Search results for "chirality"
showing 10 items of 188 documents
Proton polarizabilities: status, relevance, prospects
2013
This is a brief review of the status of understanding the proton polarizabilities in chiral perturbation theory and of their relevance to the `proton charge radius puzzle'.
Surface Plasmon Platform for Angle-Resolved Chiral Sensing
2019
Chiral sensitive techniques have been used to probe the fundamental symmetries of the universe, study biomolecular structures, and even develop safe drugs. As chiral signals are inherently weak and...
Near-unity third-harmonic circular dichroism driven by a quasibound state in the continuum in asymmetric silicon metasurfaces
2021
We use numerical simulations to demonstrate third-harmonic generation with near-unity nonlinear circular dichroism (CD) and high conversion efficiency $({10}^{\ensuremath{-}2}\phantom{\rule{4pt}{0ex}}{\text{W}}^{\ensuremath{-}2})$ in asymmetric Si-on-$\mathrm{Si}{\mathrm{O}}_{2}$ metasurfaces. The working principle relies on the spin-selective excitation of a quasibound state in the continuum, characterized by a very high $(g{10}^{5})$ quality factor. By tuning multimode interference with the variation of the metasurface geometrical parameters, we show the possibility to control both linear CD and nonlinear CD. Our results pave the way for the development of all-dielectric metasurfaces for …
Dynamic domain wall chirality rectification by rotating magnetic fields
2015
We report on the observation of magnetic vortex domain wall chirality reversal in ferromagnetic rings that is controlled by the sense of rotation of a magnetic field. We use time-resolved X-ray microscopy to dynamically image the chirality-switching process and perform micromagnetic simulations to deduce the switching details from time-resolved snapshots. We find experimentally that the switching occurs within less than 4 ns and is observed in all samples with ring widths ranging from 0.5 μm to 2 μm, ring diameters between 2 μm and 5 μm, and a thickness of 30 nm, where a vortex domain wall is present in the magnetic onion state of the ring. From the magnetic contrast in the time-resolved im…
Magnetic Gradiometer for Detection of Zero- and Ultralow-Field Nuclear Magnetic Resonance
2019
Magnetic sensors are important for detecting nuclear magnetization signals in nuclear magnetic resonance (NMR). As a complementary analysis tool to conventional high-field NMR, zero- and ultralow-field (ZULF) NMR detects nuclear magnetization signals in the sub-microtesla regime. Current ZULF NMR systems are always equipped with high-quality magnetic shieldings to ensure that ambient magnetic field noise does not dwarf the magnetization signal. An alternative approach is to separate the magnetization signal from the noise based on their differing spatial profiles, as can be achieved using a magnetic gradiometer. Here, we present a gradiometric ZULF NMR spectrometer with a magnetic gradient …
A minimal Gō-model for rebuilding whole genome structures from haploid single-cell Hi-C data
2020
Abstract We present a minimal computational model, which allows very fast, on-the-fly construction of three dimensional haploid interphase genomes from single-cell Hi-C contact maps using the HOOMD-blue molecular dynamics package on graphics processing units. Chromosomes are represented by a string of connected beads, each of which corresponds to 100,000 base pairs, and contacts are mediated via a structure-based harmonic potential. We suggest and test two minimization protocols which consistently fold into conformationally similar low energy states. The latter are similar to previously published structures but are calculated in a fraction of the time. We find evidence that mere fulfillment…
A Model of Comprehensive Unification
2017
Comprehensive – that is, gauge and family – unification using spinors has many attractive features, but it has been challenged to explain chirality. Here, by combining an orbifold construction with more traditional ideas, we address that difficulty. Our candidate model features three chiral families and leads to an acceptable result for quantitative unification of couplings. A potential target for accelerator and astronomical searches emerges.
Reply to “Comment on ‘Polarizability of the pion: No conflict between dispersion theory and chiral perturbation theory’”
2009
We show that the alleged discrepancies between chiral perturbation theory (ChPT) and dispersion theory, reported for the polarizability of the pion by Fil'kov and Kashevarov [Phys. Rev. C 72, 035211 (2005)], result from applying dispersion theory to nonanalytic functions.
The polarizability of the pion: no conflict between dispersion theory and chiral perturbation theory
2008
Recent attempts to determine the pion polarizability by dispersion relations yield values that disagree with the predictions of chiral perturbation theory. These dispersion relations are based on specific forms for the absorptive part of the Compton amplitudes. The analytic properties of these forms are examined, and the strong enhancement of intermediate-meson contributions is shown to be connected with spurious singularities. If the basic requirements of dispersion relations are taken into account, the results of dispersion theory and effective field theory are not inconsistent.
ScalarΛNandΛΛinteraction in a chiral unitary approach
2006
We study the central part of the {lambda}N and {lambda}{lambda} potential by considering the correlated and uncorrelated two-meson exchange in addition to the {omega} exchange contribution. The correlated two-meson exchange is evaluated within a chiral unitary approach. We find that a short-range repulsion is generated by the correlated two-meson potential, which also produces an attraction in the intermediate-distance region. The uncorrelated two-meson exchange produces a sizable attraction in all cases that is counterbalanced by the {omega} exchange contribution.