Abstract
This paper presents the preface of the proceedings for the 4th International Conference on Sustainable Futures: Environmental, Technological, Social, and Economic Matters (ICSF 2023), a ...multidisciplinary event that explores the challenges and opportunities of sustainability in various domains. The preface outlines the conference’s objectives, themes, workshops, and topics, as well as its contribution to advancing sustainable development and global dialogue. It also acknowledges the efforts and inputs of various stakeholders who have made the conference possible, especially in light of the pandemic situation. Furthermore, it thanks IOP Publishing for its support and flexibility in facilitating open access publishing. The paper concludes by looking forward to future editions of ICSF and the ongoing quest for a more sustainable and interconnected world. The paper invites readers to delve into the rich and diverse content that shapes this influential conference.
Abstract
This paper represents a preface to the Proceedings of the 3rd International Conference on Sustainable Futures: Environmental, Technological, Social, and Economic Matters (ICSF 2022) held at ...the Kryvyi Rih, Ukraine, 24–27 May 2022. Background information and the organizational structure of the meeting, program committee, and acknowledgments of the contributions of the many people who made the conference a success are presented.
The upper boundary layer of the sea is most affected by the atmosphere, and the motions formed there have a significant influence on the horizontal and vertical fluxes of heat, momentum, and other ...substances. The vertical turbulent exchange in this layer is determined by the action of several mechanisms at once, one of which is the surface wave. Estimates of the contribution of a wave to the overall generation of turbulence have been made by many researchers using a variety of approaches. To verify the proposed turbulence generation models, experimental data on the intensity of turbulent velocity fluctuations in the near-surface sea layer obtained on an oceanographic platform are used. The turbulent energy dissipation rate is calculated using the vertical component of velocity vector fluctuations using the Kolmogorov hypothesis and Taylor’s frozen turbulence hypothesis. A comparison of model and experimental data of dissipation rate values show the validity of the basic assumption that the intensity of wave-induced turbulence depends on the energy characteristics of the wave. At the same time, in situ data decrease with depth much slower than calculated data. A possible explanation could be the influence of turbulent diffusion and shear effects, as well as the inadequate parameterization of the wave energy transformation into turbulence.
Purpose. The study is aimed at qualitative and quantitative analysis (based on the updated previously proposed multiscale model) of the experimental data on turbulence intensity and their comparison ...with theoretical and semi-empirical relationships for the purpose of describing the contributions of various turbulence sources. Methods and Results. A comparative analysis of experimental data and model calculations of turbulence characteristics near the sea surface was performed. The methods of theoretical assessing generation of turbulence in the near-surface sea layer by various physical processes are considered. The results of calculations by the well-known models of turbulent exchange were compared with the experimental data collected by the scientists of the Turbulence Department of MHI, RAS, using the specialized equipment. The analysis results made it possible to determine the possibility of applying the considered models for calculating turbulence intensity under different hydrometeorological conditions. At light winds, none of the models yielded the results which matched the measurement data. At moderate winds, the simulation results showed quite satisfactory agreement with the experiment data; and for strong winds, the multiscale model results were the best. This model was modified to assess the contributions of two other mechanisms of turbulence generation: the Stokes drift and the Langmuir circulations. Conclusions. Objective assessment of the turbulent exchange intensity requires taking into account of three main mechanisms of turbulence generation, namely flow velocity shear, wave motions and wave breaking. Depending on the hydrometeorological situation, each of these mechanisms can dominate in a certain depth range. The calculations performed using the updated model showed that the Stokes drift added 2–17 % to the total dissipation in the upper 30-meter layer, whereas the contribution of the Langmuir circulations calculated through dependence of the vertical velocity of kinetic energy transfer upon the Langmuir number, can reach 15 % for small Langmuir numbers.
Purpose. The purpose of the study is to assess the coefficient of vertical turbulent exchange for different layers of the Black Sea basin based on the experimental data on microstructure of the ...physical fields obtained for the period 2004–2019 in the Black Sea and using the semi-empirical models. Methods and Results. For the upper mixed layer, the turbulent energy dissipation rate ɛ and the exchange coefficient were calculated using the velocity fluctuation spectra based on the Kolmogorov hypotheses on the turbulence spectrum inertial range. In the stratified layers, the turbulence coefficient and the dissipation rate were experimentally determined both from the spectra of the velocity horizontal fluctuations’ gradients and the vertical spectra of temperature fluctuations using the concept of the effective scale of turbulent patches. Depending on the features of the hydrological regime and the prevailing energy contributors to turbulence generation, five layers were identified and described (including their characteristic power dependences of the vertical turbulent diffusion coefficients K on the buoyancy frequency N) using the 1.5D-model of vertical turbulent exchange for the basin under study. For the stratified layers, the 1.5D-model results were comparatively analyzed with those of the other semi-empirical and theoretical models describing the most probable hydrophysical processes in each specific layer; the relations for the vertical turbulent exchange coefficient were obtained depending on the buoyancy frequency. Conclusions. Comparison of the experimental data collected under different hydrometeorological conditions with the simulations resulted from the known turbulence models for the sea upper layer showed that the best agreement between the simulation and measurement data was provided by a multiscale model taking into account three basic mechanisms of turbulence generation: current velocity shear, instability of wave motions, and wave breaking. The turbulent exchange coefficient dependencies on depth are conditioned by the effect of the turbulence dominant source at a given level. In the stratified layers, the exchange coefficient dependence on buoyancy frequency is determined by the hydrophysical processes in each layer; the relations obtained for individual layers indicate intensity of the contributions of vertical advection, internal wave breakings, turbulence diffusion and geothermal flux.
An adequate description of the interaction between the atmosphere and ocean remains one of the most important problems of modern oceanology and climatology. The extremely wide variety of physical ...processes occurring in the coupled layers, large range of scales, and moving boundary all significantly complicate the creation of models that would allow calculating the physical characteristics in both media with the necessary accuracy. In this paper the temporal variability of dynamic parameters in the driving layer of the atmosphere and in the near-surface layer of the sea on small and submesoscales from one to several tens of hours is considered. The experimental data show a very high correlation between the friction wind velocity and turbulence intensity in the upper sea layer on all scales recorded. One important distinguishing feature of all measured physical quantities in both media is the presence of quasi-periodic oscillations with different periods. For a more accurate description of momentum and energy fluxes from the atmosphere, a nonstationary model of turbulent exchange in the near-surface layer of the sea is proposed. It takes into account quasi-periodicity in the intensity of dynamic interaction between the atmosphere and the sea at these scales. In the model we use the equations of momentum and turbulent energy balance, the system of equations is solved numerically, and the calculation results are compared with other models and with experimental data. It is shown that taking into account the nonstationarity of the wind strain improves the correspondence between the calculations and the experimental data. It is noted that, in the nonstationary case, the energy and momentum flux from the atmosphere and the turbulence intensity increases compared to the action of a constant average wind of the same duration. Therefore, the strong averaging often used in global models may markedly underestimate the intensity of the dynamic interaction between the atmosphere and ocean.
Phytochromes are light sensor proteins found in plants, bacteria, and fungi. They function by converting a photon absorption event into a conformational signal that propagates from the chromophore ...through the entire protein. However, the structure of the photoactivated state and the conformational changes that lead to it are not known. We report time-resolved x-ray scattering of the full-length phytochrome from Deinococcus radiodurans on micro- and millisecond time scales. We identify a twist of the histidine kinase output domains with respect to the chromophore-binding domains as the dominant change between the photoactivated and resting states. The time-resolved data further show that the structural changes up to the microsecond time scales are small and localized in the chromophore-binding domains. The global structural change occurs within a few milliseconds, coinciding with the formation of the spectroscopic meta-Rc state. Our findings establish key elements of the signaling mechanism of full-length bacterial phytochromes.
On the basis of experimental physical field's microstructure data in the upper stratified layers of the Black Sea, the annual variability of the vertical turbulent exchange coefficient in the ...seasonal thermocline is investigated. The data were collected during eight expedition periods in 2007 - 2017, and they cover the north-western part of the Black Sea. The studies were conducted in different hydrological seasons from April to November. The measurements were carried out by the probing complex "Sigma-1", the evaluation of turbulence energy dissipation was made by velocity pulsation gradients. The desired coefficient of vertical turbulent diffusion was calculated on the basis of the obtained experimental estimates of energy dissipation by known Osborn's relationship. The analysis of these measurements makes it possible to calculate and use the vertical turbulent diffusion coefficient dependence on stratification to evaluate the vertical fluxes of heat, salt and other dissolved chemical and biological substances in the studied Black Sea region.
A simple 1.5-dimensional model of vertical exchange for heat, salt, and other dissolved substances has been developed for the Cariaco Basin. The model parameters are derived based on the temperature ...and salinity data collected monthly at a deepwater station in the eastern part of the basin from 1995 through 2007 during the CARIACO time series program. The model describes the processes of turbulent (eddy) diffusion, which includes the integrated effect of diffusive exchange mechanisms acting in the basin, and of vertical advection, which arises following injection of dense water into deep layers following an inflow from the Caribbean Sea. The model takes into account the changes in the horizontal cross-section area of the basin with respect to depth.
Temporal variability is an important feature of the hydrography of the Cariaco Basin. To assess profiles of the vertical eddy diffusion coefficient and vertical advection velocity, we examined a time series of CTD profiles (potential temperature and salinity). Two distinct time intervals were identified as the result of this examination. During the first period, the thermohaline structure of the basin was apparently influenced by one or more inflows. The second period, in contrast, showed little or no influence of an inflow. The data from the second period, where no inflows were observed, were incorporated into corresponding transfer equations to assess the profile of the vertical eddy diffusion coefficient, k(z). Then, the result of this assessment was used with the data from the first period to estimate the profile of the vertical advection velocity, W(z), for a time when the effects of an inflow were evident. For that case, the transfer equations include the terms describing the effect of the inflow.
Analysis of the vertical profile of the turbulent diffusion coefficient suggests that, in the upper stratified part of the water column, the diffusion mechanism is mostly associated with transient mixing events, which occur due to shear instability in the field of low frequency internal waves. We speculate that below 400m bottom friction over the sloping bottom and geothermal heat flux play the decisive role in the vertical exchange. Analysis of the W(z) profiles reveals two layers dominated by the entrainment of the ambient fluid into the down flow of dense water from the Caribbean Sea, and two layers where this down flow breaks down through the formation of isopycnal intrusions.
► We have estimated intensity of vertical exchange of heat and salt in the basin. ► We have found key mechanisms of vertical exchange in the Cariaco Basin. ► We will use our results to assess vertical fluxes of chemical substances in the basin.
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