Localized Electron States Near a Metal-Semiconductor Nanocontact

The electronic structure of nanowires in contact with metallic electrodes of experimentally relevant sizes is calculated by incorporating the electrostatic polarization potential into the atomistic single particle Schr\"odinger equation. We show that the presence of an electrode produces localized electron/hole states near the electrode, a phenomenon only exhibited in nanostructures and overlooked in the past. This phenomenon will have profound implications on electron transport in such nanosystems. We calculate several electrode/nanowire geometries, with varying contact depths and nanowire radii. We demonstrate the change in the band gap of up to 0.5 eV in 3 nm diameter CdSe nanowires and calculate the magnitude of the applied electric field necessary to overcome the localization.Comment: 11 pages 4 figure

A Public Health Framework for Screening Mammography: Evidence-Based Versus Politically Mandated Care

This Viewpoint highlights the societal risks of politically motivated mandates relating to public health guidelines. Although the Affordable Care Act mandated insurance coverage for U.S. Preventive Services Task Force (USPSTF)-recommended preventive services, it went further for mammography screening. Instead of relying on the most recent USPSTF guidelines, Congress amended the ACA to require the Department of Health and Human Services (DHHS) to use its 2002 guidelines, which recommended screening every 1-2 years starting at age 40. The FY 2016 Consolidated Appropriations Act instructs DHHS to interpret any reference to “current” USPSTF breast cancer screening recommendations to mean those issued “before 2009” — in other words, its 2002 recommendations. Essentially, Congress is requiring health insurers to ignore modern scientific assessments, and instead use 14-year-old guidance. The ACA improved the public’s health by guaranteeing that insurers provide uniform, cost-free access to preventive services based on modern evidence of effectiveness. The public’s health is best served when women’s personal decisions about screening are informed by evidence rather than political considerations. The Congress’s paternalistic response to USPSTF mammography-screening recommendations vividly illuminate the social costs of politically mandated care. Rather than benefiting women, political interference with science can discourage shared decision-making, increase harms from screening, and sow public doubt about the value and integrity of science

Sliding of Electron Crystal of Finite Size on the Surface of Superfluid He-4 Confined in a Microchannel

We present a new study of the nonlinear transport of a two-dimensional electron crystal on the surface of liquid helium confined in a 10 micrometer-wide channel in which the effective length of the crystal can be varied from 10 to 215 micrometers. At low driving voltages, the moving electron crystal is strongly coupled to deformation of the liquid surface arising from resonant excitation of surface capillary waves, ripplons, while at higher driving voltages the crystal decouples from the deformation. We find strong dependence of the decoupling threshold of the driving electric field acting on the electrons, on the size of the crystal. In particular, the threshold electric field significantly decreases when the length of the crystal becomes shorter than 25 micrometers. We explain this effect as arising from weakening of surface deformations due to radiative loss of resonantly-excited ripplons from an electron crystal of finite size, and we account for the observed effect using an instructive analytical model.Comment: 5 figure

Fine Splitting in Charmonium Spectrum with Channel Coupling Effect

We study the fine splitting in charmonium spectrum in quark model with the channel coupling effect, including $DD$, $DD^*$, $D^*D^*$ and $D_sD_s$, $D_sD_s^*$, $D_s^*D_s^*$ channels. The interaction for channel coupling is constructed from the current-current Lagrangian related to the color confinement and the one-gluon exchange potentials. By adopting the massive gluon propagator from the lattice calculation in the nonperturbative region, the coupling interaction is further simplified to the four-fermion interaction. The numerical calculation still prefers the assignment $1^{++}$ of X(3872).Comment: Submitted to Chinese Physics

Galaxy alignment on large and small scales

Galaxies are not randomly distributed across the universe but showing different kinds of alignment on different scales. On small scales satellite galaxies have a tendency to distribute along the major axis of the central galaxy, with dependence on galaxy properties that both red satellites and centrals have stronger alignment than their blue counterparts. On large scales, it is found that the major axes of Luminous Red Galaxies (LRGs) have correlation up to 30Mpc/h. Using hydro-dynamical simulation with star formation, we investigate the origin of galaxy alignment on different scales. It is found that most red satellite galaxies stay in the inner region of dark matter halo inside which the shape of central galaxy is well aligned with the dark matter distribution. Red centrals have stronger alignment than blue ones as they live in massive haloes and the central galaxy-halo alignment increases with halo mass. On large scales, the alignment of LRGs is also from the galaxy-halo shape correlation, but with some extent of mis-alignment. The massive haloes have stronger alignment than haloes in filament which connect massive haloes. This is contrary to the naive expectation that cosmic filament is the cause of halo alignment.Comment: 4 pages, 3 figures, To appear in the proceedings of the IAU Symposium 308 "The Zeldovich Universe: Genesis and Growth of the Cosmic Web