230 research outputs found
Synthesis of phase-pure highly-doped MAX-phase (Cr1-xMnx)2AlC
No full textMn doped (Cr1-xMnx)2AlC compounds constitute a family of MAX-phases of great interest due to the possibility of tuning the magnetic properties they possess. Their synthesis, however, is not an easy task. Two main issues make its preparation difficult. First is the strong tendency secondary phases have to segregate when manganese is added to the parent compound and, secondly, the resulting doping level which remains relatively low due to the poor incorporation of Mn atoms into the MAX-phase hexagonal structure [Cr2AlC-type]. In the present work the highest dopant concentration so far reported for bulk materials of 18.3 at.% Mn has been obtained through the exploitation of the arc-melting technique. At the same time, the use of the Cr3C2, as a precursor from the initial stage of the synthesis procedure, led to the preservation of the phase content in the Mn-doped samples. Finally, chemical post-treatment in acid solutions (HF, HCl) proved to be effective and helpful to dissolve the remaining secondary intermetallic phases; the final material resulting in a pure MAX-phase powder (>99 vol%). However, the doping level reached seems to be the limit for the arc fusion technique used; additional manganese no longer dissolves into the MAX-phase structure but tends to form some new Mn-based secondary phases, such as the perovskite Mn3AlC and the carbide MnC2. After the chemical etching, pure MAX-phase powders can be compacted into bulk using spark plasma sintering technique. However, while this method is useful for the non-doped Cr2AlC, it needs further optimization for (Cr1-xMnx)2AlC as it leads to a partial decomposition of Mn-containing MAX-phase
Highly Textured FeCo Thin Films Deposited by Low Temperature Pulsed Laser Deposition
No full textThe effect of the deposition temperature (Tdep) on the crystallographic orientation of pulsed laser-deposited FeCo/MgO(100) thin film was determined by means of X-ray reflectivity and high resolution trasmission electron microscopy analysis and was correlated with the magnetic anisotropy properties measured by angle dependent hysteresis loops. Highly textured films with a bcc structure and very smooth surface were obtained even at room temperature, the film being [100] and [110] oriented, at Tdep = 25 °C and 150 °C, respectively. The cubic symmetry is reflected in the angular dependence of remanent magnetization, showing a 4-fold character, whose in-plane distribution is consistent with the different crystallographic orientations of the films. The high structural quality, even at room temperature, is reflected in a high value of the saturation magnetization and low coercivity, matching the requirements for technological applications
Metabolic and Bactericidal Effects of Targeted Suppression of NadD and NadE Enzymes in Mycobacteria
No full textMycobacterium tuberculosis remains a major cause of death due to the lack of treatment accessibility, HIV coinfection, and drug resistance. Development of new drugs targeting previously unexplored pathways is essential to shorten treatment time and eliminate persistent M. tuberculosis. A promising biochemical pathway which may be targeted to kill both replicating and nonreplicating M. tuberculosis is the biosynthesis of NAD(H), an essential cofactor in multiple reactions crucial for respiration, redox balance, and biosynthesis of major building blocks. NaMN adenylyltransferase (NadD) and NAD synthetase (NadE), the key enzymes of NAD biosynthesis, were selected as promising candidate drug targets for M. tuberculosis. Here we report for the first time kinetic characterization of the recombinant purified NadD enzyme, setting the stage for its structural analysis and inhibitor development. A protein knockdown approach was applied to validate bothNadD and NadE as target enzymes. Induced degradation of either target enzyme showed a strong bactericidal effect which coincided with anticipated changes in relative levels of NaMN and NaAD intermediates (substrates of NadD and NadE, respectively) and ultimate depletion of the NAD(H) pool. A metabolic catastrophe predicted as a likely result of NAD(H) deprivation of cellular metabolism was confirmed by 13C biosynthetic labeling followed by gas chromatography-mass spectrometry (GC-MS) analysis. A sharp suppression of metabolic flux was observed in multiple NAD(P)(H)-dependent pathways, including synthesis of many amino acids (serine, proline, aromatic amino acids) and fatty acids. Overall, these results provide strong validation of the essential NAD biosynthetic enzymes, NadD and NadE, as antimycobacterial drug target
From precursor to 3D print: Transformation of PVDF-CoFe2O4composite in fabrication process
No full textThis study explores the influence of the molecular weight and phase composition of polyvinylidene fluoride (PVDF) precursors on the structural, mechanical, and magnetoelectric properties of PVDF/cobalt ferrite (PVDF/CFO) composites fabricated by fused deposition modeling (FDM). It was shown that the composite PVDF/CFO printed from a precursor with a lower molecular weight contains a higher content of the electroactive phase, which eventually leads to a higher magnitude of the magnetoelectric coefficient. The lower molecular weight is advantageous due to its reduced melting point which simplifies the printing process. Despite the higher magnitude of the Young’s modulus of the composite PVDF/CFO printed from low molecular weight PVDF, the filaments remain suitable for additive manufacturing. Overall, the results demonstrate that precursor selection is a key parameter for optimizing the functionality and printability of FDM-printed magnetoelectric composites
Mycobacterium tuberculosis pyrazinamide resistance determinants: a multicenter study
No full textPyrazinamide (PZA) is a prodrug that is converted to pyrazinoic acid by the enzyme pyrazinamidase, encoded by the pncA gene in Mycobacterium tuberculosis. Molecular identification of mutations in pncA offers the potential for rapid detection of pyrazinamide resistance (PZAr). However, the genetic variants are highly variable and scattered over the full length of pncA, complicating the development of a molecular test. We performed a large multicenter study assessing pncA sequence variations in 1,950 clinical isolates, including 1,142 multidrug-resistant (MDR) strains and 483 fully susceptible strains. The results of pncA sequencing were correlated with phenotype, enzymatic activity, and structural and phylogenetic data. We identified 280 genetic variants which were divided into four classes: (i) very high confidence resistance mutations that were found only in PZAr strains (85%), (ii) high-confidence resistance mutations found in more than 70% of PZAr strains, (iii) mutations with an unclear role found in less than 70% of PZAr strains, and (iv) mutations not associated with phenotypic resistance (10%). Any future molecular diagnostic assay should be able to target and identify at least the very high and high-confidence genetic variant markers of PZAr; the diagnostic accuracy of such an assay would be in the range of 89.5 to 98.8%.IMPORTANCE: Conventional phenotypic testing for pyrazinamide resistance in Mycobacterium tuberculosis is technically challenging and often unreliable. The development of a molecular assay for detecting pyrazinamide resistance would be a breakthrough, directly overcoming both the limitations of conventional testing and its related biosafety issues. Although the main mechanism of pyrazinamide resistance involves mutations inactivating the pncA enzyme, the highly diverse genetic variants scattered over the full length of the pncA gene and the lack of a reliable phenotypic gold standard hamper the development of molecular diagnostic assays. By analyzing a large number of strains collected worldwide, we have classified the different genetic variants based on their predictive value for resistance which should lead to more rapid diagnostic tests. This would assist clinicians in improving treatment regimens for patients
Transformation of Dry Steppe Soils under Long Term Agrogenic Impacts in the Area of Ancient Olbia
Get PDFThe results of the study of dark chestnut soils (Kastanozems) differing in the time and intensity of their agricultural use and in the duration of the fallow stage are analyzed. Soil sequences differing in the char acter of their agrogenic changes were studied in the rural area of ancient Olbia with a centuries long history of diverse economic activities, including crop growin
Transformation of Dry Steppe Soils under Long Term Agrogenic Impacts in the Area of Ancient Olbia
No full textThe results of the study of dark chestnut soils (Kastanozems) differing in the time and intensity of their agricultural use and in the duration of the fallow stage are analyzed. Soil sequences differing in the char acter of their agrogenic changes were studied in the rural area of ancient Olbia with a centuries long history of diverse economic activities, including crop growin
Systematization of Factors Influencing Innovative Development of an Enterprise in the Modern Economic Environment
Get PDFScientific aspects of the development of the concept “innovation” are considered. Works of foreign and Ukrainian scientists, namely, C. McConnell, S. Brue, Ph. Kotler, B. Rayzberg, P. Lemerl, S. Illiashenko, P. Mykytiuk, and others, are analyzed. The researchers associate innovative development of an enterprise with a constant search for innovations and their implementation to provide a possibility for more effective enterprise management. Based on the existing scientific approaches to the concept “innovation”, the authors propose a definition of the term “innovation” with consideration for the specificity of seaports. It should be noted that innovative development is influenced by numerous factors that either contribute to the development of innovations or hinder their implementation. After analyzing works of researchers engaged in studying factors that affect innovative activities at different economic levels, namely: S. Illiashenko, L. Goncharenko, Yu. Arutyunov, M. Rusinko, V. Koyuda, I. Sheiko, I. Rodionova, and others, the authors identified, using the main classification criteria, and proposed the factors influencing performance indicators of enterprises, determined their nature and strength of influence to ensure efficiency of innovative development of enterprises in the modern economic environment
СТАТИСТИЧЕСКИЙ АНАЛИЗ И МОДЕЛИРОВАНИЕ ДИНАМИКИ УДОВЛЕТВОРЕННОСТИ ЖИЗНЬЮ В РОССИИ: ВОЗРАСТНОЙ АСПЕКТ
Get PDFThe author examines life satisfaction of Russian citizens and identifies its main trends. Life satisfaction is an important indicator of life quality in each country. At the same time, modern studies have shown that age-life satisfaction profiles in developed countries have U-shaped forms. The data of the Russia Longitudinal Monitoring Survey - Higher School of Economics (RLMS-HSE) from age perspectives for the period of 1994-2013 were analyzed. Russian data indicate that the level of life satisfaction decreases with older ages: young respondents are happier, while aged people are less satisfied with their lives. Dynamics of life satisfaction level during 1994-2013 had a positive trend from age perspectives: respondents in all age groups had become more satisfied with their lives by 2013. On the basis of ARIMA-models for life satisfaction the forecast until 2019 has been simulated. The results demonstrate that life satisfaction gap will remain in different age groups. Young population (under 20 years) will be the happiest in Russia and the highest rates of life dissatisfaction will be observed in the oldest age group (over 60 years). Note also that a gender gap in life satisfaction remains in the older age group (over 60 years). In the first place, this is caused by feminization of the older population
Hercostomus exarticulatoides Stackelberg 1949
No full text<i>Hercostomus exarticulatoides</i> Stackelberg, 1949 <p>(Figs 16–23)</p> <p> <i>Hercostomus exarticulatoides</i> Stackelberg, 1949: 680.</p> <p> <i>Hercostomus exarticulatus</i>: Negrobov, Rodionova, 2004: 202 (misidentification).</p> <p> <b>Material.</b> Lecotype, ♂ (ZIN), labeled: Rakhaty, Gissar Valley, Tajikistan, 6.08.1943, Stackelberg (in Russian), “ Syntypus <i>Hercostomus exarticulatoides</i> Stackelberg, 1949 ”, “Lecotype <i>Hercostomus exarticulatoides</i> Stack., des. Grichanov, 2019”. Paralectotypes: 1♂, 1♀ (ZIN), same 1 st and 3 rd labels with collecting dates 6.08 (♂) and 5.08.1949. Lecotype is designated here according to the articles 61.1 and 74.7.3 of the International Code of Zoological Nomenclature [1999] to fix the current taxonomic concept and ensure consistent future interpretation.</p> <p> <b>Diagnosis.</b> Fore coxa and femora light yellow; hind tibia entirely yellow; hind tibia with sclerotized triangular dorsolateral apical projection; hypandrium with 2 pairs of arms concealed, more or less straight, thin and curved at apex; outer hypandrial arm worm-like at apex; cercus yellow, dark at apex.</p> <p> <b>Notes.</b> Stackelberg [1949] provided two pictures (figs 11 and 15) for this species with different shape of male cercus. His picture (fig. 36) and description of hind leg is correct from lateral aspect, but being incorrect, if looking from other aspects. The black and thick transverse spine at base of hind tarsus is visible from only ventrolateral aspect. In fact, the sclerotized dorsolateral apical projection on the hind tibia looks like a regular triangle from lateral aspect, but resembling strongly curved spine from dorsolateral aspect. <i>Hercostomus exarticulatoides</i> was never recorded again after its description. However, Negrobov and Rodionova [2004] mentioned <i>H. exarticulatus</i> females (including one <i>H. exarticulatoides</i> topotype) from Tajikistan (Gissar Range) and Kyrgyzstan (Chatkal Range) that must be associated with <i>H. exarticulatoides</i>. The exact type locality of the species is unknown for us; we were not able to trace the geographical name “Rakhaty” within the borders of Tajikistan. Anyway, <i>H. exarticulatoides</i> types were certainly collected in one of gorges on southern slope of the Gissar Range between Tajik-Uzbek border and Kofarnihon River head (the distance is about 100 km), i.e., in the same area of the country where several other species were described by Stackelberg.</p> <p> <b>Distribution.</b> Type locality: Tajikistan, “Rakhaty, Gissar Valley” (originally published as “Rakhaty, Gissar Range, 1000–1200 m ”). Palaearctic: Kyrgyzstan, Tajikistan.</p>Published as part of <i>Grichanov, I. Ya., Nourti, M. & Kettani, K., 2020, The Hercostomus exarticulatus species group in the Palaearctic Region (Diptera: Dolichopodidae), pp. 27-34 in Caucasian Entomological Bulletin (Caucas. entomol. bull.) (Caucas. entomol. bull.) 16 (1)</i> on page 33, DOI: 10.23885/181433262020161-2734, <a href="http://zenodo.org/record/10124535">http://zenodo.org/record/10124535</a>
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