34 research outputs found
Traveling Wave Magnetic Particle Imaging for determining the iron-distribution in rock: Traveling Wave Magnetic Particle Imaging for determining the iron-distribution in rock
Determining the composition of solid materials is of high interest in areas such as material research or quality assurance. There are several
modalities at disposal with which various parameters of the material can be observed, but of those only magnetic resonance imaging
(MRI) or computer tomography (CT) offer anon-destructive determination of material distribution in 3D. A novel non-destructive imaging method is Magnetic Particle Imaging (MPI), which uses
dynamic magnetic fields for a direct determination of the distribution of magnetic materials in 3D. With this approach, it is possible to determine and differentiate magnetic and non-magnetic behaviour.
In this paper, the first proof-of-principle measurements of magnetic properties in solid environments are presented using a home-built traveling wave magnetic particle imaging scanner
Possible Worlds Truth Table Task
In this paper, a novel experimental task is developed for testing the highly influential, but experimentally underexplored, possible worlds account of conditionals (Stalnaker, 1968; Lewis, 1973). In Experiment 1, this new task is used to test both indicative and subjunctive conditionals. For indicative conditionals, five competing truth tables are compared, including the previously untested, multi-dimensional possible worlds semantics of Bradley (2012). In Experiment 2, these results are replicated and it is shown that they cannot be accounted for by an alternative hypothesis proposed by our reviewers. In Experiment 3, individual variation in truth assignments of indicative conditionals is investigated via Bayesian mixture models that classify participants as following one of several competing models. As a novelty of this study, it is found that a possible worlds semantics of Lewis and Stalnaker is capable of accounting for participantsâ aggregate truth value assignments in this task. Applied to indicative conditionals, we show across three experiments, that the theory both captures participantsâ truth values at the aggregate level (Experiments 1 and 2) and that it makes up the largest subgroup in the analysis of individual variation in our experimental paradigm (Experiment 3)
Cancellation, negation, and rejection
In this paper, new evidence is presented for the assumption that the reason-relation reading of indicative conditionals ('if A, then C') reflects a conventional implicature. In four experiments, it is investigated whether relevance effects found for the probability assessment of indicative conditionals (Skovgaard-Olsen, Singmann, and Klauer, 2016a) can be classified as being produced by a) a conversational implicature, b) a (probabilistic) presupposition failure, or c) a conventional implicature. After considering several alternative hypotheses and the accumulating evidence from other studies as well, we conclude that the evidence is most consistent with the Relevance Effect being the outcome of a conventional implicature. This finding indicates that the reason-relation reading is part of the semantic content of indicative conditionals, albeit not part of their primary truth-conditional content
VAG/AVO Revision â Evolution oder Revolution? - Tagungsband 2022
Reflektieren die am 18. MĂ€rz 2022 verabschiedete Vorlage zur Teilrevision des Versicherungsaufsichtsgesetzes (VAG) sowie der am 17. Mai 2022 publizierte Entwurf zur Teilrevision der Aufsichtsverordnung (AVO) eine graduelle Entwicklung oder einen tief(er)greifenden Umbruch? Eine Evolution oder eine Revolution? Lassen sich derartige PhĂ€nomene und Schattierungen dazwischen in der vorliegenden Revision des VAG und der AVO identifizieren? Antworten auf diese Fragestellungen zu finden, war Gegenstand einer Tagung des Europa Instituts an der UniversitĂ€t ZĂŒrich am 25. August 2022. Verschiedene Mitwirkende haben in Teilbereichen nach Antworten gesucht. Um die so gewonnenen Erkenntnisse einer weiteren Leserschaft zugĂ€nglich zu machen, liegen nun auf den VortrĂ€gen beruhende Artikel und Berichte ĂŒber die beiden Diskussionsrunden im vorliegenden Tagungsband vor
MUNDUS project : MUltimodal neuroprosthesis for daily upper limb support
Background: MUNDUS is an assistive framework for recovering direct interaction capability of severely motor impaired people based on arm reaching and hand functions. It aims at achieving personalization, modularity and maximization of the userâs direct involvement in assistive systems. To this, MUNDUS exploits any residual control of the end-user and can be adapted to the level of severity or to the progression of the disease allowing the user to voluntarily interact with the environment. MUNDUS target pathologies are high-level spinal cord injury (SCI) and neurodegenerative and genetic neuromuscular diseases, such as amyotrophic lateral sclerosis, Friedreich ataxia, and multiple sclerosis (MS). The system can be alternatively driven by residual voluntary muscular activation, head/eye motion, and brain signals. MUNDUS modularly combines an antigravity lightweight and non-cumbersome exoskeleton, closed-loop controlled Neuromuscular Electrical Stimulation for arm and hand motion, and potentially a motorized hand orthosis, for grasping interactive objects.
Methods: The definition of the requirements and of the interaction tasks were designed by a focus group with experts and a questionnaire with 36 potential end-users. Five end-users (3 SCI and 2 MS) tested the system in the configuration suitable to their specific level of impairment. They performed two exemplary tasks: reaching different points in the working volume and drinking. Three experts evaluated over a 3-level score (from 0, unsuccessful, to 2, completely functional) the execution of each assisted sub-action.
Results: The functionality of all modules has been successfully demonstrated. Userâs intention was detected with a 100% success. Averaging all subjects and tasks, the minimum evaluation score obtained was 1.13â±â0.99 for the release of the handle during the drinking task, whilst all the other sub-actions achieved a mean value above 1.6. All users, but one, subjectively perceived the usefulness of the assistance and could easily control the system. Donning time ranged from 6 to 65 minutes, scaled on the configuration complexity.
Conclusions: The MUNDUS platform provides functional assistance to daily life activities; the modules integration depends on the userâs need, the functionality of the system have been demonstrated for all the possible configurations, and preliminary assessment of usability and acceptance is promising
Automatic Negative Evaluation of Suffocation Sensations in Individuals With Suffocation Fear.
The Quality of Response Time Data Inference: A Blinded, Collaborative Assessment of the Validity of Cognitive Models
Most data analyses rely on models. To complement statistical models, psychologists have developed cognitive models, which translate observed variables into psychologically interesting constructs. Response time models, in particular, assume that response time and accuracy are the observed expression of latent variables including 1) ease of processing, 2) response caution, 3) response bias, and 4) non-decision time. Inferences about these psychological factors, hinge upon the validity of the modelsâ parameters. Here, we use a blinded, collaborative approach to assess the validity of such model-based inferences. Seventeen teams of researchers analyzed the same 14 data sets. In each of these two-condition data sets, we manipulated properties of participantsâ behavior in a two-alternative forced choice task. The contributing teams were blind to the manipulations, and had to infer what aspect of behavior was changed using their method of choice. The contributors chose to employ a variety of models, estimation methods, and inference procedures. Our results show that, although conclusions were similar across different methods, these "modelerâs degrees of freedom" did affect their inferences. Interestingly, many of the simpler approaches yielded as robust and accurate inferences as the more complex methods. We recommend that, in general, cognitive models become a typical analysis tool for response time data. In particular, we argue that the simpler models and procedures are sufficient for standard experimental designs. We finish by outlining situations in which more complicated models and methods may be necessary, and discuss potential pitfalls when interpreting the output from response time models
Fully Integrated Traveling-Wave-MPI-MRI-Hybrid Scanner
Magnetic Particle Imaging (MPI) ist ein neuartiges tomographisches Bildgebungsverfahren,
welches in der Lage ist, dreidimensional die Verteilung von superparamagnetischen
Nanopartikeln zu detektieren. Aufgrund des direkten Nachweises
des Tracers ist MPI ein sehr schnelles und sensitives Verfahren [12] und benötigt fĂŒr
eine Einordnung des Tracers (z.B. im Gewebe) eine weitere bildgebende ModalitÀt
wie die Magnetresonanztomographie (MRI) oder die Computertomographie. Die
strukturelle Einordnung wird hĂ€ufig mit dem Fusion-Imaging-Verfahren durchgefĂŒhrt,
bei dem die Proben separat in den GerÀten vermessen und die DatensÀtze
retrospektiv korreliert werden [75][76]. In einem ersten Experiment wurde bereits
ein Traveling-Wave-MPI-Scanner (TWMPI) [17] mit einem Niederfeld-MRI-Scanner
kombiniert und die ersten Hybridmessung durchgefĂŒhrt [15]. Der technische Aufwand,
zwei separate GerÀte aufzubauen sowie die Tatsache, dass ein MRI-GerÀt
bei 30mT sehr lange benötigt, diente als Motivation fĂŒr ein integriertes TWMPIMRI-
Hybridsystem, bei dem das dynamische lineare Gradientenarray (dLGA) eines
TWMPI-Scanners intrinsisch das B0-Feld fĂŒr ein MRI-GerĂ€t erzeugen sollte.
Das Ziel dieser Arbeit war es, die Grundlagen fĂŒr einen integrierten TWMPI-MRIHybridscanner
zu schaffen. Die Geometrie des dLGAs sollte dabei nicht verÀndert
werden, damit TWMPI-Messungen weiterhin ohne EinschrÀnkungen möglich sind.
Zusammenfassend werden hier noch mal die wichtigsten Schritte und Ergebnisse
dieser Arbeit aufgezeigt.
Zu Beginn dieser Arbeit wurde mittels Magnetfeldsimulationen nach einer geeigneten
Stromverteilung gesucht, um allein mit dem dLGA ein ausreichend homogenes
Magnetfeld erzeugen zu können. Die Ergebnisse der Simulationen zeigten,
dass bereits zwei unterschiedliche Ströme in 14 der 20 Einzelspulen des dLGAs
genĂŒgten, um ein Field of View (FOV) mit der GröĂe 36mm x 12mm mit ausreichender
HomogenitÀt zu erreichen. Die HomogenitÀt innerhalb des FOVs betrug
dabei 3000 ppm. FĂŒr die angestrebte FeldstĂ€rke von 235mT waren StromstĂ€rken
von 129A und 124A nötig.
Die hohen Ströme des dLGAs erforderten die Entwicklung eines dafĂŒr angepassten
VerstĂ€rkers. Das ursprĂŒngliche Konzept, welches auf einem linear angesteuerten
Leistungstransistors aufbaute, wurde in zahlreichen Schritten so weit verbessert,
dass die nötigen StromstÀrken stabil an- und ausgeschaltet werden konnten.
Mithilfe eines Ganzkörper-MRIs konnte erstmals das B0-Feld des dLGAs, welches
durch den selbstgebauten VerstÀrker erzeugt wurde, gemessen und mit der Simulation
verglichen werden. Zwischen den beiden VerlÀufen zeigte sich eine qualitativ
gute Ăbereinstimmung.
Das Finden des NMR-Signals stellte wegen des selbstgebauten VerstÀrkers eine
Herausforderung dar, da zu diesem Zeitpunkt die nötige PrÀzision noch nicht erreicht
wurde und der wichtigste Parameter, die MagnetfeldstÀrke im dLGA, nicht
gemessen werden konnte. Dagegen konnte die LĂ€nge der Pulse fĂŒr die Spin-Echo-
Sequenz sehr gut gemessen werden, jedoch war der optimale Wert noch nicht bekannt.
Durch iterative Messungen wurden die richtigen Einstellungen gefunden,
die nach Ănderungen an der Hardware jeweils angepasst wurden.
Die Performanz des VerstÀrkers konnte anhand wiederholter Messungen des NMRSignals
genauer untersucht werden. Es zeigte sich, dass die PrÀzision weiter verbessert
werden musste, um reproduzierbare Ergebnisse zu erhalten. Mithilfe des
NMR-Signals konnten auch das B0-Feld ausgemessen werden. Es zeigte eine gute
Ăbereinstimmung zur Simulation. Mithilfe von vier Segmentspulen des dLGAs
war es möglich einen linearen Gradienten entlang der z-Achse zu erzeugen. Ein
Gradient wurde zusÀtzlich zum B0-Feld geschaltet und ebenfalls ausgemessen.
Auch dieser Verlauf zeigte eine gute Ăbereinstimmung zur Simulation.
Mithilfe des Gradienten wurde erfolgreich die Frequenzkodierung und die Phasenkodierung
implementiert, durch die bei beiden Messungen zwei Proben anhand
des Ortes unterschieden werden konnten. Damit war die Entwicklung des MRIScanners
abgeschlossen.
Der Aufbau des TWMPI-Scanners benötigte neben dem Bau des dLGAs die Anfertigung
von Sattelspulen. FĂŒr die MPI-Messungen konnte der fehlende Teil der
Sendekette sowie die gesamte Empfangskette von einer frĂŒheren Version benutzt
werden. Auch fĂŒr das MPI wurde die FunktionalitĂ€t mithilfe einer Punktprobe und
eines Phantoms ĂŒberprĂŒft, allerdings hier in zwei Dimensionen.
Die Erweiterung zu einem Hybridscanner erforderte weitere Modifikationen gegenĂŒber
einem reinen TWMPI- bzw. MRI-Scanner. Es musste ein Weg gefunden
werden, die Beschaltung des dLGAs fĂŒr die jeweilige ModalitĂ€t zĂŒgig anzupassen.
DafĂŒr wurde ein Steckbrett gebaut, das es erlaubt, die Verkabelung des dLGAs in
kurzer Zeit zu Ă€ndern. AuĂerdem mussten innerhalb des dLGAs die Sattelspulen
und die Empfangsspule des TWMPIs sowie die Empfangsspule des MRIs untergebracht
werden. Ein modulares System erlaubte die gleichzeitige Anordnung aller
Komponenten innerhalb des dLGAs. Das messbare FOV des MRIs ist der HomogenitÀt
des B0-Feldes angepasst, das FOV des TWMPI ist ausgedehnter.
Zum Ende dieser Arbeit wurde erfolgreich eine Hybridmessung durchgefĂŒhrt. Das
Phantom bestand aus je zwei Kugeln gefĂŒllt mit Ăl und mit einem MPI-Tracer
(Resovist). Mit TWMPI war die rÀumliche Abbildung der Resovistkugeln möglich,
wĂ€hrend mit MRI die der Ălkugeln möglich war. Diese in situ Messung zeigte die
erfolgreiche Umsetzung des Konzeptes fĂŒr den TWMPI-MRI-Hybridscanner.
Zusammenfassend wurden in dieser Arbeit die Grundlagen fĂŒr einen TWMPIMRI-
Hybridscanner gelegt. Die gröĂte Schwierigkeit bestand darin, ein ausreichend
homogenes B0-Feld fĂŒr das MRI zu erzeugen, mit dem man ein gutes NMRSignal
aufnehmen konnte. Mit einer einfachen Stromverteilung, bestehend aus zwei
unterschiedlichen Strömen, konnte ein ausreichend homogenes B0-Feld erzeugt
werden. Durch komplexere Stromverteilungen lÀsst sich die HomogenitÀt noch verbessern
und somit das FOV vergröĂern.
Die MRI-Bildgebung wurde in dieser Arbeit fĂŒr eine Dimension implementiert und
soll in fortfĂŒhrenden Arbeiten auf 2D und 3D ausgedehnt werden. Letztendlich
soll anhand eines MRI-Bildes die Partikelverteilung des MPI-Tracers in Lebewesen
deren Anatomie zugeordnet werden. In [76][77][78] sind die ersten prÀklinischen
Anwendungen mit dem TWMPI-Scanner durchgefĂŒhrt worden. Diese Anwendungen
erlangen eine höhere Aussagekraft durch die zusÀtzlichen Informationen eines
TWMPI-MRI-Hybridscanners.
In weiteren Arbeiten sollte zusĂ€tzlich die GröĂe des FOVs fĂŒr das MRI erweitert
werden. AuĂerdem macht es Sinn, einen elektronischen Schalter zum Umschalten
des dLGAs zwischen MRI und MPI zu realisieren.
Die nÀchste Version des Hybridscanners könnte beispielsweise ein komplett neu
gestaltetes dLGA enthalten, in dem jede Segmentspule in radialer Richtung einmal
geteilt wird und dadurch in eine innere und eine Ă€uĂere Spule zerlegt wird. FĂŒr
das MRI werden die beiden Spulenteile gegen geschaltet, um ein homogenes Feld
in radialer Richtung zu erhalten. FĂŒr das TWMPI werden die Spulenteile gleichgeschaltet,
um einen möglichst starken Feldgradienten zu erreichen.
In dieser Arbeit wurde fĂŒr die nĂ€chste Version eines TWMPI-MRI-Hybridscanners
viel Wissen generiert, das Ă€uĂerst hilfreich fĂŒr das neue Design sein wird. Anhand
der Vermessung des B0-Feldes hat sich gezeigt, dass die simulierten Magnetfelder
gut mit den gemessenen Magnetfeldern ĂŒbereinstimmen. AuĂerdem wurde viel
gelernt ĂŒber die Kombination von TWMPI mit MRI.Magnetic Particle Imaging (MPI) is a novel tomographic imaging technique, which
can detect the distribution of superparamagnetic iron oxides in three dimensions.
MPI is a fast and sensitive technique due to its immediate tracer detection [12] but
needs another imaging modality like magnetic resonance imaging (MRI) or computed
tomography for tracer classification (e.g. to tissue). The classification is often
done with the fusion imaging technology where the sample is measured in different
systems and the data are correlated afterwards [75][76]. In a first experiment
a traveling-wave-MPI-scanner (TWMPI) [17] was combined with a low-field-MRIscanner
and first hybrid measurements were acquired [15]. The motivation for an
integrated TWMPI-MRI-hybrid system, in which the dynamic linear gradient array
(dLGA) generates the main magnetic field B0 intrinsically, was such that an
MRI-system at 30mT needs a long time for data acquisition as well as the higher
technical effort for assembling two separate systems.
The aim of this work was to establish the basic principles of an integrated TWMPIMRI-
hybrid scanner. The geometry of the dLGA should not be altered in this
process so that TWMPI-measurements are still possible without limitations. All
important steps and measurements of this work are presented here in summary.
At the beginning of this work it was necessary to find a suitable current configuration
by the use of magnetic field simulations. The aim was to generate a magnetic
field that is homogenous enough for NMR measurements only with the dLGA
coils. The results of the simulations showed that only two different currents in 14
of the 20 dLGA coils are necessary to obtain a field of view (FOV) with a sufficiently
homogeneity of 3000ppm and a size of 36mm x 12 mm. For the target field
strength of 235mT currents of 129A and 124A are required.
The high currents in the dLGA made it necessary to develop a custom amplifier.
The original concept, which is based on a linear controlled power transistor, was
improved in numerous steps so that the high currents could be turned on and off
in a stable way.
The magnetic field B0 of the dLGA, which was generated by the custom amplifier,
could firstly be measured with the aid of a full-body MRI. Its comparison to the
simulation showed a qualitative good agreement.
A challenge was to find the NMR-signal because of the custom amplifier which did
not have the necessary precision at this particular time and also the most important
parameter, the magnetic field strength inside the dLGA, could not be measured. In
contrast the length of the pulses for the spin-echo-sequence could be measured
accurately, but the ideal value was not known. Iterative measurements were used
to find the right adjustments, which had to be adapted after each change in the
hardware.
The amplifier performance could be analyzed more in detail by repeated measurements
of the NMR-signal. They indicated that the precision had to be improved
further to achieve reproducible results. The B0-field could be measured by means
of the NMR-signal. It showed good agreement to the simulation. By means of
four segment coils of the dLGA it was possible to create a linear gradient along the
z-axis. as well as the gradient along the z-axis
By means of the gradient frequency encoding and phase encoding were successfully
implemented. Two samples could be differentiated by its location for both
encoding methods. That completes the development of the MRI-scanner.
The design of the TWMPI-scanner required the construction of the saddle coils besides
the production of the dLGA. The missing parts of the transmit chain and the
whole receive chain could be used from an earlier version for MPI-measurements.
The functionality of the MPI was tested with a point sample and a phantom, but
this time in two dimensions.
The extension to a hybrid scanner required additional modifications compared to
a pure TWMPI- or MRI-scanner. An efficient way had to be found to change the
connections of the dLGA for the particular modality. A pinboard was built which
made a rapid change of the connections of the dLGA possible. Furthermore the
saddle coils and the receive coil of the TWMPI-system as well as the receive coil
of the MRI had to be placed inside the dLGA. This problem was solved with a
modular system which made it possible to simultaneously place all components
inside the dLGA. The measurable FOV of the MRI is adapted to the homogeneity
of the B0-field, the FOV of the TWMPI is larger.
At the end of this work a hybrid measurement was successfully performed. The
phantom consisted of two spheres filled with oil and another two spheres filled
with an MPI-tracer (Resovist). With TWMPI the spatial resolution of the Resovist
spheres was possible, while with MRI it was possible for the oil spheres. This
in situ measurement showed the successful implementation of the TWMPI-MRIhybrid
scanner concept.
In summary the basic principles for a TWMPI-MRI-hybrid scanner were established
in this work. The highest obstacle was the generation of a homogenous
magnetic field B0 for MRI, which lead to a good NMR-signal. A simple current configuration,
consisting of two different currents, generated a sufficient homogenous
magnetic field. With more complex current configurations a more homogenous
field and thereby a larger FOV is possible.
MRI-imaging was implemented in this work in one dimension and should be extended
to 2D and 3D in further projects. Eventually an MRI-image should be used
to display a relation between particle distribution of the MPI-tracer in living creatures
and their anatomy. The first preclinical applications were implemented with
the TWMPI-scanner [76][77][78]. These applications would reach a higher information
value with the use of a TWMPI-MRI-hybrid scanner.
The size of the FOV for the MRI should be extended in further projects. Furthermore
it is reasonable to realize an electric switch for changing the connections of
the dLGA between MRI and MPI.
The next version of the hybrid scanner could contain for example a completely
newly designed dLGA in which every segment coil is divided radially. The segment
coils would consist of an inner and an outer part. For MRI-measurements
both magnetic fields work against each other to create a radially homogenous
magnetic field. For TWMPI both magnetic fields work together to create a high
magnetic field gradient.
For the next version of a TWMPI-MRI-hybrid scanner a lot of know-how was created
which will be helpful for the new design. By means of the B0 measurements
it was shown that the simulated magnetic fields fit well to the measured ones.
Furthermore plenty was learned for the combination of TWMPI and MRI
What Will Happen To The Teen Drivers Of Today? A Triage Of Research And Intervention Issues
The purpose of this panel session is to reflect on and debate the advances and challenges associated with driving as a teen. Traffic crashes are the leading cause of death in the U.S. and worldwide in this age group. What research has contributed to our understanding of this state of affairs and what research and interventions are still needed? A group of internationally known researchers will present research on the contributions of driving behavior (e.g. secondary task engagement) and driving conditions (e.g. teenage passengers) on teen crash risk and the potential for interventions, such as education, training, and graduated drivers licensing (GDL) to reduce this risk. The breadth and depth of the panelists\u27 knowledge will be tested by audience questions and directed by the provocateur as a range of additional possible contributions and countermeasures are considered and prioritized