scholarly journals Dissecting the paleocontinental and paleoenvironmental dynamics of the great Ordovician biodiversification

Paleobiology ◽  
2019 ◽  
Vol 45 (02) ◽  
pp. 221-234 ◽  
Author(s):  
Franziska Franeck ◽  
Lee Hsiang Liow
Keyword(s):  
High Energy ◽  
Extinction Rate ◽  
Time Intervals ◽  
Diversification Rates ◽  
Extinction Rates ◽  
Regional Dynamics ◽  
Genus Richness ◽  
Very High

AbstractThe Ordovician was a time of drastic biological and geological change. Previous work has suggested that there was a dramatic increase in global diversity during this time, but also has indicated that regional dynamics and dynamics in specific environments might have been different. Here, we contrast two paleocontinents that have different geological histories through the Ordovician, namely Laurentia and Baltica. The first was situated close to the equator throughout the whole Ordovician, while the latter has traversed tens of latitudes during the same time. We predict that Baltica, which was under long-term environmental change, would show greater average and interval-to-interval origination and extinction rates than Laurentia. In addition, we are interested in the role of the environment in which taxa originated, specifically, the patterns of onshore–offshore dynamics of diversification, where onshore and offshore areas represent high-energy and low-energy environments, respectively. Here, we predict that high-energy environments might be more conducive for originations.Our new analyses show that the global Ordovician spike in genus richness from the Dapingian to the Darriwilian Stage resulted from a very high origination rate at the Dapingian/Darriwilian boundary, while the extinction rate remained low. We found substantial interval-to-interval variation in the origination and extinction rates in Baltica and Laurentia, but the probabilities of origination and extinction are somewhat higher in Baltica than Laurentia. Onshore and offshore areas have largely indistinguishable origination and extinction rates, in contradiction to our predictions. The global spike in origination rates at the Dapingian/Darriwilian boundary is apparent in Baltica, Laurentia, and onshore and offshore areas, and abundant variability in diversification rates is apparent over other time intervals for these paleocontinents and paleoenvironments. This observation hints at global mechanisms for the spike in origination rates at the Dapingian/Darriwilian boundary but a domination of more regional and local mechanisms over other time intervals in the Ordovician.

The role of toroidal rotation in the very high energy confinement quality observed in super H-mode experiments on DIII-D

2021 ◽  
Vol 28 (11) ◽  
pp. 112504
Author(s):  
S. Ding ◽  
A. M. Garofalo ◽  
X. Jian ◽  
C. Holland ◽  
B. A. Grierson ◽  
...  
Keyword(s):  
High Energy ◽  
Energy Confinement ◽  
Toroidal Rotation ◽  
Very High Energy ◽  
Very High

scholarly journals Long-term multiwavelength view of the blazar 1ES 1218+304

2019 ◽  
Vol 489 (4) ◽  
pp. 5076-5086 ◽  
Author(s):  
K K Singh ◽  
B Bisschoff ◽  
B van Soelen ◽  
A Tolamatti ◽  
J P Marais ◽  
...  
Keyword(s):  
High Energy ◽  
Host Galaxy ◽  
Energy Bands ◽  
X Ray ◽  
Very High Energy ◽  
Γ Ray ◽  
Activity State ◽  
Low Activity ◽  
Very High

ABSTRACT In this work, we present a multiwavelength study of the blazar 1ES 1218+304 using near simultaneous observations over 10 yr during the period 2008 September 1 to 2018 August 31 (MJD 54710–58361). We have analysed data from Swift-UVOT, Swift-XRT, and Fermi-LAT to study the long term behaviour of 1ES 1218+304 in different energy bands over the last decade. We have also used the archival data from OVRO, MAXI, and Swift-BAT available during the above period. The near simultaneous data on 1ES 1218+304 suggest that the long term multiwavelength emission from the source is steady and does not show any significant change in the source activity. The optical/UV fluxes are found to be dominated by the host galaxy emission and can be modelled using the pegase code. However, the time averaged X-ray and γ-ray emissions from the source are reproduced using a single zone leptonic model with log-parabolic distribution for the radiating particles. The intrinsic very high energy γ-ray emission during a low activity state of the source is broadly consistent with the predictions of the leptonic model for blazars. We have investigated the physical properties of the jet and the mass of the supermassive black hole at the centre of the host galaxy using long term X-ray observations from the Swift-XRT which is in agreement with the value derived using blackbody approximation of the host galaxy. We also discuss the extreme nature of the source on the basis of X-ray and γ-ray observations.

scholarly journals Enzymatic treatment of long-term human marrow cultures reveals the preferential location of primitive hemopoietic progenitors in the adherent layer

Blood ◽  
1983 ◽  
Vol 62 (2) ◽  
pp. 291-297 ◽  
Author(s):  
L Coulombel ◽  
AC Eaves ◽  
CJ Eaves
Keyword(s):  
Stem Cells ◽  
Marrow Cell ◽  
Point Of View ◽  
Adherent Cell ◽  
Reproducible Method ◽  
Preferential Location ◽  
Very High ◽  
Marrow Cultures

Abstract Recent studies with long-term mouse marrow cultures have indicated the importance of the adherent layer as a primary reservoir of the most primitive stem cells, from which derivative stem cells and more differentiated progenitors are continuously generated. We have now examined the role of the adherent cell layer in long-term human marrow cultures from this point of view. Prerequisite to such an undertaking was the development of a nontoxic and reproducible method for detaching the adherent layer and making it into a single-cell suspension suitable for characterization by colony assays. Both trypsin and collagenase could be used to obtain suspensions that met these criteria. Lack of toxicity was demonstrated by the preservation of CFU-E, BFU-E, and CFU- C plating efficiency in fresh human marrow cell suspensions exposed to the same enzymatic treatments. Collagenase treatment of long-term marrow culture adherent layers was considered superior because it freed all hemopoietic colony-forming cells but left some of the other cells still adherent. Using this method, we found that CFU-C, BFU-E, and CFU- G/E were consistently detectable in the adherent layer for at least 8 wk, with the majority of the BFU-E and CFU-G/E being located in the adherent layer (70%-75% after 2–3 wk and more than 90% by 7–8 wk). Although corresponding numerical differences in adherent and nonadherent CFU-C populations were not observed, the colonies derived from them showed marked differences in the size they achieved; the adherent layer being the exclusive site of CFU-C, with a very high proliferative capacity. These findings emphasize the importance of assessing the progenitor content of the adherent layer of long-term human marrow cultures and provide an appropriate methodology.

scholarly journals Neuropeptide Y in normal eating and in genetic and dietary-induced obesity

2006 ◽  
Vol 361 (1471) ◽  
pp. 1159-1185 ◽  
Author(s):  
B Beck
Keyword(s):  
Neuropeptide Y ◽  
Diet Composition ◽  
High Energy ◽  
Glucose Sensing ◽  
Feeding Regulation ◽  
Treatment Of Obesity ◽  
The Brain ◽  
Diet Type

Neuropeptide Y (NPY) is one the most potent orexigenic peptides found in the brain. It stimulates food intake with a preferential effect on carbohydrate intake. It decreases latency to eat, increases motivation to eat and delays satiety by augmenting meal size. The effects on feeding are mediated through at least two receptors, the Y1 and Y5 receptors. The NPY system for feeding regulation is mostly located in the hypothalamus. It is formed of the arcuate nucleus (ARC), where the peptide is synthesized, and the paraventricular (PVN), dorsomedial (DMN) and ventromedial (VMN) nuclei and perifornical area where it is active. This activity is modulated by the hindbrain and limbic structures. It is dependent on energy availability, e.g. upregulation with food deprivation or restriction, and return to baseline with refeeding. It is also sensitive to diet composition with variable effects of carbohydrates and fats. Leptin signalling and glucose sensing which are directly linked to diet type are the most important factors involved in its regulation. Absence of leptin signalling in obesity models due to gene mutation either at the receptor level, as in the Zucker rat, the Koletsky rat or the db / db mouse, or at the peptide level, as in ob / ob mouse, is associated with increased mRNA abundance, peptide content and/or release in the ARC or PVN. Other genetic obesity models, such as the Otsuka–Long–Evans–Tokushima Fatty rat, the agouti mouse or the tubby mouse, are characterized by a diminution in NPY expression in the ARC nucleus and by a significant increase in the DMN. Further studies are necessary to determine the exact role of NPY in these latter models. Long-term exposure to high-fat or high-energy palatable diets leads to the development of adiposity and is associated with a decrease in hypothalamic NPY content or expression, consistent with the existence of a counter-regulatory mechanism to diminish energy intake and limit obesity development. On the other hand, an overactive NPY system (increased mRNA expression in the ARC associated with an upregulation of the receptors) is characteristic of rats or rodent strains sensitive to dietary-induced obesity. Finally, NPY appears to play an important role in body weight and feeding regulation, and while it does not constitute the only target for drug treatment of obesity, it may nevertheless provide a useful target in conjunction with others.

On the role of enemies in divergence and diversification of prey: a review and synthesis

2005 ◽  
Vol 83 (7) ◽  
pp. 894-910 ◽  
Author(s):  
Steven M Vamosi
Keyword(s):  
Visual Cues ◽  
Phenotypic Diversity ◽  
Theoretical Models ◽  
Ecological Interactions ◽  
Closely Related Species ◽  
Diversification Rates ◽  
Extinction Rates ◽  
Phenotypic Divergence ◽  
Experimental Approaches

Understanding the contribution of ecological interactions to the origin and maintenance of diversity is a fundamental challenge for ecologists and evolutionary biologists, and one that is currently receiving a great deal of attention. Natural enemies (e.g., predators, parasites, and herbivores) are ubiquitous in food webs and are predicted to have significant impacts on phenotypic diversity and on speciation, and extinction rates of their prey. Spurred by the development of a theoretical framework beginning in the late 1970s, there is now a growing body of literature that addresses the effects of enemy–prey interactions on the evolution of prey. A number of theoretical models predict that enemies can produce phenotypic divergence between closely related species, even in the absence of interspecific competition for resources. Effects on diversification of prey are more variable, and enemies may either enhance or depress speciation and extinction rates of their prey. Empirical evidences from a number of study systems, notably those involving predators and prey in aquatic environments and interactions between insects and flowering plants, confirm both predictions. There is now considerable evidence for the role of enemies, especially those that are size-selective or use visual cues when identifying suitable prey, on phenotypic divergence of sympatric and allopatric taxa. Enemies may spur diversification rates in certain groups under some circumstances, and hinder diversification rates in other cases. I suggest that further research should focus on the role of enemies in diversification of prey, with significant insights likely to be the product of applying traditional experimental approaches and emerging comparative phylogenetic methods.

scholarly journals MAXIINVESTIGATION INTO THE LONG-TERM X-RAY VARIABILITY FROM THE VERY-HIGH-ENERGY γ-RAY BLAZAR Mrk 421

2014 ◽  
Vol 798 (1) ◽  
pp. 27 ◽  
Author(s):  
Naoki Isobe ◽  
Ryosuke Sato ◽  
Yoshihiro Ueda ◽  
Masaaki Hayashida ◽  
Megumi Shidatsu ◽  
...  
Keyword(s):  
High Energy ◽  
X Ray ◽  
Very High Energy ◽  
Γ Ray ◽  
Very High

Dose- and time-intensified ABVD without radiotherapy (RT) for advanced-stage Hodgkin lymphoma (HL) with mediastinal bulky disease (MBD).

2012 ◽  
Vol 30 (15_suppl) ◽  
pp. 8066-8066
Author(s):  
Gaetano Corazzelli ◽  
Filippo Russo ◽  
Ferdinando Frigeri ◽  
Francesco Volzone ◽  
Gaetana Capobianco ◽  
...  
Keyword(s):  
Event Free Survival ◽  
Cardiac Events ◽  
Bulky Disease ◽  
Free Survival ◽  
Nail Changes ◽  
Disease Free ◽  
Very High ◽  
Free Status

8066 Background: The role of consolidation RT on MBD after upfront chemotheraphy for advanced HL is debated, also given the supradditive iatrogenic risk. We present the results achieved in the subset of patients (pts) with MBD (max width > 1/3 of thoracic diameter) accrued in a phase II study of an intensified ABVD program without RT. Methods: The current analysis derives from the final evaluation of our trial for advanced HL (stage IIXB-IV) conducted from 06/2004 to 03/2010 (Russo et al, ASH 2009 abst 715). Pts were scheduled to 6 cycles of a ‘time-densified’ ABVD (3-week intercycle, drugs on days 1 and 11) with the first 4 cycles being also ‘dose-intensified’: doxorubicin (ADM) 35 mg/m2, days 1 and 11 and G-CSF on days 6-8 and 17-19. Results: Of 82 accrued pts, 39 had BMD at presentation. Median age was 29yrs (r 16-58); male 46%; stage IIB 48%, III 8%, IV 43%; B-sympt 87%, E-disease 53%; IP Score ≥3 51%. All pts completed the intensified program. Median actual dose intensities for ADM, bleomycin, vinblastine and dacarbazine were 23.12, 6.69, 3.96 and 245 mg/week, respectively; the increase over conventional ABVD was 85% for ADM and averaged 32% for the other agents. PET2 negativity was achieved in 36/39 (92%; 95% CI 79-98), complete responses (CR) in 37/39 [94%; 95% CI 82-99]. At a median f.u. of 54 mo.s (r 20-91) all pts are alive with an event-free survival of 89% (95% CI, 80-98). Events were: <CR (n=1, CS IVB), progression (n=1, CS IIIA), relapse [n=2; at 10 (CS IVA ) and 15 (CS IIB) months after treatment]; all these pts had isolated mediastinal recurrence. CTCAE v3.0 toxicity: Grade (G) 2 nail changes (31%), G2-G3 hemorrhoids (12%-3%), G3 infection (13%) and constipation (5%), G3-G4 stomatitis (7%-2%). No acute or delayed G3-G4 cardiac events, nor G3-G4 decline in pulmonary function (FEV1, DLCO,FEF25-75) were seen. Conclusions: Intensified ABVD can achieve PET2 negativity in a very high proportion of pts with MBD and ensure a long-term disease-free status even without RT. While results need confirmation on a randomized basis, the low mediastinal failure rate seems in line with recent suggestions that RT could be omitted in MBD when CR is achieved upon intensified chemotheraphy.

Taxonomic evolution in North American Neogene horses (subfamily Equinae): the rise and fall of an adaptive radiation

Paleobiology ◽  
1993 ◽  
Vol 19 (2) ◽  
pp. 216-234 ◽  
Author(s):  
Richard C. Hulbert
Keyword(s):  
Species Richness ◽  
Steady State ◽  
Adaptive Radiation ◽  
Middle Miocene ◽  
Extinction Rate ◽  
Extinction Rates ◽  
Speciation Rates ◽  
History Of ◽  
Very High ◽  
Radiation Phase

The 18 m.y. history of the subfamily Equinae (exclusive of Archaeohippus and “Parahippus”) in North America consisted of a 3-m.y. radiation phase, a 9-m.y. steady-state diversity phase, and a 6-m.y. reduction phase. During the steady-state phase, species richness varied between 14 and 20, with two maxima at about 13.5 and 6.5 Ma. Species richness of the tribes Hipparionini and Equini was about equal through the middle Miocene, but hipparionines consistently had more species in the late Miocene and early Pliocene. Overall mean species duration was 3.2 m.y. (n = 50), or an average extinction rate of 0.31 m.y.-1 During the radiation phase, speciation rates were very high (0.5 to 1.4 m.y.-1), while extinction rates were low (<0.10 m.y.-1). Speciation and extinction rates both averaged about 0.15 m.y.-1 during the steady-state phase, with extinction rates having more variation. Extinction rates increased fourfold during the reduction phase, while speciation rates declined slightly. Late Hemphillian extinctions affected both tribes severely, not just the three-toed hipparionines, and were correlated with global climatic change.

scholarly journals Supernova remnants in the very–high–energy gamma-ray domain: the role of the Cherenkov telescope array

2017 ◽  
Vol 471 (1) ◽  
pp. 201-209 ◽  
Author(s):  
P. Cristofari ◽  
S. Gabici ◽  
T. B. Humensky ◽  
M. Santander ◽  
R. Terrier ◽  
...  
Keyword(s):  
Supernova Remnants ◽  
Gamma Ray ◽  
High Energy ◽  
Telescope Array ◽  
Cherenkov Telescope ◽  
High Energy Gamma ◽  
Very High Energy ◽  
Energy Gamma ◽  
Very High

scholarly journals Testing two-component models on very high-energy gamma-ray-emitting BL Lac objects

2020 ◽  
Vol 640 ◽  
pp. A132
Author(s):  
◽  
V. A. Acciari ◽  
S. Ansoldi ◽  
L. A. Antonelli ◽  
A. Arbet Engels ◽  
...  
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Component Model ◽  
Bl Lac Objects ◽  
Two Component ◽  
Very High Energy ◽  
Component Models ◽  
Very High ◽  
Optical Polarisation

Context. It has become evident that one-zone synchrotron self-Compton models are not always adequate for very high-energy (VHE) gamma-ray-emitting blazars. While two-component models perform better, they are difficult to constrain due to the large number of free parameters. Aims. In this work, we make a first attempt at taking into account the observational constraints from very long baseline interferometry (VLBI) data, long-term light curves (radio, optical, and X-rays), and optical polarisation to limit the parameter space for a two-component model and test whether or not it can still reproduce the observed spectral energy distribution (SED) of the blazars. Methods. We selected five TeV BL Lac objects based on the availability of VHE gamma-ray and optical polarisation data. We collected constraints for the jet parameters from VLBI observations. We evaluated the contributions of the two components to the optical flux by means of decomposition of long-term radio and optical light curves as well as modelling of the optical polarisation variability of the objects. We selected eight epochs for these five objects based on the variability observed at VHE gamma rays, for which we constructed the SEDs that we then modelled with a two-component model. Results. We found parameter sets which can reproduce the broadband SED of the sources in the framework of two-component models considering all available observational constraints from VLBI observations. Moreover, the constraints obtained from the long-term behaviour of the sources in the lower energy bands could be used to determine the region where the emission in each band originates. Finally, we attempt to use optical polarisation data to shed new light on the behaviour of the two components in the optical band. Our observationally constrained two-component model allows explanation of the entire SED from radio to VHE with two co-located emission regions.

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