504 research outputs found
Convergence acceleration and stabilization for dynamical-mean-field-theory calculations
The convergence to the self-consistency in the dynamical-mean-field-theory
(DMFT) calculations for models of correlated electron systems can be
significantly accelerated by using an appropriate mixing of hybridization
functions which are used as the input to the impurity solver. It is shown that
the techniques and the past experience with the mixing of input charge
densities in the density-functional-theory (DFT) calculations are also
effective in DMFT. As an example, the increase of the computational
requirements near the Mott metal-insulator transition in the Hubbard model due
to critical slowing down can be strongly reduced by using the modified
Broyden's method to numerically solve the non-linear self-consistency equation.
Speed-up factors as high as 3 were observed in practical calculations even for
this relatively well behaved problem. Furthermore, the convergence can be
achieved in difficult cases where simple linear mixing is either not effective
or even leads to divergence. Unstable and metastable solutions can also be
obtained. We also determine the linear response of the system with respect to
the variations of the hybridization function, which is related to the
propagation of the information between the different energy scales during the
iteration.Comment: 9 pages, 8 figure
Quantum phase transitions in the systems of parallel quantum dots
We study the low-temperature transport properties of the systems of parallel
quantum dots described by the N-impurity Anderson model. We calculate the
quasiparticle scattering phase shifts, spectral functions and correlations as a
function of the gate voltage for N up to 5. For any N, the conductance at the
particle-hole symmetric point is unitary. For N >= 2, a transition from
ferromagnetic to antiferromagnetic impurity spin correlations occurs at some
gate voltage. For N >= 3, there is an additional transition due to an abrupt
change in average impurity occupancy. For odd N, the conductance is
discontinuous through both quantum phase transitions, while for even N only the
magnetic transition affects the conductance. Similar effects should be
experimentally observable in the systems of quantum dots with ferromagnetic
conduction-band-mediated inter-dot exchange interactions.Comment: 5 pages, 4 figure
Stellar and Gaseous Nuclear Disks Observed in Nearby (U)LIRGs
We present near-infrared integral field spectroscopy of the central
kiloparsec of 17 nearby luminous and ultra-luminous infrared galaxies
undergoing major mergers. These observations were taken with OSIRIS assisted by
the Keck I and II Adaptive Optics systems, providing spatial resolutions of a
few tens of parsecs. The resulting kinematic maps reveal gas disks in at least
16 out of 19 nuclei and stellar disks in 11 out of 11 nuclei observed in these
galaxy merger systems. In our late-stages mergers, these disks are young
(stellar ages Myr) and likely formed as gas disks which became unstable
to star formation during the merger. On average, these disks have effective
radii of a few hundred parsecs, masses between and ,
and between 1 and 5. These disks are similar to those created in
high-resolution hydrodynamical simulations of gas-rich galaxy mergers, and
favor short coalescence times for binary black holes. The few galaxies in our
sample in earlier stages of mergers have disks which are larger
( pc) and likely are remnants of the galactic disks that
have not yet been completely disrupted by the merger.Comment: accepted for publication in Ap
Catechol estrogens stimulate insulin secretion in pancreatic β-cells via activation of the transient receptor potential A1 (TRPA1) channel
Estrogen hormones play an important role in controlling glucose homeostasis and pancreatic β-cell function. Despite the significance of estrogen hormones for regulation of glucose metabolism, little is known about the roles of endogenous estrogen metabolites in modulating pancreatic β-cell function. In this study, we evaluated the effects of major natural estrogen metabolites, catechol estrogens, on insulin secretion in pancreatic β-cells. We show that catechol estrogens, hydroxylated at positions C2 and C4 of the steroid A ring, rapidly potentiated glucose-induced insulin secretion via a nongenomic mechanism. 2-Hydroxyestrone, the most abundant endogenous estrogen metabolite, was more efficacious in stimulating insulin secretion than any other tested catechol estrogens. In insulin-secreting cells, catechol estrogens produced rapid activation of calcium influx and elevation in cytosolic free calcium. Catechol estrogens also generated sustained elevations in cytosolic free calcium and evoked inward ion current in HEK293 cells expressing the transient receptor potential A1 (TRPA1) cation channel. Calcium influx and insulin secretion stimulated by estrogen metabolites were dependent on the TRPA1 activity and inhibited with the channel-specific pharmacological antagonists or the siRNA. Our results suggest the role of estrogen metabolism in a direct regulation of TRPA1 activity with potential implications for metabolic diseases
A Comparative Perspective of Imprisonment Trends in Slovenia and Europe from 2005 to 2014
This paper analyses trends in imprisonment in Slovenia from 2005 to 2014, and compares them with the ones observed
in the rest of Europe. Data were taken from the Council of Europe Annual Penal Statistics – SPACE I. The primary
results show that Slovenia increased its prison population by 30% during the period under study and, after 2011, the
prison population of Slovenia was increasing, while in the rest of Europe, it was decreasing. Nevertheless, Slovenia still
has one of the lowest prison population rates in Europe, which can be explained mainly by the fact that the average
length of imprisonment is lower in Slovenia than in the rest of Europe. The paper also analyses the evolution of the
structure of the Slovenian prison population in terms of gender, nationality, and type of offence for which prisoners are
convicted. Furthermore, it discusses the influence of legislative changes, the creation of new places for prisoners, and
crime trends on the prison population rate
Polarimetric analysis of STEREO observations of sungrazing kreutz comet C/2010 E6 (STEREO)
Twin STEREO spacecraft pre-perihelion photometric and polarimetric observations of the sungrazing Kreutz comet C/2010 E6 (STEREO) in March 2010 at heliocentric distances 3−28 R⊙ were investigated using a newly created set of analysis routines. The comet fully disintegrated during its perihelion passage. Prior to that, a broadening and an increase of the intensity peak with decreasing heliocentric distance was accompanied by a drop to zero polarization at high phase angles (∼105°–135°, STEREO-B) and the emergence of negative polarization at low phase angles (∼25°–35°, STEREO-A). Outside the near-comet region, the tail exhibited a steep slope of increasing polarization with increasing cometocentric distance, with the slope becoming less prominent as the comet approached the Sun. The steep slope may be attributed to sublimation of refractory organic matrix and the processing of dust grains, or to presence of amorphous carbon. The change in slope with proximity to the Sun is likely caused by the gradual sublimation of all refractory material. The polarization signatures observed at both sets of phase angles closer to the comet photocentre as the comet approached the Sun are best explained by fragmentation of the nucleus, exposing fresh Mg-rich silicate particles, followed by their gradual sublimation. The need for further studies of such comets, both observational and theoretical, is highlighted, as well as the benefit of the analysis routines created for this work
Josephson current in strongly correlated double quantum dots
We study the transport properties of a serial double quantum dot (DQD)
coupled to two superconducting leads, focusing on the Josephson current through
the DQD and the associated 0- transitions which result from the subtle
interplay between the superconductivity, the Kondo physics, and the inter-dot
superexchange interaction. We examine the competition between the
superconductivity and the Kondo physics by tuning the relative strength
of the superconducting gap and the Kondo temperature
, for different strengths of the superexchange coupling determined by the
interdot tunneling relative to the dot level broadening . We find
strong renormalization of , a significant role of the superexchange coupling
, and a rich phase diagram of the 0 and -junction regimes. In
particular, when both the superconductivity and the exchange interaction are in
close competion with the Kondo physics (), there appears
an island of -phase at large values of the superconducting phase
difference.Comment: 4 pages, 4 figure
Multiplex giant magnetoresistive biosensor microarrays identify interferon-associated autoantibodies in systemic lupus erythematosus.
High titer, class-switched autoantibodies are a hallmark of systemic lupus erythematosus (SLE). Dysregulation of the interferon (IFN) pathway is observed in individuals with active SLE, although the association of specific autoantibodies with chemokine score, a combined measurement of three IFN-regulated chemokines, is not known. To identify autoantibodies associated with chemokine score, we developed giant magnetoresistive (GMR) biosensor microarrays, which allow the parallel measurement of multiple serum antibodies to autoantigens and peptides. We used the microarrays to analyze serum samples from SLE patients and found individuals with high chemokine scores had significantly greater reactivity to 13 autoantigens than individuals with low chemokine scores. Our findings demonstrate that multiple autoantibodies, including antibodies to U1-70K and modified histone H2B tails, are associated with IFN dysregulation in SLE. Further, they show the microarrays are capable of identifying autoantibodies associated with relevant clinical manifestations of SLE, with potential for use as biomarkers in clinical practice
Mesozoic-Cenozoic crustaceans preserved within echinoid tests and bivalve shells
Associations of crustaceans with echinoids (Echinodermata) and bivalves (Mollusca) are not uncommon in modern
oceans. Here we record the occurrence of anomurans, brachyurans and isopods within echinoid tests and bivalve shells
from the Middle Jurassic of France, the Upper Jurassic of the Czech Republic, the Eocene of Croatia and the Miocene of
Austria. Additionally a new genus and species of fossil cirolanid isopod from the Middle Jurassic of France is described.
The present examples are interpreted as crustacean sheltering, probably for safe and undisturbed moulting (ecdysis),
within a vacant host test or shell. However, accidental association (washed in) or even food remains cannot be ruled out
entirelyWeb of Science90361160
- …