Exchange and correlation effects on drag in low density electron bilayers: Coulomb and virtual-optical-phonon-mediated electron-electron interaction

We investigate the effect of exchange and correlation (xc) in low-density electron bilayers. Along with the direct Coulomb interaction, the effective electron-electron interaction mediated by the exchange of virtual polar optical (PO) phonons is considered. We find that the introduction of xc corrections results in a significant enhancement of the transresistivity and qualitative changes in its temperature dependence. The virtual PO-phonon contribution behaves similarly to the Coulomb drag and reduces noticeably the total drag thereby resulting in a better agreement with the recent experimental findings.Comment: 5 pages, 4 figures, Int. Conf. EP2DS-1

Medication adherence among the older adults: challenges and recommendations

No abstract available

Theoretical models of the halo occupation distribution : separating central and satellite galaxies

The halo occupation distribution (HOD) describes the relation between galaxies and dark matter at the level of individual dark matter halos. The properties of galaxies residing at the centers of halos differ from those of satellite galaxies because of differences in their formation histories. Using a smoothed particle hydrodynamics (SPH) simulation and a semianalytic (SA) galaxy formation model, we examine the separate contributions of central and satellite galaxies to the HOD, more specifically to the probability P(N|M) that a halo of virial mass M contains N galaxies of a particular class. In agreement with earlier results for dark matter subhalos, we find that the mean occupation function langNrangM for galaxies above a baryonic mass threshold can be approximated by a step function for central galaxies plus a power law for satellites and that the distribution of satellite numbers is close to Poisson at fixed halo mass. Since the number of central galaxies is always zero or one, the width of P(N|M) is narrower than a Poisson distribution at low N and approaches Poisson at high N. For galaxy samples defined by different baryonic mass thresholds, there is a nearly linear relation between the minimum halo mass Mmin required to host a central galaxy and the mass M1 at which an average halo hosts one satellite, with M1 ≈ 14Mmin (SPH) or M1 ≈ 18Mmin (SA). The stellar population age of central galaxies correlates with halo mass, and this correlation explains much of the age dependence of the galaxy HOD. The mean occupation number of young galaxies exhibits a local minimum at M ~ 10Mmin where halos are too massive to host a young central galaxy but not massive enough to host satellites. Using the SA model, we show that the conditional galaxy mass function at fixed halo mass cannot be described by a Schechter function because central galaxies produce a "bump" at high masses. We suggest parameterizations for the HOD and the conditional luminosity function that can be used to model observed galaxy clustering. Many of our predictions are in good agreement with recent results inferred from clustering in the Sloan Digital Sky Survey

Electron-electron interactions and two-dimensional - two-dimensional tunneling

We derive and evaluate expressions for the dc tunneling conductance between interacting two-dimensional electron systems at non-zero temperature. The possibility of using the dependence of the tunneling conductance on voltage and temperature to determine the temperature-dependent electron-electron scattering rate at the Fermi energy is discussed. The finite electronic lifetime produced by electron-electron interactions is calculated as a function of temperature for quasiparticles near the Fermi circle. Vertex corrections to the random phase approximation substantially increase the electronic scattering rate. Our results are in an excellent quantitative agreement with experiment.Comment: Revtex style, 21 pages and 8 postscript figures in a separate file; Phys. Rev. B (in press

Nonadiabatic approach to dimerization gap and optical absorption coefficient of the Su-Schrieffer-Heeger model

An analytical nonadiabatic approach has been developed to study the dimerization gap and the optical absorption coefficient of the Su-Schrieffer-Heeger model where the electrons interact with dispersive quantum phonons. By investigating quantitatively the effects of quantum phonon fluctuations on the gap order and the optical responses in this system, we show that the dimerization gap is much more reduced by the quantum lattice fluctuations than the optical absorption coefficient is. The calculated optical absorption coefficient and the density of states do not have the inverse-square-root singularity, but have a peak above the gap edge and there exist a significant tail below the peak. The peak of optical absorption spectrum is not directly corresponding to the dimerized gap. Our results of the optical absorption coefficient agree well with those of the experiments in both the shape and the peak position of the optical absorption spectrum.Comment: 14 pages, 7 figures. to be published in PR

Global persistence exponent of the two-dimensional Blume-Capel model

The global persistence exponent $\theta_g$ is calculated for the two-dimensional Blume-Capel model following a quench to the critical point from both disordered states and such with small initial magnetizations. Estimates are obtained for the nonequilibrium critical dynamics on the critical line and at the tricritical point. Ising-like universality is observed along the critical line and a different value $\theta_g =1.080(4)$ is found at the tricritical point.Comment: 7 pages with 3 figure

Interethnic differences in neuroimaging markers and cognition in Asians, a population-based study

We examined interethnic differences in the prevalence of neuroimaging markers of cerebrovascular and neurodegenerative disease in 3 major Asian ethnicities (Chinese, Malays, and Indians), as well as their role in cognitive impairment. 3T MRI brain scans were acquired from 792 subjects (mean age: 70.0 ± 6.5years, 52.1% women) in the multi-ethnic Epidemiology of Dementia In Singapore study. Markers of cerebrovascular disease and neurodegeneration were identified. Cognitive performance was evaluated using Mini Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and a neuropsychological assessment. Compared to Chinese, Malays had a higher burden of intracranial stenosis (OR: 2.28. 95%CI: 1.23-4.20) and cortical atrophy (β: -0.60. 95%CI: -0.78, -0.41), while Indians had a higher burden of subcortical atrophy (β: -0.23. 95%CI: -0.40, -0.06). Moreover, Malay and Indian ethnicities were likely to be cognitively impaired (OR for Malays: 3.79. 95%CI: 2.29-6.26; OR for Indians: 2.87. 95%CI: 1.74-4.74) and showed worse performance in global cognition (β for Malays: -0.51. 95%CI: -0.66, -0.37; and Indians: -0.32. 95%CI: -0.47, -0.17). A higher burden of cerebrovascular and neurodegenerative markers were found in Malays and Indians when compared to Chinese. Further research is required to fully elucidate the factors and pathways that contribute to these observed differences

Universality and scaling study of the critical behavior of the two-dimensional Blume-Capel model in short-time dynamics

In this paper we study the short-time behavior of the Blume-Capel model at the tricritical point as well as along the second order critical line. Dynamic and static exponents are estimated by exploring scaling relations for the magnetization and its moments at early stage of the dynamic evolution. Our estimates for the dynamic exponents, at the tricritical point, are $z= 2.215(2)$ and $\theta= -0.53(2)$.Comment: 12 pages, 9 figure

Incidence, risk factors, and temporal trends of penile cancer:a global population-based study

Objectives: To examine the global disease burden and country-specific trends of penile cancer incidence by age group and investigate its associations with several factors. Materials and Methods: The Global Cancer Observatory database was interrogated for penile cancer incidence. The 10-year cancer incidence rates were collected from the Cancer Incidence in Five Continents Plus. The country-specific data were extracted from the World Health Organization Global Health Observatory and Global Burden of Disease databases for conducting risk factors analysis. The penile cancer incidence was presented using age-standardised rates. Its associations with various factors were examined by linear regression, while the incidence trend was estimated using joinpoint regression and presented as average annual percentage change with 95% confidence intervals in different age groups. Results: There were an estimated 36 068 new cases of penile cancer in 2020. There was a considerable geographical disparity in the disease burden of penile cancer, with South America reporting the highest incidence. Overall, alcohol drinking, human immunodeficiency virus (HIV) infection, and unsafe sex were positively associated with a higher penile cancer incidence, while circumcision was found to be a protective factor. There has been a mixed trend in penile cancer incidence overall, but an increasing trend was found among younger males. Conclusions: There was a global variation in the penile cancer burden associated with prevalence of alcohol drinking, HIV infection, unsafe sex, and circumcision. The increasing penile cancer incidence in the younger population is worrying and calls for early detection and preventive interventions.</p

Incidence, risk factors, and temporal trends of penile cancer:a global population-based study

Objectives: To examine the global disease burden and country-specific trends of penile cancer incidence by age group and investigate its associations with several factors. Materials and Methods: The Global Cancer Observatory database was interrogated for penile cancer incidence. The 10-year cancer incidence rates were collected from the Cancer Incidence in Five Continents Plus. The country-specific data were extracted from the World Health Organization Global Health Observatory and Global Burden of Disease databases for conducting risk factors analysis. The penile cancer incidence was presented using age-standardised rates. Its associations with various factors were examined by linear regression, while the incidence trend was estimated using joinpoint regression and presented as average annual percentage change with 95% confidence intervals in different age groups. Results: There were an estimated 36 068 new cases of penile cancer in 2020. There was a considerable geographical disparity in the disease burden of penile cancer, with South America reporting the highest incidence. Overall, alcohol drinking, human immunodeficiency virus (HIV) infection, and unsafe sex were positively associated with a higher penile cancer incidence, while circumcision was found to be a protective factor. There has been a mixed trend in penile cancer incidence overall, but an increasing trend was found among younger males. Conclusions: There was a global variation in the penile cancer burden associated with prevalence of alcohol drinking, HIV infection, unsafe sex, and circumcision. The increasing penile cancer incidence in the younger population is worrying and calls for early detection and preventive interventions.</p