173 research outputs found
A Survey of Cattle Ectoparasites and a Study of Psoroptic Mange in Southeast Georgia
A comparison of traditional scrapings vs. a vacuum cleaner method of collecting cattle ectoparasites determined the vacuum method to be as efficient as the scraping method for collecting Psoroptes ovis, and possibly as effective for collecting Bovicola bovis.
In a survey of cattle ectoparasites in southeast Georgia, using the vacuum method, B. bovis were collected from cattle in a sales barn with an average of 15% parasitism from January 21 to March 18, 1985. Private herds sampled by the vacuum method, showed no ectoparasites. Cattle grubs (Hypoderma lineatum) were found on cattle in a sales barn from January to early March, 1985, while 4 private herds were virtually grub-free. One private herd of 16 calves was examined regularly for grubs from November, 1984 through March, 1985 with a peak of 73% parasitized and an average of 14 grubs per parasitized animal. The cattle grub season for southeast Georgia seems to begin by November and end around mid-March.
Sixteen Hereford heifers, divided into 2 groups (5 stanchioned and 11 unstanchioned) were infested 3 times with P. ovis over 5 weeks, December, 1984 through January 2, 1985. All unstanchioned claves showed no clinical signs of P. ovis5 weeks after the last innoculation with mites. All 5 stanchioned calves developed psoroptic mange. Considerable variation in the progression of the disease was noted. When stanchioned calves with psoroptic mange were released and allowed to self groom, lesions were rapidly removed, indicating self grooming is a natural host control of P. ovis
An angle-resolved soft x-ray spectroscopy study of the electronic states of single crystal MgB2
Angle-resolved soft x-ray measurements made at the boron K-edge in single
crystal MgB2 provide new insights into the B-2p local partial density of both
unoccupied and occupied band states. The strong variation of absorption with
incident angle of exciting x-rays permits the clear separation of contributions
from \sigma states in the boron plane and \pi states normal to the plane. A
careful comparison with theory accurately determines the energy of selected
critical points in the conduction band. Resonant inelastic x-ray emission
at an incident angle of 15 degrees shows a large enhancement of the emission
spectra within about 0.5 eV of the Fermi level that is absent at 45 degrees and
is much reduced at 60 degrees. We conclude that momentum transferred from the
resonant inelastic x-ray scattering (RIXS) process couples empty and filled
states across the Fermi level.Comment: Accepted to PRB. 13 pages, 6 figure
Soft x-ray spectroscopy experiments on the near K-edge of B in MB2 (M=Mg, Al, Ta, and Nb)
Soft X-ray absorption and emission measurements are performed for the K- edge
of B in MB (M=Mg, Al, Ta and Nb). Unique feature of MgB with a high
density of B 2-state below and above the Fermi edge, which
extends to 1 eV above the edge, is confirmed. In contrast, the B 2 density
of states in AlB and TaB, both of occupied and unoccupied states,
decreased linearly towards the Fermi energy and showed a dip at the Fermi
energy. Furthermore, there is a broadening of the peaks with
-character in XES and XAS of AlB, which is due to the increase of
three dimensionality in the -band in AlB. The DOS of NbB has a
dip just below the Fermi energy. The present results indicate that the large
DOS of B-2 states near the Fermi energy are crucial for the
superconductivity of MgB.Comment: 3 pages text and 4 pages figures. accepted for publication to Phys.
Rev.
Electron Correlation Effects in Resonant Inelastic X-ray Scattering of NaV2O5
Element- and site-specific resonant inelastic x-ray scattering spectroscopy
(RIXS) is employed to investigate electron correlation effects in {}. In contrast to single photon techniques, RIXS at the vanadium
edge is able to probe transitions between V d-bands. A sharp energy
loss feature is observed at -1.56 eV, which is well reproduced by a model
calculation including correlation effects. The calculation identifies the loss
feature as excitation between the lower and upper Hubbard bands and permits an
accurate determination of the Hubbard interaction term eV.Comment: 15 pages, four figures, accepted to Phys. Rev. Let
Soft x-ray spectroscopy measurements of the p-like density of states of B in MgB2 and evidence for surface boron oxides on exposed surfaces
Soft X-ray absorption and fluorescence measurements are reported for the
K-edge of B in MgB2. The measurements confirm a high density of B
pxy(sigma)-states at the Fermi edge and extending to approximately 0.9 eV above
the edge. A strong resonance is observed in elastic scattering through a
core-exciton derived from out-of-plane pz(pi*)-states. Another strong
resonance, observed in both elastic and inelastic spectra, is identified as a
product of surface boron oxides.Comment: 7 pages total, 4 figures, submitted to Phys. Rev. Let
X-Ray Magnetic Circular Dichroism of Pulsed Laser Deposited Co2MnSn and Co2MnSb Thin Films Grown on GaAs (001)
We present the structural and element specific magnetic properties of Co2MnSn and Co2MnSb thin films grown on GaAs (100) substrates using pulsed laser deposition. X-ray magnetic circular dichroism (XMCD) spectra were measured for 400 A thick films at the L2,3 edges of Co and Mn. Element specific moments for Co and Mn in Co2MnSn were calculated from the x-ray absorption and XMCD spectra using the XMCD sum rules. The ratios of orbital to spin magnetic moments for Co and Mn were calculated for Co2MnSn and Co2MnSb
Magnetic-field-induced singularities in spin dependent tunneling through InAs quantum dots
Current steps attributed to resonant tunneling through individual InAs
quantum dots embedded in a GaAs-AlAs-GaAs tunneling device are investigated
experimentally in magnetic fields up to 28 T. The steps evolve into strongly
enhanced current peaks in high fields. This can be understood as a
field-induced Fermi-edge singularity due to the Coulomb interaction between the
tunneling electron on the quantum dot and the partly spin polarized Fermi sea
in the Landau quantized three-dimensional emitter.Comment: 5 pages, 4 figure
Electronic structure of MgB: X-ray emission and absorption studies
Measurements of x-ray emission and absorption spectra of the constituents of
MgB are presented. The results obtained are in good agreement with
calculated x-ray spectra, with dipole matrix elements taken into account. The
comparison of x-ray emission spectra of graphite, AlB, and MgB in the
binding energy scale supports the idea of charge transfer from to
bands, which creates holes at the top of the bonding bands and
drives the high-TComment: final version as published in PR
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