1,805 research outputs found
The design and implementation of the Technical Facilities Controller (TFC) for the Goldstone deep space communications complex
The Technical Facilities Controller is a microprocessor-based energy management system that is to be implemented in the Deep Space Network facilities. This system is used in conjunction with facilities equipment at each of the complexes in the operation and maintenance of air-conditioning equipment, power generation equipment, power distribution equipment, and other primary facilities equipment. The implementation of the Technical Facilities Controller was completed at the Goldstone Deep Space Communications Complex and is now operational. The installation completed at the Goldstone Complex is described and the utilization of the Technical Facilities Controller is evaluated. The findings will be used in the decision to implement a similar system at the overseas complexes at Canberra, Australia, and Madrid, Spain
Seven Years of White-Tailed Deer Immunocontraceptive Research at Penn State University: A Comparison of Two Vaccines
PZP and GnRH immunocontraceptive vaccines were each tested in white-tailed deer (Odocoileus virginianus) . Vaccination with PZP produced reversible infertility lasting 1 to 4 years. The first two years of active immunization resulted in an 89% reduction in fawning. Reduction in fawning for the 7-year study containing 4 years of no boosting was 72%. PZP immunization resulted in multi-estrus behavior, with contracepted deer returning to estrus up to 7 times. A five year study of GnRH immunization was conducted in both male and female deer. Treatment of does led to reduced fawning rates, reduced estrus behavior and reduced concentrations of progesterone. During active immunization GnRH does bred to untreated bucks had an 88% reduction in fawning caused by either immunocontraception or immunocontragestion. Reduction in fawning for the 5 year study containing 2 years of no boosting was 74%. The vaccine effect was reversible and directly related to the antibody titer. Infertility lasted up to two years without boosting. GnRH immunized bucks had no interest in sexual activity when paired with control females. Depending on the immunization schedule, antlers either dropped early or remained in velvet
Ultralong-Range Rydberg Molecules in a Divalent-Atomic System
We report the creation of ultralong-range Sr molecules comprising one
ground-state atom and one atom in a Rydberg state
for ranging from 29 to 36. Molecules are created in a trapped ultracold
atomic gas using two-photon excitation near resonant with the
intermediate state, and their formation is detected through ground-state atom
loss from the trap. The observed molecular binding energies are fit with the
aid of first-order perturbation theory that utilizes a Fermi pseudopotential
with effective -wave and -wave scattering lengths to describe the
interaction between an excited Rydberg electron and a ground-state Sr atom.Comment: 5 pages, 2 figure
Ultracold Neutral Plasmas
Ultracold neutral plasmas are formed by photoionizing laser-cooled atoms near
the ionization threshold. Through the application of atomic physics techniques
and diagnostics, these experiments stretch the boundaries of traditional
neutral plasma physics. The electron temperature in these plasmas ranges from
1-1000 K and the ion temperature is around 1 K. The density can approach
cm. Fundamental interest stems from the possibility of
creating strongly-coupled plasmas, but recombination, collective modes, and
thermalization in these systems have also been studied. Optical absorption
images of a strontium plasma, using the Sr
transition at 422 nm, depict the density profile of the plasma, and probe
kinetics on a 50 ns time-scale. The Doppler-broadened ion absorption spectrum
measures the ion velocity distribution, which gives an accurate measure of the
ion dynamics in the first microsecond after photoionization.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004,
Nice (France
Experimental Realization of an Exact Solution to the Vlasov Equations for an Expanding Plasma
We study the expansion of ultracold neutral plasmas in the regime in which
inelastic collisions are negligible. The plasma expands due to the thermal
pressure of the electrons, and for an initial spherically symmetric Gaussian
density profle, the expansion is self-similar. Measurements of the plasma size
and ion kinetic energy using fluorescence imaging and spectroscopy show that
the expansion follows an analytic solution of the Vlasov equations for an
adiabatically expanding plasma.Comment: 4 pages, 4 figure
Electron Temperature Evolution in Expanding Ultracold Neutral Plasmas
We have used the free expansion of ultracold neutral plasmas as a
time-resolved probe of electron temperature. A combination of experimental
measurements of the ion expansion velocity and numerical simulations
characterize the crossover from an elastic-collision regime at low initial
Gamma_e, which is dominated by adiabatic cooling of the electrons, to the
regime of high Gamma_e in which inelastic processes drastically heat the
electrons. We identify the time scales and relative contributions of various
processes, and experimentally show the importance of radiative decay and
disorder-induced electron heating for the first time in ultracold neutral
plasmas
Stable Isotope Analysis of the Inca Mummy from Nevado de Chuscha (Salta, Argentina)
This paper presents the carbon (13C/12C), nitrogen (15N/14N), oxygen (18O/16O), hydrogen (2H/1H) and sulfur (34S/32S) stable isotope values measured in the hair of a female individual from north-western Argentina. The analysis of segments of this tissue allows for the recording of the diet and migratory changes with a short time resolution. The sample is from a mummified young female individual discovered in Chuscha mount, Salta province. It was found at more than 5000 masl, in a mountain sanctuary of the Inca expansion (capacochas). The paper discusses the paleodiet and mobility patterns of this individual in the period before her death, focusing on the isotopic variations in a limited time scale. The results indicate that the individual moved from a different region to the place where she was sacrificed. Furthermore, in the last year the individual was alive, a shift in the isotopic composition of the food consumed is detected: a variation in the importance of C4 over C3 resources is evident. The results are compared with the isotopic estimations for other children and young people recovered in archaeological contexts associated with capacochas to infer variability in the geographical trajectories covered during their last months of life.Fil: Killian Galván, Violeta Anahí. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Instituto Interdisciplinario Tilcara; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tessone, Augusto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotópica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; ArgentinaFil: Valenzuela, Luciano Oscar. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Sociales. Departamento de Arqueología. Laboratorio de Ecología Evolutiva Humana (Sede Quequén); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Sharp, Z. D.. Universidad de Nuevo México.; Estados UnidosFil: Panarello, Hector Osvaldo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotópica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; Argentin
Evolution of Ultracold, Neutral Plasmas
We present the first large-scale simulations of an ultracold, neutral plasma,
produced by photoionization of laser-cooled xenon atoms, from creation to
initial expansion, using classical molecular dynamics methods with open
boundary conditions. We reproduce many of the experimental findings such as the
trapping efficiency of electrons with increased ion number, a minimum electron
temperature achieved on approach to the photoionization threshold, and
recombination into Rydberg states of anomalously-low principal quantum number.
In addition, many of these effects establish themselves very early in the
plasma evolution ( ns) before present experimental observations begin.Comment: 4 pages, 3 figures, submitted to PR
Repumping and spectroscopy of laser-cooled Sr atoms using the (5s5p)3P2 - (5s4d)3D2 transition
We describe repumping and spectroscopy of laser-cooled strontium (Sr) atoms
using the (5s5p)3P2 - (5s4d)3D2 transition. Atom number in a magneto-optical
trap is enhanced by driving this transition because Sr atoms that have decayed
into the (5s5p)3P2 dark state are repumped back into the (5s2)1S0 ground state.
Spectroscopy of 84Sr, 86Sr, 87Sr, and 88Sr improves the value of the (5s5p)3P2
- (5s4d)3D2 transition frequency for 88Sr and determines the isotope shifts for
the transition.Comment: 4 pages, 5 figure
- …