526 research outputs found
Pure Stationary States of Open Quantum Systems
Using Liouville space and superoperator formalism we consider pure stationary
states of open and dissipative quantum systems. We discuss stationary states of
open quantum systems, which coincide with stationary states of closed quantum
systems. Open quantum systems with pure stationary states of linear oscillator
are suggested. We consider stationary states for the Lindblad equation. We
discuss bifurcations of pure stationary states for open quantum systems which
are quantum analogs of classical dynamical bifurcations.Comment: 7p., REVTeX
A Variation in the Cerebroside Sulfotransferase Gene is Linked to Exercise-Modified Insulin Resistance and to Type 2 Diabetes
Aims. The glycosphingolipid ÎČ-galactosylceramide-3-O-sulfate (sulfatide) is present in the secretory granules of the insulin producing ÎČ-cells and may act as a molecular chaperone of insulin. The final step in sulfatide synthesis is performed by cerebroside sulfotransferase (CST) (EC 2.8.2.11). The aim of this study was to investigate whether two single nucleotide polymorphisms (SNP), rs2267161 located in an exon or rs42929 located in an intron, in the gene encoding CST are linked to type 2 diabetes (T2D). Methods. As a population survey, 265 male and female patients suffering from T2D and 291 gender matched controls were examined. Results. A higher proportion of T2D patients were heterozygous at SNP rs2267161 with both T (methionine) and C (valine) alleles present (49.8% versus 41.3%, P = .04). The calculated odd risk for T2D was 1.47 (1.01â2.15, P = .047). Among female controls, the homozygous CC individuals displayed lower insulin resistance measured by HOMA-IR (P = .05) than the C/T or TT persons; this was particularly prevalent in individuals who exercise (P = .03). Conclusion. Heterozygosity at SNP rs2267161 in the gene encoding the CST enzyme confers increased risk of T2D. Females with the CC allele showed lower insulin resistance
Global and local relaxation of a spin-chain under exact Schroedinger and master-equation dynamics
We solve the Schroedinger equation for an interacting spin-chain locally
coupled to a quantum environment with a specific degeneracy structure. The
reduced dynamics of the whole spin-chain as well as of single spins is
analyzed. We show, that the total spin-chain relaxes to a thermal equilibrium
state independently of the internal interaction strength. In contrast, the
asymptotic states of each individual spin are thermal for weak but non-thermal
for stronger spin-spin coupling. The transition between both scenarios is found
for couplings of the order of , with denoting
the Zeeman-splitting. We compare these results with a master equation
treatment; when time averaged, both approaches lead to the same asymptotic
state and finally with analytical results.Comment: RevTeX, 8 pages, 14 figures, added DOI and forgotten reference
Symplectic evolution of Wigner functions in markovian open systems
The Wigner function is known to evolve classically under the exclusive action
of a quadratic hamiltonian. If the system does interact with the environment
through Lindblad operators that are linear functions of position and momentum,
we show that the general evolution is the convolution of the classically
evolving Wigner function with a phase space gaussian that broadens in time. We
analyze the three generic cases of elliptic, hyperbolic and parabolic
Hamiltonians. The Wigner function always becomes positive in a definite time,
which is shortest in the hyperbolic case. We also derive an exact formula for
the evolving linear entropy as the average of a narrowing gaussian taken over a
probability distribution that depends only on the initial state. This leads to
a long time asymptotic formula for the growth of linear entropy.Comment: this new version treats the dissipative cas
The role of HOXB2 and HOXB3 in acute myeloid leukemia.
Acute myeloid leukemia (AML) is a heterogeneous aggressive disease and the most common form of adult leukemia. Mutations in the type III receptor tyrosine kinase FLT3 are found in more than 30% of patients. Drugs against FLT3 have been developed for the treatment of AML, but they lack specificity, show poor response and lead to the development of a resistant phenotype upon treatment. Therefore, a deeper understanding of FLT3 signaling will facilitate identification of additional pharmacological targets in FLT3-driven AML. In this report, we identify HOXB2 and HOXB3 as novel regulators of oncogenic FLT3-ITD-driven AML. We show that HOXB2 and HOXB3 expression is upregulated in a group of AML patients carrying FLT3-ITD. Overexpression of HOXB2 or HOXB3 in mouse pro-B cells resulted in decreased FLT3-ITD-dependent cell proliferation as well as decreased colony formation and increased apoptosis. Expression of HOXB2 or HOXB3 resulted in a significant decrease in FLT3-ITD-induced AKT, ERK, p38 and STAT5 phosphorylation. Our data suggest that HOXB2 and HOXB3 act as a tumor suppressors in FLT3-ITD driven AML
In situ measurements of the functional response of benthic suspension feeders exposed to cadmium and anti-fouling paint
In situ measurements of the functional response (feeding, respiration and excretion) of Mytilus edulis and Ciona intestinalis showed that the effects of 2.5 ”g 1-1 tributyl tin and 100 ”g 1-1 cadmium on an assemblage of the two species was lower than what could be predicted from the response of the two species separately. This is explained by biological interactions between the species and by the fact that the two species may react in different ways to the same disturbance. Thus, results from single species tests seem inadequate for making predictions of pollution effects in marine environments, and tests should instead be carried out at the community or ecosystem level
Glycaemic control, disease duration and beta-cell function in patients with Type 2 diabetes in a Swedish community. Skaraborg Hypertension and Diabetes Project.
AimsTo examine determinants for glycaemic control in primary care patients with Type 2 diabetes. MethodsIn a community-based surveillance of primary care patients with Type 2 diabetes, 190 men and 186 women were consecutively identified and examined for cardiovascular risk factors. Insulin resistance and beta-cell function were estimated using homeostasis model assessment (HOMA). Good glycaemic control was defined as HbA1c = 6.5% was associated with duration of diabetes (10.6 vs. 6.4 years, P = 6.5% by 5 years diabetes duration = 1.7; 95% confidence interval (CI) 1.4-2.1) but was lost following additional adjustment for beta-cell function (OR for HbA1c>= 6.5% = 1.3; 95% CI 0.96-1.7). In a separate linear regression with beta-cell function as the dependent variable there was a significant association with HbA1c after adjustments for differences in age, gender, WHR, serum triglyceride levels and diabetes duration (P < 0.001). ConclusionsIncreasing HbA1c by time was associated with declining beta-cell function
Dynamics of Dissipative Quantum Systems--from Path Integrals to Master Equations
The path integral approach offers not only an exact expression for the non-
equilibrium dynamics of dissipative quantum systems, but is also a convenient
starting point for perturbative treatments. An alternative way to explore the
influence of friction in the quantum realm is based on master equations which
require, however, in one or the other aspect approximations. Here it is
discussed under which conditions and limitations Markovian master equations can
be derived from exact path integrals thus providing a firm basis for their
applicability.Comment: 10 pages, 1 figur
On the behavior of micro-spheres in a hydrogen pellet target
A pellet target produces micro-spheres of different materials, which are used
as an internal target for nuclear and particle physics studies. We will
describe the pellet hydrogen behavior by means of fluid dynamics and
thermodynamics. In particular one aim is to theoretically understand the
cooling effect in order to find an effective method to optimize the working
conditions of a pellet target. During the droplet formation the evaporative
cooling is best described by a multi-droplet diffusion-controlled model, while
in vacuum, the evaporation follows the (revised) Hertz-Knudsen formula.
Experimental observations compared with calculations clearly indicated the
presence of supercooling, the effect of which is discussed as well.Comment: 22 pages, 8 figures (of which two are significantly compressed for
easier download
Convolutionless Non-Markovian master equations and quantum trajectories: Brownian motion revisited
Stochastic Schr{\"o}dinger equations for quantum trajectories offer an
alternative and sometimes superior approach to the study of open quantum system
dynamics. Here we show that recently established convolutionless non-Markovian
stochastic Schr{\"o}dinger equations may serve as a powerful tool for the
derivation of convolutionless master equations for non-Markovian open quantum
systems. The most interesting example is quantum Brownian motion (QBM) of a
harmonic oscillator coupled to a heat bath of oscillators, one of the
most-employed exactly soluble models of open system dynamics. We show
explicitly how to establish the direct connection between the exact
convolutionless master equation of QBM and the corresponding convolutionless
exact stochastic Schr\"odinger equation.Comment: 18 pages, RevTe
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