3,105 research outputs found
Surprisingly Little O VI Emission Arises in the Local Bubble
This paper reports the first study of the O VI resonance line emission (1032,
1038 Angstroms) originating in the Local Bubble (or Local Hot Bubble)
surrounding the solar neighborhood. In spite of the fact that O VI absorption
within the Local Bubble has been observed, no resonance line emission was
detected during our 230 ksec Far Ultraviolet Spectroscopic Explorer observation
toward a ``shadowing'' filament in the southern Galactic hemisphere. As a
result, tight 2 sigma upper limits are set on the intensities in the 1032 and
1038 Angstrom emission lines: 500 and 530 photons cm^{-2} s^{-1} sr^{-1},
respectively. These values place strict constraints on models and simulations.
They suggest that the O VI-bearing plasma and the X-ray emissive plasma reside
in distinct regions of the Local Bubble and are not mixed in a single plasma,
whether in equilibrium with T ~ 10^6 K or highly overionized with T ~ 4 to 6 x
10^4 K. If the line of sight intersects multiple cool clouds within the Local
Bubble, then the results also suggest that hot/cool transition zones differ
from those in current simulations. With these intensity upper limits, we
establish limits on the electron density, thermal pressure, pathlength, and
cooling timescale of the O VI-bearing plasma in the Local Bubble. Furthermore,
the intensity of O VI resonance line doublet photons originating in the
Galactic thick disk and halo is determined (3500 to 4300 photons cm^{-2} s^{-1}
sr^{-1}), and the electron density, thermal pressure, pathlength, and cooling
timescale of its O VI-bearing plasma are calculated. The pressure in the
Galactic halo's O VI-bearing plasma (3100 to 3800 K cm^{-3}) agrees with model
predictions for the total pressure in the thick disk/lower halo. We also report
the results of searches for other emission lines.Comment: accepted by ApJ, scheduled for May 2003, replacement astro-ph
submission corrects typos and grammatical errors in original versio
One-dimensional spin-liquid without magnon excitations
It is shown that a sufficiently strong four-spin interaction in the spin-1/2
spin ladder can cause dimerization. Such interaction can be generated either by
phonons or (in the doped state) by the conventional Coulomb repulsion between
the holes. The dimerized phases are thermodynamically undistinguishable from
the Haldane phase, but have dramatically different correlation functions: the
dynamical magnetic susceptibility, instead of displaying a sharp single magnon
peak near , shows only a two-particle threshold separated from the
ground state by a gap.Comment: 9 pages, LaTex, to be published in Phys. Rev. Lett., vol. 78, May
199
Effect of protein and energy sources and bulk density of diets on growth performance of chicks
Four completely randomized designed experiments (EXP) were conducted to determine the effect of energy, amino acid (AA) levels, and bulk density of diets on growth performance of chicks fed diets containing corn (C) or cornstarch:dextrose (CD) as energy sources and soybean meal (SBM) or soy protein isolate (SPI) as protein sources. The chicks were fed C-SBM diets 6 to 8 d posthatching before allotment to treatment, and the assay periods ranged from 7 to 14 d. Initial weights were 86, 93, 94, and 71 g in EXP 1 to 4, respectively. Treatments were replicated 6 to 8 times with 4, 5, or 6 chicks per replicate. In EXP 1, the treatments were 1) CSBM (1.26% Lys and 3,200 kcal of ME/kg); 2) CD-SPI (1.26% Lys and 3,460 kcal of ME/kg); 3) CD-SPI (1.36% Lys and 3,460 kcal of ME/kg); and 4) CD-SPI (1.26% Lys and 3,200 kcal of ME/kg). The AA in all diets were increased in proportion to Lys. In EXP 2, chicks were fed C or CD as the energy source and SBM or SPI as the protein source in a 2 x 2 factorial arrangement. In EXP 3, the treatments were 1) C-SBM (1.26% Lys and 3,200 kcal of ME/kg); 2) CD-SPI (1.26% Lys and 3,200 kcal of ME/kg); 3) Diet 1 limit-fed to chicks consuming 90% of Diet 2; 4) Diet 2 limit-fed to chicks consuming 90% of Diet 2. In EXP 4, Diets 1 and 2 were the same as Diets 1 and 2 in EXP 3, but fed in mash or pelleted form. In all EXP, chicks with access ad libitum to diets with SPI had decreased (P \u3c 0.02) average daily gain (ADG) and feed intake (ADFI) compared with those with access ad libitum to diets with SBM. In EXP 2, feeding C- or CD-dextrose as the energy source had no effect (P \u3e 0.05) on ADG, ADFI, or gain:feed. In EXP 3, ADG was decreased in chicks fed the diets with SPI relative to those fed diets with SBM, but the decrease was much greater in chicks that had access ad libitum to feed (protein source x feed intake, P \u3c 0.01) than in those limit-fed to the same feed intake. In EXP 4, ADG, ADFI, and gain:feed were decreased (P \u3c 0.01) in chicks fed diets with SPI as the protein source. Pelleting increased (P \u3c 0.01) ADG, ADFI, and gain:feed regardless of protein source, but the increase was much greater in chicks fed the diets with SPI (protein source x feed form, P \u3c 0.01). Results from these EXP indicate that diets with SPI compared with SBM do not result in maximum growth performance in commercial broilers, and the problem may be due somewhat to nutrient deficiency but more to the physical form of the diet. ©2005 Poultry Science Association, Inc
FUSE Detection of Galactic OVI Emission in the Halo above the Perseus Arm
Background observations obtained with the Far Ultraviolet Spectroscopic
Explorer (FUSE) toward l=95.4, b=36.1 show OVI 1032,1038 in emission. This
sight line probes a region of stronger-than-average soft X-ray emission in the
direction of high-velocity cloud Complex C above a part of the disk where
Halpha filaments rise into the halo. The OVI intensities, 1600+/-300
ph/s/cm^2/sr (1032A) and 800+/-300 ph/s/cm^2/sr (1038A), are the lowest
detected in emission in the Milky Way to date. A second sight line nearby
(l=99.3, b=43.3) also shows OVI 1032 emission, but with too low a
signal-to-noise ratio to obtain reliable measurements. The measured
intensities, velocities, and FWHMs of the OVI doublet and the CII* line at
1037A are consistent with a model in which the observed emission is produced in
the Galactic halo by hot gas ejected by supernovae in the Perseus arm. An
association of the observed gas with Complex C appears unlikely.Comment: accepted for publication in ApJL, 11 pages including 3 figure
CYTOPLASMIC PARTICLES AND AMINOACYL TRANSFERASE I ACTIVITY
It has been possible to show by electron microscopy of samples selected from sucrose gradients that particles of specific size and shape are present in supernatant fluids derived from nucleated animal and plant cells, but not in extracts from Escherichia coli. Aminoacyl transferase I activity in these same gradients sediments in two peaks representing material of approximately 5–7S and 18–20S. A rectangular particle, 100 x 145 A in size, sediments at 19S and coincides with the second peak of transferase I activity. The possibility that the rectangular particle may be a "carrier" particle associated with transferase I is discussed
Alfalfa variety yield trials - 1988
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Damage Detection and Verification System (DDVS) for In-Situ Health Monitoring
Project presentation for Game Changing Program Smart Book Release. Detection and Verification System (DDVS) expands the Flat Surface Damage Detection System (FSDDS) sensory panels damage detection capabilities and includes an autonomous inspection capability utilizing cameras and dynamic computer vision algorithms to verify system health. Objectives of this formulation task are to establish the concept of operations, formulate the system requirements for a potential ISS flight experiment, and develop a preliminary design of an autonomous inspection capability system that will be demonstrated as a proof-of-concept ground based damage detection and inspection system
Probing Supersymmetry With Third-Generation Cascade Decays
The chiral structure of supersymmetric particle couplings involving third
generation Standard Model fermions depends on left-right squark and slepton
mixings as well as gaugino-higgsino mixings. The shapes and intercorrelations
of invariant mass distributions of a first or second generation lepton with
bottoms and taus arising from adjacent branches of SUSY cascade decays are
shown to be a sensitive probe of this chiral structure. All possible cascade
decays that can give rise to such correlations within the MSSM are considered.
For bottom-lepton correlations the distinctive structure of the invariant mass
distributions distinguishes between decays originating from stop or sbottom
squarks through either an intermediate chargino or neutralino. For decay
through a chargino the spins of the stop and chargino are established by the
form of the distribution. When the bottom charge is signed through soft muon
tagging, the structure of the same-sign and opposite-sign invariant mass
distributions depends on a set function of left-right and gaugino-higgsino
mixings, as well as establishes the spins of all the superpartners in the
sequential two-body cascade decay. Tau-lepton and tau-tau invariant mass
distributions arising from MSSM cascade decays are likewise systematically
considered with particular attention to their dependence on tau polarization.
All possible tau-lepton and tau-tau distributions are plotted using a
semi-analytic model for hadronic one-prong taus. Algorithms for fitting tau-tau
and tau-lepton distributions to data are suggested.Comment: 35 pages, 17 .eps figure
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