Daiichi Institute of Technology

Abstract Study aim: This study aimed to analyze the compensatory mechanisms during shoulder abduction by increased scapulothoracic joint upward rotation, focusing on acromiohumeral distance, shoulder muscle forces, and glenohumeral joint stability, using a musculoskeletal model simulation. Material and methods: Fifteen healthy males performed shoulder abduction along scapular plane. Acromiohumeral distance, shoulder muscle forces, and glenohumeral joint stability were estimated using a musculoskeletal model. Data estimated from the three models with different scapulothoracic joint upward rotation were compared using one-dimensional statistical parametric mapping. Differences among three models were analyzed using one-way repeated measures analysis of variance. As a post hoc test, paired t -tests with Bonferroni correction for multiple comparisons were used. Results: The model that increased scapulothoracic joint upward rotation showed significantly greater acromiohumeral distance, and greater muscle forces of supraspinatus and deltoid compared with the models with normal scapulothoracic joint upward rotation. Conversely, glenohumeral joint stability significantly decreased from the mid and late phase of arm elevation in the increased scapulothoracic joint upward rotation model. Conclusions: During shoulder abduction, increased scapulothoracic joint upward rotation magnified acromiohumeral distance for pain avoidance and contributed to increased muscle forces; it also decreased glenohumeral joint stability. In conclusion, the current study revealed the positive and negative aspects associated with increased scapulothoracic joint upward rotation. Therapists engaging in shoulder rehabilitation should remain mindful of these issues.

This paper presents the development of a mobile diary application in conjunction with a robotics-based smart device. This system was designed to address the challenges faced by elderly individuals, such as loneliness and social isolation, which can result from low self-efficacy. The app comprises a graphical user interface, an experience extraction model, a self-growing memory agent, a chat agent, and a feedback interactive. The latter processes diary entries from elderly users, generating empathic responses based on successful experiences that match the individual's capabilities. This is done while learning and adapting to their behavioral patterns and emotional states. By recognizing the user's emotions and history of human-like interactions, and by integrating user feedback, the system aims to motivate the behavior of elderly people, thereby increasing their self-efficacy and improving their overall well-being.

We often encounter a situation where linear wave equations around a black hole solution can be regarded as continuous deformations of simpler ones, or modifications from the general relativity case by continuous parameters. We develop a general framework to compute high-order perturbative corrections to quasinormal mode frequencies in such deformed problems. Our method has many applications, and it allows us to compute numerical values of the high-order corrections very accurately. For several examples, we perform this computation explicitly and discuss analytic properties of the quasinormal mode frequencies for deformation parameters.

Roller massage has been recognized as an effective intervention for managing various conditions. However, data on the effects of roller massage on the dynamic mechanisms of the myofascial and soft tissues of the lower back are limited. This study aimed to examine the effect of the self-myofascial release of the lower back on myofascial gliding, lumbar flexibility, and abdominal trunk muscle strength using a roller massager. This crossover study included 24 college athletes who underwent three interventions—roller massage, static stretching, and control (rest). Before and after the intervention, lumbar and fascial gliding were evaluated using ultrasonography. Long-seat anteflexion (lumbar flexibility) and abdominal trunk muscle strength were assessed. The movement velocities of the subcutaneous tissue and the multifidus muscle over time were calculated using echo video analysis software, and gliding was estimated using the cross-correlation coefficient between the velocities. Gliding, lumbar flexibility, and abdominal trunk muscle strength showed significant intervention-by-time interactions. Roller massage significantly improved gliding, lumbar flexibility, and abdominal trunk muscle strength. The self-myofascial release of the lower back using a roller massager improved the lumbar/fascia gliding, lumbar flexibility, and abdominal trunk muscle strength compared to static stretching.

In order to investigate the effect of microstructure in the surface layer produced by shot peening on fatigue properties of a maraging steel, rotating bending fatigue tests were carried out using shot-peened specimens and electro-polished ones of a 350 grade 18% Ni maraging steel. A grain refinement and a precipitation of reversion austenite were confirmed in the surface layer of the shot-peened specimen. Ring-shaped fracture surface along the surface layer in the shot-peened specimen was formed by coalescence of a surface crack and an internal one and difference in the grain sizes between the ring-shaped surface layer and the matrix. Fatigue strength in the shot-peened specimen was strengthened due to the grain refinement and the precipitation of reversion austenite, in addition to hardening and formation of compressive residual stress.

We propose a physically sensible formulation of initial value problem for black hole perturbations in higher-order scalar–tensor theories. As a first application, we study monopole perturbations around stealth Schwarzschild solutions in a shift- and reflection-symmetric subclass of degenerate higher-order scalar–tensor (DHOST) theories. In particular, we investigate the time evolution of the monopole perturbations by solving a two-dimensional wave equation and analyze the Vishveshwara’s classical scattering experiment, i.e., the time evolution of a Gaussian wave packet. As a result, we confirm that stealth Schwarzschild solutions in the DHOST theory are dynamically stable against the monopole perturbations with the wavelength comparable or shorter than the size of the black hole horizon. We also find that the damped oscillations at the late time do not show up unlike the ringdown phase in the standard case of general relativity. Moreover, we investigate the characteristic curves of the monopole perturbations as well as a static spherically symmetric solution with monopole hair.

A photon sphere is known as the geometrical structure shaping a black hole shadow. The mechanism is well understood for static or stationary black hole spacetimes such as the Schwarzschild and the Kerr spacetimes. In this paper, we investigate and explicitly specify a photon sphere that shapes a black hole shadow in a dynamical spacetime while taking the global structure of the spacetime into account. We consider dynamical and eternal black hole cases of the Vaidya spacetime, which represents a spherically symmetric black hole with accreting null dust. First, we numerically show that there are the dynamical photon sphere and photon orbits corresponding to the shadow edge in a moderate accretion case. Second, the photon spheres are derived analytically in special cases. Finally, we discuss the relation between our photon sphere and the several notions defined as a photon sphere generalization.

Rotating bending fatigue tests were carried out to investigate the effect of microstructure in subsurface on the fatigue properties of a shot peened maraging steel. The steel had a fine-grained microstructure formed at the surface layer with 50-70 μm in depth. Especially a thin surface layer showed a nano-size structure. A surface fracture occurred at high stress levels, while the combined fracture occurred due to coalescence of a surface crack and an internal one initiated independently with decreasing in stress level until 108 cycles. In all of the macroscopic fracture surfaces in the shot-peened specimen, a ring-shaped flat area was observed at the surface layer irrespective of the fracture mode and the depth of the area nearly corresponded to the one of the fine-grained microstructure. The formation mechanism of the ring-shaped area was explained from the initiation and propagation properties of a surface crack in the surface layer in connection with the microstructure.