Energy Theory Research Articles

Accurate and efficient representation of intramolecular energy in ab initio generation of crystal structures. Part III: partitioning into torsional groups.

We present an approach to reduce this computational cost substantially, based on the partitioning of the molecule into geometrically separated torsional groups, with the dependence of the intramolecular energy and atomic point charges and dependent degrees of freedom on molecular conformation being computed as a linear combination of the contributions of these groups. This can lead to large savings in computational cost without a significant impact on accuracy, as demonstrated in the cases of N-acetyl-para-aminophenol (paracetamol) and methyl 4-hydroxybenzoate (methyl paraben). The approach is also applied successfully to two larger molecules, benzyl [4-(4-methyl-5-[(4-methylphenyl)sulfonyl]-1,3-thiazol-2-yl)phenyl]carbamate (molecule XX from the fifth CSP blind test) and (2S)-2-[4-(3-fluorobenzyloxy)benzylamino]propionamide (safinamide), for which we conduct the first reported CSP study. In both cases, the use of torsional groups results in over 99% reduction in computational cost, which enables the generation of an initial CSP landscape with high-quality structures found within the standard cutoff of 20 kJ mol-1 for progression to refinement.

Effects of ionic strength, cation type and pH on the cotransport of microplastics with PFOA in saturated porous media.

Both perfluorooctanoic acid (PFOA) and polystyrene microplastics (PS-MPs) are emerging contaminants commonly found in aqueous environments. In co-contaminated areas, MPs may act as carriers for PFOA, complicating transport dynamics. However, information on their cotransport in porous media is limited. This study investigates the transport behaviors of PFOA and PS-MPs in saturated quartz sand columns under varying ionic strength (IS), cation type, and pH. Using the DLVO interaction energy theory and a mathematical model, we analyzed their cotransport. The results demonstrated that PS-MPs inhibited PFOA transport due to hydrophobic adsorption, reducing PFOA mobility. However, at pH 5, PS-MPs facilitated PFOA transport through competitive adsorption on sand surfaces. Conversely, PFOA significantly accelerated PS-MPs transport, likely due to electrostatic repulsion and reduced PS-MPs size. The promoting effect of PFOA on PS-MPs was similar in NaCl and CaCl2 solutions. It is noteworthy that under acidic conditions, the increased electrostatic attraction between PS-MPs and quartz sand leads to substantial adsorption of PS-MPs onto the quartz sand surface. Under these conditions, PFOA exerts almost no promoting effect on PS-MPs. This study showed that the coexistence of PS-MPs and PFOA would influence the mobility of each other in the saturated porous media. Overall, the findings from this work could greatly improve our understanding of cotransport behaviors and environmental risk of PS-MPs and PFOA.

Generalized Positive Energy Representations of the Group of Compactly Supported Diffeomorphisms

Motivated by asymptotic symmetry groups in general relativity, we consider projective unitary representations ρ¯ of the Lie group Diffc(M) of compactly supported diffeomorphisms of a smooth manifold M that satisfy a so-called generalized positive energy condition. In particular, this captures representations that are in a suitable sense compatible with a KMS state on the von Neumann algebra generated by ρ¯. We show that if M is connected and dim(M)>1 1$$\\end{document}]]>, then any such representation is necessarily trivial on the identity component Diffc(M)0. As an intermediate step towards this result, we determine the continuous second Lie algebra cohomology Hct2(Xc(M),R) of the Lie algebra of compactly supported vector fields. This is subtly different from Gelfand–Fuks cohomology in view of the compact support condition.

Strain Energy and Biomechanical Constituent Models in Blood Vessel Tissues

Objective: To show the analysis of mechanical constitutive models in blood vessel tissues with a continuous media approach based on strain energy, which serve as a reference for new mathematical modeling proposals in them. Theoretical Framework: The mechanics of blood vessels, describes the structural and functional behavior of blood vessels and can characterize various cardiovascular diseases. Harmful changes that alter the mechanical response of the walls of blood vessels produce severe alterations in the health of the circulatory system. Predicting the mechanical behavior of blood vessels based on physiological status using biomechanical models is paramount for diagnosis. Therefore, in the present work, an analysis of the constitutive models is carried out with a continuous media approach based on strain energy. Method: Bibliographic review that identifies, analyzes and synthesizes the existing scientific proposals on blood vessel tissue modeling based on the deformation energy theory. Results and Discussion: A bibliographic study of the biomechanical constitutive models of blood vessel walls, generated over time, is presented. The behavior of the vascular wall is analyzed from the deformation energy approach. The benefits, limitations and potentialities of the models are also exposed: a) Strain energy with a transversely isotropic and homogeneous matrix; b) Strain energy with axis-symmetric fiber constants; c) Strain energy with collagen fibers subject to dispersion; d) Strain energy of four families of fibers without dispersion; and e) Strain energy of two families of fibers with anisotropic elastin and fiber recruitment. Implications of the research: The conclusions and analyzes presented serve as a basis for future research and mathematical modeling of the phenomenon of degradation and deformation of blood vessels, which will facilitate the understanding of the phenomenon and the subsequent strengthening of alternative treatment strategies that combat the clinical conditions derived from the transformations of mechanical properties in the same blood vessels. Originality/Value: This study contributes by giving order to the multiple bibliographic information related to the subject. The relevance of this research is evidenced in the conclusions issued when analyzing models based on the theory of continuous media as a function of strain energy.

Flexible framework of computing binding free energy using the energy representation theory of solution.

Host-guest binding plays a crucial role in the functionality of various systems, and its efficiency is often quantified using the binding free energy, which represents the free-energy difference between the bound and dissociated states. Here, we propose a methodology to compute the binding free energy based on the energy representation (ER) theory of solution, which enables us to evaluate the free-energy difference between the systems of interest with the molecular dynamics (MD) simulations. Unlike the other free-energy methods, such as the Bennett acceptance ratio (BAR), the ER theory does not require the MD simulations for hypothetical intermediate states connecting the systems of interest, leading to reduced computational costs. By constructing the thermodynamic cycle of the binding process that is suitable for the ER theory, a robust calculation of the binding free energy is realized. We apply the present method to the self-association of N-methylacetamide in different solvents and the binding of aspirin to β-cyclodextrin (CD) in water. In the former case, the present method estimates that the binding free energy decreases as the solvent polarity decreases. This trend is consistent with the experimental finding. For the latter system, the binding free energies for the two representative CD-aspirin bound complexes, primary (P) and secondary (S) complexes, are estimated to be -5.2 ± 0.1 and -5.03 ± 0.09kcalmol-1, respectively. These values are satisfactorily close to those from the BAR method [-4.2 ± 0.2 and -4.1 ± 0.2kcalmol-1 for P and S, respectively]. Furthermore, the interaction-energy component analysis reveals that the van der Waals interaction between aspirin and CD dominantly contributes to the stabilization of the bound complexes, which is in harmony with the well-known binding mechanism in the CD systems.

Study of Interface Adhesion Between Polyurethane and Aggregate Based on Surface Free Energy Theory and Molecular Dynamics Simulation

In order to eliminate the negative effects caused by traditional pavements, permeable pavements are gradually being used in road construction. In recent years, polyurethane (PU) has been used as a new binder in permeable pavement mixtures. However, compared to traditional pavement mixtures, the adhesion properties between PU and aggregate have not been systematically analyzed. In addition, no clear standards have been established for the performance testing of PU mixtures, posing significant challenges for the selection of materials and the optimization of formulations for PU mixtures. Therefore, this paper proposes new methods for evaluating the performance of PU mixtures from a microscopic point of view, aiming at evaluating the adhesion properties between PU and aggregates. In this study, a PU binder was synthesized. The adhesion properties of this PU binder with aggregate were evaluated by surface free energy measurement and molecular dynamics (MD) simulation. Finally, the effects of different environmental conditions and aggregate types on the PU–aggregate adhesion properties were investigated. The results showed that the adhesion between PU and basalt is consistently better than that with limestone, although the adhesion between PU and aggregate decreased under acidic conditions. It implies that the PU–basalt mixture has better water resistance than the PU–limestone mixture. Furthermore, the results of the surface free energy measurements and MD simulations for the evaluation of adhesion at the PU–aggregate interface showed good correlation with the macroscopic performance experiments, which can be extended to the study of the adhesion properties of other materials.

Energy of Functional Brain States Correlates With Cognition in Adolescent-Onset Schizophrenia and Healthy Persons.

Adolescent-onset schizophrenia (AOS) is relatively rare, under-studied, and associated with more severe cognitive impairments and poorer outcomes than adult-onset schizophrenia. Neuroimaging has shown altered regional activations (first-order effects) and functional connectivity (second-order effects) in AOS compared to controls. The pairwise maximum entropy model (MEM) integrates first- and second-order factors into a single quantity called energy, which is inversely related to probability of occurrence of brain activity patterns. We take a combinatorial approach to study multiple brain-wide MEMs of task-associated components; hundreds of independent MEMs for various sub-systems were fit to 7 Tesla functional MRI scans. Acquisitions were collected from 23 AOS individuals and 53 healthy controls while performing the Penn Conditional Exclusion Test (PCET) for executive function, which is known to be impaired in AOS. Accuracy of PCET performance was significantly reduced among AOS compared with controls. A majority of the models showed significant negative correlation between PCET scores and the total energy attained over the fMRI. Severity of psychopathology was correlated positively with energy. Across all instantiations, the AOS group was associated with significantly more frequent occurrence of states of higher energy, assessed with a mixed effects model. An example MEM instance was investigated further using energy landscapes, which visualize high and low energy states on a low-dimensional plane, and trajectory analysis, which quantify the evolution of brain states throughout this landscape. Both supported patient-control differences in the energy profiles. The MEM's integrated representation of energy in task-associated systems can help characterize pathophysiology of AOS, cognitive impairments, and psychopathology.

Study on the effect of acid rain erosion on the adhesion properties of asphalt-aggregate interface

ABSTRACT This study investigates the impact of acid rain on the adhesion properties of the asphalt-aggregate interface in asphalt mixtures. By employing surface-free energy theory and the sessile drop method to analyse wetting behaviour, the adhesion work and energy indicator ER were calculated. The interface adhesion characteristics were evaluated using the water boiling method and pull-off tests. It was found that acid rain significantly reduces the interface adhesion work, which worsens with increasing erosion cycles and concentrations. The ER value decreases, adhesion becomes poorer and the lower the pH value, the more severe the damage. The acidic environment accelerates the stripping of the asphalt film and weakens the interactive forces. Acid rain increases the polarity between asphalt and aggregates, reducing the adhesion energy and leading to failure. SBS-modified asphalt exhibits better adhesion performance than 70# petroleum asphalt.

Free Energy-Based Refinement of DNA Force Field via Modification of Multiple Nonbonding Energy Terms.

The amber-OL21 force field (ff) was developed to better describe noncanonical DNA, including Z-DNA. Despite its improvements for DNA simulations, this study found that OL21's scope of application was limited by embedded ff artifacts. In a benchmark set of seven DNA molecules, including two double-stranded DNAs transitioning between B- and Z-DNA and five single-stranded DNAs folding into mini-dumbbell or G-quadruplex structures, the free energy landscapes obtained using OL21 revealed several issues: Z-DNA was overly stabilized; misfolded states in mini-dumbbell DNAs were most stable; DNA GQ folding was consistently biased toward an antiparallel topology. To address these issues, a simple van der Waals (vdW) correction scheme, referred to as vdW5, was proposed for OL21. This involved revising multiple nonbonding energy terms to improve the overall quality of the free energy landscapes. The vdW5 correction effectively eliminated the artifacts in OL21, providing significantly improved free energy representations for DNAs tested. The vdW5-level revision substantially enhanced the predictive power of DNA simulations, thereby extending the scope of application for amber-OL21.

Underestimation of Wave Energy from ERA5 Datasets: Back Analysis and Calibration in the Central Tyrrhenian Sea

Characterizing wave climate is crucial for coastal and offshore engineering applications. Reanalysis models, such as ERA5, are increasingly used due to their efficiency and lower costs compared to in situ measurements. However, their accuracy has not been thoroughly examined. This study addresses this gap by calibrating wave data from the ERA5 dataset with the available years of measurements from wave buoys in the Central Mediterranean Sea, specifically near Ponza, Cetraro, and Civitavecchia. A calibration approach was developed to adjust ERA5 wave data by aligning the model predictions closely with the co-located wave buoy observations. Results indicate that ERA5 systematically underestimates significant wave heights and periods, leading to an underestimation of wave power by up to 42% compared to buoy data. Calibration improved alignment between ERA5 and buoy measurements, enhancing wave energy representation and increasing estimated wave power by 35–48% annually. These findings underscore the importance of calibrating reanalysis datasets like ERA5 with in situ data to accurately assess wave energy potential, particularly in regions where model data may not fully capture local wave conditions. The outcomes provide valuable insights for wave energy projects in the Central Tyrrhenian Sea and similar semi-enclosed seas.

Constraining dark energy with the integrated Sachs-Wolfe effect

We use the integrated Sachs-Wolfe (ISW) effect, by now detectable at ∼5σ within the context of Λ cold dark matter (ΛCDM) cosmologies, to place strong constraints on dynamical dark energy theories. Working within an effective field theory (EFT) framework for dark energy we find that including ISW constraints from galaxy–cosmic microwave background (CMB) cross-correlations significantly strengthens existing large-scale structure constraints, yielding bounds consistent with ΛCDM and approximately reducing the viable parameter space by ∼70%. This is a direct consequence of O(1) changes induced in these cross-correlations by otherwise viable dark energy models, which we discuss in detail. We compute constraints by adapting the ΛCDM ISW likelihood from Stölzner [] for dynamical dark energy models using galaxy data from 2 MASS, wide-field infrared survey explorer (WISE) × SuperCOSMOS, Sloan Digital Sky Survey Data Release 12, the catalog of photometric quasars and NRAO Very Large Array Sky Survey, CMB data from Planck 18, and baryon acoustic oscillation and redshift space distortion large-scale structure measurements from BOSS and 6dF. We show constraints both in terms of EFT-inspired αi and phenomenological μ/Σ parametrizations. Furthermore we discuss the approximations involved and related aspects of bias modeling in detail and highlight what these constraints imply for the underlying dark energy theories. Published by the American Physical Society 2024

Impact of solar panel spacing on wind load in an elevated solar panel structure

This study looks at the modeling and stability analysis of an existing elevated solar structure to allow solar energy production and agriculture on the same land (Agrivoltaics). The existing elevated structure accommodates 32 solar panels, each with a capacity of 345 W at a height of approximately 6 m at the center. The impact of the gaps in the 32-panel configuration at this height on the wind load in the elevated solar structure is determined.The study uses computational fluid dynamics (Solid Works Flow simulation) followed by the results used in the static study (Solid Works simulation) to assess the overall stress and strain resulting in the elevated structure. Distortion Energy theory is followed to compare the von Mises stress resulting from the simulation with the Yield strength of the material used to construct the elevated support structure. The findings demonstrate that solar panel spacing can be a key factor in lowering wind loads on the raised support structure.

Asymptotic homogenization of energy-limited nonlinear microperiodic composites with imperfect interfaces to model failure of masonry structures under uniaxial compression

In this work, a masonry prismatic structure made of alternating layers of mortar and bricks is modeled as a periodic two-phase elastic composite with one-dimensional heterogeneity along the layering direction. The prediction of its mechanical behavior (failure mainly) is important to estimate the allowable stress and stiffness used in the masonry design. At the mortar-brick interfaces, both ideally perfect contact and spring-type imperfect contact are considered. In order to model both classical and failure behaviors simultaneously, a nonlinear constitutive relation, which results from limiting the classical Hookean energy by inserting it into the so-called softening hyperelasticity energy representation, is adopted. The model is a two-point boundary value problem, which is stated by subjecting the resulting mechanical equilibrium nonlinear differential equation to the contact conditions at the interfaces and the mixed boundary conditions corresponding to uniaxial compression in the layering direction. The masonry structure exhibits separation of scales, as its size is generally much greater than the size of the mortar-brick periodicity cell, so its mechanical properties are rapidly oscillating, and also the equivalent homogeneity is guaranteed, justifying the application of the asymptotic homogenization method. Here, the effective law, that is, the constitutive relation of the equivalent homogeneous structure, is obtained via the asymptotic homogenization method. Finally, comparisons with experimental results from the literature are provided, which show qualitative agreement and that the model with imperfect contact is more accurate than the one with perfect contact.

Investigating the Dynamic Behavior and Tensile Properties of Coal Gangue Shotcrete Under Impact Loading Conditions SHPB Device

Shotcrete is the primary support material for coal mine tunnel linings and is often subjected to dynamic loads such as blasting and impact. To promote the resource utilization of coal gangue (CG), this study incorporated it into shotcrete and investigated the dynamic mechanical properties of coal gangue shotcrete (CGSC) at different coal gangue aggregate (CGA) replacement ratios. Impact tensile splitting tests were conducted using a split Hopkinson pressure bar (SHPB) device, and the specimen failure process was recorded with a high-speed camera. The results showed that the dynamic tensile splitting strength (DSTS) and energy absorption of CGSC exhibit a significant strain rate effect, with the strain rate sensitivity of DSTS decreasing as the CGA replacement ratio increases. As the strain rate increases, the elastic limit stress of the specimens rises, and the failure mode tends to become more fragmented. Based on energy theory, this paper establishes a dynamic tensile splitting strength model for CGSC, providing theoretical support for its application in engineering.

Efficient compression of redshift-space distortion data for late-time modified gravity models

Current cosmological observations allow for deviations from the standard growth of large-scale structures in the universe. These deviations could indicate modifications to General Relativity on cosmological scales or suggest the dynamical nature of dark energy. It is important to characterize these departures in a model-independent manner to understand their significance objectively and explore their fundamental causes more generically across a wider spectrum of theories and models. In this paper, we compress the information from redshift-space distortion data into 2–3 parameters μ i , which control the ratio between the effective gravitational coupling in Poisson's equation and Newton's constant in several redshift bins in the late universe. We test the efficiency of this compression using mock final-year data from the Dark Energy Spectroscopic Instrument (DESI) and considering three different models within the class of effective field theories of dark energy. The constraints on the parameters of these models, obtained from both the direct fit to the data and the projection of the compressed parameters onto the parameters of the models, are fully consistent, demonstrating the method's good performance. Then, we apply it to current data and find hints of a suppressed matter growth in the universe at ∼ 2.7σ C.L., in full accordance with previous works in the literature. Finally, we perform a forecast with DESI data and show that the uncertainties on the parameters μ 1 at z < 1 and μ 2 at 1 < z < 3 are expected to decrease by approximately 40% and 20%, respectively, compared to those obtained with current data. Additionally, we project these forecasted constraints onto the parameters of the aforesaid models.

Prediction of Rock Fracture Pressure in Hydraulic Fracturing with Interpretable Machine Learning and Mechanical Specific Energy Theory

Prediction of Rock Fracture Pressure in Hydraulic Fracturing with Interpretable Machine Learning and Mechanical Specific Energy Theory

Development of a thermoplastic constitutive model for steel based on the generalized Mises yield criterion

Steel is widely used in building structures, and the constitutive model that describes the steel's response to load is an essential component of structural mechanics analysis. This paper aims to investigate the thermoplastic behavior of steel at elevated temperatures. Based on the classical elastoplastic mechanics framework, this study introduces a generalized Mises yield criterion derived from energy theory, which takes into account the temperature effect. In conjunction with relevant assumptions, hardening condition, flow rule, the generalized Hooke's law, and consistency condition, we derive a novel incremental thermoplastic constitutive model for steel. And the new thermoplastic constitutive model's rationality is further verified by utilizing high-temperature steady-state tensile test data. It is encouraging that this new model can accurately describe the mechanical behavior of steel in high-temperature environment such as fire, which is of significant importance for fire safety design of building structures.

Tracking cortical entrainment to stages of optic-flow processing

In human visual processing, information from the visual field passes through numerous transformations before perceptual attributes such as motion are derived. Determining the sequence of transforms involved in the perception of visual motion has been an active field since the 1940s. One plausible family of models are the spatiotemporal energy models, based on computations of motion energy computed from the spatiotemporal features the visual field. One of the most venerated is that of Heeger (1988), which hypotheses that motion is estimated by matching the predicted spatiotemporal energy in frequency space. In this study, we investigate the plausibility of Heeger’s model by testing for evidence of cortical entrainment to its components. Entrainment of cortical activity to these components was estimated using measurements of electro- and magnetoencephalographic (EMEG) activity, recorded while healthy subjects watched videos of dots moving left and right across their visual field. We find entrainment to several components of Heeger’s model bilaterally in occipital lobe regions, including representations of motion energy at a latency of 80 ms, overall velocity at 95 ms, and acceleration at 130 ms. We find little evidence of entrainment to displacement. We contrast Heeger’s biologically inspired model with alternative baseline models, finding that Heeger’s model provides a closer fit to the observed data. These results help shed light on the processes through which perception of motion arises in the visual processing stream.

Impacts of hydroxyl and bond energy on laser‐induced damage in mid‐infrared chalcogenide glass

AbstractMid‐infrared chalcogenide glasses often suffer from a low laser damage threshold due to their weak bond energy and the presence of impurities, particularly at the specific wavelength of 2.94 µm, which is widely used in medical applications. In this paper, we first investigated the effect of the hydroxyl (OH⁻) peak absorption coefficient on the laser damage properties of As2S3 glasses. The surface temperature distribution of chalcogenide glasses under laser irradiation was also analyzed using the finite element method (FEM) and in‐situ heat monitoring. The results showed that the surface temperature of the glass increases exponentially with the rise in the absorption coefficient at the OH− peak position. Subsequently, Raman spectra analysis and average bond energy (ABE) theory were employed to compare five typical chalcogenide glasses without hydroxyl absorption, revealing the relationship between the laser damage threshold and the bond energies of the glass networks. Finally, an optimized glass composition of Ge25As10S65 was identified, possessing the highest laser damage threshold of 340.98 J/cm2, more than twice that of traditional As2S3. These findings provide essential glass host and data references for the future development of mid‐ and far‐infrared optical fibers and waveguide devices.

Viscoelastic plastic creep constitutive model based on energy conservation law and strain energy theory

On the basis of the law of conservation of energy, the three stages of rock creep are analyzed. The reasons for the difficulty in studying the accelerated creep stage of rocks using the traditional creep model are expounded. The triaxial creep deformation law and critical point parameter values of rocks are obtained by carrying out rock creep tests under different confining pressures. Based on strain energy theory, the law of conservation of energy, and Perzyna viscoplastic theory, a creep constitutive model, which can describe the whole process of primary creep, steady-state creep, and accelerated creep, is established. Results show that the model can well reflect the creep characteristics of rocks, especially when the load of rocks is greater than the long-term strength. It has an obvious effect on highlighting the accelerated creep stage of rocks. The fitting degree of the creep model curve and test curve is considerably greater than that of the Nishihara model curve and test curve. The model not only describes the whole process of rock primary creep, steady-state creep, and accelerated creep thoroughly but also compensates for the shortcomings of traditional models in describing accelerated creep. This model can provide a theoretical basis for further revealing the objective law of rock creep.