Development of anatomically accurate brain phantom for experimental validation of stimulation strengths during TMS.

Transcranial magnetic stimulation (TMS) is a non-invasive technique for diagnosis and treatment of various neurological conditions. However, the lack of realistic physical models to test the safety and efficacy of stimulation from magnetic fields generated by the coils has hindered the development of new TMS treatment and diagnosis protocols for several neurological conditions. We have developed an anatomically and geometrically accurate brain and head phantom with an adjustable electrical conductivity matching the average conductivity of white matter and grey matter of the human brain and the cerebrospinal fluid. The process of producing the phantom starts with segmenting the MRI images of the brain and then creating shells from the segmented and reconstructed model ready for 3-D printing and serving as a mold for the conductive polymer. Furthermore, we present SEM images and conductivity measurements of the conductive polymer composite as well as confirmation of the anatomical accuracy of the phantom with computed tomography (CT) images. Finally, we show the results of induced voltage measurements obtained from TMS on the brain phantom.

Evolution of two-step magnetic transition on nanogranular Gd5Si1.3Ge2.7 thin film.

A multi-functional Gd5Si1.3Ge2.7 thin film deposited by pulsed laser ablation in the form of an ensemble of nanoparticles was studied for 18 thermal cycles via electron transport measurements together with structural and magnetic characterization. A general negative thermal dependency of the resistivity (ρ) is observed, which contrasts with the metallic-like behavior observed in bulk Gd5Si x Ge4-x compounds. This general trend is interrupted by a two-step, positive-slope transition in ρ(T) throughout the [150, 250] K interval, corresponding to two consecutive magnetic transitions: a fully coupled magnetostructural followed by a magnetic order on heating. An avalanche-like behavior is unveiled by the ∂ρ/∂T(T) curves and is explained based on the severe strains induced cyclically by the magnetostructural transition, leading to a cycling evolution of the transition onset temperature ([Formula: see text]/∂n ∼ 1.6 K/cycle, n being the number of cycles). Such behavior is equivalent to the action of a pressure of 0.56 kBar being formed and building up at every thermal cycle due to the large volume induced change across the magnetostructural transition. Moreover the thermal hysteresis, detected in both ρ and magnetization versus temperature curves, evolves significantly along the cycles, decreasing as n increases. This picture corroborates the thermal activation energy enhancement-estimated via an exponential fitting of the ∂ρ/∂T(T) in the avalanche regime. This work demonstrates the importance of using a short-range order technique, to probe both magnetic and magnetostructural transitions and their evolution with thermal cycles.

Effect of Addition of Multiwalled Carbon Nanotubes on the Piezoelectric Properties of Polypropylene Filaments.

The effect of addition of multiwalled carbon nanotubes (CNTs) on the piezoelectric properties of polypropylene (PP) monofilaments has been investigated. Various amounts of CNTs (0%, 0.01%, 0.1% and 1% weight ratios) were melt-blended with PP and the resulting nanocomposites were extruded in a continuous process with simultaneous on-line poling to produce monofilaments. Concurrent stretching at a draw ratio of 5:1 and polarisation at applied electric fields of 15 kV of PP/CNT filaments was observed to enhance the piezoelectric properties. The microstructure and crystallinity of the filaments was analysed using scanning electron microscopy (SEM), differential scanning calorimetric (DSC) and Fourier transform infrared spectroscopy (FTIR) techniques. Voltage generation by the CNT-modified PP filaments was determined by the application of predetermined load impact. The results show that the incorporation of CNTs in the PP fibre structure has a considerable impact on the enhancement of piezoelectric properties of the PP filament obtained that the peak voltage generation was almost four fold (from 0.76 V to 2.92 V) when 0.1 wt% of CNTs added into the polymer. This is owing to the fact that carbon nanotubes act as nucleating agent for enhancing the crystallisation during the melt extrusion process.