Knee joint kinematics of the pendulum test in children with and without Down syndrome

Background: The Wartenberg pendulum test is a common clinical test that is used to measure stiffness about the knee in persons with and without disabilities such as cerebral palsy and Down syndrome (DS). Adults and adolescents with DS show fewer number of swing cycles and a lower relaxation index than healthy controls. However, it is not clear if children with DS show a similar trend compared to typically developing (TD) children. Research question: Was the knee joint kinematics different between children with and without DS during the pendulum test? Methods: Thirteen children with DS and 13 TD children participated in this study. There were two load conditions: no load (NL) and with ankle load (AL) equal to 2 % of the subject’s body weight. Five trials of a pendulum test were collected for each condition. Results: The DS group showed a smaller first flexion excursion, a lower relaxation index, lower mean and peak velocities and accelerations during the first and second flexion and extension, and greater variability of acceleration during the first flexion than the TD group across both load conditions. This suggests that the DS group may have greater stiffness of the knee than the TD group to compensate for joint instability. Significance: The pendulum test appears to be a valid test to evaluate the passive stiffness of the knee in children with DS. The lower relaxation index in children with DS suggests that larger bursts of quadriceps may be activated during a pendulum test, particularly in the first flexion excursion, to assure the knee joint stability

Adaptive mesh refinement based simulations of three-dimensional detonation combustion in supersonic combustible mixtures with a detailed reaction model

Detonation combustion initiated with a hot jet in supersonic H2-O2-Ar mixtures are investigated by large-scale three-dimensional (3D) simulations in Tianhe-2 computing system with adaptive mesh refinement method. The reactive Euler equations are utilized as the governing equations with a detailed reaction model where the molar ratio of the combustible mixture is 2:1:7 under the condition of pressure 10kPa and temperature 298K. Results show that the Mach stem surface which is formed after the shock surface reflection on the upper wall is actually a local overdriven detonation. The side walls in 3D simulations can play an important role in detonation initiation in supersonic combustible mixtures, because they can help realize triple lines collisions and reflections during the initiation process. The width of the channel has an important influence on the strength of side-wall reflections, and under certain condition there might exist a critical width between the front and back sides of the channel for the successful initiation. Both the two-dimensional (2D) and the 3D detonations are overdriven and have a constant but different overdrive after their complete initiations. Although the overdrive degree of the 3D detonation is smaller than that of the 2D case, more complex and irregular detonation fronts can be observed in the 3D case compared with the 2D detonation, which is likely because of the propagation of transverse waves and collisions of triple lines in multi-directions in 3D detonations. After the hot jet is shut down, the newly formed 2D Chapman-Jouguet (CJ) detonation has almost the same characteristic parameters with the corresponding 3D case, indicating that the 2D instabilities can be perfectly preserved in 3D simulations. However, the slapping wave reflections on the side walls in the 3D detonation result in the second oscillation along with the main one, which presents stronger instabilities compared with the 2D case. The inherent stronger 3D instabilities is also verified through the quantitative comparison between the 2D and 3D cases where the 3D result always shows stronger fluctuations than the 2D case

Three-dimensional simulation of detonation initiation and propagation in supersonic combustible mixtures

Detonation initiation and propagation in supersonic combustible mixtures using a hot jet have been investigated in three-dimensional numerical simulations with the detailed reaction model on Tianhe-2 system. Results indicate that the side walls can help realize the triple lines collisions and triple lines reflections, which play an important role in the detonation initiation. There should exists a critical width between the front and back sides of the three-dimensional channel for the successful initiation, which is totally different from that of two-dimensional cases. When the width exceeds the critical value, there will be not the effective reflections of the bow shock surface on the side walls, hence resulting in the failure of detonation initiation. For the detonation propagation, none of the standard detonation modes(rectangular mode, diagonal mode and spinning mode) is observed in the three-dimensional case. The initiated detonation is actually in an overdriven state because of the presence of the hot jet in the supersonic flow field, thus resulting in more complex detonation fronts than that in the CJ detonation. Because of both directions of three-dimensional detonation development than that of the two-dimensional case where the transverse waves propagation and the collisions of triple points can be realized only in one direction, the detonation fronts in three-dimensional simulation shows significantly larger irregularities and variations

An allosteric modulator activates BK channels by perturbing coupling between Ca2+ binding and pore opening

BK type C

Numerical simulation of detonation initiation and propagation in supersonic combustible mixtures with non-uniform species

Adaptive high-resolution simulations of gaseous detonation using a hot jet initiation were conducted in supersonic combustible mixtures with spatially non-uniform species. The two-dimensional Euler equations were used as the governing equations in combination with a detailed hydrogen-oxygen reaction model. Three different groups of mixtures, which represent various degrees of chemical reactivity, were investigated. The results show that when the mixtures generally have a high degree of chemical reactivity, detonation initiation can eventually be realized successfully by Mach reflection as well as the DDT mechanism, independent of the spatial distribution of the mixture in the channel. A recurring four-stage sequence of detonation initiation, detonation attenuation, initiation failure and detonation reinitiation can be identified. When the mixtures generally have an intermediate degree of chemical reactivity, detonation combustion can be fully realized in the channel, where different degrees of overdrive are found in the upper lower half. After the shutdown of the hot jet, the overdriven detonation attenuates gradually and eventually a slightly overdriven detonation and a slightly underdriven detonation are generated, which can be regarded as a new stable state of propagation. However, whether a detonation can be initiated successfully is determined by the spatial mixture distribution. In mixtures with low degree of chemical reactivity, detonation initiation can generally not be realized. In this case, successful realization of detonation initiation should be realizable by using of a stronger hot jet