Chemical structures and theoretical models of lean premixed atmospheric-pressure propene/O2/N2 flames

To better understand the chemistry involved in the lean-fuel combustion, the chemical structure of lean premixed propene-oxygen-nitrogen flames stabilized on a flat-flame burner at atmospheric pressure was determined experimentally. The species mole fraction profiles were also computed by the Premix code and three detailed reaction mechanisms. A very good agreement was observed for the main properties: reactants consumption, final products (CO2, H2O) and the main intermediates: CO and H2. Only a general agreement is also observed between predicted and measured mole fraction profiles for minor intermediates. Marked differences occurred in the prediction of active intermediate species present in small concentrations. Pathways analyses were performed to identify the origins of these discrepancies. It was shown that the same reactions were involved in the three mechanisms to describe the consumption of propene, but with marked differences in their importance. C2H5, C2H4, and C3H5 are the main species formed in the first step and their consumption increases the differences between the mechanisms either by the use of different kinetics data for common reactions or by differences in the nature of the consumption reactions. KEY WORDS: Flame structure, Lean flame, Propene, Combustion mechanisms Bull. Chem. Soc. Ethiop. 2012, 26(2), 211-226.DOI: http://dx.doi.org/10.4314/bcse.v26i2.

Formation of carbonyl compounds in lean premixed atmospheric-pressure Ethylene/O2/N2 flames

Motivated by a better understanding of lean-fuel combustion, the present study has determined experimentally the chemical structure of four lean ethylene-oxygen-nitrogen flames stabilized on the flat-flame burner at atmospheric pressure (φ = 0.47, 0.508, 0.693 and 0.81). Species mole fraction profiles were also computed by the Premix code (Chemkin II version) and three detailed reaction mechanisms .A very good agreement was observed between the main flame properties: reactants consumption, final products (CO2, H2O), main intermediates, and other hydrocarbons in small concentrations, and the modeling. A special care was brought to the examination of the relative importance of carbonyl compounds formation and consumption, mainly (CH2O and CH3CHO). Pathway analyses were performed to identify the formation from the direct consumption of ethylene through the C2H3 and CH2HCO. Sensitivity analyses were also performed in order to delineate the most sensitive reaction on the formation and consumption of these two carbonyl compounds.Keywords: Flame structure, lean flames, ethylene, carbonyl compounds, combustion, mechanisms

Place de la matière azotée dans le mécanisme de la coagulation présure du lait

Les proteines jouent un role tres important dans le processus de gelification du lait. Parmi ces proteines du lait, les caseines constituent la fraction majeure et la plus determinante en matiere de technologielaitiere. Les caseines se presentent sous la forme de micelles formees par lfassociation de differents constituants parmi lesquels on cite : les caseines ƒ¿s1 et ƒ¿s2, la caseine ƒÀ, la caseine ƒÈ et des mineraux,notamment du calcium et du phosphate. La caseine ƒÈ, bien que non majoritaire dans la micelle, 3,3 g l-1, est la proteine laitiere qui detient le role clef dans la coagulation du lait par la presure. Elle comporte deux variantes genetiques, la caseine ƒÈ A qui est la plus frequemment rencontree dans le lait (75-85%) des cas et la caseine ƒÈ B (15-25%) des cas. Les micelles de caseine peuvent etre destabilisees par une acidification ou par lfaction de certaines enzymes proteolytiques comme la presure. Cette destabilisation entraine la coagulation du lait. Cfestainsi qufune addition de presure au lait provoque sa coagulation par hydrolyse de la caseine ƒÈ situee en peripherie de la micelle. Cette hydrolyse scinde le lien 105-106 (lien Phe-Met) et libere le glycomacropeptide qui est la partie hydrophile de la ƒÈ-caseine chargee negativement et responsable des repulsions electrostatiques. La coagulation du lait par la presure est influencee par plusieurs facteurs parmi lesquels on cite la concentration en enzyme, la temperature, le pH et la concentration en ions Ca 2+. Lfobjectif de ce travail est de faire unerevue des connaissances sur les proteines du lait et leurs roles dans le mecanisme de la coagulation laitiere.Mots cles: Lait, proteines, coagulation, caseine, presure

Surface band bending in as-grown and plasma-treated n-type GaN films using surface potential electric force microscopy

The surface band bending, as well as the effect of plasma-induced damage on band bending, on GaN surfaces, was investigated. The upward band bending, measured by surface potentialelectric force microscopy (a variant of atomic force microscopy), for the as-grown n -type GaNwas about 1.0 eV which increased to ∼1.4 eV after reactive ion etching (RIE). UV illuminationdecreased the band bending by 0.3 eV with time constants on the order of seconds and hundreds of seconds for the as-grown and RIE treated GaN, respectively. This implies that there is a higher density of the surface states in the samples subjected to the RIE process. After the RIE treatment, the shape of the photoluminescence spectrum remained unchanged, but the intensity dropped by a factor of 3. This effect can be attributed to nonradiative defects created near the surface by the RIE treatment

Chloroquine and Hydroxychloroquine for the Prevention or Treatment of Novel Coronavirus Disease (COVID-19) in Africa: Caution for Inappropriate Off-Label Use in Healthcare Settings

The novel severe acute respiratory syndrome-coronavirus-2 pandemic has spread to Africa, where nearly all countries have reported laboratory-confirmed cases of novel coronavirus disease (COVID-19). Although there are ongoing clinical trials of repurposed and investigational antiviral and immune-based therapies, there are as yet no scientifically proven, clinically effective pharmacological treatments for COVID-19. Among the repurposed drugs, the commonly used antimalarials chloroquine (CQ) and hydroxychloroquine (HCQ) have become the focus of global scientific, media, and political attention despite a lack of randomized clinical trials supporting their efficacy. Chloroquine has been used worldwide for about 75 years and is listed by the WHO as an essential medicine to treat malaria. Hydroxychloroquine is mainly used as a therapy for autoimmune diseases. However, the efficacy and safety of CQ/HCQ for the treatment of COVID-19 remains to be defined. Indiscriminate promotion and widespread use of CQ/HCQ have led to extensive shortages, self-treatment, and fatal overdoses. Shortages and increased market prices leave all countries vulnerable to substandard and falsified medical products, and safety issues are especially concerning for Africa because of its healthcare system limitations. Much needed in Africa is a cross-continental collaborative network for coordinated production, distribution, and post-marketing surveillance aligned to low-cost distribution of any approved COVID-19 drug; this would ideally be piggybacked on existing global aid efforts. Meanwhile, African countries should strongly consider implementing prescription monitoring schemes to ensure that any off-label CQ/HCQ use is appropriate and beneficial during this pandemic

Survey on white spot virus infection in wild shrimps and crabs in Bushehr province coastal waters

After severe mortality due to white spot disease incidence in cultured shrimps of Helleh grows out farms, disease spread to Delvar,Mond, Boeyrat and Bandar Rig sites in Bushehr province during 2005. Many crustaceans keep this virus in the body, act as a carrier, and can spread of the infection. In order to investigate status of contamination of wild shrimp and crab's population to white spot virus in Bushehr province waters (north of Persian Gulf), samples were collected and tested by Nested PCR for detection of WSV from estuaries and input and output channels water around the Helleh, Shif and Mond sites during 2007 and 2008. Total tested shrimps were 401 peaces, includes green tiger shrimp (Penaeus semisulcatus) 220 pieces, white shrimp (Metapenaeus affinis) 181 pieces, also total tested crabs were 292 pieces includes Ocypode rotundata 68 pieces and Portunus pelagicus 224 pieces. All the samples showed negative results of WSV contamination. However, it can never be sure that the population is free from WSV unless we collect a random sample of 300 pieces from each species and test them individually for WSV. Therefore, we will be confident up to 95% that the wild sources in that area have no prevalence of 1% or upper WSV contamination

BMC Psychiatry

Background Depression is one of the most common psychiatric disorders in people living with HIV (PLHIV). Depression has a negative impact on both mental and physical health and is mainly associated with suboptimal HIV treatment outcomes. To encourage successful aging and the achievement of the 3 × 90 objectives in older PLHIV, the psychological domain must not be neglected. In this context and as data are scarce in West Africa, this study aimed to evaluate the prevalence and the factors associated with severe depressive symptoms in older PLHIV living in this region of the world. Methods Data from PLHIV aged ≥50 years and on ART since ≥6 months were collected in three clinics (two in Côte d’Ivoire, one in Senegal) participating in the West Africa International epidemiological Databases to Evaluate AIDS (IeDEA) collaboration. The severity of depressive symptoms was measured using the Center for Epidemiological Studies Depression scale (CES-D), and associated factors were identified using logistic regressions. Results The median age of the 334 PLHIV included in the study was 56.7 (53.5–61.1), 57.8% were female, and 87.1% had an undetectable viral load. The prevalence of severe depressive symptoms was 17.9% [95% Confidence Interval (95% CI): 13.8–22.0]. PLHIV with severe depressive symptoms were more likely to be unemployed (adjusted Odd Ratio (aOR) = 2.8; 95% CI: 1.4–5.7), and to be current or former tobacco smokers (aOR = 2.6; 95% CI: 1.3–5.4) but were less likely to be overweight or obese (aOR = 0.4; 95% CI: 0.2–0.8). Conclusions The prevalence of severe depressive symptoms is high among older PLHIV living in West Africa. Unemployed PLHIV and tobacco smokers should be seen as vulnerable and in need of additional support. Further studies are needed to describe in more details the reality of the aging experience for PLHIV living in SSA. The integration of screening and management of depression in the standard of care of PLHIV is crucial

PLoS One

Although physical function decline is common with aging, the burden of this impairment remains underestimated in patients living with HIV (PLHIV), particularly in the older people receiving antiretroviral treatment (ART) and living in sub-Saharan Africa (SSA). PLHIV aged ≥50 years old and on ART since ≥6 months were included (N = 333) from three clinics (two in Côte d’Ivoire, one in Senegal) participating in the International epidemiological Databases to Evaluate AIDS (IeDEA) West Africa collaboration. Physical function was measured using the Short Physical Performance Battery (SPPB), the unipodal balance test and self-reported questionnaires. Grip strength was also assessed. Logistic regression was used to identify the factors associated with SPPB performance specifically. Median age was 57 (54–61) years, 57.7% were female and 82.7% had an undetectable viral load. The mean SPPB score was 10.2 ±1.8. Almost 30% had low SPPB performance with the 5-sit-to-stand test being the most altered subtest (64%). PLHIV with low SPPB performance also had significantly low performance on the unipodal balance test (54.2%, p = 0.001) and low mean grip strength (but only in men (p = 0.005)). They also showed some difficulties in daily life activities (climbing stairs, walking one block, both p<0.0001). Age ≥60 years (adjusted OR (aOR) = 3.4; CI95% = 1.9–5.9,), being a female (aOR = 2.1; CI95% = 1.1–4.1), having an abdominal obesity (aOR = 2.1; CI95% = 1.2–4.0), a longer duration of HIV infection (aOR = 2.9; CI95% = 1.5–5.7), old Nucleoside reverse transcriptase inhibitors (NRTIs) (i.e., AZT: zidovudine, ddI: didanosine, DDC: zalcitabine, D4T: stavudine) in current ART (aOR = 2.0 CI95% = 1.1–3.7) were associated with low SPPB performance. As in western countries, physical function limitation is now part of the burden of HIV disease complications of older PLHIV living in West Africa, putting this population at risk for disability. How to screen those impairments and integrate their management in the standards of care should be investigated, and specific research on developing adapted daily physical activity program might be conducted

Cost-utility analysis of four WHO-recommended sofosbuvir-based regimens for the treatment of chronic hepatitis C in sub-Saharan Africa

Background Although direct-acting antivirals (DAA) have become standard care for patients with chronic hepatitis C worldwide, there is no evidence for their value for money in sub-Saharan Africa. We assessed the cost-effectiveness of four sofosbuvir-based regimens recommended by the World Health Organization (WHO) in Cameroon, Côte d’Ivoire and Senegal. Methods Using modelling, we simulated chronic hepatitis C progression with and without treatment in hypothetical cohorts of patients infected with the country’s predominant genotypes (1, 2 and 4) and without other viral coinfections, history of liver complication or hepatocellular carcinoma. Using the status-quo ‘no DAA treatment’ as a comparator, we assessed four regimens: sofosbuvir-ribavirin, sofosbuvir-ledipasvir (both recommended in WHO 2016 guidelines and assessed in the TAC pilot trial conducted in Cameroon, Côte d’Ivoire and Senegal), sofosbuvir-daclatasvir and sofosbuvir-ledipasvir (two pangenotypic regimens recommended in WHO 2018 guidelines). DAA effectiveness, costs and utilities were mainly estimated using data from the TAC pilot trial. Secondary data from the literature was used to estimate disease progression probabilities with and without treatment. We considered two DAA pricing scenarios: S1) originator prices; S2) generic prices. Uncertainty was addressed using probabilistic and deterministic sensitivity analyses and cost-effectiveness acceptability curves. Results With slightly higher effectiveness and significantly lower costs, sofosbuvir/velpatasvir was the preferred DAA regimen in S1 with incremental cost-effectiveness ratios (ICERs) ranging from US$526 to US$632/QALY. At the cost-effectiveness threshold (CET) of 0.5 times the 2017 country’s per-capita gross domestic product (GDP), sofosbuvir/velpatasvir was only cost-effective in Senegal (probability > 95%). In S2 at generic prices, sofosbuvir/daclatasvir was the preferred regimen due to significantly lower costs. ICERs ranged from US$139 to US$216/QALY according to country i.e. a 95% probability of being cost-effective. Furthermore, this regimen was cost-effective (probability> 95%) for all CET higher than US$281/QALY, US$223/QALY and US$195/QALY in Cameroon, Côte d’Ivoire and Senegal, respectively, corresponding to 0.14 (Côte d’Ivoire and Senegal) and 0.2 (Cameroon) times the country’s per-capita GDP. Conclusions Generic sofosbuvir/daclatasvir is very cost-effective for treating chronic hepatitis C in sub-Saharan Africa. Large-scale use of generics and an increase in national and international funding for hepatitis C treatment must be priorities for the HCV elimination agenda

Machine learning in marine ecology: an overview of techniques and applications

Machine learning covers a large set of algorithms that can be trained to identify patterns in data. Thanks to the increase in the amount of data and computing power available, it has become pervasive across scientific disciplines. We first highlight why machine learning is needed in marine ecology. Then we provide a quick primer on machine learning techniques and vocabulary. We built a database of ∼1000 publications that implement such techniques to analyse marine ecology data. For various data types (images, optical spectra, acoustics, omics, geolocations, biogeochemical profiles, and satellite imagery), we present a historical perspective on applications that proved influential, can serve as templates for new work, or represent the diversity of approaches. Then, we illustrate how machine learning can be used to better understand ecological systems, by combining various sources of marine data. Through this coverage of the literature, we demonstrate an increase in the proportion of marine ecology studies that use machine learning, the pervasiveness of images as a data source, the dominance of machine learning for classification-type problems, and a shift towards deep learning for all data types. This overview is meant to guide researchers who wish to apply machine learning methods to their marine datasets.Machine learning in marine ecology: an overview of techniques and applicationspublishedVersio