SUMMARY Koi carps frequently swim in burst-and-coast style, which consists of a burst phase and a coast phase. We quantify the swimming kinematics and the flow patterns generated by the carps in burst-and-coast swimming. In the burst phase, the carps burst in two modes: in the first, the tail beats for at least one cycle (multiple tail-beat mode); in the second, the tail beats for only a half-cycle (half tail-beat mode). The carp generates a vortex ring in each half-cycle beat. The vortex rings generated during bursting in multiple tail-beat mode form a linked chain, but only one vortex ring is generated in half tail-beat mode. The wake morphologies, such as momentum angle and jet angle, also show much difference between the two modes. In the burst phase, the kinematic data and the impulse obtained from the wake are linked to obtain the drag coefficient (C_d,burst≈0.242). In the coast phase, drag coefficient (C_d,coast≈0.060) is estimated from swimming speed deceleration. Our estimation suggests that nearly 45% of energy is saved when burst-and-coast swimming is used by the koi carps compared with steady swimming at the same mean speed.

SUMMARY: A fifth‐order accurate multistep weighted essentially non‐oscillatory (WENO) scheme is constructed in this paper. Different from the traditional WENO schemes, which are designed to have (2r−1)th order accuracy in the smooth regions directly from r candidate stencils, the new scheme is constructed through (r−1) weighting steps. In each step, only two neighboring stencils are used to construct the intermediate fluxes (or the final flux), which are only one order higher than the fluxes obtained from the previous step. Henrick's mapping function is used in each step to satisfy the sufficient condition of fifth‐order convergence for a fifth‐order WENO scheme; hence, the new scheme is fifth‐order accurate in smooth regions. The distinctive advantage of the new scheme is that it can improve the accuracy by one order higher than the traditional WENO schemes at transition points (connecting a smooth region and a discontinuity point); and hence, it improves the accuracy in the regions near discontinuities. Numerical examples show that the new scheme is robust and is less dissipative than the traditional fifth‐order WENO schemes. Copyright © 2014 John Wiley & Sons, Ltd.

Spontaneous swimming behaviors of koi carp Cyprinus carpio koi were recorded using a video tracking system. Routine single-beat turns were selected from the recorded image sequences for kinematic and hydrodynamic analysis. As with C-starts, the turns can be divided into two stages (stage 1 and stage 2), based on kinematics. Stage 1 involves a bend to one side forming a C-shaped curve in the body, while stage 2 corresponds to the return flip of the body and tail. The turning angle in stage 1 accounts for the greatest portion of the total turning angle and the mean turning rate in stage 1 reflects the intensity of turn. The effects of the turning rate in stage 1 on both kinematics and hydrodynamics were examined. The duration of stage 1 remained relatively stable over a nearly tenfold change in turning rate. Consequently, the turning angle is dominated by the turning rate in stage 1. The turning radius is not related to the swimming speed. Moreover, except in very fast turns, the turning radius is also not affected by the turning rate. The angle between the side jet and the carp's initial orientation of a turn does not change substantially with the turning rate, and it is always close to 90° (94.2±3.1°, N=41), so the orientation of the side jet in the forthcoming turn can be predicted. The angle between the jet and the line joining the center of mass of the carp and the trailing edge of the tail (mean value in stage 1) is also always close to 90° (95.3±1.3°, N=41). It is helpful for the carp to maximize the torque so as to improve the turning efficiency. In stage 1, the impulsive moment obtained from the beat of the body and tail and the mean angular momentum of the carp show an agreement in magnitude. Two types of flow patterns in the wake of routine single-beat turns are revealed. The difference between the two types of wakes is in whether or not a vortex ring and a thrust jet are generated in stage 2. The recoil speed of the tail, the bending amplitude of the turn, and the angle of attack of the tail are three probable factors influencing the flow patterns in stage 2.

Herein, a polyethylenimine derivative N-acetyl-L-leucine-polyethylenimine (N-Ac-L-Leu-PEI) was employed as a carrier to achieve the delivery of DNAzyme targeting aurora kinase A using PC-3 cell as a model. Flow cytometry and confocal laser scanning microscopy demonstrated that the derivative could realize the cellular uptake of nanoparticles in an energy-dependent and clathrin-mediated pathway and obtain a high DNAzyme concentration in the cytoplasm through further endosomal escape. After DNAzyme transfection, expression level of aurora kinase A would be downregulated at the protein level. Meanwhile, the inhibition of cell proliferation was observed through 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and cell colony formation assay, attributing to the activation of apoptosis and cell cycle arrest. Through flow cytometric analysis, an early apoptotic ratio of 25.93% and G2 phase of 22.58% has been detected after N-Ac-L-Leu-PEI-mediated DNAzyme transfection. Finally, wound healing and Transwell migration assay showed that DNAzyme transfection could efficiently inhibit the cell migration. These results demonstrated that N-Ac-L-Leu-PEI could successfully mediate the DNAzyme delivery and downregulate the expression level of aurora kinase A, triggering a significant inhibitory effect of excessive proliferation and migration of tumor cells.

A conservative, single‐cell‐based semi‐Lagrangian transport model is proposed in this paper. Using multi‐moment concept, an additional moment, i.e. volume‐integrated average (VIA), is treated as the model variable besides the point value (PV) updated in the traditional semi‐Lagrangian schemes. A quadratic interpolation function is constructed based on local degrees of freedom defined within each single cell. The PV moment is advanced by the semi‐Lagrangian formulation, whereas the VIA moment is updated by a finite volume formulation to rigorously ensure the numerical conservation. The numerical fluxes are computed from the PV moments defined along the boundary edges of the control volume. The scheme is extended to the spherical geometry through the application of the cubed‐sphere grid that eliminates the polar singularity in the conventional longitude/latitude coordinates by using the quasi‐uniform grid spacing covering the whole sphere. The single‐cell‐based scheme is well suited for the treatment of the connections between different patches. A simple quasi‐monotone limiter to the PV moment is applied to suppress non‐physical oscillations. The proposed scheme has been validated via representative benchmark tests and the performance is competitive to other existing transport schemes. Copyright © 2010 John Wiley & Sons, Ltd.

A novel method based on video tracking system for simultaneous measurement of kinematics and flow in the wake of a freely swimming fish is described. Spontaneous and continuous swimming behaviors of a variegated carp (Cyprinus carpio) are recorded by two cameras mounted on a translation stage which is controlled to track the fish. By processing the images recorded during tracking, the detailed kinematics based on calculated midlines and quantitative analysis of the flow in the wake during a low-speed turn and burst-and-coast swimming are revealed. We also draw the trajectory of the fish during a continuous swimming bout containing several moderate maneuvers. The results prove that our method is effective for studying maneuvers of fish both from kinematic and hydrodynamic viewpoints.