1,584 research outputs found
Scaling Behavior of the Activated Conductivity in a Quantum Hall Liquid
We propose a scaling model for the universal longitudinal conductivity near
the mobility edge for the integer quantum Hall liquid. We fit our model with
available experimental data on exponentially activated conductance near the
Landau level tails in the integer quantum Hall regime. We obtain quantitative
agreement between our scaling model and the experimental data over a wide
temperature and magnetic field range.Comment: 9 pages, Latex, 2 figures (available upon request), #phd0
Analysis of trace elements in forages by near infrared reflectance spectroscopy
Use of near infrared reflectance spectroscopy (NIRS) for elemental
analysis has been limited to a few elements including Ca, P, K,
and Mg. However, other elements are of interest in the agricultural
industry. Therefore, NIRS spectra were collected on forage samples
consisting of tall fescue (Festuca arundinacea Schreb.), crested
wheatgrass (Agropyron cristatum and A. desertorum), and alfalfa
(Medicago sativa L.). Elemental concentrations of Ba, Li, Mo, Ni,
Pb, V, Al, S, and Si were determined by ICP (Inductively Coupled
Argon Plasma) analysis while selenium (Se) was determined by fluorometry.
The elemental analyses were regressed against NIRS apparent
absorption from 1100 to 2500 nm at 2-nm increments. Coefficients
of variation /CV = (standard error of performance / the mean
from the chemical procedure) X 1001 ranged from a high of 211%
for Li in crested wheatgrass to 11% for S in alfalfa. Determination
of Ba, Li, Mo, Ni, Pb, and V exhibited enough inconsistency in CVs
among the three forages to preclude their determination with NIRS.
Aluminum and S appear to be present in an organic form that NIRS
is able to detect (CV = 22 and 15, 21 and 12, and 28 and 11%, for
tall fescue, crested wheatgrass, and alfalfa, respectively). Silica exhibited
slightly more variation than S or Al, with alfalfa having the
highest CV (49%). Selenium was only determined on a tall fescue
population with a CV = 27%. Using the statistical values as parameters
indicative of NIRS utility, it appears that Al and S are the
only elements in this group of minerals that can be determined with
NIRS for these forage types
Response to Selection for Reduced Grass Tetany Potential in Crested Wheatgrass
Grass tetany (hypomagnesemia) has caused substantial economic
losses in ruminant animals grazing crested wheatgrass (Agropyron
spp.) and other cool-season (C3) grasses. This malady is most prevalent
in early lactating animals grazing forage that is deficient in Mg, Ca,
and carbohydrates and with high levels of K. The K/(Ca + Mg) ratio
expressed as moles of charge is often used to estimate the grass tetany
potential of forage samples. Previous studies have shown that heritable
variation exists in crested wheatgrass populations for traits associated
with grass tetany, and research was conducted to determine the genetic
response to selection for these traits. Selections were made during
1985 from two crested wheatgrass breeding populations in Utah (`I-28'
and Hycrest) based on a reduced grass tetany potential (RTP) index,
which incorporates the K/(Ca + Mg) ratio along with concentrations
of Ca, Mg, and K. Mean values for the K/(Ca + Mg) were reduced by
5% in 1-28 and 11% in Hycrest after one cycle of selection. Narrow-sense
heritability values based on actual genetic advance and parent-progeny
regression ranged from 0.62 to 0.82 in analyses of data combined
across two sampling dates and two years (1988 and 1989). Genetic
response to selection on the basis of RTP index was closely associated
with the K/(Ca + Mg) ratio and concentrations of Ca and Mg but
not with levels of K. Correlations between the K/(Ca + Mg) ratio
and crude protein content and digestibility suggested that selection
for RTP would likely be accompanied by improved forage quality in
the Hycrest breeding population
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Seasonal trends in herbage yield and quality of Agropyrons
Crested wheatgrasses (Agropyron spp.) are grown on 6 million
ha in the U.S. and Canada, where they provide excellent early-season
forage, but lose nutritional quality by midsummer. Some
producers believe that A. fragile maintains its quality longer than
other crested wheatgrasses. This study compared herbage yield and
quality of 3 A. fragile entries with A. desertorum, A. cristatum,
1-28 (induced tetraploid of A. cristatum), and the hybrid 'Hycrest'.
Entries were established near Logan, Ut., on 1-m spacings. Herbage
yield and quality were determined in year 2 and 3 at vegetative,
boot, flower, seed ripe, and post-seed-ripe maturity stages
(harvests 1 through 5) and on regrowth following the vegetative
and boot-stage harvests. All entries flowered within 1 to 2 days of
each other. Dry-matter yield increased for all grasses, but digestibility
(IVDMD), crude protein, and elemental concentrations
declined with maturity. Mean IVDMD values for all grasses were
741,642,534,485, and 444 mg g-1 for harvests 1 through 5 and 490
and 560 mg g-1 for the regrowth following harvest 1 and 2. The A.
fragile entries had higher N, Ca, P, and Ca/P, but lower yield,
IVDMD, and grass tetany potential values than other Agropyrons.
Contrary to expectations, IVDMD of A. fragile decreased to 500
mg g-1 , 6 to 11 days earlier than for the other Agropyrons. The 1-28
and Hycrest entries had higher yield, IVDMD, K, and grass tetany
risk and lower N, Ca, P, and Ca/P than the other Agropyrons
Mineral analysis of forages with near infrared reflectance spectrosopy
Mineral concentration data could easily be generated by near infrared
reflectance spectroscopy (NIRS) while determining quality
parameters in forage samples. However, which minerals can be analyzed
and why they can be determined has not been documented
adequately. Therefore, NIRS spectra were collected on 200 samples
of crested wheatgrass (Agropyron spp.), 203 tall fescue (Festuca
arundinacea Schreb.), and 59 alfalfa (Medicago sativa L.) hays. Concentrations
of Na, K, Ca, P, Mg, Fe, Mn, Cu, and Zn, as determined
by atomic absorption, and calculated values of the Ca/P, K/Mg, and
K/(Ca + Mg) ratios were regressed against reflectance values measured
in 2-nm increments between 1100 and 2500 nm for each sample.
Approximately one half of the samples in each forage set was
used to develop the calibration equations, while the other half was
used to validate the equations. The coefficients of variation [CV =
(standard error of analysis Ă· the mean)X 100] generally ranged from
10 to 20% for K, Mg, Ca, and P concentrations in each forage type.
The Ca/P ratio in alfalfa was determined with a CV of 18%. The
CV values of other minerals and mineral ratios generally exceeded
20%. Chlorophyll and some inorganic salts and organic-acid salts
of Ca, Mg, and K were scanned with NIRS for wavelength comparisons
with those wavelengths used to determine mineral concentrations
in forages. Some of the wavelengths used in the equations
for Ca, K, and Mg were related to peaks and changes in slope observed
in chlorophyll and organic-acid salts of Ca, K, and Mg, suggesting
that NIRS is indirectly measuring these minerals by their
association with organic molecules. Accurate use of NIRS to determine
mineral cation composition in forages appears limited to certain
major minerals (Ca, P, K, and Mg)
Self-consistent description of nuclear compressional modes
Isoscalar monopole and dipole compressional modes are computed for a variety
of closed-shell nuclei in a relativistic random-phase approximation to three
different parametrizations of the Walecka model with scalar self-interactions.
Particular emphasis is placed on the role of self-consistency which by itself,
and with little else, guarantees the decoupling of the spurious
isoscalar-dipole strength from the physical response and the conservation of
the vector current. A powerful new relation is introduced to quantify the
violation of the vector current in terms of various ground-state form-factors.
For the isoscalar-dipole mode two distinct regions are clearly identified: (i)
a high-energy component that is sensitive to the size of the nucleus and scales
with the compressibility of the model and (ii) a low-energy component that is
insensitivity to the nuclear compressibility. A fairly good description of both
compressional modes is obtained by using a ``soft'' parametrization having a
compression modulus of K=224 MeV.Comment: 28 pages and 10 figures; submitted to PR
Equation of state and magnetic susceptibility of spin polarized isospin asymmetric nuclear matter
Properties of spin polarized isospin asymmetric nuclear matter are studied
within the framework of the Brueckner--Hartree--Fock formalism. The
single-particle potentials of neutrons and protons with spin up and down are
determined for several values of the neutron and proton spin polarizations and
the asymmetry parameter. It is found an almost linear and symmetric variation
of the single-particle potentials as increasing these parameters. An analytic
parametrization of the total energy per particle as a function of the asymmetry
and spin polarizations is constructed. This parametrization is employed to
compute the magnetic susceptibility of nuclear matter for several values of the
asymmetry from neutron to symmetric matter. The results show no indication of a
ferromagnetic transition at any density for any asymmetry of nuclear matter.Comment: 23 pages, 8 figures, 2 tables (submitted to Phys. Rev. C
Search for exotic baryons in double radiative capture on pionic hydrogen
We report a search for low-lying exotic baryons via double radiative capture
on pionic hydrogen. The data were collected at the TRIUMF cyclotron using the
RMC spectrometer by detecting gamma-ray pairs from pion stops in liquid
hydrogen. No evidence was found to support an earlier claim for exotic baryons
of masses 1004 and 1044 MeV/. We obtain upper limits on the branching
ratios for double radiative capture via these exotic states of and respectively.Comment: 13 pages, 4 figure
Implementing NICE guidelines for the psychological treatment of depression and anxiety disorders: The IAPT experience
The Improving Access to Psychological Therapies (IAPT) programme is a large-scale initiative that aims to greatly increase the availability of NICE recommended psychological treatment for depression and anxiety disorders within the National Health Service in England. This article describes the background to the programme, the arguments on which it is based, the therapist training scheme, the clinical service model, and a summary of progress to date. At mid-point in a national roll-out of the programme progress is generally in line with expectation, and a large number of people who would not otherwise have had the opportunity to receive evidence-based psychological treatment have accessed, and benefited from, the new IAPT services. Planned future developments and challenges for the programme are briefly described
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