open_UMR

Aaron Beller

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Welcome to open_UMR!

Open_UMR is a cross faculty publication hub. We collect scientific publications, resources, research data and software from members of Philipps-University Marburg and make it openly accessible. To ensure high standards of quality and re-usability, submissions to open_UMR are subject to curation.

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Recent Submissions

Open Access
QEVO®-Assisted Anatomical Inspection of Adjacent Perforators in Microsurgical Clipping — Technical Note
(MDPI) Ahmetspahic, Adi; Burazerovic, Eldin; Rizvanovic, Hana; Selimovic, Ema; Kujaca, Eleonora; Pojskic, Mirza; Feletti, Alberto; Arnautovic, Kenan
first_page settings Order Article Reprints Open AccessTechnical Note QEVO®-Assisted Anatomical Inspection of Adjacent Perforators in Microsurgical Clipping—Technical Note by Adi Ahmetspahic 1,2 [ORCID] , Eldin Burazerovic 1, Hana Rizvanovic 2, Ema Selimovic 2 [ORCID] , Eleonora Kujaca 2, Mirza Pojskic 3,* [ORCID] , Alberto Feletti 4 and Kenan Arnautovic 5 [ORCID] 1 Department of Neurosurgery, Clinical Center of University of Sarajevo, 71000 Sarajevo, Bosnia and Herzegovina 2 Department of Medicine, University Sarajevo School of Science and Technology, 71000 Sarajevo, Bosnia and Herzegovina 3 Department of Neurosurgery, Philipps University of Marburg, 35043 Marburg, Germany 4 Department of Neurosciences, Biomedicine, and Movement Sciences, Institute of Neurosurgery, University of Verona, 37126 Verona, Italy 5 Department of Neurosurgery, The University of Tennessee Health Science Center, Memphis, TN 38138, USA * Author to whom correspondence should be addressed. Brain Sci. 2025, 15(3), 300; https://doi.org/10.3390/brainsci15030300 [Titel anhand dieser DOI in Citavi-Projekt übernehmen] Submission received: 27 January 2025 / Revised: 4 March 2025 / Accepted: 6 March 2025 / Published: 12 March 2025 (This article belongs to the Special Issue Current Research in Neurosurgery) Download keyboard_arrow_down Browse Figures Versions Notes Abstract Introduction: Aneurysms of brain vessels are life-threatening conditions with various adverse outcomes, some stemming from microsurgical intervention, particularly when major vessel perforators are inadequately protected. The use of endoscopes enhances the approach to aneurysms by providing closer visualization (180–360 degrees) of the local anatomy, potentially reducing accidental damage. To improve visualization and efficiency, a microscope-integrated 45-degree angled microinspection endoscopic tool (QEVO®, Carl Zeiss, OberkochenTM) has been developed and employed in various neurosurgical procedures. Methods: Between 2021 and 2025, 27 brain aneurysms were treated with QEVO® assistance at the Department of Neurosurgery, Clinical Center of the University of Sarajevo. The choice of the videos corresponds to the best image quality in videos and on the microscopic determination of adjacent vessel perforators, which were not adequately seen purely by the surgical microscope in specific cases. Exclusion criteria included cases without a need for QEVO® assistance in perforator visualization, severe brain edema, intraoperative aneurysm rupture, posterior circulation, or low video quality. Results: Case 1 demonstrates an anterior choroidal artery (AchA) aneurysm; Case 2 presents an anterior communicating artery (AcommA) aneurysm; and Case 3 features contralateral middle cerebral artery (MCA) microsurgical clipping with QEVO® assistance. Conclusions: The QEVO® tool significantly improves the visualization of aneurysm–perforator relationships, increasing the likelihood of preserving perforators during standard microsurgical clipping. This innovative approach may reduce surgical complications and enhance patient outcomes, highlighting the tool’s potential as an adjunct in aneurysm microsurgery.
Open Access
Spatial resources in pre-service teachers’ instructional practices in VR tandems: co-constructing shared spaces and embodied spatial scaffolding
(Frontiers) Lazovic, Milica
This study examines the use of spatial resources in instructional practices during virtual reality (VR) tandem interactions between pre-service teachers of German as a foreign language and learners with A2 language proficiency. These interactions take place within the highly immersive virtual environment Wander, designed to facilitate (inter)cultural learning. The linguistic, perceptual, epistemological, and technical asymmetries within this setting necessitate scaffolding the coparticipant through the virtual environment, guiding them in spatial exploration, orienting them to usability cues, leveraging spatial resources to support interactive and learning processes, developing embodied practices, and fostering mutual alignment. The analysis focuses on pre-service teachers’ use of spatial resources and their practices of embodied spatial scaffolding to support learning in three key areas: instructing on app functionality, developing new embodied action patterns, and fostering a functional understanding of virtual objects. Prior to this, the study examines the instructional grounding for upcoming actions, such as directing instructions, by focusing on two key aspects: the co-construction of shared focus and the alignment of perspectives. This is achieved through eliciting, monitoring, and adjusting according to the position of the co-participant’s avatar in situations of dynamic spatial perception. These situations are characterized by the interplay between changing position, orientation, and floating attention in the context of exploratory spatial navigation, the presence of distractors, or transitions. Methodologically, this study is grounded in conversation analysis and interactional linguistics. Video recordings capture participants’ perspectives in a split-screen format, documenting parallel perspectivization in action flow and revealing shifts in interactional coordination. The results indicate, among other things, that participants prefer using pointing gestures accompanied by local adverbs, which are semantically subsequently extended, specified, varied, or reduced in a scaffolded way. Over time, synchronized co-referencing practices involving joint and matched pointing become central to negotiating a blended origo. The sequential analysis identifies meta-regulatory practices for perspective alignment by eliciting the other’s perspective and monitoring the co-participants’ avatar orientation and spatial relation to align for goal-directed action before coconstructing the focus. This study contributes to the understanding of immersive instruction in virtual learning environments by highlighting key aspects such as pre-instructional spatial self-and other-monitoring activities designed to support spatial self-alignment. Embodied spatial scaffolding involves some of the following supporting aspects: the adjustment of the internal spatial interface, the transition from static to dynamic interaction within the virtual environment, the management of spatial relations (explorative vs. concrete references), the control of spatial interaction and coherence, the orientation to calls for alignment, the bridging of spatial transformations in the action flow, and the monitoring of the co-participants’ avatar. The interactions tend to emphasize spatial engagement, with participants sometimes “overdoing” spatial elements rather than using spatial cues to develop more complex interactions.
Open Access
Computationally efficient multi-layer thickness determination using sparse CW THz spectroscopy
(Optica Publishing Group) Jäckel, Alexander; Mach, Cornelius; Schwenson, Lauri Maximilian; Castro-Camus, Enrique; Liebermeister, Lars; Kohlhaas, Robert; Koch, Martin
Continuous wave (CW) terahertz spectroscopy systems are a proven and convenient solution for industrial non-destructive testing and multi-layer thickness determination. For these systems to find use in real-time inline monitoring applications, a high acquisition and data evaluation rate is required. One approach that can increase and potentially enable kHz acquisition rates is to scan through only a few selected frequencies instead of a full spectrum. However, the data analysis can become a bottleneck when realizing measurement systems capable of operating at these speeds. Here we show the feasibility of extracting multi-layer thicknesses from a sparsely sampled spectrum by using a real-time evaluation scheme capable of runtimes below a millisecond with a thickness uncertainty comparable to a full spectrum evaluation. This is achieved by reducing the number of computations by three orders of magnitude. The proposed measurement scheme requires complete knowledge of the sample composition and the refractive index of each layer. Additionally, achieving these high evaluation rates assumes that individual layer thicknesses deviate by no more than 200 µm from their nominal values. However, both conditions are often met in an industrial setting. The sparse evaluation is demonstrated on a three layer sample, the achieved standard deviation of the layer thicknesses remains below 5 µm for each layer. These measurements confirm the effectiveness of the sparse sampling approach for THz spectroscopy and demonstrate the ability to address industrial applications with measurement rates in the kilohertz range.
Open Access
Handelsgeschäft als Vertragsgegenstand - Eine rechtsvergleichende Betrachtung
(2026-04-21) Zaghloul, Hend; Helms, Tobias; Möslein, Florian
Die vorliegende Arbeit beinhaltet eine rechtsvergleichende Betrachtung des Handelsgeschäfts als Vertragsgegenstand aus Sicht eines grenzüberschreitenden Asset Deals. Der Begriff und Umfang des Handelsgeschäfts wird aus deutscher und ägyptischer Sicht sowie aus Sicht einiger arabischer Rechtssysteme betrachtet. Weiter werden die Rechte und Forderungen im Zusammenhang mit dem Handelsgeschäft betrachtet, insbesondere im Hinblick darauf, inwieweit diese mit der Übertragung des Handelsgeschäfts an den Erwerber übertragbar sind. Die verschiedenen Wege der Übertragung des Handelsgeschäfts nach ägyptischem und – wo vergleichbar – nach deutschem Recht werden erörtert und beurteilt. Im Allgemeinen wird ein Schwerpunkt auf das Handelsgeschäft aus moderner Sicht und insbesondere das Online-Handelsgeschäft sowie das Handelsgeschäft mit Auslandsbezug gesetzt. Ziel ist die Beurteilung, inwiefern die Vorschriften zum klassischen Handelsgeschäft auf Online-Handelsgeschäfte anwendbar bzw. ausreichend sind. Zum Schluss werden die Vorschriften hinsichtlich des Handelsgeschäfts im Verhältnis mit anderen rechtlichen Themen betrachtet.
Open Access
Diffusion Tensor Imaging bei Patienten mit chronischen Spannungskopfschmerzen
(2026-04-15) Vacik, Lena; Knake, Susanne; Bopp, Miriam H. A.
Einleitung: Der Kopfschmerz vom Spannungstyp (TTH) ist die häufigste primäre Kopf- schmerzerkrankung mit einer geschätzten Jahresprävalenz von 26% bis 38%. Die Ursachen der Pathophysiologie sind bisher noch unzureichend verstanden, eine suffiziente Therapie bei chro- nischen Spannungskopfschmerzen (CTTH) ist häufig schwierig. Da die Pathophysiologie bisher noch weitestgehend unklar ist, war es Ziel dieser Arbeit, nach mikrostrukturellen Veränderungen bei CTTH mittels Diffusionstensorbildgebung (DTI) zu su- chen, um die Pathogenese besser verstehen zu können. Material und Methoden: Wir schlossen insgesamt 9 Patientinnen mit CTTH im Alter von 18 bis 63 Jahren (Durchschnittsalter 37,9 +/- 18,6 Jahre) und 10 gesunde weibliche Kontrollperso- nen im Alter von 19 bis 62 Jahren (Durchschnittsalter 37,3 +/- 14,3 Jahre) ein. Die Kopf- schmerzpatientinnen wurden ausführlich in einem Erstgespräch bezüglich Ein- und Ausschluss- kriterien befragt sowie durch einen kopfschmerzerfahrenen Neurologen untersucht. Alle Teil- nehmer unterzogen sich einer Magnetresonanztomographie (MRT) mit Diffusions-Tensor- Imaging (DTI)-Sequenz. Aus dem Diffusionstensor wurde die fraktionierte Anisotropie (FA), die axiale Diffusivität (AD), die radiale Diffusivität (RD), die NODDI-Parameter, der Orientie- rungsdispersionsindex (ODI) und der Neuritendichteindex (NDI) berechnet. Ergebnisse: Mit Hilfe der verschiedenen skalaren Indizes konnten wir mikrostruktrurelle Ver- änderungen im Cerebellum rechts, Tectum, Gyrus fusiformis occipitalis rechts, im Cortex ce- rebri links, im Gyrus frontalis inferior links, im Gyrus temporalis medialis rechts und links, im Gyrus frontalis medialis links, im Gyrus angularis rechts, im Gyrus postcentralis rechts, im Fasciculus longitudinalis superior links, im Gyrus fusiformis/parahippocampus temporalis rechts und im Gyrus cinguli rechts finden. Schlussfolgerungen: Bei Patienten, die an CTTH leiden, wurden mikrostrukturelle Verände- rungen in mehreren Hirnregionen festgestellt. Sie stehen im Zusammenhang mit Hirnregionen, die zur Schmerzmatrix, zum trigeminalen System oder zu Assoziationsfasern gehören und inter- agieren.