Translational Momentum Research Articles

Anisotropic Photodetachment of Positronium Negative Ions with Linearly Polarized Light.

We report on the anisotropic photodetachment of positronium negative ions, followed by the dissociation into p-wave electrons and positronium atoms, with a linearly polarized laser beam. We have observed a strong recoil effect of the photoelectrons on the translation momentum of the dissociated positronium atoms. With polarization angle-resolved measurements, the asymmetry parameter of the photoemission angular distribution of the ions at a photon energy of 1.165eV was determined to be 1.97±0.04(stat)±0.07(syst), in agreement with a theoretical prediction. The present method can be applied to explore the unrevealed dissociation dynamics of exotic particle systems and their manipulation with polarized light.

Applying the Action Principle of Classical Mechanics to the Thermodynamics of the Troposphere

Advances in applied mechanics have facilitated a better understanding of the recycling of heat and work in the troposphere. This goal is important to meet practical needs for better management of climate science. Achieving this objective may require the application of quantum principles in action mechanics, recently employed to analyze the reversible thermodynamics of Carnot’s heat engine cycle. The testable proposals suggested here seek to solve several problems including (i) the phenomena of decreasing temperature and molecular entropy but increasing Gibbs energy with altitude in the troposphere; (ii) a reversible system storing thermal energy to drive vortical wind flow in anticyclones while frictionally warming the Earth’s surface by heat release from turbulence; (iii) vortical generation of electrical power from translational momentum in airflow in wind farms; and (iv) vortical energy in the destructive power of tropical cyclones. The scalar property of molecular action (@t ≡ ∫mvds, J-sec) is used to show how equilibrium temperatures are achieved from statistical equality of mechanical torques (mv2 or mr2ω2); these are exerted by Gibbs field quanta for each kind of gas phase molecule as rates of translational action (d@t/dt ≡ ∫mr2ωdϕ/dt ≡ mv2). These torques result from the impulsive density of resonant quantum or Gibbs fields with molecules, configuring the trajectories of gas molecules while balancing molecular pressure against the density of field energy (J/m3). Gibbs energy fields contain no resonant quanta at zero Kelvin, with this chemical potential diminishing in magnitude as the translational action of vapor molecules and quantum field energy content increases with temperature. These cases distinguish symmetrically between causal fields of impulsive quanta (Σhν) that energize the action of matter and the resultant kinetic torques of molecular mechanics (mv2). The quanta of these different fields display mean wavelengths from 10−4 m to 1012 m, with radial mechanical advantages many orders of magnitude greater than the corresponding translational actions, though with mean quantum frequencies (v) similar to those of radial Brownian movement for independent particles (ω). Widespread neglect of the Gibbs field energy component of natural systems may be preventing advances in tropospheric mechanics. A better understanding of these vortical Gibbs energy fields as thermodynamically reversible reservoirs for heat can help optimize work processes on Earth, delaying the achievement of maximum entropy production from short-wave solar radiation being converted to outgoing long-wave radiation to space. This understanding may improve strategies for management of global changes in climate.

Translational momentum of deformable submarine landslides off a slope

It has been reported that, in submarine landslides down a slope, only a small part of the landslide momentum was transferred to the tsunami while most was lost in the further propagation over the flat bed. The high momentum of landslides off a slope meant a long run-out and a great impact on underwater infrastructure. Nevertheless, little attention has been paid to the variation of momentum of deformable submarine landslides off a slope, i.e. the loss of momentum when the slides flow away from the slope over a flat bottom. In this paper, the translational momentum of deformable submarine granular landslides running down a non-erodible inclined bed is investigated with a two-phase smoothed particle hydrodynamics model. After flowing down the slope, the transport rate and flux of the landslide translational momentum along the propagation over the flat bottom are examined. The effects of physical variables of the slide, particularly the grain size, the initial compaction and the front intrusion angle on the variation of the translational momentum, are explored. Accordingly, scaling relations of the spatial-temporal maximum transport rate and flux of the landslide translational momentum, as well as those of the slide final run-out and the generated leading wave height, are proposed. These scaling relations, although based on numerical data of small-scale granular landslides, demonstrate a preliminary attempt to develop practical expressions in the framework of momentum for estimating the run-out of real submarine landslides and the impact on underwater infrastructure.

Localized Bound Multiexcitons in Engineered Quasi-2D Perovskites Grains at Room Temperature for Efficient Lasers.

Reducing the excitation threshold to minimize the Joule heating is critical for the realization of perovskite laser diodes. Although bound excitons are promising for low threshold laser, how to generate them at room temperature for laser applications is still unclear in quasi-2D perovskite-based devices. In this work, via engineering quasi-2D perovskite PEA2 (CH3 NH3 )n -1 Pbn Br3 n +1 microscopic grains by the anti-solvent method, room-temperature multiexciton radiative recombination is successfully demonstrated at a remarkably low pump density of 0.97 µJ cm-2 , which is only one-fourth of that required in 2D CdSe nanosheets. In addition, the well-defined translational momentum in quasi-2D perovskite grains can restrict the Auger recombination which is detrimental to radiative emission. Furthermore, the quasi-2D perovskite grains are favorable for increasing binding energies of excitons and biexcitons and so as the related radiative recombination. Consequently, the prepared <n= 8> phase quasi-2D perovskite film renders a threshold of room-temperature stimulated emission as low as 13.7 µJ cm-2 , reduced by 58.6% relative to the amorphous counterpart with larger grains. The findings in this work are expected to facilitate the development of solution-processable perovskite multiexcitonic laser diodes.

Comparative Study on the Models of Thermoreversible Gelation.

A critical survey on the various theoretical models of thermoreversible gelation, such as the droplet model of condensation, associated-particle model, site–bond percolation model, and adhesive hard sphere model, is presented, with a focus on the nature of the phase transition predicted by them. On the basis of the classical tree statistics of gelation, combined with a thermodynamic theory of associating polymer solutions, it is shown that, within the mean-field description, the thermoreversible gelation of polyfunctional molecules is a third-order phase transition analogous to the Bose–Einstein condensation of an ideal Bose gas. It is condensation without surface tension. The osmotic compressibility is continuous, but its derivative with respect to the concentration of the functional molecule reveals a discontinuity at the sol–gel transition point. The width of the discontinuity is directly related to the amplitude of the divergent term in the weight-average molecular weight of the cross-linked three-dimensional polymers. The solution remains homogeneous in the position space, but separates into two phases in the momentum space; particles with finite translational momentum (sol) and a network with zero translational momentum (gel) coexist in a spatially homogeneous state. Experimental methods used to detect the singularity at the sol–gel transition point are suggested.

Sonoporation‐Enhanced Delivery of STING Agonist Induced Robust Immune Modulation and Tumor Regression

AbstractSonoporation, the temporal cell membrane openings that can arise after ultrasound exposure, has been explored across many preclinical applications but has lacked translational momentum. This can be attributed to a lack of quantitative characterization of the sonoporation process. Additionally, the impact of sonoporation on modulating the tumor microenvironment is not well understood. Using a cyclic dinucleotide‐based STING (stimulator of interferon genes) agonist, MSA‐1, that is analogous to MK‐1454, and approved microbubbles and diagnostic ultrasound, the authors report a 5 min sonoporation procedure enhanced the tumor local concentration of systemically administered MSA‐1 by 6.58‐fold 15 min post sonoporation. The improved pharmacokinetic profile translates into greater STING‐mediated cytokine production, including TNF‐α, IFN‐α, and IFN‐β. Furthermore, through immunophenotyping, the authors report sonoporation could sustain STING‐mediated immune activation while reversing its impact on immune suppression. In both unilaterally and bilaterally inoculated syngeneic tumor models, the authors demonstrate that the sonoporation treated group significantly outperformed other controls at equivalent dosing conditions. These findings may further the understanding of the sonoporation process and its impact on immune modulation, which will accelerate the translational momentum of sonoporation.

Cone-complementary manifold method for stability and failure analysis of jointed/fractured rock masses

Taking advantage of a unique dual-cover system, the numerical manifold method (NMM) is a powerful tool for analyzing stability and progressive failure of jointed/fractured rock masses. In this study, a new implicit cone complementary (CC) formulation is integrated into the NMM to capture the dynamic frictional-cohesive contact problems in jointed/fractured rock masses. The innovative numerical method, termed as the CC-NMM, circumvents numerical difficulties of using artificial contact penalty and open-close iteration in the original NMM. Benchmark examples demonstrate that both mechanical energy and translational momentum of the system are conserved in the proposed CC-NMM. Several examples are further designed to illustrate the excellent performance of the CC-NMM in simulating the progressive failure pattern and stability of the jointed/fractured rock masses.

Behavioral Teleporting of Individual Ethograms onto Inanimate Robots: Experiments on Social Interactions in Live Zebrafish.

SummarySocial behavior is widespread in the animal kingdom, and it remarkably influences human personal and professional lives. However, a thorough understanding of the mechanisms underlying social behavior is elusive. Integrating the seemingly different fields of robotics and preclinical research could bring new insight on social behavior. Toward this aim, we established “behavioral teleporting” as an experimental solution to independently manipulate multiple factors underpinning social interactions. Behavioral teleporting consists of real-time transfer of the complete ethogram of a live zebrafish onto a remotely-located robotic replica. Through parallel and simultaneous behavioral teleporting, we studied the interaction between two live fish swimming in remotely-located tanks: each live fish interacted with an inanimate robot that mirrored the behavior of the other fish, and the morphology of each robot was independently tailored. Our results indicate that behavioral teleporting can preserve natural interaction between two live animals, while allowing fine control over morphological features that modulate social behavior.

Design calculations and simulation dynamics of banana screen

The banana screen is a device used to classify materials widely used in screenings factories at home and abroad. It's working ability depends on many factors (kinematic parameters, technological parameters, particle size, and material moisture,...). If using the traditional method to determine suitable parameters to reach high efficiency, it is very difficult. Because the calculated results are not accurate, it takes a designer much time and makes the manufacturing cost increase. In this study, the author uses the computer software CREO, ADAMS, ANSYS to design and simulate the dynamics of the screen. The results of study are the dynamic parameters of the screen during the working time and are shown in different graphs (Elastic pillow deformation of spring; the force exerted on the elastic pillow; the center velocity of vibration box; center acceleration of vibration box; static energy of vibrates box; translational momentum of vibration box; moment momentum of vibration box). These results also can be applied to design banana screens, which have a high capacity and efficiency as well as a long lifetime.

Path Integral Quantization of Volume

A hyperlink is a finite set of non-intersecting simple closed curves in $$\mathbb {R} \times \mathbb {R}^3$$. Let R be a compact set inside $$\mathbb {R}^3$$. The dynamical variables in General Relativity are the vierbein e and a $$\mathfrak {su}(2)\times \mathfrak {su}(2)$$-valued connection $$\omega $$. Together with Minkowski metric, e will define a metric g on the manifold. Denote $$V_R(e)$$ as the volume of R, for a given choice of e. The Einstein–Hilbert action $$S(e,\omega )$$ is defined on e and $$\omega $$. We will quantize the volume of R by integrating $$V_R(e)$$ against a holonomy operator of a hyperlink L, disjoint from R, and the exponential of the Einstein–Hilbert action, over the space of vierbein e and $$\mathfrak {su}(2)\times \mathfrak {su}(2)$$-valued connection $$\omega $$. Using our earlier work done on Chern–Simons path integrals in $$\mathbb {R}^3$$, we will write this infinite-dimensional path integral as the limit of a sequence of Chern–Simons integrals. Our main result shows that the volume operator can be computed by counting the number of nodes on the projected hyperlink in $$\mathbb {R}^3$$, which lie inside the interior of R. By assigning an irreducible representation of $$\mathfrak {su}(2)\times \mathfrak {su}(2)$$ to each component of L, the volume operator gives the total kinetic energy, which comes from translational and angular momentum.

Comparison of Translational Momentum and Mechanical Energy Produced by Lower Limb Muscles between Horizontal and Vertical Jumps – A Computer Simulation Study

Comparison of Translational Momentum and Mechanical Energy Produced by Lower Limb Muscles between Horizontal and Vertical Jumps – A Computer Simulation Study

Taming two interacting particles with disorder

We compute the scaling properties of the localization length $\xi_2$ of two interacting particles in a one-dimensional chain with diagonal disorder, and the connectivity properties of the Fock states. We analyze record large system sizes (up to $N=20000$) and disorder strengths (down to $W=0.5$). We vary the energy $E$ and the on-site interaction strength $u$. At a given disorder strength the largest enhancement of $\xi_2$ occurs for $u$ of the order of the single particle band width, and for two-particle states with energies at the center of the spectrum, $E=0$. We observe a crossover in the scaling of $\xi_2$ with the single particle localization length $\xi_1$ into the asymptotic regime for $\xi_1 > 100$ ($W < 1.0$). This happens due to the recovery of translational invariance and momentum conservation rules in the matrix elements of interconnected Fock eigenstates for $u=0$. The entrance into the asymptotic scaling is manifested through a nonlinear scaling function $\xi_2/\xi_1=F(u\xi_1)$.

Direct numerical simulations of viscous suspensions with variably shaped crystals

Our ability to numerically model and understand the complex flow behavior of solid-bearing suspensions has increased significantly over the last couple of years, partly due to direct numerical simulations that compute flow around individual immersed particles. Direct numerical simulations hence resolve suspension dynamics in unprecedented detail. While most previous studies focus on spherical particles, we develop a direct numerical approach to also capture rectangular particles. Our approach uses distributed Lagrange multipliers to enforce rigid-body motion in the solid domain in combination with an immersed boundary method to correctly enforce the no-slip constraint on the solid-fluid interfaces. An important component of our model is an efficient particle collision scheme that prevents overlap between particles of different shapes and allows for the transfer of both translational and angular momentum during particle collision. We verify and validate our numerical method through several benchmark cases. Applied to particulate suspensions, we test the hypothesize that particle rotations alter the aggregated dynamics of the suspension even if the relative rotational energy of the particles remains small as compared to the translational energy. At low solid fraction, we reproduce experimental observations of strongly nonlinear coupling between rectangular particles that is reminiscent of particle aggregation in the inertial regime but occurs at zero Reynolds number as a result of the long-range interaction between non-spherical particles. At intermediate solid fraction, we show that particle rotations can destabilize force chains. The dynamic consequences include the delayed onset of jamming and strong nonlinear coupling to the flow field in the fluid domain, which channelizes more strongly for rectangular as compared to spherical particles. Our model was motivated specifically by the need to better understand hazardous, crystal-bearing lava flows, but our insights generalize to viscous suspension flow in other scientific or engineering contexts.

Analytical model for computing translational and rotational angular momentum occurring in treadmill walking

The kinematical modifications of human gait associated with treadmill walking are well studied in the literature. Fewer researches are focusing on computing the dynamical parameters of the gait, in this particular situation. Starting from kinematical data recorded in treadmill walking, the paper proposes an analytical model of the lower limbs that allows computation of translational and rotational angular momentum for each segment. The experimental data used in the study were recorded using ultrasound based, 3D motion equipment. By mean of this system, relative and absolute angles of the lower limb can be computed using Cartesian coordinates of each anatomical landmark. The velocities and accelerations were obtained by numerical derivative. In order to compute the dynamical parameters, segment masses and inertias were collected from the literature. The masses are based on percentage of total body weight while the segment inertias are based on geometrical characteristics of lower limb segments.

A time-varying mass metamaterial for non-reciprocal wave propagation

A new type of metamaterial element is proposed to possess time-dependent effective inertial mass, and proved to be valid for the design of the space-time lattice metamaterial that enables non-reciprocal wave propagation. The cell structure is a three-body dynamic system, consisting of a primary body plus two additional bodies that move along the circular orbit. The translational momentum contributed by the orbiting bodies varies periodically depending on their temporal phases, accounting for the time-driven inertial mass observed macroscopically, as verified by the rigorous theoretical derivation. Based on the time-varying mass element, we present the design of the lattice metamaterials with inertial mass that varies periodically in both space and time. Non-reciprocal wave phenomena due to the wave-like modulation of mass are demonstrated by use of the Bloch-based method and the effective-mass representation. The influence of the modulating frequency and amplitude on the asymmetric bandgap is analyzed. The proposed time-varying metamaterial with the non-reciprocal wave behavior is expected to open a new avenue towards unprecedented control over waves and vibrations.

Resurrecting the partially isotropic Haldane-Shastry model

We present a new and simpler expression for the Hamiltonian of the partially isotropic (XXZ-like) version of the Haldane-Shastry model, which was derived by D. Uglov over two decades ago in an apparently little-known preprint. While resembling the pairwise long-range form of the Haldane-Shastry model our formula accounts for the multi-spin interactions obtained by Uglov. Our expression is physically meaningful, makes hermiticity manifest, and is computationally more efficient. We discuss the model's properties, including its limits and (ordinary and quantum-affine) symmetries. In particular we introduce the appropriate notions of translational invariance and momentum. We review the model's exact spectrum found by Uglov for finite spin-chain length, which parallels the isotropic case up to level splitting due to the anisotropy. We also extend the partially isotropic model to higher rank, with $SU(n)$ 'spins', for which the spectrum is determined by $\mathfrak{sl}_n$-motifs.

Curved momentum spaces from quantum groups with cosmological constant

We bring the concept that quantum symmetries describe theories with nontrivial momentum space properties one step further, looking at quantum symmetries of spacetime in presence of a nonvanishing cosmological constant Λ. In particular, the momentum space associated to the κ-deformation of the de Sitter algebra in (1+1) and (2+1) dimensions is explicitly constructed as a dual Poisson–Lie group manifold parametrized by Λ. Such momentum space includes both the momenta associated to spacetime translations and the ‘hyperbolic’ momenta associated to boost transformations, and has the geometry of (half of) a de Sitter manifold. Known results for the momentum space of the κ-Poincaré algebra are smoothly recovered in the limit Λ→0, where hyperbolic momenta decouple from translational momenta. The approach here presented is general and can be applied to other quantum deformations of kinematical symmetries, including (3+1)-dimensional ones.

Endovascular Crossing of Chronic Total Occlusions Using an Impulse: An Explorative Design Study

In this study we investigated whether exerting an impulse on a Chronic Total Occlusion (CTO) improves the success rate of CTO crossing as compared to the currently used method of statically pushing the guidewire against the CTO. A prototype (Ø2 mm) was developed that generates translational momentum using a spring-loaded indenter and converts it to an impulse during impact. Mechanical performance was evaluated by measuring the peak force and momentum for different spring compressions and strike distances in air and blood-mimicking fluid. Puncture performance, in terms of number of punctures, number of strikes to puncture, and energy transfer from the indenter to the CTO, was assessed for six tip shapes (stamp, wedge, spherical, pointed, hollow spherical, and ringed) on three CTO models with different weight percentages of gelatin and calcium. As a control, a Ø0.4 mm rigid rod was tested. A maximum indenter momentum of 1.3 mNs (velocity of 3.4 m/s), a peak force of 19.2 N (vs. 1.5 N reported in literature and 2.7 N for the control), and CTO displacement of 1.4 mm (vs. 2.7 mm for the control) were measured. The spherical and ringed tips were most effective, with on average 2.3 strikes to puncture the most calcified CTO model. The prototype generated sufficient peak forces to puncture highly calcified CTO models, which are considered most difficult to cross during PCI. Furthermore, CTO displacement was minimized, resulting in a more effective procedure. In future, a smaller, faster, and flexible clinical prototype will be developed.

Separation of rotational and translational segmental momentum to assess movement coordination during walking

This investigation presents an analysis of segmental angular momentum to describe segmental coordination during walking. Generating and arresting momentum is an intuitive concept, and also forms the foundation of Newton-Euler dynamics. Total segmental angular momentum is separated into separate components, translational angular momentum (TAM) and rotational angular momentum (RAM), which provide different but complementary perspectives of the segmental dynamics needed to achieve forward progression during walking. TAM was referenced to the stance foot, which provides insight into the mechanisms behind how forward progression is achieved through coordinated segmental motion relative to the foot. Translational and rotational segmental moments were calculated directly from TAM and RAM, via Euler’s 1st and 2nd laws in angular momentum form, respectively, and are composed of the effects of intersegmental forces and joint moments. Using data from 14 healthy participants, the effort required to generate and arrest momentum were assessed by linking the features of segmental angular momentum and the associated segmental moments to well-known spatiotemporal and kinetic features of the gait cycle. Segmental momentum provides an opportunity to explore and understand system-wide dynamics of coordination from an alternative perspective that is rooted in fundamentals of dynamics, and can be estimated using only segmental kinematic measurements.

Exploring the Angstrom Excursion of Au Nanoparticles Excited away from a Metal Surface by an Impulsive Acoustic Perturbation.

We report the anharmonic angstrom dynamics of self-assembled Au nanoparticles (Au:NPs) away from a nickel surface on top of which they are coupled by their near-field interaction. The deformation and the oscillatory excursion away from the surface are induced by picosecond acoustic pulses and probed at the surface plasmon resonance with femtosecond laser pulses. The overall dynamics are due to an efficient transfer of translational momentum from the Ni surface to the Au:NPs, therefore avoiding usual thermal effects and energy redistribution among the electronic states. Two modes are clearly revealed by the oscillatory shift of the Au:NPs surface plasmon resonance-the quadrupole deformation mode due to the transient ellipsoid shape and the excursion mode when the Au:NPs bounce away from the surface. We find that, contrary to the quadrupole mode, the excursion mode is sensitive to the distance between Au:NPs and Ni. Importantly, the excursion dynamics display a nonsinusoidal motion that cannot be explained by a standard harmonic potential model. A detailed modeling of the dynamics using a Hamaker-type Lennard-Jones potential between two media is performed, showing that each Au:NPs coherently evolves in a nearly one-dimensional anharmonic potential with a total excursion of ∼1 Å. This excursion induces a shift of the surface plasmon resonance detectable because of the strong near-field interaction. This general method of observing the spatiotemporal dynamics with angstrom and picosecond resolutions can be directly transposed to many nanostructures or biosystems to reveal the interaction and contact mechanism with their surrounding medium while remaining in their fundamental electronic states.