Angular Restrictions Research Articles

Pediatric ACL Reconstruction in Children-An Evaluation of the Transphyseal Technique's Efficacy and Safety.

Injuries of the anterior cruciate ligament (ACL) are commonly found in the general population, both among adult and pediatric patients, and their incidence has been increasing in recent years. Most of the late literature agrees that surgical reconstruction of the ACL is effective in improving long-term outcomes in pediatric patients, while others in the past have pleaded for non-surgical management. Our study aims to verify if ACL reconstruction (ACLR) using transphyseal technique in skeletally immature patients will provide angular deviations or growth restrictions. Retrospective cohort study; Level of evidence 4. We perfomed a retrospective study to verify if transphyseal ACLR in children with less than or equal to 2 years of remaining growth leads to either limb length discrepancies or axis deviations. Most patients who were treated using transphyseal technique showed significant improvements in their functional scores. There were statistically significant differences in lateral distal femoral angles (LDFA) and medial proximal tibial angles (MPTA), with no clinical impact. There was no significant limb length discrepancy (LLD) during the 2-year follow-up. Transphyseal ACLR is safe among children who have less than or equal to 2 years of remaining growth and brings no risk of axis deviations or limb length discrepancy.

Dense U-Net for Limited Angle Tomography of Sound Pressure Fields

Tomographic reconstruction allows for the recovery of 3D information from 2D projection data. This commonly requires a full angular scan of the specimen. Angular restrictions that exist, especially in technical processes, result in reconstruction artifacts and unknown systematic measurement errors. We investigate the use of neural networks for extrapolating the missing projection data from holographic sound pressure measurements. A bias flow liner was studied for active sound dampening in aviation. We employed a dense U-Net trained on synthetic data and compared reconstructions of simulated and measured data with and without extrapolation. In both cases, the neural network based approach decreases the mean and maximum measurement deviations by a factor of two. These findings can enable quantitative measurements in other applications suffering from limited angular access as well.

Hybrid State Constraint Adaptive Disturbance Rejection Controller for a Mobile Worm Bio-Inspired Robot

This study presents the design of a hybrid active disturbance rejection controller (H-ADRC) which regulates the gait cycle of a worm bio-inspired robotic device (WBRD). The WBRD is designed as a full actuated six rigid link robotic manipulator. The controller considers the state restrictions in the device articulations; this means the maximum and minimum angular ranges, to avoid any possible damage to the structure. The controller uses an active compensation method to estimate the unknown dynamics of the WBRD by means of an extended state observer. The sequence of movements for the gait cycle of a WBRD is represented as a class of hybrid system by alternative reference frameworks placed at the first and the last link. The stability analysis employs a class of Hybrid Barrier Lyapunov Function to ensure the fulfillment of the angular restrictions in the robotic device. The proposed controller is evaluated using a numerical simulation system based on the virtual version of the WBRD. Moreover, experimental results confirmed that the H-ADRC may endorse the realization of the proposed gait cycle despite the presence of perturbations and modeling uncertainties. The H-ADRC is compared against a proportional derivative (PD) controller and a proportional-integral-derivative (PID) controller. The H-ADRC shows a superior performance as a consequence of the estimation provided by the homogeneous extended state observer.

The Influence of Dissipation on the Dispersion Characteristics of Surface Spin Waves

Dissipation of surface spin waves propagating in arbitrary directions in a magnetized ferromagnetic film is studied. It is shown that the allowance for dissipation restricts the domain of possible wave vectors to a finite region and leads to the appearance above this region of the continuation of a dispersion surface in the form of an inverted cap with a negative slope and a large damping of the waves. It is noted that the solution gives an infinite number of almost coincident dispersion surfaces with a sharp increase in the damping coefficient with each next surface, so that the waves become practically nonpropagating. The analysis of the dispersion surfaces shows that the lower part has a positive slope and describes forward waves, the damping of which is proportional to a small dissipation constant but, in the upper part of the surface, the damping coefficient sharply increases. It is found that the directions of the group velocities of the waves substantially change in comparison with a dissipationless medium and some frequency and angular restrictions on the propagation of surface waves also become different.

Gaussian semiflexible rings under angular and dihedral restrictions.

Semiflexible polymer rings whose bonds obey both angular and dihedral restrictions [M. Dolgushev and A. Blumen, J. Chem. Phys. 138, 204902 (2013)], are treated under exact closure constraints. This allows us to obtain semianalytic results for their dynamics, based on sets of Langevin equations. The dihedral restrictions clearly manifest themselves in the behavior of the mean-square monomer displacement. The determination of the equilibrium ring conformations shows that the dihedral constraints influence the ring curvature, leading to compact folded structures. The method for imposing such constraints in Gaussian systems is very general and it allows to account for heterogeneous (site-dependent) restrictions. We show it by considering rings in which one site differs from the others.

ELEMENTARY PARTICLES, ATOMIC NUCLEI AND MOLECULES ACCORDING TO THE BSM – SUPERGRAVITATION UNIFIED THEORY

The Basic Structures of Matter – Supergravitation Unified Theory (BSM-SG) is based on alternative concept of the physical vacuum. At small distance below 1 angstrom the Supergravitational forces appear as strong nuclear forces, while at larger distance they converge to the Newtonian gravity. Amongst the major outcomes from BSM-SG theory are derived material structures of the stable elementary particles forming the material structure of atomic nuclei. The protons and neutrons are not spherical but having a shape of twisted and folded torus, respectively. They are thin but with much larger size than the size of the atomic nuclei according to the QM models, so the Coulomb field is not converged to a size in the order of 10E-15 m but is distributed over much larger size of the proton. The BSM-SG models of nuclear structures exhibit an excellent match to the pattern of Periodic Table, showing signatures of valences, Pauli Exclusion Principle and Hunds rule. They also define the angular restrictions of the chemical bonds.

WE‐C‐BRB‐10: Dynamic Accelerated Partial Breast Arc Irradiation via Synchronized Trajectories of Couch and Gantry

Purpose: Accelerated partial breast irradiation (APBI) and external beam boosts of the lumpectomy cavity are accessible non‐invasive alternatives to brachytherapy techniques. However, the utilization of IMRT, in a manner to adequately spare normal tissue beyond the chest wall, is limited due to angular and geometrical clearance restrictions in isocentric breast setups. To address this, a novel method is introduced in which synchronized motion of the gantry and couch, in conjunction with a prone breast setup, enables the placement of horizontal arcs around the ipsilateral breast and provides conformal coverage of complex targets with substantial sparing of normal tissue. Methods: Optimization algorithms were developed to determine non‐collisional gantry and couch trajectories that can concurrently maintain the target within beam apertures defined by a multi‐leaf collimator. The Varian TrueBeam STx, which in Developer Mode allows for customized programmable motion of the couch during beam‐on, was used to implement the method. Patient scans, simulated in the prone position on an in‐house immobilization board were used for treatment planning of non‐isocentric intensity modulated arcs. The dosimetric results were quantified against conventional limited angle IMRT for the clinical cases of APBI and lumpectomy boosts. Results: Relative to a typical 5 field IMRT APBI beam arrangement as suggested by RTOG‐0413, the proposed dynamic arc method resulted in 44% lower volume of normal tissue receiving 50% of the prescription (V50), and 40% lower volume of normal tissue receiving 100% of the prescription (V100). Conclusions: Recent reports have correlated the occurrence of unacceptable cosmesis in APBI to the volume of normal breast tissue receiving 50% and 100% of the prescription dose. From the results of this study, it is anticipated that the proposed method of synchronous treatment trajectories of the couch and gantry can allow for more clinically favorable APBI treatments.

The relative neighbourhood graph is a part of every 30°-triangulation

We study sets of points in the two-dimensional Euclidean plane. The relative neighbourhood graph (RNG) of a point set is a straight line graph that connects two points from the point set if and only if there is no other point in the set that is closer to both points than they are to each other. A triangulation of a point set is a maximal set of nonintersecting line segments (called edges) with vertices in the point set. We introduce angular restrictions in the triangulations. Using the well-known method of exclusion regions, we show that the relative neighbourhood graph is a part of every triangulation all of the angles of which are greater than or equal to 30°.

Reversible geminate recombination of hydrogen-bonded water molecule pair

The (history independent) autocorrelation function for a hydrogen-bonded water molecule pair, calculated from classical molecular dynamics trajectories of liquid water, exhibits a t(-3/2) asymptotic tail. Its whole time dependence agrees quantitatively with the solution for reversible diffusion-influenced geminate recombination derived by Agmon and Weiss [J. Chem. Phys. 91, 6937 (1989)]. Agreement with diffusion theory is independent of the precise definition of the bound state. Given the water self-diffusion constant, this theory enables us to determine the dissociation and bimolecular recombination rate parameters for a water dimer. (The theory is indispensable for obtaining the bimolecular rate coefficient.) Interestingly, the activation energies obtained from the temperature dependence of these rate coefficients are similar, rather than differing by the hydrogen-bond (HB) strength. This suggests that recombination requires displacing another water molecule, which meanwhile occupied the binding site. Because these activation energies are about twice the HB strength, cleavage of two HBs may be required to allow pair separation. The autocorrelation function without the HB angular restriction yields a recombination rate coefficient that is larger than that for rebinding to all four tetrahedral water sites (with angular restrictions), suggesting the additional participation of interstitial sites. Following dissociation, the probability of the pair to be unbound but within the reaction sphere rises more slowly than expected, possibly because binding to the interstitial sites delays pair separation. An extended diffusion model, which includes an additional binding site, can account for this behavior.

Particle scattering factor of pearl necklace chains

AbstractThe particle scattering behaviour of a pearl necklace chain is derived. The chain is composed of sphere‐like pearls, separated by rod‐like segments of fixed length, which have no angular restrictions. By calculating several series of model scattering curves, the important structural features are retrieved. The model is believed to be useful in interpreting intermediate structures of collapsing macromolecules or polyelectrolytes. A first application to a shrinking polyelectrolyte coil generated by molecular dynamic simulations (Limbach and Holm, J.Phys.Chem. 2003) is presented and used to discuss the potentials and limits of the model.

Dynamics of dendrimers and of randomly built branched polymers

We focus on the dynamical properties of dendrimers and of randomly built branched polymers, which allows us to assess theoretically the role of disorder on the relaxation forms. We model the random polymers through a stochastic growth algorithm. Our studies are carried out both in the Rouse and also in the Zimm framework; the latter accounts for hydrodynamic interactions. Moreover, we also mimic the local geometry by imposing conditions on the average values of the angles between neighboring segments. Excluded volume interactions, however, are neglected throughout. The storage G′(ω) and the loss G″(ω) moduli, which we calculate, turn out to depend more on the hydrodynamic and the angular restrictions than on randomness. Furthermore, we find that both the randomness and the angular restrictions slow down the relaxation. Given that G′(ω), G″(ω) and also C(t), a function related to the radius of gyration, are all connected to the relaxation function G(t), a fact which we recall, we also calculate numerically G(t) and C(t); moreover we fit, following previous works, C(t) to stretched-exponential forms. Interestingly, it appears that from all functions considered G(t) is most sensitive to disorder.

Local-scaling transformation version of density functional theory: Application to atoms and diatomic molecules

Applications of the local-scaling transformation version of density functional theory, LS-DFT, to atoms and diatomic molecules are presented. In the case of atoms, explicit kinetic- and exchange-energy functionals for first- and second-row atoms at the Hartree–Fock level are constructed. The emphasis given in LS-DFT to the symmetry problem, namely, to the inclusion of spin and angular momentum restrictions in energy density functionals, is illustrated by the construction of explicit energy functionals (at the Hartree–Fock level) for the 1S, 3P and 1D terms of the 1s22s22p2 configuration of the carbon atom. Also, applications of LS-DFT that go beyond the Hartree–Fock method are presented. In this respect, the decomposition of the electron correlation energy into its dynamical and nondynamical parts is analyzed for the case of four-electron atoms and ions. It is shown that a “reference wave function”—differing from the exact one only in the dynamical correlation energy component—can always be found. Based on this wave function, the correlation energy is partitioned into “long-range” and “short-range” contributions. A method based on a cluster-expansion technique is advanced for the purpose of treating the dynamical “short-range” correlation component. In the case of diatomic molecules, the derivation of coupled first-order integral equations for density transformations of prolate-spheroidal coordinates is discussed. Applications of these density transformations to molecular orbitals involving single ζ atomic functions are carried out and a comparison is made between the energies coming from the original and the locally scaled orbitals. Also, the minimization of the kinetic energy at fixed Hartree–Fock density is discussed as this procedure is equivalent to solving the Kohn–Sham x-only equations. Finally, some extensions of LS-DFT to polyatomic systems (molecules and solids) are discussed. In particular, the possibility of generating a molecular energy density functional as a collection of atom-centered functionals and of applying nonisotropic density transformations to solids is considered. © 1999 John Wiley & Sons, Inc. J Comput Chem 20: 155–183, 1999

Rotationally resolved photoelectron spectroscopy of autoionizing states of water

Rotationally resolved photoelectron spectra are reported for rovibronically state-selected autoionizing levels of water. These photoelectron spectra are helpful for the spectroscopic assignment of the autoionizing levels and provide considerable dynamical information on the mechanisms for the transfer of energy and angular momentum between the ion core and the Rydberg electron. As a result of angular momentum restrictions, photoelectron spectra for J=0 autoionizing levels provide a direct partial wave analysis for the ejected photoelectrons.

Complete resolution of the solid-state NMR spectrum of a uniformly 15N-labeled membrane protein in phospholipid bilayers.

Complete resolution of the amide resonances in a three-dimensional solid-state NMR correlation spectrum of a uniformly 15N-labeled membrane protein in oriented phospholipid bilayers is demonstrated. The three orientationally dependent frequencies, 1H chemical shift, 1H-15N dipolar coupling, and 15N chemical shift, associated with each amide resonance are responsible for resolution among resonances and provide sufficient angular restrictions for protein structure determination. Because the protein is completely immobilized by the phospholipids on the relevant NMR time scales (10 kHz), the linewidths will not degrade in the spectra of larger proteins. Therefore, these results demonstrate that solid-state NMR experiments can overcome the correlation time problem and extend the range of proteins that can have their structures determined by NMR spectroscopy to include uniformly 15N-labeled membrane proteins in phospholipid bilayers.

Angular restrictions on the glass transition and on the c-axis correlated liquid phase in twinned YBa 2Cu 3O 7−δ

We have measured the angular dependence of the vortex velocity correlation temperature T th( H) in twinned YBa 2Cu 3O 7−δ single crystals. The data show that the c-axis correlated vortex liquid phase exists up to angles much larger than expected within a single vortex pinning picture. Despite this, the second-order solid-liquid glass transition is shown to be restricted only to external magnetic fields applied within a few degrees from the c-axis direction.

Acoustic gas slip induced by surface waves

A boundary kinetic effect has been predicted on the basis of a model of interaction between Rayleigh surface acoustic waves (SAW) and a gas. The effect resembles some classic boundary effects such as thermal or diffusion gas slip. The functional dependence of the effect on gas and SAW parameters is presented. The slip phenomenon takes place due to angular restrictions of the scattered gas molecules because of the deformation of the solid surface.

Effects of Ltot-conservation and quantization of vibrational energy in statistical simulations of the reaction Cs∗ (72P12,) + H2 → CsH + H

Abstract The crossed beam experiments of L' Hermite et al.(1990–1991) on the reaction Cs ∗ (72P 1 2 , 3 2 ) + H2 → CsH + H are simulated using the statistical algorithm RRKM-SA. Good agreement between the experimental and calculated rotational quantum number distributions as well as the fractional values of total energy in different degrees of freedom, are obtained. Quantization of vibrational energy is included in the otherwise classical calculations and is shown to be important. The reaction is found to be statistical but with a very strong dependence on the conservation of total angular momentum. In a so-called triangular plot it can be seen that it is the low total available energy that makes the angular momentum restrictions so important. This constraint also means that a considerable portion of the translational energy at the exit centrifugal barrier is instead found in molecular and complex rotational energy. Branching ratios are calculated for the reaction involving both Cs(72P 1 2 ) and Cs(72P 3 2 ) and good agreement with the approximate experimental values are obtained.

Cone Beam Tomography of the Heart Using Single-Photon Emission-Computed Tomography

The authors evaluated cone beam single-photon emission-computed tomography (SPECT) of the heart. A new cone beam reconstruction algorithm was used to reconstruct data collected from "short scan" acquisitions (of slightly more than 180 degrees) of a detector anteriorally traversing a noncircular orbit. The less than 360 degrees acquisition was used to minimize the attenuation artifacts that result from reconstructing posterior projections of 201T1 emissions from the heart. The algorithm includes a new method for reconstructing truncated projections of background tissue activity that eliminates reconstruction ring artifacts. Phantom and patient results are presented which compare a high-resolution cone beam collimator (50-cm focal length; 6.0-mm full width at half maximum [FWHM] at 10 cm) to a low-energy general purpose (LEGP) parallel hole collimator (8.2-mm FWHM at 10 cm) which is 1.33 times more sensitive. The cone beam tomographic results are free of reconstruction artifacts and show improved spatial and contrast resolution over that obtained with the LEGP parallel hole collimator. The limited angular sampling restrictions and truncation problems associated with cone beam tomography do not deter from obtaining diagnostic information. However, even though these preliminary results are encouraging, a thorough clinical study is still needed to investigate the specificity and sensitivity of cone beam tomography.

Statistical description of rotational distributions of OH( v, N) from the reaction O( 3P) + HCl( v, J) → OH + Cl

A statistical simulation of the state-to-state experiments by Rakestraw, McKendrick and Zare on the reaction O( 3P) + HCl( v, J) → OH( v, N) + Cl is presented, using our statistical algorithm UNIMOL. Good agreement with the experimental rotational distributions has been found by implementing a realistic procedure for the vibrational quantization in the exit channels. The vibrational branching ratio is in fair agreement with experiments. The dominating effect in the reaction is the angular momentum restrictions imposed at the entrance and exit centrifugal barriers. A version of the algorithm is used which is adapted to the fact that the rotational motions at the exit barrier are one-dimensional in this system. The only parameter used in the calculation is the potential energy barrier, for which we find the best-fit value to be 5.9 × 10 −20 J.

Rate constants for reactions O( 3P) + X 2 → OX + X (X = Br, I) determined by an RRKM-type statistical algorithm employing Monte Carlo simulation

Thermal and crossed molecular beam experiments have independently given information on the reactions O( 3P) + Br 2 → OBr + Br and O( 3P) + I 2 → OI + I, which proceed through long-lived reaction complexes. Our previously described statistical RRKM-type simulation algorithm is now modified to calculate detailed and macroscopic rate constants for these reactions. Good agreement is found with the experimental thermal rate constant for O + I 2, while reasonable results are found for O + Br 2 when a potential energy barrier with a height of 4.2 kJ/mol is included in the entrance channel. A somewhat larger energy barrier may be needed to reach good agreement with experiments. Angular momentum restrictions are shown to considerably lower the rate constants for these reactions. It is demonstrated that the detailed reaction model largely influences the energy dependence of the detailed rate constants, and also that extrapolations to other temperatures for thermal rate constants depend strongly on the potential energy model used.