35 research outputs found
Persistent currents in Moebius strips
Relation between the geometry of a two-dimensional sample and its equilibrium
physical properties is exemplified here for a system of non-interacting
electrons on a Moebius strip. Dispersion relation for a clean sample is derived
and its persistent current under moderate disorder is elucidated, using
statistical analysis pertinent to a single sample experiment. The flux
periodicity is found to be distinct from that in a cylindrical sample, and the
essential role of disorder in the ability to experimentally identify a Moebius
strip is pointed out.Comment: 5 pages, 4 figure
Unrelated umbilical cord blood transplantation for familial erythrophagocytic lymphohistiocytosis
Pentagonal nanowires: a first-principles study of atomic and electronic structure
We performed an extensive first-principles study of nanowires in various
pentagonal structures by using pseudopotential plane wave method within the
density functional theory. Our results show that nanowires of different types
of elements, such as alkali, simple, transition and noble metals and inert gas
atoms, have a stable structure made from staggered pentagons with a linear
chain perpendicular to the planes of the pentagons and passing through their
centers. This structure exhibits bond angles close to those in the icosahedral
structure. However, silicon is found to be energetically more favorable in the
eclipsed pentagonal structure. These quasi one dimensional pentagonal nanowires
have higher cohesive energies than many other one dimensional structures and
hence may be realized experimentally. The effect of magnetic state are examined
by spin-polarized calculations. The origin of the stability are discussed by
examining optimized structural parameters, charge density and electronic band
structure, and by using analysis based on the empirical Lennard-Jones type
interaction. Electronic band structure of pentagonal wires of different
elements are discussed and their effects on quantum ballistic conductance are
mentioned. It is found that the pentagonal wire of silicon exhibits metallic
band structure.Comment: 4 figures, accepted for publication in Phys. Rev.
Resonance approximation and charge loading/unloading in adiabatic quantum pumping
Quantum pumping through mesoscopic quantum dots is known to be enhanced by
resonant transmission. The pumped charge is close to an integer number of
electrons when the pumping contour surrounds a resonance, but the transmission
remains small on the contour. For non-interacting electrons, we give a
quantitative account of the detailed exchange of electrons between the dot and
the leads (to the electron reservoirs) during a pumping cycle. Near isolated
distinct resonances, we use approximate Breit-Wigner expressions for the dot's
Green function to discuss the loading/unloading picture of the pumping: the
fractional charge exchanged between the dot and each lead through a single
resonance point is related to the relative couplings of the dot and the leads
at this resonance. If each resonance point along the pumping contour is
dominated by the coupling to a single lead (which also implies a very small
transmission), then the crossing of each such resonance results in a single
electron exchange between the dot and that lead, ending up with a net quantized
charge. When the resonance approximation is valid, the fractional charges can
also be extracted from the peaks of the transmissions between the various
leads.Comment: 10 pages, 4 figure
National identity predicts public health support during a global pandemic
Changing collective behaviour and supporting non-pharmaceutical interventions is an important component in mitigating virus transmission during a pandemic. In a large international collaboration (Study 1, N = 49,968 across 67 countries), we investigated self-reported factors associated with public health behaviours (e.g., spatial distancing and stricter hygiene) and endorsed public policy interventions (e.g., closing bars and restaurants) during the early stage of the COVID-19 pandemic (April-May 2020). Respondents who reported identifying more strongly with their nation consistently reported greater engagement in public health behaviours and support for public health policies. Results were similar for representative and non-representative national samples. Study 2 (N = 42 countries) conceptually replicated the central finding using aggregate indices of national identity (obtained using the World Values Survey) and a measure of actual behaviour change during the pandemic (obtained from Google mobility reports). Higher levels of national identification prior to the pandemic predicted lower mobility during the early stage of the pandemic (r = −0.40). We discuss the potential implications of links between national identity, leadership, and public health for managing COVID-19 and future pandemics.publishedVersio
The Comparative Potency of Hydrocortisone Analogs in Suppressing Growth of Hair in the Rat121From the Departments of Dermatology and Syphilology and of Anatomy, University of Michigan Medical School, Ann Arbor, Michigan.2Supported in part by research grants from the National Institutes of Health, United States Public Health Service (A-131 (C5)), the University of Michigan Memorial-Phoenix Project #145 and The Upjohn Company.
Global desertification: building a science for dryland development
In this millennium, global drylands face a myriad of problems that present tough research, management, and policy challenges. Recent advances in dryland development, however, together with the integrative approaches of global change and sustainability science, suggest that concerns about land degradation, poverty, safeguarding biodiversity, and protecting the culture of 2.5 billion people can be confronted with renewed optimism. We review recent lessons about the functioning of dryland ecosystems and the livelihood systems of their human residents and introduce a new synthetic framework, the Drylands Development Paradigm (DDP). The DDP, supported by a growing and well-documented set of tools for policy and management action, helps navigate the inherent complexity of desertification and dryland development, identifying and synthesizing those factors important to research, management, and policy communities