Identical Legs Research Articles

Nanoscale Tripodal 1,3,5,7‐Tetrasubstituted Adamantanes for AFM Applications.

The synthesis of four novel nanoscale 1,3,5,7-tetrasubstituted adamantanes 22 and 25-27 designed for atomic force microscopy (AFM) applications is described. Each tetrahedrally shaped molecule incorporates a broad tripodal base made up of three identical legs that terminate with a sulfur-containing moiety, which is either a 4-acetylsulfanylmethylphenyl unit or else a (1,2,5-dithiazepan-1-yl)phenyl unit. The sulfur atoms are intended for eventual binding of the molecule multivalently to the apex of a gold-coated commercial AFM tip through formation of multiple S-Au bonds. In each molecule, the fourth terminus is a para-substituted benzoic acid methyl ester that is designed to scan the sample. We demonstrate that 27 is sufficiently large and rigid to be imaged by a conventional AFM tip. Adamantanes 22 and 25-27 may also find application as chemically well-defined nanoscale objects for calibration of AFM tips.

Nanoscale tripodal 1,3,5,7-tetrasubstituted adamantanes for AFM applications.

The synthesis of four novel nanoscale 1,3,5,7-tetrasubstituted adamantanes 22 and 25-27 designed for atomic force microscopy (AFM) applications is described. Each tetrahedrally shaped molecule incorporates a broad tripodal base made up of three identical legs that terminate with a sulfur-containing moiety, which is either a 4-acetylsulfanylmethylphenyl unit or else a (1,2,5-dithiazepan-1-yl)phenyl unit. The sulfur atoms are intended for eventual binding of the molecule multivalently to the apex of a gold-coated commercial AFM tip through formation of multiple S-Au bonds. In each molecule, the fourth terminus is a para-substituted benzoic acid methyl ester that is designed to scan the sample. We demonstrate that 27 is sufficiently large and rigid to be imaged by a conventional AFM tip. Adamantanes 22 and 25-27 may also find application as chemically well-defined nanoscale objects for calibration of AFM tips.

V˙o 2 kinetics in heavy exercise is not altered by prior exercise with a different muscle group

We examined whether lactic acidemia-induced hyperemia at the onset of high-intensity leg exercise contributed to the speeding of pulmonary O(2) uptake (VO(2)) after prior heavy exercise of the same muscle group or a different muscle group (i.e., arm). Six healthy male subjects performed two protocols that consisted of two consecutive 6-min exercise bouts separated by a 6-min baseline at 0 W: 1) both bouts of heavy (work rate: 50% of lactate threshold to maximal VO(2)) leg cycling (L1-ex to L2-ex) and 2) heavy arm cranking followed by identical heavy leg cycling bout (A1-ex to A2-ex). Blood lactate concentrations before L1-ex, L2-ex, and A2-ex averaged 1.7 +/- 0.3, 5.6 +/- 0.9, and 6.7 +/- 1.4 meq/l, respectively. An "effective" time constant (tau) of VO(2) with the use of the monoexponential model in L2-ex (tau: 36.8 +/- 4.3 s) was significantly faster than that in L1-ex (tau: 52.3 +/- 8.2 s). Warm-up arm cranking did not facilitate the VO(2) kinetics for the following A2-ex [tau: 51.7 +/- 9.7 s]. The double-exponential model revealed no significant change of primary tau (phase II) VO(2) kinetics. Instead, the speeding seen in the effective tau during L2-ex was mainly due to a reduction of the VO(2) slow component. Near-infrared spectroscopy indicated that the degree of hyperemia in working leg muscles was significantly higher at the onset of L2-ex than A2-ex. In conclusion, facilitation of VO(2) kinetics during heavy exercise preceded by an intense warm-up exercise was caused principally by a reduction in the slow component, and it appears unlikely that this could be ascribed exclusively to systemic lactic acidosis.

Control Strategy for Dynamic Locomotion Design of Walking Quadruped

The purpose of this paper is to design the control for a dynamic locomotion of a quadruped. To reach this goal some control strategy is proposed. We simulate a quadruped walking on a horizontal plane. Our walking robot is composed of a body (platform) and four identical two-link legs. We examine a quadruped gait which is similar to gallop, but without fly. This gait involves simultaneous motions of two front and two rear legs. By this way the quadruped model with four legs is reduced to the model with two virtual legs. We consider the quadruped motion in sagittal plane. This motion is divided into four phases: a single support phase on the rear virtual leg, a double support phase, a single support phase on the front virtual leg and a double support phase finally. Quadruped transfers from the double support phase to the phase with supporting rear virtual leg by pushing the front leg off the ground. During this single support phase the distance between the feet increases. After, the front leg touches the ground with passive impact and double support phase begins. Then quadruped transfers from this double support phase to the phase with supporting front leg by pushing the rear leg off the ground. During this single support phase the distance between the feet decreases. After, the rear leg touches the ground with passive impact and next double support phase begins. By this way, quadruped moves forward. For the realization of proposed here control strategy we use technic of computed control torques.

The Metabolic Cost of Two Ranges of Arm Position Height with and without Hand Weights during Low Impact Aerobic Dance

To determine the energy cost of low impact aerobic dance while varying arm movement height and the use of hand weights, 10 adults volunteered to participate in four choreographed trials. All trials consisted of identical leg movements. Arm movements, however, were performed above shoulder level both with and without 0.9-kg hand weights and below shoulder level both with and without 0.9-kg hand weights. Open circuit spirometry was employed throughout the 10-min videotape guided trials, and heart rate was measured by telemetry. Neither the use of hand weights nor the change in arm position height significantly altered the energy cost of low impact aerobic dance. However, heart rate responses were significantly different. Caution should be observed by aerobics instructors and participants as to the use of heart rate as an indicator of intensity for low impact aerobic dance.

Finite state control of quadruped locomotion

Previous work relating to the control of legged locomo tion systems has suggested that it might be possible to achieve stable locomotion in a machine using only on-off actuators at each joint. It has further been hypothesized that the coordination of joint motions could be accom plished by a simple finite algorithm implemented as an extremely small special-purpose digital computer. The re search reported in this paper establishes the validity of these conjectures by means of a successful experiment. A quadruped with four identical legs, each with a powered hip joint and knee joint, has been constructed and tested. The results obtained have significance both with respect to prosthetics and orthotics and with respect to the design of vehicles for off-the-road transportation.