Contribution à l'étude des phases Lix(Co,M)O2 en tant que matériaux d'électrode positive des batteries Li-ion. Effets combinés de la surstoéchiométrie en lithium et dela substitution (M=Ni,Mg).

Des matériaux d'électrode positive pour batteries Li-ion de formule Lix0(Co,M)O2 (M =Ni,Mg ; x0 > ou = 1.0) ont été préparés à haute température (900ƒC) et caractérisés par diffraction des rayons X, tests galvanostatiques, spectroscopie de RMN MAS du 7Li et mesures électriques. Alors que les propriétés de la phase LiCoO2 sont en accord avec la littérature, dans tous les cas, l'ajout d'un excès de lithium lors de la synthèse conduit dans le matériau final à la présence d'un défaut structural constitué de lacunes d'oxygène et d'ions Co3+ spin intermédiaire (Co3+(IS)) en site pyramidal à base carrée. Ce défaut influe considérablement sur les propriétés des phases désintercalées puisqu'il supprime toutes les transitions de phase habituellement observées lors du cyclage galvanostatique de la phase LiCoO2. La substitution du nickel au cobalt permet de séparer la contribution des ions NiIII et Co3+(IS) quant à la disparition des transitions de phase lors de la désintercalation du lithium. La substitution du magnésium au cobalt, même sans excès de lithium, induit systématiquement la présence de ce type de défaut (Co3+(IS)). Cette particularité a été corrélée au comportement électrochimique de ces matériaux Lix(Co,Mg)O2 en cyclage.Lix0(Co,M)O2 (M =Ni,Mg ; x0 > or = 1.0) materials used as positive electrode for Li-ion batteries have been prepared at high temperature (900ƒC) and characterised by X-ray diffraction, galvanostatic measurements, 7Li MAS NMR spectroscopy and electrical properties measurements. If the results on the LiCoO2 phase agree with the literature, the adding of an excess of lithium during synthesis leads to the presence in the actual materials of oxygen vacancies and intermediate spin Co3+ ions (Co3+(IS)) in a square-based environment. This defect suppresses all the phase transitions usually observed upon lithium deintercalation in LixCoO2. The partial substitution by Ni ions allows us to separate the relative contribution of NiIII and Co3+(IS) ions in the suppression of the various phase transitions upon cycling. Mg doping, even without any lithium excess, systematically induces some oxygen vacancies and Co3+(IS) ions in the material. This observation had been correlated to the behaviour of the Lix(Co,Mg)O2 system upon cycling

Room-temperature single-phase Li insertion/extraction in nanoscale LixFePO4

Classical electrodes for Li-ion technology operate by either single-phase or two-phase Li insertion/de-insertion processes, with single-phase mechanisms presenting some intrinsic advantages with respect to various storage applications. We report the feasibility to drive the well-established two-phase room-temperature insertion process in LiFePO4 electrodes into a single-phase one by modifying the material's particle size and ion ordering. Electrodes made of LiFePO4 nanoparticles (40 nm) formed by a low-temperature precipitation process exhibit sloping voltage charge/discharge curves, characteristic of a single-phase behaviour. The presence of defects and cation vacancies, as deduced by chemical/physical analytical techniques, is crucial in accounting for our results. Whereas the interdependency of particle size, composition and structure complicate the theorists' attempts to model phase stability in nanoscale materials, it provides new opportunities for chemists and electrochemists because numerous electrode materials could exhibit a similar behaviour at the nanoscale once their syntheses have been correctly worked out

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

Contribution à l'étude des phases Lix(Co,M)O2 en tant que matériaux d'électrode positive des batteries Li-ion. Effets combinés de la surstoechiométrie en lithium et de la substitution (M = Ni, Mg)

Lix0(Co,M)O2 (M = Ni, Mg ; x0 ≥ 1.0) materials used as positive electrode for Li-ion batteries have been prepared at high temperature (900° C) and characterised by X-ray diffraction, galvanostatic measurements, 7Li MAS NMR spectroscopy and electrical properties measurements. If the results on the LiCoO2 phase agree with the literature, the adding of an excess of lithium during synthesis leads to the presence in the actual materials to the presence of oxygen vacancies and intermediate spin Co3+ ions (Co3+(IS)) in a square-based environment. This defect suppresses all the phase transitions usually observed upon lithium deintercalation in LixCoO2. The partial substitution by Ni ions allows us to separate the relative contribution of NiIII and Co3+(IS) ions in the suppression of the various phase transitions upon cycling. Mg doping, even without any lithium excess, systematically induces some oxygen vacancies and Co3+(IS) ions in the material. This observation had been correlated to the behaviour of the Lix(Co,Mg)O2 system upon cycling.Des matériaux d'électrode positive pour batteries Li-ion de formule Lix0(Co,M)O2 (M = Ni, Mg ; x0 ≥ 1.0) ont été préparés à haute température (900° C) et caractérisés par diffraction des rayons X, tests galvanostatiques, spectroscopie de RMN MAS du 7Li et mesures électriques. Alors que les propriétés de la phase LiCoO2 sont en accord avec la littérature, dans tous les cas, l'ajout d'un excès de lithium lors de la synthèse conduit dans le matériau final à la présence d'un défaut structural constitué de lacunes d'oxygène et d'ions Co3+ spin intermédiaire (Co3+(IS)) en site pyramidal à base carrée. Ce défaut influe considérablement sur les propriétés des phases désintercalées puisqu'il supprime toutes les transitions de phase habituellement observées lors du cyclage galvanostatique de la phase LiCoO2. La substitution du nickel au cobalt permet de séparer la contribution des ions NiIII et Co3+(IS) quant à la disparition des transitions de phase lors de la désintercalation du lithium. La substitution du magnésium au cobalt, même sans excès de lithium, induit systématiquement la présence de ce type de défaut (Co3+(IS)). Cette particularité a été corrélée au comportement électrochimique de ces matériaux Lix(Co,Mg)O2 en cyclage

Contribution à l'étude des phases Lix(Co,M)O2 en tant que matériaux d'électrode positive des batteries Li-ion. Effets combinés de la surstoechiométrie en lithium et de la substitution (M = Ni, Mg)

Des matériaux d'électrode positive pour batteries Li-ion de formule Lix0(Co,M)O2 (M = Ni, Mg ; x0 ≥ 1.0) ont été préparés à haute température (900° C) et caractérisés par diffraction des rayons X, tests galvanostatiques, spectroscopie de RMN MAS du 7Li et mesures électriques. Alors que les propriétés de la phase LiCoO2 sont en accord avec la littérature, dans tous les cas, l'ajout d'un excès de lithium lors de la synthèse conduit dans le matériau final à la présence d'un défaut structural constitué de lacunes d'oxygène et d'ions Co3+ spin intermédiaire (Co3+(IS)) en site pyramidal à base carrée. Ce défaut influe considérablement sur les propriétés des phases désintercalées puisqu'il supprime toutes les transitions de phase habituellement observées lors du cyclage galvanostatique de la phase LiCoO2. La substitution du nickel au cobalt permet de séparer la contribution des ions NiIII et Co3+(IS) quant à la disparition des transitions de phase lors de la désintercalation du lithium. La substitution du magnésium au cobalt, même sans excès de lithium, induit systématiquement la présence de ce type de défaut (Co3+(IS)). Cette particularité a été corrélée au comportement électrochimique de ces matériaux Lix(Co,Mg)O2 en cyclage.Lix0(Co,M)O2 (M = Ni, Mg ; x0 ≥ 1.0) materials used as positive electrode for Li-ion batteries have been prepared at high temperature (900° C) and characterised by X-ray diffraction, galvanostatic measurements, 7Li MAS NMR spectroscopy and electrical properties measurements. If the results on the LiCoO2 phase agree with the literature, the adding of an excess of lithium during synthesis leads to the presence in the actual materials to the presence of oxygen vacancies and intermediate spin Co3+ ions (Co3+(IS)) in a square-based environment. This defect suppresses all the phase transitions usually observed upon lithium deintercalation in LixCoO2. The partial substitution by Ni ions allows us to separate the relative contribution of NiIII and Co3+(IS) ions in the suppression of the various phase transitions upon cycling. Mg doping, even without any lithium excess, systematically induces some oxygen vacancies and Co3+(IS) ions in the material. This observation had been correlated to the behaviour of the Lix(Co,Mg)O2 system upon cycling

Tracking Mycoviruses in Public RNAseq Datasets of <i>Malassezia</i>: Three Original Totiviruses Revealed

Mycoviruses are viruses that selectively infect and multiply in fungal cells. Malassezia is the most abundant fungus on human skin and is associated with a variety of conditions, including atopic eczema, atopic dermatitis, dandruff, folliculitis, pityriasis versicolor, and seborrheic dermatitis. Here, we conducted mycovirome studies on 194 public transcriptomes of Malassezia (2,568,212,042 paired-end reads) screened against all available viral proteins. Transcriptomic data were assembled de novo resulting in 1,170,715 contigs and 2,995,306 open reading frames (ORFs) that were subsequently tracked for potential viral sequences. Eighty-eight virus-associated ORFs were detected in 68 contigs from 28 Sequence Read Archive (SRA) samples. Seventy-five and thirteen ORFs were retrieved from transcriptomes of Malassezia globosa and Malassezia restricta, respectively. Phylogenetic reconstructions revealed three new mycoviruses belonging to the Totivirus genus and named Malassezia globosa-associated-totivirus 1 (MgaTV1); Malassezia restricta-associated-totivirus 1 (MraTV1) and Malassezia restricta-associated-totivirus 2 (MraTV2). These viral candidates extend our understanding of the diversity and taxonomy of mycoviruses as well as their co-evolution with their fungal hosts. These results reflected the unexpected diversity of mycoviruses hidden in public databases. In conclusion, this study sheds light on the discovery of novel mycoviruses and opens the door to study their impact on disease caused by the host fungus Malassezia and globally, their implication in clinical skin disorders

On the dual effect of Mg doping in LiCoO2 and Li1+dCoO2 : structural, electronic properties, and 7Li MAS NMR studies

HT-Lix0Co1-yMgyO2 (where x0 is the Li/(Co + Mg) ratio; x0 = 0.98, 1.0, 1.10; y = 0.0, 0.03, 0.06, and 0.10) materials were synthesized via a solid-state reaction. These samples were characterized by X-ray diffraction, 7Li MAS NMR spectroscopy, and electrical properties measurements. The XRD study showed that pure phases are obtained for 0.0 ≤ y < 0.10 and x0 ≥ 1.0. 7Li MAS NMR spectra of the Mg-doped phases exhibit two types of new signals at 55 ppm and 325, 7, −9, and − 27 ppm in addition to the signal at 0 ppm resulting from the presence of diamagnetic CoIII ions. On the basis of our general knowledge of Li NMR in layered oxides with electron spins, we suggest that Mg doping in LiCoO2 always leads to the simultaneous presence of CoIV ions (sharing an itinerant electron hole with neighboring CoIII ions) and, to a smaller extent, of intermediate spin Co3+(IS) ions trapped in a square-based pyramidal environment because of an oxygen vacancy. This feature is further enhanced by lithium overstoichiometry

Combined effects of Ni and Li doping on the phase transitions in LixCoO2: electrochemical and 7Li nuclear magnetic resonance studies

High temp. Lix0Co1-yNiyO2 (x0=1.0, 1.10; yr=0.0, 0.03, 0.06, and 0.10) phases were synthesized by solid-state chem. Their characterization by X-ray diffraction and galvanostatic measurements shows that 3% of Ni ions substituted for Co in the LiCoO2 lattice suppress the two-phase domain, related to the semiconductor-to-metal transition, that is obsd. at the beginning of the charge process in LixCoO2. These ions, trapped in the lattice, prevent the phase sepn. On the other hand, more than 10% of Ni ions need to be substituted for Co in order to inhibit the monoclinic distortion due to a lithium/vacancy ordering in the interslab for Li0.50Co1-yNiyO2. Besides, a Li/(Ni+Co) ratio (x0) strictly higher than one in Lix0Co0.97Ni0.03O2 leads, as in the case of the unsubstituted Li1.10CoO2 phase, to the disappearance of all the phase transitions upon deintercalation. 7Li magic angle spinning NMR measurements show that NiIII ions are the only paramagnetic species in the LiCo1-yNiyO2 phases while in the overlithiated Lix0Co1-yNiyO2 (x0>1.0) phases, NiIII and intermediate spin Co3+(IS) are present. This suggests the existence of structural defects assocd. with O vacancies which are responsible for the suppression of the electronic delocalization and of the lithium/vacancy ordering upon lithium deintercalation

On the LixCo1-yMgyO2 system upon deintercalation: electrochemical, electronic properties and 7Li MAS NMR studies

A detailed characterization of the structural modifications and redox processes occurring upon lithium deintercalation from the Lix0Co1−yMgyO2 materials (x0=1.0 and 1.10; y=0.0, 0.03, 0.05 and 0.06) was performed in order to determine the effect of Mg doping on the cycling properties. Using electrochemical tests, X-ray diffraction (XRD), 7Li MAS NMR and electrical properties measurements, we show that the LixCo1−yMgyO2 system exhibits a solid solution existing in the whole deintercalation range studied (0.30≤×≤1.0). These phases exhibit reversible capacities equivalent to that of LiCoO2 upon cycling with a good structural stability. Moreover, the 7Li MAS NMR study shows that the structural defects (O vacancies and intermediate spin Co3+ ions) which are present in the starting Mg-doped phases govern the electronic properties upon lithium deintercalation. Indeed, regardless of the presence of Mg ions in the structure, a behavior similar to that of the LixCoO2 (

Combinatorics of H-primes in quantum matrices

For q epsilon C transcendental over Q, we give an algorithmic construction of an order-isomorphism between the set of H-primes of O-q (M-n (C)) and the sub-poset S of the (reverse) Bruhat order of the symmetric group S-2n consisting of those permutations that move any integer by no more than it positions. Further, we describe the permutations that correspond via this bijection to rank t H-primes. More precisely, we establish the following result. Imagine that there is a barrier between positions n and it + 1. Then a 2n-permuation sigma epsilon S corresponds to a rank t H-invariant prime ideal Of O-q (M-n (Q) if and only if the number of integers that are moved by sigma from the right to the left of this barrier is exactly n - t. The existence of such an order-isomorphism was conjectured by Goodearl and Lenagan