Impact of Returns Time Dependency on the Estimation of Extreme Market Risk

The estimation of Value-at-Risk generally used models assuming independence. However, financial returns tend to occur in clusters with time dependency. In this paper we study the impact of negligence of returns dependency in market risk assessment. The main methods which take into account returns dependency to assess market risk are: Declustering, Extremal index and Time series-Extreme Value The- ory combination. Results shows an important reduction of the estimation error under dependency assumption. For real data, methods which take into account returns dependency have generally the best performances.Value-at-Risk, Market risk, Dependency, Declustering, Extremal index, Time Series-EVT Combination.

Facile diazonium modification of pomegranate peel biochar: A stupendous derived relationship between thermal and Raman analyses

There is an ever growing interest worldwide in the development of biochar from a large variety of agrowastes. This work contributes to the domain by tackling an agrowaste represented in pomegranate peels powder. The latter was activated by acid treatment and then pyrolyzed to generate low cost biochar. To enrich the surface of the resulting biochar, it was arylated with various in-situ generated diazonium salts of 4-aminobenzoic acid (H2N-C6H4-COOH), sulfanilic acid (H2N-C6H4-SO3H) and Azure A dye. The effect of diazonium nature and concentration on the arylation process was monitored essentially using thermal gravimetric analysis (TGA), and Raman spectroscopy. These techniques showed gradual changes in the arylation of biochar at low concentrations of 10-5, 10-4 and 10-3 M of 4-aminobenzoic acid. Interestingly, Azure A diazonium salt induces lower extent of surface modification, likely due to steric hindrance. One key feature of this work is the correlation between D/G Raman peak intensity ratio and the mass loading of the aryl groups. To the very best of our knowledge this is the first report ever on diazonium modification of agrowaste-derived biochar and opens new avenues for such carbon allotrope, i.e. surface arylation and applications

COVID-19 in Tunisia (North Africa): Seroprevalence of SARS-CoV-2 in the general population of the capital city Tunis

International audienceBackground: Monitoring the coronavirus disease-19 (COVID-19) pandemic is primarily based on Reverse transcription polymerase chain reaction (RT PCR) detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). As this test is mainly applied on persons with symptomatic disease, it may overlook individuals with pauci- or a-symptomatic infection. Seroprevalence studies are thus essential to get an accurate estimate of the actual SARS-CoV-2 diffusion within the populations. We report on the findings of the first serosurvey conducted in the capital city of Tunisia prior to the implementation of mass vaccination and analyzed factors associated with seropositivity. Methods: A cross sectional survey was conducted among households living in two areas of the governorate of Tunis, the capital city of the country. The survey was realized between March and April 2021, spanning the end of the second wave and the beginning of the third wave of COVID-19 and prior to the implementation of mass vaccination in Tunisia. SARS-CoV-2 specific immunoglobulin G (IgG) antibodies to the spike (S-RBD) or the nucleocapsid (N) proteins were detected using an in-house ELISA test. Results were adjusted for test performance. Multivariate logistic regression analysis was performed to determine factors independently associated with SARS-COV-2 seropositivity. Results: The survey included 1676 individuals from 431 households. The mean age and sex ratio were 43.3±20.9 years and 0.6 respectively. The weighted and test-performance adjusted prevalence of IgG antibodies to the N and the S-RBD proteins were 26.6% [22.9-30.8] and 25.1% [22.2-28.4] respectively. The weighted seroprevalence of anti-N and/or anti-S-RBD IgG antibodies was equal to 38.0% [34.6-41.5]. In multivariate analysis, age under 10, no tobacco use, previous diagnosis of COVID-19, a history of COVID-19 related symptoms and contact with a COVID-19 case within the household, were independently associated with higher SARS-CoV-2 seroprevalence. Conclusions: After the end of the second epidemic wave, more than one third of people living in Tunis got antibodies to SARS-CoV-2. Further studies are needed to monitor changes in these figures as Tunisian population is confronted to the subsequent epidemic waves and to guide the vaccine strategy

COVID-19 in Tunisia (North Africa): Seroprevalence of SARS-CoV-2 in the General Population of the Capital City Tunis

Seroprevalence studies are essential to get an accurate estimate of the actual SARS-CoV-2 diffusion within populations. We report on the findings of the first serosurvey conducted in Tunis prior to the implementation of mass vaccination and analyzed factors associated with seropositivity. A household cross sectional survey was conducted (March–April 2021) in Tunis, spanning the end of the second wave and the beginning of the third wave of COVID-19. SARS-CoV-2 specific immunoglobulin G (IgG) antibodies to the spike (S-RBD) or the nucleocapsid (N) proteins were detected by in-house ELISA tests. The survey included 1676 individuals from 431 households. The mean age and sex ratio were 43.3 ± 20.9 years and 0.6, respectively. The weighted seroprevalence of anti-N and/or anti-S-RBD IgG antibodies was equal to 38.0% (34.6–41.5). In multivariate analysis, age under 10, no tobacco use, previous diagnosis of COVID-19, a history of COVID-19 related symptoms and contact with a COVID-19 case within the household, were independently associated with higher SARS-CoV-2 seroprevalence. More than one third of people living in Tunis obtained antibodies to SARS-CoV-2. Further studies are needed to monitor changes in these figures as Tunisian population is confronted to the subsequent epidemic waves and to guide the vaccine strategy

The Mediterranean region under climate change

This book has been published by Allenvi (French National Alliance for Environmental Research) to coincide with the 22nd Conference of Parties to the United Nations Framework Convention on Climate Change (COP22) in Marrakesh. It is the outcome of work by academic researchers on both sides of the Mediterranean and provides a remarkable scientific review of the mechanisms of climate change and its impacts on the environment, the economy, health and Mediterranean societies. It will also be valuable in developing responses that draw on “scientific evidence” to address the issues of adaptation, resource conservation, solutions and risk prevention. Reflecting the full complexity of the Mediterranean environment, the book is a major scientific contribution to the climate issue, where various scientific considerations converge to break down the boundaries between disciplines