Real Space Observations of Magnesium Hydride Formation and Decomposition

The mechanisms of magnesium hydride formation and thermal decomposition are directly examined using in-situ imaging.Comment: 3 pages, 4 figure

Maladies et plantes vasculaires du Karité (Vitellaria paradoxa Gaertn) au Bénin

La présente étude vise à évaluer les maladies et les plantes vasculaires du karité (Vitellaria paradoxa C. F. Gaertn) dans les savanes Soudanienne (SS) et Nord guinéenne (SNG) du Bénin. Pour ce faire, quarante sites au total ont été prospectés au cours du mois de juillet 2018. Sur chaque site, l’incidence et la sévérité des symptômes de maladies, la densité et la distribution des plantes vasculaires ont été étudiées. Des échantillons de feuilles malades, des plantes vasculaires du karité ont été prélevés pour lʼidentification au laboratoire. Lasiodiplodia theobromae, Colletotrichum gloeosporioides, Pestalotiopsis sp, Xanthomonas sp ont été les agents pathogènes identifiés. Les valeurs d’incidence étaient élevées dans la SS (59,6% L. theobromae, et de 42,2% Xanthomonas sp) et dans la SNG (67,5% Pestalotiopsis sp et de 55% L. theobromae). Les valeurs de sévérité étaient élevées dans la SS (39% L. theobromae et de 30,6% Xanthomonas sp) et dans la SNG (54,7% Pestalotiopsis sp et 43% L. theobromae). Les données collectées sur la densité des plantes vasculaires ont montré une Orchidiaceae holo-épiphyte (Calyptrochilum christyanum), une Moraceae hémi-épiphyte (Ficus thonningii), une Renonculaceae (Alafia barteri) et deux Loranthaceae (Tapinanthus dodoneifolius, Tapinanthus globiferus). T. dodoneifolius et T. globiferus sont plus répandus avec des taux d’infestation moyens respectifs de 68,67% et de 66,58% et des densités moyennes par plant respectives de 5,64 touffes et de 2,52 touffes. Ainsi, les efforts d’amélioration de la production de karité doivent prendre en compte les stratégies de lutte contre ces agents pathogènes et plantes vasculaires.   The present study aims to assess diseases and vascular plants of the shea-butter tree (Vitellaria paradoxa C. F. Gaertn) in Sudan Savanna (SS) and Northern Guinea Savanna (NGS) of Benin. Thus, forty (40) sites in total were surveyed in July 2018. On each site, incidence and severity of the disease symptoms, and density and distribution of vascular plants of the shea-butter tree were studied. Samples of diseased leaves and vascular plants of the sheabutter tree were collected for laboratory identification. The pathogens Lasiodiplodia theobromae, Colletotrichum gloeosporioides, Pestalotiopsis sp) and Xanthomonas sp were identified. The incidence values were high in SS (59.6% L. theobromae and 42.2% Xanthomonas sp) and in NGS (67.5% Pestalotiopsis sp and 55% L. theobromae). The severity values were high in SS (39% L. theobromae and 30.6% Xanthomonas sp) and in NGS (54.7% Pestalotiopsis sp and 43% L. theobromae). Data collected on the density of vascular plants of the shea-butter tree showed one holo-epiphytic Orchidiaceae (Calyptrochilum christyanum), one Moraceae (Ficus thonningii), one Renonculaceae (Alafia barteri) and two Loranthaceae (Tapinanthus dodoneifolius, Tapinanthus globiferus). T. dodoneifolius and T. globiferus were more widespread with respectively infestation rate of 68.67% and 66.58%, and respectively average densities per shea plant of 5.64 tufts and 2.52 tufts. Thus, efforts to improve shea-butter production must take into account strategies for disease pathogens and vacular plants control in the sheabutter parklands in Benin

Electron spin-lattice relaxation of Yb3+ and Gd3+ ions in glasses

The electron spin-lattice relaxation rate (T1 -1) was measured in two glass samples: (i) a phosphate glass doped with 1 wt% Yb2O3 and (ii) a Li2Si4O9 glass sample doped with 0.2 wt% Gd2O3. In the Yb3+-doped glass sample, T1, was measured by an electron-spin-echo technique from 4.2 to 6 K, by the modulation method from 10 to 26 K and by the EPR linewidth from 30 to 100 K. It was found that (T1 -1) ∝ Tn with n = 9 in the range 4.2-6 K. n decreased gradually as the temperature was increased and tended towards 2 above 40 K. Over the entire temperature range 4.2-100 K, (T1 -1) was fitted to AT + BT9J8 (ΘD/T) (where A and B are two temperature-independent constants, J8 is the well-known Van Vleck integral and ΘD is the Debye temperature). The value of ΘD (= 46.3±0.9 K) so determined is in good agreement with that of Stevens and Stapleton from their T1, measurements in the range 1.5 to 7 K. In the Gd3+-doped glass, it was observed that (T1 -1) ∝ T over the range 50-150 K. The data for Ye3+-doped glass sample were accounted for by assuming that the phonon modulation of the ligand field is the dominant mechanism, associated with a low Debye temperature in accordance with the published data obtained by using other techniques to study lattice dynamics. On the other hand, the data on the Gd3+-doped glass sample were explained to be predominantly due to a mechanism involving Two-Level-Systems (TLS). © Springer-Verlag 1996 Printed in Austria

Breeding maize (Zea mays) for striga resistance: past, current and prospects in sub-Saharan Africa

Open Access Article; Published online: 01 Mar 2021Striga hermonthica, causes up to 100% yield loss in maize production in Sub‐Saharan Africa. Developing Striga‐resistant maize cultivars could be a major component of integrated Striga management strategies. This paper presents a comprehensive overview of maize breeding activities related to Striga resistance and its management. Scientific surveys have revealed that conventional breeding strategies have been used more than molecular breeding strategies in maize improvement for Striga resistance. Striga resistance genes are still under study in the International Institute for Tropical Agriculture (IITA) maize breeding programme. There is also a need to discover QTL and molecular markers associated with such genes to improve Striga resistance in maize. Marker Assistance Breeding is expected to increase maize breeding efficiency with complex traits such as resistance towards Striga because of the complex nature of the host‐parasite relationship and its intersection with other environmental factors. Conventional alongside molecular tools and technical controls are promising methods to effectively assess Striga in Sub‐Saharan Africa

Haemostatic changes in urogenital schistosomiasis haematobium: A case-control study in Gabonese schoolchildren

In many tropical areas schistosomiasis is a major health problem causing hepatosplenic, intestinal or urogenital complaints. Hepatosplenic schistosomiasis mansoni is also characterized by blood coagulation abnormalities. Liver pathology plays a role in the development of haemostatic changes and the parasitic infection may directly affect coagulation. However, these contributing factors cannot be studied separately in hepatosplenic schistosomiasis infections. This pilot study provides insight in haemostatic changes in urinary schistosomiasis by studying coagulation parameters in schistosomiasis haematobium-infected Gabonese schoolchildren. Selection on urinary schistosomiasis patients without hepatosplenic complaints allows for the investigation of the direct effects of the parasite on haemostasis. Levels of von Willebrand Factor (VWF) antigen, active VWF and osteoprotegerin were elevated, indicating inflammation-mediated endothelial activation. In contrast to hepatosplenic schistosomiasis, thrombin-antithrombin complex and D-dimer levels were not affected. Despite its small sample size, this study clearly indicates that Schistosoma haematobium directly alters the activation status of the endothelium, without initiation of coagulation

Intramuscular Artesunate for Severe Malaria in African Children: A Multicenter Randomized Controlled Trial.

BACKGROUND: Current artesunate (ARS) regimens for severe malaria are complex. Once daily intramuscular (i.m.) injection for 3 d would be simpler and more appropriate for remote health facilities than the current WHO-recommended regimen of five intravenous (i.v.) or i.m. injections over 4 d. We compared both a three-dose i.m. and a three-dose i.v. parenteral ARS regimen with the standard five-dose regimen using a non-inferiority design (with non-inferiority margins of 10%). METHODS AND FINDINGS: This randomized controlled trial included children (0.5-10 y) with severe malaria at seven sites in five African countries to assess whether the efficacy of simplified three-dose regimens is non-inferior to a five-dose regimen. We randomly allocated 1,047 children to receive a total dose of 12 mg/kg ARS as either a control regimen of five i.m. injections of 2.4 mg/kg (at 0, 12, 24, 48, and 72 h) (n = 348) or three injections of 4 mg/kg (at 0, 24, and 48 h) either i.m. (n = 348) or i.v. (n = 351), both of which were the intervention arms. The primary endpoint was the proportion of children with ≥ 99% reduction in parasitemia at 24 h from admission values, measured by microscopists who were blinded to the group allocations. Primary analysis was performed on the per-protocol population, which was 96% of the intention-to-treat population. Secondary analyses included an analysis of host and parasite genotypes as risks for prolongation of parasite clearance kinetics, measured every 6 h, and a Kaplan-Meier analysis to compare parasite clearance kinetics between treatment groups. A post hoc analysis was performed for delayed anemia, defined as hemoglobin ≤ 7 g/dl 7 d or more after admission. The per-protocol population was 1,002 children (five-dose i.m.: n = 331; three-dose i.m.: n = 338; three-dose i.v.: n = 333); 139 participants were lost to follow-up. In the three-dose i.m. arm, 265/338 (78%) children had a ≥ 99% reduction in parasitemia at 24 h compared to 263/331 (79%) receiving the five-dose i.m. regimen, showing non-inferiority of the simplified three-dose regimen to the conventional five-dose regimen (95% CI -7, 5; p = 0.02). In the three-dose i.v. arm, 246/333 (74%) children had ≥ 99% reduction in parasitemia at 24 h; hence, non-inferiority of this regimen to the five-dose control regimen was not shown (95% CI -12, 1; p = 0.24). Delayed parasite clearance was associated with the N86YPfmdr1 genotype. In a post hoc analysis, 192/885 (22%) children developed delayed anemia, an adverse event associated with increased leukocyte counts. There was no observed difference in delayed anemia between treatment arms. A potential limitation of the study is its open-label design, although the primary outcome measures were assessed in a blinded manner. CONCLUSIONS: A simplified three-dose i.m. regimen for severe malaria in African children is non-inferior to the more complex WHO-recommended regimen. Parenteral ARS is associated with a risk of delayed anemia in African children. TRIAL REGISTRATION: Pan African Clinical Trials Registry PACTR201102000277177

Metal hydrides for concentrating solar thermal power energy storage

The development of alternative methods for thermal energy storage is important for improving the efficiency and decreasing the cost for Concentrating Solar-thermal Power (CSP). We focus on the underlying technology that allows metal hydrides to function as Thermal Energy Storage (TES) systems and highlight the current state-of-the-art materials that can operate at temperatures as low as room-temperature and as high as 1100 oC. The potential of metal hydrides for thermal storage is explored while current knowledge gaps about hydride properties, such as hydride thermodynamics, intrinsic kinetics and cyclic stability, are identified. The engineering challenges associated with utilising metal hydrides for high-temperature thermal energy storage are also addressed

Surface and Particle-Size Effects on Hydrogen Desorption from Catalyst-Doped MgH2

With their high capacity, light-metal hydrides like MgH2 remain under scrutiny as reversible H-storage materials, especially to develop control of H-desorption properties by decreasing size (ball-milling) and/or adding catalysts. By employing density functional theory and simulated annealing, we study initial H2 desorption from semi-infinite stepped rutile (110) surface and Mg31H62 nanoclusters, with(out) transition-metal catalyst dopants (Ti or Fe). While Mg31H62structures are disordered (amorphous), the semi-infinite surfaces and nanoclusters have similar single, double, and triple H-to-metal bond configurations that yield similar H-desorption energies. Hence, there is no size effect on desorption energetics with reduction in sample size, but dopants do reduce the H-desorption energy. All desorption energies are endothermic, in contrast to a recent report