397 research outputs found
Exploring the Relationship of Enrollment in IDR to Borrower Demographics and Financial Outcomes
As federal policymakers consider changes to income-driven repayment (IDR) schemes, research examining the characteristics and financial behaviors of student loan borrowers participating in IDR is necessary. Using the nationally representative Survey of Consumer Finances, we examined the demographics of IDR enrollment. Counter to expectations, low-income borrowers, and borrowers with high debt-to-income ratios are less likely to enroll in IDR. Conditional on having a large amount of debt, married women of color are likely to enroll in IDR programs. Findings concerning IDR participation may be highly sensitive to how groups are defined and what covariates are in models. IDR participation does not predict engagement in other financial behaviors such as retirement savings or homeownership
Another Lesson on Caution in IDR Analysis: Using the 2019 Survey of Consumer Finances to Examine Income-Driven Repayment and Financial Outcomes
We update Collier et al. (2021) by using the Survey of Consumer Finances (SCF) 2019 dataset to explore characteristics of enrollees in Income-Driven Repayment (IDR). SCF 2019 is more likely to include borrowers engaged in REPAYE. Findings support an ongoing need to encourage greater IDR participation for lowest-income borrowers and reinforce greater participation by female borrowers. Again, model specification affects findings regarding IDR enrollment. REPAYE appears to have widened access to IDR by lowering the debt floor for entry. IDR enrollment was correlated with less money in a traditional checking account and a lower chance of engaging in retirement savings
The r-Process Enriched Low Metallicity Giant HD 115444
New high resolution, very high signal-to-noise spectra of ultra-metal-poor
(UMP) giant stars HD 115444 and HD 122563 have been gathered with the
High-Resolution Echelle Spectrometer of the McDonald Observatory 2.7m
Telescope. With these spectra, line identification and model atmosphere
analyses have been conducted, emphasizing the neutron-capture elements. Twenty
elements with Z > 30 have been identified in the spectrum of HD 115444. This
star is known to have overabundances of the neutron-capture elements, but it
has lacked a detailed analysis necessary to compare with nucleosynthesis
predictions. The new study features a line-by-line differential abundance
comparison of HD 115444 with the bright, well-studied halo giant HD 122563. For
HD 115444, the overall metallicity is [Fe/H]~ -3.0. The abundances of the light
and iron-peak elements generally show the same pattern as other UMP stars (e.g.
overdeficiencies of manganese and chromium, overabundances of cobalt), but the
differential analysis indicates several nucleosynthesis signatures that are
unique to each star.Comment: To Appear in the Astrophysical Journa
Robustness to misalignment of low-cost, compact quantitative phase imaging architectures.
Non-interferometric approaches to quantitative phase imaging could enable its application in low-cost, miniaturised settings such as capsule endoscopy. We present two possible architectures and both analyse and mitigate the effect of sensor misalignment on phase imaging performance. This is a crucial step towards determining the feasibility of implementing phase imaging in a capsule device. First, we investigate a design based on a folded 4f correlator, both in simulation and experimentally. We demonstrate a novel technique for identifying and compensating for axial misalignment and explore the limits of the approach. Next, we explore the implications of axial and transverse misalignment, and of manufacturing variations on the performance of a phase plate-based architecture, identifying a clear trade-off between phase plate resolution and algorithm convergence time. We conclude that while the phase plate architecture is more robust to misalignment, both architectures merit further development with the goal of realising a low-cost, compact system for applying phase imaging in capsule endoscopy
Neutron-Capture Elements in the Early Galaxy: Insights from a Large Sample of Metal-Poor Giants
New abundances for neutron-capture (n-capture) elements in a large sample of
metal-poor giants from the Bond survey are presented. The spectra were acquired
with the KPNO 4-m echelle and coude feed spectrographs, and have been analyzed
using LTE fine-analysis techniques with both line analysis and spectral
synthesis. Abundances of eight n-capture elements (Sr, Y, Zr, Ba, La, Nd, Eu,
Dy) in 43 stars have been derived from blue (lambda = 4070--4710, R~20,000, S/N
ratio~100-200) echelle spectra and red (lambda = 6100--6180, R~22,000, S/N
ratio~100-200) coude spectra, and the abundance of Ba only has been derived
from the red spectra for an additional 27 stars. Overall, the abundances show
clear evidence for a large star-to-star dispersion in the heavy element-to-iron
ratios. The new data also confirm that at metallicities [Fe/H] <~ --2.4, the
abundance pattern of the heavy (Z >= 56) n-capture elements in most giants is
well-matched to a scaled Solar System r-process nucleosynthesis pattern. The
onset of the main r-process can be seen at [Fe/H] ~ --2.9. Contributions from
the s-process can first be seen in some stars with metallicities as low as
[Fe/H] ~ --2.75, and are present in most stars with metallicities [Fe/H] >
--2.3. The lighter n-capture elements (Sr-Y-Zr) are enhanced relative to the
heavier r-process element abundances. Their production cannot be attributed
solely to any combination of the Solar System r- and main s-processes, but
requires a mixture of material from the r-process and from an additional
n-capture process which can operate at early Galactic time.Comment: Text + 5 Tables and 11 Figures: Submitted to the Astrophysical
Journa
Implementing the global plan to stop TB, 2011-2015 - optimizing allocations and the global fund's contribution: A scenario projections study
Background: The Global Plan to Stop TB estimates funding required in low- and middle-income countries to achieve TB control targets set by the Stop TB Partnership within the context of the Millennium Development Goals. We estimate the contribution and impact of Global Fund investments under various scenarios of allocations across interventions and regions. Methodology/Principal Findings: Using Global Plan assumptions on expected cases and mortality, we estimate treatment costs and mortality impact for diagnosis and treatment for drug-sensitive and multidrug-resistant TB (MDR-TB), including antiretroviral treatment (ART) during DOTS for HIV-co-infected patients, for four country groups, overall and for the Global Fund investments. In 2015, China and India account for 24% of funding need, Eastern Europe and Central Asia (EECA) for 33%, sub-Saharan Africa (SSA) for 20%, and other low- and middle-income countries for 24%. Scale-up of MDR-TB treatment, especially in EECA, drives an increasing global TB funding need - an essential investment to contain the mortality burden associated with MDR-TB and future disease costs. Funding needs rise fastest in SSA, reflecting increasing coverage need of improved TB/HIV management, which saves most lives per dollar spent in the short term. The Global Fund is expected to finance 8-12% of Global Plan implementation costs annually. Lives saved through Global Fund TB support within the available funding envelope could increase 37% if allocations shifted from current regional demand patterns to a prioritized scale-up of improved TB/HIV treatment and secondly DOTS, both mainly in Africa - with EECA region, which has disproportionately high per-patient costs, funded from alternative resources. Conclusions/Significance: These findings, alongside country funding gaps, domestic funding and implementation capacity and equity considerations, should inform strategies and policies for international donors, national governments and disease control programs to implement a more optimal investment approach focusing on highest-impact populations and interventions
The Rise of the s-Process in the Galaxy
From newly-obtained high-resolution, high signal-to-noise ratio spectra the
abundances of the elements La and Eu have been determined over the stellar
metallicity range -3<[Fe/H]<+0.3 in 159 giant and dwarf stars. Lanthanum is
predominantly made by the s-process in the solar system, while Eu owes most of
its solar system abundance to the r-process. The changing ratio of these
elements in stars over a wide metallicity range traces the changing
contributions of these two processes to the Galactic abundance mix. Large
s-process abundances can be the result of mass transfer from very evolved
stars, so to identify these cases, we also report carbon abundances in our
metal-poor stars. Results indicate that the s-process may be active as early as
[Fe/H]=-2.6, alalthough we also find that some stars as metal-rich as [Fe/H]=-1
show no strong indication of s-process enrichment. There is a significant
spread in the level of s-process enrichment even at solar metallicity.Comment: 64 pages, 15 figures; ApJ 2004 in pres
The Chemical Composition and Age of the Metal-Poor Halo Star BD +17^\circ 3248
We have combined new high-resolution spectra obtained with the Hubble Space
Telescope (HST) and ground-based facilities to make a comprehensive new
abundance analysis of the metal-poor, halo star BD +17^\circ 3248. We have
detected the third r-process peak elements osmium, platinum, and (for the first
time in a metal-poor star) gold, elements whose abundances can only be reliably
determined using HST. Our observations illustrate a pattern seen in other
similar halo stars with the abundances of the heavier neutron-capture elements,
including the third r-process peak elements, consistent with a scaled solar
system r-process distribution. The abundances of the lighter neutron-capture
elements, including germanium and silver, fall below that same scaled solar
r-process curve, a result similar to that seen in the ultra-metal-poor star CS
22892--052. A single site with two regimes or sets of conditions, or perhaps
two different sites for the lighter and heavier neutron-capture elements, might
explain the abundance pattern seen in this star. In addition we have derived a
reliable abundance for the radioactive element thorium. We tentatively identify
U II at 3859 A in the spectrum of BD +17^\circ 3248, which makes this the
second detection of uranium in a very metal-poor halo star. Our combined
observations cover the widest range in proton number (from germanium to
uranium) thus far of neutron-capture elements in metal-poor Galactic halo
stars. Employing the thorium and uranium abundances in comparison with each
other and with several stable elements, we determine an average
cosmochronological age for BD +17^\circ 3248 of 13.8 +/- 4 Gyr, consistent with
that found for other similar metal-poor halo stars.Comment: 58 pages, 4 tables, 11 figures; To appear in ApJ Typo correcte
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