From the Laser Plume to the Laser Ceramics

The main stages of preparation of ceramic active elements of solid-state lasers are considered. The physical principles of laser synthesis of nanopowders are described. The features and processes taking place during compaction and compacts sintering are specified. Also we report on the investigation of characteristics of highly transparent ceramics on the basis of nanopowders synthesized in laser plume. It is shown that this approach enables to increase the “orange peel” formation threshold in the ceramics with strongly disordered crystalline structure. It opens the road to relatively simple synthesis technology from oxide materials and application of this ceramics as the gain media with oscillation efficiency higher than 50% and also leads to simplification of the synthesis technology of magnetoactive ceramics and to production of highly transparent YAG samples without the use of sintering heterovalent additives

Phase locked 270-440 GHz local oscillator based on flux flow in long Josephson tunnel junctions

The combination of narrow linewidth and wide band tunability makes the Josephson flux flow oscillator (FFO) a perfect on-chip local oscillator for integrated sub-mm wave receivers for, e.g., spectral radio astronomy. The feasibility of phase locking the FFO to an external reference oscillator is demonstrated experimentally. A FFO linewidth as low as 1 Hz (determined by the resolution bandwidth of the spectrum analyzer) has been measured in the frequency range 270-440 GHz relative to a reference oscillator. This linewidth is far below the fundamental level given by shot and thermal noise of the free-running tunnel junction. The results of residual FFO phase noise measurements are also presented. Finally, we propose a single-chip fully superconductive receiver with two superconductor-insulator-superconductor mixers and an integrated phase-locked loop. (C) 2000 American Institute of Physics. [S0034-6748(00)01701-9]

History of National Economic System Formation in the Republic of South Africa

The article analyses specific historic features of formation of agrarian and industrial sectors of Republic of South Africa since the establishment of Cape Colony. These features resulted from much earlier colonization of South Africa in comparison with other Sub-Saharan African countries on the one hand and from a large-scale influx of Europeans to the South Africa on the other hand. The two most important of these specific features are the following. First. Contrary to other countries of Sub-Saharan Africa development of the agrarian sector of Republic of South Africa was based on private property and western technologies from the start. Second. The sector is not divided into «African» and «European» sub-sectors, and South-African agricultural produce has always been oriented to both: external and internal markets. Development of industrial sector of Republic of South Africa started with creation of extractive industries, namely: extraction of diamonds and of gold. The authors specifically emphasize the role of gold extraction which grace to its effect of multiplicator opened the way for industrial revolution in the South of Africa. Development of manufacturing was mainly based on import-substitution. The article argues that there were several stages of import-substitution and analyses their outcomes. The authors point out to the special importance of import-substitution during the period of I World War and II World War

To kill or to be killed: pangenome analysis of Escherichia coli strains reveals a tailocin specific for pandemic ST131.

BACKGROUND: Escherichia coli (E. coli) has been one of the most studied model organisms in the history of life sciences. Initially thought just to be commensal bacteria, E. coli has shown wide phenotypic diversity including pathogenic isolates with great relevance to public health. Though pangenome analysis has been attempted several times, there is no systematic functional characterization of the E. coli subgroups according to the gene profile. RESULTS: Systematically scanning for optimal parametrization, we have built the E. coli pangenome from 1324 complete genomes. The pangenome size is estimated to be ~25,000 gene families (GFs). Whereas the core genome diminishes as more genomes are added, the softcore genome (≥95% of strains) is stable with ~3000 GFs regardless of the total number of genomes. Apparently, the softcore genome (with a 92% or 95% generation threshold) can define the genome of a bacterial species listing the critically relevant, evolutionarily most conserved or important classes of GFs. Unsupervised clustering of common E. coli sequence types using the presence/absence GF matrix reveals distinct characteristics of E. coli phylogroups B1, B2, and E. We highlight the bi-lineage nature of B1, the variation of the secretion and of the iron acquisition systems in ST11 (E), and the incorporation of a highly conserved prophage into the genome of ST131 (B2). The tail structure of the prophage is evolutionarily related to R2-pyocin (a tailocin) from Pseudomonas aeruginosa PAO1. We hypothesize that this molecular machinery is highly likely to play an important role in protecting its own colonies; thus, contributing towards the rapid rise of pandemic E. coli ST131. CONCLUSIONS: This study has explored the optimized pangenome development in E. coli. We provide complete GF lists and the pangenome matrix as supplementary data for further studies. We identified biological characteristics of different E. coli subtypes, specifically for phylogroups B1, B2, and E. We found an operon-like genome region coding for a tailocin specific for ST131 strains. The latter is a potential killer weapon providing pandemic E. coli ST131 with an advantage in inter-bacterial competition and, suggestively, explains their dominance as human pathogen among E. coli strains

Fabrication, microstructure and mid-infrared luminescence of Er:(ScxY1-x)2O3 transparent ceramics

Compositionally “mixed” (yttria-scandia) sesquioxide transparent ceramics doped with erbium ions, ∼7 at.% Er:(ScxY1-x)2O3 (where x = 0–0.445) were fabricated by vacuum sintering at 1750 °C for 5 h using 1.7 mol% ZrO2 as a sintering additive. For this, nanopowders of the same composition obtained by laser ablation and sedimentation were used. The as-prepared nanoparticles (monoclinic sp. gr. C2/m) had a mean size of 20 nm and they were transformed into the stable cubic phase by calcination at 870–1150 °C. The ceramics were of single-phase nature (C-type bixbyite structure, sp. gr. Ia-3). For the (Er0.074Sc0.114Y0.812)2O3 ceramic, the lattice constant was a = 10.5067 Å, the mean grain size – 21.6 μm, the average content of pores – 4.2 ppm and the transmission at 1.1 μm - 81.9%. The X-ray diffraction and Raman studies of ceramics confirmed the existence of a solid-solution composition. With increasing the Sc3+ content in the ceramics, their lattice shrinked, the mean grain size increased and the thermal conductivity decreased from 6.14 to 3.66 Wm−1K−1 at room temperature. The “mixed” ceramics exhibited intense inhomogeneously broadened emission around 2.8 μm making them promising for mid-infrared lasers. © 2023Russian Foundation for Basic Research, РФФИ: 21-53-15014; Ministry of Education and Science of the Russian Federation, Minobrnauka: 075-15-2021-680, 075-15-2021-687, RF - 2296.61321X0029; Centre National de la Recherche Scientifique, CNRS: 00432The reported study was funded by RFBR (Russia) according to the research project No. 21-53-15014 and CNRS (France) according to the project IEA No. 00432. The thermal behaviors (TG-DTA) of the as-synthesized nanopowders were studied at the “Geoanalitik” shared research facilities of the IGG UB RAS. The re-equipment and comprehensive development of the “Geoanalitik” shared research facilities of the IGG UB RAS is financially supported by the grant of the Ministry of Science and Higher Education of the Russian Federation (Agreement No. 075-15-2021-680). The XRD, EDS and thermal properties of ceramics were studied using the equipment of the Center for Collective Use of the North-Caucasus Federal University financially supported by the Ministry of Education and Science of Russia, unique project identifier RF - 2296.61321X0029 (agreement No. 075-15-2021-687). R. M. wishing to thank Dr. A.N. Orlov (IEP UrB RAS) for the measurements of transmission spectra. R. M. also acknowledges the research funding from the Ministry of Science and Higher Education of the Russian Federation (Ural Federal University Program of Development within the Priority-2030 Program). P. L. also acknowledges the support from the “RELANCE” Chair of Excellence project funded by the Normandy Region.The reported study was funded by RFBR (Russia) according to the research project No. 21-53-15014 and CNRS (France) according to the project IEA No. 00432 . The thermal behaviors (TG-DTA) of the as-synthesized nanopowders were studied at the “Geoanalitik” shared research facilities of the IGG UB RAS. The re-equipment and comprehensive development of the “Geoanalitik” shared research facilities of the IGG UB RAS is financially supported by the grant of the Ministry of Science and Higher Education of the Russian Federation (Agreement No. 075-15-2021-680 ). The XRD, EDS and thermal properties of ceramics were studied using the equipment of the Center for Collective Use of the North-Caucasus Federal University financially supported by the Ministry of Education and Science of Russia, unique project identifier RF - 2296.61321X0029 (agreement No. 075-15-2021-687 ). R. M. wishing to thank Dr. A.N. Orlov (IEP UrB RAS) for the measurements of transmission spectra. R. M. also acknowledges the research funding from the Ministry of Science and Higher Education of the Russian Federation ( Ural Federal University Program of Development within the Priority-2030 Program ). P. L. also acknowledges the support from the “RELANCE” Chair of Excellence project funded by the Normandy Region

Conserved sequence motifs in human TMTC1, TMTC2, TMTC3, and TMTC4, new O-mannosyltransferases from the GT-C/PMT clan, are rationalized as ligand binding sites

Background: The human proteins TMTC1, TMTC2, TMTC3 and TMTC4 have been experimentally shown to be components of a new O-mannosylation pathway. Their own mannosyl-transferase activity has been suspected but their actual enzymatic potential has not been demonstrated yet. So far, sequence analysis of TMTCs has been compromised by evolutionary sequence divergence within their membrane-embedded N-terminal region, sequence inaccuracies in the protein databases and the difficulty to interpret the large functional variety of known homologous proteins (mostly sugar transferases and some with known 3D structure). Results: Evolutionary conserved molecular function among TMTCs is only possible with conserved membrane topology within their membrane-embedded N-terminal regions leading to the placement of homologous long intermittent loops at the same membrane side. Using this criterion, we demonstrate that all TMTCs have 11 transmembrane regions. The sequence segment homologous to Pfam model DUF1736 is actually just a loop between TM7 and TM8 that is located in the ER lumen and that contains a small hydrophobic, but not membrane-embedded helix. Not only do the membrane-embedded N-terminal regions of TMTCs share a common fold and 3D structural similarity with subgroups of GT-C sugar transferases. The conservation of residues critical for catalysis, for binding of a divalent metal ion and of the phosphate group of a lipid-linked sugar moiety throughout enzymatically and structurally well-studied GT-Cs and sequences of TMTCs indicates that TMTCs are actually sugar-transferring enzymes. We present credible 3D structural models of all four TMTCs (derived from their closest known homologues 5ezm/5f15) and find observed conserved sequence motifs rationalized as binding sites for a metal ion and for a dolichyl-phosphate-mannose moiety. Conclusions: With the results from both careful sequence analysis and structural modelling, we can conclusively say that the TMTCs are enzymatically active sugar transferases belonging to the GT-C/PMT superfamily. The DUF1736 segment, the loop between TM7 and TM8, is critical for catalysis and lipid-linked sugar moiety binding. Together with the available indirect experimental data, we conclude that the TMTCs are not only part of an O-mannosylation pathway in the endoplasmic reticulum of upper eukaryotes but, actually, they are the sought mannosyl-transferases.Agency for Science, Technology and Research (A*STAR)Published versionThis work has been supported by the Biomedical Research Council of the Agency for Science, Technology and Research (A*STAR). We thank Shazib Pervaiz (National University Singapore) for drawing our attention to the sequence-based function prediction of human TMTC2 in 2012.There was no dedicated funding for this project. The writing of this article benefitted from the shutdown of other activities during the COVID-19 lock-down. General financial support from A*STAR is gratefully acknowledged. QWT received an A*STAR Graduate Academy (AGA) scholarship (AUS) for her university studies. The internship of VS was supported by a SIPGA grant from AGA

Highly efficient lasing and thermal properties of Tm:Y2O3 and Tm:(Y,Sc)2O3 ceramics

We report on thermal, spectroscopic, and laser properties of transparent 5 at.% Tm 3+ -doped yttria and “mixed” yttria-scandia ceramics fabricated by vacuum sintering at 1750°C using nanoparticles produced by laser ablation. The solid-solution (Tm 0.05 Y 0.698 Sc 0.252 ) 2 O 3 ceramic features a broadband emission extending up to 2.3 µm (gain bandwidth, 167 nm) and high thermal conductivity of 4.48 W m −1 K −1 . A Tm:Y 2 O 3 ceramic laser generated 812 mW at 2.05 µm with a slope efficiency η of 70.2%. For the Tm:(Y,Sc) 2 O 3 ceramic, the output power was 523 mW at 2.09 µm with η = 44.7%. These results represent record-high slope efficiencies for any parent or “mixed” Tm 3+ -doped sesquioxide ceramics

Laser Ablation Synthesis and Characterization of Tb₂O₃ Nanoparticles for Magneto-Optical Ceramics

In this study, nano-sized individual Tb2O3 particles synthesized by the laser ablation method were extensively characterized and assessed as suitable precursors for the fabrication of transparent magneto-optical ceramics without requiring the introduction of grain growth inhibitors and stabilizing additives. The as-produced powder comprised 13 nm particles with a spherical shape and monoclinic crystal structure, whose full transformation into cubic phase was achieved after heating at 950 °C and 700 °C under vacuum and Ar gas, respectively. After subjecting the nanopowder compact to pre-sintering at 1350 °C, the microstructural features were investigated along with their correlation to the optical transmittance of Tb2O3 ceramic hot isostatically pressed (HIPed) for 2 h at 1450 °C under 200 MPa. The as-HIPed sample had a brownish color, with an optical transmittance of 65.3% at a wavelength of 1060 nm and an average grain size of 14 μm. The Verdet constant measured at wavelengths of 633 nm and 1060 nm was 471 rad T−1 m−1 and 142 rad T−1 m−1 to confirm a very high content of magneto-active Tb3+ ions. The obtained results indicate that laser ablation synthesis of nanoparticles followed by pre-sintering and HIP is a promising approach for the manufacture of magneto-optical Tb2O3 ceramics without specific sintering aids

Laser Ablation Synthesis and Characterization of Tb2O3 Nanoparticles for Magneto-Optical Ceramics

In this study, nano-sized individual Tb2O3 particles synthesized by the laser ablation method were extensively characterized and assessed as suitable precursors for the fabrication of transparent magneto-optical ceramics without requiring the introduction of grain growth inhibitors and stabilizing additives. The as-produced powder comprised 13 nm particles with a spherical shape and monoclinic crystal structure, whose full transformation into cubic phase was achieved after heating at 950 °C and 700 °C under vacuum and Ar gas, respectively. After subjecting the nanopowder compact to pre-sintering at 1350 °C, the microstructural features were investigated along with their correlation to the optical transmittance of Tb2O3 ceramic hot isostatically pressed (HIPed) for 2 h at 1450 °C under 200 MPa. The as-HIPed sample had a brownish color, with an optical transmittance of 65.3% at a wavelength of 1060 nm and an average grain size of 14 μm. The Verdet constant measured at wavelengths of 633 nm and 1060 nm was 471 rad T−1 m−1 and 142 rad T−1 m−1 to confirm a very high content of magneto-active Tb3+ ions. The obtained results indicate that laser ablation synthesis of nanoparticles followed by pre-sintering and HIP is a promising approach for the manufacture of magneto-optical Tb2O3 ceramics without specific sintering aids