Physical metallurgy of Ti–Ni-based shape memory alloys

Recent developments in the research of shape memory alloys

Zero-field splitting in metal complexes

Electron paramagnetic resonance (EPR) spectroscopy provides a variety of tools to study structures and structural changes of large biomolecules or complexes thereof. In order to unravel secondary structure elements, domain arrangements or complex formation, continuous wave and pulsed EPR methods capable of measuring the magnetic dipole coupling between two unpaired electrons can be used to obtain long-range distance constraints on the nanometer scale. Such methods yield reliably and precisely distances of up to 80 A, can be applied to biomolecules in aqueous buffer solutions or membranes, and are not size limited. They can be applied either at cryogenic or physiological temperatures and down to amounts of a few nanomoles. Spin centers may be metal ions, metal clusters, cofactor radicals, amino acid radicals, or spin labels. In this review, we discuss the advantages and limitations of the different EPR spectroscopic methods, briefly describe their theoretical background, and summarize important biological applications. The main focus of this article will be on pulsed EPR methods like pulsed electron-electron double resonance (PELDOR) and their applications to spin-labeled biosystems.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S003358350700460X

Long-range distance determinations in biomacromolecules by EPR spectroscopy.

Restricted diffusion is a common feature of many physicochemical, biological, and industrial processes. Nuclear magnetic resonance techniques are often used to survey the atomic or molecular motion in confining media by applying inhomogeneous magnetic fields to encode the trajectories of spin-bearing particles. The diversity and complexity of diffusive NMR phenomena, observed in experiments, result from the specific properties of reflected Brownian motion. Here the focus is on the mathematical aspects of this stochastic process, their physical interpretations, and their practical applications. The main achievements in this field, from Hahn’s discovery of spin echoes to present-day research, are presented in a unified mathematical language. A long-standing problem of restricted diffusion under arbitrary magnetic field is reformulated in terms of multiple correlation functions of the reflected Brownian motion. Many classical results are retrieved, extended, and critically discussed.

https://pmc.polytechnique.fr/pagesperso/dg/publi/2007_01.pdf

NMR survey of reflected brownian motion

An electromagnetic imaging method for electromagnetically measuring physical parameters of a pipe CJ, CC by means of a plurality of measuring arrangement ZMA, MCMA, MonMa, ImMA comprising a plurality of transmitter coil ZTX, LFTX, DTX and a plurality of receiver coil ZRX1 , ZR2, MRX, MC, PRX1 , PRX2, PRX3, PRX4, PRX5, PRX6, PRX7, PRX8, PRX9, PRX10, PRX11 , PRX12, PRX13, PRX14, PRX15, PRX16, PRX17, PRX18, the transmitter coils and receiver coils being associated so as to form the plurality of measuring arrangement, the plurality of measuring arrangement being adapted to be positioned into the pipe and displaced through the pipe, the physical parameters being measured for a plurality of position along the pipe, the method comprising the steps of: a) determining a first value of an average ratio of magnetic permeability to electrical conductivity and a first value of an average inner diameter of the pipe Z-MES, b) determining an average electromagnetic thickness of the pipe MC-MES, c) determining a second value of the average ratio of magnetic permeability to electrical conductivity and a second value of the average inner diameter of the pipe Mon-MES according to excitation frequencies which are substantially lower than the excitation frequencies used to determine the first values Z-MES, d) determining a first image EMTIM of the pipe electromagnetic thickness and the pipe defects Im-MES, e) discriminating the defects at an inside perimeter of the pipe from the defects at an outside perimeter of the pipe Dis-MES, and f) forming a corrected first image IOFIM of the pipe taking into account a position of the defects.

An electromagnetic imaging method and device

The authors present measurements of the elastic constants on a single crystal of the shape-memory alloy NiTi in a wide temperature range. Step-like anomalies and hysteresis are detected at the austenitic-martensitic phase transition which provide evidence for the strain-order parameter coupling in the pre-martensitic phases. The results are discussed in the framework of existing Landau theory models.

https://iopscience.iop.org/article/10.1088/0953-8984/3/48/004/pdf

Elastic properties of NiTi

ESR and magnetization measurements have been performed up to 14 T in the compound ${\mathrm{CuGeO}}_{3}$. Two kinds of magnetic transitions are observed, between excited states and from the ground state. The former result essentially from a Zeeman splitting of the $S=1$ magnetic triplet state characterizing the spin Peierls gap which exists at the wave vector $\mathbf{Q}=[1,1,1]$ of the magnetic Brillouin zone. The latter provide the first evidence of a Zeeman splitting on a spin Peierls gap. It is observed at $\mathbf{Q}=[0,0,0]$.

High-field electron spin resonance and magnetization in the dimerized phase of CuGeO3.

The 4 K 245-GHz/8.7-T electron paramagnetic resonance spectrum of the stable tyrosyl radical in photosystem II, known as TyrD., has been measured. Illumination at 200 K enhances the signal intensity of TyrD. by a factor of > 40 compared to the signal obtained from dark-adapted samples. This signal enhancement and the unusual line shape of the TyrD. resonance result from the magnetic dipolar coupling of the radical to the manganese cluster involved in oxygen evolution. The relative angular orientation of the manganese cluster with respect to TyrD. has been determined from line-shape analysis. The resonance arising from TyrD. in Tris-washed manganese-free photosystem II sample is also distorted. This effect probably originates from the influence of the nonheme iron on the spin relaxation of the tyrosyl radical. The relative angular orientation of the nonheme iron has also been determined. Oriented samples were used to determine the angular orientation of TyrD. with respect to the membrane plane. Combining angular data with published distances, we have constructed a three-dimensional picture of the relative positions of TyrD., the manganese cluster, and the nonheme iron. The data suggest a more symmetrical placement of the manganese relative to TyrD. and TyrZ, the tyrosine involved in electron transfer, than is usually assumed in current models of photosystem II.

Angular orientation of the stable tyrosyl radical within photosystem II by high-field 245-GHz electron paramagnetic resonance

The apparatus employs the remote field eddy-current (RFEC) inspection technique to electromagnetically measure physical parameters of a metallic pipe. RFEC devices inserted into and displaced along a cylindrical pipes may be used to measure the ratio of pipe thickness to electromagnetic skin-depth and thus allow for the non-invasive detection of flaws or metal loss. Typically these RFEC thickness measurements exhibit a so-called double-indication of flaws, an undesired artifact due to a double-peaked geometrical sensitivity function of the device. The method describes a means by which this double indication artifact may be removed by an appropriate processing of RFEC measurements performed by an apparatus specifically designed for this purpose. The invention is particularly well designed for applications in the oilfield industry.

T. M. Brill

Papers

An electromagnetic imaging method and device

Elastic properties of NiTi

High-field electron spin resonance and magnetization in the dimerized phase of CuGeO3.

Angular orientation of the stable tyrosyl radical within photosystem II by high-field 245-GHz electron paramagnetic resonance

Method and apparatus for removal of the double indication of defects in remote eddy current inspection of pipes