Rheo-small-angle neutron scattering at the National Institute of Standards and Technology Center for Neutron Research

We describe the design and operation of a modified commercial rheometer to simultaneously perform rheological measurements and structural studies by small angle neutron scattering (SANS). The apparatus uses a Couette geometry shear cell allowing two of the three scattering planes to be observed by performing experiments in either the radial or tangential geometries. The device enables small angle neutron scattering patterns to be obtained simultaneously with a wide variety of rheological measurements such as stress/strain flow curves, oscillatory deformations, and creep, recovery and relaxation tests, from -20?°C to 150?°C, for samples with viscosities varying by several orders of magnitude. We give a brief report of recent experiments performed on a dispersion of acicular nanoparticles and biopolymer network under stress demonstrating the utility of such measurements. This device has been developed at the National Institute of Standards and Technology's Center for Neutron Research (NCNR) and made available to the complex fluids community as part of the standard sample environment equipment.     

Photocatalytic reduction of Cr(VI) in a fully illuminated fluidized bed reactor

The potential of a fluidized bed reactor for the UV-A photocatalytic reduction of Cr(VI), a priority water pollutant, by utilizing a TiO(2)/quartz sand composite, was explored. The effects of oxalic acid (OA) as a sacrificial agent in the heterogeneous system was also investigated and compared with the homogeneous photoreduction by the same dicarboxylic acid under both oxygenated or anoxic conditions of the reacting media. The performance of the 'preconditioned' photocatalyst, either by pretreating it with the OA solution (at dark or under UV-A illumination) or by letting the catalyst stand wet with the OA solution, during designated time intervals (1-5 weeks) prior to its reuse, was assessed. Then, up to 95% reduction of Cr(VI) to Cr(III) was achieved in less than 100 min.     

Control and Virtual Reality Simulation of Tendon Driven Mechanisms

In this paper the authors present a control strategy for tendon driven mechanisms. The aim of the control system is to find the correct torques which the motors have to exert to make the end effector describe a specific trajectory. In robotic assemblies this problem is often solved with closed loop algorithm, but here a simpler method, based on a open loop strategy, is developed. The difficulties in the actuation are in keeping the belt tight during all working conditions. So an innovative solution of this problem is presented here. This methodology can be easily applied in real time monitoring or very fast operations. For this reason several virtual reality simulations, developed using codes written in Virtual Reality Markup Language, are also presented. This approach is very efficient because it requires a very low cpu computation time, small size files, and the manipulator can be easily put into different simulated scenarios.     

Determination of standard pH values for potassium hydrogen phthalate reference buffer solutions in 10, 20, 50, 64 and 84.2 wt per cent methanol/water mixed solvents at temperatures from 283.15 to 313.15 K

Standard pH⁰ values for 0.05 mol kg^?1 potassium phthalate reference buffer solutions in 10, 20, 50, 64 and 84.2 wt % methanol/water solvent mixtures have been obtained from cells without transport, in the temperature range 283.15–313.15 K. The consistency of results has been analysed by a new method of multilinear regression of the quantity p(a_Hγ_Cl) as a function of both temperature and solution composition. The pH° values found can be reproduced within ± 0.01 by the equation pH⁰ = 4.00 + 4.38x ? 5.02x² + 4.23x³ + 0.13z ? 0.91xz, where x = mole fraction of methanol in the solvent mixture, z = (T ? θ)/θ and θ = 298.15 K. Subsidiary values of the first ionization constant of o-phthalic acid in the above solvent mixtures have also been obtained by the buffered cell method.     

Non-isothermal bioreactors in enzymatic remediation of waters polluted by endocrine disruptors: BPA as a model of pollutant

The bioremediation of waters polluted by Bisphenol A, taken as a model for endocrine disruptors, has been pursued by means of catalytic membranes in bioreactors operating under isothermal and non-isothermal conditions. Laccase from Trametes versicolor was immobilized on nylon membranes grafted with Glycidyl Methacrylate and using Phenylendiamine as spacer. The behaviour of the catalytic membrane was studied as a function of BPA concentration. Affinities of immobilized laccase towards BPA were found to increase with average temperature and under non-isothermal conditions. Percentage increases of enzyme activity, proportional to the applied temperature differences, were found to decrease with the increase of BPA concentrations. Interestingly, the highest levels of BPA biodegradation occurred at the lowest concentrations, in other words those present in wastewaters given the small water solubility of this compound. The results are discussed in terms of the process of thermodialysis by considering the additional BPA fluxes towards the immobilized enzymes driven by the temperature gradients.     

Effect of the mechanical activation on the photoelectrochemical properties of anatase powders

Mechanically activated anatase powders were used to assemble thin film electrodes for electrophotocatalytic applications. Flat band potential of the different samples, estimated from the dependence of photopotential on the light intensity, as well as photocurrent vs potential curves were measured at samples milled for different times and compared with those of the untreated anatase. The maximum performance is achieved at samples milled for very short times, at which the mechanical process gives rise to a mixed-phase titania catalyst constituted by anatase and TiO₂(II) phases. Electrochemical Impedance Spectroscopy measurements were also performed in order to individuate the controlling step of the photoelectrochemical process of water splitting.     

Development of Novel Amides as Noncovalent Inhibitors of Immunoproteasomes

The development of immunoproteasome-selective inhibitors is a promising strategy for treating hematologic malignancies, autoimmune and inflammatory diseases. In this context, we report the design, synthesis, and biological evaluation of a new series of amide derivatives as immunoproteasome inhibitors. Notably, the designed compounds act as noncovalent inhibitors, which might be a promising therapeutic option because of the lack of drawbacks and side effects associated with irreversible inhibition. Among the synthesized compounds, we identified a panel of active inhibitors with K_i values in the low micromolar or sub-micromolar ranges toward the β5i and/or β1i subunits of immunoproteasomes. One of the active compounds was shown to be the most potent and selective inhibitor with a K_i value of 21 nm against the single β1i subunit. Docking studies allowed us to determine the mode of binding of the molecules in the catalytic site of immunoproteasome subunits.     

Mechanical and Vibration Characteristics of Laminated Composite Plates Embedding Shape Memory Alloy Superelastic Wires

Currently, there is a great interest in the study of shape memory alloy (SMA) composites, since SMA wires with a small diameter have become commercially available. Many potential uses have been found for SMA composites in shape control, vibration control, and for the realization of structures with improved damage tolerance. In this work, two types of SMA-hybridized composites are presented for investigating the mechanical and vibration characteristics. The first one contains unidirectional superelastic SMA wires, while the other has been realized with embedded knitted SMA layers. The samples from these laminates have been tested according to “Charpy method” (ASTM D256) and static flexural test method (ASTM D790) to evaluate the influence of the integration of thin superelastic SMA wires on the impact behavior and the mechanical properties of the hybrid composites. Moreover, since the SMA wires are expected to give damping capacity, by measuring the vibration mode of a clamped cantilever using laser vibrometry, the influence of both SMA arrangements on the vibration characteristics has been investigated. Finally, further tests have been carried out on composite panels realized by embedding unidirectional steel wires to distinguish the influence of the martensitic transformation from the pure introduction of a metallic wire into the polymeric matrix.     

Real-time myoprocessors for a neural controlled powered exoskeleton arm

Exoskeleton robots are promising assistive/rehabilitative devices that can help people with force deficits or allow the recovery of patients who have suffered from pathologies such as stroke. The key component that allows the user to control the exoskeleton is the human machine interface (HMI). Setting the HMI at the neuro-muscular level may lead to seamless integration and intuitive control of the exoskeleton arm as a natural extension of the human body. At the core of the exoskeleton HMI there is a model of the human muscle, the "myoprocessor," running in real-time and in parallel to the physiological muscle, that predicts joint torques as a function of the joint kinematics and neural activation levels. This paper presents the development of myoprocessors for the upper limb based on the Hill phenomenological muscle model. Genetic algorithms are used to optimize the internal parameters of the myoprocessors utilizing an experimental database that provides inputs to the model and allows for performance assessment. The results indicate high correlation between joint moment predictions of the model and the measured data. Consequently, the myoprocessor seems an adequate model, sufficiently robust for further integration into the exoskeleton control system.