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A high input impedance circuit to convert a single-ended (SE) voltage to its differential counterpart is proposed. It allows setting the common-mode (CM) output voltage to a reference voltage vR, while providing gain and a balanced output. The circuit, intended to work as sensor front-end for instrumentation applications, can be implemented by using available commercial devices, thus proving a solution for board-level design of instrumentation systems. It is based on operational amplifiers and can be tailored to specific requirements such as low noise levels, low bias currents or limited power supply voltages. The CM output voltage is controlled by a closed loop scheme, that results in a very good balance between circuit outputs. In order to test the proposed topology, two single-ended to differential output amplifiers were built and tested: a low-noise amplifier that presents a noise of 70nVRMS in a 0.1 Hz-1 kHz bandwidth with a noise spectral density lower than nV.√Hz for higher frequencies, and a low input bias current amplifier for coaxial piezoelectric sensors. Fil: Spinelli, Enrique Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina Fil: Haberman, Marcelo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina Fil: Guerrero, Federico Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina Fil: Garcia, Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina

Here we present a novel electronic model of seismoelectric (SE) measurements. It allows to obtain the impedance seen by the electronic acquisition system while the SE effect is taking place. This i...

Real-time acquisition and processing of electroencephalographic signals have promising applications in the implementation of brain-computer interfaces. These devices allow the user to control a device without performing motor actions, and are usually made up of a biopotential acquisition stage and a personal computer (PC). This structure is very flexible and appropriate for research, but for final users it is necessary to migrate to an embedded system, eliminating the PC from the scheme. The strict real-time processing requirements of such systems justify the choice of a system on a chip field-programmable gate arrays (SoC-FPGA) for its implementation. This article proposes a platform for the acquisition and processing of electroencephalographic signals using this type of device, which combines the parallelism and speed capabilities of an FPGA with the simplicity of a general-purpose processor on a single chip. In this scheme, the FPGA is in charge of the real-time operation, acquiring and processing the signals, while the processor solves the high-level tasks, with the interconnection between processing elements solved by buses integrated into the chip. The proposed scheme was used to implement a brain-computer interface based on steady-state visual evoked potentials, which was used to command a speller. The first tests of the system show that a selection time of 5 seconds per command can be achieved. The time delay between the user’s selection and the system response has been estimated at 343 µs.

Magnetic hyperthermia is an oncological therapy where magnetic nanostructures, under a radiofrequency field, act as heat transducers increasing tumour temperature and killing cancerous cells. Nanostructure heating efficiency depends both on the field conditions and on the nanostructure properties and mobility inside the tumour. Such nanostructures are often incorrectly bench-marketed in the colloidal state and using field settings far off from the recommended therapeutic values. Here, we prepared nanoclusters composed of iron oxide magnetite nanoparticles crystallographically aligned and their specific absorption rate (SAR) values were calorimetrically determined in physiological fluids, agarose-gel-phantoms and ex vivo tumours extracted from mice challenged with B16-F0 melanoma cells. A portable, multipurpose applicator using medical field settings; 100 kHz and 9.3 kA m−1, was developed and the results were fully analysed in terms of nanoclusters’ structural and magnetic properties. A careful evaluation of the nanoclusters’ heating capacity in the three milieus clearly indicates that the SAR values of fluid suspensions or agarose-gel-phantoms are not adequate to predict the real tissue temperature increase or the dosage needed to heat a tumour. Our results show that besides nanostructure mobility, perfusion and local thermoregulation, the nanostructure distribution inside the tumour plays a key role in effective heating. A suppression of the magnetic material effective heating efficiency appears in tumour tissue. In fact, dosage had to be increased considerably, from the SAR values predicted from fluid or agarose, to achieve the desired temperature increase. These results represent an important contribution towards the design of more efficient nanostructures and towards the clinical translation of hyperthermia., Instituto de Física La Plata, Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales, Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas

La función de una interfaz para control cerebral basada en señales de electroencefalograma (EEG), en forma general denominada BCI (Brain control Interface), es establecer un enlace directo entre el cerebro y una máquina, sin utilizar acciones motoras directas. Una BCI permite realizar operaciones simples a partir de la interpretación de las señales de EEG. Su desarrollo está principalmente orientado hacia la ayuda a personas con discapacidades motoras severas, que poseen deterioros en el sistema nervioso y muscular, pero no presentan lesiones cerebrales. Existen diversos paradigmas en la concepción de estas interfaces. En este trabajo se analizan fundamentalmente aquellas estrategias basadas en el procesamiento de los llamados "ritmos cerebrales". Estas señales se observan en la actividad cerebral bajo determinadas circunstancias, y pueden acondicionarse para generar acciones de control. Gran parte de los ensayos fueron realizados sobre solo un sujeto. Si bien la estadística no es significativa, los resultados obtenidos concuerdan aceptablemente con los reportados en la literatura. El objetivo de estos ensayos no fue arribar a conclusiones definitivas sino introducirnos en el tema, validar el sistema diseñado y fundamentalmente definir sus requerimientos que fueron surgiendo a lo largo del trabajo de tesis., Facultad de Ingeniería

Sigma Delta analogue-to-digital converters allow acquiring the full dynamic range of biomedical signals at the electrodes, resulting in less complex hardware and increased measurement robustness. However, the increased data size per sample (typically 24 bits) demands the transmission of extremely large volumes of data across the isola- tion barrier, thus increasing power consumption on the patient side. This problem is accentuated when a large number of channels is used as in current 128-256 elec- trodes biopotential acquisition systems, that usually opt for an optic bre link to the computer. An analogous problem occurs for simpler low-power acquisition platforms that transmit data through a wireless link to a computing platform. In this paper, a low-complexity encoding method is presented to decrease sample data size with- out losses, while preserving the full DC-coupled signal. The method achieved a 2.3 average compression ratio evaluated over an ECG and EMG signal bank acquired with equipment based on Sigma-Delta converters. It demands a very low processing load: a C language implementation is presented that resulted in an 110 clock cycles average execution on an 8-bit microcontroller., Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales

We present a device based on a parallel LC resonant circuit optimized to generate altemating magnetic fields of 100 kHz frequency and amplitude adjustable from 2 to 15 kA/m. It is suitable for research aimed to the development of new nanotherapies that involve the use of magnetic materials and alternating magnetic field for fighting cancer, like magnetic hyperthermia and drug and gene delivery triggered by magnetic stimuli. The equipment is portable, air-cooled, versatile and functional to allow expérimentation with materials, in vitro and in vivo. In addition, the design guarantees environmental bioterium conditions (ventilation, Ught, noise, humidity and temperature) for in vivo and of cell culture conditions (pH, temperature, osmotic pressure, partial pressure of O2 and CO2) required for in vitro experiments. Fil: Gonzalez, Sergio Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Electrotecnia; Argentina Fil: Spinelli, Enrique Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Electrotecnia; Argentina Fil: Veiga, Alejandro Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería. Departamento de Electrotecnia; Argentina Fil: Coral, Diego Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Fernández van Raap, Marcela Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Mendoza Zélis, Pedro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Pasquevich, Gustavo Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina Fil: Sánchez, Francisco Homero. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentina

The present work proposes an embedded real time hardware-software platform for brain computer interfaces (BCI) based on steady state visual evoked potentials (SSVEP) and alpha rhythm. The complete implementation of the embedded system is described, including the electroencephalogram (EEG) amplifier, signal acquisition and processing stages, and practical implementation. The device is a 25 characters hybrid-BCI speller that uses 5 visual stimulus and visual alpha waves for control instructions. The system focuses on simplicity and portability, using only two electrodes, a simple EEG amplifier and an embedded computer. The speller does not require any training from the user and provides real time biofeedback to increase attention on stimuli. The platform is based on an embedded system with a real time operative system, Windows CE. Experimental results are presented in order to show the feasibility of the proposed system.

In this work, the signal modes necessary for the analysis of amplifiers for double differential and normal double differential electrodes are obtained for the first time. Superficial electromyographic (sEMG) electrodes may have multiple dry contacts with particular geometric arrangements in order to better pick up signals originated in motor units just below the electrode while rejecting other EMG signals. The amplifiers used for these electrodes are thus not differential and in order to evaluate their performance, the commonly used decomposition into common mode and differential mode is not applicable. Hence, a set of orthogonal signal modes were derived considering linear combinations of the input signals of a selection of spatial filter amplifiers. The first signal mode was associated with the desired output and the second to common mode electromagnetic interference, but there are other modes present in the amplifier that account for EMG crosstalk interference. The rejection coefficients associated with these modes were derived and the obtained laws were applied to a comparison of two double-differential electrode circuit designs.

This paper presents an improved driven right leg (DRL) circuit compensation together with a practical implementation. The proposed design allows to increase common mode voltage attenuation compared with the widely used dominant pole compensation while maintaining the same proven stability margin and design criteria, and requiring only a modification of its passive feedback network. A sample implementation of the proposed DRL was obtained estimating the values of interference model parameters for a dry electrode measurement system. A dominant pole compensated DRL with the same stability margin was also implemented in order to experimentally validate the proposed design against this established alternative. Measurements were conducted under both controlled and uncontrolled interference conditions. The proposed compensation experimentally demonstrated achieving a better reduction of power line harmonics, with a peak comparative improvement of around 18 dB at 50 Hz. Fil: Guerrero, Federico Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina Fil: Spinelli, Enrique Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales. Universidad Nacional de La Plata. Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señales; Argentina

In this paper we present an analysis of the voltage amplifier needed for double differential (DD) sEMG measurements and a novel, very simple circuit for implementing DD active electrodes. The three-input amplifier that standalone DD active electrodes require is inherently different from a differential amplifier, and general knowledge about its design is scarce in the literature. First, the figures of merit of the amplifier are defined through a decomposition of its input signal into three orthogonal modes. This analysis reveals a mode containing EMG crosstalk components that the DD electrode should reject. Then, the effect of finite input impedance is analyzed. Because there are three terminals, minimum bounds for interference rejection ratios due to electrode and input impedance unbalances with two degrees of freedom are obtained. Finally, a novel circuit design is presented, including only a quadruple operational amplifier and a few passive components. This design is nearly as simple as the branched electrode and much simpler than the three instrumentation amplifier design, while providing robust EMG crosstalk rejection and better input impedance using unity gain buffers for each electrode input. The interference rejection limits of this input stage are analyzed. An easily replicable implementation of the proposed circuit is described, together with a parameter design guideline to adjust it to specific needs. The electrode is compared with the established alternatives, and sample sEMG signals are obtained, acquired on different body locations with dry contacts, successfully rejecting interference sources. Fil: Guerrero, Federico Nicolás. Universidad Nacional de la Plata. Facultad de Ingeniería. Departamento de Electrotecnia. Laboratorio de Electrónica Industrial, Control e Instrumentación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Spinelli, Enrique Mario. Universidad Nacional de la Plata. Facultad de Ingeniería. Departamento de Electrotecnia. Laboratorio de Electrónica Industrial, Control e Instrumentación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Haberman, Marcelo Alejandro. Universidad Nacional de la Plata. Facultad de Ingeniería. Departamento de Electrotecnia. Laboratorio de Electrónica Industrial, Control e Instrumentación; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

Fully-Differential (F-D) circuits are widely used because of its immunity to common mode interference and high dynamic range, being well suited for battery-powered devices. The analysis and design of this circuits call for specific techniques; this paper presents a method to estimate the output noise of F-D circuits due to its components. An example and also experimental data are included.