Maximum Angular Momentum Research Articles

A comparison of bone bed preparation with laser and conventional drill on the relationship between implant stability quotient (ISQ) values and implant insertion variables

PURPOSEThe aim of this study was to investigate a comparison of implant bone bed preparation with Er,Cr:YSGG laser and conventional drills on the relationship between implant stability quotient (ISQ) values and implant insertion variables.MATERIALS AND METHODSForty implants were inserted into two different types of pig rib bone. One group was prepared with conventional drills and a total of 20 implants were inserted into type I and type II bone. The other group was prepared with a Er,Cr:YSGG laser and a total of 20 implants were inserted into type I and type II bone. ISQ, maximum insertion torque, angular momentum, and insertion torque energy values were measured.RESULTSThe mean values for variables were significantly higher in type I bone than in type II bone (P < .01). In type I bone, the ISQ values in the drill group were significantly higher than in the laser group (P < .05). In type II bone, the ISQ values in the laser group were significantly higher than in the drill group (P < .01). In both type I and type II bone, the maximum insertion torque, total energy, and total angular momentum values between the drill and laser groups did not differ significantly (P ≥ .05). The ISQ values were correlated with maximum insertion torque (P < .01, r = .731), total energy (P < .01, r = .696), and angular momentum (P < .01, r = .696).CONCLUSIONWithin the limitations of this study, the effects of bone bed preparation with Er,Cr:YSGG laser on the relationship between implant stability quotient (ISQ) values and implant insertion variables were comparable to those of drilling.

Rotational Resistance of Surface-Treated Mini-Implants

To test the hypothesis that there is no difference in the stability and resistance to rotational moments of early loaded sandblasted and acid-etched (SLA) mini-implants and those of machined-surface implants of the same size and shape. A randomized complete block design was used in 12 skeletally mature male beagle dogs. Ninety-six orthodontic mini-implants were tested. Two types of implants were used: some had SLA surface treatment and some had machined surfaces without coating. After 3 weeks of healing, rotational moments of 150 g were applied. The success rates, maximum torque values, angular momentum, and total energy absorbed by the bone were compared. All values were subjected to mixed-model analysis to evaluate the influence of surface treatment, rotational force direction, and site of implantation. The maximum insertion torque and angular momentum of SLA implants were significantly lower than those of machined implants (P = .034, P = .039). The SLA implants had a significantly higher value for total removal energy than the machined implants (P = .046). However, there were no significant differences in total insertion energy, maximum removal torque, and removal angular momentum between the 2 groups. There was no significant difference between clockwise and counterclockwise rotation in all measurements. SLA mini-implants showed relatively lower insertion torque value and angular momentum and higher total energy during removal than the machined implants, suggesting osseointegration of the SLA mini-implant after insertion.

Cross sections of projectile-like fragments in the reactionF19+Zn66in the beam energy range of 3–6 MeV/nucleon

Angular distributions of projectile-like fragments (PLFs) have been measured in the reaction $^{19}\mathrm{F}+^{66}\mathrm{Zn}$ at ${E}_{\mathrm{lab}}=61,82,92$, and 109 MeV to understand their formation in the low energy domain ($ \ensuremath{\lesssim}7$ MeV nucleon). In this energy range, maximum angular momentum `${l}_{\mathrm{max}}$' in the reaction is lower than or close to the critical or limiting angular momentum for complete fusion `${l}_{\mathrm{lim}}$(CF).' The sum-rule model was modified to explain the cross sections of PLFs in the present study. For the first time, the modified sum-rule model, with a competition of incomplete fusion (ICF) reaction with complete fusion below ${l}_{\mathrm{lim}}$(CF) reasonably reproduced the cross sections of PLFs in the beam energy range of the present study. It was observed that the cross sections of lighter PLFs fall more rapidly with decreasing beam energy compared to those of heavier PLFs, suggesting a change in the reaction mechanism from heavier to lighter PLFs. Transfer probabilities for peripheral collisions were calculated within the framework of a semiclassical formalism. The parameters of the nuclear potential required for the calculation of transfer probability were obtained by fitting the elastic scattering data measured in the present work. Calculated transfer probabilities were significantly lower compared to the corresponding experimental values, suggesting a significant overlap of the projectile and the target nuclei in incomplete fusion reactions. The present analysis showed that the overlap of the projectile and the target nuclei increases with increasing mass transfer at a given beam energy and for a given PLF, overlap increases with increasing beam energy.

Decay ofBa118,122*compound nuclei formed inKr78,82+Ca40reactions using the dynamical cluster-decay model of preformed clusters

Application of the preformed clusters based dynamical cluster-decay model (DCM) is made to the recent data on decay of the compound systems $^{118,122}\mathrm{Ba}{}^{*}$ at a relatively low bombarding energy of 5.5 MeV/$A$. The same model has been applied earlier to the intermediate mass fragment (IMF) data of $^{116}\mathrm{Ba}{}^{*}$, observed at medium and higher incident energies. For the heavier $^{118,122}\mathrm{Ba}{}^{*}$ systems, however, a complete mass fragmentation spectrum is observed experimentally. Except for a small narrow region of heavier mass fragments ($8\ensuremath{\leqslant}{Z}_{L}\ensuremath{\leqslant}15$), the DCM gives an overall reasonable description of the observed data on both the intermediate mass fragments and the fusion-fission cross-sections, whereas the statistical model calculations based on BUSCO and GEMINI codes describe the intermediate mass fragment data and the heavier mass fragment and fusion-fission data, respectively. Within the DCM (with preformation factor ${P}_{0}=1$), the possibility of non-compound-nucleus decay contributing to the region $8\ensuremath{\leqslant}{Z}_{L}\ensuremath{\leqslant}15$ of heavier mass fragments is also explored. All three models use the maximum angular momentum ${\ensuremath{\ell}}_{\mathrm{max}}$ as a fitting parameter, which in the DCM is fixed via a neck-length parameter for the penetrability $P\ensuremath{\rightarrow}1$.

Potential approach for constrained autonomous manoeuvres of a spacecraft equipped with a cluster of control moment gyroscopes

A potential function approach for attitude manoeuvres in the presence of constraints on admissible attitudes is implemented for a spacecraft controlled by a cluster of control moment gyroscopes. An angular velocity command derived from the potential function defined in the quaternion error vector space is directly implemented by means of a gimbal position command generation algorithm. The manoeuvre is performed by tracking the maximum angular momentum component, corresponding to the commanded angular velocity parallel to the eigenaxis that takes the spacecraft directly onto the desired final attitude. Corrections to the resulting desired angular velocity are implemented if the attitude gets close to one of the forbidden attitudes (‘obstacles’), represented by peaks of the Lyapunov function in the attitude space. Numerical simulations are used to demonstrate the validity of the approach and to compare the overall performance with results reported in the literature.

New BPS configurations of BMN matrix theory

We explore the 1/2 BPS configurations in BMN matrix theory with SO(3) angular momentum of $SO(3)\times SO(6)$ symmetry. The fluctuation analysis of the BPS configurations near the abelian solutions and also the fuzzy two sphere vacua reveals how nonabelian BPS configurations emerge. Especially the irreducible nonabelian configurations seem to have the maximal angular momentum of order $N^3$, beyond which they collapse to abelian ones. We also find some new BPS configurations explicitly.

Rydberg and autoionizing triplet states in Helium up to the N = 5 threshold

Energy levels of highly excited bound Rydberg states, the position and widths of autoionizing states, and oscillator strengths are calculated for He 3S, 3P e, 3P o, 3D e and 3D o symmetries up to the N = 5 He + excitation threshold. The calculations are performed with the K-matrix B-spline method with maximum orbital angular momentum ℓ max = 8. Reliable doubly excited-state parameters up to the n = 20 multiplet below each ionization threshold are presented. One thousand and six hundred newly identified bound and metastable states, seven times those available in literature, fill many gaps, reveal a dozen intruder states, and allow new speculations on propensity rules and radiative decays of triplet Rydberg states.

3S, 3Po,e, 3De,o resonance series in helium

Resonance parameters for more than 1700 doubly excited states in 3S, 3Po,e and 3De,o manifolds up to N = 5 threshold are obtained by means of the B-spline K-matrix method with maximum orbital angular momentum ℓmax = 8. Excellent agreement is found with the best available data in the literature. A detailed analysis of the resonances based on the propensity rules for all relevant channels arranged in schematic patterns allows one to classify the series according to the usual approximate models. The analysis, made possible by the extended energy range considered, helps to asses the limits of these models for the triplet series and discloses the occurrence of nine intruder states and many ‘collisions’ between resonance series.

Extrapolation of electron correlation energies to finite and complete basis set targets

The electron correlation energy of two-electron atoms is known to converge asymptotically as approximately (L+1)(-3) to the complete basis set limit, where L is the maximum angular momentum quantum number included in the basis set. Numerical evidence has established a similar asymptotic convergence approximately X(-3) with the cardinal number X of correlation-consistent basis sets cc-pVXZ for coupled cluster singles and doubles (CCSD) and second order perturbation theory (MP2) calculations of molecules. The main focus of this article is to probe for deviations from asymptotic convergence behavior for practical values of X by defining a trial function X(-beta) that for an effective exponent beta=beta(eff)(X,X+1,X+N) provides the correct energy E(X+N), when extrapolating from results for two smaller basis sets, E(X) and E(X+1). This analysis is first applied to "model" expansions available from analytical theory, and then to a large body of finite basis set results (X=D,T,Q,5,6) for 105 molecules containing H, C, N, O, and F, complemented by a smaller set of 14 molecules for which accurate complete basis set limits are available from MP2-R12 and CCSD-R12 calculations. beta(eff) is generally found to vary monotonically with the target of extrapolation, X+N, making results for large but finite basis sets a useful addition to the limited number of cases where complete basis set limits are available. Significant differences in effective convergence behavior are observed between MP2 and CCSD (valence) correlation energies, between hydrogen-rich and hydrogen-free molecules, and, for He, between partial-wave expansions and correlation-consistent basis sets. Deviations from asymptotic convergence behavior tend to get smaller as X increases, but not always monotonically, and are still quite noticeable even for X=5. Finally, correlation contributions to atomization energies (rather than total energies) exhibit a much larger variation of effective convergence behavior, and extrapolations from small basis sets are found to be particularly erratic for molecules containing several electronegative atoms. Observed effects are discussed in the light of results known from analytical theory. A carefully calibrated protocol for extrapolations to the complete basis set limit is presented, based on a single "optimal" exponent beta(opt)(X,X+1,infinity) for the entire set of molecules, and compared to similar approaches reported in the literature.

Finite N index and angular momentum bound from gravity

We exactly compute the finite N index and BPS partition functions for \({\mathcal{N}}=4\) SYM theory in a newly proposed maximal angular momentum limit. The new limit is not predicted from the superconformal algebra, but naturally arises from the supergravity dual. We show that the index does not receive any finite N corrections while the free BPS partition function does.

Shell model and mean-field description of band termination in theA∼44 nuclei

We study nuclear high-spin states undergoing the transition to the fully stretched configuration with maximum angular momentum I{sub max} within the space of valence nucleons. To this end, we perform a systematic theoretical analysis of non-fully-stretched I{sub max}-2 and I{sub max}-1 f{sub 7/2}{sup n} seniority isomers and d{sub 3/2}{sup -1}f{sub 7/2}{sup n + 1} intruder states in the A{approx}44 nuclei from the lower-fp shell. We employ two theoretical approaches: (i) the density functional theory based on the cranked self-consistent Skyrme-Hartree-Fock method, and (ii) the nuclear shell model in the full sdfp configuration space allowing for 1p-1h cross-shell excitations. We emphasize the importance of restoration of broken angular momentum symmetry inherently obscuring the mean-field treatment of high-spin states. Overall good agreement with experimental data is obtained.

Cosmic microwave background alignment in multi-connected universes

The low multipoles of the cosmic microwave background (CMB) anisotropy possess some strange properties such as the alignment of the quadrupole and the octopole, and the extreme planarity or the extreme sphericity of some multipoles. In this paper, the CMB anisotropy of several multi-connected space forms is investigated with respect to the maximal angular momentum dispersion and the Maxwellian multipole vectors in order to settle the question of whether such spaces can explain the low multipole anomalies in the CMB. The following spaces are considered: the Picard topology in hyperbolic space, three spherical spaces (Poincaré dodecahedron, binary tetrahedron and binary octahedron) and a hypertorus in flat space. Although these spaces are able to produce the large-scale suppression of the CMB anisotropy, they do not describe the CMB alignment. From the models considered, the Picard universe shows the strongest alignment properties.

Black hole formation from collisions of cosmic fundamental strings

We develop the general formalism for joining, splitting and interconnection of closed and open strings. As an application, we study examples of fundamental cosmic string collisions leading to gravitational collapse. We find that the interconnection of two strings of equal and opposite maximal angular momentum and arbitrarily large mass generically leads to the formation of black holes, provided their relative velocity is small enough.

Convergence of configuration-interaction single-center calculations of positron-atom interactions

The configuration interaction (CI) method using orbitals centered on the nucleus has recently been applied to calculate the interactions of positrons interacting with atoms. Computational investigations of the convergence properties of binding energy, phase shift, and annihilation rate with respect to the maximum angular momentum of the orbital basis for the ${e}^{+}\mathrm{Cu}$ and PsH bound states, and the ${e}^{+}\text{\ensuremath{-}}\mathrm{H}$ scattering system were completed. The annihilation rates converge very slowly with angular momentum, and moreover the convergence with radial basis dimension appears to be slower for high angular momentum. A number of methods of completing the partial wave sum are compared; an approach based on a $\ensuremath{\Delta}{X}_{J}=a{(J+\frac{1}{2})}^{\ensuremath{-}n}+b{(J+\frac{1}{2})}^{\ensuremath{-}(n+1)}$ form [with $n=4$ for phase shift (or energy) and $n=2$ for the annihilation rate] seems to be preferred on considerations of utility and underlying physical justification.

Handbook on string decay

We explain simple semi-classical rules to estimate the lifetime of any given highly-excited quantum state of the string spectrum in flat spacetime. We discuss both the decays by splitting into two massive states and by massless emission. As an application, we study a solution describing a rotating and pulsating ellipse which becomes folded at an instant of time -- the ``squashing ellipse''. This string interpolates between the folded string with maximum angular momentum and the pulsating circular string. We explicitly compute the quantum decay rate for the corresponding quantum state, and verify the basic rules that we propose. Finally, we give a more general (4-parameter) family of closed string solutions representing rotating and pulsating elliptical strings.

Noncommutative geometry, quantum effects and DBI-scaling in the collapse of D0-D2 bound states

We study fluctuations of time-dependent fuzzy two-sphere solutions of the non-abelian DBI action of D0-branes, describing a bound state of a spherical D2-brane with N D0-branes. The quadratic action for small fluctuations is shown to be identical to that obtained from the dual abelian D2-brane DBI action, using the non-commutative geometry of the fuzzy two-sphere. For some of the fields, the linearized equations take the form of solvable Lam\'e equations. We define a large-N DBI-scaling limit, with vanishing string coupling and string length, and where the gauge theory coupling remains finite. In this limit, the non-linearities of the DBI action survive in both the classical and the quantum context, while massive open string modes and closed strings decouple. We describe a critical radius where strong gauge coupling effects become important. The size of the bound quantum ground state of multiple D0-branes makes an intriguing appearance as the radius of the fuzzy sphere, where the maximal angular momentum quanta become strongly coupled.

Binaries and core-ring structures in self-gravitating systems

Low-energy states of self-gravitating systems with finite angular momentum are considered. A constraint is introduced to confine cores and other condensed objects within the system boundaries by gravity alone. This excludes previously observed astrophysically irrelevant asymmetric configurations with a single core. We show that, for an intermediate range of a short-distance cutoff and small angular momentum, the equilibrium configuration is an asymmetric binary. For larger angular momentum or for a smaller range of the short-distance cutoff, the equilibrium configuration consists of a central core and an equatorial ring. The mass of the ring varies between zero for vanishing rotation and the full system mass for the maximum angular momentum L(max) a localized gravitationally bound system can have. The value of L(max) scales as square root of ((ln(1/x0)), where x0 is a ratio of a short-distance cutoff range to the system size. An example of the soft gravitational potential is considered; the conclusions are shown to be valid for other forms of short-distance regularization.

Bias Momentum Attitude Control System Using Energy/Momentum Wheels

The integrated power and attitude control for a bias momentum attitude control system is investigated. A pair of counter spinning wheels is used to provide the bias angular momentum and store/discharge energy for power requirement of the devices on the spacecraft. The roll/yaw motion is controlled by pitch magnetic dipole moment. The torque based control law of the wheels is designed, so that the desired pitch control torque is provided and the operation of charging/discharging energy is carried out based on the given power. System singularity in the control law of wheels is fully avoided by keeping the wheels counter spinning. A power management scheme using kinetic energy feedback is proposed to keep energy balance, which can avoid wheel saturation caused by superfluous energy. The minimum moment of inertia of the wheels is limited by the maximum bias angular momentum and the minimum energy, such constrains are analyzed in combination with the geometrical method. Numerical simulation results are presented to demonstrate the effectiveness of the control scheme.

On the correspondence between a screw dislocation in gradient elasticity and a regularized vortex

It is shown that the extreme Kerr black hole, i.e. the one with the maximal angular momentum for a given mass, is the only candidate for a black hole limit of rotating fluid bodies in equilibrium.

Quasistationary collapse to the extreme Kerr black hole

AbstractIt is shown that the extreme Kerr black hole, i.e. the one with the maximal angular momentum for a given mass, is the only candidate for a black hole limit of rotating fluid bodies in equilibrium.