Isolation of a potassium bis(1,2,3-triazol-5-ylidene) carbazolide: a stabilizing pincer ligand for reactive late transition metal complexes

The synthesis and X-ray crystal structure of a potassium adduct of a monoanionic CNC-pincer ligand featuring two mesoionic carbenes is reported. Owing to the peculiar electronic and steric properties of this ligand, the first neutral stable Ni(II)-hydride, and an unusual Cu(II) complex displaying a seesaw geometry, have been isolated

Ruthenium(II) pincer complexes featuring an anionic CNC bis(1,2,3-triazol-5-ylidene)carbazolide ligand coordinated in a meridional fashion

Please read abstract in the article.GGB thanks the MINECO for a postdoctoral grant (IJCI-2015-23407); EP gratefully acknowledges financial support from MINECO of Spain (CTQ2014-51999-P) and the Universitat Jaume I (P11B2014-02); DIB and GK gratefully acknowledge the National Research Foundation, South Africa (NRF 10552, 105740 and 92521), and Sasol Technology R&D Pty. Ltd., South Africa.http://www.elsevier.com/locate/poly2019-03-15hj2017Chemistr

The eye contact effect: mechanisms and development

The ‘eye contact effect’ is the phenomenon that perceived eye contact with another human face modulates certain aspects of the concurrent and/or immediately following cognitive processing. In addition, functional imaging studies in adults have revealed that eye contact can modulate activity in structures in the social brain network, and developmental studies show evidence for preferential orienting towards, and processing of, faces with direct gaze from early in life. We review different theories of the eye contact effect and advance a ‘fast-track modulator’ model. Specifically, we hypothesize that perceived eye contact is initially detected by a subcortical route, which then modulates the activation of the social brain as it processes the accompanying detailed sensory information

A cytotoxic bis(1,2,3-triazol-5-ylidene)carbazolide gold(III) complex targets DNA by partial intercalation

The syntheses of bis(triazolium)carbazole precursors and their corresponding coinage metal (Au, Ag) complexes are reported. For alkylated triazolium salts, di- or tetranuclear complexes with bridging ligands were isolated, while the bis (aryl) analogue afforded a bis(carbene) AuI -CNC pincer complex suitable for oxidation to the redox-stable [AuIII(CNC) Cl]+ cation. Although the ligand salt and the [AuIII(CNC)Cl]+ complex were both notably cytotoxic toward the breast cancer cell line MDA-MB-231, the AuIII complex was somewhat more selective. Electrophoresis, viscometry, UV-vis, CD and LD spectroscopy suggest the cytotoxic [AuIII(CNC)Cl]+ complex behaves as a partial DNA intercalator. In silico screening indicated that the [AuIII(CNC)Cl]+ complex can target DNA three-way junctions with good specificity, several other regular B-DNA forms, and Z-DNA. Multiple hydrophobic πtype interactions involving T and A bases appear to be important for B-form DNA binding, while phosphate O···Au interactions evidently underpin Z-DNA binding. The CNC ligand effectively stabilizes the AuIII ion, preventing reduction in the presence of glutathione. Both the redox stability and DNA affinity of the hit compound might be key factors underpinning its cytotoxicity in vitro.https://chemistry-europe.onlinelibrary.wiley.com/journal/15213765pm2021ChemistryPhysiolog

A year of genomic surveillance reveals how the SARS-CoV-2 pandemic unfolded in Africa

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A year of genomic surveillance reveals how the SARS-CoV-2 pandemic unfolded in Africa.

The progression of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic in Africa has so far been heterogeneous, and the full impact is not yet well understood. In this study, we describe the genomic epidemiology using a dataset of 8746 genomes from 33 African countries and two overseas territories. We show that the epidemics in most countries were initiated by importations predominantly from Europe, which diminished after the early introduction of international travel restrictions. As the pandemic progressed, ongoing transmission in many countries and increasing mobility led to the emergence and spread within the continent of many variants of concern and interest, such as B.1.351, B.1.525, A.23.1, and C.1.1. Although distorted by low sampling numbers and blind spots, the findings highlight that Africa must not be left behind in the global pandemic response, otherwise it could become a source for new variants

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

Experiments on sedimentation in wide reservoirs and erosion following dam removal

Sedimentary deposits in reservoir lakes record the sediment transport capacity of the up-stream river and past water levels of the downstream basin. Volumes and morphologies of deltas can be used to calculate flow and sediment dynamics. We constructed circular basins to which we fed constant flow discharge over a feeder channel of gravelly sand with different ratios of added silica flour. During water level rise, the fan radius decreased over time. During water level fall, after dam removal, the deltas were partially destroyed. Surprisingly, for low discharges the channel markedly destroyed the deposit through transverse movements of the initial channel whereas for higher discharges the terraces were pre-served for a longer time. Our results indicate that dam removal at wide lakes may lead to an unexpected inverse relation between discharge and erosion of the deposit, which has consequences for the subsequent sediment pulse magnitude. Point-modelling of sediment transport capacity yielded volumes in good agreement with observed volumes, proving that the time scale of activity can be inferred from feeder channel dimensions and delta volume. Our results suggest that these parameters can yield consistent re-construction of formative time scale also on Mars, which has consequences for interpretation of ancient climate

Synthesis, complexion and reactivity studies of novel bis (1,2,3-triazol-5-ylidene) carbazolide ligands

Please read abstract in article.Dissertation (MSc)--University of Pretoria, 2014.ChemistryMScUnrestricte