Perturbation Components Research Articles

Dose-response relationship and effect modifier of stabilisation exercises in nonspecific low back pain: a project-wide individual patient data re-analysis on 1483 intervention participants.

This planned MiSpEx-Network reanalysis was designed to derive a dose-response relationship under consideration of further effect modifiers in exercises on low back pain. One thousand four hundred eighty three intervention participants with low back pain (mean age, 40.9 years [SD 14 years]) performed stabilisation exercises (3 weeks supervised, 9 weeks self-administered). Patients reported pain intensity, disability, and disability days at baseline, 3 weeks, 12 weeks, and 6 months post randomisation. Exercise characteristics and effect modifiers were prospectively monitored. Beyond the comparison to the results of the control group, linear mixed models were calculated to determine a dose-response relationship. The interventions led to small but significantly larger symptom reductions than in the control group at each measurement. Longer durations of the intervention led to larger symptom reductions. Higher exercise frequencies were associated with a decrease in pain intensity: to train once more per week led to a mean decrease of 0.93 points in pain intensity [95% CI = -1.54 to -0.32]. Disability days were also impacted (estimate = -0.07 [-0.14 to 0.00]), but disability was not (-0.09 [-0.67 to 0.48]). Adding perturbation was superior to adding stretching or a behavioural module. The relationships were robust when additional effect modifiers were considered and against the control group' effects. The odds ratio for a clinically important effect with higher exercise frequencies decreased at 3 weeks (OR = 0.71 [0.618-0.813] for >2.5*week -1 ) and increased at 12 weeks (1.13 [1.006-1.270], >1.5*week -1 ). Using longer intervention durations, adding a perturbation component to the stabilisation trainings and using higher frequencies (up to a certain point) may lead to an even more beneficial response on exercise in patients with low back pain. Developing strategies to maintain a training frequency of at least 2 times per week may be relevant in stabilisation exercises to treat low back pain.

Multi-league sports scheduling with different leagues sizes

This paper introduces a general multi-league sports scheduling problem where timetables for multiple leagues must be determined simultaneously, a practical and challenging problem in amateur and youth sports. We consider round robin leagues with different numbers of teams, and hence also requiring different numbers of rounds. As the number of simultaneous home games that clubs can organize for their teams is limited by the capacity of their venue, the objective is to minimize capacity violations. Along with a mixed integer programming model which is formulated to optimize the starting round of each league as well as to settle when teams have their home games, we develop various methods to construct an initial solution, and a heuristic with several local search and perturbation components to improve on this. Extensive computational experiments reveal that our heuristic can efficiently provide high-quality solutions for artificial and realistic instances. We also illustrate the impact of using different sets of home-away patterns on the total venue capacity violations. Results on a real-life application from the Belgian national football association indicate that schedules based on our heuristic allow teams to substantially decrease their venue capacity without causing meaningfully more violations.

Resummation effects in the bottom-quark fragmentation function

We compute the perturbative component of the fragmentation function of the b quark to the best of the present theoretical knowledge. The fixed-order calculation to order {alpha}_s^2 of the fragmentation function at the initial scale is matched with soft-emission logarithm resummation to next-to-next-to-leading logarithmic accuracy, so that order- {alpha}_s^2 corrections are accounted for exactly, and logarithmically enhanced contributions from loops of b quarks are included. This requires the calculation of the Mellin transform of the order- {alpha}_s^2 result in the whole complex plane for the Mellin variable, which we provide for the first time for all the fragmenting partons. Evolution is performed to next-to-next-to-leading log accuracy, and mixing with the gluon fragmentation function is taken into account. The perturbative fragmentation functions are made available via LHAPDF grids.

Design of the ASSUT-FF Algorithm for GTO Satellite CNS/BDS Integrated Navigation

The velocity and acceleration of geostationary transfer orbit (GTO) satellites change dramatically and periodically, and the operating area extends from hundreds of kilometers to 36,000 km above the Earth’s surface. This leads to the limitation of navigation methods of GTO satellites, the complexity of perturbation components and the increase of sensor measurement noise. Therefore, in this paper, a celestial navigation system/Beidou navigation system (CNS/BDS) integrated navigation method based on the adaptive spherical simplex unscented transformation federated Kalman filter (ASSUT-FF) algorithm is designed for GTO satellite high-precision autonomous navigation, considering the integrated navigation method and filtering algorithm. A Beidou observation model based on the relative pseudorange/pseudorange rate is established. Even when the GTO satellite moves to the high orbit region, it can still use BDS navigation information to determine the orbit. In addition, the designed adaptive algorithm can still ensure the filter stability in a complex space environment. The CNS/BDS integrated navigation method based on the ASSUT-FF algorithm proposed in this paper can realize continuous and high-precision autonomous navigation of GTO satellites. The simulation results show that the orbit determination accuracy of the proposed navigation method is 96.23% and 84.06% higher than that of the single celestial navigation method and the traditional Beidou geometric positioning correction celestial navigation method, respectively. The performance test results of the adaptive algorithm also show that the ASUT-FF algorithm has good robustness.

Statistical Analysis of Medium‐Scale Traveling Ionospheric Disturbances Over Japan Based on Deep Learning Instance Segmentation

AbstractMedium‐scale traveling ionospheric disturbances (MSTIDs) are observed as parallelly arrayed wavelike perturbations of Total Electron Content (TEC) in ionospheric F region leading to satellite navigation error and communication signal scintillation. The observation method for MSTIDs, detrended TEC (dTEC) map, summarizes the perturbation component of TEC having the merits of full‐time and two‐dimensional. However, previous automatic processing methods for dTEC map cannot discriminate MSTIDs from other irregular ionospheric perturbations intelligently. With the development of artificial intelligence in recent years, deep learning approach is expecting to clarify the controversy of MSTID external dependence (season and solar/geomagnetic activity) under debating for decades. Therefore, this research proposes a real‐time processing algorithm for dTEC maps based on Mask Region‐Convolutional Neural Network (R‐CNN) model of deep learning instance segmentation to detect wavelike perturbations intelligently with an accuracy of about 80% and a processing speed of about 8 fps. Then isolated perturbations are eliminated and only MSTID waveforms are chosen to obtain statistical characteristics of MSTIDs. With this algorithm, we analyzed up to 1,209,600 dTEC maps from 1997 to 2019 over Japan automatically and established a database of hourly averaged MSTID characteristics. This research introduces the partial correlation coefficient for the first time to clarify the solar/geomagnetic activity dependence of MSTID characteristics which is independent with each other.

Direct numerical simulation of interaction between a stationary crossflow instability and forward-facing steps

The interaction between forward-facing steps of several heights and a pre-existing critical stationary crossflow instability of a swept-wing boundary layer is analysed. Direct numerical simulations (DNS) are performed of the incompressible three-dimensional laminar base flow and the stationary distorted flow that arise from the interaction between an imposed primary stationary crossflow perturbation and the steps. These DNS are complemented with solutions of the linear and the nonlinear parabolised stability equations, used towards identifying the influence of linearity and non-parallelism near the step. A fully stationary solution of the Navier–Stokes equations is enforced numerically, in order to isolate the mechanisms pertaining to the interaction of the stationary disturbance with the step. Results provide insight into the salient modifications of the base laminar boundary layer due to the step, and the response of the incoming crossflow instability to these changes. The fundamental spanwise Fourier mode of the disturbance field gradually lifts up as it approaches the step and passes over it. The flow environment around the step is characterised by a sudden spanwise modulation of the base-flow streamlines. Additional stationary perturbation structures are induced at the step, which manifest in the form of spanwise-aligned velocity streaks near the wall. Shortly downstream of the step, the fundamental component of the crossflow perturbation maintains a rather constant amplification for the smallest steps studied. For the largest step, however, the fundamental crossflow perturbation is stabilised significantly shortly downstream of the largest step. This surprising result is ascribed to a modulation of the kinetic energy transfer between the base flow and the fundamental perturbation field, which is brought forward as a new step interaction mechanism. Possible non-modal growth effects at the step are discussed. Furthermore, the results from DNS indicate significant amplification of the high-order harmonic crossflow components downstream of the step.

On using a double-thin-shell approach and TEC perturbation component to sound night-time mid-latitude E–F coupling

Observations and theoretical analysis on the night-time mid-latitude ionospheric irregularities support the postulation of frequently coupled E and F regions. In this paper, we attempt at asserting this notion while using total electron content (TEC) measurements. The TECs are from a dense GNSS receiver network over Japan with more than 1200 stations and a mean distance of ~ 25 km between receivers; thus, ideal for analyzing small-scale perturbations in ionospheric electron density. We take an ansatz that mid-latitude night-time plasma instabilities concentrate at E and F layers. Then the integrated three-dimensional density perturbations are parameterized with a double-thin-shell model. At each shell, perturbation components are assumed identical at any point within a given grid block. Two days with events of night-time medium-scale traveling ionospheric disturbances (MSTIDs), but with different amplitudes, were investigated. Results show that the newly developed technique can infer several horizontal characteristics on E–F coupled instabilities; the coexistence of northwest–southeast (NW–SE) aligned irregular structures in E and F regions is evident. Both E- and F-region irregularities share similar propagation parameters, a shred of clear evidence of strong coupling.Graphical

Global Geomagnetic Perturbation Forecasting Using Deep Learning

AbstractGeomagnetically Induced Currents (GICs) arise from spatio‐temporal changes to Earth's magnetic field, which arise from the interaction of the solar wind with Earth's magnetosphere, and drive catastrophic destruction to our technologically dependent society. Hence, computational models to forecast GICs globally with large forecast horizon, high spatial resolution and temporal cadence are of increasing importance to perform prompt necessary mitigation. Since GIC data is proprietary, the time variability of the horizontal component of the magnetic field perturbation (dB/dt) is used as a proxy for GICs. In this work, we develop a fast, global dB/dt forecasting model, which forecasts 30 min into the future using only solar wind measurements as input. The model summarizes 2 hr of solar wind measurement using a Gated Recurrent Unit and generates forecasts of coefficients that are folded with a spherical harmonic basis to enable global forecasts. When deployed, our model produces results in under a second, and generates global forecasts for horizontal magnetic perturbation components at 1 min cadence. We evaluate our model across models in literature for two specific storms of 5 August 2011 and 17 March 2015, while having a self‐consistent benchmark model set. Our model outperforms, or has consistent performance with state‐of‐the‐practice high time cadence local and low time cadence global models, while also outperforming/having comparable performance with the benchmark models. Such quick inferences at high temporal cadence and arbitrary spatial resolutions may ultimately enable accurate forewarning of dB/dt for any place on Earth, resulting in precautionary measures to be taken in an informed manner.

Large-scale structure with superhorizon isocurvature dark energy

The standard cosmological model assumes a homogeneous and isotropic universe as the background spacetime on large scales called the cosmological principle. However, some observations suggest the possibility of an inhomogeneous and anisotropic universe at large scales. In this paper, we investigate a model of the Universe with random inhomogeneities and anisotropies on very large scales, motivated by the supercurvature dark energy model in Nan et al. [Phys. Rev. D 99, 103512 (2019)]. In this model, the authors introduced a scalar field with $\mathcal{O}(1)$ inhomogeneities on a scale sufficiently larger than the current horizon scale (superhorizon scale), and the potential energy of the scalar field explains the accelerating expansion, with slight deviations from the cosmological principle. We aim at clarifying the theoretical prediction on the large-scale structure (LSS) of the matter component in this model. Based on the work on the superhorizon scale fluctuations (superhorizon mode) presented in Y. Nan and K. Yamamoto [Phys. Rev. D 105, 063518 (2022)], we derive the equations that the perturbative components to the LSS obey as a generalization of the cosmological perturbations theory, which is solved to find the influence of the dark energy inhomogeneities on the formation of the LSS. Finally, we show that the model can be consistent with observations by comparing the ${\ensuremath{\sigma}}_{8}$ predicted by the numerical solution of the model with the ${\ensuremath{\sigma}}_{8}$ indicated by observations such as Planck and the Sloan Digital Sky Survey.

Sliding mode control strategy based lead screw control design in electromechanical tracking drive system

This article presents the research synthesis method of electromechanical tracking system for lead screw control using alternating current (AC) servo motors applied in machine tools, based on the framework of sliding mode control method and the state observer. Control algorithms are capable of compensating for perturbation components, with a state observation to be established to evaluate and compensate for uncertain nonlinear components. The chattering reduction techniques of sliding mode surface are proposed to improve the control effectiveness. The research results are verified by simulation on MATLAB-Simulink, showing that the proportional integral derivative (PID) controller has not met the control quality, but requires the sliding mode control law and state observation as proposed. Then this tracking drive system will work with better quality and can be developed for lead screw system of machine tool. The research results in the paper are also the completed development for calculating, designing, and manufacturing intelligent electrical drive systems in industrial applications.

Radial Interplanetary Magnetic Field‐Induced North‐South Asymmetry in the Solar Wind‐Magnetosphere‐Ionosphere Coupling: A Case Study

AbstractIn this paper, we present a case study of the radial interplanetary magnetic field (IMF Bx)‐induced asymmetric solar wind‐magnetosphere‐ionosphere (SW‐M‐I) coupling between the northern and southern polar caps using ground‐based and satellite‐based data. Under prolonged conditions of strong earthward IMF on 5 March 2015, we find significant discrepancies between polar cap north (PCN) and polar cap south (PCS) magnetic indices with a negative bay‐like change in the PCN and a positive bay‐like change in the PCS. The difference between these indices (PCN‐PCS) reaches a minimum of −1.63 mV/m, which is approximately three times higher in absolute value than the values for most of the time on this day (within ±0.5 mV/m). The high‐latitude plasma convection also shows an asymmetric feature such that there exists an additional convection cell near the noon sector in the northern polar cap, but not in the southern polar cap. Meanwhile, negative bays in the north‐south component of ground magnetic field perturbations (less than 50 nT) observed in the nightside auroral region of the Northern Hemisphere are accompanied with the brightening and widening of the nightside auroral oval in the Southern Hemisphere, implying a weak, but clear energy transfer to the nightside ionosphere of both hemispheres. After the hemispheric asymmetries in the polar caps disappear, a substorm onset takes place. All these observations indicate that IMF Bx‐induced single lobe reconnection that occurred in the Northern Hemisphere plays an important role in hemispheric asymmetry in the energy transfer from the solar wind to the polar cap through the magnetosphere.

Linear Stability of Black Holes and Naked Singularities

A review of the current status of the linear stability of black holes and naked singularities is given. The standard modal approach, that takes advantage of the background symmetries and analyze separately the harmonic components of linear perturbations, is briefly introduced and used to prove that the naked singularities in the Kerr–Newman family, as well as the inner black hole regions beyond Cauchy horizons, are unstable and therefore unphysical. The proofs require a treatment of the boundary condition at the timelike boundary, which is given in detail. The nonmodal linear stability concept is then introduced, and used to prove that the domain of outer communications of a Schwarzschild black hole with a non-negative cosmological constant satisfies this stronger stability condition, which rules out transient growths of perturbations, and also to show that the perturbed black hole settles into a slowly rotating Kerr black hole. The encoding of the perturbation fields in gauge invariant curvature scalars and the effects of the perturbation on the geometry of the spacetime is discussed. These notes follow from a course delivered at the V José Plínio Baptista School of Cosmology, held at Guarapari (Espírito Santo) Brazil, from 30 September to 5 October 2021.

Post-Newtonian waveforms from spinning scattering amplitudes

We derive the classical gravitational radiation from an aligned spin binary black hole on closed orbits, using a dictionary built from the 5-point QFT scattering amplitude of two massive particles exchanging and emitting a graviton. We show explicitly the agreement of the transverse-traceless components of the radiative linear metric perturbations — and the corresponding gravitational wave energy flux — at future null infinity, derived from the scattering amplitude and those derived utilizing an effective worldline action in conjunction with multipolar post-Minkowskian matching. At the tree-level, this result holds at leading orders in the black holes’ velocities and up to quadratic order in their spins. At sub-leading order in black holes’ velocities, we demonstrate a matching of the radiation field for quasi-circular orbits in the no-spin limit. At the level of the radiation field, and to leading order in the velocities, there exists a one-to-one correspondence between the binary black hole mass and current quadrupole moments, and the scalar and linear-in-spin scattering amplitudes, respectively. Therefore, we show explicitly that waveforms, needed to detect gravitational waves from inspiraling binary black holes, can be derived consistently, to the orders considered, from the classical limit of quantum scattering amplitudes.

RF design and tuning of a deuteron RFQ for detecting impurity deposition on a tokamak

Peking University and Southwestern Institute of Physics are jointly developing a new deuteron Radio Frequency Quadrupole (RFQ) accelerator to study the migration and deposition of impurities on the first wall of a tokamak facility. The RFQ operates at 162.5 MHz with the duty factor of 1%, which can accelerate 10 mA deuteron beam from 40 keV up to 1.5 MeV within 2.2 m length. Such four-vane RFQ is divided into two segments and equipped with 40 tuners in total. In the electromagnetic (EM) design, the dipole stabilizer rods (DSRs) were optimized to obtain a mode separation of 3.1 MHz. The tuners and undercuts were also designed and optimized to fulfill the requirements of the resonant frequency, flat longitudinal field distribution and field tuning. Following the EM design, multi-physics analysis and structure error analysis was carried out. The cavity was fabricated with 99.9% oxygen-free electronic (OFE) copper. The assembly and braze of each RFQ module have been completed, the results of metrological measurements via coordinate measuring machine (CMM) indicate that there was no unexpected deformation. The intrinsic Q-value of the whole cavity is 12834 in the low level radio frequency (RF) measurements, which is 87% of the theoretical simulation with electrical conductivity of 5.8 × 107 S/m. After tuning, the quadrupole perturbative component decreased from 2.6% to 0.6%, and the dipole perturbative components decreased from 6.1% to 1%.

Is adipose tissue responsible for cardiovascular disease in hypertensive and normotensive pregnant animal models?

We previously demonstrated that hypertensive and metabolic disorder established before pregnancy lead to cardiac and renal end-organ damage. Adipose tissue mitochondrial dysfunction is emerging as a key component of metabolic perturbation. Our aim was to evaluate changes in pathways regulated by the adipose tissue in hypertensive and normotensive models on high fat (HF) diet.

Passive deconfinement of runaway electrons using an in-vessel helical coil

A helical coil designed to passively generate non-axisymmetric fields during a plasma disruption is shown (via electromagnetic analysis, linear MHD modeling, and relativistic drift orbit tracing) to be effective at deconfining runaway electrons (REs) on a time scale significantly faster than the plasma current quench. Magnetic equilibria from DIII-D RE-producing scenarios are used to calculate the toroidal electric field generated during the current quench phase of a disruption, which in turn drives current in the proposed n = 1 in-vessel helical coil, without the need for any external power supplies or disruption detection or prediction techniques. Simulations of the plasma evolution using the TokSys GS Evolve code predict the inductive coupling of coil currents up to 12% of the pre-disruption plasma current into the helical coil. The coil geometry is parametrically varied to maximize both the non-resonant and resonant components of the 3D magnetic perturbation, resulting in δB/B ≈ 10−2 and a vacuum island overlap width of up to 0.7ψ N . The REORBIT module of the MARS-F code is used to model the full non-axisymmetric magnetic field and trace RE drift orbits to determine the effect on RE deconfinement, with up to 70% of the RE orbits lost after 0.2 ms. A two-stage evolution of the RE orbit loss fraction is observed to be caused by resonant trapping between multiple magnetic island chains. Finally, electromagnetic and thermal stresses on the coil are calculated to be within operational limits for installation in DIII-D, and scale favorably to a reactor-size device. These findings motivate future experimental study of the helical coil concept in DIII-D or other tokamaks.

Jet fragmentation transverse momentum distributions in pp and p-Pb collisions at sqrt{s} , sqrt{s_{mathrm{NN}}} = 5.02 TeV

Jet fragmentation transverse momentum (jT) distributions are measured in proton-proton (pp) and proton-lead (p-Pb) collisions at sqrt{s_{mathrm{NN}}} = 5.02 TeV with the ALICE experiment at the LHC. Jets are reconstructed with the ALICE tracking detectors and electromagnetic calorimeter using the anti-kT algorithm with resolution parameter R = 0.4 in the pseudorapidity range |η| < 0.25. The jT values are calculated for charged particles inside a fixed cone with a radius R = 0.4 around the reconstructed jet axis. The measured jT distributions are compared with a variety of parton-shower models. Herwig and Pythia 8 based models describe the data well for the higher jT region, while they underestimate the lower jT region. The jT distributions are further characterised by fitting them with a function composed of an inverse gamma function for higher jT values (called the “wide component”), related to the perturbative component of the fragmentation process, and with a Gaussian for lower jT values (called the “narrow component”), predominantly connected to the hadronisation process. The width of the Gaussian has only a weak dependence on jet transverse momentum, while that of the inverse gamma function increases with increasing jet transverse momentum. For the narrow component, the measured trends are successfully described by all models except for Herwig. For the wide component, Herwig and PYTHIA 8 based models slightly underestimate the data for the higher jet transverse momentum region. These measurements set constraints on models of jet fragmentation and hadronisation.

On the Lichnerowicz operator in traversable wormhole spacetimes

The evaluation of Casimir energies in curved background spacetimes is an essential ingredient to study the stability of traversable wormholes. In practice one has to calculate the contribution of the transverse-traceless component of the metric perturbation on a curved spacetime background. This implies the study of an eigenvalue equation involving a modified form of the Lichnerowicz operator. For arbitrary background spacetimes, however, such an operator does not display transverse-traceless properties, a fact that impedes the determination of the eigenvalues. Against this background, we show that the problem can be circumvented. Casimir energies can be calculated by gauging the original form of the modified Lichnerowicz operator into a transverse-traceless one.

Global Pc5 Pulsations From the Polar Cap to the Equator: Wave Characteristics, Phase Variations, Disturbance Current System, and Signal Transmission

AbstractWe present observations of global Pc5 pulsations by ∼180 ground magnetometers during the recovery phase of an intense geomagnetic storm. Measurements of magnetic fields along four latitudinal magnetometer chains and one longitudinal magnetometer chain are used to determine the wave characteristics of Pc5 pulsations. Many new features of Pc5 pulsations are identified from a single event for the first time. The Pc5 pulsations occur simultaneously at all latitudes and longitudes/local times, and the period of the Pc5 pulsations is about 10 min and does not depend on latitude and longitude. The latitudinal distributions of the northward (H) component and magnetic pressure of Pc5 perturbations are derived. The phase of the H component reverses across 50–70° magnetic latitude (MLat) but is nearly the same at middle and low latitudes. The phase of the H component at low latitudes does not vary much with longitude/local time. The phase of the D component magnetic field reverses near the equator in the latitudinal direction and also reverses around dawn, noon, dusk, and midnights in the longitudinal direction. The distribution and evolution of global ionospheric equivalent disturbance currents during Pc5 pulsations are derived. A coupled magnetospheric‐ionospheric current system is proposed to explain the observed characteristics of global Pc5 pulsations. It is suggested that the variations of the phase of Pc5 pulsations with latitude and local time are determined by the global distribution of the coupled magnetospheric‐ionospheric current system but not caused by propagation delay of the signals.

Giant Third-Order Nonlinear Response of Liquids at Terahertz Frequencies

The nonlinear response of liquids in the terahertz regime has recently attracted significant interest, even though very few measurements have been reported. Here, we report on our measurements based on a $z$-scan technique of the nonlinear refractive-index coefficient ${n}_{2}$ at terahertz frequencies for several liquids with noncentrosymmetric molecules, specifically, water, ethanol, and $\ensuremath{\alpha}$-pinene. We describe how the value of ${n}_{2}$ depends on the physical parameters of these molecules. The measured values of ${n}_{2}$ of the liquids in the terahertz region are as much as 6 orders of magnitude larger than their corresponding values in the visible or near-IR. Through a simple theoretical model, we confirm that the predominant source of this large third-order nonlinearity is the second-order perturbative component of the vibrational response of these molecules, which have resonances in the mid-IR.