Restoring unassisted natural gait to paraplegics via functionalneuromuscular stimulation: a computer simulation study

Functional neuromuscular stimulation (FNS) of paralyzed muscles has enabled spinal-cord-injured patients to regain a semblance of lower-extremity control, for example to ambulate while relying heavily on the use of walkers. Given the limitations of FNS, specifically low muscle strengths, high rates of fatigue, and a limited ability to modulate muscle excitations, it remains unclear, however, whether FNS can be developed as a practical means to control the lower extremity musculature to restore aesthetic, unsupported gait to paraplegics. A computer simulation of FNS-assisted bipedal gait shows that it is difficult, but possible to attain undisturbed, level gait at normal speeds provided the electrically-stimulated ankle plantarflexors exhibit either near-normal strengths or are augmented by an orthosis, and at least seven muscle-groups in each leg are stimulated. A combination of dynamic programming and an open-loop, trial-and-error adjustment process was used to find a suboptimal set of discretely-varying muscle stimulation patterns needed for a 3-D, 8 degree-of-freedom dynamic model to sustain a step. An ankle-foot orthosis was found to be especially useful, as it helped to stabilize the stance leg and simplified the task of controlling the foot during swing. It is believed that the process of simulating natural gait with this model will serve to highlight difficulties to be expected during laboratory and clinical trials.     

Recrystallization controlled rolling and accelerated cooling for high strength and toughness in V-Ti-N steels

Optimum thermomechanically controlled process parameters have been established for the production of Ti-V-N microalloyed high-strength low-alloy (HSLA) steels. On the basis of laboratory simulation and full-scale processing, it has been shown that nitrogen is an essential alloying element addition and full appreciation of its effects leads to the ability to utilize high nitrogen steel in connection with hot rolling in a high-temperature regime to produce HSLA products with very favorable combinations of yield strength and toughness. The effects of reheating temperature, rolling reduction, cooling rate, and finish-cooling temperature (FCT) on the ferrite grain size and mechanical properties have been examined. It has been shown that the potential for precipitation strengthening is dependent on vanadium, nitrogen, and cooling parameters. Accelerated cooling (ACC) prevents precipitation of vanadium nitrides in austenite and enhances both grain refinement and precipitation strengthening. By adjusting nitrogen content and processing parameters, a yield strength of 500 MPa and impact transition temperature (ITT) below -60 ‡C can be obtained in the as-hot-rolled condition in Ti-V-N steels, using high finish-temperature hot rolling and accelerated cooling.     

Effect of alkalis on enforced carbonation of cement paste: Mechanism of reaction

In the present research, an alternative approach to produce supplementary cementitious materials (SCMs) based on the carbon capture and utilization is developed. The approach focuses on enforced carbonation of cement pastes obtained from recycled concrete and its application as SCM. This work focuses on the effect of alkalis in the starting solution on the carbonation mechanism of ground hydrated cement pastes in a wet reactor. The enforced carbonation of cement paste is a rapid process at ambient temperature and pressure being close to complete reaction within a few hours of carbonation, independently on alkali concentration. However, alkalis have a complex impact on the carbonation reaction as they accelerate the initial stages of the carbonation reaction, while the kinetics of the middle stages is retarded. The final degree of carbonation is only slightly affected by the alkali concentration in the solution. The origin of these effects can be explained by relating them to the evolution of solid and solution properties. Additionally, the alkali concentration has an impact on the morphology of the main carbonation products, that is, calcite and the alumina-silica gel.     

Time‐Resolved Studies of Energy Transfer in Thin Films of Green and Red Fluorescent Proteins

Biologically derived fluorescent proteins are attractive candidates for lasing and sensing due to their excellent optical properties, including their high quantum yield, spectral tunability, and robustness against concentration quenching. Here, a time‐resolved study of the fluorescence dynamics of protein thin films is reported for the enhanced green fluorescent protein (EGFP), the red‐emitting tandem‐dimer protein tdTomato, and blends of EGFP and tdTomato. The exciton dynamics are characterized by using spectrally and time‐resolved measurements of fluorescence and a threefold reduction in lifetime is observed when going from solution to thin film, down to 1 and 0.6 ns for EGFP and tdTomato, respectively. This finding is attributed to a dipole–dipole nonradiative Förster resonant energy transfer (FRET) in solid state. The temporal characteristics of FRET in blended thin films are also studied and increased nonradiative transfer rates are found. Finally, efficient sensitization of a semiconductor surface with a protein thin film is reported. Such a configuration may have important implications for energy harvesting in hybrid organic–inorganic solar cells and other hybrid optoelectronic devices.     

Experimental investigation and modeling of hydration and performance evolution of fly ash cement

A systematic study on several mix designs has been carried out to correlate the microstructural properties, i.e. degree of hydration, C–S–H composition, capillary porosity to the mechanical properties, such as compressive strength and elastic modulus. For this purpose, thermodynamic modeling was used to calculate the type and amount of hydrates formed during ongoing hydration of ordinary Portland and blended fly ash cements. Obtained results of the phase development over the hydration time agree well with the measured amount of the phases. Additionally, by plotting the measured compressive strength versus the modeled porosity, a quasi-unique relationship for both, OPC and OPC blended systems, is obtained. This new finding gives further insights allowing us to develop a micromechanical model linking the mineralogical composition of anhydrous systems to corresponding mechanical properties. On the other hand, it provides a possibility to improve the composition of cementitious systems to improve their properties and performance.     

Application priority mathematical model of operating parameters in advanced manufacturing technology

The present work is devoted to the geometric calculation of shape parameters of the working surfaces of disk-shaver teeth for use in finishing cylindrical gears with an evolvent profile. These are primarily gears for the transmissions of cars and light trucks, which must meet strict noise requirements. This imposes corresponding requirements on their machining precision.     

A model for interphase precipitation in V-microalloyed structural steels

A model for interphase precipitation, with a predictive capacity, is presented. This article deals with its application to V-microalloyed steels. The model rests on an analysis of the growth of the V-depleted zone ahead of a sheet of V(C,N) particles and the simultaneous advance of the γ/α interface in which it was nucleated. It is shown that volume diffusion of V cannot explain the observed intersheet spacings and that a faster diffusion process is required. It is postulated that the γ/α boundary will bow out some time after a sheet of V(C,N) particles has formed in it. Part of the V in the γ will then be fed to V(C,N) particles in the sheet by boundary diffusion as the γ transforms to α. The V content at the front will, thus, be lower than the initial content in the austenite. However, the reduction will be less the further the interface has moved away from the sheet of V(C,N) particles. At a sufficient distance, the V content is again high enough to allow new V(C,N) particles to nucleate, and a new sheet of particles will form. Between the two sheets, there will be a ledge (or superledge) that will advance along the first sheet. The height of the ledge will, thus, be determined by the distance in which V(C,N) particles can again be nucleated. The model exhibits reasonably good agreement with observed values of intersheet spacing, with its temperature dependence and transition from interphase to general precipitation, and with its dependence on C, V, and N content. It also provides physically sound explanations of these dependencies.     

Determination of Ketchup Sensory Texture Acceptability and Examination of Determining Factors as a Basis for Product Optimization

The aim of this study was to examine possible usage of instrumental determination of selected texture parameters to estimate sensory texture acceptability of ketchups. Likewise, the authors focused on examination whether the consumer’s perception of texture acceptability is connected to the selected factors related to the ingredients and production technology. Yet another aim was to describe the selected textural parameters of ketchups available in the European market. Within the frame of this study, 29 samples of ketchups were analyzed by means of instrumental and sensory texture analysis. Further, a survey research was carried out with the results showing that the texture was the second most significant parameter for the consumer’s choice of a particular product. The average evaluation of sensory texture acceptability reached the values from 3.78 to 7.67. Analysis of the evaluation results of textural parameters based on the values of Pearson’s correlation coefficient confirmed a high correlation (p < 0.05) between instrumental and sensory determined viscosity and density. However, none of these partial textural parameters affected the sensory acceptability of the texture separately. Thus, using the instrumental analysis for estimation of the sensory texture acceptability of ketchups is not possible. For the optimization and control of ketchup texture in practice, sensory analysis is essential.     

Electron cyclotron-electron Bernstein wave emission diagnostics for the COMPASS tokamak

The COMPASS tokamak recently started operation at the Institute of Plasma Physics AS CR, v.v.i., Prague. A new 16-channel radiometer, operating alternatively in three frequency bands, has been designed and constructed. The system is prepared for detection of normal electron cyclotron emission (O1 or X2) or oblique electron Bernstein wave emission. The end-to-end calibration method includes all components that influence the antenna radiation pattern. A steady recalibration is possible using a noise generator connected to the radiometer input through a fast waveguide PIN-switch. Measurements of the antenna radiation characteristics (2D electric field) were performed in free space as well as in the tokamak chamber, showing the degradation effect of structures on the Gaussian beam shape. First plasma radiation temperature measurements from low-field circular plasmas are available.