Angular Rotation Term Research Articles

Biomechanical analysis of occipitocervical stabilization techniques: emphasis on integrity of osseous structures at the occipital implantation sites.

The objective of the current study was to quantify and compare the multidirectional flexibility properties of occipital anchor fixation with conventional methods of occipitocervical screw fixation using nondestructive and destructive investigative methods. Fourteen cadaveric occipitocervical specimens (Oc-T2) were randomized to reconstruction with occipital anchors or an occipital plate and screws. Using a 6-degree-of-freedom spine simulator with moments of ± 2.0 Nm, initial multidirectional flexibility analysis of the intact and reconstructed conditions was performed followed by fatigue loading of 25,000 cycles of flexion-extension (x-axis, ± 2.0 Nm), 15,000 cycles of lateral bending (z-axis, ± 2.0 Nm), and 10,000 cycles of axial rotation (y-axis, ± 2.0 Nm). Fluoroscopic images of the implantation sites were obtained before and after fatigue testing and placed on an x-y coordinate system to quantify positional stability of the anchors and screws used for reconstruction and effect, if any, of the fatigue component. Destructive testing included an anterior flexural load to construct failure. Quantification of implant, occipitocervical, and atlantoaxial junction range of motion is reported as absolute values, and peak flexural failure moment in Newton-meters (Nm). Absolute value comparisons between the intact condition and 2 reconstruction groups demonstrated significant reductions in segmental flexion-extension, lateral bending, and axial rotation motion at the Oc-C1 and C1-2 junctions (p < 0.05). The average bone mineral density at the midline keel (1.422 g/cm3) was significantly higher compared with the lateral occipital region at 0.671 g/cm3 (p < 0.05). There were no significant differences between the occipital anchor and plate treatments in terms of angular rotation (degrees; p = 0.150) or x-axis displacement (mm; p = 0.572), but there was a statistically significant difference in y-axis displacement (p = 0.031) based on quantitative analysis of the pre- and postfatigue fluoroscopic images (p > 0.05). Under destructive anterior flexural loading, the occipital anchor group failed at 90 ± 31 Nm, and the occipital plate group failed at 79 ± 25 Nm (p > 0.05). Both reconstructions reduced flexion-extension, lateral bending, and axial rotation at the occipitocervical and atlantoaxial junctions, as expected. Flexural load to failure did not differ significantly between the 2 treatment groups despite occipital anchors using a compression-fit mechanism to provide fixation in less dense bone. These data suggest that an occipital anchor technique serves as a biomechanically viable clinical alternative to occipital plate fixation.

Core effect on the diamagnetic spectrum of barium Rydberg states

We study the core effect of nonhydrogenic alkaline-earth-metal barium in its diamagnetic spectrum by one photon transition from the ground state $6{s}^{2}$ ${}^{1}\phantom{\rule{-0.16em}{0ex}}{S}_{0}$ experimentally and theoretically. The non-Coulombic potential of the ion core introduces an extra energy shift compared with hydrogen and a level anticrossing between different $n$ manifolds, characterized by the quantum defect of the concerned angular momentum states. With a complex rotation coordinate technique and a $B$-spline expansion method, we develop a matrix-form Hamiltonian based on an effective potential incorporating the angular-dependent quantum defect into the angular rotation term. The nonhydrogen core effects are investigated by sweeping the quantum defects of different channels in the calculation. Results show that quantum defects of $p$ and $f$ states have a undeniable effect on the intensities and positions of the spectral lines, although barium is closely hydrogenlike in the energy range examined. The anticrossing spectral lines are also identified with the aid of theoretical calculations. The calculations are in good agreement with the experimental observations.

The effect of listener head movement on perceived envelopment and apparent source width

Current research examining listeners' perceived spatial impression of a concert hall relies on a fixed-head worldview, since the overwhelming majority of listening tests conducted to determine subjective spaciousness [listener envelopment (LEV) and apparent source width (ASW)] has required listeners to keep their heads fixed. Such a worldview is an incomplete one, because listeners make noticeable exploratory head movements while evaluating sonic environments, including the more common task of source localization as well as the more involved task of evaluating the spaciousness of a concert hall. This study investigates the role of listener head movement in the evaluation of perceived LEV and ASW under 15 different concert hall conditions simulated over eight loudspeakers using Virtual Microphone Control. The conditions consist of both varying ratios of front-to-back energy and varying levels of cross-correlated reverberant energy. Head movements are monitored in terms of angular rotation (azimuth, elevation, and roll) using a head tracker while listeners are prompted to give subjective ratings of LEV and ASW ranging from 1 (least) to 7 (most). The listening tests are then repeated while subjects are asked to keep their heads fixed. The head movements are analyzed and results of the tests are compared.

A Generalized-Laguerre–Fourier–Hermite Pseudospectral Method for Computing the Dynamics of Rotating Bose–Einstein Condensates

A time-splitting generalized-Laguerre–Fourier–Hermite pseudospectral method is proposed for computing the dynamics of rotating Bose–Einstein condensates (BECs) in two and three dimensions. The new numerical method is based on the following: (i) the use of a time-splitting technique for decoupling the nonlinearity; (ii) the adoption of polar coordinates in two dimensions and cylindrical coordinates in three dimensions such that the angular rotation term becomes constant coefficient; and (iii) the construction of eigenfunctions for the linear operator by properly scaling the generalized-Laguerre, Fourier, and Hermite functions. The new method enjoys the following properties: (i) it is explicit, time reversible, and time transverse invariant; (ii) it conserves the position density and is spectrally accurate in space and second-order or fourth-order accurate in time; and (iii) it solves the problem in the original whole space instead of in a truncated artificial computational domain. The method is also extended to solve the coupled Gross–Pitaevskii equations for the dynamics of rotating two-component and spin-1 BECs. Extensive numerical results for the dynamics of BECs are reported to demonstrate the accuracy and efficiency of the new method for rotating BECs.

Pelvic positions during lifting, a multi factor analysis

The study is dedicated to the evaluation of the pelvic movements during the common acts involved in occupational lifting. Pelvic kinematics in terms of angular rotation has been analyzed in a controlled set of experiments under three methods of lifting while performing various lifting assignments, by male and female subjects. The study was designed to evaluate positioning differences in anatomical geometry due to subject gender, object's weight and reach to object distances. Measurements of angular displacements describe the geometrical motion of the pelvic during five phases of the lifting act. Analysis of the variance was performed on angular displacement, as recorded for each lifting assignment. The findings are discussed in two modes, one for different values of lifting weights, and the other for different horizontal reach distances. The paper presents an analysis of the factors affecting the performance of lifting, which contributes to the effort directed toward prevention of back injury. Relevance to industry The analysis of angular displacement in the human pelvic during the lifting act is important for the study of low-back pain and safety in manual materials handling.