R.C. Martins

Biosignals for Everyone

Physical computing has spun a true global revolution in the way that the digital world now interfaces with the physical one. From Twitter-controlled Christmas trees to bicycle jackets with turn signal lights, the do-it-yourself movement is driving endless innovations and stimulating an age of creative engineering. The authors present a novel development platform that extends the principles of physical computing to the physiological domain, changing the way in which projects and applications involving physiological data can be made.

BIT: Biosignal Igniter Toolkit.

The study of biosignals has had a transforming role in multiple aspects of our society, which go well beyond the health sciences domains to which they were traditionally associated with. While biomedical engineering is a classical discipline where the topic is amply covered, today biosignals are a matter of interest for students, researchers and hobbyists in areas including computer science, informatics, electrical engineering, among others. Regardless of the context, the use of biosignals in experimental activities and practical projects is heavily bounded by the cost, and limited access to adequate support materials. In this paper we present an accessible, albeit versatile toolkit, composed of low-cost hardware and software, which was created to reinforce the engagement of different people in the field of biosignals. The hardware consists of a modular wireless biosignal acquisition system that can be used to support classroom activities, interface with other devices, or perform rapid prototyping of end-user applications. The software comprehends a set of programming APIs, a biosignal processing toolbox, and a framework for real time data acquisition and postprocessing.

A Fast Forward Problem Solver for the Reconstruction of Biological Maps in Magnetic Induction Tomography

The magnetic induction tomography (MIT) image reconstruction is a distributed parameter estimation problem normally solved iteratively, where each iteration engages several 3-D harmonic eddy-current problems. These calculations are the main time-consuming process in the MIT reconstruction. In this paper, an approach to accelerate the resolution of a set of similar eddy-current problems to be used in the reconstruction process is presented. Each eddy-current problem is described by a reduced magnetic vector potential eddy-current formulation using the finite integration technique (FIT) framework defined over an octree based subgridding scheme with several performance precautions. The solver accuracy is compared with analytical solutions of appropriate geometrical scenarios. A performance assessment is presented for a full set of eddy-current problems that constitutes a forward problem. The new method reduced the computing time approximately to 11% of a similar problem without performance concerns maintaining a relative mean error inferior to 1.5% relatively to analytical simulations.

Dimensioning and Characterization of a New Magnetic Induction Tomography Experimental Setup

Magnetic Induction Tomography (MIT) is an imaging technique for passive electrical properties used in industrial and biological imaging. In the case of biological purposes, high resolution measures of the magnetic field induced in the body and the ability to acquire data at several points along its border with several incident field angles are two major technological objectives of MIT. This paper presents a new prototype that allows moving sensing coils and the body in analysis. Its characterization and dimensioning are presented along with preliminary acquisitions results, benchmarking some of the known cancelation techniques for a moving prototype.

An Optimized Forward Problem Solver for the Complete Characterization of the Electromagnetic Properties of Biological Tissues in Magnetic Induction Tomography

A new method for solving the magnetic induction tomography forward problem is presented. It is based on the combination of an OcTree type multi-level adaptive orthogonal mesh generation algorithm with a conformal finite integration technique-like formulation. The results obtained were compared with both analytical solutions and the response from a previously validated method. The presented method was proven to be capable of dealing with both complex electrical conductivity and magnetic permeability, giving a response with a low relative error, even when fairly coarse grids are used, thus reducing the overall system size and consequently the time for the attainment of the solution. This method is shown to be sensitive enough to be useful for image reconstruction in biological applications, where very small conductivities and relative permeabilities are usually found.

Development of an indoor Wireless Personal Area Network based on mechanically steered millimeter-wave lens antenna

In this paper, the development and early implementation stages of a 60 GHz indoor Wireless Personal Area Network (WPAN) demonstrator is presented. The transmission system is based on a millimeter-wave lens antenna which is mechanically steered to keep track of the transmitting unit. The need for increasing data rate of personal communication systems has led to the use of millimeter-wave systems for indoor use. These systems use the unlicensed spectrum from 57 GHz to 66 GHz. Applications can include for example, the transmission of full HD video or camcorder wireless connection to the home video system. The developed system contains a FPGA based device that receives data from a PC by a USB link, encodes it and sends it to the moveable transmit unit. In the stationary unit end, the received RF power is used in a tracking controller which mechanically steers the receiving antenna beam to maximize the received power. The received signal is also processed by a second FPGA based device which then sends the data by USB to the receiving PC.

Improvements in the measurement system of a biological Magnetic Induction Tomographical experimental setup

Magnetic Induction Tomography (MIT) is an imaging technique that allows mapping the internal structure complex conductivity of a body. In this paper a feasibility study to implement a higher resolution MIT system for biological tissues is carried out. Recent improvements in measured signal stability and accuracy as well as a much improved angular resolution measurement of the multi-coil setup are presented which, together with a new mechanical design allows obtaining longer stable and more accurate acquisitions. This allows improving the number of measurements without trends or external perturbations, leading to a better conductivity resolution and to an enhanced image reconstruction. Throughout the paper experimental data is used to consolidate results.

Fabrication and response of high concentration SIMPLE superheated droplet detectors with different liquids

Abstract The combined measurement of dark matter interactions with different superheated liquids has recently been suggested as a cross-correlation technique in identifying WIMP candidates. We describe the fabrication of high concentration superheated droplet detectors based on the light nuclei liquids C3F8, C4F8, C4F10 and CCl2F2, and investigation of their irradiation response with respect to C2ClF5. The results are discussed in terms of the basic physics of superheated liquid response to particle interactions, as well as the necessary detector qualifications for application in dark matter search investigations. The possibility of heavier nuclei SDDs is explored using the light nuclei results as a basis, with CF3I provided as an example.

Low-cost mechanically steered millimeter-wave lens antenna system for indoor LANs

The expected need in the near-future to increase the data rate of personal communication systems up to a few GBit/s, calls for the possibility to explore the millimeter wave part of the electromagnetic spectrum especially for very short range indoor radio links to replace for instance the current Bluetooth or other domestic Personal Area Networks (PANs). High gain antennas in the order of 20 dBi are required to favor the link budget at these frequencies, but the antenna directionality limits user mobility unless at least one antenna in the link can automatically track the other antenna. A new antenna concept that is appropriate for this objective was recently developed by the authors. The objective of this paper is to demonstrate the complete concept by integrating the developed antenna with a simplified RF front-end for data transmission, along with the tracking control system and required algorithms so that a fully operational video transmission can be accomplished with this wireless mm-wave system using low-cost solutions.

SIMPLE limits on spin-dependent WIMP interactions

An improved SIMPLE experiment comprising four superheated droplet detectors with a total exposure of 0.42 kg.d yields ~factor 10 improvement in the previously-reported results. Despite the low exposure, the result provides restrictions on the allowed phase space of spin-dependent coupling strengths almost equivalent to those from the significantly larger exposure NAIAD-CDMS/ZEPLIN searches.