Spectral Inversion of Multi-Line Full-Disk Observations of Quiet Sun Magnetic Fields

Spectral inversion codes are powerful tools to analyze spectropolarimetric observations, and they provide important diagnostics of solar magnetic fields. Inversion codes differ by numerical procedures, approximations of the atmospheric model, and description of radiative transfer. Stokes Inversion based on Response functions (SIR) is an implementation widely used by the solar physics community. It allows to work with different atmospheric components, where gradients of different physical parameters are possible, e.g., magnetic field strength and velocities. The spectropolarimetric full-disk observations were carried out with the Stokesmeter of the Solar Telescope for Operative Predictions (STOP) at the Sayan Observatory on 3 February 2009, when neither an active region nor any other extended flux concentration was present on the Sun. In this study of quiet Sun magnetic fields, we apply the SIR code simultaneously to 15 spectral lines. A tendency is found that weaker magnetic field strengths occur closer to the limb. We explain this finding by the fact that close to the limb, we are more sensitive to higher altitudes in an expanding flux tube, where the field strength should be smaller since the magnetic flux is conserved with height. Typically, the inversions deliver two populations of magnetic elements: (1) high magnetic field strengths (1500-2000 G) and high temperatures (5500-6500 K) and (2) weak magnetic fields (50-150 G) and low temperatures (5000-5300 K).Comment: 10 pages, 6 figures, accepted for Solar Physic

Interrogation of an Enzyme Library Reveals the Catalytic Plasticity of Naturally Evolved [4+2] Cyclases

\ua9 2023 The Authors. ChemBioChem published by Wiley-VCH GmbH.Stereoselective carbon-carbon bond forming reactions are quintessential transformations in organic synthesis. One example is the Diels-Alder reaction, a [4+2] cycloaddition between a conjugated diene and a dienophile to form cyclohexenes. The development of biocatalysts for this reaction is paramount for unlocking sustainable routes to a plethora of important molecules. To obtain a comprehensive understanding of naturally evolved [4+2] cyclases, and to identify hitherto uncharacterised biocatalysts for this reaction, we constructed a library comprising forty-five enzymes with reported or predicted [4+2] cycloaddition activity. Thirty-one library members were successfully produced in recombinant form. In vitro assays employing a synthetic substrate incorporating a diene and a dienophile revealed broad-ranging cycloaddition activity amongst these polypeptides. The hypothetical protein Cyc15 was found to catalyse an intramolecular cycloaddition to generate a novel spirotetronate. The crystal structure of this enzyme, along with docking studies, establishes the basis for stereoselectivity in Cyc15, as compared to other spirotetronate cyclases

Assessment of phenolic herbicide toxicity and mode of action by different assays

A phytotoxicity assay based on seed germination/root elongation has been optimized and used to evaluate the toxic effects of some phenolic herbicides. The method has been improved by investigating the influence of experimental conditions. Lepidium sativum was chosen as the most suitable species, showing high germinability, good repeatability of root length measurements, and low sensitivity to seed pretreatment. DMSO was the most appropriate solvent carrier for less water-soluble compounds. Three dinitrophenols and three hydroxybenzonitriles were tested: dinoterb, DNOC, 2,4-dinitrophenol, chloroxynil, bromoxynil, and ioxynil. Toxicity was also determined using the Vibrio fischeri MicrotoxA (R) test, and a highly significant correlation was found between EC50 values obtained by the two assays. Dinoterb was the most toxic compound. The toxicity of hydroxybenzonitriles followed the order: ioxynil > bromoxynil > chloroxynil; L. sativum exhibited a slightly higher sensitivity than V. fischeri to these compounds. A QSAR analysis highlighted the importance of hydrophobic, electronic, and hydrogen-bonding interactions, in accordance with a mechanism of toxic action based on protonophoric uncoupling of oxidative phosphorylation. The results suggest that the seed germination/root elongation assay with L. sativum is a valid tool for the assessment of xenobiotic toxicity and can be recommended as part of a test battery

The Pre-Aksumite Period: indigenous origins and development in the Horn of Africa

The Pre-Aksumite Period (mid-second to late first millennia BC) witnessed the rise of complex societies in the Horn of Africa. Archaeological survey and excavations in the Gulo Makeda region of Eastern Tigrai by the Eastern Tigrai Archaeological Project (ETAP) have produced new data and insights into this critical juncture in the cultural history of the region. Based on data from Mezber and other archaeological sites, we present a new Pre-Aksumite chronology and discuss the material culture, settlement, political organisation, economy, agricultural history and regional interactions of this period. We recommend the use of the term ‘Pre-Aksumite Period’ to encompass this time when the earliest polities developed in the region. Mezber provides us with a glimpse into the lifeways of indigenous peoples inhabiting the northern Horn of Africa who encountered South Arabian visitors to the region during the early first millennium BC. Data from Mezber shift our focus from external influences to considering the culture and development of autochthonous peoples of the Ethiopian/Eritrean highlands who had an active role in negotiating cultural contacts. This perspective constitutes a missing piece of the puzzle needed to better understand the broader socio-economic, political and cultural dynamics of the Pre-Aksumite Period.ETAP investigations at Mezber were financially supported by three grants from the Social Sciences and Humanities Research Council of Canada (SSHRC), including Standard Research Grants 410-2007-2472, 410-2011-1646 and Insight Grant 435-2014-01. Further support was obtained by grants from Simon Fraser University, including four SSHRC/SFU Institutional Grants and a VP Research SSHRC 4A grant. Field and laboratory microbotanical work completed by AR-G and CL was developed within the framework of the RAINDROPS project, funded by the European Research Council (ERC-Stg 759800) and both are part of CaSEs, a recognised research group of the Generalitat De Catalunya (AGAUR SGR-e-2017-212)