154092 research outputs found
Sort by
Herbaria Heritage:Visualizing Colonial Bias in Natural History Collections
Get PDFAs a result of the colonial entanglements of many natural history collections, much of the world’s biodiversity heritage is housed in Europe. Increasingly, natural history institutions have begun to address their colonial past. However, in this regard, computational methods for analyzing large collections tend to consist of static visualizations of collection provenance. Moreover, in regions where cutting-edge visualization technologies are only scarcely available - often these are the same areas from which most European plantcollections originate - there is a lack of simple, accessible solutions that can generate meaningful results. Thus, we argue that accessible, simple, yet interactive visualizations of collection provenance allow users to understand colonial bias in natural history collections better. Our solution allows users to focus on content gaps and highlights historical patterns and trends in collection data. Using a dataset containing metadata of five million entries from the Naturalis Biodiversity Center botanical collection as a use case, we created an interactive visualization with Microsoft PowerBI. The visualization showcases the origins and movements of botanical specimens from former Dutch colonies to the Netherlands on an interactive map and timeline. This addresses not only a gap in historical research on the colonial legacy of Dutch botanical collections but also a gap in digi-tal humanities research regarding simple and easy-to-use computational techniques for distant reading of natural heritage data. The particular use case demonstrates only a fraction of the research possibilities that this tool enables. Our interactive visualization increases the accessibility of the available scientific data, and contributes to a better understanding of the relationship between cultural history and natural history, highlighting the greater importance of easy-to-use, interactive and accessible visualiza-tions of biodiversity collection histories. Ultimately, our project suggests a way forward for natural history museums not only in the Netherlands to reinterpret the colonial past of their collections
A Universal Model for Hydrogen−Induced Reduction of Transition Metal Compounds
Get PDFPrediction and optimization of the chemical interactions between reactive hydrogen and transition metal (TM) compounds−including nitrides, oxides, and carbides (collectively referred to as TMX)−are crucial for a wide range of advanced technological applications. These applications range from energy production systems, such as fusion reactors, to semiconductor fabrication processes, including extreme ultraviolet lithography machines. In such systems, TMX coatings are exposed to reactive hydrogen, leading to their chemical degradation. This degradation primarily occurs through reduction reactions, resulting in the loss of X−atoms. Consequently, this undermines system performance and poses significant operational risks. This thesis, therefore, focuses on identifying the key material parameters that govern the reduction reaction of TMX thin films in hydrogen radicals (H*) and low−energy hydrogen plasma (H−plasma).The thesis demonstrates that the work function serves as a predictive and tunable parameter governing the hydrogen−induced reduction of TMX. Group 3–5 TMX thin films exposed to H* and H−plasma show that the TMX reduction reaction effectively stops once they reach a specific chemical composition. At this stage, the TMX work function consistently measures 4.3 ± 0.5 eV. It is proposed that the TMX reduction reaction stops at this threshold due to the preferential binding of H* to TM—atoms rather than X—atoms, thus preventing the formation of volatile (XHy) species.Further, the thesis shows that the work function of TMX can be modulated through alloying. Increasing the fraction of a low−work function TM decreases the work function of the TMX alloy, thereby decreasing its reducibility in hydrogen. This, in turn, stabilizes the higher oxidation states of a high−work function TM, which would otherwise readily reduce. The insights presented in the thesis offer a comprehensive framework for the strategic selection and development of TMX coatings, tailored to meet the specific needs of hydrogen−based systems
Spatial-temporal patterns of agricultural drought severity in the Lake Urmia Basin Iran:A cloud-based integration of multi-temporal and multi-sensor remote sensing data
Get PDFThe Lake Urmia Basin (LUB) in Iran has been experiencing significant drought conditions with severe impacts on its agricultural sector. This study analyzed the spatiotemporal patterns of agricultural drought across the LUB during growing seasons from 2000 to 2019. The analysis integrated multiple drought indices including the Vegetation Condition Index (VCI), Thermal Condition Index (TCI), Vegetation Health Index (VHI), Composite Index (CI), Precipitation Condition Index (PCI), and Rainfall Anomaly Index (RAI). These indices were derived from 8,279 satellite images combining MODIS, TRMM, and GridSat-B1 data processed in Google Earth Engine. The study's primary innovation lies in developing a real-time algorithm for mapping spatial patterns and calculating temporal trends of agricultural drought through time-series analysis of drought indices in a cloud-based environment. For validation purposes, Standardized Precipitation Index (SPI) values at 3-, 6-, and 9-month intervals were calculated using precipitation data from seven synoptic stations. Positive Pearson correlations were observed between VCI and all SPI intervals across stations, with most stations showing significant correlations (R=0.35). VCI analysis revealed that while most of the LUB remained unaffected by drought, the remaining areas experienced mild, moderate, severe, and extreme drought conditions in descending order of extent. The maximum and minimum extents of extreme and severe drought were observed during 2000-2018, while moderate and mild drought peaks occurred during 2000-2002 and 2002-2018, respectively. Analysis of Variance (ANOVA) with Duncan Post Hoc testing demonstrated significant differences among indices, though VHI and CI showed no significant distinction from each other. The PERSIANN-CDR-derived RAI identified five major drought events between 2000 and 2019, showing a correlation of R=0.576 with the mean RAI from the seven stations. Temporal trend analysis using Ordinary Least Squares (OLS) regression revealed that 73.3% and 20% of the LUB experienced wet and drying trends, respectively, with 22.2% showing significant wet trends and 1.7% showing significant drying trends
Unravelling Mangrove Storm Damage Resistance for Sustainable Flood Defense Safety Using 3D-Printed Mimics
Get PDFMangrove forests are vital for flood reduction, yet their failure mechanisms during storms are poorly known, hampering their integration into engineered coastal protection. In this paper, we aimed to unravel the relationship between the resistance of mangrove trees to overturning and root distribution and the properties of the soil, while avoiding damage to natural mangrove forests. We therefore (i) tested the stability of 3D-printed tree mimics that imitate typical shallow mangrove root systems, mimicking both damaged and intact root systems, in sediments representing the soil properties of contrasting mangrove sites, and subsequently (ii) tested if the existing stability models for terrestrial trees are applicable for mangrove tree species, which have unique shallow root systems to survive waterlogged soils. Root systems of different complexities were modeled after Avicennia alba, Avicennia germinans, and Rhizophora stylosa, and printed at a 1:100 scale using material densities matching those of natural tree roots, to ensure the geometric scaling of overturning moments. The mimic stability increased with the soil shear strength and root plate surface area. The optimal root configuration for mimic stability depended on the sediment properties: spreading root systems performed better in softer sediments, while concentrating root biomass near the trunk improved stability in stronger sediments. An adapted terrestrial tree resistance model reproduced our measurements well, suggesting that such models could be adapted to predict the stability of shallow-rooted mangroves living in waterlogged soils. Field tree-pulling experiments are needed to further confirm our conclusions with real-world data, examine complicating factors like root intertwining, and consider mangrove tree properties like aerial roots. Overall, this work establishes a foundation for incorporating mangrove storm damage into hybrid coastal protection systems
The Port-Hamiltonian Structure of Continuum Mechanics
Get PDFIn this paper, we present a novel approach to the geometric formulation of solid and fluid mechanics within the port-Hamiltonian framework, which extends the standard Hamiltonian formulation to non-conservative and open dynamical systems. Leveraging Dirac structures, instead of symplectic or Poisson structures, this formalism allows the incorporation of energy exchange within the spatial domain or through its boundary, which allows for a more comprehensive description of continuum mechanics. Building upon our recent work in describing nonlinear elasticity using exterior calculus and bundle-valued differential forms, this paper focuses on the systematic derivation of port-Hamiltonian models for solid and fluid mechanics in the material, spatial, and convective representations using Hamiltonian reduction theory. This paper also discusses constitutive relations for stress within this framework including hyper-elasticity, for both finite and infinitesimal strains, as well as viscous fluid flow governed by the Navier–Stokes equations.</p
No-touch aorta off-pump LIMA-radial Y-graft CABG:A safe strategy for all-comers: Long term follow up of a preferred treatment approach
No full textObjectives: Survival of no-touch aorta, total arterial off-pump CABG (OPCAB) with LIMA - radial artery Y-graft in 2004 - 2021 for all-comers for isolated CABG regardless of preoperative factors.Patients and methods: All patients with OPCAB no-touch aorta total arterial LIMA- RA Y-graft surgeries performed between 2004 and 2021 without any concomitant interventions were included. OPCAB was performed by a team of experienced surgeons. For 5 year survival times, Kaplan-Meier test and Cox regression were used. Patients were categorised into 5 age groups (<50 y.o.;50-59;60-69; 70-79; >80 years).Results: 2174 patients were included. Median follow-up time was 3266 days. Mean number of grafts was 3,7 with little variation between age groups ranging from 3.6 to 3.8 (p=0.09), respectively. The 5 year survival probability was 90% (n=1767) and ranged between age groups from 98% to 65% (log rank: p=<0.0001). A Cox regression model observed that sex, age, NYHA class>1, CCS class IV, left ventricular ejection fraction, previous stroke, diabetes, PAD, chronic lung disease, EuroSCORE I (log) were potential predictors for long-term mortality.Conclusion: This study shows that total arterial no-touch aorta LIMA-RA Y-graft OPCAB as regular practice for all patients, regardless of age, is safe and effective. Our findings underline the strength of experience in a total arterial treatment strategy. Further research should identify risk factors influencing other outcomes after revascularization ensuring optimal outcomes across diverse patient populations
Predictive value of resting-state fMRI graph measures in hypoxic encephalopathy after cardiac arrest
Get PDFIntroduction: Current multimodal prediction models can determine the prognosis of about half of comatose cardiac arrest patients. We investigated whether whole-brain graph-theoretical measures from early resting-state functional magnetic resonance imaging (fMRI) three days after cardiac arrest discriminate between good and poor outcome and improve outcome prediction.Methods: We conducted a prospective cohort study on comatose cardiac arrest patients on intensive care units. Resting-state fMRI three days after cardiac arrest was used to quantify whole-brain functional connectivity, global efficiency, clustering coefficient, and modularity. Neurological outcome at six months was classified as good or poor (Cerebral Performance Category 1–2 vs 3–5). Logistic regression models were used to examine between-group differences and study the additional value of graph-theoretical measures to clinical and EEG-based prediction.Results: In seventy included patients (good outcome n = 44, poor n = 26), whole-brain functional connectivity and clustering coefficient (but not global efficiency and modularity) were significantly lower in patients with poor outcome. Connectivity of nodes in posterior brain areas most prominently correlated with outcome. Clustering coefficient showed strong correlation with whole-brain functional connectivity. Patients with continuous EEG patterns differed in whole-brain functional connectivity levels from those with suppressed or epileptiform patterns. Combining functional connectivity or graph measures with clinical and EEG-based predictors slightly improved outcome prediction.Conclusion: fMRI-based whole-brain functional connectivity is a sensitive measure for encephalopathy severity after cardiac arrest, according to relations with established EEG categories and discrimination between good and poor outcome. Additional predictive values for outcome seem small. Graph measures do not provide complementary information.</p
Photon distillation with reduced resource costs for fault-tolerant quantum computation
Get PDFPhoton distillation creates a low-error single photon from multiple imperfect ones via interference and partial measurements. We present a cost-efficient version with constant gate success probability, regardless of indistinguishability error reduction, ideal for photonic quantum computing architectures
Potential of Sentinel-1 time-series data for monitoring the phenology of European temperate forests
Get PDFTime series from optical sensors are frequently used to retrieve phenology information of forests. While SAR (synthetic aperture radar) sensors can potentially provide even denser time series than optical data, their potential to retrieve phenological information of forests is still underexplored. In addition, the backscatter information from SAR is frequently exploited in the same way (e.g., via dynamic thresholding) as optical data to retrieve phenological information. Sentinel-1 backscatter coefficients of VH (vertical–horizontal) and VV (vertical–vertical) polarizations and their ratio were retrieved for temperate deciduous broad-leaf and evergreen needle-leaf forests in Europe. Breakpoints and dynamic thresholds were retrieved in the locally smoothed time-series data and compared to reference data from PhenoCam and fluxtower networks. It was generally found that breakpoints outperform dynamic thresholds in both forest types in terms of root mean squared differences, bias and R². Best results were achieved using breakpoints on the Sentinel-1 backscatter ratio with RMSEs of 18.4 days for the start of the season (SOS) and 14.0 days for the end of the season (EOS) compared to the 25% dynamic threshold of the seasonal amplitude in the reference data in deciduous broad-leaf forests. Substantially higher RMSE values of 56.7 days for SOS and 56.5 days for EOS were found in evergreen needle-leaf forests. This study suggests the potential of Sentinel-1 for the phenological retrieval of forests, in particular deciduous broad-leaf forests. This information could be used in combination with frequently used optical data to provide comprehensive phenological information on a large scale
The Land Administration Domain Model: An overview
Get PDFThis publication marks the first time FIG provides an overview publication of the decades-long efforts to provide a generic, accessible, and available Land Administration Domain Model (LADM). The various reports and academic papers relating to LADM are numerous, each focussing on different aspects. This publication seeks to give a summarised view of the background, but, also introduction to LADM for a larger audience, especially management.After ISO publishing the first edition in 2012 with a focus on land tenure, a revised edition has now been virtually completed. In addition to land tenure, this edition now also focuses on land value and planned land use.In this publication the following questions are addressed:What is LADM?The LADM standard is a universal, conceptual information model that covers basic information-related components of land administration. It involves information on ‘people to land relationships’. Its history is briefly reviewed.Why LADM is needed?Responsible stakeholders as surveyors, notaries, lawyers, planners, valuers, bank employees, brokers, colleagues in governments and citizens must share a common view of land administration. LADM provides this view. It serves as a common language that can be used by experts from different disciplines for land policy development and for land administration system and information infrastructure development and operation (information storage). It contributes to achieving the global agenda.Which LADM demands are there?The development of an LADM is based on user demands, providing a solid foundation. These demands are derived from global guidelines and requirements, as well as from the outcomes of several LADM and 3D Cadastre workshops. The general demands are briefly outlined, along with more specific demands from the perspectives of land tenure, land value, and planned land use.How does LADM look?The components are sub-models (called LADM packages) on parties, RRRs (rights, restrictions and responsibilities), spatial units, land survey, valuation information and spatial plan information on planned land use.What are LADM benefits?The key benefit is that a common language, a terminology is available now for communication between all experts, especially between land administrators and experts from the GIS and DBMS industry. Further benefits are in the possible use of country profiles, participatory approaches and the management of conflicts. LADM supports the creation of nationwide overview of responsibilities and required coordination in land administration.Conclusions and recommendationsConclusions and recommendations with proposals for future developments are given