15,336 research outputs found
Errors in hybrid computers
Method is described for reduction of error components in numerical integration, sampling with zero hold order, and execution time delay
Effects of Enamel Paint on the Behavior and Survival of the Periodical Cicada, \u3ci\u3eMagicicada Septendecim\u3c/i\u3e (Homoptera) and the Lesser Migratory Grasshopper, \u3ci\u3eMelanoplus Sanguinipes (Orthoptera).
We present information compiled from several studies on the effects of methods for marking individual arthropods on their longevity and behavior. Results from our own research on effects of enamel paint marking on two in- sect species, the periodical cicada, Magicicada septendecim, and the lesser migratory grasshopper, Melanoplus sanguinipes, are also presented. Neither species showed any adverse survivorship or behavioral effects from marking
Leech Parasitism of the Gulf Coast Box Turtle, Terrapene carolina major (Testudines:Emydidae) in Mississippi, USA
Ten leeches were collected from a Gulf Coast box turtle, Terrapene carolina major, found crossing a road in Gulfport, Harrison County, Mississippi, USA. Eight of the leeches were identified as Placobdella multilineata and 2 were identified as Helobdella europaea. This represents the second vouchered report of leeches from a box turtle. Helobdella europaea is reported for the first time associated with a turtle and for the second time from the New World
The maximum density droplet to lower density droplet transition in quantum dots
We show that, Landau level mixing in two-dimensional quantum dot wave
functions can be taken into account very effectively by multiplying the exact
lowest Landau level wave functions by a Jastrow factor which is optimized by
variance minimization. The comparison between exact diagonalization and fixed
phase diffusion Monte Carlo results suggests that the phase of the many-body
wave functions are not affected much by Landau level mixing. We apply these
wave functions to study the transition from the maximum density droplet state
(incipient integer quantum Hall state with angular momentum L=N(N-1)/2) to
lower density droplet states (L>N(N-1)/2).Comment: 8 pages, 5 figures, accepted for publication in Phys. Rev.
Fluid infusion system
Development of a fluid infusion system was undertaken in response to a need for an intravenous infusion device operable under conditions of zero-g. The initial design approach, pursued in the construction of the first breadboard instrument, was to regulate the pressure of the motive gas to produce a similar regulated pressure in the infusion liquid. This scheme was not workable because of the varying bag contact area, and a major design iteration was made. A floating sensor plate in the center of the bag pressure plate was made to operate a pressure regulator built into the bellows assembly, effectively making liquid pressure the directly controlled variable. Other design changes were made as experience was gained with the breadboard. Extensive performance tests were conducted on both the breadboard and the prototype device; accurately regulated flows from 6 m1/min to 100 m1/min were achieved. All system functions were shown to operate satisfactorily
Two-dimensional molecular para-hydrogen and ortho-deuterium at zero temperature
We study molecular para-hydrogen (p-) and ortho-deuterium
(o-) in two dimensions and in the limit of zero temperature by
means of the diffusion Monte Carlo method. We report energetic and structural
properties of both systems like the total and kinetic energy per particle,
radial pair distribution function, and Lindemann's ratio in the low pressure
regime. By comparing the total energy per particle as a function of the density
in liquid and solid p-, we show that molecular para-hydrogen, and
also ortho-deuterium, remain solid at zero temperature. Interestingly, we
assess the quality of three different symmetrized trial wave functions, based
on the Nosanow-Jastrow model, in the p- solid film at the
variational level. In particular, we analyze a new type of symmetrized trial
wave function which has been used very recently to describe solid He and
found that also characterizes hydrogen satisfactorily. With this wave function,
we show that the one-body density matrix of solid p- possesses off-diagonal long range order, with a condensate fraction
that increases sizably in the negative pressure regime.Comment: 11 pages, 9 figure
XUV Frequency Combs via Femtosecond Enhancement Cavities
We review the current state of tabletop extreme ultraviolet (XUV) sources
based on high harmonic generation (HHG) in femtosecond enhancement cavities
(fsEC). Recent developments have enabled generation of high photon flux (1014
photons/sec) in the XUV, at high repetition rates (>50 MHz) and spanning the
spectral region from 40 nm - 120 nm. This level of performance has enabled
precision spectroscopy with XUV frequency combs and promises further
applications in XUV spectroscopic and photoemission studies. We discuss the
theory of operation and experimental details of the fsEC and XUV generation
based on HHG, including current technical challenges to increasing the photon
flux and maximum photon energy produced by this type of system. Current and
future applications for these sources are also discussed.Comment: invited review article, 38 page
Dipolar Bose gases: Many-body versus mean-field description
We characterize zero-temperature dipolar Bose gases under external spherical
confinement as a function of the dipole strength using the essentially exact
many-body diffusion Monte Carlo (DMC) technique. We show that the DMC energies
are reproduced accurately within a mean-field framework if the variation of the
s-wave scattering length with the dipole strength is accounted for properly.
Our calculations suggest stability diagrams and collapse mechanisms of dipolar
Bose gases that differ significantly from those previously proposed in the
literature
An evaluation of helicopter noise and vibration ride qualities criteria
Two methods of quantifying helicopter ride quality; absorbed power for vibration only and the NASA ride comfort model for both noise and vibration are discussed. Noise and vibration measurements were obtained on five operational US Army helicopters. The data were converted to both absorbed power and DISC's (discomfort units used in the NASA model) for specific helicopter flight conditions. Both models indicate considerable variation in ride quality between the five helicopters and between flight conditions within each helicopter
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