390 research outputs found
Assessing the Reliability of the Retrospective Reproductive Calendar: Evidence from Urban Kenya
The reproductive calendar is a data collection tool that collects month-by-month retrospective histories of contraceptive use. This survey instrument is implemented in large-scale demographic surveys, but its reliability is not well-understood. Our analysis helps to address this research gap, using longitudinal panel data with overlapping calendars from urban Kenya. Our findings indicate calendar data collected in 2014 underestimated 2012 reports of current use by 5 percentage points. And while the overall percentage of women reporting at least one episode of contraceptive use was similar across the two calendars (67 percent vs. 70 percent), there was notable disagreement in contraceptive behavior when comparing the histories of individual women; less than 20 percent of women with any contraceptive use reported the exact same pattern of use in both calendars. Low calendar reliability was especially apparent for younger women and those with complicated contraceptive histories. Individual-level discordance resulted in a small difference in 12-month discontinuation rates for the period of calendar overlap; when surveyed in 2014, women reported a 12-month discontinuation rate of 39 percent, compared to a rate of 34 percent reported in 2012. When using retrospective calendar data, attention must be paid to the potential for individual reporting errors
Inferring physical conditions in interstellar clouds of H_2
We have developed a code that models the formation, destruction, radiative
transfer, and vibrational/rotational excitation of H_2 in a detailed fashion.
We discuss how such codes, together with FUSE observations of H_2 in diffuse
and translucent lines of sight, may be used to infer various physical
parameters. We illustrate the effects of changes in the major physical
parameters (UV radiation field, gas density, metallicity), and we point out the
extent to which changes in one parameter may be mirrored by changes in another.
We provide an analytic formula for the molecular fraction, f_H2, as a function
of cloud column density, radiation field, and grain formation rate of H_2. Some
diffuse and translucent lines of sight may be concatenations of multiple
distinct clouds viewed together. Such situations can give rise to observables
that agree with the data, complicating the problem of uniquely identifying one
set of physical parameters with a line of sight. Finally, we illustrate the
application of our code to an ensemble of data, such as the FUSE survey of H_2
in the Large and Small Magellanic Clouds (LMC/SMC), in order to constrain the
elevated UV radiation field intensity and reduced grain formation rate of H_2
in those low- metallicity environments.Comment: 33 pages (aastex, manuscript), 9 figures (3 color). accepted to Ap
Understanding healthcare provider absenteeism in Kenya: a qualitative analysis
Background: Healthcare worker absenteeism is common in resource limited settings and contributes to poor quality of care in maternal and child health service delivery. There is a dearth of qualitative information on the scope, contributing factors, and impact of absenteeism in Kenyan healthcare facilities. Methods: In-depth semi-structured interviews were conducted between July 2015 and June 2016 with 20 healthcare providers in public and private healthcare facilities in Central and Western Kenya. Interviews were audiorecorded, transcribed, coded, and analyzed using an iterative thematic approach. Results: Half of providers reported that absenteeism occurs in both private and public health facilities. Absenteeism was most commonly characterized by providers arriving late or leaving early during scheduled work hours. The practice was attributed to institutional issues including: infrequent supervision, lack of professional consequences, limited accountability, and low wages. In some cases, healthcare workers were frequently absent because they held multiple positions at different health facilities. Provider absences result in increased patient wait times and may deter patients from seeking healthcare in the future. Conclusion: There is a significant need for policies and programs to reduce provider absenteeism in Kenya. Intervention approaches must be cognizant of the contributors to absenteeism which occur at the institutional level
A Budget and Accounting of Metals at z~0: Results from the COS-Halos Survey
We present a budget and accounting of metals in and around star-forming
galaxies at . We combine empirically derived star formation histories
with updated supernova and AGB yields and rates to estimate the total mass of
metals produced by galaxies with present-day stellar mass of
--. On the accounting side of the ledger, we
show that a surprisingly constant 20--25% mass fraction of produced metals
remain in galaxies' stars, interstellar gas and interstellar dust, with little
dependence of this fraction on the galaxy stellar mass (omitting those metals
immediately locked up in remnants). Thus, the bulk of metals are outside of
galaxies, produced in the progenitors of today's galaxies. The COS-Halos
survey is uniquely able to measure the mass of metals in the circumgalactic
medium (to impact parameters of kpc) of low-redshift
galaxies. Using these data, we map the distribution of CGM metals as traced by
both the highly ionized OVI ion and a suite of low-ionization species; combined
with constraints on circumgalactic dust and hotter X-ray emitting gas out to
similar impact parameters, we show that % of metals produced by
galaxies can be easily accounted for out to
150 kpc. With the current data, we cannot rule out a constant mass of metals
within this fixed physical radius. This census provides a crucial boundary
condition for the eventual fate of metals in galaxy evolution models.Comment: 19 pages, 12 figures, 2 tables. ApJ, in pres
A Deep Search For Faint Galaxies Associated With Very Low-redshift C IV Absorbers: III. The Mass- and Environment-dependent Circumgalactic Medium
Using Hubble Space Telescope Cosmic Origins Spectrograph observations of 89
QSO sightlines through the Sloan Digital Sky Survey footprint, we study the
relationships between C IV absorption systems and the properties of nearby
galaxies as well as large-scale environment. To maintain sensitivity to very
faint galaxies, we restrict our sample to 0.0015 < z < 0.015, which defines a
complete galaxy survey to L > 0.01 L* or stellar mass log M_* > 8 Msun. We
report two principal findings. First, for galaxies with impact parameter rho <
1 rvir, C IV detection strongly depends on the luminosity/stellar mass of the
nearby galaxy. C IV is preferentially associated with galaxies with log M_* >
9.5 Msun; lower mass galaxies rarely exhibit significant C IV absorption
(covering fraction f = 9 +12-6% for 11 galaxies with log M_* < 9.5 Msun).
Second, C IV detection within the log M_* > 9.5 Msun population depends on
environment. Using a fixed-aperture environmental density metric for galaxies
with rho < 160 kpc at z < 0.055, we find that 57+/-12% (8/14) of galaxies in
low-density regions (regions with fewer than seven L > 0.15 L* galaxies within
1.5 Mpc) have affiliated C IV absorption; however, none (0/7) of the galaxies
in denser regions show C IV. Similarly, the C IV detection rate is lower for
galaxies residing in groups with dark-matter halo masses of log Mhalo > 12.5
Msun. In contrast to C IV, H I is pervasive in the CGM without regard to mass
or environment. These results indicate that C IV absorbers with log N(C IV) >
13.5 cm^-2 trace the halos of log M_* > 9.5 Msun galaxies but also reflect
larger scale environmental conditions.Comment: 26 pages, 13 figures. ApJ, in pres
New HST Observations of the Halo Gas of NGC 3067: Limits on the Extragalactic Ionizing Background at Low Redshift and the Lyman Continuum Escape Fraction
We present UV spectroscopy from HST/GHRS and reanalyze existing H_alpha
images of the quasar/galaxy pair 3C 232/NGC 3067 and of the halo gas associated
with NGC 3067. The spectra permit measurement of, or limits on, the column
densities of Fe I, Fe II, Mg I, and Mg II in the absorbing cloud. Two distinct
models of the extragalactic radiation field are considered: (1) the ionizing
spectrum is dominated by a power-law extragalactic continuum, and (2) the
power-law spectrum contains a Lyman break, implying enhanced flux longward of
912 A relative to the hydrogen-ionizing flux. The H_alpha images constrain the
escape fraction of Lyman continuum photons from the galaxy to f_esc <= 0.02.
With the assumption that the cloud is shielded from all galactic contributions,
we can constrain the intensity and shape of the extragalactic continuum. For an
AGN-dominated power-law extragalactic spectrum, we derive a limit on the
extragalactic ionizing flux Phi_ion >= 2600 photons cm^-2 s^-1, or I_0 >=
10^-23 erg cm^-2 s^-1 Hz^-1 sr^-1 for an ionizing spectrum with power-law index
of 1.8 and a cloud of constant density. When combined with previous upper
limits from the absence of H_alpha recombination emission from intergalactic
clouds, our observations require 2600 <= Phi_ion <= 10000 photons cm^-2 s^-1.
We show that if galactic contributions to the incident radiation are important,
it is difficult to constrain Phi_ion. These results demonstrate that galactic
halo opacities and their wavelength dependence are crucial to understanding the
abundance of low-ionization metals in the IGM.Comment: 25 Pages LaTex, 8 PostScript Figures, accepted for publication in AJ,
Nov. 99 issu
Probing the IGM/Galaxy Connection V: On the Origin of Lya and OVI Absorption at z<0.2
We analyze the association of galaxies to Lya and OVI absorption, the most
commonly detected transitions in the low-z intergalactic medium (IGM), in the
fields of 14 quasars with z_em = 0.06-0.57. Confirming previous studies, we
observe a high covering fraction for Lya absorption to impact parameter rho =
300kpc: 33/37 of our L>0.01L* galaxies show Lya equivalent width W_Lya>50mA.
Galaxies of all luminosity L>0.01L* and spectral type are surrounded by a
diffuse and ionized circumgalactic medium (CGM), whose baryonic mass is
estimated at ~10^(10.5 +/- 0.3) Msun for a constant N_H. The virialized halos
and extended CGM of present-day galaxies are responsible for most strong Lya
absorbers (W_Lya > 300mA) but cannot reproduce the majority of observed lines
in the Lya forest. We conclude that the majority of Lya absorption with
W_Lya=30-300mA occurs in the cosmic web predicted by cosmological simulations
and estimate a characteristic width for these filaments of ~400kpc. Regarding
OVI, we observe a near unity covering fraction to rho=200kpc for L>0.1L*
galaxies and to rho = 300kpc for sub-L* (0.1 L*<L<L*) galaxies. Similar to our
Lya results, stronger OVI systems (W_OVI > 70mA) arise in the virialized halos
of L>0.1L* galaxies. Unlike Lya, the weaker OVI systems (W_OVI~30mA) arise in
the extended CGM of sub-L* galaxies. The majority of OVI gas observed in the
low-z IGM is associated with a diffuse medium surrounding individual galaxies
with L~0.3L*, and rarely originates in the so-called warm-hot IGM (WHIM)
predicted by cosmological simulations.Comment: Submitted to the Astrophysical Journal; 26 pages, 9 figures. See
http://www.ucolick.org/~xavier/WFCCDOVI/index.html for mor
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