Backstepping-induced terminal sliding mode control with strict Lyapunov function. - In: IEEE CCTA 2020, (2020), S. 851-856
https://doi.org/10.1109/CCTA41146.2020.9206398
Collagen-iron oxide nanoparticle based ferrogel: large reversible magnetostrains with potential for bioactuation. - In: Multifunctional materials, ISSN 2399-7532, Volume 3 (2020), number 3, 035001, Seite 1-10
Smart materials such as stimuli responsive polymeric hydrogels offer unique possibilities for tissue engineering and regenerative medicine. As, however, most synthetic polymer systems and their degradation products lack complete biocompatibility and biodegradability, this study aims to synthesize a highly magnetic responsive hydrogel, based on the abundant natural biopolymer collagen. As the main component of vertebratal extracellular matrix, it reveals excellent biocompatibility. In combination with incorporated magnetic iron oxide nanoparticles, a novel smart nano-bio-ferrogel can be designed. While retaining its basic biophysical properties and interaction with living cells, this collagen-nanoparticle hydrogel can be compressed to 38% of its original size and recovers to 95% in suitable magnetic fields. Besides the phenomenology of this scenario, the underlying physical scenarios are also discussed within the framework of network models. The observed reversible peak strains as large as 150% open up possibilities for the fields of biomedical actuation, soft robotics and beyond.
https://doi.org/10.1088/2399-7532/abaa2d
OPM magnetorelaxometry in the presence of a DC bias field. - In: EPJ Quantum Technology, ISSN 2196-0763, Bd. 7 (2020), 12, insges. 14 S.
Spatial quantitative information about magnetic nanoparticle (MNP) distributions is a prerequisite for biomedical applications like magnetic hyperthermia and magnetic drug targeting. This information can be gathered by means of magnetorelaxometry (MRX) imaging, where the relaxation of previously aligned MNP's magnetic moments is measured by sensitive magnetometers and an inverse problem is solved. To remove or minimize the magnetic shielding in which MRX imaging is carried out today, the knowledge of the influence of background magnetic fields on the MNP's relaxation is a prerequisite. We show MRX measurements using an intensity-modulated optically pumped magnetometer (OPM) in background magnetic fields of up to 100 [my]T. We show that the relaxation parameters alter or may be intentionally altered significantly by applying static fields parallel or antiparallel to the MNPs alignment direction. Further, not only the relaxation process of the MNP's magnetic moments could be measured with OPM, but also their alignment due to the MRX excitation field.
https://doi.org/10.1140/epjqt/s40507-020-00087-3
Personenwiedererkennung mittels maschineller Lernverfahren für öffentliche Einsatzumgebungen. - Ilmenau : Universitätsverlag Ilmenau, 2020. - 1 Online-Ressource (xix, 523 Seiten)
Technische Universität Ilmenau, Dissertation 2019
Die erscheinungsbasierte Personenwiedererkennung in öffentlichen Einsatzumgebungen ist eines der schwierigsten, noch ungelösten Probleme der Bildverarbeitung. Viele Teilprobleme können nur gelöst werden, wenn Methoden des maschinellen Lernens mit Methoden der Bildverarbeitung kombiniert werden. In dieser Arbeit werden maschinelle Lernverfahren eingesetzt, um alle Abarbeitungsschritte einer erscheinungsbasierten Personenwiedererkennung zu verbessern: Mithilfe von Convolutional Neural Networks werden erscheinungsbasierte Merkmale gelernt, die eine Wiedererkennung auf menschlichem Niveau ermöglichen. Für die Generierung des Templates zur Beschreibung der Zielperson wird durch Einsatz maschineller Lernverfahren eine automatische Auswahl personenspezifischer, diskriminativer Merkmale getroffen. Durch eine gelernte Metrik können beim Vergleich von Merkmalsvektoren szenariospezifische Umwelteinflüsse kompensiert werden. Eine Fusion komplementärer Merkmale auf Score Level steigert die Wiedererkennungsleistung deutlich. Dies wird vor allem durch eine gelernte Gewichtung der Merkmale erreicht. Das entwickelte Verfahren wird exemplarisch anhand zweier Einsatzszenarien - Videoüberwachung und Robotik - evaluiert. Bei der Videoüberwachung ermöglicht die Wiedererkennung von Personen ein kameraübergreifendes Tracking. Dies hilft menschlichen Operateuren, den Aufenthaltsort einer gesuchten Person in kurzer Zeit zu ermitteln. Durch einen mobilen Serviceroboter kann der aktuelle Nutzer anhand einer erscheinungsbasierten Wiedererkennung identifiziert werden. Dies hilft dem Roboter bei der Erfüllung von Aufgaben, bei denen er den Nutzer lotsen oder verfolgen muss. Die Qualität der erscheinungsbasierten Personenwiedererkennung wird in dieser Arbeit anhand von zwölf Kriterien charakterisiert, die einen Vergleich mit biometrischen Verfahren ermöglichen. Durch den Einsatz maschineller Lernverfahren wird bei der erscheinungsbasierten Personenwiedererkennung in den betrachteten unüberwachten, öffentlichen Einsatzfeldern eine Erkennungsleistung erzielt, die sich mit biometrischen Verfahren messen kann.
https://doi.org/10.22032/dbt.45621
Age-related differences of motor cortex plasticity in adults: a transcranial direct current stimulation study. - In: Brain stimulation, ISSN 1876-4754, Bd. 13 (2020), 6, S. 1588-1599
Background - Cognitive, and motor performance are reduced in aging, especially with respect to acquisition of new knowledge, which is associated with a neural plasticity decline. Animal models show a reduction of long-term potentiation, but not long-term depression, in higher age. Findings in humans are more heterogeneous, with some studies showing respective deficits, but others not, or mixed results, for plasticity induced by non-invasive brain stimulation. One reason for these heterogeneous results might be the inclusion of different age ranges in these studies. In addition, a systematic detailed comparison of the age-dependency of neural plasticity in humans is lacking so far. - Objective - We aimed to explore age-dependent plasticity alterations in adults systematically by discerning between younger and older participants in our study. - Methods - We recruited three different age groups (Young: 18-30, Pre-Elderly: 50-65, and Elderly: 66-80 years). Anodal, cathodal, or sham transcranial direct current stimulation (tDCS) was applied over the primary motor cortex with 1 mA for 15 min to induce neuroplasticity. Cortical excitability was monitored by single-pulse transcranial magnetic stimulation as an index of plasticity. - Results - For anodal tDCS, the results show a significant excitability enhancement, as compared to sham stimulation, for both, Young and the Pre-Elderly groups, while no LTP-like plasticity was obtained in the Elderly group by the applied stimulation protocol. Cathodal tDCS induced significant excitability-diminishing plasticity in all age groups. - Conclusion - Our study provides further insight in age-related differences of plasticity in healthy humans, which are similar to those obtained in animal models. The decline of LTP-like plasticity in higher age could contribute to cognitive deficits observed in aging.
https://doi.org/10.1016/j.brs.2020.09.004
Investigation of magnetically driven passage of magnetic nanoparticles through eye tissues for magnetic drug targeting. - In: Nanotechnology, ISSN 1361-6528, Bd. 31 (2020), 49, 495101, S. 1-12
This paper elucidates the feasibility of magnetic drug targeting to the eye by using magnetic nanoparticles (MNPs) to which pharmaceutical drugs can be linked. Numerical simulations revealed that a magnetic field gradient of 20 T m^-1 seems to be promising for dragging magnetic multicore nanoparticles of about 50 nm into the eye. Thus, a targeting magnet system made of superconducting magnets with a magnetic field gradient at the eye of about 20 T m^-1 was simulated. For the proof-of-concept tissue experiments presented here the required magnetic field gradient of 20 T m^-1 was realized by a permanent magnet array. MNPs with an optimized multicore structure were selected for this application by evaluating their stability against agglomeration of MNPs with different coatings in water for injections, physiological sodium chloride solution and biological media such as artificial tear fluid. From these investigations, starch turned out to be the most promising coating material because of its stability in saline fluids due to its steric stabilization mechanism. To evaluate the passage of MNPs through the sclera and cornea of the eye tissues of domestic pigs (Sus scrofa domesticus), a three-dimensionally printed setup consisting of two chambers (reservoir and target chamber) separated by the eye tissue was developed. With the permanent magnet array emulating the magnetic field gradient of the superconducting setup, experiments on magnetically driven transport of the MNPs from the reservoir chamber into the target chamber via the tissue were performed. The resulting concentration of MNPs in the target chamber was determined by means of quantitative magnetic particle spectroscopy. It was found that none of the tested particles passed the cornea, but starch-coated particles could pass the sclera at a rate of about 5 ng mm^-2 within 24 h. These results open the door for future magnetic drug targeting to the eye.
https://doi.org/10.1088/1361-6528/abb0b4
Estimating the shape of the fetal pulse curve for transabdominal pulse oximetry using synchronous averaging. - In: 42nd Annual International Conferences of the IEEE Engineering in Medicine and Biology Society in conjunction with the 43rd Annual Conference of the Canadian Medical and Biological Engineering Society, (2020), S. 1-4
https://doi.org/10.1109/EMBC44109.2020.9176692
MNP enhanced microwave imaging by means of pseudo-noise sensing with different external magnetic field modulations. - In: 42nd Annual International Conferences of the IEEE Engineering in Medicine and Biology Society in conjunction with the 43rd Annual Conference of the Canadian Medical and Biological Engineering Society, (2020), S. 1795-1798
https://doi.org/10.1109/EMBC44109.2020.9175940
The influence of the stimulus design on the harmonic components of the steady-state visual evoked potential. - In: Frontiers in human neuroscience, ISSN 1662-5161, Bd. 14 (2020), 343, insges. 11 S.
https://doi.org/10.3389/fnhum.2020.00343
FisheyeDistanceNet : self-supervised scale-aware distance estimation using monocular fisheye camera for autonomous driving. - In: 2020 IEEE International Conference on Robotics and Automation (ICRA), (2020), S. 574-581
https://doi.org/10.1109/ICRA40945.2020.9197319