The effect of dipole housing and feeding wires in physical phantoms for EEG

Current dipoles are well established models in the localization of neuronal activity to electroencephalography (EEG) data. In physical phantoms, current dipoles can be used as signal sources. Current dipoles are often powered by constant current sources connected via twisted pair wires mostly consisting of copper. The poles are typically formed by platinum wires. These wires as well as the dipole housing might disturb the electric potential distributions in physical phantom measurements. We aimed to quantify this distortion by comparing simulation setups with and without the wires and the housing. The electric potential distributions were simulated using finite element method (FEM). We chose a homogenous volume conductor surrounding the dipoles, which was 100 times larger than the size of the dipoles. We calculated the difference of the electric potential at thesurface of the volume conductor between the simulations with and without the connecting wires and the housing. Comparing simulations neglecting all connecting wires and the housing rod to simulations considering them, the electric potential at the surface of the volume conductor differed on average by 2.85 %. Both platinum and twisted pair copper wires had a smaller effect on the electric potentials with a maximum average change of 6.38 ppm. Consequently, source localization of measurements in physical head phantoms should consider these rods in the forward model

Influence of silver/silver chloride electroless plating on the Shore hardness of polyurethane substrates for dry EEG electrodes

Dry electrodes enable a shorter preparation time for infant EEG. Since infant skin is more sensitive than adult skin, soft electrodes are required to reduce the mechanical stress for this sensitive skin. Thus, soft electrodes are crucial for eventual repetitive and long-term use like in neonatal intensive care units. A biocompatible polyurethane (PU) can be produced in low hardness resulting in a soft and flexible electrode substrate. Silver/silver chloride (Ag/AgCl) electroless plating provides a conductive, electrochemically stable coating but the process may alter the mechanical properties of the electrode substrate. In this study, we assess the hardness of PU material before and after Ag/AgCl plating. The test sample design for Shore hardness measurement is based on ISO 7619-1:2010. Sample production consists of a 3D print master model, silicone molding, PU casting, and finally electroless plating. UPX 8400-1 (Sika AG, Switzerland) is used for the sample substrates. Test samples are produced with 7 different Shore hardness (range A40-A95) and 14 samples (each hardness: 1 uncoated and 1 coated). The hardness measurements are carried out with a lever-operated test stand Shore hardness tester model with a digital hardness tester (TI-AC with HDA 100-1, KERN & SOHN GmbH, Germany). It is shown that there is a hardness increase (Shore A) due to Ag/AgCl coating with a grand average of 1.1±0.7 (p<0.05). The largest increase of 2.1±0.2 is seen on the initial lowest Shore hardness sample (Shore hardness: 43.4±0.1). The absolute increase of hardness due to the Ag/AgCl coating decreases with increasing substrate hardness. It is concluded that there is no strong hardness increase of PU substrates due to Ag/AgCl plating. Therefore, the material is suitable as a soft electrode for repetitive and long-term use in infant applications

The Simulated Classroom Biology—A simulated classroom environment for capturing the action‐oriented professional knowledge of pre‐service teachers about evolution

Background: The professional knowledge of pre-service teachers is highly important for effective and successful teaching. In recent years, many research groups have been engaged in developing simulated classroom environments to capture especially the pedagogical knowledge (PK) of pre-service teachers, neglecting the content-related facets of professional knowledge such as pedagogical content knowledge (PCK). Objectives: In the present study, we describe the development of a simulated class- room environment — the Simulated Classroom Biology (SCR Bio) — and provide evidence regarding its validity to assess pre-service biology teachers' action-oriented PCK in the area of evolution. Methods: This study examined the evidence supporting the validity of using the SCR Bio to investigate action-oriented PCK of pre-service biology teachers. The (1) evidence based on test content (expert ratings) and the (2) evidence based on relation to other variables (known-groups comparison) was obtained. We tested the SCR Bio with N = 76 German pre-service biology teachers. Results and Conclusions: Our results show the successfully operationalized PCK in the SCR Bio through explicit allocation of specific misconceptions to each virtual student's answer and the valid measurement of pre-service biology teachers' action-oriented PCK. This results in a validated simulated classroom environment for pre-service but also in-service teachers. In the future, the SCR Bio will be developed from an assessment instrument to a training tool to simulate explicit teaching situations. This allows to complement the predominantly theoretical components of university-based teacher education with practice-based simulated classroom environments

Don't Just Judge the Spelling! The Influence of Spelling on Assessing Second-Language Student Essays

When judging subject-specific aspects of students’ texts, teachers should assess various characteristics, e.g., spelling and content, independently of one another since these characteristics are indicators of different skills. Independent judgments enable teachers to adapt their classroom instruction according to students’ skills. It is still unclear how well teachers meet this challenge and which intervention could be helpful to them. In Study 1, N = 51 pre-service teachers assessed four authentic English as a Second Language (ESL) essays with different overall text qualities and different qualities of spelling using holistic and analytic rating scales. Results showed a negative influence of the experimentally manipulated spelling errors on the judgment of almost all textual characteristics. In Study 2, an experimental prompt was used to reduce this judgment error. Participants who were made aware of the judgment error caused by spelling errors formed their judgments in a less biased way, indicating a reduction of bias. The determinants of the observed effects and their practical implications are discussed

The Arch electrode: a novel dry electrode concept for improved wearing comfort

Electroencephalography (EEG) is increasingly used for repetitive and prolonged applications like neurofeedback, brain computer interfacing, and long-term intermittent monitoring. Dry-contact electrodes enable rapid self-application. A common drawback of existing dry electrodes is the limited wearing comfort during prolonged application. We propose a novel dry Arch electrode. Five semi-circular arches are arranged parallelly on a common baseplate. The electrode substrate material is a flexible thermoplastic polyurethane (TPU) produced by additive manufacturing. A chemical coating of Silver/Silver-Chloride (Ag/AgCl) is applied by electroless plating using a novel surface functionalization method. Arch electrodes were manufactured and validated in terms of mechanical durability, electrochemical stability, in vivo applicability, and signal characteristics. We compare the results of the dry arch electrodes with dry pin-shaped and conventional gel-based electrodes. 21-channel EEG recordings were acquired on 10 male and 5 female volunteers. The tests included resting state EEG, alpha activity, and a visual evoked potential. Wearing comfort was rated by the subjects directly after application, as well as at 30 min and 60 min of wearing. Our results show that the novel plating technique provides a well-adhering electrically conductive and electrochemically stable coating, withstanding repetitive strain and bending tests. The signal quality of the Arch electrodes is comparable to pin-shaped dry electrodes. The average channel reliability of the Arch electrode setup was 91.9 ± 9.5%. No considerable differences in signal characteristics have been observed for the gel-based, dry pin-shaped, and arch-shaped electrodes after the identification and exclusion of bad channels. The comfort was improved in comparison to pin-shaped electrodes and enabled applications of over 60 min duration. Arch electrodes required individual adaptation of the electrodes to the orientation and hairstyle of the volunteers. This initial preparation time of the 21-channel cap increased from an average of 5 min for pin-like electrodes to 15 min for Arch electrodes and 22 min for gel-based electrodes. However, when re-applying the arch electrode cap on the same volunteer, preparation times of pin-shaped and arch-shaped electrodes were comparable. In summary, our results indicate the applicability of the novel Arch electrode and coating for EEG acquisition. The novel electrode enables increased comfort for prolonged dry-contact measurement

Measurement and analysis of partial lightning currents in a head phantom

Direct lightning strikes to the human head can lead to various effects, ranging from burnings to death. The biological and physical mechanisms of a direct lightning strike in the human head are not well understood. The aim of this paper is to design an experimental setup to measure the spatial and temporal current distribution during a direct lightning strike to physical head phantoms to establish normative values for personal lightning protection equipment design and testing. We created head phantoms made of agarose, replicating the geometric and dielectric properties of scalp, skull, and intracranial volume. The bases of the three compartments were galvanically contacted via copper electrodes to measure the current per compartment. We used pulse generators to apply aperiodic voltage and current signals that modelled lightning components. Our experiments indicated that the scalp compartment was exposed to the current with a fraction of 80–90%. The brain and skull compartments were exposed between 6–13% and 3–6% of the total measured current respectively. In case of a flashover, most of the current (98–99%) flowed through the discharge channel. Unlike previous theoretical estimates and measurements in technical setups, we observed considerably longer times for the flashover to build up. In our experiments, the time to build up a fully formed flashover varied from approximately 30–700 μs. The observed current patterns in cases without and with flashover provided information on regions of possible damage in the human head. Consequently, we identified the phenomenon of a flashover as a potential mechanism for humans to survive a lightning strike. Our measured current distributions and amplitudes formed the base for normative values, which can be used in later experimental investigations regarding the possibilities of individual lightning protection equipment for humans

The Republic Of Acastus v. The State Of Rubia: The Case Concerning The Elysian Fields

The differences between the Republic of Acastus and the State of Rubria concerning the Elysian Fields have been brought before the International Court of Justice in accordance with Article 40(1) of its statute by notification of the Compromis for Submission to the International Court of Justice of the Differences between the Republic of Acastus (Applicant) and the State of Rubria (Respondent) Concerning the Elysian Fields

Analyse diagnostischer Kompetenzen angehender Grundschullehrer*innen mit Studienfach Sachunterricht / Naturwissenschaften

Die Diagnose von Schülerleistungen stellt eine Kernaufgabe von Lehrkräften dar. Der Beitrag nimmt daher diagnostische Kompetenzen angehender Grundschullehrer*innen mit Studienfach Sachunterricht/Naturwissenschaften in den Blick, welche mit Hilfe des Simulierten Klassenzimmers (SCR) erfasst wurden. Die Autoren erläutern, dass die diagnostischen Kompetenzen der untersuchten Studierenden des Grundschullehramts mit Fach Sachunterricht / Naturwissenschaften dringend weiterer Förderung bedürfen. (DIPF/Orig.)The diagnosis of student performance is one of the most important tasks of teachers. On the one hand, performance diagnoses form the basis for adaptive instructional planning, and on the other hand, performance-related assessments and prognoses (e.g., the recommendation for subsequent schooling) influence the students’ educational pathways and thus their future. The analysis of teachers’ diagnostic competencies, however, is very difficult due to the large number of variables relevant to practice. One possibility to obtain reliable information about diagnostic competencies of (prospective) teachers is the use of the Simulated Classroom (SCR), a digital tool for simulating complex and dynamic interactions during classroom discussions. In this article, we pursue the question: what is the state of diagnostic competencies of elementary student teachers majoring in integrated science? For this purpose, we developed the SCR Integrated Science (SCR Science) and asked N = 72 elementary student teachers of integrated science to conduct a classroom discussion with 12 simulated students in the SCR Science. Beforehand, the student teachers were given the task of judging the difficulties of the tasks used in the SCR Science. During the simulated classroom discussion, the task was to judge the qualities of individual student answers. At the end of the simulation, the students’ overall performances were to be judged by the student teachers. In this contribution, we present the SCR Science and selected results. (DIPF/Orig.

Evaluating the Performance of Ultra-Low-Field MRI for In-vivo 3D Current Density Imaging of the Human Head

Magnetic fields associated with currents flowing in tissue can be measured non-invasively by means of zero-field-encoded ultra-low-field magnetic resonance imaging (ULF MRI) enabling current density imaging (CDI) and possibly conductivity mapping of human head tissues. Since currents applied to a human are limited by safety regulations and only a small fraction of the current passes through the relatively high-resistive skull, a sufficient signal-to-noise ratio (SNR) may be difficult to obtain when using this method. In this work, we study the relationship between the image SNR and the SNR of the field reconstructions from zero-field-encoded data. We evaluate these results for two existing ULF MRI scanners, one ultra-sensitive single-channel system and one whole-head multi-channel system, by simulating sequences necessary for current-density reconstruction. We also derive realistic current-density and magnetic-field estimates from finite-element-method simulations based on a three-compartment head model. We found that existing ULF-MRI systems reach sufficient SNR to detect intra-cranial current distributions with statistical uncertainty below 10%. However, they also reveal that image artifacts influence the reconstruction quality. Further, our simulations indicate that current-density reconstruction in the scalp requires a resolution less than 5 mm and demonstrate that the necessary sensitivity coverage can be accomplished by multi-channel devices.Comment: 18 pages, 8 figures. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 68686

Global Hippocampal Volume Reductions and Local CA1 Shape Deformations in Amyotrophic Lateral Sclerosis

There is increasing evidence for hippocampal involvement in Amyotrophic Lateral Sclerosis (ALS). Recent neuroimaging studies have been focused on disease-related hippocampal volume alterations while changes in hippocampal shape have been investigated less frequently. Here, we aimed to characterize the patterns of hippocampal degeneration using both an automatic and manual volumetric and surface-based approach in a group of 31 patients with ALS and 29 healthy controls. Irrespective of the segmentation type, left, and right hippocampal volumes were significantly reduced in ALS compared to controls. Local shape alterations were identified in the hippocampal head region of patients with ALS that corresponds to the cornu ammonis field 1 (CA1), a region known to be involved in novelty detection, memory processing, and integration of hippocampal input and output information. The results suggest a global hippocampal volume loss in ALS that is complemented by local shape deformations in a highly interconnected region within the hippocampus