Differential Equations for a Changing World:How to Engage Students in Learning and Applying Differential Equations

In this article, I share my decade-long experience teaching an intensive five-week summer Differential Equation course covering complex topics and tips for creating an interactive and supportive learning environment to optimize student engagement. This article provides my detailed approach to planning and teaching an asynchronous course with rigor and flexibility for each student. An interactive teaching approach and variety of learning activities will augment students’ mathematical fluency and appreciation of the importance of differential equations in modeling a wide variety of real-world situations with special attention to ways differential equations can be relevant to creating public policy

Variations Saisonnières Des Stades Preimaginaux Culicidien Dans Deux Zones Marécageuses De La Ville De Yaoundé (Cameroun) : Relation Avec Quelques Facteurs Abiotiques

Par leur large distribution et leur abondance, Les Culicidae ou moustiques sont impliqués dans la transmission de nombreuses maladies pathogènes humaines et animales. La lutte contre ces insectes nécessite la connaissance de leurs écologies. C’est dans ce contexte qu’une étude sur la variation saisonnière des stades preimaginaux a été conduite dans deux marécages de la ville de Yaoundé plus précisément dans les quartiers Tongolo et Nkolbisson. Ainsi, une étude a été menée de novembre 2022 à décembre 2023 en Grande Saison Sèche et en Petite Saison de pluie. Pour ce faire, la température, le pH, la couleur, la teneur en oxygène dissout, les matières en suspension (MES) et la densité des stades preimaginaux culicidien ont été estimés. L’étude a mis en évidence des affinités entre les differents stades preimaginaux et les conditions physico-chimiques du milieu. Un total de 1570  larves et 750 nymphes de moustique a été récolté avec les genres culex (73%) et Aedes (23%) représentés et quatre espèces observées (Culex pipiens 14,75%,  Culex quiquefasciatus 27,86%, Aedes metallicus 24,60%  et Aedes albopictus 32,79%). L’abondance des stades preimaginaux a été plus élevée en grande Saison Sèche (présence de tous les stades preimaginaux) qu’en Petite Saison de pluie,  cette différence serait liée à certains facteurs biotiques et abiotiques du milieu

Role of Retinoid X Receptors (RXRs) and dietary vitamin A in Alzheimer's disease: Evidence from clinicopathological and preclinical studies.

BACKGROUND Vitamin A (VitA), via its active metabolite retinoic acid (RA), is critical for the maintenance of memory function with advancing age. Although its role in Alzheimer's disease (AD) is not well understood, data suggest that impaired brain VitA signaling is associated with the accumulation of β-amyloid peptides (Aβ), and could thus contribute to the onset of AD. METHODS We evaluated the protective action of a six-month-long dietary VitA-supplementation (20 IU/g), starting at 8 months of age, on the memory and the neuropathology of the 3xTg-AD mouse model of AD (n = 11-14/group; including 4-6 females and 7-8 males). We also measured protein levels of Retinoic Acid Receptor β (RARβ) and Retinoid X Receptor γ (RXRγ) in homogenates from the inferior parietal cortex of 60 participants of the Religious Orders study (ROS) divided in three groups: no cognitive impairment (NCI) (n = 20), mild cognitive impairment (MCI) (n = 20) and AD (n = 20). RESULTS The VitA-enriched diet preserved spatial memory of 3xTg-AD mice in the Y maze. VitA-supplementation affected hippocampal RXR expression in an opposite way according to sex by tending to increase in males and decrease in females their mRNA expression. VitA-enriched diet also reduced the amount of hippocampal Aβ40 and Aβ42, as well as the phosphorylation of tau protein at sites Ser396/Ser404 (PHF-1) in males. VitA-supplementation had no effect on tau phosphorylation in females but worsened their hippocampal Aβ load. However, the expression of Rxr-β in the hippocampus was negatively correlated with the amount of both soluble and insoluble Aβ in both males and females. Western immunoblotting in the human cortical samples of the ROS study did not reveal differences in RARβ levels. However, it evidenced a switch from a 60-kDa-RXRγ to a 55-kDa-RXRγ in AD, correlating with ante mortem cognitive decline and the accumulation of neuritic plaques in the brain cortex. CONCLUSION Our data suggest that (i) an altered expression of RXRs receptors is a contributor to β-amyloid pathology in both humans and 3xTg-AD mice, (ii) a chronic exposure of 3xTg-AD mice to a VitA-enriched diet may be protective in males, but not in females

Influence des sols salins et calcaires sur la croissance, la nutrition minérale et les composantes agronomiques du niébé (Vigna unguiculata (L.) Walp.) dans trois zones agro écologiques du Cameroun

Objectif: le présent travail consiste à évaluer les effets des sols salins et calcaires sur la croissance, la nutrition minérale et les composantes agronomiques de cinq variétés de niébé (Vigna unguiculata (L) Walp) var. Garoua PG, Mouola PG, Garoua GG, Mouola GG et Tsacre) dans trois zones agro-écologiques du Cameroun.Méthodologie et résultats: le dispositif expérimental est un bloc complètement randomisé avec cinq répétitions. Les résultats obtenus révèlent que la biomasse sèche des feuilles des variétés Mouola PG a augmenté significativement dans les sols calcaires de Baré comparativement aux sols témoins de Yagoua. Dans les sols salins de Kribi, elle baisse significativement chez les variétés Mouola PG, Garoua GG et Tsacre. Les rendements en graines augmentent significativement chez les variétés Garoua PG et Mouola GG dans les sols de Kribi d’une part et d’autre part chez la variété Mouola PG dans les sols de Baré. Les fortes concentrations en Na+ des sols de Kribi ont entrainé une baisse remarquable des concentrations en K+, Ca2+, Mg2+ et N dans les feuilles des variétés Mouola PG, Garoua GG et Tsacre. Par contre, dans le sol de Baré riche en Ca2+, les concentrations en Na+, K+, Mg2+ et P ont augmenté nettement chez les différentes variétés.Conclusion et application des résultats: l’examen de l’ensemble des paramètres étudiés révèle que la zone agro-écologique à pluviométrie uni-modale aux sols salins serait propice à la culture des variétés Mouola GG et Garoua PG tandis que la variété Mouola PG pousserait mieux dans la zone agro-écologique des hauts plateaux aux sols calcaires.Mots clés: Niébé, croissance, nutrition minérale, rendement, sol salin, sol calcaireEnglish Title:  Effects of saline and calcareous soils on the growth, mineral nutrition and agronomic components of cowpea (Vigna unguiculata (L) Walp) in three agro-ecological areas of CameroonEnglish AbstractObjective: the present work evaluates the effects of saline and calcareous soils on the growth, mineral nutrition and agronomic components of five varieties of cowpea (Vigna unguiculata (L) Walp) var. Garoua PG, Mouola PG, Garoua GG, Mouola GG and Tsacre) in three agro-ecological areas of Cameroon.Methodology and results: the experimental setup is a completely randomized block with five repetitions. The results obtained show that the dry biomass of the leaves of the Mouola PG varieties increased significantly in the calcareous soils (Baré) compared to the control soils of Yagoua. In saline soils of Kribi, the dry biomass decreases significantly in leaves of Mouola PG, Garoua GG and Tsacre. In Kribi soils, seed yields increased significantly in the Garoua PG and Mouola GG varieties, while in Baré, the Mouola PG variety grew better. The high Na+ concentration of Kribi soils resulted in a remarkable reduction of K+, Ca2+, Mg2+ and N concentrations in the leaves of the varieties Mouola PG, Garoua GG and Tsacre. On the other hand, in the soils of Baré rich in Ca2+, the concentrations in Na+, K+, Mg2+ and P increased markedly in the different varieties.Conclusion and application of results: Examination of all the studied parameters reveals that the agroecological zone with a modal rainfall with saline soil would be favorable for the cultivation of the varieties Mouola GG and Garoua PG while the variety Mouola PG would grow better in the ecological highlands plateau with calcareous soils.Keywords: Cowpea, growth, mineral nutrition, yield, saline soil, calcareous soi

Raphtory: The temporal graph engine for Rust and Python

Raphtory is a platform for building and analysing temporal networks. The library includes methods for creating networks from a variety of data sources; algorithms to explore their structure and evolution; and an extensible GraphQL server for deployment of applications built on top. Raphtory’s core engine is built in Rust, for efficiency, with Python interfaces, for ease of use. Raphtory is developed by network scientists, with a background in Physics, Applied Mathematics, Engineering and Computer Science, for use across academia and industry

Raphtory: The temporal graph engine for Rust and Python

Raphtory is a platform for building and analysing temporal networks. The library includes methods for creating networks from a variety of data sources; algorithms to explore their structure and evolution; and an extensible GraphQL server for deployment of applications built on top. Raphtory's core engine is built in Rust, for efficiency, with Python interfaces, for ease of use. Raphtory is developed by network scientists, with a background in Physics, Applied Mathematics, Engineering and Computer Science, for use across academia and industry

Investissement en santé préventive et biais comportementaux

Healthcare systems that primarily rely on out-of-pocket payment by users — such as the majority of systems in low and middle-income countries— tend to underinvest in preventive health. This thesis explores the effects of this underinvestment through the lens of behavioral biases. Chapter 1 shows that between 2000 and 2016 in Malawi, individuals exposed to foreign aid-funded HIV prevention programs did not screen significantly more than those who were not exposed. However, stigma increased in areas that were exposed to such programs. Chapter 2 analyzes the adoption of preventive treatment with a discrete choice model that incorporates a risk behavior parameter. The theoretical stylized facts are then tested using a simultaneous equations model and a novel longitudinal database collected among female sex workers in Côte d’Ivoire. This study shows that the decision to adhere to preventive treatment depends on the level of risk in sexual behavior and and suggests better comprehending the threat of risk compensation behavior. In the context of rising obesity rates, Chapter 3 analyzes the effect of a tax on sugar-sweetened beverages as an in-utero shock on children’s health in Mexico. This chapter shows that tax policy is not sufficient to change mothers’ nutritional behavior and improve children’s health. Finally, the last chapter was written and published in the midst of the Covid-19 pandemic to predict the spread of the virus in Ghana, Kenya, and Senegal. It proposes a susceptible-infected-recovered model taking into account the time-invariant characteristics of the countries studied and the heterogeneity of the infectious status of individuals. This chapter shows that having a young and mainly rural population limits the spread and severity of the pandemic in the countries studied.Les régions du monde où le reste-à-charge est encore la principale source de financement du système de santé sont particulièrement vulnérables au sous-investissement dans la santé préventive. Cette thèse propose quatre articles empiriques pour analyser les raisons de ce sous-investissement par le prisme des biais comportementaux et, pour contribuer à mieux définir les politiques publiques. Le Chapitre 1 montre qu’entre 2000 et 2016, au Malawi, les individus exposés à des programmes de prévention VIH financés par l’aide internationale ne se sont pas significativement plus dépistés que ceux qui n’étaient pas exposés. Par contre, la stigmatisation a augmenté dans les régions qui ont été exposées auxdits programmes. Le Chapitre 2 analyse l’adoption d’un traitement préventif avec un modèle de choix discrets qui intègre le paramètre du comportement à risque. Les faits stylisés théoriques sont ensuite testés grâce un modèle d’équations simultanées et à une base de données longitudinale inédite collectée auprès de travailleuses du sexe en Côte d’Ivoire. Cette étude montre que la décision d’adhérer au traitement préventif dépend du niveau de risque dans le comportement sexuel et invite à relativiser la menace de comportement de compensation des risques. Dans un contexte de croissance du taux d’obésité, le Chapitre 3 analyse l’effet d’une taxe sur les boissons sucrées comme un choc intra-utero sur la santé des enfants, au Mexique. Ce chapitre montre que la politique fiscale n’est pas suffisante pour infléchir le comportement nutritionnel des mères et améliorer la santé des enfants. Enfin, le dernier chapitre a été écrit au cœur de la pandémie de Covid-19 pour prédire la propagation du virus au Ghana, Kenya et Sénégal. Il propose un modèle susceptibles-infectés-rétablis en prenant en compte les caractéristiques invariantes dans le temps des pays étudiés et l’hétérogénéité du statut infectieux des individus. Ce chapitre montre que le fait d’avoir une population jeune et une population essentiellement rurale limite la propagation et la sévérité de la pandémie dans les pays étudiés

Threshold cointegration test of the Fisher effect

According to the Fisher hypothesis, the nominal interest rate moves one-to-one with the rate of inflation anticipated by the public, and the expected real rate of return is constant over time. The hypothesis implies that in the long run there is a one-to-one correspondence between changes of the nominal interest rate and the changes of inflation, which is often referred to as the Fisher effect in the literature.;To test the Fisher hypothesis, most of the previous empirical studies are using linear models in time series, which was predicated on the assumption that the path of adjustment towards long-run equilibrium is necessarily symmetric. The assumption of symmetric adjustment, however, may not be warranted. It is frequently argued that some fundamental economic variables, including the real GNP and the unemployment rate, display asymmetric adjustment paths, which cannot be properly modeled by linear models. Since the real interest rate is closely related to these variables, it may also follow an asymmetric adjustment path.;In this dissertation, we study the Fisher relationship within a fresh nonlinear framework. The dissertation is filling several blanks in the empirical literature. First, we test the stationarity of the nominal interest rate and the inflation rate under a nonlinear threshold autoregressive model, and it seems a unit root can not be rejected for most of countries under our study. Second, a two-stage threshold cointegration analysis has been applied to test for the presence of nonlinearity in the long-term equilibrium between the nominal interest rate and the inflation rate. We find some evidences nonlinearity in the Fisher relationship. Third, a two-regime threshold vector error correction model (TVECM) is used to explicitly model the nonlinearity and encompassing tests are carried out to compare the out-of-sample forecast efficiency of linear and nonlinear models. Our study seems to support the existence of the Fisher effect in the long run, which is consistent with previous studies.</p

Fuzzy logic controller in quadcopter

This report presents the findings of implementing fuzzy logic controller in UAV itself. The main focus here is to compare the difference between the conventional PID controller and fuzzy logic controller in terms of stability. UAV possess nonlinear characteristics. PID controller is a type of linear control. Undoubtedly, using a linear controller to control a nonlinear system is bound to have instability issues. However, fuzzy logic controller is a type of nonlinear controller. Logically speaking, using fuzzy controller to control a nonlinear system will yield a better performance. Matlab is used to design the fuzzy controller and was tested with Simulink simulation. The result has shown that fuzzy controller has a better steady state response in accordance to the setpoint over PID controller. Fuzzy controller was also converted to C language and implemented into multiwii source codes. After testing the fuzzy codes on quadcopter, it was found that quadcopter reacts much quicker than the PID controller.Bachelor of Engineerin