On the cryogenic removal of NOy from the Antarctic polar stratosphere

We review current knowledge about the annual cycle of transport of nitrogen oxides to, and removal from, the polar stratosphere, with particular attention to Antarctica where the annual winter denitrifi cation process is both regular in occurrence and severe in effect. Evidence for a large downward fl ux of NOy from the mesosphere to the stratosphere, fi rst seen briefl y in the Limb Infrared Monitor of the Stratosphere (LIMS) data from the Arctic winter of 1978-1979, has been found during the 1990s in both satellite and ground-based observations, though this still seems to be omitted from many atmospheric models. When incorporated in the Stony Brook- St. Petersburg two dimensional (2D) transport and chemistry model, more realistic treatment of the NOy fl ux, along with sulfate transport from the mesosphere, sulfate aerosol formation where temperature is favorable, and the inclusion of a simple ion-cluster reaction, leads to good agreement with observed HNO3 formation in the mid-winter middle to upper stratosphere. To further emphasize the importance of large fl uxes of thermospheric and mesospheric NOy into the polar stratosphere, we have used observations, supplemented with model calculations, to defi ne new altitude dependent correlation curves between N2O and NOy. These are more suitable than those previously used in the literature to represent conditions within the Antarctic vortex region prior to and during denitrifi cation by Polar Stratospheric Cloud (PSC) particles. Our NOy -N2O curves lead to a 40% increase in the average amount of NOy removed during the Antarctic winter with respect to estimates calculated using NOy-N2O curves from the Atmospheric Trace Molecule Spectroscopy (ATMOS)/ATLAS-3 data set

Transposase-DNA complex structures reveal mechanisms for conjugative transposition of antibiotic resistance

Conjugative transposition drives the emergence of multidrug resistance in diverse bacterial pathogens, yet the mechanisms are poorly characterized. The Tn1549 conjugative transposon propagates resistance to the antibiotic vancomycin used for severe drug-resistant infections. Here, we present four high-resolution structures of the conserved Y-transposase of Tn1549 complexed with circular transposon DNA intermediates. The structures reveal individual transposition steps and explain how specific DNA distortion and cleavage mechanisms enable DNA strand exchange with an absolute minimum homology requirement. This appears to uniquely allow Tn916-like conjugative transposons to bypass DNA homology and insert into diverse genomic sites, expanding gene transfer. We further uncover a structural regulatory mechanism that prevents premature cleavage of the transposon DNA before a suitable target DNA is found and generate a peptide antagonist that interferes with the transposase-DNA structure to block transposition. Our results reveal mechanistic principles of conjugative transposition that could help control the spread of antibiotic resistance genes

Landscape of mobile genetic elements and their antibiotic resistance cargo in prokaryotic genomes

Prokaryotic Mobile Genetic Elements (MGEs) such as transposons, integrons, phages and plasmids, play important roles in prokaryotic evolution and in the dispersal of cargo functions like antibiotic resistance. However, each of these MGE types is usually annotated and analysed individually, hampering a global understanding of phylogenetic and environmental patterns of MGE dispersal. We thus developed a computational framework that captures diverse MGE types, their cargos and MGE-mediated horizontal transfer events, using recombinases as ubiquitous MGE marker genes and pangenome information for MGE boundary estimation. Applied to ∼84k genomes with habitat annotation, we mapped 2.8 million MGE-specific recombinases to six operational MGE types, which together contain on average 13% of all the genes in a genome. Transposable elements (TEs) dominated across all taxa (∼1.7 million occurrences), outnumbering phages and phage-like elements (<0.4 million). We recorded numerous MGE-mediated horizontal transfer events across diverse phyla and habitats involving all MGE types, disentangled and quantified the extent of hitchhiking of TEs (17%) and integrons (63%) with other MGE categories, and established TEs as dominant carriers of antibiotic resistance genes. We integrated all these findings into a resource (proMGE.embl.de), which should facilitate future studies on the large mobile part of genomes and its horizontal dispersal

Recovering the observable part of the initial data of an infinite-dimensional linear system with skew-adjoint generator

We consider the problem of recovering the initial data (or initial state) of infinite-dimensional linear systems with unitary semigroups. It is well-known that this inverse problem is well posed if the system is exactly observable, but this assumption may be very restrictive in some applications. In this paper we are interested in systems which are not exactly observable, and in particular, where we cannot expect a full reconstruction. We propose to use the algorithm studied by Ramdani et al. in (Automatica 46:1616–1625, 2010) and prove that it always converges towards the observable part of the initial state. We give necessary and sufficient condition to have an exponential rate of convergence. Numerical simulations are presented to illustratethe theoretical results

SORPTION LEACHING OF SCANDIUM FROM THE ‘RED MUD’ FROM URALS ALUMINUM PLANT

The work is devoted to scandium separation from ‘red mud’ using the sorption sulfuric acid leaching technology with ANCF-221, S-940, TP-260 and S-950 ampholytes. It was established that the ANCF-221 ampholyte is the most selective for scandium under studied conditions. Solutions of sodium, potassium and ammonium carbonates were used for scandium desorption. Sodium carbonate was the most effective and selective solution for scandium removal from the ANCF-221 resin; this allows obtaining a concentrate containing 2% of scandium.Работа выполнена при финансовой поддержке Минобрнауки России рамках соглашения о предоставлении субсидии от 29.09.2014 г. № 14.581.21.0002 в рамках ФЦП «Исследования и разработки по приоритетным направлениям развития научно-технологического комплекса России на 2014-2020 годы»

SULFURIC ACID EXTRACTION FROM A DILUTED ACIDIC SULFATE EFFLUENT

The paper is devoted to study recovery of sulfuric acid form diluted acidic effluents using liquid extraction. Among the extractants studied, the extraction system containing triisooctyl amine, 1-octanol and ditolilphosphinic acids was found to be the most suitable for sulfuric acid revovery.Работа выполнена при финансовой поддержке Минобрнауки России, соглашение о предоставлении субсидии от 26.09.2017 г. № 14.575.21.0137 (уникальный идентификатор соглашения RFMEFI57517X0137), в рамках ФЦП “Исследования и разработки по приоритетным направлениям развития научно-технологического комплекса России на 2014–2020 годы”

INTENSIFICATION OF REE EXTRACTION FROM PHOSPHOGYPSUM

Phosphogypsum(FG) contains traces of rare earth elements (REEs), ranging from 4000 to 5000 g/t. However, REEmay be regarded as s secondary source for REE since large tonnages of FG are mined annually and used in phosphoric acid production.In this work, batchleaching tests were conducted to examе FG processes in order to determine REE recovery. Then REE was extracted in-line during FGtreatment using grinding and ultra-ultrasound.It was also found that REE was efficiently extracted by ion exchange resin

SORPTION RECOVERY OF RHENIUM FROM SULFURIC ACID SOLUTIONS

The possibility of rhenium extraction from simulated solutions using weak base anion exchange resins was researched. It was found that rhenium is adsorbed by these resins completely. The most selective resin was chosen.Работа выполнена при финансовой поддержке Минобрнауки России, соглашение о предоставлении субсидии от 26.09.2017 г. № 14.575.21.0137 (уникальный идентификатор соглашения RFMEFI57517X0137), в рамках ФЦП “Исследования и разработки по приоритетным направлениям развития научно-технологического комплекса России на 2014–2020 годы”