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Demonstrates the third law of using magnets by mathematician Isaac Newton through combined kinesthetic experience with quantitative experiments. Procedure of a kinesthetic demonstration that allows the students to feel the interaction forces between a magnet and a piece of iron; Guide for determining Newton's third law in repulsion through the combination of kinesthetic experience with quantitative experiments.

This paper proposes the first linear scaling implementation for the domain decomposition approach of the polarizable continuum model (ddPCM) for the computation of the solvation energy and forces. The ddPCM-equation consists of a (non-local) integral equation on the van der Waals or solvent accessible surface of the solute's cavity resulting in a dense solution matrix, and, in turn, one matrix–vector multiplication has a quadratic arithmetic complexity with respect to the number of atoms of the solute molecule. The use of spherical harmonics as basis functions makes it natural to employ the fast multipole method (FMM) in order to provide an asymptotically linear scaling method. In this paper, we employ the FMM in a non-uniform manner with a clusterization based on a recursive inertial bisection. We present some numerical tests illustrating the accuracy and scaling of our implementation. [ABSTRACT FROM AUTHOR]

In this paper we describe a simple alternative to the telephone book friction experiment, a classic demonstration where a small force (generated for example by the bending of the outer pages) is amplified by the large number of surfaces in contact, resulting in a huge maximum static friction force that has to be counterbalanced in order to separate the books. The aim of our experiment is to illustrate the friction force in a dramatic way and to simplify the tedious job of interleaving a large number of book pages, by using the minimum number of sheets necessary to sustain the weight of a person using the normal force produced by their fingers. [ABSTRACT FROM AUTHOR]

This series of papers is devoted to identifying and explaining the properties of strongly correlating liquids, i.e., liquids with more than 90% correlation between their virial W and potential energy U fluctuations in the NVT ensemble. Paper IV [N. Gnan et al., J. Chem. Phys. 131, 234504 (2009)] showed that strongly correlating liquids have 'isomorphs,' which are curves in the phase diagram along which structure, dynamics, and some thermodynamic properties are invariant in reduced units. In the present paper, using the fact that reduced-unit radial distribution functions are isomorph invariant, we derive an expression for the shapes of isomorphs in the WU phase diagram of generalized Lennard-Jones systems of one or more types of particles. The isomorph shape depends only on the Lennard-Jones exponents; thus all isomorphs of standard Lennard-Jones systems (with exponents 12 and 6) can be scaled onto a single curve. Two applications are given. One tests the prediction that the solid-liquid coexistence curve follows an isomorph by comparing to recent simulations by Ahmed and Sadus [J. Chem. Phys. 131, 174504 (2009)]. Excellent agreement is found on the liquid side of the coexistence curve, whereas the agreement is less convincing on the solid side. A second application is the derivation of an approximate equation of state for generalized Lennard-Jones systems by combining the isomorph theory with the Rosenfeld-Tarazona expression for the temperature dependence of the potential energy on isochores. It is shown that the new equation of state agrees well with simulations. [ABSTRACT FROM AUTHOR]

Presents a classroom experiment on the conversion of potential to kinetic energy. Materials used in the experiment; Mechanism involved in the conversion of potential to kinetic energy.

Capacitors with dielectric in series Before discussing capacitors with dielectric in series, it is necessary to consider a triple conductor-plate model, shown in Fig. This paper offers a technique for abstracting capacitors partially filled with a dielectric into parallel and series capacitor models with enlightening visualization approaches. Capacitors with dielectric in parallel Although not directly taught in most textbooks, capacitors partially filled with a dielectric almost always appear as exercise problems in textbooks. [Extracted from the article]

This document serves as a preface to a special topic collection in the journal "Physics of Plasmas" that focuses on the study of relativistic plasma in supercritical fields. The collection includes papers from a mini-conference held at the 2022 meeting of the American Physical Society Division of Plasma Physics. The objective of the mini-conference was to bring together researchers from different physics communities to address the physics of matter in extreme astrophysical objects and high-power laser systems. The papers in the collection cover topics such as electron-positron pair production, extreme astrophysics, radiation reaction, and vacuum physics. The mini-conference aimed to facilitate knowledge exchange and inspire future research in this emerging field of plasma physics. The authors of this document, Alec G. R. Thomas and Stepan S. Bulanov, declare that they have no conflicts of interest to disclose and were supported by the U.S. Department of Energy Office of Science Offices of High Energy Physics and Fusion Energy Sciences. [Extracted from the article]

Previous studies of two-dimensional (2D) aerodynamic admittance function (AAF) identification methods have basically ignored the effects of different turbulence components, which may lead to unpredictable errors for practical engineering applications. This paper presents pressure measurement experiments on thin sections with a geometric ratio of 1:50 in various turbulent fields. Based on the three-dimensional (3D) two-wavenumber theoretical analytical framework, the two-wavenumber coherence function is obtained by fitting the measured spanwise root-coherence function at the effective spacing with an empirical model. A new method is proposed, assuming that the ratio relationship between the lift AAFs due to longitudinal and vertical turbulence components of the measured model section satisfies its corresponding theoretical solution ratio relationship. The 2D lift AAFs of the airfoil section induced by different turbulence components are identified following the proposed identification framework. Consistent with the previous research, force correlation is significantly larger than turbulence correlation, and the traditional 3D one-wavenumber AAFs obtained are different in different turbulent fields. The separated 2D lift AAFs demonstrate that the contributions of u- and w- turbulence to the buffeting lift force are significantly different, and are more precise, according to the ratio between the Horlock function and Sears function. Then, the method is successfully extended to estimate the AAFs with respect to the u- and w-turbulence components of a streamlined box girder section, further validating the applicability of the identification method to the streamlined box girder. Furthermore, comparing the separated 2D lift AAFs under different turbulence fields reveals their independence from turbulence characteristics. [ABSTRACT FROM AUTHOR]

We apply the theories developed in the preceding paper (paper I) to calculate various energy quantities of charge transfer (CT) reactions in nine solvents that cover a wide range of polarity, and for which interaction site models (ISM’s) may be found in the literature. Besides the two surrogate Hamiltonian theories developed in paper I, the renormalized site-density theory (RST) and the renormalized dielectric theory (RDT), we also investigate a simple harmonic approximation (HXA) for the diabatic free energy profiles, whose characteristic parameters are calculated taking specific advantage of the expression given by the extended reference interaction site method (XRISM) for the free energy of solvation. For each CT process we analyze (a) the solvent reorganization energy λ, (b) the shift of the absorption transition energy due to the solvatochromic effect, and (c) the solvent contribution to the free energy change ΔA. In addition, for a few selected examples, we also report the detailed diabatic free energy profiles. The calculations reported rely on solute–solvent and solvent–solvent pair correlation functions obtained with the XRISM integral equation method applied to nonpolarizable (with fixed mean partial charges) ISM representations of the solute and solvent molecules. To rectify the omission of the solvent electronic degrees of freedom, we correct the dielectric part of the solvent reorganization energy with an additive term designed to compensate for the use of fixed charge ISM models. Contact with theories in which the solvent is represented as a dielectric continuum medium (with or without spatial dispersion) and the solute as a set of charges inside spherical cavities carved out of the dielectric is made straightforwardly within the RDT theory by considering a particularly simple form of the solute–solvent RISM site–site direct correlation functions. Using simple ISM models for several solute species,... [ABSTRACT FROM AUTHOR]

We investigate transport of point Brownian particles in a tube formed by identical periodic compartments of varying diameter, focusing on the effects due to the compartment asymmetry. The paper contains two parts. First, we study the force-dependent mobility of the particle. The mobility is a symmetric non-monotonic function of the driving force, F, when the compartment is symmetric. Compartment asymmetry gives rise to an asymmetric force-dependent mobility, which remains non-monotonic when the compartment asymmetry is not too high. The F-dependence of the mobility becomes monotonic in tubes formed by highly asymmetric compartments. The transition of the F-dependence of the mobility from non-monotonic to monotonic behavior results in important consequences for the particle motion under the action of a time-periodic force with zero mean, which are discussed in the second part of the paper: In a tube formed by moderately asymmetric compartments, the particle under the action of such a force moves with an effective drift velocity that vanishes at small and large values of the force amplitude having a maximum in between. In a tube formed by highly asymmetric compartments, the effective drift velocity monotonically increases with the amplitude of the driving force and becomes unboundedly large as the amplitude tends to infinity. [ABSTRACT FROM AUTHOR]

This paper presents the nonadiabatic molecular dynamics simulation in the solution phase using the spin-flip time-dependent density functional theory (SF-TDDFT). Despite the single-reference level of theory, the SF-TDDFT method can generate the correct topology of S0/S1 crossing points, thus providing a natural S1 → S0 nonadiabatic transition. We extend the gas-phase trajectory surface hopping simulation with the SF-TDDFT [N. Minezawa and T. Nakajima, J. Chem. Phys. 150, 204120 (2019)] to the hybrid quantum mechanical/molecular mechanics (QM/MM) scheme. To this end, we modify the code to evaluate the electrostatic interaction between the QM and MM atoms and to extract the classical MM energy and forces from the MM program package. We apply the proposed method to the photoisomerization reaction of aqueous E-azomethane and anionic green fluorescent protein chromophore in water and compare the results with those of the previous simulation studies based on the multireference methods. [ABSTRACT FROM AUTHOR]

The self-referential method [M. B. Sweatman, Phys. Rev. E 72, 016711 (2005)] for calculating the free energy of crystalline solids via molecular simulation is combined with thermodynamic integration to produce a technique that is convenient and efficient. Results are presented for the chemical potential of hard sphere and Lennard-Jones face centered cubic crystals that agree well with this previous work. For the small system sizes studied, this technique is about 100 times more efficient than the parameter hopping technique used previously. [ABSTRACT FROM AUTHOR]

Modal and non-modal stability analyses are applied to Hagen–Poiseuille flow with a non-ideal fluid. The non-ideal fluid is defined as a fluid close to its vapor–liquid critical point. In this region, properties of the fluid deviate significantly from the assumptions of the ideal gas model. In this paper, the specific example of CO2 near the critical point is taken as a non-ideal fluid. We studied fluids at supercritical pressure and different wall temperatures so that the centerline temperatures can be lower, equal, and higher than the pseudo-critical temperature. Flow instability is characterized by the Reynolds number, and the product of the Prandtl and Eckert numbers. In modal stability analysis, we observe that there is no unstable mode in Hagen–Poiseuille flow with a non-ideal fluid. Regarding the growth rate, as the axial wavenumber increases, another mode becomes the least stable. The non-modal theory is employed to investigate the optimal response to harmonic external force and transient energy growth. The influence of axial and azimuthal wave numbers, Prandtl and Eckert numbers, and thermodynamic states are also taken into account. In this study, we identify an generalized inflection point in the transcritical base profile, causing the transcritical state to be the most unstable. In non-modal instability, we observe that the optimal response mainly occurs at time invariant axisymmetric disturbance. This suggests that the axisymmetric disturbance could potentially initiate the transition to turbulence. [ABSTRACT FROM AUTHOR]

This paper numerically investigates the influence of a fixed downstream control cylinder on the flow-induced vibration of an elastically supported primary cylinder. These two cylinders are situated in a tandem arrangement with small dimensionless center-to-center spacing (L/D, L is the intermediate spacing and D is the cylinder diameter). The present two-dimensional (2D) simulations are carried out in the low Reynolds number (Re) regime. The primary focus of this study is to reveal the underlying flow physics behind the transition from vortex-induced vibration to galloping in the response of the primary cylinder due to the presence of another fixed downstream cylinder. Two distinct flow field regimes, namely, steady flow and alternate attachment regimes, are observed for different L/D and Re values. Depending on the evolution of the near-field flow structures, four different wake patterns, "2S," "2P," "2C," and "aperiodic," are observed. The corresponding vibration response of the upstream cylinder is characterized as interference galloping and extended vortex-induced vibration. As the L/D ratio increases, the lift enhancement due to flow-induced vibration is seen to be weakened. The detailed correlation between the force generation and the near-wake interactions is investigated. The present findings will augment our understanding of vibration reduction or flow-induced energy harvesting of tandem cylindrical structures. [ABSTRACT FROM AUTHOR]

The objective of this paper is to demonstrate that the addition of properly tuned nonlinearities to a nonlinear system can increase the range over which a specific resonance responds linearly. Specifically, we seek to enforce two important properties of linear systems, namely, the forcedisplacement proportionality and the invariance of resonance frequencies. Numerical simulations and experiments are used to validate the theoretical findings. [ABSTRACT FROM AUTHOR]

Dispersion forces start to play role in modern micro/nanoelectromechanical devices, but the methods to measure these forces at distances close to contact (< 50 nm) suffer from pull-in instability. The method of adhered cantilever proposed recently has no instability and is able to make measurements at short separations. To measure the force at the average distance between surfaces in contact, one has to know the shape of an elastic beam with one end fixed at a height of 1–10 μm and the other end adhered to the substrate. The maximum contribution to this shape from the dispersion forces is in a range of 30–100 nm, which is well measurable by the interferometric methods. This paper describes the instrument, measurements, and data processing that make possible the reconstruction of the beam shape with an accuracy of 1 nm in a height range of at least 5000 nm. Critical steps of the fabrication procedure of cantilevers that are 12 mm long, 200 μm wide, and 10 μm thick are described. The interferometer measures the shape based on the differential interference-contrast method; the scanning is realized by a stage with a step of 0.1 μm. The signal recorded from the adhered cantilever has a noise level of 0.33 nm at a maximum sensitivity in a frequency band of 20 MHz. It is concluded that the instrument and data processing algorithm can be used to measure the dispersion forces and adhesion energies between rough surfaces in unloaded contact. [ABSTRACT FROM AUTHOR]

The observed increase in the steric effect of the reaction Ca(1D)+CH3F(JKM=111) →CaF(2Π)+CH3 with increasing energy has been tentatively ascribed to a reorientation of the initially oriented CH3F axis, due to anisotropic long-range forces [M. H. M. Janssen, D. H. Parker, and S. Stolte, J. Phys. Chem. 95, 8142 (1991)]. Here we present ab initio calculations and use these to construct a long-range potential. To this potential we fit an isotropic model potential and two anisotropic model potentials. On the long-range potential and on the model potentials we perform classical trajectory calculations, and we compare the two methods presented in the preceding paper [G. C. Groenenboom and A. J. H. M. Meijer, J. Chem. Phys. 101, 7592 (1994)] for the extraction of the steric effect. We conclude that already the attractive isotropic model presented in this paper can account for the observed energy dependence of the steric effect for this reaction via a ‘‘trapping’’ mechanism. We show that although reorientation is possible, it contributes little to the positive energy dependence of the steric effect. [ABSTRACT FROM AUTHOR]

This paper deals with a recently proposed device for energy harvesting from environmental vibrations, employing a magnetostrictive material. Even if most of the modeling efforts were focused on a linear approach, more complex and nontrivial phenomena are experimentally observed. A sample of such nontrivial behaviors, suggesting the definition of potentially more effective models, is described and discussed in this paper [ABSTRACT FROM AUTHOR]

The representability and transferability of effective pair potentials used in multiscale simulations of soft matter systems is ill understood. In this paper, we study liquid state systems composed of n-alkanes, the coarse-grained (CG) potential of which may be assumed pairwise additive and has been obtained using the conditional reversible work (CRW) method. The CRW method is a free-energy-based coarse-graining procedure, which, by means of performing the coarse graining at pair level, rigorously provides a pair potential that describes the interaction free energy between two mapped atom groups (beads) embedded in their respective chemical environments. The pairwise nature of the interactions combined with their dependence on the chemically bonded environment makes CRW potentials ideally suited in studies of chemical transferability. We report CRW potentials for hexane using a mapping scheme that merges two heavy atoms in one CG bead. It is shown that the model is chemically and thermodynamically transferable to alkanes of different chain lengths in the liquid phase at temperatures between the melting and the boiling point under atmospheric (1 atm) pressure conditions. It is further shown that CRW-CG potentials may be readily obtained from a single simulation of the liquid state using the free energy perturbation method, thereby providing a fast and versatile molecular coarse graining method for aliphatic molecules. [ABSTRACT FROM AUTHOR]

The multiscale coarse-graining (MS-CG) method is a method for constructing a coarse-grained (CG) model of a system using data obtained from molecular dynamics simulations of the corresponding atomically detailed model. The formal statistical mechanical derivation of the method shows that the potential energy function extracted from an MS-CG calculation is a variational approximation for the true potential of mean force of the CG sites, one that becomes exact in the limit that a complete basis set is used in the variational calculation if enough data are obtained from the atomistic simulations. Most applications of the MS-CG method have employed a representation for the nonbonded part of the CG potential that is a sum of all possible pair interactions. This approach, despite being quite successful for some CG models, is inadequate for some others. Here we propose a systematic method for including three body terms as well as two body terms in the nonbonded part of the CG potential energy. The current method is more general than a previous version presented in a recent paper of this series [L. Larini, L. Lu, and G. A. Voth, J. Chem. Phys. 132, 164107 (2010)], in the sense that it does not make any restrictive choices for the functional form of the three body potential. We use hierarchical multiresolution functions that are similar to wavelets to develop very flexible basis function expansions with both two and three body basis functions. The variational problem is solved by a numerical technique that is capable of automatically selecting an appropriate subset of basis functions from a large initial set. We apply the method to two very different coarse-grained models: a solvent free model of a two component solution made of identical Lennard-Jones particles and a one site model of SPC/E water where a site is placed at the center of mass of each water molecule. These calculations show that the inclusion of three body terms in the nonbonded CG potential can lead to significant improvement in the accuracy of CG potentials and hence of CG simulations. [ABSTRACT FROM AUTHOR]

In principle, all of the dynamical complexities of many-body systems are encapsulated in the potential energy landscapes on which the atoms move—an observation that suggests that the essentials of the dynamics ought to be determined by the geometry of those landscapes. But what are the principal geometric features that control the long-time dynamics? We suggest that the key lies not in the local minima and saddles of the landscape, but in a more global property of the surface: its accessible pathways. In order to make this notion more precise we introduce two ideas: (1) a switch to a new ensemble that deemphasizes the concept of potential barriers, and (2) a way of finding optimum pathways within this new ensemble. The potential energy landscape ensemble, which we describe in the current paper, regards the maximum accessible potential energy, rather than the temperature, as a control variable. We show here that while this approach is thermodynamically equivalent to the canonical ensemble, it not only sidesteps the idea of barriers it allows us to be quantitative about the connectivity of a landscape. We illustrate these ideas with calculations on a simple atomic liquid and on the Kob-Andersen [Phys. Rev. E 51, 4626 (1995)] of a glass-forming liquid, showing, in the process, that the landscape of the Kob-Anderson model appears to have a connectivity transition at the landscape energy associated with its empirical mode-coupling transition. We turn to the problem of finding the most efficient pathways through potential energy landscapes in our companion paper. [ABSTRACT FROM AUTHOR]

How useful it is to think about the potential energy landscape of a complex many-body system depends in large measure on how direct the connection is to the system’s dynamics. In this paper we show that, within what we call the potential-energy-landscape ensemble, it is possible to make direct connections between the geometry of the landscape and the long-time dynamical behaviors of systems such as supercooled liquids. We show, in particular, that the onset of slow dynamics in such systems is governed directly by the lengths of their geodesics—the shortest paths through their landscapes within the special ensemble. The more convoluted and labyrinthine these geodesics are, the slower that dynamics is. Geodesics in the landscape ensemble have sufficiently well-defined characteristics that it is straightforward to search for them numerically, a point we illustrate by computing the geodesic lengths for an ordinary atomic liquid and a binary glass-forming atomic mixture. We find that the temperature dependence of the diffusion constants of these systems, including the precipitous drop as the glass-forming system approaches its empirical mode-coupling transition, is predicted quantitatively by the growth of the geodesic path lengths. [ABSTRACT FROM AUTHOR]

The research described in this paper primarily involves mesoscale simulations: dissipative particle dynamics (DPD) of packed assemblies of oriented fibers suspended in a viscous medium. Computer simulations have been performed in order to explore how the aspect ratio and degree of fiber alignment affect the critical volume fraction (percolation threshold) required to achieve electrical conductivity. The fiber network impedance was assessed using Monte Carlo simulations after establishing the structural arrangement with DPD. The predictions are compared with the predictions of classical percolation theory and found to be in close agreement. The approach is thus validated and can be extended to systems that cannot be tackled analytically; in particular, the work is motivated by long-standing interest in materials which display a complex percolation behavior. [ABSTRACT FROM AUTHOR]

High-level ab initio potential-energy curves and transition dipole moments for the OH X 2Π, 2 2Π, 1 2Σ-, D 2Σ-, 3 2Σ-, A 2Σ+, B 2Σ+, 1 2Δ, 1 4Σ-, and 1 4Π states are computed. The results are used to estimate the (2+1) resonance enhanced multiphoton ionization spectrum for the (D,3)2Σ-(υ′)←2hνX 2Π(υ″) transitions, which are compared with experiments by Greenslade et al. [see M. E. Greenslade, M. I. Lester, D. C. Radenovic, J. A. van Roij, and D. H. Parker, J. Chem. Phys. 123, 074309 (2005), preceeding paper]. We use the discrete variable representation-absorbing boundary condition method to incorporate the effect of the dissociative intermediate 1 2Σ- state. We obtain qualitative agreement with experiment for the line strengths. Radiative and predissociative decay rates of the Rydberg (D,3)2Σ- states of OH and OD were computed, including spin-orbit coupling effects and the effect of spin-electronic and gyroscopic coupling. We show that the lifetime of the Rydberg 2Σ- states for rotationally cold molecules is limited mainly by predissociation caused by spin-orbit coupling. [ABSTRACT FROM AUTHOR]

Deterministic thermostats are frequently employed in nonequilibrium molecular dynamics simulations in order to remove the heat produced irreversibly over the course of such simulations. The simplest thermostat is the Gaussian thermostat, which satisfies Gauss’s principle of least constraint and fixes the peculiar kinetic energy. There are of course infinitely many ways to thermostat systems, e.g., by fixing ∑i|pi|μ+1. In the present paper we provide, for the first time, convincing arguments as to why the conventional Gaussian isokinetic thermostat (μ=1) is unique in this class. We show that this thermostat minimizes the phase space compression and is the only thermostat for which the conjugate pairing rule holds. Moreover, it is shown that for finite sized systems in the absence of an applied dissipative field, all other thermostats (μ≠1) perform work on the system in the same manner as a dissipative field while simultaneously removing the dissipative heat so generated. All other thermostats (μ≠1) are thus autodissipative. Among all μ thermostats, only the μ=1 Gaussian thermostat permits an equilibrium state. [ABSTRACT FROM AUTHOR]

An intriguing energy-transfer experiment was recently carried out in methanol/carbon tetrachloride solutions. It turned out to be possible to watch vibrational energy accumulating in three of carbon tetrachloride’s modes following initial excitation of O-H and C-H stretches in methanol, in effect making those CCl4 modes “molecular thermometers” reporting on methanol’s relaxation. In this paper, we use the example of a CCl4 molecule dissolved in liquid argon to examine, on a microscopic level, just how this kind of thermal activation occurs in liquid solutions. The fact that even the lowest CCl4 mode has a relatively high frequency compared to the intermolecular vibrational band of the solvent means that the only solute-solvent dynamics relevant to the vibrational energy transfer will be extraordinarily local, so much so that it is only the force between the instantaneously most prominent Cl and solvent atoms that will significantly contribute to the vibrational friction. We use this observation, within the context of a classical instantaneous-pair Landau-Teller calculation, to show that energy flows into CCl4 primarily via one component of the nominally degenerate, lowest frequency, E mode and does so fast enough to make CCl4 an excellent choice for monitoring methanol relaxation. Remarkably, within this theory, the different symmetries and appearances of the different CCl4 modes have little bearing on how well they take up energy from their surroundings—it is only how high their vibrational frequencies are relative to the solvent intermolecular vibrational band edge that substantially favors one mode over another. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

An efficient and general method for the analytic computation of the nonandiabatic coupling vector at the multireference configuration interaction (MR-CI) level is presented. This method is based on a previously developed formalism for analytic MR-CI gradients adapted to the use for the computation of nonadiabatic coupling terms. As was the case for the analytic energy gradients, very general, separate choices of invariant orbital subspaces at the multiconfiguration self-consistent field and MR-CI levels are possible, allowing flexible selections of MR-CI wave functions. The computational cost for the calculation of the nonadiabatic coupling vector at the MR-CI level is far below the cost for the energy calculation. In this paper the formalism of the method is presented and in the following paper [Dallos et al., J. Chem. Phys. 120, 7330 (2004)] applications concerning the optimization of minima on the crossing seam are described. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In a previous theoretical study [J. Chem. Phys. 117, 5827 (2002)] we calculated the vibrational lifetimes of the three fundamentals of HOD in liquid D[SUB2]O. In that calculation the D[SUB2]O solvent was treated as rigid, not allowing for the possibility of intermolecular vibrational energy transfer as a relaxation mechanism. In this paper we use both flexible and rigid solvent models, enabling us to include the possibility of intermolecular vibrational energy transfer, and also to estimate branching ratios for vibrational and nonvibrational relaxation channels. Our theoretical value for the lifetime of the OH stretch decreases modestly from 2.7 ps (in the original calculation) to 2.3 ps, which should be compared to the experimental value of about 1 ps. The lifetime of the OD stretch decreases dramatically from 18 ps to 390 fs due to resonant energy transfer to the solvent stretch. Our lifetime value for the bend actually increases from 220 to 380 fs, not because of the vibrational energy transfer channel, but rather because we find that Fermi's Golden Rule (used in the original calculation) breaks down for this very fast process. We have calculated all the state-to-state rate constants for the low-lying vibrational energy levels of HOD, which allows us to construct and solve the vibrational master equation. We find that after excitation of the OH stretch, population flows into the HOD bend states (and to a lesser extent the OD stretch of HOD) on the time scale of 1 ps, in agreement with recent infrared pump/Raman probe measurements of Dlott and co-workers. From our results we estimate that for each quantum of OH stretch excitation, 0.26 quanta of solvent stretch is excited by direct intermolecular energy transfer, and yet we find, surprisingly, that there is almost no direct excitation of solvent bend. On the other hand, we suggest that because of the intramolecular Fermi resonance in D[SUB2]O, rapid intramolecular vibrational relaxation occurs from solvent... [ABSTRACT FROM AUTHOR]

Energy components and neutron yield for a 600 mg/cm3 Be, Ag, and Ta plasma shell (liner) compressing a 6 mg/cm3 deuterium plasma: kinetic E m, magnetic E k, and internal electron E e and ion E i energies. Response to Comment on "Staged Z-pinch modeling of high and low atomic number liners compressing deuterium targets using parameters of the Z pulsed power facility" [Phys. Radial velocity and thermal plasma pressure profiles during the first (left column) and second (right column) shock heating interval from a 1-D MACH2 simulation of a 600mg/cm3 silver liner compressing a 6mg/cm3 deuterium fuel plasma. The sum of these four energy components (dotted line) is smaller, or at most equal to the total circuit E cir energy driving the system, indicating that the energy in the simulation is conserved. [Extracted from the article]

The concept underlying conservation of energy in a force field is that the work done by particles moving against the force represents energy removed from particles and added to energy in the field. For electromagnetic fields and charged particles, the transfer of energy between charges and local fields is described by Poynting's theorem. However, a similar local model for gravitational energy is not usually taught. In this paper, I derive the equations describing local conservation of energy in Newtonian gravity, discuss the well-known non-uniqueness of various terms, and show how comparison with Poynting's theorem provides insight into conditions for physical significance. [ABSTRACT FROM AUTHOR]

The effects of the Coriolis force in inhomogeneous rotating turbulence are studied in the paper. Linear analyses and numerical simulations both reveal that energy is transported to the slowly rotating fields, and the energy distribution is proportional to Ω 3 − 2 (x 3). The scale energy is almost spatially self-similar, and the inverse cascade is reduced by inhomogeneous rotation. The corresponding evolution equation of the scale energy, i.e., the generalized Kolmogorov equation, is calculated to study the scale transport process in the presence of inhomogeneity. The equation is reduced to twice the energy transport equation at sufficiently large scales, which is verified by numerical results. In addition, the results reveal the dominant role of the corresponding pressure of the Coriolis force in the spatial energy transport. An extra turbulent convention effect in r-space solely in slowly rotating fields is also recognized. It can be associated with the small-scale structures with strong negative vorticity, whose formation mechanism is similar to rotating condensates. Finally, by vortex dynamic analyses, we find that the corresponding pressure of the Coriolis force transports energy by vorticity tube shrinking and thickening. The effects of the Coriolis force can be divided into two components: one is related to the gradient of rotation, and the other is associated with the strength of rotation. [ABSTRACT FROM AUTHOR]

The effect of magnetic force on nonlinear energy harvesting performance is discussed theoretically and experimentally in this paper. A kind of nonlinear magnetic coupled piezoelectric energy harvester (NMPEH) is designed. The bidirectional screw is used to adjust the relative location of the tip magnets and external magnets to get different nonlinear magnetic forces. It is well known that the nonlinear magnetic force will influence the broadband energy harvesting performance. In order to describe the nonlinear dynamic behavior of the NMPEH, harmonic balance method is employed and its excitation test are performed at different accelerations over the range of 5-30Hz. It is also found that the analytical solutions match well with experimental output voltage. The nonlinear energy collector under the influence of symmetric magnetic force studied in this paper can not only reduce the resonance frequency of the system, but also increase the vibration amplitude of the cantilever beam, thus increasing the power obtained from the vibration environment. [ABSTRACT FROM AUTHOR]

Nowadays, in almost any country in the world, it is difficult to find a young person who has never played with, seen, or heard of the most famous toy in 2017: the fidget spinner. According to Wikipedia: "The fidget spinner is a toy that consists of a ball-bearing in the center of a multi-lobed flat structure made from metal or plastic designed to spin along its axis with little effort." Articles on educational proposals related to fidget spinners have been presented recently. Naturally, an issue arises from this polemic context: can fidget spinners be used to illustrate or explain physics concepts such as moment of inertia, torque, and angular momentum? This paper presents a simpler, cheaper, and easier experimental setup to obtain moments of inertia of the fidget spinner by using the free software Tracker for video analysis. A consistency test with an aluminum cylindrical shell ensures the reliability of the experimental setup. [ABSTRACT FROM AUTHOR]

The article focuses on the concept of vacuum energy and inflation in physics. It discusses four papers which were presented at a Gordon Conference on "Astronomy's Discoveries and Physics Education" in the year 2012, and deal with the behavior of space and basic cosmology. It states that the papers considered the mathematical model of an expanding universe and reexpressed Newton's law of gravity, the conservation of energy and the first law of thermodynamics in terms of scale factor.

In this paper, we present the implementation of the ‘‘conductorlike screening model’’ (COSMO) into the density functional program DMol. The electronic structure and geometry of the solute are described by a density functional method (DFT). The solute is placed into a cavity which has the shape of the solute molecule. Outside of the cavity, the solvent is represented by a homogeneous dielectric medium. The electrostatic interaction between solute and solvent is modeled through cavity surface charges induced by the solvent. The COSMO theory, based on the screening in conductors, allows for the direct determination of the surface charges within the SCF procedure using only the electrostatic potentials. This represents the major computational advantage over many of other reaction field methods. Since the DMol/COSMO energy is fully variational, accurate gradients with respect to the solute coordinates can be calculated for the first time, without any restriction on the shape of the cavity. The solvation energies and optimized molecular structures are calculated for several polar solutes. In addition, the trends in basicity of amines and the relative stabilities of molecular conformers are studied. Our results suggest that for neutral solutes, agreement between calculated and experimental solvation energies of better than about 2 kcal/mol can be achieved. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

In this paper we study three methods designed to calculate energy levels in a range of interest. The methods are applied to a one-dimensional (1-D) Morse oscillator and to HCN/HNC (in three-dimensions). Energy levels in the chosen range are computed using the filter-diagonalization method proposed by Neuhauser [J. Chem. Phys. 93, 2611 (1990)], a spectral transform Lanczos method, and a guided Lanczos method we suggest in this paper. In the guided Lanczos method convergence of the energy levels of interest is favored by choosing the Lanczos starting vector so that it has a substantial overlap only with eigenvectors of the eigenvalues in the chosen range. This biased starting vector is calculated from a solution of the time-dependent Schroedinger equation. Of the three methods the guided Lanczos is the most efficient for both the Morse oscillator and HCN/HNC. None of the methods designed to favor a chosen energy range are, however, (for the two problems we considered) as efficient as a straightforward Lanczos method (without an optimized starting vector). © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We recently proposed a theory [Suresh, J. Chem. Phys. 113, 9727 (2000)], based on the principles of statistical mechanics, for describing the temperature variation of static dielectric constant of water and the average number of H-bonds per molecule in the liquid phase. The theoretical model contains three parameters; two of them pertain to the energy and entropy changes accompanying bond-formation, and the third ([variant_greek_epsilon]∞) represents the dielectric constant at a frequency that is sufficiently low for atomic and electronic polarization, but sufficiently high for intermolecular relaxation processes involving the movement of permanent dipole moments to be inoperative. In the absence of a consensus in the literature for the value of [variant_greek_epsilon]∞ to be used in dielectric constant calculations, it was arbitrarily set to a commonly accepted value of 1.77 (corresponding to refractive index of 1.33). Values for H-bond parameters were then estimated by best fitting model calculations to experimental data for dielectric constant across temperatures ranging from melting to the critical point of water. It is the purpose of the present Note to eliminate the ambiguity on the choice of [variant_greek_epsilon]∞ and propose refined values for the H-bond parameters. [ABSTRACT FROM AUTHOR]

In this paper, we derive a boundary condition at the interface between a free fluid and a porous medium stating that the stress is transferred both to the fluid within the porous medium and to the solid skeleton. A zero stress jump is obtained so that the total stress is preserved at the interface. The boundary condition is obtained with the volume averaging method following the approach of Ochoa-Tapia and Whitaker ["Momentum transfer at the boundary between a porous medium and a homogeneous fluid--I. Theoretical development," Int. J. Heat Mass Transfer 38(14), 2635-2646 (1995)], but starting from the momentum balances written on the fluid and on the solid of the porous region, the latter was derived in part I of this paper. In the same way, also the boundary condition at the interface between a porous medium and a homogeneous solid is obtained. Both boundary conditions describe the equilibrium of forces at the interface, where part of the stress is carried by the solid skeleton and part by the fluid within the porous medium. With the derived boundary conditions, together with the stress transfer equation within the solid skeleton, it is now possible to satisfy the overall force equilibrium on a shear cell partially filled with a porous medium. [ABSTRACT FROM AUTHOR]

In this paper, we have studied adsorption and thermal desorption of methanol CH3OH on graphite surface, with the specific aim to derive from experimental data quantitative parameters that govern the desorption, namely, adsorption energy Eads and prefactor of the Polanyi-Wigner law. In low coverage regime, these two values are interconnected and usually the experiments can be reproduced with any couple (Eads), which makes intercomparison between studies difficult since the results depend on the extraction method. Here, we use a method for determining independently the average adsorption energy and a prefactor value that works over a large range of incident methanol coverage, from a limited set of desorption curves performed at different heating rates. In the low coverage regime the procedure is based on a first order kinetic law, and considers an adsorption energy distribution which is not expected to vary with the applied heating rate. In the case of CH3OH multilayers, Eads is determined as 430 meV with a prefactor of 5 × 1014 s-1. For CH3OH submonolayers on graphite, adsorption energy of 470 ± 30 meV and a prefactor of (8 ± 3) × 1016 s-1 have been found. These last values, which do not change between 0.09 ML and 1 ML initial coverage, suggest that the methanol molecules form island-like structure on the graphite even at low coverage. [ABSTRACT FROM AUTHOR]

The method calculating the effective diffusion coefficient in an arbitrary periodic two-dimensional channel, presented in our previous paper [P. Kalinay, J. Chem. Phys. 141, 144101 (2014)], is generalized to 3D channels of cylindrical symmetry, as well as to 2D or 3D channels with particles driven by a constant longitudinal external driving force. The next possible extensions are also indicated. The former calculation was based on calculus in the complex plane, suitable for the stationary diffusion in 2D domains. The method is reformulated here using standard tools of functional analysis, enabling the generalization. [ABSTRACT FROM AUTHOR]