N-tert-Butanesulfinyl imines in the asymmetric synthesis of nitrogen-containing heterocycles

The synthesis of nitrogen-containing heterocycles, including natural alkaloids and other compounds presenting different types of biological activities have proved to be successful employing chiral sulfinyl imines derived from tert-butanesulfinamide. These imines are versatile chiral auxiliaries and have been extensively used as eletrophiles in a wide range of reactions. The electron-withdrawing sulfinyl group facilitates the nucleophilic addition of organometallic compounds to the iminic carbon with high diastereoisomeric excess and the free amines obtained after an easy removal of the tert-butanesulfinyl group can be transformed into enantioenriched nitrogen-containing heterocycles. The goal of this review is to the highlight enantioselective syntheses of heterocycles involving the use of chiral N-tert-butanesulfinyl imines as reaction intermediates, including the synthesis of several natural products. The synthesis of nitrogen-containing heterocycles in which the nitrogen atom is not provided by the chiral imine will not be considered in this review. The sections are organized according to the size of the heterocycles. The present work will comprehensively cover the most pertinent contributions to this research area from 2012 to 2020. We regret in advance that some contributions are excluded in order to maintain a concise format.We thank the continuous financial support from the Spanish Ministerio de Economía y Competitividad (MINECO; project CTQ2014-53695-P, CTQ2014-51912-REDC, CTQ2016-81797-REDC, CTQ2017-85093-P), Ministerio de Ciencia, Innovación y Universidades (RED2018-102387-T, PID2019-107268GB-100), FEDER, the Generalitat Valenciana (PROMETEOII/2014/017), and the University of Alicante (VIGROB-068). We are also grateful for the financial support from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Discretização de modelos hidrológicos de grande escala: grade regular x mini-bacias.

O emprego de modelos hidrológicos distribuídos (MHD) de grande escala para diversos propósitos é tema de pesquisa bastante relevante atualmente, principalmente para avaliação de impactos potenciais de cenários de variabilidade climática ou de mudança de uso da terra sobre os recursos hídricos. A etapa inicial da aplicação de MHD é a subdivisão ou discretização da bacia em elementos menores e o estabelecimento da rede de drenagem que os conecta. Devido à falta de conhecimento e às facilidades propiciadas por ferramentas automáticas, aspectos importantes dessa etapa são muitas vezes negligenciados pelos usuários. Este artigo discute os principais métodos de discretização, com foco principal na grade regular e mini-bacias. Tomando a bacia do rio Ji-Paraná (RO) como estudo de caso, são apresentadas vantagens e limitações de cada método. Os resultados evidenciaram que, enquanto o uso de grade regular uniformiza o tamanho dos elementos, a dificuldade em definir as direções de fluxo e os trechos de rio para propagação do escoamento permanece como principal desvantagem, a despeito de metodologias propostas mais recentemente. A abordagem em mini-bacias supera tais limitações, mas causa o inconveniente de ter que lidar com enorme variação de área superficial e comprimentos de trecho de rio entre os elementos

Link between the North Atlantic Oscillation and the surface mass balance components of the Greenland Ice Sheet under preindustrial and last interglacial climates: a study with a coupled global circulation model

The relationship between the surface mass balance (SMB) components (accumulation and melting) of the Greenland Ice Sheet (GrIS) and the North Atlantic Oscillation (NAO) is examined from numerical simulations performed with a new atmospheric stretched grid configuration of the Centre National de Recherches Météorologiques Coupled Model (CNRM-CM) version 5.2 under three periods: preindustrial climate, a warm phase (early Eemian, 130&thinsp;ka&thinsp;BP) and a cool phase (late Eemian, 115&thinsp;ka&thinsp;BP) of the last interglacial. The horizontal grid of the atmospheric component of CNRM-CM5.2 is stretched from the tilted pole on Baffin Bay (72°&thinsp;N, 65°&thinsp;W) in order to obtain a higher spatial resolution on Greenland. The correlation between simulated SMB anomalies averaged over Greenland and the NAO index is weak in winter and significant in summer (about 0.6 for the three periods). In summer, spatial correlations between the NAO index and SMB components display different patterns from one period to another. These differences are analyzed in terms of the respective influence of the positive and negative phases of the NAO on accumulation and melting. Accumulation in south Greenland is significantly correlated with the positive (negative) phase of the NAO in a warm (cold) climate. Under preindustrial and 115&thinsp;ka&thinsp;BP climates, melting along the margins is more correlated with the positive phase of the NAO than with its negative phase, whereas at 130&thinsp;ka&thinsp;BP it is more correlated with the negative phase of the NAO in north and northeast Greenland.</p

L-DAWA: Layer-wise Divergence Aware Weight Aggregation in Federated Self-Supervised Visual Representation Learning

The ubiquity of camera-enabled devices has led to large amounts of unlabeled image data being produced at the edge. The integration of self-supervised learning (SSL) and federated learning (FL) into one coherent system can potentially offer data privacy guarantees while also advancing the quality and robustness of the learned visual representations without needing to move data around. However, client bias and divergence during FL aggregation caused by data heterogeneity limits the performance of learned visual representations on downstream tasks. In this paper, we propose a new aggregation strategy termed Layer-wise Divergence Aware Weight Aggregation (L-DAWA) to mitigate the influence of client bias and divergence during FL aggregation. The proposed method aggregates weights at the layer-level according to the measure of angular divergence between the clients' model and the global model. Extensive experiments with cross-silo and cross-device settings on CIFAR-10/100 and Tiny ImageNet datasets demonstrate that our methods are effective and obtain new SOTA performance on both contrastive and non-contrastive SSL approaches

Enantioselective Synthesis, DFT Calculations, and Preliminary Antineoplastic Activity of Dibenzo 1-Azaspiro[4.5]decanes on Drug-Resistant Leukemias

The addition of 2-bromobenzylmagnesium bromide to chiral N-tert-butanesulfinyl imines derived from tetralone-type ketones proceeds with high levels of diastereocontrol. The resulting sulfinamide derivatives were transformed into dibenzoazaspiro compounds after a palladium-catalyzed intramolecular N-arylation. DFT calculations have been performed to rationalize the stereochemical course of the reaction. Similar results have been obtained considering either diethyl ether or toluene as a solvent, in both cases in an excellent agreement with experimental findings. NCI topological calculations have also been used to evidence crucial noncovalent interactions. In addition, the azaspiro compounds reduced the viability of chronic myeloid leukemia cells in the micromolar range. Notably, both the halogen-substituted (R)- and (S)-8g and -8h as well as (R)-8j were at least two times more effective on a multidrug-resistant derivative than on the parental cell line, exerting a collateral sensitivity effect.We acknowledge the continued financial support from the Spanish Ministerio de Economía y Competitividad (MINECO; project CTQ2014-53695-P, CTQ2014-51912-REDC, CTQ2016-81797-REDC, CTQ2016-76155-R, CTQ2017-85093-P), FEDER, the Generalitat Valenciana (PROMETEOII/2014/017), and the University of Alicante. We thankfully acknowledge the resources from the supercomputers “Memento” and “Cierzo” and technical expertise and assistance provided by BIFI-ZCAM (Universidad de Zaragoza, Spain). We also thank Prof. Vivian M. Rumjanek for providing FEPS cells and Prof. Adriano D. Andricopulo for the preliminary cytotoxicity screening. This study was also financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001

A first look into the carbon footprint of federated learning

Despite impressive results, deep learning-based technologies also raise severe privacy and environmental concerns induced by the training procedure often conducted in datacenters. In response, alternatives to centralized training such as Federated Learning (FL) have emerged. Perhaps unexpectedly, FL, in particular, is starting to be deployed at a global scale by companies that must adhere to new legal demands and policies originating from governments and civil society for privacy protection. However, the potential environmental impact related to FL remains unclear and unexplored. This paper offers the first-ever systematic study of the carbon footprint of FL. First, we propose a rigorous model to quantify the carbon footprint, hence facilitating the investigation of the relationship between FL design and carbon emissions. Then, we compare the carbon footprint of FL to traditional centralized learning. Our findings show that FL, despite being slower to converge in some cases, may result in a comparatively greener impact than a centralized equivalent setup. We performed extensive experiments across different types of datasets, settings, and various deep learning models with FL. Finally, we highlight and connect the reported results to the future challenges and trends in FL to reduce its environmental impact, including algorithms efficiency, hardware capabilities, and stronger industry transparency.Comment: arXiv admin note: substantial text overlap with arXiv:2010.0653

How well can the LHC distinguish between the SM light Higgs scenario, a composite Higgs and the Higgsless case using VV scattering channels?

A complete parton level analysis of ll + four jets l = e,mu and 3lv + two jets production at the LHC is presented, including all processes at order \ordEW, \ordQCD and \ordQCDsq when appropriate. The infinite Higgs mass scenario, which is considered as a benchmark for strong scattering theories and is the limiting case for composite Higgs models, and one example of a model incorporating a Strongly Interacting Light Higgs are confronted with the Standard Model light Higgs predictions. This analysis is combined with the results in the lv + four jets channel presented in a previous paper, in order to determine whether a composite Higgs signal can be detected as an excess of events in boson--boson scattering.Comment: Introduced some representative Feynman diagrams. Rearranged section 4. Typos fixed. Published in JHE

Vector boson scattering processes: Status and prospects

Insight into the electroweak (EW) and Higgs sectors can be achieved through measurements of vector boson scattering (VBS) processes. The scattering of EW bosons are rare processes that are precisely predicted in the Standard Model (SM) and are closely related to the Higgs mechanism. Modifications to VBS processes are also predicted in models of physics beyond the SM (BSM), for example through changes to the Higgs boson couplings to gauge bosons and the resonant production of new particles. In this review, experimental results and theoretical developments of VBS at the Large Hadron Collider, its high luminosity upgrade, and future colliders are presented