sanitation coupled with retreat of the world-wide pandemic, there have been no human cases in this country associated with urban rats since 1924. However, sporadic cases, fewer than 10 per year, are reported as due to contact with wild rodents, lagomorphs, rural rats, and/or their fleas. Recent observations suggest that: a) in the current decade there has been an increase in human plague cases; b) there continues to be a serious potential of a single undiagnosed and untreated case, which possibility is intensified by the very paucity of human cases decreasing the likelihood of a correct diagnosis and by changing patterns of life exhibited by members of our society (e.g., hippie communes and a generally increased mobility); and c) the apparent distribution of plague only in the area west of the 100th meridian might be found to represent an unrealistic generalization if adequate surveillance were carried out. At the present time human plague cases from wild animal sources tend to be isolated events both spatially and temporally and often cannot be attributed to confined and definable epizootic sources amenable to effective control programs. Improved means for epizootic control and long-term management of enzootic plague sources must be sought aggressively. These measures should include development of: a) a surveillance network to detect plague activity in rodent and lagomorph populations throughout the western United States; b) effective, yet ecologically sound, means of ectoparasite control, including suitable materials and methods of application; c) methods for management of plague-susceptible wild animal populations, particularly where they exist in contact with high use recreation and residential areas; and d) more extensive knowledge of enzootic plague and the factors that bring about epizootic plague and potential human contact
Synopsis of current satellite snow mapping techniques, with emphasis on the application of near-infrared data
The Skylab EREP S192 Multispectral Scanner data have provided for the first time an opportunity to examine the reflectance characteristics of snowcover in several spectral bands extending from the visible into the near-infrared spectral region. The analysis of the S192 imagery and digital tape data indicates a sharp drop in reflectance of snow in the near-infrared, with snow becoming essentially nonreflective in Bands 11 (1.55-1.75 micron) and 12 (2.10-2.35 micron). Two potential applications to snow mapping of measurements in the near-infrared spectral region are possible: (1) the use of a near-infrared band in conjunction with a visible band to distinguish automatically between snow and water droplet clouds; and (2) the use of one or more near-infrared bands to detect areas of melting snow
A New Experiment to Study Hyperon CP Violation and the Charmonium System
Fermilab operates the world's most intense antiproton source, now exclusively
dedicated to serving the needs of the Tevatron Collider. The anticipated 2009
shutdown of the Tevatron presents the opportunity for a world-leading low- and
medium-energy antiproton program. We summarize the status of the Fermilab
antiproton facility and review physics topics for which a future experiment
could make the world's best measurements.Comment: 16 pages, 3 figures, to appear in Proceedings of CTP symposium on
Supersymmetry at LHC: Theoretical and Experimental Perspectives, The British
University in Egypt, Cairo, Egypt, 11-14 March 200
Homological Localisation of Model Categories
One of the most useful methods for studying the stable homotopy category is localising at some spectrum E. For an arbitrary stable model category we introduce a candidate
for the E–localisation of this model category. We study the properties of this new construction and relate it to some well–known categories
Possible Tool Use by Beavers, Castor canadensis, in a Northern Ontario Watershed
At a remote active Beaver (Castor canadensis) dam site in the Chapleau Crown Game Preserve of northern Ontario, I noted an instance where a Beaver had used a willow stem as a prop to allow it to cut other willow stems at an unrealistic height. The use of this tool (prop) meant less land foraging that in turn reduced the risk of predation and prevented undue thermal stress. This is the first account in the literature of a Beaver possibly using a tool to aid in foraging
BB Intermeson Potentials in the Quark Model
In this paper we derive quark model results for scattering amplitudes and
equivalent low energy potentials for heavy meson pairs, in which each meson
contains a heavy quark. This "BB" system is an attractive theoretical
laboratory for the study of the nuclear force between color singlets; the
hadronic system is relatively simple, and there are lattice gauge theory (LGT)
results for V_BB(r) which may be compared to phenomenological models. We find
that the quark model potential (after lattice smearing) has qualitative
similarities to the LGT potential in the two B*B* channels in which direct
comparison is possible, although there is evidence of a difference in length
scales. The quark model prediction of equal magnitude but opposite sign for I=0
and I=1 potentials also appears similar to LGT results at intermediate r. There
may however be a discrepancy between the LGT and quark model I=1 BB potentials.
A numerical study of the two-meson Schrodinger equations in the (bqbar)(bqbar)
and (cqbar)(cqbar) sectors with the quark model potentials finds a single
"molecule", in the I=0 BB* sector. Binding in other channels might occur if the
quark model forces are augmented by pion exchange.Comment: 30 pages, 5 figures, revtex and epsfig. Submitted to Phys. Rev.
A study to develop improved spacecraft show survey methods using Skylab/EREP data: Demonstration of the utility of the S190 and S192 data
The author has identified the following significant results. This interim report provides a demonstration of the utility of spacecraft acquired Skylab S190A and S190B photography and S192 imagery for mapping areal extent of snow cover in western United States test site areas. The data sample is from the SL-2 mission flown in June 1973. Results of the investigation indicate that areal snow cover extent can be mapped more accurately from the S190A and S190B photography than from any other spacecraft system, including ERTS. The results of a qualitative analysis of the S192 imagery indicate considerable potential for the utility of multispectral snow cover analysis; the potential for distinguishing snow from clouds automatically is particularly significant
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