Interchanges and movements of humpback whales in Japanese waters: Okinawa, Ogasawara, Amami, and Hokkaido, using an automated matching system.

Humpback whales in the western North Pacific are considered endangered due to their small population size and lack of information. Although previous studies have reported interchanges between regions within a population, the relationship between the geographic regions of a population in Japan is poorly understood. Using 3,532 fluke photo IDs of unique individuals obtained from four areas in Japan: Hokkaido, six IDs (2009-2019); Ogasawara, 1,477 IDs, from two organizations (1) Everlasting nature of Asia (1987-2020) and (2) Ogasawara Whale Watching Association, (1990-2020); Amami, 373 IDs (1992-1994, 2005-2016); Okinawa, 1,676 IDs (1990-2018), interchanges were analyzed. The ID matchings were conducted using an automated system with an 80.9% matching accuracy. Interchange and within-region return indices were also calculated. As a result, number of matches and interchange indices follow locations, Hokkaido-Okinawa (3, 0.31), Amami-Ogasawara (36, 0.06), Amami-Okinawa (222, 0.37), and Okinawa-Ogasawara (225, 0.08), respectively. Interchange indices among Japanese areas were much higher than the indices between Ogasawara/Okinawa and Hawaii (0.01) and Mexico (0.00) reported in previous studies, indicating that the Japanese regions are utilized by the same population. At the same time, the frequency of interchanges among the three breeding areas vary, and the high within-region return indices in respective breeding areas suggest the site fidelity of the whales in each area at some level. These results indicate the existence of several groups within the population which are possibly be divided into at least two groups based on geographical features: one tend to utilize Ogasawara and the Mariana Archipelago; the other utilize Amami, Okinawa, and the Philippines, migrating along the Ryukyu and Philippine Trench. The matching results also suggest that Hokkaido is possibly be utilized as a corridor between northern feeding areas and southern breeding areas at least by individuals migrating to Okinawa area.

Effect of Leg Extension Angle on Knee Flexion Angle during Swing Phase in Post-Stroke Gait.

Background and Objectives: Leg extension angle is important for increasing the propulsion force during gait and is a meaningful indicator for evaluating gait quality in stroke patients. Although leg extension angle during late stance might potentially also affect lower limb kinematics during the swing phase, the relationship between these two remains unclear. This study aimed to investigate the relationship between leg extension angle and knee flexion angle during pre-swing and swing phase in post-stroke gait. Materials and Methods: Twenty-nine stroke patients walked along a 16 m walkway at a self-selected speed. Tilt angles and acceleration of pelvis and paretic lower limb segments were measured using inertial measurement units. Leg extension angle, consisting of a line connecting the hip joint with the ankle joint, hip and knee angles, and increments of velocity during pre-swing and swing phase were calculated. Correlation analysis was conducted to examine the relationships between these parameters. Partial correlation analysis adjusted by the Fugl-Meyer assessment-lower limb (FMA-LL) was also performed. Results: On the paretic side, leg extension angle was positively correlated with knee flexion angle during the swing phase (r = 0.721, p < 0.001) and knee flexion angle and increments of velocity during the pre-swing phase (r = 0.740-0.846, p < 0.001). Partial correlation analysis adjusted by the FMA-LL showed significant correlation between leg extension angle and knee flexion angle during the swing phase (r = 0.602, p = 0.001) and knee flexion angle and increments of velocity during the pre-swing phase (r = 0.655-0.886, p < 0.001). Conclusions: Leg extension angle affected kinematics during the swing phase in post-stroke gait regardless of the severity of paralysis, and was similar during the pre-swing phase. These results would guide the development of effective gait training programs that enable a safe and efficient gait for stroke patients.

The Relationship between Leg Extension Angle at Late Stance and Knee Flexion Angle at Swing Phase during Gait in Community-Dwelling Older Adults.

This study aimed to clarify the relationship between leg extension angle and knee flexion angle during gait in older adults. The subjects of this cross-sectional study were 588 community-dwelling older adults (74.6 ± 6.1 y). Segment angles and acceleration were measured using five inertial measurement units during comfortable gait, and bilateral knee and hip joint angles, and leg extension angle, reflecting whole lower limb extension at late stance, were calculated. Propulsion force was estimated using the increase in velocity calculated from anterior acceleration of the sacrum during late stance. Correlation analysis showed that leg extension angle was associated with knee flexion angle at swing phase and hip extension angle and increase in velocity at late stance (r = 0.444-508, p < 0.001). Multiple regression analysis showed that knee flexion angle at mid-swing was more affected by leg extension angle (ß = 0.296, p < 0.001) than by gait speed (ß = 0.219, p < 0.001) and maximum hip extension angle (ß = -0.150, p < 0.001). These findings indicate that leg extension angle may be a meaningful parameter for improving gait function in older adults due to the association with knee kinematics during swing as well as propulsion force at late stance.

Distribution and Local Movement of Humpback Whales in Okinawan Waters Depend on Sex and Reproductive Status.

The distribution and local movement patterns of humpback whales in waters off the west coast of Okinawa Island, southwest Japan, were investigated using line transect and photo-identification methodologies. Line transect surveys were conducted from 2011 to 2014 and photo-identification survey from 2006 to 2012. During the surveys, humpback whales aggregated in the areas around Ie and Kerama Islands, and tended to travel along the inshore coast of Okinawa Island when they move locally between those two sites. A total of 496 humpback whales of the known sex were photo-identified (322 males, 75 females and 99 females with a calf). Of these, 24.8% were confirmed moving locally between the sites of Ie and Kerama Islands within the same season. Frequency rates of the local movement for males, females and females with a calf were 41.9, 25.0, and 15.1%, respectively; the frequency of local movement for males was significantly higher than that for females and females with a calf. These results indicate that male humpback whales tend to move more actively between the local breeding sites as compared to females and females with a calf. We speculate that the males search for more opportunities to mate, whereas females with a calf tend to remain in the same areas to nurse their calves. These findings extend our knowledge of the habitat use and reproductive ecology of humpback whales in Okinawan waters, which remain poorly understood.

Visualization of in-plane dispersion of hole subbands by photoelectron spectroscopy.

The in-plane dispersion of the hole subband (HSB) in a Si quantum well is obtained for the first time by applying angle-resolved photoemission spectroscopy and surface science techniques. The entire shape of the HSB over a wide ranged wave vector, including admixing of heavy and light hole subbands around the crossing point and the camelback structure inducing negative effective mass, is visualized directly. Energy separations between the subbands are quantitatively explained.