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Consider, for example, a baseball, pitched as a gyroball, so that its spin axis is aligned with the direction of the pitch. It will have one helicity with respect to the point of view of the players on the field, but would appear to have a flipped helicity in any frame moving faster than the ball.
Helicity is a pseudo-scalar quantity: it changes sign under change from a right-handed to a left-handed frame of reference; it can be considered as a measure of the handedness (or chirality) of the flow. Helicity is one of the four known integral invariants of the Euler equations; the other three are energy, momentum and angular momentum.
The chirality of a molecule that has a helical, propeller, or screw-shaped geometry is called helicity [5] or helical chirality. [6] [7] The screw axis or the D n, or C n principle symmetry axis is considered to be the axis of chirality. Some sources consider helical chirality to be a type of axial chirality, [7] and some do not.
To see an in depth discussion of the two with examples, which also shows how chirality and helicity approach the same thing as speed approaches that of light, click the link entitled "Chirality and Helicity in Depth" on the same page. History of science: parity violation; Helicity, Chirality, Mass, and the Higgs (Quantum Diaries blog)
TURBOMOLE is an ab initio computational chemistry program that implements various quantum chemistry methods. It was initially developed by the group of Prof. Reinhart Ahlrichs at the University of Karlsruhe. In 2007, TURBOMOLE GmbH, founded by R. Ahlrichs, F. Furche, C. Hättig, W. Klopper, M. Sierka, and F. Weigend, took over the ...
The two-component helicity eigenstates satisfy ^ (^) = (^) where are the Pauli matrices, ^ is the direction of the fermion momentum, = depending on whether spin is pointing in the same direction as ^ or opposite.
Quantum ESPRESSO (Quantum Open-Source Package for Research in Electronic Structure, Simulation, and Optimization; QE) [2] [3] is a suite for first-principles electronic-structure calculations and materials modeling, distributed for free and as free software under the GNU General Public License.
APBS (previously also Advanced Poisson-Boltzmann Solver) is a free and open-source software for solving the equations of continuum electrostatics intended primarily for the large biomolecular systems. [1] [2] It is available under the BSD license. PDB2PQR prepares the protein structure files from Protein Data Bank for use with APBS.