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"Benson, B. A."
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Dusty starburst galaxies in the early Universe as revealed by gravitational lensing
A spectroscopic redshift survey of extraordinarily bright millimetre-wave-selected sources of carbon monoxide line emission — originating from star-forming molecular gas — shows that at least ten of these sources lie at redshifts greater than four, indicating that the fraction of dusty starburst galaxies at high redshifts is greater than previously thought.
ALMA focused on star-forming galaxies
Luminous, dusty, starburst galaxies were abundant in the early Universe, but it has been difficult to measure the complete redshift distribution of these objects, especially at the highest redshifts. The ALMA interferometer in Chile, now coming on-stream, provides high-resolution imaging at the millimetre/submillimetre wavelengths at which star-forming gases are best observed. Using ALMA, Joaquin Vieira and co-workers targeted carbon monoxide line emissions from gravitationally lensed galaxies discovered in a wide-field survey using the South Pole Telescope. The ten
z
> 4 objects revealed in this work more than double the number of spectroscopically confirmed, ultra-luminous galaxies discovered at extreme redshifts. Two sources at
z
= 5.7 are among the most distant ultra-luminous starburst galaxies known, seen as they were about a billion years after the Big Bang.
In the past decade, our understanding of galaxy evolution has been revolutionized by the discovery that luminous, dusty starburst galaxies were 1,000 times more abundant in the early Universe than at present
1
,
2
. It has, however, been difficult to measure the complete redshift distribution of these objects, especially at the highest redshifts (
z
> 4). Here we report a redshift survey at a wavelength of three millimetres, targeting carbon monoxide line emission from the star-forming molecular gas in the direction of extraordinarily bright millimetre-wave-selected sources. High-resolution imaging demonstrates that these sources are strongly gravitationally lensed by foreground galaxies. We detect spectral lines in 23 out of 26 sources and multiple lines in 12 of those 23 sources, from which we obtain robust, unambiguous redshifts. At least 10 of the sources are found to lie at
z
> 4, indicating that the fraction of dusty starburst galaxies at high redshifts is greater than previously thought. Models of lens geometries in the sample indicate that the background objects are ultra-luminous infrared galaxies, powered by extreme bursts of star formation.
Journal Article
The best American science & nature writing. 2023
\"Twenty science and nature essays that represent the best examples of the form published in 2022.\" -- Provided by publisher.
Book
Malaria vector abundance is associated with house structures in Baringo County, Kenya
Malaria, a major cause of morbidity and mortality, is the most prevalent vector borne disease in Baringo County; a region which has varied house designs in arid and semi-arid areas. This study investigated the association between house structures and indoor-malaria vector abundance in Baringo County. The density of malaria vectors in houses with open eaves was higher than that for houses with closed eaves. Grass thatched roof houses had higher density of malaria vectors than corrugated iron sheet roofs. Similarly, mud walled houses had higher vector density than other wall types. Houses in the riverine zone were significantly associated with malaria vector abundance (p<0.000) possibly due to more varied house structures. In Kamnarok village within riverine zone, a house made of grass thatched roof and mud wall but raised on stilts with domestic animals (sheep/goats) kept at the lower level had lower mosquito density (5.8 per collection) than ordinary houses made of same materials but at ground level (30.5 mosquitoes per collection), suggestive of a change in behavior of mosquito feeding and resting. House modifications such as screening of eaves, improvement of construction material and building stilted houses can be incorporated in the integrated vector management (IVM) strategy to complement insecticide treated bed nets and indoor residual spray to reduce indoor malaria vector density.
Journal Article
SPT-SLIM: A Line Intensity Mapping Pathfinder for the South Pole Telescope
The South Pole Telescope Summertime Line Intensity Mapper (SPT-SLIM) is a pathfinder experiment that will demonstrate the use of on-chip filter-bank spectrometers for mm-wave line intensity mapping. The SPT-SLIM focal plane consists of 18 dual-polarization filter-bank spectrometers covering 120–180 GHz with resolving power of 300, coupled to aluminum kinetic inductance detectors. A compact cryostat holds the detectors at 100 mK. SPT-SLIM will be deployed to the 10-m South Pole Telescope for observations during the 2023–2024 austral summer without removing the primary receiver. We discuss the overall instrument design, expected detector performance, and sensitivity to the carbon monoxide line signal at
0.5
<
z
<
2
. The technology and observational techniques demonstrated by SPT-SLIM will enable next-generation line intensity mapping experiments that constrain cosmology beyond the redshift reach of galaxy surveys.
Journal Article
Sensitivity of vegetation to climate variability and its implications for malaria risk in Baringo, Kenya
The global increase in vector borne diseases has been linked to climate change. Seasonal vegetation changes are known to influence disease vector population. However, the relationship is more theoretical than quantitatively defined. There is a growing demand for understanding and prediction of climate sensitive vector borne disease risks especially in regions where meteorological data are lacking. This study aimed at analyzing and quantitatively assessing the seasonal and year-to-year association between climatic factors (rainfall and temperature) and vegetation cover, and its implications for malaria risks in Baringo County, Kenya. Remotely sensed temperature, rainfall, and vegetation data for the period 2004-2015 were used. Poisson regression was used to model the association between malaria cases and climatic and environmental factors for the period 2009-2012, this being the period for which all datasets overlapped. A strong positive relationship was observed between the Normalized Difference Vegetation Index (NDVI) and monthly total precipitation. There was a strong negative relationship between NDVI and minimum temperature. The total monthly rainfall (between 94 -181mm), average monthly minimum temperatures (between 16-21°C) and mean monthly NDVI values lower than 0.35 were significantly associated with malaria incidence rates. Results suggests that a combination of climatic and vegetation greenness thresholds need to be met for malaria incidence to be significantly increased in the county. Planning for malaria control can therefore be enhanced by incorporating these factors in malaria risk mapping.
Journal Article
Effect of intermittent preventive treatment of malaria on health and education in schoolchildren: a cluster-randomised, double-blind, placebo-controlled trial
Malaria is a major cause of morbidity and mortality in early childhood, yet its consequences for health and education during the school-age years remain poorly understood. We examined the effect of intermittent preventive treatment (IPT) in reducing anaemia and improving classroom attention and educational achievement in semi-immune schoolchildren in an area of high perennial transmission.
A stratified, cluster-randomised, double-blind, placebo-controlled trial of IPT was done in 30 primary schools in western Kenya. Schools were randomly assigned to treatment (sulfadoxine-pyrimethamine in combination with amodiaquine or dual placebo) by use of a computer-generated list. Children aged 5–18 years received three treatments at 4-month intervals (IPT n=3535, placebo n=3223). The primary endpoint was the prevalence of anaemia, defined as a haemoglobin concentration below 110 g/L. This outcome was assessed through cross-sectional surveys 12 months post-intervention. Analysis was by both intention to treat, excluding children with missing data, and per protocol. This study is registered with
ClinicalTrials.gov, number
NCT00142246.
2604 children in the IPT group and 2302 in the placebo group were included in the intention-to-treat analysis of the primary outcome; the main reason for exclusion was loss to follow-up. Prevalence of anaemia at 12 months averaged 6·3% in the IPT group and 12·6% in the placebo group (adjusted risk ratio 0·52, 95% CI 0·29–0·93; p=0·028). Significant improvements were also seen in two of the class-based tests of sustained attention, with a mean increase in code transmission test score of 6·05 (95% CI 2·83–9·27; p=0·0007) and counting sounds test score of 1·80 (0·19–3·41; p=0·03), compared with controls. No effect was shown for inattentive or hyperactive-compulsive behaviours or on educational achievement. The per-protocol analysis yielded similar results. 23 serious adverse events were reported within 28 days of any treatment (19 in the IPT group and four in the placebo group); the main side-effects were problems of balance, dizziness, feeling faint, nausea, and/or vomiting shortly after treatment.
IPT of malaria improves the health and cognitive ability of semi-immune schoolchildren. Effective malaria interventions could be a valuable addition to school health programmes.
Gates Malaria Partnership, the Norwegian Education Trust Fund and multidonor Education Development Programme Fund of the World Bank, DBL Centre for Health Research and Development, and the Wellcome Trust.
Journal Article
Larval species diversity, seasonal occurrence and larval habitat preference of mosquitoes transmitting Rift Valley fever and malaria in Baringo County, Kenya
Background
Baseline information that is essential for determining the areas to target with larval control includes estimates of vector diversity and larval habitat preferences. Due to a lack of such information in Baringo County, Kenya, this study assessed species diversity and larval habitat preference of potential mosquito vectors of Rift Valley fever (RVF) and malaria.
Methods
Mosquito larvae were sampled from nine types of larval habitats and were identified morphologically. Species diversity was estimated by the Shannon’s diversity index while larval habitat preference by RVF and malaria vectors was determined by ANOVA.
Results
A total of 7724 immature mosquitoes comprising 17 species belonging to four genera, namely
Anopheles
,
Culex
,
Aedes
and
Mansonia
, were identified. Among the 17 species, three
Anopheles
species are responsible for malaria transmission:
An. gambiae
(
s.l.
),
An. funestus
(
s.l.
) and
An. pharoensis
. Rift Valley fever vectors included
Mansonia
spp. and
Culex
spp. The highest Shannon's diversity index was observed during the cold dry season (
H
= 2.487) and in the highland zone (
H
= 2.539) while the lowest diversity was recorded during the long rain season (
H
= 2.354) and in the riverine zone (
H
= 2.085). Ditches had the highest mean number of
Anopheles
larvae (16.6 larvae per sample) followed by swamp (12.4) and seasonal riverbed (10.7). Water pit and water pan had low mean numbers of
Anopheles
larvae (1.4 and 1.8, respectively) but relatively high mean numbers of culicines (16.9 and 13.7, respectively). Concrete tank was the least sampled type of habitat but had highest mean number of culicine larvae (333.7 l) followed distantly by water spring (38.9) and swamp (23.5). Overall, larval habitats were significantly different in terms of larval density (
F
(8,334)
= 2.090,
P
= 0.036).
Conclusions
To our knowledge, the present study reports culicine larval species diversity in Baringo for the first time and the most preferred habitats were concrete tanks, water springs and swamps. Habitats preferred by
Anopheles
were mainly riverbed pools, ditches and swamps. Environmental management targeting the habitats most preferred by potential vectors can be part of integrated vector control in Baringo, especially during dry seasons.
Journal Article
Effect of climatic variability on malaria trends in Baringo County, Kenya
Background
Malaria transmission in arid and semi-arid regions of Kenya such as Baringo County, is seasonal and often influenced by climatic factors. Unravelling the relationship between climate variables and malaria transmission dynamics is therefore instrumental in developing effective malaria control strategies. The main aim of this study was to describe the effects of variability of rainfall, maximum temperature and vegetation indices on seasonal trends of malaria in selected health facilities within Baringo County, Kenya.
Methods
Climate variables sourced from the International Research Institute (IRI)/Lamont-Doherty Earth Observatory (LDEO) climate database and malaria cases reported in 10 health facilities spread across four ecological zones (riverine, lowland, mid-altitude and highland) between 2004 and 2014 were subjected to a time series analysis. A negative binomial regression model with lagged climate variables was used to model long-term monthly malaria cases. The seasonal Mann–Kendall trend test was then used to detect overall monotonic trends in malaria cases.
Results
Malaria cases increased significantly in the highland and midland zones over the study period. Changes in malaria prevalence corresponded to variations in rainfall and maximum temperature. Rainfall at a time lag of 2 months resulted in an increase in malaria transmission across the four zones while an increase in temperature at time lags of 0 and 1 month resulted in an increase in malaria cases in the riverine and highland zones, respectively.
Conclusion
Given the existence of a time lag between climatic variables more so rainfall and peak malaria transmission, appropriate control measures can be initiated at the onset of short and after long rains seasons.
Journal Article
“We don’t want our clothes to smell smoke”: changing malaria control practices and opportunities for integrated community-based management in Baringo, Kenya
Background
The decline in global malaria cases is attributed to intensified utilization of primary vector control interventions and artemisinin-based combination therapies (ACTs). These strategies are inadequate in many rural areas, thus adopting locally appropriate integrated malaria control strategies is imperative in these heterogeneous settings. This study aimed at investigating trends and local knowledge on malaria and to develop a framework for malaria control for communities in Baringo, Kenya.
Methods
Clinical malaria cases obtained from four health facilities in the riverine and lowland zones were used to analyse malaria trends for the 2005–2014 period. A mixed method approach integrating eight focus group discussions, 12 key informant interviews, 300 survey questionnaires and two stakeholders’ consultative forums were used to assess local knowledge on malaria risk and develop a framework for malaria reduction.
Results
Malaria cases increased significantly during the 2005–2014 period (tau = 0.352;
p
< 0.001) in the riverine zone. March, April, May, June and October showed significant increases compared to other months. Misconceptions about the cause and mode of malaria transmission existed. Gender-segregated outdoor occupation such as social drinking, farm activities, herding, and circumcision events increased the risk of mosquito bites. A positive relationship occurred between education level and opinion on exposure to malaria risk after dusk (χ
2
= 2.70,
p
< 0.05). There was over-reliance on bed nets, yet only 68% (204/300) of respondents owned at least one net. Complementary malaria control measures were under-utilized, with 90% of respondents denying having used either sprays, repellents or burnt cow dung or plant leaves over the last one year before the study was conducted.
Baraza,
radios, and mobile phone messages were identified as effective media for malaria information exchange. Supplementary strategies identified included unblocking canals, clearing
Prosopis
bushes, and use of community volunteers and school clubs to promote social behaviour change.
Conclusions
The knowledge gap on malaria transmission should be addressed to minimize the impacts and enhance uptake of appropriate malaria management mechanisms. Implementing community-based framework can support significant reductions in malaria prevalence by minimizing both indoor and outdoor malaria transmissions.
Journal Article