Simulation numérique du transport spatial et temporel des concentrations de CO₂ et de CH₄ atmosphériques et comparaisons avec les observations

L'effet de la pollution atmosphérique se fait de plus en plus ressentir de nos jours. Plusieurs études font valoir la nécessité de développer des techniques de mesures et de simulations pour la surveillance continue de son évolution dans l'atmosphère. La modélisation numérique est de plus en plus utilisée pour estimer la dispersion des nuages de polluants dans le temps et dans l'espace. Elle présente a priori des avantages certains par rapport aux techniques physiques que sont les essais in situ ou à échelle réduite. La présente étude consiste en une modélisation inverse des concentrations de CO₂ obtenues à l'été 2007 par la mesure en continu sur le site de Lethbridge, Alberta (Fluxnet Canada). Cette première étape dite de "calage de modèle" a permis ainsi d'optimiser les paramètres d'entrée du modèle de chimie-transport. Il a ainsi été possible de s'assurer de la qualité et de la reproductibilité des simulations par rapport aux observations. L'écart relatif maximal (de l'ordre de 12,3 %) entre simulations et observations sur le site (mai-août 2007) démontrent la bonne qualité des données d'entrée du modèle. Nos résultats ont montré également la grande influence des vents sur ce site dans la dispersion atmosphérique des polluants. Les vents de l'ordre de 44 km/h dispersent les polluants (ici le CO₂), tandis que ceux de l'ordre de 7 km/h favorisent l'accumulation des polluants sur le site de mesure. Dans une seconde étape, les concentrations de CO₂ et de CH₄ mesurées sur le champ expérimental de culture de l'Université Laval au cours de l'été 2005, grâce au dispositif conçu au LP AM (Laboratoire de physique atomique et moléculaire, Département de physique de génie physique et d'optique, Université Laval), ont été calculées grâce à nos codes (TRANSCHIM). Une erreur relative maximale de ~7 % pour le CH₄ et de ~2 % pour le CO₂ ont été observées entre les mesures et les simulations. Une fois de plus la grande influence du vent sur la dispersion atmosphérique des polluants a été mise en évidence. Les indicateurs statistiques, choisis pour déterminer la qualité des résultats dans cette deuxième étape, ont été généralement meilleurs malgré certaines données qui semblaient parfois physiquement irréalistes. Néanmoins le but de jeter les jalons d'une recherche combinée de mesures expérimentales et de simulations numériques conduisant à des résultats convergents a été atteint

Pengembangan e-modul berbasis pendekatan kontekstual adaptif untuk meningkatkan literasi sains peserta didik pada materi usaha dan energi

Studi ini merupakan penelitian pengembangan e-modul berbasis pendekatan kontekstual adaptif untuk meningkatkan literasi sains peserta didik pada materi usaha dan energi. Tujuan dari penelitian ini yaitu untuk mengetahui 1) kelayakan e-modul berbasis pendekatan kontekstual adaptif, 2) keterlaksanaan pembelajaran menggunakan e-modul berbasis pendekatan kontekstual adaptif, dan 3) peningkatan literasi sains peserta didik setelah menggunakan e-modul berbasis pendekatan kontekstual adaptif. Pendekatan penelitian ini menggunakan mixed methodes dengan metode penelitian Research and Development (R&D) tipe ADDIE (Analysis, Design, Development, Implementation, and Investiagtion). Penelitian ini menghasilkan 1) pengembangan e-modul berbasis pendekatan kontekstual adaptif layak digunakan sebagai bahan ajar berdasarkan hasil validasi ahli materi dan media dengan koefisien validitas memperoleh nilai sebesar 1; 2) keterlaksanaan pembelajaran menggunakan e-modul berbasis pendekatan kontekstual adaptif selama tiga pertemuan dengan presentase rata-rata sebesar 86,91% untuk guru, dan 86,30% peserta didik; 3) peningkatan literasi sains peserta didik setelah menggunakan e-modul berbasis pendekatan kontekstual adaptif dalam kegiatan pembelajaran dapat meningkatkan literasi sain peserta didik dengan nilai n-gain sebesar 0,84

Health Indicators of Pregnant Women in Tonkolili District, Rural Sierra Leone

Despite having reported one of the highest maternal mortality ratios and neonatal mortality rates in the world, surprisingly little is known about the general health status of pregnant women in rural parts of Sierra Leone. Malaria, anaemia and malnutrition are known contributors to adverse pregnancy outcomes. Although their prevalence is known to be high, the burden of these conditions in the rural pregnant population remains unknown. Our study aimed to gain more insight into the health status of pregnant women. An observational retrospective descriptive study was conducted at the Lion Heart Medical Centre using antenatal care (ANC) registers. The study revealed high prevalence of malaria (35.2%), maternal undernutrition (10.4%) and anaemia (65.9%). The proportion of teenage pregnancies in the ANC population was 16.4%. Both malaria and anaemia were more prevalent in this group, with odds ratios of 2.1 and 1.7, respectively. The findings reveal alarming high rates of anaemia, acute undernutrition and malaria among pregnant women and high numbers of pregnancy among adolescents, with increased health risks. These results will be used to advocate for a malnutrition program, specifically for pregnant women. Our study further emphasises the importance of preventing malaria and anaemia in pregnant women

Comparison of Different Models to Estimate Global Solar Irradiation in the Sudanese Zone of Chad

Sustainable future development relies on solar radiation, which is the main source of renewable energy. Thus, in this article, the monthly average global solar irradiation of four sites in the Sudanian zone region of Chad is estimated using different empirical models. The data used in this study were collected at the General Directorate of Meteorology of Chad. The reliability and accuracy of six models estimating global solar radiation were validated and compared by statistical indicators identifying the most accurate model. The results obtained show that the Allen model has the best performance for the Moundou site (5.760 kWh/m²/d, R2=0.843), the Angstrom Prescott model for the Sarh sites (5.658 kWh/m²/d, R2=0.805) and Pala (5.793 kWh/m²/d, R²=0.889), the Sabbagh model for the Bongor site (5.657 kWh/m²/d, R²=0.888). These models are validated against NASA data. The results show that the Sudanian zone of Chad has good solar potential and is therefore suitable for possible exploitation

Sociocultural factors affecting first-year medical students’ adjustment to a PBL program at an African medical school

Background: Besides regulatory learning skills, learning also requires students to relate to their social context and negotiate it as they transition and adjust to medical training. As such, there is a need to consider and explore the role of social and cultural aspects in student learning, particularly in problem-based learning, where the learning paradigm differs from what most students have previously experienced. In this article, we report on the findings of a study exploring first-year medical students’ experiences during the first semester of an undergraduate problem-based learning medical program at an African medical school. Method: We employed a qualitative case study approach using in-depth interviews with 23 first-year medical students. Participants ranged in age from 18 to 25 years. All students were bi/multilingual (some spoke three to five languages), with English as the learning language. We conducted an inductive thematic analysis to systematically identify and analyze patterns in the data using the Braun and Clarke framework. Results: Before medical school, students worked hard to compete for admission to medical school, were primarily taught using a teacher-centered approach, and preferred working alone. At the beginning of medical school, students found it challenging to understand the problem-based learning process, the role of the case, speaking and working effectively in a group, managing a heavy workload, and taking increased responsibility for their learning. By the end of the first semester, most students were handling the workload better, were more comfortable with their peers and facilitators, and appreciated the value of the problem-based learning approach. Conclusions: Our study highlights the importance of interrogating contextual sociocultural factors that could cause tension when implementing problem-based learning in non-western medical schools. Adjustment to problem-based learning requires a conceptual and pedagogic shift towards learner-centered practice, particularly concerning self direction, the role of the case, and collaborative learning. As such, there is a need to develop and implement research informed learning development programs that enable students to reflect on their sociocultural beliefs and practices, and enhance their regulatory learning competence to optimize meaningful and early engagement with the problem based learning process

Complicated Odontogenic Infections at 2 District Hospitals in Tonkolili District, Sierra Leone:Protocol for a Prospective Observational Cohort Study (DELAY)

BACKGROUND: Deficits in global oral health care are paramount, and complications of odontogenic infections constitute a considerable global health problem, particularly in low-income countries. A high mortality rate has been observed for patients who have been admitted with complicated odontogenic infections to our facilities in Tonkolili District, Sierra Leone, although exact data have not been published yet. Data regarding who in this region is at risk and why are lacking. OBJECTIVE: The Dental Abscess Study (DELAY) aims to prospectively investigate morbidity and mortality from complicated dental abscesses and to analyze patients’ characteristics and microbial findings to examine predisposing factors for poor outcomes. In particular, the incidence and the clinical and microbial characteristics of complicated odontogenic infections, as well as the sociodemographic data and comorbidities of affected patients, will be studied to develop improved management algorithms based on circumstance-specific factors. METHODS: Patients who present with complicated dental infections requiring hospital admission in Masanga Hospital or Lion Heart Medical Centre will be consecutively selected for possible inclusion in the study (starting on September 4, 2021) over a study period of 1 year, and individual routine follow-ups will be conducted at least 3 months after discharge. The results of standardized questionnaires will be obtained, and clinical measurements as well as medical photos will be taken. Standard laboratory tests (eg, full blood count and HIV status tests) will be performed, and pus specimens will be examined. Local treatment guidelines will be adhered to, and data on medical and surgical treatment as well as data on outcomes will be collected. The study results will be reported according to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) criteria. Routine follow-ups will take place at 1 and 3 months postdischarge. RESULTS: The DELAY protocol was endorsed by the Masanga Medical Research Unit’s Scientific Review Committee on June 16, 2021, and ethical approval was granted on July 5, 2021, by the Sierra Leone National Ethics Committee. The funding of the budgeted study costs was approved by Dental Health International Netherlands in August 2021. The projected start date of data collection was September 4, 2021, and the study period will most likely last for 1 year. As such, data collection is expected to be complete in November 2022. CONCLUSIONS: The aim of our prospective observational cohort study is to gain more knowledge about complicated odontogenic infections in Tonkolili District, Sierra Leone, to further improve treatment strategies. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/3367

Perspectives of health workers on the referral of women with obstetric complications: a qualitative study in rural Sierra Leone

Objectives Sierra Leone has one of the highest maternal mortality ratios in the world. Timely and well-coordinated referrals are necessary to reduce delays in providing adequate care for women with obstetric complications. This study describes factors affecting timely and adequate referral of women with obstetric complications in rural areas of Sierra Leone as viewed by health workers in rural health facilities.Design Qualitative research with semi-structured interviews using open-ended questions. Data were analysed by systematic text condensation.Setting Interviews were held in nine peripheral health units in rural Sierra Leone.Participants 19 health workers including nurses, midwives and clinical health officers participated in nine interviews.Results From the interviews, four major themes describing possible factors of delay in referral of women in need of emergency obstetric care emerged: (1) communication between healthcare workers; (2) underlying influences on decision-making; (3) women’s compliance to referral and (4) logistic constraints.Several factors in rural Sierra Leone are perceived to complicate timely and adequate referral of women in need of emergency obstetric care. Notable among these factors are fear among women for being referred and fear among healthcare workers for having maternal deaths or severe obstetric complications occurring at their own facilities. Furthermore, decision-making of healthcare workers whether to refer a woman or not is negatively influenced by a hierarchical culture with high power distance between healthcare workers.Conclusion Factors identified that complicate timely and adequate referral of women in need of emergency obstetric care must be considered in efforts to reduce maternal mortality. Possible interventions that may reduce delay in referral include increased communication by mobile phones between health workers for advice and feedback regarding referrals, involvement of influential stakeholders to increase women’s compliance to referral, and consistent use of standardised management protocols

Optimal Design and Comparative Analysis of a PV/Mini-Hydropower and a PV/Battery Used for Electricity and Water Supply

This work proposed an optimal design of PV-system-based water-pumped energy storage for both electricity and water supply. A case study was considered in a rural community in Cameroon. The parameters of the assessment of the system were reliability, represented in the present work by the system supply deficiency (SSD), and economic accessibility, represented by the levelized cost of energy (LCOE). The obtained results showed that for 0% SSD, the optimal configuration of the system was composed of 438 PV modules of 235 W, an immersed solar motor pump of 35 kW, a hydroelectric turbine of 51.7 kW, an upper reservoir of 2307.1 m3, an inverter of 25.27 kW, and a total dynamic head of 88 m. The corresponding LCOE to this configuration is 0.224 USD/kWh. The economic accessibility of the designed system was evaluated by comparison with a PV-system-based battery energy storage. The optimal design configuration of the studied PV-system-based battery energy storage was a PV generator (120 PV modules of 235 W), solar motor pump (15 kW), upper reservoir (590.4 m3), battery capacity (351.78 kWh), inverter (25.27 kW), and total dynamic head (81 m). The corresponding LCOE to this configuration was 0.1857 USD/kWh. Although the PV-system-based battery storage appeared to be economically more cost-effective than the PV-system-based water-pumped energy storage, the sensitivity analysis revealed that there was the possibility for the PV-system-based water-pumped energy storage to be economically more profitable than the PV-system-based battery energy storage. This economic outperformance occurred when the project lifetime was a multiple of 7.5 years or when the costs of the storage components were reduced from 20% to 60%

A NEW ANALYTICAL MODELING METHOD FOR PHOTOVOLTAIC SOLAR CELLS BASED ON DERIVATIVE POWER FUNCTION

<p>This paper presents a simple method of optimizing the photovoltaic (PV) generator based on the one diode electrical model. The method consists in solving a second degree equation representing the derivative of the power function. The maximum current and voltage are determined, and the maximum power is deduced. Two popular types of photovoltaic panels constructed with different materials have been considered for the test: the multi-crystalline silicon (Shell S75), and the mono-crystalline silicon (Shell SP70). For various environmental conditions, a comparative study is done between the simulated results and the product manufacturer data. The obtained results prove the efficiency of the proposed method.</p

A NOVEL TECHNIQUE FOR IMPROVING THE EFFICIENCY OF A PHOTOVOLTAIC SOLAR CELL BASED ON THE BAND-TRAP IMPACT IONIZATION PHENOMENON

<p>In this paper, we consider a photovoltaic silicon solar cell in which the charge carriers are moved solitary. To evaluate the number of charge carriers in the solar cell, the proposed nonlinear reaction-diffusion equation describing the phenomena of carriers transport in solar cell under the effect of band-trap impact ionization has been solved. The results from this equation are solitary solutions. The maximum efficiency of the proposed model has been evaluated for various photo-generation coefficients. The range of the external applied electric field E_oto be avoided has been carried out. The conditions to reach the peak of the maximum efficiency have been also identified. The interest of the obtained results is firstly economical since it could be useful in avoiding strong and undesirable external applied electric field on solar cells. The second interest is that they permit to identify the approximate maximum efficiency value of solar cell band-trap impact ionization working in dynamical regime.</p