Cap Electrode Research Articles

The impact of electrode selection for ocular correction on the reward positivity and late positive potential components in adolescents.

Electroencephalography (EEG) data processing to derive event-related potentials (ERPs) follows a standard set of procedures to maximize signal-to-noise ratio. This often includes ocular correction, which corrects for artifacts introduced by eye movements, typically measured by electrooculogram (EOG) using facial electrodes near the eyes. Yet, attaching electrodes to the face may be uncomfortable for some populations, best to avoid in some situations, and contribute to data loss. Eye movements can also be measured using electrodes in a standard 10-20 EEG cap. An examination of the impact of electrode selection on ERPs is needed to inform best practices. The present study examined data quality when using different electrodes to measure eye movements for ocular correction (i.e., facial electrodes, cap electrodes, and no ocular correction) for two well-established and widely studied ERP components (i.e., reward positivity, RewP; and late positive potential, LPP) elicited in adolescents (N = 34). Results revealed comparable split-half reliability and standardized measurement error (SME) between facial and cap electrode approaches, with lower SME for the RewP with facial or cap electrodes compared to no ocular correction. Few significant differences in mean amplitude of ERPs were observed, but the LPP to positive images differed when using facial compared to cap electrodes. Findings provide preliminary evidence of the ability to collect high-quality ERP data without facial electrodes. However, when using cap electrodes for EOG measurement and ocular correction, it is recommended to use consistent procedures across the sample or statistically examine the impact of ocular correction procedures on results.

Structure optimization of Spindt-type emitter fabricated by triode high power pulsed magnetron sputtering

Spindt-type emitters were fabricated with cavities made of Al/Mo/SiO2 using the triode high power pulsed magnetron sputtering method. We explored the process parameters (gas pressure and voltage of the additional cap electrode) to optimize the sharpness of the emitter shape. We found that the intermediate pressure and voltage were suited to obtain sharp emitters. Further, we elucidated the crucial effect of the cavity dimensions, such as the cavity depth and hole diameter in the cavity ceiling, on the emitter shape. At a cavity depth of 480 nm, the aspect ratio (AR) of the emitter increased monotonously with an increase in the hole diameter. With a large hole diameter (900 nm) and even shallower cavity (380 nm depth), we attempted to reoptimize the process parameters. Consequently, a very sharp emitter cone structure with an AR exceeding 1.3 was obtained. The cap voltage that produced the optimum AR was found to decrease for the larger-hole and shallower-depth cavities. Finally, the applicability of the process for preparing a working emitter is discussed.

An Endoscopic Cap Electrode for Posterior Cricoarythenoid Muscle Stimulation in a Porcine Model.

Laryngeal pacing (LP) is a highly anticipated therapeutic option for patients suffering from bilateral vocal fold paralysis with synkinesis. Identification of candidate patients requires confirmation of a stimulable posterior cricoidarythenoid muscle (PCA) by neuromuscular electrical stimulation (NMES). A silicone endoscopic cap electrode (ECE50) was designed to be operated as an endoscopic extension tip for selective PCA stimulation and confirmation of a glottic opening movement in a setting comparable to a gastroscopy procedure. A porcine animal model (n=6) was applied to develop and test endoscopic cap prototypes in general anesthesia and sedation at a biomedical research center. Two ENT endoscopy experts evaluated and refined the cap design and performance in regard to procedure safety, endoscope handling, accessibility of the PCA by the transoral approach and selective muscle stimulation. Vocal fold opening movements could be evoked by the investigators in 9 of 12 PCA muscles to stimulate with similar electric parameters. The endoscopic approach using the ECE50 proved to be atraumatic and sufficiently controlled under sedation to locate the required hotspot for NMES of the PCA. The functionality of the novel endoscopic cap concept has been proven in a porcine model. It can be expected to be transferable to human application and to be of diagnostic importance in the screening and identification of LP candidate patients in future. NA Laryngoscope, 133:2279-2284, 2023.

Modulating the microscopic lattice distortions through the Al-rich layers for boosting the ferroelectricity in Al:HfO2 nanofilms

Combining the experimental characterization with the large-scale density functional theory calculations based on finite-element discretization (DFT-FE), we address the stabilization of polar orthorhombic phases (o-HfO2) in Al:HfO2 nanofilms by means of the atomic registry distortions and lattice deformation caused by Al substitutional defects (AlHf) and Schottky defects (2AlHf + VO) in tetragonal phases (t-HfO2) or monoclinic phases (m-HfO2). The phase transformation directly from the t-HfO2 into polar o-HfO2 are also elucidated within a heterogeneous distribution of Al dopants in both t-HfO2 bulk crystal structure and Al:HfO2 nanofilm. It is revealed using large-scale DFT calculations that the Al substitutional defects (AlHf) or the Schottky defect (2AlHf + VO) could induce the highly extended atomic registry distortions or lattice deformation in the t- and m-HfO2 phases, but such effects are greatly diminished in ferroelectric orthorhombic phase. By purposely engineering the multiple AlHf defects to form dopant-rich layers in paraelectric t-HfO2 nanofilm or bulk crystal, the induced extended lattice distortions surrounding the defect sites exhibit the shearing-like atomic displacement vector field. The large-scale DFT calculations further predicted that the shearing-like microscopic lattice distortions could directly induce the phase transformation from the t-HfO2 into polar orthorhombic phase in both Al:HfO2 bulk crystal and nanofilms, leading to the large remanent polarization observed in Al:HfO2 nanofilms with the presence of Al-rich layers. The current study demonstrates that the ferroelectricity of HfO2 bulk crystal or thin film can be optimized and tuned by delicately engineering both the distribution and concentration of Al dopants in atomic layer deposition without applying the top capping electrode, providing the extra flexibility for designing the HfO2 based electronic devices in the future.

Translation-deformation coupling effects on the Rayleigh instability of an electrodynamically levitated charged droplet.

The breakup pathway of the Rayleigh fission process observed in the past experiments carried out using high-speed imaging of a charged drop levitated in an AC quadrupole trap has shown to exhibit several cycles of shape and center-of-mass oscillations followed by asymmetric breakup by ejecting a jet in the upward direction (i.e., opposite to the direction of gravity). We recently attempted to explain this using boundary integral simulations in the Stokes flow limit, wherein the position of the droplet and the polarity of the end cap electrodes were assigned using physical arguments, and the center-of-mass motion was not estimated consistently invoking quasi-static conditions. In this work, we explain the experimental observation of upward breakup of charged droplets in a quadrupolar field, using numerical calculations based on the boundary element method considering inviscid droplets levitated electrodynamically using quadrupole electric fields. The center-of-mass motion and the end cap are consistently calculated in the numerical scheme. The simulations show that the gravity-induced downward shift in the equilibrium position of the drop in the trap causes significant, large-amplitude shape oscillations superimposed over the center-of-mass oscillations of the drop. An important observation here is that the shape oscillations due to the applied quadrupole fields result in sufficient deformations that act as triggers for the onset of the instability below the Rayleigh limit, thereby admitting a subcritical instability. The center-of-mass oscillations of the droplet within the trap, which follow the applied frequency, are out of phase with the applied AC signal. Thus the combined effect of shape deformations and dynamic position of the drop leads to an asymmetric breakup such that the Rayleigh fission occurs upward via the ejection of a jet at the north pole of the deformed drop.

Enhanced ferroelectric polarization with less wake-up effect and improved endurance of Hf0.5Zr0.5O2 thin films by implementing W electrode

1. Ferroelectric polarization value and o-/t- mixed phase fraction of HZO thin films can be largely enhanced by implementing W capping electrode. 2. Less wake-up effect (10.1%) and superior fatigue properties up to 1.5 × 10 10 cycles were obtained for W/HZO/W capacitor. 3. The influence of the top electrode on the ferroelectricity of metal/HZO/metal capacitor is more important than that of the bottom electrode. This paper reports the improvement of electrical, ferroelectric and endurance of Hf 0.5 Zr 0.5 O 2 (HZO) thin-film capacitors by implementing W electrode. The W/HZO/W capacitor shows excellent pristine 2 P r values of 45.1 μC/cm 2 at ±6 V, which are much higher than those of TiN/HZO/W (34.4 μC/cm 2 ) and W/HZO/TiN (26.9 μC/cm 2 ) capacitors. Notably, the maximum initial 2 P r value of W/HZO/W capacitor can reach as high as 57.9 μC/cm 2 at ±7.5 V. These strong ferroelectric polarization effects are ascribed to the W electrode with a fairly low thermal expansion coefficient which provides a larger in-plane tensile strain compared with TiN electrode, allowing for enhancement of o-phase formation. Moreover, the W/HZO/W capacitor also exhibits higher endurance, smaller wake-up effect (10.1%) and superior fatigue properties up to 1.5 × 10 10 cycles compared to the TiN/HZO/W and W/HZO/TiN capacitors. Such improvements of W/HZO/W capacitor are mainly due to the decreased leakage current by more than an order of magnitude compared to the W/HZO/TiN capacitor. These results demonstrate that capping electrode material plays an important role in the enhancement of o-phase formation, reduces oxygen vacancies, mitigates wake-up effect and improves reliability.

(Invited) Ferroelectric Hafnium Oxide for Non-Volatile Memory Applications: From Single Capacitors to Memory Arrays

This year marks the 10th anniversary of the public announcement of the discovery of ferroelectricity in HfO2-based thin films. Tremendous strides have been made in both the physical understanding and the technological use of ferroelectric HfO2. These unique fluorite-structured ferroelectrics have outstanding potential for commercial applications due to their scalability, CMOS-compatibility, and facile manufacturability. Such advantages make ferroelectric HfO2 particularly attractive for nonvolatile memories technologies such as ferroelectric random access memory (FRAM) and ferroelectric field effect transistors. Due to the wide variety of conditions in which ferroelectricity can emerge in HfO2 thin films, there has been a vast effort by the international scientific community to enhance and optimize the ferroelectric properties using a wide variety of approaches. Advancements in thin film ferroelectric capacitor and memory array technologies are therefore progressing rapidly.The structural properties of HfO2 are a major focal point for technology development because the competition between several crystalline phases in HfO2 thin films can have a major impact on device performance. For thin film memory capacitors, stabilizing the polar orthorhombic phase and eliminating secondary paraelectric phases is paramount in achieving robust polycrystalline HfO2 ferroelectrics. Doping and the presence of a capping electrode during crystallization have been extensively demonstrated to influence the emergence and stability of the ferroelectric orthorhombic phase. Greater attention has been placed recently on the thin film growth conditions in atomic layer deposition and physical vapor deposition, especially with regard to the oxidation conditions that have been shown to have a substantial impact on the device performance of ferroelectric HfO2 and Hf0.5Zr0.5O2 capacitors. Composition, film growth, and the crystallization processes are critical aspects for thin film ferroelectric capacitor development and the latest developments will be comprehensively reviewed in the context of how the material properties relate to nonvolatile memory performance.Developments in thin film HfO2 ferroelectric capacitors are now coming to fruition with the emergence of ferroelectric random access memory arrays and demonstrators. Thin film ferroelectric HfO2 based capacitors are successfully being demonstrated in back-end-of-line (BEOL) processes at the 130nm CMOS technology. The performance of these early demonstrator memory arrays show very promising long term data retention, large memory windows with good statistical distributions, and projections for area scaling to nanoscale dimensions. The transition from large-scale micron-sized laboratory devices to smaller scale integrated capacitors has proven to be a major step forward in endurance cycling with >1011 cycles being reported in memory arrays. The most recent integration of thin film ferroelectric HfO2 capacitors into FRAM memory arrays and what future developments are expected for HfO2 ferroelectric random access memories will be presented. Figure 1

Velocity distribution of 43Ca+ion cloud in the low temperature limit in a quadrupole Penning Trap

Penning trap has electric field created by DC voltage applied between ring and end cap electrodes and magnetic field is applied along symmetry axis, as the electric field confines ions in the axial direction through an electric potential minimum and the magnetic field confines the ions in the radial direction. The trapping potential created by the DC voltage applied between the end cap and ring electrodes in the low temperature limit is cancelled by Coulomb interaction of ions and the total energy is mainly kinetic energy of ions. The velocity distribution of 43Ca+ ions along axial direction, in radial plane and total velocity distribution due to resulting motion of both axial and radial motion of ions in low temperature limit in a Quadrupole Penning trap are presented here. These results reveal the properties of 43Ca+ ion cloud and are useful to study confining techniques for different types of ions in low temperature limit and a qubit can be encoded in the hyperfine ground states of 43Ca+ isotope for ion trap quantum computation.

A new approach to achieving strong ferroelectric properties in TiN/Hf0.5Zr0.5O2/TiN devices

In this paper, we propose a method to improve the performance of TiN/Hf0.5Zr0.5O2 (HZO)/TiN Nano-capacitors used in memory devices. Instead of direct fabrication of the TiN/HZO/TiN device, our method involves an intermediate step in which W metal is used as a capping material to induce a large in-plane tensile strain during rapid thermal annealing, resulting in a total suppression of the monoclinic phase and the appearance of the ferroelectric phase. Consequently, after removing the W capping electrode through an etching process and the post-deposition of a TiN top electrode at room temperature, a high remnant polarization of approximately 40 μC cm−2 and a 65% increase of coercive field were obtained. Moreover, the leakage current was reduced by an order of magnitude compared to the normal TiN/HZO/TiN capacitor; this result is attributed to the presence (absence) of the W/HZO (TiN/HZO) top interface during thermal annealing. The formation of a TiO x interfacial layer at elevated temperatures, which pulls oxygen from the HZO layer, resulting in the formation of oxygen vacancies, is the main cause of the high leakage current through the TiN/HZO/TiN stacks. It was confirmed that the re-capped TiN/HZO/TiN capacitor has a comparable endurance to a normal capacitor. Our results offer the re-capping process as a promising approach to fabricating HfO2-based ferroelectric memory devices with various electrode materials.

Flat electron mirror

Electron beams can be reflected by an electrode that is at a more negative potential than the cathode from which the beam is emitted. We want to design a mirror with a flat mirror electrode where the electrons are reflected at a plane very close to the electrode. The wave front of an electron can then be shaped when the mirror contains a surface topography or modulated potential. However, electron beams reflected by flat electron mirrors are usually characterized by high coefficients of chromatic and spherical aberration. When the mirror is combined with an electrostatic lens to form a tetrode mirror system, the situation deteriorates even further. This places a restrictive limit on the maximum aperture angle of the beam, and consequently also limits the attainable resolution at the image plane. We have numerically studied the dependence of these aberrations as a function of design parameters of the tetrode mirror consisting of a ground, lens, cap, and mirror electrode, and limited ourselves to only using flat electrodes with round apertures, at fixed electrode spacing. It turns out that the third order spherical aberration can be made negative. The negative third order aberration is then used to partially compensate the positive fifth order aberration. This way, a system configuration is obtained that, at 2 keV beam energy, provides a diffraction limited resolution of 7.6 nm at an image plane 25 mm from the mirror at beam semi-angles of 2.3 mrad, enabling an illumination radius of 40 μm at the mirror. The presented tetrode mirror design could spark innovative use of patterned electron mirrors as phase plates for electron microscopy in general, and for use as coherent beam splitters in Quantum Electron Microscopy in particular. An appendix presents a method to calculate the spot size of a focused beam in the presence of both third and fifth order spherical aberration coefficients, which is also applicable to Scanning (Transmission) Electron Microscopes with aberration correctors.

Crystalline Phase-Controlled High-Quality Hafnia Ferroelectric With RuO₂ Electrode

Electrical and reliability characteristics of hafnia ferroelectric capacitor are influenced by a capping electrode layer which controls the type of stress and the amount of oxygen vacancy inside hafnia. Here, we present the impact of metal nitride and metal oxide electrode on the ferroelectricity of a Hf0.5Zr0.5O2 (HZO) capacitor. For comparison, we employed two different top electrodes (RuO2 and TiN) with hafnia ferroelectric layer, forming RuO2/HZO/TiN and TiN/HZO/TiN capacitors. The RuO2 top electrode provides additional oxygen to the HZO film, lowering the amount of oxygen vacancies in the film. From material analysis, we found that the top RuO2/HZO interface exhibits less oxygen vacancy in comparison to the top TiN/HZO interface. In addition, for RuO2/HZO/TiN, due to different thermal expansion coefficient between top and bottom electrodes, the HZO film experiences significant tensile stress, resulting in the high o-phase formation and remnant polarization ( $\sim 20~\mu \text{C}$ /cm2) as compared with that of TiN/HZO/TiN capacitor ( $\sim 13~\mu \text{C}$ /cm2). This article suggests an efficient solution to reduce the interfacial defects and oxygen vacancies as well as to enhance o-phase formation and ferroelectricity.

Resident Use of EEG Cap System to Rule Out Nonconvulsive Status Epilepticus.

Nonconvulsive status epilepticus (NCSE) requires an EEG for diagnosis and in many centers access may be limited. The authors aimed to test whether neurology residents can be trained to use and interpret full-montage EEGs using an EEG cap electrode system to detect NCSE while on-call. Neurology residents were trained to interpret EEG recordings using the American Clinical Neurophysiology Society critical care EEG terminology. Residents who achieved a score of 70% or higher in the American Clinical Neurophysiology Society certification test and attended a training session were eligible to use the EEG cap on-call with patients suspected of having NCSE. Residents' experience and interpretation of observed EEG patterns were evaluated using a questionnaire. Each EEG recording was independently reviewed by three epilepsy specialists to determine the interpretability of each study and whether the residents correctly identified the EEG patterns. Sixteen residents undertook the training and 12 (75%) achieved a score of 70% or higher on the certification test. Seven of these residents performed 14 EEG cap studies between August 2017 and May 2018. The percent agreement between residents and electroencephalographers was 78.6% for EEG interpretability and 57.1% for description of EEG pattern. Residents did not miss any malignant patterns concerning for NCSE, which accounted for 1 of 14 EEGs but "overcalled" patterns as malignant in 3 of 14 recordings. This study suggests that neurology residents can be taught to perform and interpret EEGs using a cap system to monitor for NCSE. Additional training will help improve EEG interpretation and sensitivity.

Energy distribution of an ion cloud in a quadrupole Penning Trap

Ions are confined in Penning trap by the combination of electric field and magnetic field, as the electric field confines ions in the axial direction through an electric potential minimum and the magnetic field applied along the axis of the trap confines the ions in the radial direction. In the high temperature limit Coulomb interaction of ions can be neglected and the total energy is due to the electrostatic potential energy of the charge of ions and kinetic energy due to thermal energy. However, in the low temperature limit the trapping potential created by the dc voltage applied between the end cap and ring electrodes is cancelled by Coulomb interaction of ions and the total energy is mainly kinetic energy of ions. The probability density of energy distribution of ions along axial direction, in radial plane and total probability density of energy distribution due to resulting motion of both axial and radial motion of ions under high temperature and low temperature limits in a Quadrupole Penning trap are presented here. These results reveal the energy properties of ion cloud and are useful to carry out accurate measurement experiments on single stored particle, antiparticles with energy related parameters, under high temperature and low temperature limits in a Quadrupole Penning trap.

Predictive value of acute EEG measurements for seizures and epilepsy after stroke using a dry cap electrode EEG system — Study design and proof of concept

The development of seizures is a common complication in patients with stroke. A recent study suggests that electroencephalography (EEG) could be useful to predict the occurrence of seizures after stroke. However, EEG is not routinely performed in the follow-up after stroke.We present the design and proof of concept of a large prospective cohort study in which we seek to evaluate the predictive usefulness of a single dry cap EEG measurement in the acute phase after stroke or transient ischemic attack (TIA) with respect to the development of poststroke epilepsy (PSE).In patients with ischemic stroke (IS), TIA, or intracerebral hemorrhage (ICH), an acute EEG measurement using a dry cap electrode EEG (dEEG) system is performed within 7 days of symptom onset. Electroencephalography data will be analyzed quantitatively and qualitatively looking for background asymmetry, different band power ratios, and epileptiform activity. The development of seizures will be assessed repeatedly during the first 2 years after stroke or TIA using a validated questionnaire.Results from the pilot phase of 11 patients showed that the dry cap EEG measurements in patients with acute stroke and TIA are feasible. In comparison with conventional EEG, a higher proportion of noise and artifacts was detected.This article is part of the Special Issue “Seizure & Stroke”

Evaluation of Bulk and SOI FeFET Architecture for Non-Volatile Memory Applications

The stress induced by the capping electrode is critical to stabilizing the ferroelectric phase in Si-doped HfO2 which is being actively explored for embedded non-volatile memory applications. While TiN is commonly used as the electrode of choice owing to its thermodynamic stability with HfO2, its work function (WF) (=4.8eV) results in reduced memory window (MW), and higher interlayer field ( $\text{E}_{\mathrm{ IL}}$ ) in bulk Ferroelectric FETs (FeFETs). This is attributed to the built-in electric-field that arises from the WF difference between the metal and the semiconductor. This effectively reduces the ferroelectric hysteresis, and thus, the MW at the read current. Optimizing the MW and the $\text{E}_{\mathrm{ IL}}$ would entail changing the WF, and thus, the capping electrode—essential to retaining the desired ferroelectric properties. We, therefore, propose using the silicon on insulator (SOI)-FeFET architecture which provides an additional knob—back-gate bias ( $\text{V}_{\mathrm{ bg}}$ )—to optimize the MW while reducing the $\text{E}_{\mathrm{ IL}}$ . Further, we show that unlike the bulk FeFET, where a small deviation from the optimal WF dramatically shrinks the MW, the SOI-FeFET facilitates a relatively constant MW over a wide range of $\text{V}_{\mathrm{ bg}}$ . Thus, the SOI-FeFET simplifies the MW & $\text{E}_{\mathrm{ IL}}$ optimization and provides an improved MW versus $\text{E}_{\mathrm{ IL}}$ trade-off in comparison to the bulk FeFET.

Three-Dimensional Model and Evaluation of an Insulin Injection Pen for Precise Dose Capacitive Measurement

A fully parameterized three-dimensional model with specific dimensions has been developed in ANSYS for an insulin injection pen used by diabetic persons. The insulin injection pen has a smart pen cap which hosts four electrodes used for the smart pen cap electrode capacitive measurement. The addition of the smart cap on top of the insulin injection pens is novel and essential for storing and transmitting injection dose and time data to help patients successfully manage their treatment. The simulations can be used to decide the number and exact shape of the electrodes, as well as to evaluate different misalignment and asymmetries of the electrode fabrication process or of the liquid misplacement. Using Maxwell 3D tool the electrode capacitance was numerically evaluated, which is necessary for sensing and ultimately for insulin dose precise detection. Experimental results have been provided using an AD7746 high-resolution sigma-delta capacitance-to-digital converter (CDC). Simulation and experimental results for the sense electrode capacitance, in the case of both smart pen cap and complete insulin injection pen + smart pen cap system, have been obtained, using two different configurations (1 vs 3 and 2 vs 2 respectively). Smart pen cap electrode capacitance variation for different insulin fill states has been numerically evaluated and the linear behavior of the injection has been proven.

Interfacial magnetic-phase transition mediated large perpendicular magnetic anisotropy in FeRh/MgO by a heavy transition-metal capping

Stacking a magnetic memory junction in spintronic devices necessarily involves making contacts with a transitional-metal capping electrode. Herein, by means of first-principles calculations, we reveal the importance of heavy transition-metal capping on magnetic-phase transition from antiferromagnetic (AFM) to ferromagnetic (FM) order and the large perpendicular magnetic anisotropy (PMA) found in Ta-capped FeRh films on MgO substrate. While magnetization of FeRh films reorients from in-plane to PMA when in contact with MgO, the presence of Ta capping further enhances the magnitude of the PMA energy by at least five times. This large PMA is associated with the AFM-FM transition at the interface, which in turn modifies the out-of-plane Fe 3d orbital states through the hybridization with the strong spin-orbit coupled Ta 5d orbitals. Furthermore, the magnetic-phase transition at the interface is the result of the mutual mechanisms of the capping-induced volume/tetragonal expansion in the interfacial FeRh layers and the competition between the direct and indirect exchange interactions. These findings suggest that Ta/FeRh/MgO multilayers may represent highly favourable memory materials with net interfacial ferromagnetism and large PMA in antiferromagnet spintronics.

Application of polymer sensitive MRI sequence to localization of EEG electrodes

BackgroundThe growing popularity of simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) opens up the possibility of imaging EEG electrodes while the subject is in the scanner. Such information could be useful for improving the fusion of EEG-fMRI datasets. New methodHere, we report for the first time how an ultra-short echo time (UTE) MR sequence can image the materials of an MR-compatible EEG cap, finding that electrodes and some parts of the wiring are visible in a high resolution UTE. Using these images, we developed a segmentation procedure to obtain electrode coordinates based on voxel intensity from the raw UTE, using hand labeled coordinates as the starting point. ResultsWe were able to visualize and segment 95% of EEG electrodes using a short (3.5min) UTE sequence. We provide scripts and template images so this approach can now be easily implemented to obtain precise, subject-specific EEG electrode positions while adding minimal acquisition time to the simultaneous EEG-fMRI protocol. Comparison with existing method(s)T1 gel artifacts are not robust enough to localize all electrodes across subjects, the polymers composing Brainvision cap electrodes are not visible on a T1, and adding T1 visible materials to the EEG cap is not always possible. We therefore consider our method superior to existing methods for obtaining electrode positions in the scanner, as it is hardware free and should work on a wide range of materials (caps). ConclusionsEEG electrode positions are obtained with high precision and no additional hardware.

Alarm assessment using EEG markers of alertness.

Recent studies indicate that more than 40% of individuals ignore alert sounds, making the improvement of the specificity of alarm systems a vital task. Here, we decided to evaluate if EEG markers may better dissect the alert effectiveness and advance alert design. Eleven university students (7 males, 4 females), with ages ranging between 18-25 years, participated as volunteer subjects. The subjects remained seated during the session with their eyes closed, while listening to the alarm sound through noise canceling headphones for 60 seconds. The alarm sound contained random bursts of sound beats (2-5 beats every 20-30 seconds). The EEG was recorded by using a LabScribe3 software package and an iWorx EEG System with five reusable gold cap electrodes, placed on the subject’s forehead, over the right and left temporal lobes, and upon the parietal-occipital areas. Eight EEG markers (alpha and beta waves’ amplitudes and frequencies for each hemisphere) were obtained during 10 second recordings made before and during beat bursts and compared using a paired samples T-test. A significant effect of the sound effects onto the amplitude of alpha waves recorded in the right hemisphere was detected (t(18)=2.1, p =0.01). The analysis of the rest of the EEG markers did not demonstrate any significant differences. In conclusion, the study clearly indicates that EEG markers can be used for the assessment of alert efficacy. This simple, cost effective method proposed here may greatly improve the quality of alarms and the safety of various industrial and medical settings.

Continued alarm sound was not associated with expression of eeg markers of mental fatigue.

Mental fatigue is one of the main factors which leads to performance errors. Previous studies indicated that mental fatigue can be detected using EEG. Here, we attempted to see if comparable EEG changes can be observed after an exposure to a continuing alarm sound.Eleven university students (7 males, 4 females), with ages ranging between 18•25 years, participated as volunteer subjects. The participants had no medical, psychiatric, or head injury records, or any known problems with their hearing. The subjects remained seated during the session with their eyes closed. The EEG was recorded by using an iWorx EEG System with five reusable gold cap electrodes 4mm in diameter placed on the subject’s forehead, over the right and left temporal lobes, and on the right and left parietal-occipital areas. A standard alarm sound with waves of high frequency (up to 6500Hz) was introduced to the subject for 70 seconds through noise cancelling headphones, using sound volume at or below 75 db. The frequencies and amplitudes of the alpha and beta waves were calculated using LabScribe3 software packages. After the movement artifacts and failures of electrode placement were dissected, the effect of fatigue on EEG markers was analyzed in 10 second increments, using 1- way ANOVA. The preliminary finding demonstrated great individual variability between the subjects, but did not reveal a significant effect of fatigue on the EEG markers. We postulated that fatigue has more prominent influences on theta waves which were not measured in this study. Applications of the findings are discussed.