The possibility of creation of high-nitrogen steels and alloys with superequilibrium concentrations of nitrogen and principally novel and high properties by the method of gas thermobaric treatment ...(GTBT) in compressed molecular nitrogen is considered. The process of GTBT in compressed nitrogen is shown to be efficient for low-alloy structural steels, tool steels, steels with specific physical properties and hard alloys. It also shown that nitrogen layers with a thickness of about 2 mm can be formed on the surface of semiproducts from low-alloy steels in several hours. The technology is ecologically safe and economically efficient.
A possibility of improving protective characteristics of transmission lines by cascading of multiconductor modal filters (MFs) with different geometric configurations is studied. Three-conductor MFs ...based on an asymmetric coaxial structure and a microstrip line and four variants of cascade structures consisting of two and three sections of such MFs are considered. Simulation of the time response to an ultrashort pulse (USP) and parametric optimization are performed. Attenuation of USP by a factor of 27.4 is achieved.
Various strategies for producing lanthanide-containing luminescent sensors, which were used mainly in the studies of 2015–2021, are considered. The review is structured according to the types of ...sensor response and analyte nature. Particular attention is focused on the mechanisms of sensor response to a certain analyte.
Antigen recognition by T-cells is guided by the T-cell receptor (TCR) heterodimer formed by α and β chains. A huge diversity of TCR sequences should be maintained by the immune system in order to be ...able to mount an effective response towards foreign pathogens, so, due to cooperative binding of α and β chains to the pathogen, any constraints on chain pairing can have a profound effect on immune repertoire structure, diversity and antigen specificity. By integrating available structural data and paired chain sequencing results we were able to show that there are almost no constraints on pairing in TCRαβ complexes, allowing naive T-cell repertoire to reach the highest possible diversity. Additional analysis reveals that the specific choice of contacting amino acids can still have a profound effect on complex conformation. Moreover, antigen-driven selection can distort the uniform landscape of chain pairing, while small, yet significant, differences in the pairing can be attributed to various specialized T-cell subsets such as MAIT and iNKT T-cells, as well as other TCR sets specific to certain antigens.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•The activation methods to improve the activity, basicity and stability of CaO.•Calcium glyceroxide is formed during transesterification and acts as the active phase.•The activation with glycerol is ...more efficient for the increasing of the CaO activity.
The activation methods to improve the activity, basicity and stability of CaO as the catalyst for the transesterification of soybean oil have been investigated.
It was determined that calcium glyceroxide complex is formed during the transesterification and acts as the most active phase. Moreover, it was observed that the catalytic activity of spent calcium oxide after transesterification was significantly increased comparing to the fresh catalyst. Thus, activation with glycerol is more efficient technique for the increasing of the CaO transesterification activity compare to the traditional techniques such as thermal treatment and activation with methanol. The synthesized calcium glyceroxide catalyst showed the highest catalytic activity. Under the study conditions, with a methanol to oil molar ratio of 9:1 and a reaction temperature of 60°C 82.6% FAMEs yield was obtained within 120min with only 1.3wt.% (respect to the oil mass) of calcium glyceroxide. At same time, the FAMEs yield was only about 76.9% when CaO activated with methanol was used.
The present critical review reports the recent progress of the last 15 years in the selective epoxidation of vegetable oils and their derivatives, in particular unsaturated fatty acids (UFAs) and ...fatty acid methyl esters (FAMEs). Epoxidized vegetable oils (EVOs) have drawn much attention in recent years in the chemical industry since they are environmentally friendly, biodegradable, renewable, highly available and non-toxic. Four major types of catalysts are used to produce epoxidized fatty acid compounds: homogeneous, heterogeneous, polyoxometalates and lipases. EVOs are currently produced in industry by a homogeneous catalytic conventional epoxidation process, in which the unsaturated oils are converted with percarboxylic acids, such as peracetic or performic acid. However, this method suffers from several drawbacks such as (1) relatively low selectivity for epoxides due to oxirane ring opening, (2) corrosion problems caused by the strong acids in an oxidizing environment,
etc.
Thus, in view of the principles of green chemistry, the development of new catalytic systems for the selective epoxidation of vegetable oils and their derivatives is an actual task. Furthermore, in our opinion, epoxidized fatty acids and epoxidized fatty acid methyl esters can be a promising substitute for EVOs because the starting materials for their production have a lower viscosity and higher reactivity, which will significantly increase the productivity of the epoxidation process. In this work, we tried to determine the prospects of using the main catalytic methods in industry to obtain epoxidized fatty acid compounds.
The present critical review reports the recent progress of the last 15 years in the selective epoxidation of vegetable oils and their derivatives, in particular unsaturated fatty acids (UFAs) and fatty acid methyl esters (FAMEs).
Kizimen volcano in Kamchatka is well known as a source of highly heterogeneous poorly mingled magmas ranging from dacites to basaltic andesites. In 2010–2013, the volcano produced its first ...historical magmatic eruption with the deposition of 0.27 km
3
of block and ash pyroclastic flows accompanied by slow extrusion of a 200-m-thick, highly viscous (10
10
–10
11
Pa s) block lava flow with a volume of 0.3 km
3
. The total volume of erupted magma comprised approximately 0.4 km
3
DRE. We provide description of the eruption chronology, as well as the lithology and petrology of eruptive products. The erupted material is represented by banded dacite and high-silica andesite. The dacitic magma was formed during a long dormancy after the previous magmatic eruption several hundred years ago with mineral compositions indicating average pre-eruptive temperatures of ~ 810 °C, fO
2
of 0.9–1.6 log units above the nickel–nickel oxide (NNO) buffer and shallow crustal storage conditions at ~ 123 MPa. The silica-rich andesite represents a hybrid magma, which shows signs of recent thermal and compositional disequilibrium. We suggest that the hybrid magma started to form in 1963 when a swarm of deep earthquakes indicated an input of mafic magma from depth into the 6–11-km-deep silicic magma chamber. It took the following 46 years until the magma filling the chamber reached an eruptible state. Poor mingling of the two melts is attributed to its unusually high viscosity that could be associated with the pre-eruptive long-term leakage of volatiles from the chamber through a regional tectonic fault. Our investigations have shown that shallow magma chambers of dormant volcanoes demonstrating strong persistent fumarolic activity can contain highly viscous, degassed magma of evolved composition. Reactivation of such magma chambers by injection of basic magma takes a long time (several decades). Thus, eruption forecasts at such volcanoes should include a possibility of long time lag between a swarm of deep earthquakes (indicating the recharge of basic magma from depth) and the following swarm of shallow earthquakes (indicating final ascent of the hybrid magma towards the surface). Due to the high viscosity of the magma, the shallow swarm can last for more than a year. The forthcoming eruption can be of moderate to low explosivity and include extrusion of viscous lava flows and domes composed of poorly mingled magmas of contrasting compositions.
Three novel lanthanide complexes with the ligand 4,4-difluoro-1-(1,5-dimethyl-1H-pyrazol-4-yl)butane-1,3-dione (HL), namely LnL3(H2O)2, Ln = Eu, Gd and Tb, were synthesized, and, according to ...single-crystal X-ray diffraction, are isostructural. The photoluminescent properties of these compounds, as well as of three series of mixed metal complexes EuxTb1-xL3(H2O)2 (EuxTb1-xL3), EuxGd1-xL3(H2O)2 (EuxGd1-xL3), and GdxTb1-xL3(H2O)2 (GdxTb1-xL3), were studied. The EuxTb1-xL3 complexes exhibit the simultaneous emission of both Eu3+ and Tb3+ ions, and the luminescence color rapidly changes from green to red upon introducing even a small fraction of Eu3+. A detailed analysis of the luminescence decay made it possible to determine the observed radiative lifetimes of Tb3+ and Eu3+ and estimate the rate of excitation energy transfer between these ions. For this task, a simple approximation function was proposed. The values of the energy transfer rates determined independently from the luminescence decays of terbium(III) and europium(III) ions show a good correlation.
Abstract
The work presents the results of simulation and optimization of multiconductor modal filters with a circular cross section. Four 2–5 conductor structures with a circular cross-section were ...considered. Optimization was performed according to the amplitude and time criteria. As a result, a complete decomposition of the exciting interference signal was achieved in all structures with a maximum attenuation of 4.18 times.
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