1,404 research outputs found
Checkerboard order in the t--J model on the square lattice
We propose that the inhomogeneous patterns seen by STM in some underdoped
superconducting cuprates could be related to a bond-order-wave instability of
the staggered flux state, one of the most studied "normal" state proposed to
compete with the d-wave RVB superconductor. A checkerboard pattern is obtained
by a Gutzwiller renormalized mean-field theory of the t-J model for doping
around 1/8. It is found that the charge modulation is always an order of
magnitude smaller than the bond-order modulations. This is confirmed by an
exact optimization of the wavefunction by a variational Monte Carlo scheme. The
numerical estimates of the order parameters are however found to be strongly
reduced w.r.t their mean-field values
A Convex Model for Edge-Histogram Specification with Applications to Edge-preserving Smoothing
The goal of edge-histogram specification is to find an image whose edge image
has a histogram that matches a given edge-histogram as much as possible.
Mignotte has proposed a non-convex model for the problem [M. Mignotte. An
energy-based model for the image edge-histogram specification problem. IEEE
Transactions on Image Processing, 21(1):379--386, 2012]. In his work, edge
magnitudes of an input image are first modified by histogram specification to
match the given edge-histogram. Then, a non-convex model is minimized to find
an output image whose edge-histogram matches the modified edge-histogram. The
non-convexity of the model hinders the computations and the inclusion of useful
constraints such as the dynamic range constraint. In this paper, instead of
considering edge magnitudes, we directly consider the image gradients and
propose a convex model based on them. Furthermore, we include additional
constraints in our model based on different applications. The convexity of our
model allows us to compute the output image efficiently using either
Alternating Direction Method of Multipliers or Fast Iterative
Shrinkage-Thresholding Algorithm. We consider several applications in
edge-preserving smoothing including image abstraction, edge extraction, details
exaggeration, and documents scan-through removal. Numerical results are given
to illustrate that our method successfully produces decent results efficiently
RAGs and Regulation of Autoantibodies
Autoreactive antibodies are etiologic agents in a number of autoimmune diseases. Like all other antibodies these antibodies are produced in developing B cells by V(D)J recombination in the bone marrow. Three mechanisms regulate autoreactive B cells: deletion, receptor editing, and anergy. Here we review the prevalence of autoantibodies in the initial antibody repertoire, their regulation by receptor editing, and the role of the recombinase proteins (RAG l and RAG2) in this process
Bond-order modulated staggered flux phase for the model on the square lattice
Motivated by the observation of inhomogeneous patterns in some high-T
cuprate compounds, several variational Gutzwiller-projected wave-functions with
built-in charge and bond order parameters are proposed for the extended
model on the square lattice at low doping. First, following a recent
Gutzwiller-projected mean-field approach by one of us (Phys. Rev. B. {\bf 72},
060508(R) (2005)), we investigate, as a function of doping and Coulomb
repulsion, the stability of the staggered flux phase with respect to small
spontaneous modulations of squared unit cells ranging from to
. It is found that a bond-order (BO)
modulation appears spontaneously on top of the staggered flux pattern for hole
doping around 1/8. A related wave-function is then constructed and optimized
accurately and its properties studied extensively using an approximation-free
variational Monte Carlo scheme. Finally, the competition of the BO-modulated
staggered flux wave-function w.r.t. the d-wave RVB wave-function or the
commensurate flux state is investigated. It is found that a short range Coulomb
repulsion penalizes the d-wave superconductor and that a moderate Coulomb
repulsion brings them very close in energy. Our results are discussed in
connection to the STM observations in the under-doped regime of some cuprates.Comment: 10 pages, 9 figure
Magnetization plateaux in an extended Shastry-Sutherland model
We study an extended two-dimensional Shastry-Sutherland model in a magnetic
field where besides the usual Heisenberg exchanges of the Shastry-Sutherland
model two additional SU(2) invariant couplings are included. Perturbative
continous unitary transformations are used to determine the leading order
effects of the additional couplings on the pure hopping and on the long-range
interactions between the triplons which are the most relevant terms for small
magnetization. We then compare the energy of various magnetization plateaux in
the classical limit and we discuss the implications for the two-dimensional
quantum magnet SrCu(BO).Comment: 8 pages, Proceedings of the HFM2008 Conferenc
Low Energy Singlets in the Excitation Spectrum of the Spin Tetrahedra System Cu_2Te_2O_5Br_2
Low energy Raman scattering of the s=1/2 spin tetrahedra system
Cu_2Te_2O_5Br_2 is dominated by an excitation at 18 cm^{-1} corresponding to an
energy E_S=0.6\Delta, with \Delta the spin gap of the compound. For elevated
temperatures this mode shows a soft mode-like decrease in energy pointing to an
instability of the system. The isostructural reference system Cu_2Te_2O_5Cl_2
with a presumably larger inter-tetrahedra coupling does not show such a low
energy mode. Instead its excitation spectrum and thermodynamic properties are
compatible with long range Neel-ordering. We discuss the observed effects in
the context of quantum fluctuations and competing ground states.Comment: 5 pages, 2 figures, ISSP-Kashiwa 2001, Conference on Correlated
Electron
Time-reversal symmetry breaking Abelian chiral spin liquid in Mott phases of three-component fermions on the triangular lattice
We provide numerical evidence in favor of spontaneous chiral symmetry
breaking and the concomitant appearance of an Abelian chiral spin liquid for
three-component fermions on the triangular lattice described by an SU(3)
symmetric Hubbard model with hopping amplitude () and on-site
interaction . This chiral phase is stabilized in the Mott phase with one
particle per site in the presence of a uniform -flux per plaquette, and in
the Mott phase with two particles per site without any flux. Our approach
relies on effective spin models derived in the strong-coupling limit in powers
of for general SU and arbitrary uniform charge flux per plaquette,
which are subsequently studied using exact diagonalizations and variational
Monte Carlo simulations for , as well as exact diagonalizations of the
SU() Hubbard model on small clusters. Up to third order in , and for
the time-reversal symmetric cases (flux or ), the low-energy
description is given by the - model with Heisenberg coupling and real
ring exchange . The phase diagram in the full - parameter range
contains, apart from three already known, magnetically long-range ordered
phases, two previously unreported phases: i) a lattice nematic phase breaking
the lattice rotation symmetry and ii) a spontaneous time-reversal and parity
symmetry breaking Abelian chiral spin liquid. For the Hubbard model, an
investigation that includes higher-order itinerancy effects supports the
presence of a phase transition inside the insulating region, occurring at
[] between the
three-sublattice magnetically ordered phase at small and this Abelian
chiral spin liquid.Comment: 21 pages, 23 figure
KETEPATAN DAN KEPATUHAN KONSUMSI DIIT DIABETES MELLITUS PENDERITA RAWAT INAP DI RSU BRAYAT MINULYA SURAKARTA
Background: The main basis for the therapy of Diabetes mellitus (DM) is the regulation of the diet that full fills the energy needs of the patient. in theory, to determine the total energy needs, first one has to determine the nutritional state of the patient by calculating the Relative Body weight of the patient. In reality, doctor often determines the diet only based on an estimation of the patient's body weight Several .factors influence the patients' obedience to the die, among others the taste of food, food habits, and their knowledge of the illness. This examination concerned the Accuracy of as well as the obedience to DM diet of the patient in Brayat Minulya General Hospital in Surakarta. The aim of this examination was to get to know the degree of accuracy of the obedience to the consumption of DM diet of patients in Brayat Minulya General Hospital in Surakarta. Method: The accuracy of DM diet was evaluated by comparing the total calorie value af the nutritional state of patients. The obedience of the patients was evaluated by measuring the average of the leftovers during three days, expressed in per cents. The taste of food, food habitats, and patients' knowledge af DM were evaluated by way of scoring the patients' answers to the questionnaire. The results obtain C show that 88, 9% of the diets prescribed by the doctors were not accurate as to the total calorie value, whereas 8 I, 5% of the patients obeyed the diet given. The result of the evaluations of the factors influencing the obedience of the patients to the diet showed that Bl,5%found that the food was tqstefull,82,5% had food habits in accordance with the food served to them in the hospital, and 74, l% of the patients had a good knowledge of DM. There is a correlation between the taste of food, food habits, and the patients' knowledge of DM on one side and their obedience to the DM diet on the other side. Conclusion: a great number of DM diets prescribed by the doctors are not accurate as to the total calorie value. A great number of patients obey the diet. The more tasteful the diet, the more in accordance with food habits of the patients, and the better their knowledge of diabetes mellitus, the better the patients obits the diet. Keywords: DM, diet, accurate, obedienc
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