A series of mono- and polyfunctional carborane organosilicon derivatives were prepared with good yields based on the hydrosilylation reactions of allylcarboranes with hydride-containing organosilicon ...compounds such as tetramethyldisiloxane, decamethylpentasiloxane and triethoxysilane in the presence of Karstedt's catalyst. The functionalization of the double bonds in the allylcarboranes proceeded regioselectively in accordance with the Farmer's rule, providing efficient access to carborane silicon compounds. It was found for 9-
o
- and 9-
m
-allylcarboranes that an excess of Karstedt's catalyst could promote the migration of a double bond in allylcarboranes to form boron-substituted propenyl derivatives; the structure of the ortho-isomer was supported by X-ray diffraction analysis.
A series of mono- and polyfunctional carborane organosilicon derivatives were prepared with good yields based on the hydrosilylation reactions of allylcarboranes with hydride-containing organosilicon compounds such as tetramethyldisiloxane, decamethylpentasiloxane and triethoxysilane in the presence of Karstedt's catalyst.
Spatially explicit forecasting of changes in species richness is key to designing informative scenarios on the development of diversity on our planet. It might be possible to predict changes in the ...richness of inadequately investigated groups from that of groups for which enough information is available. Here we evaluate the reliability of this approach by reviewing 237 richness correlations extracted from the recent literature. Of the 43 taxa covered, beetles, vascular plants, butterflies, birds, ants, and mammals (in that order) were the most common ones examined. Forests and grasslands strongly dominated the ecosystem types studied. The variance explanation (R) could be calculated for 152 cases, but only 53 of these were significant. An average correlation effect size of 0.374 (95% CI = ±0.0678) indicates positive but weak correlations between taxa within the very heterogeneous data set. None of the examined explanatory variables (spatial scale, taxonomic distance, trophic position, biome) could account for this heterogeneity. However, studies focusing on 10-km grid cells had the highest variance explanation. Moreover, within-phylum between-class comparisons had marginally significantly lower correlations than between-phylum comparisons. And finally, the explanatory power of studies conducted in the tropics was significantly higher than that of studies conducted in temperate regions. It is concluded that the potential of a correlative approach to species richness is strongly diminished by the overall low level of variance explanation. So far, no taxon has proved to be a universal or even particularly good predictor for the richness of other taxa. Some suggestions for future research are inclusion of several taxa in models aiming at regional richness predictions, improvement of knowledge on species correlations in human dominated systems, and a better understanding of mechanisms underlying richness correlations.
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BFBNIB, FZAB, GIS, IJS, INZLJ, KILJ, NLZOH, NMLJ, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZRSKP
•In situ annealing FIB lamella obtained from nanostructured WC-Co hardmetal in TEM.•Annealing at 950 °C leads to the dissolution of Co interlayers and small Co pools.•The surface of the WC grains ...adjacent to Co pools contains much cobalt.•Abnormally fast Co diffusion is caused by high temperature and electron irradiation.
In situ annealing a FIB lamella obtained from nanostructured WC-Co hardmetal in a transmission electron microscope at 950 °C leads to the dissolution of some Co interlayers and small Co pools. The surface of the WC grains adjacent to the dissolved Co pools contains significant amounts of cobalt diffused to the surface of these WC grains from the Co pools. The observed new phenomenon of the abnormally fast Co diffusion at WC/Co grain boundaries is presumably caused by the combined effect of the high temperature and electron irradiation by an electron beam in the transmission electron microscope.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The synthesis of novel stereoregular carborane-containing phenylcyclosiloxanes (4, 5, 6, 8, and 12 -SiO- units in the ring) has been developed. The structures of all compounds were confirmed by a ...series of physicochemical methods. Tris-
cis
-tris-
trans
-dodecaphenyl(1(3-(9-
m
-carboranyl)propyl)dimethylsiloxy)cyclododecasiloxane has been studied by NMR spectroscopy and it was found that such a configuration of the ring makes two methyl groups diastereotopic, resulting in magnetic non-equivalence of the protons of these groups. The results of thermal studies of the obtained compounds are also described.
The synthesis of novel stereoregular carborane-containing phenylcyclosiloxanes (4, 5, 6, 8, and 12 -SiO- units in the ring) has been developed.
Local laser heating of the liquid film leads to simultaneous self-organization of both cellular convective structures and a cluster of micron-scale particles. The cluster is formed on the free ...surface of the layer and consists of hexagonal structures with a size of 50-100 μm. The height of the liquid film (0.5 mm) is ten times the diameter of the convective cells. Experimental data on the distribution of particle sizes and sizes of hexagonal cells in the cluster are presented. The cluster shape may be either a circle with a diameter of 110-140 μm, or an ellipse. Due to the instability of the velocity field, the toroid is not formed, and convective cells are formed only near the heating center. Self-organization of a cluster of particles and cellular structures using local heating can be effectively used to create new promising materials, as well as in micro-biology and medicine.
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•Convective cells and a cluster of particles are studied at laser heating.•Perturbations at a micro-scale control the average flow at a macro-scale.•The integral convection scale reflects the intensity of heat and mass transfer.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
To date, heat transfer, convection and particle deposition have been mainly investigated for the case of homogeneous wall heating. Convection and particle deposition during local heating, when there ...are one or more local heating sources, have not been practically studied. Experimental studies of free convection and particle deposition in a layer of colloidal solution have been carried out. Convection was created by heating the liquid using one and two laser beams. The colloidal solution consisted of water and microscopic TiO2 particles. The novelty of the work is the demonstration of the effectiveness of local heating in creating high rates of convection and particle deposition at low energy costs. With two-point laser heating, the convection rate is higher than with single-point heating. When using two laser beams, the Marangoni number increases in comparison with single-point laser heating. As a result, the Bo number becomes lower than the critical value and the stability of the velocity field increases. In contrast to single-point heating, the use of two laser beams does not change the vortex flow pattern with increasing layer height. The particle deposition rate is higher when using a single laser beam than when using two beams and is two orders higher than the deposition without convection. An expression linking the deposition rate with time, layer height and fluid velocity is derived. The obtained results on the use of local heating sources are applicable for enhancing convection, as well as in technologies for cleaning solutions from solid impurities.
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•Free convection and particle deposition of a colloidal solution have been studied.•With two-point laser heating, convection rate is higher than with single-point heating.•With two-point laser heating, the stability of the velocity field increases.•The particle deposition rate is higher when using a single laser beam.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In the 1st part of this article, hardmetal deformation processes caused by bending loads were examined in-situ by transmission electron microscopy. The major objective of this work is to examine ...hardmetal deformation processes in special thin hardmetal samples as a result of applying tensile loads in-situ directly in a transmission electron microscope with the aid of the push-to-pull method. Applying tensile loads to the samples results in the plastic deformation of the Co-based binder phase leading to the formation of different crystal lattice defects in the binder. Force-time and displacement-time curves recorded when loading the samples and maintaining the loads provide evidence for continuous processes of the formation and movement of crystal lattice defects, presumably dislocations, in the WC phase and Co-based binder leading to a high rate of the binder plastic deformation. After increasing the tensile loads up to a certain level leading to the severe plastic deformation of the binder phase, the samples suddenly fail as a result of the crack initiation and propagation at WC-Co interfaces. Presence of cobalt on the WC surface after the cracking suggests that the cracks propagate through the binder region adjacent to the interface rather than through the interface itself.
•The deformation behavior of hardmetal under tensile loads was investigated using in situ TEM techniques.•Applying tensile loads to the samples is found to result in the plastic deformation of the Co-based binder.•Crack propagation path lies in Co-based binder in the area, adjacent to the WC-Co interface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A new polytype of the quasi-one-dimensional conductor NbS
3
with high-temperature charge density waves has been synthesized. The transmission electron microscopy study at room temperature has ...revealed only one of the two superstructures existing in the previously studied monoclinic phase with the period along chains close to
b
/0.352. In addition, a new incommensurate distortion of the lattice with the period close to 2
b
has been observed. The transport properties of the samples under study are in agreement with the study of the superstructure. The main lattice constants are somewhat different from the respective parameters in the previously studied monoclinic phase. The new phase can assumingly be intermediate between the two main known phases of NbS
3
, monoclinic and triclinic. Its properties can be explained within a model where a unit cell of the monoclinic phase can be considered as the superposition of unit cells of the triclinic phase.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper considers an original valve electromagnet with integrated armature, designed to implement an electromagnetic overcurrent release of a circuit breaker. Theoretical and experimental studies ...of the proposed electromagnet have been carried out to determine the most important parameters of circuit breakers such as sensitivity and high-speed performance. Calculations and experiments have shown the possibility of increasing the sensitivity and speed of the electromagnetic overcurrent release based on the proposed electromagnet with integrated armature in comparison with existing structures used in modern circuit breakers.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Water layer evaporation under local heating was investigated.•Gas convection effect was several times greater than diffusion and buoyancy of vapor.•Local heating allowed achieving high values of the ...heat transfer coefficient.•Obtained results were important for the development of new methods of heat exchange enhancement.
The evaporative behavior of a water layer and the heat transfer under local heating were investigated. Non-stationary and non-isothermal heat exchange conditions were created by laser heating. The thermal field on the free surface of the layer was registered using thermal imaging technology. Changes in the liquid mass due to evaporation were determined using the gravimetric method. The key factors affecting water evaporation were estimated and the characteristic heat fluxes associated with evaporation, radiation and convection are compared. The effect of free convection in the gas phase on the evaporation rate of the water film is several times higher than the effect of diffusion and buoyancy of vapor. The local heating allowed achieving high values of the heat transfer coefficient and heat fluxes at considerably smaller liquid temperatures and heating area, which is advantageous from an energy point of view. The obtained results were important for the development of new methods of heat exchange enhancement, as well as for the prediction of heat fluxes and hydrodynamic flows and evaluation of non-isothermal, non-stationary and inhomogeneous heat exchange.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
