46 research outputs found
Recommended from our members
Attribution analysis of property portfolios
This paper aims to clarify the potential confusion about the application of attribution analysis to real estate portfolios. Its three primary objectives are:
· To review, and as far as possible reconcile, the varying approaches to attribution analysis evident in the literature.
· To give a clear statement of the purposes of attribution analysis, and its meaning for real-world property managers.
· To show, using real portfolio data from IPD's UK performance measurement service, the practical implications of applying different attribution methods
Topological Dirac Semimetal Na3Bi Films in the Ultrathin Limit via Alternating Layer Molecular Beam Epitaxy
Ultrathin films of Na3Bi on insulating substrates are desired for opening a
bulk band gap and generating the quantum spin Hall effect from a topological
Dirac semimetal, though continuous films in the few nanometer regime have been
difficult to realize. Here, we utilize alternating layer molecular beam epitaxy
(MBE) to achieve uniform and continuous single crystal films of Na3Bi(0001) on
insulating Al2O3(0001) substrates and demonstrate electrical transport on films
with 3.8 nm thickness (4 unit cells). The high material quality is confirmed
through in situ reflection high-energy electron diffraction (RHEED), scanning
tunneling microscopy (STM), x-ray diffraction (XRD), and x-ray photoelectron
spectroscopy (XPS). In addition, these films are employed as seed layers for
subsequent growth by codeposition, leading to atomic layer-by-layer growth as
indicated by RHEED intensity oscillations. These material advances facilitate
the pursuit of quantum phenomena in thin films of Dirac semimetals.Comment: 11 pages, 5 figure
Avian influenza at both ends of a migratory flyway: characterizing viral genomic diversity to optimize surveillance plans for North America
Although continental populations of avian influenza viruses are genetically distinct, transcontinental reassortment in low pathogenic avian influenza (LPAI) viruses has been detected in migratory birds. Thus, genomic analyses of LPAI viruses could serve as an approach to prioritize species and regions targeted by North American surveillance activities for foreign origin highly pathogenic avian influenza (HPAI). To assess the applicability of this approach, we conducted a phylogenetic and population genetic analysis of 68 viral genomes isolated from the northern pintail (Anas acuta) at opposite ends of the Pacific migratory flyway in North America. We found limited evidence for Asian LPAI lineages on wintering areas used by northern pintails in California in contrast to a higher frequency on breeding locales of Alaska. Our results indicate that the number of Asian LPAI lineages observed in Alaskan northern pintails, and the nucleotide composition of LPAI lineages, is not maintained through fall migration. Accordingly, our data indicate that surveillance of Pacific Flyway northern pintails to detect foreign avian influenza viruses would be most effective in Alaska. North American surveillance plans could be optimized through an analysis of LPAI genomics from species that demonstrate evolutionary linkages with European or Asian lineages and in regions that have overlapping migratory flyways with areas of HPAI outbreaks
ELemental abundances of Planets and brown dwarfs Imaged around Stars (ELPIS): I. Potential Metal Enrichment of the Exoplanet AF Lep b and a Novel Retrieval Approach for Cloudy Self-luminous Atmospheres
AF Lep A+b is a remarkable planetary system hosting a gas-giant planet that
has the lowest dynamical mass among directly imaged exoplanets. We present an
in-depth analysis of the atmospheric composition of the star and planet to
probe the planet's formation pathway. Based on new high-resolution spectroscopy
of AF Lep A, we measure a uniform set of stellar parameters and elemental
abundances (e.g., [Fe/H] = dex). The planet's dynamical mass
( M) and orbit are also refined using published
radial velocities, relative astrometry, and absolute astrometry. We use
petitRADTRANS to perform chemically-consistent atmospheric retrievals for AF
Lep b. The radiative-convective equilibrium temperature profiles are
incorporated as parameterized priors on the planet's thermal structure, leading
to a robust characterization for cloudy self-luminous atmospheres. This novel
approach is enabled by constraining the temperature-pressure profiles via the
temperature gradient , a departure from previous studies
that solely modeled the temperature. Through multiple retrievals performed on
different portions of the m spectrophotometry, along with
different priors on the planet's mass and radius, we infer that AF Lep b likely
possesses a metal-enriched atmosphere ([Fe/H] dex). AF Lep b's
potential metal enrichment may be due to planetesimal accretion, giant impacts,
and/or core erosion. The first process coincides with the debris disk in the
system, which could be dynamically excited by AF Lep b and lead to planetesimal
bombardment. Our analysis also determines K,
dex, and the presence of silicate clouds and
dis-equilibrium chemistry in the atmosphere. Straddling the L/T transition, AF
Lep b is thus far the coldest exoplanet with suggested evidence of silicate
clouds.Comment: AJ, in press. Main text: Pages 1-32, Figures 1-15, Tables 1-6. All
figures and tables after References belong to the Appendix (Pages 32-58,
Figures 16-20, Table 7). For supplementary materials, please refer to the
Zenodo repository https://doi.org/10.5281/zenodo.826746
Tunable Indistinguishable Photons From Remote Quantum Dots
Single semiconductor quantum dots have been widely studied within devices
that can apply an electric field. In the most common system, the low energy
offset between the InGaAs quantum dot and the surrounding GaAs material limits
the magnitude of field that can be applied to tens of kVcm^-1, before carriers
tunnel out of the dot. The Stark shift experienced by the emission line is
typically 1 meV. We report that by embedding the quantum dots in a quantum well
heterostructure the vertical field that can be applied is increased by over an
order of magnitude whilst preserving the narrow linewidths, high internal
quantum efficiencies and familiar emission spectra. Individual dots can then be
continuously tuned to the same energy allowing for two-photon interference
between remote, independent, quantum dots
Parent experiences of inpatient pediatric care in relation to health care delivery and sociodemographic characteristics: results of a Norwegian national survey
Impact of the California Lead Ammunition Ban on Reducing Lead Exposure in Golden Eagles and Turkey Vultures
Predatory and scavenging birds may be exposed to high levels of lead when they ingest shot or bullet fragments embedded in the tissues of animals injured or killed with lead ammunition. Lead poisoning was a contributing factor in the decline of the endangered California condor population in the 1980s, and remains one of the primary factors threatening species recovery. In response to this threat, a ban on the use of lead ammunition for most hunting activities in the range of the condor in California was implemented in 2008. Monitoring of lead exposure in predatory and scavenging birds is essential for assessing the effectiveness of the lead ammunition ban in reducing lead exposure in these species. In this study, we assessed the effectiveness of the regulation in decreasing blood lead concentration in two avian sentinels, golden eagles and turkey vultures, within the condor range in California. We compared blood lead concentration in golden eagles and turkey vultures prior to the lead ammunition ban and one year following implementation of the ban. Lead exposure in both golden eagles and turkey vultures declined significantly post-ban. Our findings provide evidence that hunter compliance with lead ammunition regulations was sufficient to reduce lead exposure in predatory and scavenging birds at our study sites