970 research outputs found
The SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Quasar Target Selection
As part of the Sloan Digital Sky Survey (SDSS) IV the extended Baryon Oscillation Spectroscopic Survey (eBOSS) will improve measurements of the cosmological distance scale by applying the Baryon Acoustic Oscillation (BAO) method to quasar samples. eBOSS will adopt two approaches to target quasars over 7500 deg^2. First, a "CORE" quasar sample will combine the optical selection in ugriz using a likelihood-based routine called XDQSOz, with a mid-IR-optical color cut. eBOSS CORE selection (to g 2.1 quasars. Second, a selection based on variability in multi-epoch imaging from the Palomar Transient Factory should recover an additional ~3–4 deg^(−2)z > 2.1 quasars to g 2.1 will be used to improve BAO measurements in the Lyα Forest. Beyond its key cosmological goals, eBOSS should be the next-generation quasar survey, comprising >500,000 new quasars and >500,000 uniformly selected spectroscopically confirmed 0.9 < z < 2.2 quasars. At the conclusion of eBOSS, the SDSS will have provided unique spectra for more than 800,000 quasars
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In-situ resonant band engineering of solution-processed semiconductors generates high performance n-type thermoelectric nano-inks.
Thermoelectric devices possess enormous potential to reshape the global energy landscape by converting waste heat into electricity, yet their commercial implementation has been limited by their high cost to output power ratio. No single "champion" thermoelectric material exists due to a broad range of material-dependent thermal and electrical property optimization challenges. While the advent of nanostructuring provided a general design paradigm for reducing material thermal conductivities, there exists no analogous strategy for homogeneous, precise doping of materials. Here, we demonstrate a nanoscale interface-engineering approach that harnesses the large chemically accessible surface areas of nanomaterials to yield massive, finely-controlled, and stable changes in the Seebeck coefficient, switching a poor nonconventional p-type thermoelectric material, tellurium, into a robust n-type material exhibiting stable properties over months of testing. These remodeled, n-type nanowires display extremely high power factors (~500 µW m-1K-2) that are orders of magnitude higher than their bulk p-type counterparts
One Year Later and the Myth of a Post-Racial Society
Many commentators, both conservative and liberal, have celebrated the election of Barack Obama as president of the United States, claiming the election signified America has truly become a “post-racial” society. It is not just Lou Dobbs who argues the United States in the “21st century [is a] post-partisan, post-racial society.” This view is consistent with beliefs the majority of White Americans have held for well over a decade: that African Americans have achieved, or will soon achieve, racial equality in the United States despite substantial evidence to the contrary. Indeed, this view is consistent with opinions found in the Boston Globe, Wall Street Journal, New York Times, and elsewhere—attitudes that even the tragic events following the Katrina disaster had nothing to do with race.African and African American Studie
Transport infrastructure and welfare an application to nigeria
Transport infrastructure is deemed to be central to development and consumes a large fraction of the development assistance envelope. Yet there is debate about the economic impact of road projects. This paper proposes an approach to assess the differential development impacts of alternative road construction and prioritize various proposals, using Nigeria as a case study. Recognizing that there is no perfect measure of economic well-being, a variety of outcome metrics are used, including crop revenue, livestock revenue, non-agricultural income, the probability of being multi-dimensionally poor, and local gross domestic product for Nigeria. Although the measure of transport is the most accurate possible, it is still endogenous because of the nonrandom placement of road infrastructure. This endogeneity is addressed using a seemingly novel instrumental variable termed the natural path: the time it would take to walk along the most logical route connecting two points without taking into account other, bias-causing economic benefits. Further, the analysis considers the potential endogeneity from nonrandom placement of households and markets through carefully chosen control variables. It finds that reducing transportation costs in Nigeria will increase crop revenue, non-agricultural income, the wealth index, and local gross domestic product. Livestock sales increase as well, although this finding is less robust. The probability of being multi-dimensionally poor will decrease. The results also cast light on income diversification and structural changes that may arise. These findings are robust to relaxing the exclusion restriction. The paper also demonstrates how to prioritize alternative road programs by comparing the expected development impacts of alternative New Partnership for Africas Development projects.
Document type: Boo
Slow-Speed Supernovae from the Palomar Transient Factory: Two Channels
Since the discovery of the unusual prototype SN 2002cx, the eponymous class
of low-velocity, hydrogen-poor supernovae has grown to include at most another
two dozen members identified from several heterogeneous surveys, in some cases
ambiguously. Here we present the results of a systematic study of 1077
hydrogen-poor supernovae discovered by the Palomar Transient Factory, leading
to nine new members of this peculiar class. Moreover we find there are two
distinct subclasses based on their spectroscopic, photometric, and host galaxy
properties: The "SN 2002cx-like" supernovae tend to be in later-type or more
irregular hosts, have more varied and generally dimmer luminosities, have
longer rise times, and lack a Ti II trough when compared to the "SN
2002es-like" supernovae. None of our objects show helium, and we counter a
previous claim of two such events. We also find that these transients comprise
5.6+17-3.7% (90% confidence) of all SNe Ia, lower compared to earlier
estimates. Combining our objects with the literature sample, we propose that
these subclasses have two distinct physical origins.Comment: 49 pages, 36 figures, submitted to Ap
The new scalar politics of evaluation: An emerging governance role for evaluation
In this article we analyze how roles for evaluation are described and argued for in key texts produced and/or promoted by three influential international networks: the High Level Forum on Aid Effectiveness; the Organisation for Economic Cooperation and Development Assistance Committee’s Network on Development Evaluation; and the Network of Networks for Impact Evaluation. We contend that these complex multilateral networks are working supranationally through soft power to promote: common standards of evaluation practice; a dominant model of evaluation (impact evaluation); and new evaluation roles, relationships and practices for the field of development. Moreover, we argue that this emerging complex multilateral agenda for evaluation may position evaluation and evaluators within a global governance strategy allowing greater influence to international development organizations. We conclude with a discussion of the implications of the analysis for evaluators working in the field of international development
The Palomar Transient Factory Orion Project: Eclipsing Binaries and Young Stellar Objects
The Palomar Transient Factory (PTF) Orion project is an experiment within the
broader PTF survey, a systematic automated exploration of the sky for optical
transients. Taking advantage of the wide field of view available using the PTF
camera at the Palomar 48" telescope, 40 nights were dedicated in December
2009-January 2010 to perform continuous high-cadence differential photometry on
a single field containing the young (7-10Myr) 25 Ori association. The primary
motivation for the project is to search for planets around young stars in this
region. The unique data set also provides for much ancillary science. In this
first paper we describe the survey and data reduction pipeline, and present
initial results from an inspection of the most clearly varying stars relating
to two of the ancillary science objectives: detection of eclipsing binaries and
young stellar objects. We find 82 new eclipsing binary systems, 9 of which we
are candidate 25 Ori- or Orion OB1a-association members. Of these, 2 are
potential young W UMa type systems. We report on the possible low-mass (M-dwarf
primary) eclipsing systems in the sample, which include 6 of the candidate
young systems. 45 of the binary systems are close (mainly contact) systems; one
shows an orbital period among the shortest known for W UMa binaries, at
0.2156509 \pm 0.0000071d, with flat-bottomed primary eclipses, and a derived
distance consistent with membership in the general Orion association. One of
the candidate young systems presents an unusual light curve, perhaps
representing a semi-detached binary system with an inflated low-mass primary or
a star with a warped disk, and may represent an additional young Orion member.
Finally, we identify 14 probable new classical T-Tauri stars in our data, along
with one previously known (CVSO 35) and one previously reported as a candidate
weak-line T-Tauri star (SDSS J052700.12+010136.8).Comment: 66 pages, 27 figures, accepted to Astronomical Journal. Minor
typographical corrections and update to author affiliation
The PTF Orion Project: a Possible Planet Transiting a T-Tauri Star
We report observations of a possible young transiting planet orbiting a
previously known weak-lined T-Tauri star in the 7-10 Myr old Orion-OB1a/25-Ori
region. The candidate was found as part of the Palomar Transient Factory (PTF)
Orion project. It has a photometric transit period of 0.448413 +- 0.000040
days, and appears in both 2009 and 2010 PTF data. Follow-up low-precision
radial velocity (RV) observations and adaptive optics imaging suggest that the
star is not an eclipsing binary, and that it is unlikely that a background
source is blended with the target and mimicking the observed transit. RV
observations with the Hobby-Eberly and Keck telescopes yield an RV that has the
same period as the photometric event, but is offset in phase from the transit
center by approximately -0.22 periods. The amplitude (half range) of the RV
variations is 2.4 km/s and is comparable with the expected RV amplitude that
stellar spots could induce. The RV curve is likely dominated by stellar spot
modulation and provides an upper limit to the projected companion mass of M_p
sin i_orb < 4.8 +- 1.2 M_Jup; when combined with the orbital inclination, i
orb, of the candidate planet from modeling of the transit light curve, we find
an upper limit on the mass of the planetary candidate of M_p < 5.5 +- 1.4
M_Jup. This limit implies that the planet is orbiting close to, if not inside,
its Roche limiting orbital radius, so that it may be undergoing active mass
loss and evaporation.Comment: Corrected typos, minor clarifications; minor updates/corrections to
affiliations and bibliography. 35 pages, 10 figures, 3 tables. Accepted to
Ap
Positron emission tomography and magnetic resonance imaging methods and datasets within the Dominantly Inherited Alzheimer Network (DIAN)
The Dominantly Inherited Alzheimer Network (DIAN) is an international collaboration studying autosomal dominant Alzheimer disease (ADAD). ADAD arises from mutations occurring in three genes. Offspring from ADAD families have a 50% chance of inheriting their familial mutation, so non-carrier siblings can be recruited for comparisons in case-control studies. The age of onset in ADAD is highly predictable within families, allowing researchers to estimate an individual\u27s point in the disease trajectory. These characteristics allow candidate AD biomarker measurements to be reliably mapped during the preclinical phase. Although ADAD represents a small proportion of AD cases, understanding neuroimaging-based changes that occur during the preclinical period may provide insight into early disease stages of \u27sporadic\u27 AD also. Additionally, this study provides rich data for research in healthy aging through inclusion of the non-carrier controls. Here we introduce the neuroimaging dataset collected and describe how this resource can be used by a range of researchers
The Long-Baseline Neutrino Experiment: Exploring Fundamental Symmetries of the Universe
The preponderance of matter over antimatter in the early Universe, the
dynamics of the supernova bursts that produced the heavy elements necessary for
life and whether protons eventually decay --- these mysteries at the forefront
of particle physics and astrophysics are key to understanding the early
evolution of our Universe, its current state and its eventual fate. The
Long-Baseline Neutrino Experiment (LBNE) represents an extensively developed
plan for a world-class experiment dedicated to addressing these questions. LBNE
is conceived around three central components: (1) a new, high-intensity
neutrino source generated from a megawatt-class proton accelerator at Fermi
National Accelerator Laboratory, (2) a near neutrino detector just downstream
of the source, and (3) a massive liquid argon time-projection chamber deployed
as a far detector deep underground at the Sanford Underground Research
Facility. This facility, located at the site of the former Homestake Mine in
Lead, South Dakota, is approximately 1,300 km from the neutrino source at
Fermilab -- a distance (baseline) that delivers optimal sensitivity to neutrino
charge-parity symmetry violation and mass ordering effects. This ambitious yet
cost-effective design incorporates scalability and flexibility and can
accommodate a variety of upgrades and contributions. With its exceptional
combination of experimental configuration, technical capabilities, and
potential for transformative discoveries, LBNE promises to be a vital facility
for the field of particle physics worldwide, providing physicists from around
the globe with opportunities to collaborate in a twenty to thirty year program
of exciting science. In this document we provide a comprehensive overview of
LBNE's scientific objectives, its place in the landscape of neutrino physics
worldwide, the technologies it will incorporate and the capabilities it will
possess.Comment: Major update of previous version. This is the reference document for
LBNE science program and current status. Chapters 1, 3, and 9 provide a
comprehensive overview of LBNE's scientific objectives, its place in the
landscape of neutrino physics worldwide, the technologies it will incorporate
and the capabilities it will possess. 288 pages, 116 figure
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