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Interferometric Scattering Microscopy for High Spatio-Temporal 3D Tracking of Nanoparticles
No full textThe advent of single-particle tracking (SPT) techniques has significantly advanced our ability to study processes at the nanoscale, providing a crucial tool for understanding various biological and physical phenomena. However, performing three-dimensional (3D) SPT on complex surfaces—environments with inherent intricacies and heterogeneity—presents significant challenges. Factors such as background signals and optical aberrations often compromise the precision and accuracy of tracking. Additionally, conventional 3D SPT techniques frequently face limitations on axial range.
In this work, we address these challenges through the application and further development of interferometric scattering microscopy (iSCAT), a potent microscopy technique which offers significant advantages for 3D-SPT. iSCAT harnesses the interference of light scattered from a nano-object with a reference beam, enhancing the scattered electric field imprint and offering higher temporal resolution and longer tracking duration than fluorescence-based techniques. Despite iSCAT's proven efficacy for high-speed tracking in various systems, its application in 3D-SPT has been limited due to factors such as restricted axial range and speckle noise— granular interference which arises inherently and degrades the quality of images produced by coherent imaging systems, particularly in complex environments.
Our research begins by introducing the fundamentals of iSCAT, including the modeling of the iSCAT point spread function (iPSF) and its properties, followed by a comprehensive exploration of 3D iSCAT image formation. We then present a novel, high-precision, long-range 3D tracking algorithm using iSCAT, demonstrating its ability to track the motion of single gold nanoparticles in water.
Addressing the challenge of speckle noise in iSCAT is a key focus of this thesis. We explore the phenomena of speckle in iSCAT and its various regimes in the context of single particle tracking, systematically studying different speckle scenarios experimentally and proposing strategies for 3D tracking under these conditions. We introduce a data analysis toolbox which allows us to model the speckle pattern and iPSF distortion on scattering surfaces, providing us with phase information and enabling nanoparticle tracking in highly speckled environments.
In the penultimate chapter, we introduce the speckle-free iSCAT method to image complex environments in a label-free manner. We demonstrate the potential of this approach for label-free cell imaging of COS-7 cells in their native environment, visualizing subcellular compartments such as the endoplasmic reticulum and vesicles with high spatio-temporal resolution and a large field of view.
In conclusion, this work enhances the capabilities of iSCAT for 3D-SPT and label-free imaging of complex environments, offering novel approaches to tracking nanoscale processes
Synchronized Sensor Insoles for Clinical Gait Analysis in Home-Monitoring Applications
No full textWearable sensor systems are of increasing interest in clinical gait analysis. However, little information about gait dynamics of patients under free living conditions is available, due to the challenges of integrating such systems unobtrusively into a patient’s everyday live. To address this limitation, new, fully integrated low power sensor insoles are proposed, to target applications particularly in home-monitoring scenarios. The insoles combine inertial as well as pressure sensors and feature wireless synchronization to acquire biomechanical data of both feet with a mean timing offset of 15.0 μs. The proposed system was evaluated on 15 patients with mild to severe gait disorders against the GAITRite ® system as reference. Gait events based on the insoles’ pressure sensors were manually extracted to calculate temporal gait features such as double support time and double support. Compared to the reference system a mean error of 0.06 s ± 0.06 s and 3.89 % ± 2.61 % was achieved, respectively. The proposed insoles proved their ability to acquire synchronized gait parameters and address the requirements for home-monitoring scenarios, pushing the boundaries of clinical gait analysis
Increased Herpesvirus Entry Mediator Expression on Circulating Monocytes and Subsets Predicts Poor Outcomes in Pancreatic Ductal Adenocarcinoma Patients
No full textPancreatic ductal adenocarcinoma (PDAC) is aggressive, with a 5-year survival rate of only 12.8%, and its increasing incidence in Western countries highlights the urgent need for better early-stage detection and treatment methods. Early diagnosis significantly improves the chances of survival, but non-specific symptoms and undetectable precursor lesions pose a major challenge. To date, there are no reliable screening tools to detect PDAC at an early stage. Herpesvirus entry mediator (HVEM) has already been proposed as a prognostic marker in numerous cancer types. Therefore, we investigated the role of HVEM in PDAC. Flow cytometry was used to analyze HVEM expression in immune cells and its inhibitory receptors (CD160 and BTLA) on T-cells, as well as its subsets in the peripheral blood of 57 diagnosed PDAC patients and 17 clinical controls. In addition, survival analyses were performed within the PDAC cohort, changes in HVEM expression were analyzed in relation to clinicopathological parameters, and a correlation analysis between HVEM expression and cytokine levels of IL-6 and IL-10 was conducted. Furthermore, HVEM expression on monocytes and their subsets was evaluated as a potential prognostic marker and compared with the prognostic utility of CA19-9. We found that HVEM expression is significantly elevated on immune cells, particularly on monocytes ( p < 0.0001) and their subsets, in PDAC patients, and is associated with reduced survival ( p = 0.0067) and clinicopathological features such as perineural, lymphovascular, and vascular invasion. Moreover, HVEM-expressing monocytes demonstrated superior predictive value compared to CA19-9, highlighting their potential as part of a combined screening tool for PDAC. In conclusion, HVEM on monocytes could serve as a novel prognostic marker for PDAC.This work was in part supported by the German Research Foundation grants WE4892/3-1, WE4892/4-1, WE4892/8-1, and WE4892/9-1, as well as in part by the BMBF grant 03INT506CA (all to G.F.W.). BMBF KI-VesD (161L0244A), and BMBF KI-VesD-2 (16LW0338K) to J.V.German Research FoundationBMBFBMBF KI-VesDBMBF KI-VesD-
Machine-based emotion-assessment in waiting rooms – a feasibility and acceptance study
No full textBackground: Due to an aging society and changing health behaviors, emergency room crowding has become a major problem in western health care systems. Empowering patients and health care workers to assess necessary and relevant information is critical to streamline clinical workflows. Health kiosks, designed for services like self-check-in or (ideally contactless) health self-assessment may be instrumental in solving this issue. Based on the collected data, automated workflows such as flagging critical patients, inducing specific diagnostics or early symptomatic treatment could be implemented. Objective: Using an AI-supported software, which visually analyzes and categorizes facial expressions, the emotional status of hemato-oncologic patients in a German oncology outpatient clinic was examined. Additionally a survey was conducted, evaluating the acceptance of such a self-assessment solution. Results: 98% of the participants were not stressed by the real-time emotion analysis. However, the current set of registered emotion categories was found to be only partially sufficient to adequately describe the emotional status of the patients. More importantly, 88% of the participants found such a system to be meaningful. Also, 84% of the participants agreed that such a self-analysis could be of potential assistance. No relevant generation- or gender-specific differences could be observed. Discussion: Automated analysis of patients’ emotional status can be a first step toward a more comprehensive assessment of the respective health status. Patients, in particular the elderly, approve to the vision and development of such a system. Next steps are a further improvement of the AI-based emotion recognition software with respect to more emotional states as well as the definition, inclusion and ideally contactless acquisition of physical biomarkers (as e.g. heart rate or respiratory rate) determining physical and mental well-being
Optimising speech recognition using LLMs: an application in the surgical domain
No full textAutomatic speech recognition (ASR), powered by deep learning techniques, is crucial for enhancing humancomputer interaction. However, its full potential remains unrealized in diverse real-world environments, with challenges such as dialects, accents, and domain-specific jargon, particularly in fields like surgery, persisting. Here, we investigate the potential of large language models (LLMs) as error correction modules for ASR.We leverage Whisper-medium or ASRLibriSpeech for speech recognition, and GPT-3.5 or GPT-4 for error correction.We employ various prompting methods, from zero-shot to few-shot with leading questions and sample medical terms to correct wrong transcriptions. Results, measured by word error rate (WER), reveal Whisper’s superior transcription accuracy over ASR-LibriSpeech, with a WER of 11.93% compared to 32.09%. GPT-3.5, with the few-shot with medical terms prompting method, further enhances performance, achieving a 64.29% and 37.83% WER-reduction for Whisper and ASR-LibriSpeech, respectively. Additionally, Whisper exhibits faster execution speed. Substituting GPT-3.5 with GPT- 4 further enhances transcription accuracy. Despite some few challenges, our approach demonstrates the potential of leveraging domain-specific knowledge through LLM prompting for accurate transcription, particularly in sophisticated domains like surgery
Investigation and experimental evaluation of a mono-pixel X-ray system in healthcare
Get PDFThe acquisition of two-dimensional X-ray images (of non-human objects) is quite expensive, primarily due to the costly flat-panel or line detectors. Reducing these costs could open up new possibilities in healthcare applications, such as inspecting limb prostheses for cracks and defects or safety-related material testing of helmets and child seats. In this contribution, two different setups of low-cost mono-pixel X-ray scanners are described: a small scanner with a working volume of 20 x 20 x 20 cm 3 and a large system with a volume of 150 x 230 x 110 cm 3 . Using these novel mono-pixel X-ray scanning systems, various objects - ranging from an X-ray phantom and a human skull phantom to a high-end limb prosthesis with integrated electronics - were scanned and investigated. Compared to conventional X-ray systems, the mono-pixel systems can depict these objects without the distortion problems of cone beam detectors. Although the scanning procedure is time-consuming, the results are quite promising. Mono-pixel X-ray-scanning is a novel modality capable of scanning largescale objects with low-dose radiation. While it is currently not suitable for human applications due to the long scanning times, it can still be used for the non-destructive testing of large-scale medical devices, such as e.g. arm and leg prosthesis
In Vivo Vascularization of Cell-Supplemented Spider Silk-Based Hydrogels in the Arteriovenous Loop Model
No full textThe goal of reconstructive surgery in treating tissue defects is to achieve a stable reconstructive outcome while minimizing donor site morbidity. As a result, tissue engineering has emerged as a key focus in the pursuit of this goal. One approach is to create a tissue container that can be preconditioned and later transplanted into the defect area. The characteristics of the matrices used in the tissue container are critical to this approach’s success. Matrices generated with recombinant, functionalized spider silk (eADF4(C16)-RGD) have been reported to be biocompatible and easy to vascularize. However, the effect of exogenously added proangiogenic cells, such as endothelial cells (T17b), on the vascularization process of matrices generated with this hydrogel in vivo has not been described yet. In this study, we implanted arteriovenous (AV) loop containers filled with a spider silk hydrogel consisting of an eADF4(C16)-RGD matrix and encapsulated, differentiated endothelial T17b cells producing the reporter protein TNFR2-Fc-Flag-GpL. The histological and µCT analyses revealed spontaneous angiogenesis and fibrovascular tissue formation in the container at 2 and 4 weeks post-implantation. The reporter protein was detected after 4 weeks. No severe immune response was observed. Altogether, this study demonstrates that cell-supplemented recombinant spider silk is a highly promising hydrogel to produce matrices for tissue engineering applications.This project was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project number 326 998 133—TRR 225 (Subprojects C04 and C01).Deutsche Forschungsgemeinschaft (DFG, German Research Foundation
Combinatorial ab initio calculations and core spectroscopy unravel the electronic structure of nickel cobalt manganese oxide
No full textThe rising interest in complex oxides for energy storage applications calls for the development of efficient computational schemes that enable exploring the vast configurational space of these materials to guide and complement experiments. In this work, we adopt a high-throughput screening method based on density-functional theory to investigate the electronic-structure fingerprints of a specific stoichiometry of lithiated manganese-cobalt-nickel oxide, , which are relevant for the identification of the material in X-ray spectroscopy experiments. After creating the candidate structures in an automated fashion, we inspect their structural characteristics and electronic properties focusing specifically on the Ni and O contributions to the density of states. To do so, we exploit data analysis schemes that provide us with a metric to classify the considered structures according to the properties of interest, including the oxidation state. Comparison with X-ray absorption spectroscopy measurements confirms the robustness of the developed computational approach and reveals the most likely composition of the probed sample.Open Access funding enabled and organized by Projekt DEAL.Carl von Ossietzky Universität Oldenburg (3092
Revealing key parameters to minimize the diameter of polypropylene fibers produced in the melt electrospinning process
No full textThis study deals with the subject of optimizing the melt electrospinning process of polypropylene with the aim of producing nanoscale fibers. A feasibility study with two polypropylene types and different additives to adapt the material composition is performed. The polypropylene types are of different molar masses to adapt the viscosity to the process. The used additives, sodium stearate and Irgastat ® P 16, have a positive effect on the electrical conductivity of the polymer melt. In addition, process parameter optimization is done by varying the climate chamber temperature, using different collector voltages and varying the nozzle-collector distance. A strong influence of the climate chamber temperature has been proven and leads to a desired temperature of 100°C. The fiber diameter is dependent on process parameters, material melt viscosity and electrical conductivity. With optimized process and material parameters, the fiber diameter could be minimized to a median value of 210 nm