Biomechanical features of level walking by transtibial amputees wearing prosthetic feet with and without adaptive ankles

This study aimed to evaluate the kinematics and kinetics of the lower limb in both the intact and amputated leg in individuals with transtibial amputations wearing Energy storage and return feet (ESRFs) with fixed ankles and Prosthetic feet with adaptive ankles (PFAAs) during level walking. Three individuals with transtibial amputations walked on level ground wearing their own ESRFs and PFAAs. Spatiotemporal parameters, kinematics, and kinetics of the lower-extremity joints were measured in the amputated and intact legs. There were differences in the kinematics of the joints in the amputated leg and of the ankle in the intact leg between ESRFs and PFAAs. Differences in joint moments, power, and stiffness in most joints in both legs and braking impulse were found between ESRFs and PFAAs. Thus, although it was a pilot study with three subjects, ankle angle control mechanisms (ESRFs: Fixed ankle vs. propriofoot: Mechanical motor vs. élan and echelon: Hydraulic actuator) might affect biomechanical features during level walking.

     

A procedure to determine the optimum imaging parameters for atomic/molecular resolution frequency modulation atomic force microscopy

We propose a general procedure to determine the optimum imaging parameters (spring constant and oscillation amplitude) to obtain the optimum resolution in frequency modulation atomic force microscopy. We calculated the effective signal-to-noise ratio for various spring constants and oscillation amplitudes, based on the measurement of frequency shift and energy dissipation versus tip-sample distance curves, to find the optimum. We applied this procedure for imaging a lead phthalocyanine (PbPc) thin film on a MoS(2)(0001) substrate, and found that the optimum parameters were about 5 N/m and 20 nm, respectively. An improved signal-to-noise ratio was attained in a preliminary experiment using parameters which were close to the calculated optimum.     

Autocalibrating Stokes polarimeter for materials characterization

The design and construction of an ellipsometer based on a fixed-wavelength rotating-retarder Stokes polarimeter is described. Details are provided for an automated calibration scheme that provides two advantages for its operation. The first allows the phase of the lock-in amplifiers to be set based on the raw data, without a known calibration sample. The second illustrates that the relative amplitude of the acquired signals may also be calibrated in a similar manner. As an illustration, the refractive index and thickness of a glass cover slide are determined over a range of incident angles.     

Changes in mixing states of styrene–butadiene copolymer rubber and general-purpose polystyrene resin mill blend by heat treatment

The effect of heat treatment in the so-called phase inversion region was studied using uncured mill blends of various commercial styrene—butadiene copolymer rubbers (styrene content, 23.5 to 48 wt-%; styrene block, 0 to 18 wt-%) with general-purpose polystyrene resin (blend ratio, 80–40: 20–60, in wt-%). It was found that the effect of heat treatment on the hardening or softening phenomenon of blends is different in the random type from that in the block-type styrene—butadiene copolymer rubber. A thorough discussion led us to conclude that this difference is caused by the strong interaction between the polystyrene block of the copolymer and the styrene homopolymer of general-purpose polystyrene resin.     

Atom-selective imaging and mechanical atom manipulation using the non-contact atomic force microscope

We succeeded in distinguishing between oxygen and silicon atoms on an oxygen-adsorbed Si(111)7 x 7 surface, and also distinguished between silicon and tin atoms on Si(111)7 x 7-Sn intermixed and Si(111) square root(3) x square root(3)-Sn mosaic-phase surfaces using non-contact atomic force microscopy (NC-AFM) at room temperature. Atom species of individual atoms are specified from the number of each atom in NC-AFM images, the tip-sample distance dependence of NC-AFM images and/or the surface distribution of each atom. Further, based on the NC-AFM method but using soft nanoindentation, we achieved two kinds of mechanical vertical manipulation of individual atoms: removal of a selected Si adatom and deposition of a Si atom into a selected Si adatom vacancy on the Si(111)7 x 7 surface at 78 K. Here, we carefully and slowly indented a Si atom on top of a clean Si tip apex onto a predetermined Si adatom to remove the targeted Si adatom and onto a predetermined Si adatom vacancy to deposit a Si atom, i.e. to repair the targeted Si adatom vacancy. By combining the atom-selective imaging method with two kinds of mechanical atom manipulation, i.e. by picking up a selected atom species and by depositing that atom one by one at the assigned site, we hope to construct nanomaterials and nanodevices made from more than two kinds of atom species in the near future.