Biomechanical mechanism of lateral trunk lean gait for knee osteoarthritis patients

The biomechanical mechanism of lateral trunk lean gait employed to reduce external knee adduction moment (KAM) for knee osteoarthritis (OA) patients is not well known. This mechanism may relate to the center of mass (COM) motion. Moreover, lateral trunk lean gait may affect motor control of the COM displacement. Uncontrolled manifold (UCM) analysis is an evaluation index used to understand motor control and variability of the motor task. Here we aimed to clarify the biomechanical mechanism to reduce KAM during lateral trunk lean gait and how motor variability controls the COM displacement. Twenty knee OA patients walked under two conditions: normal and lateral trunk lean gait conditions. UCM analysis was performed with respect to the COM displacement in the frontal plane. We also determined how the variability is structured with regards to the COM displacement as a performance variable. The peak KAM under lateral trunk lean gait was lower than that under normal gait. The reduced peak KAM observed was accompanied by medially shifted knee joint center, shortened distance of the center of pressure to knee joint center, and shortened distance of the knee–ground reaction force lever arm during the stance phase. Knee OA patients with lateral trunk lean gait could maintain kinematic synergy by utilizing greater segmental configuration variance to the performance variable. However, the COM displacement variability of lateral trunk lean gait was larger than that of normal gait. Our findings may provide clinical insights to effectively evaluate and prescribe gait modification training for knee OA patients.     

Time-correlated flights of juvenile and mature locusts: A comparison between free and tethered animals

The flights of free and tethered Locusta migratoria were followed from initiation with a high-speed film camera. A longer sequence of wing-beat cycles can thus be correlated unequivocally with the animals's movement in time and space. In both flight situations the locusts start with approximately the same instantaneous wing-beat frequency. During the early flight phase free-flying animals increase their wing-beat frequency, whereas for tethered locusts this parameter remains constant or even decreases. The general flight pattern is similar in juvenile and mature locusts; the juveniles however, fly with alower wing-beat frequency and flight speed. The differences in the wing-beat frequencies for both flight performances are discussed with respect to differences in the sensory inputs to the flight motor centre.     

Depth telemetry from the sixgill shark,Hexanchus griseus,at Bermuda

Synopsis Transmitters were attached to two female sixgill sharks, Hexanchus griseus, which were followed in course and depth for periods of 4 and 2 days. The sharks swam slowly (10 to 20 cm s^-1) and continuously, generally moving parallel to the bottom contours within a limited (less than 10 km long) area. The greatest depth was an excursion to 1500 m, but otherwise the sharks remained near the bottom at depths ranging from 600 to 1100 m.     

A Carbon Footprint of High‐Speed Railways in China: A Case Study of the Beijing‐Shanghai Line

A carbon footprint (CF) assessment of Chinese high‐speed railways (HSRs) can help guide further development of the world's longest HSR network. In this research, a hybrid economic input‐output and life cycle assessment (EIO‐LCA) method was applied to estimate the CF of the Beijing‐Shanghai HSR line. Specific CFs were analyzed of different subsystems of the line, different stages of production, and three calculation scopes. Results showed that the annual CF of the Beijing‐Shanghai HSR is increasing, whereas the per‐passenger CF constantly declined between 2011 and 2014. Scope 1 emissions account for an average of 4% of the total annual CF, Scope 2 contribute 71%, and Scope 3 comprise 25%. Among the different stages, operation contributes the largest (71%), followed by construction (20%) and maintenance (9%). In the construction stage, the bridges have the largest CF, followed by trains, and then rails. A trade‐off exists between the increase in carbon emissions due to construction of bridges and the reduction in operation emissions affected by leveling changes in terrain. The Beijing‐Shanghai HSR line has a relatively higher per‐passenger CF than eight other HSR lines, which is largely due to China's coal‐based carbon‐intensive energy mix of electricity generation, high proportion of bridges, higher operating speed, and heavier train body. In the future, cleaner electricity supply options, more efficient raw material production, and improvement of trains are keys to reducing the CF of Chinese HSRs.     

MAXIMUM SWIM SPEEDS OF CAPTIVE AND FREE-RANGING DELPHINIDS: CRITICAL ANALYSIS OF EXTRAORDINARY PERFORMANCE

Research into dolphin swimming historically was guided by false assumptions pertaining to maximum speed. Accurate measurements on swimming speed and duration of effort of free-ranging dolphins are rare. To examine the variance of maximum swimming speeds, nearly 2,000 speed measurements were obtained for both captive and free-ranging dolphins, including Tursiops truncatus, Pseudorca crassidens, Delphinus capensis , and Delphinus delpbis . Measurements were made from videotapes of dolphins trained to swim fast around a large pool or jumping to a maximum height, videotapes of captured wild dolphins immediately after release, and sequential aerial photographs of a school of free-ranging dolphins startled by a passing airplane. Maximum horizontal speeds for trained animals were 8.2 m/sec for T. truncatus , 8.0 m/sec for D. delphis , and 8.0 m/sec for P. crassidens . Maximum speeds for T. truncatus swimming upwards, prior to vertical leaps ranged from 8.2 to 11.2 m/sec. Wild T. truncatus demonstrated a maximum speed of 5.7 m/sec. Maximum swimming speed of free-ranging D. capensis responding to multiple passes by a low flying airplane was 6.7 m/sec. There was no evidence that the freeranging dolphins have superior swimming capabilities to captive animals. The results of this study imply that realistic maximum swimming speeds for dolphins are lower than previous reports which were based on sparse data and imprecise measurement techniques.     

Invasions with density-dependent ecological parameters

The speed and the minimum carrying capacity needed for a successful population expansion into new territory are addressed using a reaction-diffusion model. The model is able to encapsulate a rich collection of ecological behaviours, including the Allee effect, resource depletion due to consumption, dispersal adaptation due to population pressure, biological control agents, and a range of breeding suppression mechanisms such as embryonic diapause, delayed development and sperm storage. It is shown how many of these phenomena can be characterised as density-dependence in a few fundamental ecological parameters. With the help of a powerful mathematical technique recently developed by Balasuriya and Gottwald (J. Math. Biol. 61, pp. 377-399, 2010), explicit formulae for the effect on the speed and minimum carrying capacity are obtained.     

The influence of habitat on travel speed, intermittent locomotion, and vigilance in a diurnal rodent

We studied effects of habitat structure on routine travel velocities, intermittent locomotion, and vigilance by the degu (Octodondegus), a diurnal rodent of central Chile. We predicted thattravel speed, pauses during locomotion, and vigilance wouldbe greater in open (riskier) than in shrub (safer) habitats.Video recordings of marked individuals in the wild were used to measure speed and other variables of spontaneous locomotionnot triggered by predatory attack or any other noticeable stimulusduring nonforaging periods. Time spent vigilant while foragingwas also measured. Because degus use bare-ground runways fordistant movements (e.g., between burrow openings and/or foodpatches), data on locomotion decisions were not confounded by effects of obstructive vegetation cover and/or resource abundance.When moving across the habitat between different feeding places,degus showed an intermittent pattern of locomotion, interruptingrunning events with short pauses. As predicted, travel speedand the duration of pauses between locomotion bursts were significantlygreater in open habitats. Further, the duration of locomotionbursts between feeding sites or between feeding sites and burrowswas significantly longer in open habitats. Our assumption that pauses and velocities are independent decisions was supportedby the lack of correlation between pauses and speeds duringlocomotion events. During foraging, degus devoted more timeto vigilance in open than in shrub habitats. The static positionadopted by degus during pauses, the speeds attained during movements, and the concordance between pausing behavior andvigilance across habitats suggest that pausing has an antipredatoryrole and is not limited to orientation and/or physiologicalrecovery. Our results support the view that degus perceivehigher predation risk in open areas and that flexible movement behavior reflects an adaptive antipredator response.     

Body size effects on locomotion and load carriage in the highly polymorphic leaf-cutting ants Atta colombica and Atta cephalotes

Leaf-cutting ants reduce their walking speed under the weightof the leaf fragments they carry, an effect likely to havesome consequence for the foraging performance of a colony.I manipulated loads carried by workers from two Atta speciesto determine how load mass and body size affect walking speed.A comparison of speeds before and after load manipulation indicatesthat change in load mass has a linear effect on velocity. Several different regression models of speed as a function of loadsand body size have similar fit to the data, so a single bestmodel cannot easily be identified. However, there is statisticalevidence that the slope of the linear effect is more pronouncedfor smaller ants, an outcome most consistent with a regression model based on loading ratio, a metric that scales load massrelative to body mass. I then examined the effect of loadingratio on the leaf transport rate (the product of load massand carriage velocity). It has been claimed that this rateis maximized over a range of loading ratios that is the samefor all ants regardless of their size. However, I found thata latent body mass effect persists in the relation of transportrate to loading ratio, even though loading ratio is alreadyscaled relative to body mass. The maxima seem to be reachedonly at artificially elevated loading ratios, so that transportrates with natural fragments tend to be sub-maximal. This conclusionis in agreement with analytical predictions of rate-maximizingload masses derived from the regression models. Thus, loadingratio does not adequately scale load mass relative to bodysize when used in this context (effect on leaf transport rate),and should be used cautiously. Ants are likely to accommodateloads through modulation of both stride length and step frequency,but precisely how this takes place requires future study.