No abstract

Severe acute respiratorysyndrome coronavirus‐2 (SARS‐CoV‐2) pandemic spread rapidly and this scenario is concerning worldwide, presenting more than 590 million coronavirus disease 2019 cases and 6.4 million deaths. The emergence of novel lineages carrying several mutations in the spike protein has raised additional public health concerns worldwide during the pandemic. The present study review and summarizes the temporal spreading and molecular evolution of SARS‐CoV‐2 clades and variants worldwide. The evaluation of these data is important for understanding the evolutionary histories of SARSCoV‐2 lineages, allowing us to identify the origins of each lineage of this virus responsible for one of the biggest pandemics in history. A total of 2897 SARS‐CoV‐2 whole‐genome sequences with available information from the country and sampling date (December 2019 to August 2022), were obtained and were evaluated by Bayesian approach. The results demonstrated that the SARS‐CoV‐2 the time to the most recent common ancestor (tMRCA) in Asia was 2019‐12‐26 (highest posterior density 95% [HPD95%]: 2019‐12‐18; 2019‐12‐29), in Oceania 2020‐01‐24 (HPD95%: 2020‐01‐15; 2020‐01‐30), in Africa 2020‐02‐27 (HPD95%: 2020‐02‐21; 2020‐03‐04), in Europe 2020‐02‐27 (HPD95%: 2020‐02‐20; 2020‐03‐06), in North America 2020‐03‐12 (HPD95%: 2020‐03‐05; 2020‐03‐18), and in South America 2020‐03‐15 (HPD95%: 2020‐03‐09; 2020‐03‐28). Between December 2019 and June 2020, 11 clades were detected (20I [Alpha] and 19A, 19B, 20B, 20C, 20A, 20D, 20E [EU1], 20F, 20H [Beta]). From July to December 2020, 4 clades were identified (20J [Gamma, V3], 21 C [Epsilon], 21D [Eta], and 21G [Lambda]). Between January and June 2021, 3 clades of the Delta variant were detected (21A, 21I, and 21J). Between July and December 2021, two variants were detected, Delta (21A, 21I, and 21J) and Omicron (21K, 21L, 22B, and 22C). Between January and June 2022, the Delta (21I and 21J) and Omicron (21K, 21L, and 22A) variants were detected. Finally, between July and August 2022, 3 clades of Omicron were detected (22B, 22C, and 22D). Clade 19A was first detected in the SARS‐CoV‐2 pandemic (Wuhan strain) with origin in 2019‐12‐16 (HPD95%: 2019‐12‐15; 2019‐12‐25); 20I (Alpha) in 2020‐11‐24 (HPD95%: 2020‐11‐15; 2021‐12‐02); 20H (Beta) in 2020‐11‐25 (HPD95%: 2020‐11‐13; 2020‐11‐29); 20J (Gamma) was 2020‐12‐21 (HPD95%: 2020‐11‐05; 2021‐01‐15); 21A (Delta) in 2020‐09‐20 (HPD95%: 2020‐05‐17; 2021‐02‐03); 21J (Delta) in 2021‐02‐26 (2020‐11‐02; 2021‐04‐24); 21M (Omicron) in 2021‐01‐25 (HPD95%: 2020‐09‐16; 2021‐08‐08); 21K (Omicron) in 2021‐07‐30 (HPD95%: 2021‐05‐30; 2021‐10‐19); 21L (Omicron) in 2021‐10‐03 (HPD95%: 2021‐04‐16; 2021‐12‐23); 22B (Omicron) in 2022‐01‐25 (HPD95%: 2022‐01‐10; 2022‐02‐05); 21L in 2021‐12‐20 (HPD95%: 2021‐05‐16; 2021‐12‐31). Currently, the Omicron variant predominates worldwide, with the 21L clade branching into 3 (22A, 22B, and 22C). Phylogeographic data showed that Alpha variant originated in the United Kingdom, Beta in South Africa, Gamma in Brazil, Delta in I...

No abstract

Este trabalho descreve um novo método para a reação de acoplamento entre selenetos e teluretos vinílicos e reagentes de Grignard, catalisada por Fe(acac) 3 e à temperatura ambiente. A reação ocorre com retenção da configuração, fornecendo os respectivos alquenos em bons a excelentes rendimentos. Este método também é eficiente para a reação de acoplamento de calcogenetos bisvinílicos com reagentes de Grignard.A general new method for the cross-coupling reaction between vinylic selenides and tellurides and Grignard reagents catalyzed by Fe(acac) 3 at room temperature is described. This reaction proceeded with retention of configuration, providing the respective alkenes in good to excellent yields. This method is also efficient for the coupling reaction of divinyl chalcogenides with Grignard reagents. Keywords: iron-catalyzed, vinylic chalcogenides, cross-coupling, Grignard reagents IntroductionOrganochalcogenium compounds became the key component of a variety of versatile and useful reagents for organic synthesis. The multiple applications of organochalcogenium chemistry have been well described in a number of review articles 1-6 and books. 7-11 Functionalized alkynyl 12-18 and alkenyl [19][20][21][22][23] chalcogenides have a great potential in organic synthesis, since they are valuable intermediates for the selective preparation of several organic compounds.Among the many applications of vinylic selenides, divinylic selenides and vinylic sulfides, the cross-coupling reaction with Grignard reagents catalyzed by Ni 18,24-27 and Pd 28,29 to give the corresponding cross-coupled products, has been described. On the other hand, Pd 19,30 and Ni 24,[31][32][33] catalyzed cross coupling reactions and tellurium/metal exchange reactions [34][35][36][37][38][39][40][41][42] are demonstrative of the usefulness of vinylic tellurides.Transition-metal-catalyzed C-C bond coupling reactions are very important in many areas of science. 43,44 Most current methods require expensive transitionmetal catalysts and ligands. However, in the last years Fe-catalyzed C-C bond cross coupling reactions of vinylic substrates and Grignard reagents became a subject of intense interest. [45][46][47][48][49][50][51] The vinylic counterpart is quite broad in scope, since vinylic halides, triflates, sulfonates, tosylates and enol phosphates can be used. [45][46][47][48][49][50][51] In continuation to our interest on the synthesis and synthetic applications of vinylic chalcogenides 52-58 we decided to study the feasibility of their use in cross coupling reaction with Grignard species catalyzed by iron. To the best of our knowledge, iron catalysts have never been used for the coupling of vinylic selenides and tellurides as electrophiles. The possible use of iron catalysts would represent a great improvement over the high cost of palladium precursors and from the concerns about the toxicity of nickel salts. In light of the above comments it is of interest to design a simple, efficient, and versatile method for the stereoselective coupling of vinylic se...

Deep Reinforcement Learning (RL) has considerably advanced over the past decade. At the same time, state-of-the-art RL algorithms require a large computational budget in terms of training time to converge. Recent work has started to approach this problem through the lens of quantum computing, which promises theoretical speed-ups for several traditionally hard tasks. In this work, we examine a class of hybrid quantumclassical RL algorithms that we collectively refer to as variational quantum deep Q-networks (VQ-DQN). We show that VQ-DQN approaches are subject to instabilities that cause the learned policy to diverge, study the extent to which this afflicts reproduciblity of established results based on classical simulation, and perform systematic experiments to identify potential explanations for the observed instabilities. Additionally, and in contrast to most existing work on quantum reinforcement learning, we execute RL algorithms on an actual quantum processing unit (an IBM Quantum Device) and investigate differences in behaviour between simulated and physical quantum systems that suffer from implementation deficiencies. Our experiments show that, contrary to opposite claims in the literature, it cannot be conclusively decided if known quantum approaches, even if simulated without physical imperfections, can provide an advantage as compared to classical approaches. Finally, we provide a robust, universal and well-tested implementation of VQ-DQN as a reproducible testbed for future experiments.