Hasil untuk "Thermodynamics"

Amal Mohammed Darweesh, Adel Salim Tayyah, Sarem H. Hadi et al.

In this paper, we introduce a new logarithmic integral operator that unifies differentiation and fractional integration within the complex domain. The present work addresses this gap by applying the proposed operator to analytic functions represented by alternating power series. The method demonstrates that the coefficients can be reorganized in a controlled manner without affecting convergence or analytic behavior. Using this framework, we derive third-order differential subordination and superordination results, which naturally lead to corresponding sandwich-type results. The findings confirm that the introduced operator offers an effective analytical tool for studying distortion, growth, and mapping properties of analytic functions, with promising potential for future applications in fluid mechanics.

Ying Pan, Tao Wang, Runjia Wang et al.

Abstract Control of chiral assembly across length scales is desirable but challenging. Herein, we demonstrate controllable construction of microscopic chiral twists through hierarchical assembly of enantiomeric styrylpyridinium-derived glutamide amphiphiles (L/D-SPG). By combining variable-temperature spectroscopy with in-situ real-time optical microscopic observation, the dynamic chirality transfer process across spatial and length scales during assembly is elucidated. It is revealed that hydrophobic interactions between alkyl chains and intermolecular hydrogen bonds dominate the initial assembly of SPG oligomers, which subsequently elongate into microscopic twists through synergistic action of multiple non-covalent bonds under stereochemical control. The coherent cross-length-scale chirality transfer drives a dramatic amplification of chiroptical signals, evolving from undetectable circularly polarized luminescence (CPL) in the monomeric state and weak CPL with a small luminescence dissymmetry factor (|g lum | = 2.8 × 10−3) in the non-hierarchical nanostructures to a |g lum| value of 0.11 among single-component supramolecular gel systems. This work not only provides a direct spatiotemporal observation of chirality transfer from molecular to micron scales, but also establishes a supramolecular design strategy for high-performance CPL materials through optimized hierarchical organization.

Bakht Muhammad Khan, Abdul Wadood, Herie Park et al.

Efficient coordination of directional overcurrent relays (DOCRs) is vital for maintaining the stability and reliability of electrical power systems (EPSs). The task of optimizing DOCR coordination in complex power networks is modeled as an optimization problem. This study aims to enhance the performance of protection systems by minimizing the cumulative operating time of DOCRs. This is achieved by effectively synchronizing primary and backup relays while ensuring that coordination time intervals (CTIs) remain within predefined limits (0.2 to 0.5 s). A novel optimization strategy, the fractional-order derivative war optimizer (FODWO), is proposed to address this challenge. This innovative approach integrates the principles of fractional calculus (FC) into the conventional war optimization (WO) algorithm, significantly improving its optimization properties. The incorporation of fractional-order derivatives (FODs) enhances the algorithm’s ability to navigate complex optimization landscapes, avoiding local minima and achieving globally optimal solutions more efficiently. This leads to the reduced cumulative operating time of DOCRs and improved reliability of the protection system. The FODWO method was rigorously tested on standard EPSs, including IEEE three, eight, and fifteen bus systems, as well as on eleven benchmark optimization functions, encompassing unimodal and multimodal problems. The comparative analysis demonstrates that incorporating fractional-order derivatives (FODs) into the WO enhances its efficiency, enabling it to achieve globally optimal solutions and reduce the cumulative operating time of DOCRs by 3%, 6%, and 3% in the case of a three, eight, and fifteen bus system, respectively, compared to the traditional WO algorithm. To validate the effectiveness of FODWO, comprehensive statistical analyses were conducted, including box plots, quantile–quantile (QQ) plots, the empirical cumulative distribution function (ECDF), and minimal fitness evolution across simulations. These analyses confirm the robustness, reliability, and consistency of the FODWO approach. Comparative evaluations reveal that FODWO outperforms other state-of-the-art nature-inspired algorithms and traditional optimization methods, making it a highly effective tool for DOCR coordination in EPSs.

Sameeha Ali Raad, Mohamed Abdella Abdou

In this paper, the authors consider a problem with comprehensive properties in terms of form and content in the space <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi mathvariant="script">L</mi></mrow><mrow><mn>2</mn></mrow></msub><mfenced open="[" close="]" separators="|"><mrow><mfenced separators="|"><mrow><mi>a</mi><mo>,</mo><mi>b</mi></mrow></mfenced><mo>×</mo><mfenced separators="|"><mrow><mi mathvariant="normal">c</mi><mo>,</mo><mi mathvariant="normal">d</mi></mrow></mfenced></mrow></mfenced><mo>×</mo><mi>C</mi><mfenced open="[" close="]" separators="|"><mrow><mn>0</mn><mo>,</mo><mi>T</mi></mrow></mfenced><mo>,</mo><mi>T</mi><mo><</mo><mn>1</mn></mrow></semantics></math></inline-formula>. In terms of time form, we assume that the time phase delay is implicitly contained in a nonlinear differential integral equation. The positional part is considered in two dimensions, and the position’s kernel is a general singular kernel, many different forms of which will be derived. In terms of content, all of the previously established numerical techniques are only appropriate for studying special cases of the kernel separately but are not suitable for studying the general kernel. This led to the use of the Toeplitz matrix method, which deals with the kernel in its extended nonlinear form and the special kernels will be studied as applications of the method. Moreover, this method has the advantage of converting all single integrals into regular integrals that can be easily solved. Additionally, the researchers examine the solution’s existence, uniqueness, and convergence in this paper. The error and its stability are also studied. At the end of the research, the authors studied some numerical applications of some of the singular kernels derived from the general kernel, examining the approximation error in each application separately.

Junchao Yu, Zichao Xi, Jinhui Su et al.

Electrochemical nitrate reduction reaction in alkaline condition involves two reactants, the nitrate (NO3−) and the water (H2O). Although the significance of the active ∗H species produced from the dissociation of H2O has been proved, the correlation between the reaction pathways and the ∗H species is often overlooked. Herein, Co(OH)2–CoP supported Ru nanoclusters is designed for electrocatalytic nitrate reduction and shows a record-high faradaic efficiency of 99.7% at an ultralow potential of 0.1 ​V versus reversible hydrogen electrode. Experiments and theoretical calculations reveal that in addition to the faster proton transfer kinetics, the reaction pathway is strongly correlated with ∗H supply with the aid of CoP, that is, the direct hydrogenation of ∗NOH instead of deprotonation over Ru sites with the lowest energy barrier is promoted with the moderate production of ∗H species. This work provides new insights into the impact of ∗H species on the thermodynamics and kinetics of electrocatalytic nitrate reduction.

Dănuț Cristian Urduza, Lavinia Grosu, Adalia Andreea Percembli (Chelmuș) et al.

Air liquefaction systems are essential in cryogenic engineering and energy storage, yet their performance is often constrained by significant exergy destruction. This study develops an exergy-based assessment of the Linde–Hampson air liquefaction cycle to identify dominant sources of inefficiency and explore strategies for improvement. The analysis shows that throttling (≈41%) and compression (≈40%) represent the major contributions to exergy losses, followed by finite-temperature heat transfer (≈15%) in the recuperative heat exchanger. To mitigate these losses, fractional throttling and optimized inlet conditions are proposed, leading to reduced compressor work and improved overall efficiency. A comparative study of a two-stage throttling configuration demonstrates a decrease in throttling-related exergy destruction to approximately 30%. Reverse Pinch analysis is employed to verify the thermal coupling of hot and cold streams and to determine the minimum feasible temperature difference. The design optimization of the recuperative heat exchanger identifies an optimal velocity ratio that minimizes pressure losses and quantifies how compression pressure affects the required heat transfer surface area. The results provide a systematic framework for improving the thermodynamic performance of air liquefaction cycles, highlighting exergy analysis as a powerful tool for guiding structural modifications and functional optimization.

Hafiz Ali Hamza Gondal, Seong In Jeong, Won Ho Jang et al.

The accurate classification of plant diseases is vital for global food security, as diseases can cause major yield losses and threaten sustainable and precision agriculture. The classification of plant diseases in low-light noisy environments is crucial because crops can be continuously monitored even at night. Important visual cues of disease symptoms can be lost due to the degraded quality of images captured under low-illumination, resulting in poor performance of conventional plant disease classifiers. However, researchers have proposed various techniques for classifying plant diseases in daylight, and no studies have been conducted for low-light noisy environments. Therefore, we propose a novel model for classifying plant diseases from low-light noisy images called dilated pixel attention network (DPA-Net). DPA-Net uses a pixel attention mechanism and multi-layer dilated convolution with a high receptive field, which obtains essential features while highlighting the most relevant information under this challenging condition, allowing more accurate classification results. Additionally, we performed fractal dimension estimation on diseased and healthy leaves to analyze the structural irregularities and complexities. For the performance evaluation, experiments were conducted on two public datasets: the PlantVillage and Potato Leaf Disease datasets. In both datasets, the image resolution is 256 × 256 pixels in joint photographic experts group (JPG) format. For the first dataset, DPA-Net achieved an average accuracy of 92.11% and harmonic mean of precision and recall (F1-score) of 89.11%. For the second dataset, it achieved an average accuracy of 88.92% and an F1-score of 88.60%. These results revealed that the proposed method outperforms state-of-the-art methods. On the first dataset, our method achieved an improvement of 2.27% in average accuracy and 2.86% in F1-score compared to the baseline. Similarly, on the second dataset, it attained an improvement of 6.32% in average accuracy and 6.37% in F1-score over the baseline. In addition, we confirm that our method is effective with the real low-illumination dataset self-constructed by capturing images at 0 lux using a smartphone at night. This approach provides farmers with an affordable practical tool for early disease detection, which can support crop protection worldwide.

Yang Wang, Baoyuan Zhong, Yunsheng Zhang et al.

The wetting behavior of shale oil and gas on shale surfaces is determined by the interplay of organic matter (OM), mineral composition, and the intricate pore network structure of the shale. In this paper, the sensitivity responses of the Frenkel–Halsey–Hill (FHH), Neimark (NM), and Wang–Li (WL) fractal models to marine shale with varying material components are analyzed, based on liquid nitrogen adsorption experiments and fractal theory. The wettability evolution model of shale with different maturity stages is established to reveal the heterogeneity characteristics of wettability in shale with complex pore structures. Results show that the NM and WL models offer distinct advantages in evaluating the reservoir structure of shale oil and gas resources. The existence of large-diameter pores is conducive to the homogeneous development of the pore structure. The coupling relationship between pore volume, pore size and pore specific surface affects the fractal characteristics of the pore structure. For highly overmature shale, with an increase in fractal dimension, the wettability of shale changes from neutral-wet to water-wet. For ultramature shale, the higher heterogeneity of the pore structure leads to larger contact angles, causing the wettability to transition gradually from water-wet to oil-wet. In addition, the sensitivity analysis of wettability to fractal structure parameters is examined from the perspective of OM maturation and evolution.

Yulin SONG, Yuxing LI

Objective Hydrogen energy has drawn significant attention as the strategy of energy transition pushing forward, making it essential to establish reliable hydrogen transmission systems. For the construction of hydrogen service pipelines, it is vital to evaluate the risk of material failure due to hydrogen embrittlement in pipes. Hydrogen embrittlement occurs when hydrogen comes into contact with pipeline steel through a process consisting of six steps, among which hydrogen generation and adsorption lack of well-developed theories, leading to disparities among scholars in their understanding of the hydrogen adsorption mechanism. Therefore, studying the dissociative adsorption mechanism of hydrogen on pipeline steel is particularly crucial. Methods Focusing on hydrogen generation and adsorption, this paper presents a systematic review of the dissociative adsorption mechanism of hydrogen on pipeline steel. Lennard-Jones potential curves are incorporated to illustrate the interaction process between hydrogen and the iron surface. The dissociative adsorption modes of hydrogen on the iron surface were simulated and calculated leveraging thermodynamics and density functional theory. By analyzing orbital bonding and charge transfer, the dissociative adsorption mechanism of hydrogen on the iron surface was identified. This paper summarizes three influencing factors in the dissociative adsorption of hydrogen: the environment, the surface, and the hydrogen itself, while proposing corresponding methods to inhibit the dissociative adsorption of hydrogen. Results Hydrogen was found to be adsorbed on the surface of pipeline steel through activated dissociation into hydrogen atoms, which then enter the pipes. This process follows the primary mechanism in which orbital hybridization between H2 and Fe leads to the rupture of the H-H bonds and the subsequent formation of H-Fe bonds. Several factors were observed to influence the dissociative adsorption of hydrogen to varying degrees, including hydrogen concentration, hydrogen flow state, gas impurities, temperature, and the condition of the iron surface. Based on these findings, three methods were proposed to enhance hydrogen resistance: coating, corrosion films, and protective gas. All these methods aim to prevent hydrogen from coming into contact with pipeline steel and causing embrittlement from the perspective of surface adsorption, with the protective gas method identified as the most economical and convenient option. Conclusion This research clarifies the specific process of H2 dissociative adsorption on the surface of pipeline steel. Future research is recommended to explore the dissociative adsorption of hydrogen under multi-factor coupling conditions, to identify economical and effective hydrogen resistance options. These outcomes will establish a foundation for the integrity management of hydrogen service pipelines and ensure the safety of pipes in contact with hydrogen.

Vansh Kharbanda, Benedikt Sabass

Sensory adaptation enables organisms to adjust their perception in a changing environment. A paradigm is bacterial chemotaxis, where the output activity of chemoreceptors is adapted to different baseline concentrations via receptor methylation. The range of internal receptor states limits the stimulus magnitude to which these systems can adapt. Here, we employ a highly idealized, Langevin-equation based model to study how the finite range of state variables affects the adaptation accuracy and the energy dissipation in individual and coupled systems. Maintaining an adaptive state requires constant energy dissipation. We show that the steady-state dissipation rate increases approximately linearly with the adaptation accuracy for varying stimulus magnitudes in the so-called perfect adaptation limit. This result complements the well-known logarithmic cost-accuracy relationship for varying chemical driving. Next, we study linearly coupled pairs of sensory units. We find that the interaction reduces the dissipation rate per unit and affects the overall cost-accuracy relationship. A coupling of the slow methylation variables results in a better accuracy than a coupling of activities. Overall, the findings highlight the significance of both the working range and collective operation mode as crucial design factors that impact the accuracy and energy expenditure of molecular adaptation networks.

Eman M. Saad, Manar Wagdy, Adel S. Orabi

Abstract This research focuses on the utilization of nano glauconite clay as an environmentally friendly sorbent for the removal of cationic dyes, particularly Methylene Blue (MB), from polluted water. The glauconite clay was sourced from the El Gidida region of Egypt and subjected to grinding in a laboratory-type ball mill to ensure homogeneity and increase the active sites available for the adsorption process. The resulting ball milled nano clay (BMNC) was characterized using techniques such as X-ray fluorescence (XRF), Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The concentration of MB dye was monitored using UV–Vis spectroscopy to assess the adsorption capacity of BMNC under various conditions including pH, time, dose, and temperature. The optimal conditions for the adsorption process were determined to be a pH range of 7–8, a contact time of 60 min, and a dose of 200 ppm, resulting in an adsorption capacity of 128 mg/g. This process demonstrated both low cost and high speed. The adsorption mechanism of MB on the BMNC surface was evaluated through kinetics, adsorption isotherms, and thermodynamics. The experimental data indicated an endothermic, spontaneous, and thermodynamically favourable adsorption process, which was further supported by simulated modelling results using Forcite program. The in-silico data aligned well with the experimental findings. Additionally, the study assessed the interference of salts, metal ions, and other dyes on MB adsorption onto BMNC, showing promising results. These findings strongly support the effectiveness of our sorbent substrate under challenging conditions.

Guanchu Guo, Chuanlei Liu, Yuxiang Chen et al.

The separation of mixtures with close boiling points is a critical task in the petrochemical industry, and one such mixture that requires separation is o-xylene/styrene. The STED process is used to separate o-xylene/styrene, which contains a certain amount of organic sulfur in the product due to the limitations of the process. In this study, the process underwent enhancements to attain the effective separation of styrene and accomplish deep desulfurization. A mixture of sulfolane (SUL) and N-methylpyrrolidone (NMP) was selected as the extraction solvent after calculating the UNIFAC group contributions. An orthogonal experiment was conducted to investigate the effects of the solvent/oil ratio, reflux ratio, water addition rate, and solvent ratio on the product. The correspondence between each factor and the indexes examined was determined, enabling the optimization and prediction of the styrene product quality. The final optimized conditions for the extractive distillation column are as follows: solvent/oil ratio of 7, reflux ratio of 4.5, water addition rate of 6000 kg/h, and a solvent ratio of 9:1. Under optimal conditions, the purity of the product was observed to be greater than that of the original process and the sulfur content of the product can be reduced to lower than 10 ppm at the cost of an increase of 12.31% in energy consumption.

Шачнева Е.Ю.

В статье описан процесс расчета основных термодинамических показателей комплексообразования химических соединений, отличающихся особым типом взаимодействия – донорно-акцепторным взаимодействием. Они представлены широким классом химических соединений с многообразными структурами, электронным строением и свойствами, довольно часто встречающимися в живой и неживой природе. Рассмотренная группа веществ нашла широкое использование в промышленности, сельском хозяйстве и медицине.Описана роль константы устойчивости, энергии Гиббса, энтальпии и энтропии процесса. Приведены уравнения расчеты потенциальной энергии комплексообразования в процессах накопления металлов в растениях. Приведена зависимость величины постоянной экранирования от числа лигандов в комплексе. Представлено высокое значение коэффициента корреляции.Описано влияние термохимического радиуса на термодинамические свойства ионов. Охарактеризованы перспективы создания новых функциональных материалов для решения важнейшей экологической и сырьевой проблемы.

Jorge E. Macías-Díaz, Tassos Bountis

For the first time, a new dissipation-preserving scheme is proposed and analyzed to solve a Caputo–Riesz time-space-fractional multidimensional nonlinear wave equation with generalized potential. We consider initial conditions and impose homogeneous Dirichlet data on the boundary of a bounded hyper cube. We introduce an energy-type functional and prove that the new mathematical model obeys a conservation law. Motivated by these facts, we propose a finite-difference scheme to approximate the solutions of the continuous model. A discrete form of the continuous energy is proposed and the discrete operator is shown to satisfy a conservation law, in agreement with its continuous counterpart. We employ a fixed-point theorem to establish theoretically the existence of solutions and study analytically the numerical properties of consistency, stability and convergence. We carry out a number of numerical simulations to verify the validity of our theoretical results.

Adam Hewgill, Gabriele De Chiara, Alberto Imparato

Local master equations are a widespread tool to model open quantum systems, especially in the context of many-body systems. These equations, however, are believed to lead to thermodynamic anomalies and violation of the laws of thermodynamics. In contrast, here we rigorously prove that local master equations are consistent with thermodynamics and its laws without resorting to a microscopic model, as done in previous works. In particular, we consider a quantum system in contact with multiple baths and identify the relevant contributions to the total energy, heat currents, and entropy production rate. We show that the second law of thermodynamics holds when one considers the proper expression we derive for the heat currents. We confirm the results for the quantum heat currents by using a heuristic argument that connects the quantum probability currents with the energy currents, using an analogous approach as in classical stochastic thermodynamics. We finally use our results to investigate the thermodynamic properties of a set of quantum rotors operating as thermal devices and show that a suitable design of three rotors can work as an absorption refrigerator or a thermal rectifier. For the machines considered here, we also perform an optimization of the system parameters using an algorithm of reinforcement learning.

Radouan Boukharfane, Aimad Er-raiy, Linda Alzaben et al.

The decomposition of the local motion of a fluid into straining, shearing, and rigid-body rotation is examined in this work for a compressible isotropic turbulence by means of direct numerical simulations. The triple decomposition is closely associated with a basic reference frame (BRF), in which the extraction of the biasing effect of shear is maximized. In this study, a new computational and inexpensive procedure is proposed to identify the BRF for a three-dimensional flow field. In addition, the influence of compressibility effects on some statistical properties of the turbulent structures is addressed. The direct numerical simulations are carried out with a Reynolds number that is based on the Taylor micro-scale of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>Re</mi><mi>λ</mi></msub><mo>=</mo><mn>100</mn></mrow></semantics></math></inline-formula> for various turbulent Mach numbers that range from <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>Ma</mi><mi>t</mi></msub><mo>=</mo><mn>0.12</mn></mrow></semantics></math></inline-formula> to <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>Ma</mi><mi>t</mi></msub><mo>=</mo><mn>0.89</mn></mrow></semantics></math></inline-formula>. The DNS database is generated with an improved seventh-order accurate weighted essentially non-oscillatory scheme to discretize the non-linear advective terms, and an eighth-order accurate centered finite difference scheme is retained for the diffusive terms. One of the major findings of this analysis is that regions featuring strong rigid-body rotations or straining motions are highly spatially intermittent, while most of the flow regions exhibit moderately strong shearing motions in the absence of rigid-body rotations and straining motions. The majority of compressibility effects can be estimated if the scaling laws in the case of compressible turbulence are rescaled by only considering the solenoidal contributions.

Tahir Naseem, Umar Nazir, Essam R. El-Zahar et al.

The current research is prepared to address the transport phenomenon in a hydro-magnetized flow model on a porous stretching sheet. Mass and heat transport are modeled via temperature dependent models of thermal conductivity and diffusion coefficients. Accordingly, the involvement of radiation, chemical reaction, the Dufour effect, and the Soret effect are involved. The flow presenting expression has been modeled via boundary layer approximation and the flow is produced due to the experimental stretching sheet. The governing equations have been approximated numerically via shooting method. The efficiency of the scheme is established by including the comparative study. Moreover, a decline in the velocity field is recorded against the escalating values of the porosity parameter and the magnetic parameter.

Salvatore Caruso, Claudio Giberti, Lamberto Rondoni

An exact response theory has recently been developed within the field of Nonequilibrium Molecular Dynamics. Its main ingredient is known as the Dissipation Function, <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">Ω</mi></semantics></math></inline-formula>. This quantity determines nonequilbrium properties like thermodynamic potentials do with equilibrium states. In particular, <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">Ω</mi></semantics></math></inline-formula> can be used to determine the exact response of particle systems obeying classical mechanical laws, subjected to perturbations of arbitrary size. Under certain conditions, it can also be used to express the response of a single system, in contrast to the standard response theory, which concerns ensembles of identical systems. The dimensions of <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">Ω</mi></semantics></math></inline-formula> are those of a rate, hence <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">Ω</mi></semantics></math></inline-formula> can be associated with the entropy production rate, provided local thermodynamic equilibrium holds. When this is not the case for a particle system, or generic dynamical systems are considered, <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">Ω</mi></semantics></math></inline-formula> can equally be defined, and it yields formal, thermodynamic-like, relations. While such relations may have no physical content, they may still constitute interesting characterizations of the relevant dynamics. Moreover, such a formal approach turns physically relevant, because it allows a deeper analysis of <inline-formula><math display="inline"><semantics><mi mathvariant="sans-serif">Ω</mi></semantics></math></inline-formula> and of response theory than possible in case of fully fledged physical models. Here, we investigate the relation between linear and exact response, pointing out conditions for the validity of the response theory, as well as difficulties and opportunities for the physical interpretation of certain formal results.

Rodrigo Guillermo, Fares Mario A

<p>Abstract</p> <p>Background</p> <p>The potential role of RNA molecules as gene expression regulators has led to a new perspective on the intracellular control and genome organization. Because secondary structures are crucial for their regulatory role, we sought to investigate their robustness to mutations and environmental changes.</p> <p>Results</p> <p>Here, we dissected the structural robustness landscape of the small non-coding RNAs (sncRNAs) encoded in the genome of the bacterium <it>Escherichia coli</it>. We found that bacterial sncRNAs are not significantly robust to both mutational and environmental perturbations when compared against artificial, unbiased sequences. However, we found that, on average, bacterial sncRNAs tend to be significantly plastic, and that mutational and environmental robustness strongly correlate. We further found that, on average, epistasis in bacterial sncRNAs is significantly antagonistic, and positively correlates with plasticity. Moreover, the evolution of robustness is likely dependent upon the environmental stability of the cell, with more fluctuating environments leading to the emergence and fixation of more robust molecules. Mutational robustness also appears to be correlated with structural functionality and complexity.</p> <p>Conclusion</p> <p>Our study provides a deep characterization of the structural robustness landscape of bacterial sncRNAs, suggesting that evolvability could be evolved as a consequence of selection for more plastic molecules. It also supports that environmental fluctuations could promote mutational robustness. As a result, plasticity emerges to link robustness, functionality and evolvability.</p>

Matthew L Rizk, James C Liao

Ensemble Modeling (EM) is a recently developed method for metabolic modeling, particularly for utilizing the effect of enzyme tuning data on the production of a specific compound to refine the model. This approach is used here to investigate the production of aromatic products in Escherichia coli. Instead of using dynamic metabolite data to fit a model, the EM approach uses phenotypic data (effects of enzyme overexpression or knockouts on the steady state production rate) to screen possible models. These data are routinely generated during strain design. An ensemble of models is constructed that all reach the same steady state and are based on the same mechanistic framework at the elementary reaction level. The behavior of the models spans the kinetics allowable by thermodynamics. Then by using existing data from the literature for the overexpression of genes coding for transketolase (Tkt), transaldolase (Tal), and phosphoenolpyruvate synthase (Pps) to screen the ensemble, we arrive at a set of models that properly describes the known enzyme overexpression phenotypes. This subset of models becomes more predictive as additional data are used to refine the models. The final ensemble of models demonstrates the characteristic of the cell that Tkt is the first rate controlling step, and correctly predicts that only after Tkt is overexpressed does an increase in Pps increase the production rate of aromatics. This work demonstrates that EM is able to capture the result of enzyme overexpression on aromatic producing bacteria by successfully utilizing routinely generated enzyme tuning data to guide model learning.