Large-body impact and extinction in the Phanerozoic

Paleobiology ◽  
1992 ◽  
Vol 18 (1) ◽  
pp. 80-88 ◽  
Author(s):  
David M. Raup
Keyword(s):  
Large Body ◽  
Marine Species ◽  
Radiometric Dating ◽  
Species Extinction ◽  
Crater Diameter ◽  
Extinction Rates ◽  
Kill Curve ◽  
The Impact ◽  
Impact Events

The kill curve for Phanerozoic marine species is used to investigate large-body impact as a cause of species extinction. Current estimates of Phanerozoic impact rates are combined with the kill curve to produce an impact-kill curve, which predicts extinction levels from crater diameter, on the working assumption that impacts are responsible for all “pulsed” extinctions. By definition, pulsed extinction includes the approximately 60% of Phanerozoic extinctions that occurred in short-lived events having extinction rates greater than 5%. The resulting impact-kill curve is credible, thus justifying more thorough testing of the impact-extinction hypothesis. Such testing is possible but requires an exhaustive analysis of radiometric dating of Phanerozoic impact events.

The biotic effects of large bolide impacts: size versus time and place

2008 ◽  
Vol 7 (3-4) ◽  
pp. 209-215 ◽  
Author(s):  
Gordon Walkden ◽  
Julian Parker
Keyword(s):  
Carbonate Platform ◽  
Late Triassic ◽  
Crater Diameter ◽  
Impact Processes ◽  
Eastern Usa ◽  
Post Impact ◽  
Biotic Effects ◽  
Kill Curve ◽  
The Impact ◽  
Continental Interior

AbstractIn estimating the biotic effects of large terrestrial impacts we are reliant upon apparent crater diameter as a proxy for impact magnitude. This underlies the ‘kill-curve’ approach which graphs crater diameter directly against likely percentage losses of taxa. However, crater diameter is a complex product of syn- and post-impact processes that can be site-dependent. Furthermore, location (global positioning) and timing (moment in geological history) also strongly influence biotic effects. We examine four of our largest and best-documented Phanerozoic impacts to explore this more holistic size–time–place relationship. Only the c. 180 km end-Cretaceous Chicxulub crater (Mexico) links to any substantial immediate extinction and some of the worst effects stem from where it struck the planet (a continental margin carbonate platform site) and when (a time of high regional and global biodiversity). Both the c. 100 km late Triassic Manicouagan crater in NE Canada (arid continental interior, low regional and world biodiversity) and the c. 35 Ma 100 km Popigai crater, Siberia (continental arctic desert) provide much less damaging scenarios. However the c. 90 km Chesapeake Bay crater, Eastern USA (also c. 35 Ma) marks a far more sensitive (Chicxulub-like) site but it also proved relatively benign. Here the rheologically varied shallow marine target site produced an anomalously broad crater, and the scale of the impact has evidently been overestimated. We offer a new approach to the graphical prediction of biotic risk in which both crater diameter and a generalised time/place factor we term ‘vulnerability’ are variables.

Extinction selectivity among lower taxa: gradational patterns and rarefaction error in extinction estimates

Paleobiology ◽  
1995 ◽  
Vol 21 (3) ◽  
pp. 300-313 ◽  
Author(s):  
Michael L. McKinney
Keyword(s):  
Niche Breadth ◽  
Large Body ◽  
Data Sets ◽  
Species Extinction ◽  
Environmental Disturbances ◽  
Extinction Rates ◽  
Higher Taxa ◽  
Extinction Selectivity ◽  
Spatio Temporal ◽  
Species Extinctions

Documenting past environmental disturbances will provide a very incomplete explanation of extinctions until more data on intrinsic (e.g., phylogenetic) responses to disturbances are collected. Taxonomic selectivity can be used to infer phylogenetic inheritance of extinction-biasing traits. Selectivity patterns among higher taxa, such as between mammals and bivalves, are well documented. Selectivity patterns among lower taxa (genus, species) have great potential for understanding the dynamics underlying higher taxic turnover. Two echinoid data sets, of fossil and living taxa, indicate that species extinctions do not occur randomly within genera. Reverse rarefaction estimates of past species extinction rates assume random species extinction within higher taxa, so these widely cited extinction estimates may be inaccurate. Revised estimates based on a simulated curve imply that past species extinctions rates may be 6%–15% lower than previously cited. Possible causes for the observed selectivity patterns are discussed. These include nonrandom phylogenetic nesting of species with traits often cited as enhancing extinction vulnerability, into certain taxa. Such traits include low abundance, large body size, narrow niche breadth, and many others. Phylogenetic nesting of extinction-biasing traits at many taxonomic levels does not predict that a dichotomy of mass-background selectivity based on a few traits will occur. Instead, it predicts patterns of selectivity at many taxonomic levels, and at many spatio-temporal scales.

scholarly journals Iterative evolution of large-bodied hypercarnivory in canids benefits species but not clades

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Mairin A. Balisi ◽  
Blaire Van Valkenburgh
Keyword(s):  
Extinction Risk ◽  
Large Body ◽  
Costs And Benefits ◽  
Ecological Specialization ◽  
Large Body Size ◽  
The Past ◽  
Extinction Rates ◽  
The Rich ◽  
Iterative Evolution ◽  
The Impact

AbstractEcological specialization has costs and benefits at various scales: traits benefitting an individual may disadvantage its population, species or clade. In particular, large body size and hypercarnivory (diet over 70% meat) have evolved repeatedly in mammals; yet large hypercarnivores are thought to be trapped in a macroevolutionary “ratchet”, marching unilaterally toward decline. Here, we weigh the impact of this specialization on extinction risk using the rich fossil record of North American canids (dogs). In two of three canid subfamilies over the past 40 million years, diversification of large-bodied hypercarnivores appears constrained at the clade level, biasing specialized lineages to extinction. However, despite shorter species durations, extinction rates of large hypercarnivores have been mostly similar to those of all other canids. Extinction was size- and carnivory-selective only at the end of the Pleistocene epoch 11,000 years ago, suggesting that large hypercarnivores were not disadvantaged at the species level before anthropogenic influence.

scholarly journals A Person-to-Person and Person-to-Place COVID-19 Contact Tracing System Based on OGC IndoorGML

2020 ◽  
Vol 10 (1) ◽  
pp. 2 ◽  
Author(s):  
Soroush Ojagh ◽  
Sara Saeedi ◽  
Steve H. L. Liang
Keyword(s):  
Data Model ◽  
Low Cost ◽  
Large Body ◽  
Contact Tracing ◽  
Trajectory Data ◽  
Sequential Order ◽  
Human Contact ◽  
Wide Availability ◽  
Data Points ◽  
The Impact

With the wide availability of low-cost proximity sensors, a large body of research focuses on digital person-to-person contact tracing applications that use proximity sensors. In most contact tracing applications, the impact of SARS-CoV-2 spread through touching contaminated surfaces in enclosed places is overlooked. This study is focused on tracing human contact within indoor places using the open OGC IndoorGML standard. This paper proposes a graph-based data model that considers the semantics of indoor locations, time, and users’ contexts in a hierarchical structure. The functionality of the proposed data model is evaluated for a COVID-19 contact tracing application with scalable system architecture. Indoor trajectory preprocessing is enabled by spatial topology to detect and remove semantically invalid real-world trajectory points. Results show that 91.18% percent of semantically invalid indoor trajectory data points are filtered out. Moreover, indoor trajectory data analysis is innovatively empowered by semantic user contexts (e.g., disinfecting activities) extracted from user profiles. In an enhanced contact tracing scenario, considering the disinfecting activities and sequential order of visiting common places outperformed contact tracing results by filtering out unnecessary potential contacts by 44.98 percent. However, the average execution time of person-to-place contact tracing is increased by 58.3%.

Cyber Place Management and Crime Prevention: The Effectiveness of Cybersecurity Awareness Training Against Phishing Attacks

2021 ◽  
pp. 104398622110016
Author(s):  
Sinchul Back ◽  
Rob T. Guerette
Keyword(s):  
Crime Prevention ◽  
Research University ◽  
Management Strategies ◽  
Large Body ◽  
The United States ◽  
Place Management ◽  
Online Setting ◽  
Using Data ◽  
Virtual Domain ◽  
The Impact

Criminologists and crime prevention practitioners recognize the importance of geographical places to crime activities and the role that place managers might play in effectively preventing crime. Indeed, over the past several decades, a large body of work has highlighted the tendency for crime to concentrate across an assortment of geographic areas, where place management tends to be absent or weak. Nevertheless, there has been a paucity of research evaluating place management strategies and cybercrime within the virtual domain. The purpose of this study was to investigate the effectiveness of place management techniques on reducing cybercrime incidents in an online setting. Using data derived from the information technology division of a large urban research university in the United States, this study evaluated the impact of an anti-phishing training program delivered to employees that sought to increase awareness and understanding of methods to better protect their “virtual places” from cybercrimes. Findings are discussed within the context of the broader crime and place literature.

Low Velocity Impact Resistance of CPVC Pipes Exposed to Natural Outdoor Weathering Conditions

2012 ◽  
Vol 445 ◽  
pp. 959-964
Author(s):  
Z. Khan ◽  
Necar Merah ◽  
A. Bazoune ◽  
S. Furquan
Keyword(s):  
Impact Resistance ◽  
Outdoor Exposure ◽  
Impact Testing ◽  
Low Velocity Impact ◽  
Pipe Material ◽  
Low Velocity ◽  
Impact Energies ◽  
The Impact ◽  
Impact Events ◽  
Outdoor Weathering

Low velocity drop weight impact testing of CPVC pipes was conducted on 160 mm long pipe sections obtained from 4-inch (100 mm) diameter schedule 80 pipes. Impact test were carried out for the base (as received) pipes and after their exposure to out door natural weathering conditions in Dhahran, Saudi Arabia. The results of the impact testing on the natural (outdoor exposure) broadly suggest that the natural outdoor exposures produce no change in the impact resistance of CPVC pipe material for the impact events carrying low incident energies of 10 and 20J. At the impact energies of 35 and 50J the natural outdoor exposures appear to cause appreciable degradation in the impact resistance of the CPVC pipe material. This degradation is noted only for the longer exposure periods of 12 and 18 months.

Changes in Ecosystems of Bodies of Water Resulting from of the Aaggregates Extraction

2021 ◽  
Vol 25 (9) ◽  
pp. 44-49
Author(s):  
S.S. Uskova
Keyword(s):  
Food Supply ◽  
Small Body ◽  
Large Body ◽  
Small Rivers ◽  
Complete Destruction ◽  
Research Findings ◽  
Downstream Flow ◽  
Bodies Of Water ◽  
The Impact ◽  
Lower Capacity

The evaluation issues on the aggregate’s extraction on the ecosystem of bodies of water has been considered. The dredgers' impact of various capacities on bodies of water of different capacities have been compared, as well as on food supply change of bodies of water for benthos eater. The research findings have showed the dragger's impact of a higher capacity is bigger on a large body of water than this of a lower capacity on a small body of water. The impact manifests itself in decreasing the number and biomass of macrozoobenthos in the area used for the oil and lubricants extraction and the downstream flow. It has been found that the complete destruction of macrozoobenthos at the site of hydraulic engineering activities has not been detected either in small rivers or in large reservoirs.

The Impact of Environmental Pollution on Ethnic Unrest in Xinjiang: A Uyghur Perspective

Modern China ◽  
2018 ◽  
Vol 45 (5) ◽  
pp. 504-536 ◽  
Author(s):  
Nimrod Baranovitch
Keyword(s):  
Environmental Degradation ◽  
Large Body ◽  
Han Chinese ◽  
Ethnic Violence ◽  
Chinese Government ◽  
Autonomous Region ◽  
Mass Migration ◽  
Ethnic Tension ◽  
Xinjiang Uyghur Autonomous Region ◽  
The Impact

Since the early 1990s, the Xinjiang Uyghur Autonomous Region has been one of the most restive areas in China, and in recent years, following the July 2009 Urumchi riots, it has experienced frequent incidents of severe ethnic violence. A large body of scholarship has attempted to explain the sources of Uyghur discontent and pointed to various factors, including cultural and religious repression, unemployment, discrimination, and the mass migration of Han Chinese settlers into the region. This article proposes that environmental degradation, a factor that so far has received little attention in the research that focuses on ethnic tension in Xinjiang, is another important contributing factor. Focusing on air and water pollution in Xinjiang, but also addressing other types of environmental degradation, the article examines the attitudes of Uyghurs toward the phenomenon and shows how their perceptions have affected and been affected by their tense relationship with the Chinese government and the Han Chinese settlers in the region.

scholarly journals LABORATORY OBSERVATIONS OF IMPACTS ON COARSE SEDIMENT BEACHES

2011 ◽  
Vol 1 (32) ◽  
pp. 53
Author(s):  
Ian Ball ◽  
Edgar Mendoza-Baldwin ◽  
David Simmonds ◽  
Adrián Pedrozo-Acuña ◽  
Dominic E Reeve
Keyword(s):  
Full Scale ◽  
Impact Pressure ◽  
Coarse Grained ◽  
Laboratory Measurements ◽  
Coarse Sediment ◽  
Full Scale Tests ◽  
The Impact ◽  
Impact Events ◽  
Plunging Breaker

In this paper we present laboratory observations of plunging wave breaker impact pressure responses on a steep coarse-grained beach, extending previous work conducted by Pedrozo-Acuña et al. (2008). Scale laboratory measurements of plunging breaker impact events are reported and compared with the previous full-scale tests. These tests extend the previous relationships to a wider range of surf-similarity parameters and indicate a continued reduction in impact pressure as the transition from plunging impacts to surging impacts is approached. Additional results from scale tests conducted on a smooth impermeable slope also indicate the presence of a maximum impact pressure within the plunging breaker region; however also suggest it may be necessary to include roughness and permeability in the parameterization of the impact pressure.

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