1,283 research outputs found
Mirages and enhanced magnetic interactions in quantum corrals
We develop a theory for the interactions between magnetic impurities in
nanoscopic systems. The case of impurities in quantum corrals built on the
(111) Cu surface is analyzed in detail. For elliptical corrals with one
impurity, clear magnetic mirages are obtained. This leads to an enhancement of
the inter-impurity interactions when two impurities are placed at special
points in the corral. We discuss the enhancement of the conduction electron
response to the local perturbation in other nanoscopic systems.Comment: 7 pages, 5 figure
Spin order in the one-dimensional Kondo and Hund lattices
We study numerically the one-dimensional Kondo and Hund lattices consisting
of localized spins interacting antiferro or ferromagnetically with the
itinerant electrons, respectively. Using the Density Matrix Renormalization
Group we find, for both models and in the small coupling regime, the existence
of new magnetic phases where the local spins order forming ferromagnetic
islands coupled antiferromagnetically. Furthermore, by increasing the
interaction parameter we find that this order evolves toward the
ferromagnetic regime through a spiral-like phase with longer characteristic
wave lengths. These results shed new light on the zero temperature magnetic
phase diagram for these models.Comment: PRL, to appea
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
Detection of topological transitions by transport through molecules and nanodevices
We analyze the phase transitions of an interacting electronic system weakly
coupled to free-electron leads by considering its zero-bias conductance. This
is expressed in terms of two effective impurity models for the cases with and
without spin degeneracy. We demonstrate using the half-filled ionic Hubbard
ring that the weight of the first conductance peak as a function of external
flux or of the difference in gate voltages between even and odd sites allows
one to identify the topological charge transition between a correlated
insulator and a band insulator.Comment: 4 pages, 5 figures, to appear in Phys. Rev. Let
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
Long-term effects of a novel continuous remote care intervention including nutritional ketosis for the management of type 2 diabetes: A 2-year non-randomized clinical trial
Self-Consistent Tensor Product Variational Approximation for 3D Classical Models
We propose a numerical variational method for three-dimensional (3D)
classical lattice models. We construct the variational state as a product of
local tensors, and improve it by use of the corner transfer matrix
renormalization group (CTMRG), which is a variant of the density matrix
renormalization group (DMRG) applied to 2D classical systems. Numerical
efficiency of this approximation is investigated through trial applications to
the 3D Ising model and the 3D 3-state Potts model.Comment: 12 pages, 6 figure
Post hoc analyses of surrogate markers of non-alcoholic fatty liver disease (NAFLD) and liver fibrosis in patients with type 2 diabetes in a digitally supported continuous care intervention: An open-label, non-randomised controlled study
OBJECTIVE:
One year of comprehensive continuous care intervention (CCI) through nutritional ketosis improves glycosylated haemoglobin(HbA1c), body weight and liver enzymes among patients with type 2 diabetes (T2D). Here, we report the effect of the CCI on surrogate scores of non-alcoholic fatty liver disease (NAFLD) and liver fibrosis.
METHODS:
This was a non-randomised longitudinal study, including adults with T2D who were self-enrolled to the CCI (n=262) or to receive usual care (UC, n=87) during 1 year. An NAFLD liver fat score (N-LFS) >-0.640 defined the presence of fatty liver. An NAFLD fibrosis score (NFS) of >0.675 identified subjects with advanced fibrosis. Changes in N-LFS and NFS at 1 year were the main endpoints.
RESULTS:
At baseline, NAFLD was present in 95% of patients in the CCI and 90% of patients in the UC. At 1 year, weight loss of ≥5% was achieved in 79% of patients in the CCI versus 19% of patients in UC (p<0.001). N-LFS mean score was reduced in the CCI group (-1.95±0.22, p<0.001), whereas it was not changed in the UC (0.47±0.41, p=0.26) (CCI vs UC, p<0.001). NFS was reduced in the CCI group (-0.65±0.06, p<0.001) compared with UC (0.26±0.11, p=0.02) (p<0.001 between two groups). In the CCI group, the percentage of individuals with a low probability of advanced fibrosis increased from 18% at baseline to 33% at 1 year (p<0.001).
CONCLUSIONS:
One year of a digitally supported CCI significantly improved surrogates of NAFLD and advanced fibrosis in patients with T2D
An Improved Initialization Procedure for the Density-Matrix Renormalization Group
We propose an initialization procedure for the density-matrix renormalization
group (DMRG): {\it the recursive sweep method}. In a conventional DMRG
calculation, the infinite-algorithm, where two new sites are added to the
system at each step, has been used to reach the target system size. We then
need to obtain the ground state for a different system size for every site
addition, so 1) it is difficult to supply a good initial vector for the
numerical diagonalization for the ground state, and 2) when the system reduced
to a 1D system consists of an array of nonequivalent sites as in ladders or
Hubbard-Holstein model, special care has to be taken. Our procedure, which we
call the {\it recursive sweep method}, provides a solution to these problems
and in fact provides a faster algorithm for the Hubbard model as well as more
complicated ones such as the Hubbard-Holstein model.Comment: 4 pages, 4 figures, submitted to JPS
Shadow band in the one-dimensional large Hubbard model
We show that the factorized wave-function of Ogata and Shiba can be used to
calculate the dependent spectral functions of the one-dimensional, infinite
Hubbard model, and of some extensions to finite . The resulting spectral
function is remarkably rich: In addition to low energy features typical of
Luttinger liquids, there is a well defined band, which we identify as the
shadow band resulting from spin fluctuations. This band should be
detectable experimentally because its intensity is comparable to that of the
main band for a large range of momenta.Comment: Latex file. 4 pages. Figures upon reques
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