An Extended Mean Field Game for Storage in Smart Grids

We consider a stylized model for a power network with distributed local power generation and storage. This system is modeled as network connection a large number of nodes, where each node is characterized by a local electricity consumption, has a local electricity production (e.g. photovoltaic panels), and manages a local storage device. Depending on its instantaneous consumption and production rates as well as its storage management decision, each node may either buy or sell electricity, impacting the electricity spot price. The objective at each node is to minimize energy and storage costs by optimally controlling the storage device. In a non-cooperative game setting, we are led to the analysis of a non-zero sum stochastic game with $N$ players where the interaction takes place through the spot price mechanism. For an infinite number of agents, our model corresponds to an Extended Mean-Field Game (EMFG). In a linear quadratic setting, we obtain and explicit solution to the EMFG, we show that it provides an approximate Nash-equilibrium for $N$-player game, and we compare this solution to the optimal strategy of a central planner.Comment: 27 pages, 5 figures. arXiv admin note: text overlap with arXiv:1607.02130 by other author

The dynamic programming equation for the problem of optimal investment under capital gains taxes

This paper considers an extension of the Merton optimal investment problem to the case where the risky asset is subject to transaction costs and capital gains taxes. We derive the dynamic programming equation in the sense of constrained viscosity solutions. We next introduce a family of functions, which converges to our value function uniformly on compact subsets, and which is characterized as the unique constrained viscosity solution of an approximation of our dynamic programming equation. In particular, this result justifies the numerical results reported in the accompanying paper by the authors

Modeling continuous-time financial markets with capital gains taxes

We formulate a model of continuous-time financial market consisting of a bank account with constant interest rate and one risky asset subject to capital gains taxes. We consider the problem of maximizing expected utility from future consumption in infinite horizon. This is the continuous-time version of the model introduced by Dammon, Spatt and Zhang [11]. The taxation rule is linear so that it allows for tax credits when capital gains losses are experienced. In this context, wash sales are optimal. Our main contribution is to derive lower and upper bounds on the value function in terms of the corresponding value in a tax-free and frictionless model. While the upper bound corresponds to the value function in a tax-free model, the lower bound is a consequence of wash sales. As an important implication of these bounds, we derive an explicit first order expansion of our value function for small interest rate and tax rate coefficients. In order to examine the accuracy of this approximation, we provide a characterization of the value function in terms of the associated dynamic programming equation, and we suggest a numerical approximation scheme based on finite differences and the Howard algorithm. The numerical results show that the first order Taylor expansion is reasonably accurate for reasonable market data

Interactive Effects of Cd and NaCl on Growth and Mineral Nutrition in Hordeum vulgare L. (Var. Raihane)

In this work, we investigated the combined effect of salt and cadmium on plant nutrition and Cd accumulation in the most cultivated barley variety in Tunisia, Raihane. Seedling were hydroponically subjected to four different treatment: the control without salt and Cd, 50mM NaCl alone, 10µM Cd alone and to the combination of Cd (10 µM) and NaCl (50 mM) during 1 month. At the harvest, plant growth, Cd content in shoots and roots and tissue nutrient concentrations in shoots(Ca, Fe, Mn and Zn) were measured. 50 mM NaCl alone does not significantly affected the morphology and the biomass of plants. However, when subjected to 10 µM Cd alone, plants of barley were less developed and produced low biomass as compared to control ones. NaCl addition to the Cd-treated plants further reduces the development and biomass production. With respect to nutrient acquisition results showed that NCl alone reduced Ca2+ and Fe2+ concentration in the shoots but not affected that of Zn and Mn. But Cd, applied alone or combined with NaCl disturbed all measured element concentration in the shoots. However, the addition of salt to the Cd-containing medium reduced significantly Cd accumulation in the roots and the shoots of plants. In conclusion, salt in the water irrigation is able to reduce Cd accumulation in this barley variety but it accentuated in the same time the toxic effect of this heavy metal in barley. View Article DOI: 10.47856/ijaast.2022.v09i10.00

Higher thermal and ethanol tolerance of a yeast strain isolated from oral cavity

Efficient bioethanol producing microorganisms must be endowed with peculiar physiological and technological traits, such as, higher thermal and ethanol tolerance. This encompasses a strain thermotolerance and an ability to grow at elevated sugar and ethanol concentration or ability to sustain dehydration process such as freeze drying. In this study, we characterized a thermotolerant yeast strain isolated from the human oral cavity regarding the above mentioned parameters. Such an uncommon niche was considered as the great potential reservoir, to isolate strains endowed with metabolic aptitudes requested for ethanol production. In the process, we have defined the YTerm-1strain ability to sustain high sugar and ethanol concentration that are two technological constrains in bioethanol production. Finally, we highlighted that the strain YTerm-1 was able to accumulate, at a high level, trehalose and β-glucan, two compounds conferring the cells an increased resistance to freeze drying process and osmotic stress. Our results suggest that the Yterm-1 strain showed a better growth ability and higher ethanol yield as compared to the industrial strain. Other metabolic traits, such as resistance to dehydration stress, tolerance to ethanol, accumulation of intracellular trehalose or membrane β-glucan confer to that isolate all the characteristics requested in industrial production of ethanol

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Quelques contributions au contrôle des risques en finance mathématique

La première partie de cette thèse traite des mesures de risque vectorielles. Dans le Chapitre 1, nous généralisons la notion de mesure de risque vectorielle cohérente en mesure convexe. Nous obtenons un résultat de représentation duale qui étend la caractérisation des mesures de risque cohérentes. Dans le Chapitre 2, nous définissons une mesure de risque vectorielle basée sur les distributions; nous montrons qu'elle coïncide, sous certaines conditions, avec une mesure de risque cohérente. Dans la deuxième partie, nous faisons appel au techniques du contrôle stochastique pour traiter deux problèmes. Chapitre 3, présente une caractérisation et une solution numérique de la fonction valeur relative à un problème d'optimisation de consommation et d'investissement dans un marché financier comportant de taxes sur les gains en capitaux. Chapitre 4 présente une solution explicite de la stratégie de sur-réplication d'un actif contingent en présence de coûts de transaction partiels.PARIS-DAUPHINE-BU (751162101) / SudocSudocFranceF

VECTOR-VALUED COHERENT RISK MEASURE PROCESSES

Introduced by Artzner et al. (1998) the axiomatic characterization of a static coherent risk measure was extended by Jouini et al. (2004) in a multi-dimensional setting to the concept of vector-valued risk measures. In this paper, we propose a dynamic version of the vector-valued risk measures in a continuous-time framework. Particular attention is devoted to the choice of a convenient risk space. We provide dual characterization results, we study different notions of time consistency and we give examples of vector-valued risk measure processes