1,447 research outputs found
Estimation of Dietary Iron Bioavailability from Food Iron Intake and Iron Status
Currently there are no satisfactory methods for estimating dietary iron absorption (bioavailability) at a population level, but this is essential for deriving dietary reference values using the factorial approach. The aim of this work was to develop a novel approach for estimating dietary iron absorption using a population sample from a sub-section of the UK National Diet and Nutrition Survey (NDNS). Data were analyzed in 873 subjects from the 2000–2001 adult cohort of the NDNS, for whom both dietary intake data and hematological measures (hemoglobin and serum ferritin (SF) concentrations) were available. There were 495 men aged 19–64 y (mean age 42.7±12.1 y) and 378 pre-menopausal women (mean age 35.7±8.2 y). Individual dietary iron requirements were estimated using the Institute of Medicine calculations. A full probability approach was then applied to estimate the prevalence of dietary intakes that were insufficient to meet the needs of the men and women separately, based on their estimated daily iron intake and a series of absorption values ranging from 1–40%. The prevalence of SF concentrations below selected cut-off values (indicating that absorption was not high enough to maintain iron stores) was derived from individual SF concentrations. An estimate of dietary iron absorption required to maintain specified SF values was then calculated by matching the observed prevalence of insufficiency with the prevalence predicted for the series of absorption estimates. Mean daily dietary iron intakes were 13.5 mg for men and 9.8 mg for women. Mean calculated dietary absorption was 8% in men (50th percentile for SF 85 µg/L) and 17% in women (50th percentile for SF 38 µg/L). At a ferritin level of 45 µg/L estimated absorption was similar in men (14%) and women (13%). This new method can be used to calculate dietary iron absorption at a population level using data describing total iron intake and SF concentration
Spin-orbit coupling and electron spin resonance for interacting electrons in carbon nanotubes
We review the theoretical description of spin-orbit scattering and electron
spin resonance in carbon nanotubes. Particular emphasis is laid on the effects
of electron-electron interactions. The spin-orbit coupling is derived, and the
resulting ESR spectrum is analyzed both using the effective low-energy field
theory and numerical studies of finite-size Hubbard chains and two-leg Hubbard
ladders. For single-wall tubes, the field theoretical description predicts a
double peak spectrum linked to the existence of spin-charge separation. The
numerical analysis basically confirms this picture, but also predicts
additional features in finite-size samples.Comment: 19 pages, 4 figures, invited review article for special issue in J.
Phys. Cond. Mat., published versio
Nottingham Health Profile and Short-Form 36 Health Survey questionnaires in patients with chronic lower limb ischemia: Before and after revascularization
AbstractObjective: The purpose of this study was to compare the usefulness of the Nottingham Health Profile (NHP) and the Short-Form 36 Health Survey (SF-36) as general outcome measures after vascular intervention for lower limb ischemia with respect to patients' quality of life, on the basis of validity, reliability, and responsiveness analyses. Patients and Methods: Eighty patients, 40 with claudication and 40 with critical ischemia, were assessed before and one month after revascularization by using comparable domains of the NHP and the SF-36 questionnaires. Results: The SF-36 scores were less skewed and were distributed more homogeneously than the NHP scores. Discriminate validity results showed that NHP was better than SF-36 in discriminating among levels of ischemia with respect to pain and physical mobility. For both questionnaires, the reliability standards were satisfactory in most respects. The NHP was more responsive than the SF-36 in detecting within-patient changes. All of the NHP domains not zero at baseline were improved significantly one month after hemodynamically successful revascularization for patients with claudication, whereas patients with critical ischemia showed significant abatement of pain and improvements in physical mobility and social isolation. The SF-36 scores indicated a significant decrease in bodily pain and improvements in physical functioning and vitality for patients with claudication, and decrease in bodily pain and improvement in physical functioning for patients with critical ischemia. Conclusions: The findings indicated that both NHP and SF-36 were reliable. The SF-36 scores were less skewed than the NHP scores, whereas NHP discriminated better among levels of ischemia and was more responsive in detecting quality-of-life changes over time than SF-36 in these particular patients. (J Vasc Surg 2002;36:310-7.
A Farmdalian Pollen Diagram From East-Central Iowa
Pollen analysis of the Butler Farm buried peat in east-central Iowa suggests that a spruce-pine forest grew in the area during the Farmdalian Substage. Pine decreased and spruce increased in dominance as the peat accumulated. Radiocarbon dates indicate that the peat was deposited from 28,800 to 22,750 RCYBP. It is overlain by late Wisconsinan loess and underlain by a Sangamon paleosol developed on Illinoian till. The regional pollen data suggest a general cooling trend through Farmdale time
Well-Water Quality Data from a Volunteer Sampling Program: Audubon County, Iowa
This study presents the results of a countywide volunteer sampling of private well-water. Volunteers collected 231 well-water samples in Audubon County for nitrate-nitrogen (NO3,-N) and total coliform bacteria analyses during September 1988. Questionnaires were completed at all sites to document well construction, age and depth of well, well placement relative to septic system, barnyard/feedlots, location of chemical mixing/tank rinsing, and presence of abandoned wells
Response of finite spin-S Heisenberg chains to local perturbations
We consider the properties of finite isotropic antiferromagnetic Heisenberg
chains with S=1/2, 1, 3/2 spins when a weak magnetic field is applied on a few
sites, using White's density matrix renormalization group (DMRG) method. For
the S=1 chain there exists only one length scale in the system which determines
the behavior of the one- and two-point correlation functions both around the
local perturbation and near the free boundary. For the critical,
half-odd-integer spin cases the exponent of the spin-spin correlation function
was found to be , and the exponent of the decay of the site
magnetization around the perturbed site is . Close to a free
boundary, however, the behavior is completely different for S=1/2 and .Comment: 13 pages, 7 figure
A Renormalization Group Method for Quasi One-dimensional Quantum Hamiltonians
A density-matrix renormalization group (DMRG) method for highly anisotropic
two-dimensional systems is presented. The method consists in applying the usual
DMRG in two steps. In the first step, a pure one dimensional calculation along
the longitudinal direction is made in order to generate a low energy
Hamiltonian. In the second step, the anisotropic 2D lattice is obtained by
coupling in the transverse direction the 1D Hamiltonians. The method is applied
to the anisotropic quantum spin half Heisenberg model on a square lattice.Comment: 4 pages, 4 figure
Two-state behaviour of Kondo trimers
The electronic properties and spectroscopic features of a magnetic trimer
with a Kondo-like coupling to a non-magnetic metallic substrate are analyzed at
zero temperature. The substrate density of states is depressed in the trimer
neighbourhood, being exactly zero at the substrate chemical potential. The size
of the resonance strongly depends on the magnetic state of the trimer, and
exhibits a two-state behavior. The geometrical dependence of these results
agree qualitatively with recent experiments and could be reproduced in a
triangular quantum dot arrangement.Comment: 5 pages, including 4 figure
Density matrix renormalisation group for a quantum spin chain at non-zero temperature
We apply a recent adaptation of White's density matrix renormalisation group
(DMRG) method to a simple quantum spin model, the dimerised chain, in
order to assess the applicabilty of the DMRG to quantum systems at non-zero
temperature. We find that very reasonable results can be obtained for the
thermodynamic functions down to low temperatures using a very small basis set.
Low temperature results are found to be most accurate in the case when there is
a substantial energy gap.Comment: 6 pages, Standard Latex File + 7 PostScript figures available on
reques
Dynamical Correlation Functions using the Density Matrix Renormalization Group
The density matrix renormalization group (DMRG) method allows for very
precise calculations of ground state properties in low-dimensional strongly
correlated systems. We investigate two methods to expand the DMRG to
calculations of dynamical properties. In the Lanczos vector method the DMRG
basis is optimized to represent Lanczos vectors, which are then used to
calculate the spectra. This method is fast and relatively easy to implement,
but the accuracy at higher frequencies is limited. Alternatively, one can
optimize the basis to represent a correction vector for a particular frequency.
The correction vectors can be used to calculate the dynamical correlation
functions at these frequencies with high accuracy. By separately calculating
correction vectors at different frequencies, the dynamical correlation
functions can be interpolated and pieced together from these results. For
systems with open boundaries we discuss how to construct operators for specific
wavevectors using filter functions.Comment: minor revision, 10 pages, 15 figure
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