Characterizing Width Uniformity by Wave Propagation

This work describes a novel image analysis approach to characterize the uniformity of objects in agglomerates by using the propagation of normal wavefronts. The problem of width uniformity is discussed and its importance for the characterization of composite structures normally found in physics and biology highlighted. The methodology involves identifying each cluster (i.e. connected component) of interest, which can correspond to objects or voids, and estimating the respective medial axes by using a recently proposed wavefront propagation approach, which is briefly reviewed. The distance values along such axes are identified and their mean and standard deviation values obtained. As illustrated with respect to synthetic and real objects (in vitro cultures of neuronal cells), the combined use of these two features provide a powerful description of the uniformity of the separation between the objects, presenting potential for several applications in material sciences and biology.Comment: 14 pages, 23 figures, 1 table, 1 referenc

The Alvarez impact theory of mass extinction; limits to its applicability and the „great expectations syndrome”

For the past three decades, the Alvarez impact theory of mass extinction, causally related to catastrophic meteorite impacts, has been recurrently applied to multiple extinction boundaries. However, these multidisciplinary research efforts across the globe have been largely unsuccessful to date, with one outstanding exception: the Cretaceous-Paleogene boundary. The unicausal impact scenario as a leading explanation, when applied to the complex fossil record, has resulted in force-fitting of data and interpretations ("great expectations syndrome". The misunderstandings can be grouped at three successive levels of the testing process, and involve the unreflective application of the impact paradigm: (i) factual misidentification, i.e., an erroneous or indefinite recognition of the extraterrestrial record in sedimentological, physical and geochemical contexts, (ii) correlative misinterpretation of the adequately documented impact signals due to their incorrect dating, and (iii) causal overestimation when the proved impact characteristics are doubtful as a sufficient trigger of a contemporaneous global cosmic catastrophe. Examples of uncritical belief in the simple cause-effect scenario for the Frasnian-Famennian, Permian-Triassic, and Triassic-Jurassic (and the Eifelian-Givetian and Paleocene-Eocene as well) global events include mostly item-1 pitfalls (factual misidentification), with Ir enrichments and shocked minerals frequently misidentified. Therefore, these mass extinctions are still at the first test level, and only the F-F extinction is potentially seen in the context of item-2, the interpretative step, because of the possible causative link with the Siljan Ring crater (53 km in diameter). The erratically recognized cratering signature is often marked by large timing and size uncertainties, and item-3, the advanced causal inference, is in fact limited to clustered impacts that clearly predate major mass extinctions. The multi-impact lag-time pattern is particularly clear in the Late Triassic, when the largest (100 km diameter) Manicouagan crater was possibly concurrent with the end-Carnian extinction (or with the late Norian tetrapod turnover on an alternative time scale). The relatively small crater sizes and cratonic (crystalline rock basement) setting of these two craters further suggest the strongly insufficient extraterrestrial trigger of worldwide environmental traumas. However, to discuss the kill potential of impact events in a more robust fashion, their location and timing, vulnerability factors, especially target geology and palaeogeography in the context of associated climate-active volatile fluxes, should to be rigorously assessed. The current lack of conclusive impact evidence synchronous with most mass extinctions may still be somewhat misleading due to the predicted large set of undiscovered craters, particularly in light of the obscured record of oceanic impact events

Identifying the Big Questions in paleontology: a community-driven project

Paleontology provides insights into the history of the planet, from the origins of life billions of years ago to the biotic changes of the Recent. The scope of paleontological research is as vast as it is varied, and the field is constantly evolving. In an effort to identify “Big Questions” in paleontology, experts from around the world came together to build a list of priority questions the field can address in the years ahead. The 89 questions presented herein (grouped within 11 themes) represent contributions from nearly 200 international scientists. These questions touch on common themes including biodiversity drivers and patterns, integrating data types across spatiotemporal scales, applying paleontological data to contemporary biodiversity and climate issues, and effectively utilizing innovative methods and technology for new paleontological insights. In addition to these theoretical questions, discussions touch upon structural concerns within the field, advocating for an increased valuation of specimen-based research, protection of natural heritage sites, and the importance of collections infrastructure, along with a stronger emphasis on human diversity, equity, and inclusion. These questions offer a starting point—an initial nucleus of consensus that paleontologists can expand on—for engaging in discussions, securing funding, advocating for museums, and fostering continued growth in shared research directions. La paleontología permite conocer la historia del planeta, desde los orígenes de la vida hace miles de millones de años hasta los cambios bióticos de épocas recientes. El ámbito de la investigación paleontológica es tan vasto como variado y está en constante evolución. En un esfuerzo por identificar las “grandes preguntas” de la paleontología, expertos de todo el mundo se reunieron para elaborar una lista de cuestiones prioritarias que el campo puede abordar en los próximos años. Las 89 preguntas aquí presentadas (agrupadas en 11 temas) representan las contribuciones de casi 200 científicos internacionales. Estas preguntas se refieren a temas comunes, entre los que se incluyen los motores y patrones de la biodiversidad, la integración de diferentes tipos de datos a lo largo de escalas espacio-temporales, la aplicación de datos paleontológicos para resolver cuestiones contemporáneas de biodiversidad y clima, y la utilización eficaz de métodos y tecnologías innovadoras para obtener nuevos conocimientos paleontológicos. Además de estos interrogantes teóricos, los debates abordan inquietudes estructurales dentro del campo, y abogan por una mayor valoración de la investigación basada en especímenes, la protección de los sitios del patrimonio natural y la importancia de la infraestructura de las colecciones; junto con un mayor énfasis en la diversidad humana, la equidad y la inclusión. Estas preguntas representan un punto de partida—un núcleo inicial de consenso que los paleontólogos pueden ampliar—para fomentar debates, obtener financiación, abogar por el apoyo a los museos y estimular el crecimiento continuo en direcciones de investigación compartidas. La paleontologia offre spunti fondamentali per comprendere la storia del pianeta, dalle origini della vita miliardi di anni fa fino ai cambiamenti biotici più recenti. L’ambito della ricerca paleontologica è tanto vasto quanto diversificato e rappresenta un campo in continua evoluzione. In questo studio, esperti provenienti da tutto il mondo si sono riuniti per redigere un elenco di “Grandi Domande” prioritarie che la paleontologia potrà affrontare nei prossimi anni. Le 89 domande qui presentate, raggruppate in 11 temi, rappresentano il contributo di circa 200 scienziati internazionali. Queste domande riguardano tematiche come i meccanismi e i pattern di biodiversità, l’integrazione di varie tipologie di dati su scale spazio-temporali multiple, l’applicazione delle conoscenze paleontologiche ai problemi attuali della crisi climatica e della biodiversità, e l’uso efficace di metodi e tecnologie innovative per ottenere nuove intuizioni paleontologiche. Oltre a questi temi teorici, la discussione si focalizza su problematiche strutturali del campo, promuovendo una maggiore valorizzazione della ricerca basata sugli esemplari, la protezione dei siti di interesse culturale e paleontologico, e l’importanza delle infrastrutture per preservare le collezioni, insieme a una crescente enfasi su un apporto multiculturale, equo e inclusivo. Queste domande costituiscono un punto di partenza—un nucleo di consenso iniziale che i paleontologi possono espandere—per avviare discussioni, ottenere finanziamenti, promuovere i musei e favorire una crescita continua verso direzioni condivise di ricerca