Optical properties of biological coenzyme FAD in an aqueous solution have been studied. Two fluorescence lifetimes, a rotational diffusion time, and an anisotropy parameter have been determined from ...experiments by recording the decay of polarized fluorescence excited by picosecond laser pulses. The results obtained are discussed and compared with the results of other authors.
The study results of the hydropneumatic impact devices striker movement impact on the energy performance during the operating stroke are presented. The energy parameters of the hydropneumatic impact ...units include power and single impact energy. The mathematical model of the hydropneumatic impact unit operating process is briefly described. The idle stroke, deceleration, operating stroke of the hydropneumatic impact unit striker are characterized. The software for conducting the hydropneumatic impact unit study is developed. The impact devices energy performance depends on the striker velocity at the time of impact, as well as on the striker mass and stroke. Gas pressure in the pneumatic accumulator also influences the energy performance. The striker velocity and single impact energy graphic dependences on the striker stroke and mass, gas pressure in the pneumatic accumulator are represented. The analysis of the obtained dependences is provided. The velocity at the time of the hydropneumatic impact device tool impact on the ground can vary in a wide range from 4.5 to 8 m/s at the stroke of the striker from 50 to 100 mm. It makes possible to use a hydropneumatic impact device as various replacing equipment of road building machines such as excavators.
A planar magnetron with a rotating central anode has been developed. The central flat anode, which functions as a target sputtered by an ion beam, is installed with the possibility of rotation and at ...an angle of 45°–50° relative to the direction of incidence of the sputtering ion beam, and the anode rotation axis coincides with the symmetry axis of the ion beam. Calculation of the sputtering coefficient of the central copper anode of the magnetron shows that, under oblique incidence of sputtering ions and all other conditions being equal, the sputtering coefficient of the copper anode of the magnetron increases from six to nine atoms per incident ion, while the maximum accuracy of sputtered copper atoms on the growth surface of the substrates is achieved. The planar magnetron of the proposed design has wider functionality, in particular, in the synthesis of nanostructured TiN–Cu composite coatings. The homogeneous globular structure of the growth surface of the TiN–Cu coating with globule sizes in the range of 50–100 nm indicates a normal (unfaceted) growth mechanism. The microhardness of the coatings is approximately 42 GPa.
—
Pr
1 –
x
Sr
x
Fe
0.8
Co
0.2
O
3
(PSFC) (
x
= 0.3, 0.4) materials and composites based on them are thought to be promising cathode materials for solid oxide fuel cells. The PSFC powders with ...micron-sized particles were prepared by self-propagating high-temperature synthesis. Zr
0.84
Y
0.16
O
2 – δ
(YSZ) and Ce
0.73
Gd
0.27
O
2 – δ
(GDC) nanopowders were used as a second component of the composites. It was found that at 1000°C PSFC reacts with the YSZ electrolyte to form SrZrO
3
, whereas there is no chemical interaction with GDC even at 1200°C. The electrical conductivity of the PSFC with
x
= 0.4 has been shown to be more than twice that of the material with
x
= 0.3. Herewith the increase of the Sr concentration in the PSFC leads to an increase of its thermal expansion coefficient (TEC), which exceeds that of GDC. The formation of PSFC/GDC composites makes it possible to achieve a better match in thermal expansion and sintering kinetics between the cathode and electrolyte materials. However, the electrical conductivity of the studied composites is a factor of 2–5 lower than that of the initial PSFC materials.
The aim of this study was to investigate the metal content in the hair of children living near abandoned nonferrous metal mines located in the rural settlements Tubinsk, Ishmurzino and Semenovsk the ...South Urals (Russia), and in the soils obtained from the same area. The hair and soils samples were examined for the presence of the following metals: copper (Cu), zinc (Zn), iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), lead (Pb) and cadmium (Cd). The results of this study showed that soil from this territory contained an increased level of Cu, Fe, Zn, Mn, Pb, Cd, exceeding the maximum permissible concentration (MPC) 38.3, 16.8, 4.5, 1.5, 1.4, 1.5 - fold, respectively. These values are indicative of severe soil pollution in the studied locality, thus calling for further detailed investigations. Mineral analysis of the hair samples was performed using a combination of atomic emission spectrometry and inductively coupled plasma mass spectrometry. In the hair samples, positive correlations between the following pairs of the studied metals were observed (p < 0.05): Pb-Cd (r= 0.73), Mn-Cd (r= 0.79), Fe-Cd (r= 0.56), Fe-Co (r= 0.85), Mn-Co (r= 0.65), Ni-Co (r= 0.67), Mn-Fe (r= 0.78), Ni-Fe- (r= 0.45), Pb-Fe (r= 0.46); Pb-Mn (r= 0.58). The comparison between Zn and Pb showed a negative linear correlation for the hair samples (r= −0.50; p<0.05) and for the soil samples (r= −0.68; p<0.05) suggesting that the presence of Zn and Pb in the hair could correlate with the content of these two metals in the soil. Comparison of the data on hair from this study with the average reference data for Russia showed the presence of an excess of Fe, Mn and Zn in the hair samples of the majority of the studied population: 100, 72.5 and 54.5 percent, respectively. We also observed an excess of Ni, Cd and Pb in a small number of children (in 18.2, 13.6 and 9.1 percent of the studied population, respectively). A deficiency of Cu and Co, the essential microelements for human health, was found in 27.3 percent of the studied population. The results of this study could be used to analyze the internal toxic metal burden in contaminated areas of Bashkortostan and could also serve as reference for further studies.
Abstract
The location of significant volumes of the lower level reserves close to an open pit which produces the adjacent Niorkpakhk deposit considerably complicates underground mining of the Oleniy ...Ruchey rockburst-hazardous deposit. The progress of underground excavations into the under-pit space is permitted if the undermined rock thickness and open pit walls remain stable. 3D numerical studies of stress-strain state have indicated particularities in deformation such as increase in undermined thickness stability under high tectonic stresses. The parameters of safe mining of temporary inactive reserves were scientifically substantiated. The boundaries of maximal development of underground mining were determined. The stability of overlying rocks and open pit walls is maintained by forming an advance of overlying sublevels relative underlying ones under 45° angle and providing the monitoring for the undermined rock mass. The mining method in a protective pillar the authors propose allows increasing reserves of the first mining stage by 76.9% and avoiding decrease in production volumes when mining operations terminate.
Abstract
The paper presents the main approaches and their advancing for the systems of rock mass stress-strain state forecasting during mining of adjacent rockburst hazardous deposits. Such systems ...based on the original Sigma GT software are used at several Russian mining companies which develop solid rock deposits, prone to brittle fracturing and undergoing the gravitational-tectonic stress-strain state. At that, the mining-induced impact on the rock mass is accompanied by occurrence of dynamic rock pressure. The geomechanical situation forecast systems have been applied directly at mining companies for more than 10 years and have shown their high efficiency. The efficiency is associated primarily with the operative calculation of stress-strain state in case of exacerbations of the geodynamic situation and the potential consideration of various mining options in order to reduce stress concentration and give recommendations for supporting and unloading measures in mine workings. In addition, the Sigma GT software is used in annual and long-term mining planning. Initially, such systems were developed for individual rockburst hazardous mining blocks, and their efficient operation time was limited to a 3-5 year period, that is, the block mining time. Further on, taking into account the needs of companies, the systems began to include a whole deposit or even several deposits. Being applied, the system is constantly developed and advanced and adapted to specific conditions and tasks. The most actual tasks are combination of the results of stress-strain state modeling with seismic monitoring data; creation of a hierarchical system of interconnected multiscale volume models; more complete consideration of structural heterogeneities of the rock mass and development of a recommendation block for safe mining operations, taking into account the geomechanical situation forecast data. The solution of these problems is considered on the example of a section of the Khibiny apatite arc, within which underground and open mining is carried out in the zone of mutual influence.
Abstract
The paper proposes a variant of the algorithm for 3D numerical simulation of the rock mass stress-strain state in the vicinity of structural heterogeneities by the finite element method. ...Modeling of the stress-strain state is used, among other things, when analyzing the fractures in the rock mass, which can occur as a breakage or a shear along the weakening planes. The rock massif has a block structure, where the boundaries of various-scale blocks are structural disturbances of different orders. The surface planes of structural heterogeneities usually have complex geometry and spatial orientation, so the most adequate results can be obtained by 3D modeling of the disturbed rock mass. Besides, it is important to take into account the type of the stress-strain state, which can be not only gravitational, but also gravitational-tectonic, including horizontal loading of the rock mass. Accounting these features allows obtaining the most adequate geomechanical model of the studied object. For this purpose, the authors have studied and analyzed the existing approaches to modeling heterogeneities in the rock mass, including using the Goodman contact element, and developed its 3D modification. A mining engineer needs to have a handy tool that allows creating and editing a geomechanical model, taking into account mining plans and related sections. The model navigation, edition of its individual blocks to specify geology and creation of local sub-models make it necessary to use structured meshes of finite elements. Modification of the model with the introduction of contact elements entails the creation of an unstructured mesh, which complicates further manipulations with it. To solve this problem, a special zero element was developed, which allows saving a structured mesh format when implementing a contact element. This zero element, like the contact element, has zero thickness, and its nodes have averaged strength characteristics of adjacent blocks of the undisturbed rock mass. The result of these studies is a tool that allows creating 3D models of the rock mass stress-strain state, taking into account its structural heterogeneities and preserving the regular structure of the finite element mesh.
Changes in morphological and optical parameters of HeLa cells preincubated with 5-aminolevulinic acid (5-ALA), after photodynamic treatment (PDTr) with different intensity of excitation radiation are ...studied by digital holographic microscopy. Optimization of the algorithm of cell segmentation on their phase image is performed. The developed algorithm allows for automatic data acquisition on extended amounts of cells in a sample (over 600). The morphological and optical parameters of cells at different doses of PDTr were determined, and the lognormal distribution of average phase shift of the cells was demonstrated. Changes in the cell parameters at different radiation doses which initiate programmed cell death and necrosis were recorded.
The high-cycle fatigue behavior of smooth and notched samples of ultrafine-grained titanium prepared by severe plastic deformation is compared with the corresponding properties of conventional ...titanium. It is shown that the combination of high strength and enhanced ductility of ultrafine-grained titanium lead to an increase of the fatigue endurance limit. Using a combination of equal-channel angular pressing and subsequent thermal and mechanical treatment, it was possible to increase the fatigue endurance limit of commercial-purity titanium by a factor of 1.5. Furthermore, it is shown that post-deformation annealing can additionally enhance the ductility of the ultrafine-grained Ti and lower fatigue-notch sensitivity particularly in comparison with Ti-6Al-4V.
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