Investigating Usability and Efficiency of Virtual Reality for Research, Rehabilitation, and Simulation of Visual Field Defects in the Example of Retinitis Pigmentosa

Diese Thesis befasst sich mit der vielversprechenden Anwendung von Virtueller Realität (VR) in den Bereichen der Sehforschung und visuellen Rehabilitation, insbesondere im Hinblick auf periphere Gesichtsfelddefekte (VFDs) bei Retinitis-Pigmentosa(RP)-Patienten. Der fortschreitende Verlust des Gesichtsfelds, der durch RP und andere VFDs verursacht wird, kann alltägliche Aufgaben, geistige Gesundheit und Lebensqualität der Betroffenen stark beeinträchtigen. Darüber hinaus gibt es für über 99% der RP-Patienten keine wirksame medizinische Behandlung, um den Gesichtsfeldverlust zu verhindern. Daraus ergibt sich ein dringender Bedarf nach innovativen Rehabilitationsmethoden sowie nach neuen Ansätzen, um die alltäglichen Schwierigkeiten von Menschen mit VFD zu identifizieren und zu verringern. VR-Technologie hat in den letzten Jahren große Fortschritte im Bezug auf Zugänglichkeit, Leistung und erleichterte Nutzbarkeit erfahren. Das macht sie, in Verbindung mit ihrer Fähigkeit, kontrollierte und immersive visuelle Szenen darzustellen, zu einem vielversprechenden, jedoch im Kontext der Sehforschung und der visuellen Rehabilitation nur wenig erforschten Medium. Die Arbeit konzentriert sich auf das Design und die Entwicklung eines VR-basierten Frameworks für visuelle Aufgaben, genannt 'GazeQuest'. Die entwickelte Anwendung bildete die Grundlage für drei experimentelle Versuche, die in dieser Arbeit vorgestellt und diskutiert werden. In der ersten Studie wurden - unter Verwendung der GazeQuest - die Auswirkungen verschiedener systematischer Blickmuster als kompensatorische Strategie bei Gesichtsfeldverlust im peripheren Bereich experimentell untersucht. Die Ergebnisse zeigen positive Auswirkungen auf die Vermeidung von Kollisionen und auf das Blickverhalten, offenbaren jedoch auch eine Verringerung der Laufgeschwindigkeit. Ergebnisse und Feedback aus der Studie haben die weitere Entwicklung der GazeQuest und das Design nachfolgender Studien beeinflusst. In der zweiten Studie wurde die Wirksamkeit von VR-basiertem, von zu Hause durchgeführtem Visualtraining evaluiert. Die Analyse der Ergebnisse zeigt signifikante positive Auswirkungen des Trainings auf die Navigationsfähigkeit von RP-Patienten in realer Umgebung. In der dritten Studie wurde untersucht, inwieweit die VR-basierte Simulation peripherer VFDs bei visuell gesunden Teilnehmern die Auswirkungen einer tatsächlichen RP-Erkrankung auf verschiedene virtuelle Aufgaben widerspiegelt. Die Ergebnisse zeigen eine hohe Übereinstimmung in der Performance beider Gruppen. Das legt nahe, dass die VR-basierte Simulation von Gesichtsfelddefekten die Entwicklung und Erforschung von nutzerfreundlichen Designs für VFD-Patienten unterstützen kann. Insgesamt liefern die in dieser Arbeit gewonnenen Erkenntnisse Leitlinien für die Machbarkeit und das Design zukünftiger VR-basierter Lösungen in Forschung und Rehabilitation von VFDs. Darüber hinaus wird, angeregt durch die Ergebnisse der experimentellen Studien, die fortlaufende Entwicklung der GazeQuest zu einer effektiven und adaptiven Rehabilitationsanwendung diskutiert.This thesis explores the potential of Virtual Reality (VR) in the field of vision science and visual rehabilitation, in particular addressing peripheral visual field defects (VFDs) in retinitis pigmentosa (RP) patients. The progressive loss of the visual field caused by RP and other VFD conditions can severely impact everyday tasks, mental health, and quality of life of those affected. Additionally, for over 99% of RP patients, no effective medical treatment to cure or halt the condition exists. This calls for innovative alternative rehabilitation methods, as well as for ways to better assess how to reduce difficulties encountered by individuals with VFDs. VR technology's advancements in accessibility, performance, and flexibility, coupled with its ability to offer controlled and immersive visual scenes, make it a promising but under-explored tool in the field of vision science and visual rehabilitation. To provide new insights into the effectiveness of VR based rehabilitation and into the feasibility of simulating VFDs for experimental approaches, a VR based visual task framework, named 'GazeQuest', is designed and developed. This framework provided the foundation for three experimental trials that are presented and discussed in this work. The first study involved preparatory experiments, utilizing the GazeQuest to assess the impact of different systematic gaze patterns as compensatory strategies in peripheral visual field loss. Results demonstrate positive impact on collision avoidance and gaze behavior, but also reveal adverse effects in walking speed. Findings and feedback from this study shaped subsequent development and study design. The second study evaluated the efficacy of VR-based visual exercises in a home-based environment, revealing their significant positive impact on the real-world navigation performance in RP patients. The third study investigated to which degree the VR based simulation of peripheral VFDs in visually healthy participants can reflect the effects of actual RP conditions in different virtual tasks. Findings show high agreement in performance of both groups, suggesting that simulated visual field loss could facilitate research on more accessible designs and new visual aids for VFD patients. Overall, the insights gained in this work provide guidelines for feasibility and design of future VR based tools for research and rehabilitation of VFDs. Furthermore, prompted by the findings of the experimental trials, the continued development of the GazeQuest into an effective, adaptable rehabilitation tool beyond research settings is discussed

Ab initio vibrational free energies including anharmonicity for multicomponent alloys

A density-functional-theory based approach to efficiently compute numerically exact vibrational free energies - including anharmonicity - for chemically complex multicomponent alloys is developed. It is based on a combination of thermodynamic integration and a machine-learning potential. We demonstrate the performance of the approach by computing the anharmonic free energy of the prototypical five-component VNbMoTaW refractory high entropy alloy

Two pandemic years greatly reduced young people’s life satisfaction: evidence from a comparison with pre-COVID-19 panel data

How much did young people suffer from the COVID-19 pandemic? A growing number of studies address this question, but they often lack a comparison group that was unaffected by the pandemic, and the observation window is usually short. Here, we compared the 2-year development of life satisfaction of German high school students during COVID-19 (N = 2,698) with the development in prepandemic cohorts (N = 4,834) with a difference-in-differences design. We found a decline in life satisfaction in winter 2020/2021 (Cohen’s d = -0.40) that was approximately three times stronger than that in the general population and persisted until winter 2021/2022. Young people found some restrictions particularly burdensome, especially travel restrictions, bans on cultural events, and the closure of bars/clubs

Assessing carbon dioxide emission reduction potentials of improved manufacturing processes using multiregional input output frameworks

Evaluating innovative process technologies has become highly important within the last decades. As standard tools different Life Cycle Assessment methods have been established, which are continuously improved. While those are designed for evaluating single processes they run into difficulties when it comes to assessing environmental impacts of process innovations at macroeconomic level. In this paper we develop a multi-step evaluation framework building on multi regional input–output data that allows estimating macroeconomic impacts of new process technologies, considering the network characteristics of the global economy. Our procedure is as follows: i) we measure differences in material usage of process alternatives, ii) we identify where the standard processes are located within economic networks and virtually replace those by innovative process technologies, iii) we account for changes within economic systems and evaluate impacts on emissions. Within this paper we exemplarily apply the methodology to two recently developed innovative technologies: longitudinal large diameter steel pipe welding and turning of high-temperature resistant materials. While we find the macroeconomic impacts of very specific process innovations to be small, its conclusions can significantly differ from traditional process based approaches. Furthermore, information gained from the methodology provides relevant additional insights for decision makers extending the picture gained from traditional process life cycle assessment.DFG, SFB 1026, Sustainable Manufacturing - Globale Wertschöpfung nachhaltig gestalte

The First Measurement of Spectral Lines in a Short-Period Star Bound to the Galaxy's Central Black Hole: A Paradox of Youth

We have obtained the first detection of spectral absorption lines in one of the high-velocity stars in the vicinity of the Galaxy's central supermassive black hole. Both Brgamma (2.1661 micron) and He I (2.1126 micron) are seen in absorption in S0-2 with equivalent widths (2.8+-0.3 Ang & 1.7+-0.4 Ang) and an inferred stellar rotational velocity (220+-40 km/s) that are consistent with that of an O8-B0 dwarf, which suggests that it is a massive (~15 Msun), young (<10 Myr) main sequence star. This presents a major challenge to star formation theories, given the strong tidal forces that prevail over all distances reached by S0-2 in its current orbit (130 - 1900 AU) and the difficulty in migrating this star inward during its lifetime from further out where tidal forces should no longer preclude star formation. The radial velocity measurements (-510+-40 km/s) and our reported proper motions for S0-2 strongly constrain its orbit, providing a direct measure of the black hole mass of 4.1(+-0.6)x10^6(Ro/8kpc)^3 Msun. The Keplerian orbit parameters have uncertainities that are reduced by a factor of 2-3 compared to previously reported values and include, for the first time, an independent solution for the dynamical center; this location, while consistent with the nominal infrared position of Sgr A*, is localized to a factor of 5 more precisely (+-2 milli-arcsec). Furthermore, the ambiguity in the inclination of the orbit is resolved with the addition of the radial velocity measurement, indicating that the star is behind the black hole at the time of closest approach and counter-revolving against the Galaxy. With further radial velocity measurements in the next few years, the orbit of S0-2 will provide the most robust estimate of the distance to the Galactic Center.Comment: 14 pages, Latex, Accepted for Publication in ApJ Letter

Coronal hole boundaries at small scales: III. EIS and SUMER views

We report on the plasma properties of small-scale transient events identified in the quiet Sun, coronal holes and their boundaries. We use spectroscopic co-observations from SUMER/SoHO and EIS/Hinode combined with high cadence imaging data from XRT/Hinode. We measure Doppler shifts using single and multiple Gauss fits of transition region and coronal lines as well as electron densities and temperatures. We combine co-temporal imaging and spectroscopy to separate brightening expansions from plasma flows. The transient brightening events in coronal holes and their boundaries were found to be very dynamical producing high density outflows at large speeds. Most of these events represent X-ray jets from pre-existing or newly emerging coronal bright points at X-ray temperatures. The average electron density of the jets is logNe ~ 8.76 cm^-3 while in the flaring site it is logNe ~ 9.51 cm^-3. The jet temperatures reach a maximum of 2.5 MK but in the majority of the cases the temperatures do not exceed 1.6 MK. The footpoints of jets have temperatures of a maximum of 2.5 MK though in a single event scanned a minute after the flaring the measured temperature was 12 MK. The jets are produced by multiple microflaring in the transition region and corona. Chromospheric emission was only detected in their footpoints and was only associated with downflows. The Doppler shift measurements in the quiet Sun transient brightenings confirmed that these events do not produce jet-like phenomena. The plasma flows in these phenomena remain trapped in closed loops.Comment: 16 pages, accepted for publication in A&

From electrons to phase diagrams with classical and machine learning potentials: automated workflows for materials science with pyiron

We present a comprehensive and user-friendly framework built upon the pyiron integrated development environment (IDE), enabling researchers to perform the entire Machine Learning Potential (MLP) development cycle consisting of (i) creating systematic DFT databases, (ii) fitting the Density Functional Theory (DFT) data to empirical potentials or MLPs, and (iii) validating the potentials in a largely automatic approach. The power and performance of this framework are demonstrated for three conceptually very different classes of interatomic potentials: an empirical potential (embedded atom method - EAM), neural networks (high-dimensional neural network potentials - HDNNP) and expansions in basis sets (atomic cluster expansion - ACE). As an advanced example for validation and application, we show the computation of a binary composition-temperature phase diagram for Al-Li, a technologically important lightweight alloy system with applications in the aerospace industry

Novel diffusion mechanism on the GaAs(001) surface: the role of adatom-dimer interaction

Employing first principles total energy calculations we have studied the behavior of Ga and Al adatoms on the GaAs(001)-beta2 surface. The adsorption site and two relevant diffusion channels are identified. The channels are characterized by different adatom-surface dimer interaction. Both affect in a novel way the adatom migration: in one channel the diffusing adatom jumps across the surface dimers and leaves the dimer bonds intact, in the other one the surface dimer bonds are broken. The two channels are taken into account to derive effective adatom diffusion barriers. From the diffusion barriers we conclude a strong diffusion anisotropy for both Al and Ga adatoms with the direction of fastest diffusion parallel to the surface dimers. In agreement with experimental observations we find higher diffusion barriers for Al than for Ga.Comment: 4 pages, 2 figures, Phys. Rev. Lett. 79 (1997). Other related publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm