Thermal activation of transient receptor potential (TRP) cation channels is one of the most striking examples of temperature-controlled processes in cell biology. As the evidence indicating the ...fundamental role of such processes in thermosensation builds at a fast pace, adequately accurate tools that would allow heat receptor logic behind thermosensation to be examined on a single-cell level are in great demand. Here, we demonstrate a specifically designed fiber-optic probe that enables thermal activation with simultaneous online thermometry of individual cells expressing genetically encoded TRP channels. This probe integrates a fiber-optic tract for the delivery of laser light with a two-wire microwave transmission line. A diamond microcrystal fixed on the fiber tip is heated by laser radiation transmitted through the fiber, providing a local heating of a cell culture, enabling a well-controlled TRP-assisted thermal activation of cells. Online local temperature measurements are performed by using the temperature-dependent frequency shift of optically detected magnetic resonance, induced by coupling the microwave field, delivered by the microwave transmission line, to nitrogen--vacancy centers in the diamond microcrystal. Activation of TRP channels is verified by using genetically encoded fluorescence indicators, visualizing an increase in the calcium flow through activated TRP channels.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Toroidal Dipolar Response in a Metamaterial Kaelberer, T; Fedotov, V.A; Papasimakis, N ...
Science (American Association for the Advancement of Science),
12/2010, Volume:
330, Issue:
6010
Journal Article
Peer reviewed
Open access
Toroidal multipoles are fundamental electromagnetic excitations different from those associated with the familiar charge and magnetic multipoles. They have been held responsible for parity violation ...in nuclear and particle physics, but direct evidence of their existence in classical electrodynamics has remained elusive. We report on the observation of a resonant electromagnetic response in an artificially engineered medium, or metamaterial, that cannot be attributed to magnetic or charge multipoles and can only be explained by the existence of a toroidal dipole. Our direct experimental evidence of the toroidal response brings attention to the often ignored electromagnetic interactions involving toroidal multipoles, which could be present in naturally occurring systems, especially at the macromolecule level, where toroidal symmetry is ubiquitous.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
We perform a complete calculation of electron-seeded pair creation (the trident process) in a constant crossed electromagnetic background. Unlike earlier treatments, we include the interference ...between exchange diagrams. We find that this exchange interference can be written as a contribution solely to the one-step process, and for small quantum nonlinearity parameter is of the same order as other one-step terms. We find that the exchange interference further suppresses the one-step process in this parameter regime. Our findings further support the crucial assumption made in laser-plasma simulation codes that at high intensities, the trident process can be well approximated by the repeated iteration of the single-vertex subprocesses. The applicability of this assumption to higher-vertex processes has fundamental importance to the development of simulation capabilities.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
By considering radiative corrections of up to 3rd-loop order, Ritus and Narozhny conjectured that the proper expansion parameter for QED in a strong constant crossed field is g = αχ2/3, where the ...dynamical quantum parameter χ = e√−(Fp)2/m3 combines the particle momentum p with the external field strength tensor F . Here we present and discuss the first nonperturbative result in this context, the resummed bubble-type polarization corrections to the electron self-energy in a constant crossed field. Our analysis confirms the relevance of the scaling parameter g to the enhancement of bubble-type radiative corrections. This parameter actually represents the characteristic value of the ratio of the 1-loop polarization bubble to the photon virtuality. After an all-order resummation we identify and discuss two contributions to the self-energy with different formation regions and asymptotic behavior for g ≫ 1. Whereas the breakdown of perturbation theory occurs already for g ≳ 1, the leading-order result remains dominant until the asymptotic regime g ≫ 1 is reached. However, the latter is specific to processes like elastic scattering or photon emission and does not have to remain true for general higher-order QED processes.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
An experimental-analytical model of homogenised elastic moduli of matrix composites has been developed based on the Mori-Tanaka analytical model. The fitting parameter of the model is the ratio of ...the constrained strains of the experimental sample matrix and the model composite and is determined by one experimental point for the basic composition of the composite. A linear dependence of the fitting parameter on the volume fraction of inclusions is used for composites of arbitrary composition. Good agreement is obtained between the calculation results and experimental data for isotropic and transversally isotropic composites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Based on the numerical model and the Mori-Tanaki analytical model, a quasi-numerical model for predicting the elastic moduli of matrix composites has been developed. In the quasi-numerical model, the ...results of the calculation by the analytical model are fitted to the results of the calculation of the numerical model. The fitting parameter is the ratio of the constrained strain of the matrix in the numerical model to the constrained strain of the matrix in the analytical model. The “slow” numerical model is used only once to calculate the properties of the composite of the base composition and the fitting parameter. The elastic moduli of composites of arbitrary composition are calculated using a “fast” analytical model. A good agreement between the calculation results and reference values was obtained.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This research focuses on the hydrometallurgical processing of auriferous ores and their processing products, namely, flotation and gravity concentrates. The main valuable component of an ore sample ...of any deposit is gold. The gold content should be in the range of 11.11–12.87 g/ton. The main rock-forming minerals of the original ore are quartz (60.1%), quartz–chlorite–micaceous aggregates (3.8%), and carbonates (7.1%). In this study, original ores of various sizes were treated by direct and sorption cyanidation under various leaching modes, and the results obtained were presented. The original ore was leached with various concentrations of sodium cyanide (NaCN) in solution to study the effect of the complexing agent concentration on gold recovery. Data on the dynamics of leaching revealed that a decrease in the concentration of NaCN in solution from 0.2% to 0.03% leads to a decrease in gold recovery in solution by 26.81%. Original ores could easily be processed using hydrometallurgical methods. The recovery of gold with a coarseness of 95% − 0.045 mm from the original ore averaged 97.77%.
This work features a full range of studies on the hydrometallurgical processing of concentrates and gravity tailings, as well as the effects of flotation concentration of gold recovery. The gravity concentrate is resistant to intensive cyanidation (i.e., only 67.07% gold recovery into the solution). The use of 1% lead nitrate (PbNO
3
) during intensive cyanidation could reduce the refractoriness of the concentrate and increase the recovery of gold into the solution by up to 94.35%. The total gold recovery from gravity concentrate is 98.71%, and the recovery of gold by cyanidation of gravity tailings with a cyanide concentration of 0.2% averages 96.57%. The recovery of gold during leaching of the flotation concentrate at the original size (95.5% − 0.074 mm) and a cyanide concentration of 0.2% is 96.64%. A decrease in the size of the flotation concentrate from 95.5% − 0.074 mm to 95% − 0.02 mm leads to a decrease in gold recovery by 35.43% because of the strong chemical activation of the material during grinding.
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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, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Currently, special attention is paid to the search for new ceramic materials based on wide-gap oxides, as well as to the study of their structure and properties with a view to their application in ...various areas of electronic and optoelectronic industry.
Conventional double-step ceramic technology has been used to obtain samples in this experiment. After compacting at the pressure of 6 GPa of ZnO and ZnO-FexOy powders in different weight relations, the samples were subjected to the procedure of synthesis at 1173 K for 2 h and then to the annealing at 1473 K for 3 h on air.
The samples structure was investigated by the Scanning Electron Microscopy (SEM), Energy-dispersive X-ray Spectroscopy (EDX), X-ray Diffraction (XRD) and Raman spectroscopy methods. Temperature dependences of resistivity, magnetoresistance, Hall and Seebeck effects were experimentally studied in the range from 4 to 700 K.
As the experiments have shown, the size of grains in the obtained ceramic samples after synthesis was in submicron range. An XRD study showed the saving of the wurtzite structure in Zn1-δFeδO solid solutions where 0.66 < δ < 0.81 at. % regardless of the type of the doping agent. At the same time, the replacement of zinc by iron atoms led to the contraction of the ZnO lattice.
All the samples studied (ZnO and Zn1-δFeδO) demonstrate n-type conductivity. The temperature dependencies of resistivity have shown two specific features: the presence of energy level about 0.35 eV below the conduction band bottom for the doped ceramic samples (unknown in literature) and conductance with the changing activation energy at temperatures below 200 K for the undoped ZnO ceramic samples. Seebeck coefficient increased by100–150% with doping due to growth of electron concentration. Some model concepts about scattering mechanisms and reasons of Seebeck effect enhancement have been developed.
•Ceramic materials based on wide-gap oxides.•Investigation by SEM, EDX, XRD and Raman spectroscopy methods.•Size of grains in the obtained ceramic samples after synthesis was in submicron range.•Saving of the wurtzite structure in Zn1-δFeδO solid solutions.•Studied samples (ZnO and Zn1-δFeδO) demonstrate n-type conductivity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
An interface model of homogenization was proposed, this model considers the influence of the inclusions size of the micrometre range on the elastic properties of composites. The appearance of surface ...strains and shear stresses at the interphase boundary is associated with the "sticking" of the matrix to the surface of the inclusions. The effective modulus of elasticity of a composite is the sum of two terms: a constant part in the form of a modulus of elasticity of a bulk material, and a variable part that is caused by a shift at the interphase boundary and depends on the particles size. Absolute of particles sizes were considered by introducing within the interfacial model empirical elasticity modulus of the composite with the one basic particle size. The results of the calculation are in good agreement with the experimental data for Young's modulus of polymer composites with spherical particles.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Thermogenetics is a promising innovative neurostimulation technique, which enables robust activation of neurons using thermosensitive transient receptor potential (TRP) cation channels. Broader ...application of this approach in neuroscience is, however, hindered by a limited variety of suitable ion channels, and by low spatial and temporal resolution of neuronal activation when TRP channels are activated by ambient temperature variations or chemical agonists. Here, we demonstrate rapid, robust and reproducible repeated activation of snake TRPA1 channels heterologously expressed in non-neuronal cells, mouse neurons and zebrafish neurons in vivo by infrared (IR) laser radiation. A fibre-optic probe that integrates a nitrogen-vacancy (NV) diamond quantum sensor with optical and microwave waveguide delivery enables thermometry with single-cell resolution, allowing neurons to be activated by exceptionally mild heating, thus preventing the damaging effects of excessive heat. The neuronal responses to the activation by IR laser radiation are fully characterized using Ca
imaging and electrophysiology, providing, for the first time, a complete framework for a thermogenetic manipulation of individual neurons using IR light.
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