Orientation Of Structural Elements Research Articles

Structural and geochemical features of coal-bearing sediments and sources of rare element impurities in coals of the Rakovka depression, Primorsky Krai, Russia

There are known brown coal deposits in Primorsky Krai (Russian Federation), where coals contain rare elements (Ge, U, REE, etc.) up to industrial concentrations. One of the known metalliferous coals is the Rakovka coal-bearing depression, located on the southern edge of the Khanka (Prikhankaiskaya) Lowland, with an area of about 70 km2. Rare-metal granites with a developed weathering crust are spread in its basement and flanks. The structural conditions forming the depression were studied using measurements of orientations of structural elements (layering, contacts, veins, and dikes) with regard to kinematic conditions of faulting. The coal and host rocks were sampled in sections in the cross strike of the coal seam. Granites and dikes cutting them were sampled by separate rock chip samples. The chemical composition and element content were determined for all samples. It was found that the adjacent rocks played a major role in the formation of the Rakovka rare-metal-coal deposit. The rare-elements enrichment is not associated with active tectonics, faults, and hydrothermal sources, as was previously assumed. Rather, it was caused by the hydrogenic and clastogenic removal of these metals from the weathering crust of granites of the depression's flanks and argillated basite dikes cutting the granites. The hydrogenic nature of the anomalous accumulation of U in sorbed form on organic matter of coals is confirmed by the predominant enrichment of low-ash beds. Rare earth elements entered coal seams both in mineral and dissolved forms. A model of REE and uranium input into the coal-bearing sediments of the Rakovka depression was proposed.

Влияние направления проката АМг5 на микроструктуру и свойства сварных соединений, полученных сваркой трением с перемешиванием

Introduction. Heat emission and plastic deformation during friction stir welding (FSW) cause profound changes in the microstructure and structural properties of weld joints. The grain size, crystallographic texture evolution and second-phase precipitate are the most important microstructural changes during welding of aluminum alloys, which largely influence the strength properties of weld joints. In addition to process-dependent parameters (instrument sump force, its rotation frequency, and travel rate) of the FSW process, a significant factor, determining the properties of the obtained weld joints, is also a mutual orientation of structural elements of the weld material and the direction of the instruments impact on the material during welding. In this regard, the purpose of the work is to analyze the combined influence of the direction of the initial rolling and the instrument pressure during FSW on the structure and properties of weld joints from the AA5056 aluminum alloy. Methods. Research methods are mechanical tests for statistical tension, microhardness as well as metallographic analysis of the structure of welded joints. Results and discussion. As a result, it is established that at low values of the axial force on the instrument (7 kN), defects such as the joint line and voids are observed in welded joints both rolling and transverse directions. When the load increases from 8 kN to 12 kN, defect-free weld joints with enhanced mechanical properties form. It is determined that the rolling direction of AA5056 during FSW does not influence the structure and tensile strength of the weld joints, but it influences the relative elongation and microhardness. It is shown that in the stir zone of the weld joint, obtained by FSW in the transverse direction of AA5056 flats, the relative elongation is 1.3-2 times greater, and the microhardness is by 4-10% greater than that in the stir zone of weld joints, obtained by FSW in the rolling direction of AA5056 flats.

High-temperature polymetamorphism in the central zone of the Limpopo granulite complex (South Africa): Structural and petrological evidence

The problem of confirmation of HT (hightemperature) metamorphism in Precambrian granulite complexes appeared rather recently. The central zone ofthe Limpopo complex (Fig. 1) is the best polygon forits solution. The results of our investigations demonstrate that gneiss, which underwent deformations (D)and granulite metamorphism (M) in the Neoarchean(D2/M2), was subjected to one more stage of HT metamorphism, but in the Paleoproterozoic (D3/M3).Started from isobaric heating (IH) of rocks in the middle crust, the event D3/M3 was finished with theirdecompression cooling (DC), i.e., exhumation ofrocks from the middle part of the continental crusttowards the surface [2, 4–6, 10]. This evidence wasbased on studies of circular structures, namely sheathfolds. This report contains the first data on analogousphenomena within the shear zones (shift deformations) on a regional scale. The absence of signs of earlier events was suggested in them, but it turned out tobe completely wrong.We studied the regional system of Voorburg–Tshipise shear zones (Fig. 1) where found an outcrop inwhich the structural elements D2/M2 are overprintedby younger D3/M3 structures principally differentfrom the first by foliation and lineation. This is clearlyobserved not only on the projection stereogram forthese elements, but directly in the field as well (Fig. 2).It is evident that overprinted deformations should bealso reflected on paragenetic relationships, becausethey are ductile (deep). For this purpose, we collectedtwo samples on the outcrop with two orientations ofstructural elements. One of them, RB66 (D2/M2),was taken from layers with a relatively steep dip of foliation and southwestern lineation strike reflecting themotion of the material towards the surface with anangle of ~42°. The second sample, RB55 (D3/M3),was taken from the layer of moderate dip (~12 °). Bothsamples have the same mineral composition: garnet(

Classification of trabeculae into three‐dimensional rodlike and platelike structures via local inertial anisotropy

Trabecular bone microarchitecture is a significant determinant of the bone's mechanical properties and is thus of major clinical relevance in predicting fracture risk. The three-dimensional nature of trabecular bone is characterized by parameters describing scale, topology, and orientation of structural elements. However, none of the current methods calculates all three types of parameters simultaneously and in three dimensions. Here the authors present a method that produces a continuous classification of voxels as belonging to platelike or rodlike structures that determines their orientation and estimates their thickness. The method, dubbed local inertial anisotropy (LIA), treats the image as a distribution of mass density and the orientation of trabeculae is determined from a locally calculated tensor of inertia at each voxel. The orientation entropies of rods and plates are introduced, which can provide new information about microarchitecture not captured by existing parameters. The robustness of the method to noise corruption, resolution reduction, and image rotation is demonstrated. Further, the method is compared with established three-dimensional parameters including the structure-model index and topological surface-to-curve ratio. Finally, the method is applied to data acquired in a previous translational pilot study showing that the trabecular bone of untreated hypogonadal men is less platelike than that of their eugonadal peers.

A structural analysis of a metamorphic fold–thrust belt, northeast Gagnon terrane, Grenville Province

Northeast Gagnon terrane is located within the Parautochthonous Belt of the Grenville Orogen, near the projected intersection of the front zones of the Grenville and New Quebec orogens. The area consists principally of supracrustal units of the Early Proterozoic Knob Lake Group, and a newly recognized unit, the Equus Lake formation. Both are intruded by the Middle Proterozoic Shabogamo gabbro. Structural elements in the rocks record evidence of a polyorogenic history that is attributed to both the ca. 1800 Ma Hudsonian and the ca. 1000 Ma Grenvillian orogenies. This paper is concerned with the latter.Grenvillian deformation resulted in the formation of a relatively deep-level fold–thrust belt. Three thrust sheets can be defined on the basis of basal thrusts, variations in morphology and orientation of structural elements, and internal thrust sheet geometry. The polydeformational style of the area, rotation of fold axes into subparallelism with the tectonic transport direction, and internal imbrication lead to a complex internal thrust sheet geometry. Thrusting has produced and inverted the metamorphic gradient, with lower greenschist facies in the basal thrust sheet and upper greenschist facies in the upper thrust sheet.Documentation of the northeastern margin of Gagnon terrane as a north- to northwest-directed metamorphic fold–thrust belt corroborates similar interpretations for Gagnon terrane from elsewhere along the Grenville Front and is in accord with the models of the Grenville Province as a collisional orogen. Furthermore, it is suggested that northeast Gagnon terrane is an exhumed, internal, ductile part of a fold–thrust belt.

Understanding structural relationships proteins of unsolved three‐dimensional structure

The locations of functionally important sequences and general structural motifs have been assigned to Ile-tRNA synthetase. However, a function has not been established for some segments of the protein (e.g., CP1). The method of structural modeling described here cannot establish the details of a 3 A crystal structure, and, in contrast to a crystal structure, the precision of the model varies according to the extent of a sequence similarity or the functional importance of a region. In Ile-tRNA synthetase, the signature sequence and the flanking regions are likely to be similar in structure to the proteins on which the model is based. For other regions, it may be possible to build a three-dimensional model by connecting well defined regions and refining the positions of the connecting elements by energy minimization. Structural modelling of this kind must be done cautiously, because the order and orientation of the elements of a structural motif can change in subtle ways. In the case of Tyr-tRNA synthetase, the beta-strand nearest the N-terminus is the outermost strand of the nucleotide binding fold; in Met-tRNA synthetase, the same strand is innermost. Furthermore, the orientation of this strand may be antiparallel (Tyr-tRNA synthetase) or parallel (Met-tRNA synthetase). Because multiple structures that differ in their orientations of structural elements are possible, the structural analogies between proteins should not be naively extrapolated without independent experimental support. As described above, some regions of proteins tolerate internal deletions and insertions. This provides further experimental support for the practice of allowing for gaps in computer-generated sequence alignments. Nevertheless, because some regions are more tolerant of insertions and deletions than others, the structural and functional significance of a region of broken alignment must be assessed carefully. All gaps in sequence alignments cannot be treated equally, and each must be evaluated within its own context. In the synthetases of known structure, structural analogy can be used to identify important functional elements. For example, the amino acid binding site of Met-tRNA synthetase might be formed, at least in part, by a peptide that encompasses Ala50; this amino acid aligns with Gly94 of the Ile-tRNA synthetase. This is an example in which results on a protein of unknown structure (Ile-tRNA synthetases) can lead to identification of a potential substrate binding site in a protein of known structure (Met-tRNA synthetase).

All-union scientific and technological conference on technology and automation of the heat treatmentof metals

1. After heat treatment of 37KhN3 and 40Kh1NVA steel specimens, a stable tensile strength of 245–255 kg/ mm2, with a reduction in area of 25 to 30% is obtained. 2. The good mechanical properties of heat-treated specimens are also accounted for by high dispersion and some orientation of structural elements. 3. A heat treatment at which deformation occurs above c3 is better since it ensures an optimal combination of strength and plasticity. 4. The use of a magnetic field during the transformation of austenite to martensite produces homogenous mechanical properties and slightly improves strength characteristics.