Search results for "rotation"

Silence of Binary Kerr Black Holes

2020

A nontrivial S matrix generally implies a production of entanglement: starting with an incoming pure state, the scattering generally returns an outgoing state with nonvanishing entanglement entropy. It is then interesting to ask if there exists a nontrivial S matrix that generates no entanglement. In this Letter, we argue that the answer is the S-matrix for the scattering of classical black holes. We study the spin entanglement in the scattering of arbitrary spinning particles. Augmenting the S-matrix with Thomas–Wigner rotation factors, we derive the entanglement entropy from the gravitational induced 2→2 amplitude. In the Eikonal limit, we find that the relative entanglement entropy, defi…

A Detailed Account of The Inconsistent Labelling Problem of Stutter-Preserving Partial-Order Reduction

2021

One of the most popular state-space reduction techniques for model checking is partial-order reduction (POR). Of the many different POR implementations, stubborn sets are a very versatile variant and have thus seen many different applications over the past 32 years. One of the early stubborn sets works shows how the basic conditions for reduction can be augmented to preserve stutter-trace equivalence, making stubborn sets suitable for model checking of linear-time properties. In this paper, we identify a flaw in the reasoning and show with a counter-example that stutter-trace equivalence is not necessarily preserved. We propose a stronger reduction condition and provide extensive new correc…

Influence of Operator's Experience on Root Canal Shaping Ability with a Rotary Nickel-Titanium Single-File Reciprocating Motion System

2013

The aim of this study was to evaluate the influence of the operator's experience on the shaping of double-curvature simulated root canals with a nickel-titanium single-file reciprocating motion system.Sixty double-curvature root canals simulated in methacrylate blocks were prepared by 10 students without any experience in endodontics and by 10 professionals who had studied endodontics at the postgraduate level. The Reciproc-VDW system's R25 file was used in the root canal preparation. The blocks were photographed before and after the instrumentation, and the time of instrumentation was also evaluated. Changes in root canal dimensions were analyzed in 6 positions.Significant differences (P.0…

Influence of Whole-Body Dynamics on 15N PISEMA NMR Spectra of Membrane Proteins: A Theoretical Analysis

2009

AbstractMembrane proteins and peptides exhibit a preferred orientation in the lipid bilayer while fluctuating in an anisotropic manner. Both the orientation and the dynamics have direct functional implications, but motions are usually not accessible, and structural descriptions are generally static. Using simulated data, we analyze systematically the impact of whole-body motions on the peptide orientations calculated from two-dimensional polarization inversion spin exchange at the magic angle (PISEMA) NMR. Fluctuations are found to have a significant effect on the observed spectra. Nevertheless, wheel-like patterns are still preserved, and it is possible to determine the average peptide til…

Canonical azimuthal rotations and flanking residues constrain the orientation of transmembrane helices.

2013

AbstractIn biological membranes the alignment of embedded proteins provides crucial structural information. The transmembrane (TM) parts have well-defined secondary structures, in most cases α-helices and their orientation is given by a tilt angle and an azimuthal rotation angle around the main axis. The tilt angle is readily visualized and has been found to be functionally relevant. However, there exist no general concepts on the corresponding azimuthal rotation. Here, we show that TM helices prefer discrete rotation angles. They arise from a combination of intrinsic properties of the helix geometry plus the influence of the position and type of flanking residues at both ends of the hydrop…

Quantum Chemical Parametrization and Spectroscopic Characterization of the Frenkel Exciton Hamiltonian for a J-Aggregate Forming Perylene Bisimide Dye

2012

Quantum chemical and quantum dynamical calculations are performed for a bay-substituted perylene bisimide dye up to its hexameric aggregate. The aggregate structure is determined by employing the self-consistent charge density functional tight-binding (SCC-DFTB) approach including dispersion corrections. It is characterized by a stabilization via two chains of hydrogen bonds facilitated by amide functionalities. Focusing on the central embedded dimer, the Coulomb coupling for this J-aggregate is determined by means of the time-dependent density functional theory (TDDFT) to be -514 cm(-1). Exciton vibrational coupling is treated within the shifted oscillator model from which five strongly co…

United Atom Force Field for Molecular Dynamics Simulations of 1,4-Polybutadiene Based on Quantum Chemistry Calculations on Model Molecules

1998

We present a united atom force field for simulations of 1,4-polybutadiene based on ab initio quantum chemistry calculations on model molecules. The geometries and energies of conformers and rotational energy barriers in model alkenes and dienes have been determined from high-level quantum chemistry calculations. A rotational isomeric state (RIS) model for 1,4-polybutadiene based on the conformer geometries and energies of the model molecules has been derived. The characteristic ratio and its temperature dependence for cis-1,4-polybutadiene and trans-1,4-polybutadiene, and the characteristic ratio of a random copolymer of cis and trans units, as predicted by the RIS model, are in good agreem…

A Dendrimer Chiroptical Switch Based on the Reversible Intramolecular Photoreaction of Anthracene and Benzene Rings

2010

A series of Fréchet-type dendrimers with 9-benzyloxymethylanthracene cores were synthesized and characterized. The chiral source for the dendrimers was an (S)-2-methyl-1-butoxy group in the 3-position of the benzene ring. Irradiation at 366 nm of a dilute benzene solution led to the formation of two diastereomers (1:1) through a quantitative intramolecular [4pi+4pi] cycloaddition between the central anthracene ring and the neighboring benzene ring. The process can be reversed with 254 nm UV light or heat. The benzene rings in the dendrons work as a light-harvesting system. The optical rotation values measured for the reversible process showed fatigue resistance. Thus, a promising new type o…

2018

AbstractKnowledge of the Earth’s changing rotation is fundamental to positioning objects in space and on the planet. Nowadays, the Earth’s orientation in space is expressed by five Earth Orientation Parameters (EOP). Many applications in astronomy, geosciences, and space missions require accurate EOP predictions. Operational predictions are released daily by the Rapid Service/Prediction Centre of the International Earth Rotation and Reference Systems Service (IERS). The prediction procedures and performances differ for the three EOP classes: polar motion, rotation angle (UT1-UTC), and the two celestial pole offsets (CPO), dX and dY. The IERS Annual Report 2016 shows Rapid Service CPO predic…

Benefits of learning technologies in medical training, from full-scale simulators to virtual reality and multimedia presentations

2010

The rapid growth of technology provides a wide range of new learning tools such as multimedia presentations of materials, interactive animated images for anatomy learning, 3-D models, full-scale (FS) patient simulators, and microworld training software, which are virtual reality tools that include high-level interactive haptic properties. These new learning approaches have been recently used in medical training and education.