The European Physical Journal E最新文献

{"title":"A simulation study of electrical conductivity of porous rocks: effect of clay, porosity, temperature and Peclet number.","authors":"Supti Sadhukhan, Tapati Dutta","doi":"10.1140/epje/s10189-025-00494-3","DOIUrl":"https://doi.org/10.1140/epje/s10189-025-00494-3","url":null,"abstract":"<p><p>This study investigates the impact of clay content and temperature variation on the electrical conductivity of three-dimensional fluid-filled porous rocks. The role of varying pore throat radii has been included in the course of clay fraction variation in the conducting channels of the rock samples. The research identifies a critical ratio of clay conductance to fluid conductance that dictates the regime of electrical conductance behaviour. A nonlinear increase in electrical conductance is observed when the clay-to-fluid conductance ratio exceeds the critical ratio, whereas a linear relationship is maintained below this critical ratio. A modified form of Archie's law relating effective conductivity and porosity has been proposed for the clay coated channels. The intricate relationship between Peclet number, pore throat size, and temperature on the electrical conductivity of fluid-filled straight channels in three dimensions has also been investigated. Results revealed a quadratic increase in conductance with porosity under steady-state conditions across all Peclet number ranges examined. While the conductivity remained constant with porosity for each Peclet number, the rate of increase in conductivity diminished with it. Nonlinear increase in conductivity was observed with temperature in the transient flow regime with a threshold temperature marking the onset of conductivity. Conductivity was augmented with increase in observation time in the transient state for the entire temperature range considered. Close to the attainment of saturation in electrical conductivity, the conductivity changed linearly with temperature until a steady value was reached.</p>","PeriodicalId":790,"journal":{"name":"The European Physical Journal E","volume":"48 4-5","pages":"29"},"PeriodicalIF":1.8,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144155488","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dynamical networking using Gaussian fields","authors":"Nadine du Toit,&nbsp;Kristian K. Müller-Nedebock","doi":"10.1140/epje/s10189-025-00489-0","DOIUrl":"10.1140/epje/s10189-025-00489-0","url":null,"abstract":"<p>A novel field theoretical approach towards modelling dynamic networking in complex systems is presented. An equilibrium networking formalism which utilises Gaussian fields is adapted to model the dynamics of particles that can bind and unbind from one another. Here, <i>networking</i> refers to the introduction of instantaneous co-localisation constraints and does not necessitate the formation of a well-defined transient or persistent network. By combining this formalism with Martin–Siggia–Rose generating functionals, a weighted generating functional for the networked system is obtained. The networking formalism introduces spatial and temporal constraints into the Langevin dynamics, via statistical weights, thereby accounting for all possible configurations in which particles can be networked to one another. A simple example of Brownian particles which can bind and unbind from one another demonstrates the tool and that this leads to results for physical quantities in a collective description. Applying the networking formalism to model the dynamics of cross-linking polymers in a mixture, we can calculate the average number of networking instances. As expected, the dynamic structure factors for each type of polymer show that the system collapses once networking is introduced, but that the addition of a repulsive time-dependent potential above a minimum strength prevents this. The examples presented in this paper indicate that this novel approach towards modelling dynamic networking could be applied to a range of synthetic and biological systems to obtain theoretical predictions for experimentally verifiable quantities.</p>","PeriodicalId":790,"journal":{"name":"The European Physical Journal E","volume":"48 4-5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epje/s10189-025-00489-0.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144125868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Travelling-wave gel dipolophoresis of hydrophobic conducting colloids","authors":"Touvia Miloh,&nbsp;Eldad J. Avital","doi":"10.1140/epje/s10189-025-00492-5","DOIUrl":"10.1140/epje/s10189-025-00492-5","url":null,"abstract":"<div><p>A unified ‘weak-field’ formulation is provided for calculating the combined nonlinear effect of dielectrophoresis and the induced-charge electrophoresis (dipolophoresis) of polarized rigid hydrophobic spherical colloids freely suspended in an electrolyte-saturated Brinkman-hydrogel (porous) medium under a general (direct or alternating currents) non-uniform electric forcing. Explicit expressions for the modified total dipolophoretic mobility of a conducting (metallic) spherical colloid are given in terms of the Brinkman (Darcy), Navier slip, and Debye (screening) length scales. Also presented is a rigorous derivation of the Helmholtz–Smoluchowski slip velocity in terms of these three length scales, including the induced electroosmotic flow field around a hydrophobic rigid colloid embedded in a Brinkman medium that is forced by an arbitrary (non-uniform) ambient electric field. The available solutions for a free (non-porous) electrolyte solution under a uniform forcing and no-slip surface are obtained as limiting cases. For the purpose of illustration, we present and analyse some newly explicit solutions for the mobility and the associated induced-charge electroosmotic velocity field of a slipping colloid set in an effective (hydrogel) porous medium, which is exposed to an ambient ‘sinusoidal’ travelling-wave excitation depending on frequency and wave number.</p><h3>Graphical abstract</h3><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":790,"journal":{"name":"The European Physical Journal E","volume":"48 4-5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epje/s10189-025-00492-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144131660","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Non-Markovian equilibrium and non-equilibrium barrier-crossing kinetics in asymmetric double-well potentials","authors":"Laura Lavacchi,&nbsp;Benjamin A. Dalton,&nbsp;Roland R. Netz","doi":"10.1140/epje/s10189-025-00488-1","DOIUrl":"10.1140/epje/s10189-025-00488-1","url":null,"abstract":"<p>Barrier-crossing processes in nature are often non-Markovian and typically occur over an asymmetric double-well free-energy landscape. However, most theories and numerical studies on barrier-crossing rates assume symmetric free-energy profiles. Here, we use a one-dimensional generalized Langevin equation (GLE) to investigate non-Markovian reaction kinetics in asymmetric double-well potentials. We derive a general formula, confirmed by extensive simulations, that accurately predicts mean first-passage times from well to barrier top in an asymmetric double-well potential with arbitrary memory time and reaction coordinate mass. We extend our formalism to non-equilibrium non-Markovian systems, confirming its broad applicability to equilibrium and non-equilibrium systems in biology, chemistry, and physics.</p>","PeriodicalId":790,"journal":{"name":"The European Physical Journal E","volume":"48 4-5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epje/s10189-025-00488-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144117701","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Influence of the stability of boundary vortex on drag reduction induced by transverse V-grooves","authors":"Zhiping Li,&nbsp;Long He,&nbsp;Tianyu Pan,&nbsp;Yao Yin,&nbsp;Shaobin Li,&nbsp;Wei Yuan,&nbsp;Bo Meng","doi":"10.1140/epje/s10189-025-00490-7","DOIUrl":"10.1140/epje/s10189-025-00490-7","url":null,"abstract":"<div><p>Previous studies revealed the skin-friction drag reduction properties induced by transverse grooves. However, the effects of unsteady characteristics of vortices within the grooves on the drag reduction properties have not been investigated. A hypothesis that the unsteady motion of vortices may reduce the friction drag-reduction rate induced by transverse V-grooves is proposed in this paper. To verify this hypothesis, we use the LES (large eddy simulation) method to investigate the flow field in the range of Reynolds number 0.5E5 to 7.5E5 over the different profiles of symmetric V-grooves, whose depths are 0.2 mm and AR’s are 0.5, 1, 2, 5, and 8. The results show that the AR (aspect ratio of a transverse groove) affects the stability of boundary vortices, thus driving the variation of total viscous drag and pressure drag. With the increase of AR, the boundary vortices tend to be stable at first and then gradually become unstable. When AR is 2, the boundary vortices are stable within the grooves, corresponding to optimal drag reduction. In this case, the slip velocities induced by boundary vortices are the largest, and the Reynolds shear stress is the least, suggesting that the grooves have the strongest abilities to reduce the total viscous drag. When the stability of the boundary vortices is broken, a larger area containing high pressure and low pressure is formed in the groove, and the difference also becomes greater between the high pressure and low pressure. The results provide improved understandings of the drag reduction mechanism of transverse grooves.</p><h3>Graphical Abstract</h3>\u0000<div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":790,"journal":{"name":"The European Physical Journal E","volume":"48 4-5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143929913","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Improved QSAR methods for predicting drug properties utilizing topological indices and machine learning models","authors":"Muhammad Shoaib Sardar,&nbsp;Muhammad Shahid Iqbal,&nbsp;Muhammad Mudassar Hassan,&nbsp;Changjiang Bu,&nbsp;Sharafat Hussain","doi":"10.1140/epje/s10189-025-00491-6","DOIUrl":"10.1140/epje/s10189-025-00491-6","url":null,"abstract":"&lt;p&gt;This research investigates the anticipated physicochemical and topological properties of compounds such as drug complexity (C), molecular weight (MW), and topological polar surface area (TPSA) using quantitative structure–activity relationship (QSAR) analysis. Several machine learning models, including Linear Regression, Ridge Regression, Lasso Regression, Random Forest Regression, and Gradient Boosting, were developed to improve prediction accuracy using topological indices. The datasets were combined with appropriate topological indices for individual compounds. Model performance was evaluated using Mean Squared Error (MSE) and &lt;span&gt;(R^2)&lt;/span&gt; score after hyperparameter tuning via GridSearchCV. Ridge and Lasso Regression models stood out due to their lowest Test MSE averages (3617.74 and 3540.23, respectively) and highest &lt;span&gt;(R^2)&lt;/span&gt; scores (0.9322 and 0.9374, respectively), demonstrating their effectiveness in handling multicollinearity and preventing overfitting. Linear Regression also performed robustly, achieving an MSE of 5249.97 and an &lt;span&gt;(R^2)&lt;/span&gt; of 0.8563, highlighting the suitability of simpler models for datasets with inherent linear relationships. While Random Forest and Gradient Boosting Regression are capable of capturing nonlinear relationships, their performance varied. Random Forest Regression achieved an MSE of 6485.45 and an &lt;span&gt;(R^2)&lt;/span&gt; of 0.6643, while Gradient Boosting initially performed poorly with an MSE of 4488.04 and an &lt;span&gt;(R^2)&lt;/span&gt; of 0.5659. After fine-tuning Gradient Boosting with an expanded hyperparameter grid, its performance improved significantly, achieving a Test MSE of 1494.74 and an &lt;span&gt;(R^2)&lt;/span&gt; of 0.9171. However, it still ranked fourth, suggesting that simpler models like Linear, Ridge, and Lasso Regression may be better suited for this dataset. This work emphasizes the significance of accurate model selection and optimization in QSAR analysis, demonstrating how these approaches can be used to develop dependable predictive models in computational drug discovery and cheminformatics.&lt;/p&gt;&lt;p&gt;A machine learning pipeline for predicting physicochemical and topological properties of chemical compounds using QSAR analysis. The process begins with compound data collection from PubChem, followed by data preprocessing, feature engineering, and feature selection. The selected features are used to train various regression models-including Linear, Ridge, Lasso, Random Forest, and Gradient Boosting Regression-evaluated using MSE and &lt;span&gt;(R^2)&lt;/span&gt; metrics for performance comparison.caption for the graphical abstract: Caption for Graphical Abstract: A machine learning pipeline for predicting physicochemical and topological properties of chemical compounds using QSAR analysis. The process begins with compound data collection from PubChem, followed by data preprocessing, feature engineering, and feature selection. The selected features are used to train various regression models-incl","PeriodicalId":790,"journal":{"name":"The European Physical Journal E","volume":"48 4-5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143929914","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effective viscosity of a two-dimensional passive suspension in a liquid crystal solvent","authors":"S. Dang,&nbsp;C. Blanch-Mercader,&nbsp;L. Berlyand","doi":"10.1140/epje/s10189-025-00479-2","DOIUrl":"10.1140/epje/s10189-025-00479-2","url":null,"abstract":"<p>Suspension of particles in a fluid solvent are ubiquitous in nature, for example water mixed with sugar or bacteria self-propelling through mucus. Particles create local flow perturbations that can modify drastically the effective (homogenized) bulk properties of the fluid. Understanding the link between the properties of particles and the fluid solvent, and the effective properties of the medium is a classical problem in fluid mechanics. Here we study a special case of a two-dimensional model of a suspension of undeformable particles in a liquid crystal solvent. In the dilute regime, we calculate asymptotic solutions of the perturbations of the velocity and director fields and derive an explicit formula for an effective shear viscosity of the liquid crystal medium. Such effective shear viscosity increases linearly with the area fraction of particles, similar to Einstein formula but with a different prefactor. We provide explicit asymptotic formulas for the dependence of this prefactor on the material parameters of the solvent. Finally, we identify a case of decreasing the effective viscosity by increasing the magnitude of the shear-flow alignment coefficient of the liquid crystal solvent.\u0000\u0000\u0000</p>","PeriodicalId":790,"journal":{"name":"The European Physical Journal E","volume":"48 4-5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143925619","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Emergent collective behavior of cohesive, aligning particles","authors":"Jeanine Shea,&nbsp;Holger Stark","doi":"10.1140/epje/s10189-025-00482-7","DOIUrl":"10.1140/epje/s10189-025-00482-7","url":null,"abstract":"<p>Collective behavior is all around us, from flocks of birds to schools of fish. These systems are immensely complex, which makes it pertinent to study their behavior through minimal models. We introduce such a minimal model for cohesive and aligning self-propelled particles in which group cohesion is established through additive, non-reciprocal torques. These torques cause a particle’s orientation vector to turn toward its neighbor so that it aligns with the separation vector. We additionally incorporate an alignment torque, which competes with the cohesive torque in the same spatial range. By changing the strength and range of these torque interactions, we uncover six states which we distinguish via their static and dynamic properties: a disperse state, a multiple worm state, a line state, a persistent worm state, a rotary worm state, and an aster state. Their occurrence strongly depends on initial conditions and stochasticity, so the model exhibits multistabilities. A number of the states exhibit collective dynamics which are reminiscent of those seen in nature.</p>","PeriodicalId":790,"journal":{"name":"The European Physical Journal E","volume":"48 4-5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epje/s10189-025-00482-7.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143918931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Machine learning approaches for modeling the physiochemical characteristics of polycyclic aromatic hydrocarbons","authors":"Ali N. A. Koam,&nbsp;Muhammad Usamah Majeed,&nbsp;Shahid Zaman,&nbsp;Ali Ahmad,&nbsp;Ibtisam Masmali,&nbsp;Abdullah Ali H. Ahmadini","doi":"10.1140/epje/s10189-025-00487-2","DOIUrl":"10.1140/epje/s10189-025-00487-2","url":null,"abstract":"<p>Supervised machine learning methods like random forests and extreme gradient boosting plays an important role in drug development for predicting bioactivity and resolving structure-activity correlations. These approaches use topological descriptors in the study of polycyclic aromatic hydrocarbons that represent molecular structural characteristics to enhance the prediction capacity of quantitative structure–property relationships (QSPR). The objective is to identify the physoichemical properties such as density, boiling point, flash point, enthalpy, polarizability, surface tension, molar volume, molecular weight and complexity that significantly impact physicochemical attributes. The combination of machine learning and QSPR also demonstrates the potential of computational techniques in drug development. Then effective algorithms are constructed to express the link between the eccentricity-based topological indices and the physicochemical characteristics of each of the polycyclic aromatic hydrocarbons, which grows our understanding of their behavior and paves the way for future development of environmental forecasting techniques and toxicological evaluations of polycyclic aromatic hydrocarbons.</p>","PeriodicalId":790,"journal":{"name":"The European Physical Journal E","volume":"48 4-5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143902803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Viscoelastic friction in sliding a non-cylindrical asperity","authors":"M. Ciavarella,&nbsp;M. Tricarico,&nbsp;A. Papangelo","doi":"10.1140/epje/s10189-025-00484-5","DOIUrl":"10.1140/epje/s10189-025-00484-5","url":null,"abstract":"<p>We investigate the 2D contact problem of sliding a non-cylindrical punch on a viscoelastic halfplane, assuming a power law shape <span>(left| xright| ^{k})</span> with <span>(k&gt;2)</span>. We find with a full boundary element numerical solution that the Persson analytical solution for friction, which works well for the cylindrical punch case assuming the pressure remains identical in form to the elastic case, in this case leads to significant qualitative errors. However, we find that the friction coefficient follows a much simpler trend; namely, we can use as a first approximation the solution for the cylinder, provided we normalize friction coefficient with the modulus and mean pressure at zero speed, despite that we show the complex behaviour of the pressure distribution in the viscoelastic regime. We are unable to numerically solve satisfactorily the ill-defined limit of sharp flat punch, for which Persson’s solution predicts finite friction even at zero speed.</p>","PeriodicalId":790,"journal":{"name":"The European Physical Journal E","volume":"48 4-5","pages":""},"PeriodicalIF":1.8,"publicationDate":"2025-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1140/epje/s10189-025-00484-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"物理与天体物理","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}