scholarly journals An enormous sulfur isotope excursion indicates marine anoxia during the end-Triassic mass extinction

2020 ◽  
Vol 6 (37) ◽  
pp. eabb6704
Author(s):  
Tianchen He ◽  
Jacopo Dal Corso ◽  
Robert J. Newton ◽  
Paul B. Wignall ◽  
Benjamin J. W. Mills ◽  
...  
Keyword(s):  
Mass Extinction ◽  
Large Scale ◽  
Sulfur Isotope ◽  
Oxygen Demand ◽  
Methane Flux ◽  
Global Scale ◽  
Late Triassic ◽  
Carbonate Associated Sulfate ◽  
Water Oxygen

The role of ocean anoxia as a cause of the end-Triassic marine mass extinction is widely debated. Here, we present carbonate-associated sulfate δ34S data from sections spanning the Late Triassic–Early Jurassic transition, which document synchronous large positive excursions on a global scale occurring in ~50 thousand years. Biogeochemical modeling demonstrates that this S isotope perturbation is best explained by a fivefold increase in global pyrite burial, consistent with large-scale development of marine anoxia on the Panthalassa margin and northwest European shelf. This pyrite burial event coincides with the loss of Triassic taxa seen in the studied sections. Modeling results also indicate that the pre-event ocean sulfate concentration was low (<1 millimolar), a common feature of many Phanerozoic deoxygenation events. We propose that sulfate scarcity preconditions oceans for the development of anoxia during rapid warming events by increasing the benthic methane flux and the resulting bottom-water oxygen demand.

Calcite interval in aragonite seas: Geochemical characterization of post-extinction oolites at the Triassic-Jurassic boundary and their implications

2021 ◽  
Author(s):  
Ingrid Urban ◽  
Sylvain Richoz
Keyword(s):  
Mass Extinction ◽  
Major And Trace Elements ◽  
Late Triassic ◽  
Geochemical Data ◽  
Mass Extinctions ◽  
Icp Ms ◽  
Petrographic Analyses ◽  
Isotope System ◽  
Extinction Events

&lt;p&gt;The End-Triassic Mass Extinction (ETME) is one of the five major mass extinctions of the Phanerozoic. The deposition of ooids is atypically high in the direct aftermath of major extinction events, including the ETME. Ooids were intensively investigated both petrographically and sedimentologically in the past decades; but only recently their potentialities as archives for the original chemical composition of the oceans where they formed, have gained awareness. Here we present stratigraphical, sedimentological and geochemical aspects for a mid-Norian-Hettangian section from the Emirates.&lt;/p&gt;&lt;p&gt;Petrographic analyses provided a detailed morphological classification of post-ETME coated grains, supported by point counting of two isochronous geological sections. FE-SE-EDX imaging unraveled peculiar &amp;#181;m-scale features linked to morphology, diagenesis and biotic interaction in the cortex. LA-ICP-MS analyses were performed for specific major and trace elements. Post-extinction oolites show high variability in size and development of the cortex. They range from small (~ 300 &amp;#181;m) and superficial coating, to bigger (up to 800 &amp;#181;m) and well developed. The degree of micritization highlights different oxic conditions in the diagenetic environment. LA-ICP-MS analyses give insights into seawater redox conditions during ooids formation, siliciclastic contamination, diagenetic processes and the role of bacterial strain in shaping the ooids. Petrographical and geochemical data point out to a calcitic deposition of these ooids as odd with the general consideration that the Late Triassic to Early Jurassic was part of the Aragonite sea. This has major implication on the understanding of the carbonate saturation in the oceans just after the mass-extinction and on the interpretation of several proxies as the C and Ca isotope-system.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

scholarly journals Grappling with uncertainties in physical climate impact projections of water resources

2020 ◽  
Vol 163 (3) ◽  
pp. 1379-1397 ◽  
Author(s):  
Rutger Dankers ◽  
Zbigniew W. Kundzewicz
Keyword(s):  
Large Scale ◽  
Weather Prediction ◽  
Global Scale ◽  
Climate Impact ◽  
Climate Modelling ◽  
Large Uncertainty ◽  
Sources Of Uncertainty ◽  
Hydrological Extremes ◽  
Model Ensembles

AbstractThis paper reviews the sources of uncertainty in physical climate impact assessments. It draws on examples from related fields such as climate modelling and numerical weather prediction in discussing how to interpret the results of multi-model ensembles and the role of model evaluation. Using large-scale, multi-model simulations of hydrological extremes as an example, we demonstrate how large uncertainty at the local scale does not preclude more robust conclusions at the global scale. Finally, some recommendations are made: climate impact studies should be clear about the questions they want to address, transparent about the uncertainties involved, and honest about the assumptions being made.

scholarly journals Trans-oceanic host dispersal explains high seabird tick diversity on Cape Verde islands

2012 ◽  
Vol 8 (4) ◽  
pp. 616-619 ◽  
Author(s):  
E. Gómez-Díaz ◽  
J. A. Morris-Pocock ◽  
J. González-Solís ◽  
K. D. McCoy
Keyword(s):  
Genetic Diversity ◽  
Genetic Structure ◽  
Large Scale ◽  
Evolutionary Ecology ◽  
Global Scale ◽  
Cape Verde ◽  
Metapopulation Dynamics ◽  
Biogeographic Patterns ◽  
Genetic Diversity And Structure

Parasites represent ideal models for unravelling biogeographic patterns and mechanisms of diversification on islands. Both host-mediated dispersal and within-island adaptation can shape parasite island assemblages. In this study, we examined patterns of genetic diversity and structure of Ornithodoros seabird ticks within the Cape Verde Archipelago in relation to their global phylogeography. Contrary to expectations, ticks from multiple, geographically distant clades mixed within the archipelago. Trans-oceanic colonization via host movements probably explains high local tick diversity, contrasting with previous research that suggests little large-scale dispersal in these birds. Although host specificity was not obvious at a global scale, host-associated genetic structure was found within Cape Verde colonies, indicating that post-colonization adaptation to specific hosts probably occurs. These results highlight the role of host metapopulation dynamics in the evolutionary ecology and epidemiology of avian parasites and pathogens.

Critique of a Large-Scale Organ System Model: Guytonian Cardiovascular Model

1975 ◽  
Vol 97 (3) ◽  
pp. 259-265
Author(s):  
K. Sagawa
Keyword(s):  
Renal Function ◽  
Arterial Pressure ◽  
Large Scale ◽  
Renal Hypertension ◽  
Experimental Studies ◽  
Oxygen Demand ◽  
Sensitivity Tests ◽  
Vascular Autoregulation

This paper reviews Guyton’s model which is large not only in the number of its components but also in the time scale that it spans. The evolution of this model is explained in three stages. Guyton started with a drastically simplified model of the entire cardiovascular system as a closed hydraulic loop. It accounted for short-term regulations of cardiac output with a special emphasis on the role of blood volume and the vascular capacity. Guyton’s research objective was then directed toward the analysis of longterm regulation of arterial pressure. Two slowly acting mechanisms were considered as particularly important: (1) the marked increase or decrease of urinary output with only slight increase or decrease in arterial pressure (the renal function curve in the Guytonian model) and (2) long-term vascular autoregulation which includes changes in the extent of vascularization as well as constriction or dilation of existing vessels to match the blood flow with the oxygen demand in tissues. This second-stage model explained the transient dynamics and steady equilibrium of renal hypertension. The current version of Guyton’s model incorporates a variety of additional endocrine and neural mechanisms which parametrically control the renal function curve. With the enormous growth, the identification (or estimation) capability of the model is bound to degrade while its use for multiple parameter sensitivity tests expands. The modeller’s group has attempted to minimize the hazards by frequent checks of model predictions with experimental studies. This interactive effort, plus their concern over these long-term regulatory mechanisms, make the Guytonian model a unique venture in modern cardiovascular physiology.

scholarly journals Positive Sulfate Sulfur Isotope Excursion Indicates Large-Scale Pyrite Burial and Marine Anoxia during the End–Triassic Mass Extinction

2020 ◽  
Author(s):  
Tianchen He ◽  
Jacopo Dal Corso ◽  
Robert J. Newton ◽  
Paul B. Wignall ◽  
Benjamin J.W. Mills ◽  
...  
Keyword(s):  
Mass Extinction ◽  
Large Scale ◽  
Sulfur Isotope ◽  
Sulfate Sulfur

The roles of mass extinction and biotic interaction in large-scale replacements: a reexamination using the fossil record of stromboidean gastropods

Paleobiology ◽  
1996 ◽  
Vol 22 (3) ◽  
pp. 436-452 ◽  
Author(s):  
Kaustuv Roy
Keyword(s):  
Mass Extinction ◽  
Large Scale ◽  
Biotic Interactions ◽  
Taxonomic Diversity ◽  
Global Scale ◽  
General Nature ◽  
Biotic Interaction ◽  
Geographic Scale ◽  
Climatic Fluctuations ◽  
Extinction Rates

The macroevolutionary processes underlying large-scale biotic replacements are still poorly understood. Opinion remains divided regarding the roles of mass extinction, biotic interaction, and environmental perturbations in these replacement events. Previous attempts to test replacement hypotheses have largely focused on taxonomic diversity patterns. Taxonomic data alone, however, provide little insight about ecological interactions and hence other approaches are needed to understand mechanics of biotic replacements. Here I propose a conceptual model of replacement based on predation-mediated biotic interactions, and attempt a test using analysis of the Cenozoic replacement of the gastropod family Aporrhaidae by a closely related group, the Strombidae.Taxonomic, morphologic, and geographic data analyzed in this study all suggest a replacement of aporrhaids by strombids following the end-Cretaceous mass extinction. While most of the taxonomic replacement was associated with a mass extinction, some replacement also occurred during background times and was mediated by higher origination rates in strombids rather than by higher extinction rates in aporrhaids. Morphologically, the replacement was largely confined to the portion of the morphospace unaffected by the end-Cretaceous extinction. At a global scale, the geographic overlap between the two groups declined through the Cenozoic, reflecting increasing restriction of aporrhaids to colder, temperate waters while strombids flourished in the tropics. However, at a finer geographic scale a more mosaic pattern of replacement is evident and coincides with Eocene and Oligocene climatic fluctuations.The results of this study suggest that mass extinction, long-term biotic interaction, and environmental change can all play significant roles in biotic replacements. Since the relative importance of each factor would vary from one event to another, an understanding of the general nature of large-scale biotic replacements requires a knowledge of the relative intensities of each of these processes.

scholarly journals SOME ASPECTS OF EPIDEMIOLOGY AND ETIOPATHOGENESIS OF METABOLIC SYNDROME

2020 ◽  
pp. 580-594
Author(s):  
S. M. ABDULLOZODA ◽  
Keyword(s):  
Risk Factors ◽  
Metabolic Syndrome ◽  
Large Scale ◽  
Sleep Apnea Syndrome ◽  
Global Scale ◽  
Advantages And Disadvantages ◽  
Obstructive Sleep ◽  
Causes And Risk Factors ◽  
Preventive Diagnostics

A review of literature data carried out on the most important aspects of epidemiology, risk factors and pathogenesis of metabolic syndrome (MS). Metabolic syndrome has been found in approximately one quarter of the world’s population, and, despite the large-scale treatment, preventive and health-improving promotion programs on a global scale, the number of persons with MS tends to increase annually, especially among young ablebodied age. There are many risk factors in its genesis, including genetic predisposition, low physical activity, poor diet, smoking, intestinal microbiota, obstructive sleep apnea syndrome and others, the role of most of which needs to be studied in more depth. Many criteria have been proposed for the diagnosis of MS, each of them has its own advantages and disadvantages. With MS, most organs and systems are affected, and with the combined involvement of the cardiovascular, endocrine, urinary, digestive and respiratory systems burdened clinical course of MS. In connection with the above, there is a reason for further scientific research to identify the causes and risk factors for the development of MS, development of preventive ways of prevention, preventive diagnostics and early treatment of MS. Keywords: metabolic syndrome, epidemiology, pathogenesis, diabetes mellitus, insulin resistance, obesity, hypercholesterolemia.

The Role of Sense of Direction and Other Factors During Navigation in a Large-Scale, Unconstrained Environment

2013 ◽  
Author(s):  
Elisabeth J. Ploran ◽  
Ericka Rovira ◽  
James C. Thompson ◽  
Raja Parasuraman
Keyword(s):  
Large Scale ◽  
Sense Of Direction

Magnetic Properties of xCeO2•(50 − x) PbO•50B2O3 Glasses and Glass Ceramics

2017 ◽  
Vol 13 (1) ◽  
pp. 4486-4494 ◽  
Author(s):  
G.El Damrawi ◽  
F. Gharghar
Keyword(s):  
Magnetic Properties ◽  
Large Scale ◽  
Glass Ceramics ◽  
Magnetic Behavior ◽  
Crystal Formation ◽  
Dual Roles ◽  
Effective Agent ◽  
Ordered Structures ◽  
Essential Change

Cerium oxide in borate glasses of composition xCeO2·(50 − x)PbO·50B2O3 plays an important role in changing both microstructure and magnetic behaviors of the system. The structural role of CeO2 as an effective agent for cluster and crystal formation in borate network is clearly evidenced by XRD technique. Both structure and size of well-formed cerium separated clusters have an effective influence on the structural properties. The cluster aggregations are documented to be found in different range ordered structures, intermediate and long range orders are the most structures in which cerium phases are involved. The nano-sized crystallized cerium species in lead borate phase are evidenced to have magnetic behavior.  The criteria of building new specific borate phase enriched with cerium as ferrimagnetism has been found to keep the magnetization in large scale even at extremely high temperature. Treating the glass thermally or exposing it to an effective dose of ionized radiation is evidenced to have an essential change in magnetic properties. Thermal heat treatment for some of investigated materials is observed to play dual roles in the glass matrix. It can not only enhance alignment processes of the magnetic moment but also increases the capacity of the crystallite species in the magnetic phases. On the other hand, reverse processes are remarked under the effect of irradiation. The magnetization was found to be lowered, since several types of the trap centers which are regarded as defective states can be produced by effect of ionized radiation. 

The Impact of Quantitative Easing on Emerging Markets – Literature Review

e-Finanse ◽  
2018 ◽  
Vol 14 (4) ◽  
pp. 67-76
Author(s):  
Piotr Bartkiewicz
Keyword(s):  
Emerging Markets ◽  
Large Scale ◽  
Empirical Literature ◽  
Quantitative Easing ◽  
Methodological Choices ◽  
The Subject ◽  
Methodological Approaches ◽  
The Impact ◽  
Sufficient Precision

AbstractThe article presents the results of the review of the empirical literature regarding the impact of quantitative easing (QE) on emerging markets (EMs). The subject is of interest to policymakers and researchers due to the increasingly larger role of EMs in the world economy and the large-scale capital flows occurring after 2009. The review is conducted in a systematic manner and takes into consideration different methodological choices, samples and measurement issues. The paper puts the summarized results in the context of transmission channels identified in the literature. There are few distinct methodological approaches present in the literature. While there is a consensus regarding the direction of the impact of QE on EMs, its size and durability have not yet been assessed with sufficient precision. In addition, there are clear gaps in the empirical findings, not least related to relative underrepresentation of the CEE region (in particular, Poland).

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