Intrinsic galaxy shapes and alignments II: Modelling the intrinsic alignment contamination of weak lensing surveys

Intrinsic galaxy alignments constitute the major astrophysical systematic of forthcoming weak gravitational lensing surveys but also yield unique insights into galaxy formation and evolution. We build analytic models for the distribution of galaxy shapes based on halo properties extracted from the Millennium Simulation, differentiating between early- and late-type galaxies as well as central galaxies and satellites. The resulting ellipticity correlations are investigated for their physical properties and compared to a suite of current observations. The best-faring model is then used to predict the intrinsic alignment contamination of planned weak lensing surveys. We find that late-type galaxy models generally have weak intrinsic ellipticity correlations, marginally increasing towards smaller galaxy separation and higher redshift. The signal for early-type models at fixed halo mass strongly increases by three orders of magnitude over two decades in galaxy separation, and by one order of magnitude from z=0 to z=2. The intrinsic alignment strength also depends strongly on halo mass, but not on galaxy luminosity at fixed mass, or galaxy number density in the environment. We identify models that are in good agreement with all observational data, except that all models over-predict alignments of faint early-type galaxies. The best model yields an intrinsic alignment contamination of a Euclid-like survey between 0.5-10% at z>0.6 and on angular scales larger than a few arcminutes. Cutting 20% of red foreground galaxies using observer-frame colours can suppress this contamination by up to a factor of two.Comment: 23 pages, 14 figures; minor changes to match version published in MNRA

Abyssal hills: influence of topography on benthic foraminiferal assemblages

Abyssal plains, often thought of as vast flat areas, encompass a variety of terrains including abyssal hills, features that constitute the single largest landscape type on Earth. The potential influence on deep-sea benthic faunas of mesoscale habitat complexity arising from the presence of abyssal hills is still poorly understood. To address this issue we focus on benthic foraminifera (testate protists) in the >150-?m fraction of Megacorer samples (0–1 cm layer) collected at five different sites in the area of the Porcupine Abyssal Plain Sustained Observatory (NE Atlantic, 4850 m water depth). Three sites are located on the tops of small abyssal hills (200–500 m elevation) and two on the adjacent abyssal plain. We examined benthic foraminiferal assemblage characteristics (standing stock, diversity, composition) in relation to seafloor topography (hills vs. plain). Density and rarefied diversity were not significantly different between the hills and the plain. Nevertheless, hills do support a higher species density (i.e. species per unit area), a distinct fauna, and act to increase the regional species pool. Topographically enhanced bottom-water flows that influence food availability and sediment type are suggested as the most likely mechanisms responsible for these differences. Our findings highlight the potential importance of mesoscale heterogeneity introduced by relatively modest topography in regulating abyssal foraminiferal diversity. Given the predominance of abyssal hill terrain in the global ocean, we suggest the need to include faunal data from abyssal hills in assessments of abyssal ecology

Farmers, consumers and gatekeepers and their attitudes towards biotechnology

In 1999, a project to develop insect resistance maize for Africa was launched. Social scientists from this team used participatory rural appraisals, consumer studies, a baseline and gatekeeper survey to study the awareness and attitudes towards biotechnology among farmers, consumers and gatekeepers. Farmers’ awareness of biotechnology was very low (12.7%). Awareness on genetically modified (GM) crops among consumers was also found to be low, although it was higher among urban consumers (38%) than among rural ones (31%). Radio was the main source of information. A large majority of consumers agreed to statements expressing the benefits of biotechnology such as increasing productivity. However, they had environmental and health concerns. Half of the urban consumers expressed concerns about the environment, in particular, loss of biodiversity. In contrast, awareness about GM was found to be high for the gatekeepers (87% for millers, and 79% for supermarkets). A majority of gatekeepers in the food industry were concerned that GM food could cause allergic reactions or antibiotic-resistant diseases. Almost all consumers were willing to purchase GM maize meal at the same price. Of those in the industry, more than two thirds, were hesitant to use them preferring to make the decision on a case-by-case basis.Key words: Biotechnology, genetically modified (GM), consumer, attitudes, gatekeeper

Epidemiology of malaria in irrigated parts of Tana River County, Kenya

Irrigation schemes introduced in areas of high malaria endemicity often amplify malaria burden especially if no mitigation or adaptation measures are implemented (Renshaw et al., 1998). Thias study was conducted in Bura and Hola irrigation schemes in Tana River County to (i) understand the knowledge, attitude and practices of the community in relation to malaria control and transmission, (ii) determine malaria prevalence and the associated risk factors of infection and (iii) develop and validate a transmission model for analyzing the effects of irrigation on malaria burden. A cross sectional survey was conducted in 48 households where 160 people were screened for malaria parasites using Rapid Diagnostic Test. A deterministic model was developed and validated using field data. The community demonstrated good knowledge on causes, symptoms, transmission and control of malaria. The main malaria control measure was use of bed nets where one net was shared by two people. Only 12% of the households practice environmental management to control malaria. Treatment of malaria was mainly based on Artemether-lumefantrine (AL) which is freely available in the government health facilities. The prevalence of malaria was 5% with the clinical records showing a declining trend of malaria cases. Households located ≤5kms to the nearest facility had lower risk of malaria infection (OR=0.104, p-value=0.013) than those located >5kms. Household size was also associated with malaria infection (OR=1.685, p-value=0.022). The model predicted the observed prevalence data. The high usage of bed nets and AL could have led to the observed decrease in malaria prevalence despite the intensification of irrigated agriculture. The model developed could be used to predict the prevalence of malaria in this area enabling decision makers to implement appropriate control measures in good time

Modelling malaria transmission dynamics in irrigated areas of Tana River County, Kenya

Development of irrigation schemes is usually associated with escalation of the malaria problem. Mathematical models can be used to explain the effects of irrigation on malaria transmission dynamics. This study aimed at developing and validating a one-host one-vector deterministic model made up of a mosquito population sub-module and disease transmission sub-module. Model parameters were obtained from the literature. Data covering the year 2013 were collected and these included the amount of irrigation water per unit area of irrigated land, rainfall, temperature and prevalence of malaria from the local hospitals. The Fuzzy distribution function was used to relate rainfall and irrigation patterns with oviposition and mortality rates of acquatic stages of mosquitoes. The model was fitted to malaria prevalence data obtained from the local hospitals by varying the parameters of the Fuzzy distribution function. Parameter values that gave the least variance between predicted and observed prevalence were used. The model was implemented in MS Excel using difference equations.The model fitted the data well and predicts an upsurge in the number of malaria cases 2-3 months after the rains or active irrigation. The model could be used to predict the prevalence of malaria in this area enabling decision makers to implement appropriate control measures in good time. Data from non-irrigated areas and covering a longer period of time should be collected for more rigorous model validation and simulation of the effectiveness of various the interventions

The hemisessile lifestyle and feeding strategies of Iosactis vagabunda (Actiniaria, Iosactiidae), a dominant megafaunal species of the Porcupine Abyssal Plain

Iosactis vagabunda Riemann-Zürneck, 1997 (Actiniaria, Iosactiidae) is a small endomyarian anemone, recently quantified as the greatest contributor to megafaunal density (48%; 2372 individuals ha−1) on the Porcupine Abyssal Plain (PAP). We used time-lapse photography to observe 18 individuals over a period of approximately 20 months at 8-h intervals, and one individual over 2 weeks at 20-mine intervals, and report observations on its burrowing activity, and both deposit and predatory feeding behaviours. We recorded the apparent subsurface movement of an individual from an abandoned burrow to a new location, and burrow creation there. Raptorial deposit feeding on settled phytodetritus particles was observed, as was predation on a polychaete 6-times the estimated biomass of the anemone. Though essentially unnoticed in prior studies of the PAP, I. vagabunda may be a key component of the benthic community, and may make a critical contribution to the carbon cycling at the PAP long-term time-series study site

Subtle variation in abyssal terrain induces significant change in benthic megafaunal abundance, diversity, and community structure

Bathymetric gradients in the deep sea are known to affect key benthic community characteristics such as diversity. However, most studies investigate large-scale bathymetric variation, while habitat heterogeneity related to modest bathymetric variation has generally been overlooked because of limitations to sampling technology. We investigate the role of modest bathymetric variation (~10 m water depth intervals) on an abyssal hill, and horizontal variation at the 0.1–10 km scale, in the structuring of abyssal megafaunal assemblages. We assess numerical density, biomass density, diversity, and assemblage composition using seabed photographs captured with an autonomous underwater vehicle and sediment characteristics determined from cores. We detect significant differences in sediment particle size and organic carbon content, in relation to modest topographic elevation, with a greater fraction of fine particles and organic carbon on the abyssal plain than the hill. Total megafaunal numerical and biomass density, diversity, and the numerical densities of feeding groups were significantly different with modest topographic elevation; similarly, megafaunal composition varied significantly between ~10 m depth intervals. In relation to mesoscale horizontal variation, we also record significant differences between megabenthic communities in two abyssal plain areas with no significant differences in measured sedimentary characteristics and only a 2 m difference in water depth. Differences in these communities were detected in terms of dominance, assemblage composition by density and biomass, and numerical densities of feeding groups. These observations strongly indicate that previous general concepts of the abyssal environment greatly underestimate this mesoscale heterogeneity, such that beta- and gamma-diversity in the abyss may be higher than estimated. Importantly, these results also have clear implications for the design and interpretation of environmental survey and monitoring programmes in the abyss

Incidence and severity of respiratory syncytial virus pneumonia in rural Kenyan children identified through hospital surveillance

Background.Although necessary for developing a rationale for vaccination, the burden of severe respiratory syncytial virus (RSV) disease in children in resource‐poor settings remains poorly defined. Methods.We conducted prospective surveillance of severe and very severe pneumonia in children aged <5 years admitted from 2002 through 2007 to Kilifi district hospital in coastal Kenya. Nasal specimens were screened for RSV antigen by immunofluorescence. Incidence rates were estimated for the well‐defined population. Results.Of 25,149 hospital admissions, 7359 patients (29%) had severe or very severe pneumonia, of whom 6026 (82%) were enrolled. RSV prevalence was 15% (20% among infants) and 27% during epidemics (32% among infants). The proportion of case patients aged 3 months was 65%, and the proportion aged 6 months was 43%. Average annual hospitalization rates were 293 hospitalizations per 100,000 children aged <5 years (95% confidence interval, 271–371 hospitalizations per 100,000 children aged <5 years) and 1107 hospitalizations per 100,000 infants (95% confidence interval, 1012–1211 hospitalizations per 100,000 infants). Hospital admission rates were double in the region close to the hospital. Few patients with RSV infection had life‐threatening clinical features or concurrent serious illnesses, and the associated mortality was 2.2%. Conclusions.In this low‐income setting, rates of hospital admission with RSV‐associated pneumonia are substantial; they are comparable to estimates from the United States but considerably underestimate the burden in the full community. An effective vaccine for children aged >2 months (outside the age group of poor responders) could prevent a large portion of RSV disease. Severity data suggest that the justification for RSV vaccination will be based on the prevention of morbidity, not mortality