127 research outputs found
Knowledge Annotation within Research Data Management System for Oxygen-Free Production Technologies
The comprehensive implementation of digital technologies in product manufacturing leads to changes in engineering processes and requires new approaches to data management. An important role belongs to the processes of organizing the collection, storage and reuse of research data obtained and used in the process of product, system or technology development, taking into account the FAIR data principles. This article describes a Research Data Management System for the organization of documentation and measurement requests in the research and development of new oxygen-free production technologies
Copper valence, structural separation and lattice dynamics in tennantite (fahlore): NMR, NQR and SQUID studies
Electronic and magnetic properties of tennantite subfamily of tetrahedrite-group minerals have been studied by copper nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) and SQUID magnetometry methods. The temperature dependences of copper NQR frequencies and line-width, nuclear spin-lattice relaxation rate T1 -1 and nuclear spin-echo decay rate T2 -1 in tennantite samples in the temperature range 4.2-210 K is evidence of the presence of field fluctuations caused by electronic spins hopping between copper CuS3 positions via S2 bridging atom. The analysis of copper NQR data at low temperatures points to the magnetic phase transition near 65 K. The magnetic susceptibility in the range 2-300 K shows a Curie-Weiss behavior, which is mainly determined by Fe2+ paramagnetic substituting ions. © Springer-Verlag 2007
Contribution of copper Nqr spectroscopy to the geological studies of complex sulfides and oxides
Many energy-related areas such as nuclear waste isolation, continental drilling, fossil fuel recovery, and geothermal energy are directly associated with an in-depth understanding of the earth sciences. Of particular interest is the development of analytical techniques which can augment existing ones in developing a better understanding of mineralogy. Presently, available instrumental techniques for studying mineralogical problems such as x-ray, electron and neutron diffraction, nuclear gamma resonance (NGR or Mössbauer spectroscopy), electron microscopy and transmission electron microscopy have inherent limitations. These manifest themselves in being unable to characterize mineral samples fully, especially if they are polycrystalline. Nuclear Quadrupole Resonance (NQR) spectroscopy offers the potential for being able to obtain accurate high resolution spectra. These can then be interpreted to give structural information which can be related to local electronic structure, atomic arrangement, order/disorder phenomena, and crystal phase transformation. In addition, internal dynamics (ionic diffusion, metallic behavior, rotations, and so on) in the solid state can be studied. Furthermore, since NQR data are sensitive to changes in temperature and pressure, there is the possibility of obtaining stress/strain information. As applied to mineralogical and geological problems, NQR can also provide additional information, for example: chemical activity of minerals (genetic and technological aspects) at different hydrothermal conditions, the studies of impurity configurations in ore minerals and their distribution in crystal lattice, and other. This chapter highlights some NQR studies in copper sulfides, which demonstrate how NQR method can contribute to our understanding of geological problems. Examples are taken primarily from author's investigate groups. © 2009 Springer Science+Business Media B.V
Phase transition and anomalous electronic behavior in the layered superconductor CuS probed by NQR
Nuclear quadrupole resonance (NQR) on copper nuclei has been applied for studies of the electronic properties of quasi-two-dimensional (2D) low-temperature superconductor CuS (covellite) in the temperature range of 1.47-290 K. Two NQR signals corresponding to two structural nonequivalent sites of copper, Cu(1) and Cu(2), have been found. The temperature dependences of copper quadrupole frequencies, linewidths, and spin-lattice relaxation rates altogether demonstrate the structural phase transition near 55 K, which is accompanied by transformations of the electronic spectrum not typical for simple metals. The analysis of NQR results and their comparison with literature data show that the valence of copper ions at both sites is intermediate between monovalent and divalent states with the dominance of the former. It has been found that there is a strong hybridization of the Cu(1) and Cu(2) conduction bands at low temperatures, indicating that the charge delocalization between these ions takes place even in 2D regime. On the basis of our data, the occurrence of an energy gap, charge fluctuations, and charge-density waves, as well as the nature of the phase transition in CuS, are discussed. It is concluded that some physical properties of CuS are similar to those of high-temperature superconductors in the normal state. © 2009 The American Physical Society
Micron- to nano-scale intergrowths among members of the cuprobismutite series and paderaite: HRTEM and microanalytical evidence
Copyright © 2004 The Mineralogical SocietyCoherent intergrowths, at the lattice scale, between cuprobismutite (N = 2) and structurally related padraite along both major axes (15 Åand 17 Årepeats) of the two minerals are reported within skarn from Ocna de Fier, Romania. The structural subunit, DTD, 3 layers of padraite, is involved at interfaces of the two minerals along the 15 Årepeat, as well as in transposition of 1 padraite unit to 2 cuprobismutite units along the 17 Årepeat in slip defects. Lattice images obtained by HRTEM across intervals of 200 -400 nm show short- to long-range stacking sequences of cuprobismutite and padraite ribbons. Such nanoscale slabs mimic µm-scale intergrowths observed in back-scattered electron images at three orders of magnitude greater. These slabs are compositionally equivalent to intermediaries in the cuprobismutite-padraite range encountered during microanalysis. Hodrushite (N = 1.5) is identified in the µm-scale intergrowths, but its absence in the lattice images indicates that, in this case, formation of polysomes between structurally related phases is favoured instead of stacking disorder among cuprobismutite homologues. The tendency for short-range ordering and semi-periodic occurrence of polysomes suggests they are the result of an oscillatory chemical signal with periodicity varying from one to three repeats of 15 Å, rather than simple 'accidents' or irregular structural defects. Lead distribution along the polysomes is modelled as an output signal modulated by the periodicity of stacking sequences, with Pb carried within the D units of padraite. This type of modulator acts as a patterning operator activated by chemical waves with amplitudes that encompass the chemical difference between the minerals. Conversion of the padraite structural subunit DTD to the C unit of cuprobismutite, conserving interval width, emphasizes that polysomatic modularity also assists interference of chemical signals with opposite amplitudes. Observed coarsening of lattice-scale intergrowths up to the µm-scale implies coupling between diffusion-controlled structural modulation, and rhythmic precipitation at the skarn front during crystallization.C.L. Ciobanu, A. Pring and N.J. Coo
NQR/NMR and Mössbauer spectroscopy of sulfides: Potential and versatility
Nuclear quadrupole resonance (NQR), nuclear magnetic resonance (NMR) and nuclear gamma-resonance (NGR or Mössbauer Effect) methods are generally described as highly sensitive tools in studies of local electronic structure and symmetry in solid-state materials. This is due to high informativity in electronic structure investigations, high resolution in phase-structural diagnostics (down to nano-scale), possibility to study polycrystalline and complex compounds, and to the non-destructive character of these methods. As applied to Earth sciences, both NQR/NMR and Mössbauer spectroscopy methods contribute to mineralogical material science and mineral physics. Another important aspect is the fact that these methods, as demonstrated recently, belong to unique techniques suitable for on-line bulk mineralogical analysis. This includes remotely operated sensors used with conveyor systems in mining/materials handling and similar applications where real-time data collection/processing provides significant commercial benefits. These developments open new pathways for NQR/NMR and Mössbauer spectroscopy applications. Notably, NQR/NMR and Mössbauer effects are observed primarily on different nuclei-probes but provide similar information about the local properties of materials (hyperfine fields, electric field gradients and relaxation effects). This makes NQR/NMR and Mössbauer methods mutually complementary despite their significant technical differences. This paper includes examples of recent applications of NQR, NMR and Mössbauer spectroscopic tools to studies of copper-, antimony- and iron-containing sulfides, demonstrating how these methods can contribute to an improved understanding of geochemical problems. © 2013 E. Schweizerbart'sche Verlagsbuchhandlung, D-70176 Stuttgart
Phase transition and anomalous electronic behavior in layered dichalcogenide CuS (covellite) probed by NQR
Nuclear quadrupole resonance (NQR) on copper nuclei has been applied for
studies of the electronic properties of quasi-two-dimensional low-temperature
superconductor CuS (covellite) in the temperature region between 1.47 and 290
K. Two NQR signals corresponding to two non-equivalent sites of copper in the
structure, Cu(1) and Cu(2), has been found. The temperature dependences of
copper quadrupole frequencies, line-widths and spin-lattice relaxation rates,
which so far had never been investigated so precisely for this material,
altogether demonstrate the structural phase transition near 55 K, which
accompanies transformations of electronic spectrum not typical for simple
metals. The analysis of NQR results and their comparison with literature data
show that the valence of copper ions at both sites is intermediate in character
between monovalent and divalent states with the dominant of the former. It has
been found that there is a strong hybridization of Cu(1) and Cu(2) conduction
bands at low temperatures, indicating that the charge delocalization between
these ions takes place even in 2D regime. Based on our data, the occurrence of
energy gap, charge fluctuations and charge-density waves, as well as the nature
of phase transition in CuS are discussed. It is concluded that some physical
properties of CuS are similar to those of high-temperature superconductors
(HTSC) in normal state.Comment: to be publishe
Генетическая дивергенция между дикорастущими популяциями рапса и культурными сортами Brassica napus L.
The study assessed the genetic diversity of commercial varieties and feral populations of oilseed rape (Brassica napus L.) grown in the Republic of Belarus according to the genotyping data of 7 microsatellite loci – Na12D08, Ol12D04-1, Ol12D04-2, Ra2A05, Na10H03, Na14H11, Ol11B05. The following parameters were calculated: the average number of alleles per locus, the effective number of alleles, the levels of expected and observed heterozygosity, % of polymorphic loci. The results indicate a greater genetic diversity in feral oilseed rape populations. According to the cluster analysis, one feral population fell into a cluster of commercial varieties and demonstrated similarities with the variety Atora, which indicates its recent wildness and the preservation of the genetic characteristics inherent in cultivated varieties. The variety Mercedes was clustered together with samples of feral populations, which may indicate its hybrid origin. An analysis of the structure of the genotype distribution in the Structure software showed the division into three clusters – commercial varieties, feral populations and samples of B. rapa. The established genetic divergence between feral populations and commercial varieties indicates that feral oilseed rape is able to maintain persistent populations inBelarus. In practice, this should be taken into account while assessing the environmental risk when transgenic rape is released into the environment. When cultivating transgenic rapeseed, special attention should be paid to measures to prevent the occurrence of its free-growing populations.Дана оценка генетического разнообразия сортов и дикорастущих популяций масличного рапса (Brassica napus L.), произрастающих на территории Республики Беларусь, по данным генотипирования 7 микросателлитных локусов – Na12D08, Ol12D04-1, Ol12D04-2, Ra2A05, Na10H03, Na14H11, Ol11B05. Рассчитаны среднее число аллелей на локус, эффективное число аллелей, уровни ожидаемой и наблюдаемой гетерозиготности, процент полиморфных локусов. Результаты свидетельствуют о большем генетическом разнообразии в дикорастущих популяциях рапса. По данным кластерного анализа, одна из девяти дикорастущих популяций кластеризовалась с культурными сортами и продемонстрировала генетическое сходство с сортом Атора, что свидетельствует о ее недавнем формировании и сохранении генетических характеристик, присущих культурным сортам. В противоположность этому сорт Мерседес кластеризовался вместе с образцами дикорастущих популяций, что может свидетельствовать о его гибридном происхождении и наличии в дикорастущих популяциях генотипов, которые являлись прародителями данного сорта. Анализ структуры распределения генотипов в программе Structure показал, что наиболее вероятно разделение исследуемой группы на три кластера – культурные сорта, дикорастущие популяции B. napus и образцы B. rapa. Установленная нами генетическая дивергенция между дикорастущими популяциями и сортами указывает на то, что дикорастущий масличный рапс способен формировать и поддерживать стабильные популяции в условиях Беларуси. На практике это следует учитывать при оценке экологического риска при высвобождении трансгенного рапса в окружающую среду. А при возделывании трансгенного рапса особое внимание необходимо уделять мерам по предотвращению возникновения его свободнорастущих популяций
РОЛЬ ГЕНОВ RLM И AVRLM В РЕАЛИЗАЦИИ СПЕЦИФИЧЕСКОЙ УСТОЙЧИВОСТИ К ФОМОЗУ У РАПСА
As part of the study, DNA markers for local races L. maculans were identified and found that the AvrLm4-7 sequence in the selected fungus population is specifically recognized by the resistance Rlm4 and Rlm7 genes. The SCAR marker BN204 was identified, which allows us to identify homozygous and heterozygous plants carrying the Rlm4 gene. The work collection, including 22 varieties and 39 hybrids of rape, was analyzed using the DNA marker BN204. PCR results allowed us to establish that the number of individual plants with the resistance Rlm4 gene was higher than the number of stable forms characterized by the infection of leaf explants with pathogen races carrying the AvrLm4-7 sequence. It is supposed that these individual plants contain the Rlm4 gene, but they lack the Rlm7 gene.В ходе исследования выявлены ДНК-маркеры к местным расам L. maculans и установлено, что в популяции отобранного гриба присутствует последовательность AvrLm4-7, которая специфично распознается генами устойчивости Rlm4 и Rlm7. Выявлен SCAR-маркер BN204, позволяющий идентифицировать гомозиготные и гетерозиготные растения, несущие ген Rlm4. С использованием ДНК-маркера BN204 была проанализирована рабочая коллекция, включающая 22 сорта и 39 сортообразцов рапса. Результаты ПЦР позволили установить, что количество индивидуальных растений с геном устойчивости Rlm4 было выше, чем количество устойчивых форм, охарактеризованных путем заражения листовых эксплантов расами патогена, несущими последовательность AvrLm4-7. Предполагается, что данные индивидуальные растения содержат ген Rlm4, однако у них отсутствует ген Rlm7.
Search for ultra-high energy photons through preshower effect with gamma-ray telescopes: Study of CTA-North efficiency
Indexación ScopusAs ultra-high energy photons (EeV and beyond) propagate from their sources of production to Earth, radiation-matter interactions can occur, leading to an effective screening of the incident flux. In this energy domain, photons can undergo e+/e− pair production when interacting with the surrounding geomagnetic field, which in turn can produce a cascade of electromagnetic particles called preshower. Such cascade can initiate air showers in the Earth's atmosphere that gamma-ray telescopes, such as the next-generation gamma-ray observatory Cherenkov Telescope Array, can detect through Cherenkov emission. In this paper, we study the feasibility of detecting such phenomenon using Monte-Carlo simulations of nearly horizontal air showers for the example of the La Palma site of the Cherenkov Telescope Array. We investigate the efficiency of multivariate analysis in correctly identifying preshower events initiated by 40 EeV photons and cosmic ray dominated background simulated in the energy range 10 TeV – 10 EeV. The effective areas for such kind of events are also investigated and event rate predictions related to different ultra-high energy photons production models are presented. While the expected number of preshowers from diffuse emission of UHE photons for 30 hours of observation is estimated around 3.3×10−5 based on the upper limits put by the Pierre Auger Observatory, this value is at the level of 2.7×10−4 (5.7×10−5) when considering the upper limits of the Pierre Auger Observatory (Telescope Array) on UHE photon point sources. However, UHE photon emission may undergo possible ”boosting” due to gamma-ray burst, increasing the expected number of preshower events up to 0.17 and yielding a minimum required flux of ~ 0.2 km−2yr−1 to obtain one preshower event, which is about a factor 10 higher than upper limits put by the Pierre Auger Observatory and Telescope Array (0.034 and 0.019 km−2yr−1, respectively). © 2020https://www-sciencedirect-com.recursosbiblioteca.unab.cl/science/article/pii/S092765052030061X?via%3Dihu
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