A Comparison of a Brain-Computer Interface and an Eye Tracker: Is There a More Appropriate Technology for Controlling a Virtual Keyboard in an ALS Patient?

The ability of people affected by amyotrophic lateral sclerosis (ALS), muscular dystrophy or spinal cord injuries to physically interact with the environment, is usually reduced. In some cases, these patients suffer from a syndrome known as locked-in syndrome (LIS), defined by the patient’s inability to make any move-ment but blinks and eye movements. Tech communication systems available for people in LIS are very limited, being those based on eye-tracking and brain-computer interface (BCI) the most useful for these patients. A comparative study between both technologies in an ALS patient is carried out: an eye tracker and a visual P300-based BCI. The purpose of the study presented in this paper is to show that the choice of the technology could depend on user´s preference. The evaluation of performance, workload and other subjective measures will allow us to determine the usability of the systems. The obtained results suggest that, even if for this patient the BCI technology is more appropriate, the technology should be always tested and adapted for each user.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Development of a Disposable Gold Electrodes-Based Sensor for Electrochemical Measurements of cDNA Hybridization

AbstractThis work deals with the development of a disposable electrochemical biosensor for the specific detection of short DNA sequences. The sensor is an amperometric transducer with three planar electrodes, comprising a working, a counter and a pseudo-reference electrode, all made of a gold layer over a polycarbonate substrate. For the development of the genosensor, the working electrode was modified using thiol-tethered 33-mer DNA probe by chemisorptions, in a concentration range from 0.1 μM to 5 μM. Immobilization of ssDNA on gold surface was monitored with electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) in Fe(CN)64−/13− and Ruthenium(II)/(III) solutions. The time dependence of ssDNA probe immobilization was also studied. The hybridization detection is then compared with EIS and DPV measurements

An automated method for detection of layer activation order in information processing pathway of rat barrel cortex under mechanical whisker stimulation

Rodents perform object localization, texture and shape discrimination very precisely through whisking. During whisking, microcircuits in corresponding barrel columns get activated to segregate and integrate tactile information through the information processing pathway. Sensory signals are projected through the brainstem and thalamus to the corresponding ‘barrel columns’ where different cortical layers are activated during signal projection. Therefore, having precise information about the layer activation order is desirable to better understand this signal processing pathway. This work proposes an automated, computationally efficient and easy to implement method to determine the cortical layer activation from intracortically recorded local field potentials (LFPs) and derived current source density (CSD) profiles: 1. Barrel cortex LFPs are represented by a template of four subsequent events: small positive/negative (E1) → large negative (E2) → slow positive (E3)→ slow long negative (E4). The method exploits the layer specific characteristics of LFPs to obtain latencies of the individual events (E1–E4), then taking the latency of E2 for calculating the layer activation order. 2. The corresponding CSD profile is calculated from the LFPs and the first sink’s peak is considered as a reference point to calculate latencies and evaluate the layer activation order. Other reference points require manual calculation. Similar results of layer activation sequence are found using LFPs and CSDs. Extensive tests on LFPs recorded using standard borosilicate micropipettes demonstrated the method’s workability. An interpretation of layer activation order and CSD profiles on the basis of a simplified interacortical barrel column architecture is also provided

Characterization of Cs-free negative ion production in the ion source SPIDER by Cavity Ring-Down Spectroscopy

The Neutral beam Injectors of the ITER experiment will be based on negative ion sources for the generation of beams composed by 1 MeV H/D particles. The prototype of these sources is currently under testing in the SPIDER experiment, part of the Neutral Beam Test Facility of Consorzio RFX, Padua, Italy. Among the targets of the experimentation in SPIDER, it is of foremost importance to maximize the beam current density extracted from the source acceleration system. The SPIDER operating conditions can be optimized thanks to a Cavity Ring-down Spectroscopy diagnostic, which is able to give line-integrated measurements of negative ion density in proximity of the acceleration system apertures. Regarding the diagnostic technique, this work presents a phenomenon of drift in ring down time measurements, which develops in a time scale of few hours. This issue may significantly affect negative ion density measurements for plasma pulses of 1 h duration, as required by ITER. Causes and solutions are discussed. Regarding the source performance, this paper presents how negative ion density is influenced by the RF power used to sustain the plasma, and by the magnetic filter field present in SPIDER to limit the amount of co-extracted electrons. In this study, SPIDER was operated in hydrogen and deuterium, in Cs-free conditions.Comment: 9 pages, 5 figures. Accepted manuscript of a published articl

Numerical and experimental investigations of a microwave interferometer for the negative ion source SPIDER

The electron density close to the extraction grids and the co-extracted electrons represent a crucial issue when operating negative ion sources for fusion reactors. An excessive electron density in the plasma expansion region can indeed inhibit the negative ion production and introduce potentially harmful electrons in the accelerator. Among the set of plasma and beam diagnostics proposed for SPIDER upgrade, a heterodyne microwave (mw) interferometer at 100 GHz is being explored as a possibility to measure electron density in the plasma extraction region. The major issue in applying this technique in SPIDER is the poor accessibility of the probing microwave beam through the source metal walls and the long distance of 4 m at which mw modules should be located outside the vacuum vessel. Numerical investigations in a full-scale geometry showed that the power transmitted through the plasma source apertures was sufficient for the microwave module sensitivity. An experimental proof-of-principle of the setup was then performed. The microwave system was tested on an experimental full-scale test-bench mimicking SPIDER viewports accessibility constraints, including the presence of a SPIDER-like plasma. The outcome of first tests revealed that, despite the geometrical constraints, in certain conditions, the electron density measurements are possible. The main issue arises from decoupling the one-pass signal from spurious multipaths generated by mw beam reflections, requiring signal cross correlation analysis. These preliminary tests demonstrate that despite the 4 m distance between the mw modules and the presence of metal walls, plasma density measurement is possible when the 80-mm diameter ports are available. In this contribution, we discuss the numerical simulations, the preliminary experimental tests and suggest design upgrades of the interferometric setup to enhance signal transmission

Negative ion density in the ion source SPIDER in Cs free conditions

The SPIDER experiment, operated at the Neutral Beam Test Facility of Consorzio RFX, Padua, hosts the prototype of the H-/D- ion source for the ITER neutral beam injectors. The maximization of the ion current extracted from the source and the minimization of the amount of co-extracted electrons are among the most relevant targets to accomplish. The Cavity Ring-Down Spectroscopy diagnostic measures the negative ion density in the source close to the acceleration system, so as to have feedback information to optimize the source parameters and to maximize the amount of negative ions that can be extracted at optimal beam divergence. This work shows how the magnetic filter field and the bias currents, present in SPIDER to limit the amount of co-extracted electrons and the electron-ion stripping reactions, affect the density of negative ions available for extraction. Moreover, the influence of the extraction process on the density of negative ions available for extraction is also presented. In this study SPIDER was operated in hydrogen and deuterium in Cs-free conditions, therefore negative ions were mostly produced by reactions in the plasma volume.Comment: 13 pages, 8 figures. Preprint of a published pape

Characterization of cesium and H-/D- density in the negative ion source SPIDER

The Heating Neutral Beam Injectors (HNBs) for ITER will have to deliver 16.7 MW beams of H/D particles at 1 MeV energy. The beams will be produced from H-/D- ions, generated by a radiofrequency plasma source coupled to an ion acceleration system. A prototype of the ITER HNB ion source is being tested in the SPIDER experiment, part of the ITER Neutral Beam Test Facility at Consorzio RFX. Reaching the design targets for beam current density and fraction of coextracted electrons is only possible by evaporating cesium in the source, in particular on the plasma facing grid (PG) of the acceleration system. In this way the work function of the surfaces decreases, significantly increasing the amount of surface reactions that convert neutrals and positive ions into H-/D-. It is then of paramount importance to monitor the density of negative ions and the density of Cs in the proximity of the PG. Monitoring the Cs spatial distribution along the PG is also essential to guarantee the uniformity of the beam current. In SPIDER, this is possible thanks to the Cavity Ringdown Spectroscopy (CRDS) and the Laser absorption Spectroscopy diagnostics (LAS), which provide line-integrated measurements of negative ion density and neutral, ground state Cs density, respectively. The paper discusses the CRDS and LAS measurements as a function of input power and of the magnetic and electric field used to reduce the coextraction of electrons. Negative ion density data are in qualitative agreement with the results in Cs-free conditions. In agreement with simulations, Cs density is peaked in the center of the source; a top/bottom non uniformity is however present. Several effects of plasma on Cs deposition are presented.Comment: 17 pages, 9 figures. Paper (Preprint) following the poster contribution at the SOFT 2022 conference. The destination journal is Fusion Engineering and Desig

Produtividade de clones da variedade vitoria sob sistema de cultivo sequeiro no vale de Jequitinhonha-MG.

A variedade vitória que se caracteriza pela tolerância à seca, alta adaptabilidade e estabilidade de produção, surge como uma alternativa ao cultivo sequeiro na região do Vale do Jequitinhonha-MG. Entretanto, como os clones possuem heterogeneidade genética pode haver variação na sua capacidade de aclimatação. Assim, esse trabalho objetivou avaliar a produtividade inicial de clones da variedade vitória sob cultivo sequeiro no vale do Jequitinhonha. Para tanto, foram implantados 13 clones da variedade Vitória no delineamento foi blocos casualizados, com quatro repetições e parcelas constituídas por seis plantas e espaçamento de 3,0 x 1,0 m. A média de produtividade de todos os clones que compõem a variedade no biênio 2011/2012 foi de 51,53 sc.benef./há, sendo que a segunda colheita apresentou produtividade média 85% maior em relação a primeira. Os clones que mais se destacaram foram os 7V, 9V e 10V, com produtividades médias do primeiro biênio oscilando entre 69,53 a 82,11 sc. benef./ha. Houve variabilidade genética e ambiental entre os clones quanto às características relação coco/beneficiado, percentagem de frutos chochos, percentagem de grãos com peneira média superior a 13 e percentagem de grãos tipo moca, porém a maioria dos clones apresentaram esses parâmetros dentro de limites aceitáveis para a variedade Vitória. De maneira geral, a variedade Vitória possui elevada capacidade produtiva inicial nas condições no Vale do Jequitinhonha