Small Asymmetry Research Articles

The Qweak Experiment: First Direct Measurement of the Weak Charge of the Proton

The recently completed Qweak experiment at Jefferson Laboratory made the first direct determination of the proton's weak charge, QpW, via a measurement of the parity-violating asymmetry in elastic electron-proton scattering at low four-momentum transfer. The Standard Model (SM) makes a precise prediction of QpW (SM) = 0.0710 ± 0.0007. A deviation from this prediction could be an indicator of new physics. A longitudinally polarized electron beam was scattered off a liquid hydrogen target and detected in eight azimuthally symmetric fused silica detectors. The small asymmetry, Aep = -279 ± 35 (stat) ±31 (syst) ppb, was measured by observing the difference in rates seen in the detectors when the helicity of the electron beam was rapidly reversed. The measured asymmetry is the most precise and smallest asymmetry ever measured in an e⃗p scattering experiment. Combining this asymmetry with previous parity- violating electron scattering (PVES) data, we obtained a value of QpW(PVES) = 0.064 ± 0.012, which agrees well with the SM value. The results of the experiment's commissioning run, which constitutes about 4% of the total data set, are reported here. Analysis of the remainder of the data set is ongoing and will significantly reduce the statistical and systematic uncertainties; several aspects of this analysis will be highlighted.

The resonance motions of a statically stable Lagrange top at small nutation angles

The resonance motion modes of a Lagrange top with small mass asymmetry upon passage through low-order resonances are analysed. The motion of a rigid body with a prolate ellipsoid of inertia is considered in the vicinity of a lower, statically stable equilibrium position at small nutation angles. The original system of equations is reduced to the equation of motion of a pendulum with small perturbations using an averaging method. The conditions for plunging the phase trajectory of the system into oscillation regions of the pendulum, i.e., the possibility of capture into resonance under the action of the perturbations considered, are analysed. Cases in which captures into resonance are possible and in which they are not are established. Numerical calculations that illustrate the analytical estimates obtained are presented.

Preformation Versus Epigenesis in Early Mammalian Development.

Whether or not early mammalian development results from preformation or epigenesis remains an unresolved issue. Evidence for or against either is weak, inconclusive, and often misinterpreted. Yet, one can parsimoniously conceptualize formation of the mouse blastocyst as a series of random, stochastic events stemming from initial and sequential small asymmetries in egg, zygote, and cleavage stages. Differential compartmentalized gene expression does not lead but follows the morphogenesis and cell fate allocation in the mammalian blastocyst.

Coverage of coherent output states in parallel-coupled dual-racetrack microresonators

Parallel-coupled dual-racetrack silicon microresonators can potentially be used for quadrature amplitude modulation. We analyze the evolution of the coverage of coherent output states of devices with varying device parameters. As the coupling constant increases, the coverage of coherent states initially improves then degrades, which is unexpected based on a prior preference for overcoupling. Increasing the quality factor generally improves the coverage. The influence of the refractive index modulation is found to saturate after reaching a certain level. Analytic formulas are developed to provide insight into the coverage evolution. These results are fairly robust against a small asymmetry of device parameters.

Research of Influence of Small Asymmetries Construction on the Dynamics Motion of Space Landing Vehicle with Considering Resonance

This article provides an analytical methodology rapid assessment of the impact of small asymmetries on motion dynamics of space landing vehicle in a resonant motion. The methodology allows to analyze the value of the design parameters and the aerodynamic coefficients on the degree of their influence through the asymmetry of a deviation from the longitudinal axis of the vehicle velocity vector. The methodology is based on the assumption that the rapid development of resonant modes of motion. An example of the calculations for the proposed method, which showed the adequacy of the results according to the calculations for modeling the spatial movement.

Parity violation in electron scattering

By comparing the cross sections for left- and right-handed electrons scattered from various unpolarized nuclear targets, the small parity-violating asymmetry can be measured. These asymmetry data probe a wide variety of important topics, including searches for new fundamental interactions and important features of nuclear structure that cannot be studied with other probes. A special feature of these experiments is that the results are interpreted with remarkably few theoretical uncertainties, which justifies pushing the experiments to the highest possible precision. To measure the small asymmetries accurately, a number of novel experimental techniques have been developed.

Coastal zones in integrated river basin management in the West Coast of India: Delineation, boundary issues and implications

The management of the coastal region, its resources and stakeholder rights are treated in isolation from the associated river basins in most of the countries across the world. Incorporating the coastal stretch as an integral part of the basin becomes necessary due to the reciprocal relationships that exist between the coastal ‘tail-end’ ecosystems and upstream stretches. The present study addresses the challenges involved in integrating the coastal zones into the Integrated River Basin Management (IRBM) framework, especially in developing countries like India. As a part of this study, the river basins and their coastal watersheds in the west coast of India, a highly bio-diverse and densely populated region, is delineated using multiple high resolution datasets. A case study of one of the western coastal tracts is also attempted to identify the boundaries that have to be considered in the coastal zones for basin delineation. The ambiguities in the coastal drainage and floodplain boundaries due to the numerous cross-linkages that exist with the neighbouring estuaries, the multitude of small independent coastal catchments and asymmetries between surface and groundwater boundaries present difficulties in undertaking a strict hydrological delineation in the study region. Apart from these natural boundaries, various administrative/political units, coastal management frameworks, resource dependencies and livelihoods present additional boundary concerns for sustainable coastal management within IRBM. Taking these multiple boundaries of the coastal zone into account within the river basin regime becomes essential for resource sharing and legitimate interventions in upstream basin decisions that jeopardise the coastal ecosystem and livelihoods.

Asymmetric wave functions from tiny perturbations

The quantum mechanical behavior of a particle in a double well defies our intuition based on classical reasoning. Not surprisingly, an asymmetry in the double well will restore results more consistent with the classical picture. What is surprising, however, is how a very small asymmetry can lead to essentially classical behavior. In this paper, we use the simplest version of a double-well potential to demonstrate these statements. We also show how this system accurately maps onto a two-state system, which we refer to as a “toy model.”

Strategic entry in a triopoly market of firms with asymmetric cost structures

This paper examines the strategic investment timing decision in a triopoly market comprising firms with asymmetric cost structures. We present three novel results. First, in the case where there are relatively small cost asymmetries between firms and a relatively small first-mover advantage, the firm with the lowest cost structure is not always the first investor. In other cases, the firm with the lowest cost structure is the first investor. Second, an increase in volatility increases the possibility that a firm without the lowest cost structure is the first investor. Finally, even in the three-asymmetric-firm model, we show that the first investor threshold is larger in a triopoly than in a duopoly, although it is smaller in a duopoly than in a monopoly.

Coordination of the shoulder complex for pointing in the peripersonal workspace

The shoulder complex allows a large redundancy for the control of goal directed movements. Our aim was to investigate the contribution of scapula-thoracic motion to pointing movements in the peripersonal workspace. Ten healthy participants performed pointing movements with both sides toward nine targets. The kinematics of the shoulder was recorded using a Polhemus Fastrak 6 DoF electromagnetic device with 4 sensors fixed on the trunk, scapula, upper arm and wrist. The 3D rotations between trunk, scapula and humerus and the 3D displacement of the center of the scapula were measured at rest and for each pointing movement. Ratios of the global angles were used to compute a scapula-humeral rhythm. We performed a principal component analysis to study the coupling between scapula movements. A direct kinematic procedure was used to compute the contribution of scapula motion to the workspace of the hand. Trunk and shoulder (glenohumeral [GH] and scapulothoracic [ST]) movements were finely tuned to target position, with small asymmetries. For all pointing movements, 3D global rotation angles of the GH and ST joints varied according to a scapulohumeral rhythm approximately equal to 2/1. Three principal components (1: internal rotation and lateral and anterior displacement, 2: posterior tilt and inferior displacement, 3: lateral rotation) could explain 76.5% of the variability of scapula motion. The direct kinematics showed that the contribution of ST motion to the hand workspace was major (reaching ∼15 cm) and depended on the target. ST motion contributes significantly to the workspace of the hand. The scapulo-humeral rhythm classically described in the planar movements of the shoulder can be generalized in 3D and remains constant during pointing movements. ST motion should be taken into account in the evaluation and understanding of the movements of the upper limb.

Thermal stability of ice on Ceres with rough topography

AbstractThe dwarf planet Ceres may have an ice‐rich crust, and subsurface ice exposed by impacts or endogenic activity would be subject to sublimation. We model surface and subsurface temperatures on Ceres to assess lifetimes of water ice and other volatiles. Topographic shadowing allows a small but nonnegligible fraction (∼0.4%) of Ceres' surface to be perennially below the ∼110 K criterion for 1 Gyr of stability. These areas are found above 60° latitude. Other molecules (CH3OH, NH3, SO2, and CO2) may be cold trapped in smaller abundances. A model for the transport, gravitational escape, and photoionization of H2O molecules suggests net accumulation in the cold traps. Buried ice is stable within a meter for > 1 Gyr at latitudes higher than ∼50°. An illuminated polar cap of water ice would be stable within a few degrees of the poles only if it maintained a high albedo (>0.5) at present obliquity. If the obliquity exceeded 5° in the geologically recent past, then a putative polar cap would have been erased. At latitudes 0°–30°, ice is stable under solar illumination only briefly (∼10–100 years), unless it has high albedo and thermal inertia, in which case lifetimes of > 104 years are possible. Finally, a small hemispheric asymmetry exists due to the timing of Ceres' perihelion passage, which would lead to a detectable enhancement of ice in the northern hemisphere if the orbital elements vary slowly relative to the ice accumulation rate. Our model results are potentially testable during the Dawn science mission.

NEAR-IR POLARIZED SCATTERED LIGHT IMAGERY OF THE DoAr 28 TRANSITIONAL DISK

We present the first spatially resolved polarized scattered light H-band detection of the DoAr 28 transitional disk. Our two epochs of imagery detect the scattered light disk from our effective inner working angle of 0.10" (13 AU) out to 0.50" (65 AU). This inner working angle is interior to the location of the system's gap inferred by previous studies using SED modeling (15 AU). We detected a candidate point source companion 1.08" northwest of the system; however, our second epoch of imagery strongly suggests that this object is a background star. We constructed a grid of Monte Carlo Radiative Transfer models of the system, and our best fit models utilize a modestly inclined (50 deg), 0.01 Msun disk that has a partially depleted inner gap from the dust sublimation radius out to ~8 AU. Subtracting this best fit, axi-symmetric model from our polarized intensity data reveals evidence for two small asymmetries in the disk, which could be attributable to variety of mechanisms.

Conductance through single biphenyl molecules: symmetric and asymmetric coupling to electrodes.

The contacts and the chemical bonds formed between metallic electrodes and molecules determine to a large extent the conductive properties of single molecular junctions, which represent the smallest possible active elements in an electronic circuit. We therefore investigated in a comparative study, using the break junction technique (MCBJ), the conductive properties of [1,1’-biphenyl]-4,4’-dithiol (M1) and of 4’-mercapto-[1,1’-biphenyl]-4-carbonitrile (M2) between gold electrodes. As a function of electrode separation, characterized by the conductance close to 0 V, we found several plateaus of relative stability, with those close to 0.01G0 being the most pronounced. The overall conductance of symmetric and asymmetric molecules were surprisingly similar, only the range of stability was smaller for M2. While M1 yielded symmetric I–V-curves, only small asymmetries were detected for M2. These are also reflected in the comparable values for coupling parameters using the single level resonance model. The high conductance for the asymmetric molecule is interpreted as a result of coherent coupling of electronic states through the whole molecule, so that the outcome cannot be predicted just by adding conductive properties of individual molecular groups.

Spin-orbit coupling and chaotic rotation for circumbinary bodies

We investigate the resonant rotation of circumbinary bodies in planar quasi-circular orbits. Denoting $n_b$ and $n$ the orbital mean motion of the inner binary and of the circumbinary body, respectively, we show that spin-orbit resonances exist at the frequencies $n\pm k\nu/2$, where $\nu = n_b - n$, and $k$ is an integer. Moreover, when the libration at natural frequency has the same magnitude as $\nu$, the resonances overlap and the rotation becomes chaotic. We apply these results to the small satellites in the Pluto-Charon system, and conclude that their rotations are likely chaotic. However, the rotation can also be stable and not synchronous for small axial asymmetries.

The Evaluation of Vertical Pole Configuration and Location on Assisting the Sit-to-Stand Movement in Older Adults with Mobility Limitations

Grab-bars and transfer poles are common sit-to-stand aids for mobility limited older adults. This study investigated differences in kinetics and kinematics to characterize the lower-limb strength and dynamic balance requirements across different pole configurations and positions in nine mobility limited older adults. Poles were varied by location (near and far) and configuration (single vertical pole, double vertical poles, vertical pole with a horizontal bar). Results indicated that the far pole condition resulted in increased trunk (p < 0.001) and hip flexion (p < 0.01 and < 0.0001 for contralateral and ipsilateral sides, respectively), and a reduced peak vertical force applied to the pole (p < 0.001). Peak extension moments at the hip and knee were unchanged, and, therefore, pole position had no effect on task demands. Placing the pole unilaterally introduced a small kinetic asymmetry, which significantly increased peak knee extension moments on the ipsilateral side (p < 0.05). Finally, dynamic balance was relatively unchanged across pole conditions. These findings offer novel insight into pole use and the effect of varying pole location and configuration in a sample of older adults with mobility impairment, and provide the basis for future work.

Correction of small volume breast asymmetry using deep parenchymal resection and identical silicone implants: an early experience.

Virtually all patients presenting for augmentation mammaplasty will exhibit some degree of asymmetry. The use of asymmetric implants to address small- volume breast asymmetry introduces uncontrolled variables into the longevity of postoperative results. We described a novel method of addressing small-volume asymmetry using deep parenchymal resection (DPR) to achieve symmetry prior to insertion of identical implants. We also compared our results with this technique to a cohort of standard augmentation mammaplasty patients. All patients underwent 3-dimensional (3D) imaging during consultation. In patients with small-volume breast asymmetry, a uniform disk of deep parenchymal tissue was resected from the base of the larger breast cone through an inframammary incision. A standard submuscular augmentation was then completed. Five patients (DPR group) with appreciable small-volume asymmetry underwent DPR in the larger breast prior to insertion of identical implants. Fifty-six consecutive patients with no appreciable volume asymmetry (standard group) underwent standard submuscular breast augmentation. Using 3D imaging preoperatively, DPR-group patients had an estimated breast volume asymmetry of 86 ± 58 g and had 55 ± 27 g excised from the larger breast intraoperatively, allowing for insertion of identical implants in each patient. Complications in the standard group included 1 case of rippling and 2 cases of malposition. One case of malposition was noted in the DPR group. No other complications were recorded in either group over 6 months. Our novel method of addressing small-volume breast asymmetry allows for the use of identical implants and presents no increase in early complications.

An Integrated Analysis of Leg Length Differences and the Effect of Correctional Techniques on Stroke Mechanics and Performance Indicators in Competitive Cyclists

Leg length discrepancy amongst the general population is relatively common, increasing susceptibility to a range of injuries potentially transferable to endurance cyclists. While the effects of such conditions are widely reported for the general population, little is known regarding a repetitive and constrained activity such as cycling. Therefore, the purpose of this study was to assess pedal mechanical asymmetries of trained cyclists with mild leg length discrepancies and the subsequent effects of compensatory strategies (crank length and cleat wedge) on physiological measures of gross efficiency. Participants completed three 15 min trials at a sub maximal intensity for each condition in a single blind (participants) and balanced order with 15 min recovery between conditions. Torque, vastuslateralis Electromyography (EMG), mechanical angles at the hip, knee and ankle, of both left and right sides were recorded along with expired air analysis and heart rate in order to calculate changes in gross efficiency. The main findings show that participants with 5.4 ± 2.9 mm differences in leg lengths showed small asymmetries in mechanical angles, torque production and muscle activity for which compensatory interventions made positive small changes. Interestingly, these changes resulted in a negative effect on gross efficiency, which would require an adaptation period to remedy any neuromuscular compensatory adaptations. Therefore, cyclists recognized as having leg length discrepancies are recommended to use compensatory interventions such as orthosis, rather than crank length modifications, and that a period of gradual adaptation period be allocated.

Low temperature behavior of hyperfine fields in amorphous and nanocrystalline FeMoCuB

Low temperature (4.2 K) magnetic behavior of Fe76Mo8Cu1B15 metallic glass was studied by 57Fe Mössbauer spectrometry (MS) and 57Fe NMR. Distributions of hyperfine magnetic fields P(B) were determined for as-quenched and annealed (nanocrystalline) samples with relative fraction of the grains about 43%. P(B) distributions were derived for both the amorphous matrix and nanocrystalline grains. NMR of alloys with natural and 57Fe enriched Fe enabled to assess the contribution of 11B to the total NMR signal. P(B) distribution of the as-quenched alloy derived from MS matches reasonably well the one from NMR of the enriched sample. NMR signal from the sample with natural Fe exhibits contributions from 11B nuclei. The principal NMR lines of the annealed alloys at 47 MHz correspond to bcc Fe nanocrystals. Small asymmetry of the lines towards higher frequencies might be an indication of possible impurity atoms in the bcc structure. The observed differences between natural and enriched samples are attributed to higher sensitivity in the latter. Positions of the lines attributed to bcc Fe nanocrystals obtained from MS and NMR are in perfect agreement.

FFLO state with angle-dependent gap in asymmetric nuclear matter

We consider the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) state with an angle-dependent gap (ADG) for the arbitrary angle between the direction of the Cooper pair momentum and the symmetry axis of the ADG in asymmetric nuclear matter. We find two kinds of locally stable states, i.e., the FFLO–ADG–orthogonal and FFLO–ADG–parallel states, which correspond to and , respectively. Furthermore, the FFLO–ADG–orthogonal state is located at small asymmetry, whereas the FFLO–ADG–parallel state is favored for large asymmetry. The critical isospin asymmetry , where the superfluid vanishes, is enhanced largely by considering the Cooper pair momentum with an ADG.

Tracking hole localization inK-shell and core-valence-excited acetylene photoionization via body-frame photoelectron angular distributions

Asymmetry in the molecular-frame photoelectron angular distributions from core-hole- or core-valence-excited polyatomic targets with symmetry-equivalent atoms can provide direct evidence for core-hole localization. Using acetylene as an example, we contrast the small asymmetry that can be seen in direct core-level ionization, due to the competition between two competing pathways to the continuum, with ionization from core-valence-excited HCCH, which offers the prospect of observing markedly greater asymmetry.