389 research outputs found
Charge gaps and quasiparticle bands of the ionic Hubbard model
The ionic Hubbard model on a cubic lattice is investigated using analytical
approximations and Wilson's renormalization group for the charge excitation
spectrum. Near the Mott insulating regime, where the Hubbard repulsion starts
to dominate all energies, the formation of correlated bands is described. The
corresponding partial spectral weights and local densities of states show
characteristic features, which compare well with a hybridized-band picture
appropriate for the regime at small , which at half-filling is known as a
band insulator. In particular, a narrow charge gap is obtained at half-filling,
and the distribution of spectral quasi-particle weight reflects the fundamental
hybridization mechanism of the model
Two Forms of Activation-Induced Cytidine Deaminase Differing in Their Ability to Bind Agarose
Background: Activation-induced cytidine deaminase (AID) is a B-cell-specific DNA mutator that plays a key role in the formation of the secondary antibody repertoire in germinal center B cells. In the search for binding partners, protein coimmunoprecipitation assays are often performed, generally with agarose beads. Methodology/Principal Findings: We found that, regardless of whether cell lysates containing exogenous or endogenous AID were examined, one of two mouse AID forms bound to agarose alone. Conclusions/Significance: These binding characteristics may be due to the known post-translational modifications of AID; they may also need to be considered in coimmunoprecipitation experiments to avoid false-positive results
The asymmetric single-impurity Anderson model - the modified perturbation theory
We investigate the single-impurity Anderson model by means of the recently
introduced modified perturbation theory. This approximation scheme yields
reasonable results away from the symmetric case. The agreement with exactly
known results for the symmetric case is checked, and results for the
non-symmetric case are presented. With decreasing conduction band occupation,
the breakdown of the screening of the local moment is observed. In the
crossover regime between Kondo limit and mixed-valence regime, an enhanced
zero-temperature susceptibility is found.Comment: 7 pages, 7 figures, to appear in Physica
Resonant Enhancement of Electronic Raman Scattering
We present an exact solution for electronic Raman scattering in a
single-band, strongly correlated material, including nonresonant, resonant and
mixed contributions. Results are derived for the spinless Falicov-Kimball
model, employing dynamical mean field theory; this system can be tuned through
a Mott metal-insulator transition.Comment: 4 pages, 3 figures, contribution to the SNS'2004 conferenc
Optimization of Gutzwiller Wavefunctions in Quantum Monte Carlo
Gutzwiller functions are popular variational wavefunctions for correlated
electrons in Hubbard models. Following the variational principle, we are
interested in the Gutzwiller parameters that minimize e.g. the expectation
value of the energy. Rewriting the expectation value as a rational function in
the Gutzwiller parameters, we find a very efficient way for performing that
minimization. The method can be used to optimize general Gutzwiller-type
wavefunctions both, in variational and in fixed-node diffusion Monte Carlo.Comment: 9 pages RevTeX with 10 eps figure
5-Lipoxygenase: Underappreciated Role of a Pro-Inflammatory Enzyme in Tumorigenesis
Leukotrienes constitute a group of bioactive lipids generated by the 5-lipoxygenase (5-LO) pathway. An increasing body of evidence supports an acute role for 5-LO products already during the earliest stages of pancreatic, prostate, and colorectal carcinogenesis. Several pieces of experimental data form the basis for this hypothesis and suggest a correlation between 5-LO expression and tumor cell viability. First, several independent studies documented an overexpression of 5-LO in primary tumor cells as well as in established cancer cell lines. Second, addition of 5-LO products to cultured tumor cells also led to increased cell proliferation and activation of anti-apoptotic signaling pathways. 5-LO antisense technology approaches demonstrated impaired tumor cell growth due to reduction of 5-LO expression. Lastly, pharmacological inhibition of 5-LO potently suppressed tumor cell growth by inducing cell cycle arrest and triggering cell death via the intrinsic apoptotic pathway. However, the documented strong cytotoxic off-target effects of 5-LO inhibitors, in combination with the relatively high concentrations of 5-LO products needed to achieve mitogenic effects in cell culture assays, raise concern over the assignment of the cause, and question the relationship between 5-LO products and tumorigenesis
Effect of a conventional energy-restricted modified diet with or without meal replacement on weight loss and cardiometabolic risk profile in overweight women
<p>Abstract</p> <p>Background</p> <p>Abdominal obesity, atherogenic dyslipidemia and hypertension are essential risk factors for cardiovascular diseases. Several studies showed favorable effects of weight loss in overweight subjects on cardiometabolic risk profile.</p> <p>Methods</p> <p>This open-label, randomized, controlled study investigated the effect of an energy-restricted modified diet with (MR) or without meal replacements for weight control (C) on weight loss, body composition and cardiometabolic risk profile in overweight women. Of 105 randomized participants, 87 were eligible for per protocol analysis. Anthropometric, clinical, blood, 24 h-urine parameters and dietary intake were assessed at baseline and after 12 weeks.</p> <p>Results</p> <p>Dietary intervention resulted in a significant weight loss in both groups (MR: -5.98 ± 2.82 kg; p < 0.001, C: -4.84 ± 3.54 kg; p < 0.001). However, the rate of responder (weight loss >5%) was higher in MR (77%) versus C group (50%) (p = 0.010). A significant reduction in waist circumference (WC) and body fat mass (BFM) was observed in both groups. Body cell mass (BCM) and lean body mass (LBM) decreased, while percentage of BCM of body weight increased in MR more than in C group. Systolic and diastolic blood pressure (BP) significantly decreased and to a similar extent in both groups. Total cholesterol (TC), LDL-C but also HDL-C declined significantly in both groups, while no change occurred in triglycerides.</p> <p>Conclusions</p> <p>Both dietary intervention strategies had a similar effect on weight loss and body fat distribution, but rate of responder was significantly higher in MR group. Systolic BP decreased to a similar extent in both groups. Cardiometabolic risk profile improved only partly in both groups.</p
AnsĂ€tze zur nachhaltigen Sicherung der botanischen Artenvielfalt auf SchutzĂ€ckern â eine Aufgabe fĂŒr Biobetriebe?
Der drastische ArtenrĂŒckgang unter den AckerwildkrĂ€utern war Anlass zur Suche nach neuen Schutzkonzepten. Das Projekt âErrichtung eines bundesweiten Schutzgebietsnetzes fĂŒr AckerwildkrĂ€uterâ verfolgt das Ziel, ein nachhaltiges Schutzgebiets-Netzwerk zum Erhalt bedrohter Segetalarten in Deutschland zu konzipieren und umzusetzen. Eine Anzahl von mindestens 100 geeigneten Ackerstandorten (â100 Ăcker fĂŒr die Vielfaltâ) soll fĂŒr eine âdauerhafte Sicherungâ selten gewordener AckerwildkrĂ€uter unter Schutz gestellt werden und ihre spezielle, auf den Erhalt und Förderung der entsprechenden Arten ausgerichtete Bewirtschaftung langfristig sichergestellt werden.
Ăkologisch bewirtschaftete Felder sind dazu besonders geeignet. Das innovative Beispiel eines ökologisch wirtschaftenden Landwirts wird vorgestellt. Die Herausforderung ist die Sicherstellung des langfristigen Schutzes durch vertragliche Vereinbarungen
The Full Event Interpretation -- An exclusive tagging algorithm for the Belle II experiment
The Full Event Interpretation is presented: a new exclusive tagging algorithm
used by the high-energy physics experiment Belle II. The experimental setup of
Belle II allows the precise measurement of otherwise inaccessible meson
decay-modes. The Full Event Interpretation algorithm enables many of these
measurements. The algorithm relies on machine learning to automatically
identify plausible meson decay chains based on the data recorded by the
detector. Compared to similar algorithms employed by previous experiments, the
Full Event Interpretation provides a greater efficiency, yielding a larger
effective sample size usable in the measurement.Comment: 11 pages, 7 figures, 1 tabl
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