Numerical Simulation of Electric Field and Charge Structure within an Isolated Thunderstorm

The study of electrical structure of thunderstorm is a deterministic factor in characterizing the behavior of lightning. It is impossible to measure the value of electric field at every point within the thunderstorm, even when the in situ measurements are made, they are done along the path of balloon-borne instruments or other methods employed in the measurement. The average data obtained from past measurements were employed in determining the electric field generated by the thunderstorm as observed along the horizontal distance using the cylindrical charge model. The data consisted of a screening charge layer firstly located “between” 1.8-2.0 km and later between 10.0-10.2 km respectively above the ground level (agl) to see the effect of positioning on the resultant computation. The lower positive charge center with radius ranging from 0.5 km to 2.0 km was placed at various heights between 2.0 and 6.0 km. This is to determine the effect of cloud base height on the resulting field profile. The main negative charge is accommodated between 4.0 and 7.5 km and the upper positive charge layer existed between 7.5- 10.0 km agl for a cloud base height of 2.0 km and 6.0- 9.5 km agl for a negative charge layer, 7.5- 11.0 km agl for upper positive charge with a cloud base of 4.0 km high. The resulting potential gradient (PG) profiles were obtained for spatial distribution with screening charge layer playing no active role in the thunderstorm electrification. The effects of wind shear due to increasing wind speed with height were also investigated to have a clear picture of the cloud charge dynamics; hence the vertical PG patterns produced by a moving thunderstorm for various cloud cell life-times were modeled. The results showed that a typical tropical thunderstorm can exhibit charge layer more than the normal tripolar structure, and the pocket of lower positive charge can be more than one or larger than the usual size. Wind shear was found to enhance lightning discharges at the surface of charge discontinuities. Keywords: Potential gradient, Wind shear, Cloud charge, Lower positive charge center, Noninductive charging.

Universal and Non-Universal First-Passage Properties of Planar Multipole Flows

The dynamics of passive Brownian tracer particles in steady two-dimensional potential flows between sources and sinks is investigated. The first-passage probability, $p(t)$, exhibits power-law decay with a velocity-dependent exponent in radial flow and an order-dependent exponent in multipolar flows. For the latter, there also occur diffusive ``echo'' shoulders and exponential decays associated with stagnation points in the flow. For spatially extended dipole sinks, the spatial distribution of the collected tracer is independent of the overall magnitude of the flow field.Comment: 7 pages, LaTe

"Ground-truthing" efficacy of biological control for aflatoxin mitigation in farmers' fields in Nigeria: from field trials to commercial usage, a 10-year study

Open Access JournalIn sub-Saharan Africa (SSA), diverse fungi belonging to Aspergillus section Flavi frequently contaminate staple crops with aflatoxins. Aflatoxins negatively impact health, income, trade, food security, and development sectors. Aspergillus flavus is the most common causal agent of contamination. However, certain A. flavus genotypes do not produce aflatoxins (i.e., are atoxigenic). An aflatoxin biocontrol technology employing atoxigenic genotypes to limit crop contamination was developed in the United States. The technology was adapted and improved for use in maize and groundnut in SSA under the trademark Aflasafe. Nigeria was the first African nation for which an aflatoxin biocontrol product was developed. The current study includes tests to assess biocontrol performance across Nigeria over the past decade. The presented data on efficacy spans years in which a relatively small number of maize and groundnut fields (8–51 per year) were treated through use on circa 36,000 ha in commercially-produced maize in 2018. During the testing phase (2009–2012), fields treated during one year were not treated in the other years while during commercial usage (2013–2019), many fields were treated in multiple years. This is the first report of a large-scale, long-term efficacy study of any biocontrol product developed to date for a field crop. Most (>95%) of 213,406 tons of maize grains harvested from treated fields contained 90%) contained 80% less aflatoxin content than untreated crops. The frequency of the biocontrol active ingredient atoxigenic genotypes in grains from treated fields was significantly higher than in grains from control fields. A higher proportion of grains from treated fields met various aflatoxin standards compared to grains from untreated fields. Results indicate that efficacy of the biocontrol product in limiting aflatoxin contamination is stable regardless of environment and cropping system. In summary, the biocontrol technology allows farmers across Nigeria to produce safer crops for consumption and increases potential for access to premium markets that require aflatoxin-compliant crops

Primacy of effective communication and its influence on adherence to artemether-lumefantrine treatment for children under five years of age: a qualitative study.

BACKGROUND\ud \ud Prompt access to artemesinin-combination therapy (ACT) is not adequate unless the drug is taken according to treatment guidelines. Adherence to the treatment schedule is important to preserve efficacy of the drug. Although some community based studies have reported fairly high levels of adherence, data on factors influencing adherence to artemether-lumefantrine (AL) treatment schedule remain inadequate. This study was carried-out to explore the provider's instructions to caretakers, caretakers' understanding of the instructions and how that understanding was likely to influence their practice with regard to adhering to AL treatment schedule.\ud \ud METHODS\ud \ud A qualitative study was conducted in five villages in Kilosa district, Tanzania. In-depth interviews were held with providers that included prescribers and dispensers; and caretakers whose children had just received AL treatment. Information was collected on providers' instructions to caretakers regarding dose timing and how to administer AL; and caretakers' understanding of providers' instructions.\ud \ud RESULTS\ud \ud Mismatch was found on providers' instructions as regards to dose timing. Some providers' (dogmatists) instructions were based on strict hourly schedule (conventional) which was likely to lead to administering some doses in awkward hours and completing treatment several hours before the scheduled time. Other providers (pragmatists) based their instruction on the existing circumstances (contextual) which was likely to lead to delays in administering the initial dose with serious treatment outcomes. Findings suggest that, the national treatment guidelines do not provide explicit information on how to address the various scenarios found in the field. A communication gap was also noted in which some important instructions on how to administer the doses were sometimes not provided or were given with false reasons.\ud \ud CONCLUSIONS\ud \ud There is need for a review of the national malaria treatment guidelines to address local context. In the review, emphasis should be put on on-the-job training to address practical problems faced by providers in the course of their work. Further research is needed to determine the implication of completing AL treatment prior to scheduled time

Aflatoxin contamination of maize, groundnut, and sorghum grown in Burkina Faso, Mali, and Niger and aflatoxin exposure assessment

Open Access Journal; Published online: 12 Oct 2022Aflatoxin contamination of staple crops by Aspergillus flavus and closely related fungi is common across the Sahel region of Africa. Aflatoxins in maize, groundnut, and sorghum collected at harvest or from farmers’ stores within two weeks of harvest from Burkina Faso, Mali, and Niger were quantified. Thereafter, aflatoxin exposure values were assessed using per capita consumption rates of those crops. Mean aflatoxin concentrations in maize were high, 128, 517, and 659 µg/kg in Mali, Burkina Faso, and Niger, respectively. The estimated probable daily intake (PDI) of aflatoxins from maize ranged from 6 to 69, 29 to 432, and 310 to 2100 ng/kg bw/day in Mali, Burkina Faso, and Niger, respectively. Similarly, mean aflatoxin concentrations in sorghum were high, 76 and 259 µg/kg in Mali and Niger, respectively, with an estimated PDI of 2–133 and 706–2221. For groundnut, mean aflatoxin concentrations were 115, 277, and 628 µg/kg in Mali, Burkina Faso, and Niger, respectively. Aflatoxin exposure values were high with an estimated 9, 28, and 126 liver cancer cases/100,000 persons/year in Mali, Burkina Faso, and Niger, respectively. Several samples were extremely unsafe, exceeding manyfold regulatory levels of diverse countries (up to 2000 times more). Urgent attention is needed across the Sahel for integrated aflatoxin management for public health protection, food and nutrition security, and access to trade opportunities

A qualitative study of the feasibility and community perception on the effectiveness of artemether-lumefantrine use in the context of home management of malaria in south-west Nigeria

<p>Abstract</p> <p>Background</p> <p>In Nigeria ACT use at the community level has not been evaluated and the use of antimalarial drugs (commonly chloroquine (CQ)) at home has been shown to be largely incorrect. The treatment regimen of ACT is however more complicated than that of CQ. There is thus a need to determine the feasibility of using ACT at the home level and determine community perception on its use.</p> <p>Methods</p> <p>A before and after qualitative study using key informant interviews (KII) and focus group discussions (FGDs) was conducted in selected villages in Ona-Ara local government area. At baseline, 14 FGDs and 14 KIIs were conducted. Thereafter, community medicine distributors (CMDs) were trained in each village to dispense artemeter-lumenfantrine (AL) to febrile children aged 6–59 months presumed to have uncomplicated malaria. After one year of drug distribution, nine KIIs and 10 FGDs were conducted. Participants and key informants were mothers and fathers with children under five years, traditional heads of communities, opinion leaders and health workers.</p> <p>Results</p> <p>None of the participants have heard of AL prior to study. Participants were favourably disposed to introduction of AL into the community. Mothers/caregivers were said to have used AL in place of the orthodox drugs and herbs reported commonly used prior to study after commencement of AL distribution. The use of CMDs for drug distribution was acceptable to the participants and they were judged to be efficient as they were readily available, distributed correct dose of AL and mobilised the community effectively. AL was perceived to be very effective and no significant adverse event was reported. Major concerns to the sustainability of the program were the negative attitudes of health workers towards discharge of their duties, support to the CMDs and the need to provide CMDs incentives. In addition regular supply of drugs and adequate supervision of CMDs were advised.</p> <p>Conclusion</p> <p>Our findings showed that the use of AL at home and community level is feasible with adequate training of community medicine distributors and caregivers. Community members perceived AL to be effective thus fostering acceptability. The negative attitudes of the health workers and issue of incentives to CMDs need to be addressed for successful scaling-up of ACT use at community level.</p

Performance of broilers fed with maize colonized by either toxigenic or atoxigenic strains of Aspergillus flavus with and without an aflatoxin-sequestering agent

Open Access Journal; Published online: 26 Sept 2019In warm agricultural areas across the globe, maize, groundnut, and other crops become frequently contaminated with aflatoxins produced primarily by the fungus Aspergillus flavus. Crop contamination with those highly toxic and carcinogenic compounds impacts both human and animal health, as well as the income of farmers and trade. In Nigeria, poultry productivity is hindered by high prevalence of aflatoxins in feeds. A practical solution to decrease crop aflatoxin content is to use aflatoxin biocontrol products based on non-toxin-producing strains of A. flavus. The biocontrol product Aflasafe® was registered in 2014 for use in maize and groundnut grown in Nigeria. Its use allows the production of aflatoxin-safe maize and groundnut. A portion of the maize treated with Aflasafe in Nigeria is being used to manufacture feeds used by the poultry industry, and productivity is improving. One of the conditions to register Aflasafe with the national regulator was to demonstrate both the safety of Aflasafe-treated maize to avian species and the impact of Aflasafe as a public good. Results presented here demonstrate that the use of maize colonized by an atoxigenic strain of Aflasafe resulted in superior (p < 0.05) broiler performance in all evaluated parameters in comparison to broilers fed with toxigenic maize. Use of an aflatoxin-sequestering agent (ASA) was not sufficient to counteract the harmful effects of aflatoxins. Both the safety and public good value of Aflasafe were demonstrated during our study. In Nigeria, the availability of aflatoxin-safe crops as a result of using Aflasafe allows poultry producers to improve their productivity, their income, and the health of consumers of poultry products

The clinical efficacy of artemether/lumefantrine (Coartem®)

Current World Health Organization (WHO) guidelines for the treatment of uncomplicated falciparum malaria recommend the use of artemisinin-based combination therapy (ACT). Artemether/lumefantrine is an ACT prequalified by the WHO for efficacy, safety and quality, approved by Swissmedic in December 2008 and recently approved by the USA FDA. Coartem® is a fixed-dose combination of artemether and lumefantrine. Its two components have different modes of action that provide synergistic anti-malarial activity. It is indicated for the treatment of infants, children and adults with acute, uncomplicated infection due to Plasmodium falciparum or mixed infections including P. falciparum. A formulation with improved palatability has been developed especially for children (Coartem® Dispersible), which rapidly disperses in a small amount of water for ease of administration