154092 research outputs found
Sort by
Multitask Deep Learning for Automated Detection of Endoleak at Digital Subtraction Angiography during Endovascular Aneurysm Repair
No full textPurpose: To develop and evaluate a novel multitask deep learning framework for automated detection and localization of endoleaks at aortic digital subtraction angiography (DSA) performed during real-world endovascular aneurysm repair (EVAR) procedures for abdominal aortic aneurysm.Materials and Methods: This retrospective study analyzed intraoperative aortic DSA images from patients undergoing EVAR (January 2017–December 2021). An expert panel assessed each sequence for endoleaks. Each sequence was processed into three input channels: peak density, time to peak, and area under the time-density curve, generating three two-dimensional perfusion maps per patient. These maps served as input into a convolutional neural network for binary detection (classification) and localization (regression) of endoleaks through multitask learning. Fivefold cross-validation was performed, with patients split 80:20 into training and testing datasets for each fold. Performance metrics included area under the receiver operating characteristic curve, F1 score, precision, and recall and were compared with human experts.Results: The study included 220 patients (median age, 74 years [IQR, 68–79]; 181 male). Endoleaks were visible in 111 of 220 (50.5%) patients. The model identified and localized endoleaks with an area under the receiver operating characteristic curve of 0.85 ± 0.0031 (SD), F1 score of 0.78 ± 0.21, 95% precision, and 73% recall. Compared with the procedural team (94% precision, 63% recall), it had higher values in both metrics, with an F1 score within the human observer range (0.75–0.85). Balancing regression and classification by multitask learning delivered optimal results. The interobserver agreement among human experts was moderate (Fleiss κ = 0.404).Conclusion: A novel, fully automated deep learning method accurately detected and localized endoleaks at DSA imaging from EVAR procedures.</p
Offloading Strategies Used for Plantar Diabetic Foot Ulcers and Their Outcomes in Real-Life Clinical Practice
No full textIntroduction: International guidelines describe offloading to facilitate healing as a cornerstone in the treatment of diabetes-related foot ulcers. In present-day clinics, various offloading devices are used. The aim of this paper is to describe the effectiveness in healing of different offloading devices used in real-life clinical practice in patients with diabetes-related foot ulcers.Methods: A retrospective cohort study of 235 patients with a plantar foot ulcer in one diabetic foot centre of expertise was used. Clinical outcomes were determined during a follow-up period of 12 months. Groups were defined according to the types of offloading. Univariate and multivariate analysis was performed to assess ulcer-related outcomes in different offloading devices.Results: Of the 235 patients, 3% were treated with a Total Contact Cast (TCC), 9% with an ankle-high removable device, 32% with a custom-made orthopaedic shoe, 16% with a bandage shoe, and 39% with felted foam. Patients who received a bandage shoe or felted foam had a higher UT classification (Stage D in 21% and 18%, respectively, p = 0.001) and more ulcers per foot (13% and 5%, respectively, p = 0.002). The overall healing rate at 12 weeks was 33% and was not significantly different between the offloading device groups (p = 0.255). Healing rates at 20 and 52 weeks were 51.5% and 77%.Conclusions: Removable ankle-high offloading devices, orthopaedic shoes, bandage shoes, and felted foam are the most frequently used for plantar diabetic foot ulcers in clinical practice. This seems to be the result of various physician- and patient-related factors such as logistical reasons, patient factors, and severity of complicated ulcers. Diabetic foot ulcer healing after 12 weeks, 20 weeks, and 1-year follow-up were consistent with previous observational studies.</p
Novel strategies to encode engineered living matter with self-feeding properties
No full textThe field of tissue engineering aims to replace or repair damaged or diseased tissue, typically by combining cells with various biomaterials and growth factors. Although a plethora of approaches have been developed and researched, the field has so far lacked the impact it promised. One of the main challenges for translating engineered tissues towards patients is the upscaling of these structures from small lab to clinically relevant sizes. Specifically, upon implantation, engineered tissues typically lack functional vascularization that offers continuous nutrient and oxygen supply. This typically results in the development of ischaemia that leads to a necrotic core and hence implant failure. This thesis highlights the ability to preserve cell viability and function under oxygen deprived conditions similar to those found in large engineered tissues. As typical nutrients, such as glucose, are characteristically small and hydrophilic, the scientific chapters represent the developmental path of a nutrient releasing system to be integrated into engineered tissues and to provide these structures with self-feeding properties. The incorporation of glucose into a hydrophobic carrier enables controlled and sustained release into the surrounding, which is build upon on by 3D-printing the first of its kind mechanical life support. Lastly, the work on the previous self-feeding approaches led to the discovery of glycogen as potent and novel glucose releasing system, with straightforward integration into tissue engineering applications. This cell-mediated nutrient release ensures glucose availability for the cells at the time of need. To summarize, this thesis introduces novel self-feeding approaches with the aim to give tissue engineered constructs the chance to “grow up” towards clinically relevant sizes
Shark skin-inspired surface designs for drag reduction in drinking water distribution pipes
No full textIn drinking water distribution systems (DWDS), drag caused by turbulent flow results in significant energy losses and increased energy consumption. Biomimetic riblet surfaces, inspired by shark skin, are a widely explored solution for reducing drag and enhancing efficiency. However, their behavior in circular pipes under turbulent flow has received limited attention due to fabrication challenges and assumptions of similarity with channel flows. In this study, we experimentally investigated the drag reduction performance of blade riblets in circular pipes of different diameters (12, 20, and 28 mm). Riblet structures were 3D printed, and their drag reduction capabilities were evaluated using a water flow experimental setup. Results showed that the optimal riblet spacing (sopt+) for maximum drag reduction varied significantly with pipe diameter (D) and height to spacing ratio (h/s). Lower D resulted in Lower sopt+, while increasing D shifted sopt+ to higher s+ values, approaching behavior observed in channel flow studies. The transition from drag reduction to drag increase was also effected by both D and h/s ratio, with larger D shifting the transition to higher s⁺ values and larger h/s ratios shifting the transition to lower s⁺ values. Riblets with h/s ratios of 0.4 and 0.5 demonstrated the highest drag reduction capabilities, achieving up to 6 % reduction across all tested pipe diameters. A practical correlation was developed to predict sopt+ based on riblet geometry and pipe diameter, which was validated against experimental data with <5 % error across all tested cases. Furthermore, a conceptual model based on vortex–riblet interactions was proposed to explain the results. These findings underscore the necessity of tailoring riblet designs to specific pipe dimensions and flow conditions to maximize drag reduction in DWDS.</p
Technology Roadmap of Micro/Nanorobots
Get PDFInspired by Richard Feynman’s 1959 lecture and the 1966 film Fantastic Voyage, the field of micro/nanorobots has evolved from science fiction to reality, with significant advancements in biomedical and environmental applications. Despite the rapid progress, the deployment of functional micro/nanorobots remains limited. This review of the technology roadmap identifies key challenges hindering their widespread use, focusing on propulsion mechanisms, fundamental theoretical aspects, collective behavior, material design, and embodied intelligence. We explore the current state of micro/nanorobot technology, with an emphasis on applications in biomedicine, environmental remediation, analytical sensing, and other industrial technological aspects. Additionally, we analyze issues related to scaling up production, commercialization, and regulatory frameworks that are crucial for transitioning from research to practical applications. We also emphasize the need for interdisciplinary collaboration to address both technical and nontechnical challenges, such as sustainability, ethics, and business considerations. Finally, we propose a roadmap for future research to accelerate the development of micro/nanorobots, positioning them as essential tools for addressing grand challenges and enhancing the quality of life.</p
LSD flattens the hierarchy of directed information flow in fast whole-brain dynamics
No full textPsychedelics are serotonergic drugs that profoundly alter consciousness, yet their neural mechanisms are not fully understood. A popular theory, RElaxed Beliefs Under pSychedelics (REBUS), posits that psychedelics flatten the hierarchy of information flow in the brain. Here, we investigate hierarchy based on the imbalance between sending and receiving brain signals, as determined by directed functional connectivity. We measure properties of directed functional hierarchy in a magnetoencephalography (MEG) dataset of 16 healthy human participants who were administered a psychedelic dose (75 micrograms, intravenous) of lysergic acid diethylamide (LSD) under four different conditions: eyes-closed with or without music and eyes-open with or without a video stimulus. Across the whole brain, LSD diminishes the asymmetry of directed connectivity when averaged across time. Additionally, we demonstrate that machine learning classifiers distinguish between LSD and placebo more accurately when trained on one of our hierarchy metrics than when trained on traditional measures of functional connectivity. Taken together, these results indicate that LSD weakens the hierarchy of directed connectivity in the brain by increasing the balance between senders and receivers of neural signals.</p
Symmetry Breaking in Chemical Systems:Engineering Complexity Through Self-Organization and Marangoni Flows
No full textFar from equilibrium, chemical and biological systems can form complex patterns and waves through reaction-diffusion coupling. Fluid motion often interferes with these self-organized concentration patterns. This study examines the influence of Marangoni-driven flows inside a thin layer of fluid ascending the outer surfaces of hydrophilic obstacles on the spatio-temporal dynamics of chemical waves in the modified Belousov–Zhabotinsky reaction. These observations reveal that circular waves originate nearly simultaneously at the obstacles and propagate outward. In a covered setup, where evaporation is minimal, the wavefronts maintain their circular shape. However, in an uncovered setup with significant evaporation and resulting Marangoni flows, the interplay between surface tension-driven Marangoni flows and gravity destabilizes the wavefronts, creating distinctive flower-like patterns around the obstacles. Experiments further show that the number of petals increases linearly with obstacle diameter, though a minimum diameter is required for these instabilities to appear. Our complementary numerical analysis indicates that solutal Marangoni forces dominate thermal ones in this system. These findings demonstrate the potential to “engineer” specific wave patterns, offering a method to control and direct reaction dynamics. This capability is especially important for developing microfluidic devices requiring precise control over chemical wave propagation.</p
Strongly Inhibiting the Spontaneous Emission of PbS Quantum Dots that are Covalently
No full textWe study emission from PbS quantum dots covalently bound to polymer brush layers grafted from Si-air interfaces inside 3D photonic crystals. We observe broad and strong inhibition in the full 3D band gap
Transformational leadership transitions and employees’ entrepreneurial behavior in higher education institutions:a fuzzy set qualitative comparative analysis
No full textThis study explores how transitions impact employees’ psychological empowerment and entrepreneurial behavior via changes in transformational leadership style within higher education institutions (HEIs). Grounded in Implicit Leadership Theory, Contrast Theory, and Leadership Transference, the research examines how employees compare new and previous leaders and how these comparisons influence their psychological states and employee entrepreneurial behavior. Utilizing a two-wave longitudinal survey conducted in a Dutch university faculty, where a dean transition occurred in 2022, the study uses fuzzy set qualitative comparative analysis (fsQCA). The findings indicate that maintaining or enhancing transformational leadership and employees’ psychological empowerment during leadership transitions significantly fosters employees’ entrepreneurial behavior. The fsQCA results reveal several pathways, including Empowered Performance Collectives and Supportive Leadership Dynamics. This study contributes to the literature by extending the understanding of transformational leadership’s role before and after transitions. The practical implications show that strategic succession planning and leadership development programs are important to support employee entrepreneurial behavior and, in turn, innovation and adaptability in HEI.</p
Broadband Packaged Erbium-Doped Polycrystalline Al<sub>2</sub>O<sub>3</sub> Waveguide Amplifier with 24 dB External Net Gain
No full textWe present a packaged erbium-doped waveguide amplifier (EDWA) based on polycrystalline Al2O3, demonstrating high external fiber-to-fiber gain, stable performance over a broad wavelength range, and robustness to temperature variations. The device was integrated with fiber arrays and thermoelectric control, facilitating efficient characterization and practical deployment. With bidirectional pumping at 1480 nm, a 50 cm long waveguide amplifier achieves an external net gain of 24 dB and an off-chip output power exceeding 54 mW at 1550 nm. The amplifier exhibits a broad gain bandwidth, covering the entire C-band and extending into the L-band, with external net gain measured over a 90 nm span (1525 – 1615 nm). Temperature dependent measurements show that the amplifier maintains useful performance up to 95°C, with 17 dB of external net gain in the small-signal regime. These results highlight the potential of polycrystalline Al2O3:Er3+ as a scalable platform for high-performance optical amplification in photonic integrated circuits.</p