31 research outputs found
Pattern recognition with a magnon-scattering reservoir
Magnons are elementary excitations in magnetic materials and undergo
nonlinear multimode scattering processes at large input powers. In experiments
and simulations, we show that the interaction between magnon modes of a
confined magnetic vortex can be harnessed for pattern recognition. We study the
magnetic response to signals comprising sine wave pulses with frequencies
corresponding to radial mode excitations. Three-magnon scattering results in
the excitation of different azimuthal modes, whose amplitudes depend strongly
on the input sequences. We show that recognition rates above 95\% can be
attained for four-symbol sequences using the scattered modes, with strong
performance maintained with the presence of amplitude noise in the inputs
Genetic polymorphisms of manganese-superoxide dismutase and glutathione-S-transferase in chronic alcoholic pancreatitis
Chronic alcohol consumption is a major risk factor for the development of chronic pancreatitis. However, chronic pancreatitis occurs only in a minority of heavy drinkers. This variability may be due to yet unidentified genetic factors. Several enzymes involved in the degradation of reactive oxidants and xenobiotics, such as glutathione-S-transferase P1 (GSTP1) and manganese-superoxide dismutase (MnSOD) reveal functional polymorphisms that affect the antioxidative capacity and may therefore modulate the development of chronic pancreatitis and long-term complications like endocrine and exocrine pancreatic insufficiency. Two functional polymorphisms of the MnSOD and the GSTP1 gene were assessed by polymerase chain reaction and restriction fragment length polymorphism in 165 patients with chronic alcoholic pancreatitis, 140 alcoholics without evidence of pancreatic disease and 160 healthy control subjects. The distribution of GSTP1 and MnSOD genotypes were in Hardy-Weinberg equilibrium in the total cohort. Genotype and allele frequencies for both genes were not statistically different between the three groups. Although genotype MnSOD Ala/Val was seemingly associated with the presence of exocrine pancreatic insufficiency, this subgroup was too small and the association statistically underpowered. None of the tested genotypes affected the development of endocrine pancreatic insufficiency. Polymorphisms of MnSOD and GSTP1 are not associated with chronic alcoholic pancreatitis. The present data emphasize the need for stringently designed candidate gene association studies with well-characterized cases and controls and sufficient statistical power to exclude chance observation
Magnetic domain-wall motion by propagating spin waves
We found by micromagnetic simulations that the motion of a transverse wall
(TW) type domain wall in magnetic thin-film nanostripes can be manipulated via
interaction with spin waves (SWs) propagating through the TW. The velocity of
the TW motion can be controlled by changes of the frequency and amplitude of
the propagating SWs. Moreover, the TW motion is efficiently driven by specific
SW frequencies that coincide with the resonant frequencies of the local modes
existing inside the TW structure. The use of propagating SWs, whose frequencies
are tuned to those of the intrinsic TW modes, is an alternative approach for
controlling TW motion in nanostripes
Nontrivial Aharonov-Bohm effect and alternating dispersion of magnons in cone-state ferromagnetic rings
Soft magnetic dots in the form of thin rings have unique topological
properties. They can be in a vortex state with no vortex core. Here, we study
the magnon modes of such systems both analytically and numerically. In an
external magnetic field, magnetic rings are characterized by easy-cone
magnetization and shows a giant splitting of doublets for modes with the
opposite value of the azimuthal mode quantum number. The effect of the
splitting can be refereed as a magnon analog of the topology-induced
Aharonov-Bohm effect. For this we develop an analytical theory to describe the
non-monotonic dependence of the mode frequencies on the azimuthal mode number,
influenced by the balance between the local exchange and non-local dipole
interactions.Comment: 8 pages, 3 figure
A spin-wave frequency doubler by domain wall oscillation
We present a new mechanism for spin-wave excitation using a pinned domain
wall which is forced to oscillate at its eigenfrequency and radiates spin
waves. The domain wall acts as a frequency doubler, as the excited spin waves
have twice the frequency of the domain wall oscillation. The investigations
have been carried out using micromagnetic simulations and enable the
determination of the main characteristics of the excited spin-waves such as
frequency, wavelength, and velocity. This behavior is understood by the
oscillation in the perpendicular magnetization which shows two anti-nodes
oscillating out of phase with respect to each other.Comment: 8 pages, 3 figure