Double Extinction Research Articles

Trilobites showed strong resilience capacity through the Late Devonian events despite an inexorable decline

The Kellwasser events constituted a major biocrisis at the Frasnian–Famennian boundary, that killed many organisms. The subsequent Hangenberg event also had important effects on marine fauna, although it is not traditionally considered a mass extinction. This study aims to understand the tempo and mode of the Late Devonian extinctions using trilobites as a case of study. To estimate the trilobite dynamics both taxonomic richness and morphological disparity were assessed. The diversity was calculated using conodont biozones, which provide a high-resolution timeline, allowing tracking changes in taxonomic richness and the environmental events implied. The morphological disparity was analysed using space occupancy measures and visualized in morphospaces. The Frasnian began with a diversification of trilobites at generic levels. The number of orders remained constant and relatively high with the presence of Corynexochida, Harpetida, Odontopleurida, Phacopida and Proetida. Environmental conditions were favourable for the proliferation of trilobites until the late Frasnian. However, the Kellwasser events disrupted trilobite evolution, leading to a double extinction event. A first random extinction affected low taxonomic levels, while the second extinction was selective, causing losses at both the generic and order levels, and a strong decrease in morphological disparity. Nonetheless, in response to the end-Frasnian environmental changes, blind and reduced-eye trilobites became more common. Following a dip in generic richness at the beginning of the Famennian, the two surviving orders, Phacopida and Proetida, recovered. Although no novelties characterized them, they partially refilled the morphospace. A slight decline occurred in the middle Famennian before a strong morphological and taxonomical diversification was identified in the expansa and preasulcata zones. The final Hangenberg event at the end of the Famennian affected trilobites at all taxonomic ranks as the Kellwasser events. Only Proetida survived.

Consequences of Traceable Mobility in Populations Exhibiting Strong Allee Effect

In this research, we study the impacts of the traceable mobility in a two-patch environment when the population in each patch exhibits strong Allee effects. Traveling individuals are traced across patches by budgeting the average time spent in each patch while keeping their place of residency. Particularly, we focus on the impact that the effective population (residents and visitors) produces on regional dynamics.Our results show that low mobility across regions produces simple dynamics, where orbits converge to single or double extinction, or to a coexistence steady state. We derive mobility conditions under which an endangered population may benefit of the presence of a visitant one and avoid extinction -- the rescue effect. Nonetheless, increments in the visiting population would also lead the resident population to extinction -- the induced extinction effect.

The Generation of Positrons from Mega-STN and Function as an Alternative Energy Source

Paul Dirac (1902-1984) theoretically predicted the existence of positrons for the first time in 1928, and Carl Anderson (1905-1991) found the positrons through cosmic ray observation experiments in 1932. Positrons are the antiparticle of electron, and their spin and mass are equal to electrons and they have the same electric charge but are different in sign. That is, their spin is ½ Fermion, their electric charge is base charge +e, and their mass is approximately 9.11×10−31 kg. Because positrons are the lightest particle with a positive charge, they have an infinite lifespan without collapsing into other particles. But if positron meets with another electron surrounding them, double extinction of positron and electron occurs, and positrons disappear with electrons, and then photons are generated. Because the earth has many electrons, double extinction occurs immediately in most cases even if positrons are created. There is gravity, electromagnetic force, weak interaction in the interaction of positrons, and the isotopes emitting positrons include carbon-11, nitrogen-13, oxygen-15, fluorine-18. For example, carbon- 11 turns into boron-11. These isotopes are used on positron emission tomography device. Electron capture is another way of decay that can occur competitively with positron emission, but the larger the difference of energy is, the higher the probability of decaying due to positron emission is. Researchers say that positrons are generated if there is collision between high energies by the interaction of positrons, but we think that this should be supplemented more. There is a hypothesis that positrons are generated when the unstable radioactive isotopes created during a supernova explosion collapse. It is inevitable that it will cost a lot of time and money when generating radioactive isotopes according to this hypothesis. This makes us try new methods about positrons emission breaking away from conventional fusion methods. Our new methods for generating positrons are to make artificially the fusion with micro/nanoparticles and isotopes emitting positrons and the interchangeability between them, and to create a great deal of heat energy by making micro/ nanoparticles collide into each other with using thermal energy and waves between micro/nanoparticles. We think that our new methods are the best way to generate high heat with a small energy source. To put our ideas into practice, we made a stainless steel rectangular plate using the combined materials of MEGA-STN, that is the new types fused with each of micro/nanoparticles and isotopes emitting positrons, and added MEGA-STN to materials of the existing stainless steel heater stick. We measured temperature changes depending on whether or not the materials are present and depending on the content of the materials, and checked even positrons emission in our study. We also measured the air quality and the amount of oxygen as well as humidity. Consequently, we found out obtaining high-temperature heat energy by investing less energy. The surface temperature of the existing stainless-steel heater stick did not exceed 320℃ when 3Kw electricity was supplied, but one of stainless-steel heater stick which is mixed with the materials of MEGA-STN was 1000℃. Based on these results, we think that our MEGA-STN can be replaced as a heat energy source which is necessary for all industries using fossil fuel, nuclear power, sunlight generation, wind power and so on, and this can bring good synergy to climate and environment. We expect that our emitted positrons cause the changes of the amount of oxygen and air quality, affect plants and animals including ecological growth, and so make a big difference in human life.

The Relation between MEGA-STN and Positron Wave Thermal Energy

Paul Dirac(1902-1984) theoretically predicted the existence of positrons for the first time in 1928, and Carl Anderson(1905-1991) found the positrons through cosmic ray observation experiments in 1932. Positrons are the antiparticle of electron, and their spin and mass are equal to electrons and they have the same electric charge but are different in sign. That is, their spin is ½ Fermion, their electric charge is base charge +e, and their mass is approximately 9.11×10−31 kg. Because positrons are the lightest particle with a positive charge, they have an infinite lifespan without collapsing into other particles. But if positron meets with another electron surrounding them, double extinction of positron and electron occurs, and positrons disappear with electrons, and then photons are generated. Because the earth has many electrons, double extinction occurs immediately in most cases even if positrons are created. There are gravity, electromagnetic force, weak interaction in the interaction of positrons, and the isotopes emitting positrons include carbon-11, nitrogen-13, oxygen-15, fluorine-18. For example, carbon11 turns into boron-11. These isotopes are used on positron emission tomography device. Electron capture is another way of decay that can occur competitively with positron emission, but the larger the difference of energy is, the higher the probability of decaying due to positron emission is. Researchers say that positrons are generated if there is collision between high energies by the interaction of positrons, but we think that this should be supplemented more. There is a hypothesis that positrons are generated when the unstable radioactive isotopes created during a supernova explosion collapse. It is inevitable that it will cost a lot of time and money when generating radioactive isotopes according to this hypothesis. This makes us try new methods about positrons emission breaking away from conventional fusion methods. Our new methods for generating positrons are to make artificially the fusion with micro/nanoparticles and isotopes emitting positrons and the interchangeability between them, and to create a great deal of heat energy by making micro/nanoparticles collide into each other with using thermal energy and waves between micro/ nanoparticles. We think that our new methods are the best way to generate high heat with a small energy source. To put our ideas into practice, we made a stainless steel rectangular plate using the combined materials of MEGA-STN, that is the new types fused with each of micro/nanoparticles and isotopes emitting positrons, and added MEGA-STN to materials of the existing stainless steel heater stick. We measured temperature changes depending on whether or not the materials are present and depending on the content of the materials, and checked even positrons emission in our study. Consequently, we found increasing to 200~300℃ compared to the general temperature when a constant temperature is created with minimal energy, making a marked change in temperature of our MEGA-STN and emitting positrons at a particular temperature. It is believed to have paved the way for the use of energy sources throughout the industry. Additionally, we realized that photon production caused by the double annihilation of positrons and electrons can affect plants (growth and yields) and insects (the activity of bees in winter) ecologically, cause changes in the environment such as the quality of air and water, and have a positive impact in all areas of our life.

Planktonic foraminiferal biostratigraphy and lithology of the Upper Cretaceous (upper Campanian-Maastrichtian) and Palaeogene succession of the Palmyrides (Syria)

An upper Campanian to upper Oligocene stratigraphic succession has been examined from six deep exploration wells in the Palmyrides area of Syria. Most of the sedimentary succession contains rich and well to moderately preserved planktonic foraminiferal assemblages that enable successful age determination. The upper Campanian and Maastrichtian planktonic fauna is highly diverse with domination of warm water taxa such as Globotruncana aegyptiaca, Gansserina gansseri, Globotruncanella havanensis, Globotruncanita angulata and Pseudotextularia elegans. The most dramatic turnover occurred across the Cretaceous/Palaeocene boundary when most planktonic foraminiferal species became extinct. The oldest Palaeocene planktonic foraminiferal assemblage, rich in the number of specimens, but not very diverse, includes the following species: Eoglobigerina eobulloides, Globanomalina archeocompressa, Chiloguembelina morsei, Woodringina claytonensis and Parasubbotina pseudobulloides. The late Palaeocene is marked by origination of the morozovellids, acarininids and globanomalinids, while the early Eocene is characterized by a tropical assemblage, dominated by muricate species, and by intensive speciation of Acarinina and Subbotina in the latest part. Most of these species continue into the middle Eocene and become a significant component of the planktonic community. The middle Eocene is characterized by intensive speciation and domination of warm water genera such as Acarinina, Morozovelloides, and to a lesser degree Turborotalia, Globigerinatheka and Hantkenina. The middle/late Eocene boundary is marked by double extinction of the last muricate taxa Acarinina mcgowrani and Morozovelloides crasssatus, which indicate a variable climate, water column instability, and loss of surface habitats. In contrast, Turborotalia and Globigerinateheka become more important in the late Eocene. The Eocene/Oligocene boundary is marked by the extinction of most warm water taxa including Turborotalia cerroazulensis group, Hantkenina, Globigerinatheka and some subbotinids. The beginning of the early Oligocene is indicated by the domination of cool water taxa such as Dentoglobigerina, Globorotaloides, Tenuitella and Chiloguembelina. Speciation of the spinose surface dweller Ciperoella ciperoensis group reflects warming in the late Oligocene. The combined observations of lithology with the diversity and composition of planktonic foraminifera assemblages indicate that the Palmyrides area in Syria was a Tethyan bioprovince with a tropical to subtropical climate from the late Campanian to the end of the Eocene with deposition in deep sea environments (upper bathyal to outer shelf). In contrast, Oligocene deposits and their microfossil content suggest temperate to warm climate conditions and sedimentation in middle to inner shelf environments.

Effect of prism adaptation on neglect hemianesthesia

Prism adaptation (PA) has proven to be effective in alleviating many signs of unilateral spatial neglect (USN). Generally, the principal improvement after PA treatment was found to be in the high-level cognitive function. Nevertheless, some evidence has also been found for it in somatosensory function. We have aimed to test the influence of PA on neglect hemianesthesia, a condition in which the high-level neglect-related deficit mimics hemianesthesia. Twenty-one USN patients were enrolled in the study. Each patient performed two sessions of PA, one with neutral glasses and one with prism glasses using a cross-over design. Sensitivity on the upper limb was tested using two methods. The first task was the sensibility subtest which was derived from the standard clinical examination. The second was the perceptual and motor electro-cutaneous threshold on the forearms using an electro-cutaneous stimulator. Four neuropsychological tests were used to diagnose USN and to check improvement: Star cancellation, Line bisection, Sentence reading and the Comb & Razor test. Comparing prism with sham conditions, our results show significant improvements in double extinction and in the electro-cutaneous perceptual threshold only for the contralesional hand. No improvement was found for the ipsilesional hand, for the motor threshold, and for neutral glasses. Significant improvement was found in personal neglect. Replication of the task in a subgroup of patients confirmed the primary results. The improvements in somatosensory perception together with the amelioration of personal neglect suggest that PA also has a specific effect on the neglect hemianesthesia.

Drivers and interrelationships among multiple dimensions of rarity for freshwater fishes

Species can be rare or common in three different dimensions: geographic range size, habitat breadth, and local abundance. Understanding drivers of rarity are not only fundamentally interesting; it is also pertinent for their conservation. We addressed this challenge by analyzing the rarity of 291 native freshwater fishes occurring in ca 3500 independent stream reaches that span a broad environmental gradient across continental USA. Using phylogenetic regression and path analysis, we examined the concordance among the three rarity dimensions, and identified possible mechanisms by which species life‐history, habitat affinities, and biogeography drive variation in rarity. Weak double extinction jeopardies were driven by weakly positive correlations between habitat breadth and local abundance, and between habitat breadth and geographic range size. However, a triple extinction jeopardy was averted as local abundance and range size were not positively linked in our study. This is because large‐river and lacustrine habitat use mediated a trade‐off between local abundance and range size. Large rivers and lacustrine habitats represent important dispersal pathways and refugia that enabled fishes to acquire wide ranges; however, species using these habitats are less abundant overall because they are less adapted to small lotic channels, which comprise the majority of stream habitats in the US. Life‐history traits were key in governing the relationship between abundance and range size as large‐river and lacustrine habitat use were driven by body size, egg size, and parental care. Our analysis contributes novel insights into mechanisms that underlie multiple dimensions of rarity in freshwater fish and informs the prioritization of multiply rare species for conservation.

Reentrant superconductivity in superconductor/ferromagnetic-alloy bilayers

We studied the Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) like state establishing due to the proximity effect in superconducting Nb/Cu41Ni59 bilayers. Using a special wedge-type deposition technique, series of 20-35 samples could be fabricated by magnetron sputtering during one run. The layer thickness of only a few nanometers, the composition of the alloy, and the quality of interfaces were controlled by Rutherford backscattering spectrometry, high resolution transmission electron microscopy, and Auger spectroscopy. The magnetic properties of the ferromagnetic alloy layer were characterized with superconducting quantum interference device (SQUID) magnetometry. These studies yield precise information about the thickness, and demonstrate the homogeneity of the alloy composition and magnetic properties along the sample series. The dependencies of the critical temperature on the Nb and Cu41Ni59 layer thickness, Tc(dS) and Tc(dF), were investigated for constant thickness dF of the magnetic alloy layer and dS of the superconducting layer, respectively. All types of non-monotonic behaviors of Tc versus dF predicted by the theory could be realized experimentally: from reentrant superconducting behavior with a broad extinction region to a slight suppression of superconductivity with a shallow minimum. Even a double extinction of superconductivity was observed, giving evidence for the multiple reentrant behavior predicted by theory. All critical temperature curves were fitted with suitable sets of parameters. Then, Tc(dF) diagrams of a hypothetical F/S/F spin-switch core structure were calculated using these parameters. Finally, superconducting spin-switch fabrication issues are discussed in detail in view of the achieved results.

Quasi-one-dimensional Fulde-Ferrell-Larkin-Ovchinnikov-like state in Nb/Cu0.41Ni0.59 bilayers

In a ferromagnet (F) being in contact with a superconductor (S) an unconventional finite-momentum pairing of electrons forming Cooper pairs occurs. As a consequence, interference effects of the pairing wave function, leading to an oscillation of the critical temperature for increasing F-layer thickness in S/F bilayers, including extinction and recovery of the superconducting state, were predicted by theory. We observed experimentally all types of this behavior, calculated theoretically, in Nb/Cu1 − xNix bilayers (x = 0.59) of nanometer film thickness, prepared by magnetron sputtering (utilizing a moving magnetron deposition technique to provide a superb homogeneity of the ultrathin Nb layers), including a double extinction of superconductivity, giving evidence for a multiple reentrant state.

Macrofossils associated with the fossil fern spore Cyatheacidites annulatus and their significance for Southern hemisphere biogeography

Oligocene–Early Miocene macrofossils of parts of a fertile frond are assigned to the extant South American species Lophosoria quadripinnata (Gmel.)C.Chr. These macrofossils bear the dispersed spore species Cyatheacidites annulatus Cookson ex Potonié, which has an extensive recorded history in the Southern hemisphere, only recently retracting to its current range. This history suggests major episodes of expansion and extinction, with a double extinction occurring in Australia and the Falkland Plateau and Cenozoic introductions to the Kerguelen Islands and the Falkland Plateau that probably involved transoceanic dispersal. Cretaceous Lophosoria records may or may not include L. quadripinnata, but they probably included several related species, especially in the southern South America–Antarctic Peninsula region, where other dispersed spore species of Cyatheacidites and the macrofossil species L. cupulatus are recognised. This species diversity probably collapsed during the Cretaceous, possibly due to angiosperm radiation. The Cenozoic record of C. annulatus in Australia appears to represent a radiation of L. quadripinnata, probably from South America and possibly involving long distance dispersal via West Antarctica.

Reef ecosytem recovery after the Early Cambrian extinction

Abstract Revised and new stratigraphic data indicate a complex extinction event in the late Early Cambrian which consisted of two, temporally separate, but related phases. The earliest phase (mid-Botomian, Sinsk Event) may be related to widespread anoxia due to eutrophication and phytoplankton blooms. The later event (early Toyonian, Hawke Bay Event), is connected to a world wide regression. This double extinction event severely injured the reefal biota which has undergone a further rejuvenation during the remainder of the Cambrian. As a result of the lowering of grazing pressure and unhealthy metazoan-calcimicrobial interactions, the remaining metazoan reef-builders were eliminated by the end of the Early Cambrian. Consequent reduction of space heterogenity led to the decline of calcified microbes ( Renalcis , etc.) in both diversity and abundance which gave way to the thrombolite-stromatolite community. The recovery of the reefal biota occurred during the very end of the Late Cambrian-Early Ordovician and may be attributed to Elvis-taxa, with the exception of the spicular demosponges. This recovering biota intruded into the thrombolite-stromatolite community and created a space for the more successful encrusting reef dwellers of Middle-Late Ordovician time.

Particle diagnosis in multiphase media

Abstract

Optical properties of fractal clusters of small metallic particles

In this paper we describe a method to calculate the optical properties of deterministic fractal clusters. Our method takes advantage of the fact that deterministic fractals can be constructed by an iterative rule. We calculate first the optical properties of a small cluster that describes one stage in the iteration. The optical properties of this cluster are then assigned to an “effective particle”. A small number of these produce the next stage in the fractal construction. We performed the calculations for metallic particles with dielectric functions described by the hydrodynamic model. Results in the dipolar and quadrupolar approximations for a cluster at the second fractal stage shows the double extinction peak often seen in experimental studies.

Accurate validation of visible infrared double extinction simultaneous measurements of particle sizes and number densities by using densely laden standard media

Simultaneous measurements of particle sizes and number densities by means of the visible infrared double extinction technique are carried out and accurately validated. Accurate validation has been made possible by using a new kind of standard media, i.e., embedding the particles under study in a high viscosity gel. A byproduct of the work is a discussion of Beer-Lambert law limitations for multiple scattering in densely laden media.

Visible Infra‐red Double Extinction Measurements in Densely Laden Media, New Progress

AbstractThis paper describes new progress obtained with an optical technique called V.I.D.E. (Visible Infra‐red Double Extinction) which simultaneously measures mean particle size in the range of 10–120 μm and mean number density in densely laden media (up to 0.1% volume fraction). The underlying theory, taking account of multiple light scattering, is recalled. Simultaneous size and concentration measurements are obtained by simultaneously recording transmittances of the medium at two well chosen wavelengths. Experimental results for suspensions of glass particles in air, are described and discussed. The size of particles given by the technique agrees with that given by optical microscopy and Malvern diffractometry. The V.I.D.E. technique is shown to be very suitable to investigate dense media whose optical thickness is up to nine and for which other techniques fail.

Optical measurements of particle size and concentration in densely laden media using a visible/infrared double extinction technique

Measurements of sizes and concentrations of coal particles in densely laden media are carried out by means of a visible/infrared double extinction technique and the underlying theory is explained. It is shown that simultaneous sizing and concentration measurements can be obtained by recording the transmittances of the medium under study at two well chosen wavelengths simultaneously (for instance in the visible and in the far infrared ranges). Experimental results for coal particles sieved between 20 and 80 mu m are described and discussed. The size of particles given by the described technique agrees with the one given by optical microscopy and Malvern diffractometry. The technique is shown to be very suitable for investigating densely laden flows up to 5*109 m-3 (1 kg m-3), for example in the case of 60 mu m coal particles within a 0.25 m length medium.