Brillouin Light Scattering from Magnetic Excitations.

Brillouin light scattering (BLS) has been established as a standard technique to study thermally excited sound waves with frequencies up to ~100 GHz in transparent materials. In BLS experiments, one usually uses a Fabry-Pérot interferometer (FPI) as a spectrometer. The drastic improvement of the FPI contrast factor over 1010 by the development of the multipass type and the tandem multipass type FPIs opened a gateway to investigate low energy excitations (hω ≤ 1 meV) in various research fields of condensed matter physics, including surface acoustic waves and spin waves from opaque surfaces. Over the last four decades, the BLS technique has been successfully applied to study collective spin waves (SWs) in various types of magnetic structures including thin films, ultrathin films, multilayers, superlattices, and artificially arranged dots and wires using high-contrast FPIs. Now, the BLS technique has been fully established as a unique and powerful technique not only for determination of the basic magnetic constants, including the gyromagnetic ratio, the magnetic anisotropy constants, the magnetization, the SW stiffness constant, and other features of various magnetic materials and structures, but also for investigations into coupling phenomena and surface and interface phenomena in artificial magnetic structures. BLS investigations on the Fe/Cr multilayers, which exhibit ferromagnetic-antiferromagnetic arrangements of the adjacent Fe layer's magnetizations depending on the Cr layer's thickness, played an important role to open the new field known as "spintronics" through the discovery of the giant magnetoresistance (GMR) effect. In this review, I briefly surveyed the historical development of SW studies using the BLS technique and theoretical background, and I concentrated our BLS SW studies performed at Tohoku University and Ishinomaki Senshu University over the last thirty five years. In addition to the ferromagnetic SW studies, the BLS technique can be also applied to investigations of high-frequency magnetization dynamics in superparamagnetic (SPM) nanogranular films in the frequency domain above 10 GHz. One can excite dipole-coupled SPM excitations under external magnetic fields and observe them via the BLS technique. The external field strength determines the SPM excitations' frequencies. By performing a numerical analysis of the BLS spectrum as a function of the external magnetic field and temperature, one can investigate the high-frequency magnetization dynamics in the SPM state and determine the magnetization relaxation parameters.

A Randomized Controlled Trial for the Intervention Effect of Early Exercise Therapy on Axial Pain after Cervical Laminoplasty.

Introduction: Cervical isometric muscle strengthening and cervical range of motion (ROM) training are recommended after laminoplasty (LP). However, their preventive effects on axial pain are unclear. We examined whether neck extension muscle strengthening and cervical ROM training from the early postoperative period effectively suppress postoperative axial pain. Methods: Sixty-one patients undergoing a muscle-preserving LP attached to C2 and C7 for cervical spondylotic myelopathy or ossification of the posterior longitudinal ligament were randomly allocated to the cervical exercise (33 patients) or nonexercize (28 patients) groups. Postoperative cervical collars were not worn in any cases. The cervical exercise group underwent neck extension isometric muscle strengthening and cervical ROM exercises for 3 months starting on postoperative day 2. Changes in axial pain (visual analog scale [VAS]) from baseline at 2 weeks and 3 months after surgery were evaluated as the primary outcome. Cervical muscle strength, cervical ROM, and Japanese Orthopedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ) scores were evaluated as secondary outcomes. Results: Axial pain was significantly exacerbated at 2 weeks after LP compared with before surgery, and then, a significant improvement was observed at 3 months after surgery. No significant interaction was observed between the intervention and nonintervention groups. There was no difference in secondary outcomes between groups. The change in the VAS of axial pain from before surgery to 3 months after surgery showed a greater decreased neck extension muscle strength resulting in severer axial pain. Conclusions: Cervical muscle strengthening and cervical ROM exercise from the early postoperative period did not relieve axial pain at 2 weeks and 3 months after a muscle-preserving LP attached to C2 and C7. No significant difference in neck extension muscle and cervical movement was observed between the intervention and nonintervention groups. Therefore, a muscle-preserving LP attached to C2 and C7 is a good strategy to prevent axial pain in the early postoperative period.Clinical Trials Registration Number: UMIN000040692.

Can Hip-Knee Line Angle Distinguish the Size of Pelvic Incidence?-Development of Quick Noninvasive Assessment Tool for Pelvic Incidence Classification.

This study aimed to explore effective measurement angles for pelvic incidence (PI) classification and to develop a quick, noninvasive assessment tool for PI classification. We defined five variation types of hip-knee line (HKL) angles and tested the discrimination ability of the receiver operating characteristic (ROC) analysis using 125 photographs of upright standing posture from the right lateral side. ROC analysis revealed an applicable HKL angle defined by the line connecting the most raised part of the buttock and the central point of the knee and the midthigh line. The acceptable cut-off points for discriminating small or large PIs in terms of HKL angle were 18.5° for small PI (sensitivity, 0.91; specificity, 0.79) and 21.5° for large PI discrimination (sensitivity, 0.74; specificity, 0.72). In addition, we devised a quick noninvasive assessment tool for PI classification using the cut-offs of the HKL angle with a view to practical application. The results of intra- and inter-rater reliability ensured a substantial/moderate level of the tool (Cohen's kappa coefficient, 0.79; Fleiss's kappa coefficient, 0.50-0.54). These results revealed that the HKL angle can distinguish the size of the PI with a high/moderate discrimination ability. Furthermore, the tool indicated acceptable inter-/intra-rater reliability for practical applications.