Effect Of Torsional Stress Research Articles

The Effect of Torsional Stresses on the Giant Magnetoimpedance of Amorphous Microwires with Induced Magnetic Anisotropy

The Effect of Torsional Stresses on the Giant Magnetoimpedance of Amorphous Microwires with Induced Magnetic Anisotropy

Torsional behavior of chromatin is modulated by rotational phasing of nucleosomes.

Torsionally stressed DNA plays a critical role in genome organization and regulation. While the effects of torsional stresses on naked DNA have been well studied, little is known about how these stresses propagate within chromatin and affect its organization. Here we investigate the torsional behavior of nucleosome arrays by means of Brownian dynamics simulations of a coarse-grained model of chromatin. Our simulations reveal a strong dependence of the torsional response on the rotational phase angle Ψ0 between adjacent nucleosomes. Extreme values of Ψ0 lead to asymmetric, bell-shaped extension-rotation profiles with sharp maxima shifted toward positive or negative rotations, depending on the sign of Ψ0, and to fast, irregular propagation of DNA twist. In contrast, moderate Ψ0 yield more symmetric profiles with broad maxima and slow, uniform propagation of twist. The observed behavior is shown to arise from an interplay between nucleosomal transitions into states with crossed and open linker DNAs and global supercoiling of arrays into left- and right-handed coils, where Ψ0 serves to modulate the energy landscape of nucleosomal states. Our results also explain the torsional resilience of chromatin, reconcile differences between experimentally measured extension-rotation profiles, and suggest a role of torsional stresses in regulating chromatin assembly and organization.

Asymmetric giant magnetoimpedance of amorphous microwires under the action of torsional stresses

The effect of torsional stresses on the directcurrentinduced asymmetric giant magnetoimped� ance in an amorphous microwire with negative magnetostriction has been theoretically studied. The appear� ance of asymmetry in the dependence of the impedance on the external magnetic field is related to the inter� action of a circular field of the direct current and a helicoidal anisotropy of the wire that is induced by the applied torsional stresses. It is established that torsional stresses significantly influence a threshold value of the currentgenerated bias field, above which a hysteres is in the dependence of the impedance on the external field disappears. The obtained results can be used for the creation of weak magneticfield sensors.

Asymmetric magnetoimpedance in amorphous microwires due to bias current: Effect of torsional stress

The influence of torsional stress on the asymmetric magnetoimpedance in a glass-coated negative magnetostrictive amorphous microwire due to bias current is studied theoretically. The longitudinal and off-diagonal impedance components are found assuming a simplified spatial distribution of the magnetoelastic anisotropy induced by the torsional stress. The asymmetry in the field dependence of the impedance components is attributed to the combination of the circular magnetic field produced by the bias current and a helical anisotropy induced by the torsional stress. The asymmetry in the magnetoimpedance and the low-field hysteresis are analyzed as a function of the bias current and torsional stress. It is shown that the application of torsional stress significantly changes the value of the bias current required to suppress the hysteresis effect. The results obtained may be useful for applications in magnetic-field and stress sensors.

Torsional dependence of second-harmonic amplitude of giant magnetoimpedance in FeCoSiB amorphous wire

The effect of torsional stresses in the magnetoimpedance response of a (Co/sub 0.94/Fe/sub 0.06/)/sub 72.5/Si/sub 12.5/B/sub 15/ amorphous wire is analyzed. In particular, the occurrence of a second-harmonic contribution of the magnetoimpedance voltage is analyzed and compared with the first-harmonic amplitude (impedance). The evolution of both harmonic components are correlated to the estimated permeability contributions obtained through the analysis of the estimated rotational hysteresis loops. The highest torsional dependence of the second-harmonic contribution can be used in the development of new magnetoelastic sensors.

回転曲げ疲労破面のＸ線フラクトグラフィ

X-ray fractography is a technique for estimating the loading conditions at fractures from the information obtained by X-ray stress analysis on fatigue fractured surfaces. This technique was applied to a rotating bending fatigue fractured surface. The specimens were actual size “Shinkansen (Bullet train)” axles bench tested at the Railway Technology Research Institute.The axles are 209 or 210mm in diameter, induction hardened 0.38% carbon steel (JIS S38C) with semi-elliptical artificial flaws. Fatigue fracture was caused mainly by rotating bending stress, and the effect of torsional stress was very slight. The residual stress at the fatigue fractured surface was tensile at the initial crack propagation region, increased to a tensile maximum value, then decreased to a compressive maximum value and increased again toward zero near the final fractured area.The results were compared to the residual stress distribution on fatigue fractured surfaces of CCT specimens under a tension-compression fatigue load of stress ratio R=-1. The general tendencies of residual stress distributions on both fatigue fractured surfaces agree well qualitatively.

Effects of Torsional Stress on the Interaction of DNA with Radiation and Chemicals

Abstract The purpose of this work is to investigate a mechanism for synergistic interaction between exposures to radiation and chemicals. The mechanism that we propose is based on the torsional stress that DNA sequences in active genes experience as a consequence of gene expression. Our approach involves experiments on an in vitro plasmid DNA system in conjunction with computer modeling to aid in the interpretation of experimental findings. We have observed that the torsional stress from normal physiological levels of negative supercoiling increases the susceptibility of plasmid pIBI 30 to the induction of single-strand breaks by X rays. Calculations of the conformational equilibrium of pIBI 30 at various levels of torsional stress identified a region of the plasmid that was rich in adenine-thymine (A-T) base pairs and particularly sensitive to melting of the double helix. In this article we present experimental evidence that this region of pIBI 30 is hypersensitive to radiation-induced strand scission. S...

Abstract: Effects of torsional stress on magnetic tape cores carrying electric current

Extensive investigations on the effects of torsional stress on magnetic tape cores carrying electric current are reported. A number of core samples including Metglass 2826, 2605, 2605A; three amorphous samples x, y, z belonging to the FeCo, Fe, and FeNi groups respectively; and several others including 50%Ni–Fe cores were studied. The following main phenomena are observed: (a) when a ferromagnetic tape core carrying an electric current is twisted, a shift in the two vertical portions of the corresponding B–H loop is observed, the shifts being simultaneous and usually in the same direction (b) the shifts are a function of both the magnitude of the conducting current and the applied torsion (c) the direction of the observed shift, rightwards or leftwards, depends on the direction of the current flow and the torsion (d) the shift is a function of the material of the core sample and its dimensions. Other subphenomena, peculiar to the type of core sample being studied, have also been noted. It is considered that the shifting of the B–H loops is due to the magnetization introduced by torsion interacting with the field due to the core current and the alternating drive field, resulting in asymmetric magnetic flux for each half of the exciting cycle. The above is shown by the proportionality seen for the sample magnetostrictions with respect to the corresponding shifts: the larger the value of magnetostriction the larger being the shift. For an exciting field of 198 ATm−1, 20 Hz, and a core current in the range of several hundred milliamperes, the shifts for the samples x, y, z are respectively in the ratio 1:2.5:8 which are in agreement with the magnetostriction ratio, approximately 0:4:30. AC core current characteristics differ from dc.

The effect of torsional stress on pure twist boundaries

Abstract The twisting behaviour of pure [111] twist boundaries in zone-refined aluminium bicrystals has been studied as a function of torsional stress for two boundary misorientation angles. The bicrystals initially twisted or untwisted at a rapid rate, which steadily decreased with time. This hardening was non-recoverable even after reannealing the samples at 0-98 Tm or removing the surface layer. The effect of the variation of misorientation angle on the experimental results is examined and the implications discussed.

Effect of Torsional Stress on the Electrode Potential of Copper

The emf of a galvanic cell which consisted of a stressed metal electrode and an unstressed metal electrode was measured. The experimental data showed that for low torsional stresses there was a parabolic relationship between the emf and the torsional stress. It was observed that the stressed electrode was more anodic with respect to the unstressed reference electrode in agreement with the majority of the previous investigations. Experimental data of emf and torsional stresses for B & S gauge 12, 14, and 16 hard-drawn copper wires are presented.