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Study of the effect of thermal dispersion on internal natural convection in porous media using Fourier series
No full textNatural convection in a porous enclosure in the presence of thermal dispersion is investigated. The Fourier-Galerkin (FG) spectral element method is adapted to solve the coupled equations of Darcy's flow and heat transfer with a full velocity-dependent dispersion tensor, employing the stream function formulation. A sound implementation of the FG method is developed to obtain accurate solutions within affordable computational costs. In the spectral space, the stream function is expressed analytically in terms of temperature, and the spectral system is solved using temperature as the primary unknown. The FG method is compared to finite element solutions obtained using an in-house code (TRACES), OpenGeoSys and COMSOL Multiphysics (R). These comparisons show the high accuracy of the FG solution which avoids numerical artifacts related to time and spatial discretization. Several examples having different dispersion coefficients and Rayleigh numbers are tested to analyze the solution behavior and to gain physical insight into the thermal dispersion processes. The effect of thermal dispersion coefficients on heat transfer and convective flow in a porous square cavity has not been investigated previously. Here, taking advantage of the developed FG solution, a detailed parameter sensitivity analysis is carried out to address this gap. In the presence of thermal dispersion, the Rayleigh number mainly affects the convective velocity and the heat flux to the domain. At high Rayleigh numbers, the temperature distribution is mainly controlled by the longitudinal dispersion coefficient. Longitudinal dispersion flux is important along the adiabatic walls while transverse dispersion dominates the heat flux toward the isothermal walls. Correlations between the average Nusselt number and dispersion coefficients are derived for three Rayleigh number regimes
Monitoring the presence of trypanosomes' DNA - Including Trypanosoma brucei gambiense DNA - From the midguts of riverine Glossina trapped in the south east outskirts of Kinshasa City (Democratic Republic of Congo)
No full textEven if the number of Human African Trypanosomiasis (HAT) cases from Kinshasa province in DRC is going towards elimination for the last decade, cases still occur in the periphery of the city. The diagnosis of 21 cases in the south periphery of Kinshasa, between 2015 and 2017 gives evidence of the existence of an active focus in this area. Here, we present the results of a punctual entomological survey that was realized in july 2014 in the outskirts of the southeast of Kinshasa. Using pyramidal traps, we caught tsetse flies during 2 days, dissecting the fresh ones for further molecular analysis. The average Apparent Density of flies per Trap and per Day was three with a maximum of 5.6 flies in Nganda PIO. Polymerase chain reaction analysis of the midguts provided evidence of a high prevalence (57.2%) of infected flies. Ninety three percent of the trypanosomes that were identified belonged to the Nanomonas species, but Trypanozoon trypanosomes were also present in 24% of the infected flies, including mixed infections with Nanomonas, including 3 flies carrying Trypanosoma brucei gambiense, the human pathogen of trypanosomiasis. These results show that at the time of the field's study there was an active reservoir of trypanosomes, closed to pigsties, knowing that pig is a potential animal reservoir. It also demonstrates that xenomonitoring using the entomological approach can be an efficient tool for monitoring sleeping sickness. Finally, results are discussed in the frame of WHO's HAT elimination project. Regarding Kinshasa, it points out the need of regular epidemiologic surveys
Acceptability and feasibility of using raltegravir oral granules for the treatment of neonates in a low-resource setting
No full textBackground: Raltegravir granules for oral suspension, now recommended by World Health Organization for use in neonates with HIV infection, may be challenging for caregivers because of the multistep preparation required. Methods: We evaluated the acceptability and feasibility of preparing granules for oral suspension in a low-to-middle-income country setting. Thirty-four caregivers and 10 health-care workers were enrolled from an HIV clinic in Durban, South Africa. Health-care workers were provided with pictorial instruction booklet, demonstration kit and guidance on preparation of granules for oral suspension. The health-care workers then trained caregivers on the preparation of granules for oral suspension. Caregivers were evaluated during the preparation process and instructed to practice at home with a sample kit and return to the clinic for repeat evaluation 5-7 days later. Caregivers and health-care workers were interviewed and participated in a focus group discussion regarding their experiences. Results: The median age of the caregivers was 31 years (interquartile range: 9.7); 70% had received secondary-level education, 37% were employed. The median preparation time was 7.95 minutes (interquartile range: 5.08 minutes) and 7.48 minutes (3.55 minutes) at initial and repeated observation, respectively. Major errors were insufficient mixing time and incorrect suspension volume. The average number of errors between the 2 observation time points was significantly reduced at the repeat session (2.5 vs. 0.87, P = 0.023). Most participants found the preparation difficult at first but gained confidence over time. Conclusion: Despite the complexity involved in the preparation of the granules for oral suspension, with practice, this formulation was found to be acceptable and feasible to majority of participants in this low-resource setting. As a result, this formulation was included in the 2018 World Health Organization recommendations for first line in neonates living with HIV
Forest aboveground biomass stock and resilience in a tropical landscape of Thailand
No full textHalf of Asian tropical forests were disturbed in the last century resulting in the dominance of secondary forests in Southeast Asia. However, the rate at which biomass accumulates during the recovery process in these forests is poorly understood. We studied a forest landscape located in Khao Yai National Park (Thailand) that experienced strong disturbances in the last century due to clearance by swidden farmers. Combining recent field and airborne laser scanning (ALS) data, we first built a high-resolution aboveground biomass (AGB) map of over 60 km(2) of forest landscape. We then used the random forest algorithm and Landsat time series (LTS) data to classify landscape patches as non-forested versus forested on an almost annual basis from 1972 to 2017. The resulting chronosequence was then used in combination with the AGB map to estimate forest carbon recovery rates in secondary forest patches during the first 42 years of succession. The ALS-AGB model predicted AGB with an error of 14 % at 0.5 ha resolution (RMSE = 45 Mg ha(-1)) using the mean top-of-canopy height as a single predictor. The mean AGB over the landscape was 291 Mg ha(-1), showing a high level of carbon storage despite past disturbance history. We found that AGB recovery varies non-linearly in the first 42 years of the succession, with an increasing rate of accumulation through time. We predicted a mean AGB recovery rate of 6.9 Mg ha(-1) yr(-1), with a mean AGB gain of 143 and 273 Mg ha(-1) after 20 and 40 years, respectively. This rate estimate is about 50 % larger than the rate prescribed for young secondary Asian tropical rainforests in the 2019 refinement of the 2006 IPCC guidelines for national greenhouse gas inventories. Our study hence suggests that the new IPCC rates, which were based on limited data from Asian tropical rainforests, strongly underestimate the carbon potential of forest regrowth in tropical Asia. Our recovery estimates are also within the range of those reported for the well-studied Latin American secondary forests under similar climatic conditions. This study illustrates the potential of ALS data not only for scaling up field AGB measurements but also for predicting AGB recovery dynamics when combined with long-term satellite data. It also illustrates that tropical forest landscapes that were disturbed in the past are of utmost importance for the regional carbon budget and thus for implementing international programs such as REDD+
Enhanced hydrogen production by a sequential dark and photo fermentation process : effects of initial feedstock composition, dilution and microbial population
No full textTwo-stage process of dark fermentation (DF) and photo fermentation (PF), using fruit and vegetable waste (FVW) and cheese whey powder (CWP), was used as an approach to enhance the hydrogen (H-2) production. FVW and CWP at C/N ratios of 34, 39, 60, 71 and 82 were tested as substrates for DF. Dilution (1:2, 1:5, 1:10) of the DF effluents was used as a coupling strategy. DF effluents with low-butyrate and high lactate concentrations were obtained as a function of an increased C/N ratio, which results in high H-2 production during the PF. Maximum overall H-2 yields of 793.7 and 695.4 mLH(2)/gChemical Oxygen Demand (COD) were obtained using a 1:10 dilution, at a C/N ratio of 60 and 70, respectively. These H-2 yields were higher than those obtained with the individual processes. The C/N ratio at the DF stage regulate not only H-2 production but also the distribution and concentrations of by-products. These metabolites, in turn, control the H-2 production during the PF. Predominant microbial population for both processes (DF: C/N = 34 Acetobacter lovaniensis, Clostridium butyricum; C/N = 39 C butyricum, Enterobacter sp, Bifidobacterium; C/N = 82 Lactobacillus casei; PF: Rhodopseudomonas palustris) were in accordance with the final metabolic products
A large-scale species level dated angiosperm phylogeny for evolutionary and ecological analyses
No full textPhylogenies are a central and indispensable tool for evolutionary and ecological research. Even though most angiosperm families are well investigated from a phylogenetic point of view, there are far less possibilities to carry out large-scale meta-analyses at order level or higher. Here, we reconstructed a large-scale dated phylogeny including nearly 1/8th of all angiosperm species, based on two plastid barcoding genes, matK (incl. trnK) and rbcL. Novel sequences were generated for several species, while the rest of the data were mined from GenBank. The resulting tree was dated using 56 angiosperm fossils as calibration points. The resulting megaphylogeny is one of the largest dated phylogenetic tree of angiosperms yet, consisting of 36,101 sampled species, representing 8,399 genera, 426 families and all orders. This novel framework will be useful for investigating different broad scale research questions in ecological and evolutionary biology
Rare and unique adaptations to cancer in domesticated species : an untapped resource ?
No full textStrong and ongoing artificial selection in domestic animals has resulted in amazing phenotypic responses that benefit humans, but often at a cost to an animal's health, and problems related to inbreeding depression, including a higher incidence of cancer. Despite high rates of cancer in domesticated species, little attention has been devoted to exploring the hypothesis that persistent artificial selection may also favour the evolution of compensatory anticancer defences. Indeed, there is evidence for effective anti-cancer defences found in several domesticated species associated with different cancer types. We also suggest that artificial selection can favour the "domestication" of inherited oncogenic mutations in rare instances, retaining those associated to late and/or less aggressive cancers, and that by studying these seemingly rare anticancer adaptations, novel cancer treatments may be found
Health insurance in Sub-Saharan Africa : a scoping review of the methods used to evaluate its impact
No full textWe conducted a scoping review with the objective of synthesizing available literature and mapping what designs and methods have been used to evaluate health insurance reforms in sub-Saharan Africa. We systematically searched for scientific and grey literature in English and French published between 1980 and 2017 using a combination of three key concepts: "Insurance" and "Impact evaluation" and "sub-Saharan Africa". The search led to the inclusion of 66 articles with half of the studies pertaining to the evaluation of National Health Insurance schemes, especially the Ghanaian one, and one quarter pertaining to Community-Based Health Insurance and Mutual Health Organization schemes. Sixty-one out of the 66 studies (92%) included were quantitative studies, while only five (8%) were defined as mixed methods. Most studies included applied an observational design (n=37; 56%), followed by a quasi-experimental (n=27; 41%) design; only two studies (3%) applied an experimental design. The findings of our scoping review are in line with the observation emerging from prior reviews focused on content in pointing at the fact that evidence on the impact of health insurance is still relatively weak as it is derived primarily from studies relying on observational designs. Our review did identify an increase in the use of quasi-experimental designs in more recent studies, suggesting that we could observe a broadening and deepening of the evidence base on health insurance in Africa over the next few years
District-level health system strengthening for universal health coverage : evidence from a longitudinal cohort study in rural Madagascar, 2014-2018
No full textIntroduction Despite renewed commitment to universal health coverage and health system strengthening (HSS) to improve access to primary care, there is insufficient evidence to guide their design and implementation. To address this, we conducted an impact evaluation of an ongoing HSS initiative in rural Madagascar, combining data from a longitudinal cohort and primary health centres. Methods We carried out a district representative household survey at the start of the HSS intervention in 2014 in over 1500 households in Ifanadiana district, and conducted follow-up surveys at 2 and 4 years. At each time point, we estimated maternal, newborn and child health coverage; economic and geographical inequalities in coverage; and child mortality rates; both in the HSS intervention and control catchments. We used logistic regression models to evaluate changes associated with exposure to the HSS intervention. We also estimated changes in health centre per capita utilisation during 2013 to 2018. Results Child mortality rates decreased faster in the HSS than in the control catchment. We observed significant improvements in care seeking for children under 5 years of age (OR 1.23; 95% CI 1.05 to 1.44) and individuals of all ages (OR 1.37, 95% CI 1.19 to 1.58), but no significant differences in maternal care coverage. Economic inequalities in most coverage indicators were reduced, while geographical inequalities worsened in nearly half of the indicators. Conclusion The results demonstrate improvements in care seeking and economic inequalities linked to the early stages of a HSS intervention in rural Madagascar. Additional improvements in this context of persistent geographical inequalities will require a stronger focus on community health
Post-2020 biodiversity targets need to embrace climate change
No full textRecent assessment reports by the Intergovernmental Panel on Climate Change (IPCC) and the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) have highlighted the risks to humanity arising from the unsustainable use of natural resources. Thus far, land, freshwater, and ocean exploitation have been the chief causes of biodiversity loss. Climate change is projected to be a rapidly increasing additional driver for biodiversity loss. Since climate change and biodiversity loss impact human societies everywhere, bold solutions are required that integrate environmental and societal objectives. As yet, most existing international biodiversity targets have overlooked climate change impacts. At the same time, climate change mitigation measures themselves may harm biodiversity directly. The Convention on Biological Diversity's post-2020 framework offers the important opportunity to address the interactions between climate change and biodiversity and revise biodiversity targets accordingly by better aligning these with the United Nations Framework Convention on Climate Change Paris Agreement and the Sustainable Development Goals. We identify the considerable number of existing and proposed post 2020 biodiversity targets that risk being severely compromised due to climate change, even if other barriers to their achievement were removed. Our analysis suggests that the next set of biodiversity targets explicitly addresses climate change-related risks since many aspirational goals will not be feasible under even lower-end projections of future warming. Adopting more flexible and dynamic approaches to conservation, rather than static goals, would allow us to respond flexibly to changes in habitats, genetic resources, species composition, and ecosystem functioning and leverage biodiversity's capacity to contribute to climate change mitigation and adaptation