20,082 research outputs found
AGRICULTURAL TRANSITION: ITS IMPLICATIONS FOR AGRICULTURAL ECONOMICS EXTENSION IN THE SOUTHEAST
Teaching/Communication/Extension/Profession,
Principal Component Analysis of RR Lyrae light curves
In this paper, we analyze the structure of RRab star light curves using
Principal Component Analysis. We find this is a very efficient way to describe
many aspects of RRab light curve structure: in many cases, a Principal
Component fit with 9 parameters can describe a RRab light curve including bumps
whereas a 17 parameter Fourier fit is needed. As a consequence we show
statistically why the amplitude is also a good summary of the structure of a RR
Lyrae light curve. We also use our analysis to derive an empirical relation
relating absolute magnitude to light curve structure. In comparing this formula
to those derived from exactly the same dataset but using Fourier parameters, we
find that the Principal Component Analysis approach has disticnt advantages.
These advantages are, firstly, that the errors on the coefficients in such
formulae are smaller, and secondly, that the correlation between Principal
Components is significantly smaller than the correlation between Fourier
amplitudes. These two factors lead to reduced formal errors, in some cases
estimated to be a factor of 2, on the eventual fitted value of the absolute
magnitude. This technique will prove very useful in the analysis of data from
existing large scale survey projects concerning variable stars.Comment: 8 pages, 10 figures, revised version, accepted for publication to
MNRA
High discharge rate characteristics of nickel-cadmium batteries for pulse load filtering
Several tests of specially fabricated nickel-cadmium batteries having circular disk type electrodes were considered. These batteries were evaluated as filter elements between a constant current power supply and a five hertz pulsed load demanding approximately twice the power supply current during the load on portion of the cycle. Short tests lasting 10,000 cycles were conducted at up to a 21 C rate and an equivalent energy density of over 40 Joules per pound. In addition, two batteries were subjected to 10 to the 7 charge/discharge cycles, one at a 6.5 C rate and the other at a 13 C rate. Assuming an electrode to battery weight ratio of 0.5, these tests represent an energy density of about 7 and 14 Joules per pound respectively. Energy density, efficiency, capacitance, average voltage, and available capacity were tracked during these tests. After 10 to the 7 cycles, capacity degradation was negligible for one battery and about 20% for the other. Cadmium electrode failure may be the factor limiting lifetime at extremely low depth of discharge cycling. The output was examined and a simple equivalent circuit was proposed
Evidence for Three Nucleon Force Effects in p-d Elastic Scattering
A new measurement of the p-d differential cross section at Ep= 1 MeV has been
performed. These new data and older data sets at energies below the deuteron
breakup are compared to calculations using the two-nucleon Argonne v18 and the
three-nucleon Urbana IX potentials. A quantitative estimate of the capability
of these interactions to describe the data is given in terms of a chi^2
analysis. The chi^2 per datum drastically improves when the three-nucleon
interaction is included in the Hamiltonian.Comment: 13 pages, 5 figures, to be published in Phys. Rev.
Sea turtle nesting activity along Eglin Air Force Base on Cape San Blas and Santa Rosa Island, Florida from 1994 to 1997.
Along EAFB on Cape San BIas, the only sea turtle species nest observed has been
the loggerhead turtle. The first green turtle nest documented along the Florida panhandle
coast was observed on EAFB property, however (D. Atencio, EAFB, pers. comm). Santa
Rosa Island, located approximately 150 miles west of Cape San BIas supports a small but
consistent, group of nesting green turtles (Fig. 2). Although erosion is not as severe along
Santa Rosa Island as it is on Cape San BIas, and vehicular traffic is not permitted, sea
turtles nesting on this barrier island must survive severe tropical storms, predation, and
artificial lighting to be successful. Because this area supports a rare group of nesting green
turtles and is disturbed by intense artificial lighting from Air Force missions and adjacent
resort towns, continued monitoring is necessary. The sea turtle species that nest along this
barrier island, and the human activities that disturb those sea turtles present unique
circumstances for management ofthis area. Protection ofthe significant nesting
populations of sea turtles on EAFB properties on Cape San BIas and Santa Rosa Island
requires yearly monitoring of the nesting activity and the natural and human disturbances
influencing the nesting females.
The objectives ofthis study were to monitor sea turtle nesting along EAFB on
Cape San BIas to determine number of nests and hatching success, assess disturbances,
and determine proper management to ensure successful nesting and hatching.(56 page document
The Cape San Blas Ecological Study
Eglin AFB on Cape San Blas consists of approximately 250 acres located about
180 miles east of the main Eglin reservation. This area lies on the S1. Joseph peninsula,
part of a dynamic barrier island chain that extends across the northern Gulf of Mexico.
Due to the natural forces that formed Cape San Blas and those that maintain this area, St.
Joseph Peninsula has experienced severe land form change over time (see GIS land form
change maps). These changes allow for fluctuations in habitat types along Cape San Blas
(see GIS land cover change maps)that influence the floral and faunal species using this
area.
The dynamic environment along Cape San Blasincludes flatwoods, interdunal
swale, rosemary scrub, and beachfront. These habitats support a wide array of species,
including several threatened and endangered species such as the loggerhead sea turtle
(Caretta caretta), PipingPlover (Charadnus melodus), Least Tern (Sterna antillarum),
and Bald Eagle (Haliaeetus leucocephalus). Proper management of these species and their
habitats require knowledge of their abundance and distribution, and the effects
disturbances have on their survival.
In addition to threatened and endangered flora and fauna, Cape San Blas also
supports tourists and recreationists. Although Gulf County is sparsely populated, with
approximately 13,000 inhabitants throughout 578 square miles, summer tourism and heavy
recreational use of beaches for fishing, crabbing, and shelling place continued and
increasing pressure on the natural resources of these areas (Rupert 1991). Gulf County is
also one of the few remaining counties in Florida that permits vehicular traffic on its
beaches, including Cape San Blas. In addition to recreational use of these habitats;EAFB
also uses the area for military missions. Air Force property on Cape San Blas is primarily
used for radar tracking of flying missions over the Gulf of Mexico, although in recent
years it has been used for missile launchings and other various military activities.
To allow continued military and public use of Air Force property while also
protecting the unique flora and fauna of the area,EAFB proposed a characterization of the
resources found along Cape San Blas. A complete inventory of the physical features of the
area included investigating topography, soil chemistry, hydrology, archeology, and the
dynamics of land mass and land cover change over time. Various thematic layers within a
geographic information system (GIS) were used to spatially portray georeferenced data.
Large scale changes over time were assessed using stereo aerial photography. Vegetation
transects, soil samples, elevation transects, an archeological survey, freshwater wells, and
a tidal monitor were used to investigate the remaining features. (247 page document
Kinetic pinning and biological antifreezes
Biological antifreezes protect cold-water organisms from freezing. An example
are the antifreeze proteins (AFPs) that attach to the surface of ice crystals
and arrest growth. The mechanism for growth arrest has not been heretofore
understood in a quantitative way. We present a complete theory based on a
kinetic model. We use the `stones on a pillow' picture. Our theory of the
suppression of the freezing point as a function of the concentration of the AFP
is quantitatively accurate. It gives a correct description of the dependence of
the freezing point suppression on the geometry of the protein, and might lead
to advances in design of synthetic AFPs.Comment: 4 pages, 4 figure
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