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Multicolor Wavefront Shaping
No full textWe do multicolor wavefront shaping with a digital micromirror device (DMD). DMDs are popular shaping devices with superior modulation rates. However, DMDs have angular dispersion, hindering broadband operation. Therefore, we developed a new Lee-holography technique; the same setup can now be used for different wavelengths without having to change or adjust any component
An integrated view on the uncertainties of sea-level rise, hazards and impacts, and adaptation
Get PDFWhile adapting to future sea-level rise (SLR) and its hazards and impacts is a multidisciplinary challenge, the interaction of scientists across different research fields, and with practitioners, is limited. To stimulate collaboration and develop a common research agenda, a workshop held in June 2024 gathered 22 scientists and policymakers working in the Netherlands. Participants discussed the interacting uncertainties across three different research fields: sea-level projections, hazards and impacts, and adaptation. Here, we present our view on the most important uncertainties within each field and the feasibility of managing and reducing those uncertainties. We find that enhanced collaboration is urgently needed to prioritize uncertainty reductions, manage expectations and increase the relevance of science to adaptation planning. Furthermore, we argue that in the coming decades, significant uncertainties will remain or newly arise in each research field and that rapidly accelerating SLR will remain a possibility. Therefore, we recommend investigating the extent to which early warning systems can help policymakers as a tool to make timely decisions under remaining uncertainties, in both the Netherlands and other coastal areas. Crucially, this will require viewing SLR, its hazards and impacts, and adaptation as a whole
Radiofrequency Ablation for Thyroid Nodules (RATED Study):Analysis of a Learning Curve and Predictors of Success
No full textContext: Radiofrequency ablation (RFA) is used as treatment for symptomatic thyroid nodules. Factors influencing the volume reduction ratio (VRR) at 12 months are not yet fully understood.Objective: The primary objective of this work was evaluating the VRR at 12 months after RFA. Secondary objectives were the assessment of a learning curve and factors influencing the VRR at 12 months.Methods: A retrospective observational cohort study was conducted at 3 Dutch referral hospitals of patients who underwent RFA for symptomatic thyroid nodules with available ultrasound (US) follow-up. Main outcome measures included US-based VRR at 12 months and chronologically numbered RFA procedures. All patients’ baseline, treatment, and early follow-up factors were assessed for correlation with VRR at 12 months.Results: A total of 337 patients with 356 nodules were included in the learning curve analysis. VRR at 12 months increased for the first 20 treatments per center and stabilized thereafter, indicating a plateau phase after a learning curve. These initial cases were removed from further analysis. In the remaining 299 nodules, median VRR at 3, 6, and 12 months was 57.1%, 65.6%, and 70.8%. Baseline nodule volume negatively correlated with VRR at 12 months but VRR was high for every volume category. Energy delivered per volume did not correlate with VRR.Conclusion: In RFA for thyroid nodules, a stable treatment efficacy is achieved after 20 treatments, with a median VRR of 70.8%. Baseline nodule volume, energy delivered, and prolonged follow-up 6 months after treatment may not be clinically relevant to predict treatment success
Retina-on-chip with local oxygen sensing
Get PDFOver hundreds of millions of people are affected by visual impairment, with most cases linked to pathophysiological changes associated with age-related macular degeneration (AMD). The underlying disease mechanisms remain poorly understood, leading to a limited availability of effective treatments. To develop novel treatments for AMD and other retinal diseases, these disease mechanisms need to be investigated. Retina-on-chip models can be helpful for such investigations by providing more physiologically relevant and accessible retinal models compared to animal models, ex vivo models, and conventional cell culture models. In this thesis, we have developed a novel Retina-on-Chip model that shows a pathophysiological response to retinal disease-relevant stimulation
SAR images for benchmark dataset creation, urban polycentricity and deformation dynamics
Get PDFIn recent years, significant advancements in SAR sensors have resulted in a substantial increase in SAR images for urban environment applications. Effectively and massively using those remains challenging. In this thesis, I focus on applications in three aspects: benchmark dataset for training deeplearning models in land cover classification, land cover change detection for urban polycentricity analysis, and localized deformation detection and prediction. First, a repeatable and scientific framework is proposed for creating SAR benchmark dataset for land cover classification. The framework considers three categories of SAR images: single polarimetric features, multipolarimetric features, and additional geospatial data. A hybrid radarcoding method is introduced to convert reference data into radar coordinates, aligning the radarcoded reference data with feature maps to form the SAR benchmark dataset. The attribute quality of the dataset is assessed by means of local and global attribute tables, and quantitative quality is determined by considering variance, mismatch, and uncertainty of feature maps. The dataset is stored in SpatioTemporal Asset Catalogs (STAC) format for easy sharing. The framework has been applied in Groningen, the Netherlands, using Sentinel-1 SAR images. The result demonstrates its effectiveness in generating high-quality benchmark dataset for land cover classification. Second, a Kittler and Illingworth with Modified Model (KI-MM) method is proposed for detecting land cover changes in urban environments. This method leverages statistical information from SAR images to define a threshold that separates changed and unchanged pixels. The obtained identical threshold regarding the varied distribution of SAR images ensures the experiment is repeatable and scientific. The detected changes are linked to polycentric urban development (PUD) analysis and quantified using mean distance and mean patch area parameters. The method has been applied in Shanghai, China, using time-series Sentinel-1 and Sentinel-2 images. The result shows a successful pioneer application of SAR images in PUD analysis with the KI-MM method. Third, a spatiotemporal concatenation method is proposed to detect wide-range deformation based upon persistent scatterers (PS). To assess the precision and accuracy, posterior variance and double difference validation have been used. The deformation results were used as input for hierarchical classification method and Getis-Ord Gi statistic to identify localized deformation in urban environments. Taking advantage of big intermediate InSAR products, such as a large number of (un)wrapped interferograms, a High-resolution network (HRNet) was trained to predict deformations. The methods have been implemented in highly developed Western Europe countries using three Sentinel-1 SAR frames. Results showed the efficiency of the concatenation method and its ability to detect and predict localized deformation. In summary, this thesis has enriched the SAR benchmark dataset for land cover classification, strengthened analysis methods for polycentricity development, and detected and predicted localized deformation. This work thus provides a systematic approach to monitoring urban land dynamics using SAR images
Dry versus Wet Particle Assembly:Toward Solvent-Free Fabrication
Get PDFFor over three decades, the continuous demand for miniaturized devices has prompted scientists to explore the fundamental principles of colloidal or particle (10 nm to 10 μm) assembly to construct large ordered structures. So far, most of the assembly has been performed in wet conditions, i.e., in a solution. Over the past decade, solvent-free (or dry) assembly methods have gained more attention, offering a more sustainable alternative. In this perspective, we highlight the promising aspects of the dry assembly method, which is not only easy to use, rapidly performed, and clean but also abandons the use of solvents while ensuring that the quality of the created particle assembly matches or exceeds that of wet particle assemblies. However, challenges remain for ordered multilayers, binary layers, and nonspherical particle assemblies due to strong surface forces and limited control. Learning from strategies used in wet assembly and gaining a deeper fundamental understanding of surface interactions at the micro- and nanoscale could help bridge these gaps. In this perspective, the challenges and opportunities of dry particle assembly are thoroughly explored, providing a roadmap for advancing the solvent-free assembly field and contributing to a more sustainable world.</p
Understanding delays in breast cancer diagnosis in Africa:Key insights and contributing factors
Get PDFAfrica has the highest age-standardized breast cancer (BC) mortality rates, largely due to diagnostic delays. Therefore, this scoping review aims to identify individual-level factors that contribute to diagnostic delay of BC in African women. We conducted a global scoping review on cancer diagnostic delays in women, following PRISMA-ScR guidelines. In this scoping review, diagnostic delay is defined as the time from first symptom recognition to pathological diagnosis. Qualitative and quantitative studies involving cancer patients or healthcare professionals published between 2018 and November 28, 2023, were included. We searched PubMed/MEDLINE and Scopus, excluding non-English studies and those focused solely on screening. Two reviewers independently screened titles, full texts, and extracted data. Disagreements were resolved by discussion. Consultations followed Arksey and O'Malley's framework, with input from a general practitioner, psychologist, and epidemiologist. Factors were classified using Bronfenbrenner's ecological model to analyze BC diagnostic delays in Africa. Of 9699 studies, 128 were relevant; 30 focused on African BC patients. Delays were linked to microsystem factors: lack of awareness, fear, young age, low education, finances, mesosystem factors: family duties, limited access, delayed care, symptom disclosure, exosystem factors: traditional healers, mistrust, referral inefficiencies, and macrosystem factors: religious beliefs, education gaps, cultural norms. Diagnostic delays in women with BC in Africa are mainly due to low awareness, cultural beliefs, and reliance on traditional healers. Expanding current interventions and integrating them into healthcare systems, along with engaging religious leaders, is important. Future research should focus on culturally tailored strategies to improve early detection and outcomes
Developing empirical fragility functions for lava flow building damage
Get PDFFragility functions are vital tools in volcanic risk assessments to evaluate the probability of damage to structures at given hazard intensities. Traditionally, lava flow damage is assumed to be binary, whereby in contact with lava results in complete destruction and not in contact with lava remains undamaged. However, past studies present examples of structures exhibiting resistance to lava and not destruction. Developing empirical fragility functions requires damage data. We collected data from field campaigns and aerial imagery to assess damage across three case studies: 2021 Cumbre Vieja lava flows, La Palma, 2018 lower East Rift Zone lava flows, Kīlauea, Hawai'i, and 2014-2015 Fogo lava flows, Cabo Verde. This involved manually digitising 4,545 structure footprints and assigning types and damage state categories to 10,439 structures. Of the impacted structures, 6% were classified as damaged (not destroyed). Using this dataset, we developed the first empirical fragility functions from multiple eruptions for assessing lava flow damage, for masonry, metal, and timber building types. The functions reflect the probability of a structure sustaining any of six levels of damage severity given final lava flow thickness. Lava flows thicker than 6 m generally destroy structures, but some structures, particularly masonry buildings or those with a circular shape, can resist flows thinner than 6 m. The fragility functions reflect that impacts are not binary, and that structure types and shape are important. These empirical fragility functions can differentiate between structural attributes, enhancing damage, risk, and impact assessments for lava flows, for places with similar building types
Piezoelectric damping of position dependent parasitic resonances for improved performance of flexure-based manipulators
Get PDFThe performance of precision machinery is often limited by parasitic vibration modes of the system. These parasitic resonances typically limit the actuation bandwidth, can lead to long settling times and can degrade the end-effector standstill performance when disturbance forces or floor vibrations are present. As a complicating factor, the parasitic resonance frequencies may vary over the workspace of the system. Conventional design guidelines focuses on stiff and lightweight design, leading to high parasitic resonance frequencies. However, for further improvement in performance, damping of some of the problematic resonances is required. In this work, a flexure-based manipulator is considered that exhibits performance limiting resonances, of which the frequencies vary with the deflection of the manipulator. An active damping approach, based on integrating piezoelectric material in the flexures which actively suppress the parasitic vibration modes is proposed and experimentally validated. Using a scheduled vibration controller, the actuation budget is effectively and efficiently used to suppress targeted parasitic resonances over the entire workspace, leading to a significant increase in the dynamic and steady state performance of the flexure-based manipulator. The resonance peak height of the first four parasitic resonances is reduced by a factor 10 over the majority of the workspace. This results in a modal damping of these resonances in the range 2-7%. Due to the resonance peak suppression, the control bandwidth of the Lorentz actuator for the intended motion of the manipulator can effectively be doubled. Lastly, it is shown that the higher control bandwidth and improved settling behaviour of parasitic resonances lead to better disturbance rejection and faster cycle times for an indexing setpoint task.<br/
Agent-based modelling of beach visitation patterns:insights for sustainable coastal design and management
Get PDFCoastal areas are complex socio-environmental systems, yet most models focus on biophysical processes, with few addressing social systems or their interaction with biophysical dynamics. This paper introduces an agent-based model (ABM) simulating beach visitor spatial behaviour, considering factors like landscape design and its impact on visitor distribution. We analyse how service and facility placement affects areas with high and low visitation intensity. Tailored for Dutch beaches created by mega-nourishments like the Sand Motor, the model’s modular design allows adaptation to other coastal areas. Qualitative calibration and validation against field data ensured realistic predictions of daily visitor numbers and representation of areas of high and low visitation intensity across the beach. We analysed model sensitivity by varying visitor activities and pathway preference probabilities, finding that pathway probabilities significantly influence visitor choices. The model was also applied to assess the impact of adding an entrance with access to a restaurant and car parking on visitor numbers, affected areas, and impact intensity. Scenario analysis, combined with its application to two case studies with different landscape layouts, highlights the model’s versatility as a valuable tool for designing beaches to effectively explore and manage visitation intensity and its effects on ecological systems, such as vegetation.</p