Deflection Of Trajectories Research Articles

Is adiposity related to repeat measures of blood leukocyte DNA methylation across childhood and adolescence?

Epigenetic modifications such as DNA methylation may influence gene expression and phenotypes, including obesity in childhood. The directionality of this relationship is nevertheless unclear, and some evidence suggests that adiposity modifies the epigenome, rather than the other way around. In this pilot study, we utilize data from the Early Life Exposures in Mexico to Environmental Toxicants (ELEMENT) study to examine whether measures of adiposity in childhood and early adolescence are associated with repeated measures of blood leukocyte DNA methylation at LINE-1 repetitive elements and two genes implicated in growth and adiposity: H19 and HSD11B2. Longitudinal epigenetic data were generated from cord blood and blood from follow-up visits in early and late adolescence. We assessed interactions between age and measures of body mass index (BMI) at 5 years of age and weight, BMI and waist circumference in early adolescence to infer whether adiposity deflects age-related DNA methylation changes throughout childhood. Applying linear mixed-effects models, we found an inverse association between measures of childhood BMI (kg/m2 ) and early-teen weight (kg) with repeat measures of H19 DNA methylation. We did not observe any statistically significant associations (p-value <.05) between any anthropometric measures and DNA methylation at LINE-1 or HSD11B2. We did not demonstrate statistically significant evidence in support of deflection of age-related DNA methylation trajectories by adiposity-related measures (age by adiposity interaction term). Given the pilot nature of this study, the relationships between repeat measures of DNA methylation and adiposity-measures across childhood merit further exploration in larger study populations.

MRI-LINAC dosimetry approach by Monte Carlo codes coupling charged particle radiation transport with strong magnetic fields

This study investigates the dosimetric effects due to the strong magnetic fields in the MRI guided radiotherapy. FLUKA and PENELOPE Monte Carlo codes were used to study the deflection of the electron trajectories, while evaluating dosimetric effects, considering both simplified arrangements and complex realistic clinical applications setups. Simulation codes proved to be suitable, and comparisons with analytic approaches were satisfactory, thus remarking non-negligible dosimetry effects as a consequence of the presence of strong magnetic fields.

The deviation angle for one-lane roundabouts: A general mathematical formulation and application

Properly designed roundabouts may lead to safety improvements based on both reducing approaching speeds and controlling traffic. Measurements of deflection of vehicle trajectories are commonly used to estimate roundabout speed control. One of these measurements is the deviation angle, which is mentioned in both the Italian and Swiss road standards and, in specific conditions, can be more effective than other methods. This article presents a general mathematical formulation for linking several geometric parameters with the deviation angle in different rural and urban one-lane roundabout configurations, which is currently missing in the literature. For urban roundabouts, refuge islands for pedestrians and cyclists were considered. Based on the proposed formulation, a sensitivity analysis of the influential geometric parameters was conducted. Results suggest that an insufficient deflection of trajectories (deviation angle less than 45°) is always present for roundabouts with inscribed circle diameter less than 25 m; for urban roundabouts with refuge islands for pedestrians and cyclists having inscribed circle diameter less than 34 m and orthogonal legs; and for roundabouts with angles between opposite legs smaller than 140°. The main parameters which are responsible for a decrease in the deviation angle are: a decrease in the inscribed circle diameter; a decrease in the angle between opposite legs; and an increase in the width of the circulatory lane. Some optimized procedures for roundabout design, the generalized application of the deviation angle method and alternative speed control measures in cases of small deviation angles are discussed. • The deviation angle is an effective measure of the deflection of trajectories and speed reduction at roundabouts. • A mathematical formulation for linking geometric parameters with the deviation angle in one-lane roundabouts is proposed. • The general framework is applicable for both rural/urban one-lane roundabouts, considering the presence of vulnerable users. • The most influential parameters on the deflection of trajectories were discussed through a detailed sensitivity analysis. • Some measures were proposed, alternative to the geometrically-induced deflection of trajectories, in different cases.

Peripheral Collisions of Ice-covered Silica Dust Grains

Abstract Collisions with ice-covered silica grains are studied using molecular-dynamics simulation, with a focus on the influence of the impact parameter on the collision dynamics. The ice mantle induces an attractive interaction between the colliding grains, which is caused by the melting of the mantles in the collision zone and their fusion. For noncentral collisions, this attractive interaction leads to a deflection of the grain trajectories and, at smaller velocities, to the agglomeration (“sticking”) of the colliding grains. The bouncing velocity, which is defined as the smallest velocity at which grains bounce off each other rather than stick, shows only a negligible dependence on the impact parameter. Close to the bouncing velocity, a temporary bridge builds up between the colliding grains, which, however, ruptures when the collided grains separate and relaxes to the grains. At higher velocities, the ice in the collision zone is squeezed out from between the silica cores, forming an expanding disk, which ultimately tears and dissolves into a multitude of small droplets. An essential fraction of the ice cover in the collision zone is then set free to space. Astrophysical implications include the possibility that organic species that might be present in small concentrations on the ice surface or at the ice–silica interface are liberated to space in such noncentral collisions.

The impact of path estimates in iterative ion CT reconstructions for clinical-like cases

Ion computed tomography (CT) promises to mitigate range uncertainties inherent in the conversion of x-ray Hounsfield units into ion relative stopping power (RSP) for ion beam therapy treatment planning. To improve accuracy and spatial resolution of ion CT by accounting for statistical multiple Coulomb scattering deflection of the ion trajectories from a straight line path (SLP), the most likely path (MLP) and the cubic spline path (CSP) have been proposed. In this work, we use FLUKA Monte Carlo simulations to investigate the impact of these path estimates in iterative tomographic reconstruction algorithms for proton, helium and carbon ions. To this end the ordered subset simultaneous algebraic reconstruction technique was used and coupled with a total variation superiorization (TVS). We evaluate the image quality and dose calculation accuracy in proton therapy treatment planning of cranial patient anatomies. CSP and MLP generally yielded nearly equal image quality with an average RSP relative error improvement over the SLP of 0.6%, 0.3% and 0.3% for proton, helium and carbon ion CT, respectively. Bone and low density materials have been identified as regions of largest enhancement in RSP accuracy. Nevertheless, only minor differences in dose calculation results were observed between the different models and relative range errors of better than 0.5% were obtained in all cases. Largest improvements were found for proton CT in complex scenarios with strong heterogeneities along the beam path. The additional TVS provided substantially reduced image noise, resulting in improved image quality in particular for soft tissue regions. Employing the CSP and MLP for iterative ion CT reconstructions enabled improved image quality over the SLP even in realistic and heterogeneous patient anatomy. However, only limited benefit in dose calculation accuracy was obtained even though an ideal detector system was simulated.

Signatures of folded branches in the scanning gate microscopy of ballistic electronic cavities

We demonstrate the emergence of classical features in electronic quantum transport for the scanning gate microscopy response in a cavity defined by a quantum point contact and a micron-sized circular reflector. The branches in electronic flow characteristic of a quantum point contact opening on a two-dimensional electron gas with weak disorder are folded by the reflector, yielding a complex spatial pattern. Considering the deflection of classical trajectories by the scanning gate tip allows to establish simple relationships of the scanning pattern, which are in agreement with recent experimental findings.

Polarization Flipping of Even-Order Harmonics in Monolayer Transition-Metal Dichalcogenides

We present a systematic study of the crystal-orientation dependence of high-harmonic generation in monolayer transition-metal dichalcogenides, WS 2 and MoSe 2 , subjected to intense linearly polarized midinfrared laser fields. The measured spectra consist of both odd- and even-order harmonics, with a high-energy cutoff extending beyond the 15th order for a laser-field strength around ~1 V/nm. In WS 2 , we find that the polarization direction of the odd-order harmonics smoothly follows that of the laser field irrespective of the crystal orientation, whereas the direction of the even-order harmonics is fixed by the crystal mirror planes. Furthermore, the polarization of the even-order harmonics shows a flip in the course of crystal rotation when the laser field lies between two of the crystal mirror planes. By numerically solving the semiconductor Bloch equations for a gapped-graphene model, we qualitatively reproduce these experimental features and find the polarization flipping to be associated with a significant contribution from interband polarization. In contrast, high-harmonic signals from MoSe 2 exhibit deviations from the laser-field following of odd-order harmonics and crystal-mirror-plane following of even-order harmonics. We attribute these differences to the competing roles of the intraband and interband contributions, including the deflection of the electron-hole trajectories by nonparabolic crystal bands.

Simulation of a muographic analysis of a volcanic dome in Geant4

Here we present a Monte Carlo simulation of a muographic campaign on Methana volcano, Greece. In order to estimate the absorption parameters and the pattern of muon scattering at various incident energies (GeV to TeV), a radar-derived digital terrain model (DTM) was submitted to irradiation by horizontal muons in Geant4 and the penetrating muons were collected by a hypothetical MicroMegas particle detector on the other side of the DTM. Monte Carlo simulation demonstrated that muon energies at least as high as 10 TeV are required for whole-scale radiography of Methana and one has to reduce the scale of study to smaller structures (e.g. ~ 600 m - wide volcanic domes) in order to exploit the more affluent lower energy muons (~ 600 GeV). Coulomb scattering, on the other hand, brings about deflection of muon trajectories away from the detector, resulting in loss of information. Additionally, scattering adds Gaussian blurring to the scanned objects. With the intention of improving contrast and extract objects in muographic image we recommend the use of spatial operators (filters) employed in image analysis.

Ripple formation on Si surfaces during plasma etching in Cl2

Nanoscale surface roughening and ripple formation in response to ion incidence angle has been investigated during inductively coupled plasma etching of Si in Cl2, using sheath control plates to achieve the off-normal ion incidence on blank substrate surfaces. The sheath control plate consisted of an array of inclined trenches, being set into place on the rf-biased electrode, where their widths and depths were chosen in such a way that the sheath edge was pushed out of the trenches. The distortion of potential distributions and the consequent deflection of ion trajectories above and in the trenches were then analyzed based on electrostatic particle-in-cell simulations of the plasma sheath, to evaluate the angular distributions of ion fluxes incident on substrates pasted on sidewalls and/or at the bottom of the trenches. Experiments showed well-defined periodic sawtooth-like ripples with their wave vector oriented parallel to the direction of ion incidence at intermediate off-normal angles, while relatively weak corrugations or ripplelike structures with the wave vector perpendicular to it at high off-normal angles. Possible mechanisms for the formation of surface ripples during plasma etching are discussed with the help of Monte Carlo simulations of plasma-surface interactions and feature profile evolution. The results indicate the possibility of providing an alternative to ion beam sputtering for self-organized formation of ordered surface nanostructures.

Flux penetration in a superconducting film partially capped with a conducting layer

The influence of a conducting layer on the magnetic flux penetration in a superconducting Nb film is studied by magneto-optical imaging. The metallic layer partially covering the superconductor provides an additional velocity-dependent damping mechanism for the flux motion that helps to protect the superconducting state when thermomagnetic instabilities develop. If the flux advances with a velocity slower than omega = 2/mu(0)sigma t, where sigma is the cap layer conductivity and t is its thickness, the flux penetration remains unaffected, whereas for incoming flux moving faster than w, the metallic layer becomes an active screening shield. When the metallic layer is replaced by a perfect conductor, it is expected that the flux braking effect will occur for all flux velocities. We investigate this effect by studying Nb samples with a thickness step. Some of the observed features, namely the deflection of the flux trajectories at the border of the thick center, as well as the favored flux penetration at the indentation, are reproduced by time-dependent Ginzburg-Landau simulations.

Search for the sources of cosmic rays with energies above 1020 eV

The sources of ultrahigh energy cosmic rays (UHECRs, E >1018 eV) are still unknown, mainly due to the loss of the direction to the source after the deflection of cosmic rays’ (CRs) trajectories in the galactic and extragalactic magnetic fields. With the increase in CR energy (rigidity), the influence of the magnetic field weakens; therefore, the most promising approach is to search for the sources of events with the highest energy. In our work, we expand the existing UHECR (E > 1020 eV) sample from 33 to 42 events by calibrating the AUGER events. The sample is characterized by the presence of an event triplet in a circle of radius 3°. The highest-energy event is still the shower (E = 3.2 × 1020 eV) detected with the Fly’s Eye fluorescent detector (FE-event) in 1993. The possible sources of the triplet and the FE-event are analyzed. Taking into account the deflection of CR trajectories in the extragalactic and galactic magnetic fields, it is shown that transient sources of the FE-event and the triplet may be galaxies with active star formation, where CRs are accelerated by newborn millisecond pulsars. Among the galactic sources, the potential candidates are young pulsars that might have had millisecond periods at birth and giant magnetar flares.

Testing general relativity on accelerators

Within the general theory of relativity, the curvature of spacetime is related to the energy and momentum of the present matter and radiation. One of the more specific predictions of general relativity is the deflection of light and particle trajectories in the gravitational field of massive objects. Bending angles for electromagnetic waves and light in particular were measured with a high precision. However, the effect of gravity on relativistic massive particles was never studied experimentally. Here we propose and analyze experiments devoted to that purpose. We demonstrate a high sensitivity of the laser Compton scattering at high energy accelerators to the effects of gravity. The main observable – maximal energy of the scattered photons – would experience a significant shift in the ambient gravitational field even for otherwise negligible violation of the equivalence principle. We confirm predictions of general relativity for ultrarelativistic electrons of energy of tens of GeV at a current level of resolution and expect our work to be a starting point of further high-precision studies on current and future accelerators, such as PETRA, European XFEL and ILC.

Extending the reach of mousetracking in numerical cognition: a comment on Fischer and Hartmann (2014).

Extending the reach of mousetracking in numerical cognition: a comment on Fischer and Hartmann (2014).

Hydrodynamic interaction between a platelet and an erythrocyte: effect of erythrocyte deformability, dynamics, and wall proximity.

We present three-dimensional numerical simulations of hydrodynamic interaction between a red blood cell (RBC) and a platelet in a wall-bounded shear flow. The dynamics and large deformation of the RBC are fully resolved in the simulations using a front-tracking method. The objective is to quantify the influence of tank treading and tumbling dynamics of the RBC, and the presence of a bounding wall on the deflection of platelet trajectories. We observe two types of interaction: A crossing event in which the platelet comes in close proximity to the RBC, rolls over it, and continues to move in the same direction; and a turning event in which the platelet turns away before coming close to the RBC. The crossing events occur when the initial lateral separation between the cells is above a critical separation, and the turning events occur when it is below the critical separation. The critical lateral separation is found to be higher during the tumbling motion than that during the tank treading. When the RBC is flowing closer to the wall than the platelet, the critical separation increases by several fold, implying the turning events have higher probability to occur than the crossing events. On the contrary, if the platelet is flowing closer to the wall than the RBC, the critical separation decreases by several folds, implying the crossing events are likely to occur. Based on the numerical results, we propose a mechanism of continual platelet drift from the RBC-rich region of the vessel towards the wall by a succession of turning and crossing events. The trajectory deflection in the crossing events is found to depend nonmonotonically on the initial lateral separation, unlike the monotonic trend observed in tracer particle deflection and in deformable sphere-sphere collision. This nonmonotonic trend is shown to be a consequence of the deformation of the RBC caused by the platelet upon collision. An estimation of the platelet diffusion coefficient yields values that are similar to those reported in experiments and computer simulations with multicellular suspension.

Over-ablation and deflection of hydrogen pellets injected into neutral beam injection heated plasmas in the Large Helical Device

During hydrogen pellet injection experiments in the Large Helical Device (LHD), over-ablation caused by fast ions (due to tangential neutral beam injection (NBI) heating at 150–180 keV beam energy) is shown to dominate the measured penetration depths. The neutral gas and plasma shielding model, including the interaction of the pellet with fast ions, is applied, and its predictions are shown to agree well with the measured Hα emission profiles. The toroidal deflection of the pellet trajectories observed in the direction of beam injection is reproduced by the model when unbalanced ablation on the two sides of the pellet is included. The attenuation of the fast-ion and electron heat fluxes entering the ablation cloud is examined, showing that the high-energy part of the fast-ion distribution function is responsible for the high ablation rates, and that the thermal electron population is not the dominant ablating species. An analytical scaling for the balanced NBI condition is derived, which reasonably reproduces the measured penetration depths included in the LHD database. In the LHD, for given pellet parameters and beam energy, the fast-ion density is shown to be the major parameter affecting the experimental penetration.

Multisubband transport and magnetic deflection of Fermi electron trajectories in three terminal junctions and rings

We study the electron transport in three terminal junctions and quantum rings looking for the classical deflection of electron trajectories in the presence of intersubband scattering. We indicate that although the Aharonov–Bohm oscillations and the Lorentz force effects co-exist in the low subband transport, for higher Fermi energies a simultaneous observation of both effects is difficult and calls for carefully formed structures. In particular, in quantum rings with channels wider than the input lead the Lorentz force is well resolved but the Aharonov–Bohm periodicity is lost in chaotic scattering events. In quantum rings with equal lengths of the channels and T-shaped junctions the Aharonov–Bohm oscillations are distinctly periodic but the Lorentz force effects are not well pronounced. We find that systems with wedge-shaped junctions allow for observation of both the periodic Aharonov–Bohm oscillations and the magnetic deflection.

Spin accumulation and spin read out without magnetic field

An idea for construction of two spintronic single-electron nanodevices is presented and supported by a quantum-mechanical simulation of their operation. The first device selects electrons of a given spin orientation and the other performs the spin read out. The operation of proposed devices exploits the spin-dependent deflection of electron trajectories induced by the spin-orbit Rashba coupling and does not require application of an external magnetic field. The operation of the nanodevice requires application of weak voltages applied to the electrodes only.

Effects of the galactic magnetic field upon large scale anisotropies of extragalactic cosmic rays

The large scale pattern in the arrival directions of extragalactic cosmic rays that reach the Earth is different from that of the flux arriving to the halo of the Galaxy as a result of thepropagation through the galactic magnetic field. Two different effects are relevant in this process: deflections of trajectories and (de)acceleration by the electric field component due to the galactic rotation.The deflection of the cosmic ray trajectories makes the flux intensity arriving to the halo from some direction to appear reaching the Earth from another direction. This applies to any intrinsic anisotropy in the extragalactic distribution or, even in the absence of intrinsic anisotropies, to the dipolar Compton-Getting anisotropy induced when the observer is moving with respect to the cosmic rays rest frame. For anobserver moving with the solar system, cosmic rays traveling through far away regions of the Galaxy also experience an electric force coming from the relative motion (due to the rotation of the Galaxy) of thelocal system in which the field can be considered as being purely magnetic. This produces small changes in the particlesmomentum that can originate large scale anisotropies even for an isotropic extragalactic flux.

Magnetic forces and stationary electron flow in a three-terminal semiconductor quantumring

We study stationary electron flow through a three-terminal quantum ringand describe effects due to deflection of electron trajectories by classicalmagnetic forces. We demonstrate that generally at high magnetic field (B) the current is guided by magnetic forces to follow a classical path, which forB > 0 leads via the left arm of the ring to the left output terminal. The transport to the leftoutput terminal is blocked for narrow windows of magnetic field for which the interferencewithin the ring leads to formation of wavefunctions that are only weakly coupled to theoutput channel wavefunctions. These interference conditions are accompanied by injectionof the current to the right arm of the ring and by appearance of sharp peaks of the transferprobability to the right output terminal. We find that these peaks at high magnetic fieldare attenuated by thermal widening of the transport window. We also demonstrate that theinterference conditions that lead to their appearance vanish when elastic scatteringwithin the ring is present. The clear effect of magnetic forces on the transferprobabilities disappears along with Aharonov–Bohm oscillations in a chaotic transportregime that is found for rings whose width is larger than the width of the channels.

Evolution of intraplate stress fields under multiple remote compressions: The case of the Iberian Chain (NE Spain)

The stress evolution of the central-eastern Iberian Chain during the Tertiary compression has been a matter of discussion during the last decades. In particular, there is not a complete agreement on whether the tectonic evolution is controlled by different external stress fields or it is essentially related to a single stress field with multiple stress perturbations. A systematic procedure to discriminate between these two hypotheses is proposed. The procedure involves statistical computing of local compression directions, identifying and ‘filtering’ stress deviations on outcrop to map scale, and timing of paleostresses. The latter has been interpreted from both analysis of cross-cut relationships of structures and consideration of the palaeostress record through the sequence of syntectonic sedimentary units. The results suggest that a single stress field with multiple perturbations cannot explain the ensemble of compression directions inferred in the region. The final proposed model includes three different, partially superposed Intraplate Stress Fields ISF ( NE–SW, ESE–WNW to SSE–NNW, and NNE–SSW ISFs), driven by genetically independent far-field tectonic forces related with the active Iberia plate margins, and showing both local and regional deflection of stress trajectories.