Although cliffs form approximately 75% of the world's coastline, the understanding of the processes through which they evolve remains limited because of a lack of quantitative data on the ...morphological changes they undergo. In this paper the combination of terrestrial time‐of‐flight laser scanning with high‐resolution digital photogrammetry is examined to generate high‐quality data‐sets pertaining to the geomorphic processes governing cliff development. The study was undertaken on a section of hard rock cliffs in North Yorkshire, UK, which has been monitored over a 12‐month period. High‐density, laser‐scanned point clouds have been used to produce an accurate representation of these complex surfaces, free from the optical variations that degrade photographic data. These data‐sets have been combined with high‐resolution photographic monitoring, resampled with the fixed accuracies of the terrestrial laser survey, to generate a new approach to recording the volumetric changes in complex coastal cliffs. This has led to significant improvements in the understanding of the activity patterns of coastal cliffs.
Résumé
Bien que les falaises forment environ 75% du littoral mondial, notre compréhension des processus qui marquent leur évolution reste limitée par suite du manque de données quantitatives sur les modifications morphologiques qu'elles subissent. On étudie dans cet article une combinaison de levés comprenant un balayage terrestre au laser (basé sur les temps de propagation) et une saisie par photogrammétrie numérique à haute résolution permettant de générer des jeux de données de grande qualité se rapportant aux processus géographiques qui régissent le développement des falaises. On a mené cette étude sur une partie des falaises de roche dure du Yorkshire du Nord (Royaume Uni) en s'assurant d'un suivi sur une période de 12 mois. A partir des nuages de points, à haute densité, issus du balayage laser, on a réalisé une représentation précise de ces surfaces complexes, exempte des variations optiques qui perturbent les données photographiques. En combinant le suivi photographique à haute résolution avec le relevé terrestre au laser qui en assoyait le ré‐échantillonnage précis, on a obtenu une nouvelle façon de traiter les enregistrements des changements volumétriques des falaises littorales complexes. Cela a amenéà des améliorations significatives dans notre compréhension des schémas de la dynamique des falaises littorales.
Zusammenfassung
Obwohl ungefähr 75% der Küstenlinien in der Welt durch Klippen geformt sind, ist unser Verständnis ihres Entwicklungsprozesses begrenzt, da quantitative Daten zu den ablaufenden morphologischen Veränderungen fehlen. In diesem Beitrag wird die Kombination von terrestrischem Laserscanning mit hochauflösender Digitaler Photogrammetrie beschrieben, um qualitativ hochwertige Datensätze zu den geomorphologischen Prozessen zu erfassen, die die Entwicklung der Küstenklippen bestimmen. Ein Abschnitt der Steilküste in North Yorkshire in UK wurde über einen Zeitraum von 12 Monaten intensiv überwacht. Die Geometrie der komplexen Oberflächen wird dabei durch dichte Punktwolken aus dem terrestrischen Laserscanning repräsentiert. Hochauflösende photographische Aufnahmen werden auf die Geometrie der Laserdaten umgebildet und mit diesen kombiniert. Mit diesem kombinierten Datenmodell lassen sich volumetrische Änderungen von komplexen Küstenklippen aufnehmen und analysieren. Dies trug wesentlich dazu bei, die komplexen geomorphologischen Bewegungsmuster von Küstenklippen besser zu verstehen.
Resumen
Aunque los acantilados están presentes en el 75% de las costas continentales del mundo, nuestro conocimiento de los procesos evolutivos continua siendo limitado por la falta de datos cuantitativos sobre los cambios morfológicos que sufren. En este artículo examinamos la combinación del escaneado láser terrestre y la fotogrametría digital de alta resolución para obtener datos de alta calidad sobre los procesos geomorfológicos implicados en el desarrollo de los acantilados. El estudio se ha llevado a cabo en una sección de acantilados de roca dura en North Yorkshire, Reino Unido, que ha sido monitorizado durante 12 meses. Las nubes de puntos de alta densidad obtenidas por escaneado láser han sido utilizadas para obtener una representación exacta de esas complejas estructuras libre de las variaciones ópticas que degradan las fotografías. Esta información se combinó con una secuencia fotográfica de alta resolución, remuestreada con los datos exactos del levantamiento láser terrestre, lo que constituye una nueva forma de registrar los cambios volumétricos en acantilados costeros complejos. Ello ha permitido mejorar significativamente nuestro conocimiento de los patrones de actividad de los mismos.
The strong nuclear interaction between nucleons (protons and neutrons) is the effective force that holds the atomic nucleus together. This force stems from fundamental interactions between quarks and ...gluons (the constituents of nucleons) that are described by the equations of quantum chromodynamics. However, as these equations cannot be solved directly, nuclear interactions are described using simplified models, which are well constrained at typical inter-nucleon distances but not at shorter distances. This limits our ability to describe high-density nuclear matter such as that in the cores of neutron stars. Here we use high-energy electron scattering measurements that isolate nucleon pairs in short-distance, high-momentum configurations, accessing a kinematical regime that has not been previously explored by experiments, corresponding to relative momenta between the pair above 400 megaelectronvolts per c (c, speed of light in vacuum). As the relative momentum between two nucleons increases and their separation thereby decreases, we observe a transition from a spin-dependent tensor force to a predominantly spin-independent scalar force. Here, these results demonstrate the usefulness of using such measurements to study the nuclear interaction at short distances and also support the use of point-like nucleon models with two- and three-body effective interactions to describe nuclear systems up to densities several times higher than the central density of the nucleus.
Laser calibration system for time of flight scintillator arrays Denniston, A.; Segarra, E. P.; Olivenboim, M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2020, Letnik:
973, Številka:
C
Journal Article
Measurably evolving pathogens in the genomic era Biek, Roman; Pybus, Oliver G.; Lloyd-Smith, James O. ...
Trends in ecology & evolution (Amsterdam),
06/2015, Letnik:
30, Številka:
6
Journal Article
Recenzirano
Odprti dostop
•Pathogens are measurably evolving if new mutational changes are detectable between genetic samples taken at different times.•Whole-genome sequencing has massively increased the range of measurably ...evolving pathogens.•In the future we expect novel and important insights into pathogen population dynamics to come from genomic data.•Considerable analytical challenges will need to be overcome to fully realize this potential.
Current sequencing technologies have created unprecedented opportunities for studying microbial populations. For pathogens with comparatively low per-site mutation rates, such as DNA viruses and bacteria, whole-genome sequencing can reveal the accumulation of novel genetic variation between population samples taken at different times. The concept of ‘measurably evolving populations’ and related analytical approaches have provided powerful insights for fast-evolving RNA viruses, but their application to other pathogens is still in its infancy. We argue that previous distinctions between slow- and fast-evolving pathogens become blurred once evolution is assessed at a genome-wide scale, and we highlight important analytical challenges to be overcome to infer pathogen population dynamics from genomic data.
Human mobility is an important driver of geographic spread of infectious pathogens. Detailed information about human movements during outbreaks are, however, difficult to obtain and may not be ...available during future epidemics. The Ebola virus disease (EVD) outbreak in West Africa between 2014-16 demonstrated how quickly pathogens can spread to large urban centers following one cross-species transmission event. Here we describe a flexible transmission model to test the utility of generalised human movement models in estimating EVD cases and spatial spread over the course of the outbreak. A transmission model that includes a general model of human mobility significantly improves prediction of EVD's incidence compared to models without this component. Human movement plays an important role not only to ignite the epidemic in locations previously disease free, but over the course of the entire epidemic. We also demonstrate important differences between countries in population mixing and the improved prediction attributable to movement metrics. Given their relative rareness, locally derived mobility data are unlikely to exist in advance of future epidemics or pandemics. Our findings show that transmission patterns derived from general human movement models can improve forecasts of spatio-temporal transmission patterns in places where local mobility data is unavailable.
Transmission of Zika virus (ZIKV) in the Americas was first confirmed in May 2015 in northeast Brazil. Brazil has had the highest number of reported ZIKV cases worldwide (more than 200,000 by 24 ...December 2016) and the most cases associated with microcephaly and other birth defects (2,366 confirmed by 31 December 2016). Since the initial detection of ZIKV in Brazil, more than 45 countries in the Americas have reported local ZIKV transmission, with 24 of these reporting severe ZIKV-associated disease. However, the origin and epidemic history of ZIKV in Brazil and the Americas remain poorly understood, despite the value of this information for interpreting observed trends in reported microcephaly. Here we address this issue by generating 54 complete or partial ZIKV genomes, mostly from Brazil, and reporting data generated by a mobile genomics laboratory that travelled across northeast Brazil in 2016. One sequence represents the earliest confirmed ZIKV infection in Brazil. Analyses of viral genomes with ecological and epidemiological data yield an estimate that ZIKV was present in northeast Brazil by February 2014 and is likely to have disseminated from there, nationally and internationally, before the first detection of ZIKV in the Americas. Estimated dates for the international spread of ZIKV from Brazil indicate the duration of pre-detection cryptic transmission in recipient regions. The role of northeast Brazil in the establishment of ZIKV in the Americas is further supported by geographic analysis of ZIKV transmission potential and by estimates of the basic reproduction number of the virus.
Summary Background Since late 2015, an epidemic of yellow fever has caused more than 7334 suspected cases in Angola and the Democratic Republic of the Congo, including 393 deaths. We sought to ...understand the spatial spread of this outbreak to optimise the use of the limited available vaccine stock. Methods We jointly analysed datasets describing the epidemic of yellow fever, vector suitability, human demography, and mobility in central Africa to understand and predict the spread of yellow fever virus. We used a standard logistic model to infer the district-specific yellow fever virus infection risk during the course of the epidemic in the region. Findings The early spread of yellow fever virus was characterised by fast exponential growth (doubling time of 5–7 days) and fast spatial expansion (49 districts reported cases after only 3 months) from Luanda, the capital of Angola. Early invasion was positively correlated with high population density (Pearson's r 0·52, 95% CI 0·34–0·66). The further away locations were from Luanda, the later the date of invasion (Pearson's r 0·60, 95% CI 0·52–0·66). In a Cox model, we noted that districts with higher population densities also had higher risks of sustained transmission (the hazard ratio for cases ceasing was 0·74, 95% CI 0·13–0·92 per log-unit increase in the population size of a district). A model that captured human mobility and vector suitability successfully discriminated districts with high risk of invasion from others with a lower risk (area under the curve 0·94, 95% CI 0·92–0·97). If at the start of the epidemic, sufficient vaccines had been available to target 50 out of 313 districts in the area, our model would have correctly identified 27 (84%) of the 32 districts that were eventually affected. Interpretation Our findings show the contributions of ecological and demographic factors to the ongoing spread of the yellow fever outbreak and provide estimates of the areas that could be prioritised for vaccination, although other constraints such as vaccine supply and delivery need to be accounted for before such insights can be translated into policy. Funding Wellcome Trust.
The yellow fever virus (YFV) epidemic in Brazil is the largest in decades. The recent discovery of YFV in Brazilian
species mosquitos highlights a need to monitor the risk of reestablishment of urban ...YFV transmission in the Americas. We use a suite of epidemiological, spatial, and genomic approaches to characterize YFV transmission. We show that the age and sex distribution of human cases is characteristic of sylvatic transmission. Analysis of YFV cases combined with genomes generated locally reveals an early phase of sylvatic YFV transmission and spatial expansion toward previously YFV-free areas, followed by a rise in viral spillover to humans in late 2016. Our results establish a framework for monitoring YFV transmission in real time that will contribute to a global strategy to eliminate future YFV epidemics.
Cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in Manaus, Brazil, resurged in late 2020 despite previously high levels of infection. Genome sequencing of viruses ...sampled in Manaus between November 2020 and January 2021 revealed the emergence and circulation of a novel SARS-CoV-2 variant of concern. Lineage P.1 acquired 17 mutations, including a trio in the spike protein (K417T, E484K, and N501Y) associated with increased binding to the human ACE2 (angiotensin-converting enzyme 2) receptor. Molecular clock analysis shows that P.1 emergence occurred around mid-November 2020 and was preceded by a period of faster molecular evolution. Using a two-category dynamical model that integrates genomic and mortality data, we estimate that P.1 may be 1.7- to 2.4-fold more transmissible and that previous (non-P.1) infection provides 54 to 79% of the protection against infection with P.1 that it provides against non-P.1 lineages. Enhanced global genomic surveillance of variants of concern, which may exhibit increased transmissibility and/or immune evasion, is critical to accelerate pandemic responsiveness.
The United Kingdom's COVID-19 epidemic during early 2020 was one of world's largest and was unusually well represented by virus genomic sampling. We determined the fine-scale genetic lineage ...structure of this epidemic through analysis of 50,887 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) genomes, including 26,181 from the UK sampled throughout the country's first wave of infection. Using large-scale phylogenetic analyses combined with epidemiological and travel data, we quantified the size, spatiotemporal origins, and persistence of genetically distinct UK transmission lineages. Rapid fluctuations in virus importation rates resulted in >1000 lineages; those introduced prior to national lockdown tended to be larger and more dispersed. Lineage importation and regional lineage diversity declined after lockdown, whereas lineage elimination was size-dependent. We discuss the implications of our genetic perspective on transmission dynamics for COVID-19 epidemiology and control.
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