The relationship between consistency of propulsive cycles and maximum angular velocity during wheelchair racing

The purposes of this study were to examine the consistency of wheelchair athletes' upper-limb kinematics in consecutive propulsive cycles and to investigate the relationship between the maximum angular velocities of the upper arm and forearm and the consistency of the upper-limb kinematical pattern. Eleven elite international wheelchair racers propelled their own chairs on a roller while performing maximum speeds during wheelchair propulsion. A Qualisys motion analysis system was used to film the wheelchair propulsive cycles. Six reflective markers placed on the right shoulder, elbow, wrist joints, metacarpal, wheel axis, and wheel were automatically digitized. The deviations in cycle time, upper-arm and forearm angles, and angular velocities among these propulsive cycles were analyzed. The results demonstrated that in the consecutive cycles of wheelchair propulsion the increased maximum angular velocity may lead to increased variability in the upper-limb angular kinematics. It is speculated that this increased variability may be important for the distribution of load on different upper-extremity muscles to avoid the fatigue during wheelchair racing.     

The effect of Reynolds number on the propulsive efficiency of a biomorphic pulsed-jet underwater vehicle

The effect of Reynolds number on the propulsive efficiency of pulsed-jet propulsion was studied experimentally on a self-propelled, pulsed-jet underwater vehicle, dubbed Robosquid due to the similarity of its propulsion system with squid. Robosquid was tested for jet slug length-to-diameter ratios (L/D) in the range 2-6 and dimensionless frequency (St(L)) in the range 0.2-0.6 in a glycerin-water mixture. Digital particle image velocimetry was used for measuring the impulse and energy of jet pulses from the velocity and vorticity fields of the jet flow to calculate the pulsed-jet propulsive efficiency, and compare it with an equivalent steady jet system. Robosquid's Reynolds number (Re) based on average vehicle velocity and vehicle diameter ranged between 37 and 60. The current results for propulsive efficiency were compared to the previously published results in water where Re ranged between 1300 and 2700. The results showed that the average propulsive efficiency decreased by 26% as the average Re decreased from 2000 to 50 while the ratio of pulsed-jet to steady jet efficiency (η(P)/η(P, ss)) increased up to 0.15 (26%) as the Re decreased over the same range and for similar pulsing conditions. The improved η(P)/η(P, ss) at lower Re suggests that pulsed-jet propulsion can be used as an efficient propulsion system for millimeter-scale propulsion applications. The Re = 37-60 conditions in the present investigation, showed a reduced dependence of η(P) and η(P)/η(P, ss)on L/D compared to higher Re results. This may be due to the lack of clearly observed vortex ring pinch-off as L/D increased for this Re regime.     

Why do arms extract less oxygen than legs during exercise?

To determine whether conditions for O2 utilization and O2 off-loading from the hemoglobin are different in exercising arms and legs, six cross-country skiers participated in this study. Femoral and subclavian vein blood flow and gases were determined during skiing on a treadmill at approximately 76% maximal O2 uptake (V(O2)max) and at V(O2)max with different techniques: diagonal stride (combined arm and leg exercise), double poling (predominantly arm exercise), and leg skiing (predominantly leg exercise). The percentage of O2 extraction was always higher for the legs than for the arms. At maximal exercise (diagonal stride), the corresponding mean values were 93 and 85% (n = 3; P < 0.05). During exercise, mean arm O2 extraction correlated with the P(O2) value that causes hemoglobin to be 50% saturated (P50: r = 0.93, P < 0.05), but for a given value of P50, O2 extraction was always higher in the legs than in the arms. Mean capillary muscle O2 conductance of the arm during double poling was 14.5 (SD 2.6) ml.min(-1).mmHg(-1), and mean capillary P(O2) was 47.7 (SD 2.6) mmHg. Corresponding values for the legs during maximal exercise were 48.3 (SD 13.0) ml.min(-1).mmHg(-1) and 33.8 (SD 2.6) mmHg, respectively. Because conditions for O2 off-loading from the hemoglobin are similar in leg and arm muscles, the observed differences in maximal arm and leg O2 extraction should be attributed to other factors, such as a higher heterogeneity in blood flow distribution, shorter mean transit time, smaller diffusing area, and larger diffusing distance, in arms than in legs.     

Resonant frequencies of arms and legs identify different walking patterns

The present study is aimed at investigating changes in the coordination of arm and leg movements in young healthy subjects. It was hypothesized that with changes in walking velocity there is a change in frequency and phase coupling between the arms and the legs. In addition, it was hypothesized that the preferred frequencies of the different coordination patterns can be predicted on the basis of the resonant frequencies of arms and legs with a simple pendulum model. The kinematics of arms and legs during treadmill walking in seven healthy subjects were recorded with accelerometers in the sagittal plane at a wide range of different velocities (i.e., 0.3-1. 3m/s). Power spectral analyses revealed a statistically significant change in the frequency relation between arms and legs, i.e., within the velocity range 0.3-0.7m/s arm movement frequencies were dominantly synchronized with the step frequency, whereas from 0.8m/s onwards arm frequencies were locked onto stride frequency. Significant effects of walking speed on mean relative phase between leg and arm movements were found. All limb pairs showed a significantly more stable coordination pattern from 0.8 to 1.0m/s onwards. Results from the pendulum modelling demonstrated that for most subjects at low-velocity preferred movement frequencies of the arms are predicted by the resonant frequencies of individual arms (about 0.98Hz), whereas at higher velocities these are predicted on the basis of the resonant frequencies of the individual legs (about 0.85Hz). The results support the above-mentioned hypotheses, and suggest that different patterns of coordination, as shown by changes in frequency coupling and phase relations, can exist within the human walking mode.     

Effect of body roll amplitude and arm rotation speed on propulsion of arm amputee swimmers

Only a limited amount of research has gone into evaluating the contribution made by the upper arm to the propulsion of elite swimmers with an amputation at elbow level. With assistance of computational fluid dynamics (CFD) modelling, the swimming technique of competitive arm amputee swimmers can be assessed through numerical simulations which test the effect of various parameters on the effectiveness of the swimming propulsion.This numerical study investigates the effect of body roll amplitude and of upper arm rotation speed on the propulsion of an arm amputee swimmer, at different mean swimming speeds. Various test cases are simulated resulting in a thorough analysis of the complex body/fluid interaction with a detailed quantitative assessment of the effect of the variation of each parameter on the arm propulsion. It is found that a body roll movement with an amplitude of 45° enhances greatly the propulsive contribution from the upper arm with an increase of about 70% in the propulsive force compared to the no roll condition. An increase in the angular velocity of the upper arm also leads to a concomitant increase in the propulsive forces produced by the arm.Such results have direct implications for competitive arm amputee front crawl swimmers and for those who coach them. One important message that emerges in this present work is that there exists, for any given swimming speed, a minimum angular velocity at which the upper arm must be rotated to generate effective propulsion. Below this velocity, the upper arm will experience a net resistive drag force which adversely affects swimming performance.     

Controlling propulsive forces in gait initiation in transfemoral amputees

During prosthetic gait initiation, transfemoral (TF) amputees control the spatial and temporal parameters that modulate the propulsive forces, the positions of the center of pressure (CoP), and the center of mass (CoM). Whether their sound leg or the prosthetic leg is leading, the TF amputees reach the same end velocity. We wondered how the CoM velocity build up is influenced by the differences in propulsive components in the legs and how the trajectory of the CoP differs from the CoP trajectory in able bodied (AB) subjects. Seven TF subjects and eight AB subjects were tested on a force plate and on an 8 m long walkway. On the force plate, they initiated gait two times with their sound leg and two times with their prosthetic leg. Force measurement data were used to calculate the CoM velocity curves in horizontal and vertical directions. Gait initiated on the walkway was used to determine the leg preference. We hypothesized that because of the differences in propulsive components, the motions of the CoP and the CoM have to be different, as ankle muscles are used to help generate horizontal ground reaction force components. Also, due to the absence of an active ankle function in the prosthetic leg, the vertical CoM velocity during gait initiation may be different when leading with the prosthetic leg compared to when leading with the sound leg. The data showed that whether the TF subjects initiated a gait with their prosthetic leg or with their sound leg, their horizontal end velocity was equal. The subjects compensated the loss of propulsive force under the prosthesis with the sound leg, both when the prosthetic leg was leading and when the sound leg was leading. In the vertical CoM velocity, a tendency for differences between the two conditions was found. When initiating gait with the sound leg, the downward vertical CoM velocity at the end of the gait initiation was higher compared to when leading with the prosthetic leg. Our subjects used a gait initiation strategy that depended mainly on the active ankle function of the sound leg; therefore, they changed the relative durations of the gait initiation anticipatory postural adjustment phase and the step execution phase. Both legs were controlled in one single system of gait propulsion. The shape of the CoP trajectories, the applied forces, and the CoM velocity curves are described in this paper.     

Mutual influences of upper and lower extrimities during cyclic movements

The possibility of muscle activation of passive arm during its cyclic movements, imposed by active movements of contralateral arm or by experimenter was studied, as well as the influence of lower extremities cyclic movements onto arm muscles activity. In addition to that the activity of legs muscles was estimated in dependence on motor task condition for arms. Ten healthy supine subjects carried out opposite movements of arms with and without stepping-like movements of both legs. The experiment included three conditions for arm movements: 1) the active movements of both arms; 2) the active movements of one arm, when other entirely passive arm participated in the movement by force; 3) passive arm movement caused by experimenter. In the condition 2) additional load on active arm was applied (30 N and 60 N). In all three conditions the experiment was carried out with arms movements only or together with legs movements. The capability of passive moving arm muscles activation depended on increasing afferent inflow from muscles of contralateral arm was demonstrated. Emerging electrical activity was modulated in the arms movements cycle and depended on the degree of active arm loading. During combined active movements of arms and legs the reduction of activity in the flexor muscles of shoulder and forearm was observed. Concomitant arms movements increased the magnitude ofelectromiographic bursts during passive stepping-like movements in the most of recorded muscles, and the same increasing was only observed in biceps femoris and tibialis anterior muscles during active legs movement. The increasing of loading of one arm caused essential augmentation of EMG-activity in the majority of recording legs muscles. The data obtained are the additional proof of existence of functionally significant neuronal interaction both between arms and between upper and lower extremities, which is evidently depend on the intraspinal neuronal connections.     

Gytogenetics of Chironomus riparius L. from the fishpond in Borok village (Diptera, Chironomidae)

We have found three inherited inversions in Chironomus riparius populations from the Borok fishpond, namely: (A3d-B1a) in the arm A (C5a-C6a) in the arm D and (B3b-4d/e) in the arm F. Increase of heterochromatin in some bands of chromosome F (B3h, B3h + B3c--C1a) and puffs appearance in the arms C, D and E have been observed. We saw also changes in functional activity of nucleolar organizer (N) and Balbiani rings (BRe/BRb). It has been found that some of inversion breakpoints coincide with the Alu and Hinf satellite DNA localization sites.     

Strength-velocity relationship and fatiguability of unilateral versus bilateral arm extension

Strength-velocity relations and fatigue resistance in an arm bench press manoeuvre were compared between conditions of bilateral (BL, both arms acting together) and unilateral muscle contraction in 9 young men. BL and UL (sum of the 2 arms acting singly) strength was similar for isometric and slow isokinetic maximal voluntary contractions (MVC); at high velocities BL MVC declined more than UL. In both types of contractions a curvilinear relation was observed between strength and velocity, with significantly higher peak torques (PT) being produced under isometric conditions than for slow velocity efforts (p less than 0.01). Mean declines in PT during 100 repetitive MVCs of approximately 70s were to 25% of initial values for the BL fatigue test and to 37% for UL (p less than 0.01). In contrast to results of a similar investigation of leg extension in the same subjects, the arms showed no BL deficit of strength in the initial part of the strength-velocity curve and approximately twice as much fatigue in repetitive contractions. These physiological differences may stem from the varying habitual activity patterns of the arms and legs.     

The bop2-1 mutation reveals radial asymmetry in the inner dynein arm region of Chlamydomonas reinhardtii

Strains of Chlamydomonas reinhardtii with a mutant allele at the BOP2 locus swim slowly and have an abnormal flagellar waveform similar to previously identified strains with defects in the inner arm region. Double mutant strains with the bop2-1 allele and any of 17 different mutations that affect the dynein arm region swim more slowly than either parent, which suggests that the bop2-1 mutation does not affect solely the outer dynein arms, the I1 or ida4 inner dynein arms, or the dynein regulatory complex. Flagellar axonemes isolated from bop2-1 cells are missing a phosphorylated polypeptide of 152 kD. Electron microscopic analysis shows that bop2-1 axonemes are missing density in the inner dynein arm region. Surprisingly, two populations of images were observed in longitudinal sections of axonemes from the bop2-1 strain. In the 10 longitudinal axonemes examined, a portion of the dynein regulatory complex and a newly identified structure, the projection, are affected. In five of these 10 longitudinal axonemes examined, two lobes of the ida4 inner arm are also missing. By examining the cross-sectional images of wild-type and bop2-1 axonemes at each outer doublet position around the axoneme, we have determined that the bop2-1 mutation affects the assembly of inner arm region components in a doublet specific manner. Doublets 5, 6, and 8 have the most severe deficiency, doublet 9 has an intermediate phenotype, and doublets 2, 3, 4, and 7 have the least severe phenotype. The bop2-1 mutation provides the first evidence of radial asymmetry in the inner dynein arm region.     

Swimming of spermatozoa in a linear viscoelastic fluid.

A modified resistive force theory is developed for a spermatozoon swimming in a general linear viscoelastic fluid. The theory is based on a Fourier decomposition of the flagellar velocity, which leads to solving the Stokes flow equations with a complex viscosity. We use a model spermatozoon with a spherical head which propagates small amplitude sinusoidal waves along its flagellum. Results are obtained for the velocity of propulsion and the rate of working for a free swimming spermatozoon and the thrust on a fixed spermatozoon. There is no change in propulsive velocity for a viscoelastic fluid compared to a Newtonian fluid. The rate of working does change however, decreasing with increasing elasticity of the fluid, for a Maxwell fluid. Thus the theory predicts that a spermatozoon can swim faster in a Maxwell fluid with the same expenditure of energy for a Newtonian fluid.     

Effects of training on maximal working capacity and haemodynamic response during arm and leg-exercise in a group of paddlers.

Maximal oxygen uptake and circulatory adaptation to work with legs and arms were studied in a group of 5 paddlers members of the Belgian national squad and a control-group of 9 trained subjects. The results showed that the specific armtraining of paddlers induced changes in the arm-to-leg ration of physiological parameters at submaximal and maximal work. In the group of paddlers maximal oxygen intake and workload during arm-exercise averaged respectively 88.6% and 80.3% of the scores obtained with leg-exercise. In the control group the arm to leg ratio varied between 81.2% and 65.2%. At a submaximal load of 100 W the difference in heartfrequency was 21 beats/min in the canoe group and 35 beats/min in the control group. Oxygen consumption and ventilation during work with the arms was lower in the group of paddlers. The data of our study suggest that the specific training of paddlers do result in a effect on the haemodynamic adaptations to arm work.     

Active drag related to velocity in male and female swimmers

Propulsive arm forces of 32 male and 9 female swimmers were measured during front crawl swimming using arms only, in a velocity range between 1.0 m s-1 and 1.8 m s-1. At constant velocity, the measured mean propulsive force Fp equals the mean active drag force (Fd). It was found that Fd is related to the swimming velocity v raised to the power 2.12 +/- 0.20 (males) or 2.28 +/- 0.35 (females). Although many subjects showed rather constant values of Fd/v2, 12 subjects gave significantly (p less than 0.01) stronger or weaker quadratic relationships. Differences in drag force and coefficient of drag between males and females (drag: 28.9 +/- 5.1 N, 20.4 +/- 1.9 N, drag coefficient: 0.64 +/- 0.09, 0.54 +/- 0.07 respectively) are especially apparent at the lowest swimming velocity (1 m s-1), which become less at higher swimming velocities. Possible explanations for the deviation of the power of the velocity from the ideal quadratic dependency are discussed.     

Integrative mapping of Gossypium hirsutum L. by meiotic fluorescent in situ hybridization of a tandemly repetitive sequence (B77)

We determined the relative positions of the tandem-repeat molecular cytogenetic marker B77, translocation breakpoints, and telosome arms in Gossypium hirsutum cytogenetic stocks by fluorescence in situ hybridization (FISH) analysis of meiotic quadrivalents in 16 single and 2 double translocation heterozygotes and five monotelodisomics. Results delimited the B77 FISH locus to the right arm of the D-subgenome chromosome 14 (14R) and the short arm (14sh), respectively. By equating 14R with 14sh and 14L (left) with 14Lo (long), the findings established a unified nomenclature for the arms of chromosome 14. Previously reported chromosome 14 arm locations were confirmed for four of the five translocations involving chromosome 14, namely NT1L-14L (2780), NT2R-14R (2B-1), NT14L-23R (2777), and NT14R-24R (2781), whereas the location of breakpoint T6L-14L was not confirmed and was reassigned to arm 14R. When used as a probe on Southern blots, the B77 signal was associated with a terminus of the D-subgenome RFLP linkage group (LG) D04 by linkage analysis of an interspecific F(2) population, now known to be chromosome 20. However, additional codominant DNA marker information in the affected region excluded the B77 polymorphism detected by Southern blot hybridization from chromosome 20 and, indeed, from the remainder of the genome.     

Dosage effects on morphological and quantitative traits in maize aneuploids.

Dosage effects generated by either loss or gain of a chromosome segment were used to identify chromosome regions associated with morphological and quantitative characters in maize (Zea mays L.). Using B-A translocation stocks introgressed into a B73Ht background, a chromosome arm dosage series in a Mo17Ht x B73Ht F1 hybrid background was created for 18 of the 20 chromosome arms. The dosage series was then evaluated for 12 quantitatively inherited characters to associate specific phenotypic changes in a trait with a specific chromosome arm. Not only did our results show the familiar aneuploid syndrome phenomenon, but differential dosage effects among particular chromosome arms were demonstrated. All the quantitative traits measured and all the chromosome arms examined in this study were responsive to changes in chromosome arm dosage. The possible bases behind those differences and their utility in identifying quantitative trait loci, as well as the genetic relationships among the group of quantitatively inherited characters studied, are considered. Key words : corn, chromosome arm, B-A translocations, dosage analysis.     

Propulsion in Cubomedusae: Mechanisms and Utility

Evolutionary constraints which limit the forces produced during bell contractions of medusae affect the overall medusan morphospace such that jet propulsion is limited to only small medusae. Cubomedusae, which often possess large prolate bells and are thought to swim via jet propulsion, appear to violate the theoretical constraints which determine the medusan morphospace. To examine propulsion by cubomedusae, we quantified size related changes in wake dynamics, bell shape, swimming and turning kinematics of two species of cubomedusae, Chironex fleckeri and Chiropsella bronzie. During growth, these cubomedusae transitioned from using jet propulsion at smaller sizes to a rowing-jetting hybrid mode of propulsion at larger sizes. Simple modifications in the flexibility and kinematics of their velarium appeared to be sufficient to alter their propulsive mode. Turning occurs during both bell contraction and expansion and is achieved by generating asymmetric vortex structures during both stages of the swimming cycle. Swimming characteristics were considered in conjunction with the unique foraging strategy used by cubomedusae.     

嗜人按蚊的唾腺染色体

本文描述了我国疟疾媒介嗜人按蚊(Anopheles anthropophagus)的唾腺染色体图。此蚊的唾腺染色体由五个臂组成。第1号染色体为性染色体,又称X-染色体,是近端着丝粒,只有一个臂,它是各臂中最短的,此臂分为5个区;第2号染色体是中心着丝粒,左、右臂约等长,两臂共分为16个区;第3号染色体为亚中心着丝粒,右臂是各臂中最长的,左臂则是常染色体中最短的,两臂共分为18个区。     

Abnormalities in mutual influences of upper and lower limbs in patients with stroke

Previously, in healthy subjects the common pattern of muscle activation and specifics of interlimb neuron connections during performance of rhythmic separate and simultaneous movements of arms and legs in the lying position, which reflect functional meaningful of interlimb interactions, were shown. The aim of this research was to investigate such mutual influences of upper and lower limbs during the execution of similar motor tasks by patients with stroke. In sixteen poststroke patients with different stage of hemiparesis arms movements together with or without legs movements were performed, while lying supine. It was demonstrated that the common pattern of muscle activity distribution under the execution of voluntary cyclic movements by both arms was disordered. Passive rhythmic movements of each arm caused the phased EMG activity in shoulder muscles in patients with mild hemiparesis, but no activation was observed in patients with severe paresis. The loading of nonparetic arm resulted in an increasing of activity in shoulder flexor muscles of paretic arm in patients with weak paresis (which was typical for healthy subjects), while it not exerted essential influences in patients with severe paresis. Under connecting the cyclic movements of arms with stepping movements of legs in diagonal synergy the activity in proximal muscles of both arms was decreased irrespective of the paresis degree, as it was seeing in healthy subjects. Simultaneous arms and legs movements did not change the muscle activity in non-paretic leg in both groups of patients, but in some muscles of paretic leg the activity even decreased. The results obtained revealed important features of poststroke motor disturbances, which caused the changes of interlimb interaction and in great degree depended on the level of paresis. The data of investigation can be of a great importance for developing the new methods for rehabilitative procedure in patients with stroke.     

Genetic Map of Diploid Wheat, Triticum Monococcum L., and Its Comparison with Maps of Hordeum Vulgare L

A genetic map of diploid wheat, Triticum monococcum L., involving 335 markers, including RFLP DNA markers, isozymes, seed storage proteins, rRNA, and morphological loci, is reported. T. monococcum and barley linkage groups are remarkably conserved. They differ by a reciprocal translocation involving the long arms of chromosomes 4 and 5, and paracentric inversions in the long arm of chromosomes 1 and 4; the latter is in a segment of chromosome arm 4L translocated to 5L in T. monococcum. The order of the markers in the inverted segments in the T. monococcum genome is the same as in the B and D genomes of T. aestivum L. The T. monococcum map differs from the barley maps in the distribution of recombination within chromosomes. The major 5S rRNA loci were mapped on the short arms of T. monococcum chromosomes 1 and 5 and the long arms of barley chromosomes 2 and 3. Since these chromosome arms are colinear, the major 5S rRNA loci must be subjected to positional changes in the evolving Triticeae genome that do not perturb chromosome colinearity. The positional changes of the major 5S rRNA loci in Triticeae genomes are analogous to those of the 18S-5.8S-26S rRNA loci.     

Ontogenetic changes in the bell morphology and kinematics and swimming behavior of rowing medusae: the special case of the limnomedusa Liriope tetraphylla

Swimming animals may experience significant changes in the Reynolds number (Re) of their surrounding fluid flows throughout ontogeny. Many medusae experience Re environments with significant viscous forces as small juveniles but inertially dominated Re environments as adults. These different environments may affect their propulsive strategies. In particular, rowing, a propulsive strategy with ecological advantages for large adults, may be constrained by viscosity for small juvenile medusae. We examined changes in the bell morphology and swimming kinematics of the limnomedusa Liriope tetraphylla at different stages of development. L. tetraphylla maintained an oblate bell (fineness ratio ≈ 0.5-0.6), large velar aperture ratio (R(v) ≈ 0.5-0.8), and rapid bell kinematics throughout development. These traits enabled it to use rowing propulsion at all stages except the very smallest sizes observed (diameter = 0.14 cm). During the juvenile stage, very rapid bell kinematics served to increase Re sufficiently for rowing propulsion. Other taxa that use rowing propulsion as adults, such as leptomedusae and scyphomedusae, typically utilize different propulsive strategies as small juveniles to function in low Re environments. We compared the performance values of the different propulsive modes observed among juvenile medusae.