Localized to extended states transition for two interacting particles in a two-dimensional random potential

We show by a numerical procedure that a short-range interaction $u$ induces extended two-particle states in a two-dimensional random potential. Our procedure treats the interaction as a perturbation and solve Dyson's equation exactly in the subspace of doubly occupied sites. We consider long bars of several widths and extract the macroscopic localization and correlation lengths by an scaling analysis of the renormalized decay length of the bars. For $u=1$, the critical disorder found is $W_{\rm c}=9.3\pm 0.2$, and the critical exponent $\nu=2.4\pm 0.5$. For two non-interacting particles we do not find any transition and the localization length is roughly half the one-particle value, as expected.Comment: 4 two-column pages, 4 eps figures, Revtex, to be published in Europhys. Let

Critical Spectral Statistics at the Metal-Insulator Transition in Interacting Fermionic Systems

The spectral properties of a disordered system with few interacting three-dimensional spinless fermions are investigated. We show the existence of a critical spacings distribution which is invariant upon increase of the system size, but strongly depends on the number of particles. At the critical point, we report a substantial decrease of the degree of level repulsion as the number of particles increases indicating a decrease of nearest level correlations associated with the sparsity of the Hamiltonian matrix.Comment: Revtex, 4 pages, 3 encapsulated postscript figures appended Final version as accepted for publication in PR

Do interactions increase or reduce the conductance of disordered electrons? It depends!

We investigate the influence of electron-electron interactions on the conductance of two-dimensional disordered spinless electrons. By using an efficient numerical method which is based on exact diagonalization in a truncated basis of Hartree-Fock states we are able to determine the exact low-energy properties of comparatively large systems in the diffusive as well as in the localized regimes. We find that weak interactions increase the d.c. conductance in the localized regime while they decrease the d.c. conductance in the diffusive regime. Strong interactions always decrease the conductance. We also study the localization of single-particle excitations close to the Fermi energy which turns out to be only weakly influenced by the interactions.Comment: final version as publsihed, 4 pages REVTEX, 6 EPS figures include

Environmental predictability drives adaptive within- and transgenerational plasticity of heat tolerance across life stages and climatic regions

This is the author accepted manuscript. The final version is available from Wiley via the DOI in this recordData availability statement: Data generated in the current study were deposited in Appendix S3 of Supporting InformationAlthough environmental variability and predictability have been proposed as the underlying ecological context in which transgenerational plasticity (TGP) arises, the adaptive significance and interaction with within‐generation plasticity (WGP) in such scenarios is still poorly understood. To investigate these questions, we considered the tolerance to upper thermal limits of larvae and adults of the desert endemic Drosophila mojavensis adapted to different climatic regions (Desert vs. Mediterranean climate). Thermal plasticity was investigated by acclimating parents and offspring at 36°C (vs. at 25°C). We then used historical temperature variation data from both regions to perform individual‐based simulations by modelling expected components of adaptive plasticity in multiple life stages. Our results indicated that thermal response to ramping heat shocks was more pronounced in larvae, where acclimation treatments in parents and offspring increased their heat‐shock performance, while heat knockdown in adults was only increased by offspring acclimation of adults. The relative contribution of WGP and TGP was greater for the population from the more thermally variable Sonoran Desert. Similarly, individual‐based simulations of evolving maternal effects indicated that variation in tolerance to upper thermal limits across life stages and climates is expected from its adaptive significance in response to environmental predictability. Our approach offers a new perspective and interpretation of adaptive plasticity, demonstrating that environmental predictability can drive thermal responses across generations and life stages in a scenario with regional climate variability.University of ArizonaNational Science Foundation (NSF)Leverhulme Trus

Magnetic Field Effect for Two Electrons in a Two Dimensional Random Potential

We study the problem of two particles with Coulomb repulsion in a two-dimensional disordered potential in the presence of a magnetic field. For the regime, when without interaction all states are well localized, it is shown that above a critical excitation energy electron pairs become delocalized by interaction. The transition between the localized and delocalized regimes goes in the same way as the metal-insulator transition at the mobility edge in the three dimensional Anderson model with broken time reversal symmetry.Comment: revtex, 7 pages, 6 figure

Severe Psychiatric Problems in Right Hepatic Lobe Donors for Living Donor Liver Transplantation

The morbidity and mortality from donation of a right hepatic lobe for living donor liver transplantation (LDLT) is an important issue for this procedure. We report the prevalence of severe psychiatric postoperative complications from the Adult-to-Adult Living Donor Liver Transplantation Cohort study (A2ALL), which was established to define the risks and benefits of LDLT for donors and recipients

Dynamics of short time--scale energy relaxation of optical excitations due to electron--electron scattering in the presence of arbitrary disorder

A non--equilibrium occupation distribution relaxes towards the Fermi--Dirac distribution due to electron--electron scattering even in finite Fermi systems. The dynamic evolution of this thermalization process assumed to result from an optical excitation is investigated numerically by solving a Boltzmann equation for the carrier populations using a one--dimensional disordered system. We focus on the short time--scale behavior. The logarithmically long time--scale associated with the glassy behavior of interacting electrons in disordered systems is not treated in our investigation. For weak disorder and short range interaction we recover the expected result that disorder enhances the relaxation rate as compared to the case without disorder. For sufficiently strong disorder, however, we find an opposite trend due to the reduction of scattering probabilities originating from the strong localization of the single--particle states. Long--range interaction in this regime produces a similar effect. The relaxation rate is found to scale with the interaction strength, however, the interplay between the implicit and the explicit character of the interaction produces an anomalous exponent.Comment: 4 pages, 3 EPS figure

Assessment of Elder Mistreatment in Two American Indian Samples: Psychometric Characteristics of the HS-EAST and the Native Elder Life–Financial Exploitation and –Neglect Measures

Although elder mistreatment among ethnic minorities is increasingly gaining attention, our empirical knowledge of this phenomenon among American Indians remains quite limited, especially with respect to measurement. The Shielding American Indian Elders (SAIE) Project used a collaborative approach to explore culturally informed measurement of elder mistreatment in two American Indian elder samples (a Northern Plains reservation and a South Central metropolitan area). The project sought to investigate the performance characteristics of the commonly used Hwalek-Sengstock Elder Abuse Screening Test (HS-EAST), as well as to examine the psychometric properties of a new measure developed to capture culturally salient aspects of mistreatment in American Indian contexts—the Native Elder Life Scale (NELS). Using methods and samples comparable to those in the literature, the HS-EAST performed adequately in these Native samples. The NELS also shows promise for use with this population and assesses different aspects of elder mistreatment than does the HS-EAST.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline

Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members. II. age dependencies and new insights

Models of stellar structure and evolution can be constrained by measuring accurate parameters of detached eclipsing binaries in open clusters. Multiple binary stars provide the means to determine helium abundances in these old stellar systems, and in turn, to improve estimates of their age. In the first paper of this series, we demonstrated how measurements of multiple eclipsing binaries in the old open cluster NGC6791 sets tighter constraints on the properties of stellar models than has previously been possible, thereby potentially improving both the accuracy and precision of the cluster age. Here we add additional constraints and perform an extensive model comparison to determine the best estimates of the cluster age and helium content, employing as many observational constraints as possible. We improve our photometry and correct empirically for differential reddening effects. We then perform an extensive comparison of the CMDs and eclipsing binary measurements to Victoria and DSEP isochrones to estimate cluster parameters. We also reanalyse a spectrum of the star 2-17 to improve [Fe/H] constraints. We find a best estimate of the age of ~8.3 Gyr while demonstrating that remaining age uncertainty is dominated by uncertainties in the CNO abundances. The helium mass fraction is well constrained at Y = 0.30 \pm 0.01 resulting in dY/dZ ~ 1.4 assuming that such a relation exists. During the analysis we firmly identify blue straggler stars, including the star 2-17, and find indications for the presence of their evolved counterparts. Our analysis supports the RGB mass-loss found from asteroseismology and we determine precisely the absolute mass of stars on the lower RGB, 1.15\pm0.02Msun. This will be an important consistency check for the detailed asteroseismology of cluster stars.Comment: 18 Pages, 9 Figures, accepted for publication in A&