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Number density of plasma-generated atoms or molecules is an important parameter for both fundamental research and applications. It can be measured in a straightforward manner, using vacuum-ultraviolet absorption spectroscopy, which is mainly possible in laboratory conditions as it may require bulky equipment, such as lasers. By contrast, optical actinometry is an alternative approach that only uses spontaneous emission from the plasma. This technique relies on the so-called corona excitation and uses emission line ratios between the gases with unknown and known concentrations (called actinometer in the last case). As a result of using line ratios, the additional density calibration is not required if the excitation cross sections are known. This study discusses Ar-based actinometry in low-pressure (roughly < 1 kPa) plasma discharges with an emphasis on multiple line ratios. The work is particularly focused on the method's applicability, the choice of Ar cross sections, and potential error sources. The influence of the additional excitation mechanisms is analyzed based on both experiments and modeling. The optical transitions for F, O, H, N, and P atoms along with expressions for their number density are presented, not requiring high optical resolution for measurements. For the sake of method validation, it is shown that in low-pressure radiofrequency discharges, a nearly excellent agreement between the actinometry data and the calibrated measurements can be achieved by careful selection of optical transitions. [ABSTRACT FROM AUTHOR]

Simulating electrolyte–electrode systems poses challenges due to the need to account for the electrode's response to ion movements in order to maintain a constant electrode potential, which slows down the simulations. To circumvent this, computationally more efficient constant charge (CC) simulations are sometimes employed. However, the accuracy of CC simulations in capturing the behavior of electrolyte–electrode systems remains unclear, especially for microporous electrodes. Herein, we consider electrolyte-filled slit nanopores and systematically analyze the in-pore ion structure and diffusivity using CC and constant potential simulations. Our results indicate that CC simulations provide comparable pore occupancies at high bulk ion densities and for highly charged pores, but they fail to accurately describe the ion structure and dynamics, particularly in quasi-2D (single-layer) pores and at low ion densities. We attribute these results to the superionic state emerging in conducting nanoconfinement and its interplay with excluded volume interactions. [ABSTRACT FROM AUTHOR]

Investigation and implementation of Active Willis Metamaterials (AWM) have been done exclusively, in all the available literature, by approaches that do not rely on any solid control theory basis. When coupled with piezoelectric control elements, the available approaches have not included, from the first principles, the exact form of the constitutive relationship of the piezoelectric materials. Furthermore, in all these approaches, stability analysis, robustness, ability to accommodate uncertainty or parameter changes, or consideration of disturbance rejection has not been addressed at all. More importantly, the available formulations have always mixed the flow and effort variables of the AWM, resulting in a form that is totally incompatible for the use in generating, investigating, or even designing any appropriate sensing or control applications of the material. In this paper, the piezoelectric-based AWM is modeled, from the first principles, to develop a constitutive coupling form that enables its use in actuation, sensing, and as an integrated controller that can be analyzed, designed, and optimized using the classical, optimal, and robust control system theories. Lagrange dynamics formulation is used to generate the equations governing the Willis coupling, the piezoelectric coupling, as well as the active robust controller. With this developed controlled-based structure of the AWM, the inherent and powerful capabilities of the AWM that lie in its ability to robustly control the material properties themselves such as the compliance (or stiffness) and specific volume (or density) are demonstrated in great detail via several numerical examples. Controlling these properties enables the AWM to be used in numerous important and imaginative applications such as cloaking, beam shifting, beam focusing, as well as many other applications that are limited only by our imagination. [ABSTRACT FROM AUTHOR]

Improved two-body and three-body potentials for helium have been used to calculate from first principles the third density and acoustic virial coefficients for both 4He and 3He. For the third density virial coefficient C(T), uncertainties have been reduced by a factor of 4–5 compared to the previous state of the art; the accuracy of first-principles C(T) now exceeds that of the best experiments by more than two orders of magnitude. The range of calculations has been extended to temperatures as low as 0.5 K. For the third acoustic virial coefficient γa(T), we applied the Schlessinger point method, which can calculate γa and its uncertainty based on the C(T) data, overcoming some limitations of direct path-integral calculation. The resulting γa are calculated at temperatures down to 0.5 K; they are consistent with available experimental data but have much smaller uncertainties. The first-principles data presented here will enable improvement of primary temperature and pressure metrology based on gas properties. [ABSTRACT FROM AUTHOR]

The x-ray restrained wave function (XRW) method is a quantum crystallographic technique to extract wave functions compatible with experimental x-ray diffraction data. The approach looks for wave functions that minimize the energies of the investigated systems and also reproduce sets of x-ray structure factors. Given the strict relationship between x-ray structure factors and electron distributions, the strategy practically allows determining wave functions that correspond to given (usually experimental) electron densities. In this work, the capabilities of the XRW approach were further tested. The aim was to evaluate whether the XRW technique could serve as a tool for suggesting new exchange-correlation functionals for density functional theory or refining existing ones. Additionally, the ability of the method to address the influences of the crystalline environment was also assessed. The outcomes of XRW computations were thus compared to those of traditional gas-phase, embedding quantum mechanics/molecular mechanics, and fully periodic calculations. The results revealed that, irrespective of the initial conditions, the XRW computations practically yield a consensus electron density, in contrast to the currently employed density functional approximations (DFAs), which tend to give a too large range of electron distributions. This is encouraging in view of exploiting the XRW technique to develop improved functionals. Conversely, the calculations also emphasized that the XRW method is limited in its ability to effectively address the influences of the crystalline environment. This underscores the need for a periodic XRW technique, which would allow further untangling the shortcomings of DFAs from those inherent to the XRW approach. [ABSTRACT FROM AUTHOR]

Polyethylene oxide (PEO) holds significant importance in the field of batteries due to its high processability, intrinsic properties, and potential for high ionic conductivity. Achieving simulation at different scales is crucial for gaining a comprehensive understanding of its properties and thus improving them. In this context, we conducted a comparative study on the molecular physical structure, thermodynamic, and dynamic properties of PEO using three distinct coarse-grained (CG) procedures and all-atom (AA) simulations. The three CG simulation procedures involved modeling with MARTINI forcefield, SPICA forcefield, and an IBI derived potential from AA simulations. The AA simulation has been performed using the class 2 pcff+ forcefield. The ensuing simulated densities align significantly with the literature data, indicating the reliability of our approach. The solubility parameter from the AA simulation closely corresponds to literature reported values. MARTINI and SPICA yield almost similar solubility parameters, consistent with the similar density predicted by both the forcefields. Notably, SPICA forcefield closely reproduces the intermolecular structure of atomistic systems, as evidenced by radial distribution function (RDF). It also comprehensively replicates the distribution of radius of gyration (Rg) and the end-to-end distance (Re) of the atomistic samples. IBI ranks second to SPICA in emulating the structural properties of the atomistic systems, such as Rg, Re, and RDF. However, IBI falls short in accurately representing the solubility parameter of the amorphous PEO samples, while MARTINI does not provide an accurate representation of the structural properties of the systems. The use of SPICA forcefield results in enhanced dynamics of the systems in comparison with IBI and MARTINI. [ABSTRACT FROM AUTHOR]

Purpose: The study aimed to conduct a comparative analysis of physical performance indicators and assess the levels of performance monotony and strain experienced by basketball referees. Methods: The study involved the participation of 12 basketball referees (mean age: 40.0 [4.9] y) affiliated with the International Basketball Federation. The investigation was carried out throughout 2 density tournaments, wherein the maximum heart rate, average heart rate, performance monotony, and performance strain were documented for 3 variables. Results: The findings indicated significant variations in the mean heart rate, maximum heart rate, total distance monotony, total distance strain, the total number of sprints monotony, the total number of sprints strain, calories monotony, and calories strain (P <.05). Decreasing the density of elite-level basketball competitions has been observed to reduce the monotony and strain experienced by referees. However, this action does not increase motion distance or speed zones. Conclusions: The environmental stressors experienced by senior-level athletes (World Cup) differ from those encountered by younger athletes (World Cup Under 19). Further investigation is required to ascertain the potential effects of competition monotony and strain on decision-making processes and the overall quality of refereeing. [ABSTRACT FROM AUTHOR]

In recent papers, Becke et al. [J. Chem. Phys. 158, 151103 (2023)] and then Becke [J. Chem. Phys. 159, 241101 (2023)] have developed a novel double hybrid density functional, "DH23," whose terms are based on good local physics. Its 12 coefficients are trained on the GMTKN55 (general main-group thermochemistry, kinetics, and noncovalent interactions) chemical database of Goerigk et al. [Phys. Chem. Chem. Phys. 19, 32184 (2017)]. The lowest GMTKN55 "WTMAD2" error to date for any hybrid or double hybrid density functional was obtained (1.73 kcal/mol for the revDH23 variant). Here, we simplify DH23 by introducing a dispersion damping scheme involving atomic numbers only and one global parameter. The resulting new functional, "DH24," performs as well as its predecessors. [ABSTRACT FROM AUTHOR]

A femtosecond laser induced photofragmentation fluorescence (fs-LIPF) scheme for the sensitive detection and imaging of water vapor is presented. Two photons of 244.3 nm excite water to the D ̃ state and produce hydroxyl radicals in the fluorescing A ̃ state. Two more photons promote electrons from the D ̃ state to a neutral Rydberg state of the (1b2)−1 ionic core through a 2 + 2 doubly resonant process. The resulting high-lying Rydberg state undergoes neutral dissociation, and the energetic hydrogen fragments are detected from their Balmer series fluorescence. These channels (in the low-pressure limit) have detection sensitivities around 1012 molecules per cubic centimeters, orders of magnitude more sensitive than laser-induced fluorescence based approaches, allowing for sensitive non-invasive detection and imaging of water density for many important processes. [ABSTRACT FROM AUTHOR]

We present a method for calculating the mass ejected during the reflection of a shock wave on a triangular groove. This calculation is based on the combination of two models taken from the literature, BMPT-2, on the one hand, for the calculation of the velocity and density of the jet, and fragmentation zone propagation (FZP) on the other hand, for the calculation of the ejected mass, certain parameters required for FZP being determined by BMPT-2. Compared with previous work, FZP has been extended to deal with the various stages of jet formation. The approach was first evaluated on tin using a large-scale molecular dynamics simulation. This first step validated the overall phenomenology and the associated theoretical tools, and enabled us to propose a procedure for adjusting FZP. Next, we used the BMPT-2/FZP combination to analyze ejected mass measurement experiments using Asay foil. The areal mass curves are well reproduced with few parameters, showing that there is no inconsistency between BMPT-2/FZP and the experiments. Finally, a more detailed analysis of the results obtained enables us to set the limits of the jet thickness at the moment of rupture, and to propose a simple analytical form of its profile compatible with the model used. [ABSTRACT FROM AUTHOR]

The bulk water density data are studied in a very large temperature–pressure range, from stable liquid to glass in the frame of water polymorphism. Because this thermodynamic variable evidences a crossover T*, above which the hydrogen bond (HB) is unable to arrange tetrahedral networks, the T-dependence of their isobars was considered. Such an analysis also shows pressure, P*, around which their thermal behaviors are completely different: concave below P* (with maxima and minima) and convex above (without extremes). Having ρ's measured values of the bimodal structures of the liquid phase, HDL (ρHDL), made of not-bonded monomers (ρNHB) and partially bonded dimers plus trimers (ρNHB), and LDL tetramers (ρLDL) the isobars of the relative distributions [W(P, T)] of the three species (WLDL, WPHB, and WNHB) have been evaluated. The results were studied by means of a logistic function (LF) that details the evolutions of the relative polpulations of the water LDL and HDL phases by decreasing T (for the isobars, in the range of 0.1–400 MPa). The LFs analysis obtained by proposing a full connection between liquid water from its supercooled metastable phase to the stable up to the boiling temperature identifies the Widom line quite satisfactorily and fully supports the presence of the liquid–liquid critical point in the deep supercooled region, located at about 190 K and in the range 200 > P > 180 MPa. [ABSTRACT FROM AUTHOR]

We present comprehensive numerical results from a study of model H, which describes phase separation kinetics in binary fluid mixtures. We study the pattern dynamics of both density and velocity fields in d = 2, 3. The density length scales show three distinct regimes, in accordance with analytical arguments. The velocity length scale shows a diffusive behavior. We also study the scaling behavior of the morphologies for density and velocity fields and observe dynamical scaling in the relevant correlation functions and structure factors. Finally, we study the effect of quenched random field disorder on spinodal decomposition in model H. [ABSTRACT FROM AUTHOR]

It is shown that the transport coefficients (self-diffusion, shear viscosity, and thermal conductivity) of the Weeks–Chandler–Andersen (WCA) fluid along isotherms exhibit a freezing density scaling (FDS). The functional form of this FDS is essentially the same or closely related to those in the Lennard-Jones fluid, hard-sphere fluid, and some liquefied noble gases. This proves that this FDS represents a quasi-universal corresponding state principle for simple classical fluids with steep interactions. Some related aspects, such as a Stokes–Einstein relation without a hydrodynamic diameter and gas-to-liquid dynamical crossover, are briefly discussed. Simple fitting formulas for the transport coefficients of the dense WCA fluid are suggested. [ABSTRACT FROM AUTHOR]

Experimental and theoretical advances for understanding the temperature of maximum density (TMD) of aqueous solutions are outlined. The main equations that relate the TMD behavior to key thermodynamic properties are stated. The experimental TMD data are classified as a function of the nature of the solute (inorganic electrolytes, non-electrolytes, organic salts and ionic liquids, and amino acids and proteins). In addition, the experimental results that explore the effect of pressure are detailed. These experimental data are rationalized by making use of qualitative and semi-quantitative arguments based on the thermodynamics of aqueous systems. The main theoretical and simulation advances in TMD for aqueous solutions are also shown—including new calculations in the context of the scaled particle theory—and their ability to reproduce the experimental data is evaluated. Finally, new experiments and theoretical and simulation developments, which could give important insights into the problem of TMD for aqueous solutions, are proposed. [ABSTRACT FROM AUTHOR]

In many modern applications, it is important to understand mechanisms of non-equilibrium chemistry and physics that are driven by low energy ion bombardment of solid surfaces. However, the study of these processes has been challenging as it demands a relatively unique balance between chemical fidelity and computational cost. To this end, we have proposed and constructed a new, high-throughput simulation pipeline based on density functional tight binding simulations. Additionally, we have extended the parameter set pbc-0-3 with the addition of Ar, thereby enabling the simulation of Ar bombardment. This pipeline was then applied to study the structural and compositional evolution of silicon nitride (SiN) under Ar bombardment. We identified a possible rate limiting step of bombardment-driven sputtering of SiN and suggested underlying mechanisms of Si and N removal. Damage from the bombardment, including generation of surface defects and Ar implantation, are further discussed. These findings and the newly developed simulation framework will serve as a useful foundation for further research in processes driven by ion bombardment. [ABSTRACT FROM AUTHOR]

A variety of scattering-based, microscopy-based, and mobility-based methods are frequently used to probe the size distributions of colloidal nanoparticles with transmission electron microscopy (TEM) often considered to be the "gold standard". Charge detection mass spectrometry (CDMS) is an alternative method for nanoparticle characterization that can rapidly measure the mass and charge of individual nanoparticle ions with high accuracy. Two low polydispersity, ∼100 nm diameter nanoparticle size standards with different compositions (polymethyl methacrylate/polystyrene copolymer and 100% polystyrene) were characterized using both TEM and CDMS to explore the merits and complementary aspects of both methods. Mass and diameter distributions are rapidly obtained from CDMS measurements of thousands of individual ions of known spherical shape, requiring less time than TEM sample preparation and image analysis. TEM image-to-image variations resulted in a ∼1-2 nm range in the determined mean diameters whereas the CDMS mass precision of ∼1% in these experiments leads to a diameter uncertainty of just 0.3 nm. For the 100% polystyrene nanoparticles with known density, the CDMS and TEM particle diameter distributions were in excellent agreement. For the copolymer nanoparticles with unknown density, the diameter from TEM measurements combined with the mass from CDMS measurements enabled an accurate measurement of nanoparticle density. Differing extents of charging for the two nanoparticle standards measured by CDMS show that charging is sensitive to nanoparticle surface properties. A mixture of the two samples was separated based on their different extents of charging despite having overlapping mass distributions centered at 341.5 and 331.0 MDa.

The exchange-only virial relation due to Levy and Perdew is revisited. Invoking the adiabatic connection, we introduce the exchange energy in terms of the right-derivative of the universal density functional w.r.t. the coupling strength λ at λ = 0. This agrees with the Levy–Perdew definition of the exchange energy as a high-density limit of the full exchange–correlation energy. By relying on v-representability for a fixed density at varying coupling strength, we prove an exchange-only virial relation without an explicit local-exchange potential. Instead, the relation is in terms of a limit (λ ↘ 0) involving the exchange–correlation potential v x c λ , which exists by assumption of v-representability. On the other hand, a local-exchange potential vx is not warranted to exist as such a limit. [ABSTRACT FROM AUTHOR]

In gas gun experiments, a graded density impactor (GDI) is used to achieve quasi-isentropic loading. However, inconsistency between the designed and experimental loading profiles, mainly caused by by-products during preparation, limits the application of GDI for a long time. In this work, a kind of W/Ti GDI with advantages of a wide density range of 4.5–19.3 g/cm3 and high structural designability was designed and synthesized. Each of mid-layers of the W/Ti GDI was composed of W and Ti without the formation of an intermetallic compound, and had good parallelism and flatness. This provides a prerequisite for good agreement between the designed and experimental loading profiles. Due to the high designability of the GDI, quasi-isentropic loading with different stress-paths was achieved by controlling the structure of the GDI. Then, independently controlling peak stress and strain rates of loading was successfully achieved by changing the flyer velocity and the type of the W/Ti GDI. The W/Ti GDI has enormous application potential in studying the dynamic response of materials under quasi-isentropic loading with stress and strain rate controlled. [ABSTRACT FROM AUTHOR]

A synchrotron based vacuum ultraviolet absorption spectrum for γ-pyrone has been interpreted in terms of singlet excited electronic states using a variety of coupled cluster, configuration interaction, and density functional calculations. The extremely weak spectral onset at 3.557 eV shows eight vibrational peaks, which following previous analyses, are attributed to a forbidden 1A2 state. A contrasting broad peak with a maximum at 5.381 eV has a relatively high cross-section of 30 Mb; this arises from three overlapping states, where a 1A1 state dominates over progressively weaker 1B2 and 1B1 states. After fitting the second band to a polynomial Gaussian function and plotting the regular residuals over 20 vibrational peaks, we have had limited success in analyzing this fine structure. However, the small separation between these three states clearly shows that their vibrational satellites must overlap. Singlet valence and Rydberg state vibrational profiles were determined by configuration interaction using the CAM-B3LYP density functional. Vibrational analysis using both the Franck–Condon and Herzberg–Teller procedures showed that both procedures contributed to the profiles. Theoretical Rydberg states were evaluated by a highly focused CI procedure. The superposition of the lowest photoelectron spectral band on the vacuum ultraviolet spectrum near 6.4 eV shows that the 3s and 3p Rydberg states based on the 2B2 ionic state are present; those based on the other low-lying ionic state (X2B1) are destroyed by broadening; this is a dramatic extension of the broadening previously witnessed in our studies of halogenobenzenes. [ABSTRACT FROM AUTHOR]

Kohn–Sham density functional theory has been the most popular method in electronic structure calculations. To fulfill the increasing accuracy requirements, new approximate functionals are needed to address key issues in existing approximations. It is well known that nonlocal components are crucial. Current nonlocal functionals mostly require orbital dependence such as in Hartree–Fock exchange and many-body perturbation correlation energy, which, however, leads to higher computational costs. Deviating from this pathway, we describe functional nonlocality in a new approach. By partitioning the total density to atom-centered local densities, a many-body expansion is proposed. This many-body expansion can be truncated at one-body contributions, if a base functional is used and an energy correction is approximated. The contribution from each atom-centered local density is a single finite-range nonlocal functional that is universal for all atoms. We then use machine learning to develop this universal atom-centered functional. Parameters in this functional are determined by fitting to data that are produced by high-level theories. Extensive tests on several different test sets, which include reaction energies, reaction barrier heights, and non-covalent interaction energies, show that the new functional, with only the density as the basic variable, can produce results comparable to the best-performing double-hybrid functionals, (for example, for the thermochemistry test set selected from the GMTKN55 database, BLYP based machine learning functional gives a weighted total mean absolute deviations of 3.33 kcal/mol, while DSD-BLYP-D3(BJ) gives 3.28 kcal/mol) with a lower computational cost. This opens a new pathway to nonlocal functional development and applications. [ABSTRACT FROM AUTHOR]

The effect of changing magnetic parameters on the size and density of skyrmions in a hexagonal lattice is investigated using micromagnetic simulations. Achieving control of the skyrmion density, for instance, by applied voltages, is a route to magnetic neuromorphic computing devices. Here, we show how small changes in the uniaxial magnetic anisotropy and Dzyaloshinskii–Moriya interaction lead to large changes in the skyrmion size and density, which occurs for parameters that do not support isolated skyrmions. The effect of a grain structure on the density of skyrmions is modeled through the introduction of a locally varying anisotropy. This shows that a higher density of skyrmions is favored for a wider distribution of magnetic anisotropy. The results provide a clear understanding of systems where the skyrmion density can be externally controlled and assist the design of functional skyrmion-based devices. [ABSTRACT FROM AUTHOR]

Low-crosslinked polymer networks have recently been found to behave auxetically when subjected to small tensions, that is, their Poisson's ratio ν becomes negative. In addition, for specific state points, numerical simulations revealed that diamond-like networks reach the limit of mechanical stability, exhibiting values of ν = −1, a condition that we define as hyper-auxeticity. This behavior is interesting per se for its consequences in materials science but is also appealing for fundamental physics because the mechanical instability is accompanied by evidence of criticality. In this work, we deepen our understanding of this phenomenon by performing a large set of equilibrium and stress–strain simulations in combination with phenomenological elasticity theory. The two approaches are found to be in good agreement, confirming the above results. We also extend our investigations to disordered polymer networks and find that the hyper-auxetic behavior also holds in this case, still manifesting a similar critical-like behavior as in the diamond one. Finally, we highlight the role of the number density, which is found to be a relevant control parameter determining the elastic properties of the system. The validity of the results under disordered conditions paves the way for an experimental investigation of this phenomenon in real systems, such as hydrogels. [ABSTRACT FROM AUTHOR]

XYG3-type doubly hybrid (xDH) approximations have gained widespread recognition for their accuracy in describing a diverse range of chemical and physical interactions. However, a recent study [Song et al., J. Phys. Chem. Lett. 12, 800–807 (2021)] has highlighted the limitation of xDH methods in calculating the dissociation of NaCl molecules. This issue has been related to the density and orbitals used for evaluating the energy in xDH methods, which are obtained from lower-rung hybrid density functional approximations (DFAs) and display substantial density errors in the dissociation limit. In this work, we systematically investigate the influence of density on several challenging datasets and find that xDH methods are less sensitive to density errors compared to semi-local and hybrid DFAs. Furthermore, we demonstrate that the self-interaction corrected SCAN density approach offers superior accuracy compared to the self-consistent SCAN density and Hartree–Fock density approaches, as evidenced by performing charge analysis on the dissociation of heterodimers, such as NaCl and LiF. Building on these insights, we propose a five-parameter xDH method using the SCAN density and orbitals corrected by the PZ-SIC scheme. This new xDH@SCAN(SIC) method provides a balanced and accurate description across a wide range of challenging systems. [ABSTRACT FROM AUTHOR]

Separating the Coulomb potential into short-range and long-range components enables the use of different electron repulsion integral algorithms for each component. The short-range part can be efficiently computed using the analytical algorithm due to the locality in both the Gaussian-type orbital basis and the short-range Coulomb potentials. The integrals for the long-range Coulomb potential can be approximated with the density fitting method. A very small auxiliary basis is sufficient for the density fitting method to accurately approximate the long-range integrals. This feature significantly reduces the computational efforts associated with the N4 scaling in density fitting algorithms. For large molecules, the range separation and long-range density fitting method outperforms the conventional analytical integral evaluation scheme employed in Hartree–Fock calculations and provides more than twice the overall performance. In addition, this method offers a higher accuracy compared to conventional density fitting methods. The error in the Hartree–Fock energy can be easily reduced to 0.1 μEh per atom or smaller. [ABSTRACT FROM AUTHOR]

Density functional calculations of Rydberg excited states up to high energy are carried out for several molecules using an approach where the orbitals are variationally optimized by converging on saddle points on the electronic energy surface within a real space grid representation. Remarkably good agreement with experimental estimates of the excitation energy is obtained using the generalized gradient approximation (GGA) functional of Perdew, Burke, and Ernzerhof (PBE) when Perdew–Zunger self-interaction correction is applied in combination with complex-valued orbitals. Even without the correction, the PBE functional gives quite good results despite the fact that corresponding Rydberg virtual orbitals have positive energy in the ground state calculation. Results obtained using the Tao, Perdew, Staroverov, and Scuseria (TPSS) and r2SCAN meta-GGA functionals are also presented, but they do not provide a systematic improvement over the results from the uncorrected PBE functional. The grid representation combined with the projector augmented-wave approach gives a simpler and better representation of diffuse Rydberg orbitals than a linear combination of atomic orbitals with commonly used basis sets, the latter leading to an overestimation of the excitation energy due to confinement of the excited states. [ABSTRACT FROM AUTHOR]

Since the development of generalized gradient approximations in the 1990s, approximations based on density functional theory have dominated electronic structure theory calculations. Modern approximations can yield energy differences that are precise enough to be predictive in many instances, as validated by large- and small-scale benchmarking efforts. However, assessing the quality of densities has been the subject of far less attention, in part because reliable error measures are difficult to define. To this end, this work introduces the mean-field error, which directly assesses the quality of densities from approximations. The mean-field error is contextualized within existing frameworks of density functional error analysis and understanding and shown to be part of the density-driven error. It is demonstrated in several illustrative examples. Its potential use in future benchmarking protocols is discussed, and some conclusions are drawn. [ABSTRACT FROM AUTHOR]

Solving the Liouville–von-Neumann equation using a density operator provides a more complete picture of dynamical quantum phenomena than by using a wavepacket and solving the Schrödinger equation. As density operators are not restricted to the description of pure states, they can treat both thermalized and open systems. In practice, however, they are rarely used to study molecular systems as the computational resources required are even more prohibitive than those needed for wavepacket dynamics. In this paper, we demonstrate the potential utility of a scheme based on the powerful multi-layer multi-configurational time-dependent Hartree algorithm for propagating multi-dimensional density operators. Studies of two systems using this method are presented at a range of temperatures and including up to 13 degrees of freedom. The first case is single proton transfer in salicylaldimine, while the second is double proton transfer in porphycene. A comparison is also made with the approach of using stochastic wavepackets. [ABSTRACT FROM AUTHOR]

We present a novel diagnostic system, based on the principle of capacitive sensing, capable of detecting the conduction zone of detonating explosives. The method relies on measuring the change in the capacitive coupling between a printed circuit and its surroundings, induced by an increase in local conductivity. A high frequency wave generator provides the driving signal, which is modified by the change in coupling. This method boasts greater sensitivity than existing conductivity-based techniques, with comparable spatial and temporal resolution. The subject material was pentaerythritol tetranitrate (PETN) powder, pressed into low density (50%–85% theoretical maximum density) cylindrical columns. Previous attempts to measure the reaction zone of low density PETN have faced difficulties because of its short length and low conductivity compared to other explosives. The PETN was initiated using a laser flyer detonator in order to reach detonation promptly and with a minimum of electrical noise. Application of the capacitive sensor diagnostic and subsequent analysis yielded a density dependent steady-state reaction zone length of between 45 and 78 μ m. [ABSTRACT FROM AUTHOR]

The use of oriented external electric fields (OEEFs) as a potential tool for catalyzing chemical reactions has gained traction in recent years. Electronic structure calculations using OEEFs are commonly done using methods based on density functional theory (DFT), but until now, the performance of DFT methods for calculating molecules in OEEFs had not been assessed in a more general scope. Looking at the accuracy of molecular geometries, electronic energies, and electric dipole moments compared to accurate coupled-cluster with perturbative triples data, we have investigated a wide variety of density functionals using different basis sets to determine how well the individual functionals perform on various types of chemical bonds. We found that most functionals accurately calculate geometries in OEEFs and that small basis sets are sufficient in many cases. Calculations of electronic energies show a significant error introduced by the OEEF, which the use of a larger basis set helps mitigate. Our findings show that DFT methods can be used for accurate calculations in OEEFs, allowing researchers to make full use of the advantages that they bring. [ABSTRACT FROM AUTHOR]

Air refractive index alteration is an important research technique used to examine blast density and pressure. However, precise time-course measurements of refractive index changes at a fixed point caused by air blast waves are challenging due to the necessity for high precision and noise immunity. This study proposes a dual-probe, dual-frequency fiber-optic displacement interferometer that achieves nanometer-level accuracy and can tolerate light intensity fluctuations and transmission-fiber interference. The specially designed sensor enables the measurement of refractive index at a fixed point resulting from explosive-driven air blast waves, further allowing for obtaining the pressure and density information. [ABSTRACT FROM AUTHOR]

Comb-like polymers have shown potential as advanced materials for a diverse palette of applications due to the tunability of their polymer architecture. To date, however, it still remains a challenge to understand how the conformational properties of these polymers arise from the interplay of their architectural parameters. In this work, extensive simulations were performed using dissipative particle dynamics to investigate the effect of grafting density, backbone length, and sidechain length on the conformations of comb-like polymers immersed in a good solvent. To quantify the effect of these architectural parameters on polymer conformations, we computed the asphericity, radius of gyration, and backbone and sidechain end-to-end distances. Bond–bond correlation functions and effective Kuhn lengths were computed to quantify the topological stiffness induced by sidechain–sidechain interactions. Simulation results reveal that the effective Kuhn length increases as grafting density and sidechain length increase, in agreement with previous experimental and theoretical studies. This increase in stiffness results in comb-like polymers adopting extended conformations as grafting density and sidechain length increase. Simulation results regarding the radius of gyration of comb-like polymers as a function of grafting density are compared with scaling theory predictions based on a free energy proposed by Morozova and Lodge [ACS Macro Lett. 6, 1274–1279 (2017)] and scaling arguments by Tang et al. [Macromolecules 55, 8668–8675 (2022)]. [ABSTRACT FROM AUTHOR]

Density functional theory is the workhorse of chemistry and materials science, and novel density functional approximations are published every year. To become available in program packages, the novel density functional approximations (DFAs) need to be (re)implemented. However, according to our experience as developers of Libxc [Lehtola et al., SoftwareX 7, 1 (2018)], a constant problem in this task is verification due to the lack of reliable reference data. As we discuss in this work, this lack has led to several non-equivalent implementations of functionals such as Becke–Perdew 1986, Perdew–Wang 1991, Perdew–Burke–Ernzerhof, and Becke's three-parameter hybrid functional with Lee–Yang–Parr correlation across various program packages, yielding different total energies. Through careful verification, we have also found many issues with incorrect functional forms in recent DFAs. The goal of this work is to ensure the reproducibility of DFAs. DFAs must be verifiable in order to prevent the reappearance of the above-mentioned errors and incompatibilities. A common framework for verification and testing is, therefore, needed. We suggest several ways in which reference energies can be produced with free and open source software, either with non-self-consistent calculations with tabulated atomic densities or via self-consistent calculations with various program packages. The employed numerical parameters—especially the quadrature grid—need to be converged to guarantee a ≲0.1 μEh precision in the total energy, which is nowadays routinely achievable in fully numerical calculations. Moreover, as such sub-μEh level agreement can only be achieved when fully equivalent implementations of the DFA are used, the source code of the reference implementation should also be made available in any publication describing a new DFA. [ABSTRACT FROM AUTHOR]

Sex allocation theory predicts that mothers should bias investment in offspring toward the sex that yields higher fitness returns; one such bias may be a skewed offspring sex ratio. Sex allocation is well-studied in birds with cooperative breeding systems, with theory on local resource enhancement and production of helpers at the nest, but little theoretical or empirical work has focused on birds with brood parasitic breeding systems. Wood ducks (Aix sponsa) are a conspecific brood parasite, and rates of parasitism appear to increase with density. Because female wood ducks show high natal philopatry and nest sites are often limiting, local resource competition (LRC) theory predicts that females should overproduce male offspring-the dispersing sex-when competition (density) is high. However, the unique features of conspecific brood parasitism generate alternative predictions from other sex allocation theory, which we develop and test here. We experimentally manipulated nesting density of female wood ducks in 4 populations from 2013 to 2016, and analyzed the resulting sex allocation of >2000 ducklings. In contrast to predictions we did not find overproduction of male offspring by females in high-density populations, females in better condition, or parasitic females; modest support for LRC was found in overproduction of only female parasitic offspring with higher nest box availability. The lack of evidence for sex ratio biases, as expected for LRC and some aspects of brood parasitism, could reflect conflicting selection pressures from nest competition and brood parasitism, or that mechanisms of adaptive sex ratio bias are not possible.

Materials for additive manufacturing (AM), such as PLA and PEEK, are often used in biomedical applications, which involve interaction with liquid media. Consequently, the degradation process is a part of the service life of such polymers that can alter their mechanical response due to gradual changes in materials' properties. Studying the behaviour of polymers in such environments is thus important for the prediction of the mechanical performance of biomedical devices. This paper examines the process of accelerated degradation of AM PLA and PEEK samples in saline solution and distilled water at elevated temperatures. An analysis of changes in mechanical properties, such as tensile strength and density, of PLA and PEEK with the immersion time was performed. The influence of heat treatment on the degradation process was investigated. It was found that the degradation rate of PLA in distilled water was higher than in NaCl. The trends in density changes measured with hydrostatic weighing correspond to those in the strength properties of the studied samples. [ABSTRACT FROM AUTHOR]

The density of diethylene glycol monomethyl ether (DGME) and dimethyl sulphoxide (DMSO) was measured, and the coefficient of thermal expansion was calculated within the temperature range of 293.15–318.15 K. Spectroscopic and computational chemistry techniques were employed to investigate the intermolecular forces in the mixed solutions. It was found that the intermolecular forces of the binary system were strongest at a DGME percentage of 0.55. In addition, from a microscopic point of view, the addition of DMSO disrupted the self-doping behaviour of DGME, leading to the formation of a new hydrogen bond between DGME and DMSO, where the O atom of DMSO formed hydrogen bonds with the H atoms on the hydroxyl groups in DGME. [ABSTRACT FROM AUTHOR]

We present a broadband spectral analysis of the soft-intermediate and soft states using Insight-HXMT observations of the black hole binary MAXI J1348–630 during its outburst in 2019. We employ a combination of reflection and continuum fitting methods to measure the spin of the black hole and determine a spin of a = 0.79 ± 0.13, which is consistent with most of the previous results. Additionally, we investigate some sources of systematic uncertainty that could bias the measurement. The valid spectral hardening factor can partially account for the spin evolution observed during the outburst. Other potential factors, such as assumptions about the corona's structure and their interaction with reflected photons, can also affect the accuracy of spin measurements. Furthermore, our analysis reveals that MAXI J1348–630 exhibits a significantly high disk density (∼1022 cm−3), with a moderate iron abundance of approximately 2.5 times solar. [ABSTRACT FROM AUTHOR]

Using the bilinear neural network method (BNNM) and the symbolic computation system Mathematica, this paper explains how to find an exact solution for the (2+1)-dimensional Korteweg–de Vries–Sawada–Kotera–Ramani (KdVSKR) equation. In terms of activation function and weight coefficient, BNNM is a more appealing option for users than traditional symbolic computation methods. It is possible to develop a wide range of solutions and expand the classes of exact solutions by modifying the activation function. The activation function's versatility allows it to generate a wide range of solutions with several theoretical and practical uses. The analytical solution is obtained by using a double layer type, while the rogue wave solution and mixed solutions are obtained by using a single layer type. The evolution of these waves is then illustrated using various 3D graphs, 2D graphs, and density plots. [ABSTRACT FROM AUTHOR]

Phosphate treatment at the Kpémé plant uses hydrocycloning with seawater, which produces phosphate sludge wastes discharged into the sea without any prior treatment. This waste is highly enriched in trace elements and is the source of water and coastal sediment pollution. The objective of this study is to highlight the pollutant load of the different phases of phosphate mud mining waste and their possible impact on the marine environment of the Togolese coast and certain neighboring countries, depending on their density. The methodology consists of a classification using a mini hydrocyclone Galaxi–Tower and a geochemical characterization of the phases of these sludgy mining wastes. A study of the bulk density of the phases obtained shows that the apatite-rich phase is denser than the clay-rich phase. Clay-rich phases will be transported over longer distances than apatite-rich phases, in accordance with the sea environment conditions prevailing on the coast. The clay-rich phase has a higher degree of acidity and redox potential than the apatite-rich phase. These phosphate sludgy wastes and the various phases are enriched in Cr, Cd, Cu, Co, Zn, Ni and Hg compared with the earth's crust. On the other hand, the light phase is more enriched in trace elements than the apatite-rich phase. The light phase has a higher apparent partition coefficient for all elements than the apatite-rich phase, except for Cd and Zn. In the dissolved solutions of clay-rich phases, Fe, Zn and Hg contents are higher than in apatite-rich phases. In contrast, Al, Cr, Cd, Cu and Ni contents are higher in apatite-rich phases than in clay-rich phases. Article Highlights: Separation of phosphate sludge waste phases according to density in seawater using a mini hydrocyclone Galaxi-Tower Assessment of trace element load of the particles constituting this sludgy phosphate waste and each separated phase Demonstration of trace element level in dissolved solution of phases during their possible transit in marine environment [ABSTRACT FROM AUTHOR]

Liquid fuel density is an essential physical parameter in the design and application processes. This paper employed the Gibbs free energy technique with quantitative structure‐property relationship (QSPR) for determining the density of pure fatty acid ethyl ester (FAEE) and ethyl ester biodiesel at temperature 283.15–363.15 K. The density (ρ) of biodiesel can be estimated from (1) the number of carbon atoms of fatty acids (z) and the number of double bonds (nd): ln ρ = −0.4466–0.0009z + 88.28/T + 0.2092z/T + 0.01734nd–1.578nd/T or (2) the saponification number (SN) and iodine value (IV): ln ρ = −0.4436–3.60/SN + 87.594/T + 836.8/(T × SN) + 0.0380 IV/SN – 3.4222 IV/(T × SN), where T is the absolute temperature. The predicted densities at different temperatures for pure FAEEs and ethyl ester biodiesel have average absolute deviations (AAD) of 0.100% and 0.200%, respectively. [ABSTRACT FROM AUTHOR]

When LiDAR scans woodlands, the three-dimensional (3D) point cloud data of woodlands directly collected usually contain a large number of noise points, which is caused by equipment performance, environmental interference, or other factors. The poor data quality of the point cloud data affects the accuracy of the extracted individual tree feature parameters and forest 3D reconstruction. To improve the quality of forest 3D point cloud data, a curvature- and density-based denoising method has been proposed in this study. First, the surface curvature features were calculated for the noise-dense trunk area of the forest for primary denoising, and the initial denoising results were used to construct the K-dimensional-Tree (KD-Tree) space index to search the spherical neighbourhood. The denoising was completed according to the proposed density calculation method (SN-NN, Spherical Neighbourhood and Nearest Neighbour). To evaluate the comprehensive performance of the proposed denoising method, a new denoising evaluation index has been designed by integrating the denoising precision and effective data retention degree of the forest point cloud data. The proposed method was validated based on forest point cloud data collected using Terrestrial LiDAR. The results show that the denoising precision and effective data retention degree of the proposed method are both preferable, which can effectively improve the quality of forest point cloud data. [ABSTRACT FROM AUTHOR]

A new wavelet-based estimator of the conditional density is investigated. The estimator is constructed by combining a special ratio technique and applying a non negative estimator to the density function in the denominator. We used a wavelet shrinkage technique to find an adaptive estimator for this problem. In particular, a block thresholding estimator is proposed, and we prove that it enjoys powerful mean integrated squared error properties over Besov balls. Moreover, it is shown that convergence rates for the mean integrated squared error (MISE) of the adaptive estimator are optimal under some mild assumptions. Finally, a numerical example has been considered to illustrate the performance of the estimator. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the long time existence of the classical solution to 2D one-fluid Euler-Poisson system of electrons with non-zero vorticity in the standard Sobolev spaces so that both the local solution and long time solution lie in the same Sobolev space framework without any extra restrictions of space-decay rates at infinity. It is shown that the lifespan of the classical solution is at least T ε , δ = min ⁡ { e ε − 2 | l n ε | − α , κ δ } , where ε > 0 is the size of the initial perturbed density and velocity, δ > 0 is the size of the initial vorticity, α > 0 is any fixed number, κ > 0 is a suitable constant. We decompose the Euler-Poisson system into three bilinear interaction parts: dispersion–dispersion, vorticity–dispersion, and vorticity–vorticity. Based on the Strichartz inequality, the related quartic energy estimates, the conservation of specific vorticity along the streamline and some delicate analysis, the precise bound of lifespan T ε , δ is obtained. By the way, for the 2D irrotational one-fluid Euler-Poisson system with small amplitude ε of the perturbed initial data in the Sobolev spaces, we obtain an interesting long time existence result with lifespan T ε ≥ e ε − 2 | l n ε | − α (α > 0 is any fixed constant). [ABSTRACT FROM AUTHOR]

In this paper, we classify 1-cocycles of the Witt algebra with coefficients in the tensor product of two arbitrary tensor density modules. In a special case, we recover a theorem originally established by Ng and Taft in [24]. Furthermore, by these 1-cocycles, we determine Lie bialgebra structures over certain infinite-dimensional Lie algebras containing the Witt algebra. [ABSTRACT FROM AUTHOR]

In clinical practice, the effect of a high vault on corneal endothelial cells after implantable collamer lens (ICL) implantation remains unclear. Many clinicians theoretically assume that a high postoperative vault leads to rapid endothelial damage, but no study has yet proven this hypothesis. We conducted a paired-eye study to compare changes in corneal endothelial cell density (ECD) between high and low postoperative vault groups. This retrospective study included 150 eyes of 75 patients with bilateral postoperative vault levels differing by more than 200 μm after ICL implantation. Patients were followed up for 7 years with ECD measurements, and changes in ECD were assessed between 6 months and 7 years post-surgery. Over the 7-year follow-up period, the percentage of ECD loss was 15.04% and 14.45% in the high- and low-vault groups, respectively. The bilateral paired-eye comparison revealed a significant reduction in ECD in the high-vault group at 3, 5, and 7 years postoperatively (P-value < 0.001). In this paired-eye comparison of long-term observations, a higher vault was associated with greater ECD loss. Our study confirms that a high vault level may be an important risk factor for ECD loss following ICL implantation. [ABSTRACT FROM AUTHOR]

In this paper, we explore a modified black brane within AdS space–time, characterized by the Lagrangian density 1qarcsin(qR)−2Λ. Due to the absence of an analytic solution, we approach the Einstein equations using a perturbative method, extending our analysis to the second order in q. Subsequently, we compute the ratio of shear viscosity to entropy density. Our results suggest that the KSS Bound is not saturated in this model. [ABSTRACT FROM AUTHOR]

Imbalanced data classification problem is a prevalent concern within the realms of machine learning and data mining. However, conventional methods primarily concentrate on between-class imbalance, ignoring noisy, overlap and within-class issues. To address these issues, a new adaptive over-sampling method for imbalanced data based on simultaneous clustering and filtering noisy (ASCFNO) was proposed in this study. First, this method develops a new DPINF (Density Peak Clustering with Improved Noise Filter) clustering algorithm not only to identify minority class sub-clusters with various sizes and densities but also simultaneously filter noisy instances, which can deal with noisy problem and be more beneficial for the subsequent steps to solve between-class and within-class imbalance problems. Second, an adaptive strategy determines the over-sampling size for each minority class sub-cluster, which assigns various weights to each sub-cluster by considering different factors to settle the issues of within-class imbalance. In the end, novel synthetic minority instances are generated between two instances located in the same sub-cluster that are selected according to their probability distribution, which prevents the generation of any noisy or overlapped synthetic instances by the traditional SMOTE method. The performance of the proposed ASCFNO was assessed on 32 benchmark imbalanced datasets. The experiment results prove the effectiveness and feasibility of the above improvements. [ABSTRACT FROM AUTHOR]

The aim of this study is to determine the misconceptions of Greek junior high school students regarding the floating and sinking of a body through the concept of density. Density is included in most international curricula for this age group and is revisited in Greek junior high schools after being introduced in primary school. After interviews with teachers who teach the physics course, in order to discover the students' way of thinking and their common misconceptions, the researchers of this study created targeted questionnaires for students aged 11-12 years old. During the 2022-23 school year, the questionnaires were handed out to 47 first-grade students at a junior high school in Athens, Greece. Before being administered to the students, the questionnaires were subjected to a content validity test by five physics experts according to Aiken's V index. Then, they were completed by the students before the lesson was taught. After the students had completed the initial questionnaire, a teaching proposal focused on the density-based approach was presented to them. Subsequently, the students filled out the same questionnaire again following the instructional session. Statistical analysis demonstrated a notable enhancement in the comprehension of the misconceptions addressed in this study, with the rates of improvement varying between 18.08% and 52.13%. Consequently, the instructional proposal proved to be instrumental in advancing students' conceptual understanding of floating and sinking within the framework of density interpretation. [ABSTRACT FROM AUTHOR]