A portable meter for measuring the modulus of the reflectivity of various material objects over a wide range of frequencies using a low-intensity noise probe signal is described. The operation of the ...meter is analyzed with the real characteristics of its high-frequency components and of the elements of the circuit taken into account. Formulas are obtained for estimating the deviation of the measured absolute values of the reflectivity from the ideal values. It is found that the main contribution to the difference in the deviations is from damping of the signal from the noise generator in the meter as the signal passes toward the antenna through the circuit elements. An adjustable attenuator for the generator signal is included in the meter to account for the damping. A way of reducing the systematic error is examined and the permissible values of the characteristics of the circuit components of the meter are determined.
Nowadays droplet microfluidics is widely used to perform high throughput assays and for the synthesis of micro- and nanoparticles. These applications usually require packaging several reagents into ...droplets and their mixing to start a biochemical reaction. For rapid mixing microfluidic devices usually require additional functional elements that make their designs more complex. Here we perform a series of 2D numerical simulations, followed by experimental studies, and introduce a novel asymmetric flow-focusing droplet generator, which enhances mixing during droplet formation due to a 2D or 3D asymmetric vortex, located in the droplet formation area of the microfluidic device. Our results suggest that 2D numerical simulations can be used for qualitative analysis of two-phase flows and droplet generation process in quasi-two-dimensional devices, while the relative simplicity of such simulations allows them to be easily applied to fairly complicated microfluidic geometries. Mixing inside droplets formed in the asymmetric generator occurs up to six times faster than in a conventional symmetric one. The best mixing efficiency is achieved in a specific range of droplet volumes, which can be changed by scaling the geometry of the device. Thus, the droplet generator suggested here can significantly simplify designs of microfluidic devices because it enables both the droplet formation and fast mixing of the reagents within droplets. Moreover, it can be used to precisely estimate reaction kinetics.
Resistive switching (RS) is studied in a memristor based on a ZrO2(Y)/Ta2O5 stack under a white Gaussian noise voltage signal. We have found that the memristor switches between the low resistance ...state and the high resistance state in a random telegraphic signal (RTS) mode. The effective potential profile of the memristor shows from two to three local minima and depends on the input noise parameters and the memristor operation. These observations indicate the multiplicative character of the noise on the dynamical behavior of the memristor, that is the noise perceived by the memristor depends on the state of the system and its electrical properties are influenced by the noise signal. The detected effects manifest the fundamental intrinsic properties of the memristor as a multistable nonlinear system.
A simple digital spectral absorption meter for optical radiation from liquids designed for operation in the field is described. High measurement stability and linearity of the transfer characteristic ...were achieved through the use of a modification of the zero-measurement method. The maximum value of the nonlinearity of the transfer characteristic of the meter for the full measurement range did not exceed three to four low bits of the 10-digit digital code.
•Preferential CO oxidation (CO PROX).•Nanopowder of unordered solid solution Pt0.5Co0.5 shows high CO PROX performance.•Pt0.5Co0.5 is more active in total CO oxidation than Pt.•DFT calculations of ...the oxidation of CO on Pt13 and Pt12Co clusters.•Higher activity of Pt12Co due to an electronic effect.
CO preferential (PROX) and total (TOX) oxidation were studied over Pt and Pt0.5Co0.5 nanopowders. Pt0.5Co0.5 exhibited much higher CO PROX performance than Pt, being highly active and selective at 0–80 °C. Low-temperature activity in CO oxidation was shown to be the key feature of bimetallic Pt-Co catalysts in comparison with monometallic Pt. Density functional theory calculations of the oxidation of CO on Pt13 and Pt12Co clusters revealed that a better catalytic activity of bimetallic cluster is due to an electronic effect: the calculated atomic charges on platinum atoms change when cobalt is introduced into its composition.
To create a high throughput system for screening single cells in "water-in-oil" droplets, a key role is played by the method of controlling fluid flows in a microfluidic droplet generator. This is ...due to the fact that it is required to obtain monodisperse drops-microcapsules, place cells in them and be able to manipulate them. For these purposes, not only systems based on syringe pumps are suitable, but also pressure control units may be used. Unfortunately, pressure control instruments on the market for researchers are represented by only a few companies and are quite expensive. In this work, we develop a homemade microfluidic pressure controller based on SMC ITV 0010 pneumatic regulators and show its operability. Also, we investigated the conditions for reproducible generation of water-in-oil emulsions in a microfluidic flow focusing droplet generator by pressure driven fluid flows.
The stochastic resonance phenomenon has been studied experimentally and theoretically for a state-of-art metal-oxide memristive device based on yttria-stabilized zirconium dioxide and tantalum ...pentoxide, which exhibits bipolar filamentary resistive switching of anionic type. The effect of white Gaussian noise superimposed on the sub-threshold sinusoidal driving signal is analyzed through the time series statistics of the resistive switching parameters, the spectral response to a periodic perturbation and the signal-to-noise ratio at the output of the nonlinear system. The stabilized resistive switching and the increased memristance response are revealed in the observed regularities at an optimal noise intensity corresponding to the stochastic resonance phenomenon and interpreted using a stochastic memristor model taking into account an external noise source added to the control voltage. The obtained results clearly show that noise and fluctuations can play a constructive role in nonlinear memristive systems far from equilibrium.
Macro- and fractographic studies of fractures of CTOD specimens after fatigue testing of essential steel rolled products with a thickness of 82 mm for fixed offshore structures of the S420MLO quality ...category, produced using the technology of thermomechanical processing with accelerated cooling, are presented. Fracture nature and the mechanisms of fatigue crack propagation at test temperatures of minus 10 and minus 30°C were studied. The potential reasons for the formation of a “secondary” fatigue crack propagation front and its potentially negative impact on the final test results are described. Research results and testing were used in passing, with a positive result of certification tests of rolled products of quality categories S355MLO and S420MLO with a thickness of up to 82 mm in accordance with the requirements of EN10225-1:2019 and NORSOK M-120.
To characterize the effect of oxidative stress (OS) on the ability of erythrocytes to pass through microvessels and capillaries, we studied the dynamics of the movement of human erythrocytes in ...vitro, in the channels of a microfluidic device, under the action of an OS inducer, tert-butyl hydroperoxide (tBH), and compared it with a cytological assessment of the transformation of cell membranes. OS induced the impairment of the control over the shape and volume of cells, the decrease in passage speed, and the occlusions of microchannels. The developed microfluidic device provided an assessment of the microreology of erythrocytes under the action of hydroperoxide. In the future, it is possible to use microfluidic analysis of erythrocytes in patients to assess the effect of xenobiotics on microrheology.
Lymphocyte phosphatase-associated phosphoprotein (LPAP) is a molecular partner of CD45 phosphatase that plays a key role in the regulation of antigen-specific activation of lymphocytes. The functions ...of LPAP still remain unknown. We believe that studying LPAP phosphorylation pathways could shed light on its functions. In this work, we studied the phosphorylation of LPAP ectopically expressed in non-lymphoid cells in order to determine the effect of LPAP interaction partners on its phosphorylation. We found that phosphorylation at Ser153 and Ser163 in non-hematopoietic HEK293 cells was conserved, while phosphorylation at Ser99 and Ser172 was almost absent. The pattern of LPAP phosphorylation in K562 erythroid and U937 myeloid cells expressing endogenous CD45 protein was similar to that observed in T and B lymphocytes. We demonstrated for the first time that LPAP is a substrate for protein kinase CK2 that phosphorylates it at Ser153, presumably ensuring LPAP resistance to degradation.
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