24 research outputs found
Detection of an X-Ray Hot Region in the Virgo Cluster of Galaxies with ASCA
Based on mapping observations with ASCA, an unusual hot region with a spatial
extent of 1 square degree was discovered between M87 and M49 at a center
coordinate of R. A. = 12h 27m 36s and Dec. = (J2000). The X-ray
emission from the region has a 2-10 keV flux of ergs
s cm and a temperature of keV, which is
significantly higher than that in the surrounding medium of keV. The
internal thermal energy in the hot region is estimated to be ergs with a gas density of cm. A power-law
spectrum with a photon index is also allowed by the data. The hot
region suggests there is an energy input due to a shock which is probably
caused by the motion of the gas associated with M49, infalling toward the M87
cluster with a velocity km s.Comment: 12 pages, 3 figures, accepted to ApJ
Reducing child undernutrition through dietary diversification, reduced aflatoxin exposure, and improved hygiene practices: the immediate impacts in central Tanzania
Open Access Article; Published online: 28 Nov 2019The study aimed to quantify the immediate effects of dietary diversification, food safety, and hygiene interventions on child undernutrition in four rural villages in Kongwa district of central Tanzania. One hundred mothers with their children of less than 24 months old were recruited for this study. The difference-in-difference (DID) method was used to assess the effects of intensive intervention through a learning-by-doing process on the topic of aflatoxin free diversified food utilization and improved hygiene practices. Periodic anthropometric measurements were conducted on the 0th, 7th, 14th, and 21st days, and DID estimator showed the significant and positive average marginal effects of the intervention on Z-Scores being 0.459, 0.252, and 0.493 for wasting, stunting, and underweight, respectively. Notably, at the end of the study, the mean aflatoxin M1 level in urine samples decreased by 64% in the intervention group, while it decreased by 11% in the control group. The study provides quantitative evidence on intensive 21-day training for mothers incorporating integrated technologies yielded positive impacts on their children’s nutritional outcomes
An Empirical Analysis of Expanding Rice Production in Sub-Sahara Africa, The Impact of Training on Technology Adoption and Productivity of Rice Farming in Tanzania: Is Farmer-to-Farmer Extension Effective
How far can new technologies taught to a small number of selected farmers diffuse to other farmers in a village? In order to answer this question, this paper investigates the impact of JICA training on the adoption of rice cultivation technologies and productivity in an irrigation scheme in Tanzania. By using a unique five-year panel data set and spatial econometric techniques, we found that non-trained farmers learned new technologies from trained farmers through social networks and by observing their plots. As a result, the paddy yield of directly trained farmers increased from 3.1 tons per hectare in 2008 to 4.7 tons per hectare in 2012, while that of non-trained farmers increased from around 2.6 tons per hectare in 2008 to 3.7 tons per hectare in 2012
Discovery of the Central Excess Brightness in Hard X-rays in the Cluster of Galaxies Abell 1795
Using the X-ray data from \ASCA, spectral and spatial properties of the
intra-cluster medium (ICM) of the cD cluster Abell 1795 are studied, up to a
radial distance of ( kpc). The ICM
temperature and abundance are spatially rather constant, although the cool
emission component is reconfirmed in the central region. The azimuthally-
averaged radial X-ray surface brightness profiles are very similar between soft
(0.7--3 keV) and hard (3--10 keV) energy bands, and neither can be fitted with
a single- model due to a strong data excess within of the
cluster center. In contrast, double- models can successfully reproduce
the overall brightness profiles both in the soft and hard energy bands, as well
as that derived with the \ROSAT PSPC. Properties of the central excess
brightness are very similar over the 0.2--10 keV energy range spanned by \ROSAT
and \ASCA. Thus, the excess X-ray emission from the core region of this cluster
is confirmed for the first time in hard X-rays above 3 keV. This indicates that
the shape of the gravitational potential becomes deeper than the King-type one
towards the cluster center. Radial profiles of the total gravitating matter,
calculated using the double- model, reveal an excess mass of within kpc of the cluster
center. This suggests a hierarchy in the gravitational potential corresponding
to the cD galaxy and the entire cluster.Comment: 27 pages, 8 figures; to appear ApJ 500 (June 20, 1998
Log N - Log S Relations and Spectral Properties of Sources from the ASCA Large Sky Survey --- their Implications for the Origin of the Cosmic X-ray Background (CXB)
We carried out the first wide-area unbiased survey with the ASCA satellite in
the 0.7-10 keV band around a north Galactic-pole region covering a continuous
area of 7 square degrees (Large Sky Survey; LSS). To make the best use of ASCA
capability, we developed a new source-detection method where the complicated
detector responses are fully taken into account. Applying this method to the
entire LSS data independently in the total (0.7-7 keV), hard (2-10 keV), and
soft (0.7-2 keV) band, we detected 107 sources altogether with sensitivity
limits of 6 x 10E-14 (0.7-7 keV), 1 x 10E-13 (2-10 keV), and 2 x 10E-14 erg
sE-1 cmE-2 (0.7-2 keV), respectively. A complete list of the detected sources
is presented. Based on detailed studies by Monte Carlo simulations, we
evaluated effects of the source confusion and accurately derived Log N - Log S
relation in each survey band. The Log N - Log S relation in the hard band is
located on the extrapolation from the GINGA and HEAO1 results with the
Euclidean slope of -3/2, while that in the soft band is consistent with the
results by ROSAT. At these flux limits, 30 (+/- 3) percent of the CXB in the
0.7-7 keV band and 23 (+/- 3) percent in the 2-10 keV band have been resolved
into discrete sources. The average spectrum of faint sources detected in the
total band shows a photon index of 1.63 +/- 0.07 in the 0.7-10 keV range,
consistent with the comparison of source counts between the hard and the soft
energy band. Those detected in the hard band show a photon index of 1.49 +/-
0.10 in the 2-10 keV range. These spectral properties suggest that contribution
of sources with hard energy spectra become significant at a flux of 10E-13 erg
sE-1 cmE-2 (2-10 keV). The most plausible candidates are type-II AGNs, as
indicated by on-going optical identifications.Comment: 28 pages, 11 figures, to appear in ApJ 518, 1999; figure 1 replaced,
minor errors in text correcte
Reducing Child Undernutrition through Dietary Diversification, Reduced Aflatoxin Exposure, and Improved Hygiene Practices: The Immediate Impacts in Central Tanzania
The study aimed to quantify the immediate effects of dietary
diversification, food safety, and hygiene interventions on child undernutrition in four rural villages in Kongwa district of central Tanzania. One hundred mothers with their children of less than 24 months old were recruited for this study. The difference-in-difference (DID) method was used to assess the effects of intensive intervention through a learning-by-doing process on the topic of aflatoxin free diversified food utilization and
improved hygiene practices. Periodic anthropometric measurements were conducted on the 0th, 7th, 14th, and 21st days, and DID estimator showed the significant and positive average marginal effects of the intervention on Z-Scores being 0.459, 0.252, and 0.493 for wasting, stunting, and underweight, respectively. Notably, at the end of the study, the mean aflatoxin M1 level in urine samples decreased by 64% in the intervention group, while it decreased by 11% in the control group. The study provides quantitative evidence on intensive 21-day training for mothers incorporating integrated technologies
yielded positive impacts on their children’s nutritional
outcomes
Discovery of a Large-Scale Abundance Gradient in the Cluster of Galaxies AWM7 with ASCA
A large-scale gradient in the metal abundance has been detected with ASCA
from an X-ray bright cluster of galaxies AWM7. The metal abundance shows a peak
of 0.5 solar at the center and smoothly declines to <~ 0.2 solar at a radius of
500 kpc. The gas temperature is found to be constant at 3.8 keV. The radial
distribution of iron can be fit with a beta-model with beta ~ 0.8 assuming the
same core radius (115 kpc) as that of the intracluster medium. The metal
distribution in AWM7 suggests that the gas injected from galaxies is not
efficiently mixed in the cluster space and traces the distribution of galaxies.Comment: 14 pages with 3 figures, LaTeX with AASTeX v4.0 style file, accepted
for publication in ApJ
Occurrence of aflatoxins and its management in diverse cropping systems of central Tanzania
The staple crops, maize, sorghum, bambara nut, groundnut, and sunflower common in semi-arid agro-pastoral farming systems of central Tanzania are prone to aflatoxin contamination. Consumption of such crop produce, contaminated with high levels of aflatoxin B1 (AFB1), affects growth and health. In this paper, aflatoxin contamination in freshly harvested and stored crop produce from central Tanzania was examined, including the efficacy of aflatoxin mitigation technologies on grain/kernal quality. A total of 312 farmers were recruited, trained on aflatoxin mitigation technologies, and allowed to deploy the technologies for 2 years. After 2 years, 188 of the 312 farmers were tracked to determine whether they had adopted and complied with the mitigation practices. Aflatoxigenic Aspergillus flavus and aflatoxin B1 contamination in freshly harvested and stored grains/kernels were assessed. A. flavus frequency and aflatoxin production by fungi were assayed by examining culture characteristics and thin-layer chromatography respectively. AFB1 was assayed by enzyme-linked immunosorbent assay. The average aflatoxin contamination in freshly harvested samples was 18.8 μg/kg, which is above the acceptable standard of 10 μg/kg. Contamination increased during storage to an average of 57.2 μg/kg, indicating a high exposure risk. Grains and oilseeds from maize, sorghum, and sunflower produced in aboveground reproductive structures had relatively low aflatoxin contamination compared to those produced in geocarpic structures of groundnut and bambara nut. Farmers who adopted recommended post-harvest management practices had considerably lower aflatoxin contamination in their stored kernels/grains. Furthermore, the effects of these factors were quantified by multivariate statistical analyses. Training and behavioral changes by farmers in their post-harvest practice minimize aflatoxin contamination and improve food safety. Moreover, if non-trained farmers receive mitigation training, aflatoxin concentration is predicted to decrease by 28.9 μg/kg on average
Hard X-ray phase-contrast microscope for observing transparent specimens
A hard X-ray transmission imaging microscope has been in use at the beamline BL24XU of SPring-8. It
makes use of a phase zone plate made of tantalum as its X-ray lens, and is capable of imaging the structure as fine as
125-nm line-and-space pattern. The Zernike's phase-contrast method has been implemented to the microscope with
phase plates made of gold. The photon energy was tuned to 12Â keV just above the L absorption edge of gold (11.9Â keV) in order to increase the image contrast. Polystyrene micro particles as transparent specimens were imaged
clearly in the opposite image contrast with phase plates to shift the phase of the central order spectra in the back
focal plane of the objective by one-quarter and three-quarters of a period, while the absorption contrast image
showed little image contrast. Performance of the newly developed phase zone plate has been tested and it was
confirmed that the structure as fine as 60-nm line-and-space pattern was able to be imaged