Constant External Conditions Research Articles

Implementation of Cyclical Processes in the Moisture Electricity Generation for Continuous Operation

The article presents the results of a study on the generation of electricity using porous Ca6H2O19Si6 structures as an example during moisture adsorption. It has been determined that the potential difference at the contacts of a single‐layer structure of compacted Ca6H2O19Si6 particles depends on the time of formation of the potential‐determining and diffusion layers and processes that destroy the diffusion layer or prevent its formation can increase the efficiency of moisture electric generator. The concept for creating the moisture electric generators based on multilayer structures, which may allow the use of such structures as moisture electric generators for continuous operation under constant external conditions, has been proposed.

The interplay between metabolic stochasticity and cAMP-CRP regulation in single E. coli cells

The inherent stochasticity of metabolism raises a critical question for understanding homeostasis: are cellular processes regulated in response to internal fluctuations? Here, we show that, in E. coli cells under constant external conditions, catabolic enzyme expression continuously responds to metabolic fluctuations. The underlying regulatory feedback is enabled by the cyclic AMP (cAMP) and cAMP receptor protein (CRP) system, which controls catabolic enzyme expression based on metabolite concentrations. Using single-cell microscopy, genetic constructs in which this feedback is disabled, and mathematical modeling, we show how fluctuations circulate through the metabolic and genetic network at sub-cell-cycle timescales. Modeling identifies four noise propagation modes, including one specific to CRP regulation. Together, these modes correctly predict noise circulation at perturbed cAMP levels. The cAMP-CRP system may thus have evolved to control internal metabolic fluctuations in addition to external growth conditions. We conjecture that second messengers may more broadly function to achieve cellular homeostasis.

Robust actuator based on photothermally responsive hydrogel with fast recovery capability

Propulsion by deformation and oscillation is a familiar law of motion in nature. Often, these motions are signaled and driven by constant external conditions, such as the phototropism of plants. Here, we have prepared a soft photosensitive material utilizing ice templates and cryo-polymerization, which combines light absorbers and thermally responsive hydrogels and thus possesses superb photothermal conversion, mechanical deformation, and fast recovery capabilities. The soft actuator based on this material generates a dynamically balanced oscillation with intermittent shadows creating a continuous self-feedback loop, allowing the actuator to operate continuously and durably under constant illumination. Combining the modules of conjugate heat transfer, non-isothermal flow, and fluid-solid coupling, we have gained a deeper understanding of the interaction of the soft actuator with the temperature and flow fields. In the future, the soft actuator can be widely developed and combined with other conventional drive strategies in an attempt to apply in soft robotics, underwater operations, and other fields.

Multi-Signal Approaches for Repeated Sampling Schemes in Inertial Sensor Calibration

Inertial sensor calibration plays a progressively important role in many areas of research among which navigation engineering. By performing this task accurately, it is possible to significantly increase general navigation performance by correctly filtering out the deterministic and stochastic measurement errors that characterize such devices. While different techniques are available to model and remove the deterministic errors, there has been considerable research over the past years with respect to modelling the stochastic errors which have complex structures. In order to do the latter, different replicates of these error signals are collected and a model is identified and estimated based on one of these replicates. While this procedure has allowed to improve navigation performance, it has not yet taken advantage of the information coming from all the other replicates collected on the same sensor. However, it has been observed that there is often a change of error behaviour between replicates which can also be explained by different (constant) external conditions under which each replicate was taken. Whatever the reason for the difference between replicates, it appears that the model structure remains the same between replicates but the parameter values vary. Assuming the model structure has been identified, in this work we therefore consider and study the properties of different approaches that allow to combine the information from all replicates considering this phenomenon, confirming their validity both in simulation settings and also when applied to real inertial sensor error signals. By taking into account parameter variation between replicates, this work highlights how these approaches can improve the average navigation precision as well as obtain reliable estimates of the uncertainty of the navigation solution.

Green Synthesis and Characterization of Silver Nanoparticles Using Myrsine africana Leaf Extract for Their Antibacterial, Antioxidant and Phytotoxic Activities.

Nanotechnology is the study and control of materials at length scales between 1 and 100 nanometers (nm), where incredible phenomena enable new applications. It affects all aspects of human life and is the most active research topic in modern materials science. Among the various metallic nanoparticles used in biomedical applications, silver nanoparticles (AgNPs) are among the most important and interesting nanomaterials. The aim of this study was to synthesize AgNPs from the leaf extract of Myrsine africana to investigate their antibacterial, antioxidant, and phytotoxic activities. When the leaf extract was treated with AgNO3, the color of the reaction solution changed from light brown to dark brown, indicating the formation of AgNPs. The UV-visible spectrum showed an absorption peak at 438 nm, confirming the synthesis of AgNPs. Scanning electron microscopy (SEM) showed that the AgNPs were spherical and oval with an average size of 28.32 nm. Fourier transform infrared spectroscopy confirms the presence of bio-compound functional groups on the surface of the AgNPs. The crystalline nature of the AgNPs was confirmed by XRD pattern. These biosynthesized AgNPs showed pronounced antibacterial activity against Gram-positive and Gram-negative bacteria, with higher inhibitory activity against Escherichia coli. At 40 µg/mL AgNPs, the highest antioxidant activity was obtained, which was 57.7% and an IC50 value of 77.56 µg/mL. A significant positive effect was observed on all morphological parameters when AgNPs were applied to wheat seedlings under constant external conditions at the different concentrations. The present study provides a cost-effective and environmentally friendly method for the synthesis of AgNPs, which can be effectively used in the field of therapeutics, as antimicrobial and diagnostic agents, and as plant growth promoters.

TORC1 and PKA activity towards ribosome biogenesis oscillates in synchrony with the budding yeast cell cycle.

Recent studies have revealed that the growth rate of budding yeast and mammalian cells varies during the cell cycle. By linking a multitude of signals to cell growth, the highly conserved target of rapamycin complex 1 (TORC1) and protein kinase A (PKA) pathways are prime candidates for mediating the dynamic coupling between growth and division. However, measurements of TORC1 and PKA activity during the cell cycle are still lacking. By following the localization dynamics of two TORC1 and PKA targets via time-lapse microscopy in hundreds of yeast (Saccharomyces cerevisiae) cells, we found that the activity of these pathways towards ribosome biogenesis fluctuates in synchrony with the cell cycle even under constant external conditions. Analysis of the effects of mutations of upstream TORC1 and PKA regulators suggests that internal metabolic signals partially mediate these activity changes. Our study reveals a new aspect of TORC1 and PKA signaling, which will be important for understanding growth regulation during the cell cycle.

Research of the quasistable self-potential effect of highly-metamorphic coal in laboratory conditions

The article focuses on a quasistable electrical potential registered on samples of highly-metamorphic and high-ash coal in normal laboratory conditions. The purpose of the study is to determine the possible conditions for the appearance of their effect in the coal and carbon-like argillite and the parameters of its structure. The appearance of an uncompensated charge is not associated with thermoelectric and electrokinetic phenomena and it has not been previously described. Most samples are characterized by an uneven distribution of charges along the surface in the form of a polydomain structure. Polarized samples have a layered coal-mineral structure. The charge magnitude depends on the thickness and density of the layers. In heterogeneous and heterophase substances the Maxwell-Wagner polarization is realized, arising on the boundary layers of dielectric micrograins of various substances, as well as between the areas of one dielectric with an amorphous and crystalline phase. Microinclusions and anthracite layers, which increase the potential ability of mineral components to their own polarization, can be conductors. Charged samples may have a stable, non-compensated monodomain residual charge under constant external conditions, which is characteristic of the electrets. The detected effect can be useful when creating alternative devices accumulating electricity.

New computer technologies to determine postmortem interval by the Henssge method

Background: The Henssge method is still the main thermometric method to determine postmortem interval. However, its existing software implementations are characterized by several disadvantages associated with copying simplified nomographic variants of the original mathematical models without any optimization attempts, as well as procedural imperfection in finding the roots of implicit functions. In this paper, methods are proposed for optimizing solutions to the Henssge mathematical models and determine their errors, as well as software application implementation. Aim: Optimization of the Henssge algorithm and development of a series of applications based on the obtained data, designed to determine postmortem interval. Material and methods: Methods for solving double exponential Henssge models and determining their errors based on computational mathematics and regression modeling using the least-squares method with subsequent implementation in the format of computer programs in C# language optimized. Results: The discrete nature of residual variance changes of the double exponential Henssge models intended to determine the postmortem interval according to rectal and cranioencephalic thermometry data under constant external temperature conditions is eliminated. The interval estimate determination of postmortem interval at any confidence probability is possible. The application program Warm Bodies HR was developed, which implements applied optimization methods. The application program Warm Bodies AHBG, designed to determine postmortem interval by the Henssge method in a single discrete decrease or increase conditions in the constant temperature of the external environment, including a change in the cooling conditions of the corpse, was developed. The search for the roots of implicit functions in programs is carried out using the Newton tangent method, which ensures continuous source data nature and eliminates errors associated with the need to round directly measured physical quantities. Conclusions: The developed programs are recommended for forensic medical expert practice to determine postmortem interval.

Multi-Signal Approaches for Repeated Sampling Schemes in Inertial Sensor Calibration

Inertial sensor calibration plays a progressively important role in many areas of research among which navigation engineering. By performing this task accurately, it is possible to significantly increase general navigation performance by correctly filtering out the deterministic and stochastic measurement errors that characterize such devices. While different techniques are available to model and remove the deterministic errors, there has been considerable research over the past years with respect to modelling the stochastic errors which have complex structures. In order to do the latter, different replicates of these error signals are collected and a model is identified and estimated based on one of these replicates. While this procedure has allowed to improve navigation performance, it has not yet taken advantage of the information coming from all the other replicates collected on the same sensor. However, it has been observed that there is often a change of error behaviour between replicates which can also be explained by different (constant) external conditions under which each replicate was taken. Whatever the reason for the difference between replicates, it appears that the model structure remains the same between replicates but the parameter values vary. In this work we therefore consider and study the properties of different approaches that allow to combine the information from all replicates considering this phenomenon, confirming their validity both in simulation settings and also when applied to real inertial sensor error signals. By taking into account parameter variation between replicates, this work highlights how these approaches can improve the average navigation precision as well as obtain reliable estimates of the uncertainty of the navigation solution.

ASYNCHRONOUS DEVELOPMENT OF REEFS AND REEF-BUILDING BIOTA. PALEOZOIC

This work analyses the development of reefs, which represent thick morphologically expressed carbonate massifs created by the activity of frame-forming organisms. Major stages in the development of reefs include the periods of Early Cambrian, Ordovician, Silurian-Devonian, Late Visean-Serpukhovian and Permian, the upper boundaries of which are generally determined by mass extinction events. The main reef builders during the Early Cambrian were archaeocyatha and epiphytaceans, while Ordovician reefs were created by sponges, stromatoporoids, tabulata and bryozoans. Stromatoporoid, tabulata, rugose and, to a lesser extent, bryozoans were the reef builders during the longest Silurian-Devonian period. Bryozoans and corals served as the frame-forming organisms for Upper Visean-Serpukhovian reefs. However, during the Permian, reefs were built primarily by sponges and, to a lesser extent, by bryozoans and corals. It is shown that there is no strict correspondence between the termination of reef formation and the beginning of extinction events. During extinction periods, potential reef builders did exist, although beyond the reef biocoenosis structure. Similarly, the beginning of reef formation occurs somewhat later than the appearance of the corresponding frame-forming organisms. Apparently, it takes time for organisms to develop such a biocoenosis that could trigger the formation of reef ecosystems. Reef ecosystems are stable under relatively constant external conditions, changes in which cause first the degradation of the biocoenosis and then the extinction of its constituent organisms. Therefore, the process of reef formation is terminated before the actual extinction of organisms.

Controls on the lateral channel‐migration rate of braided channel systems in coarse non‐cohesive sediment

AbstractLateral movements of alluvial river channels control the extent and reworking rates of alluvial fans, floodplains, deltas, and alluvial sections of bedrock rivers. These lateral movements can occur by gradual channel migration or by sudden changes in channel position (avulsions). Whereas models exist for rates of river avulsion, we lack a detailed understanding of the rates of lateral channel migration on the scale of a channel belt. In a two‐step process, we develop here an expression for the lateral migration rate of braided channel systems in coarse, non‐cohesive sediment. On the basis of photographic and topographic data from laboratory experiments of braided channels performed under constant external boundary conditions, we first explore the impact of autogenic variations of the channel‐system geometry (i.e. channel‐bank heights, water depths, channel‐system width, and channel slope) on channel‐migration rates. In agreement with theoretical expectations, we find that, under such constant boundary conditions, the laterally reworked volume of sediment is constant and lateral channel‐migration rates scale inversely with the channel‐bank height. Furthermore, when channel‐bank heights are accounted for, lateral migration rates are independent of the remaining channel geometry parameters. These constraints allow us, in a second step, to derive two alternative expressions for lateral channel‐migration rates under different boundary conditions using dimensional analysis. Fits of a compilation of laboratory experiments to these expressions suggest that, for a given channel bank‐height, migration rates are strongly sensitive to water discharges and more weakly sensitive to sediment discharges. In addition, external perturbations, such as changes in sediment and water discharges or base level fall, can indirectly affect lateral channel‐migration rates by modulating channel‐bank heights. © 2019 The Author. Earth Surface Processes and Landforms published by John Wiley & Sons, Ltd. © 2019 The Author. Earth Surface Processes and Landforms published by John Wiley & Sons, Ltd.

Determination of the Relationship between Cell Network Parameters with a Cubic Hermite Spline

One of the most urgent tasks during the organization of cellular networks is the task of improving the quality of service provision by the cellular operator. The paper presents a method for determining the relationship between the cellular network parameters KPI and KQI by using cubic Hermite spline. First of all, the theoretical principle of calculating and constructing a cubic Hermite spline is given in satisfaction of the conditions of the least squares’ method. The use of splines, as a signal model, can significantly improve the quality of signal processing due to the continuity of values and part of the derivatives in the nodes of spline gluing. Cubic Hermite splines, in turn, differ in their simplicity of calculations from the global one, which ensures high performance in computing, which is important for real-time operation when processing large amounts of data.On the basis of this, to evaluate the use of this spline an experimental study was conducted to establish the functional dependence between KPI and KQI network parameters. Namely, within the framework of the work, the Internet access service has been tested on the basis of the use of 3G cellular technology. The experiment consists of 50 experiments. Data was obtained under constant external conditions to ensure the purity of the experiment. On the basis of the measured data for each parameter, the ordinates vector of the spline bonding nodes was calculated and an approximation of the parameters was made using Cubic Hermite splines.The next step is to establish the influence degree of each KPI parameter on the single KQI parameter. The analytical connection coefficients were found taking into account that the mean square error of the KQI parameter prediction from the KPI parameters would be minimal. As a result, on the above data basis, the statistical alignment of the time series of the KQI parameter was performed, that is, it was leveled the KQI physics process using already found KPI approximated parameters.The use of splines allows us to find not only statistical estimates of the desired parameters of the spline approximations, but also their confidence intervals, which increases the accuracy and reliability of the results and it is undoubtedly the advantage of the chosen approach. In our case, this allows you to get a KQI forecast from KPI.In the future, research under such conditions will be followed by the implementation of a specific KPI parameter choice in order to its improvement to improve the quality of service provided to users of the cellular communication operator.Ref. 11, fig. 10.

Creep of concrete caused by freeze and thaw cycle

To the best knowledge available today, the creep of concrete is understood as slow plastic deformation caused by continuous external factors. Changes occurring in the structure of concrete are however not discussed. Creep as a phenomenon is typically perceived “in purity”, in an invariable and favorable environment. Evolution of creep deformations thus has a fading character and usually goes along with consolidation of concrete. It is only under loads near the threshold of concrete’s long-term strength that micro-destructions tend to grow during the first phase following application of the load. Creep phenomenon is researched «in pure form», i.e. in constant favorable external conditions. Developing of creep deformations has fading character and accompanied by seal of concrete. In real exploitation conditions of constructions appears changes in temperature and humidity, influencing on development of creep deformation. Alternate freezing and thawing of concrete, which most affects durability, causes in unloaded concrete significant extension deformations. Deformation development under the joint action of loads and alternate freezing and thawingalmost was not researched. In the article presented results of concrete deformation research, differing by frost resistance, under loads in the range from 0.2 to 0.7 of prismatic strength. Obtained results allows reasonable take stress value in consideration with expected deformations in the process of operation.

Thermodynamic Analysis of Organic Rankine Cycle with Hydrofluoroethers as Working Fluids

Abstract This paper presents an analysis of organic Rankine cycle (ORC) using hydrofluoroethers including HFE7000, HFE7100 and HFE7500 as working fluids under constant external conditions. A computer program has been developed to parametrically compare the first and second law efficiencies, power output, turbine size factor with increase in turbine entry temperature. The results show that HFE7000 produces the maximum thermodynamic efficiencies and performs better in view of the net power output under the given working conditions. Moreover, HFE7000 has the lowest turbine size factor comparing with HFE7100 and HFE7500. Therefore, HFE7000 can be recommended to be used as working fluid in ORC to convert low-grade heat into power.

Concrete Deformations under Simultaneous Impact of Loading and Alternate Freezing and Thawing

To the best knowledge available today, the creep of concrete is understood as slow plastic deformation caused by continuous external factors. Changes occurring in the structure of concrete are however not discussed. Creep as a phenomenon is typically perceived “in purity”, in an invariable and favorable environment. Evolution of creep deformations thus has a fading character and usually goes along with consolidation of concrete. It is only under loads near the threshold of concrete’s long-term strength that micro-destructions tend to grow during the first phase following application of the load. Creep phenomenon is researched «in pure form», i.e. in constant favorable external conditions. Developing of creep deformations has fading character and accompanied by seal of concrete. In real exploitation conditions of constructions appears changes in temperature and humidity, influencing on development of creep deformation. Alternate freezing and thawing of concrete, which most affects durability, causes in unloaded concrete significant extension deformations. Deformation development under the joint action of loads and alternate freezing and thawingalmost was not researched. In the article presented results of concrete deformation research, differing by frost resistance, under loads in the range from 0,2 to 0,7 of prismatic strength.

Model development and analysis of the evolution of coal permeability under different boundary conditions

Coal permeability is an important parameter for coalbed methane (CBM) production and CO2-enhanced coalbed methane (ECBM) recovery. Coal permeability is mainly controlled by the structure of the coal. In this study, based on the pore-elasticity principle and the coal matrix-fracture interactions, we developed an analytical coal permeability model and its five forms under the corresponding specific boundary conditions, and four of them are validated by matching the corresponding field data or experimental data. The study presents a discussion of the permeability evolution for the different forms. The results show that the coal permeability under constant volume and constant effective stress conditions are controlled by the matrix sorption deformation and that the coal permeability under uniaxial strain and constant external stress conditions is governed by both the effective stress and the matrix sorption deformation. The constant volume model may be a special form of the constant effective stress model. For the same pressure drawdown, the permeability that is predicted under constant external stress conditions decreases more than that the permeability that is predicted under uniaxial strain conditions, and the permeability change induced by the matrix sorption deformation depended on the values of the internal swelling partition. The boundary conditions are important to the model, and different boundary conditions will lead to different evolutions of coal permeability. The permeability model can only be used to predict the evolution of permeability under the corresponding boundary conditions.

Diagnostics of the anti-seepage screen of a protective dam in permafrost on using an inverse problem with piezometric measurement data

Using the finite elementmethod we designed and implemented a nonlinear geomechanical model of the rock mass in the vicinity of the protective dam of tailing facilities in the permafrost of the Kumtor mine (the Kyrgyz Republic). The model takes into account the information on the structure of the object, the data on the strain-strength, thermophysical and filtration properties of frozen and thawed soil, as well as on the seasonal variations in air temperature. Numerical experiments showed that, under constant external conditions, the invariant properties of the rock mass, and the position of the neutral layer, the zero isotherm separating frozen and thawed rocks reaches a stationary position in 12–15 years after filling the storage; minor damage to the antiseepage screen can lead to a vast destruction area in the body of the dam. Using synthetic data, we demonstrated the solvability of the inverse boundary-value problem of determining the timing and location of damage in the anti-seepage screen from the data of piezometric measurements at several observation wells.

Sequential metabolic phases as a means to optimize cellular output in a constant environment.

Temporal changes of gene expression are a well-known regulatory feature of all cells, which is commonly perceived as a strategy to adapt the proteome to varying external conditions. However, temporal (rhythmic and non-rhythmic) changes of gene expression are also observed under virtually constant external conditions. Here we hypothesize that such changes are a means to render the synthesis of the metabolic output more efficient than under conditions of constant gene activities. In order to substantiate this hypothesis, we used a flux-balance model of the cellular metabolism. The total time span spent on the production of a given set of target metabolites was split into a series of shorter time intervals (metabolic phases) during which only selected groups of metabolic genes are active. The related flux distributions were calculated under the constraint that genes can be either active or inactive whereby the amount of protein related to an active gene is only controlled by the number of active genes: the lower the number of active genes the more protein can be allocated to the enzymes carrying non-zero fluxes. This concept of a predominantly protein-limited efficiency of gene expression clearly differs from other concepts resting on the assumption of an optimal gene regulation capable of allocating to all enzymes and transporters just that fraction of protein necessary to prevent rate limitation. Applying this concept to a simplified metabolic network of the central carbon metabolism with glucose or lactate as alternative substrates, we demonstrate that switching between optimally chosen stationary flux modes comprising different sets of active genes allows producing a demanded amount of target metabolites in a significantly shorter time than by a single optimal flux mode at fixed gene activities. Our model-based findings suggest that temporal expression of metabolic genes can be advantageous even under conditions of constant external substrate supply.

On Defining Climate and Climate Change

The aim of the paper is to provide a clear and thorough conceptual analysis of the main candidates for a definition of climate and climate change. Five desiderata on a definition of climate are presented: it should be empirically applicable, it should correctly classify different climates, it should not depend on our knowledge, is should be applicable to the past, present and future and it should be mathematically well-defined. Then five definitions are discussed: climate as distribution over time for constant external conditions, climate as distribution over time when the external conditions vary as in reality, climate as distribution over time relative to regimes of varying external conditions, climate as the ensemble distribution for constant external conditions, and climate as the ensemble distribution when the external conditions vary as in reality. The third definition is novel and is introduced as a response to problems with existing definitions. The conclusion is that most definitions encounter serious problems and that the third definition is most promising.

A Stochastic Model for Reliability Analysis in Freeway Networks

The capacity of a freeway is traditionally considered as a constant value in traffic engineering. In reality, capacities vary according to external conditions such as dry or wet road surfaces, daylight or darkness, and to the prevailing travel purpose of drivers on the freeway. Even under constant external conditions different capacities can be observed on freeways because of variations in driver behaviors. A capacity in this sense is no longer a constant value. Empirical analyses of traffic flow patterns show that this type of capacity can be treated as Weibull distributed. Using the distribution function of capacities, the probability of traffic breakdowns and thus the reliability of the freeway can be estimated. Up to now stochastic capacities have been mainly analyzed at specific points which are considered as bottlenecks. The stochastic relationship between the adjacent bottlenecks has not been taken into account. Furthermore, if a long segment of a freeway without clearly defined bottlenecks is analyzed, no methods are available for estimating the distributed capacities of several combined bottlenecks along a freeway. This paper introduces a concept dealing with the stochastic interpretation of capacity and breakdown probability within a larger freeway network. The stochastic methodology presented delivers a theoretical average capacity and the probability of breakdowns for freeway segments with different lengths. The methodology can also be used to identify the effects of consecutive freeway segments and bottlenecks such as on-ramps, off-ramps, and weaving areas with different characteristics. Using the proposed method, it is possible to determine the probability distribution function of breaking down from free flow into congested flow for a freeway segment as a function of the average volume or density. Using the methodology presented in this paper, the risk of disturbance of traffic flow along a freeway segment or within a freeway network can be analyzed.