Calibration of quasi-static aberrations in exoplanet direct-imaging instruments with a Zernike phase-mask sensor

Context. Several exoplanet direct imaging instruments will soon be in operation. They use an extreme adaptive optics (XAO) system to correct the atmospheric turbulence and provide a highly-corrected beam to a near-infrared (NIR) coronagraph for starlight suppression. The performance of the coronagraph is however limited by the non-common path aberrations (NCPA) due to the differential wavefront errors existing between the visible XAO sensing path and the NIR science path, leading to residual speckles in the coronagraphic image. Aims. Several approaches have been developed in the past few years to accurately calibrate the NCPA, correct the quasi-static speckles and allow the observation of exoplanets at least 1e6 fainter than their host star. We propose an approach based on the Zernike phase-contrast method for the measurements of the NCPA between the optical path seen by the visible XAO wavefront sensor and that seen by the near-IR coronagraph. Methods. This approach uses a focal plane phase mask of size {\lambda}/D, where {\lambda} and D denote the wavelength and the telescope aperture diameter, respectively, to measure the quasi-static aberrations in the upstream pupil plane by encoding them into intensity variations in the downstream pupil image. We develop a rigorous formalism, leading to highly accurate measurement of the NCPA, in a quasi-linear way during the observation. Results. For a static phase map of standard deviation 44 nm rms at {\lambda} = 1.625 {\mu}m (0.026 {\lambda}), we estimate a possible reduction of the chromatic NCPA by a factor ranging from 3 to 10 in the presence of AO residuals compared with the expected performance of a typical current-generation system. This would allow a reduction of the level of quasi-static speckles in the detected images by a factor 10 to 100 hence, correspondingly improving the capacity to observe exoplanets.Comment: 11 pages, 14 figures, A&A accepted, 2nd version after language-editor correction

Water use efficiency and maximizing profitability of grain sorghum production in the Texas Panhandle

The reduction in the availability of irrigation water and the increase in pumping costs resulting from the decline in the Ogallala Aquifer make good management decisions more critical for the survival of the farm firm and the success of the agricultural sector in the Texas Panhandle. Response functions for irrigation and percentage potential evapotranspiration (PET) in the production of grain sorghum are estimated. The response functions are transferred into value product functions and combined with an irrigation energy cost function to determine the profit maximizing irrigation strategy. Three management decision variables; total water available, the level of irrigation and the water to meet crop ET requirements are evaluated. Grain sorghum yield, natural precipitation, irrigation, soil moisture content, potential evapotranspiration, and percent potential evapotranspiration (PET) data, collected over the period from 1998 through 2007 by commercial producers participating in the AgriPartners program are used to estimate the response functions. Results indicate that the optimum level of irrigation increases as the price of sorghum increases and decreases as the price of natural gas increases.Grain sorghum, ET, maximizing profit, irrigation efficiency, input use optimization, water conservation, Ogallala Aquifer, Texas Panhandle., Farm Management, Production Economics, Productivity Analysis, Resource /Energy Economics and Policy, Q12, Q15, Q25, Q32, and Q34,

Spatial and temporal variation of malaria entomological parameters at the onset of a hydro-agricultural development in central Côte d'Ivoire

A deeper understanding of the ecology and small-scale heterogeneity of malaria transmission is essential for the design of effective prevention, control and elimination interventions. The spatial and temporal distribution of malaria vectors was investigated in five villages in close proximity to a hydro-agricultural system in Côte d'Ivoire over the course of construction and the early phase of irrigated rice farming.; The study was carried out in five villages (Raffierkro, N'Douakro, Ahougui, Kpokahankro, Koffikro) near Bouaké, central Côte d'Ivoire, between early 2007 and late 2009. In each village, mosquitoes were collected by human landing catches and identified morphologically at genus and species level, and entomological parameters were determined. Plasmodium infection was assessed by dissection and an enzyme-linked immunosorbent assay.; A total of 19,404 mosquitoes belonging to the genus Anopheles were sampled during 328 human-night catches. Before the construction of the hydro-agricultural system, comparable densities of Anopheles gambiae were observed in all villages. In subsequent years, densities in Raffierkro and Ahougui were significantly higher than the other villages [Kruskal-Wallis (KW) test = 31.13, p > 0.001]. The density of Anopheles funestus in the five villages was comparable in the early stage of the project, while a high density was reported in Koffikro at the end (KW test = 11.91, p = 0.018). Transmission of Plasmodium falciparum is perennial in the study area. Over the course of the study, high entomological inoculation rates (EIRs) were found: 219-328 infectious bites per person per year with An. gambiae. For An. funestus considerably lower EIRs were observed (5.7-39.4). Changing patterns of An. gambiae were not correlated with malaria transmission.; In this study setting, located in the bioclimatic transition zone of Côte d'Ivoire, rice cultivation was not observed to increase malaria transmission. The entomological parameters recorded until the onset of rice-growing activities in a hydro-agricultural system presented considerable heterogeneity both in space and time; a strong increase of Anopheles mosquitoes was observed in two of the five villages located in close proximity to the dam and irrigated rice fields. Malaria still is a main public health problem in all villages that require adequate control measures

Epidemiology of malaria in the Taabo health and demographic surveillance system, south-central Côte d'Ivoire

A deep understanding of the local epidemiology of malaria is essential for the design and implementation of setting-specific control and elimination efforts. In Côte d'Ivoire, new initiatives are underway to reduce the burden of malaria, which requires high-quality longitudinal data. The epidemiology of malaria was studied in the Taabo health and demographic surveillance system (HDSS) in south-central Côte d'Ivoire and implications for control are discussed.; Two cross-sectional surveys were carried out in the rainy season of June/July in 2010 and 2011. Inhabitants of approximately 7 % of randomly selected households in the Taabo HDSS were invited to participate. People were clinically examined, ear temperature was measured and spleen size determined. Finger-prick blood samples were collected and subjected to a rapid diagnostic test (RDT). Additionally, thick and thin blood films were prepared on microscope slides and diagnosed under a microscope for Plasmodium infection and parasitaemia. Haemoglobin (Hb) level was determined using a HemoCue device.; A total of 1187 and 1264 people in 2010 and 2011, respectively, had complete data records. The prevalence of Plasmodium infection was 46.0 % in 2010 and 56.6 % in 2011, owing to a statistically significant difference (p < 0.05). Males showed a higher Plasmodium infection prevalence than females (49.6 and 62.8 % versus 42.6 and 51.2 %; respectively, in 2010 and 2011; both p < 0.05). The highest malaria prevalence was observed among infants and young children (aged ≤9 years). The risk of Plasmodium infection was significantly higher in villages compared to small hamlets and urban settings (p < 0.05). Fever, Hb level and splenomegaly were associated with parasitaemia.; Malaria is highly endemic in the Taabo HDSS in south-central Côte d'Ivoire with considerable spatial heterogeneity of Plasmodium infection. There is a pressing need to scale-up control interventions against malaria

Sustaining control of Schistosomiasis mansoni in western Côte d'Ivoire : results from a SCORE study, one year after initial praziquantel administration

The Schistosomiasis Consortium for Operational Research and Evaluation (SCORE) has launched several large-scale trials to determine the best strategies for gaining and sustaining control of schistosomiasis and transitioning toward elimination. In Côte d'Ivoire, a 5-year cluster-randomized trial is being implemented in 75 schools to sustain the control of schistosomiasis mansoni. We report Schistosoma mansoni infection levels in children one year after the initial school-based treatment (SBT) with praziquantel and compare with baseline results to determine the effect of the intervention.; The baseline cross-sectional survey was conducted in late 2011/early 2012 and the first follow-up in May 2013. Three consecutive stool samples were collected from 9- to 12-year-old children in 75 schools at baseline and 50 schools at follow-up. Stool samples were subjected to duplicate Kato-Katz thick smears. Directly observed treatment (DOT) coverage of the SBT was assessed and the prevalence and intensity of S. mansoni infection compared between baseline and follow-up.; The S. mansoni prevalence in the 75 schools surveyed at baseline was 22.1% (95% confidence interval (CI): 19.5-24.4%). The DOT coverage was 84.2%. In the 50 schools surveyed at baseline and one year after treatment, the overall prevalence of S. mansoni infection decreased significantly from 19.7% (95% CI: 18.5-20.8%) to 12.8% (95% CI: 11.9-13.8%), while the arithmetic mean S. mansoni eggs per gram of stool (EPG) among infected children slightly increased from 92.2 EPG (95% CI: 79.2-105.3 EPG) to 109.3 EPG (95% CI: 82.7-135.9 EPG). In two of the 50 schools, the prevalence increased significantly, despite a DOT coverage of >75%.; One year after the initial SBT, the S. mansoni prevalence had decreased. Despite this positive trend, an increase was observed in some schools. Moreover, the infection intensity among S. mansoni-infected children was slightly higher at the 1-year follow-up compared to the baseline situation. Our results emphasize the heterogeneity of transmission dynamics and provide a benchmark for the future yearly follow-up surveys of this multi-year SCORE intervention study

Prevalence and Spatial Distribution of Entamoeba histolytica/dispar and Giardia lamblia among Schoolchildren in Agboville Area (Côte d'Ivoire)

According to WHO, intestinal amoebiasis caused by Entamoeba histolytica is the third principal parasitic disease responsible for mortality in the world. This protozoal parasite infects approximately 180 million individuals throughout the world, among whom 40 to 110 thousand die from it each year. Giardiasis, caused by another protozoan parasite, Giardia lamblia, infects approximately 200 million individuals throughout the world, is a frequent cause of diarrhea in children, and can have negative impact on growth and development. Unfortunately, these intestinal protozoa are taken into account in few epidemiologic studies. The investigation we carried out to determine prevalence and spatial distribution of these infections shows the importance of these parasites in the Agboville department in southeast Cote d'Ivoire. Determination of spatial distribution of these parasites will help to focus delivery of chemotherapy in this area. In addition, our description of the relation of sources of drinking water with these parasitic infections will contribute to the development of an integrated treatment program for these parasites in this area of Côte d'Ivoire. This work will help make the population and political powers aware of the importance of these parasites and the need for safe drinking water in all localities of this area

Assessing the presence of Wuchereria bancrofti in vector and human populations from urban communities in Conakry, Guinea

The Global Programme to Eliminate Lymphatic Filariasis was launched in 2000 with the goal of interrupting transmission of lymphatic filariasis (LF) through multiple rounds of mass drug administration (MDA). In Guinea, there is evidence of ongoing LF transmission, but little is known about the most densely populated parts of the country, including the capital Conakry. In order to guide the LF control and elimination efforts, serological and entomological surveys were carried out to determine whether or not LF transmission occurs in Conakry.; The prevalence of circulating filarial antigen (CFA) of Wuchereria bancrofti was assessed by an immuno-chromatography test (ICT) in people recruited from all five districts of Conakry. Mosquitoes were collected over a 1-year period, in 195 households in 15 communities. A proportion of mosquitoes were analysed for W. bancrofti, using dissection, loop-mediated isothermal amplification (LAMP) assay and conventional polymerase chain reaction (PCR).; CFA test revealed no infection in the 611 individuals examined. A total of 14,334 mosquitoes were collected; 14,135 Culex (98.6 %), 161 Anopheles (1.1 %) and a few other species. Out of 1,312 Culex spp. (9.3 %) and 51 An. gambiae (31.7 %) dissected, none was infected with any stage of the W. bancrofti parasite. However, the LAMP assay revealed that 1.8 % of An. gambiae and 0.31 % of Culex spp. were positive, while PCR determined respective prevalences of 0 % and 0.19 %.; This study revealed the presence of W. bancrofti DNA in mosquitoes, despite the apparent absence of infection in the human population. Although MDA interventions are not recommended where the prevalence of ICT is below 1 %, the entomological results are suggestive of the circulation of the parasite in the population of Conakry. Therefore, rigorous surveillance is still warranted so that LF transmission in Conakry would be identified rapidly and adequate responses being implemented

The Six Cities Project: developing a methodology of surveying densely populated areas using social science assisted and diachronic remote sensing based classification of habitation

This paper provides a statistical evaluation of the methodology of the NSF funded Six Cities Project. The project develops a methodology for surveying densely inhabited areas by processing diachronic remote sensing imagery to create habitation strata or urban classes. These classes become part of a sampling strategy which gives every pixel associated with habitation a specified chance of selection and then draws a representative sample of pixels. These pixels become center points for household surveys which can study a variety of issues including health, environment, livelihood strategies, demographics and household labor, expenditures and income. The methodology lends itself to GIS construction and the generation of data that can be easily compared and can be of maximal use to municipalities, governments, scholars and NGOs. It also provides a long term basis for inexpensive surveys that can have a high claim to reliability and representativity. Key words: remote sensing, urbanism, survey methodology, National Science Foundation, health, environment, livelihood strategies, demographic, household labor, expenditures, income, Africa, Middle East, Morocco, Senegal, Mali, Niger, Tanzania, Botswana, Marrakech, Dakar, Bamako, Niamey, Dodoma,  Gaborone