A study of the temperature dependence of bienzyme systems and enzymatic chains

It is known that most enzyme-facilitated reactions are highly temperature dependent processes. In general, the temperature coefficient, Q10, of a simple reaction reaches 2.0-3.0. Nevertheless, some enzyme-controlled processes have much lower Q10 (about 1.0), which implies that the process is almost temperature independent, even if individual reactions involved in the process are themselves highly temperature dependent. In this work, we investigate a possible mechanism for this apparent temperature compensation: simple mathematical models are used to study how varying types of enzyme reactions are affected by temperature. We show that some bienzyme-controlled processes may be almost temperature independent if the modules involved in the reaction have similar temperature dependencies, even if individually, these modules are strongly temperature dependent. Further, we show that in non-reversible enzyme chains the stationary concentrations of metabolites are dependent only on the relationship between the temperature dependencies of the first and last modules, whilst in reversible reactions, there is a dependence on every module. Our findings suggest a mechanism by which the metabolic processes taking place within living organisms may be regulated, despite strong variation in temperature

Anti-phase locking in a two-dimensional Josephson junction array

We consider theoretically phase locking in a simple two-dimensional Josephson junction array consisting of two loops coupled via a joint line transverse to the bias current. Ring inductances are supposed to be small, and special emphasis is taken on the influence of external flux. Is is shown, that in the stable oscillation regime both cells oscillate with a phase shift equal to $\pi$ (i.e. anti-phase). This result may explain the low radiation output obtained so far in two-dimensional Josephson junction arrays experimentally.Comment: 11 pages, REVTeX, 1 Postscript figure, Subm. to Appl. Phys. Let

Noise immunity estimation of diffraction stacking method on the example of a homogeneous model

© SGEM2018. Seismic sources location is one of the main tasks of seismology (determination of earthquake hypocenters) and this is the main task in microseismic monitoring of hydraulic fracturing. When choosing a method for microseismic monitoring, noise immunity is one of the main parameters, which should be considered in order to obtain reliable results. The article is referred to the location of a point seismic source by the Diffraction Stacking method applied to synthetic signals obtained using 2D numerical simulation of seismic waves propagation in an elastic medium. Simulation of seismic wave propagation was carried out using the finite difference scheme, which allows simulating the propagation of longitudinal and vertically polarized transverse waves. Noise immunity estimation was carried out by adding random noise to the synthetically simulated signals and then finding the maximum of the image function throughout the modelled area. The results obtained make it possible to characterize the Diffraction Stacking method as weakly stable to random noise, the amplitude of which is comparable with the amplitude of the useful signal. Nevertheless, in general this method of seismic sources location can be applied to process the data with relatively high signal-to-noise ratios

Noise immunity estimation of diffraction stacking method on the example of a homogeneous model

© SGEM2018. Seismic sources location is one of the main tasks of seismology (determination of earthquake hypocenters) and this is the main task in microseismic monitoring of hydraulic fracturing. When choosing a method for microseismic monitoring, noise immunity is one of the main parameters, which should be considered in order to obtain reliable results. The article is referred to the location of a point seismic source by the Diffraction Stacking method applied to synthetic signals obtained using 2D numerical simulation of seismic waves propagation in an elastic medium. Simulation of seismic wave propagation was carried out using the finite difference scheme, which allows simulating the propagation of longitudinal and vertically polarized transverse waves. Noise immunity estimation was carried out by adding random noise to the synthetically simulated signals and then finding the maximum of the image function throughout the modelled area. The results obtained make it possible to characterize the Diffraction Stacking method as weakly stable to random noise, the amplitude of which is comparable with the amplitude of the useful signal. Nevertheless, in general this method of seismic sources location can be applied to process the data with relatively high signal-to-noise ratios

Influence of tungsten nanoparticles on microstructure and mechanical properties of an Al-5%Mg alloy produced by casting

This paper investigates the impact of tungsten nanoparticles on the microstructure and mechanical properties of the Al-5Mg alloy. Tungsten concentrations of up to 0.5 wt.% led to a slight modification of the Al-5Mg alloy microstructure, and grain refinement occurred due to the inhibition of crystal growth along the boundaries. Dispersion hardening with tungsten nanoparticles made it possible to increase the ultimate strength by the Orowan mechanism with a simultaneous increase in the plasticity of the Al-5Mg alloy. An increase in the tungsten content to 0.8 wt.% made it possible to modify the microstructure of the Al-5Mg alloy, due to the formation of the Al12W phase and an increase in crystallisation centres. The modification of the microstructure, as well as dispersion strengthening by nanoparticles, led to a simultaneous increase in the yield strength, ultimate tensile strength, and ductility of the Al-5Mg alloy

Time scales of the Greenland freshwater anomaly in the subpolar North Atlantic

Author Posting. © American Meteorological Society, 2021. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Climate 34(22), (2021): 8971–8987, https://doi.org/10.1175/JCLI-D-20-0610.1.The impact of increasing Greenland freshwater discharge on the subpolar North Atlantic (SPNA) remains unknown as there are uncertainties associated with the time scales of the Greenland freshwater anomaly (GFWA) in the SPNA. Results from numerical simulations tracking GFWA and an analytical approach are employed to estimate the response time, suggesting that a decadal time scale (13 years) is required for the SPNA to adjust for increasing GFWA. Analytical solutions obtained for a long-lasting increase of freshwater discharge show a non-steady-state response of the SPNA with increasing content of the GFWA. In contrast, solutions for a short-lived pulse of freshwater demonstrate different responses of the SPNA with a rapid increase of freshwater in the domain followed by an exponential decay after the pulse has passed. The derived theoretical relation between time scales shows that residence time scales are time dependent for a non-steady-state case and asymptote the response time scale with time. The residence time of the GFWA deduced from Lagrangian experiments is close to and smaller than the response time, in agreement with the theory. The Lagrangian analysis shows dependence of the residence time on the entrance route of the GFWA and on the depth. The fraction of the GFWA exported through Davis Strait has limited impact on the interior basins, whereas the fraction entering the SPNA from the southwest Greenland shelf spreads into the interior regions. In both cases, the residence time of the GFWA increases with depth demonstrating long persistence of the freshwater anomaly in the subsurface layers.D. S. Dukhovskoy and E. P. Chassignet were funded by the DOE (Award DE-SC0014378) and HYCOM NOPP (Award N00014-19-1-2674). The HYCOM-CICE simulations were supported by a grant of computer time from the DoD High-Performance Computing Modernization Program at NRL SSC. G. Platov was funded by the RSF N19-17-00154. P. G. Myers was funded by an NSERC Discovery Grant (Grant RGPIN 04357). A. Proshutinsky was funded by FAMOS project (NSF Grant NSF 14-584)

Evaluation of the possibility of obtaining welded joints of plates from Al-Mg-Mn aluminum alloys, strengthened by the introduction of TiB2 particles

In the work, the possibility of obtaining strong welded joints of aluminum alloys modified with particles is demonstrated. For research, strengthened aluminum alloys of the Al-Mg-Mn system with the introduction of TiB2 particles were obtained. TiB2 particles in specially prepared Al-TiB master alloys obtained by self-propagating high-temperature synthesis were introduced ex situ into the melt according to an original technique using ultrasonic treatment. Plates from the studied cast alloys were butt-welded by one-sided welded joints of various depths. To obtain welded joints, the method of electron beam welding was used. Mechanical properties of the studied alloys and their welded joints under tension were studied. It was shown that the introduction of particles resulted in a change in the internal structure of the alloys, characterized by the formation of compact dendritic structures and a decrease in the average grain size from 155 to 95 µm. The change in the internal structure due to the introduction of particles led to an increase in the tensile strength of the obtained alloys from 163 to 204 MPa. It was found that the obtained joints have sufficient relative strength values. Relative strength values reach 0.9 of the nominal strength of materials already at the ratio of the welded joint depth to the thickness of the welded plates, equal to 0.6 for the initial alloy and in the range of 0.67–0.8 for strengthened alloys

Forest Protection and Permanence of Reduced Emissions

Tropical forests are essential for climate change mitigation. As awareness grows over the use of credits from reduced emissions from deforestation and forest degradation (REDD+) and other nature-based climate solutions within both voluntary and compliance carbon markets, key concerns about the long-term durability of the reductions, or their permanence, arise for countries, corporations, regulators and policy makers. The paper seeks to analyze an efficient means of distribution and application of different policy pathways to slow down and stop deforestation and explore the longevity of reductions via modeling. The impact of policies like REDD+ most likely will have a time limitation. At some point tropical nations will take more responsibility to protect forests. REDD+ should constitute an initial intervention that will help tropical nations shock to a zero-deforestation trajectory. To establish conditions of permanence, we conduct numerical analyses using a model based on a cellular automata algorithm that learns from historical deforestation patterns and other spatial features in the Brazilian state of Mato Grosso. The model simulates future deforestation, first applying policy to reduce deforestation and then relaxing the policy intervention. Our simulations show that policies that are successful in reducing deforestation and related emissions from business as usual may have long-term positive consequences on an avoided deforestation trajectory even after potential policy reversals. Some accumulated gains could be lost but sizable benefits will remain, assuring permanence of emissions reduction during the policy implementation and potentially even after policies are relaxed. Hence, permanence depends both on the probability of policy reversals and the risk of emissions rebounding. Our results are important for advancing the understanding around the unsettled debate on the permanence of avoided emissions. Further, this paper argues that as policies to prevent deforestation or reduce emissions otherwise are reversible, permanence should be understood and discussed in a probabilistic and time-dependent framework

Theory of phase-locking in generalized hybrid Josephson junction arrays

A recently proposed scheme for the analytical treatment of the dynamics of two-dimensional hybrid Josephson junction arrays is extended to a class of generalized hybrid arrays with ''horizontal'' shunts involving a capacitive as well as an inductive component. This class of arrays is of special interest, because the internal cell coupling has been shown numerically to favor in-phase synchronization for certain parameter values. As a result, we derive limits on the circuit design parameters for realizing this state. In addition, we obtain formulas for the flux-dependent frequency including flux-induced switching processes between the in-phase and anti-phase oscillation regime. The treatment covers unloaded arrays as well as arrays shunted via an external load.Comment: 24 pages, REVTeX, 5 Postscript figures, Subm. to Phys. Rev.

Motor activity of paramecium | Dvigatel'naia aktivnost' parametsii.

A systemic study of the mechanisms of motor activity of paramecium was carried out. The movements of paramecium responding to various influences were photographed. The analysis of the data revealed the time dependences of the rate of movement, rate of rotation, and the radius and the pitch of the helix trajectory. Mathematical models of the membrane and a unit that transforms the calcium signal to programs of regulating the effectors were constructed. A system of equations for constructing the trajectory of movement was proposed. It is concluded that the biomolecular system that involves calmodulin, calmodulin-dependent ionic channels, adenylate cyclase, guanylate cyclase, phosphodiesterases, Ca(2+)-calmodulin, cAMP, cGMP-dependent protein kinases, and phosphoprotein phosphatases is capable of regulating motor reactions necessary for complex maneuvering of paramecium under various conditions