Comprehensive physicochemical study of dioctahedral palygorskite-rich clay from Marrakech High Atlas (Morocco)

This study is devoted to the physicochemical and mineralogical characterizations of palygorskite from Marrakech High Atlas, Morocco. The raw clay and its Na?-saturated\ 2 lm fraction were characterized using chemical, structural, and thermal analytical techniques. Measurements of specific surface area and porous volume are reported. The clay fraction was found to be made up of 95 %of palygorskite and 5 % of sepiolite. An original feature of this palygorskite is its deficiency in zeolitic H2O. The half-cell structural formula of its dehydrated form was determined on the basis of 21 oxygens to be (Si7.92Al0.08)(Mg2.15Al1.4Fe0.4Ti0.05h1)(Ca0.03 Na0.08K0.04)O21, while the hydrated form could be formulated as (Si7.97Al0.03)(Mg2.17Al1.46Fe0.40Ti0.05)(Ca0.03Na0.07K0,03) O20.18(OH)1.94(OH2)3.8812.43H2O. These formulas showthat the (Al3??Fe3?)/Mg2? ratio is around 0.84, revealing a pronounced dioctahedral character. Further, inside its octahedral sheet, it was determined that the inner M1 sites are occupied by vacancies, whereas the M2 sites are shared between 90 % of trivalent cations (78 % for Al3? and 22 % for Fe3?), 7.5 % of Mg2+, and 2.5 % of Ti4+, all of them linked to 1.94 of structural hydroxyls. The two remaining Mg2+ by half-cell occupy edge M3 sites and are coordinated to 3.88 molecules of OH2. Channels of this palygorskite are deficient in zeolitic H2O since they contain only 2.43 H2O molecules.A correlation was found between these results and the observation of very intense and well-resolved FTIR bands arising from dioctahedral domains (mainly Al2OH, Fe2OH, and AlFeOH) along with very small responses from a trioctahedral domain (Mg3OH). Accordingly, a schematic representation of the composition of the octahedral sheet was proposed. The cation exchange capacity, specific surface area, and total pore volume were also assessed to be ca. 21.2 meq/100 g, 116 m2/g, and 0.458 cm3/g, respectively

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

Performance Study of Steganalysis Techniques

International audienceThe performance of some state-of-the-art steganalysers is investigated according to various parameters, encompassing the choice of the steganographier, its payload, and the type of images both during training and testing stage. All these parameters are changed to determine their effects on steganalysis performance. Experiments are performed using large sets of grayscale JPEG images of different types. The results indicate that modifying parameters that are usually considered in the literature, and which are very specific, dramatically decrease steganalysis performances

Homology modeling and molecular dynamics simulation of a novel beta-galactosidase antarctic psychrophilic bacterium planococcus antarcticus dsm 14505

ß-galactosidase is an enzyme that catalyzes both hydrolytic cleavage of ß (1–4) linkage of lactose to glucose and galactose and transglycosylation reactions. The present study aims to model and validate the 3D structure of a novel cold-active ß-galactosidase from Planococcus antarcticus 14505. The 3D structure was predicted by itasser software. Model validation was performed using PROCHECK to generate the Ramachandran plot, which indicated that 86.6% of residues is in favorable regions that indicate the model is acceptable. Molecular dynamics simulation of the model protein was performed in water for 10 nanoseconds in which 31 Na+ was added to neutralize the negative charge and achieve energy minimization. The energy value and RMSD fluctuation of carbon alpha backbone of the model were computed and confirmed the stability of the model protein

Next generation sequencing shows diversity of Omicron sub-lineages of SARS-COV2 circulating in Jeddah, Saudi Arabia

The ever-evolving Omicron variant of the SARS-CoV-2 and its sub-lineages have prompted Saudi Arabia to continuously track circulating lineages. We focused on the presence of diverse SARS-CoV-2 circulation in Saudi Arabia and presented the whole genome sequencing study of 94 positive SARS-CoV-2 specimens procured between February and April 2022 in the city of Jeddah, Saudi Arabia. Following whole-genome sequencing, bioinformatics analysis was undertaken. The SARS-CoV-2 variant Omicron clades 21K and 21L constituted the entirety of sequenced specimens, belonging to BA.2 (n = 56) and BA.1.1 (n = 20), respectively, and low-frequency sub-lineages were BA.2.3 (n = 6), BA.1 (n = 4), BA.2.40.1 (n = 2), BA.1.14 (n = 1), BA.2.10 (n = 1), BA2.32 (n = 1), BA.2.57 (n = 1), BA2.64 (n = 1), and BA2.5 (n = 1). Mutational patterns were identified, as well as possible consequences for the spread of the virus. Comparative molecular docking of Omicron-specific Nucleocapsid protein harboring the mutations P13L, R203K, G204R, as well as S413R, and the deletions E31-, R32-, and S33- showed reduced interaction with human RIG-I protein with 8 interacting amino acid residues and 10 polar interactions, while the SARS-CoV-2 Nucleocapsid protein exhibited 15 interacting amino acid residues and 26 polar interactions. Ongoing monitoring is essential for assessing the genomic epidemiological consequences of tourist travel and pilgrimage in Jeddah and across Saudi Arabia, as well as the prompt identification of emerging variants for further investigation

Physico-Chemical Characterization of Medical Solid Waste Leachate: Case of the Hospital de l'Amitié of Nouakchott, Mauritania

At the Hospital de l'Amitié, hospital waste corresponds to a mixture of waste assimilated to household waste and the waste from healthcare activities with infectious risks. In the context of hospital hygiene, the conducted study focuses on the impact of this hospital waste on the people of the Hospital de l'Amitié and the environment, and their handling of hospital waste (collection and transport). From an environmental point of view, the physico-chemical characterization of the leachate leaving submerged waste in three media (drinking water, distilled water and alcoholic distilled water) show high concentrations for most of the parameters studied. Physico-chemical characterization of solid waste from Hospital de l'Amitié in Nouakchott (Mauritania) was carried out from September to December 2020. The objective was to determine the value of 14 parameters (pH, temperature, turbidity, electrical conductivity, COD, BOD5, COD/BOD5, BOD5/COD, SS/BOD5, SS, nitrite, nitrate, sulfate and phosphorus), and improve the treatment method for this solid waste by immersing it in three different mediums (drinking water, distilled water and alcoholic distilled water). Among the 14 parameters, seven exceeded the Moroccan and WHO standards for medium 1, 2 and 3 respectively, conductivity (5340.00 μs/cm, 5820.00 μs/cm and 3550.00 μs/cm), BOD5 (122.00 mg/L, 106.00 mg/L and 142.00 mg/L), BOD5/COD (2.30, 1.93 and 2.88), SS (1000.00 mg/L, 600.00 mg/L and 600.00 mg/L), nitrite (0.91 mg/L, 25.00 mg/L and 45.00 mg/L), nitrate (210.00 mg/L, 200.00 mg/L and 110.00 mg/L) and sulfate (1000.00 mg/L, 2000.00 mg/L and 1000.00 mg/L). These results indicate the existence of toxic substances in these leachates that may impact the environment. In addition, the study proposes solid waste treatment from the Hospital de l'Amitié in Nouakchott (Mauritania) before its discharge into the natural environment. This observation is consolidated by the analyses carried out on the leachate of the waste immersed in three aqueous media (drinking water, distilled water and alcoholic distilled water)