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Sample records for early spectrophotometric evolution

  1. The Early Spectrophotometric Evolution of V1186 Scorpii (Nova Scorpii 2004 No. 1)

    NASA Astrophysics Data System (ADS)

    Schwarz, G. J.; Woodward, C. E.; Bode, M. F.; Evans, A.; Eyres, S. P.; Geballe, T. R.; Gehrz, R. D.; Greenhouse, M. A.; Helton, L. A.; Liller, W.; Lyke, J. E.; Lynch, D. K.; O'Brien, T. J.; Rudy, R. J.; Russell, R. W.; Shore, S. N.; Starrfield, S. G.; Temim, T.; Truran, J. W.; Venturini, C. C.; Wagner, R. M.; Williams, R. E.; Zamanov, R.

    2007-08-01

    We report optical photometry and optical through mid-infrared spectroscopy of the classical nova V1186 Sco. This slowly developing nova had a complex light curve with multiple secondary peaks similar to those seen in PW Vul. The time to decline 2 mag, t2, was 20 days, but the erratic nature of the light curve makes determination of intrinsic properties based on the decline time (e.g., luminosity) problematic, and the often-cited relationship of maximum magnitude versus the rate of decay of the light curve of Della Valle & Livio fails to yield a plausible distance. Spectra covering 0.35-35 μm were obtained in two separate epochs during the first year of outburst. The first set of spectra, taken about 2 months after visible maximum, are typical of a CO-type nova with narrow-line emission from H I, Fe II, O I, and He I. Later data, obtained between 260 and 380 days after maximum, reveal an emerging nebular spectrum. Spitzer spectra show weakening hydrogen recombination emission with the emergence of [Ne II] (12.81 μm) as the strongest line. Strong emission from [Ne III] (15.56 μm) is also detected. Photoionization models with low effective temperature sources and only marginal neon enhancement (Ne ~ 1.3 Nesolar) are consistent with these IR fine-structure neon lines indicating that V1186 Sco did not occur on a ONeMg white dwarf. In contrast, the slow and erratic light-curve evolution, spectral development, and photoionization analysis of the ejecta imply that the outburst occurred on a low-mass CO white dwarf. We note that this is the first time strong [Ne II] lines have been detected so early in the outburst of a CO nova and suggest that the presence of mid-infrared neon lines is not directly indicative of a ONeMg nova event.

  2. Spectrophotometric Evolution of Eta Carinae's Great Eruption

    NASA Astrophysics Data System (ADS)

    Rest, Armin; Prieto, Jose Luis; Bianco, Federica; Matheson, Thomas; Smith, Nathan; Smith, Chris; Chornock, Ryan; Sinnott, Brendan; Welch, Douglas; Walborn, Nolan

    2013-06-01

    Eta Carinae is one of the most massive binaries in the Milky Way, and its expanding circumstellar nebula has been studied in detail. It was seen as the second brightest star in the sky during its 1800s "Great Eruption", but only visual estimates of its brightness were recorded. We discovered light echoes of the Great Eruption, which allowed us to obtain a spectrum of this event now, 150 years after it was first observed. We will present our new follow-up observations with which we have started to retrace its spectrophotometric evolution during and before the eruption.

  3. Spectrophotometric evolution of Nova Delphini 2013

    NASA Astrophysics Data System (ADS)

    Tarasova, T. N.; Shakhovskoi, D. N.

    2013-09-01

    We continue spectrophotometric observations with the 2.6 m telescope of CrAO (the first results were reported in our previous telegram ATel5291). We carried out observations on August 19 and on September 1 with low resolution spectrograph (R=1000) in the wavelength interval 3300-7575A and on August 20 with high resolution echelle spectrograph (R=33000) in the wavelength interval 4300-7200A.

  4. Early bioenergetic evolution

    PubMed Central

    Sousa, Filipa L.; Thiergart, Thorsten; Landan, Giddy; Nelson-Sathi, Shijulal; Pereira, Inês A. C.; Allen, John F.; Lane, Nick; Martin, William F.

    2013-01-01

    Life is the harnessing of chemical energy in such a way that the energy-harnessing device makes a copy of itself. This paper outlines an energetically feasible path from a particular inorganic setting for the origin of life to the first free-living cells. The sources of energy available to early organic synthesis, early evolving systems and early cells stand in the foreground, as do the possible mechanisms of their conversion into harnessable chemical energy for synthetic reactions. With regard to the possible temporal sequence of events, we focus on: (i) alkaline hydrothermal vents as the far-from-equilibrium setting, (ii) the Wood–Ljungdahl (acetyl-CoA) pathway as the route that could have underpinned carbon assimilation for these processes, (iii) biochemical divergence, within the naturally formed inorganic compartments at a hydrothermal mound, of geochemically confined replicating entities with a complexity below that of free-living prokaryotes, and (iv) acetogenesis and methanogenesis as the ancestral forms of carbon and energy metabolism in the first free-living ancestors of the eubacteria and archaebacteria, respectively. In terms of the main evolutionary transitions in early bioenergetic evolution, we focus on: (i) thioester-dependent substrate-level phosphorylations, (ii) harnessing of naturally existing proton gradients at the vent–ocean interface via the ATP synthase, (iii) harnessing of Na+ gradients generated by H+/Na+ antiporters, (iv) flavin-based bifurcation-dependent gradient generation, and finally (v) quinone-based (and Q-cycle-dependent) proton gradient generation. Of those five transitions, the first four are posited to have taken place at the vent. Ultimately, all of these bioenergetic processes depend, even today, upon CO2 reduction with low-potential ferredoxin (Fd), generated either chemosynthetically or photosynthetically, suggesting a reaction of the type ‘reduced iron → reduced carbon’ at the beginning of bioenergetic evolution

  5. Early stellar evolution

    NASA Technical Reports Server (NTRS)

    Stahler, Steven W.

    1994-01-01

    Research into the formation and early evolution of stars is currently an area of great interest and activity. The theoretical and observational foundations for this development are reviewed in this paper. By now, the basic physics governing cloud collapse is well understood, as is the structure of the resulting protostars. However, the theory predicts protostellar luminosities that are greater than those of most infrared sources. Observationally, it is thought that protostars emit powerful winds that push away remnant cloud gas, but both the origin of these winds and the nature of their interaction with ambient gas are controversial. Finally, the theory of pre-main-sequence stars has been modified to incorporate more realistic initial conditions. This improvement helps to explain the distribution of such stars in the H-R diagram. Many important issues, such as the origin of binary stars and stellar clusters, remain as challenges for future research.

  6. Early cellular evolution.

    NASA Technical Reports Server (NTRS)

    Margulis, L.

    1972-01-01

    Study of the evolutionary developments that occurred subsequent to the origin of ancestral cells. Microbial physiology and ecology are potential sharp tools for shaping concepts of microbial evolution. Some popular unjustified assumptions are discussed. It is considered that certain principles derived mainly from the advances of molecular biology can be used to order the natural groups (genera) of extant prokaryotes and their patterns phylogenetically.

  7. Oxygen and Early Animal Evolution

    NASA Astrophysics Data System (ADS)

    Xiao, S.

    2012-12-01

    It is often hypothesized that the rise of animals was triggered by an increase in O2 levels in the atmosphere and oceans. However, this hypothesis is remarkably difficult to test, because the timing of animal divergences is poorly resolved, the physiology of early animals is often unknown, estimates of past pO2 levels come with large error bars, and causal relationships between oxygenation and animal evolution are difficult to establish. Nonetheless, existing phylogenetic, paleontological, and geochemical data indicate that the evolution of macroscopic animals and motile macrometazoans with energetically expensive lifestyles may be temporally coupled with ocean oxygenation events in the Ediacaran Period. Thus, it is plausible that ocean oxygenation may have been a limiting factor in the early evolution of macroscopic, complex, and metabolically aggressive animals (particularly bilaterian animals). However, ocean oxygenation and animal evolution were likely engaged in two-way interactions: Ediacaran oxygenation may have initially lifted a physiological barrier for the evolution of animal size, motility, and active lifestyles, but subsequent animal diversification in the Paleozoic may have also changed oceanic redox structures. Viewed in a broader context, the early evolutionary history of animals was contingent upon a series of events, including genetic preparation (developmental genetics), environmental facilitation (oceanic oxygenation), and ecological escalation (Cambrian explosion), but the rise of animals to ecological importance also had important geobiological impacts on oceanic redox structures, sedimentary fabrics, and global geochemical cycles.

  8. EARLY EVOLUTION OF PRESTELLAR CORES

    SciTech Connect

    Horedt, G. P.

    2013-08-20

    Prestellar cores are approximated by singular polytropic spheres. Their early evolution is studied analytically with a Bondi-like scheme. The considered approximation is meaningful for polytropic exponents {gamma} between 0 and 6/5, implying radial power-law density profiles between r {sup -1} and r {sup -2.5}. Gravitationally unstable Jeans and Bonnor-Ebert masses differ at most by a factor of 3.25. Tidally stable prestellar cores must have a mean density contrast {approx}> 8 with respect to the external parent cloud medium. The mass-accretion rate relates to the cube of equivalent sound speed, as in Shu's seminal paper. The prestellar masses accreted over 10{sup 5} years cover the whole stellar mass spectrum; they are derived in simple closed form, depending only on the polytropic equation of state. The stellar masses that can be formed via strict conservation of angular momentum are at most of the order of a brown dwarf.

  9. The evolution of early neurogenesis.

    PubMed

    Hartenstein, Volker; Stollewerk, Angelika

    2015-02-23

    The foundation of the diverse metazoan nervous systems is laid by embryonic patterning mechanisms, involving the generation and movement of neural progenitors and their progeny. Here we divide early neurogenesis into discrete elements, including origin, pattern, proliferation, and movement of neuronal progenitors, which are controlled by conserved gene cassettes. We review these neurogenetic mechanisms in representatives of the different metazoan clades, with the goal to build a conceptual framework in which one can ask specific questions, such as which of these mechanisms potentially formed part of the developmental "toolkit" of the bilaterian ancestor and which evolved later. PMID:25710527

  10. Early evolution without a tree of life

    PubMed Central

    2011-01-01

    Life is a chemical reaction. Three major transitions in early evolution are considered without recourse to a tree of life. The origin of prokaryotes required a steady supply of energy and electrons, probably in the form of molecular hydrogen stemming from serpentinization. Microbial genome evolution is not a treelike process because of lateral gene transfer and the endosymbiotic origins of organelles. The lack of true intermediates in the prokaryote-to-eukaryote transition has a bioenergetic cause. This article was reviewed by Dan Graur, W. Ford Doolittle, Eugene V. Koonin and Christophe Malaterre. PMID:21714942

  11. A Galactic Weigh-in: Mass Models of SINGS Galaxies Using Chemo-spectrophotometric Galactic Evolution Models

    NASA Astrophysics Data System (ADS)

    de Denus-Baillargeon, M.-M.; Hernandez, O.; Boissier, S.; Amram, P.; Carignan, C.

    2013-08-01

    The baryonic mass-to-light ratio (Upsilonsstarf) used to perform the photometry-to-mass conversion has a tremendous influence on the measurement of the baryonic content and distribution as well as on the determination of the dark halo parameters. Since numerous clues hint at an inside-out formation process for galaxies, a radius-dependant Upsilonsstarf is needed to physically represent the radially varying stellar population. In this article, we use chemo-spectrophotometric galactic evolution (CSPE) models to determine Upsilonsstarf for a wide range of masses and sizes in the scenario of an inside-out formation process by gas accretion. We apply our method to a SINGS subsample of 10 spiral and dwarf galaxies with photometric coverage ranging from the UV to the mid-IR. The CSPE models prove to be a good tool for weighting the different photometric bands in order to obtain consistent stellar disk masses regardless of the spectral band used. On the other hand, we show that the color index versus Upsilonsstarf relation is an imperfect tool for assigning masses to young stellar populations because of the degeneracy affecting Upsilonsstarf in all bands at low color index. The disks resulting from our analysis are compatible with the maximum disk hypothesis provided that an adequate bulge/disk decomposition is performed and that the correction for the presence of a bar is not neglected since bars disturb the internal disk kinematics. Disk-mass models including Upsilonsstarf as a free parameter as well as models using our physically motivated, radially varying Upsilonsstarf are presented and discussed for each galaxy.

  12. A GALACTIC WEIGH-IN: MASS MODELS OF SINGS GALAXIES USING CHEMO-SPECTROPHOTOMETRIC GALACTIC EVOLUTION MODELS

    SciTech Connect

    De Denus-Baillargeon, M.-M.; Hernandez, O.; Carignan, C.; Boissier, S.; Amram, P.

    2013-08-20

    The baryonic mass-to-light ratio (Y{sub *}) used to perform the photometry-to-mass conversion has a tremendous influence on the measurement of the baryonic content and distribution as well as on the determination of the dark halo parameters. Since numerous clues hint at an inside-out formation process for galaxies, a radius-dependant Y{sub *} is needed to physically represent the radially varying stellar population. In this article, we use chemo-spectrophotometric galactic evolution (CSPE) models to determine Y{sub *} for a wide range of masses and sizes in the scenario of an inside-out formation process by gas accretion. We apply our method to a SINGS subsample of 10 spiral and dwarf galaxies with photometric coverage ranging from the UV to the mid-IR. The CSPE models prove to be a good tool for weighting the different photometric bands in order to obtain consistent stellar disk masses regardless of the spectral band used. On the other hand, we show that the color index versus Y{sub *} relation is an imperfect tool for assigning masses to young stellar populations because of the degeneracy affecting Y{sub *} in all bands at low color index. The disks resulting from our analysis are compatible with the maximum disk hypothesis provided that an adequate bulge/disk decomposition is performed and that the correction for the presence of a bar is not neglected since bars disturb the internal disk kinematics. Disk-mass models including Y{sub *} as a free parameter as well as models using our physically motivated, radially varying Y{sub *} are presented and discussed for each galaxy.

  13. Chemical evolution of the early Martian hydrosphere

    NASA Technical Reports Server (NTRS)

    Schaefer, M. W.

    1990-01-01

    The chemical evolution of the early Martian hydrosphere is discussed. The early Martian ocean can be modeled as a body of relatively pure water in equilibrium with a dense carbon dioxide atmosphere. The chemical weathering of lavas, pyroclastic deposits, and impact melt sheets would have the effect of neutralizing the acidity of the juvenile water. As calcium and other cations are added to the water by chemical weathering, they are quickly removed by the precipitation of calcium carbonate and other minerals, forming a deposit of limestone beneath the surface of the ocean. As the atmospheric carbon dioxide pressure and the temperature decrease, the Martian ocean would be completely frozen. Given the scenario for the chemical evolution of the northern lowland plains of Mars, it should be possible to draw a few conclusions about the expected mineralogy and geomorphology of this regions.

  14. Evolution of early lesions in leprosy.

    PubMed

    Mishra, B; Mukherjee, A; Girdhar, A; Husain, S; Malaviya, G N; Girdhar, B K

    1993-09-01

    We observed 29 patients presenting with vague peripheral neurological symptoms for 6 months or more. During this period, 16 developed clinical leprosy, 3 developed borderline tuberculoid leprosy and the other 13 developed neuritic leprosy. Of these 13 cases 11 subsequently developed skin lesions similar to those seen in indeterminate and in borderline tuberculoid leprosy. Based on the above observations, an attempt has been made to explain the evolution of early lesions of leprosy. PMID:8231606

  15. Symbiogenesis and the early evolution of life

    NASA Astrophysics Data System (ADS)

    Carrapico, Francisco; Rodrigues, Telma

    2005-09-01

    The concept of symbiogenesis was introduced in 1909 by the Russian biologist Constantin Merezhkowsky as "the origin of organisms by the combination or by the association of two or several beings which enter into symbiosis". In this article we develop this idea, associated to the Freeman Dyson's hypothesis, applied to the early evolutive stages of life, considering that it could be a possible main rule in the appearance and development of life conditions on Earth and elsewhere. A cooperative, synergistic strategy should be considered as having been the determinant in the development of the survival of the fittest, especially under extremely adverse environmental conditions. This concept must be also applied to the first communities of cells as the base supporting evolution of the early "tree of life". Cells, like we have previously described, can be included in a new cellular concept entitled, "symbiocell", since survival of the community under such adverse conditions required a cooperative, synergistic strategy. Similar principles could also be used to understand chemical pre-biotic evolution. We believe that astrobiologists should consider it as a new approach to understand organic and biological evolution.

  16. Early Precambrian crustal evolution of south India

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.

    1986-01-01

    The Early Precambrian sequence in Karnataka, South India provides evidences for a distinct trend of evolution which differs from trends exhibited in many other Early Precambrian regions of the world. The supracrustal rock associations preserved in greenstone belts and as inclusions in gneisses and granulites suggest the evolution of the terrain from a stable to a mobile regime. The stable regime is represented by (1) layered ultramafic-mafic complexes, (2) orthoquartzite-basalt-rhyodacite-iron formation, and (30 ortho-quartzite-carbonate-Mn-Fe formation. The mobile regime, which can be shown on sedimentological grounds to have succeeded the stable regime, witnessed the accumulation of a greywacke-pillow basalt-dacite-rhyolite-iron formation association. Detrital sediments of the stable zone accumulated dominantly in fluvial environment and the associated volcanics are ubaerial. The volcanics of the stable regime are tholeiites derived from a zirconium and LREE-enriched sources. The greywackes of the mobile regime are turbidities, and the volcanic rocks possess continental margin (island-arc or back-arc) affinity; they show a LREE depleted to slightly LREE-enriched pattern. The evolution from a stable to a mobile regime is in contrast to the trend seen in most other regions of the world, where an early dominantly volcanic association of a mobile regime gives way upward in the sequence to sediments characteristic of a stable regime.

  17. Early Microbial Evolution: The Age of Anaerobes.

    PubMed

    Martin, William F; Sousa, Filipa L

    2016-02-01

    In this article, the term "early microbial evolution" refers to the phase of biological history from the emergence of life to the diversification of the first microbial lineages. In the modern era (since we knew about archaea), three debates have emerged on the subject that deserve discussion: (1) thermophilic origins versus mesophilic origins, (2) autotrophic origins versus heterotrophic origins, and (3) how do eukaryotes figure into early evolution. Here, we revisit those debates from the standpoint of newer data. We also consider the perhaps more pressing issue that molecular phylogenies need to recover anaerobic lineages at the base of prokaryotic trees, because O2 is a product of biological evolution; hence, the first microbes had to be anaerobes. If molecular phylogenies do not recover anaerobes basal, something is wrong. Among the anaerobes, hydrogen-dependent autotrophs--acetogens and methanogens--look like good candidates for the ancestral state of physiology in the bacteria and archaea, respectively. New trees tend to indicate that eukaryote cytosolic ribosomes branch within their archaeal homologs, not as sisters to them and, furthermore tend to root archaea within the methanogens. These are major changes in the tree of life, and open up new avenues of thought. Geochemical methane synthesis occurs as a spontaneous, abiotic exergonic reaction at hydrothermal vents. The overall similarity between that reaction and biological methanogenesis fits well with the concept of a methanogenic root for archaea and an autotrophic origin of microbial physiology. PMID:26684184

  18. Human evolution. Evolution of early Homo: an integrated biological perspective.

    PubMed

    Antón, Susan C; Potts, Richard; Aiello, Leslie C

    2014-07-01

    Integration of evidence over the past decade has revised understandings about the major adaptations underlying the origin and early evolution of the genus Homo. Many features associated with Homo sapiens, including our large linear bodies, elongated hind limbs, large energy-expensive brains, reduced sexual dimorphism, increased carnivory, and unique life history traits, were once thought to have evolved near the origin of the genus in response to heightened aridity and open habitats in Africa. However, recent analyses of fossil, archaeological, and environmental data indicate that such traits did not arise as a single package. Instead, some arose substantially earlier and some later than previously thought. From ~2.5 to 1.5 million years ago, three lineages of early Homo evolved in a context of habitat instability and fragmentation on seasonal, intergenerational, and evolutionary time scales. These contexts gave a selective advantage to traits, such as dietary flexibility and larger body size, that facilitated survival in shifting environments. PMID:24994657

  19. Origin and early evolution of photosynthesis

    NASA Technical Reports Server (NTRS)

    Blankenship, R. E.

    1992-01-01

    Photosynthesis was well-established on the earth at least 3.5 thousand million years ago, and it is widely believed that these ancient organisms had similar metabolic capabilities to modern cyanobacteria. This requires that development of two photosystems and the oxygen evolution capability occurred very early in the earth's history, and that a presumed phase of evolution involving non-oxygen evolving photosynthetic organisms took place even earlier. The evolutionary relationships of the reaction center complexes found in all the classes of currently existing organisms have been analyzed using sequence analysis and biophysical measurements. The results indicate that all reaction centers fall into two basic groups, those with pheophytin and a pair of quinones as early acceptors, and those with iron sulfur clusters as early acceptors. No simple linear branching evolutionary scheme can account for the distribution patterns of reaction centers in existing photosynthetic organisms, and lateral transfer of genetic information is considered as a likely possibility. Possible scenarios for the development of primitive reaction centers into the heterodimeric protein structures found in existing reaction centers and for the development of organisms with two linked photosystems are presented.

  20. The evolution of early vertebrate photoreceptors

    PubMed Central

    Collin, Shaun P.; Davies, Wayne L.; Hart, Nathan S.; Hunt, David M.

    2009-01-01

    Meeting the challenge of sampling an ancient aquatic landscape by the early vertebrates was crucial to their survival and would establish a retinal bauplan to be used by all subsequent vertebrate descendents. Image-forming eyes were under tremendous selection pressure and the ability to identify suitable prey and detect potential predators was thought to be one of the major drivers of speciation in the Early Cambrian. Based on the fossil record, we know that hagfishes, lampreys, holocephalans, elasmobranchs and lungfishes occupy critical stages in vertebrate evolution, having remained relatively unchanged over hundreds of millions of years. Now using extant representatives of these ‘living fossils’, we are able to piece together the evolution of vertebrate photoreception. While photoreception in hagfishes appears to be based on light detection and controlling circadian rhythms, rather than image formation, the photoreceptors of lampreys fall into five distinct classes and represent a critical stage in the dichotomy of rods and cones. At least four types of retinal cones sample the visual environment in lampreys mediating photopic (and potentially colour) vision, a sampling strategy retained by lungfishes, some modern teleosts, reptiles and birds. Trichromacy is retained in cartilaginous fishes (at least in batoids and holocephalans), where it is predicted that true scotopic (dim light) vision evolved in the common ancestor of all living gnathostomes. The capacity to discriminate colour and balance the tradeoff between resolution and sensitivity in the early vertebrates was an important driver of eye evolution, where many of the ocular features evolved were retained as vertebrates progressed on to land. PMID:19720654

  1. The early thermal evolution of Mars

    NASA Astrophysics Data System (ADS)

    Bhatia, G. K.; Sahijpal, S.

    2016-01-01

    Hf-W isotopic systematics of Martian meteorites have provided evidence for the early accretion and rapid core formation of Mars. We present the results of numerical simulations performed to study the early thermal evolution and planetary scale differentiation of Mars. The simulations are confined to the initial 50 Myr (Ma) of the formation of solar system. The accretion energy produced during the growth of Mars and the decay energy due to the short-lived radio-nuclides 26Al, 60Fe, and the long-lived nuclides, 40K, 235U, 238U, and 232Th are incorporated as the heat sources for the thermal evolution of Mars. During the core-mantle differentiation of Mars, the molten metallic blobs were numerically moved using Stoke's law toward the center with descent velocity that depends on the local acceleration due to gravity. Apart from the accretion and the radioactive heat energies, the gravitational energy produced during the differentiation of Mars and the associated heat transfer is also parametrically incorporated in the present work to make an assessment of its contribution to the early thermal evolution of Mars. We conclude that the accretion energy alone cannot produce widespread melting and differentiation of Mars even with an efficient consumption of the accretion energy. This makes 26Al the prime source for the heating and planetary scale differentiation of Mars. We demonstrate a rapid accretion and core-mantle differentiation of Mars within the initial ~1.5 Myr. This is consistent with the chronological records of Martian meteorites.

  2. The Early Sun: Evolution and Dynamic Environment

    NASA Astrophysics Data System (ADS)

    Reipurth, B.

    2005-12-01

    An overview is given of the astrophysical processes that govern the formation and early evolution of solar-like stars, specifically aimed at meteoriticists. After a discussion of the various types of protostars and young stars and of the collapse process, the importance of binary and multiple star formation is emphasized. The frequency and properties of young binaries as derived from observations are summarized. Theoretical work demonstrates how newborn multiple stars are unstable and decay on short time scales to stable configurations, often ejecting lower-mass members through dynamical interactions. Observations of phenomena like Herbig-Haro jets and FU Orionis eruptions find a natural explanation within a scenario involving the evolution of small multiple systems and the resulting formation of close binaries. It is emphasized that the vast majority of stars in our Galaxy are formed in clusters, but that most of these clusters dissolve soon after the remaining gas has been dispersed and the gravitational potential that held the cluster together therefore is weakened. Thus, while most stars are born in clusters, only a small fraction will remain in clusters lasting hundreds of millions of years. The likelihood that the early Sun was a member of a temporary cluster at birth and perhaps even a member of a small multiple system is stressed. Possible relic evidence that the Sun was part of a cluster of a few thousand stars includes the solar obliquity, the detection of traces of 60Fe in ordinary chondrites, the sharp edge of the Kuiper belt, and the discovery of distant large objects in eccentric orbits like Sedna. The meteoritic record must be examined with the possibility in mind that the early Sun may well have been a member of a long gone cluster and that the early solar nebula may have been affected by close passages of sibling stars.

  3. LIGHT ECHOES FROM η CARINAE'S GREAT ERUPTION: SPECTROPHOTOMETRIC EVOLUTION AND THE RAPID FORMATION OF NITROGEN-RICH MOLECULES

    SciTech Connect

    Prieto, J. L.; Knapp, G. R.; Rest, A.; Walborn, N. R.; Bianco, F. B.; Matheson, T.; Smith, N.; Hsiao, E. Y.; Campillay, A.; Contreras, C.; González, C.; Morrell, N.; Phillips, M. M.; Chornock, R.; Paredes Álvarez, L.; James, D.; Smith, R. C.; Kunder, A.; Margheim, S.; Welch, D. L.; and others

    2014-05-20

    We present follow-up optical imaging and spectroscopy of one of the light echoes of η Carinae's nineteenth century Great Eruption discovered by Rest et al. By obtaining images and spectra at the same light echo position between 2011 and 2014, we follow the evolution of the Great Eruption on a 3 yr timescale. We find remarkable changes in the photometric and spectroscopic evolution of the echo light. The i-band light curve shows a decline of ∼0.9 mag in ∼1 yr after the peak observed in early 2011 and a flattening at later times. The spectra show a pure-absorption early G-type stellar spectrum at peak, but a few months after peak the lines of the Ca II triplet develop strong P-Cygni profiles and we see the appearance of [Ca II] 7291, 7324 doublet in emission. These emission features and their evolution in time resemble those observed in the spectra of some Type IIn supernovae and supernova impostors. Most surprisingly, starting ∼300 days after peak brightness, the spectra show strong molecular transitions of CN at ≳ 6800 Å. The appearance of these CN features can be explained if the ejecta are strongly nitrogen enhanced, as is observed in modern spectroscopic studies of the bipolar Homunculus nebula. Given the spectroscopic evolution of the light echo, velocities of the main features, and detection of strong CN, we are likely seeing ejecta that contributes directly to the Homunculus nebula.

  4. Light Echoes from η Carinae's Great Eruption: Spectrophotometric Evolution and the Rapid Formation of Nitrogen-rich Molecules

    NASA Astrophysics Data System (ADS)

    Prieto, J. L.; Rest, A.; Bianco, F. B.; Matheson, T.; Smith, N.; Walborn, N. R.; Hsiao, E. Y.; Chornock, R.; Paredes Álvarez, L.; Campillay, A.; Contreras, C.; González, C.; James, D.; Knapp, G. R.; Kunder, A.; Margheim, S.; Morrell, N.; Phillips, M. M.; Smith, R. C.; Welch, D. L.; Zenteno, A.

    2014-05-01

    We present follow-up optical imaging and spectroscopy of one of the light echoes of η Carinae's nineteenth century Great Eruption discovered by Rest et al. By obtaining images and spectra at the same light echo position between 2011 and 2014, we follow the evolution of the Great Eruption on a 3 yr timescale. We find remarkable changes in the photometric and spectroscopic evolution of the echo light. The i-band light curve shows a decline of ~0.9 mag in ~1 yr after the peak observed in early 2011 and a flattening at later times. The spectra show a pure-absorption early G-type stellar spectrum at peak, but a few months after peak the lines of the Ca II triplet develop strong P-Cygni profiles and we see the appearance of [Ca II] 7291, 7324 doublet in emission. These emission features and their evolution in time resemble those observed in the spectra of some Type IIn supernovae and supernova impostors. Most surprisingly, starting ~300 days after peak brightness, the spectra show strong molecular transitions of CN at >~ 6800 Å. The appearance of these CN features can be explained if the ejecta are strongly nitrogen enhanced, as is observed in modern spectroscopic studies of the bipolar Homunculus nebula. Given the spectroscopic evolution of the light echo, velocities of the main features, and detection of strong CN, we are likely seeing ejecta that contributes directly to the Homunculus nebula. This Letter includes data gathered with the 6.5 m Magellan telescope at Las Campanas Observatory, Chile.

  5. Fossil evidence for the early ant evolution

    NASA Astrophysics Data System (ADS)

    Perrichot, Vincent; Lacau, Sébastien; Néraudeau, Didier; Nel, André

    2008-02-01

    Ants are one of the most studied insects in the world; and the literature devoted to their origin and evolution, systematics, ecology, or interactions with plants, fungi and other organisms is prolific. However, no consensus yet exists on the age estimate of the first Formicidae or on the origin of their eusociality. We review the fossil and biogeographical record of all known Cretaceous ants. We discuss the possible origin of the Formicidae with emphasis on the most primitive subfamily Sphecomyrminae according to its distribution and the Early Cretaceous palaeogeography. And we review the evidence of true castes and eusociality of the early ants regarding their morphological features and their manner of preservation in amber. The mid-Cretaceous amber forest from south-western France where some of the oldest known ants lived, corresponded to a moist tropical forest close to the shore with a dominance of gymnosperm trees but where angiosperms (flowering plants) were already diversified. This palaeoenvironmental reconstruction supports an initial radiation of ants in forest ground litter coincident with the rise of angiosperms, as recently proposed as an ecological explanation for their origin and successful evolution.

  6. Calculations of the early evolution of Jupiter

    NASA Technical Reports Server (NTRS)

    Bodenheimer, P.

    1974-01-01

    The evolution of the protoplanet Jupiter is followed, using a hydrodynamic computer code with radiative energy transport. Jupiter is assumed to have formed as a subcondensation in the primitive solar nebula at a density just high enough for gravitational collapse to occur. The initial state has a density of 0.0015 nanograms per cu cm and a temperature of 43 K; the calculations are carried to an equilibrium state where the central density reaches 0.5 g per cu cm and the central temperature reaches 25,000 K. During the early part of the evolution the object contracts in quasi-hydrostatic equilibrium; later on hydrodynamic collapse occurs, induced by the dissociation of hydrogen molecules. After dissociation is complete, the planet regains hydrostatic equilibrium with a radius of a few times the present value. Further evolution beyond this point is not treated here; however the results are consistent with the existence of a high-luminosity phase shortly after the planet settles into its final quasi-static contraction.-

  7. Early dynamical evolution of substructured stellar clusters

    NASA Astrophysics Data System (ADS)

    Dorval, Julien; Boily, Christian

    2015-08-01

    It is now widely accepted that stellar clusters form with a high level of substructure (Kuhn et al. 2014, Bate 2009), inherited from the molecular cloud and the star formation process. Evidence from observations and simulations also indicate the stars in such young clusters form a subvirial system (Kirk et al. 2007, Maschberger et al. 2010). The subsequent dynamical evolution can cause important mass loss, ejecting a large part of the birth population in the field. It can also imprint the stellar population and still be inferred from observations of evolved clusters. Nbody simulations allow a better understanding of these early twists and turns, given realistic initial conditions. Nowadays, substructured, clumpy young clusters are usually obtained through pseudo-fractal growth (Goodwin et al. 2004) and velocity inheritance. Such models are visually realistics and are very useful, they are however somewhat artificial in their velocity distribution. I introduce a new way to create clumpy initial conditions through a "Hubble expansion" which naturally produces self consistent clumps, velocity-wise. A velocity distribution analysis shows the new method produces realistic models, consistent with the dynamical state of the newly created cores in hydrodynamic simulation of cluster formation (Klessen & Burkert 2000). I use these initial conditions to investigate the dynamical evolution of young subvirial clusters, up to 80000 stars. I find an overall soft evolution, with hierarchical merging leading to a high level of mass segregation. I investigate the influence of the mass function on the fate of the cluster, specifically on the amount of mass loss induced by the early violent relaxation. Using a new binary detection algorithm, I also find a strong processing of the native binary population.

  8. Spinal cord evolution in early Homo.

    PubMed

    Meyer, Marc R; Haeusler, Martin

    2015-11-01

    The discovery at Nariokotome of the Homo erectus skeleton KNM-WT 15000, with a narrow spinal canal, seemed to show that this relatively large-brained hominin retained the primitive spinal cord size of African apes and that brain size expansion preceded postcranial neurological evolution. Here we compare the size and shape of the KNM-WT 15000 spinal canal with modern and fossil taxa including H. erectus from Dmanisi, Homo antecessor, the European middle Pleistocene hominins from Sima de los Huesos, and Pan troglodytes. In terms of shape and absolute and relative size of the spinal canal, we find all of the Dmanisi and most of the vertebrae of KNM-WT 15000 are within the human range of variation except for the C7, T2, and T3 of KNM-WT 15000, which are constricted, suggesting spinal stenosis. While additional fossils might definitively indicate whether H. erectus had evolved a human-like enlarged spinal canal, the evidence from the Dmanisi spinal canal and the unaffected levels of KNM-WT 15000 show that unlike Australopithecus, H. erectus had a spinal canal size and shape equivalent to that of modern humans. Subadult status is unlikely to affect our results, as spinal canal growth is complete in both individuals. We contest the notion that vertebrae yield information about respiratory control or language evolution, but suggest that, like H. antecessor and European middle Pleistocene hominins from Sima de los Huesos, early Homo possessed a postcranial neurological endowment roughly commensurate to modern humans, with implications for neurological, structural, and vascular improvements over Pan and Australopithecus. PMID:26553817

  9. The Early Evolution of Mars' Crust

    NASA Astrophysics Data System (ADS)

    Samuel, H.; Baratoux, D.; Kurita, K.

    2014-12-01

    The Mars crustal density and thickness have been recently re-evaluated using petrological constraints from remote sensing, in-situ data, and SNC meteorites. This work indicates that the present-day Martian crust is denser and thicker than previously proposed if essentially basaltic in composition. As a consequence, the average crustal thickness would be commensurable with the depth of the basalt/eclogite transition, re-opening the question of crustal recycling on Early Mars and more generally throughout all its history. We have therefore investigated the conditions under which a thick ancient crust with an eclogitic root could survive through the history of Mars using numerical modelling. Delamination may occur if the combination of poorly constrained physical parameters induces the presence of gravitationally unstable layers and favors a rheological decoupling. To study the conditions and the time scales for the occurrence of crustal delamination on Mars, we investigated the influence of critical parameters for a plausible range of values corresponding to the Martian mantle. For each case we follow the dynamic evolution over geological times of a three-layer system (i.e., crust-mantle with a distinction between low pressure, buoyant basaltic crust and higher pressure, denser eclogitic material). We systematically varied four governing parameters within plausible ranges: (1) the basalt-eclogite transition depth, (2) the density difference between the mantle and the basaltic crust, (3) the density difference between the eclogitic crust and the lithosphere & mantle, (4) the viscous rheology. These experiments allow determining the average Martian crustal thickness at early and late evolutionary stages.

  10. Spectrophotometric probe

    DOEpatents

    Prather, W.S.; O'Rourke, P.E.

    1994-08-02

    A support structure is described bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe. 3 figs.

  11. Spectrophotometric probe

    DOEpatents

    Prather, William S.; O'Rourke, Patrick E.

    1994-01-01

    A support structure bearing at least one probe for making spectrophotometric measurements of a fluid using a source of light and a spectrophotometer. The probe includes a housing with two optical fibers and a planoconvex lens. A sleeve bearing a mirror surrounds the housing. The lens is separated from the mirror by a fixed distance, defining an interior space for receiving a volume of the fluid sample. A plurality of throughholes extending through the sleeve communicate between the sample volume and the exterior of the probe, all but one hole bearing a screen. A protective jacket surrounds the probe. A hollow conduit bearing a tube is formed in the wall of the probe for venting any air in the interior space when fluid enters. The probe is held at an acute angle so the optic fibers carrying the light to and from the probe are not bent severely on emergence from the probe.

  12. Early hydrodynamic evolution of a stellar collision

    SciTech Connect

    Kushnir, Doron; Katz, Boaz

    2014-04-20

    The early phase of the hydrodynamic evolution following the collision of two stars is analyzed. Two strong shocks propagate from the contact surface and move toward the center of each star at a velocity that is a small fraction of the velocity of the approaching stars. The shocked region near the contact surface has a planar symmetry and a uniform pressure. The density vanishes at the (Lagrangian) surface of contact, and the speed of sound diverges there. The temperature, however, reaches a finite value, since as the density vanishes, the finite pressure is radiation dominated. For carbon-oxygen white dwarf (CO WD) collisions, this temperature is too low for any appreciable nuclear burning shortly after the collision, which allows for a significant fraction of the mass to be highly compressed to the density required for efficient {sup 56}Ni production in the detonation wave that follows. This property is crucial for the viability of collisions of typical CO WD as progenitors of type Ia supernovae, since otherwise only massive (>0.9 M {sub ☉}) CO WDs would have led to such explosions (as required by all other progenitor models). The divergence of the speed of sound limits numerical studies of stellar collisions, as it makes convergence tests exceedingly expensive unless dedicated schemes are used. We provide a new one-dimensional Lagrangian numerical scheme to achieve this. A self-similar planar solution is derived for zero-impact parameter collisions between two identical stars, under some simplifying assumptions (including a power-law density profile), which is the planar version of previous piston problems that were studied in cylindrical and spherical symmetries.

  13. The early geodynamic evolution of Mars-type planets

    NASA Astrophysics Data System (ADS)

    Zhang, Siqi; O'Neill, Craig

    2016-02-01

    It is not clear whether Mars once possessed active tectonics, yet the question is critical for understanding the thermal evolution of Mars, and the origin and longevity of its early dynamo. To address these issues, we have coupled mantle flow simulations, together with parameterized core evolution models, to simulate the early evolution of Mars-like planets, and constrain the influence of early mobile-lid tectonics on core evolution. We have explored a wide parameter suite, encapsulating a range of uncertainties in initial conditions, rheological parameters, and surface strength. We present successful models that experience early mobile-lid behaviour, with a later transition into a stagnant-lid mode, which reproduce core dynamo histories similar to the magnetic history of early Mars.

  14. Natural evidence for chemical and early biological evolution

    NASA Technical Reports Server (NTRS)

    Kvenvolden, K. A.

    1974-01-01

    Oparin (1924) and Haldane (1929) have independently hypothesized that life arose under reducing conditions through an evolutionary sequence of events involving increasingly complex organic substances. The natural evidence for this hypothesis of chemical evolution is considered, giving particular attention to tangible samples which have been chemically analyzed in earth-bound laboratories. It is found that meteorites provide naturally occurring evidence in support of chemical evolution, but not of biological evolution. Studies on the early Precambrian Swaziland Sequence and the Bulawayan System of southern Africa provide evidence for very early biological evolution.

  15. The early history of chance in evolution.

    PubMed

    Pence, Charles H

    2015-04-01

    Work throughout the history and philosophy of biology frequently employs 'chance', 'unpredictability', 'probability', and many similar terms. One common way of understanding how these concepts were introduced in evolution focuses on two central issues: the first use of statistical methods in evolution (Galton), and the first use of the concept of "objective chance" in evolution (Wright). I argue that while this approach has merit, it fails to fully capture interesting philosophical reflections on the role of chance expounded by two of Galton's students, Karl Pearson and W.F.R. Weldon. Considering a question more familiar from contemporary philosophy of biology--the relationship between our statistical theories of evolution and the processes in the world those theories describe--is, I claim, a more fruitful way to approach both these two historical actors and the broader development of chance in evolution. PMID:26466463

  16. Early Cretaceous angiosperms and beetle evolution

    PubMed Central

    Wang, Bo; Zhang, Haichun; Jarzembowski, Edmund A.

    2013-01-01

    The Coleoptera (beetles) constitute almost one–fourth of all known life-forms on earth. They are also among the most important pollinators of flowering plants, especially basal angiosperms. Beetle fossils are abundant, almost spanning the entire Early Cretaceous, and thus provide important clues to explore the co-evolutionary processes between beetles and angiosperms. We review the fossil record of some Early Cretaceous polyphagan beetles including Tenebrionoidea, Scarabaeoidea, Curculionoidea, and Chrysomeloidea. Both the fossil record and molecular analyses reveal that these four groups had already diversified during or before the Early Cretaceous, clearly before the initial rise of angiosperms to widespread floristic dominance. These four beetle groups are important pollinators of basal angiosperms today, suggesting that their ecological association with angiosperms probably formed as early as in the Early Cretaceous. With the description of additional well-preserved fossils and improvements in phylogenetic analyses, our knowledge of Mesozoic beetle–angiosperm mutualisms will greatly increase during the near future. PMID:24062759

  17. Early School-Leaving in Spain: Evolution, Intensity and Determinants

    ERIC Educational Resources Information Center

    Fernandez-Macias, Enrique; Anton, Jose-Ignacio; Brana, Francisco-Javier; De Bustillo, Rafael Munoz

    2013-01-01

    Spain has one of the highest levels of early school leaving and educational failure of the European Union. The purpose of this paper is to analyse the anatomy of early school leaving in Spain and its characteristics. In order to do so, in the first part we discuss the measurement problems related with this concept and the evolution of drop-out…

  18. Solar Radiation as Driving Force In Early Evolution

    NASA Technical Reports Server (NTRS)

    Rothschild, Lynn J.; Peterson, David L. (Technical Monitor)

    2002-01-01

    Ultraviolet radiation (UVR) has provided an evolutionary challenge to life on Earth in that it is both an agent of mutation and as well as a selective force. Today surface fluxes of UVR vary diurnally, seasonally, etc. Still, the UVR flux was probably substantially higher during the early phases of evolution, suggesting that its role in evolution was even more prominent during this time. In this presentation, the creative role of UVR in evolution is discussed, specifically in connection with the role that UVR may have played in the evolution of early microbial ecosystems. The presentation will include discussions of the direct influence of UVR on such processes as photosynthesis and genetic damage, as well as the indirect influence of UVR as mediated through the production of reactive oxygen species. These biological effects of UVR will be viewed against the backdrop of the physical nature of the early Earth, surely a very different place then than now.

  19. Origin and early evolution of land plants

    PubMed Central

    2008-01-01

    The origin of the sporophyte in land plants represents a fundamental phase in plant evolution. Today this subject is controversial, and scarcely considered in textbooks and journals of botany, in spite of its importance. There are two conflicting theories concerning the origin of the alternating generations in land-plants: the “antithetic” theory and the “homologous” theory. These have never been fully resolved, although, on the ground of the evidences on the probable ancestors of land plants, the antithetic theory is considered more plausible than the homologous theory. However, additional phylogenetic dilemmas are the evolution of bryophytes from algae and the transition from these first land plants to the pteridophytes. All these very large evolutionary jumps are discussed on the basis of the phyletic gradualist neo-Darwinian theory and other genetic evolutionary mechanisms. PMID:19513262

  20. The origin and early evolution of roots.

    PubMed

    Kenrick, Paul; Strullu-Derrien, Christine

    2014-10-01

    Geological sites of exceptional fossil preservation are becoming a focus of research on root evolution because they retain edaphic and ecological context, and the remains of plant soft tissues are preserved in some. New information is emerging on the origins of rooting systems, their interactions with fungi, and their nature and diversity in the earliest forest ecosystems. Remarkably well-preserved fossils prove that mycorrhizal symbionts were diverse in simple rhizoid-based systems. Roots evolved in a piecemeal fashion and independently in several major clades through the Devonian Period (416 to 360 million years ago), rapidly extending functionality and complexity. Evidence from extinct arborescent clades indicates that polar auxin transport was recruited independently in several to regulate wood and root development. The broader impact of root evolution on the geochemical carbon cycle is a developing area and one in which the interests of the plant physiologist intersect with those of the geochemist. PMID:25187527

  1. Archean sedimentary styles and early crustal evolution

    NASA Technical Reports Server (NTRS)

    Lowe, D. R.

    1986-01-01

    The distinctions between and implications of early and late Archean sedimentary styles are presented. Early Archean greenstone belts, such as the Barberton of South Africa and those in the eastern Pilbar Block of Australia are characterized by fresh or slightly reworked pyroclastic debris, orthochemical sediments such as carbonates, evaporites, and silica, and biogenic deposits including cherts and stromatolitic units. Terrigenous deposits are rare, and it is suggested that early Archean sediments were deposited on shallow simatic platforms, with little or no components derived from sialic sources. In contrast, late Archean greenstone belts in the Canadian Shield and the Yilgarn Block of Australia contain coarse terrigenous clastic rocks including conglomerate, sandstone, and shale derived largely from sialic basement. Deposition appears to have taken place in deepwater, tectonically unstable environments. These observations are interpreted to indicate that the early Archean greenstone belts formed as anorogenic, shallow water, simatic platforms, with little or no underlying or adjacent continental crust, an environment similar to modern oceanic islands formed over hot spots.

  2. Evolution of an early Titan atmosphere

    NASA Astrophysics Data System (ADS)

    Johnson, R. E.; Tucker, O. J.; Volkov, A. N.

    2016-06-01

    Rapid escape from a proposed early CH4/NH3 atmosphere on Titan could, in principle, limit the amount of NH3 that is converted by photolysis into the present N2 atmosphere. Assuming that this conversion occurred, a recent estimate of escape driven by the surface temperature and pressure was used to constrain Titan's accretion temperature. Here we show that for the range of temperatures of interest, heating of the surface is not the primary driver for escape. Atmospheric loss from a thick Titan atmosphere is predominantly driven by heating of the upper atmosphere; therefore, the loss rate cannot be used to easily constrain the accretion temperature. We give an estimate of the solar driven escape rate from an early atmosphere on Titan, and then briefly discuss its relevance to the cooling rate, isotope ratios, and the time period suggested to convert NH3 to the present N2 atmosphere.

  3. Early photosynthetic microorganisms and environmental evolution

    NASA Technical Reports Server (NTRS)

    Golubic, S.

    1980-01-01

    Microfossils which are preserved as shrivelled kerogenous residues provide little information about cellular organization and almost none about the metabolic properties of the organisms. The distinction between prokaryotic vs eukaryotic, and phototrophic vs chemo- and organotrophic fossil microorganisms rests entirely on morphological comparisons with recent counterparts. The residual nature of the microbial fossil record promotes the conclusion that it must be biased toward (a) most abundant organisms, (b) those most resistant to degradation, and (c) those inhabiting environments with high preservation potential e.g., stromatolites. These criteria support the cyanophyte identity of most Precambrian microbial fossils on the following grounds: (1) as primary producers they dominate prokaryotic communities in modern extreme environments, e.g., intertidal zone; (2) several morphological counterparts of modern cyanophytes and microbial fossils have been established based on structure, cell division patterns and degradation sequences. The impact of anaerobic and oxygenic microbial photosynthesis on the evolution of Precambrian environments is discussed.

  4. Geometry Shapes Evolution of Early Multicellularity

    PubMed Central

    Libby, Eric; Ratcliff, William; Travisano, Michael; Kerr, Ben

    2014-01-01

    Organisms have increased in complexity through a series of major evolutionary transitions, in which formerly autonomous entities become parts of a novel higher-level entity. One intriguing feature of the higher-level entity after some major transitions is a division of reproductive labor among its lower-level units in which reproduction is the sole responsibility of a subset of units. Although it can have clear benefits once established, it is unknown how such reproductive division of labor originates. We consider a recent evolution experiment on the yeast Saccharomyces cerevisiae as a unique platform to address the issue of reproductive differentiation during an evolutionary transition in individuality. In the experiment, independent yeast lineages evolved a multicellular “snowflake-like” cluster formed in response to gravity selection. Shortly after the evolution of clusters, the yeast evolved higher rates of cell death. While cell death enables clusters to split apart and form new groups, it also reduces their performance in the face of gravity selection. To understand the selective value of increased cell death, we create a mathematical model of the cellular arrangement within snowflake yeast clusters. The model reveals that the mechanism of cell death and the geometry of the snowflake interact in complex, evolutionarily important ways. We find that the organization of snowflake yeast imposes powerful limitations on the available space for new cell growth. By dying more frequently, cells in clusters avoid encountering space limitations, and, paradoxically, reach higher numbers. In addition, selection for particular group sizes can explain the increased rate of apoptosis both in terms of total cell number and total numbers of collectives. Thus, by considering the geometry of a primitive multicellular organism we can gain insight into the initial emergence of reproductive division of labor during an evolutionary transition in individuality. PMID:25233196

  5. Some aspects of the early evolution of photosynthesis

    NASA Astrophysics Data System (ADS)

    Masinovsky, Z.; Lozovaya, G. I.; Sivash, A. A.

    The early evolution of a photocatalytic system of the porphyrin type, able to efficiently collect and utilize solar energy for primary electron transfer is discussed. Experimental results concerning some spectral and photochemical properties of the porphyrins, biosynthetic precursors of chlorophyll and their complexes with polymeric templates are reviewed. Protoporphyrin IX associated with pigmented proteinoid is demonstrated to be a favourable candidate for a role of a photosensitizer of the first photosynthetic reaction centers. The origin and early evolution of the photosynthetic electron transfer chain and of the phosphorylating mechanism are discussed with emphasis on the energetic mechanisms of archaebacteria.

  6. The early evolution of life: solution to Darwin's dilemma

    NASA Technical Reports Server (NTRS)

    Schopf, J. W.

    1994-01-01

    Recent studies of Precambrian fossils indicate that life on Earth originated earlier than assumed, microscopic life was prevalent in the Precambrian Eon, the tempo and mode of evolution during the Precambrian period were different from other periods, and that only the Precambrian fossil record can be used as evidence of early life. Implications for future research include directing the search for the origin of life away from the geological record, modification of hypotheses about molecular change, use of Precambrian microfossils in dating younger geological units, and progress in defining the nature of major events in early evolution.

  7. Prelinguistic evolution in early hominins: whence motherese?

    PubMed

    Falk, Dean

    2004-08-01

    In order to formulate hypotheses about the evolutionary underpinnings that preceded the first glimmerings of language, mother-infant gestural and vocal interactions are compared in chimpanzees and humans and used to model those of early hominins. These data, along with paleoanthropological evidence, suggest that prelinguistic vocal substrates for protolanguage that had prosodic features similar to contemporary motherese evolved as the trend for enlarging brains in late australopithecines/early Homo progressively increased the difficulty of parturition, thus causing a selective shift toward females that gave birth to relatively undeveloped neonates. It is hypothesized that hominin mothers adopted new foraging strategies that entailed maternal silencing, reassuring, and controlling of the behaviors of physically removed infants (i.e., that shared human babies' inability to cling to their mothers' bodies). As mothers increasingly used prosodic and gestural markings to encourage juveniles to behave and to follow, the meanings of certain utterances (words) became conventionalized. This hypothesis is based on the premises that hominin mothers that attended vigilantly to infants were strongly selected for, and that such mothers had genetically based potentials for consciously modifying vocalizations and gestures to control infants, both of which receive support from the literature. PMID:15773427

  8. MEVTV Workshop on Early Tectonic and Volcanic Evolution of Mars

    NASA Technical Reports Server (NTRS)

    Frey, H. (Editor)

    1988-01-01

    Although not ignored, the problems of the early tectonic and volcanic evolution of Mars have generally received less attention than those later in the evolution of the planet. Specifically, much attention was devoted to the evolution of the Tharsis region of Mars and to the planet itself at the time following the establishment of this major tectonic and volcanic province. By contrast, little attention was directed at fundamental questions, such as the conditions that led to the development of Tharsis and the cause of the basic fundamental dichotomy of the Martian crust. It was to address these and related questions of the earliest evolution of Mars that a workshop was organized under the auspices of the Mars: Evolution of Volcanism, Tectonism, and Volatiles (MEVTV) Program. Four sessions were held: crustal dichotomy; crustal differentiation/volcanism; Tharsis, Elysium, and Valles Marineris; and ridges and fault tectonics.

  9. Calibrating rates of early Cambrian evolution

    NASA Technical Reports Server (NTRS)

    Bowring, Samuel A.; Grotzinger, John P.; Isachsen, Clark E.; Knoll, Andrew H.; Pelechaty, Shane M.; Kolosov, Peter

    1993-01-01

    An explosive episode of biological diversification occurred near the beginning of the Cambrian period. Evolutionary rates in the Cambrian have been difficult to quantify accurately because of a lack of high-precision ages. Currently, uranium-lead zircon geochronology is the most powerful method for dating rocks of Cambrian age. Uranium-lead zircon data from lower Cambrian rocks located in northeast Siberia indicate that the Cambrian period began about 544 million years ago and that its oldest (Manykaian) stage lasted no less than 10 million years. Other data indicate that the Tommotian and Atdabanian stages together lasted only 5 to 10 million years. The resulting compression of Early Cambrian time accentuates the rapidity of both the faunal diversification and subsequent Cambrian turnover.

  10. Calibrating rates of early Cambrian evolution.

    PubMed

    Bowring, S A; Grotzinger, J P; Isachsen, C E; Knoll, A H; Pelechaty, S M; Kolosov, P

    1993-09-01

    An explosive episode of biological diversification occurred near the beginning of the Cambrian period. Evolutionary rates in the Cambrian have been difficult to quantify accurately because of a lack of high-precision ages. Currently, uranium-lead zircon geochronology is the most powerful method for dating rocks of Cambrian age. Uranium-lead zircon data from lower Cambrian rocks located in northeast Siberia indicate that the Cambrian period began at approximately 544 million years ago and that its oldest (Manykaian) stage lasted no less than 10 million years. Other data indicate that the Tommotian and Atdabanian stages together lasted only 5 to 10 million years. The resulting compression of Early Cambrian time accentuates the rapidity of both the faunal diversification and subsequent Cambrian turnover. PMID:11539488

  11. Early primate evolution in Afro-Arabia.

    PubMed

    Seiffert, Erik R

    2012-11-01

    The peculiar mammalian fauna that inhabited Afro-Arabia during the Paleogene first came to the attention of the scientific community in the early part of the twentieth century, when Andrews1 and Schlosser2 published their landmark descriptions of fossil mammals from the Fayum Depression in northern Egypt. Their studies revealed a highly endemic assemblage of land mammals that included the first known Paleogene records of hyraxes, proboscideans, and anthropoid primates, but which lacked ancestors of many iconic mammalian lineages that are found in Africa today, such as rhinos, zebras, bovids, giraffes, and cats. Over the course of the last century, the Afro-Arabian Paleogene has yielded fossil remains of several other endemic mammalian lineages,3 as well as a diversity of prosimian primates,4 but we are only just beginning to understand how the continent's faunal composition came to be, through ancient processes such as the movement of tectonic plates, changes in climate and sea level, and early phylogenetic splits among the major groups of placental mammals. These processes, in turn, made possible chance dispersal events that were critical in determining the competitive landscape--and, indeed, the survival--of our earliest anthropoid ancestors. Newly discovered fossils indicate that the persistence and later diversification of Anthropoidea was not an inevitable result of the clade's competitive isolation or adaptive superiority, as has often been assumed, but rather was as much due to the combined influences of serendipitous geographic conditions, global cooling, and competition with a group of distantly related extinct strepsirrhines with anthropoid-like adaptations known as adapiforms. Many of the important details of this story would not be known, and could never have been predicted, without the fossil evidence that has recently been unearthed by field paleontologists. PMID:23280921

  12. The origin and early evolution of dinosaurs.

    PubMed

    Langer, Max C; Ezcurra, Martin D; Bittencourt, Jonathas S; Novas, Fernando E

    2010-02-01

    The oldest unequivocal records of Dinosauria were unearthed from Late Triassic rocks (approximately 230 Ma) accumulated over extensional rift basins in southwestern Pangea. The better known of these are Herrerasaurus ischigualastensis, Pisanosaurus mertii, Eoraptor lunensis, and Panphagia protos from the Ischigualasto Formation, Argentina, and Staurikosaurus pricei and Saturnalia tupiniquim from the Santa Maria Formation, Brazil. No uncontroversial dinosaur body fossils are known from older strata, but the Middle Triassic origin of the lineage may be inferred from both the footprint record and its sister-group relation to Ladinian basal dinosauromorphs. These include the typical Marasuchus lilloensis, more basal forms such as Lagerpeton and Dromomeron, as well as silesaurids: a possibly monophyletic group composed of Mid-Late Triassic forms that may represent immediate sister taxa to dinosaurs. The first phylogenetic definition to fit the current understanding of Dinosauria as a node-based taxon solely composed of mutually exclusive Saurischia and Ornithischia was given as "all descendants of the most recent common ancestor of birds and Triceratops". Recent cladistic analyses of early dinosaurs agree that Pisanosaurus mertii is a basal ornithischian; that Herrerasaurus ischigualastensis and Staurikosaurus pricei belong in a monophyletic Herrerasauridae; that herrerasaurids, Eoraptor lunensis, and Guaibasaurus candelariensis are saurischians; that Saurischia includes two main groups, Sauropodomorpha and Theropoda; and that Saturnalia tupiniquim is a basal member of the sauropodomorph lineage. On the contrary, several aspects of basal dinosaur phylogeny remain controversial, including the position of herrerasaurids, E. lunensis, and G. candelariensis as basal theropods or basal saurischians, and the affinity and/or validity of more fragmentary taxa such as Agnosphitys cromhallensis, Alwalkeria maleriensis, Chindesaurus bryansmalli, Saltopus elginensis, and

  13. Open Listening: Creative Evolution in Early Childhood Settings

    ERIC Educational Resources Information Center

    Davies, Bronwyn

    2011-01-01

    This article sketches out a philosophy and practice of open listening, linking open listening to Bergson's (1998) concept of creative evolution. I draw on examples of small children at play from a variety of sources, including Reggio-Emilia-inspired preschools in Sweden. The article offers a challenge to early childhood educators to listen and to…

  14. Early Stages of the Evolution of Life: a Cybernetic Approach

    NASA Astrophysics Data System (ADS)

    Melkikh, Alexey V.; Seleznev, Vladimir D.

    2008-08-01

    Early stages of the evolution of life are considered in terms of control theory. A model is proposed for the transport of substances in a protocell possessing the property of robustness with regard to changes in the environmental concentration of a substance.

  15. Early evolution of Tubulogenerina during the Paleogene of Europe

    USGS Publications Warehouse

    Gibson, T.G.; Barbin, V.; Poignant, A.; Sztrakos, K.

    1991-01-01

    The early evolution of Tubulogenerina took place in Europe where eight species occur in lower Eocene to uppermost Oligocene or lower Miocene strata. Species diversity within Tubulogenerina dropped significantly in the early Oligocne; only a single species persisted from the late Eocene, and it became extinct before the end of the early Oligocene. Morphologic changes during the European phylogeny of Tubulogenerina include (1) the development of costate and more complex tubulopore ornamentation, and (2) the change from a single elongated apertural slit with a single toothplate to multiple apertures and toothplates. Three new Tubulogenerina species are described. -from Authors

  16. Rates of morphological evolution are heterogeneous in Early Cretaceous birds.

    PubMed

    Wang, Min; Lloyd, Graeme T

    2016-04-13

    The Early Cretaceous is a critical interval in the early history of birds. Exceptional fossils indicate that important evolutionary novelties such as a pygostyle and a keeled sternum had already arisen in Early Cretaceous taxa, bridging much of the morphological gap betweenArchaeopteryxand crown birds. However, detailed features of basal bird evolution remain obscure because of both the small sample of fossil taxa previously considered and a lack of quantitative studies assessing rates of morphological evolution. Here we apply a recently available phylogenetic method and associated sensitivity tests to a large data matrix of morphological characters to quantify rates of morphological evolution in Early Cretaceous birds. Our results reveal that although rates were highly heterogeneous between different Early Cretaceous avian lineages, consistent patterns of significantly high or low rates were harder to pinpoint. Nevertheless, evidence for accelerated evolutionary rates is strongest at the point when Ornithuromorpha (the clade comprises all extant birds and descendants from their most recent common ancestors) split from Enantiornithes (a diverse clade that went extinct at the end-Cretaceous), consistent with the hypothesis that this key split opened up new niches and ultimately led to greater diversity for these two dominant clades of Mesozoic birds. PMID:27053742

  17. Archean komatiite volcanism controlled by the evolution of early continents.

    PubMed

    Mole, David R; Fiorentini, Marco L; Thebaud, Nicolas; Cassidy, Kevin F; McCuaig, T Campbell; Kirkland, Christopher L; Romano, Sandra S; Doublier, Michael P; Belousova, Elena A; Barnes, Stephen J; Miller, John

    2014-07-15

    The generation and evolution of Earth's continental crust has played a fundamental role in the development of the planet. Its formation modified the composition of the mantle, contributed to the establishment of the atmosphere, and led to the creation of ecological niches important for early life. Here we show that in the Archean, the formation and stabilization of continents also controlled the location, geochemistry, and volcanology of the hottest preserved lavas on Earth: komatiites. These magmas typically represent 50-30% partial melting of the mantle and subsequently record important information on the thermal and chemical evolution of the Archean-Proterozoic Earth. As a result, it is vital to constrain and understand the processes that govern their localization and emplacement. Here, we combined Lu-Hf isotopes and U-Pb geochronology to map the four-dimensional evolution of the Yilgarn Craton, Western Australia, and reveal the progressive development of an Archean microcontinent. Our results show that in the early Earth, relatively small crustal blocks, analogous to modern microplates, progressively amalgamated to form larger continental masses, and eventually the first cratons. This cratonization process drove the hottest and most voluminous komatiite eruptions to the edge of established continental blocks. The dynamic evolution of the early continents thus directly influenced the addition of deep mantle material to the Archean crust, oceans, and atmosphere, while also providing a fundamental control on the distribution of major magmatic ore deposits. PMID:24958873

  18. Archean komatiite volcanism controlled by the evolution of early continents

    PubMed Central

    Mole, David R.; Fiorentini, Marco L.; Thebaud, Nicolas; Cassidy, Kevin F.; McCuaig, T. Campbell; Kirkland, Christopher L.; Romano, Sandra S.; Doublier, Michael P.; Belousova, Elena A.; Barnes, Stephen J.; Miller, John

    2014-01-01

    The generation and evolution of Earth’s continental crust has played a fundamental role in the development of the planet. Its formation modified the composition of the mantle, contributed to the establishment of the atmosphere, and led to the creation of ecological niches important for early life. Here we show that in the Archean, the formation and stabilization of continents also controlled the location, geochemistry, and volcanology of the hottest preserved lavas on Earth: komatiites. These magmas typically represent 50–30% partial melting of the mantle and subsequently record important information on the thermal and chemical evolution of the Archean–Proterozoic Earth. As a result, it is vital to constrain and understand the processes that govern their localization and emplacement. Here, we combined Lu-Hf isotopes and U-Pb geochronology to map the four-dimensional evolution of the Yilgarn Craton, Western Australia, and reveal the progressive development of an Archean microcontinent. Our results show that in the early Earth, relatively small crustal blocks, analogous to modern microplates, progressively amalgamated to form larger continental masses, and eventually the first cratons. This cratonization process drove the hottest and most voluminous komatiite eruptions to the edge of established continental blocks. The dynamic evolution of the early continents thus directly influenced the addition of deep mantle material to the Archean crust, oceans, and atmosphere, while also providing a fundamental control on the distribution of major magmatic ore deposits. PMID:24958873

  19. Evolution of entanglement entropy in the early universe

    SciTech Connect

    Chen, Pisin; Hsin, Po-Shen; Niu, Yuezhen E-mail: r01222031@ntu.edu.tw

    2014-02-01

    We investigate the entropy evolution in the early universe by computing the change of the entanglement entropy in Freedmann-Robertson-Walker quantum cosmology in the presence of particle horizon. The matter is modeled by a Chaplygin gas so as to provide a smooth interpolation between inflationary and radiation epochs, rendering the evolution of entropy from early time to late time trackable. We found that soon after the onset of the inflation, the total entanglement entropy rapidly decreases to a minimum. It then rises monotonically in the remainder of the inflation epoch as well as the radiation epoch. Our result is in qualitative agreement with the area law of Ryu and Takayanagi including the logarithmic correction. We comment on the possible implication of our finding to the cosmological entropy problem.

  20. Molecular clocks and the early evolution of metazoan nervous systems.

    PubMed

    Wray, Gregory A

    2015-12-19

    The timing of early animal evolution remains poorly resolved, yet remains critical for understanding nervous system evolution. Methods for estimating divergence times from sequence data have improved considerably, providing a more refined understanding of key divergences. The best molecular estimates point to the origin of metazoans and bilaterians tens to hundreds of millions of years earlier than their first appearances in the fossil record. Both the molecular and fossil records are compatible, however, with the possibility of tiny, unskeletonized, low energy budget animals during the Proterozoic that had planktonic, benthic, or meiofaunal lifestyles. Such animals would likely have had relatively simple nervous systems equipped primarily to detect food, avoid inhospitable environments and locate mates. The appearance of the first macropredators during the Cambrian would have changed the selective landscape dramatically, likely driving the evolution of complex sense organs, sophisticated sensory processing systems, and diverse effector systems involved in capturing prey and avoiding predation. PMID:26554040

  1. The Origin and Early Evolution of Membrane Proteins

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew; Schweighofter, Karl; Wilson, Michael A.

    2006-01-01

    The origin and early evolution of membrane proteins, and in particular ion channels, are considered from the point of view that the transmembrane segments of membrane proteins are structurally quite simple and do not require specific sequences to fold. We argue that the transport of solute species, especially ions, required an early evolution of efficient transport mechanisms, and that the emergence of simple ion channels was protobiologically plausible. We also argue that, despite their simple structure, such channels could possess properties that, at the first sight, appear to require markedly larger complexity. These properties can be subtly modulated by local modifications to the sequence rather than global changes in molecular architecture. In order to address the evolution and development of ion channels, we focus on identifying those protein domains that are commonly associated with ion channel proteins and are conserved throughout the three main domains of life (Eukarya, Prokarya, and Archaea). We discuss the potassium-sodium-calcium superfamily of voltage-gated ion channels, mechanosensitive channels, porins, and ABC-transporters and argue that these families of membrane channels have sufficiently universal architectures that they can readily adapt to the diverse functional demands arising during evolution.

  2. The Origin and Early Evolution of Membrane Channels

    NASA Astrophysics Data System (ADS)

    Pohorille, Andrew; Schweighofer, Karl; Wilson, Michael A.

    2005-02-01

    The origin and early evolution of ion channels are considered from the point of view that the transmembrane segments of membrane proteins are structurally quite simple and do not require specific sequences to fold. We argue that the transport of solute species, especially ions, required an early evolution of efficient transport mechanisms, and that the emergence of simple ion channels was protobiologically plausible. We also argue that, despite their simple structure, such channels could possess properties that, at the first sight, appear to require markedly greater complexity. These properties can be subtly modulated by local modifications to the sequence rather than global changes in molecular architecture. In order to address the evolution and development of ion channels, we focus on identifying those protein domains that are commonly associated with ion channel proteins and are conserved throughout the three main domains of life (Eukarya, Bacteria, and Archaea). We discuss the potassiumsodium- calcium superfamily of voltage-gated ion channels, mechanosensitive channels, porins, and ABC-transporters and argue that these families of membrane channels have sufficiently universal architectures that they can readily adapt to the diverse functional demands arising during evolution.

  3. Early organic evolution: Implications for mineral and energy resources

    SciTech Connect

    Schidlowski, M.

    1992-01-01

    Early Organic Evolution is the proceedings of the ninth Alfred Wegener Conference, the final meeting of IGCP Project 157 held in Germany in 1988. Over the past 15 years, Project 157 has promoted the blending of organic geochemistry, economic geology, and evolutionary biology. This IGCP publication covers a diverse set of topics and truly reflects the interdisciplinary nature of the field of early organic evolution. In the second and largest section, seventeen papers on organic matter in ancient sediments discuss the chemical analysis of early sediments, gas, and oil. The reader is treated to a review of carbon isotope chemistry and a [delta][sup 13]C walk through the past 3.8 billion years, and even deeper yet into the mantle. Following this is a series of papers carefully describing elemental, isotopic, and organic geochemical (particularly biomarker) data from ancient sediments found throughout the earth. This section ends very strongly with the paper by Fowler on the influence of a single alga on Ordovician oils and rocks from Canada. He first gives a detailed account of the considerable chemical and microscopic evidence showing that minimally reworked Gloeocapsomorpha prisca is the main contributor of organic matter to the oil and rock and then goes on to discuss the nature of the organism. In general, this book reviews information presented in other places, but still serves as a good resource for those interested in the evolution of the Earth.

  4. Bryophyte diversity and evolution: windows into the early evolution of land plants.

    PubMed

    Shaw, A Jonathan; Szövényi, Péter; Shaw, Blanka

    2011-03-01

    The "bryophytes" comprise three phyla of plants united by a similar haploid-dominant life cycle and unbranched sporophytes bearing one sporangium: the liverworts (Marchantiophyta), mosses (Bryophyta), and hornworts (Anthocerophyta). Combined, these groups include some 20000 species. As descendents of embryophytes that diverged before tracheophytes appeared, bryophytes offer unique windows into the early evolution of land plants. We review insights into the evolution of plant life cycles, in particular the elaboration of the sporophyte generation, the major lineages within bryophyte phyla, and reproductive processes that shape patterns of bryophyte evolution. Recent transcriptomic work suggests extensive overlap in gene expression in bryophyte sporophytes vs. gametophytes, but also novel patterns in the sporophyte, supporting Bower's antithetic hypothesis for origin of alternation of generations. Major lineages of liverworts, mosses, and hornworts have been resolved and general patterns of morphological evolution can now be inferred. The life cycles of bryophytes, arguably more similar to those of early embryophytes than are those in any other living plant group, provide unique insights into gametophyte mating patterns, sexual conflicts, and the efficacy and effects of spore dispersal during early land plant evolution. PMID:21613131

  5. Early animal evolution and the origins of nervous systems

    PubMed Central

    Budd, Graham E.

    2015-01-01

    Understanding the evolution of early nervous systems is hazardous because we lack good criteria for determining homology between the systems of distant taxa; the timing of the evolutionary events is contested, and thus the relevant ecological and geological settings for them are also unclear. Here I argue that no simple approach will resolve the first issue, but that it remains likely that animals evolved relatively late, and that their nervous systems thus arose during the late Ediacaran, in a context provided by the changing planktonic and benthic environments of the time. The early trace fossil provides the most concrete evidence for early behavioural diversification, but it cannot simply be translated into increasing nervous system complexity: behavioural complexity does not map on a one-to-one basis onto nervous system complexity, both because of possible limitations to behaviour caused by the environment and because we know that even organisms without nervous systems are capable of relatively complex behaviour. PMID:26554037

  6. Early animal evolution and the origins of nervous systems.

    PubMed

    Budd, Graham E

    2015-12-19

    Understanding the evolution of early nervous systems is hazardous because we lack good criteria for determining homology between the systems of distant taxa; the timing of the evolutionary events is contested, and thus the relevant ecological and geological settings for them are also unclear. Here I argue that no simple approach will resolve the first issue, but that it remains likely that animals evolved relatively late, and that their nervous systems thus arose during the late Ediacaran, in a context provided by the changing planktonic and benthic environments of the time. The early trace fossil provides the most concrete evidence for early behavioural diversification, but it cannot simply be translated into increasing nervous system complexity: behavioural complexity does not map on a one-to-one basis onto nervous system complexity, both because of possible limitations to behaviour caused by the environment and because we know that even organisms without nervous systems are capable of relatively complex behaviour. PMID:26554037

  7. The evolution of field early-type galaxies in the FDF and WHDF

    NASA Astrophysics Data System (ADS)

    Fritz, Alexander; Böhm, Asmus; Ziegler, Bodo L.

    2009-03-01

    We explore the properties of 24 field early-type galaxies in the redshift range 0.20 < z < 0.75 down to MB <= -19.30 in a sample extracted from the FORS Deep Field and the William Herschel Deep Field. Target galaxies were selected on the basis of a combination of luminosity, spectrophotometric type, morphology and photometric redshift or broad-band colours. High signal-to-noise ratio intermediate-resolution spectroscopy has been acquired at the Very Large Telescope, complemented by deep high-resolution imaging with the Advanced Camera for Surveys onboard the Hubble Space Telescope (HST) and additional ground-based multiband photometry. All galaxy spectra were observed under subarcsecond conditions and allow us to derive accurate kinematics and stellar population properties of the galaxies. To clarify the low level of star formation detected in some galaxies, we identify the amount of active galactic nuclei (AGN) activity in our sample using archive data of Chandra and XMM-Newton X-ray surveys. None of the galaxies in our sample was identified as secure AGN source based on their X-ray emission. The rest-frame B- and K-band scaling relations of the Faber-Jackson relation and the Fundamental Plane display a moderate evolution for the field early-type galaxies. Lenticular (S0) galaxies feature on average a stronger luminosity evolution and bluer rest-frame colours which can be explained that they comprise more diverse stellar populations compared to elliptical galaxies. The evolution of the FP can be interpreted as an average change in the dynamical (effective) mass-to-light ratio of our galaxies as <Δlog(M/LB)/z> = -0.74 +/- 0.08. The M/L evolution of these field galaxies suggests a continuous mass assembly of field early-type galaxies during the last 5 Gyr, which gets supported by recent studies of field galaxies up to z ~ 1. Independent evidence for recent star formation activity is provided by spectroscopic ([OII] emission, Hδ) and photometric (rest-frame broad

  8. Investigation of Early Plasma Evolution Induced by Ultrashort Laser Pulses

    PubMed Central

    Hu, Wenqian; Shin, Yung C.; King, Galen B.

    2012-01-01

    Early plasma is generated owing to high intensity laser irradiation of target and the subsequent target material ionization. Its dynamics plays a significant role in laser-material interaction, especially in the air environment1-11. Early plasma evolution has been captured through pump-probe shadowgraphy1-3 and interferometry1,4-7. However, the studied time frames and applied laser parameter ranges are limited. For example, direct examinations of plasma front locations and electron number densities within a delay time of 100 picosecond (ps) with respect to the laser pulse peak are still very few, especially for the ultrashort pulse of a duration around 100 femtosecond (fs) and a low power density around 1014 W/cm2. Early plasma generated under these conditions has only been captured recently with high temporal and spatial resolutions12. The detailed setup strategy and procedures of this high precision measurement will be illustrated in this paper. The rationale of the measurement is optical pump-probe shadowgraphy: one ultrashort laser pulse is split to a pump pulse and a probe pulse, while the delay time between them can be adjusted by changing their beam path lengths. The pump pulse ablates the target and generates the early plasma, and the probe pulse propagates through the plasma region and detects the non-uniformity of electron number density. In addition, animations are generated using the calculated results from the simulation model of Ref. 12 to illustrate the plasma formation and evolution with a very high resolution (0.04 ~ 1 ps). Both the experimental method and the simulation method can be applied to a broad range of time frames and laser parameters. These methods can be used to examine the early plasma generated not only from metals, but also from semiconductors and insulators. PMID:22806170

  9. Stochastic evolution of rotations of early type galaxies

    NASA Astrophysics Data System (ADS)

    Choi, Hoseung; Yi, Sukyoung

    2016-01-01

    Recent Integral-Field Spectrograph surveys (SAURON, ATLAS 3D, and SAMI project, for example) have revealed that early type galaxies have wide range of rotational properties even though they share similar photometric properties. High resolution numerical studies have shown that galaxy-galaxy interactions have significant effect on the rotation of early type galaxies, however, with limited number of sample galaxies.We present kinematic analysis of thousands of galaxies in 20 clusters from a set of cosmological hydrodynamic zoom-in simulations. Although galaxy mergers play an important role, the direction of change in the amount of rotation depends on many merger parameters such as mass ratio, orbital parameters, and relative direction of galaxy rotations. Furthermore, all their merger parameters themselves are results of non-linear galaxy formation and evolution processes. By compiling numerous galaxy merger events, we discuss statistical properties of the evolution of early type galaxy rotation. We present the impacts of various interactions: major and minor mergers, multiple mergers, and flybys.

  10. Early animal evolution: emerging views from comparative biology and geology

    NASA Technical Reports Server (NTRS)

    Knoll, A. H.; Carroll, S. B.

    1999-01-01

    The Cambrian appearance of fossils representing diverse phyla has long inspired hypotheses about possible genetic or environmental catalysts of early animal evolution. Only recently, however, have data begun to emerge that can resolve the sequence of genetic and morphological innovations, environmental events, and ecological interactions that collectively shaped Cambrian evolution. Assembly of the modern genetic tool kit for development and the initial divergence of major animal clades occurred during the Proterozoic Eon. Crown group morphologies diversified in the Cambrian through changes in the genetic regulatory networks that organize animal ontogeny. Cambrian radiation may have been triggered by environmental perturbation near the Proterozoic-Cambrian boundary and subsequently amplified by ecological interactions within reorganized ecosystems.

  11. Magnetic Field and Early Evolution of Circumstellar Disks

    NASA Astrophysics Data System (ADS)

    Tsukamoto, Yusuke

    2016-03-01

    The magnetic field plays a central role in the formation and evolution of circumstellar disks. The magnetic field connects the rapidly rotating central region with the outer envelope and extracts angular momentum from the central region during gravitational collapse of the cloud core. This process is known as magnetic braking. Both analytical and multidimensional simulations have shown that disk formation is strongly suppressed by magnetic braking in moderately magnetised cloud cores in the ideal magnetohydrodynamic limit. On the other hand, recent observations have provided growing evidence of a relatively large disk several tens of astronomical units in size existing in some Class 0 young stellar objects. This introduces a serious discrepancy between the theoretical study and observations. Various physical mechanisms have been proposed to solve the problem of catastrophic magnetic braking, such as misalignment between the magnetic field and the rotation axis, turbulence, and non-ideal effect. In this paper, we review the mechanism of magnetic braking, its effect on disk formation and early evolution, and the mechanisms that resolve the magnetic braking problem. In particular, we emphasise the importance of non-ideal effects. The combination of magnetic diffusion and thermal evolution during gravitational collapse provides a robust formation process for the circumstellar disk at the very early phase of protostar formation. The rotation induced by the Hall effect can supply a sufficient amount of angular momentum for typical circumstellar disks around T Tauri stars. By examining the combination of the suggested mechanisms, we conclude that the circumstellar disks commonly form in the very early phase of protostar formation.

  12. The early evolution of eukaryotes - A geological perspective

    NASA Technical Reports Server (NTRS)

    Knoll, Andrew H.

    1992-01-01

    This paper examines the goodness of fit between patterns of biological and environmental history implied by molecular phylogenies of eukaryotic organisms and the geological records of early eukaryote evolution. It was found that Precambrian geological records show evidence that episodic increases in biological diversity roughly coincided with episodic environmental changes and by sharp increases in atmospheric oxygen concentrations which significantly changed the earth surface environments. Although the goodness of fit among physical and biological changes is gratifyingly high, the records of these changes do not always coincide in time. The additional information in these fields that is needed for complete integration of geological and phylogenic records is suggested.

  13. The origin and early evolution of life on earth

    NASA Technical Reports Server (NTRS)

    Oro, J.; Miller, Stanley L.; Lazcano, Antonio

    1990-01-01

    Results of the studies that have provided insights into the cosmic and primitive earth environments are reviewed with emphasis on those environments in which life is thought to have originated. The evidence bearing on the antiquity of life on the earth and the prebiotic significance of organic compounds found in interstellar clouds and in primitive solar-system bodies such as comets, dark asteroids, and carbonaceous chondrites are assessed. The environmental models of the Hadean and early Archean earth are discussed, as well as the prebiotic formation of organic monomers and polymers essential to life. The processes that may have led to the appearance in the Archean of the first cells are considered, and possible effects of these processes on the early steps of biological evolution are analyzed. The significance of these results to the study of the distribution of life in the universe is evaluated.

  14. Late stages of accumulation and early evolution of the planets

    NASA Technical Reports Server (NTRS)

    Vityazev, Andrey V.; Perchernikova, G. V.

    1991-01-01

    Recently developed solutions of problems are discussed that were traditionally considered fundamental in classical solar system cosmogony: determination of planetary orbit distribution patterns, values for mean eccentricity and orbital inclinations of the planets, and rotation periods and rotation axis inclinations of the planets. Two important cosmochemical aspects of accumulation are examined: the time scale for gas loss from the terrestrial planet zone, and the composition of the planets in terms of isotope data. It was concluded that the early beginning of planet differentiation is a function of the heating of protoplanets during collisions with large (thousands of kilometers) bodies. Energetics, heat mass transfer processes, and characteristic time scales of these processes at the early stages of planet evolution are considered.

  15. Early Palaeogene temperature evolution of the southwest Pacific Ocean.

    PubMed

    Bijl, Peter K; Schouten, Stefan; Sluijs, Appy; Reichart, Gert-Jan; Zachos, James C; Brinkhuis, Henk

    2009-10-01

    Relative to the present day, meridional temperature gradients in the Early Eocene age ( approximately 56-53 Myr ago) were unusually low, with slightly warmer equatorial regions but with much warmer subtropical Arctic and mid-latitude climates. By the end of the Eocene epoch ( approximately 34 Myr ago), the first major Antarctic ice sheets had appeared, suggesting that major cooling had taken place. Yet the global transition into this icehouse climate remains poorly constrained, as only a few temperature records are available portraying the Cenozoic climatic evolution of the high southern latitudes. Here we present a uniquely continuous and chronostratigraphically well-calibrated TEX(86) record of sea surface temperature (SST) from an ocean sediment core in the East Tasman Plateau (palaeolatitude approximately 65 degrees S). We show that southwest Pacific SSTs rose above present-day tropical values (to approximately 34 degrees C) during the Early Eocene age ( approximately 53 Myr ago) and had gradually decreased to about 21 degrees C by the early Late Eocene age ( approximately 36 Myr ago). Our results imply that there was almost no latitudinal SST gradient between subequatorial and subpolar regions during the Early Eocene age (55-50 Myr ago). Thereafter, the latitudinal gradient markedly increased. In theory, if Eocene cooling was largely driven by a decrease in atmospheric greenhouse gas concentration, additional processes are required to explain the relative stability of tropical SSTs given that there was more significant cooling at higher latitudes. PMID:19812670

  16. Early time evolution of artificially created dusty space plasmas

    NASA Astrophysics Data System (ADS)

    Scales, Wayne

    An alternate approach to studying natural dust layers in the earth's upper atmosphere is to perform active space experiments in which a dust cloud is created in a controlled manner. Its evolution can then be more carefully observed and studied and then compared to characteristics of natural dust clouds. Such space experiments are currently under development are planned for the near future. Several important issues to be investigated include dust charging processes, plasma flows, electrodynamic structure, plasma irregularities, and coupling between the neutral components of the upper atmosphere and the dust clouds. Also possibilities of remote sensing plasma processes in these clouds through radar measurements will be studied. This talk will address some of the physical processes expected to be important during the early time phase after creation of an artificial dust cloud in the earth's ionosphere. Of principal importance will be the production of plasma irregularities which may lead to radar echoes and the possibility of their relationship to well known radar echoes observed from natural dusty space plasmas. First, a plasma model will be described that may be used for investigating early time evolution after expansion of an artificial dust cloud across the magnetic field in the ionosphere. This model will then be used to investigate the electrodynamics and possible plasma irregularity generation mechanisms after creation of an artificial dust cloud. Finally, possibilities of radar signatures observed from the dust cloud will be considered.

  17. The Origin and Early Evolution of Membrane Proteins

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew; Schweighofer, Karl; Wilson, Michael A.

    2005-01-01

    Membrane proteins mediate functions that are essential to all cells. These functions include transport of ions, nutrients and waste products across cell walls, capture of energy and its transduction into the form usable in chemical reactions, transmission of environmental signals to the interior of the cell, cellular growth and cell volume regulation. In the absence of membrane proteins, ancestors of cell (protocells), would have had only very limited capabilities to communicate with their environment. Thus, it is not surprising that membrane proteins are quite common even in simplest prokaryotic cells. Considering that contemporary membrane channels are large and complex, both structurally and functionally, a question arises how their presumably much simpler ancestors could have emerged, perform functions and diversify in early protobiological evolution. Remarkably, despite their overall complexity, structural motifs in membrane proteins are quite simple, with a-helices being most common. This suggests that these proteins might have evolved from simple building blocks. To explain how these blocks could have organized into functional structures, we performed large-scale, accurate computer simulations of folding peptides at a water-membrane interface, their insertion into the membrane, self-assembly into higher-order structures and function. The results of these simulations, combined with analysis of structural and functional experimental data led to the first integrated view of the origin and early evolution of membrane proteins.

  18. Hypermagnetic helicity evolution in early universe: leptogenesis and hypermagnetic diffusion

    SciTech Connect

    Semikoz, V.B.; Smirnov, A.Yu.; Sokoloff, D.D. E-mail: smirnoff.alexandr@gmail.com

    2013-10-01

    We study hypermagnetic helicity and lepton asymmetry evolution in plasma of the early Universe before the electroweak phase transition (EWPT) accounting for chirality flip processes via inverse Higgs decays and sphaleron transitions which violate the left lepton number and wash out the baryon asymmetry of the Universe (BAU). In the scenario where the right electron asymmetry supports the BAU alone through the conservation law B/3−L{sub eR} = const at temperatures T > T{sub RL} ≅ 10 TeV the following universe cooling leads to the production of a non-zero left lepton (electrons and neutrinos) asymmetry. This is due to the Higgs decays becoming more faster when entering the equilibrium at T = T{sub RL} with the universe expansion, Γ{sub RL} ∼ T > H ∼ T{sup 2}, resulting in the parallel evolution of both the right and the left electron asymmetries at T < T{sub RL} through the corresponding Abelian anomalies in SM in the presence of a seed hypermagnetic field. The hypermagnetic helicity evolution proceeds in a self-consistent way with the lepton asymmetry growth. The role of sphaleron transitions decreasing the left lepton number turns out to be negligible in given scenario. The hypermagnetic helicity can be a supply for the magnetic one in Higgs phase assuming a strong seed hypermagnetic field in symmetric phase.

  19. Clades reach highest morphological disparity early in their evolution

    NASA Astrophysics Data System (ADS)

    Hughes, Martin; Gerber, Sylvain; Albion Wills, Matthew

    2013-08-01

    There are few putative macroevolutionary trends or rules that withstand scrutiny. Here, we test and verify the purported tendency for animal clades to reach their maximum morphological variety relatively early in their evolutionary histories (early high disparity). We present a meta-analysis of 98 metazoan clades radiating throughout the Phanerozoic. The disparity profiles of groups through time are summarized in terms of their center of gravity (CG), with values above and below 0.50 indicating top- and bottom-heaviness, respectively. Clades that terminate at one of the "big five" mass extinction events tend to have truncated trajectories, with a significantly top-heavy CG distribution overall. The remaining 63 clades show the opposite tendency, with a significantly bottom-heavy mean CG (relatively early high disparity). Resampling tests are used to identify groups with a CG significantly above or below 0.50; clades not terminating at a mass extinction are three times more likely to be significantly bottom-heavy than top-heavy. Overall, there is no clear temporal trend in disparity profile shapes from the Cambrian to the Recent, and early high disparity is the predominant pattern throughout the Phanerozoic. Our results do not allow us to distinguish between ecological and developmental explanations for this phenomenon. To the extent that ecology has a role, however, the paucity of bottom-heavy clades radiating in the immediate wake of mass extinctions suggests that early high disparity more probably results from the evolution of key apomorphies at the base of clades rather than from physical drivers or catastrophic ecospace clearing.

  20. Clades reach highest morphological disparity early in their evolution

    PubMed Central

    Hughes, Martin; Gerber, Sylvain; Wills, Matthew Albion

    2013-01-01

    There are few putative macroevolutionary trends or rules that withstand scrutiny. Here, we test and verify the purported tendency for animal clades to reach their maximum morphological variety relatively early in their evolutionary histories (early high disparity). We present a meta-analysis of 98 metazoan clades radiating throughout the Phanerozoic. The disparity profiles of groups through time are summarized in terms of their center of gravity (CG), with values above and below 0.50 indicating top- and bottom-heaviness, respectively. Clades that terminate at one of the “big five” mass extinction events tend to have truncated trajectories, with a significantly top-heavy CG distribution overall. The remaining 63 clades show the opposite tendency, with a significantly bottom-heavy mean CG (relatively early high disparity). Resampling tests are used to identify groups with a CG significantly above or below 0.50; clades not terminating at a mass extinction are three times more likely to be significantly bottom-heavy than top-heavy. Overall, there is no clear temporal trend in disparity profile shapes from the Cambrian to the Recent, and early high disparity is the predominant pattern throughout the Phanerozoic. Our results do not allow us to distinguish between ecological and developmental explanations for this phenomenon. To the extent that ecology has a role, however, the paucity of bottom-heavy clades radiating in the immediate wake of mass extinctions suggests that early high disparity more probably results from the evolution of key apomorphies at the base of clades rather than from physical drivers or catastrophic ecospace clearing. PMID:23884651

  1. Spectrophotometric Analysis of Caffeine.

    PubMed

    Ahmad Bhawani, Showkat; Fong, Sim Siong; Mohamad Ibrahim, Mohamad Nasir

    2015-01-01

    The nature of caffeine reveals that it is a bitter white crystalline alkaloid. It is a common ingredient in a variety of drinks (soft and energy drinks) and is also used in combination with various medicines. In order to maintain the optimum level of caffeine, various spectrophotometric methods have been developed. The monitoring of caffeine is very important aspect because of its consumption in higher doses that can lead to various physiological disorders. This paper incorporates various spectrophotometric methods used in the analysis of caffeine in various environmental samples such as pharmaceuticals, soft and energy drinks, tea, and coffee. A range of spectrophotometric methodologies including chemometric techniques and derivatization of spectra have been used to analyse the caffeine. PMID:26604926

  2. Spectrophotometric Analysis of Caffeine

    PubMed Central

    Ahmad Bhawani, Showkat; Fong, Sim Siong; Mohamad Ibrahim, Mohamad Nasir

    2015-01-01

    The nature of caffeine reveals that it is a bitter white crystalline alkaloid. It is a common ingredient in a variety of drinks (soft and energy drinks) and is also used in combination with various medicines. In order to maintain the optimum level of caffeine, various spectrophotometric methods have been developed. The monitoring of caffeine is very important aspect because of its consumption in higher doses that can lead to various physiological disorders. This paper incorporates various spectrophotometric methods used in the analysis of caffeine in various environmental samples such as pharmaceuticals, soft and energy drinks, tea, and coffee. A range of spectrophotometric methodologies including chemometric techniques and derivatization of spectra have been used to analyse the caffeine. PMID:26604926

  3. Cabomba as a model for studies of early angiosperm evolution

    PubMed Central

    Vialette-Guiraud, Aurelie C. M.; Alaux, Michael; Legeai, Fabrice; Finet, Cedric; Chambrier, Pierre; Brown, Spencer C.; Chauvet, Aurelie; Magdalena, Carlos; Rudall, Paula J.; Scutt, Charles P.

    2011-01-01

    Background The angiosperms, or flowering plants, diversified in the Cretaceous to dominate almost all terrestrial environments. Molecular phylogenetic studies indicate that the orders Amborellales, Nymphaeales and Austrobaileyales, collectively termed the ANA grade, diverged as separate lineages from a remaining angiosperm clade at a very early stage in flowering plant evolution. By comparing these early diverging lineages, it is possible to infer the possible morphology and ecology of the last common ancestor of the extant angiosperms, and this analysis can now be extended to try to deduce the developmental mechanisms that were present in early flowering plants. However, not all species in the ANA grade form convenient molecular-genetic models. Scope The present study reviews the genus Cabomba (Nymphaeales), which shows a range of features that make it potentially useful as a genetic model. We focus on characters that have probably been conserved since the last common ancestor of the extant flowering plants. To facilitate the use of Cabomba as a molecular model, we describe methods for its cultivation to flowering in the laboratory, a novel Cabomba flower expressed sequence tag database, a well-adapted in situ hybridization protocol and a measurement of the nuclear genome size of C. caroliniana. We discuss the features required for species to become tractable models, and discuss the relative merits of Cabomba and other ANA-grade angiosperms in molecular-genetic studies aimed at understanding the origin of the flowering plants. PMID:21486926

  4. On the origin and early evolution of biological catalysis and other studies on chemical evolution

    NASA Technical Reports Server (NTRS)

    Oro, J.; Lazcano, A.

    1991-01-01

    One of the lines of research in molecular evolution which we have developed for the past three years is related to the experimental and theoretical study of the origin and early evolution of biological catalysis. In an attempt to understand the nature of the first peptidic catalysts and coenzymes, we have achieved the non-enzymatic synthesis of the coenzymes ADPG, GDPG, and CDP-ethanolamine, under conditions considered to have been prevalent on the primitive Earth. We have also accomplished the prebiotic synthesis of histidine, as well as histidyl-histidine, and we have measured the enhancing effects of this catalytic dipeptide on the dephosphorylation of deoxyribonucleotide monophosphates, the hydrolysis of oligo A, and the oligomerization 2', 3' cAMP. We reviewed and further developed the hypothesis that RNA preceded double stranded DNA molecules as a reservoir of cellular genetic information. This led us to undertake the study of extant RNA polymerases in an attempt to discover vestigial sequences preserved from early Archean times. In addition, we continued our studies of on the chemical evolution of organic compounds in the solar system and beyond.

  5. Early Vertebrate Evolution of the Host Restriction Factor Tetherin

    PubMed Central

    Heusinger, Elena; Kluge, Silvia F.; Kirchhoff, Frank

    2015-01-01

    ABSTRACT Tetherin is an interferon-inducible restriction factor targeting a broad range of enveloped viruses. Its antiviral activity depends on an unusual topology comprising an N-terminal transmembrane domain (TMD) followed by an extracellular coiled-coil region and a C-terminal glycosylphosphatidylinositol (GPI) anchor. One of the two membrane anchors is inserted into assembling virions, while the other remains in the plasma membrane of the infected cell. Thus, tetherin entraps budding viruses by physically bridging viral and cellular membranes. Although tetherin restricts the release of a large variety of diverse human and animal viruses, only mammalian orthologs have been described to date. Here, we examined the evolutionary origin of this protein and demonstrate that tetherin orthologs are also found in fish, reptiles, and birds. Notably, alligator tetherin efficiently blocks the release of retroviral particles. Thus, tetherin emerged early during vertebrate evolution and acquired its antiviral activity before the mammal/reptile divergence. Although there is only limited sequence homology, all orthologs share the typical topology. Two unrelated proteins of the slime mold Dictyostelium discoideum also adopt a tetherin-like configuration with an N-terminal TMD and a C-terminal GPI anchor. However, these proteins showed no evidence for convergent evolution and failed to inhibit virion release. In summary, our findings demonstrate that tetherin emerged at least 450 million years ago and is more widespread than previously anticipated. The early evolution of antiviral activity together with the high topology conservation but low sequence homology suggests that restriction of virus release is the primary function of tetherin. IMPORTANCE The continuous arms race with viruses has driven the evolution of a variety of cell-intrinsic immunity factors that inhibit different steps of the viral replication cycle. One of these restriction factors, tetherin, inhibits the

  6. Practical halving; the Nelumbo nucifera evidence on early eudicot evolution.

    PubMed

    Zheng, Chunfang; Sankoff, David

    2014-06-01

    We present a stepwise optimal genome halving algorithm designed for large eukaryote genomes with largely single-copy genes, taking advantage of a signature pattern of paralog distribution in ancient polyploids. This is applied to the genome of Nelumbo nucifera, the sacred lotus, which is the descendant of a duplicated basal eudicot genome. In concert with the reconstructed ancestor of the grape, we investigate early events in eudicot evolution and show that the chromosome number of the common ancestor of lotus and grape was likely between 5 and 7. We show that the duplication of the ancestor of lotus and the triplication of the ancestor of grape were not closely preceded by any additional such event before the divergence of their two lineages. PMID:24525373

  7. Contributions of Planetary Science to Studies of Early Biosphere Evolution

    NASA Technical Reports Server (NTRS)

    Farmer, Jack D.; Chang, Sherwood (Technical Monitor)

    1995-01-01

    The history of impact cratering on the Moon, and extrapolations of crater chronologies to the inner planets, suggests that the late accretionary history of the Earth overlapped with other crucial events in the its history, including the origin of terrestrial life. This evidence, acquired from studies of other planetary bodies in the inner solar system, has profoundly affected how we view the early history of the Earth and evolution of the biosphere. Pre-biotic chemical evolution and the origin of life would have been delayed by the probable existence of a global magma ocean until -4.2 Ga. The early crust was largely destroyed by recycling, thus accounting for the sparse Archean record on Earth. Once life had developed, large impacts may have extinguished it several times before it finally gained a foothold. Potentially sterilizing impacts could have occurred as late as 3.7 Ga. At the very least, large impacts would have forced the biosphere through major environmental "bottlenecks" thereby canalizing its subsequent evolution. One legacy of these early events may be the structure of the present RNA-tree which indicates that extreme thermophiles are primitive within the Archaea, and may be the last common ancestors of life. By 3.5 Ga, marine sedimentary sequences contain unequivocal microbial fossils that attest to the presence of a terrestrial biosphere. The diversity of microbial forms present in these earliest fossil assemblages implies a preceding interval of evolution during which major evolutionary advances (e.g. photosynthesis) could have taken place. Evidence cited above places the origin of life within the interval 3.5 and 4.2 Ga, a period of 700 Ma. Thus, it appears that terrestrial life not only evolved rapidly, but perhaps more than once. This expands the possibilities that life may have also developed elsewhere. Of the other planets in our solar system, Mars holds the greatest chance of having developed life. But, the present surface of Mars is hostile

  8. The early evolution of Jean Piaget's clinical method.

    PubMed

    Mayer, Susan Jean

    2005-11-01

    This article analyzes the early evolution of Jean Piaget's renowned "clinical method" in order to investigate the method's strikingly original and generative character. Throughout his 1st decade in the field, Piaget frequently discussed and justified the many different approaches to data collection he used. Analysis of his methodological progression during this period reveals that Piaget's determination to access the genuine convictions of children eventually led him to combine 3 distinct traditions in which he had been trained-naturalistic observation, psychometrics, and the psychiatric clinical examination. It was in this amalgam, first evident in his 4th text, that Piaget discovered the clinical dynamic that would drive the classic experiments for which he is most well known. PMID:17152748

  9. The Emergence and Early Evolution of Biological Carbon-Fixation

    PubMed Central

    Braakman, Rogier; Smith, Eric

    2012-01-01

    The fixation of into living matter sustains all life on Earth, and embeds the biosphere within geochemistry. The six known chemical pathways used by extant organisms for this function are recognized to have overlaps, but their evolution is incompletely understood. Here we reconstruct the complete early evolutionary history of biological carbon-fixation, relating all modern pathways to a single ancestral form. We find that innovations in carbon-fixation were the foundation for most major early divergences in the tree of life. These findings are based on a novel method that fully integrates metabolic and phylogenetic constraints. Comparing gene-profiles across the metabolic cores of deep-branching organisms and requiring that they are capable of synthesizing all their biomass components leads to the surprising conclusion that the most common form for deep-branching autotrophic carbon-fixation combines two disconnected sub-networks, each supplying carbon to distinct biomass components. One of these is a linear folate-based pathway of reduction previously only recognized as a fixation route in the complete Wood-Ljungdahl pathway, but which more generally may exclude the final step of synthesizing acetyl-CoA. Using metabolic constraints we then reconstruct a “phylometabolic” tree with a high degree of parsimony that traces the evolution of complete carbon-fixation pathways, and has a clear structure down to the root. This tree requires few instances of lateral gene transfer or convergence, and instead suggests a simple evolutionary dynamic in which all divergences have primary environmental causes. Energy optimization and oxygen toxicity are the two strongest forces of selection. The root of this tree combines the reductive citric acid cycle and the Wood-Ljungdahl pathway into a single connected network. This linked network lacks the selective optimization of modern fixation pathways but its redundancy leads to a more robust topology, making it more plausible than

  10. Origins and Early Evolution of the tRNA Molecule

    PubMed Central

    Tamura, Koji

    2015-01-01

    Modern transfer RNAs (tRNAs) are composed of ~76 nucleotides and play an important role as “adaptor” molecules that mediate the translation of information from messenger RNAs (mRNAs). Many studies suggest that the contemporary full-length tRNA was formed by the ligation of half-sized hairpin-like RNAs. A minihelix (a coaxial stack of the acceptor stem on the T-stem of tRNA) can function both in aminoacylation by aminoacyl tRNA synthetases and in peptide bond formation on the ribosome, indicating that it may be a vestige of the ancestral tRNA. The universal CCA-3′ terminus of tRNA is also a typical characteristic of the molecule. “Why CCA?” is the fundamental unanswered question, but several findings give a comprehensive picture of its origin. Here, the origins and early evolution of tRNA are discussed in terms of various perspectives, including nucleotide ligation, chiral selectivity of amino acids, genetic code evolution, and the organization of the ribosomal peptidyl transferase center (PTC). The proto-tRNA molecules may have evolved not only as adaptors but also as contributors to the composition of the ribosome. PMID:26633518

  11. The early phases of galaxy formation and evolution

    NASA Astrophysics Data System (ADS)

    Dickinson, Mark

    2016-05-01

    I review observations of galaxy formation and evolution from multiwavelength deep field surveys. These programs are designed to detect and study galaxies over a large range of cosmic history, with observations and many different wavelengths, each of which is important for measuring different physical processes at work in evolving galaxies. I begin with some background motivating interest in multiwavelength deep fields, and a short review of energetic processes that result in emission from galaxies in different wavelength/energy ranges. I then give a short summary of major observing facilities that are currently used for multiwavelength deep surveys, and then offer short descriptions of some of the major surveys that have produced much of the data used today by astronomers studying distant galaxy evolution. I continue with an overview of different methods that are commonly used to identify various types of galaxies at high redshift in deep field data sets. Then, for the remainder of the review, I focus on measurements of star formation rates and stellar masses in galaxies, and how they are used to evaluate the history of galaxy growth and evolution. I discuss the ways in which data at different wavelengths are used to infer star formation rates and stellar masses, concentrating on the complementarity of different techniques, as well as their limitations. I then discuss application of these methods for deriving the global history of star formation in the universe. These measurement now push back over more than 13 billion years of cosmic history and portray the rapid early growth of galaxies, and then the long, slow decline of star formation rates to the present era. I discuss recent results on the nature of star formation in galaxies at the peak epoch of galaxy growth, particularly around redshifts of 2, and their implications about the dominant physical processes that shaped the growth of most galaxies from the earliest times to the present day.

  12. Climatic influences on the evolution of early Homo?

    PubMed

    Antón, Susan C

    2007-01-01

    The nature of the human fossil record is less than ideal for the generation of precise correlations between environmental variables and patterns of evolution in specific lineages. Nonetheless, a critical look at what can and cannot be said from individual fossil morphology and the correlation of specific environmental proxies with specific hominin fossils may lead to a greater understanding of the degree of certainty with which we should embrace environmental hypotheses for the evolution of Homo. Climate shifts have been implicated in both the origin of the genus and its dispersal from Africa. Here, I consider three areas in which a climatic influence has been posited to explain evolutionary shifts in the genus Homo: the origin and dispersal of the genus from Africa; geography, climate and body size in early Homo, and the influence of climate-induced sea level rise on morphological isolation in H. erectus. Each of the data sets is far from ideal, and interpretations of each of the data sets are fraught with issues of equifinality. Of the three hypotheses discussed, the clearest link is seen between latitudinal variation (and presumably temperature) and body size in H. erectus. Similarly, climate-induced sea level change seems a reasonable isolating mechanism to explain the pattern of cranial variation in later Asian H. erectus, but the distribution could also reflect incompletely sampled clinal variation. Alternatively, only equivocal support is found for the influence of climate on the differentiation of H. erectus from H. habilis (as proxied by body/brain size scaling), and therefore the dispersal of the genus Homo cannot be as clearly linked to changes in body size and shape as it has been in the past. These preliminary data suggest that an emphasis on understanding local adaptation before looking at global (and specific) level change is critical to elucidating the importance of climatic factors on the evolution of the genus Homo. PMID:17855788

  13. Early Human Evolution in the Western Palaearctic: Ecological Scenarios

    NASA Astrophysics Data System (ADS)

    Carrión, José S.; Rose, James; Stringer, Chris

    2011-06-01

    This review presents the themes of a special issue dealing with environmental scenarios of human evolution during the Early Pleistocene (2.6-0.78 Ma; MIS 103-MIS 19) and early Middle Pleistocene (0.78-0.47 Ma; MIS 19-base of MIS 12) within the western Palaearctic. This period is one of dramatic changes in the climates and the distribution of Palaearctic biota. These changes have played their role in generating adaptive and phyletic patterns within the human ancestry, involving several species such as Homo habilis, "Homo georgicus", Homo erectus, Homo antecessor and Homo heidelbergensis. In the archaeological record, these species include the Oldowan (Mode 1) and Acheulian (Mode 2) lithic technologies. Taphonomic considerations of palaeoecological research in hominin-bearing sites are provided and evaluated. Syntheses are provided for north Africa, western Asia, the Mediterranean Basin, Britain, and continental Europe. Palaeoenvironmental reconstructions based on multidisciplinary data are given for Ain Boucherit, Ain Hanech and El-Kherba in Algeria, Dmanisi in Georgia, Atapuerca, Cueva Negra, and the Orce Basin in Spain, Monte Poggiolo and Pirro Nord in Italy, Pont-de-Lavaud in France, and Mauer in Germany. The state of the art with the Out of Africa 1 dispersal model is reviewed. A source-sink dynamics model for Palaeolithic Europe is described to explain the morphological disparity of H. heidelbergensis (we will sometimes use the informal name "Heidelbergs") and early Neanderthals. Other aspects debated here are the selective value of habitat mosaics including reconstructions based on mammal and avian databases, and the role of geological instability combined with topographic complexity. This review is completed by addressing the question of whether the appearance of evolutionary trends within hominins is concentrated in regions of highest worldwide biological diversity (biodiversity hotspots). It is concluded that the keys for the activation of evolutionary

  14. East African climate pulses and early human evolution

    NASA Astrophysics Data System (ADS)

    Maslin, Mark A.; Brierley, Chris M.; Milner, Alice M.; Shultz, Susanne; Trauth, Martin H.; Wilson, Katy E.

    2014-10-01

    Current evidence suggests that all of the major events in hominin evolution have occurred in East Africa. Over the last two decades, there has been intensive work undertaken to understand African palaeoclimate and tectonics in order to put together a coherent picture of how the environment of East Africa has varied in the past. The landscape of East Africa has altered dramatically over the last 10 million years. It has changed from a relatively flat, homogenous region covered with mixed tropical forest, to a varied and heterogeneous environment, with mountains over 4 km high and vegetation ranging from desert to cloud forest. The progressive rifting of East Africa has also generated numerous lake basins, which are highly sensitive to changes in the local precipitation-evaporation regime. There is now evidence that the presence of precession-driven, ephemeral deep-water lakes in East Africa were concurrent with major events in hominin evolution. It seems the unusual geology and climate of East Africa created periods of highly variable local climate, which, it has been suggested could have driven hominin speciation, encephalisation and dispersal out of Africa. One example is the significant hominin speciation and brain expansion event at ˜1.8 Ma that seems to have been coeval with the occurrence of highly variable, extensive, deep-water lakes. This complex, climatically very variable setting inspired first the variability selection hypothesis, which was then the basis for the pulsed climate variability hypothesis. The newer of the two suggests that the long-term drying trend in East Africa was punctuated by episodes of short, alternating periods of extreme humidity and aridity. Both hypotheses, together with other key theories of climate-evolution linkages, are discussed in this paper. Though useful the actual evolution mechanisms, which led to early hominins are still unclear and continue to be debated. However, it is clear that an understanding of East African

  15. Large-Scale Impact Cratering and Early Earth Evolution

    NASA Technical Reports Server (NTRS)

    Grieve, R. A. F.; Cintala, M. J.

    1997-01-01

    The surface of the Moon attests to the importance of large-scale impact in its early crustal evolution. Previous models of the effects of a massive bombardment on terrestrial crustal evolution have relied on analogies with the Moon, with allowances for the presence of water and a thinner lithosphere. It is now apparent that strict lunar-terrestrial analogies are incorrect because of the "differential scaling" of crater dimensions and melt volumes with event size and planetary gravity. Impact melt volumes and "ancient cavity dimensions for specific impacts were modeled according to previous procedures. In the terrestrial case, the melt volume (V(sub m)) exceeds that of the transient cavity (V(sub tc)) at diameters > or = 400 km. This condition is reached on the Moon only with transient cavity diameters > or = 3000 km, equivalent to whole Moon melting. The melt volumes in these large impact events are minimum estimates, since, at these sizes, the higher temperature of the target rocks at depth will increase melt production. Using the modification-scaling relation of Croft, a transient cavity diameter of about 400 km in the terrestrial environment corresponds to an expected final impact "basin" diameter of about 900 km. Such a "basin" would be comparable in dimensions to the lunar basin Orientale. This 900-km "basin" on the early Earth, however, would not have had the appearance of Orientale. It would have been essentially a melt pool, and, morphologically, would have had more in common with the palimpsests structures on Callisto and Ganymede. With the terrestrial equivalents to the large multiring basins of the Moon being manifested as muted palimpsest-like structures filled with impact melt, it is unlikely they played a role in establishing the freeboard on the early Earth. The composition of the massive impact melt sheets (> 10 (exp 7) cu km) produced in "basin-forming" events on the early Earth would have most likely ranged from basaltic to more mafic for the

  16. Teaching about the Early Earth: Evolution of Tectonics, Life, and the Early Atmosphere

    NASA Astrophysics Data System (ADS)

    Mogk, D. W.; Manduca, C. A.; Kirk, K.; Williams, M. L.

    2007-12-01

    The early history of the Earth is the subject of some of the most exciting and innovative research in the geosciences, drawing evidence from virtually all fields of geoscience and using a variety of approaches that include field, analytical, experimental, and modeling studies. At the same time, the early Earth presents unique opportunities and challenges in geoscience education: how can we best teach "uncertain science" where the evidence is either incomplete or ambiguous? Teaching about early Earth provides a great opportunity to help students understand the nature of scientific evidence, testing, and understanding. To explore the intersection of research and teaching about this enigmatic period of Earth history, a national workshop was convened for experts in early Earth research and undergraduate geoscience education. The workshop was held in April, 2007 at the University of Massachusetts at Amherst as part of the On the Cutting Edge faculty professional development program. The workshop was organized around three scientific themes: evolution of global tectonics, life, and the early atmosphere. The "big scientific questions" at the forefront of current research about the early Earth were explored by keynote speakers and follow-up discussion groups: How did plate tectonics as we know it today evolve? Were there plates in the Hadean Eon? Was the early Earth molten? How rapidly did it cool? When and how did the atmosphere and hydrosphere evolve? How did life originate and evolve? How did all these components interact at the beginning of Earth's history and evolve toward the Earth system we know today? Similar "big questions" in geoscience education were addressed: how to best teach about "deep time;" how to help students make appropriate inferences when geologic evidence is incomplete; how to engage systems thinking and integrate multiple lines of evidence, across many scales of observation (temporal and spatial), and among many disciplines. Workshop participants

  17. Neoproterozoic Glaciations and the Early Evolution of Animals

    NASA Astrophysics Data System (ADS)

    Narbonne, G. M.

    2004-05-01

    The intense climatic changes that characterized the Neoproterozoic world were marked by equally profound evolutionary changes that ultimately led to the Cambrian Explosion. Early and Middle Neoproterozoic oceans contained prokaryotes and diverse eukaryotic lineages, including crown-group red, green, and heterokont algae. The survival of diverse eukaryotic lineages through the Sturtian, Marinoan, and Gaskiers glaciations implies that, although these were among the most extreme glaciations Earth has ever experienced, sea ice was not as thick or pervasive as required by earlier "hard Snowball" models. Most molecular clocks predict the existence of animals well before 600 Ma and a few tantalizing hints have been found, but the oldest definite evidence of animal life are phosphatized eggs and embryos overlying Marinoan glacial deposits in China. The subsequent Late Neoproterozoic is characterized by the global occurrence of the Ediacara biota, an assemblage of cm- to m-scale fossils of soft-bodied organisms that probably represent a mixture of stem groups of modern phyla and "failed experiments" in evolution. The oldest Ediacaran fossils occur in eastern Newfoundland, and postdate the glacial diamictites and cap carbonate of the Gaskiers Formation (580 Ma) by only 5 million years, implying a causal relationship between the end of the Neoproterozoic glaciations and the proliferation of animal life. These fossils include architecturally complex fronds up to two metres long, implying either extremely rapid rates of evolution or a pre-glacial origin of the Ediacara biota. Fossils of the Mistaken Point biota (575-560 Ma) were completely sessile and show a similar fractal architecture that is difficult to relate to any existing life forms. Some of these taxa persisted into the White Sea biota (560-550 Ma), which also contains trace fossils and metameric fossils that confirm the evolution of mobile bilaterians. The youngest Ediacaran fossils (550-543 Ma) exhibit the first

  18. Early evolution of sexual dimorphism and polygyny in Pinnipedia.

    PubMed

    Cullen, Thomas M; Fraser, Danielle; Rybczynski, Natalia; Schröder-Adams, Claudia

    2014-05-01

    Sexual selection is one of the earliest areas of interest in evolutionary biology. And yet, the evolutionary history of sexually dimorphic traits remains poorly characterized for most vertebrate lineages. Here, we report on evidence for the early evolution of dimorphism within a model mammal group, the pinnipeds. Pinnipeds show a range of sexual dimorphism and mating systems that span the extremes of modern mammals, from monomorphic taxa with isolated and dispersed mating to extreme size dimorphism with highly ordered polygynous harem systems. In addition, the degree of dimorphism in pinnipeds is closely tied to mating system, with strongly dimorphic taxa always exhibiting a polygynous system, and more monomorphic taxa possessing weakly polygynous systems. We perform a comparative morphological description, and provide evidence of extreme sexual dimorphism (similar to sea lions), in the Miocene-aged basal pinniped taxon Enaliarctos emlongi. Using a geometric morphometric approach and combining both modern and fossil taxa we show a close correlation between mating system and sex-related cranial dimorphism, and also reconstruct the ancestral mating system of extant pinnipeds as highly polygynous. The results suggest that sexual dimorphism and extreme polygyny in pinnipeds arose by 27 Ma, in association with changing climatic conditions. PMID:24548136

  19. Modelling the early evolution of a Loop Current ring

    NASA Astrophysics Data System (ADS)

    Auladell, M.; Pelegrí, J. L.; García-Olivares, A.; Kirwan, A. D., Jr.; Lipphardt, B. L., Jr.; Martín, J. M.; Pascual, A.; Sangrà, P.; Zweng, M.

    2010-03-01

    The Colorado University Princeton Ocean Model (CUPOM) is used here to study the early stages in the life of Millennium, a mesoscale anticyclonic ring that detached from the Loop Current on April 2001 and lasted for more than 100 days. The numerical near-surface velocity field for the Gulf of Mexico is validated with the altimetry geostrophic velocities. The first 30 days of numerical data, before Millennium interacts with other mesoscalar features, are closely examined both from Eulerian and Lagrangian perspectives. During this time Millennium had a near-constant rotation period of 6.5 days, and particles do not leave the ring. Nevertheless, the distributions of temperature, salinity, and angular velocity confirm the existence of significant (possibly numerical) radial diffusion. Polar-coordinate phase plots for temperature-salinity anomalies and tangential-radial velocities, at several depths, illustrate the presence of an evolving oscillating pattern. Radial and tangential velocities change in phase, associated with vertical displacements of the isothermal and isohaline surfaces. A simple diffusion model with an effective diffusion coefficient of 200 m 2 s - 1 is appropriate to grossly simulate the temporal evolution of angular velocity within Millennium.

  20. Stepwise evolution of Elk-1 in early deuterostomes.

    PubMed

    Saxton, Janice; Ferjentsik, Zoltan; Ducker, Charles; Johnson, Andrew D; Shaw, Peter E

    2016-03-01

    Metazoans have multiple ETS paralogues with overlapping or indiscriminate biological functions. Elk-1, one of three mammalian ternary complex factors (TCFs), is a well-conserved, ETS domain-containing transcriptional regulator of mitogen-responsive genes that operates in concert with serum response factor (SRF). Nonetheless, its genetic role remains unresolved because the elk-1 gene could be deleted from the mouse genome seemingly without adverse effect. Here we have explored the evolution of Elk-1 to gain insight into its conserved biological role. We identified antecedent Elk-1 proteins in extant early metazoans and used amino acid sequence alignments to chart the appearance of domains characteristic of human Elk-1. We then performed biochemical studies to determine whether putative domains apparent in the Elk-1 protein of a primitive hemichordate were functionally orthologous to those of human Elk-1. Our findings imply the existence of primordial Elk-1 proteins in primitive deuterostomes that could operate as mitogen-responsive ETS transcription factors but not as TCFs. The role of TCF was acquired later, but presumably prior to the whole genome duplications in the basal vertebrate lineage. Thus its evolutionary origins link Elk-1 to the appearance of mesoderm. PMID:26613204

  1. Early Planetary Evolution: Clues from Vesta and the Moon

    NASA Astrophysics Data System (ADS)

    Pieters, Carle; Russell, C. T.; Raymond, Carol

    The Moon has long been considered a natural laboratory and small body ‘endmember’ that can be used to study early terrestrial planet evolution. With the recently completed year-long exploration of Vesta by Dawn, we now have extensive information for an even smaller differentiated planetary body with which to compare and test models and paradigms. Before Dawn arrived with modern sensors to characterize the global properties of Vesta, we had what we believe to be random samples from the surface (the HED family of meteorites) to guide our planning of scientific exploration. This is not greatly different from the progression in lunar exploration where limited samples were returned decades before an international array of sensors began to seriously document the global properties of the Moon. We now know that both Vesta and the Moon are airless differentiated silicate bodies that are ancient and essentially (but not completely) anhydrous. Both are heavily cratered and exhibit at least one enormous basin that models predict should have excavated (and possibly exposed) the mantle. Everything else about Vesta and the Moon (size, location, origin, environment, surface composition, etc.) is quite different and the observed contrasts between the two provide valuable constraints for comparison of fundamental processes acting on airless planetary bodies of the solar system.

  2. Evolution of the mandibular third premolar crown in early Australopithecus.

    PubMed

    Delezene, Lucas K; Kimbel, William H

    2011-06-01

    The Pliocene hominins Australopithecus anamensis and Australopithecus afarensis likely represent ancestor-descendent taxa--possibly an anagenetic lineage--and capture significant change in the morphology of the canine and mandibular third premolar (P(3)) crowns, dental elements that form the canine honing complex in nonhuman catarrhines. This study focuses on the P(3) crown, highlighting plesiomorphic features in A. anamensis. The A. afarensis P(3) crown, in contrast, is variable in its expression of apomorphic features that are characteristic of geologically younger hominins. Temporal variation characterizes each taxon as well. The A. anamensis P(3) from Allia Bay, Kenya expresses apomorphic character states, shared with A. afarensis, which are not seen in the older sample of A. anamensis P(3)s from Kanapoi, Kenya, while spatiotemporal differences in shape exist within the A. afarensis hypodigm. The accumulation of derived features in A. afarensis results in an increased level of P(3) molarisation. P(3) molarisation did not evolve concurrent with postcanine megadontia and neither did the appearance of derived aspects of P(3) occlusal form coincide with the loss of canine honing in hominins, which is apparent prior to the origin of the genus Australopithecus. A. afarensis P(3) variation reveals the independence of shape, size, and occlusal form. The evolution of the P(3) crown in early Australopithecus bridges the wide morphological gap that exists between geologically younger hominins on the one hand and extant apes and Ardipithecus on the other. PMID:21481921

  3. Formation and evolution of early-type galaxies.

    NASA Astrophysics Data System (ADS)

    Chiosi, C.; Merlin, E.

    In this review, we present some recent results for NB-TSPH models of early type galaxies (ETGs) made of Dark and Baryonic matter according to the Lambda -CDM model of the Universe. The models are framed in the quasi-monolithic or early hierarchical scenario. By means of fully hydrodynamical NB-TSPH simulations performed with the Padova code EVOL, we produce a number of self-similar models of ETGs for different initial total masses and over-densities with respect to the surrounding medium, and follow their evolution from the detachment from the linear regime and Hubble flow at z > 20 down to the stage of nearly complete assembly of the stellar content (at about z<1 for all of them) and often to the present epoch (z=0). We find a strong correlation between the total mass and/or over-density of the proto-haloes and the subsequent star formation histories (SFH). Massive (Mtot≃ 1013 M⊙) haloes experience a single, intense burst of star formation (with rates > 103 M⊙/yr) at early epochs, consistently with observations, with a weak dependence on the initial over-density; intermediate mass (Mtot≃ 1011 M⊙) haloes have histories that strongly depend on their initial over-density; finally, low mass haloes (Mtot≃ 109 M⊙) always have erratic, burst-like star forming histories. The model galaxies have morphological, structural, and chemical properties resembling those of real galaxies. In addition to this, we try to cast light on the physical causes of the tight correlation between the mass in stars and the size of ETGs (the Mass-Radius Relation, MRR). We suggest that the MRR is the result of two complementary mechanisms: on one hand, the result of local physical processes, which fix the star mass and the radius of individual objects; on the other hand, the action of cosmological global, statistical principles, which shape the distribution of objects in the MR-plane. In the picture emerging from this study, nature seems to play the dominant role, whereas nurture

  4. Polymerization Evaluation by Spectrophotometric Measurements.

    ERIC Educational Resources Information Center

    Dunach, Jaume

    1985-01-01

    Discusses polymerization evaluation by spectrophotometric measurements by considering: (1) association degrees and molar absorptivities; (2) association degrees and equilibrium constants; and (3) absorbance and equilibrium constants. (JN)

  5. Genesis and evolution of dust in the early Universe

    NASA Astrophysics Data System (ADS)

    Gall, Christa

    2010-10-01

    The most fascinating aspect of studying dust is the fact that small dust particles of a few micrometer which we cannot see with our naked eyes are a fundamentally important component in a Universe whose dimension we hardly can imagine. Dust grains impact the evolution of the Universe in many ways. For example they are known as the main formation site of molecular hydrogen which acts as important coolant by the formation of stars similar to our Sun. Dust is essential for the formation of planets and plays an important role in the end stages of life of most stars. Large amounts of dust have been discovered in quasars (QSOs) at high redshift where the epoch of cosmic evolution was ! 1 Gyr, but the origin and evolution of these remains elusive. Supernovae (SNe) and asymptotic giant branch (AGB) stars have been contemplated as prime dust sources due to their potential ability of generating sufficiently high amounts of dust. Though AGB stars are in fact known as the main dust source in the present Universe, their partially (too) long lifetimes questions their significance as dust contributers in the early Universe. SNe are sufficiently short-lived, but there exists a discrepancy between observationally and theoretically ascertained dust yields. The principal aim of this thesis is to elucidate the astrophysical conditions required for generating these large amounts of dust in massive starburst galaxies and QSOs at high redshift. We first intend to identify the mass ranges of the most efficient dust producing stars at high redshift. We ascertain the dust production efficiency of stars in the mass range 3-40 M⊙ using observed and theoretical dust yields of AGB stars and SNe. Based on these efficiencies we determine the total dust productivity for different stellar sources and investigate its dependency on the initial mass function (IMF). It is found that the dust production efficiency generally decreases with increasing progenitor mass. The total dust production strongly

  6. The Evolution of Brains from Early Mammals to Humans

    PubMed Central

    Kaas, Jon H.

    2012-01-01

    The large size and complex organization of the human brain makes it unique among primate brains. In particular, the neocortex constitutes about 80% of the brain, and this cortex is subdivided into a large number of functionally specialized regions, the cortical areas. Such a brain mediates accomplishments and abilities unmatched by any other species. How did such a brain evolve? Answers come from comparative studies of the brains of present-day mammals and other vertebrates in conjunction with information about brain sizes and shapes from the fossil record, studies of brain development, and principles derived from studies of scaling and optimal design. Early mammals were small, with small brains, an emphasis on olfaction, and little neocortex. Neocortex was transformed from the single layer of output pyramidal neurons of the dorsal cortex of earlier ancestors to the six layers of all present-day mammals. This small cap of neocortex was divided into 20–25 cortical areas, including primary and some of the secondary sensory areas that characterize neocortex in nearly all mammals today. Early placental mammals had a corpus callosum connecting the neocortex of the two hemispheres, a primary motor area, M1, and perhaps one or more premotor areas. One line of evolution, Euarchontoglires, led to present-day primates, tree shrews, flying lemurs, rodents and rabbits. Early primates evolved from small-brained, nocturnal, insect-eating mammals with an expanded region of temporal visual cortex. These early nocturnal primates were adapted to the fine branch niche of the tropical rainforest by having an even more expanded visual system that mediated visually guided reaching and grasping of insects, small vertebrates, and fruits. Neocortex was greatly expanded, and included an array of cortical areas that characterize neocortex of all living primates. Specializations of the visual system included new visual areas that contributed to a dorsal stream of visuomotor processing in a

  7. Archean Pb Isotope Evolution: Implications for the Early Earth.

    NASA Astrophysics Data System (ADS)

    Vervoort, J. D.; Thorpe, R.; Albarede, F.; Blichert-Toft, J.

    2008-12-01

    .728 Ga (Normetal) to 2.70 Ga (Noranda). The Pb isotopic compositions from these galenas, when normalized to a common age of 2.7 Ga, define a highly linear array in 207Pb/204Pb vs. 206Pb/204Pb. This array is nearly coincident with the 2.7 Ga geochron with a slope that corresponds to an age of ~4.4 Ga and with an extraordinary large range of 207Pb/204Pb, about the same magnitude as modern MORB. These data have important implications for the evolution of the Archean mantle. First, the slope of the Abitibi Pb-Pb array and its coincidence with the 2.7 Ga geochron suggests widespread U-Pb differentiation within the first hundred million years of Earth's history. This may have been due to either core formation or silicate/melt differentiation due to widespread melting of the mantle (e.g., formation of a magma ocean). Second, variations in μ in the Abitibi mantle and the subsequent Pb isotopic heterogeneities, whatever their cause, have not been significantly changed from 4.4 until 2.7 Ga. This implies that changes in μ in the Abitibi mantle source between 4.4 and 2.7 Ga, such as would be caused by crust extraction or recycling of older crust into this region of the mantle, were insufficient to destroy the original μ variations created at 4.4 Ga. Therefore, it appears that this portion of the mantle had essentially remained isolated and undisturbed from the early Hadean until the late Archean.

  8. Understanding the early cycling evolution behaviors for phase change memory application

    NASA Astrophysics Data System (ADS)

    Wang, Yuchan; Chen, Yifeng; Cai, Daolin; Cheng, Yan; Chen, Xiaogang; Wang, Yueqing; Xia, Mengjiao; Zhou, Mi; Li, Gezi; Zhang, Yiyun; Gao, Dan; Song, Zhitang; Feng, Gaoming

    2014-11-01

    The RESET current of T-shaped phase change memory cells with 35 nm heating electrodes has been studied to understand the behavior of early cycling evolution. Results show that the RESET current has been significantly reduced after the early cycling evolution (1st RESET) operation. Compared the transmission electron microscope images, it is found that the hexagonal Ge2Sb2Te5 (GST) crystal grains are changed into the grains with face centered cubic structure after the early cycling evolution operation, which is taken as the major reason for the reduced RESET current, confirmed by a two-dimensional finite analysis and ab initio calculations.

  9. The evolution of modern corals and their early history

    NASA Astrophysics Data System (ADS)

    Stanley, George D.

    2003-02-01

    ephemeral, "naked coral", presents the greatest potential for solution of the enigma of the origin of scleractinians. It states that different groups of soft-bodied, unrelated "anemone-like" anthozoans gave rise to various calcified scleractinian-like corals through aragonitic biomineralization. Although there is evidence for this phenomenon being more universal in the mid-Triassic interval, following a lengthy Early Triassic post-extinction perturbation, it appears to have occurred at least three other times prior to this interval. This idea suggests that, because of ephemeral characteristics, the skeleton does not represent a clade of zoantharian evolution but instead represents a grade of organization. In the fossil record, skeletons may have appeared and disappeared at different times as some clades reverted to soft-bodied existence and these phenomena could account for notable gaps in the taxonomic and fossil record. A fuller understanding and possible solution to the problem of the origin of modern corals may be forthcoming. However, it will require synthesis of diverse kinds of data and an integration of findings from paleobiology, stratigraphy, molecular biology, carbonate geochemistry, biochemistry and invertebrate physiology.

  10. Early evolution of the LIM homeobox gene family

    SciTech Connect

    Srivastava, Mansi; Larroux, Claire; Lu, Daniel R; Mohanty, Kareshma; Chapman, Jarrod; Degnan, Bernard M; Rokhsar, Daniel S

    2010-01-01

    LIM homeobox (Lhx) transcription factors are unique to the animal lineage and have patterning roles during embryonic development in flies, nematodes and vertebrates, with a conserved role in specifying neuronal identity. Though genes of this family have been reported in a sponge and a cnidarian, the expression patterns and functions of the Lhx family during development in non-bilaterian phyla are not known. We identified Lhx genes in two cnidarians and a placozoan and report the expression of Lhx genes during embryonic development in Nematostella and the demosponge Amphimedon. Members of the six major LIM homeobox subfamilies are represented in the genomes of the starlet sea anemone, Nematostella vectensis, and the placozoan Trichoplax adhaerens. The hydrozoan cnidarian, Hydra magnipapillata, has retained four of the six Lhx subfamilies, but apparently lost two others. Only three subfamilies are represented in the haplosclerid demosponge Amphimedon queenslandica. A tandem cluster of three Lhx genes of different subfamilies and a gene containing two LIM domains in the genome of T. adhaerens (an animal without any neurons) indicates that Lhx subfamilies were generated by tandem duplication. This tandem cluster in Trichoplax is likely a remnant of the original chromosomal context in which Lhx subfamilies first appeared. Three of the six Trichoplax Lhx genes are expressed in animals in laboratory culture, as are all Lhx genes in Hydra. Expression patterns of Nematostella Lhx genes correlate with neural territories in larval and juvenile polyp stages. In the aneural demosponge, A. queenslandica, the three Lhx genes are expressed widely during development, including in cells that are associated with the larval photosensory ring. The Lhx family expanded and diversified early in animal evolution, with all six subfamilies already diverged prior to the cnidarian-placozoan-bilaterian last common ancestor. In Nematostella, Lhx gene expression is correlated with neural

  11. The Formation and Early Evolution of Young Massive Clusters

    NASA Astrophysics Data System (ADS)

    Longmore, S. N.; Kruijssen, J. M. D.; Bastian, N.; Bally, J.; Rathborne, J.; Testi, L.; Stolte, A.; Dale, J.; Bressert, E.; Alves, J.

    We review the formation and early evolution of the most massive (> few 104 M⊙) and dense (radius of a few parsecs) young stellar clusters, focusing on the role that studies of these objects in our Galaxy can play in our understanding of star and planet formation as a whole. Comparing the demographics of young massive cluster (YMC) progenitor clouds and YMCs across the Galaxy shows that gas in the Galactic Center can accumulate to a high enough density that molecular clouds already satisfy the criteria used to define YMCs, without forming stars. In this case formation can proceed in situ — i.e., the stars form at protostellar densities close to the final stellar density. Conversely, in the disk, the gas either begins forming stars while it is being accumulated to high density, in a "conveyor belt" mode, or the timescale to accumulate the gas to such high densities must be much shorter than the star-formation timescale. The distinction between the formation regimes in the two environments is consistent with the predictions of environmentally dependent density thresholds for star formation. This implies that stars in YMCs of similar total mass and radius can have formed at widely different initial protostellar densities. The fact that no strong, systematic variations in fundamental properties (such as the IMF) are observed between YMCs in the disk and Galactic Center suggests that, statistically speaking, stellar mass assembly is not affected by the initial protostellar density. We then review recent theoretical advances and summarize the debate on three key open questions: the initial (proto)stellar distribution, infant (im)mortality, and age spreads within YMCs. We conclude that (1) the initial protostellar distribution is likely hierarchical, (2) YMCs likely experienced a formation history that was dominated by gas exhaustion rather than gas expulsion, (3) YMCs are dynamically stable from a young age, and (4) YMCs have age spreads much smaller than their mean

  12. The evolution of early Homo: a reply to Scott.

    PubMed

    Van Arsdale, A P; Wolpoff, M H

    2014-03-01

    Scott presents a welcome reply to our article, "A single lineage in early Pleistocene Homo" (Van Arsdale and Wolpoff ). However, Scott's reply mischaracterizes and fails to directly address the hypothesis of a single lineage that we test. Additionally, the approach taken by Scott fails to replicate the methods used in our analysis. As Scott himself suggests, our null hypothesis of a single evolving lineage in early Homo remains without refutation. Although many evolutionary scenarios might explain the complex pattern of variation present in the early Homo fossil record, the most parsimonious remains that of a single lineage displaying evolutionary change over time. PMID:24372272

  13. Inflationary gravitational waves and the evolution of the early universe

    SciTech Connect

    Jinno, Ryusuke; Moroi, Takeo; Nakayama, Kazunori E-mail: moroi@hep-th.phys.s.u-tokyo.ac.jp

    2014-01-01

    We study the effects of various phenomena which may have happened in the early universe on the spectrum of inflationary gravitational waves. The phenomena include phase transitions, entropy productions from non-relativistic matter, the production of dark radiation, and decoupling of dark matter/radiation from thermal bath. These events can create several characteristic signatures in the inflationary gravitational wave spectrum, which may be direct probes of the history of the early universe and the nature of high-energy physics.

  14. Understanding the Early Evolution of M dwarf Extreme Ultraviolet Radiation

    NASA Astrophysics Data System (ADS)

    Peacock, Sarah; Barman, Travis; Shkolnik, Evgenya

    2015-11-01

    The chemistry and evolution of planetary atmospheres depends on the evolution of high-energy radiation emitted by its host star. High levels of extreme ultraviolet (EUV) radiation can drastically alter the atmospheres of terrestrial planets through ionizing, heating, expanding, chemically modifying and eroding them during the first few billion years of a planetary lifetime. While there is evidence that stars emit their highest levels of far and near ultraviolet (FUV; NUV) radiation in the earliest stages of their evolution, we are currently unable to directly measure the EUV radiation. Most previous stellar atmosphere models under-predict FUV and EUV emission from M dwarfs; here we present new models for M stars that include prescriptions for the hot, lowest density atmospheric layers (chromosphere, transition region and corona), from which this radiation is emitted. By comparing our model spectra to GALEX near and far ultraviolet fluxes, we are able to predict the evolution of EUV radiation for M dwarfs from 10 Myr to a few Gyr. This research is the next major step in the HAZMAT (HAbitable Zones and M dwarf Activity across Time) project to analyze how the habitable zone evolves with the evolving properties of stellar and planetary atmospheres.

  15. The Evolution of the National Early Childhood Technical Assistance Center

    ERIC Educational Resources Information Center

    Gallagher, James J.; Danaher, Joan C.; Clifford, Richard M.

    2009-01-01

    This review traces the evolution from 1971 to the present of a national technical assistance (TA) program to support the creation, expansion, and improvement of services for infants, toddlers, and preschoolers with special needs. From its beginning as a TA resource for demonstration projects, to linking outreach projects' expertise with state…

  16. Mathematics in Early Childhood Education: Revolution or Evolution?

    ERIC Educational Resources Information Center

    Stipek, Deborah

    2013-01-01

    Hachey (2013) aptly describes a recent surge in attention to mathematics for young children. The value of math for children as young as preschool age, however, was discovered before the 21st century. This is presently not a revolution but rather a potentially important step in an evolution of work that began at least a half century ago. Some…

  17. Three-dimensional evolution of early solar nebula

    NASA Technical Reports Server (NTRS)

    Boss, Alan P.

    1991-01-01

    The progress is reported toward the goal of a complete theory of solar nebula formation, with an emphasis on three spatial dimension models of solar nebular formation and evolution. The following subject areas are covered: (1) initial conditions for protostellar collapse; (2) single versus binary star formation; (3) angular momentum transport mechanisms; (4) three dimensional solar nebula models; and (5) implications for planetary formation.

  18. Early evolution and ecology of camouflage in insects.

    PubMed

    Pérez-de la Fuente, Ricardo; Delclòs, Xavier; Peñalver, Enrique; Speranza, Mariela; Wierzchos, Jacek; Ascaso, Carmen; Engel, Michael S

    2012-12-26

    Taxa within diverse lineages select and transport exogenous materials for the purposes of camouflage. This adaptive behavior also occurs in insects, most famously in green lacewing larvae who nestle the trash among setigerous cuticular processes, known as trash-carrying, rendering them nearly undetectable to predators and prey, as well as forming a defensive shield. We report an exceptional discovery of a green lacewing larva in Early Cretaceous amber from Spain with specialized cuticular processes forming a dorsal basket that carry a dense trash packet. The trash packet is composed of trichomes of gleicheniacean ferns, which highlight the presence of wildfires in this early forest ecosystem. This discovery provides direct evidence of an early acquisition of a sophisticated behavioral suite in stasis for over 110 million years and an ancient plant-insect interaction. PMID:23236135

  19. A primitive protostegid from Australia and early sea turtle evolution

    PubMed Central

    Kear, Benjamin P; Lee, Michael S.Y

    2005-01-01

    Sea turtles (Chelonioidea) are a prominent group of modern marine reptiles whose early history is poorly understood. Analysis of exceptionally well preserved fossils of Bouliachelys suteri gen. et sp. nov., a large-bodied basal protostegid (primitive chelonioid) from the Early Cretaceous (Albian) of Australia, indicates that early sea turtles were both larger and more diverse than previously thought. The analysis implies at least five distinct sea turtle lineages existed around 100 million years ago. Currently, the postcranially primitive Ctenochelys and Toxochelys are interpreted as crown-group sea turtles closely related to living cheloniids (e.g. Chelonia); in contrast, the new phylogeny suggests that they are transitional (intermediate stem-taxa) between continental testudines and derived, pelagic chelonioids. PMID:17148342

  20. The Origin and Early Evolution of Roots1

    PubMed Central

    Kenrick, Paul; Strullu-Derrien, Christine

    2014-01-01

    Geological sites of exceptional fossil preservation are becoming a focus of research on root evolution because they retain edaphic and ecological context, and the remains of plant soft tissues are preserved in some. New information is emerging on the origins of rooting systems, their interactions with fungi, and their nature and diversity in the earliest forest ecosystems. Remarkably well-preserved fossils prove that mycorrhizal symbionts were diverse in simple rhizoid-based systems. Roots evolved in a piecemeal fashion and independently in several major clades through the Devonian Period (416 to 360 million years ago), rapidly extending functionality and complexity. Evidence from extinct arborescent clades indicates that polar auxin transport was recruited independently in several to regulate wood and root development. The broader impact of root evolution on the geochemical carbon cycle is a developing area and one in which the interests of the plant physiologist intersect with those of the geochemist. PMID:25187527

  1. Evolution of Planetesimals Accreted in the Early Solar System

    NASA Technical Reports Server (NTRS)

    Matson, D. L.; Johnson, T. V.; Castillo-Rogez, J. C.; Thomas, P. C.

    2011-01-01

    The purpose of this presentation is to point out that the origins and abundances of short-lived nu-clides in the early solar system had important conse-quences for "icy planetesimals". It is believed that these planetesimals, composed of ice and rock, were once very abundant in the early, outer solar system. Today, spacecraft can visit remnants of that popula-tion and measure their properties. Cassini's flyby of Saturn's satellite Phoebe may have been the first visit to an object related to this population.

  2. The evolution and orientation of early cycle 22 active regions

    NASA Technical Reports Server (NTRS)

    Cannon, Anne T.; Marquette, William H.

    1991-01-01

    The evolution of six major active regions which appeared during the first phase of the present solar cycle (cycle 22) has been studied. It was found that the northern hemisphere regions exhibited a broad range of evolutionary behavior in which the commonly accepted 'normal pattern' (whereby the follower flux moves preferentially polewards ahead of the leader flux) is represented at one end of the range. At the other end of the range, the leader flux is displaced polewards of the follower flux. In the latter cases equatorward extensions of the polar coronal hole are noted.

  3. Early Universe evolution in presence of magnetic fields

    NASA Astrophysics Data System (ADS)

    Delgado Gaspar, I.; Pérez Martínez, A.; Piccinelli, G.; Sussman, R. A.

    2015-11-01

    We analyse the evolution of a magnetised Universe in a stage between the leptonic era and the beginning of the radiation-dominated epoch using an anisotropic Bianchi I model. In our description the cosmic fluid is made of primordial radiation, neutrinos, magnetic field, non-interacting already decoupled dark matter (WIMPS), baryons, electrons, and positrons. The interaction of the field with the electron-positron gas is taken into account, resulting in anisotropic equations of state for these constituents. Numerical simulations reveal some differences between the behaviour of magnetised Bianchi I Universes and that of first order perturbations on an FLRW background.

  4. Convergence of ion channel genome content in early animal evolution.

    PubMed

    Liebeskind, Benjamin J; Hillis, David M; Zakon, Harold H

    2015-02-24

    Multicellularity has evolved multiple times, but animals are the only multicellular lineage with nervous systems. This fact implies that the origin of nervous systems was an unlikely event, yet recent comparisons among extant taxa suggest that animal nervous systems may have evolved multiple times independently. Here, we use ancestral gene content reconstruction to track the timing of gene family expansions for the major families of ion-channel proteins that drive nervous system function. We find that animals with nervous systems have broadly similar complements of ion-channel types but that these complements likely evolved independently. We also find that ion-channel gene family evolution has included large loss events, two of which were immediately followed by rounds of duplication. Ctenophores, cnidarians, and bilaterians underwent independent bouts of gene expansion in channel families involved in synaptic transmission and action potential shaping. We suggest that expansions of these family types may represent a genomic signature of expanding nervous system complexity. Ancestral nodes in which nervous systems are currently hypothesized to have originated did not experience large expansions, making it difficult to distinguish among competing hypotheses of nervous system origins and suggesting that the origin of nerves was not attended by an immediate burst of complexity. Rather, the evolution of nervous system complexity appears to resemble a slow fuse in stem animals followed by many independent bouts of gene gain and loss. PMID:25675537

  5. Convergence of ion channel genome content in early animal evolution

    PubMed Central

    Liebeskind, Benjamin J.; Hillis, David M.; Zakon, Harold H.

    2015-01-01

    Multicellularity has evolved multiple times, but animals are the only multicellular lineage with nervous systems. This fact implies that the origin of nervous systems was an unlikely event, yet recent comparisons among extant taxa suggest that animal nervous systems may have evolved multiple times independently. Here, we use ancestral gene content reconstruction to track the timing of gene family expansions for the major families of ion-channel proteins that drive nervous system function. We find that animals with nervous systems have broadly similar complements of ion-channel types but that these complements likely evolved independently. We also find that ion-channel gene family evolution has included large loss events, two of which were immediately followed by rounds of duplication. Ctenophores, cnidarians, and bilaterians underwent independent bouts of gene expansion in channel families involved in synaptic transmission and action potential shaping. We suggest that expansions of these family types may represent a genomic signature of expanding nervous system complexity. Ancestral nodes in which nervous systems are currently hypothesized to have originated did not experience large expansions, making it difficult to distinguish among competing hypotheses of nervous system origins and suggesting that the origin of nerves was not attended by an immediate burst of complexity. Rather, the evolution of nervous system complexity appears to resemble a slow fuse in stem animals followed by many independent bouts of gene gain and loss. PMID:25675537

  6. Formation, early evolution, and gravitational stability of protoplanetary disks

    NASA Technical Reports Server (NTRS)

    Nakamoto, Taishi; Nakagawa, Yoshitsugo

    1994-01-01

    The formation, viscous evolution, and gravitational stability of protoplanetary disks are investigated. The formation process is parameterized by the angular velocity of the molecular cloud core omega, while the viscous evolution is parameterized by the viscosity parameter alpha in the disk; in this study we consider a range of (0.4-6) x 10(exp -14)/s for omega and from 10(exp -5) to 10(exp -1) for alpha. The axisymmetric gravitational stabilities of the disks are checked using Toomre's criterion. The resulting disk surface temperature distribution, (d log T(sub s)/d log R) approximately = -0.6 (R is the cylindrical radius), can be attributed to two heating sources: the viscous heating dominant in the inner disk region, and the accretion shock heating dominant in the outer disk region. This surface temperature distribution matches that observed in many disks around young stellar objects. During the infall stage, disks with alpha less than 10(exp -1.5) become gravitationally unstable independent of omega. The gravitational instabilities occur at radii ranging from 5 to 40 AU. The ratio of the disk mass to the central star mass ranges from 0.2 to 0.5 at the times of instability, about 4 x 10(exp -5) x (omega/10(exp -14)/s)(exp -0.67) yr. Most disks with low alpha and high omega become gravitationally unstable during their formation phase.

  7. Understanding the early cycling evolution behaviors for phase change memory application

    SciTech Connect

    Wang, Yuchan Chen, Yifeng Cai, Daolin; Cheng, Yan; Chen, Xiaogang; Wang, Yueqing; Xia, Mengjiao; Zhou, Mi; Li, Gezi; Zhang, Yiyun; Gao, Dan; Song, Zhitang; Feng, Gaoming

    2014-11-28

    The RESET current of T-shaped phase change memory cells with 35 nm heating electrodes has been studied to understand the behavior of early cycling evolution. Results show that the RESET current has been significantly reduced after the early cycling evolution (1st RESET) operation. Compared the transmission electron microscope images, it is found that the hexagonal Ge{sub 2}Sb{sub 2}Te{sub 5} (GST) crystal grains are changed into the grains with face centered cubic structure after the early cycling evolution operation, which is taken as the major reason for the reduced RESET current, confirmed by a two-dimensional finite analysis and ab initio calculations.

  8. The Early Evolution of the Solar Nebula with Implications for the Formation of Primitive Material

    NASA Technical Reports Server (NTRS)

    Bell, K. Robbins

    2002-01-01

    I will present a review of our understanding of the early evolution of the solar nebula especially as it bears on the formation of primitive meteorites. Although my emphasis will be on the results of theoretical studies, I will also summarize some of the observational evidence supporting these conclusions. In particular, I will summarize our current best deductions about midplane temperatures and densities of the solar nebula and about both long-term and episodic evolution.

  9. A Geological Model for the Evolution of Early Continents (Invited)

    NASA Astrophysics Data System (ADS)

    Rey, P. F.; Coltice, N.; Flament, N. E.; Thébaud, N.

    2013-12-01

    Geochemical probing of ancient sediments (REE in black shales, strontium composition of carbonates, oxygen isotopes in zircons...) suggests that continents were a late Archean addition at Earth's surface. Yet, geochemical probing of ancient basalts reveals that they were extracted from a mantle depleted of its crustal elements early in the Archean. Considerations on surface geology, the early Earth hypsometry and the rheology and density structure of Archean continents can help solve this paradox. Surface geology: The surface geology of Archean cratons is characterized by thick continental flood basalts (CFBs, including greenstones) emplaced on felsic crusts dominated by Trondhjemite-Tonalite-Granodiorite (TTG) granitoids. This simple geology is peculiar because i/ most CFBs were emplaced below sea level, ii/ after their emplacement, CFBs were deformed into relatively narrow, curviplanar belts (greenstone basins) wrapping around migmatitic TTG domes, and iii/ Archean greenstone belts are richly endowed with gold and other metals deposits. Flat Earth hypothesis: From considerations on early Earth continental geotherm and density structure, Rey and Coltice (2008) propose that, because of the increased ability of the lithosphere to flow laterally, orogenic processes in the Archean produced only subdued topography (early Earth showing that, until the late Archean, most continents were flooded and Earth was largely a water world. From this, a model consistent with many of the peculiar attributes of Archean geology, can be proposed: 1/ Continents appeared at Earth's surface at an early stage during the Hadean/Archean. However, because they were i/ covered by continental flood basalts, ii/ below sea level, and iii/ deprived of modern-style mountain belts and orogenic plateaux, early felsic

  10. Evolution of morphology of bacterial cellulose scaffolds during early culture.

    PubMed

    Luo, Honglin; Zhang, Jing; Xiong, Guangyao; Wan, Yizao

    2014-10-13

    Morphological characteristics of a fibrous tissue engineering (TE) scaffold are key parameters affecting cell behavior. However, no study regarding the evolution of morphology of bacterial cellulose (BC) scaffolds during the culture process has been reported to date. In this work, BC scaffolds cultured for different times starting from 0.5h were characterized. The results demonstrated that the formation of an integrated scaffold and its 3D network structure, porosity, fiber diameter, light transmittance, and the morphology of hydroxyapatite (HAp)-deposited BC scaffolds changed with culture time. However, the surface and crystal structure of BC fibers did not change with culture time and no difference was found in the crystal structure of HAp deposited on BC templates regardless of BC culture time. The findings presented herein suggest that proper selection of culture time can potentially enhance the biological function of BC TE scaffold by optimizing its morphological characteristics. PMID:25037408

  11. Some remarks on the early evolution of Enceladus

    NASA Astrophysics Data System (ADS)

    Czechowski, Leszek

    2014-12-01

    Thermal history of Enceladus is investigated from the beginning of accretion to formation of its core (~400 My). We consider model with solid state convection (in a solid layer) as well as liquid state convection (in molten parts of the satellite). The numerical model of convection uses full conservative finite difference method. The roles of two modes of convection are considered using the parameterized theory of convection. The following heat sources are included: short lived and long lived radioactive isotopes, accretion, serpentinization, and phase changes. Heat transfer processes are: conduction, solid state convection, and liquid state convection. It is found that core formation was completed only when liquid state convection had slowed down. Eventually, the porous core with pores filled with water was formed. Recent data concerning gravity field of Enceladus confirm low density of the core. We investigated also thermal history for different values of the following parameters: time of beginning of accretion tini, duration of accretion tacr, viscosity of ice close to the melting point ηm, activation energy in formula for viscosity E, thermal conductivity of silicate component ksil, ammonia content XNH3, and energy of serpentinization cserp. All these parameters are important for evolution, but not dramatic differences are found for realistic values. Moreover, the hypothesis of proto-Enceladus (stating that initially Enceladus was substantially larger) is considered and thermal history of such body is calculated. The last subject is the Mimas-Enceladus paradox. Comparison of thermal models of Mimas and Enceladus indicates that period favorable for 'excited path of evolution' was significantly shorter for Mimas than for Enceladus.

  12. Early-time evolution of a radiative shock

    NASA Astrophysics Data System (ADS)

    Kuranz, C. C.; Drake, R. P.; Huntington, C. M.; Krauland, C. M.; Di Stefano, C. A.; Trantham, M.; Grosskopf, M. J.; Klein, S. R.; Marion, D. C.

    2013-06-01

    We have performed high-energy-density physics experiments with large radiative fluxes, relevant to radiative shocks in our universe. These experiments were performed at the Omega Laser facility and used a laser irradiance of 7.2 × 1014 W cm-2 to launch a Be disk into low-density Xe gas. The radiative shocks were observed early in time as the dense shocked Xe layer began to form. The average shock position indicates that the shock is moving over 130 km s-1. Data are compared to simulation output from the CRASH code, which was developed at the Center for Radiative Shock Hydrodynamics at the University of Michigan.

  13. Conference on Early Mars: Geologic and Hydrologic Evolution, Physical and Chemical Environments, and the Implications for Life

    NASA Technical Reports Server (NTRS)

    Clifford, S. M. (Editor); Treiman, A. H. (Editor); Newsom, H. E. (Editor); Farmer, J. D. (Editor)

    1997-01-01

    Topics considered include: Geology alteration and life in an extreme environment; developing a chemical code to identify magnetic biominerals; effect of impacts on early Martin geologic evolution; spectroscopic identification of minerals in Hematite-bearing soils and sediments; exopaleontology and the search for a Fossil record on Mars; geochemical evolution of the crust of Mars; geological evolution of the early earth;solar-wind-induced erosion of the Mars atmosphere. Also included geological evolution of the crust of Mars.

  14. A Cretaceous eutriconodont and integument evolution in early mammals.

    PubMed

    Martin, Thomas; Marugán-Lobón, Jesús; Vullo, Romain; Martín-Abad, Hugo; Luo, Zhe-Xi; Buscalioni, Angela D

    2015-10-15

    The Mesozoic era (252-66 million years ago), known as the domain of dinosaurs, witnessed a remarkable ecomorphological diversity of early mammals. The key mammalian characteristics originated during this period and were prerequisite for their evolutionary success after extinction of the non-avian dinosaurs 66 million years ago. Many ecomorphotypes familiar to modern mammal fauna evolved independently early in mammalian evolutionary history. Here we report a 125-million-year-old eutriconodontan mammal from Spain with extraordinary preservation of skin and pelage that extends the record of key mammalian integumentary features into the Mesozoic era. The new mammalian specimen exhibits such typical mammalian features as pelage, mane, pinna, and a variety of skin structures: keratinous dermal scutes, protospines composed of hair-like tubules, and compound follicles with primary and secondary hairs. The skin structures of this new Mesozoic mammal encompass the same combination of integumentary features as those evolved independently in other crown Mammalia, with similarly broad structural variations as in extant mammals. Soft tissues in the thorax and abdomen (alveolar lungs and liver) suggest the presence of a muscular diaphragm. The eutriconodont has molariform tooth replacement, ossified Meckel's cartilage of the middle ear, and specialized xenarthrous articulations of posterior dorsal vertebrae, convergent with extant xenarthran mammals, which strengthened the vertebral column for locomotion. PMID:26469049

  15. A Cretaceous eutriconodont and integument evolution in early mammals

    NASA Astrophysics Data System (ADS)

    Martin, Thomas; Marugán-Lobón, Jesús; Vullo, Romain; Martín-Abad, Hugo; Luo, Zhe-Xi; Buscalioni, Angela D.

    2015-10-01

    The Mesozoic era (252-66 million years ago), known as the domain of dinosaurs, witnessed a remarkable ecomorphological diversity of early mammals. The key mammalian characteristics originated during this period and were prerequisite for their evolutionary success after extinction of the non-avian dinosaurs 66 million years ago. Many ecomorphotypes familiar to modern mammal fauna evolved independently early in mammalian evolutionary history. Here we report a 125-million-year-old eutriconodontan mammal from Spain with extraordinary preservation of skin and pelage that extends the record of key mammalian integumentary features into the Mesozoic era. The new mammalian specimen exhibits such typical mammalian features as pelage, mane, pinna, and a variety of skin structures: keratinous dermal scutes, protospines composed of hair-like tubules, and compound follicles with primary and secondary hairs. The skin structures of this new Mesozoic mammal encompass the same combination of integumentary features as those evolved independently in other crown Mammalia, with similarly broad structural variations as in extant mammals. Soft tissues in the thorax and abdomen (alveolar lungs and liver) suggest the presence of a muscular diaphragm. The eutriconodont has molariform tooth replacement, ossified Meckel's cartilage of the middle ear, and specialized xenarthrous articulations of posterior dorsal vertebrae, convergent with extant xenarthran mammals, which strengthened the vertebral column for locomotion.

  16. Robotic surgery for early stage cervical cancer: Evolution and current trends.

    PubMed

    Medlin, Erin E; Kushner, David M; Barroilhet, Lisa

    2015-12-01

    The management of early stage cervical cancer often includes surgery in the form of radical hysterectomy, radical trachelectomy, or radical parametrectomy. Surgical techniques have evolved to include minimal invasive approaches, and more recently, to include robotic assisted techniques. This review highlights the evolution of surgical management of early cervical cancer and specifically explores robotic assisted radical hysterectomy, radical trachelectomy, radical parametrectomy, and the role of neoadjuvant chemotherapy. PMID:26768315

  17. The early spectral evolution of Nova Cassiopeiae 1993

    NASA Technical Reports Server (NTRS)

    Hauschildt, Peter H.; Starrfield, Sumner; Shore, Steven N.; Gonzalez-Riestra, Rosario; Sonneborn, George; Allard, France

    1994-01-01

    In this paper we describe the evolution of Nova Cas 1993 over the first two months of its outburst. We present an ultraviolet light curve that covers the period from announcement to just after dust began forming in the ejecta (1994 Feb. 15) and International Ultraviolet Explorer (IUE) spacecraft constraints forced us to halt our observations. We have used spherical, expanding, Non-local Thermodynamic Equilibrium (NLTE) stellar atmospheres to compute synthetic spectra and have compared the results to combined ultraviolet (low-resolution 1200-3400 A and high-resolution 2400-3300 A) spectra. Our fits show that the effective temperature of the ejecta increased from approx. 8000 to about approx. 16 000 K between 1993 Dec. 12 and 1993 Dec. 26. The temperature then increased more slowly to approx. 24 000 on 1994 Jan. 28. A preliminary abundance analysis shows evidence for hydrogen depletion, as we also found for Nova V1974 Cygni; however we find a larger enhancement of carbon, nitrogen, and oxygen. We also show that the principal mechanism for mass ejection in this nova is a radiation pressure driven wind and that mechanical driving is not necessary.

  18. Jupiter's decisive role in the inner Solar System's early evolution.

    PubMed

    Batygin, Konstantin; Laughlin, Greg

    2015-04-01

    The statistics of extrasolar planetary systems indicate that the default mode of planet formation generates planets with orbital periods shorter than 100 days and masses substantially exceeding that of the Earth. When viewed in this context, the Solar System is unusual. Here, we present simulations which show that a popular formation scenario for Jupiter and Saturn, in which Jupiter migrates inward from a > 5 astronomical units (AU) to a ≈ 1.5 AU before reversing direction, can explain the low overall mass of the Solar System's terrestrial planets, as well as the absence of planets with a < 0.4 AU. Jupiter's inward migration entrained s ≳ 10-100 km planetesimals into low-order mean motion resonances, shepherding and exciting their orbits. The resulting collisional cascade generated a planetesimal disk that, evolving under gas drag, would have driven any preexisting short-period planets into the Sun. In this scenario, the Solar System's terrestrial planets formed from gas-starved mass-depleted debris that remained after the primary period of dynamical evolution. PMID:25831540

  19. THE STRUCTURAL EVOLUTION OF FORMING AND EARLY STAGE STAR CLUSTERS

    SciTech Connect

    Jaehnig, Karl O.; Da Rio, Nicola; Tan, Jonathan C. E-mail: ndario@ufl.edu

    2015-01-10

    We study the degree of angular substructure in the stellar position distribution of young members of Galactic star-forming regions, looking for correlations with distance from cluster center, surface number density of stars, and local dynamical age. To this end we adopt the catalog of members in 18 young (∼1-3 Myr) clusters from the Massive Young Star-Forming Complex Study in Infrared and X-ray Survey and the statistical analysis of the angular dispersion parameter, δ{sub ADP,} {sub N}. We find statistically significant correlation between δ{sub ADP,} {sub N} and physical projected distance from the center of the clusters, with the centers appearing smoother than the outskirts, consistent with more rapid dynamical processing on local dynamical, free-fall or orbital timescales. Similarly, smoother distributions are seen in regions of higher surface density, or older dynamical ages. These results indicate that dynamical processing that erases substructure is already well-advanced in young, sometimes still-forming, clusters. Such observations of the dissipation of substructure have the potential to constrain theoretical models of the dynamical evolution of young and forming clusters.

  20. Early evolution of efficient enzymes and genome organization

    PubMed Central

    2012-01-01

    Background Cellular life with complex metabolism probably evolved during the reign of RNA, when it served as both information carrier and enzyme. Jensen proposed that enzymes of primordial cells possessed broad specificities: they were generalist. When and under what conditions could primordial metabolism run by generalist enzymes evolve to contemporary-type metabolism run by specific enzymes? Results Here we show by numerical simulation of an enzyme-catalyzed reaction chain that specialist enzymes spread after the invention of the chromosome because protocells harbouring unlinked genes maintain largely non-specific enzymes to reduce their assortment load. When genes are linked on chromosomes, high enzyme specificity evolves because it increases biomass production, also by reducing taxation by side reactions. Conclusion The constitution of the genetic system has a profound influence on the limits of metabolic efficiency. The major evolutionary transition to chromosomes is thus proven to be a prerequisite for a complex metabolism. Furthermore, the appearance of specific enzymes opens the door for the evolution of their regulation. Reviewers This article was reviewed by Sándor Pongor, Gáspár Jékely, and Rob Knight. PMID:23114029

  1. The Structural Evolution of Forming and Early Stage Star Clusters

    NASA Astrophysics Data System (ADS)

    Jaehnig, Karl; Da Rio, Nicola; Tan, Jonathan C.

    2016-05-01

    We study the degree of angular substructure in the stellar position distribution of young members of Galactic star-forming regions, looking for correlations with distance from cluster center, surface number density of stars, and local dynamical age. To this end we adopt the catalog of members in 18 young (∼1-3 Myr) clusters from the Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) Survey and the statistical analysis of the Angular Dispersion Parameter, δADP. We find statistically significant correlation between δADP and physical projected distance from the center of the clusters, with the centers appearing smoother than the outskirts, consistent with more rapid dynamical processing on local dynamical, free-fall or orbital timescales. Similarly, smoother distributions are seen in regions of higher surface density, or older dynamical ages. These results indicate that dynamical processing that erases substructure is already well-advanced in young, sometimes still-forming, clusters. Such observations of the dissipation of substructure have the potential to constrain theoretical models of the dynamical evolution of young and forming clusters.

  2. Evolution of attention mechanisms for early visual processing

    NASA Astrophysics Data System (ADS)

    Müller, Thomas; Knoll, Alois

    2011-03-01

    Early visual processing as a method to speed up computations on visual input data has long been discussed in the computer vision community. The general target of a such approaches is to filter nonrelevant information from the costly higher-level visual processing algorithms. By insertion of this additional filter layer the overall approach can be speeded up without actually changing the visual processing methodology. Being inspired by the layered architecture of the human visual processing apparatus, several approaches for early visual processing have been recently proposed. Most promising in this field is the extraction of a saliency map to determine regions of current attention in the visual field. Such saliency can be computed in a bottom-up manner, i.e. the theory claims that static regions of attention emerge from a certain color footprint, and dynamic regions of attention emerge from connected blobs of textures moving in a uniform way in the visual field. Top-down saliency effects are either unconscious through inherent mechanisms like inhibition-of-return, i.e. within a period of time the attention level paid to a certain region automatically decreases if the properties of that region do not change, or volitional through cognitive feedback, e.g. if an object moves consistently in the visual field. These bottom-up and top-down saliency effects have been implemented and evaluated in a previous computer vision system for the project JAST. In this paper an extension applying evolutionary processes is proposed. The prior vision system utilized multiple threads to analyze the regions of attention delivered from the early processing mechanism. Here, in addition, multiple saliency units are used to produce these regions of attention. All of these saliency units have different parameter-sets. The idea is to let the population of saliency units create regions of attention, then evaluate the results with cognitive feedback and finally apply the genetic mechanism

  3. Architecture and early evolution of the Oslo Rift

    NASA Astrophysics Data System (ADS)

    Sundvoll, B.; Larsen, B. T.

    1994-12-01

    A revised assessment of architecture and pre-rift fabric connections of the Oslo Rift has been undertaken and linked to a new appraisal of observations and data related to the initial phase of the rift evolution. In addition to half-graben segmentation, accommodation zones and transfer faults are readily identified in the linking sectors between the two main grabens and between graben segments. Axial flexures are proposed between facing half-grabens. The accommodation zones were generally sites of volcanism during rifting. Pre-rift tectonic structures played an influential role in the rift location and development. The deviant N-S axis of the Vestfold graben segment is viewed as related to pre-rift structural control through faults and shear zones. This area was probably a site of Proterozoic/Palaeozoic crustal and lithospheric attenuation. Field evidence suggests that the rift started as a crustal sag with no apparent surface faulting in a flat and low-lying land at a time about 305-310 Ma. Volcanism, sub-surface sill intrusion and faulting started about simultaneously some time after the initial sag (300-305 Ma). Faulting and basaltic volcanism were initially localized to transfer faults along accommodation zones and a NNW-SSE transtensional zone along the eastern margin of the incipient Vestfold graben segment. This transtensional zone was probably created by right-lateral simple shear tracing pre-rift structures in response to a regional stress field with the tensional axis normal and the maximum compressional axis parallel to the NNE-SSW-trending rift axis.

  4. Early events in the evolution of spider silk genes.

    PubMed

    Starrett, James; Garb, Jessica E; Kuelbs, Amanda; Azubuike, Ugochi O; Hayashi, Cheryl Y

    2012-01-01

    Silk spinning is essential to spider ecology and has had a key role in the expansive diversification of spiders. Silk is composed primarily of proteins called spidroins, which are encoded by a multi-gene family. Spidroins have been studied extensively in the derived clade, Orbiculariae (orb-weavers), from the suborder Araneomorphae ('true spiders'). Orbicularians produce a suite of different silks, and underlying this repertoire is a history of duplication and spidroin gene divergence. A second class of silk proteins, Egg Case Proteins (ECPs), is known only from the orbicularian species, Lactrodectus hesperus (Western black widow). In L. hesperus, ECPs bond with tubuliform spidroins to form egg case silk fibers. Because most of the phylogenetic diversity of spiders has not been sampled for their silk genes, there is limited understanding of spidroin gene family history and the prevalence of ECPs. Silk genes have not been reported from the suborder Mesothelae (segmented spiders), which diverged from all other spiders >380 million years ago, and sampling from Mygalomorphae (tarantulas, trapdoor spiders) and basal araneomorph lineages is sparse. In comparison to orbicularians, mesotheles and mygalomorphs have a simpler silk biology and thus are hypothesized to have less diversity of silk genes. Here, we present cDNAs synthesized from the silk glands of six mygalomorph species, a mesothele, and a non-orbicularian araneomorph, and uncover a surprisingly rich silk gene diversity. In particular, we find ECP homologs in the mesothele, suggesting that ECPs were present in the common ancestor of extant spiders, and originally were not specialized to complex with tubuliform spidroins. Furthermore, gene-tree/species-tree reconciliation analysis reveals that numerous spidroin gene duplications occurred after the split between Mesothelae and Opisthothelae (Mygalomorphae plus Araneomorphae). We use the spidroin gene tree to reconstruct the evolution of amino acid compositions of

  5. Early Events in the Evolution of Spider Silk Genes

    PubMed Central

    Starrett, James; Garb, Jessica E.; Kuelbs, Amanda; Azubuike, Ugochi O.; Hayashi, Cheryl Y.

    2012-01-01

    Silk spinning is essential to spider ecology and has had a key role in the expansive diversification of spiders. Silk is composed primarily of proteins called spidroins, which are encoded by a multi-gene family. Spidroins have been studied extensively in the derived clade, Orbiculariae (orb-weavers), from the suborder Araneomorphae (‘true spiders’). Orbicularians produce a suite of different silks, and underlying this repertoire is a history of duplication and spidroin gene divergence. A second class of silk proteins, Egg Case Proteins (ECPs), is known only from the orbicularian species, Lactrodectus hesperus (Western black widow). In L. hesperus, ECPs bond with tubuliform spidroins to form egg case silk fibers. Because most of the phylogenetic diversity of spiders has not been sampled for their silk genes, there is limited understanding of spidroin gene family history and the prevalence of ECPs. Silk genes have not been reported from the suborder Mesothelae (segmented spiders), which diverged from all other spiders >380 million years ago, and sampling from Mygalomorphae (tarantulas, trapdoor spiders) and basal araneomorph lineages is sparse. In comparison to orbicularians, mesotheles and mygalomorphs have a simpler silk biology and thus are hypothesized to have less diversity of silk genes. Here, we present cDNAs synthesized from the silk glands of six mygalomorph species, a mesothele, and a non-orbicularian araneomorph, and uncover a surprisingly rich silk gene diversity. In particular, we find ECP homologs in the mesothele, suggesting that ECPs were present in the common ancestor of extant spiders, and originally were not specialized to complex with tubuliform spidroins. Furthermore, gene-tree/species-tree reconciliation analysis reveals that numerous spidroin gene duplications occurred after the split between Mesothelae and Opisthothelae (Mygalomorphae plus Araneomorphae). We use the spidroin gene tree to reconstruct the evolution of amino acid compositions

  6. Deuterostome evolution: early development in the enteropneust hemichordate, Ptychodera flava.

    PubMed

    Henry, J Q; Tagawa, K; Martindale, M Q

    2001-01-01

    Molecular and morphological comparisons indicate that the Echinodermata and Hemichordata represent closely related sister-phyla within the Deuterostomia. Much less is known about the development of the hemichordates compared to other deuterostomes. For the first time, cell lineage analyses have been carried out for an indirect-developing representative of the enteropneust hemichordates, Ptychodera flava. Single blastomeres were iontophoretically labeled with Dil at the 2- through 16-cell stages, and their fates followed through development to the tornaria larval stage. The early cleavage pattern of P. flava is similar to that of the direct-developing hemichordate, Saccoglossus kowalevskii, as well as that displayed by indirect-developing echinoids. The 16-celled embryo contains eight animal "mesomeres," four slightly larger "macromeres," and four somewhat smaller vegetal "micromeres." The first cleavage plane was not found to bear one specific relationship relative to the larval dorsoventral axis. Although individual blastomeres generate discrete clones of cells, the appearance and exact locations of these clones are variable with respect to the embryonic dorsoventral and bilateral axes. The eight animal mesomeres generate anterior (animal) ectoderm of the larva, which includes the apical organ; however, contributions to the apical organ were found to be variable as only a subset of the animal blastomeres end up contributing to its formation and this varies from embryo to embryo. The macromeres generate posterior larval ectoderm, and the vegetal micromeres form all the internal, endomesodermal tissues. These blastomere contributions are similar to those found during development of the only other hemichordate studied, the direct-developing enteropneust, S. kowalevskii. Finally, isolated blastomeres prepared at either the two- or the four-cell stage are capable of forming normal-appearing, miniature tornaria larvae. These findings indicate that the fates of these

  7. Deuterostome evolution: early development in the enteropneust hemichordate, Ptychodera flava

    NASA Technical Reports Server (NTRS)

    Henry, J. Q.; Tagawa, K.; Martindale, M. Q.

    2001-01-01

    Molecular and morphological comparisons indicate that the Echinodermata and Hemichordata represent closely related sister-phyla within the Deuterostomia. Much less is known about the development of the hemichordates compared to other deuterostomes. For the first time, cell lineage analyses have been carried out for an indirect-developing representative of the enteropneust hemichordates, Ptychodera flava. Single blastomeres were iontophoretically labeled with Dil at the 2- through 16-cell stages, and their fates followed through development to the tornaria larval stage. The early cleavage pattern of P. flava is similar to that of the direct-developing hemichordate, Saccoglossus kowalevskii, as well as that displayed by indirect-developing echinoids. The 16-celled embryo contains eight animal "mesomeres," four slightly larger "macromeres," and four somewhat smaller vegetal "micromeres." The first cleavage plane was not found to bear one specific relationship relative to the larval dorsoventral axis. Although individual blastomeres generate discrete clones of cells, the appearance and exact locations of these clones are variable with respect to the embryonic dorsoventral and bilateral axes. The eight animal mesomeres generate anterior (animal) ectoderm of the larva, which includes the apical organ; however, contributions to the apical organ were found to be variable as only a subset of the animal blastomeres end up contributing to its formation and this varies from embryo to embryo. The macromeres generate posterior larval ectoderm, and the vegetal micromeres form all the internal, endomesodermal tissues. These blastomere contributions are similar to those found during development of the only other hemichordate studied, the direct-developing enteropneust, S. kowalevskii. Finally, isolated blastomeres prepared at either the two- or the four-cell stage are capable of forming normal-appearing, miniature tornaria larvae. These findings indicate that the fates of these

  8. Early evolution of the T-box transcription factor family.

    PubMed

    Sebé-Pedrós, Arnau; Ariza-Cosano, Ana; Weirauch, Matthew T; Leininger, Sven; Yang, Ally; Torruella, Guifré; Adamski, Marcin; Adamska, Maja; Hughes, Timothy R; Gómez-Skarmeta, José Luis; Ruiz-Trillo, Iñaki

    2013-10-01

    Developmental transcription factors are key players in animal multicellularity, being members of the T-box family that are among the most important. Until recently, T-box transcription factors were thought to be exclusively present in metazoans. Here, we report the presence of T-box genes in several nonmetazoan lineages, including ichthyosporeans, filastereans, and fungi. Our data confirm that Brachyury is the most ancient member of the T-box family and establish that the T-box family diversified at the onset of Metazoa. Moreover, we demonstrate functional conservation of a homolog of Brachyury of the protist Capsaspora owczarzaki in Xenopus laevis. By comparing the molecular phenotype of C. owczarzaki Brachyury with that of homologs of early branching metazoans, we define a clear difference between unicellular holozoan and metazoan Brachyury homologs, suggesting that the specificity of Brachyury emerged at the origin of Metazoa. Experimental determination of the binding preferences of the C. owczarzaki Brachyury results in a similar motif to that of metazoan Brachyury and other T-box classes. This finding suggests that functional specificity between different T-box classes is likely achieved by interaction with alternative cofactors, as opposed to differences in binding specificity. PMID:24043797

  9. Early Evolution of Disrupted Asteroid P/2016 G1 (PANSTARRS)

    NASA Astrophysics Data System (ADS)

    Moreno, F.; Licandro, J.; Cabrera-Lavers, A.; Pozuelos, F. J.

    2016-08-01

    We present deep imaging observations of activated asteroid P/2016 G1 (PANSTARRS) using the 10.4 m Gran Telescopio Canarias (GTC) from 2016 late April to early June. The images are best interpreted as the result of a relatively short-duration event with an onset of about {350}-30+10 days before perihelion (i.e., around 2016 February 10), starting sharply and decreasing with {24}-7+10 days (HWHM). The results of the modeling imply that the emission of ∼1.7 × 107 kg of dust, if composed of particles of 1 μm to 1 cm in radius, is distributed following a power law of index ‑3 and having a geometric albedo of 0.15. A detailed fitting of a conspicuous westward feature in the head of the comet-like object indicates that a significant fraction of the dust was ejected along a privileged direction right at the beginning of the event, which suggests that the parent body has possibly suffered an impact followed by a partial or total disruption. From the limiting magnitude reachable with the instrumental setup, and assuming a geometric albedo of 0.15 for the parent body, an upper limit for the size of possible fragment debris of ∼50 m in radius is derived.

  10. Early Evolution of Disrupted Asteroid P/2016 G1 (PANSTARRS)

    NASA Astrophysics Data System (ADS)

    Moreno, F.; Licandro, J.; Cabrera-Lavers, A.; Pozuelos, F. J.

    2016-08-01

    We present deep imaging observations of activated asteroid P/2016 G1 (PANSTARRS) using the 10.4 m Gran Telescopio Canarias (GTC) from 2016 late April to early June. The images are best interpreted as the result of a relatively short-duration event with an onset of about {350}-30+10 days before perihelion (i.e., around 2016 February 10), starting sharply and decreasing with {24}-7+10 days (HWHM). The results of the modeling imply that the emission of ˜1.7 × 107 kg of dust, if composed of particles of 1 μm to 1 cm in radius, is distributed following a power law of index ‑3 and having a geometric albedo of 0.15. A detailed fitting of a conspicuous westward feature in the head of the comet-like object indicates that a significant fraction of the dust was ejected along a privileged direction right at the beginning of the event, which suggests that the parent body has possibly suffered an impact followed by a partial or total disruption. From the limiting magnitude reachable with the instrumental setup, and assuming a geometric albedo of 0.15 for the parent body, an upper limit for the size of possible fragment debris of ˜50 m in radius is derived.

  11. Modelling of the thermal evolution and differentiation of early Ceres

    NASA Astrophysics Data System (ADS)

    Neumann, Wladimir; Breuer, Doris; Spohn, Tilman

    2015-04-01

    The asteroid 1 Ceres is one of the remaining examples of the intermediate stages of planetary accretion. Studies of such protoplanetary objects provide insight into the history of the formation of Earth and other planets. One of Ceres' remarkable properties is the relatively low average bulk density of 2077±36 kg m-3[1]. Assuming a nearly chondritic composition, this low value can be explained either by the presence of a low density phase[2,3] (possibly water ice or hydrated silicates) that could have differentiated forming an icy mantle over a rocky core[2,3], or by a relatively high average porosity[4]. The shape and the moment of inertia of Ceres are consistent with both a homogeneous and a differentiated structure. In the first case Ceres would be just a large version of a common asteroid. In the second case this body could exhibit properties characteristic for a planet rather than an asteroid: presence of a core, mantle and crust, as well as a liquid ocean in the past and maybe still a thin basal ocean today. We study the evolution of a Ceres-like body via numerical modelling in order to draw conclusions about the thermal metamorphism of the interior and its present-day structure. A numerical model of an ice-silicate planetesimal, considering both water-rock and metal-silicate differentiation of Ceres is being developed. In particular, accretion from a km-sized porous seed to a Ceres-sized asteroid is considered. Further relevant processes, such as transition from amorphous to crystalline ice, melting of ice, hydrothermal convection, as well as melting and percolation of metal and silicates are included in the model. The model is suited to prioritise between the two possible structures mentioned above and to constrain the present-day state of Ceres' interior. The necessary conditions for the differentiation as well as the influence of the vital parameters, such as the accretion duration, will be discussed. [1] Thomas, C. et al. (2005) Nature, 437, 224-226. [2

  12. A new Early Permian reptile and its significance in early diapsid evolution.

    PubMed

    Reisz, Robert R; Modesto, Sean P; Scott, Diane M

    2011-12-22

    The initial stages of evolution of Diapsida (the large clade that includes not only snakes, lizards, crocodiles and birds, but also dinosaurs and numerous other extinct taxa) is clouded by an exceedingly poor Palaeozoic fossil record. Previous studies had indicated a 38 Myr gap between the first appearance of the oldest diapsid clade (Araeoscelidia), ca 304 million years ago (Ma), and that of its sister group in the Middle Permian (ca 266 Ma). Two new reptile skulls from the Richards Spur locality, Lower Permian of Oklahoma, represent a new diapsid reptile: Orovenator mayorum n. gen. et sp. A phylogenetic analysis identifies O. mayorum as the oldest and most basal member of the araeoscelidian sister group. As Richards Spur has recently been dated to 289 Ma, the new diapsid neatly spans the above gap by appearing 15 Myr after the origin of Diapsida. The presence of O. mayorum at Richards Spur, which records a diverse upland fauna, suggests that initial stages in the evolution of non-araeoscelidian diapsids may have been tied to upland environments. This hypothesis is consonant with the overall scant record for non-araeoscelidian diapsids during the Permian Period, when the well-known terrestrial vertebrate communities are preserved almost exclusively in lowland deltaic, flood plain and lacustrine sedimentary rocks. PMID:21525061

  13. Anthropoid primates from the Oligocene of Pakistan (Bugti Hills): Data on early anthropoid evolution and biogeography

    PubMed Central

    Marivaux, Laurent; Antoine, Pierre-Olivier; Baqri, Syed Rafiqul Hassan; Benammi, Mouloud; Chaimanee, Yaowalak; Crochet, Jean-Yves; de Franceschi, Dario; Iqbal, Nayyer; Jaeger, Jean-Jacques; Métais, Grégoire; Roohi, Ghazala; Welcomme, Jean-Loup

    2005-01-01

    Asian tarsiid and sivaladapid primates maintained relictual distributions in southern Asia long after the extirpation of their close Holarctic relatives near the Eocene–Oligocene boundary. We report here the discovery of amphipithecid and eosimiid primates from Oligocene coastal deposits in Pakistan that demonstrate that stem anthropoids also survived in southern Asia beyond the climatic deterioration that characterized the Eocene–Oligocene transition. These fossils provide data on temporal and paleobiogeographic aspects of early anthropoid evolution and significantly expand the record of stem anthropoid evolution in the Paleogene of South Asia. PMID:15937103

  14. Long-Term evolution of the erosion rates during Early Mars

    NASA Astrophysics Data System (ADS)

    Quantin-Nataf, C.; Craddock, R. A.; Dubuffet, F.; Lozac'h, L.; Martinot, M.

    2015-10-01

    Many Geologic features attest to the fact that liquid water was once stable on the Martian surface. The erosional processes necessary to create these features must have been supported by a climate that is much different than today. However, the evolution of these primitives conditions toward the current dry and cold Martian climate where the erosion processes are 2-3 orders in magnitude lower represents a major gap in our understanding of the evolution of Mars history. Here we document the time-dependence of the erosion rates on Mars during early Mars, period during which the erosion rates have decreased of at least one order in magnitude.

  15. Evolution of CO2 and H2O on Mars: A cold Early History?

    NASA Technical Reports Server (NTRS)

    Niles, P. B.; Michalski, J.

    2011-01-01

    The martian climate has long been thought to have evolved substantially through history from a warm and wet period to the current cold and dry conditions on the martian surface. This view has been challenged based primarily on evidence that the early Sun had a substantially reduced luminosity and that a greenhouse atmosphere would be difficult to sustain on Mars for long periods of time. In addition, the evidence for a warm, wet period of martian history is far from conclusive with many of the salient features capable of being explained by an early cold climate. An important test of the warm, wet early Mars hypothesis is the abundance of carbonates in the crust [1]. Recent high precision isotopic measurements of the martian atmosphere and discoveries of carbonates on the martian surface provide new constraints on the evolution of the martian atmosphere. This work seeks to apply these constraints to test the feasibility of the cold early scenario

  16. Early-late life trade-offs and the evolution of ageing in the wild.

    PubMed

    Lemaître, Jean-François; Berger, Vérane; Bonenfant, Christophe; Douhard, Mathieu; Gamelon, Marlène; Plard, Floriane; Gaillard, Jean-Michel

    2015-05-01

    Empirical evidence for declines in fitness components (survival and reproductive performance) with age has recently accumulated in wild populations, highlighting that the process of senescence is nearly ubiquitous in the living world. Senescence patterns are highly variable among species and current evolutionary theories of ageing propose that such variation can be accounted for by differences in allocation to growth and reproduction during early life. Here, we compiled 26 studies of free-ranging vertebrate populations that explicitly tested for a trade-off between performance in early and late life. Our review brings overall support for the presence of early-late life trade-offs, suggesting that the limitation of available resources leads individuals to trade somatic maintenance later in life for high allocation to reproduction early in life. We discuss our results in the light of two closely related theories of ageing-the disposable soma and the antagonistic pleiotropy theories-and propose that the principle of energy allocation roots the ageing process in the evolution of life-history strategies. Finally, we outline research topics that should be investigated in future studies, including the importance of natal environmental conditions in the study of trade-offs between early- and late-life performance and the evolution of sex-differences in ageing patterns. PMID:25833848

  17. Early-late life trade-offs and the evolution of ageing in the wild

    PubMed Central

    Lemaître, Jean-François; Berger, Vérane; Bonenfant, Christophe; Douhard, Mathieu; Gamelon, Marlène; Plard, Floriane; Gaillard, Jean-Michel

    2015-01-01

    Empirical evidence for declines in fitness components (survival and reproductive performance) with age has recently accumulated in wild populations, highlighting that the process of senescence is nearly ubiquitous in the living world. Senescence patterns are highly variable among species and current evolutionary theories of ageing propose that such variation can be accounted for by differences in allocation to growth and reproduction during early life. Here, we compiled 26 studies of free-ranging vertebrate populations that explicitly tested for a trade-off between performance in early and late life. Our review brings overall support for the presence of early-late life trade-offs, suggesting that the limitation of available resources leads individuals to trade somatic maintenance later in life for high allocation to reproduction early in life. We discuss our results in the light of two closely related theories of ageing—the disposable soma and the antagonistic pleiotropy theories—and propose that the principle of energy allocation roots the ageing process in the evolution of life-history strategies. Finally, we outline research topics that should be investigated in future studies, including the importance of natal environmental conditions in the study of trade-offs between early- and late-life performance and the evolution of sex-differences in ageing patterns. PMID:25833848

  18. Crustal evolution of the early earth: The role of major impacts

    NASA Technical Reports Server (NTRS)

    Frey, H.

    1979-01-01

    The role of major impact basins (such as those which formed on the moon before 4 billion years ago) is examined to determine the effects of such impacts on the early crustal evolution of the earth. Specifically addressed is the fundamental problem of what is the origin of the earth's fundamental crustal dichotomy of low density continental and high density oceanic crust and its relationship to the superficially similar highlands/maria crustal dichotomies of the moon, Mercury and Mars.

  19. Geochemical evolution of the northern plains of Mars - Early hydrosphere, carbonate development, and present morphology

    NASA Technical Reports Server (NTRS)

    Schaefer, Martha W.

    1990-01-01

    An equilibrium geochemical model of the primitive Martian atmosphere-regolith-ocean system that could have existed early in the history of Mars is developed. The results of this model are used to examine the evolution of the volatile budget of Mars and the processes occurring in the Martian ocean that may have contributed to the deposition of large carbonate beds on the northern plains. Results of this model are compared to those of the Pollack et al. (1987) model.

  20. Early Pleistocene third metacarpal from Kenya and the evolution of modern human-like hand morphology

    PubMed Central

    Ward, Carol V.; Tocheri, Matthew W.; Plavcan, J. Michael; Brown, Francis H.; Manthi, Fredrick Kyalo

    2014-01-01

    Despite discoveries of relatively complete hands from two early hominin species (Ardipithecus ramidus and Australopithecus sediba) and partial hands from another (Australopithecus afarensis), fundamental questions remain about the evolution of human-like hand anatomy and function. These questions are driven by the paucity of hand fossils in the hominin fossil record between 800,000 and 1.8 My old, a time interval well documented for the emergence and subsequent proliferation of Acheulian technology (shaped bifacial stone tools). Modern and Middle to Late Pleistocene humans share a suite of derived features in the thumb, wrist, and radial carpometacarpal joints that is noticeably absent in early hominins. Here we show that one of the most distinctive features of this suite in the Middle Pleistocene to recent human hand, the third metacarpal styloid process, was present ∼1.42 Mya in an East African hominin from Kaitio, West Turkana, Kenya. This fossil thus provides the earliest unambiguous evidence for the evolution of a key shared derived characteristic of modern human and Neandertal hand morphology and suggests that the distinctive complex of radial carpometacarpal joint features in the human hand arose early in the evolution of the genus Homo and probably in Homo erectus sensu lato. PMID:24344276

  1. Early Pleistocene third metacarpal from Kenya and the evolution of modern human-like hand morphology.

    PubMed

    Ward, Carol V; Tocheri, Matthew W; Plavcan, J Michael; Brown, Francis H; Manthi, Fredrick Kyalo

    2014-01-01

    Despite discoveries of relatively complete hands from two early hominin species (Ardipithecus ramidus and Australopithecus sediba) and partial hands from another (Australopithecus afarensis), fundamental questions remain about the evolution of human-like hand anatomy and function. These questions are driven by the paucity of hand fossils in the hominin fossil record between 800,000 and 1.8 My old, a time interval well documented for the emergence and subsequent proliferation of Acheulian technology (shaped bifacial stone tools). Modern and Middle to Late Pleistocene humans share a suite of derived features in the thumb, wrist, and radial carpometacarpal joints that is noticeably absent in early hominins. Here we show that one of the most distinctive features of this suite in the Middle Pleistocene to recent human hand, the third metacarpal styloid process, was present ∼1.42 Mya in an East African hominin from Kaitio, West Turkana, Kenya. This fossil thus provides the earliest unambiguous evidence for the evolution of a key shared derived characteristic of modern human and Neandertal hand morphology and suggests that the distinctive complex of radial carpometacarpal joint features in the human hand arose early in the evolution of the genus Homo and probably in Homo erectus sensu lato. PMID:24344276

  2. Shape Evolution of Massive Early-type Galaxies: Confirmation of Increased Disk Prevalence at z > 1

    NASA Astrophysics Data System (ADS)

    Chang, Yu-Yen; van der Wel, Arjen; Rix, Hans-Walter; Wuyts, Stijn; Zibetti, Stefano; Ramkumar, Balasubramanian; Holden, Bradford

    2013-01-01

    We use high-resolution K-band VLT/HAWK-I imaging over 0.25 deg2 to study the structural evolution of massive early-type galaxies since z ~ 2. Mass-selected samples, complete down to log(M/M ⊙) ~ 10.7 such that "typical" (L*) galaxies are included at all redshifts, are drawn from pre-existing photometric redshift surveys. We then separate the samples into different redshift slices and classify them as late- or early-type galaxies on the basis of their specific star formation rate. Axis-ratio measurements for the ~400 early-type galaxies in the redshift range 0.6 < z < 1.8 are accurate to 0.1 or better. The projected axis-ratio distributions are then compared with lower redshift samples. We find strong evidence for evolution of the population properties: early-type galaxies at z > 1 are, on average, flatter than at z < 1 and the median projected axis ratio at a fixed mass decreases with redshift. However, we also find that at all epochs z <~ 2, the most massive early-type galaxies (log(M/M ⊙) > 11.3) are the roundest, with a pronounced lack of galaxies that are flat in projection. Merging is a plausible mechanism that can explain both results: at all epochs, merging is required for early-type galaxies to grow beyond log(M/M ⊙) ~ 11.3, and all early types over time gradually and partially lose their disk-like characteristics.

  3. SHAPE EVOLUTION OF MASSIVE EARLY-TYPE GALAXIES: CONFIRMATION OF INCREASED DISK PREVALENCE AT z > 1

    SciTech Connect

    Chang, Yu-Yen; Van der Wel, Arjen; Rix, Hans-Walter; Ramkumar, Balasubramanian; Wuyts, Stijn; Zibetti, Stefano; Holden, Bradford

    2013-01-10

    We use high-resolution K-band VLT/HAWK-I imaging over 0.25 deg{sup 2} to study the structural evolution of massive early-type galaxies since z {approx} 2. Mass-selected samples, complete down to log(M/M {sub Sun }) {approx} 10.7 such that 'typical' (L*) galaxies are included at all redshifts, are drawn from pre-existing photometric redshift surveys. We then separate the samples into different redshift slices and classify them as late- or early-type galaxies on the basis of their specific star formation rate. Axis-ratio measurements for the {approx}400 early-type galaxies in the redshift range 0.6 < z < 1.8 are accurate to 0.1 or better. The projected axis-ratio distributions are then compared with lower redshift samples. We find strong evidence for evolution of the population properties: early-type galaxies at z > 1 are, on average, flatter than at z < 1 and the median projected axis ratio at a fixed mass decreases with redshift. However, we also find that at all epochs z {approx}< 2, the most massive early-type galaxies (log(M/M {sub Sun }) > 11.3) are the roundest, with a pronounced lack of galaxies that are flat in projection. Merging is a plausible mechanism that can explain both results: at all epochs, merging is required for early-type galaxies to grow beyond log(M/M {sub Sun }) {approx} 11.3, and all early types over time gradually and partially lose their disk-like characteristics.

  4. Polarization Evolution of Early Optical Afterglows of Gamma-Ray Bursts

    NASA Astrophysics Data System (ADS)

    Lan, Mi-Xiang; Wu, Xue-Feng; Dai, Zi-Gao

    2016-01-01

    The central engine and jet composition of gamma-ray bursts (GRBs) remain mysterious. Here we suggest that observations on the polarization evolution of early optical afterglows may shed light on these questions. We first study the dynamics of a reverse shock and a forward shock that are generated during the interaction of a relativistic jet and its ambient medium. The jet is likely magnetized with a globally large-scale magnetic field from the central engine. The existence of the reverse shock requires that the magnetization degree of the jet should not be high (σ ≤ 1), so that the jet is mainly composed of baryons and leptons. We then calculate the light curves and polarization evolution of early optical afterglows and find that when the polarization position angle changes by 90° during the early afterglow, the polarization degree is zero for a toroidal magnetic field but is very likely to be nonzero for an aligned magnetic field. This result would be expected to provide a probe for the central engine of GRBs because an aligned field configuration could originate from a magnetar central engine and a toroidal field configuration could be produced from a black hole via the Blandford-Znajek mechanism. Finally, for such two kinds of magnetic field configurations, we fit the observed data of the early optical afterglow of GRB 120308A equally well.

  5. The minimal kinome of Giardia lamblia illuminates early kinase evolution and unique parasite biology

    PubMed Central

    2011-01-01

    Background The major human intestinal pathogen Giardia lamblia is a very early branching eukaryote with a minimal genome of broad evolutionary and biological interest. Results To explore early kinase evolution and regulation of Giardia biology, we cataloged the kinomes of three sequenced strains. Comparison with published kinomes and those of the excavates Trichomonas vaginalis and Leishmania major shows that Giardia's 80 core kinases constitute the smallest known core kinome of any eukaryote that can be grown in pure culture, reflecting both its early origin and secondary gene loss. Kinase losses in DNA repair, mitochondrial function, transcription, splicing, and stress response reflect this reduced genome, while the presence of other kinases helps define the kinome of the last common eukaryotic ancestor. Immunofluorescence analysis shows abundant phospho-staining in trophozoites, with phosphotyrosine abundant in the nuclei and phosphothreonine and phosphoserine in distinct cytoskeletal organelles. The Nek kinase family has been massively expanded, accounting for 198 of the 278 protein kinases in Giardia. Most Neks are catalytically inactive, have very divergent sequences and undergo extensive duplication and loss between strains. Many Neks are highly induced during development. We localized four catalytically active Neks to distinct parts of the cytoskeleton and one inactive Nek to the cytoplasm. Conclusions The reduced kinome of Giardia sheds new light on early kinase evolution, and its highly divergent sequences add to the definition of individual kinase families as well as offering specific drug targets. Giardia's massive Nek expansion may reflect its distinctive lifestyle, biphasic life cycle and complex cytoskeleton. PMID:21787419

  6. Modelling magma ocean solidification and volatile outgassing during early planetary evolution.

    NASA Astrophysics Data System (ADS)

    Nikolaou, Athanasia; Tosi, Nicola; Plesa, Ana-Catalina

    2016-04-01

    The early phases of the evolution of the Earth and terrestrial planets likely included a state characterized by one or multiple vigorously convecting magma oceans. Even super earths at a close distance to their host star can presently be in a similar hot state. Understanding magma ocean's evolution can serve to better characterise terrestrial planets that have passed through such a state in their history and possibly constrain that state in our planet. However, the temporal evolution of a vigorously convecting magma ocean is poorly known due to missing constraints on the mechanical and thermal properties of the molten material and on the blanketing effect of the overlying atmosphere, which can strongly influence the heat flowing out of the planet and retard its cooling and solidification. The outgassing of volatiles with greenhouse potential is a key process that affects both aforementioned factors. Using a simple 1D model we simulate the evolution of a primitive magma ocean coupled with a grey atmosphere. The evolution of the potential temperature dictates the rate of mantle crystallization, which proceeds from the bottom upwards because of the steeper slope of the mantle adiabat compared to the melting curve. This model allows us to represent the complex physical state of simultaneous regimes of liquid and solid convection in the mantle. In future steps we are going to replace the grey atmosphere model with a more sophisticated 1D model of radiative-convective equilibrium to better represent the emissivity of the atmosphere generated by magma ocean outgassing.

  7. Water in the lunar interior: Implications for early evolution of the moon.

    NASA Astrophysics Data System (ADS)

    Goswami, Jitendranath

    2016-07-01

    Water in the lunar interior: Implications for early evolution of the moon. J. N. Goswami*, A. Basu Sarbadhikari and K. K. Marhas Physical Research Laboratory, Ahmedabad-38009 Water and other volatiles present in lunar interior can significantly affect the early evolution of the moon. Lunar volcanic glasses and in olivine hosted melt inclusions, suggest water content ranging from ~700 to 1400 ppm in the deep lunar interior (≥500 km). Apatite in lunar basalts, that sampled magma at a shallower depth (<200 km) show significant volatile zoning making it difficult to retrieve their source volatile content. We have identified and analysed apatite in Apollo 15 sample that formed at 150-200 km below the lunar surface, in a closed system and devoid of volatile zoning. The analyses of volatiles were done using a Nano-SIMs in the imaging mode and terrestrial apatite was used as standard. Water content in two apatite grains are in the range of 2200-2850 and 3400-3750 ppm, respectively; F and Cl also show nearly uniform distribution. Considering reasonable partition coefficient of water between apatite and basaltic melt, we infer values of ~ 100-160 ppm (water), 80-90 ppm (F) and 10-20 ppm (Cl) in the parent magma of 15555 that sampled a lunar depth of 150-200 km. These values are much lower than those for lunar volcanic glasses and melt inclusions trapped in them and strongly suggest a non-uniform distribution of water and other volatiles in the lunar interior. Presence of water in lunar mantle could have significantly affected the early evolution of Moon and, in particular helped in sustaining a lunar core dynamo for an extended duration and can also influence thermo-chemical processes, e.g. differential degree of melting, in different mantle source regions during the early evolutionary stages of the Moon.

  8. The Problems of Replication in the Early Stages of Evolution: Enumeration of Variants and Spatial Configurations of Replicators

    NASA Astrophysics Data System (ADS)

    Melkikh, Alexey V.

    2014-12-01

    Two main problems of replication in the early stages of evolution are discussed: the problem of exponentially large number of conformational degrees of freedom and the problem of enumeration of variants.

  9. A Burst of miRNA Innovation in the Early Evolution of Butterflies and Moths

    PubMed Central

    Quah, Shan; Hui, Jerome H.L.; Holland, Peter W.H.

    2015-01-01

    MicroRNAs (miRNAs) are involved in posttranscriptional regulation of gene expression. Because several miRNAs are known to affect the stability or translation of developmental regulatory genes, the origin of novel miRNAs may have contributed to the evolution of developmental processes and morphology. Lepidoptera (butterflies and moths) is a species-rich clade with a well-established phylogeny and abundant genomic resources, thereby representing an ideal system in which to study miRNA evolution. We sequenced small RNA libraries from developmental stages of two divergent lepidopterans, Cameraria ohridella (Horse chestnut Leafminer) and Pararge aegeria (Speckled Wood butterfly), discovering 90 and 81 conserved miRNAs, respectively, and many species-specific miRNA sequences. Mapping miRNAs onto the lepidopteran phylogeny reveals rapid miRNA turnover and an episode of miRNA fixation early in lepidopteran evolution, implying that miRNA acquisition accompanied the early radiation of the Lepidoptera. One lepidopteran-specific miRNA gene, miR-2768, is located within an intron of the homeobox gene invected, involved in insect segmental and wing patterning. We identified cubitus interruptus (ci) as a likely direct target of miR-2768, and validated this suppression using a luciferase assay system. We propose a model by which miR-2768 modulates expression of ci in the segmentation pathway and in patterning of lepidopteran wing primordia. PMID:25576364

  10. Multiple lineages of ancient CR1 retroposons shaped the early genome evolution of amniotes.

    PubMed

    Suh, Alexander; Churakov, Gennady; Ramakodi, Meganathan P; Platt, Roy N; Jurka, Jerzy; Kojima, Kenji K; Caballero, Juan; Smit, Arian F; Vliet, Kent A; Hoffmann, Federico G; Brosius, Jürgen; Green, Richard E; Braun, Edward L; Ray, David A; Schmitz, Jürgen

    2015-01-01

    Chicken repeat 1 (CR1) retroposons are long interspersed elements (LINEs) that are ubiquitous within amniote genomes and constitute the most abundant family of transposed elements in birds, crocodilians, turtles, and snakes. They are also present in mammalian genomes, where they reside as numerous relics of ancient retroposition events. Yet, despite their relevance for understanding amniote genome evolution, the diversity and evolution of CR1 elements has never been studied on an amniote-wide level. We reconstruct the temporal and quantitative activity of CR1 subfamilies via presence/absence analyses across crocodilian phylogeny and comparative analyses of 12 crocodilian genomes, revealing relative genomic stasis of retroposition during genome evolution of extant Crocodylia. Our large-scale phylogenetic analysis of amniote CR1 subfamilies suggests the presence of at least seven ancient CR1 lineages in the amniote ancestor; and amniote-wide analyses of CR1 successions and quantities reveal differential retention (presence of ancient relics or recent activity) of these CR1 lineages across amniote genome evolution. Interestingly, birds and lepidosaurs retained the fewest ancient CR1 lineages among amniotes and also exhibit smaller genome sizes. Our study is the first to analyze CR1 evolution in a genome-wide and amniote-wide context and the data strongly suggest that the ancestral amniote genome contained myriad CR1 elements from multiple ancient lineages, and remnants of these are still detectable in the relatively stable genomes of crocodilians and turtles. Early mammalian genome evolution was thus characterized by a drastic shift from CR1 prevalence to dominance and hyperactivity of L2 LINEs in monotremes and L1 LINEs in therians. PMID:25503085

  11. Multiple Lineages of Ancient CR1 Retroposons Shaped the Early Genome Evolution of Amniotes

    PubMed Central

    Suh, Alexander; Churakov, Gennady; Ramakodi, Meganathan P.; Platt, Roy N.; Jurka, Jerzy; Kojima, Kenji K.; Caballero, Juan; Smit, Arian F.; Vliet, Kent A.; Hoffmann, Federico G.; Brosius, Jürgen; Green, Richard E.; Braun, Edward L.; Ray, David A.; Schmitz, Jürgen

    2015-01-01

    Chicken repeat 1 (CR1) retroposons are long interspersed elements (LINEs) that are ubiquitous within amniote genomes and constitute the most abundant family of transposed elements in birds, crocodilians, turtles, and snakes. They are also present in mammalian genomes, where they reside as numerous relics of ancient retroposition events. Yet, despite their relevance for understanding amniote genome evolution, the diversity and evolution of CR1 elements has never been studied on an amniote-wide level. We reconstruct the temporal and quantitative activity of CR1 subfamilies via presence/absence analyses across crocodilian phylogeny and comparative analyses of 12 crocodilian genomes, revealing relative genomic stasis of retroposition during genome evolution of extant Crocodylia. Our large-scale phylogenetic analysis of amniote CR1 subfamilies suggests the presence of at least seven ancient CR1 lineages in the amniote ancestor; and amniote-wide analyses of CR1 successions and quantities reveal differential retention (presence of ancient relics or recent activity) of these CR1 lineages across amniote genome evolution. Interestingly, birds and lepidosaurs retained the fewest ancient CR1 lineages among amniotes and also exhibit smaller genome sizes. Our study is the first to analyze CR1 evolution in a genome-wide and amniote-wide context and the data strongly suggest that the ancestral amniote genome contained myriad CR1 elements from multiple ancient lineages, and remnants of these are still detectable in the relatively stable genomes of crocodilians and turtles. Early mammalian genome evolution was thus characterized by a drastic shift from CR1 prevalence to dominance and hyperactivity of L2 LINEs in monotremes and L1 LINEs in therians. PMID:25503085

  12. Lunge feeding in early marine reptiles and fast evolution of marine tetrapod feeding guilds

    PubMed Central

    Motani, Ryosuke; Chen, Xiao-hong; Jiang, Da-yong; Cheng, Long; Tintori, Andrea; Rieppel, Olivier

    2015-01-01

    Traditional wisdom holds that biotic recovery from the end-Permian extinction was slow and gradual, and was not complete until the Middle Triassic. Here, we report that the evolution of marine predator feeding guilds, and their trophic structure, proceeded faster. Marine reptile lineages with unique feeding adaptations emerged during the Early Triassic (about 248 million years ago), including the enigmatic Hupehsuchus that possessed an unusually slender mandible. A new specimen of this genus reveals a well-preserved palate and mandible, which suggest that it was a rare lunge feeder as also occurs in rorqual whales and pelicans. The diversity of feeding strategies among Triassic marine tetrapods reached their peak in the Early Triassic, soon after their first appearance in the fossil record. The diet of these early marine tetrapods most likely included soft-bodied animals that are not preserved as fossils. Early marine tetrapods most likely introduced a new trophic mechanism to redistribute nutrients to the top 10 m of the sea, where the primary productivity is highest. Therefore, a simple recovery to a Permian-like trophic structure does not explain the biotic changes seen after the Early Triassic. PMID:25754468

  13. Lunge feeding in early marine reptiles and fast evolution of marine tetrapod feeding guilds.

    PubMed

    Motani, Ryosuke; Chen, Xiao-hong; Jiang, Da-yong; Cheng, Long; Tintori, Andrea; Rieppel, Olivier

    2015-01-01

    Traditional wisdom holds that biotic recovery from the end-Permian extinction was slow and gradual, and was not complete until the Middle Triassic. Here, we report that the evolution of marine predator feeding guilds, and their trophic structure, proceeded faster. Marine reptile lineages with unique feeding adaptations emerged during the Early Triassic (about 248 million years ago), including the enigmatic Hupehsuchus that possessed an unusually slender mandible. A new specimen of this genus reveals a well-preserved palate and mandible, which suggest that it was a rare lunge feeder as also occurs in rorqual whales and pelicans. The diversity of feeding strategies among Triassic marine tetrapods reached their peak in the Early Triassic, soon after their first appearance in the fossil record. The diet of these early marine tetrapods most likely included soft-bodied animals that are not preserved as fossils. Early marine tetrapods most likely introduced a new trophic mechanism to redistribute nutrients to the top 10 m of the sea, where the primary productivity is highest. Therefore, a simple recovery to a Permian-like trophic structure does not explain the biotic changes seen after the Early Triassic. PMID:25754468

  14. A bizarre new toothed mysticete (Cetacea) from Australia and the early evolution of baleen whales

    PubMed Central

    Fitzgerald, Erich M.G

    2006-01-01

    Extant baleen whales (Cetacea, Mysticeti) are all large filter-feeding marine mammals that lack teeth as adults, instead possessing baleen, and feed on small marine animals in bulk. The early evolution of these superlative mammals, and their unique feeding method, has hitherto remained enigmatic. Here, I report a new toothed mysticete from the Late Oligocene of Australia that is more archaic than any previously described. Unlike all other mysticetes, this new whale was small, had enormous eyes and lacked derived adaptations for bulk filter-feeding. Several morphological features suggest that this mysticete was a macrophagous predator, being convergent on some Mesozoic marine reptiles and the extant leopard seal (Hydrurga leptonyx). It thus refutes the notions that all stem mysticetes were filter-feeders, and that the origins and initial radiation of mysticetes was linked to the evolution of filter-feeding. Mysticetes evidently radiated into a variety of disparate forms and feeding ecologies before the evolution of baleen or filter-feeding. The phylogenetic context of the new whale indicates that basal mysticetes were macrophagous predators that did not employ filter-feeding or echolocation, and that the evolution of characters associated with bulk filter-feeding was gradual. PMID:17015308

  15. Symbiosis in cell evolution: Life and its environment on the early earth

    NASA Technical Reports Server (NTRS)

    Margulis, L.

    1981-01-01

    The book treats cell evolution from the viewpoint of the serial endosymbiosis theory of the origin of organelles. Following a brief outline of the symbiotic theory, which holds that eukaryotes evolved by the association of free-living bacteria with a host prokaryote, the diversity of life is considered, and five kingdoms of organisms are distinguished: the prokaryotic Monera and the eukaryotic Protoctista, Animalia, Fungi and Plantae. Symbiotic and traditional direct filiation theories of cell evolution are compared. Recent observations of cell structure and biochemistry are reviewed in relation to early cell evolution, with attention given to the geological context for the origin of eukaryotic cells, the origin of major bacterial anaerobic pathways, the relationship between aerobic metabolism and atmospheric oxygen, criteria for distinguishing symbiotic organelles from those that originated by differentiation, and the major classes of eukaryotic organelles: mitochondria, cilia, microtubules, the mitotic and meiotic apparatuses, and pastids. Cell evolution during the Phanerozoic is also discussed with emphasis on the effects of life on the biosphere

  16. Evolution of domain walls in the early universe. Ph.D. Thesis - Chicago Univ.

    NASA Technical Reports Server (NTRS)

    Kawano, Lawrence

    1989-01-01

    The evolution of domain walls in the early universe is studied via 2-D computer simulation. The walls are initially configured on a triangular lattice and then released from the lattice, their evolution driven by wall curvature and by the universal expansion. The walls attain an average velocity of about 0.3c and their surface area per volume (as measured in comoving coordinates) goes down with a slope of -1 with respect to conformal time, regardless of whether the universe is matter or radiation dominated. The additional influence of vacuum pressure causes the energy density to fall away from this slope and steepen, thus allowing a situation in which domain walls can constitute a significant portion of the energy density of the universe without provoking an unacceptably large perturbation upon the microwave background.

  17. Orbital resonances and planetary accretion in the early solar system evolution

    NASA Astrophysics Data System (ADS)

    Torbett, M. V.

    1982-03-01

    The solar system, in its early evolution, is thought to have consisted of an accretion disk around a growing central protostar. The accretion disk from which the planets ultimately formed can play a significant role in the processes of planetary and solar formation. As well as leading, by thermalization of orbital motions in the disk, to bipolar flows in the T Tauri stage of stellar evolution, the disk can influence the course of planetary accumulation. By virtue of its essentially solar composition, Jupiter was formed before the accretion disk was removed. This first formed planet then gravitationally imposed a harmonic structure on the planetesimal swarm through its commensurability resonances. Accelerated growth of planetesimals in orbital resonance with Jupiter resulted in runaway growth producing planetary embryos. These embryos accelerated growth at their own resonances in a process that propagation inward and outward forming a resonant configuration of embryos.

  18. Detection of early landscape evolution through controlled experimentation, data analysis, and numerical modeling at the Landscape Evolution Observatory

    NASA Astrophysics Data System (ADS)

    Troch, Peter A.; Pangle, Luke; Niu, Guo-Yue; Dontsova, Katerina; Barron-Gafford, Greg; van Haren, Joost; Pavao-Zuckerman, Mitch

    2014-05-01

    The Landscape Evolution Observatory (LEO) at Biosphere 2-The University of Arizona consists of three identical, sloping, 333 m2 convergent landscapes inside a 5,000 m2 environmentally controlled facility. These engineered landscapes contain 1-meter depth of basaltic tephra, ground to homogenous loamy sand that will undergo physical, chemical, and mineralogical changes over many years. Each landscape contains a spatially dense sensor and sampler network capable of resolving meter-scale lateral heterogeneity and sub-meter scale vertical heterogeneity in moisture, energy and carbon states and fluxes. The density of sensors and frequency at which they can be polled allows for data collection at spatial and temporal scales that are impossible in natural field settings. Embedded solution and gas samplers allow for quantification of biogeochemical processes, and facilitate the use of chemical tracers to study water movement at very high spatial resolutions. Each ~600 metric ton landscape has load cells embedded into the structure to measure changes in total system mass with 0.05% full-scale repeatability (equivalent to less than 1 cm of precipitation). This facilitates the real time accounting of hydrological partitioning at the hillslope scale. Each hillslope is equipped with an engineered rain system capable of raining at rates between 3 and 45 mm/hr in a range of spatial patterns. The rain systems are capable of creating long-term steady state conditions or running complex simulations. The precipitation water supply storage system is flexibly designed to facilitate addition of tracers at constant or time-varying rates for any of the three hillslopes. This presentation will discuss detection of early landscape evolution in terms of hydrological, geochemical and microbial processes through controlled experimentation, data analysis, and numerical modeling during the commissioning phase of the first hillslope at LEO.

  19. A Model of Isotope Separation in Cells at the Early Stages of Evolution

    NASA Astrophysics Data System (ADS)

    Melkikh, A. V.; Bokunyaeva, A. O.

    2016-03-01

    The separation of the isotopes of certain ions can serve as an important criterion for the presence of life in the early stages of its evolution. A model of the separation of isotopes during their transport through the cell membrane is constructed. The dependence of the selection coefficient on various parameters is found. In particular, it is shown that the maximum efficiency of the transport of ions corresponds to the minimum enrichment coefficient. At the maximum enrichment, the efficiency of the transport system approaches ½. Calculated enrichment coefficients are compared with experimentally obtained values for different types of cells, and the comparison shows a qualitative agreement between these quantities.

  20. Origin of the Directed Movement of Protocells in the Early Stages of the Evolution of Life

    NASA Astrophysics Data System (ADS)

    Melkikh, Alexey V.; Chesnokova, Oksana I.

    2012-08-01

    The origin of the directed motion of protocells during the early stages of evolution was discussed. The expenditures for movement, space orientation, and reception of information about the environment were taken into consideration, and it was shown that directed movement is evolutionarily advantageous in the following cases: when opposite gradients of different resources (for example, matter and energy) are great enough and when there is a rapid change in environmental parameters. It was also shown that the advantage of directed movement strategies depends greatly on how information about the environment is obtained by a protocell.

  1. Origin of the directed movement of protocells in the early stages of the evolution of life.

    PubMed

    Melkikh, Alexey V; Chesnokova, Oksana I

    2012-08-01

    The origin of the directed motion of protocells during the early stages of evolution was discussed. The expenditures for movement, space orientation, and reception of information about the environment were taken into consideration, and it was shown that directed movement is evolutionarily advantageous in the following cases: when opposite gradients of different resources (for example, matter and energy) are great enough and when there is a rapid change in environmental parameters. It was also shown that the advantage of directed movement strategies depends greatly on how information about the environment is obtained by a protocell. PMID:22772806

  2. The hydrodynamics of aspherical planetary nebulae. II - Numerical modelling of the early evolution

    NASA Astrophysics Data System (ADS)

    Icke, Vincent; Balick, Bruce; Frank, Adam

    1992-01-01

    Initial results are presented from numerical hydrodynamic calculations of the early evolution of aspherical planetary nebulae. It is found that the interacting winds produce the customary triple discontinuity, and that the outer shock's morphology conforms with remarkable fidelity to the analytic expectations. The inner shock develops in transient fashion, due to a reflection off the equatorial belt in which the shock deflects and focuses the fast wind. The shapes of the contact discontinuity and the flow behind the leading shock indicate two qualitatively distinct patterns.

  3. Insights into the early evolution of animal calcium signaling machinery: A unicellular point of view

    PubMed Central

    Cai, Xinjiang; Wang, Xiangbing; Patel, Sandip; Clapham, David E.

    2014-01-01

    The basic principles of Ca2+ regulation emerged early in prokaryotes. Ca2+ signaling acquired more extensive and varied functions when life evolved into multicellular eukaryotes with intracellular organelles. Animals, fungi and plants display differences in the mechanisms that control cytosolic Ca2+ concentrations. The aim of this review is to examine recent findings from comparative genomics of Ca2+ signaling molecules in close unicellular relatives of animals and in common unicellular ancestors of animals and fungi. Also discussed are the evolution and origins of the sperm-specific CatSper channel complex, cation/Ca2+ exchangers and four-domain voltage-gated Ca2+ channels. Newly identified evolutionary evidence suggests that the distinct Ca2+ signaling machineries in animals, plants and fungi likely originated from an ancient Ca2+ signaling machinery prior to early eukaryotic radiation. PMID:25498309

  4. DEVIATIONS FROM THE SCHMIDT-KENNICUTT RELATIONS DURING EARLY GALAXY EVOLUTION

    SciTech Connect

    Papadopoulos, Padelis P.; Pelupessy, Federico I.

    2010-07-10

    We utilize detailed time-varying models of the coupled evolution of stars and the H I, H{sub 2}, and CO-bright H{sub 2} gas phases in galaxy-sized numerical simulations to explore the evolution of gas-rich and/or metal-poor systems, which are expected to be numerous in the early universe. The inclusion of the CO-bright H{sub 2} gas phase and the realistic rendering of star formation as an H{sub 2}-regulated process (and the new feedback processes that this entails) allow the most realistic tracking of strongly evolving galaxies and much better comparison with observations. We find that while galaxies eventually settle into states conforming to the Schmidt-Kennicutt (S-K) relations, significant and systematic deviations of their star formation rates (SFRs) from the latter occur, and are especially pronounced and prolonged for metal-poor systems. The largest such deviations occur for gas-rich galaxies during not only the early evolutionary stages but also during brief periods at later stages. Given that gas-rich and/or metal-poor states of present-epoch galaxies are expected in the early universe while a much larger number of mergers frequently reset non-isolated systems to gas-rich states, even brief periods of sustained deviations of their SFRs from those expected from the S-K relations may come to characterize significant periods of their stellar mass built-up. This indicates potentially serious limitations of S-K-type relations as reliable sub-grid elements of star formation physics in simulations of structure formation in the early universe. We anticipate that galaxies with marked deviations from the S-K relations will be found at high redshifts as unbiased inventories of total gas mass become possible with ALMA and the EVLA.

  5. Early-state damage detection, characterization, and evolution using high-resolution computed tomography

    NASA Astrophysics Data System (ADS)

    Grandin, Robert John

    Safely using materials in high performance applications requires adequately understanding the mechanisms which control the nucleation and evolution of damage. Most of a material's operational life is spent in a state with noncritical damage, and, for example in metals only a small portion of its life falls within the classical Paris Law regime of crack growth. Developing proper structural health and prognosis models requires understanding the behavior of damage in these early stages within the material's life, and this early-stage damage occurs on length scales at which the material may be considered "granular'' in the sense that the discrete regions which comprise the whole are large enough to require special consideration. Material performance depends upon the characteristics of the granules themselves as well as the interfaces between granules. As a result, properly studying early-stage damage in complex, granular materials requires a means to characterize changes in the granules and interfaces. The granular-scale can range from tenths of microns in ceramics, to single microns in fiber-reinforced composites, to tens of millimeters in concrete. The difficulty of direct-study is often overcome by exhaustive testing of macro-scale damage caused by gross material loads and abuse. Such testing, for example optical or electron microscopy, destructive and further, is costly when used to study the evolution of damage within a material and often limits the study to a few snapshots. New developments in high-resolution computed tomography (HRCT) provide the necessary spatial resolution to directly image the granule length-scale of many materials. Successful application of HRCT with fiber-reinforced composites, however, requires extending the HRCT performance beyond current limits. This dissertation will discuss improvements made in the field of CT reconstruction which enable resolutions to be pushed to the point of being able to image the fiber-scale damage structures and

  6. Early Cretaceous mammal from North America and the evolution of marsupial dental characters.

    PubMed Central

    Cifelli, R L

    1993-01-01

    A mammal from the Early Cretaceous of the western United States, represented by a lower jaw exceptional in its completeness, presents unambiguous evidence of postcanine dental formula in an Early Cretaceous marsupial-like mammal, and prompts a reconsideration of the early evolution of marsupial dental characters. A marsupial postcanine dental formula (three premolars and four molars) and several marsupial-like features of the lower molars are present in the new taxon, but a hallmark specialization of marsupials (twinning of the hypoconulid and entoconid on lower molars) is lacking. This, coupled with recent evidence from the Late Cretaceous of the western United States, suggests that the distinctive marsupial dental formula evolved prior to the most characteristic specialization of lower molars and that apomorphies presumed to be diagnostic of the upper molars (such as auxiliary stylar cusps) were relatively more recent developments in marsupial history. Dental evidence supports the monophyly of higher (tribosphenic) mammals and suggests that the predominantly Old World Deltatheroida, recently proposed as a sister taxon to marsupials, represents a primitive and unrelated group of higher mammals; by this interpretation, early marsupials and their presumed close relatives are restricted to North America. This, together with the hypothesized relationships of South American/Australian marsupials (in the context of the North American Cretaceous radiation) and evidence from the fossil record of South America, in turn supports a North American origin for the group. Images Fig. 1 PMID:8415715

  7. Early evolution of the angiosperm clade Asteraceae in the Cretaceous of Antarctica.

    PubMed

    Barreda, Viviana D; Palazzesi, Luis; Tellería, Maria C; Olivero, Eduardo B; Raine, J Ian; Forest, Félix

    2015-09-01

    The Asteraceae (sunflowers and daisies) are the most diverse family of flowering plants. Despite their prominent role in extant terrestrial ecosystems, the early evolutionary history of this family remains poorly understood. Here we report the discovery of a number of fossil pollen grains preserved in dinosaur-bearing deposits from the Late Cretaceous of Antarctica that drastically pushes back the timing of assumed origin of the family. Reliably dated to ∼76-66 Mya, these specimens are about 20 million years older than previously known records for the Asteraceae. Using a phylogenetic approach, we interpreted these fossil specimens as members of an extinct early diverging clade of the family, associated with subfamily Barnadesioideae. Based on a molecular phylogenetic tree calibrated using fossils, including the ones reported here, we estimated that the most recent common ancestor of the family lived at least 80 Mya in Gondwana, well before the thermal and biogeographical isolation of Antarctica. Most of the early diverging lineages of the family originated in a narrow time interval after the K/P boundary, 60-50 Mya, coinciding with a pronounced climatic warming during the Late Paleocene and Early Eocene, and the scene of a dramatic rise in flowering plant diversity. Our age estimates reduce earlier discrepancies between the age of the fossil record and previous molecular estimates for the origin of the family, bearing important implications in the evolution of flowering plants in general. PMID:26261324

  8. Early evolution of the angiosperm clade Asteraceae in the Cretaceous of Antarctica

    PubMed Central

    Barreda, Viviana D.; Palazzesi, Luis; Tellería, Maria C.; Olivero, Eduardo B.; Raine, J. Ian; Forest, Félix

    2015-01-01

    The Asteraceae (sunflowers and daisies) are the most diverse family of flowering plants. Despite their prominent role in extant terrestrial ecosystems, the early evolutionary history of this family remains poorly understood. Here we report the discovery of a number of fossil pollen grains preserved in dinosaur-bearing deposits from the Late Cretaceous of Antarctica that drastically pushes back the timing of assumed origin of the family. Reliably dated to ∼76–66 Mya, these specimens are about 20 million years older than previously known records for the Asteraceae. Using a phylogenetic approach, we interpreted these fossil specimens as members of an extinct early diverging clade of the family, associated with subfamily Barnadesioideae. Based on a molecular phylogenetic tree calibrated using fossils, including the ones reported here, we estimated that the most recent common ancestor of the family lived at least 80 Mya in Gondwana, well before the thermal and biogeographical isolation of Antarctica. Most of the early diverging lineages of the family originated in a narrow time interval after the K/P boundary, 60–50 Mya, coinciding with a pronounced climatic warming during the Late Paleocene and Early Eocene, and the scene of a dramatic rise in flowering plant diversity. Our age estimates reduce earlier discrepancies between the age of the fossil record and previous molecular estimates for the origin of the family, bearing important implications in the evolution of flowering plants in general. PMID:26261324

  9. End-Devonian extinction and a bottleneck in the early evolution of modern jawed vertebrates

    PubMed Central

    Sallan, Lauren Cole; Coates, Michael I.

    2010-01-01

    The Devonian marks a critical stage in the early evolution of vertebrates: It opens with an unprecedented diversity of fishes and closes with the earliest evidence of limbed tetrapods. However, the latter part of the Devonian has also been characterized as a period of global biotic crisis marked by two large extinction pulses: a “Big Five” mass extinction event at the Frasnian-Famennian stage boundary (374 Ma) and the less well-documented Hangenberg event some 15 million years later at the Devonian-Carboniferous boundary (359 Ma). Here, we report the results of a wide-ranging analysis of the impact of these events on early vertebrate evolution, which was obtained from a database of vertebrate occurrences sampling over 1,250 taxa from 66 localities spanning Givetian to Serpukhovian stages (391 to 318 Ma). We show that major vertebrate clades suffered acute and systematic effects centered on the Hangenberg extinction involving long-term losses of over 50% of diversity and the restructuring of vertebrate ecosystems worldwide. Marine and nonmarine faunas were equally affected, precluding the existence of environmental refugia. The subsequent recovery of previously diverse groups (including placoderms, sarcopterygian fish, and acanthodians) was minimal. Tetrapods, actinopterygians, and chondrichthyans, all scarce within the Devonian, undergo large diversification events in the aftermath of the extinction, dominating all subsequent faunas. The Hangenberg event represents a previously unrecognized bottleneck in the evolutionary history of vertebrates as a whole and a historical contingency that shaped the roots of modern biodiversity. PMID:20479258

  10. End-Devonian extinction and a bottleneck in the early evolution of modern jawed vertebrates.

    PubMed

    Sallan, Lauren Cole; Coates, Michael I

    2010-06-01

    The Devonian marks a critical stage in the early evolution of vertebrates: It opens with an unprecedented diversity of fishes and closes with the earliest evidence of limbed tetrapods. However, the latter part of the Devonian has also been characterized as a period of global biotic crisis marked by two large extinction pulses: a "Big Five" mass extinction event at the Frasnian-Famennian stage boundary (374 Ma) and the less well-documented Hangenberg event some 15 million years later at the Devonian-Carboniferous boundary (359 Ma). Here, we report the results of a wide-ranging analysis of the impact of these events on early vertebrate evolution, which was obtained from a database of vertebrate occurrences sampling over 1,250 taxa from 66 localities spanning Givetian to Serpukhovian stages (391 to 318 Ma). We show that major vertebrate clades suffered acute and systematic effects centered on the Hangenberg extinction involving long-term losses of over 50% of diversity and the restructuring of vertebrate ecosystems worldwide. Marine and nonmarine faunas were equally affected, precluding the existence of environmental refugia. The subsequent recovery of previously diverse groups (including placoderms, sarcopterygian fish, and acanthodians) was minimal. Tetrapods, actinopterygians, and chondrichthyans, all scarce within the Devonian, undergo large diversification events in the aftermath of the extinction, dominating all subsequent faunas. The Hangenberg event represents a previously unrecognized bottleneck in the evolutionary history of vertebrates as a whole and a historical contingency that shaped the roots of modern biodiversity. PMID:20479258

  11. Early Evolution of Earth's Geochemical Cycle and Biosphere: Implications for Mars Exobiology

    NASA Technical Reports Server (NTRS)

    DesMarais, David J.; Chang, Sherwood (Technical Monitor)

    1997-01-01

    Carbon (C) has played multiple key roles for life and its environment. C has formed organics, greenhouse gases, aquatic pH buffers, redox buffers, and magmatic constituents affecting plutonism and volcanism. These roles interacted across a network of reservoirs and processes known as the biogeochemical C cycle. Changes in the cycle over geologic time were driven by increasing solar luminosity, declining planetary heat flow, and continental and biological evolution. The early Archean C cycle was dominated by hydrothermal alteration of crustal rocks and by thermal emanations of CO2 and reduced species (eg., H2, Fe(2+) and sulfides). Bioorganic synthesis was achieved by nonphotosynthetic CO2-fixing bacteria (chemoautotrophs) and, possibly, bacteria (organotrophs) utilizing any available nonbiological organic C. Responding both to abundant solar energy and to a longterm decline in thermal sources of chemical energy and reducing power, the blaspheme first developed anoxygenic photosynthesis, then, ultimately, oxygenic photosynthesis. O2-photosynthesis played a central role in transforming the ancient environment and blaspheme to the modem world. The geochemical C cycles of early Earth and Mars were quite similar. The principal differences between the modem C cycles of these planets arose during the later evolution of their heat flows, crusts, atmospheres and, perhaps, their blasphemes.

  12. The evolution of early cellular systems viewed through the lens of biological interactions

    PubMed Central

    Poole, Anthony M.; Lundin, Daniel; Rytkönen, Kalle T.

    2015-01-01

    The minimal cell concept represents a pragmatic approach to the question of how few genes are required to run a cell. This is a helpful way to build a parts-list, and has been more successful than attempts to deduce a minimal gene set for life by inferring the gene repertoire of the last universal common ancestor, as few genes trace back to this hypothetical ancestral state. However, the study of minimal cellular systems is the study of biological outliers where, by practical necessity, coevolutionary interactions are minimized or ignored. In this paper, we consider the biological context from which minimal genomes have been removed. For instance, some of the most reduced genomes are from endosymbionts and are the result of coevolutionary interactions with a host; few such organisms are “free-living.” As few, if any, biological systems exist in complete isolation, we expect that, as with modern life, early biological systems were part of an ecosystem, replete with organismal interactions. We favor refocusing discussions of the evolution of cellular systems on processes rather than gene counts. We therefore draw a distinction between a pragmatic minimal cell (an interesting engineering problem), a distributed genome (a system resulting from an evolutionary transition involving more than one cell) and the looser coevolutionary interactions that are ubiquitous in ecosystems. Finally, we consider the distributed genome and coevolutionary interactions between genomic entities in the context of early evolution. PMID:26539175

  13. Evolution of Network Synchronization during Early Epileptogenesis Parallels Synaptic Circuit Alterations

    PubMed Central

    Lillis, Kyle P.; Wang, Zemin; Mail, Michelle; Zhao, Grace Q.; Berdichevsky, Yevgeny; Bacskai, Brian

    2015-01-01

    In secondary epilepsy, a seizure-prone neural network evolves during the latent period between brain injury and the onset of spontaneous seizures. The nature of the evolution is largely unknown, and even its completeness at the onset of seizures has recently been challenged by measures of gradually decreasing intervals between subsequent seizures. Sequential calcium imaging of neuronal activity, in the pyramidal cell layer of mouse hippocampal in vitro preparations, during early post-traumatic epileptogenesis demonstrated rapid increases in the fraction of neurons that participate in interictal activity. This was followed by more gradual increases in the rate at which individual neurons join each developing seizure, the pairwise correlation of neuronal activities as a function of the distance separating the pair, and network-wide measures of functional connectivity. These data support the continued evolution of synaptic connectivity in epileptic networks beyond the latent period: early seizures occur when recurrent excitatory pathways are largely polysynaptic, while ongoing synaptic remodeling after the onset of epilepsy enhances intranetwork connectivity as well as the onset and spread of seizure activity. PMID:26156993

  14. Evolution of Network Synchronization during Early Epileptogenesis Parallels Synaptic Circuit Alterations.

    PubMed

    Lillis, Kyle P; Wang, Zemin; Mail, Michelle; Zhao, Grace Q; Berdichevsky, Yevgeny; Bacskai, Brian; Staley, Kevin J

    2015-07-01

    In secondary epilepsy, a seizure-prone neural network evolves during the latent period between brain injury and the onset of spontaneous seizures. The nature of the evolution is largely unknown, and even its completeness at the onset of seizures has recently been challenged by measures of gradually decreasing intervals between subsequent seizures. Sequential calcium imaging of neuronal activity, in the pyramidal cell layer of mouse hippocampal in vitro preparations, during early post-traumatic epileptogenesis demonstrated rapid increases in the fraction of neurons that participate in interictal activity. This was followed by more gradual increases in the rate at which individual neurons join each developing seizure, the pairwise correlation of neuronal activities as a function of the distance separating the pair, and network-wide measures of functional connectivity. These data support the continued evolution of synaptic connectivity in epileptic networks beyond the latent period: early seizures occur when recurrent excitatory pathways are largely polysynaptic, while ongoing synaptic remodeling after the onset of epilepsy enhances intranetwork connectivity as well as the onset and spread of seizure activity. PMID:26156993

  15. Molecular Evolution of Aminoacyl tRNA Synthetase Proteins in the Early History of Life

    NASA Astrophysics Data System (ADS)

    Fournier, Gregory P.; Andam, Cheryl P.; Alm, Eric J.; Gogarten, J. Peter

    2011-12-01

    Aminoacyl-tRNA synthetases (aaRS) consist of several families of functionally conserved proteins essential for translation and protein synthesis. Like nearly all components of the translation machinery, most aaRS families are universally distributed across cellular life, being inherited from the time of the Last Universal Common Ancestor (LUCA). However, unlike the rest of the translation machinery, aaRS have undergone numerous ancient horizontal gene transfers, with several independent events detected between domains, and some possibly involving lineages diverging before the time of LUCA. These transfers reveal the complexity of molecular evolution at this early time, and the chimeric nature of genomes within cells that gave rise to the major domains. Additionally, given the role of these protein families in defining the amino acids used for protein synthesis, sequence reconstruction of their pre-LUCA ancestors can reveal the evolutionary processes at work in the origin of the genetic code. In particular, sequence reconstructions of the paralog ancestors of isoleucyl- and valyl- RS provide strong empirical evidence that at least for this divergence, the genetic code did not co-evolve with the aaRSs; rather, both amino acids were already part of the genetic code before their cognate aaRSs diverged from their common ancestor. The implications of this observation for the early evolution of RNA-directed protein biosynthesis are discussed.

  16. Early Thermal Evolution of Planetesimals and Its Impact on Processing and Dating of Meteoritic Material

    NASA Astrophysics Data System (ADS)

    Gail, H.-P.; Trieloff, M.; Breuer, D.; Spohn, T.

    Radioisotopic ages for meteorites and their components provide constraints on the evolution of small bodies: timescales of accretion, thermal and aqueous metamorphism, differentiation, cooling, and impact metamorphism. Realizing that the decay heat of short-lived nuclides (e.g., 26Al, 60Fe) was the main heat source driving differentiation and metamorphism, thermal modeling of small bodies is of the utmost importance to set individual meteorite age data into the general context of the thermal evolution of their parent bodies, and to derive general conclusions about the nature of planetary building blocks in the early solar system. As a general result, modeling easily explains that iron meteorites are older than chondrites, as early formed planetesimals experienced a higher concentration of short-lived nuclides and more severe heating. However, core formation processes may also extend to 10 million years (m.y.) after the formation of calcium-aluminum-rich inclusions (CAIs). A general effect of the porous nature of the starting material is that relatively small bodies (less than a few kilometers) will also differentiate if they form within 2 m.y. after CAIs. A particular interesting feature to be explored is the possibility that some chondrites may derive from the outer undifferentiated layers of asteroids that are differentiated in their interiors. This could explain the presence of remnant magnetization in some chondrites due to a planetary magnetic field.

  17. Genome of Acanthamoeba castellanii highlights extensive lateral gene transfer and early evolution of tyrosine kinase signaling

    PubMed Central

    2013-01-01

    Background The Amoebozoa constitute one of the primary divisions of eukaryotes, encompassing taxa of both biomedical and evolutionary importance, yet its genomic diversity remains largely unsampled. Here we present an analysis of a whole genome assembly of Acanthamoeba castellanii (Ac) the first representative from a solitary free-living amoebozoan. Results Ac encodes 15,455 compact intron-rich genes, a significant number of which are predicted to have arisen through inter-kingdom lateral gene transfer (LGT). A majority of the LGT candidates have undergone a substantial degree of intronization and Ac appears to have incorporated them into established transcriptional programs. Ac manifests a complex signaling and cell communication repertoire, including a complete tyrosine kinase signaling toolkit and a comparable diversity of predicted extracellular receptors to that found in the facultatively multicellular dictyostelids. An important environmental host of a diverse range of bacteria and viruses, Ac utilizes a diverse repertoire of predicted pattern recognition receptors, many with predicted orthologous functions in the innate immune systems of higher organisms. Conclusions Our analysis highlights the important role of LGT in the biology of Ac and in the diversification of microbial eukaryotes. The early evolution of a key signaling facility implicated in the evolution of metazoan multicellularity strongly argues for its emergence early in the Unikont lineage. Overall, the availability of an Ac genome should aid in deciphering the biology of the Amoebozoa and facilitate functional genomic studies in this important model organism and environmental host. PMID:23375108

  18. Sibling cooperation in earwig families provides insights into the early evolution of social life.

    PubMed

    Falk, Joachim; Wong, Janine W Y; Kölliker, Mathias; Meunier, Joël

    2014-04-01

    The evolutionary transition from solitary to social life is driven by direct and indirect fitness benefits of social interactions. Understanding the conditions promoting the early evolution of social life therefore requires identification of these benefits in nonderived social systems, such as animal families where offspring are mobile and able to disperse and will survive independently. Family life is well known to provide benefits to offspring through parental care, but research on sibling interactions generally focused on fitness costs to offspring due to competitive behaviors. Here we show experimentally that sibling interactions also reflect cooperative behaviors in the form of food sharing in nonderived families of the European earwig, Forficula auricularia. Food ingested by individual offspring was transferred to their siblings through mouth-to-anus contacts and active allo-coprophagy. These transfers occurred in both the presence and the absence of the tending mothers, even though the direct contact with the mothers limited sibling food sharing. Neither food deprivation or relatedness influenced the total amount of transferred food, but relatedness affected frass release and the behavioral mechanisms mediating food sharing. Related offspring obtained food predominately through allo-coprophagy, whereas unrelated offspring obtained food through mouth-to-anus contacts. Overall, this study emphasizes that sibling cooperation may be a key process promoting the early evolution of social life. PMID:24642498

  19. The chemical evolution in the early phases of massive star formation

    NASA Astrophysics Data System (ADS)

    Gerner, Thomas; Beuther, Henrik; Semenov, Dmitry; Linz, Hendrik; Vasyunina, Tatiana; Dullemond, Cornelis; Bihr, Simon; Henning, Thomas

    2013-07-01

    Understanding the chemical evolution of young (high-mass) star-forming regions is a central topic in star formation research. The chemistry is employed as a unique tool: 1) to investigate the underlying physical processes and 2) to characterize the evolution of the chemical composition. With these aims in mind, we observed a sample of 59 high-mass star-forming regions at different evolutionary stages varying from the early starless phase of Infrared Dark Clouds (IRDC) to High Mass Protostellar Objects (HMPO) to Hot Molecular Cores (HMC) and, finally, Ultra Compact HII regions (UCHII) at 1mm and 3mm with the IRAM 30m telescope. We determined their large-scale chemical abundances and column densities and found that the chemical composition evolves along with the evolutionary stages. We modeled the chemical evolution in these environments, using a 1D physical model where density and temperature vary from stage to stage coupled with an advanced gas-grain chemical model. By varying the temperature and density structure the best-fit chi-square values of all the relevant parameters were derived. A satisfying overall agreement between observed and modeled column densities for most of the molecules in all evolutionary stages was obtained. In addition the best-fit model provided chemical ages for each phase.

  20. Scientific Goals of SPICA for Galaxy Formation and Evolution in Early Universe

    NASA Astrophysics Data System (ADS)

    Ichikawa, Takashi; Task Force, Spica; Spica Science Team

    2009-12-01

    We review the scientific goals of SPICA for galaxy formation and evolution in the early Universe, along with Japanese activities defining the goals and the specification of the relevant instruments. The main targets are: (1) discovery of first generation objects (Pop III stars) at the reionization epoch, (2) the origin of the cosmic farinfrared background and its fluctuation, (3) the star formation history of dusty galaxies and their contribution to stellar-mass assembly over the cosmic time, (4) the role of super-massive black holes in galaxy evolution, and (5) the effects of environment on galaxy evolution in cluster of galaxies and large scale structures at the high-z Universe. The Japanese community for optical and infrared astronomy has organized a dedicated team for SPICA (SPICA Task Force, SFT). STF is playing a central role in defining the scientific capabilities of SPICA and in supporting the development of SPICA instruments: a large-format MIR camera, MIR spectrometers, and a high contrast photometric and spectroscopic MIR coronagraph.

  1. The role of gas in the evolution of early type galaxies

    NASA Astrophysics Data System (ADS)

    Donovan, Jennifer L.

    Early-type galaxies continue to surprise us. Far from being the uniformly "red and dead" systems they were long believed to be, many of these galaxies are now known to exhibit significant amounts of neutral and molecular gas and even to host recent star formation. The presence of these features provides clues regarding the evolution of these galaxies; any successful theory of galaxy evolution must address how these massive systems have reached the present day in their present form. In this thesis, we study the role of gas in the evolution of early-type galaxies in several ways. We address the hypothesis that early types can grow via dissipationless, or gasless, mergers by studying the viability of a set of optical criteria for selecting remnants of this kind. We find that selecting "dry" mergers on the basis of their optical colors and magnitudes is not sufficient to ensure that they do not have gas or host recent star formation, implying that samples selected in this way may not be truly "dry". We next present an in-depth study of an example of such a "not-dry" system: ESO 381-47, an early-type galaxy which is embedded in a massive HI structure and is surrounded by a ring of recent star formation. For this system, which in optical light appears to be a normal early-type galaxy consisting of ancient stellar populations, rejuvenation is occurring in its outer parts. We discuss several possible triggers for the recent star formation within the HI disk. To address how common this phenomenon may be, we compile a complete, volume- limited sample of early-type galaxies and observe their ultraviolet properties. HI data is available for a subset of this sample, and for the first time, we are able to search for pockets of low-level star formation within the neutral gas around early-type galaxies. We find a correlation between the presence of HI and low-level near-ultraviolet emission. We also compare the colors and magnitudes of resolved "blobs" of far-ultraviolet emission

  2. Computer simulation on the cooperation of functional molecules during the early stages of evolution.

    PubMed

    Ma, Wentao; Hu, Jiming

    2012-01-01

    It is very likely that life began with some RNA (or RNA-like) molecules, self-replicating by base-pairing and exhibiting enzyme-like functions that favored the self-replication. Different functional molecules may have emerged by favoring their own self-replication at different aspects. Then, a direct route towards complexity/efficiency may have been through the coexistence/cooperation of these molecules. However, the likelihood of this route remains quite unclear, especially because the molecules would be competing for limited common resources. By computer simulation using a Monte-Carlo model (with "micro-resolution" at the level of nucleotides and membrane components), we show that the coexistence/cooperation of these molecules can occur naturally, both in a naked form and in a protocell form. The results of the computer simulation also lead to quite a few deductions concerning the environment and history in the scenario. First, a naked stage (with functional molecules catalyzing template-replication and metabolism) may have occurred early in evolution but required high concentration and limited dispersal of the system (e.g., on some mineral surface); the emergence of protocells enabled a "habitat-shift" into bulk water. Second, the protocell stage started with a substage of "pseudo-protocells", with functional molecules catalyzing template-replication and metabolism, but still missing the function involved in the synthesis of membrane components, the emergence of which would lead to a subsequent "true-protocell" substage. Third, the initial unstable membrane, composed of prebiotically available fatty acids, should have been superseded quite early by a more stable membrane (e.g., composed of phospholipids, like modern cells). Additionally, the membrane-takeover probably occurred at the transition of the two substages of the protocells. The scenario described in the present study should correspond to an episode in early evolution, after the emergence of single

  3. Major transitions in the evolution of early land plants: a bryological perspective.

    PubMed

    Ligrone, Roberto; Duckett, Jeffrey G; Renzaglia, Karen S

    2012-04-01

    Background Molecular phylogeny has resolved the liverworts as the earliest-divergent clade of land plants and mosses as the sister group to hornworts plus tracheophytes, with alternative topologies resolving the hornworts as sister to mosses plus tracheophytes less well supported. The tracheophytes plus fossil plants putatively lacking lignified vascular tissue form the polysporangiophyte clade. Scope This paper reviews phylogenetic, developmental, anatomical, genetic and paleontological data with the aim of reconstructing the succession of events that shaped major land plant lineages. Conclusions Fundamental land plant characters primarily evolved in the bryophyte grade, and hence the key to a better understanding of the early evolution of land plants is in bryophytes. The last common ancestor of land plants was probably a leafless axial gametophyte bearing simple unisporangiate sporophytes. Water-conducting tissue, if present, was restricted to the gametophyte and presumably consisted of perforate cells similar to those in the early-divergent bryophytes Haplomitrium and Takakia. Stomata were a sporophyte innovation with the possible ancestral functions of producing a transpiration-driven flow of water and solutes from the parental gametophyte and facilitating spore separation before release. Stomata in mosses, hornworts and polysporangiophytes are viewed as homologous, and hence these three lineages are collectively referred to as the 'stomatophytes'. An indeterminate sporophyte body (the sporophyte shoot) developing from an apical meristem was the key innovation in polysporangiophytes. Poikilohydry is the ancestral condition in land plants; homoiohydry evolved in the sporophyte of polysporangiophytes. Fungal symbiotic associations ancestral to modern arbuscular mycorrhizas evolved in the gametophytic generation before the separation of major present-living lineages. Hydroids are imperforate water-conducting cells specific to advanced mosses. Xylem vascular cells

  4. Primitive Early Eocene bat from Wyoming and the evolution of flight and echolocation.

    PubMed

    Simmons, Nancy B; Seymour, Kevin L; Habersetzer, Jörg; Gunnell, Gregg F

    2008-02-14

    Bats (Chiroptera) represent one of the largest and most diverse radiations of mammals, accounting for one-fifth of extant species. Although recent studies unambiguously support bat monophyly and consensus is rapidly emerging about evolutionary relationships among extant lineages, the fossil record of bats extends over 50 million years, and early evolution of the group remains poorly understood. Here we describe a new bat from the Early Eocene Green River Formation of Wyoming, USA, with features that are more primitive than seen in any previously known bat. The evolutionary pathways that led to flapping flight and echolocation in bats have been in dispute, and until now fossils have been of limited use in documenting transitions involved in this marked change in lifestyle. Phylogenetically informed comparisons of the new taxon with other bats and non-flying mammals reveal that critical morphological and functional changes evolved incrementally. Forelimb anatomy indicates that the new bat was capable of powered flight like other Eocene bats, but ear morphology suggests that it lacked their echolocation abilities, supporting a 'flight first' hypothesis for chiropteran evolution. The shape of the wings suggests that an undulating gliding-fluttering flight style may be primitive for bats, and the presence of a long calcar indicates that a broad tail membrane evolved early in Chiroptera, probably functioning as an additional airfoil rather than as a prey-capture device. Limb proportions and retention of claws on all digits indicate that the new bat may have been an agile climber that employed quadrupedal locomotion and under-branch hanging behaviour. PMID:18270539

  5. HAZMAT I: The Evolution of Far- and Near-UV Emission from Early M Stars

    NASA Astrophysics Data System (ADS)

    Shkolnik, Evgenya; Barman, T. S.; Peacock, S.

    2014-01-01

    With the recent discoveries of several super-earths orbiting M dwarfs well within their habitable zones (0.1 to 0.4 AU), and with many more such planets to come, it is critical to assess the evolution of the high-energy radiation environment of these systems. We have begun the HAZMAT (Habitable Zones and M dwarf Activity across Time) program by first measuring the drop in near-UV and far-UV flux in early M stars from 10 Myr to several Gyr using photometry from NASA's Galaxy Evolution Explorer (GALEX). We focus this study on the confirmed low-mass members of nearby young moving groups, the Hyades cluster, and old field stars. We show a relatively slow decline in UV flux up until at least 650 Myr with a sharper drop in the old M dwarfs. Yet without confirmed M dwarfs in nearby star clusters with ages of 1-2 Gyr, mapping the precise evolution at these older ages is not currently possible. The UV data also provide much-needed constraints to M dwarf upper-atmosphere models, which are insufficient for predicting UV emission from M dwarfs. Our analysis will produce empirically-motivated chromospheric profiles for the young and old M stars, which can then be used to predict the extreme-UV fluxes most critical to the evolution of a planetary atmosphere. The HAZMAT program is the first comprehensive study of the UV history of M stars, and will ultimately tell us if a planet in the canonical habitable zone can indeed be habitable.

  6. Dark-matter halos and evolution of high-z early-type galaxies

    NASA Astrophysics Data System (ADS)

    Koopmans, Leon

    2004-07-01

    Gravitational lensing and stellar dynamics provide two complementary methods to determine the mass distribution and evolution of luminous and dark-matter in early-type {E/S0} galaxies. The combined study of stellar dynamics and gravitational lensing allows one to break degeneracies inherent to each method separately, providing a clean probe of the internal structure of massive galaxies. Since most lens galaxies are at redshifts z=0.1-1.0, they also provide the required look-back time to study their structural and stellar-population evolution. We recently analyzed 5 E/S0 lens galaxies between z=0.5 and 1.0, combining exquisite Hubble Space Telescope imaging data with kinematic data from ground-based Keck spectroscopy, placing the first precise constraints on the dark-matter mass fraction and its inner slope beyond the local Universe. To expand the sample to 30 systems - required to study potential trends and evolution in the E/S0 mass profiles - we propose to target the 49 E/S0 lens-galaxy candidates discovered by Bolton et al. {2004} from the Sloan Digital Sky Survey {SDSS}. With the average lens rate being 40% and some systems having a lensing probability close to unity, we expect to discover 20 strong gravitational lenses from the sample. This will triple the current sample of 9 E/S0 systems, with data in hand. With the sample of 30 systems, we will be able to determine the average slope of the dark-matter and total mass profile of E/S0 galaxies to 10% and 4% accuracy, respectively. If present, we can simultaneously detect 10% evolution in the total mass slope with 95% confidence. This will provide unprecedented constraints on E/S0 galaxies beyond the local Universe and allow a stringent test of their formation scenarios and the standard cosmological model.

  7. Visible spectrophotometric method for amiodarone.

    PubMed

    Bosînceanu, Andreea; Popa, Graţiela; Tântaru, Gladiola; Popovici, Iuliana

    2012-01-01

    Amiodarone is an antiarrhythmic agent used for various types of tachyarrhythmia, both ventricular and supraventricular (atrial) arrhythmia. A spectrophotometric method for the assay of amiodarone was established. Based on the reduction of potassium ferricyanide in hydrochloric acid medium to potassium ferrocyanide forming a blue colored complex ferric ferrocyanide with Fe (III) ions. The compound was most stable in a mixture of ethylic alcohol and water (2:1, v/v) and it had an absorption maximum at 725 nm. The data were according to the Lambert-Beer Law in the concentration range of 0.5-5.0 microg/sample: correlation and coefficient R = 0.99977, R2 = 0.999541, slope of the line 0.12775, intercept 0.042077. The detection limit (DL) was 0.1032 microg/sample and the quantification limit (QL) 0.344 microg/ sample. PMID:23077917

  8. In-situ spectrophotometric probe

    DOEpatents

    Prather, William S.

    1992-01-01

    A spectrophotometric probe for in situ absorption spectra measurements comprising a first optical fiber carrying light from a remote light source, a second optical fiber carrying light to a remote spectrophotometer, the proximal ends of the first and second optical fibers parallel and coterminal, a planoconvex lens to collimate light from the first optical fiber, a reflecting grid positioned a short distance from the lens to reflect the collimated light back to the lens for focussing on the second optical fiber. The lens is positioned with the convex side toward the optical fibers. A substrate for absorbing analyte or an analyte and reagent mixture may be positioned between the lens and the reflecting grid.

  9. In-situ spectrophotometric probe

    DOEpatents

    Prather, W.S.

    1992-12-15

    A spectrophotometric probe is described for in situ absorption spectra measurements comprising a first optical fiber carrying light from a remote light source, a second optical fiber carrying light to a remote spectrophotometer, the proximal ends of the first and second optical fibers parallel and co-terminal, a planoconvex lens to collimate light from the first optical fiber, a reflecting grid positioned a short distance from the lens to reflect the collimated light back to the lens for focusing on the second optical fiber. The lens is positioned with the convex side toward the optical fibers. A substrate for absorbing analyte or an analyte and reagent mixture may be positioned between the lens and the reflecting grid. 5 figs.

  10. The origin and early evolution of birds: discoveries, disputes, and perspectives from fossil evidence

    NASA Astrophysics Data System (ADS)

    Zhou, Zhonghe

    2004-10-01

    The study of the origin and early evolution of birds has never produced as much excitement and public attention as in the past decade. Well preserved and abundant new fossils of birds and dinosaurs have provided unprecedented new evidence on the dinosaurian origin of birds, the arboreal origin of avian flight, and the origin of feathers prior to flapping flight. The Mesozoic avian assemblage mainly comprises two major lineages: the prevalent extinct group Enantiornithes, and the Ornithurae, which gave rise to all modern birds, as well as several more basal taxa. Cretaceous birds radiated into various paleoecological niches that included fish- and seed-eating. Significant size and morphological differences and variation in flight capabilities, ranging from gliding to powerful flight among early birds, highlight the diversification of birds in the Early Cretaceous. There is little evidence, however, to support a Mesozoic origin of modern avian groups. Controversy and debate, nevertheless, surround many of these findings, and more details are needed to give a better appreciation of the significance of these new discoveries.

  11. Early stage of implosion in inertial confinement fusion: Shock timing and perturbation evolution

    NASA Astrophysics Data System (ADS)

    Goncharov, V. N.; Gotchev, O. V.; Vianello, E.; Boehly, T. R.; Knauer, J. P.; McKenty, P. W.; Radha, P. B.; Regan, S. P.; Sangster, T. C.; Skupsky, S.; Smalyuk, V. A.; Betti, R.; McCrory, R. L.; Meyerhofer, D. D.; Cherfils-Clérouin, C.

    2006-01-01

    Excessive increase in the shell entropy and degradation from spherical symmetry in inertial confinement fusion implosions limit shell compression and could impede ignition. The entropy is controlled by accurately timing shock waves launched into the shell at an early stage of an implosion. The seeding of the Rayleigh-Taylor instability, the main source of the asymmetry growth, is also set at early times during the shock transit across the shell. In this paper we model the shock timing and early perturbation growth of directly driven targets measured on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. By analyzing the distortion evolution, it is shown that one of the main parameters characterizing the growth is the size of the conduction zone Dc, defined as a distance between the ablation front and the laser deposition region. Modes with kDc>1 are stable and experience oscillatory behavior [V. N. Goncharov, Phys. Rev. Lett. 82, 2091 (1999)]. The model shows that the main stabilizing mechanism is the dynamic overpressure due to modulations in the blow-off velocity inside the conduction zone. The long wavelengths with kDc<1 experience growth because of coupled Richtmyer-Meshkov-like and Landau-Darrieus instabilities [L. D. Landau and E. M. Lifshitz, Fluid Mechanics (Pergamon, New York, 1982)]. To match the simulation results with both the shock timing and perturbation growth measurements a new nonlocal thermal transport model is developed and used in hydrocodes.

  12. Cosmic Evolution of Size and Velocity Dispersion for Early-type Galaxies

    NASA Astrophysics Data System (ADS)

    Fan, L.; Lapi, A.; Bressan, A.; Bernardi, M.; De Zotti, G.; Danese, L.

    2010-08-01

    Massive (stellar mass M sstarf >~ 3 × 1010 M sun), passively evolving galaxies at redshifts z >~ 1 exhibit on average physical sizes smaller, by factors ≈3, than local early-type galaxies (ETGs) endowed with the same stellar mass. Small sizes are in fact expected on theoretical grounds, if dissipative collapse occurs. Recent results show that the size evolution at z <~ 1 is limited to less than 40%, while most of the evolution occurs at z >~ 1, where both compact and already extended galaxies are observed and the scatter in size is remarkably larger than it is locally. The presence at high redshift of a significant number of ETGs with the same size as their local counterparts, as well as ETGs with quite small size (lsim1/10 of the local one), points to a timescale for reaching the new, expanded equilibrium configuration of less than the Hubble time tH (z). We demonstrate that the projected mass of compact, high-redshift galaxies and that of local ETGs within the same physical radius, the nominal half-luminosity radius of high-redshift ETGs, differ substantially in that the high-redshift ETGs are on average significantly denser. This result suggests that the physical mechanism responsible for the size increase should also remove mass from central galaxy regions (r <~ 1 kpc). We propose that quasar activity, which peaks at redshift z ~ 2, can remove large amounts of gas from central galaxy regions on a timescale shorter than the triggering a puffing up of the stellar component at constant stellar mass (or a timescale on the order of the dynamical one); in this case, the size increase goes together with a decrease in the central mass. The size evolution is expected to parallel that of the quasars and the inverse hierarchy, or downsizing, seen in the quasar evolution is mirrored in the size evolution. Exploiting the virial theorem, we derive the relation between the stellar velocity dispersion of ETGs and the characteristic velocity of their hosting halos at the

  13. Evolution.

    ERIC Educational Resources Information Center

    Mayr, Ernst

    1978-01-01

    Traces the history of evolution theory from Lamarck and Darwin to the present. Discusses natural selection in detail. Suggests that, besides biological evolution, there is also a cultural evolution which is more rapid than the former. (MA)

  14. Basin Evolution of the Cretaceous-Early Eocene Xigaze Forearc, Southern Tibet

    NASA Astrophysics Data System (ADS)

    Orme, D. A.; Carrapa, B.; Kapp, P. A.; Gehrels, G. E.; Reiners, P. W.

    2013-12-01

    An understanding of the processes which control the evolution of forearc basins is important for deciphering the tectonic development of a convergent margin prior to continent-continent suturing. This study presents sedimentologic, modal petrographic and geo-thermochronologic data from the Xigaze forearc basin, preserved along ~ 600 km of the Indus-Yarlung Suture Zone in southern Tibet. From late Cretaceous to early Cenozoic time, subduction of Neo-Tethyan oceanic crust beneath the southern margin of Asia accommodated the northward motion of the Indian craton and formed the Xigaze forearc basin. Following collision with India in the early Cenozoic, the basin transitioned from predominantly marine to non-marine sedimentation and was subsequently uplifted to a mean elevation of 5000 m. Thus, the sedimentary record in the Xigaze forearc preserves information regarding the tectonic evolution of the Indo-Asia continental margin prior to and following collision. We present new measured sections and geo-thermochronologic data from Early Cretaceous to Early Eocene clastic and carbonate sedimentary rocks, preserved in two previously unexplored regions of the forearc, (1) at its western most extent, northwest of Saga, and (2) north of Lhatse. In turn, we compare our results with previously published data in order to synthesize our current understanding of forearc evolution. Strata preserved in the Lhaste region record an initial shallow marine phase of forearc sedimentation (Aptian), but quickly transition to deep marine slope and distal fan turbidite facies (Albian-Campanian). In contrast, facies preserved in the Saga region record a younger shoaling upward marine sequence (Maastrichtian-Ypresian), with the uppermost ~ 400 m consisting of fluvial channel sandstones and red-green paleosols. Facies and depositional environments in the Saga region are highly variable along strike, with turbidites, shelf limestones, estuarine siliciclastics and thick paleosols sequences all

  15. The Atmospheres of the Terrestrial Planets:Clues to the Origins and Early Evolution of Venus, Earth, and Mars

    NASA Technical Reports Server (NTRS)

    Baines, Kevin H.; Atreya, Sushil K.; Bullock, Mark A.; Grinspoon, David H,; Mahaffy, Paul; Russell, Christopher T.; Schubert, Gerald; Zahnle, Kevin

    2015-01-01

    We review the current state of knowledge of the origin and early evolution of the three largest terrestrial planets - Venus, Earth, and Mars - setting the stage for the chapters on comparative climatological processes to follow. We summarize current models of planetary formation, as revealed by studies of solid materials from Earth and meteorites from Mars. For Venus, we emphasize the known differences and similarities in planetary bulk properties and composition with Earth and Mars, focusing on key properties indicative of planetary formation and early evolution, particularly of the atmospheres of all three planets. We review the need for future in situ measurements for improving our understanding of the origin and evolution of the atmospheres of our planetary neighbors and Earth, and suggest the accuracies required of such new in situ data. Finally, we discuss the role new measurements of Mars and Venus have in understanding the state and evolution of planets found in the habitable zones of other stars.

  16. Early evolution of the extraordinary Nova Delphini 2013 (V339 Del)

    NASA Astrophysics Data System (ADS)

    Skopal, A.; Drechsel, H.; Tarasova, T.; Kato, T.; Fujii, M.; Teyssier, F.; Garde, O.; Guarro, J.; Edlin, J.; Buil, C.; Antao, D.; Terry, J.-N.; Lemoult, T.; Charbonnel, S.; Bohlsen, T.; Favaro, A.; Graham, K.

    2014-09-01

    Aims: We determine the temporal evolution of the luminosity (LWD), radius (RWD) and effective temperature (Teff) of the white dwarf (WD) pseudophotosphere of V339 Del from its discovery to around day 40. Another main objective was studying the ionization structure of the ejecta. Methods: These aims were achieved by modelling the optical/near-IR spectral energy distribution (SED) using low-resolution spectroscopy (3500-9200 Å), UBVRCIC and JHKLM photometry. Important insights in the physical conditions of the ejecta were gained from an analysis of the evolution of the Hα and Raman-scattered 6825 Å O vi line using medium-resolution spectroscopy (R ~ 10 000). Results: During the fireball stage (Aug. 14.8-19.9, 2013), Teff was in the range of 6000-12 000 K, RWD was expanding non-uniformly in time from ~66 to ~300 (d/ 3 kpc) R⊙, and LWD was super-Eddington, but not constant. Its maximum of ~9 × 1038 (d/ 3 kpc)2 erg s-1 occurred around Aug. 16.0, at the maximum of Teff, half a day before the visual maximum. After the fireball stage, a large emission measure of 1.0-2.0 × 1062 (d/ 3 kpc)2 cm-3 constrained the lower limit of LWD to be well above the super-Eddington value. The mass of the ionized region was a few × 10-4 M⊙, and the mass-loss rate was decreasing from ~5.7 (Aug. 22) to ~0.71 × 10-4 M⊙ yr-1 (Sept. 20). The evolution of the Hα line and mainly the transient emergence of the Raman-scattered O vi 1032 Å line suggested a biconical ionization structure of the ejecta with a disk-like H i region persisting around the WD until its total ionization, around day 40. On Sept. 20 (day 35), the model SED indicated a dust emission component in the spectrum. The dust was located beyond the H i zone, where it was shielded from the hard, ≳105 K, radiation of the burning WD at that time. Conclusions: Our extensive spectroscopic observations of the classical nova V339 Del allowed us to map its evolution from the very early phase after its explosion. It is evident

  17. A Devonian predatory fish provides insights into the early evolution of modern sarcopterygians

    PubMed Central

    Lu, Jing; Zhu, Min; Ahlberg, Per Erik; Qiao, Tuo; Zhu, You’an; Zhao, Wenjin; Jia, Liantao

    2016-01-01

    Crown or modern sarcopterygians (coelacanths, lungfishes, and tetrapods) differ substantially from stem sarcopterygians, such as Guiyu and Psarolepis, and a lack of transitional fossil taxa limits our understanding of the origin of the crown group. The Onychodontiformes, an enigmatic Devonian predatory fish group, seems to have characteristics of both stem and crown sarcopterygians but is difficult to place because of insufficient anatomical information. We describe the new skull material of Qingmenodus, a Pragian (~409-million-year-old) onychodont from China, using high-resolution computed tomography to image internal structures of the braincase. In addition to its remarkable similarities with stem sarcopterygians in the ethmosphenoid portion, Qingmenodus exhibits coelacanth-like neurocranial features in the otic region. A phylogenetic analysis based on a revised data set unambiguously assigns onychodonts to crown sarcopterygians as stem coelacanths. Qingmenodus thus bridges the morphological gap between stem sarcopterygians and coelacanths and helps to illuminate the early evolution and diversification of crown sarcopterygians. PMID:27386576

  18. Os isotopes in SNC meteorites and their implications to the early evolution of Mars and Earth

    NASA Technical Reports Server (NTRS)

    Jagoutz, E.; Luck, J. M.; Othman, D. Ben; Wanke, H.

    1993-01-01

    A new development on the measurement of the Os isotopic composition by mass spectrometry using negative ions opened a new field of applications. The Re-Os systematic provides time information on the differentiation of the nobel metals. The nobel metals are strongly partitioned into metal and sulphide phases, but also the generation of silicate melts might fractionate the Re-Os system. Compared to the other isotopic systems which are mainly dating the fractionation of the alkalis and alkali-earth elements, the Re-Os system is expected to disclose entirely new information about the geochemistry. Especially the differentiation and early evolution of the planets such as the formation of the core will be elucidated with this method.

  19. The role of hard turbulent thermal convection in the Earth's early thermal evolution

    NASA Technical Reports Server (NTRS)

    Hansen, Ulli; Yuen, David A.; Zhao, Wuling; Malevsky, Andrei V.

    1992-01-01

    In the last several years great progress was made in the study of a new transition in thermal convection, called hard turbulence. Initial experiments were conducted with helium gas, then with water. It was shown that for base-heated Newtonian convection a transition occurred at Rayleigh numbers between 10(exp 7) and 10(exp 8). This transition is characterized by the appearance of disconnected plume structures in contrast to continuous plumes with mushroom-shaped tops found for lower Rayleigh numbers. This new hydrodynamic transition is expected to play an important role in reshaping our concepts of mantle convection in the early stages of planetary evolution. We have conducted two-dimensional calculations for large and small aspect-ratio configuration to see whether such a transition would take place for infinite Prandtl number fluids.

  20. Supernovae and Their Expanding Blast Waves during the Early Evolution of Galactic Globular Clusters

    NASA Astrophysics Data System (ADS)

    Tenorio-Tagle, Guillermo; Muñoz-Tuñón, Casiana; Silich, Sergiy; Cassisi, Santi

    2015-11-01

    Our arguments deal with the early evolution of Galactic globular clusters and show why only a few of the supernovae (SNe) products were retained within globular clusters and only in the most massive cases (M ≥ 106 M⊙), while less massive clusters were not contaminated at all by SNe. Here, we show that SN blast waves evolving in a steep density gradient undergo blowout and end up discharging their energy and metals into the medium surrounding the clusters. This inhibits the dispersal and the contamination of the gas left over from a first stellar generation. Only the ejecta from well-centered SNe that evolve into a high-density medium available for a second stellar generation (2SG) in the most massive clusters would be retained. These are likely to mix their products with the remaining gas, eventually leading in these cases to an Fe-contaminated 2SG.

  1. Evolution of microwave sea ice signatures during early summer and midsummer in the marginal ice zone

    NASA Technical Reports Server (NTRS)

    Onstott, R. G.; Grenfell, T. C.; Matzler, C.; Luther, C. A.; Svendsen, E. A.

    1987-01-01

    Emissivities at frequencies from 5 to 94 GHz and backscatter at frequencies from 1 to 17 GHz were measured from sea ice in Fram Strait during the marginal Ice Zone Experiment in June and July of 1983 and 1984. The ice observed was primarily multiyear; the remainder, first-year ice, was often deformed. Results from this active and passive microwave study include the description of the evolution of the sea ice during early summer and midsummer; the absorption properties of summer snow; the interrelationship between ice thickness and the state and thickness of snow; and the modulation of the microwave signature, especially at the highest frequencies, by the freezing of the upper few centimeters of the ice.

  2. Some aspects of the early evolution of the Appointed Factory Doctor Service*

    PubMed Central

    Smiley, James A.

    1971-01-01

    Smiley, J. A. (1971).Brit. J. industr. Med.,28, 315-322. Some aspects of the early evolution of the Appointed Factory Doctor Service. The appointment of certifying surgeons marks the beginning of the recognition by the State of its responsibility for the supervision of the health and welfare of young people in industry. The importance of the rôle played by Leonard Horner, one of the first four inspectors of factories, is discussed. Some of the problems and vicissitudes of the service in the 19th century are outlined and it is suggested that the system is inappropriate to the needs of the present. Legislation which would integrate all the agencies which are concerned with the well-being of young people, including the Appointed Factory Doctor Service, should be actively considered. PMID:5124831

  3. A Devonian predatory fish provides insights into the early evolution of modern sarcopterygians.

    PubMed

    Lu, Jing; Zhu, Min; Ahlberg, Per Erik; Qiao, Tuo; Zhu, You'an; Zhao, Wenjin; Jia, Liantao

    2016-06-01

    Crown or modern sarcopterygians (coelacanths, lungfishes, and tetrapods) differ substantially from stem sarcopterygians, such as Guiyu and Psarolepis, and a lack of transitional fossil taxa limits our understanding of the origin of the crown group. The Onychodontiformes, an enigmatic Devonian predatory fish group, seems to have characteristics of both stem and crown sarcopterygians but is difficult to place because of insufficient anatomical information. We describe the new skull material of Qingmenodus, a Pragian (~409-million-year-old) onychodont from China, using high-resolution computed tomography to image internal structures of the braincase. In addition to its remarkable similarities with stem sarcopterygians in the ethmosphenoid portion, Qingmenodus exhibits coelacanth-like neurocranial features in the otic region. A phylogenetic analysis based on a revised data set unambiguously assigns onychodonts to crown sarcopterygians as stem coelacanths. Qingmenodus thus bridges the morphological gap between stem sarcopterygians and coelacanths and helps to illuminate the early evolution and diversification of crown sarcopterygians. PMID:27386576

  4. Unique caudal plumage of Jeholornis and complex tail evolution in early birds

    PubMed Central

    O’Connor, Jingmai; Wang, Xiaoli; Sullivan, Corwin; Zheng, Xiaoting; Tubaro, Pablo; Zhang, Xiaomei; Zhou, Zhonghe

    2013-01-01

    The Early Cretaceous bird Jeholornis was previously only known to have a distally restricted ornamental frond of tail feathers. We describe a previously unrecognized fan-shaped tract of feathers situated dorsal to the proximal caudal vertebrae. The position and morphology of these feathers is reminiscent of the specialized upper tail coverts observed in males of some sexually dimorphic neornithines. As in the neornithine tail, the unique “two-tail” plumage in Jeholornis probably evolved as the result of complex interactions between natural and sexual selective pressures and served both aerodynamic and ornamental functions. We suggest that the proximal fan would have helped to streamline the body and reduce drag whereas the distal frond was primarily ornamental. Jeholornis reveals that tail evolution was complex and not a simple progression from frond to fan. PMID:24101506

  5. Geochemical evolution of the northern plains of Mars: Early hydrosphere, carbonate development, and present morphology

    SciTech Connect

    Schaefer, M.W. )

    1990-08-30

    It is likely that early in Mars' history, abundant liquid water was available. Under a thick (several bars) carbon dioxide atmosphere, this water could have formed an ocean, located primarily in the lowlands of the northern hemisphere. An equilibrium geochemical model of this ocean and its interactions with the atmosphere and regolith of Mars was developed, and the results of this model were used to discuss the evolution of the volatile budget of Mars, including the deposition of large carbonate beds on the northern plains. Differential solutional weathering of these carbonate beds may have caused the formation of some of the enigmatic features seen on the northern plains of Mars, such as the thumbprint terrain and enclosed depressions.

  6. Early Evolution of Vertebrate Mybs: An Integrative Perspective Combining Synteny, Phylogenetic, and Gene Expression Analyses.

    PubMed

    Campanini, Emeline B; Vandewege, Michael W; Pillai, Nisha E; Tay, Boon-Hui; Jones, Justin L; Venkatesh, Byrappa; Hoffmann, Federico G

    2015-11-01

    The genes in the Myb superfamily encode for three related transcription factors in most vertebrates, A-, B-, and c-Myb, with functionally distinct roles, whereas most invertebrates have a single Myb. B-Myb plays an essential role in cell division and cell cycle progression, c-Myb is involved in hematopoiesis, and A-Myb is involved in spermatogenesis and regulating expression of pachytene PIWI interacting RNAs, a class of small RNAs involved in posttranscriptional gene regulation and the maintenance of reproductive tissues. Comparisons between teleost fish and tetrapods suggest that the emergence and functional divergence of the Myb genes were linked to the two rounds of whole-genome duplication early in vertebrate evolution. We combined phylogenetic, synteny, structural, and gene expression analyses of the Myb paralogs from elephant shark and lampreys with data from 12 bony vertebrates to reconstruct the early evolution of vertebrate Mybs. Phylogenetic and synteny analyses suggest that the elephant shark and Japanese lamprey have copies of the A-, B-, and c-Myb genes, implying their origin could be traced back to the common ancestor of lampreys and gnathostomes. However, structural and gene expression analyses suggest that their functional roles diverged between gnathostomes and cyclostomes. In particular, we did not detect A-Myb expression in testis suggesting that the involvement of A-Myb in the pachytene PIWI interacting RNA pathway is probably a gnathostome-specific innovation. We speculate that the secondary loss of a central domain in lamprey A-Myb underlies the functional differences between the cyclostome and gnathostome A-Myb proteins. PMID:26475318

  7. The Early Spectral Evolution of the Classical Nova ASASSN-15th in M33

    NASA Astrophysics Data System (ADS)

    Wagner, R. Mark; Neric, Marko; Darnley, Matt J.; Williams, Steven; Starrfield, Sumner; Woodward, Charles E.; Prieto, Jose Luis

    2016-06-01

    During the course of the All Sky Automated Survey for SuperNovae (ASAS-SN) a new transient source designated ASASSN-15th was identified on images of the nearby galaxy M33 obtained with the 14 cm Brutus telescope in Haleakala, Hawaii on 2015 Dec 1.4 UT at V ~ 16.5 mag. Given the location of the transient in M33 and its apparent V magnitude at discovery, the implied absolute visual magnitude was about -8.5 mag suggesting that the transient was a new classical nova outburst in M33. Optical spectroscopy obtained by us on 2015 Dec 2.3 showed broad emission lines of Balmer, Fe II, and Na I D with P Cygni-type line profiles superposed on a blue continuum. The spectrum was consistent with a Fe II-type classical nova in M33 discovered early in the outburst. Subsequent spectra obtained by us on 2015 Dec 10.9 UT showed significant evolution since our first spectrum in that the deep P Cygni-type line profiles seen earlier were now extremely shallow or had almost completely disappeared with the emission component growing in strength. Additional emission lines from O I, Si II, and possibly He I were also present. We obtained optical spectroscopy of ASASSN-15th on 17 epochs between 2015 Dec 1 and 2016 Feb 11 UT with the 2.4 m Hiltner telescope (+OSMOS) of the MDM Observatory, the 2 m fully robotic Liverpool Telescope (+SPRAT), and the 2 x 8.4 m Large Binocular Telescope (+MODS). We will present our spectroscopy and discuss the early evolution of ASASSN-15th in the context of Galactic Fe II-class novae.

  8. The nucleosynthetic origins and chemical evolution of phosphorus in the early universe

    NASA Astrophysics Data System (ADS)

    Frebel, Anna

    2013-10-01

    Relatively little is known about the chemical evolution of the element phosphorus, despite its relatively large abundance in the Sun and its importance for biological life. The goal of this archive proposal is to establish the chemical evolution trend of phosphorus, extending our knowledge from solar metallicity to stars with less than 1/1000th the solar metallicity.Previous studies have used weak near-infrared P I lines to establish phosphorus abundance trends from -1.0 < [Fe/H] < 0. We have identified a strong P I doublet in the UV at 2136 Angstroms, which is present in the spectra of 22 stars available in the HST archives. Our study will {1} improve on the limited observations of the abundance trend at high metallicity and extend it to metallicities lower by 2 dex and {2} determine whether [P/Fe] flattens out towards lower metallicities {like the alpha-elements Mg, Si, Ca, and Ti} or whether it continues to increase {like Co and Zn}. Our results will provide the first tight constraints on the nucleosynthesis of phosphorus and its production sites in the early Universe.We request one semester of funding to support a graduate student to lead the spectral analysis work, one month of summer salary, and miscellaneous travel and publication costs.

  9. [Symbiogenesis as a Model for Reconstructing the Early Stages of Genome Evolution].

    PubMed

    Provorov, N A; Tikhonovich, I A; Vorobyov, N I

    2016-02-01

    Symbiogenic evolution, which involves transformations of bacteria into the cellular organelles, is represented as a model for reconstructing the early stages of genome evolution, including the origin of DNA genomes from RNA genomes and the emergence of template processes on the basis of self-replicating molecular complexes in the ancestral metabolic systems. The antiquity of RNA genomes is supported by an increased evolutionary stability of ribosomal protein synthesis (translation) with respect to the DNA-dependent template processes (replication, transcription, recombination, and reparation). This stability is demonstrated by analysis of the deeply reduced genomes of symbiotic bacteria and cellular organelles as well as the "minimal" genomes which are common to phylogenetically diverse organisms. Higher evolutionary conservation of template biosynthetic processes with respect to step processes determining the metabolism and development in cells does not support the hypothesis about emergence ofgenomes within the ancestral cellular metabolic systems which are thought to be of abiogenic origin, instead suggesting dualistic origin of life on Earth. We suppose that the genome-free organelles of some eukaryotes (mitosomes, many hydrogenosomes, and some plastids) represent the products of reversion of symbiotic bacteria into ancestral forms which implemented their basic cellular functions using the informational macromolecules of exogenic origin. In the framework of this hypothesis the eukaryotic cells functioning based on the massive transfer of gene products (RNAs, proteins) from cytosol to organelles may represent the analogs of ancestral biocenoses that possessed integral hereditary systems (metagenomes). PMID:27215028

  10. Novel scenarios of early animal evolution--is it time to rewrite textbooks?

    PubMed

    Dohrmann, Martin; Wörheide, Gert

    2013-09-01

    Understanding how important phenotypic, developmental, and genomic features of animals originated and evolved is essential for many fields of biological research, but such understanding depends on robust hypotheses about the phylogenetic interrelationships of the higher taxa to which the studied species belong. Molecular approaches to phylogenetics have proven able to revolutionize our knowledge of organismal evolution. However, with respect to the deepest splits in the metazoan Tree of Life-the relationships between Bilateria and the four non-bilaterian phyla (Porifera, Placozoa, Ctenophora, and Cnidaria)-no consensus has been reached yet, since a number of different, often contradictory, hypotheses with sometimes spectacular implications have been proposed in recent years. Here, we review the recent literature on the topic and contrast it with more classical perceptions based on analyses of morphological characters. We conclude that the time is not yet ripe to rewrite zoological textbooks and advocate a conservative approach when it comes to developing scenarios of the early evolution of animals. PMID:23539635

  11. A New Basal Sauropod Dinosaur from the Middle Jurassic of Niger and the Early Evolution of Sauropoda

    PubMed Central

    Remes, Kristian; Ortega, Francisco; Fierro, Ignacio; Joger, Ulrich; Kosma, Ralf; Marín Ferrer, José Manuel; Ide, Oumarou Amadou; Maga, Abdoulaye

    2009-01-01

    Background The early evolution of sauropod dinosaurs is poorly understood because of a highly incomplete fossil record. New discoveries of Early and Middle Jurassic sauropods have a great potential to lead to a better understanding of early sauropod evolution and to reevaluate the patterns of sauropod diversification. Principal Findings A new sauropod from the Middle Jurassic of Niger, Spinophorosaurus nigerensis n. gen. et sp., is the most complete basal sauropod currently known. The taxon shares many anatomical characters with Middle Jurassic East Asian sauropods, while it is strongly dissimilar to Lower and Middle Jurassic South American and Indian forms. A possible explanation for this pattern is a separation of Laurasian and South Gondwanan Middle Jurassic sauropod faunas by geographic barriers. Integration of phylogenetic analyses and paleogeographic data reveals congruence between early sauropod evolution and hypotheses about Jurassic paleoclimate and phytogeography. Conclusions Spinophorosaurus demonstrates that many putatively derived characters of Middle Jurassic East Asian sauropods are plesiomorphic for eusauropods, while South Gondwanan eusauropods may represent a specialized line. The anatomy of Spinophorosaurus indicates that key innovations in Jurassic sauropod evolution might have taken place in North Africa, an area close to the equator with summer-wet climate at that time. Jurassic climatic zones and phytogeography possibly controlled early sauropod diversification. PMID:19756139

  12. Evolution of Cupido and Coahuila carbonate platforms, early Cretaceous, northeastern Mexico

    USGS Publications Warehouse

    Lehmann, C.; Osleger, D.A.; Montanez, I.P.; Sliter, W.; Arnaud-Vanneau, A.; Banner, J.

    1999-01-01

    The Cupido and Coahuila platforms of northeastern Mexico are part of the extensive carbonate platform system that rimmed the ancestral Gulf of Mexico during Barremian to Albian time. Exposures of Cupido and Coahuila lithofacies in several mountain ranges spanning an ???80 000 km2 area reveal information about platform morphology and composition, paleoenvironmental relations, and the chronology of platform evolution. New biostratigraphic data, integrated with carbon and strontium isotope stratigraphy, significantly improve chronostratigraphic relations across the region. These data substantially change previous age assignments of several formations and force a revision of the longstanding stratigraphy in the region. The revised stratigraphy and enhanced time control, combined with regional facies associations, allow the construction of cross sections, isopach maps, and timeslice paleogeographic maps that collectively document platform morphology and evolution. The orientation of the Cupido (Barremian-Aptian) shelf margin was controlled by the emergent Coahuila basement block to the northwest. The south-facing margin is a high-energy grainstone shoal, whereas the margin facing the ancestral Gulf of Mexico to the east is a discontinuous rudist-coral reef. A broad shelf lagoon developed in the lee of the Cupido margin, where as much as 660 m of cyclic peritidal deposits accumulated. During middle to late Aptian time, a major phase of flooding forced a retrograde backstep of the Cupido platform, shifting the locus of shallow-marine sedimentation northwestward toward the Coahuila block. This diachronous flooding event records both the demise of the Cupido shelf and the consequent initiation of the Coahuila ramp. The backstepped Coahuila ramp (Aptian-Albian) consisted of a shallow shoal margin separating an interior evaporitic lagoon from a low-energy, muddy deep ramp. More than 500 m of cyclic carbonates and evaporites accumulated in the evaporitic lagoon during early to

  13. A novel proxy links CAMP volcanism with end-Triassic mass extinction and early Jurassic evolution

    NASA Astrophysics Data System (ADS)

    Ruhl, M.; Bjerrum, C. J.; Frei, R.

    2011-12-01

    Global mass extinction events are marked by a major loss of terrestrial and marine biodiversity and the global collapse of ecosystems during times of extensive volcanic activity and the emplacement of large igneous provinces (LIPs). Large-scale greenhouse gas release, initiated by volcanism, had a profound impact on global geochemical cycles (e.g. initiating strong perturbations in δ13C records). Hence, these events may be regarded as natural deep-time analogues for studying mechanistic feedbacks between rapid and large/scale greenhouse gas emissions, environmental change and biotic crises. Such studies require high resolution stratigraphic correlation between volcanic activity, disruption of global geochemical cycles and biotic crises, which at present is poorly constrained. Here we present a novel proxy that records explosive continental volcanic activity in distant marine shale sediments. The proxy builds on the relative abundance of the trace elements Lu, Hf, Y and Nb (monitored as the (Lu/ Hf)/(Y/ Nb)-ratio). We test the method on a marine sedimentary record comprising Central Atlantic Magmatic Province (CAMP) volcanism and the associated end-Triassic global mass extinction, at ~201.38 Ma. We show that the onset of sharp well-defined peaks in the (Lu/ Hf)/(Y/ Nb)-ratio coincides with the end-Triassic biotic crisis. Subsequent subordinate peaks closely correspond to periods of early Jurassic biotic radiation and evolution. Large-scale volcanic activity therefore not only initiated the end-Triassic mass extinction, it possibly also actively punctuated and regulated the pace of early Jurassic evolution. Further, the proxy also records the timing of Siberian Traps volcanism relative to the end-Permian mass extinction, the largest extinction in Earth's history. Hence, this proxy for the first time allows causality studies between increased volcanic activity, disruption of global geochemical cycles and global biodiversity loss, in unprecedented stratigraphic

  14. Processing of meteoritic organic materials as a possible analog of early molecular evolution in planetary environments

    PubMed Central

    Pizzarello, Sandra; Davidowski, Stephen K.; Holland, Gregory P.; Williams, Lynda B.

    2013-01-01

    The composition of the Sutter’s Mill meteorite insoluble organic material was studied both in toto by solid-state NMR spectroscopy of the powders and by gas chromatography–mass spectrometry analyses of compounds released upon their hydrothermal treatment. Results were compared with those obtained for other meteorites of diverse classifications (Murray, GRA 95229, Murchison, Orgueil, and Tagish Lake) and found to be so far unique in regard to the molecular species released. These include, in addition to O-containing aromatic compounds, complex polyether- and ester-containing alkyl molecules of prebiotic appeal and never detected in meteorites before. The Sutter’s Mill fragments we analyzed had likely been altered by heat, and the hydrothermal conditions of the experiments realistically mimic early Earth settings, such as near volcanic activity or impact craters. On this basis, the data suggest a far larger availability of meteoritic organic materials for planetary environments than previously assumed and that molecular evolution on the early Earth could have benefited from accretion of carbonaceous meteorites both directly with soluble compounds and, for a more protracted time, through alteration, processing, and release from their insoluble organic materials. PMID:24019471

  15. Why do leafcutter bees cut leaves? New insights into the early evolution of bees.

    PubMed

    Litman, Jessica R; Danforth, Bryan N; Eardley, Connal D; Praz, Christophe J

    2011-12-01

    Stark contrasts in clade species diversity are reported across the tree of life and are especially conspicuous when observed in closely related lineages. The explanation for such disparity has often been attributed to the evolution of key innovations that facilitate colonization of new ecological niches. The factors underlying diversification in bees remain poorly explored. Bees are thought to have originated from apoid wasps during the Mid-Cretaceous, a period that coincides with the appearance of angiosperm eudicot pollen grains in the fossil record. The reliance of bees on angiosperm pollen and their fundamental role as angiosperm pollinators have contributed to the idea that both groups may have undergone simultaneous radiations. We demonstrate that one key innovation--the inclusion of foreign material in nest construction--underlies both a massive range expansion and a significant increase in the rate of diversification within the second largest bee family, Megachilidae. Basal clades within the family are restricted to deserts and exhibit plesiomorphic features rarely observed among modern bees, but prevalent among apoid wasps. Our results suggest that early bees inherited a suite of behavioural traits that acted as powerful evolutionary constraints. While the transition to pollen as a larval food source opened an enormous ecological niche for the early bees, the exploitation of this niche and the subsequent diversification of bees only became possible after bees had evolved adaptations to overcome these constraints. PMID:21490010

  16. Fuxianhuiid ventral nerve cord and early nervous system evolution in Panarthropoda.

    PubMed

    Yang, Jie; Ortega-Hernández, Javier; Butterfield, Nicholas J; Liu, Yu; Boyan, George S; Hou, Jin-Bo; Lan, Tian; Zhang, Xi-Guang

    2016-03-15

    Panarthropods are typified by disparate grades of neurological organization reflecting a complex evolutionary history. The fossil record offers a unique opportunity to reconstruct early character evolution of the nervous system via exceptional preservation in extinct representatives. Here we describe the neurological architecture of the ventral nerve cord (VNC) in the upper-stem group euarthropod Chengjiangocaris kunmingensis from the early Cambrian Xiaoshiba Lagerstätte (South China). The VNC of C. kunmingensis comprises a homonymous series of condensed ganglia that extend throughout the body, each associated with a pair of biramous limbs. Submillimetric preservation reveals numerous segmental and intersegmental nerve roots emerging from both sides of the VNC, which correspond topologically to the peripheral nerves of extant Priapulida and Onychophora. The fuxianhuiid VNC indicates that ancestral neurological features of Ecdysozoa persisted into derived members of stem-group Euarthropoda but were later lost in crown-group representatives. These findings illuminate the VNC ground pattern in Panarthropoda and suggest the independent secondary loss of cycloneuralian-like neurological characters in Tardigrada and Euarthropoda. PMID:26933218

  17. Why do leafcutter bees cut leaves? New insights into the early evolution of bees

    PubMed Central

    Litman, Jessica R.; Danforth, Bryan N.; Eardley, Connal D.; Praz, Christophe J.

    2011-01-01

    Stark contrasts in clade species diversity are reported across the tree of life and are especially conspicuous when observed in closely related lineages. The explanation for such disparity has often been attributed to the evolution of key innovations that facilitate colonization of new ecological niches. The factors underlying diversification in bees remain poorly explored. Bees are thought to have originated from apoid wasps during the Mid-Cretaceous, a period that coincides with the appearance of angiosperm eudicot pollen grains in the fossil record. The reliance of bees on angiosperm pollen and their fundamental role as angiosperm pollinators have contributed to the idea that both groups may have undergone simultaneous radiations. We demonstrate that one key innovation—the inclusion of foreign material in nest construction—underlies both a massive range expansion and a significant increase in the rate of diversification within the second largest bee family, Megachilidae. Basal clades within the family are restricted to deserts and exhibit plesiomorphic features rarely observed among modern bees, but prevalent among apoid wasps. Our results suggest that early bees inherited a suite of behavioural traits that acted as powerful evolutionary constraints. While the transition to pollen as a larval food source opened an enormous ecological niche for the early bees, the exploitation of this niche and the subsequent diversification of bees only became possible after bees had evolved adaptations to overcome these constraints. PMID:21490010

  18. Early mantle composition and evolution inferred from 142Nd and 182W variation in Isua samples

    NASA Astrophysics Data System (ADS)

    Rizo Garza, H. L.; Touboul, M.; Puchtel, I. S.; Walker, R. J.; Carlson, R. W.; Horan, M. F.; Boyet, M.

    2013-12-01

    The short-lived 146Sm-142Nd chronometer applied to Eoarchean rocks from Greenland led to the discovery of the oldest known mantle reservoir, likely formed during the first 150 Ma of Earth's history [1-4]. The geochemical composition and evolution of this reservoir can, thus, reveal the nature of early Earth differentiation events, and its survival provides information on the mixing rates of early heterogeneities in the mantle. High precision 142Nd analyses have revealed that the early-formed reservoir sampled by the Greenland rocks was depleted in incompatible elements, and that its obliteration by remixing into the mantle was completed around 3.3 Ga [5]. High precision 182W data are a promising tool that can provide new information about the earliest phase of Earth's evolution. Excesses in182W of ~+13 ppm relative to terrestrial standards, detected in ~ 3.8 Ga rocks from Greenland [6] were interpreted to reflect the incomplete mixing of late-accreted materials into the mantle sources of these rocks during the period between 4.5 and 3.8 Ga. Here, we measured highly siderophile element (HSE) abundances and 182W in Greenland rocks with ages ranging between 3.8 and 3.3 Ga. Platinum concentrations of ~3 to nearly 8ppb were measured in all samples, except for the of the 3.3 Ga rocks. The relatively high Pt abundances are not consistent with mantle sources characterized by strong HSE depletion. The tungsten isotopic data for the 3.8 Ga old samples show no 182W anomalies. By contrast, variable 182W excesses of as high as 13ppm are present in 3.7, 3.4 and 3.3 Ga samples. The 182W results do not correlate with the 142Nd variability in the same rocks. The 3.8 Ga samples also stand out with respect to their high W concentrations (2 - 3 ppm) compared to the other Greenland samples (0.1- 0.8 ppm). The 182W data, together with the HSE data may help to constrain the composition of the Archean mantle through time, and will allow modeling of the mixing rate of late arriving

  19. Early vertebrate chromosome duplications and the evolution of the neuropeptide Y receptor gene regions

    PubMed Central

    2008-01-01

    Background One of the many gene families that expanded in early vertebrate evolution is the neuropeptide (NPY) receptor family of G-protein coupled receptors. Earlier work by our lab suggested that several of the NPY receptor genes found in extant vertebrates resulted from two genome duplications before the origin of jawed vertebrates (gnathostomes) and one additional genome duplication in the actinopterygian lineage, based on their location on chromosomes sharing several gene families. In this study we have investigated, in five vertebrate genomes, 45 gene families with members close to the NPY receptor genes in the compact genomes of the teleost fishes Tetraodon nigroviridis and Takifugu rubripes. These correspond to Homo sapiens chromosomes 4, 5, 8 and 10. Results Chromosome regions with conserved synteny were identified and confirmed by phylogenetic analyses in H. sapiens, M. musculus, D. rerio, T. rubripes and T. nigroviridis. 26 gene families, including the NPY receptor genes, (plus 3 described recently by other labs) showed a tree topology consistent with duplications in early vertebrate evolution and in the actinopterygian lineage, thereby supporting expansion through block duplications. Eight gene families had complications that precluded analysis (such as short sequence length or variable number of repeated domains) and another eight families did not support block duplications (because the paralogs in these families seem to have originated in another time window than the proposed genome duplication events). RT-PCR carried out with several tissues in T. rubripes revealed that all five NPY receptors were expressed in the brain and subtypes Y2, Y4 and Y8 were also expressed in peripheral organs. Conclusion We conclude that the phylogenetic analyses and chromosomal locations of these gene families support duplications of large blocks of genes or even entire chromosomes. Thus, these results are consistent with two early vertebrate tetraploidizations forming a

  20. Multiple Kisspeptin Receptors in Early Osteichthyans Provide New Insights into the Evolution of This Receptor Family

    PubMed Central

    Pasquier, Jérémy; Lafont, Anne-Gaëlle; Jeng, Shan-Ru; Morini, Marina; Dirks, Ron; van den Thillart, Guido; Tomkiewicz, Jonna; Tostivint, Hervé; Chang, Ching-Fong; Rousseau, Karine; Dufour, Sylvie

    2012-01-01

    Deorphanization of GPR54 receptor a decade ago led to the characterization of the kisspeptin receptor (Kissr) in mammals and the discovery of its major role in the brain control of reproduction. While a single gene encodes for Kissr in eutherian mammals including human, other vertebrates present a variable number of Kissr genes, from none in birds, one or two in teleosts, to three in an amphibian, xenopus. In order to get more insight into the evolution of Kissr gene family, we investigated the presence of Kissr in osteichthyans of key-phylogenetical positions: the coelacanth, a representative of early sarcopterygians, the spotted gar, a non-teleost actinopterygian, and the European eel, a member of an early group of teleosts (elopomorphs). We report the occurrence of three Kissr for the first time in a teleost, the eel. As measured by quantitative RT-PCR, the three eel Kissr were differentially expressed in the brain-pituitary-gonadal axis, and differentially regulated in experimentally matured eels, as compared to prepubertal controls. Subfunctionalisation, as shown by these differences in tissue distribution and regulation, may have represented significant evolutionary constraints for the conservation of multiple Kissr paralogs in this species. Furthermore, we identified four Kissr in both coelacanth and spotted gar genomes, providing the first evidence for the presence of four Kissr in vertebrates. Phylogenetic and syntenic analyses supported the existence of four Kissr paralogs in osteichthyans and allowed to propose a clarified nomenclature of Kissr (Kissr-1 to -4) based on these paralogs. Syntenic analysis suggested that the four Kissr paralogs arose through the two rounds of whole genome duplication (1R and 2R) in early vertebrates, followed by multiple gene loss events in the actinopterygian and sarcopterygian lineages. Due to gene loss there was no impact of the teleost-specific whole genome duplication (3R) on the number of Kissr paralogs in current

  1. Dental histology of Coelophysis bauri and the evolution of tooth attachment tissues in early dinosaurs.

    PubMed

    Fong, Raymond K M; LeBlanc, Aaron R H; Berman, David S; Reisz, Robert R

    2016-07-01

    Studies of dinosaur teeth have focused primarily on external crown morphology and thus, use shed or in situ tooth crowns, and are limited to the enamel and dentine dental tissues. As a result, the full suites of periodontal tissues that attach teeth to the jaws remain poorly documented, particularly in early dinosaurs. These tissues are an integral part of the tooth and thus essential to a more complete understanding of dental anatomy, development, and evolution in dinosaurs. To identify the tooth attachment tissues in early dinosaurs, histological thin sections were prepared from the maxilla and dentary of a partial skull of the early theropod Coelophysis bauri from the Upper Triassic (Rhaetian- 209-201 Ma) Whitaker Quarry, New Mexico, USA. As one of the phylogenetically and geologically oldest dinosaurs, it is an ideal candidate for examining dental tissues near the base of the dinosaurian clade. The teeth of C. bauri exhibited a fibrous tooth attachment in which the teeth possessed five tissues: enamel, dentine, cementum, periodontal ligament (PDL), and alveolar bone. Our findings, coupled with those of more recent studies of ornithischian teeth, indicate that a tripartite periodontium, similar to that of crocodilians and mammals, is the plesiomorphic condition for dinosaurs. The occurrence of a tripartite periodontium in dinosaurs adds to the growing consensus that the presence of these tissues is the plesiomorphic condition for the major amniote clades. Furthermore, this study establishes the relative timing of tissue development and growth directions of periodontal tissues and provides the first comparative framework for future studies of dinosaur periodontal development, tooth replacement, and histology. J. Morphol. 277:916-924, 2016. © 2016 Wiley Periodicals, Inc. PMID:27087142

  2. Novel insights into early neuroanatomical evolution in penguins from the oldest described penguin brain endocast.

    PubMed

    Proffitt, J V; Clarke, J A; Scofield, R P

    2016-08-01

    Digital methodologies for rendering the gross morphology of the brain from X-ray computed tomography data have expanded our current understanding of the origin and evolution of avian neuroanatomy and provided new perspectives on the cognition and behavior of birds in deep time. However, fossil skulls germane to extracting digital endocasts from early stem members of extant avian lineages remain exceptionally rare. Data from early-diverging species of major avian subclades provide key information on ancestral morphologies in Aves and shifts in gross neuroanatomical structure that have occurred within those groups. Here we describe data on the gross morphology of the brain from a mid-to-late Paleocene penguin fossil from New Zealand. This most basal and geochronologically earliest-described endocast from the penguin clade indicates that described neuroanatomical features of early stem penguins, such as lower telencephalic lateral expansion, a relatively wider cerebellum, and lack of cerebellar folding, were present far earlier in penguin history than previously inferred. Limited dorsal expansion of the wulst in the new fossil is a feature seen in outgroup waterbird taxa such as Gaviidae (Loons) and diving Procellariiformes (Shearwaters, Diving Petrels, and allies), indicating that loss of flight may not drastically affect neuroanatomy in diving taxa. Wulst enlargement in the penguin lineage is first seen in the late Eocene, at least 25 million years after loss of flight and cooption of the flight stroke for aquatic diving. Similar to the origin of avian flight, major shifts in gross brain morphology follow, but do not appear to evolve quickly after, acquisition of a novel locomotor mode. Enlargement of the wulst shows a complex pattern across waterbirds, and may be linked to sensory modifications related to prey choice and foraging strategy. PMID:26916364

  3. Arthropod eyes: The early Cambrian fossil record and divergent evolution of visual systems.

    PubMed

    Strausfeld, Nicholas J; Ma, Xiaoya; Edgecombe, Gregory D; Fortey, Richard A; Land, Michael F; Liu, Yu; Cong, Peiyun; Hou, Xianguang

    2016-03-01

    Four types of eyes serve the visual neuropils of extant arthropods: compound retinas composed of adjacent facets; a visual surface populated by spaced eyelets; a smooth transparent cuticle providing inwardly directed lens cylinders; and single-lens eyes. The first type is a characteristic of pancrustaceans, the eyes of which comprise lenses arranged as hexagonal or rectilinear arrays, each lens crowning 8-9 photoreceptor neurons. Except for Scutigeromorpha, the second type typifies Myriapoda whose relatively large eyelets surmount numerous photoreceptive rhabdoms stacked together as tiers. Scutigeromorph eyes are facetted, each lens crowning some dozen photoreceptor neurons of a modified apposition-type eye. Extant chelicerate eyes are single-lensed except in xiphosurans, whose lateral eyes comprise a cuticle with a smooth outer surface and an inner one providing regular arrays of lens cylinders. This account discusses whether these disparate eye types speak for or against divergence from one ancestral eye type. Previous considerations of eye evolution, focusing on the eyes of trilobites and on facet proliferation in xiphosurans and myriapods, have proposed that the mode of development of eyes in those taxa is distinct from that of pancrustaceans and is the plesiomorphic condition from which facetted eyes have evolved. But the recent discovery of enormous regularly facetted compound eyes belonging to early Cambrian radiodontans suggests that high-resolution facetted eyes with superior optics may be the ground pattern organization for arthropods, predating the evolution of arthrodization and jointed post-protocerebral appendages. Here we provide evidence that compound eye organization in stem-group euarthropods of the Cambrian can be understood in terms of eye morphologies diverging from this ancestral radiodontan-type ground pattern. We show that in certain Cambrian groups apposition eyes relate to fixed or mobile eyestalks, whereas other groups reveal concomitant

  4. Variable path length spectrophotometric probe

    DOEpatents

    O'Rourke, Patrick E.; McCarty, Jerry E.; Haggard, Ricky A.

    1992-01-01

    A compact, variable pathlength, fiber optic probe for spectrophotometric measurements of fluids in situ. The probe comprises a probe body with a shaft having a polished end penetrating one side of the probe, a pair of optic fibers, parallel and coterminous, entering the probe opposite the reflecting shaft, and a collimating lens to direct light from one of the fibers to the reflecting surface of the shaft and to direct the reflected light to the second optic fiber. The probe body has an inlet and an outlet port to allow the liquid to enter the probe body and pass between the lens and the reflecting surface of the shaft. A linear stepper motor is connected to the shaft to cause the shaft to advance toward or away from the lens in increments so that absorption measurements can be made at each of the incremental steps. The shaft is sealed to the probe body by a bellows seal to allow freedom of movement of the shaft and yet avoid leakage from the interior of the probe.

  5. The Federal Role in Early Childhood Education: Evolution in the Goals, Governance, and Policy Instruments of Project Head Start

    ERIC Educational Resources Information Center

    Kalifeh, Phyllis; Cohen-Vogel, Lora; Grass, Saralyn

    2011-01-01

    The authors analyze bills, congressional records, agency reports, and newspaper articles to trace the evolution of Project Head Start, by far the nation's largest federal early childhood program, beginning with the Economic Opportunity Act of 1964. Their analysis is organized around the policy goals embedded in the program and the governance…

  6. Neoproterozoic-Early Paleozoic tectonic evolution of the western part of the Kyrgyz Ridge (Northern Tian Shan) caledonides

    NASA Astrophysics Data System (ADS)

    Degtyarev, K. E.; Ryazantsev, A. V.; Tretyakov, A. A.; Tolmacheva, T. Yu.; Yakubchuk, A. S.; Kotov, A. B.; Salnikova, E. B.; Kovach, V. P.

    2013-11-01

    The conducted comprehensive study of the western part of Kyrgyz Ridge provided new data on the structure, composition and age of Precambrian and Early Paleozoic stratified and igneous complexes. The main achievements of these studies are: (1) the establishment of a wide age spectrum, embracing the interval from the Neoproterozoic to the end of the Early Ordovician, for the clastic-carbonate units composing the cover of the Northern Tian Shan sialic massif; (2) the reconstruction and dating of Early and Late Cambrian ophiolite complexes formed in suprasubduction settings;(3) the discovery and dating of the Early-Middle Ordovician volcano-sedimentary complex of island-arc affinity; and (4) proof of the wide occurrence of Late Ordovician granitoids, some of which bear Cu-Au-Mo ores. The intricate thrust-and-fold structure of the western part of the Kyrgyz Ridge, formed in several stages from the Middle Cambrian (?) until the end of the Middle Ordovician, was scrutinized; the importance of the Early Ordovician stage was demonstrated. The intrusion of large batholiths in the early Late Ordovician accomplished the caledonide structural evolution. Formation of Neoproterozoic and Early Paleozoic caledonide complexes, which were possibly related to the protracted and entangled evolution of the active continental margin, ceased by the Late Ordovician.

  7. Early evolution and dynamics of Earth from a molten initial stage

    NASA Astrophysics Data System (ADS)

    Lourenço, Diogo; Tackley, Paul

    2015-04-01

    It is now well established that most of the terrestrial planets underwent a magma ocean stage during their accretion. On Earth, it is probable that at the end of accretion, giant impacts like the hypothesised Moon-forming impact, together with other sources of heat, melted a substantial part of the mantle. The thermal and chemical evolution of the resulting magma ocean most certainly had dramatic consequences on the history of the planet. Considerable research has been done on magma oceans using simple 1-D models (e.g.: Abe, PEPI 1997; Solomatov, Treat. Geophys. 2007; Elkins-Tanton EPSL 2008). However, some aspects of the dynamics may not be adequately addressed in 1-D and require the use of 2-D or 3-D models. Moreover, new developments in mineral physics that indicate that melt can be denser than solid at high pressures (e.g.: de Koker et al., EPSL 2013) can have very important impacts on the classical views of the solidification of magma oceans (Labrosse et al., Nature 2007). The goal of our study is to understand and characterize the influence of melting on the long-term thermo-chemical evolution of rocky planet interiors, starting from an initial molten state (magma ocean). Our approach is to model viscous creep of the solid mantle, while parameterizing processes that involve melt as previously done in 1-D models, including melt-solid separation at all melt fractions, the use of an effective diffusivity to parameterize turbulent mixing, coupling to a parameterized core heat balance and a radiative surface boundary condition. These enhancements have been made to the numerical code StagYY (Tackley, PEPI 2008). We will present results for the evolution of an Earth-like planet from a molten initial state to present day, while testing the effect of uncertainties in parameters such as melt-solid density differences, surface heat loss and efficiency of turbulent mixing. Our results show rapid cooling and crystallization until the rheological transition then much

  8. Early evolution and dynamics of Earth from a molten initial stage

    NASA Astrophysics Data System (ADS)

    Louro Lourenço, Diogo; Tackley, Paul J.

    2016-04-01

    It is now well established that most of the terrestrial planets underwent a magma ocean stage during their accretion. On Earth, it is probable that at the end of accretion, giant impacts like the hypothesised Moon-forming impact, together with other sources of heat, melted a substantial part of the mantle. The thermal and chemical evolution of the resulting magma ocean most certainly had dramatic consequences on the history of the planet. Considerable research has been done on magma oceans using simple 1-D models (e.g.: Abe, PEPI 1997; Solomatov, Treat. Geophys. 2007; Elkins-Tanton EPSL 2008). However, some aspects of the dynamics may not be adequately addressed in 1-D and require the use of 2-D or 3-D models. Moreover, new developments in mineral physics that indicate that melt can be denser than solid at high pressures (e.g.: de Koker et al., EPSL 2013) can have very important impacts on the classical views of the solidification of magma oceans (Labrosse et al., Nature 2007). The goal of our study is to understand and characterize the influence of melting on the long-term thermo-chemical evolution of rocky planet interiors, starting from an initial molten state (magma ocean). Our approach is to model viscous creep of the solid mantle, while parameterizing processes that involve melt as previously done in 1-D models, including melt-solid separation at all melt fractions, the use of an effective diffusivity to parameterize turbulent mixing, coupling to a parameterized core heat balance and a radiative surface boundary condition. These enhancements have been made to the numerical code StagYY (Tackley, PEPI 2008). We present results for the evolution of an Earth-like planet from a molten initial state to present day, while testing the effect of uncertainties in parameters such as melt-solid density differences, surface heat loss and efficiency of turbulent mixing. Our results show rapid cooling and crystallization until the rheological transition then much slower

  9. Early evolution and dynamics of Earth from a molten initial stage

    NASA Astrophysics Data System (ADS)

    Louro Lourenço, D. J.; Tackley, P. J.

    2014-12-01

    It is now well established that most of the terrestrial planets underwent a magma ocean stage during their accretion. On Earth, it is probable that at the end of accretion, giant impacts like the hypothesised Moon-forming impact, together with other sources of heat, melted a substantial part of the mantle. The thermal and chemical evolution of the resulting magma ocean most certainly had dramatic consequences on the history of the planet. Considerable research has been done on magma oceans using simple 1-D models (e.g.: Abe, PEPI 1997; Solomatov, Treat. Geophys. 2007; Elkins-Tanton EPSL 2008). However, some aspects of the dynamics may not be adequately addressed in 1-D and require the use of 2-D or 3-D models. Moreover, new developments in mineral physics that indicate that melt can be denser than solid at high pressures (e.g.: de Koker et al., EPSL 2013) can have very important impacts on the classical views of the solidification of magma oceans (Labrosse et al., Nature 2007). The goal of our study is to understand and characterize the influence of melting on the long-term thermo-chemical evolution of rocky planet interiors, starting from an initial molten state (magma ocean). Our approach is to model viscous creep of the solid mantle, while parameterizing processes that involve melt as previously done in 1-D models, including melt-solid separation at all melt fractions, the use of an effective diffusivity to parameterize turbulent mixing, coupling to a parameterized core heat balance and a radiative surface boundary condition. These enhancements have been made to the numerical code StagYY (Tackley, PEPI 2008). We will present results for the evolution of an Earth-like planet from a molten initial state to present day, while testing the effect of uncertainties in parameters such as melt-solid density differences, surface heat loss and efficiency of turbulent mixing. Our results show rapid cooling and crystallization until the rheological transition then much

  10. Lake evolution during the Early Danian Dan-C2 hyperthermal, Boltysh impact crater, Ukraine

    NASA Astrophysics Data System (ADS)

    Ebinghaus, Alena; Jolley, David W.

    2016-04-01

    Lacustrine facies record complex relationships between lake evolution and environmental conditions and provide proxies for climate changes. However, lacustrine successions formed during past hyperthermals as recorded from negative carbon isotope excursions (CIEs) are of limited availability and thus less well understood. Here, we present a complete lacustrine record of the Early Danian Dan-C2 hyperthermal at c. 65.2 Ma from a core drilled in the K-Pg Boltysh impact crater, Ukraine. This borehole allows a detailed facies analysis and reconstruction of lake evolution and associated plant ecosystem in correspondence with rapid climate change. The Boltysh borehole reveals a c. 400 m thick siliciclastic and organic-rich succession overlying impact melt-breccia dated at 65.17 ± 0.64 Ma. Based on detailed core logging, 8 distinctive facies associations are identified, including 1) littoral mudstones, 2) siliciclastic shoreline deposits, 3) siliciclastic littoral to sublittoral deposits, 4) mudstone laminites, 5) organic-rich mudstones, and deposits of 6) coarse-grained, 7) fine-grained density currents, and 8) debris flows. Based on the occurrence of these facies associations 3 major phases of lake evolution are distinguished: 1) an initial pre-CIE rising clastic-dominated lake phase characterised by the presence of coarse-grained density and debris flow deposits, 2) an organic-rich fluctuating shallow lake phase during the main phase of the CIE, characterised by alternating packages of the mudstone laminites and organic-rich mudstones; and 3) a rising clastic-dominated lake during and post-CIE recovery phase, which shows a high presence of siliciclastic shoreline and littoral to sublittoral deposits. This study provides a full record of lacustrine response to climate change during the Dan-C2 hyperthermal, and subsequently allows us to infer lake formation and environmental conditions at different stages during climate warming. The high resolution sedimentary record

  11. Chemical evolution in the early phases of massive star formation. I

    NASA Astrophysics Data System (ADS)

    Gerner, T.; Beuther, H.; Semenov, D.; Linz, H.; Vasyunina, T.; Bihr, S.; Shirley, Y. L.; Henning, Th.

    2014-03-01

    Understanding the chemical evolution of young (high-mass) star-forming regions is a central topic in star formation research. Chemistry is employed as a unique tool 1) to investigate the underlying physical processes and 2) to characterize the evolution of the chemical composition. With these aims in mind, we observed a sample of 59 high-mass star-forming regions at different evolutionary stages varying from the early starless phase of infrared dark clouds to high-mass protostellar objects to hot molecular cores and, finally, ultra-compact Hii regions at 1 mm and 3 mm with the IRAM 30 m telescope. We determined their large-scale chemical abundances and found that the chemical composition evolves along with the evolutionary stages. On average, the molecular abundances increase with time. We modeled the chemical evolution, using a 1D physical model where density and temperature vary from stage to stage coupled with an advanced gas-grain chemical model and derived the best-fit χ2 values of all relevant parameters. A satisfying overall agreement between observed and modeled column densities for most of the molecules was obtained. With the best-fit model we also derived a chemical age for each stage, which gives the timescales for the transformation between two consecutive stages. The best-fit chemical ages are ~10 000 years for the IRDC stage, ~60 000 years for the HMPO stage, ~40 000 years for the HMC stage, and ~10 000 years for the UCHii stage. Thus, the total chemical timescale for the entire evolutionary sequence of the high-mass star formation process is on the order of 105 years, which is consistent with theoretical estimates. Furthermore, based on the approach of a multiple-line survey of unresolved data, we were able to constrain an intuitive and reasonable physical and chemical model. The results of this study can be used as chemical templates for the different evolutionary stages in high-mass star formation. Based on observations carried out with the IRAM

  12. How do Early Impacts Modulate the Tectonic, Magnetic and Climatic Evolutions of Terrestrial Planets?

    NASA Astrophysics Data System (ADS)

    Jellinek, M.; Jackson, M. G.; Lenardic, A.; Weller, M. B.

    2015-12-01

    The landmark discovery showing that the 142Nd/144Nd ratio of the accessible modern terrestrial mantle is greater than ordinary-chondrites has remarkable implications for the formation, as well as the geodynamic, magnetic and climatic histories of Earth. If Earth is derived from ordinary chondrite precursors, mass balance requires that a missing reservoir with 142Nd/144Nd lower than ordinary chondrites was isolated from the accessible mantle within 20-30 Myr following accretion. Critically for Earth evolution, this reservoir hosts the equivalent of the modern continents' budget of radioactive heat-producing elements (U, Th and K). If this reservoir was lost to space through mechanical erosion by early impactors, the planet's radiogenic heat generation is 18-45% lower than chondrite-based compositional estimates. Recent geodynamic calculations suggest that this reduced heat production will favor the emergence of Earth-like plate tectonics. However, parameterized thermal history calculations favor a relatively recent transition from mostly Atlantic-sized plates to the current plate tectonic mode characterized predominantly by the subduction of Pacific-sized plates. Such a transition in the style of Earth's plate tectonics is also consistent with a delayed dynamo and an evolving rate of volcanic outgassing that ultimately favors Earth's long-term clement climate. By contrast, relatively enhanced radiogenic heat production related to a less early impact erosion reduces the likelihood of present day plate tectonics: A chondritic Earth has a stronger likelihood to evolve as a Venus-like planet characterized by potentially wild swings in tectonic and climatic regime. Indeed, differences in internal heat production related to varying extents of impact erosion may exert strong control over Earth's climate and explain aspects of the differences among the current climatic regimes of Earth, Venus and Mars.

  13. Preservation of ovarian follicles reveals early evolution of avian reproductive behaviour.

    PubMed

    Zheng, Xiaoting; O'Connor, Jingmai; Huchzermeyer, Fritz; Wang, Xiaoli; Wang, Yan; Wang, Min; Zhou, Zhonghe

    2013-03-28

    The two groups of archosaurs, crocodilians and birds, form an extant phylogenetic bracket for understanding the reproductive behaviour of dinosaurs. This behaviour is inferred from preserved nests and eggs, and even gravid individuals. Data indicate that many 'avian' traits were already present in Paraves--the clade that includes birds and their close relatives--and that the early evolution of the modern avian form of reproduction was already well on its way. Like living neornithine birds, non-avian maniraptorans had daily oviposition and asymmetrical eggs with complex shell microstructure, and were known to protect their clutches. However, like crocodilians, non-avian maniraptorans had two active oviducts (one present in living birds), relatively smaller eggs, and may not have turned their eggs in the way that living birds do. Here we report on the first discovery of fossilized mature or nearly mature ovarian follicles, revealing a previously undocumented stage in dinosaur reproduction: reproductively active females near ovulation. Preserved in a specimen of the long bony-tailed Jeholornis and two enantiornithine birds from the Early Cretaceous period lacustrine Jehol Biota in northeastern China, these discoveries indicate that basal birds only had one functional ovary, but retained primitive morphologies as a result of their lower metabolic rate relative to living birds. They also indicate that basal birds reached sexual maturity before skeletal maturity, as in crocodiles and paravian dinosaurs. Differences in follicular morphology between Jeholornis and the enantiornithines are interpreted as forming an evolutionary gradient from the reproductive condition in paravian dinosaurs towards neornithine birds. Furthermore, differences between the two enantiornithines indicate that this lineage might also have evolved advanced reproductive traits in parallel to the neornithine lineage. PMID:23503663

  14. Timing and evolution of ocean anoxic event during Early Cambrian in south China

    NASA Astrophysics Data System (ADS)

    Yang, J.; Jiang, S.; Pi, D.; Ling, H.

    2008-12-01

    The Precambrian/Cambrian (PC-C) interval is one of the most interesting intervals in the evolution of life because of the sudden diversification of animals with mineralized skeletons, known as "Cambrian Explosion". The Yangtze Platform in south China is one of the best occurrences that can provide excellent insights into the palaeo-environmental and biological changes across the PC-C boundary. Our study show that the ocean anoxia were widespread during the Early Cambrian period, however, the start of this anoxic event was not from the PC-C boundary (i.e., 542 Ma), but some 7 Ma later (~535 Ma) when the Niutitang Formation black rock series (black phosphorite, chert, and black shale) deposited along a thousand kilometer long NEE zone in the transitional facies in the Yangtze Platform, while the major Cambrian radiation (Changjiang fauna) took place during 521-511 Ma. During the Niutitang period, the depositional environment of the Early Cambrian sedimentary sequence in south China have evolved from an initial oxic/dysoxic to a major anoxic/euxinic environment, and then back to dysoxic/oxic environment. A Ni-Mo sulfide layer occurred in the lower part of the Niutitang black shales which contains extremely enrichments of many metals, and can serve as a marker layer in south China when the depositional environment turned into euxinic condition. Re-Os isotope study of the sulfide ores and host black shales show an age of 535 Ma. Initial Os isotopic compositions, Mo isotopic compositions, and rare earth elements and Pt group element geochemistry suggest involvement of submarine hydrothermal fluids during the metal enrichments in black shale.

  15. Deposition and early hydrologic evolution of Westwater Canyon wet alluvial-fan system

    SciTech Connect

    Galloway, W.E.

    1980-01-01

    The Westwater Canyon Member is one of several large, low-gradient alluvial fans that compose the Morrison Formation in the Four Corners area. Morrison fans were deposited by major laterally migrating streams entering a broad basin bounded by highlands to the west and south. The Westwater Canyon sand framework consists of a downfan succession of 1) proximal braided channel, 2) straight bed-load channel, 3) sinuous mixed-load channel, and 4) distributary mixed-load-channel sand bodies. Regional sand distribution and facies patterns are highly digitate and radiate from a point source located northwest of Gallup, New Mexico. Early ground-water flow evolution within the Westwater Canyon fan aquifer system can be inferred by analogy with Quaternary wet-fan deposits and by the interpreted paragenetic sequence of diagenetic features present. Syndepositional flow was controlled by the downfan hydrodynamic gradient and the high horizontal and vertical transmissivity of the sand-rich fan aquifer. Dissolution and transport of soluble humate would be likely in earliest ground water, which was abundant, fresh, and slightly alkaline. With increasing confinement of the aquifer below less permeable tuffaceous Brushy Basin deposits and release of soluble constituents from volcanic ash, flow patterns stabilized, and relatively more saline, uranium-rich ground water permeated the aquifer. Uranium mineralization occurred during this early postdepositional, semiconfined flow phase. Development of overlying Dakota swamps suggests a shallow water table indicative of regional dischare or stagnation. In either event, only limited downward flux of acidic water is recorded by local, bleached, kaolinized zones where the Westwater Canyon directly underlies the Dakota swamps. Subsequent ground-water flow phases have further obscured primary alteration patterns and caused local oxidation and redistribution of uranium.

  16. A multigene phylogeny of Olpidium and its implications for early fungal evolution

    PubMed Central

    2011-01-01

    Background From a common ancestor with animals, the earliest fungi inherited flagellated zoospores for dispersal in water. Terrestrial fungi lost all flagellated stages and reproduce instead with nonmotile spores. Olpidium virulentus (= Olpidium brassicae), a unicellular fungus parasitizing vascular plant root cells, seemed anomalous. Although Olpidium produces zoospores, in previous phylogenetic studies it appeared nested among the terrestrial fungi. Its position was based mainly on ribosomal gene sequences and was not strongly supported. Our goal in this study was to use amino acid sequences from four genes to reconstruct the branching order of the early-diverging fungi with particular emphasis on the position of Olpidium. Results We concatenated sequences from the Ef-2, RPB1, RPB2 and actin loci for maximum likelihood and Bayesian analyses. In the resulting trees, Olpidium virulentus, O. bornovanus and non-flagellated terrestrial fungi formed a strongly supported clade. Topology tests rejected monophyly of the Olpidium species with any other clades of flagellated fungi. Placing Olpidium at the base of terrestrial fungi was also rejected. Within the terrestrial fungi, Olpidium formed a monophyletic group with the taxa traditionally classified in the phylum Zygomycota. Within Zygomycota, Mucoromycotina was robustly monophyletic. Although without bootstrap support, Monoblepharidomycetes, a small class of zoosporic fungi, diverged from the basal node in Fungi. The zoosporic phylum Blastocladiomycota appeared as the sister group to the terrestrial fungi plus Olpidium. Conclusions This study provides strong support for Olpidium as the closest living flagellated relative of the terrestrial fungi. Appearing nested among hyphal fungi, Olpidium's unicellular thallus may have been derived from ancestral hyphae. Early in their evolution, terrestrial hyphal fungi may have reproduced with zoospores. PMID:22085768

  17. The clever strategy of a tiny crustacean eye early in the evolution of vision

    PubMed Central

    2012-01-01

    Henningsmoenicaris scutula (Walossek and Müller, 1990) (Fig. 1) is a tiny representative of Crustacea, systematically standing close to the stemline. It is found in stinkstone (‘Orsten’) nodules from the Alum Shale, where a rich fauna of small organisms is excellently preserved. Three dimensional morphology is retained by phosphatisation, which exhibits the finest details, such as cuticular structures, fine appendages and especially the morphology of the compound eyes. The stalked eyes of H. scutula investigated here were equipped with a differentiated visual surface with four different areas of vision. The most intriguing is a field of view oriented laterally to the contralateral side of each eye, so that the fields of view of both compound eyes intersect, and give information about any object moving within the vicinity. Due to this, although, for various reasons this compound eye probably was not able to form a proper image, it was able to perceive tiny prey within a wide visual field, in the same way that the movement of figures can be traced in a chess game. This can be considered as a highly sophisticated visual system that developed early in the history of reported eye evolution, as this compound eye is almost exactly half a billion years old. PMID:22808326

  18. Craniofacial modularity, character analysis, and the evolution of the premaxilla in early African hominins.

    PubMed

    Villmoare, Brian A; Dunmore, Christopher; Kilpatrick, Shaun; Oertelt, Nadja; Depew, Michael J; Fish, Jennifer L

    2014-12-01

    Phylogenetic analyses require evolutionarily independent characters, but there is no consensus, nor has there been a clear methodology presented on how to define character independence in a phylogenetic context, particularly within a complex morphological structure such as the skull. Following from studies of craniofacial development, we hypothesize that the premaxilla is an independent evolutionary module with two integrated characters that have traditionally been treated as independent. We test this hypothesis on a large sample of primate skulls and find evidence supporting the premaxilla as an independent module within the larger module of the palate. Additionally, our data indicate that the convexity of the nasoalveolar clivus and the contour of the alveolus are integrated within the premaxilla. We show that the palate itself is composed of two distinct modules: the FNP-derived premaxillae and the mxBA1-derived maxillae and palatines. Application of our data to early African hominin facial morphology suggests that at least three separate transitions contributed to robust facial morphology: 1) an increase in the size of the post-canine dentition housed within the maxillae and palatines, 2) modification of the premaxilla generating a concave clivus and reduced incisor alveolus, and 3) modification of the zygomatic, shifting the zygomatic root and lateral face anteriorly. These data lend support to the monophyly of Paranthropus boisei and Paranthropus robustus, and provide mounting evidence in favor of a Paranthropus clade. This study also highlights the utility of applying developmental evidence to studies of morphological evolution. PMID:25449953

  19. Genome-wide detection of gene extinction in early mammalian evolution.

    PubMed

    Kuraku, Shigehiro; Kuratani, Shigeru

    2011-01-01

    Detecting gene losses is a novel aspect of evolutionary genomics that has been made feasible by whole-genome sequencing. However, research to date has concentrated on elucidating evolutionary patterns of genomic components shared between species, rather than identifying disparities between genomes. In this study, we searched for gene losses in the lineage leading to eutherian mammals. First, as a pilot analysis, we selected five gene families (Wnt, Fgf, Tbx, TGFβ, and Frizzled) for molecular phylogenetic analyses, and identified mammalian lineage-specific losses of Wnt11b, Tbx6L/VegT/tbx16, Nodal-related, ADMP1, ADMP2, Sizzled, and Crescent. Second, automated genome-wide phylogenetic screening was implemented based on this pilot analysis. As a result, we detected 147 chicken genes without eutherian orthologs, which resulted from 141 gene loss events. Our inventory contained a group of regulatory genes governing early embryonic axis formation, such as Noggins, and multiple members of the opsin and prolactin-releasing hormone receptor ("PRLHR") gene families. Our findings highlight the potential of genome-wide gene phylogeny ("phylome") analysis in detecting possible rearrangement of gene networks and the importance of identifying losses of ancestral genomic components in analyzing the molecular basis underlying phenotypic evolution. PMID:22094861

  20. Probing the early chemical evolution of the Sculptor dSph with purely old stellar tracers

    NASA Astrophysics Data System (ADS)

    Martínez-Vázquez, C. E.; Monelli, M.; Gallart, C.; Bono, G.; Bernard, E. J.; Stetson, P. B.; Ferraro, I.; Walker, A. R.; Dall'Ora, M.; Fiorentino, G.; Iannicola, G.

    2016-09-01

    We present the metallicity distribution of a sample of 471 RR Lyrae (RRL) stars in the Sculptor dSph, obtained from the I-band period-luminosity relation. It is the first time that the early chemical evolution of a dwarf galaxy is characterized in such a detailed and quantitative way, using photometric data alone. We find a broad metallicity distribution (full width at half-maximum equals to 0.8 dex) that is peaked at [Fe/H] ≃ -1.90 dex, in excellent agreement with literature values obtained from spectroscopic data. Moreover, we are able to directly trace the metallicity gradient out to a radius of ˜55 arcmin. We find that in the outer regions (r > ˜32 arcmin) the slope of the metallicity gradient from the RRLs (-0.025 dex arcmin-1) is comparable to the literature values based on red giant (RG) stars. However, in the central part of Sculptor, we do not observe the latter gradients. This suggests that there is a more metal-rich and/or younger population in Sculptor that does not produce RRLs. This scenario is strengthened by the observation of a metal-rich peak in the metallicity distribution of RG stars by other authors, which is not present in the metallicity distribution of the RRLs within the same central area.

  1. Early evolution of an X-ray emitting solar active region

    NASA Technical Reports Server (NTRS)

    Wolfson, C. J.; Acton, L. W.; Leibacher, J. W.; Roethig, D. T.

    1977-01-01

    The birth and early evolution of a solar active region has been investigated using X-ray observations from the mapping X-ray heliometer on board the OSO-8 spacecraft. X-ray emission is observed within three hours of the first detection of H-alpha plage. At that time, a plasma temperature of four million K in a region having a density on the order of 10 to the 10th power per cu cm is inferred. During the fifty hours following birth almost continuous flares or flare-like X-ray bursts are superimposed on a monotonically increasing base level of X-ray emission produced by the plasma. If the X-rays are assumed to result from heating due to dissipation of current systems or magnetic field reconnection, it may be concluded that flare-like X-ray emission soon after active region birth implies that the magnetic field probably emerges in a stressed or complex configuration.

  2. Functional Characterization of Cnidarian HCN Channels Points to an Early Evolution of Ih

    PubMed Central

    Baker, Emma C.; Layden, Michael J.; van Rossum, Damian B.; Kamel, Bishoy; Medina, Monica; Simpson, Eboni; Jegla, Timothy

    2015-01-01

    HCN channels play a unique role in bilaterian physiology as the only hyperpolarization-gated cation channels. Their voltage-gating is regulated by cyclic nucleotides and phosphatidylinositol 4,5-bisphosphate (PIP2). Activation of HCN channels provides the depolarizing current in response to hyperpolarization that is critical for intrinsic rhythmicity in neurons and the sinoatrial node. Additionally, HCN channels regulate dendritic excitability in a wide variety of neurons. Little is known about the early functional evolution of HCN channels, but the presence of HCN sequences in basal metazoan phyla and choanoflagellates, a protozoan sister group to the metazoans, indicate that the gene family predates metazoan emergence. We functionally characterized two HCN channel orthologs from Nematostella vectensis (Cnidaria, Anthozoa) to determine which properties of HCN channels were established prior to the emergence of bilaterians. We find Nematostella HCN channels share all the major functional features of bilaterian HCNs, including reversed voltage-dependence, activation by cAMP and PIP2, and block by extracellular Cs+. Thus bilaterian-like HCN channels were already present in the common parahoxozoan ancestor of bilaterians and cnidarians, at a time when the functional diversity of voltage-gated K+ channels was rapidly expanding. NvHCN1 and NvHCN2 are expressed broadly in planulae and in both the endoderm and ectoderm of juvenile polyps. PMID:26555239

  3. ON THE PROGENITOR AND EARLY EVOLUTION OF THE TYPE II SUPERNOVA 2009kr

    SciTech Connect

    Fraser, M.; Takats, K.; Pastorello, A.; Smartt, S. J.; Botticella, M-T.; Valenti, S.; Mattila, S.; Ergon, M.; Sollerman, J.; Arcavi, I.; Gal-Yam, A.; Benetti, S.; Bufano, F.; Crockett, R. M.; Danziger, I. J.; Maund, J. R.; Taubenberger, S.; Turatto, M.

    2010-05-10

    We identify a source coincident with SN 2009kr in Hubble Space Telescope pre-explosion images. The object appears to be a single point source with an intrinsic color V - I = 1.1 {+-} 0.25 and M{sub V} = -7.6 {+-} 0.6. If this is a single star, it would be a yellow supergiant of log L/L {sub sun} {approx} 5.1 and a mass of 15{sup +5} {sub -4} M {sub sun}. The spatial resolution does not allow us yet to definitively determine if the progenitor object is a single star, a binary system, or a compact cluster. We show that the early light curve is similar to a Type IIL SN, but the prominent H{alpha} P-Cygni profiles and the signature of the end of a recombination phase are reminiscent of a Type IIP. The evolution of the expanding ejecta will play an important role in understanding the progenitor object.

  4. Following the Water: the Evolution of Ice-forming Regions in the Early Solar Nebula

    NASA Technical Reports Server (NTRS)

    Davis, Sanford S.

    2006-01-01

    The abundances of water-vapor and water-ice during the first ten million years of the protoplanetary solar nebula are simulated using a new condensation/sublimation model. This study builds on a "snow line" model reported in ApJ 627 L153 (2005); it uses a simple phenomenological model where water vapor molecules evolve from solar atomic abundance and eventually condenses to ice at colder points in the nebula once the water-vapor partial pressure exceeds a value determined by the phase diagram for water. The synthesis of water vapor from elementary species is modeled with a chemical network consisting of about 400 species and 4000 reactions. The evolution of the icy zone (and its relative abundance of solid ice) is traced from a limited region in the early hotter disk to its final state at the time when the gas is expelled and a planetary system begins to form. Possible effects of this dynamic motion on disk chemistry and organic molecule formation are also described.

  5. The light up and early evolution of high redshift Supermassive Black Holes

    NASA Astrophysics Data System (ADS)

    Comastri, Andrea; Brusa, Marcella; Aird, James; Lanzuisi, Giorgio

    2016-07-01

    The known AGN population at z > 6 is made by luminous optical QSO hosting Supermassive Black Holes (M > 10 ^{9}solar masses), likely to represent the tip of the iceberg of the luminosity and mass function. According to theoretical models for structure formation, Massive Black Holes (M _{BH} 10^{4-7} solar masses) are predicted to be abundant in the early Universe (z > 6). The majority of these lower luminosity objects are expected to be obscured and severely underepresented in current optical near-infrared surveys. The detection of such a population would provide unique constraints on the Massive Black Holes formation mechanism and subsequent growth and is within the capabilities of deep and large area ATHENA surveys. After a summary of the state of the art of present deep XMM and Chandra surveys, at z >3-6 also mentioning the expectations for the forthcoming eROSITA all sky survey; I will present the observational strategy of future multi-cone ATHENA Wide Field Imager (WFI) surveys and the expected breakthroughs in the determination of the luminosity function and its evolution at high (> 4) and very high (>6) redshifts.

  6. The Intricate Role of Cold Gas and Dust in Galaxy Evolution at Early Cosmic Epochs

    NASA Astrophysics Data System (ADS)

    Riechers, Dominik A.; Capak, Peter L.; Carilli, Christopher L.

    Cold molecular and atomic gas plays a central role in our understanding of early galaxy formation and evolution. It represents the component of the interstellar medium (ISM) that stars form out of, and its mass, distribution, excitation, and dynamics provide crucial insight into the physical processes that support the ongoing star formation and stellar mass buildup. We here present results that demonstrate the capability of the Atacama Large (sub-)Millimeter Array (ALMA) to detect the cold ISM and dust in ``normal'' galaxies at redshifts z=5-6. We also show detailed studies of the ISM in massive, dust-obscured starburst galaxies out to z>6 with ALMA, the Combined Array for Research in Millimeter-wave Astronomy (CARMA), the Plateau de Bure Interferometer (PdBI), and the Karl G. Jansky Very Large Array (VLA). These observations place some of the most direct constraints on the dust-obscured fraction of the star formation history of the universe at z>5 to date, showing that ``typical'' galaxies at these epochs have low dust content, but also that highly-enriched, dusty starbursts already exist within the first billion years after the Big Bang.

  7. Functional Characterization of Cnidarian HCN Channels Points to an Early Evolution of Ih.

    PubMed

    Baker, Emma C; Layden, Michael J; van Rossum, Damian B; Kamel, Bishoy; Medina, Monica; Simpson, Eboni; Jegla, Timothy

    2015-01-01

    HCN channels play a unique role in bilaterian physiology as the only hyperpolarization-gated cation channels. Their voltage-gating is regulated by cyclic nucleotides and phosphatidylinositol 4,5-bisphosphate (PIP2). Activation of HCN channels provides the depolarizing current in response to hyperpolarization that is critical for intrinsic rhythmicity in neurons and the sinoatrial node. Additionally, HCN channels regulate dendritic excitability in a wide variety of neurons. Little is known about the early functional evolution of HCN channels, but the presence of HCN sequences in basal metazoan phyla and choanoflagellates, a protozoan sister group to the metazoans, indicate that the gene family predates metazoan emergence. We functionally characterized two HCN channel orthologs from Nematostella vectensis (Cnidaria, Anthozoa) to determine which properties of HCN channels were established prior to the emergence of bilaterians. We find Nematostella HCN channels share all the major functional features of bilaterian HCNs, including reversed voltage-dependence, activation by cAMP and PIP2, and block by extracellular Cs+. Thus bilaterian-like HCN channels were already present in the common parahoxozoan ancestor of bilaterians and cnidarians, at a time when the functional diversity of voltage-gated K+ channels was rapidly expanding. NvHCN1 and NvHCN2 are expressed broadly in planulae and in both the endoderm and ectoderm of juvenile polyps. PMID:26555239

  8. The clever strategy of a tiny crustacean eye early in the evolution of vision.

    PubMed

    Schoenemann, Brigitte

    2012-03-01

    Henningsmoenicaris scutula (Walossek and Müller, 1990) (Fig. 1) is a tiny representative of Crustacea, systematically standing close to the stemline. It is found in stinkstone ('Orsten') nodules from the Alum Shale, where a rich fauna of small organisms is excellently preserved. Three dimensional morphology is retained by phosphatisation, which exhibits the finest details, such as cuticular structures, fine appendages and especially the morphology of the compound eyes. The stalked eyes of H. scutula investigated here were equipped with a differentiated visual surface with four different areas of vision. The most intriguing is a field of view oriented laterally to the contralateral side of each eye, so that the fields of view of both compound eyes intersect, and give information about any object moving within the vicinity. Due to this, although, for various reasons this compound eye probably was not able to form a proper image, it was able to perceive tiny prey within a wide visual field, in the same way that the movement of figures can be traced in a chess game. This can be considered as a highly sophisticated visual system that developed early in the history of reported eye evolution, as this compound eye is almost exactly half a billion years old. PMID:22808326

  9. Early stages of growth and crystal structure evolution of boron nitride thin films

    NASA Astrophysics Data System (ADS)

    Henry, Anne; Chubarov, Mikhail; Czigány, Zsolt; Garbrecht, Magnus; Högberg, Hans

    2016-05-01

    A study of the nucleation and crystal structure evolution at the early stages of the growth of sp2-BN thin films on 6H-SiC and α-Al2O3 substrates is presented. The growth is performed at low pressure and high temperature in a hot wall CVD reactor, using ammonia and triethylboron as precursors, and H2 as carrier gas. From high-resolution transmission electron microscopy and X-ray thin film diffraction measurements we observe that polytype pure rhombohedral BN (r-BN) is obtained on 6H-SiC substrates. On α-Al2O3 an AlN buffer obtained by nitridation is needed to promote the growth of hexagonal BN (h-BN) to a thickness of around 4 nm followed by a transition to r-BN growth. In addition, when r-BN is obtained, triangular features show up in plan-view scanning electron microscopy which are not seen on thin h-BN layers. The formation of BN after already one minute of growth is confirmed by X-ray photoelectron spectroscopy.

  10. The light up and evolution of early Massive Black Holes: Athena observations

    NASA Astrophysics Data System (ADS)

    Comastri, Andrea

    2012-07-01

    The known AGN population at z > 6 is made by luminous optical QSO hosting Supermassive Black Holes (M > 10^9 solar masses), likely to represent the tip of the iceberg of the luminosity and mass function. According to theoretical models for structure formation, Massive Black Holes (MBH -- 10^4-10^7 solar masses) are predicted to be abundant in the early Universe (z > 6). The detection of such a population would provide unique constraints on the MBH formation mechanism and subsequent growth and is within the capabilities of deep and ultradeep ATHENA surveys. I will summarize the state of the art of present deep XMM and Chandra surveys, as far as the search for and spectral characterization of high redshift AGN is concerned. I will also present the observational strategy of future multi-cone ATHENA Wide Field Imager (WFI) surveys and the expected breakthroughs in the determination of the luminosity function and its evolution at high (> 4) and very high (> 6) redshifts. Perspectives for high spectral resolution observations with the XMS calorimeter onboard ATHENA will also be outlined.

  11. Early stages in the evolution of the atmosphere and climate on the Earth-group planets

    NASA Technical Reports Server (NTRS)

    Moroz, V. I.; Mukhin, L. M.

    1977-01-01

    The early evolution of the atmospheres and climate of the Earth, Mars and Venus is discussed, based on a concept of common initial conditions and main processes (besides known differences in chemical composition and outgassing rate). It is concluded that: (1) liquid water appeared on the surface of the earth in the first few hundred million years; the average surface temperature was near the melting point for about the first two eons; CO2 was the main component of the atmosphere in the first 100-500 million years; (2) much more temperate outgassing and low solar heating led to the much later appearance of liquid water on the Martian surface, only one to two billion years ago; the Martian era of rivers, relatively dense atmosphere and warm climate ended as a result of irreversible chemical bonding of CO2 by Urey equilibrium processes; (3) a great lack of water in the primordial material of Venus is proposed; liquid water never was present on the surface of the planet, and there was practically no chemical bonding of CO2; the surface temperature was over 600 K four billion years ago.

  12. Hyperthermophilic Archaea as model systems to study origin and evolution of early organisms

    NASA Astrophysics Data System (ADS)

    Cobucci-Ponzano, Beatrice; Carpentieri, Floriana; Ciaramella, Maria; de Falco, M. Rosaria; de Felice, Mariarita; di Giulio, Massimo; di Lauro, Barbara; Mazzone, Marialuisa; Napoli, Alessandra; Perugino, Giuseppe; Pisani, Francesca M.; Salerno, Vincenzo; Rossi, Mose'; Moracci, Marco

    2002-11-01

    The current preponderance of geological and geochemical evidence favours a warm to hot Earth during the first few hundred million years after accretion. Nowadays, volcanic areas, essentially unchanged for at least 4.3 Ga, are populated by hyperthermophilic microorganisms, the majority belonging to the domain Archaea. Most Archaea live in almost any environmental niches previously thought of as insurmountable physical and chemical barriers to life. These findings expanded what we considered the limits of life stimulating the exobiological research area and increasing the likelihood that life could have evolved in planets considered totally inhospitable. The study of the biology of Archaea can provide useful answers to questions concerning the chemical-physical conditions that are compatible with the mechanisms of abiogenesis and the evolution of early life. In this framework, our group is involved since a long time in the study of hyperthermophilic Archaea. We faced some crucial questions dealing with the biology of these organisms like: was the last universal common ancestor (LUCA) a (hyper)thermophile? How are Archaea phylogenetically related to the other domains of living organisms regarding DNA replication, transcription and gene organization? How can withstand DNA and proteins of hyperthermophiles to high temperatures? We here report on recent advances we obtained on these aspects.

  13. Early evolution of the genetic basis for soma in the volvocaceae.

    PubMed

    Hanschen, Erik R; Ferris, Patrick J; Michod, Richard E

    2014-07-01

    To understand the hierarchy of life in evolutionary terms, we must explain why groups of one kind of individual, say cells, evolve into a new higher level individual, a multicellular organism. A fundamental step in this process is the division of labor into nonreproductive altruistic soma. The regA gene is critical for somatic differentiation in Volvox carteri, a multicellular species of volvocine algae. We report the sequence of regA-like genes and several syntenic markers from divergent species of Volvox. We show that regA evolved early in the volvocines and predict that lineages with and without soma descended from a regA-containing ancestor. We hypothesize an alternate evolutionary history of regA than the prevailing "proto-regA" hypothesis. The variation in presence of soma may be explained by multiple lineages independently evolving soma utilizing regA or alternate genetic pathways. Our prediction that the genetic basis for soma exists in species without somatic cells raises a number of questions, most fundamentally, under what conditions would species with the genetic potential for soma, and hence greater individuality, not evolve these traits. We conclude that the evolution of individuality in the volvocine algae is more complicated and labile than previously appreciated on theoretical grounds. PMID:24689915

  14. Norvaline and Norleucine May Have Been More Abundant Protein Components during Early Stages of Cell Evolution

    NASA Astrophysics Data System (ADS)

    Alvarez-Carreño, Claudia; Becerra, Arturo; Lazcano, Antonio

    2013-10-01

    The absence of the hydrophobic norvaline and norleucine in the inventory of protein amino acids is readdressed. The well-documented intracellular accumulation of these two amino acids results from the low-substrate specificity of the branched-chain amino acid biosynthetic enzymes that act over a number of related α-ketoacids. The lack of absolute substrate specificity of leucyl-tRNA synthase leads to a mischarged norvalyl-tRNALeu that evades the translational proofreading activites and produces norvaline-containing proteins, (cf. Apostol et al. J Biol Chem 272:28980-28988, 1997). A similar situation explains the presence of minute but detectable amounts of norleucine in place of methionine. Since with few exceptions both leucine and methionine are rarely found in the catalytic sites of most enzymes, their substitution by norvaline and norleucine, respectively, would have not been strongly hindered in small structurally simple catalytic polypeptides during the early stages of biological evolution. The report that down-shifts of free oxygen lead to high levels of intracellular accumulation of pyruvate and the subsequent biosynthesis of norvaline (Soini et al. Microb Cell Factories 7:30, 2008) demonstrates the biochemical and metabolic consequences of the development of a highly oxidizing environment. The results discussed here also suggest that a broader definition of biomarkers in the search for extraterrestrial life may be required.

  15. A New Taxon of Basal Ceratopsian from China and the Early Evolution of Ceratopsia.

    PubMed

    Han, Fenglu; Forster, Catherine A; Clark, James M; Xu, Xing

    2015-01-01

    Ceratopsia is one of the best studied herbivorous ornithischian clades, but the early evolution of Ceratopsia, including the placement of Psittacosaurus, is still controversial and unclear. Here, we report a second basal ceratopsian, Hualianceratops wucaiwanensis gen. et sp. nov., from the Upper Jurassic (Oxfordian) Shishugou Formation of the Junggar Basin, northwestern China. This new taxon is characterized by a prominent caudodorsal process on the subtemporal ramus of the jugal, a robust quadrate with an expansive quadratojugal facet, a prominent notch near the ventral region of the quadrate, a deep and short dentary, and strongly rugose texturing on the lateral surface of the dentary. Hualianceratops shares several derived characters with both Psittacosaurus and the basal ceratopsians Yinlong, Chaoyangsaurus, and Xuanhuaceratops. A new comprehensive phylogeny of ceratopsians weakly supports both Yinlong and Hualianceratops as chaoyangsaurids (along with Chaoyangsaurus and Xuanhuaceratops), as well as the monophyly of Chaoyangosauridae + Psittacosaurus. This analysis also weakly supports the novel hypothesis that Chaoyangsauridae + Psittacosaurus is the sister group to the rest of Neoceratopsia, suggesting a basal split between these clades before the Late Jurassic. This phylogeny and the earliest Late Jurassic age of Yinlong and Hualianceratops imply that at least five ceratopsian lineages (Yinlong, Hualianceratops, Chaoyangsaurus + Xuanhuaceratops, Psittacosaurus, Neoceratopsia) were present at the beginning of the Late Jurassic. PMID:26649770

  16. Early evolution of an energetic coronal mass ejection and its relation to EUV waves

    SciTech Connect

    Liu, Rui; Wang, Yuming; Shen, Chenglong

    2014-12-10

    We study a coronal mass ejection (CME) associated with an X-class flare whose initiation is clearly observed in the low corona with high-cadence, high-resolution EUV images, providing us a rare opportunity to witness the early evolution of an energetic CME in detail. The eruption starts with a slow expansion of cool overlying loops (∼1 MK) following a jet-like event in the periphery of the active region. Underneath the expanding loop system, a reverse S-shaped dimming is seen immediately above the brightening active region in hot EUV passbands. The dimming is associated with a rising diffuse arch (∼6 MK), which we interpret as a preexistent, high-lying flux rope. This is followed by the arising of a double hot channel (∼10 MK) from the core of the active region. The higher structures rise earlier and faster than lower ones, with the leading front undergoing extremely rapid acceleration up to 35 km s{sup –2}. This suggests that the torus instability is the major eruption mechanism and that it is the high-lying flux rope rather than the hot channels that drives the eruption. The compression of coronal plasmas skirting and overlying the expanding loop system, whose aspect ratio h/r increases with time as a result of the rapid upward acceleration, plays a significant role in driving an outward-propagating global EUV wave and a sunward-propagating local EUV wave, respectively.

  17. Early Evolution of an Energetic Coronal Mass Ejection and its Relation to EUV Waves

    NASA Astrophysics Data System (ADS)

    Liu, Rui; Wang, Yuming; Shen, Chenglong

    2014-12-01

    We study a coronal mass ejection (CME) associated with an X-class flare whose initiation is clearly observed in the low corona with high-cadence, high-resolution EUV images, providing us a rare opportunity to witness the early evolution of an energetic CME in detail. The eruption starts with a slow expansion of cool overlying loops (~1 MK) following a jet-like event in the periphery of the active region. Underneath the expanding loop system, a reverse S-shaped dimming is seen immediately above the brightening active region in hot EUV passbands. The dimming is associated with a rising diffuse arch (~6 MK), which we interpret as a preexistent, high-lying flux rope. This is followed by the arising of a double hot channel (~10 MK) from the core of the active region. The higher structures rise earlier and faster than lower ones, with the leading front undergoing extremely rapid acceleration up to 35 km s-2. This suggests that the torus instability is the major eruption mechanism and that it is the high-lying flux rope rather than the hot channels that drives the eruption. The compression of coronal plasmas skirting and overlying the expanding loop system, whose aspect ratio h/r increases with time as a result of the rapid upward acceleration, plays a significant role in driving an outward-propagating global EUV wave and a sunward-propagating local EUV wave, respectively.

  18. A New Taxon of Basal Ceratopsian from China and the Early Evolution of Ceratopsia

    PubMed Central

    Han, Fenglu; Forster, Catherine A.; Clark, James M.; Xu, Xing

    2015-01-01

    Ceratopsia is one of the best studied herbivorous ornithischian clades, but the early evolution of Ceratopsia, including the placement of Psittacosaurus, is still controversial and unclear. Here, we report a second basal ceratopsian, Hualianceratops wucaiwanensis gen. et sp. nov., from the Upper Jurassic (Oxfordian) Shishugou Formation of the Junggar Basin, northwestern China. This new taxon is characterized by a prominent caudodorsal process on the subtemporal ramus of the jugal, a robust quadrate with an expansive quadratojugal facet, a prominent notch near the ventral region of the quadrate, a deep and short dentary, and strongly rugose texturing on the lateral surface of the dentary. Hualianceratops shares several derived characters with both Psittacosaurus and the basal ceratopsians Yinlong, Chaoyangsaurus, and Xuanhuaceratops. A new comprehensive phylogeny of ceratopsians weakly supports both Yinlong and Hualianceratops as chaoyangsaurids (along with Chaoyangsaurus and Xuanhuaceratops), as well as the monophyly of Chaoyangosauridae + Psittacosaurus. This analysis also weakly supports the novel hypothesis that Chaoyangsauridae + Psittacosaurus is the sister group to the rest of Neoceratopsia, suggesting a basal split between these clades before the Late Jurassic. This phylogeny and the earliest Late Jurassic age of Yinlong and Hualianceratops imply that at least five ceratopsian lineages (Yinlong, Hualianceratops, Chaoyangsaurus + Xuanhuaceratops, Psittacosaurus, Neoceratopsia) were present at the beginning of the Late Jurassic. PMID:26649770

  19. Nonlinear waves during an early evolution of CO2 plume in an aquifer

    NASA Astrophysics Data System (ADS)

    Afanasyev, Andrey; Sultanova, Tatiana

    2016-04-01

    Underground storage of CO2 in saline aquifers results in complicated multiphase buoyancy-driven flows of CO2 and formation water. There is extended literature addressing late evolution of the CO2 plume in the regions remote from injection well. In this study, we consider an early period of CO2 injection when multiphase flows occur near the well, in the bottom-hole zone. We consider the self-similar Riemann problem in application to axisymmetric injection of supercritical CO2 through a vertical well. The injection occurs into a horizontal permeable aquifer of infinite lateral extension. In an asymptotic approximation, we construct the solutions of the problem by means of direct numerical simulations. We take into account thermal processes and phase transitions, and the injected CO2 can be either warmer or colder than the reservoir temperature. The wave pattern propagating from CO2 injection well in the aquifer consists of up to six nonlinear Riemann (rarefaction) waves and phase discontinuities (shock waves; displacement and temperature fronts). There can be two type of Riemann waves corresponding to different characteristic velocities. The first type corresponds to isothermal flow, whereas the second type is responsible for temperature alterations and phase transitions. We determine qualitatively different solutions depending on initial reservoir temperature and injection parameters, and we demonstrate solutions in which reservoir and injection parameters are similar to parameters at several existing storage sites. Each type of the solutions corresponds to a specific flow regime in the bottom-hole zone. Due to phase transitions, temperature distribution can be non-monotonic when moving away from the injection well. We investigate the influence of the pressure increase around CO2 injection well on the flow regimes. Finally, we evaluate accuracy of the asymptotic solution by its comparison with the results of direct numerical simulations. The solutions of the Riemann

  20. The Dependence of the Evolution of Early-Type Galaxies on their Environment

    NASA Astrophysics Data System (ADS)

    Fritz, Alexander

    2006-05-01

    This thesis describes the analysis of a data set of 121 elliptical and lenticular (S0) galaxies, located in different environments and at distances corresponding to look-back times between 2 and 5 Gyrs. Such a sample allows to study the environmental dependence of the internal properties of these early-type galaxies to draw conclusions on the formation epoch and evolutionary history of their sub-classes of elliptical and S0 galaxies.As a discrimination factor for the environment, the X-ray luminosity flux is utilised, which is proportional to the square of the mass of a galaxy. The highest galaxy density is found in rich galaxy clusters, (low-mass) poor galaxy clusters exhibit a factor of 10 lower number density whereas the lowest density is defined by individual, isolated field galaxies. Theoretical predictions based on a hierarchical structure growth suggest for various environments different evolutionary tracks which yield to a diversity of galaxy ages.All objects analysed in this work were selected based upon deep ground-based multi-band imaging data. In addition, for the central regions of the galaxy clusters and the two extended sky areas which comprise the field galaxies, the FORS Deep Field and the William Herschel Deep Field, the high resolution images of the Hubble Space Telescope (HST) provide a detailed morphological classification and structural parameter analysis. Multi-Object-Spectroscopy was conducted for all galaxies at the 8.2-m Very Large Telescope (VLT, Chile) and the Calar Alto 3.5-m telescope (Spain). Using high signal-to-noise spectroscopy the internal velocity dispersions (i.e., the random motion of the individual stars) of the galaxies are measured, which are an indicator for the total galaxy masses. Based on different scaling relations, in particular the Faber-Jackson relation between velocity dispersion and luminosity, the absolute brightnesses of the distant galaxies are compared to galaxies in the local universe. While high

  1. The first molecular phylogeny of Strepsiptera (Insecta) reveals an early burst of molecular evolution correlated with the transition to endoparasitism.

    PubMed

    McMahon, Dino P; Hayward, Alexander; Kathirithamby, Jeyaraney

    2011-01-01

    A comprehensive model of evolution requires an understanding of the relationship between selection at the molecular and phenotypic level. We investigate this in Strepsiptera, an order of endoparasitic insects whose evolutionary biology is poorly studied. We present the first molecular phylogeny of Strepsiptera, and use this as a framework to investigate the association between parasitism and molecular evolution. We find evidence of a significant burst in the rate of molecular evolution in the early history of Strepsiptera. The evolution of morphological traits linked to parasitism is significantly correlated with the pattern in molecular rate. The correlated burst in genotypic-phenotypic evolution precedes the main phase of strepsipteran diversification, which is characterised by the return to a low and even molecular rate, and a period of relative morphological stability. These findings suggest that the transition to endoparasitism led to relaxation of selective constraint in the strepsipteran genome. Our results indicate that a parasitic lifestyle can affect the rate of molecular evolution, although other causal life-history traits correlated with parasitism may also play an important role. PMID:21738621

  2. HAZMAT. I. The evolution of far-UV and near-UV emission from early M stars

    SciTech Connect

    Shkolnik, Evgenya L.; Barman, Travis S. E-mail: barman@lpl.arizona.edu

    2014-10-01

    The spectral energy distribution, variability, and evolution of the high-energy radiation from an M dwarf planet host is crucial in understanding the planet's atmospheric evolution and habitability and in interpreting the planet's spectrum. The star's extreme-UV (EUV), far-UV (FUV), and near-UV (NUV) emission can chemically modify, ionize, and erode the atmosphere over time. This makes determining the lifetime exposure of such planets to stellar UV radiation critical for both the evolution of a planet's atmosphere and our potential to characterize it. Using the early M star members of nearby young moving groups, which sample critical ages in planet formation and evolution, we measure the evolution of the GALEX NUV and FUV flux as a function of age. The median UV flux remains at a 'saturated' level for a few hundred million years, analogous to that observed for X-ray emission. By the age of the Hyades Cluster (650 Myr), we measure a drop in UV flux by a factor of 2-3 followed by a steep drop from old (several Gyrs) field stars. This decline in activity beyond 300 Myr follows roughly t {sup –1}. Despite this clear evolution, there remains a wide range, of 1-2 orders of magnitude, in observed emission levels at every age. These UV data supply the much-needed constraints to M dwarf upper-atmosphere models, which will provide empirically motivated EUV predictions and more accurate age-dependent UV spectra as inputs to planetary photochemical models.

  3. Coupled noble gas-hydrocarbon evolution of the early Earth atmosphere upon solar UV irradiation

    NASA Astrophysics Data System (ADS)

    Hébrard, E.; Marty, B.

    2014-01-01

    Using a new photochemical model of the Earth's early atmosphere, the relationship between noble gas photoionization and organic photochemistry has been investigated from the Archean eon to the present day. We have found that the enhanced UV emission of the young Sun triggered a peculiar atmospheric chemistry in a CH4-rich early atmosphere that resulted in the increased formation of an organic haze, similar to the preliminary results of a previous study (Ribas et al., 2010). We have investigated the interaction between this haze and noble gases photoionized by the UV light from the younger Sun. Laboratory experiments have shown indeed that ionized xenon trapping into organics (1) is more efficient that other ionized noble gases trapping and (2) results in a significant enrichment of heavy xenon isotopes relative to the light ones (e.g., Frick et al., 1979; Marrocchi et al., 2011). We find moreover preferential photoionization of xenon that peaks at an altitude range comparable to that of the organic haze formation, in contrast to other noble gases. Trapping and fractioning of ionized xenon in the organic haze could therefore have been far more efficient than for other noble gases, and could have been particularly effective throughout the Archean eon, since the UV irradiation flux from the young Sun was expected to be substantially higher than today (Ribas et al., 2010; Claire et al., 2012). Thus we suspect that the unique isotopic fractionation of atmospheric xenon and its elemental depletion in the atmosphere relative to other noble gases, compared to potential cosmochemical components, could have resulted from a preferential incorporation of the heaviest xenon isotopes into organics. A fraction of atmospheric xenon could have been continuously trapped in the forming haze and enriched in its heavy isotopes, while another fraction would have escaped from the atmosphere to space, with, or without isotope selection of the lightest isotopes. The combination of these

  4. The formation of galaxy bulges: Spectrophotometric constraints

    NASA Astrophysics Data System (ADS)

    Prugniel, Ph.; Maubon, G.; Simien, F.

    2001-01-01

    We have measured Mg2, Fe 5270 and Fe 5335 spectrophotometric indices (LICK system) in the bulge of 89 galaxies, mostly spirals from the Héraudeau (\\cite{her96}) sample. The indices are reduced to a null velocity dispersion and normalized to an aperture of 0.2 h-1 kpc. The mean errors are 0.009 mag on Mg2, and 0.3 Å on the iron indices. These measurements almost double the amount of similar data already available on spiral galaxies. Our data confirm the existence of the relation between Mg2, and sigma0, the central stellar velocity dispersion; we find an even tighter relation between Mg2, and Vmrot, the maximum rotational velocity of the galaxy, deduced from HI observations. For the most massive bulges, these correlations may be interpreted as a mass-metallicity relation. However, the presence of young stellar populations, traced by the detection of [OIII] lambda 5007 Å, emission, provides clear evidence that age effects do play a role. Since the contribution of the young population is anti-correlated to the mass of the galaxy, it continues the Mg2, vs. sigma0 , relation toward the low-sigma0, region and globally increases its slope. We also present evidence for a new positive correlation between Fe indices and sigma0, and for a significant correlation between the line-strength indices and the total or disk luminosity. We propose to model the whole sequence of bulges within the folowing framework: bulges are composed of a primary population formed prior to the disk, during the initial collapse, and of a secondary population formed during its evolution. The whole family of bulges can be classified into three classes: (A) the bulges dominated by young populations are generally small, have ionized gas, low velocity dispersion and low line strengths; (B) the bulges dominated by the primary population lie along the mass-metallicity sequence defined for elliptical galaxies; and (C) the bulges where the secondary population is significant are less Mg-over-abundant than

  5. Analysis of the Early Stages and Evolution of Dental Enamel Erosion.

    PubMed

    Derceli, Juliana Dos Reis; Faraoni, Juliana Jendiroba; Pereira-da-Silva, Marcelo Assumpção; Palma-Dibb, Regina Guenka

    2016-01-01

    The aim of this study was to evaluate by atomic force microscopy (AFM) the early phases and evolution of dental enamel erosion caused by hydrochloric acid exposure, simulating gastroesophageal reflux episodes. Polished bovine enamel slabs (4x4x2 mm) were selected and exposed to 0.1 mL of 0.01 M hydrochloric acid (pH=2) at 37 ?#61472;?#61616;C using five different exposure intervals (n=1): no acid exposure (control), 10 s, 20 s, 30 s and 40 s. The exposed area was analyzed by AFM in 3 regions to measure the roughness, surface area and morphological surface. The data were analyzed qualitatively. Roughness started as low as that of the control sample, Rrms=3.5 nm, and gradually increased at a rate of 0.3 nm/s, until reaching Rrms=12.5 nm at 30 s. After 40 s, the roughness presented increment of 0.40 nm only. Surface area (SA) increased until 20 s, and for longer exposures, the surface area was constant (at 30 s, SA=4.40 μm2 and at 40 s, SA=4.43 μm2). As regards surface morphology, the control sample presented smaller hydroxyapatite crystals (22 nm) and after 40 s the crystal size was approximately 60 nm. Short periods of exposure were sufficient to produce enamel demineralization in different patterns and the morphological structure was less affected by exposure to hydrochloric acid over 30 s. PMID:27224566

  6. The VLA View of the HL Tau Disk: Disk Mass, Grain Evolution, and Early Planet Formation

    NASA Astrophysics Data System (ADS)

    Carrasco-González, Carlos; Henning, Thomas; Chandler, Claire J.; Linz, Hendrik; Pérez, Laura; Rodríguez, Luis F.; Galván-Madrid, Roberto; Anglada, Guillem; Birnstiel, Til; van Boekel, Roy; Flock, Mario; Klahr, Hubert; Macias, Enrique; Menten, Karl; Osorio, Mayra; Testi, Leonardo; Torrelles, José M.; Zhu, Zhaohuan

    2016-04-01

    The first long-baseline ALMA campaign resolved the disk around the young star HL Tau into a number of axisymmetric bright and dark rings. Despite the very young age of HL Tau, these structures have been interpreted as signatures for the presence of (proto)planets. The ALMA images triggered numerous theoretical studies based on disk–planet interactions, magnetically driven disk structures, and grain evolution. Of special interest are the inner parts of disks, where terrestrial planets are expected to form. However, the emission from these regions in HL Tau turned out to be optically thick at all ALMA wavelengths, preventing the derivation of surface density profiles and grain-size distributions. Here, we present the most sensitive images of HL Tau obtained to date with the Karl G. Jansky Very Large Array at 7.0 mm wavelength with a spatial resolution comparable to the ALMA images. At this long wavelength, the dust emission from HL Tau is optically thin, allowing a comprehensive study of the inner disk. We obtain a total disk dust mass of (1–3) × 10‑3 M ⊙, depending on the assumed opacity and disk temperature. Our optically thin data also indicate fast grain growth, fragmentation, and formation of dense clumps in the inner densest parts of the disk. Our results suggest that the HL Tau disk may be actually in a very early stage of planetary formation, with planets not already formed in the gaps but in the process of future formation in the bright rings.

  7. Crustal types, distribution of salt and the early evolution of the Gulf of Mexico basin

    SciTech Connect

    Buffler, R.T. )

    1990-05-01

    A new contour map on the top of basement shows the overall configuration of the entire Gulf of Mexico basin. Basement, as used here, is all rocks lying below (older than) the extensive Middle Jurassic (Callovian ) premarine evaporites (Louann Salt, etc.) plus the Late Jurassic oceanic crust in the deep part of the basin. The contour map combined with all other available geophysical data has been used to subdivide the gulf basin into four crustal types: continental, thick transitional, thin transitional, and oceanic crust. The broad region of transitional crust and the basic architecture of the basin shown by the map is believed to have formed mainly during a separate Middle Jurassic period of widespread attenuation of the entire gulf region. The area of thick transitional crust around the periphery of the northern gulf is characterized by broad basement highs and lows with wave lengths of 200-300 km. These features controlled the general distribution and thickness of salt and the overlying Jurassic through Lower Cretaceous rocks. In the area of thin transitional crust Mesozoic basins tend to be assymetrical and generally trend more parallel to the overall basin. The boundary between thin transitional crust and oceanic crust is characterized by various salt-related features. For example, the northwest and north-central boundaries are defined by two northeast trending salt-cored foldbelts, the Perdido and Mississippi fan foldbelts, respectively. The offset between the two foldbelts may represent a major transform boundary related to the northwest opening of the gulf basin. All these data put important constraints on models for early gulf evolution.

  8. Alternative haplotypes of antigen processing genes in zebrafish diverged early in vertebrate evolution.

    PubMed

    McConnell, Sean C; Hernandez, Kyle M; Wcisel, Dustin J; Kettleborough, Ross N; Stemple, Derek L; Yoder, Jeffrey A; Andrade, Jorge; de Jong, Jill L O

    2016-08-23

    Antigen processing and presentation genes found within the MHC are among the most highly polymorphic genes of vertebrate genomes, providing populations with diverse immune responses to a wide array of pathogens. Here, we describe transcriptome, exome, and whole-genome sequencing of clonal zebrafish, uncovering the most extensive diversity within the antigen processing and presentation genes of any species yet examined. Our CG2 clonal zebrafish assembly provides genomic context within a remarkably divergent haplotype of the core MHC region on chromosome 19 for six expressed genes not found in the zebrafish reference genome: mhc1uga, proteasome-β 9b (psmb9b), psmb8f, and previously unknown genes psmb13b, tap2d, and tap2e We identify ancient lineages for Psmb13 within a proteasome branch previously thought to be monomorphic and provide evidence of substantial lineage diversity within each of three major trifurcations of catalytic-type proteasome subunits in vertebrates: Psmb5/Psmb8/Psmb11, Psmb6/Psmb9/Psmb12, and Psmb7/Psmb10/Psmb13. Strikingly, nearby tap2 and MHC class I genes also retain ancient sequence lineages, indicating that alternative lineages may have been preserved throughout the entire MHC pathway since early diversification of the adaptive immune system ∼500 Mya. Furthermore, polymorphisms within the three MHC pathway steps (antigen cleavage, transport, and presentation) are each predicted to alter peptide specificity. Lastly, comparative analysis shows that antigen processing gene diversity is far more extensive than previously realized (with ancient coelacanth psmb8 lineages, shark psmb13, and tap2t and psmb10 outside the teleost MHC), implying distinct immune functions and conserved roles in shaping MHC pathway evolution throughout vertebrates. PMID:27493218

  9. The early evolution of the phosphagen kinases--insights from choanoflagellate and poriferan arginine kinases.

    PubMed

    Conejo, Maria; Bertin, Matt; Pomponi, Shirley A; Ellington, W Ross

    2008-01-01

    Arginine kinase (AK) is a member of a large family of phosphoryl transfer enzymes called phosphagen (guanidino) kinases. AKs are present in certain protozoans, sponges, cnidarians, and both lophotrochozoan and ecdysozoan protostomes. Another phosphagen kinase, creatine kinase (CK), is found in sponges, cnidarians, and both deuterostome and protostome groups but does not appear to be present in protozoans. To probe the early evolution of phosphagen kinases, we have amplified the cDNAs for AKs from three choanoflagellates and from the hexactinellid sponge Aphrocallistes beatrix and the demosponges Suberites fuscus and Microciona prolifera. Phylogenetic analysis using maximum likelihood of these choanoflagellate and sponge AKs with other AK sequences revealed that the AK from the choanoflagellate Monosiga brevicollis clusters with the AK from the glass sponge Aphrocallistes and is part of a larger cluster containing AKs from the demosponges Suberites and Microciona as well as basal and protostome invertebrates. In contrast, AKs from Codonosiga gracilis and Monosiga ovata form a distinct cluster apart from all other AK sequences. tBLASTn searches of the recently released M. brevicollis genome database showed that this species has three unique AK genes-one virtually identical to the M. brevicollis cDNA and the other two showing great similarity to C. gracilis and M. ovata AKs. Three distinct AK genes are likely present in choanoflagellates. Two of these AKs display extensive similarity to both CKs and an AK from sponges. Previous work has shown CK evolved from an AK-like ancestor prior to the divergence of sponges. The present results provide evidence suggesting that the initial gene duplication event(s) leading to the CK lineage may have occurred before the divergence of the choanoflagellate and animal lineages. PMID:18064398

  10. Evolution of Early to Middle Cambrian carbonate platform, southwest Virginia Appalachians

    SciTech Connect

    Barnaby, R.J.; Read, J.F.

    1987-05-01

    Three core transects through the Early to Middle Cambrian continental shelf margin (Shady-Rome sequence) allow its evolution to be established. The sequence was initiated on a drowned clastic shelf to form a ramp with downslope mud mounds. Overall subsidence rates are estimated to be 5-10 cm/1000 years. Mud mounds consist of rare Archaeocyathid reefs that cap stromatactis MS/WS core facies and form upper parts of shallowing-upward sequences whose basal portion is shale and nodular bedded limestone. Individual mounds (1-30 m thick) are laterally extensive; some are over 3.5 km wide. Depositional slopes on the flanks range from < 0.5/sup 0/ to > 5.0/sup 0/. Three periods of backstepping of the mud mound sequences resulted from sea level fluctuations (average period approx. = 2 m.y.). Following the second backstep, regressive shelf sands and basinal turbidites formed. Later transgression led to development of mud mounds and patch reefs above the sands. Sea level fall during Rome regression caused widespread deposition of cyclic red beds and carbonates on the slowly subsiding shelf interior. On the more rapidly subsiding outer platform where subsidence rates exceeded sea level fall, an algal reef-rimmed shelf formed landward of earlier ramp buildups. Seaward of the shelf were thick deposits of periplatform talus and foreslope sands. Small-scale shallowing-upward sequences record 10/sup 4/ to 10/sup 5/-year sea level fluctuations superimposed on longer term cycles. The platform was exposed during major regressions, resulting in meteoric diagenesis of the platform as well as the off-platform talus, which provided conduits for deeply circulating meteoric fluids.

  11. Early Evolution of the Eukaryotic Ca2+ Signaling Machinery: Conservation of the CatSper Channel Complex

    PubMed Central

    Cai, Xinjiang; Wang, Xiangbing; Clapham, David E.

    2014-01-01

    Calcium signaling is one of the most extensively employed signal transduction mechanisms in life. As life evolved into increasingly complex organisms, Ca2+ acquired more extensive and varied functions. Here, we compare genes encoding proteins that govern Ca2+ entry and exit across cells or organelles within organisms of early eukaryotic evolution into fungi, plants, and animals. Recent phylogenomics analyses reveal a complex Ca2+ signaling machinery in the apusozoan protist Thecamonas trahens, a putative unicellular progenitor of Opisthokonta. We compare T. trahens Ca2+ signaling to that in a marine bikont protist, Aurantiochytrium limacinum, and demonstrate the conservation of key Ca2+ signaling molecules in the basally diverging alga Cyanophora paradoxa. Particularly, our findings reveal the conservation of the CatSper channel complex in Au. limacinum and C. paradoxa, suggesting that the CatSper complex likely originated from an ancestral Ca2+ signaling machinery at the root of early eukaryotic evolution prior to the unikont/bikont split. PMID:25063443

  12. The mitochondrial genomes of the early land plants Treubia lacunosa and Anomodon rugelii: dynamic and conservative evolution.

    PubMed

    Liu, Yang; Xue, Jia-Yu; Wang, Bin; Li, Libo; Qiu, Yin-Long

    2011-01-01

    Early land plant mitochondrial genomes captured important changes of mitochondrial genome evolution when plants colonized land. The chondromes of seed plants show several derived characteristics, e.g., large genome size variation, rapid intra-genomic rearrangement, abundant introns, and highly variable levels of RNA editing. On the other hand, the chondromes of charophytic algae are still largely ancestral in these aspects, resembling those of early eukaryotes. When the transition happened has been a long-standing question in studies of mitochondrial genome evolution. Here we report complete mitochondrial genome sequences from an early-diverging liverwort, Treubia lacunosa, and a late-evolving moss, Anomodon rugelii. The two genomes, 151,983 and 104,239 base pairs in size respectively, contain standard sets of protein coding genes for respiration and protein synthesis, as well as nearly full sets of rRNA and tRNA genes found in the chondromes of the liverworts Marchantia polymorpha and Pleurozia purpurea and the moss Physcomitrella patens. The gene orders of these two chondromes are identical to those of the other liverworts and moss. Their intron contents, with all cis-spliced group I or group II introns, are also similar to those in the previously sequenced liverwort and moss chondromes. These five chondromes plus the two from the hornworts Phaeoceros laevis and Megaceros aenigmaticus for the first time allowed comprehensive comparative analyses of structure and organization of mitochondrial genomes both within and across the three major lineages of bryophytes. These analyses led to the conclusion that the mitochondrial genome experienced dynamic evolution in genome size, gene content, intron acquisition, gene order, and RNA editing during the origins of land plants and their major clades. However, evolution of this organellar genome has remained rather conservative since the origin and initial radiation of early land plants, except within vascular plants. PMID

  13. Raman spectroscopic detection of early stages in DMBA-induced tumor evolution in hamster buccal pouch model: an exploratory study

    NASA Astrophysics Data System (ADS)

    Ghanate, Avinash D.; Kumar, G.; Talathi, Sneha; Maru, G. B.; Krishna, C. Murali

    2010-12-01

    Oral cancers are the serious health problem in developing as well as developed world, and more so in India and other south Asian countries. Survival rate of these cancers, despite advances in treatment modalities are one of the poorest which is attributed to lack of reliable screening and early detection methods. The hamster buccal pouch (HBP)carcinogenesis model closely mimics human oral cancers. Optical spectroscopy methods are sensitive enough to detect subtle biochemical changes and thus hold great potential in early detection of cancers. However, efficacy of these techniques in classifying of sequential evolution of tumors has never been tested. Therefore, in this study, we have explored the feasibility of Raman spectroscopic classification of different stages of cancers in hamster model. Strong vibrational modes of lipids (1440, 1654, and 1746 cm-1) are seen in control tissue spectra, whereas strong protein bands are seen in spectra of DMBA treated tissues. These differences were exploited to classify control and treated tissues using Linear Discriminant Analysis (LDA), Principle Component Analysis (PCA)-Limit test, Factorial Discriminant Analysis (FDA), Quadratic Discriminant Analysis (QDA), PLS-DA and non- linear decision tree methods. All these techniques have shown good classification between spectra of different stages of tumor evolution and results were further successfully verified by leave-one-out and single blinded methods. Thus findings of this study, first of its kind,demonstrate the feasibility of Raman spectroscopic detection of early changes in tumor evolution.

  14. Raman spectroscopic detection of early stages in DMBA-induced tumor evolution in hamster buccal pouch model: an exploratory study

    NASA Astrophysics Data System (ADS)

    Ghanate, Avinash D.; Kumar, G.; Talathi, Sneha; Maru, G. B.; Krishna, C. Murali

    2011-08-01

    Oral cancers are the serious health problem in developing as well as developed world, and more so in India and other south Asian countries. Survival rate of these cancers, despite advances in treatment modalities are one of the poorest which is attributed to lack of reliable screening and early detection methods. The hamster buccal pouch (HBP)carcinogenesis model closely mimics human oral cancers. Optical spectroscopy methods are sensitive enough to detect subtle biochemical changes and thus hold great potential in early detection of cancers. However, efficacy of these techniques in classifying of sequential evolution of tumors has never been tested. Therefore, in this study, we have explored the feasibility of Raman spectroscopic classification of different stages of cancers in hamster model. Strong vibrational modes of lipids (1440, 1654, and 1746 cm-1) are seen in control tissue spectra, whereas strong protein bands are seen in spectra of DMBA treated tissues. These differences were exploited to classify control and treated tissues using Linear Discriminant Analysis (LDA), Principle Component Analysis (PCA)-Limit test, Factorial Discriminant Analysis (FDA), Quadratic Discriminant Analysis (QDA), PLS-DA and non- linear decision tree methods. All these techniques have shown good classification between spectra of different stages of tumor evolution and results were further successfully verified by leave-one-out and single blinded methods. Thus findings of this study, first of its kind,demonstrate the feasibility of Raman spectroscopic detection of early changes in tumor evolution.

  15. Microbes, Mineral Evolution, and the Rise of Microcontinents-Origin and Coevolution of Life with Early Earth.

    PubMed

    Grosch, Eugene G; Hazen, Robert M

    2015-10-01

    Earth is the most mineralogically diverse planet in our solar system, the direct consequence of a coevolving geosphere and biosphere. We consider the possibility that a microbial biosphere originated and thrived in the early Hadean-Archean Earth subseafloor environment, with fundamental consequences for the complex evolution and habitability of our planet. In this hypothesis paper, we explore possible venues for the origin of life and the direct consequences of microbially mediated, low-temperature hydrothermal alteration of the early oceanic lithosphere. We hypothesize that subsurface fluid-rock-microbe interactions resulted in more efficient hydration of the early oceanic crust, which in turn promoted bulk melting to produce the first evolved fragments of felsic crust. These evolved magmas most likely included sialic or tonalitic sheets, felsic volcaniclastics, and minor rhyolitic intrusions emplaced in an Iceland-type extensional setting as the earliest microcontinents. With the further development of proto-tectonic processes, these buoyant felsic crustal fragments formed the nucleus of intra-oceanic tonalite-trondhjemite-granitoid (TTG) island arcs. Thus microbes, by facilitating extensive hydrothermal alteration of the earliest oceanic crust through bioalteration, promoted mineral diversification and may have been early architects of surface environments and microcontinents on young Earth. We explore how the possible onset of subseafloor fluid-rock-microbe interactions on early Earth accelerated metavolcanic clay mineral formation, crustal melting, and subsequent metamorphic mineral evolution. We also consider environmental factors supporting this earliest step in geosphere-biosphere coevolution and the implications for habitability and mineral evolution on other rocky planets, such as Mars. PMID:26430911

  16. Hf-W chronology of the accretion and early evolution of asteroids and terrestrial planets

    NASA Astrophysics Data System (ADS)

    Kleine, Thorsten; Touboul, Mathieu; Bourdon, Bernard; Nimmo, Francis; Mezger, Klaus; Palme, Herbert; Jacobsen, Stein B.; Yin, Qing-Zhu; Halliday, Alexander N.

    2009-09-01

    The 182Hf- 182W systematics of meteoritic and planetary samples provide firm constraints on the chronology of the accretion and earliest evolution of asteroids and terrestrial planets and lead to the following succession and duration of events in the earliest solar system. Formation of Ca,Al-rich inclusions (CAIs) at 4568.3 ± 0.7 Ma was followed by the accretion and differentiation of the parent bodies of some magmatic iron meteorites within less than ˜1 Myr. Chondrules from H chondrites formed 1.7 ± 0.7 Myr after CAIs, about contemporaneously with chondrules from L and LL chondrites as shown by their 26Al- 26Mg ages. Some magmatism on the parent bodies of angrites, eucrites, and mesosiderites started as soon as ˜3 Myr after CAI formation and may have continued until ˜10 Myr. A similar timescale is obtained for the high-temperature metamorphic evolution of the H chondrite parent body. Thermal modeling combined with these age constraints reveals that the different thermal histories of meteorite parent bodies primarily reflect their initial abundance of 26Al, which is determined by their accretion age. Impact-related processes were important in the subsequent evolution of asteroids but do not appear to have induced large-scale melting. For instance, Hf-W ages for eucrite metals postdate CAI formation by ˜20 Myr and may reflect impact-triggered thermal metamorphism in the crust of the eucrite parent body. Likewise, the Hf-W systematics of some non-magmatic iron meteorites were modified by impact-related processes but the timing of this event(s) remains poorly constrained. The strong fractionation of lithophile Hf from siderophile W during core formation makes the Hf-W system an ideal chronometer for this major differentiation event. However, for larger planets such as the terrestrial planets the calculated Hf-W ages are particularly sensitive to the occurrence of large impacts, the degree to which impactor cores re-equilibrated with the target mantle during

  17. Reciprocal Vegetation-Flow Feedbacks Driving Early-Stage Landscape Evolution in a Restored Wet Meadow

    NASA Astrophysics Data System (ADS)

    Larsen, L.; Merritts, D. J.; Walter, R. C.; Watts, D.

    2013-12-01

    Just as taxonomic classification has improved understanding in biology, ecogeomorphologists would benefit from a functional classification of biota based on the biophysical feedbacks that they engage in. Early stages of landscape development following disturbance provide a unique opportunity to delineate and understand these feedback processes, as the diversity in functional morphotypes (a.k.a. 'ecomorphs,' to expand on a concept from terrestrial ecology) is high and the potential for self-organization of landscape pattern strong. We used the opportunity of a stream restoration that reset its floodplain to 'initial conditions' to perform a suite of biophysical measurements designed to delineate the classes of feedback that influence landscape evolution in distinct ways. The Big Spring Run restoration (Lancaster, PA), completed in November 2011, involved removal of 15,000 t of legacy sediment from the valley bottom to expose a Holocene hydric layer and reestablish wet meadow hydrology and biota. By performing repeat biogeomorphic surveys within a study grid, we tested the hypothesis that distinct ecomorphs determine the persistence and location of channel and microtopographic features. The qualitatively distinct patch types surveyed included carpet-forming mat vegetation, tussock-forming vegetation, sparsely vegetated mudflats, benthic algal mats, mixed herbaceous communities, grasses, and clonal emergent vegetation. Within each sampling location, changes in vegetation community architecture, grain size distribution, critical shear stress for sediment entrainment, and topography were monitored over time, and flow resistance was measured. An overbank flow event that completely filled the floodplain provided an additional opportunity to measure vegetation-flow-sediment interactions. Once emergent vegetation was bent over by flow, vegetation had a negligible influence on flow velocity--in contrast to most other wetlands--but continued to shelter the bed from sediment

  18. HAZMAT. I. The Evolution of Far-UV and Near-UV Emission from Early M Stars

    NASA Astrophysics Data System (ADS)

    Shkolnik, Evgenya L.; Barman, Travis S.

    2014-10-01

    The spectral energy distribution, variability, and evolution of the high-energy radiation from an M dwarf planet host is crucial in understanding the planet's atmospheric evolution and habitability and in interpreting the planet's spectrum. The star's extreme-UV (EUV), far-UV (FUV), and near-UV (NUV) emission can chemically modify, ionize, and erode the atmosphere over time. This makes determining the lifetime exposure of such planets to stellar UV radiation critical for both the evolution of a planet's atmosphere and our potential to characterize it. Using the early M star members of nearby young moving groups, which sample critical ages in planet formation and evolution, we measure the evolution of the GALEX NUV and FUV flux as a function of age. The median UV flux remains at a "saturated" level for a few hundred million years, analogous to that observed for X-ray emission. By the age of the Hyades Cluster (650 Myr), we measure a drop in UV flux by a factor of 2-3 followed by a steep drop from old (several Gyrs) field stars. This decline in activity beyond 300 Myr follows roughly t -1. Despite this clear evolution, there remains a wide range, of 1-2 orders of magnitude, in observed emission levels at every age. These UV data supply the much-needed constraints to M dwarf upper-atmosphere models, which will provide empirically motivated EUV predictions and more accurate age-dependent UV spectra as inputs to planetary photochemical models. Based on observations made with the NASA Galaxy Evolution Explorer (GALEX). GALEX was operated for NASA by the California Institute of Technology under NASA contract NAS5-98034.

  19. Early Paleozoic sedimentary record of the Chinese Altai: Implications for its tectonic evolution

    NASA Astrophysics Data System (ADS)

    Long, Xiaoping; Sun, Min; Yuan, Chao; Xiao, Wenjiao; Cai, Keda

    The Chinese Altai is a typical part of the Central Asian Orogenic Belt (CAOB), but its tectonic evolution is not well understood. Geochemical study of Early Paleozoic metasedimentary rocks was conducted to better constrain their provenance and tectonic environment. These rocks have relatively low CIA values (49 to 79), with ICV values (0.73-1.36) higher than that of post-Archean Australian average shale (PAAS), suggesting that they experienced relatively weak chemical weathering and were mainly derived from an immature source. Compared to PAAS and upper crust, the samples mostly have relatively lower high field strength elements (HFSE) (e.g. Zr, Hf, Nb, Ta) and large ion lithophile element (LILE) contents (e.g. Rb, Sr, Ba, Th, U, Pb). However, their relatively high Rb concentrations (> 40 ppm), low Rb/Sr (0.04-3.24) and Th/U (Th/U = 3-8) ratios are indicative of an acidic-intermediate igneous source that had undergone weak chemical weathering. All of the samples are moderately enriched in LREE (light REE) and show relatively flat Chondrite-normalized HREE (heavy REE) patterns (La N/Yb N = 3.2-12.6) with various negative Eu anomalies (Eu/Eu* = 0.4-0.9). Meta-arenaceous samples have moderate SiO 2 (average 72.9 wt.%), Al 2O 3 (average 11.5 wt.%), Fe 2O 3T + MgO (average 7.16 wt.%) contents and moderate Al 2O 3/SiO 2 (average 0.16), K 2O/Na 2O (average 0.93) ratios, similar to those of graywackes from continental island arcs or active continental margins. However, meta-argillaceous samples have high SiO 2 (average 60.8 wt.%), Al 2O 3 (average 17.2 wt.%), Fe 2O 3T + MgO (average 12.2 wt.%) contents and high K 2O/Na 2O (average 3.45), Al 2O 3/SiO 2 (average 0.28) ratios similar to mudstones from continental arc basins. This kind of tectonic environment is also manifested in tectonic discrimination diagrams including Th-Sc-Zr/10 and La-Th-Sc. These geochemical characteristics suggest that the metasedimentary rocks were deposited in an active continental margin or

  20. Active mountain building in Taiwan in comparison to the early postcollisional evolution of the Alps

    NASA Astrophysics Data System (ADS)

    Ustaszewski, K.; Suppe, J.; Wu, Y.-M.; Huang, S.-T.

    2009-04-01

    Taiwan represent the subaerial part of an active, bivergent thrust belt resulting from the oblique collision between the Luzon island arc of the Philippine Sea Plate and the passive margin of the Eurasian Plate since about 4 to 6.5 Ma. This collision followed the initially intraoceanic subduction of the South China Sea lithosphere below the Philippine Sea Plate, which commenced c. 15 Ma ago and which still prevails south of Taiwan in the Manila accretionary wedge. Considering the collision between Eurasia and the Luzon island arc as one between a large continental plate and a microplate, many analogies can be inferred between currently ongoing mountain building processes in Taiwan and those that occurred in the Alps following closure of the Alpine Tethys in the late Palaeogene. Based on new crustal-scale cross-sections and high-resolution earthquake tomography, we provide an overview of Taiwan's kinematics and compare this to the late Palaeogene evolution of the Alps, a time that marked its transition from an accretionary to a collisional, bivergent orogen. The Taiwan fold-and thrust belt is characterised by actively growing topography, crustal accretion by thrust propagation towards the foreland, a subsiding foreland basin and ongoing tectonic exhumation of metamorphosed continental basement and cover in the retrowedge. Exhumation is controlled by the development of a crustal-scale backfold that overprints earlier fabrics related to foreland-facing transport. Backthrusts within the Eurasian basement that were active at greenschist-facies conditions facilitated exhumation. 40Ar/39Ar ages on synkinematically deformed biotites suggest that backthrusting started as early as between ca. 3-4 Ma, i.e. shortly after or concomitant with the onset of collision between Eurasian passive margin and Luzon island arc. At the internal side of the backfold, blueschist-facies units that likely represent subducted forearc lithosphere are preserved. This structural setting bears some

  1. THE EVOLUTION OF EARLY- AND LATE-TYPE GALAXIES IN THE COSMIC EVOLUTION SURVEY UP TO z {approx} 1.2

    SciTech Connect

    Pannella, Maurilio; Gabasch, Armin; Drory, Niv; Hopp, Ulrich; Noll, Stefan; Saglia, Roberto P.; Bender, Ralf; Goranova, Yuliana; Strazzullo, Veronica

    2009-08-10

    The Cosmic Evolution Survey (COSMOS) allows for the first time a highly significant census of environments and structures up to redshift 1, as well as a full morphological description of the galaxy population. In this paper we present a study aimed to constrain the evolution, in the redshift range 0.2 < z < 1.2, of the mass content of different morphological types and its dependence on the environmental density. We use a deep multicolor catalog, covering an area of {approx}0.7 deg{sup 2} inside the COSMOS field, with accurate photometric redshifts (i {approx}< 26.5 and {delta}z/(z {sub spec} + 1) {approx} 0.035). We estimate galaxy stellar masses by fitting the multicolor photometry to a grid of composite stellar population models. We quantitatively describe the galaxy morphology by fitting point-spread function convolved Sersic profiles to the galaxy surface brightness distributions down to F814 = 24 mag for a sample of 41,300 objects. We confirm an evolution of the morphological mix with redshift: the higher the redshift the more disk-dominated galaxies become important. We find that the morphological mix is a function of the local comoving density: the morphology density relation extends up to the highest redshift explored. The stellar mass function of disk-dominated galaxies is consistent with being constant with redshift. Conversely, the stellar mass function of bulge-dominated systems shows a decline in normalization with redshift. Such different behaviors of late-types and early-types stellar mass functions naturally set the redshift evolution of the transition mass. We find a population of relatively massive, early-type galaxies, having high specific star formation rate (SSFR) and blue colors which live preferentially in low-density environments. The bulk of massive (>7 x 10{sup 10} M {sub sun}) early-type galaxies have similar characteristic ages, colors, and SSFRs independently of the environment they belong to, with those hosting the oldest stars in the

  2. The Moon as a Recorder of Organic Evolution in the Early Solar System: A Lunar Regolith Analog Study

    PubMed Central

    Court, Richard W.; Crawford, Ian A.; Jones, Adrian P.; Joy, Katherine H.; Sephton, Mark A.

    2015-01-01

    Abstract The organic record of Earth older than ∼3.8 Ga has been effectively erased. Some insight is provided to us by meteorites as well as remote and direct observations of asteroids and comets left over from the formation of the Solar System. These primitive objects provide a record of early chemical evolution and a sample of material that has been delivered to Earth's surface throughout the past 4.5 billion years. Yet an effective chronicle of organic evolution on all Solar System objects, including that on planetary surfaces, is more difficult to find. Fortunately, early Earth would not have been the only recipient of organic matter–containing objects in the early Solar System. For example, a recently proposed model suggests the possibility that volatiles, including organic material, remain archived in buried paleoregolith deposits intercalated with lava flows on the Moon. Where asteroids and comets allow the study of processes before planet formation, the lunar record could extend that chronicle to early biological evolution on the planets. In this study, we use selected free and polymeric organic materials to assess the hypothesis that organic matter can survive the effects of heating in the lunar regolith by overlying lava flows. Results indicate that the presence of lunar regolith simulant appears to promote polymerization and, therefore, preservation of organic matter. Once polymerized, the mineral-hosted newly formed organic network is relatively protected from further thermal degradation. Our findings reveal the thermal conditions under which preservation of organic matter on the Moon is viable. Key Words: Moon—Regolith—Organic preservation—Biomarkers. Astrobiology 15, 154–168. PMID:25615648

  3. The Moon as a recorder of organic evolution in the early solar system: a lunar regolith analog study.

    PubMed

    Matthewman, Richard; Court, Richard W; Crawford, Ian A; Jones, Adrian P; Joy, Katherine H; Sephton, Mark A

    2015-02-01

    The organic record of Earth older than ∼3.8 Ga has been effectively erased. Some insight is provided to us by meteorites as well as remote and direct observations of asteroids and comets left over from the formation of the Solar System. These primitive objects provide a record of early chemical evolution and a sample of material that has been delivered to Earth's surface throughout the past 4.5 billion years. Yet an effective chronicle of organic evolution on all Solar System objects, including that on planetary surfaces, is more difficult to find. Fortunately, early Earth would not have been the only recipient of organic matter-containing objects in the early Solar System. For example, a recently proposed model suggests the possibility that volatiles, including organic material, remain archived in buried paleoregolith deposits intercalated with lava flows on the Moon. Where asteroids and comets allow the study of processes before planet formation, the lunar record could extend that chronicle to early biological evolution on the planets. In this study, we use selected free and polymeric organic materials to assess the hypothesis that organic matter can survive the effects of heating in the lunar regolith by overlying lava flows. Results indicate that the presence of lunar regolith simulant appears to promote polymerization and, therefore, preservation of organic matter. Once polymerized, the mineral-hosted newly formed organic network is relatively protected from further thermal degradation. Our findings reveal the thermal conditions under which preservation of organic matter on the Moon is viable. PMID:25615648

  4. Enceladus-Mimas paradox: a result of different early evolutions of satellites?

    NASA Astrophysics Data System (ADS)

    Czechowski, Leszek; Witek, Piotr

    2015-04-01

    the coefficient of the heat conduction in the considered layer, i.e.: kconv =Nu k. This approach is used successfully in parameterized theory of convection for SSC in the Earth and other planets (e.g. [3], [4]). Parameterization of liquid state convection (LSC) is even simpler. Ra in molten region is very high (usually higher than 1016). The LSC could be very intensive resulting in almost adiabatic temperature gradient given by: dT-= gαmT-, dr cpm where αm and cpm are thermal expansion coefficient and specific heat in molten region, g is the local gravity. In Enceladus and Mimas the adiabatic gradient is low and therefore LSC region is almost isothermal. 2. Results: Comparison of thermal models of Mimas and Enceladus indicates that conditions favorable for starting tidal heating (interior hot enough) lasted for short time (~107yr) in Mimas and for ~108 yr in Enceladus. This could explain Mimas-Enceladus paradox. 3. Conclusions: The Mimas-Enceladus paradox is probably the result of short time when Mimas was hot enough to allow for substantial tidal heating. The Mimas-Tethys resonance formed later when Mimas was already cool. (see also [1, 4]) The full text of the paper will be published in Acta Geophysica [5]. Acknowledgements: The research is partly supported by National Science Centre (grant 2011/ 01/ B/ ST10/06653). References : [1] Czechowski, L. (2014) Some remarks on the early evolution of Enceladus. Planet. Sp. Sc. 104, 185-199. [2] Merk, R., Breuer, D., Spohn, T. (2002). Numerical modeling of 26Al induced radioactive melting of asteroids concerning accretion. Icarus 199, 183-191. [3] Sharpe, H.N., Peltier, W.R., (1978) Parameterized mantle convection and the Earth's thermal history. Geophys. Res. Lett. 5, 737-740. [4] Czechowski, L. (2006) Parameterized model of convection driven by tidal and radiogenic heating. Adv. Space Res. 38, 788-793. [5] Czechowski, L., Witek, P. (2015) Comparisons of early evolutions of Mimas and Enceladus. Submitted to Acta

  5. The Late Oligocene to Early Miocene early evolution of rifting in the southwestern part of the Roer Valley Graben

    NASA Astrophysics Data System (ADS)

    Deckers, Jef

    2016-06-01

    The Roer Valley Graben is a Mesozoic continental rift basin that was reactivated during the Late Oligocene. The study area is located in the graben area of the southwestern part of the Roer Valley Graben. Rifting initiated in the study area with the development of a large number of faults in the prerift strata. Some of these faults were rooted in preexisting zones of weakness in the Mesozoic strata. Early in the Late Oligocene, several faults died out in the study area as strain became focused upon others, some of which were able to link into several-kilometer-long systems. Within the Late Oligocene to Early Miocene northwestward prograding shallow marine syn-rift deposits, the number of active faults further decreased with time. A relatively strong decrease was observed around the Oligocene/Miocene boundary and represents a further focus of strain onto the long fault systems. Miocene extensional strain was not accommodated by further growth, but predominantly by displacements along the long fault systems. Since the Oligocene/Miocene boundary coincides with a radical change in the European intraplate stress field, the latter might have contributed significantly to the simultaneous change of fault kinematics in the study area.

  6. Early time evolution of negative ion clouds and electron density depletions produced during electron attachment chemical release experiments

    NASA Technical Reports Server (NTRS)

    Scales, W. A.; Bernhardt, P. A.; Ganguli, G.

    1994-01-01

    Two-dimensional electrostatic particle-in-cell simulations are used to study the early time evolution of electron depletions and negative ion clouds produced during electron attachment chemical releases in the ionosphere. The simulation model considers the evolution in the plane perpendicular to the magnetic field and a three-species plasma that contains electrons, positive ions, and also heavy negative ions that result as a by-product of the electron attachment reaction. The early time evolution (less than the negative ion cyclotron period) of the system shows that a negative charge surplus initially develops outside of the depletion boundary as the heavy negative ions move across the boundary. The electrons are initially restricted from moving into the depletion due to the magnetic field. An inhomogenous electric field develops across the boundary layer due to this charge separation. A highly sheared electron flow velocity develops in the depletion boundary due to E x B and Delta-N x B drifts that result from electron density gradients and this inhomogenous electric field. Structure eventually develops in the depletion boundary layer due to low-frequency electrostatic waves that have growth times shorter than the negative ion cyclotron period. It is proposed that these waves are most likely produced by the electron-ion hybrid instability that results from sufficiently large shears in the electron flow velocity.

  7. Spectrophotometric determination of fluorine in silicate rocks

    USGS Publications Warehouse

    Peck, L.C.; Smith, V.C.

    1964-01-01

    The rock powder is sintered with a sodium carbonate flux containing zinc oxide and magnesium carbonate, the sinter-cake leached with water and the resulting solution filtered. Fluorine is separated from the acidified filtrate by steam distillation and determined spectrophotometrically by means of a zirconium-SPADNS reagent. If a multiple-unit distillation apparatus is used, 12 determinations can be completed per man-day. ?? 1964.

  8. Evolution

    NASA Astrophysics Data System (ADS)

    Peter, Ulmschneider

    When we are looking for intelligent life outside the Earth, there is a fundamental question: Assuming that life has formed on an extraterrestrial planet, will it also develop toward intelligence? As this is hotly debated, we will now describe the development of life on Earth in more detail in order to show that there are good reasons why evolution should culminate in intelligent beings.

  9. Creating NIST-traceable Spectrophotometric Standard Stars

    NASA Astrophysics Data System (ADS)

    McGraw, John T.; Zimmer, P. C.; Stubbs, C. W.; Fraser, G. T.; Lykke, K. R.; Brown, S. W.; Woodward, J. T.; Smith, A. W.

    2010-01-01

    Though spectrophotometric standard stars enable or support thousands of astrophysical observations: 1. Fundamental calibration of stars to international standards has not been done since 1975 2. The astronomical community's fundamental standard star, Vega, is unique in that it has a debris disk and is rotating pole-on at near breakup velocity making it anything but a single-temperature, uniform surface brightness source 3. NIST has created spectrophotometric standard sources and detectors that provide sub-1% relative uncertainties allowing throughput calibration from 400nm - 1100nm 4. We have built an objective spectrometer to make standardized observations and a "clear air” lidar capable of providing sub-1% extinction measurements to correct for atmospheric extinction, the most significant systematic error in standardization. These new capabilities for directly measuring and correcting for atmospheric transmission and calibrating telescope throughput enable creation of a new generation of fundamentally calibrated standard stars. The astronomical community will certainly benefit from a new network of fundamental spectrophotometric standard stars calibrated to NIST irradiance standards. We describe the techniques and technologies required to compare optical stellar spectra to NIST calibrated detectors, and the atmospheric measurements required to correct accurately for atmospheric extinction. We discuss observations of candidate standards with V ≤ 5.5 selected from an input catalog of approximately 500 northern hemisphere stars. This project is supported by NIST Grant 60NANB9D9121 and AFRL Grant FA9451-08-C-0267.

  10. TP53 mutations are early events in chronic lymphocytic leukemia disease progression and precede evolution to complex karyotypes.

    PubMed

    Lazarian, Gregory; Tausch, Eugen; Eclache, Virginie; Sebaa, Amel; Bianchi, Vincent; Letestu, Remi; Collon, Jean-Francois; Lefebvre, Valerie; Gardano, Laura; Varin-Blank, Nadine; Soussi, Thierry; Stilgenbauer, Stephen; Cymbalista, Florence; Baran-Marszak, Fanny

    2016-10-15

    TP53 abnormalities lead to resistance to purine analogues and are found in over 40% of patients with refractory chronic lymphocytic leukemia (CLL). At diagnosis, no more than 5% of patients carry the 17p deletion, most cases harbour mutations within the other TP53 allele. The incidence of a TP53 mutation as the only alteration is approximately 5%, but this depends on the sensitivity of the technique. Recently, having a complex karyotype has been considered a strong adverse prognostic factor. However, there are no longitudinal studies simultaneously examining the presence of the 17p deletion, TP53 mutations and karyotype abnormalities. We conducted a retrospective longitudinal study of 31 relapsed/refractory CLL patients. Two to six blood samples per patient were analyzed, with a median follow-up of 8 years. In this report, we assessed the sequence of events of TP53 clonal evolution and correlated the presence of TP53 abnormalities to genetic instability during progression and treatment. Next-generation sequencing allowed the early detection of TP53 mutated clones and was able to be performed on a routine basis, demonstrating an excellent correlation between the Illumina and Ion Torrent technologies. We concluded that TP53 mutations are early events and precede clonal evolution to complex karyotypes. We strongly recommend the early and iterated detection of TP53 mutations in progressive cases. PMID:27270786

  11. Early post-metamorphic, Carboniferous blastoid reveals the evolution and development of the digestive system in echinoderms.

    PubMed

    Rahman, Imran A; Waters, Johnny A; Sumrall, Colin D; Astolfo, Alberto

    2015-10-01

    Inferring the development of the earliest echinoderms is critical to uncovering the evolutionary assembly of the phylum-level body plan but has long proven problematic because early ontogenetic stages are rarely preserved as fossils. Here, we use synchrotron tomography to describe a new early post-metamorphic blastoid echinoderm from the Carboniferous (approx. 323 Ma) of China. The resulting three-dimensional reconstruction reveals a U-shaped tubular structure in the fossil interior, which is interpreted as the digestive tract. Comparisons with the developing gut of modern crinoids demonstrate that crinoids are an imperfect analogue for many extinct groups. Furthermore, consideration of our findings in a phylogenetic context allows us to reconstruct the evolution and development of the digestive system in echinoderms more broadly; there was a transition from a straight to a simple curved gut early in the phylum's evolution, but additional loops and coils of the digestive tract (as seen in crinoids) were not acquired until much later. PMID:26510677

  12. Tidal dissipation in the lunar magma ocean and its effect on the early evolution of the Earth-Moon system

    NASA Astrophysics Data System (ADS)

    Chen, Erinna M. A.; Nimmo, Francis

    2016-09-01

    The present-day inclination of the Moon reflects the entire history of its thermal and orbital evolution. The Moon likely possessed a global magma ocean following the Moon-forming impact. In this work, we develop a coupled thermal-orbital evolution model that takes into account obliquity tidal heating in the lunar magma ocean. Dissipation in the magma ocean is so effective that it results in rapid inclination damping at semi-major axes beyond about 20 Earth radii (RE), because of the increase in lunar obliquity as the so-called Cassini state transition at ≈30 RE is approached. There is thus a "speed limit" on how fast the Moon can evolve outwards while maintaining its inclination: if it reaches 20 RE before the magma ocean solidifies, any early lunar inclination cannot be maintained. We find that for magma ocean lifetimes of 10 Myr or more, the Earth's tidal quality factor Q must have been >300 to maintain primordial inclination, implying an early Earth 1-2 orders of magnitude less dissipative than at present. On the other hand, if tidal dissipation on the early Earth was stronger, our model implies rapid damping of the lunar inclination and requires subsequent late excitation of the lunar orbit after the crystallization of the lunar magma ocean.

  13. Divergence times and the evolution of morphological complexity in an early land plant lineage (Marchantiopsida) with a slow molecular rate.

    PubMed

    Villarreal A, Juan Carlos; Crandall-Stotler, Barbara J; Hart, Michelle L; Long, David G; Forrest, Laura L

    2016-03-01

    We present a complete generic-level phylogeny of the complex thalloid liverworts, a lineage that includes the model system Marchantia polymorpha. The complex thalloids are remarkable for their slow rate of molecular evolution and for being the only extant plant lineage to differentiate gas exchange tissues in the gametophyte generation. We estimated the divergence times and analyzed the evolutionary trends of morphological traits, including air chambers, rhizoids and specialized reproductive structures. A multilocus dataset was analyzed using maximum likelihood and Bayesian approaches. Relative rates were estimated using local clocks. Our phylogeny cements the early branching in complex thalloids. Marchantia is supported in one of the earliest divergent lineages. The rate of evolution in organellar loci is slower than for other liverwort lineages, except for two annual lineages. Most genera diverged in the Cretaceous. Marchantia polymorpha diversified in the Late Miocene, giving a minimum age estimate for the evolution of its sex chromosomes. The complex thalloid ancestor, excluding Blasiales, is reconstructed as a plant with a carpocephalum, with filament-less air chambers opening via compound pores, and without pegged rhizoids. Our comprehensive study of the group provides a temporal framework for the analysis of the evolution of critical traits essential for plants during land colonization. PMID:26505145

  14. Determining the Early Childhood Curriculum: The Evolution of Goals and Strategies through Consonance and Controversy.

    ERIC Educational Resources Information Center

    Williams, Leslie R.

    Based on the premise that determining the early childhood curriculum hinges to a certain extent on discovering the nature of children, this chapter explores the origins and practices of early childhood curriculum in the United States. The chapter reveals perceptions shifting over time regarding characterizations of young children's most essential…

  15. Early 20th-century research at the interfaces of genetics, development, and evolution: reflections on progress and dead ends.

    PubMed

    Deichmann, Ute

    2011-09-01

    Three early 20th-century attempts at unifying separate areas of biology, in particular development, genetics, physiology, and evolution, are compared in regard to their success and fruitfulness for further research: Jacques Loeb's reductionist project of unifying approaches by physico-chemical explanations; Richard Goldschmidt's anti-reductionist attempts to unify by integration; and Sewall Wright's combination of reductionist research and vision of hierarchical genetic systems. Loeb's program, demanding that all aspects of biology, including evolution, be studied by the methods of the experimental sciences, proved highly successful and indispensible for higher level investigations, even though evolutionary change and properties of biological systems up to now cannot be fully explained on the molecular level alone. Goldschmidt has been appraised as pioneer of physiological and developmental genetics and of a new evolutionary synthesis which transcended neo-Darwinism. However, this study concludes that his anti-reductionist attempts to integrate genetics, development and evolution have to be regarded as failures or dead ends. His grand speculations were based on the one hand on concepts and experimental systems that were too vague in order to stimulate further research, and on the other on experiments which in their core parts turned out not to be reproducible. In contrast, Sewall Wright, apart from being one of the architects of the neo-Darwinian synthesis of the 1930s, opened up new paths of testable quantitative developmental genetic investigations. He placed his research within a framework of logical reasoning, which resulted in the farsighted speculation that examinations of biological systems should be related to the regulation of hierarchical genetic subsystems, possibly providing a mechanism for development and evolution. I argue that his suggestion of basing the study of systems on clearly defined properties of the components has proved superior to

  16. Rates and modes of body size evolution in early carnivores and herbivores: a case study from Captorhinidae

    PubMed Central

    2016-01-01

    Body size is an extremely important characteristic, impacting on a variety of ecological and life-history traits. It is therefore important to understand the factors which may affect its evolution, and diet has attracted much interest in this context. A recent study which examined the evolution of the earliest terrestrial herbivores in the Late Carboniferous and Early Permian concluded that in the four herbivorous clades examined there was a trend towards increased body size, and that this increase was more substantial than that observed in closely related carnivorous clades. However, this hypothesis was not based on quantitative examination, and phylogenetic comparative methods provide a more robust means of testing such hypotheses. Here, the evolution of body size within different dietary regimes is examined in Captorhinidae, the most diverse and longest lived of these earliest high fibre herbivores. Evolutionary models were fit to their phylogeny to test for variation in rate and mode of evolution between the carnivorous and herbivorous members of this clade, and an analysis of rate variation throughout the tree was carried out. Estimates of ancestral body sizes were calculated in order to compare the rates and direction of evolution of lineages with different dietary regimes. Support for the idea that the high fibre herbivores within captorhinids are being drawn to a higher adaptive peak in body size than the carnivorous members of this clade is weak. A shift in rates of body size evolution is identified, but this does not coincide with the evolution of high-fibre herbivory, instead occurring earlier in time and at a more basal node. Herbivorous lineages which show an increase in size are not found to evolve at a faster rate than those which show a decrease; in fact, it is those which experience a size decrease which evolve at higher rates. It is possible the shift in rates of evolution is related to the improved food processing ability of the more derived

  17. Rates and modes of body size evolution in early carnivores and herbivores: a case study from Captorhinidae.

    PubMed

    Brocklehurst, Neil

    2016-01-01

    Body size is an extremely important characteristic, impacting on a variety of ecological and life-history traits. It is therefore important to understand the factors which may affect its evolution, and diet has attracted much interest in this context. A recent study which examined the evolution of the earliest terrestrial herbivores in the Late Carboniferous and Early Permian concluded that in the four herbivorous clades examined there was a trend towards increased body size, and that this increase was more substantial than that observed in closely related carnivorous clades. However, this hypothesis was not based on quantitative examination, and phylogenetic comparative methods provide a more robust means of testing such hypotheses. Here, the evolution of body size within different dietary regimes is examined in Captorhinidae, the most diverse and longest lived of these earliest high fibre herbivores. Evolutionary models were fit to their phylogeny to test for variation in rate and mode of evolution between the carnivorous and herbivorous members of this clade, and an analysis of rate variation throughout the tree was carried out. Estimates of ancestral body sizes were calculated in order to compare the rates and direction of evolution of lineages with different dietary regimes. Support for the idea that the high fibre herbivores within captorhinids are being drawn to a higher adaptive peak in body size than the carnivorous members of this clade is weak. A shift in rates of body size evolution is identified, but this does not coincide with the evolution of high-fibre herbivory, instead occurring earlier in time and at a more basal node. Herbivorous lineages which show an increase in size are not found to evolve at a faster rate than those which show a decrease; in fact, it is those which experience a size decrease which evolve at higher rates. It is possible the shift in rates of evolution is related to the improved food processing ability of the more derived

  18. Early evolution of the earth - Accretion, atmosphere formation, and thermal history

    NASA Technical Reports Server (NTRS)

    Abe, Yutaka; Matsui, Takafumi

    1986-01-01

    The thermal and atmospheric evolution of the earth growing planetesimal impacts are studied. The generation of an H2O protoatmosphere is examined, and the surface temperatures are estimated. The evolution of an impact-induced H2O atmosphere is analyzed. Consideration is given to the formation time of a 'magma ocean'and internal water budgets. The thermal history of an accreting earth is reviewed. The wet convection and greenhouse effects are discussed, and the role of Fe oxidation on the evolution of an impact-induced H2O atmopshere is described. The relationship between differentiation processes and core segregation, the H2O and FeO content of the mantle, and the origin of the hydrosphere is also examined.

  19. Post-early cretaceous landform evolution along the western margin of the banca~nnia trough, western nsw

    USGS Publications Warehouse

    Gibson, D.L.

    2000-01-01

    Previously undated post-Devonian sediments outcropping north of Fowlers Gap station near the western margin of the Bancannia Trough are shown by plant macro- and microfossil determinations to be of Early Cretaceous (most likely Neocomian and/or Aptian) age, and thus part of the Eromanga Basin. They are assigned to the previously defined Telephone Creek Formation. Study of the structural configuration of this unit and the unconformably underlying Devonian rocks suggests that the gross landscape architecture of the area results from post-Early Cretaceous monoclinal folding along blind faults at the western margin of the trough, combined with the effects of differential erosion. This study shows that, while landscape evolution in the area has been dynamic, the major changes that have occurred are on a geological rather than human timescale.

  20. Palaeogeographic evolution of the central segment of the South Atlantic during Early Cretaceous times: palaeotopographic and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Chaboureau, A. C.; Guillocheau, F.; Robin, C.; Rohais, S.; Moulin, M.; Aslanian, D.

    2012-04-01

    The tectonic and sedimentary evolution of the Early Cretaceous rift of the central segment of the South Atlantic Ocean is debated. Our objective is to better constraint the timing of its evolution by drawing palaeogeographic and deformation maps. Eight palaeogeographic and deformations maps were drawn from the Berriasian to the Middle-Late Aptian, based on a biostratigraphic (ostracodes and pollens) chart recalibrated on absolute ages (chemostratigraphy, interstratified volcanics, Re-Os dating of the organic matter). The central segment of the South Atlantic is composed of two domains that have a different history in terms of deformation and palaeogeography. The southern domain includes Namibe, Santos and Campos Basins. The northern domain extends from Espirito Santo and North Kwanza Basins, in the South, to Sergipe-Alagoas and North Gabon Basins to the North. Extension started in the northern domain during Late Berriasian (Congo-Camamu Basin to Sergipe-Alagoas-North Gabon Basins) and migrated southward. At that time, the southern domain was not a subsiding domain. This is time of emplacement of the Parana-Etendeka Trapp (Late Hauterivian-Early Barremian). Extension started in this southern domain during Early Barremian. The brittle extensional period is shorter in the South (5-6 Ma, Barremian to base Aptian) than in the North (19 to 20 Myr, Upper Berriasian to Base Aptian). From Late Berriasian to base Aptian, the northern domain evolves from a deep lake with lateral highs to a shallower one, organic-rich with no more highs. The lake migrates southward in two steps, until Valanginian at the border between the northern and southern domains, until Early Barremian, North of Walvis Ridge. The Sag phase is of Middle to Late Aptian age. In the southern domain, the transition between the brittle rift and the sag phase is continuous. In the northern domain, this transition corresponds to a hiatus of Early to Middle Aptian age, possible period of mantle exhumation. Marine

  1. The deformation and tectonic evolution of the Huahui Basin, northeast China, during the Cretaceous-Early Cenozoic

    NASA Astrophysics Data System (ADS)

    Huang, Shiqi; Dong, Shuwen; Zhang, Yueqiao; Zhang, Fuqin; Huang, Dezhi; Wei, Shi; Li, Zhenhong; Miao, Laicheng; Zhu, Mingshuai

    2015-12-01

    The Cretaceous Huahui basin lies along the Dunhua-Mishan fault (Dun-Mi fault), which is one of the northern branches of Tan-Lu fault in northeastern China. The study of the formation and the tectonic movements that took place in the basin can provide very important information for deciphering the tectonic evolution of northeastern China during Cretaceous-Early Cenozoic. The field analysis of fault-slip data collected from different units in the basin, demonstrates changes in the paleo-stress state that reveals a three-stage tectonic movement during the Cretaceous-Early Cenozoic. The earliest tectonic movement was NW-SE extension, which was responsible for the formation of the basin and sedimentary infilling during the Early Cretaceous. Dating of the andesite in the fill indicates it began during about 119.17 ± 0.80 Ma. The extensional structures formed in the Latest Early Cretaceous imply that this tectonic movement lasted until the beginning of the Late Cretaceous. The second stage began during the Late Cretaceous when the tectonic stress state changed and was dominated by NW-SE compression and NE-SW extension, which caused the inversion of the extensional basin. This compression folded the Early Cretaceous deposits and reactivated pre-existing faults and uplifted pre-existing granite in the basin. The strata and the unconformity in the basin shows that this compressive phase probably took place during the Late Cretaceous and ended in the Early Paleogene by a compressional regime with NE-SW compression and NW-SE extension that constitutes the third stage. The tectonic stress fields documented in the Huahui basin provide insight into the influences of plate tectonics on the crustal evolution of northeastern China during the Cretaceous to Early Cenozoic. These results show that the development of Huahui basin was controlled by the northwestward subduction of the paleo-Pacific plate during the Cretaceous, and later by the far-field effects of India-Asia collision in

  2. Evolution

    ERIC Educational Resources Information Center

    Lee, Christopher Michael

    2005-01-01

    In this article the author shares his personal experiences beginning in early childhood with his own learning disabilities. As an adult with learning disabilities, he describes how he has learned to manage his language and memory barriers through assistive technology and outside support, and he nourishes himself through therapy or simply…

  3. Paleogeographic evolution of the central segment of the South Atlantic during Early Cretaceous times: Paleotopographic and geodynamic implications

    NASA Astrophysics Data System (ADS)

    Chaboureau, Anne-Claire; Guillocheau, François; Robin, Cécile; Rohais, Sébastien; Moulin, Maryline; Aslanian, Daniel

    2013-09-01

    The geodynamic processes that control the opening of the central segment of the South Atlantic Ocean (between the Walvis Ridge and the Ascension FZ) are debated. In this paper, we discuss the timing of the sedimentary and tectonic evolution of the Early Cretaceous rift by drawing eight paleogeographic and geodynamic maps from the Berriasian to the Middle-Late Aptian, based on a biostratigraphic (ostracodes and pollen) chart recalibrated on absolute ages (chemostratigraphy, interstratified volcanics, Re-Os dating of the organic matter). The central segment of the South Atlantic is composed of two domains, with a two phases evolution of the pre-drift ("rifting") times: a rift phase characterized by tilted blocks and growth strata, followed by a sag basin. The southern domain includes the Namibe, Santos and Campos Basins. The northern domain extends from the Espirito Santo and North Kwanza Basins, in the south, to the Sergipe-Alagoas and North Gabon Basins to the north. Extension started in the northern domain during the Late Berriasian (Congo-Camamu Basin to the Sergipe-Alagoas-North Gabon Basins) and migrated southward. At that time, the southern domain was not a subsiding domain (emplacement of the Parana-Etendeka Trapp). Extension started in this southern domain during the Early Barremian. The rift phase is shorter in the south (5-6 Ma, Barremian to base Aptian) than in the north (19 to 20 Myr, Upper Berriasian to base Aptian). The sag phase is of Middle to Late Aptian age. In the northern domain, this transition corresponds to a hiatus of Early to Middle Aptian age. From the Late Berriasian to base Aptian, the northern domain evolves from a deep lake with lateral highs to a shallower organic-rich one with no more highs. The lake migrates southward in two steps, until the Valanginian at the border between the northern and southern domains, until the Early Barremian, north of Walvis Ridge.

  4. THE SIZE EVOLUTION OF PASSIVE GALAXIES: OBSERVATIONS FROM THE WIDE-FIELD CAMERA 3 EARLY RELEASE SCIENCE PROGRAM

    SciTech Connect

    Ryan, R. E. Jr.; McCarthy, P. J.; Cohen, S. H.; Rutkowski, M. J.; Mechtley, M. R.; Windhorst, R. A.; Yan, H.; Hathi, N. P.; Koekemoer, A. M.; Bond, H. E.; Bushouse, H.; O'Connell, R. W.; Balick, B.; Calzetti, D.; Crockett, R. M.; Disney, M.; Dopita, M. A.; Frogel, J. A.; Hall, D. N. B.; Holtzman, J. A.; and others

    2012-04-10

    We present the size evolution of passively evolving galaxies at z {approx} 2 identified in Wide-Field Camera 3 imaging from the Early Release Science program. Our sample was constructed using an analog to the passive BzK galaxy selection criterion, which isolates galaxies with little or no ongoing star formation at z {approx}> 1.5. We identify 30 galaxies in {approx}40 arcmin{sup 2} to H < 25 mag. By fitting the 10-band Hubble Space Telescope photometry from 0.22 {mu}m {approx}< {lambda}{sub obs} {approx}< 1.6 {mu}m with stellar population synthesis models, we simultaneously determine photometric redshift, stellar mass, and a bevy of other population parameters. Based on the six galaxies with published spectroscopic redshifts, we estimate a typical redshift uncertainty of {approx}0.033(1 + z). We determine effective radii from Sersic profile fits to the H-band image using an empirical point-spread function. By supplementing our data with published samples, we propose a mass-dependent size evolution model for passively evolving galaxies, where the most massive galaxies (M{sub *} {approx} 10{sup 11} M{sub Sun }) undergo the strongest evolution from z {approx} 2 to the present. Parameterizing the size evolution as (1 + z){sup -{alpha}}, we find a tentative scaling of {alpha} Almost-Equal-To (- 0.6 {+-} 0.7) + (0.9 {+-} 0.4)log (M{sub *}/10{sup 9} M{sub Sun }), where the relatively large uncertainties reflect the poor sampling in stellar mass due to the low numbers of high-redshift systems. We discuss the implications of this result for the redshift evolution of the M{sub *}-R{sub e} relation for red galaxies.

  5. The Size Evolution of Passive Galaxies: Observations from the Wide-Field Camera 3 Early Release Science Program

    NASA Astrophysics Data System (ADS)

    Ryan, R. E., Jr.; McCarthy, P. J.; Cohen, S. H.; Yan, H.; Hathi, N. P.; Koekemoer, A. M.; Rutkowski, M. J.; Mechtley, M. R.; Windhorst, R. A.; O'Connell, R. W.; Balick, B.; Bond, H. E.; Bushouse, H.; Calzetti, D.; Crockett, R. M.; Disney, M.; Dopita, M. A.; Frogel, J. A.; Hall, D. N. B.; Holtzman, J. A.; Kaviraj, S.; Kimble, R. A.; MacKenty, J.; Mutchler, M.; Paresce, F.; Saha, A.; Silk, J. I.; Trauger, J.; Walker, A. R.; Whitmore, B. C.; Young, E.

    2012-04-01

    We present the size evolution of passively evolving galaxies at z ~ 2 identified in Wide-Field Camera 3 imaging from the Early Release Science program. Our sample was constructed using an analog to the passive BzK galaxy selection criterion, which isolates galaxies with little or no ongoing star formation at z >~ 1.5. We identify 30 galaxies in ~40 arcmin2 to H < 25 mag. By fitting the 10-band Hubble Space Telescope photometry from 0.22 μm <~ λobs <~ 1.6 μm with stellar population synthesis models, we simultaneously determine photometric redshift, stellar mass, and a bevy of other population parameters. Based on the six galaxies with published spectroscopic redshifts, we estimate a typical redshift uncertainty of ~0.033(1 + z). We determine effective radii from Sérsic profile fits to the H-band image using an empirical point-spread function. By supplementing our data with published samples, we propose a mass-dependent size evolution model for passively evolving galaxies, where the most massive galaxies (M * ~ 1011 M ⊙) undergo the strongest evolution from z ~ 2 to the present. Parameterizing the size evolution as (1 + z)-α, we find a tentative scaling of α ≈ (- 0.6 ± 0.7) + (0.9 ± 0.4)log (M */109 M ⊙), where the relatively large uncertainties reflect the poor sampling in stellar mass due to the low numbers of high-redshift systems. We discuss the implications of this result for the redshift evolution of the M *-Re relation for red galaxies. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  6. The Size Evolution of Passive Galaxies: Observations From the Wide-Field Camera 3 Early Release Science Program

    NASA Technical Reports Server (NTRS)

    Ryan, R. E., Jr.; Mccarthy, P.J.; Cohen, S. H.; Yan, H.; Hathi, N. P.; Koekemoer, A. M.; Rutkowski, M. J.; Mechtley, M. R.; Windhorst, R. A.; O’Connell, R. W.; Balick, B.; Bond, H. E.; Bushouse, H.; Calzetti, D.; Crockett, R. M.; Disney, M.; Dopita, M. A.; Frogel, J. A.; Hall, D., N., B.; Holtzman, J. A.; Kaviraj, S.; Kimble, R. A.; MacKenty, J.; Trauger, J.; Young, E.

    2012-01-01

    We present the size evolution of passively evolving galaxies at z approximately 2 identified in Wide-Field Camera 3 imaging from the Early Release Science program. Our sample was constructed using an analog to the passive BzK galaxy selection criterion, which isolates galaxies with little or no ongoing star formation at z greater than approximately 1.5. We identify 30 galaxies in approximately 40 arcmin(sup 2) to H less than 25 mag. By fitting the 10-band Hubble Space Telescope photometry from 0.22 micrometers less than approximately lambda (sub obs) 1.6 micrometers with stellar population synthesis models, we simultaneously determine photometric redshift, stellar mass, and a bevy of other population parameters. Based on the six galaxies with published spectroscopic redshifts, we estimate a typical redshift uncertainty of approximately 0.033(1+z).We determine effective radii from Sersic profile fits to the H-band image using an empirical point-spread function. By supplementing our data with published samples, we propose a mass-dependent size evolution model for passively evolving galaxies, where the most massive galaxies (M(sub *) approximately 10(sup 11) solar mass) undergo the strongest evolution from z approximately 2 to the present. Parameterizing the size evolution as (1 + z)(sup - alpha), we find a tentative scaling of alpha approximately equals (-0.6 plus or minus 0.7) + (0.9 plus or minus 0.4) log(M(sub *)/10(sup 9 solar mass), where the relatively large uncertainties reflect the poor sampling in stellar mass due to the low numbers of highredshift systems. We discuss the implications of this result for the redshift evolution of the M(sub *)-R(sub e) relation for red galaxies.

  7. Tungsten Partitioning in Silicates. A Key to Understanding the Early Evolution of the Moon

    NASA Technical Reports Server (NTRS)

    Shearer, C. K.; Righter, K.

    2000-01-01

    We investigate the partitioning behavior of W in a variety of silicates that may have been stable during LMO crystallization, evaluate their role in generating W isotopic signatures, and speculate about the early differentiation of the Moon.

  8. The evolution of the early Martian climate and the initial emplacement of crustal H2O

    NASA Technical Reports Server (NTRS)

    Clifford, S. M.

    1993-01-01

    Given the geomorphic evidence for the widespread occurrence of water and ice in the early Martian crust, and the difficulty involved in accounting for this distribution given the present climate, it has been suggested that the planet's early climate was originally more Earth-like, permitting the global emplacement of crustal H2O by direct precipitation as snow or rain. The resemblance of the Martian valley networks to terrestrial runoff channels and their almost exclusive occurrence in the planet's ancient (approximately 4-b.y.-old) heavily cratered terrain are often cited as evidence of just such a period. An alternative school of thought suggests that the early climate did not differ substantially from that of today. Advocates of this view find no compelling reason to invoke a warmer, wetter period to explain the origin of the valley networks. Rather, they cite evidence that the primary mechanism of valley formation was groundwater sapping, a process that does not require that surface water exists in equilibrium with the atmosphere. However, while sapping may successfully explain the origin of the small valleys, it fails to address how the crust was initially charged with ice as the climate evolved towards its present state. Therefore, given the uncertainty regarding the environmental conditions that prevailed on early Mars, the initial emplacement of ground ice is considered here from two perspectives: (1) the early climate started warm and wet, but gradually cooled with time, and (2) the early climate never differed substantially from that of today.

  9. The evolution of damage control orthopedics: current evidence and practical applications of early appropriate care.

    PubMed

    D'Alleyrand, Jean-Claude G; O'Toole, Robert V

    2013-10-01

    This article summarizes the evolution of literature and practice related to fracture care in polytrauma patients. Particular emphasis is given to the management of femoral shaft fractures and the concept of damage control in these complex patients. The application of these guidelines in common clinical practice is also discussed. PMID:24095066

  10. Early Precambrian Carbonate and Evapolite Sediments: Constraints on Environmental and Biological Evolution

    NASA Technical Reports Server (NTRS)

    Grotzinger, John P.

    2002-01-01

    The work accomplished under NASA Grant NAG5-6722 was very successful. Our lab was able to document the occurrence and distribution of evaporite-to-carbonate transitions in several basins during Precambrian time, to help constrain the long-term chemical evolution of seawater.

  11. GALAXY EVOLUTION IN OVERDENSE ENVIRONMENTS AT HIGH REDSHIFT: PASSIVE EARLY-TYPE GALAXIES IN A CLUSTER AT z {approx} 2

    SciTech Connect

    Strazzullo, V.; Gobat, R.; Daddi, E.; Onodera, M.; Carollo, M.; Dickinson, M.; Renzini, A.; Arimoto, N.; Cimatti, A.; Finoguenov, A.; Chary, R.-R.

    2013-08-01

    We present a study of galaxy populations in the central region of the IRAC-selected, X-ray-detected galaxy cluster Cl J1449+0856 at z = 2. Based on a sample of spectroscopic and photometric cluster members, we investigate stellar populations and the morphological structure of cluster galaxies over an area of {approx}0.7 Mpc{sup 2} around the cluster core. The cluster stands out as a clear overdensity both in redshift space and in the spatial distribution of galaxies close to the center of the extended X-ray emission. The cluster core region (r < 200 kpc) shows a clearly enhanced passive fraction with respect to field levels. However, together with a population of massive, passive galaxies mostly with early-type morphologies, the cluster core also hosts massive, actively star-forming, often highly dust reddened sources. Close to the cluster center, a multi-component system of passive and star-forming galaxies could represent the future brightest cluster galaxy still forming. We observe a clear correlation between passive stellar populations and an early-type morphology, in agreement with field studies at similar redshift. Passive early-type galaxies in this cluster are typically a factor of 2-3 smaller than similarly massive early types at z {approx} 0. On the other hand, these same objects are on average larger by a factor of {approx}2 than field early-types at similar redshift, lending support to recent claims of an accelerated structural evolution in high-redshift dense environments. These results point toward the early formation of a population of massive galaxies, already evolved both in their structure and stellar populations, coexisting with still actively forming massive galaxies in the central regions of young clusters 10 billion years ago.

  12. The Evolution of Early-type Field Galaxies Selected from a NICMOS Map of the Hubble Deep Field North

    SciTech Connect

    Somerville, R; Stanford, S A; Budavari, T; Conselice, C J

    2004-03-03

    The redshift distribution of well-defined samples of distant early-type galaxies offers a means to test the predictions of monolithic and hierarchical galaxy formation scenarios. NICMOS maps of the entire Hubble Deep Field North in the F110W and F160W filters, when combined with the available WFPC2 data, allow us to calculate photometric redshifts and determine the morphological appearance of galaxies at rest-frame optical wavelengths out to z {approx} 2.5. Here we report results for two subsamples of early-type galaxies, defined primarily by their morphologies in the F160W band, which were selected from the NICMOS data down to H{sub 160AB} < 24.0. A primary subsample is defined as the 34 galaxies with early-type galaxy morphologies and early-type galaxy spectral energy distributions. The secondary subsample is defined as those 42 objects which have early-type galaxy morphologies with non-early type galaxy spectral energy distributions. The observed redshift distributions of our two early-type samples do not match that predicted by a monolithic collapse model, which shows an overabundance at z > 1.5. A (V/V{sub max}) test confirms this result. When the effects of passive luminosity evolution are included in the calculation, the mean value of Vmax for the primary sample is 0.22 {+-} 0.05, and 0.31 {+-} 0.04 for all the early-types. A hierarchical formation model better matches the redshift distribution of the HDF-N early-types at z > 1.5, but still does not adequately describe the observed early-types. The hierarchical model predicts significantly bluer colors on average than the observed early-type colors, and underpredicts the observed number of early-types at z {approx} 2. Though the observed redshift distribution of the early-type galaxies in our HDF-NICMOS sample is better matched by a hierarchical galaxy formation model, the reliability of this conclusion is tempered by the restricted sampling area and relatively small number of early-type galaxies selected by

  13. A new ornithurine from the Early Cretaceous of China sheds light on the evolution of early ecological and cranial diversity in birds

    PubMed Central

    Huang, Jiandong; Hu, Yuanchao; Liu, Jia; Peteya, Jennifer A.

    2016-01-01

    Despite the increasing number of exceptional feathered fossils discovered in the Late Jurassic and Cretaceous of northeastern China, representatives of Ornithurae, a clade that includes comparatively-close relatives of crown clade Aves (extant birds) and that clade, are still comparatively rare. Here, we report a new ornithurine species Changzuiornis ahgmi from the Early Cretaceous Jiufotang Formation. The new species shows an extremely elongate rostrum so far unknown in basal ornithurines and changes our understanding of the evolution of aspects of extant avian ecology and cranial evolution. Most of this elongate rostrum in Changzuiornis ahgmi is made up of maxilla, a characteristic not present in the avian crown clade in which most of the rostrum and nearly the entire facial margin is made up by premaxilla. The only other avialans known to exhibit an elongate rostrum with the facial margin comprised primarily of maxilla are derived ornithurines previously placed phylogenetically as among the closest outgroups to the avian crown clade as well as one derived enantiornithine clade. We find that, consistent with a proposed developmental shift in cranial ontogeny late in avialan evolution, this elongate rostrum is achieved through elongation of the maxilla while the premaxilla remains only a small part of rostral length. Thus, only in Late Cretaceous ornithurine taxa does the premaxilla begin to play a larger role. The rostral and postcranial proportions of Changzuiornis suggest an ecology not previously reported in Ornithurae; the only other species with an elongate rostrum are two marine Late Cretacous taxa interpreted as showing a derived picivorous diet. PMID:27019777

  14. A new ornithurine from the Early Cretaceous of China sheds light on the evolution of early ecological and cranial diversity in birds.

    PubMed

    Huang, Jiandong; Wang, Xia; Hu, Yuanchao; Liu, Jia; Peteya, Jennifer A; Clarke, Julia A

    2016-01-01

    Despite the increasing number of exceptional feathered fossils discovered in the Late Jurassic and Cretaceous of northeastern China, representatives of Ornithurae, a clade that includes comparatively-close relatives of crown clade Aves (extant birds) and that clade, are still comparatively rare. Here, we report a new ornithurine species Changzuiornis ahgmi from the Early Cretaceous Jiufotang Formation. The new species shows an extremely elongate rostrum so far unknown in basal ornithurines and changes our understanding of the evolution of aspects of extant avian ecology and cranial evolution. Most of this elongate rostrum in Changzuiornis ahgmi is made up of maxilla, a characteristic not present in the avian crown clade in which most of the rostrum and nearly the entire facial margin is made up by premaxilla. The only other avialans known to exhibit an elongate rostrum with the facial margin comprised primarily of maxilla are derived ornithurines previously placed phylogenetically as among the closest outgroups to the avian crown clade as well as one derived enantiornithine clade. We find that, consistent with a proposed developmental shift in cranial ontogeny late in avialan evolution, this elongate rostrum is achieved through elongation of the maxilla while the premaxilla remains only a small part of rostral length. Thus, only in Late Cretaceous ornithurine taxa does the premaxilla begin to play a larger role. The rostral and postcranial proportions of Changzuiornis suggest an ecology not previously reported in Ornithurae; the only other species with an elongate rostrum are two marine Late Cretacous taxa interpreted as showing a derived picivorous diet. PMID:27019777

  15. Virtual endocasts of Eocene Paramys (Paramyinae): oldest endocranial record for Rodentia and early brain evolution in Euarchontoglires.

    PubMed

    Bertrand, Ornella C; Amador-Mughal, Farrah; Silcox, Mary T

    2016-01-27

    Understanding the pattern of brain evolution in early rodents is central to reconstructing the ancestral condition for Glires, and for other members of Euarchontoglires including Primates. We describe the oldest virtual endocasts known for fossil rodents, which pertain to Paramys copei (Early Eocene) and Paramys delicatus (Middle Eocene). Both specimens of Paramys have larger olfactory bulbs and smaller paraflocculi relative to total endocranial volume than later occurring rodents, which may be primitive traits for Rodentia. The encephalization quotients (EQs) of Pa. copei and Pa. delicatus are higher than that of later occurring (Oligocene) Ischyromys typus, which contradicts the hypothesis that EQ increases through time in all mammalian orders. However, both species of Paramys have a lower relative neocortical surface area than later rodents, suggesting neocorticalization occurred through time in this Order, although to a lesser degree than in Primates. Paramys has a higher EQ but a lower neocortical ratio than any stem primate. This result contrasts with the idea that primates were always exceptional in their degree of overall encephalization and shows that relative brain size and neocortical surface area do not necessarily covary through time. As such, these data contradict assumptions made about the pattern of brain evolution in Euarchontoglires. PMID:26817776

  16. A first-principles model of early evolution: emergence of gene families, species, and preferred protein folds.

    PubMed

    Zeldovich, Konstantin B; Chen, Peiqiu; Shakhnovich, Boris E; Shakhnovich, Eugene I

    2007-07-01

    In this work we develop a microscopic physical model of early evolution where phenotype--organism life expectancy--is directly related to genotype--the stability of its proteins in their native conformations-which can be determined exactly in the model. Simulating the model on a computer, we consistently observe the "Big Bang" scenario whereby exponential population growth ensues as soon as favorable sequence-structure combinations (precursors of stable proteins) are discovered. Upon that, random diversity of the structural space abruptly collapses into a small set of preferred proteins. We observe that protein folds remain stable and abundant in the population at timescales much greater than mutation or organism lifetime, and the distribution of the lifetimes of dominant folds in a population approximately follows a power law. The separation of evolutionary timescales between discovery of new folds and generation of new sequences gives rise to emergence of protein families and superfamilies whose sizes are power-law distributed, closely matching the same distributions for real proteins. On the population level we observe emergence of species--subpopulations that carry similar genomes. Further, we present a simple theory that relates stability of evolving proteins to the sizes of emerging genomes. Together, these results provide a microscopic first-principles picture of how first-gene families developed in the course of early evolution. PMID:17630830

  17. A First-Principles Model of Early Evolution: Emergence of Gene Families, Species, and Preferred Protein Folds

    PubMed Central

    Zeldovich, Konstantin B; Chen, Peiqiu; Shakhnovich, Boris E; Shakhnovich, Eugene I

    2007-01-01

    In this work we develop a microscopic physical model of early evolution where phenotype—organism life expectancy—is directly related to genotype—the stability of its proteins in their native conformations—which can be determined exactly in the model. Simulating the model on a computer, we consistently observe the “Big Bang” scenario whereby exponential population growth ensues as soon as favorable sequence–structure combinations (precursors of stable proteins) are discovered. Upon that, random diversity of the structural space abruptly collapses into a small set of preferred proteins. We observe that protein folds remain stable and abundant in the population at timescales much greater than mutation or organism lifetime, and the distribution of the lifetimes of dominant folds in a population approximately follows a power law. The separation of evolutionary timescales between discovery of new folds and generation of new sequences gives rise to emergence of protein families and superfamilies whose sizes are power-law distributed, closely matching the same distributions for real proteins. On the population level we observe emergence of species—subpopulations that carry similar genomes. Further, we present a simple theory that relates stability of evolving proteins to the sizes of emerging genomes. Together, these results provide a microscopic first-principles picture of how first-gene families developed in the course of early evolution. PMID:17630830

  18. Late-Variscan - early Alpidic magmato-sedimentary evolution of a rifted continent: examples from the Tauern Window

    NASA Astrophysics Data System (ADS)

    Veselá, P.; Lammerer, B.; Söllner, F.; Finger, F.; Gerdes, A.

    2009-04-01

    The late- and post-Variscan magmato-sedimentary evolution is documented in rock associations outcropping in the western Tauern Window. This area marks the southeastern part of the Variscan orogenic belt which evolved into a continental margin during the breakup of Pangea. An extensional regime governed the time span between Late Carboniferous and Middle Jurassic, when post-rift subsidence started and led to widespread flooding in Late Jurassic times. Our studies focus on the late Palaeozoic history, when extension within the Variscan crust led to the formation of intramontane graben systems and favored the generation and emplacement of granitoid melts, mainly as granodioritic sills or laccolithic bodies within the basement. Volcaniclastic layers and tuffs or ignimbrites were embedded at different levels of the post-Variscan sediment sequence. Widespread basement-exhumation affected the graben fillings. Fining-upwards sequences of clastic sediments filled the tectonic grabens which were separated by horsts of early Variscan crystalline basement or late Variscan granitoid intrusives. The studied area has undergone Alpine metamorphism and deformation which erased much information. However, new U-Pb age determinations on zircons and geochemical data of volcanic layers and plutonic rocks (Zentralgneise) allow now a reconstruction of the sedimentary and tectonic evolution in the time span between the late Variscan orogenic collapse and the early Alpine subsidence.

  19. Oxygen and hydrogen peroxide in the early evolution of life on earth: in silico comparative analysis of biochemical pathways.

    PubMed

    Slesak, Ireneusz; Slesak, Halina; Kruk, Jerzy

    2012-08-01

    In the Universe, oxygen is the third most widespread element, while on Earth it is the most abundant one. Moreover, oxygen is a major constituent of all biopolymers fundamental to living organisms. Besides O(2), reactive oxygen species (ROS), among them hydrogen peroxide (H(2)O(2)), are also important reactants in the present aerobic metabolism. According to a widely accepted hypothesis, aerobic metabolism and many other reactions/pathways involving O(2) appeared after the evolution of oxygenic photosynthesis. In this study, the hypothesis was formulated that the Last Universal Common Ancestor (LUCA) was at least able to tolerate O(2) and detoxify ROS in a primordial environment. A comparative analysis was carried out of a number of the O(2)-and H(2)O(2)-involving metabolic reactions that occur in strict anaerobes, facultative anaerobes, and aerobes. The results indicate that the most likely LUCA possessed O(2)-and H(2)O(2)-involving pathways, mainly reactions to remove ROS, and had, at least in part, the components of aerobic respiration. Based on this, the presence of a low, but significant, quantity of H(2)O(2) and O(2) should be taken into account in theoretical models of the early Archean atmosphere and oceans and the evolution of life. It is suggested that the early metabolism involving O(2)/H(2)O(2) was a key adaptation of LUCA to already existing weakly oxic zones in Earth's primordial environment. PMID:22970865

  20. The evolution of sand-rich systems in the early Cretaceous lake in the North Falkland Basin.

    NASA Astrophysics Data System (ADS)

    Dodd, Tom; Richards, Phil

    2016-04-01

    Examples of sand-rich lacustrine turbidite systems are relatively rare in the literature. Here we document the various styles of, and controls on, sub-aqueous sandy fan systems intercalated with organic-rich source rocks in a lacustrine petroleum system of early Cretaceous age in the North Falkland Basin. The lake system occupied an asymmetric rift basin and developed towards the end of the syn-rift phase of the basin's evolution, becoming established during the early phase of post-rift evolution. The earliest fans entering the lake were fed by river systems draining extensive hangingwall platform areas to the west of the rift, comprising mixed sedimentary and volcanoclastic terranes. Although spectacularly developed as classic fan-shaped systems as imaged on 3D reflection seismic data, they form generally poor reservoir quality sand and conglomeratic-volcaniclastic systems. These fans seem to have shut off once the lacustrine system became fully established and created balanced or over-balanced lake fill conditions. Fans entering the basin from the east, across the basin bounding fault and draining the sedimentary-dominated footwall region tend to be narrower, more linear and confined by a combination of pre-existing basin topography and prior fan systems. These fans entered the basin throughout the evolution of the lake, initially down major relay ramp systems, but subsequently down steep canyons associated with only small relay jogs in the basin bounding fault. The eastern fans, which form excellent petroleum reservoirs, may have been derived from fringing littoral settings and were shed into the lake during times of either footwall regeneration or of lake level lowering associated with climatic change which also affected the geometry and depositional processes acting within a major axial delta system that was infilling the basin coevally from the north.

  1. Morphology and histology of chimpanzee primary visual striate cortex indicate that brain reorganization predated brain expansion in early hominid evolution.

    PubMed

    Holloway, Ralph L; Broadfield, Douglas C; Yuan, Michael S

    2003-07-01

    Human brain evolution is characterized by an overall increase in brain size, cerebral reorganization, and cerebral lateralization. It is generally understood when brain enlargement occurred during human evolution. However, issues concerning cerebral reorganization and hemispheric lateralization are more difficult to determine from brain endocasts, and they are topics of considerable debate. One region of the cerebral cortex that may represent the earliest evidence for brain reorganization is the primary visual cortex (PVC), or area 17 of Brodmann. In nonhuman primates, this region is larger in volume (demarcated anteriorly by the lunate sulcus), and extends further rostrally than it does in modern humans. In early hominid fossil (Australopithecus) endocasts, this region appears to occupy a smaller area compared to that in nonhuman primates. Some have argued that the brain first underwent size expansion prior to reorganization, while others maintain that reorganization predated brain expansion. To help resolve this question, we provide a description of two male, common chimpanzee (Pan troglodytes) brains, YN77-111 and YN92-115, which clearly display a more posterior lunate sulcal morphology than seen in other chimpanzees. These data show that neurogenetic variability exists in chimpanzees, and that significant differences in organization (e.g., a reduced PVC) can predate brain enlargement. While the human brain has experienced numerous expansion and reorganization events throughout evolution, the data from these two chimpanzees offer significant support for the hypothesis that the neurogenetic basis for brain reorganization was present in our early fossil ancestors (i.e., the australopithecines) prior to brain enlargement. PMID:12808644

  2. HIV Evolution in Early Infection: Selection Pressures, Patterns of Insertion and Deletion, and the Impact of APOBEC

    PubMed Central

    Wood, Natasha; Bhattacharya, Tanmoy; Keele, Brandon F.; Giorgi, Elena; Liu, Michael; Gaschen, Brian; Daniels, Marcus; Ferrari, Guido; Haynes, Barton F.; McMichael, Andrew; Shaw, George M.; Hahn, Beatrice H.; Korber, Bette; Seoighe, Cathal

    2009-01-01

    The pattern of viral diversification in newly infected individuals provides information about the host environment and immune responses typically experienced by the newly transmitted virus. For example, sites that tend to evolve rapidly across multiple early-infection patients could be involved in enabling escape from common early immune responses, could represent adaptation for rapid growth in a newly infected host, or could represent reversion from less fit forms of the virus that were selected for immune escape in previous hosts. Here we investigated the diversification of HIV-1 env coding sequences in 81 very early B subtype infections previously shown to have resulted from transmission or expansion of single viruses (n = 78) or two closely related viruses (n = 3). In these cases, the sequence of the infecting virus can be estimated accurately, enabling inference of both the direction of substitutions as well as distinction between insertion and deletion events. By integrating information across multiple acutely infected hosts, we find evidence of adaptive evolution of HIV-1 env and identify a subset of codon sites that diversified more rapidly than can be explained by a model of neutral evolution. Of 24 such rapidly diversifying sites, 14 were either i) clustered and embedded in CTL epitopes that were verified experimentally or predicted based on the individual's HLA or ii) in a nucleotide context indicative of APOBEC-mediated G-to-A substitutions, despite having excluded heavily hypermutated sequences prior to the analysis. In several cases, a rapidly evolving site was embedded both in an APOBEC motif and in a CTL epitope, suggesting that APOBEC may facilitate early immune escape. Ten rapidly diversifying sites could not be explained by CTL escape or APOBEC hypermutation, including the most frequently mutated site, in the fusion peptide of gp41. We also examined the distribution, extent, and sequence context of insertions and deletions, and we provide

  3. Sex-specific adaptation drives early sex chromosome evolution in Drosophila.

    PubMed

    Zhou, Qi; Bachtrog, Doris

    2012-07-20

    Most species' sex chromosomes are derived from ancient autosomes and show few signatures of their origins. We studied the sex chromosomes of Drosophila miranda, where a neo-Y chromosome originated only approximately 1 million years ago. Whole-genome and transcriptome analysis reveals massive degeneration of the neo-Y, that male-beneficial genes on the neo-Y are more likely to undergo accelerated protein evolution, and that neo-Y genes evolve biased expression toward male-specific tissues--the shrinking gene content of the neo-Y becomes masculinized. In contrast, although older X chromosomes show a paucity of genes expressed in male tissues, neo-X genes highly expressed in male-specific tissues undergo increased rates of protein evolution if haploid in males. Thus, the response to sex-specific selection can shift at different stages of X differentiation, resulting in masculinization or demasculinization of the X-chromosomal gene content. PMID:22822149

  4. A bizarre theropod from the Early Cretaceous of Japan highlighting mosaic evolution among coelurosaurians.

    PubMed

    Azuma, Yoichi; Xu, Xing; Shibata, Masateru; Kawabe, Soichiro; Miyata, Kazunori; Imai, Takuya

    2016-01-01

    Our understanding of coelurosaurian evolution, particularly of bird origins, has been greatly improved, mainly due to numerous recently discovered fossils worldwide. Nearly all these discoveries are referable to the previously known coelurosaurian subgroups. Here, we report a new theropod, Fukuivenator paradoxus, gen. et sp. nov., based on a nearly complete specimen from the Lower Cretaceous Kitadani Formation of the Tetori Group, Fukui, Japan. While Fukuivenator possesses a large number of morphological features unknown in any other theropod, it has a combination of primitive and derived features seen in different theropod subgroups, notably dromaeosaurid dinosaurs. Computed-tomography data indicate that Fukuivenator possesses inner ears whose morphology is intermediate between those of birds and non-avian dinosaurs. Our phylogenetic analysis recovers Fukuivenator as a basally branching maniraptoran theropod, yet is unable to refer it to any known coelurosaurian subgroups. The discovery of Fukuivenator considerably increases the morphological disparity of coelurosaurian dinosaurs and highlights the high levels of homoplasy in coelurosaurian evolution. PMID:26908367

  5. A bizarre theropod from the Early Cretaceous of Japan highlighting mosaic evolution among coelurosaurians

    PubMed Central

    Azuma, Yoichi; Xu, Xing; Shibata, Masateru; Kawabe, Soichiro; Miyata, Kazunori; Imai, Takuya

    2016-01-01

    Our understanding of coelurosaurian evolution, particularly of bird origins, has been greatly improved, mainly due to numerous recently discovered fossils worldwide. Nearly all these discoveries are referable to the previously known coelurosaurian subgroups. Here, we report a new theropod, Fukuivenator paradoxus, gen. et sp. nov., based on a nearly complete specimen from the Lower Cretaceous Kitadani Formation of the Tetori Group, Fukui, Japan. While Fukuivenator possesses a large number of morphological features unknown in any other theropod, it has a combination of primitive and derived features seen in different theropod subgroups, notably dromaeosaurid dinosaurs. Computed-tomography data indicate that Fukuivenator possesses inner ears whose morphology is intermediate between those of birds and non-avian dinosaurs. Our phylogenetic analysis recovers Fukuivenator as a basally branching maniraptoran theropod, yet is unable to refer it to any known coelurosaurian subgroups. The discovery of Fukuivenator considerably increases the morphological disparity of coelurosaurian dinosaurs and highlights the high levels of homoplasy in coelurosaurian evolution. PMID:26908367

  6. From records to self-description: the role played by RNA in early evolutive systems.

    PubMed

    Moreno Bergareche, A; Fernández Ostolaza, J

    1992-03-01

    We study the appearance of genetic information starting from a system where self-reproductive and enzymatic functions are supported by the same sort of molecules. In a first phase, the information must have arisen in the form of rate independent sequences as records of enzymatic functions. Although this stage must have played an important role in evolution, it will be shown how its evolutive capacities were blocked by the impossibility of appearance of geno/phenotype duality. Finally, a logical scheme is proposed for a transition process toward a system with a code offering a simplification of the conditions required from the assumption of a maximum use of the double RNA capacity, both reproductive and enzymatic. PMID:1378239

  7. Inhomogeneous halo collapse and early Galactic chemical evolution - Globular cluster metallicities

    NASA Technical Reports Server (NTRS)

    Malinie, G.; Hartmann, D. H.; Mathews, G. J.

    1991-01-01

    A new solution to the observed Galactic globular cluster metallicity distribution is proposed by considering inhomogeneous collapse of a centrally condensed proto-Galaxy. In contrast to the standard one-zone model, it is shown that, for inhomogeneous models, the metallicity distribution can be reproduced without the need to decrease the nucleosynthetic yield for metal-poor stars. Chemical evolution in free fall is calculated analytically. A hybrid hydroparticle code is developed to study the effect of supernova induced pressure.

  8. Structural Evolution of Early-type Galaxies to z = 2.5 in CANDELS

    NASA Astrophysics Data System (ADS)

    Chang, Yu-Yen; van der Wel, Arjen; Rix, Hans-Walter; Holden, Bradford; Bell, Eric F.; McGrath, Elizabeth J.; Wuyts, Stijn; Häussler, Boris; Barden, Marco; Faber, S. M.; Mozena, Mark; Ferguson, Henry C.; Guo, Yicheng; Galametz, Audrey; Grogin, Norman A.; Kocevski, Dale D.; Koekemoer, Anton M.; Dekel, Avishai; Huang, Kuang-Han; Hathi, Nimish P.; Donley, Jennifer

    2013-08-01

    Projected axis ratio measurements of 880 early-type galaxies at redshifts 1 < z < 2.5 selected from CANDELS are used to reconstruct and model their intrinsic shapes. The sample is selected on the basis of multiple rest-frame colors to reflect low star-formation activity. We demonstrate that these galaxies as an ensemble are dust-poor and transparent and therefore likely have smooth light profiles, similar to visually classified early-type galaxies. Similar to their present-day counterparts, the z > 1 early-type galaxies show a variety of intrinsic shapes; even at a fixed mass, the projected axis ratio distributions cannot be explained by the random projection of a set of galaxies with very similar intrinsic shapes. However, a two-population model for the intrinsic shapes, consisting of a triaxial, fairly round population, combined with a flat (c/a ~ 0.3) oblate population, adequately describes the projected axis ratio distributions of both present-day and z > 1 early-type galaxies. We find that the proportion of oblate versus triaxial galaxies depends both on the galaxies' stellar mass, and—at a given mass—on redshift. For present-day and z < 1 early-type galaxies the oblate fraction strongly depends on galaxy mass. At z > 1, this trend is much weaker over the mass range explored here (1010 < M */M ⊙ < 1011), because the oblate fraction among massive (M * ~ 1011 M ⊙) was much higher in the past: 0.59 ± 0.10 at z > 1, compared to 0.20 ± 0.02 at z ~ 0.1. When combined with previous findings that the number density and sizes of early-type galaxies substantially increase over the same redshift range, this can be explained by the gradual emergence of merger-produced elliptical galaxies, at the expense of the destruction of pre-existing disks that were common among their high-redshift progenitors. In contrast, the oblate fraction among low-mass early-type galaxies (log (M */M ⊙) < 10.5) increased toward the present, from z = 0 to 0.38 ± 0.11 at z > 1 to 0

  9. Late Paleocene early Eocene Tethyan carbonate platform evolution — A response to long- and short-term paleoclimatic change

    NASA Astrophysics Data System (ADS)

    Scheibner, C.; Speijer, R. P.

    2008-11-01

    The early Paleogene experienced the most pronounced long-term warming trend of the Cenozoic, superimposed by transient warming events such as the Paleocene-Eocene Thermal Maximum (PETM). The consequences of climatic perturbations and associated changes on the evolution of carbonate platforms are relatively unexplored. Today, modern carbonate platforms, especially coral reefs are highly sensitive to environmental and climatic change, which raises the question how (sub)tropical reef systems of the early Paleogene reacted to gradual and sudden global warming, eutrophication of shelf areas, enhanced CO 2 levels in an ocean with low Mg/Ca ratios. The answer to this question may help to investigate the fate of modern coral reef systems in times of global warming and rising CO 2 levels. Here we present a synthesis of Tethyan carbonate platform evolution in the early Paleogene (~ 59-55 Ma) concentrating on coral reefs and larger foraminifera, two important organism groups during this time interval. We discuss and evaluate the importance of the intrinsic and extrinsic factors leading to the dissimilar evolution of both groups during the early Paleogene. Detailed analyses of two carbonate platform areas at low (Egypt) and middle (Spain) paleolatitudes and comparison with faunal patterns of coeval platforms retrieved from the literature led to the distinction of three evolutionary stages in the late Paleocene to early Eocene Tethys: Stage I, late Paleocene coralgal-dominated platforms at low to middle paleolatitudes; stage II, a transitional latest Paleocene platform stage with coralgal reefs dominating at middle paleolatitudes and larger foraminifera-dominated ( Miscellanea, Ranikothalia, Assilina) platforms at low paleolatitudes; and stage III, early Eocene larger foraminifera-dominated ( Alveolina, Orbitolites, Nummulites) platforms at low to middle paleolatitudes. The onset of the latter prominent larger foraminifera-dominated platform correlates with the Paleocene

  10. THE POTENTIAL IMPORTANCE OF BINARY EVOLUTION IN ULTRAVIOLET-OPTICAL SPECTRAL FITTING OF EARLY-TYPE GALAXIES

    SciTech Connect

    Li, Zhongmu; Mao, Caiyan; Chen, Li; Zhang, Qian; Li, Maocai

    2013-10-10

    Most galaxies possibly contain some binaries, and more than half of Galactic hot subdwarf stars, which are thought to be a possible origin of the UV-upturn of old stellar populations, are found in binaries. However, the effect of binary evolution has not been taken into account in most works on the spectral fitting of galaxies. This paper studies the role of binary evolution in the spectral fitting of early-type galaxies, via a stellar population synthesis model including both single and binary star populations. Spectra from ultraviolet to optical bands are fitted to determine a few galaxy parameters. The results show that the inclusion of binaries in stellar population models may lead to obvious change in the determination of some parameters of early-type galaxies and therefore it is potentially important for spectral studies. In particular, the ages of young components of composite stellar populations become much older when using binary star population models instead of single star population models. This implies that binary star population models will measure significantly different star formation histories for early-type galaxies compared to single star population models. In addition, stellar population models with binary interactions on average measure larger dust extinctions than single star population models. This suggests that when binary star population models are used, negative extinctions are possibly no longer necessary in the spectral fitting of galaxies (see previous works, e.g., Cid Fernandes et al. for comparison). Furthermore, it is shown that optical spectra have strong constraints on stellar age while UV spectra have strong constraints on binary fraction. Finally, our results suggest that binary star population models can provide new insight into the stellar properties of globular clusters.

  11. HAZMAT I: The Evolution of X-ray, Far-UV and Near-UV Emission from Early M Stars

    NASA Astrophysics Data System (ADS)

    Shkolnik, E.; Barman, T.

    2014-03-01

    With the recent discoveries of several super-earths orbiting M dwarfs well within their habitable zones (0.1 to 0.4 AU), and with many more such planets to come, it is critical to assess the evolution of the high-energy radiation environment of these systems. We have begun the HAZMAT (HAbitable Zones and M dwarf Activity across Time) program by first measuring the drop in near-UV and far-UV flux in early M stars from 10 Myr to several Gyr using photometry from NASA's Galaxy Evolution Explorer (GALEX). We focus this study on the confirmed low-mass members of nearby young moving groups, the Hyades cluster, and old field stars. We show a relatively slow decline in UV flux up until at least 650 Myr with a sharper drop in the old M dwarfs. Yet without confirmed M dwarfs in nearby star clusters with ages of 1-2 Gyr, mapping the precise evolution at these older ages is not currently possible. The UV data also provide much-needed constraints to M dwarf upper-atmosphere models, which are currently insufficient for predicting UV emission from M dwarfs. Our analysis will aid empirically motivated upper-atmospheric modeling for the young and old M stars, which can then be used to predict the extreme-UV fluxes most critical to the evolution of a planetary atmosphere. (See HAZMAT II abstract by Peacock et al.) The HAZMAT program is the first comprehensive study of the UV history of M stars.

  12. Purely Dry Mergers do not Explain the Observed Evolution of Massive Early-type Galaxies since z ~ 1

    NASA Astrophysics Data System (ADS)

    Sonnenfeld, Alessandro; Nipoti, Carlo; Treu, Tommaso

    2014-05-01

    Several studies have suggested that the observed size evolution of massive early-type galaxies (ETGs) can be explained as a combination of dry mergers and progenitor bias, at least since z ~ 1. In this paper we carry out a new test of the dry-merger scenario based on recent lensing measurements of the evolution of the mass density profile of ETGs. We construct a theoretical model for the joint evolution of the size and mass density profile slope γ' driven by dry mergers occurring at rates given by cosmological simulations. Such dry-merger model predicts a strong decrease of γ' with cosmic time, inconsistent with the almost constant γ' inferred from observations in the redshift range 0 < z < 1. We then show with a simple toy model that a modest amount of cold gas in the mergers—consistent with the upper limits on recent star formation in ETGs—is sufficient to reconcile the model with measurements of γ'. By fitting for the amount of gas accreted during mergers, we find that models with dissipation are consistent with observations of the evolution in both size and density slope, if ~4% of the total final stellar mass arises from the gas accreted since z ~ 1. Purely dry merger models are ruled out at >99% CL. We thus suggest a scenario where the outer regions of massive ETGs grow by accretion of stars and dark matter, while small amounts of dissipation and nuclear star formation conspire to keep the mass density profile constant and approximately isothermal.

  13. Structural Evolution of Early-type Galaxies to z=2.5 in CANDELS

    NASA Astrophysics Data System (ADS)

    Chang, Yu-Yen; van der Wel, A.; Rix, H.; CANDELS Collaboration

    2014-01-01

    Projected axis ratio measurements of 880 early-type galaxies at redshifts 1 < z < 2.5 selected from CANDELS are used to reconstruct and model their intrinsic shapes. The sample is selected on the basis of multiple rest-frame colors to reflect low star-formation activity. Similar to their present-day counterparts, the z > 1 early-type galaxies show a variety of intrinsic shapes; even at a fixed mass, the projected axis ratio distributions cannot be explained by the random projection of a set of galaxies with very similar intrinsic shapes. However, a two-population model for the intrinsic shapes, consisting of a triaxial, fairly round population, combined with a flat (c/a ~ 0.3) oblate population, adequately describes the projected axis ratio distributions of both present-day and z > 1 early-type galaxies. However, the oblate fraction among massive (M* ~ 10^11 Msun) objects was much higher in the past: 0.59 ± 0.10 at z > 1, compared to 0.20 ± 0.02 at z ~ 0.1. When combined with previous findings that the number density and sizes of early-type galaxies substantially increase over the same redshift range, this can be explained by the gradual emergence of merger-produced elliptical galaxies, at the expense of the destruction of pre-existing disks that were common among their high-redshift progenitors.

  14. Eine evolutionsbiologische Betrachtung der menschlichen Fruhentwicklung (An Evolution-Biological Perspective on the Child's Early Development).

    ERIC Educational Resources Information Center

    Keller, Heidi

    1997-01-01

    Presents an evolutionary-biological perspective on the course of human life. Discusses early development during the first few months of a child's life in the context of bonding with regard to the differentiation of diverse strategies of reproduction. Tries to integrate developmental-psychological knowledge and sociobiological assumptions. (DSK)

  15. THE ROLE OF MERGERS IN EARLY-TYPE GALAXY EVOLUTION AND BLACK HOLE GROWTH

    SciTech Connect

    Schawinski, Kevin; Dowlin, Nathan; Urry, C. Megan; Thomas, Daniel; Edmondson, Edward

    2010-05-01

    Models of galaxy formation invoke the major merger of gas-rich progenitor galaxies as the trigger for significant phases of black hole growth and the associated feedback that suppresses star formation to create red spheroidal remnants. However, the observational evidence for the connection between mergers and active galactic nucleus (AGN) phases is not clear. We analyze a sample of low-mass early-type galaxies known to be in the process of migrating from the blue cloud to the red sequence via an AGN phase in the green valley. Using deeper imaging from Sloan Digital Sky Survey Stripe 82, we show that the fraction of objects with major morphological disturbances is high during the early starburst phase, but declines rapidly to the background level seen in quiescent early-type galaxies by the time of substantial AGN radiation several hundred Myr after the starburst. This observation empirically links the AGN activity in low-redshift early-type galaxies to a significant merger event in the recent past. The large time delay between the merger-driven starburst and the peak of AGN activity allows for the merger features to decay to the background and hence may explain the weak link between merger features and AGN activity in the literature.

  16. Detection of failures in a stator of turbo-generator on early stages of their evolution

    NASA Astrophysics Data System (ADS)

    Kormyshev, V. M.; Medvedeva, M. A.; Naboychenko, E. S.; Prisyazhnyy, A. V.; Shamanov, A. P.

    2016-06-01

    Methodology of finding out defects in a stator of turbo-generator on early stage of their development is considered. Methodology is based on the analysis of measureable parameters of the temperature field on a working machine. To the number of the exposed defects behave: decline of possibility of hollow core of a winding of the stator and defects of the stators iron.

  17. Education for Sustainable Development in Early Childhood Education in Spain. Evolution, Trends and Proposals

    ERIC Educational Resources Information Center

    Agut, M. Pilar Martínez; Ull, M. Angeles; Minguet, Pilar Aznar

    2014-01-01

    This article analyses how the sustainability culture has evolved in the early childhood education setting within the Spanish education system with official documents and the sustainability training received by teachers who intervene in this stage of education since these teachers' degrees have been adapted to the European Higher Education…

  18. RECONSTRUCTING THE EARLY EVOLUTION OF FUNGI USING A SIX-GENE PHYLOGENY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The ancestors of fungi are believed to be simple aquatic forms with flagellated spores, similar to modern-day Chytridiomycete fungi (chytrids). Current classifications for the fungi assume that the chytrids form an early-diverging clade of Fungi, and imply that there was a single loss of the flagel...

  19. The natural history of the helicoidal occlusal plane and its evolution in early Homo.

    PubMed

    Tobias, P V

    1980-08-01

    In modern man the pitch of the occlusal plane may vary along the tooth-row. When anterior cheek-teeth show a plane sloping upward palatally, whilst that on posterior cheek-teeth slopes upward buccally, there results a twisted or helicoidal occlusal plane (Ackermann). Several hypotheses have been proposed for the structural basis of the helicoidal occlusal plane. Campbell's proposal ('25) has gained widest acceptance, namely that the helicoid results from anteroposterior differences in upper and lower alveolar arch width. In the early 1960s, while studying the Olduvai hominids assigned to Homo habilis, the author noted changing occlusal slopes along the tooth-row and a slight helicoid, although these featues had not been noted in other early hominids. Subsequently, Wallace showed a total absence of the helicoid from South African australopithecines, and its presence in Swartkrans Homo, SK 45 and SK 80. Recent studies confirm the presence of the helicoid in all available specimens of H. habilis, including Stw 53 found at Sterkfontein in 1976. Hence, this trait may distinguish between Australopithecus and early Homo. Measurements of the maxillary arch widths have shown that, whereas in Australopithecus arch widths increase to a maximum at M3, in early Homo maxillary arch widths are greatest at M2. The decline in posterior maxillary arch width is part of a general reduction of that region. Thus despite striking elongation of premolars and M1 in early Homo, M2 and M3 are mesiodistally abbreviated. It is hypothesized that the onset of posterior arch reduction, with the appearance of a helicoid, was a structural and functional concomitant of the transition from the presumed australopithecine ancestor to H. habilis. PMID:6774617

  20. Early evolution and dynamics of Earth from a molten initial stage

    NASA Astrophysics Data System (ADS)

    Lourenço, DL; Tackley, PJ

    2014-04-01

    It is now well established that most of the terrestrial planets underwent a magma ocean stage during their accretion. On Earth, it is probable that at the end of accretion, giant impacts like the hypothesised Moonforming impact, together with other sources of heat such as conversion of gravitational energy of formation into heat, radioactive decay, heat losses from the core at the core-mantle boundary, electromagnetic induction heating and tidal heating, melted a substantial part of the mantle. The thermal and chemical evolution of the resulting magma ocean most certainly had dramatic consequences on the history of the planet, influencing the chemical composition of the mantle after differentiation, the style of tectonic regime prevailing in the solid-state mantle and its habitability. Considerable research has been done on magma oceans using 1-D models [1], [5], [3]. However, its dynamics, evolution from a molten state to the present day solid state, and crystallisation are still not fully understood and are more complex than a 1-D formulation. Recent advances in computational methods and resources allow us to address numerically more complex problems, with higher resolution and multiple physics incorporated. Moreover, new developments in mineral physics that indicate that melt can be denser than solid at high pressures [2] can have very important impacts on the classical views of the solidification of magma oceans [4]. The goal of our study is to understand and characterize the influence of melting on the long-term thermochemical evolution of rocky planet interiors, starting from an initial molten state (magma ocean). Our approach is to model viscous creep of the solid mantle, while parameterizing processes that involve melt. We will be testing existing published 1-D parameterisations of magma ocean dynamics and extending them into 2-D models. To address this problem, the numerical code StagYY [6] is used. Some details about thiscode are the following: it uses a

  1. Evolution of dense rotating star clusters in the cores of early galaxies

    NASA Astrophysics Data System (ADS)

    Girash, J.

    1996-12-01

    We present simulations of the evolution of dense star clusters integrated using a two-dimensional Fokker-Planck approach. Effects of initial rotation, ellipticity, and stellar mergers are included. When an instability criterion is satisfied (Trot/|W| > alpha , where alpha is the stability parameter), a non-axisymmetric component of the potential is applied to model the formation of a stellar bar. Results are interpreted with a view to describing the formation of a massive ( ~ 10(3) M_sun) object near the cluster center which could evolve into the seed black hole of an AGN or quasar.

  2. On the levels of enzymatic substrate specificity: Implications for the early evolution of metabolic pathways

    NASA Technical Reports Server (NTRS)

    Lazcano, A.; Diaz-Villagomez, E.; Mills, T.; Oro, J.

    1995-01-01

    The most frequently invoked explanation for the origin of metabolic pathways is the retrograde evolution hypothesis. In contrast, according to the so-called 'patchwork' theory, metabolism evolved by the recruitment of relatively inefficient small enzymes of broad specificity that could react with a wide range of chemically related substrates. In this paper it is argued that both sequence comparisons and experimental results on enzyme substrate specificity support the patchwork assembly theory. The available evidence supports previous suggestions that gene duplication events followed by a gradual neoDarwinian accumulation of mutations and other minute genetic changes lead to the narrowing and modification of enzyme function in at least some primordial metabolic pathways.

  3. Highly sensitive catalytic spectrophotometric determination of ruthenium

    NASA Astrophysics Data System (ADS)

    Naik, Radhey M.; Srivastava, Abhishek; Prasad, Surendra

    2008-01-01

    A new and highly sensitive catalytic kinetic method (CKM) for the determination of ruthenium(III) has been established based on its catalytic effect on the oxidation of L-phenylalanine ( L-Pheala) by KMnO 4 in highly alkaline medium. The reaction has been followed spectrophotometrically by measuring the decrease in the absorbance at 526 nm. The proposed CKM is based on the fixed time procedure under optimum reaction conditions. It relies on the linear relationship where the change in the absorbance (Δ At) versus added Ru(III) amounts in the range of 0.101-2.526 ng ml -1 is plotted. Under the optimum conditions, the sensitivity of the proposed method, i.e. the limit of detection corresponding to 5 min is 0.08 ng ml -1, and decreases with increased time of analysis. The method is featured with good accuracy and reproducibility for ruthenium(III) determination. The ruthenium(III) has also been determined in presence of several interfering and non-interfering cations, anions and polyaminocarboxylates. No foreign ions interfered in the determination ruthenium(III) up to 20-fold higher concentration of foreign ions. In addition to standard solutions analysis, this method was successfully applied for the quantitative determination of ruthenium(III) in drinking water samples. The method is highly sensitive, selective and very stable. A review of recently published catalytic spectrophotometric methods for the determination of ruthenium(III) has also been presented for comparison.

  4. Spectrophotometric determination of benazepril in tablets.

    PubMed

    Belal, F; Al-Zaagi, I A; Abounassif, M A

    2000-01-01

    A simple and sensitive spectrophotometric method has been developed for the determination of benazepril HCl in pharmaceutical formulations. The method is based on the reaction of the drug with potassium permanganate in the presence of sodium hydroxide to produce a bluish-green colored species measurable at 609.4 nm. The absorbance-concentration plot is linear over the range 1-8 microg ml(-1) with minimum detectability of 0.1 microg ml(-1) (2.17 x 10(-7) M). The molar absorptivity was 4.07 x 10(4) l mol(-1) cm(-1) with correlation coefficient (n = 6) of 0.9991. The different experimental parameters affecting the development and stability of the color were studied carefully and optimized. The proposed method was applied successfully to the determination of benazepril in its dosage forms, the percentage recoveries +/- SD (n = 9) were 99.79 +/- 1.40 and 100.50 +/- 1.48 for tablets containing 10 and 20 mg, respectively. The results obtained were in good agreement with those obtained using a reference spectrophotometric method. The proposed method could be applied to the determination of benazepril in presence of the co-formulated drug, hydrochlorothiazide. A proposal of the reaction pathway was presented. PMID:11204742

  5. A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora

    PubMed Central

    Yang, Jie; Ortega-Hernández, Javier; Gerber, Sylvain; Butterfield, Nicholas J.; Hou, Jin-bo; Lan, Tian; Zhang, Xi-guang

    2015-01-01

    We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstätte in South China, an armored lobopodian with a remarkable degree of limb differentiation including a pair of antenna-like appendages, six pairs of elongate setiferous limbs for suspension feeding, and nine pairs of clawed annulated legs with an anchoring function. Collinsium belongs to a highly derived clade of lobopodians within stem group Onychophora, distinguished by a substantial dorsal armature of supernumerary and biomineralized spines (Family Luolishaniidae). As demonstrated here, luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Despite having higher disparity and appendage complexity than other lobopodians and extant velvet worms, the specialized mode of life embodied by luolishaniids became extinct during the Early Paleozoic. Collinsium and other superarmored lobopodians exploited a unique paleoecological niche during the Cambrian explosion. PMID:26124122

  6. Widespread somatic L1 retrotransposition occurs early during gastrointestinal cancer evolution

    PubMed Central

    Ewing, Adam D.; Gacita, Anthony; Wood, Laura D.; Ma, Florence; Xing, Dongmei; Kim, Min-Sik; Manda, Srikanth S.; Abril, Gabriela; Pereira, Gavin; Makohon-Moore, Alvin; Looijenga, Leendert H.J.; Gillis, Ad J.M.; Hruban, Ralph H.; Anders, Robert A.; Romans, Katharine E.; Pandey, Akhilesh; Iacobuzio-Donahue, Christine A.; Vogelstein, Bert; Kinzler, Kenneth W.; Kazazian, Haig H.; Solyom, Szilvia

    2015-01-01

    Somatic L1 retrotransposition events have been shown to occur in epithelial cancers. Here, we attempted to determine how early somatic L1 insertions occurred during the development of gastrointestinal (GI) cancers. Using L1-targeted resequencing (L1-seq), we studied different stages of four colorectal cancers arising from colonic polyps, seven pancreatic carcinomas, as well as seven gastric cancers. Surprisingly, we found somatic L1 insertions not only in all cancer types and metastases but also in colonic adenomas, well-known cancer precursors. Some insertions were also present in low quantities in normal GI tissues, occasionally caught in the act of being clonally fixed in the adjacent tumors. Insertions in adenomas and cancers numbered in the hundreds, and many were present in multiple tumor sections, implying clonal distribution. Our results demonstrate that extensive somatic insertional mutagenesis occurs very early during the development of GI tumors, probably before dysplastic growth. PMID:26260970

  7. Early Tertiary marine fossils from northern Alaska: implications for Arctic Ocean paleogeography and faunal evolution.

    USGS Publications Warehouse

    Marincovich, L., Jr.; Brouwers, E.M.; Carter, L.D.

    1985-01-01

    Marine mollusks and ostracodes indicate a post-Danian Paleocene to early Eocene (Thanetian to Ypresian) age for a fauna from the Prince Creek Formation at Ocean Point, northern Alaska, that also contains genera characteristic of the Cretaceous and Neogene-Quaternary. The life-assocation of heterochronous taxa at Ocean Point resulted from an unusual paleogeographic setting, the nearly complete isolation of the Arctic Ocean from about the end of the Cretaceous until sometime in the Eocene, in which relict Cretaceous taxa survived into Tertiary time while endemic taxa evolved in situ; these later migrated to the northern mid- latitudes. Paleobiogeographic affinities of the Ocean Point assocation with mild temperate faunas of the London Basin (England), Denmark, and northern Germany indicate that a shallow, intermittent Paleocene seaway extended through the Norwegian-Greenland Sea to the North Sea Basin. Early Tertiary Arctic Ocean paleogeography deduced from faunal evidence agrees with that inferred from plate-tectonic reconstructions.-Authors

  8. A superarmored lobopodian from the Cambrian of China and early disparity in the evolution of Onychophora.

    PubMed

    Yang, Jie; Ortega-Hernández, Javier; Gerber, Sylvain; Butterfield, Nicholas J; Hou, Jin-Bo; Lan, Tian; Zhang, Xi-guang

    2015-07-14

    We describe Collinsium ciliosum from the early Cambrian Xiaoshiba Lagerstätte in South China, an armored lobopodian with a remarkable degree of limb differentiation including a pair of antenna-like appendages, six pairs of elongate setiferous limbs for suspension feeding, and nine pairs of clawed annulated legs with an anchoring function. Collinsium belongs to a highly derived clade of lobopodians within stem group Onychophora, distinguished by a substantial dorsal armature of supernumerary and biomineralized spines (Family Luolishaniidae). As demonstrated here, luolishaniids display the highest degree of limb specialization among Paleozoic lobopodians, constitute more than one-third of the overall morphological disparity of stem group Onychophora, and are substantially more disparate than crown group representatives. Despite having higher disparity and appendage complexity than other lobopodians and extant velvet worms, the specialized mode of life embodied by luolishaniids became extinct during the Early Paleozoic. Collinsium and other superarmored lobopodians exploited a unique paleoecological niche during the Cambrian explosion. PMID:26124122

  9. STRUCTURAL EVOLUTION OF EARLY-TYPE GALAXIES TO z = 2.5 IN CANDELS

    SciTech Connect

    Chang, Yu-Yen; Van der Wel, Arjen; Rix, Hans-Walter; Holden, Bradford; Faber, S. M.; Mozena, Mark; Guo Yicheng; Kocevski, Dale D.; McGrath, Elizabeth J.; Wuyts, Stijn; Haeussler, Boris; Barden, Marco; Ferguson, Henry C.; Grogin, Norman A.; Koekemoer, Anton M.; Huang, Kuang-Han; Galametz, Audrey; Dekel, Avishai; Hathi, Nimish P.; and others

    2013-08-20

    Projected axis ratio measurements of 880 early-type galaxies at redshifts 1 < z < 2.5 selected from CANDELS are used to reconstruct and model their intrinsic shapes. The sample is selected on the basis of multiple rest-frame colors to reflect low star-formation activity. We demonstrate that these galaxies as an ensemble are dust-poor and transparent and therefore likely have smooth light profiles, similar to visually classified early-type galaxies. Similar to their present-day counterparts, the z > 1 early-type galaxies show a variety of intrinsic shapes; even at a fixed mass, the projected axis ratio distributions cannot be explained by the random projection of a set of galaxies with very similar intrinsic shapes. However, a two-population model for the intrinsic shapes, consisting of a triaxial, fairly round population, combined with a flat (c/a {approx} 0.3) oblate population, adequately describes the projected axis ratio distributions of both present-day and z > 1 early-type galaxies. We find that the proportion of oblate versus triaxial galaxies depends both on the galaxies' stellar mass, and-at a given mass-on redshift. For present-day and z < 1 early-type galaxies the oblate fraction strongly depends on galaxy mass. At z > 1, this trend is much weaker over the mass range explored here (10{sup 10} < M{sub *}/M{sub Sun} < 10{sup 11}), because the oblate fraction among massive (M{sub *} {approx} 10{sup 11} M{sub Sun }) was much higher in the past: 0.59 {+-} 0.10 at z > 1, compared to 0.20 {+-} 0.02 at z {approx} 0.1. When combined with previous findings that the number density and sizes of early-type galaxies substantially increase over the same redshift range, this can be explained by the gradual emergence of merger-produced elliptical galaxies, at the expense of the destruction of pre-existing disks that were common among their high-redshift progenitors. In contrast, the oblate fraction among low-mass early-type galaxies (log (M{sub *}/M{sub Sun }) < 10

  10. Trojan Tour and Rendezvous (TTR): A New Frontiers Mission to Explore the Origin and Evolution of the Early Solar System

    NASA Astrophysics Data System (ADS)

    Bell, J. F., III; Olkin, C.; Castillo, J. C.

    2015-12-01

    The orbital properties, compositions, and physical properties of the diverse populations of small outer solar system bodies provide a forensic map of how our solar system formed and evolved. Perhaps the most potentially diagnostic, but least explored, of those populations are the Jupiter Trojan asteroids, which orbit at ~5 AU in the L4 and L5 Lagrange points of Jupiter. More than 6200 Jupiter Trojans are presently known, but these are predicted to be only a small fraction of the 500,000 to 1 million Trojans >1 km in size. The Trojans are hypothesized to be either former Kuiper Belt Objects (KBOs) that were scattered into the inner solar system by early giant planet migration and then trapped in the 1:1 Jupiter mean motion resonance, or bodies formed near 5 AU in a much more quiescent early solar system, and then trapped at L4 and L5. The 2011 Planetary Science Decadal Survey identified important questions about the origin and evolution of the solar system that can be addressed by studying of the Trojan asteroids, including: (a) How did the giant planets and their satellite systems accrete, and is there evidence that they migrated to new orbital positions? (b) What is the relationship between large and small KBOs? Is the small population derived by impact disruption of the large one? (c) What kinds of surface evolution, radiation chemistry, and surface-atmosphere interactions occur on distant icy primitive bodies? And (d) What are the sources of asteroid groups (Trojans and Centaurs) that remain to be explored by spacecraft? The Trojan Tour and Rendezvous (TTR) is a New Frontiers-class mission designed to answer these questions, and to test hypotheses for early giant planet migration and solar system evolution. Via close flybys of a large number of these objects,, and orbital characterization of at least one large Trojan, TTR will enable the first-time exploration of this population. Our primary mission goals are to characterize the overall surface geology

  11. Early time evolution of high-energy heavy-ion collisions

    NASA Astrophysics Data System (ADS)

    Fries, Rainer J.

    2007-08-01

    We solve the Yang Mills equations in the framework of the McLerran Venugopalan model for small times τ after a collision of two nuclei. An analytic expansion around τ = 0 leads to explicit results for the field strength and the energy momentum tensor of the gluon field at early times. We then discuss constraints for the energy density, pressure and flow of the plasma phase that emerges after thermalization of the gluon field.

  12. Lower Cambrian polychaete from China sheds light on early annelid evolution.

    PubMed

    Liu, Jianni; Ou, Qiang; Han, Jian; Li, Jinshu; Wu, Yichen; Jiao, Guoxiang; He, Tongjiang

    2015-06-01

    We herein report a fossilized polychaete annelid, Guanshanchaeta felicia gen. et sp. nov., from the Lower Cambrian Guanshan Biota (Cambrian Series 2, stage 4). The new taxon has a generalized polychaete morphology, with biramous parapodia (most of which preserve the evidence of chaetae), an inferred prostomium bearing a pair of appendages, and a bifid pygidium. G. felicia is the first unequivocal annelid reported from the Lower Cambrian of China. It represents one of the oldest annelids among those from other early Paleozoic Lagerstätten including Sirius Passet from Greenland (Vinther et al., Nature 451: 185-188, 2011) and Emu Bay from Kangaroo island (Parry et al., Palaeontology 57: 1091-1103, 2014), and adds to our increasing roll of present-day animal phyla recognized in the early Cambrian Guanshan Biota. This finding expands the panorama of the Cambrian 'explosion' exemplified by the Guanshan Biota, suggesting the presence of many more fossil annelids in the Chengjiang Lagerstätte and the Kaili Biota. In addition, this new taxon increases our knowledge of early polychaete morphology, which suggests that polychaete annelids considerably diversified in the Cambrian. PMID:26017277

  13. Lower Cambrian polychaete from China sheds light on early annelid evolution

    NASA Astrophysics Data System (ADS)

    Liu, Jianni; Ou, Qiang; Han, Jian; Li, Jinshu; Wu, Yichen; Jiao, Guoxiang; He, Tongjiang

    2015-06-01

    We herein report a fossilized polychaete annelid, Guanshanchaeta felicia gen. et sp. nov., from the Lower Cambrian Guanshan Biota (Cambrian Series 2, stage 4). The new taxon has a generalized polychaete morphology, with biramous parapodia (most of which preserve the evidence of chaetae), an inferred prostomium bearing a pair of appendages, and a bifid pygidium. G. felicia is the first unequivocal annelid reported from the Lower Cambrian of China. It represents one of the oldest annelids among those from other early Paleozoic Lagerstätten including Sirius Passet from Greenland (Vinther et al., Nature 451: 185-188, 2008) and Emu Bay from Kangaroo island (Parry et al., Palaeontology 57: 1091-1103, 2014), and adds to our increasing roll of present-day animal phyla recognized in the early Cambrian Guanshan Biota. This finding expands the panorama of the Cambrian `explosion' exemplified by the Guanshan Biota, suggesting the presence of many more fossil annelids in the Chengjiang Lagerstätte and the Kaili Biota. In addition, this new taxon increases our knowledge of early polychaete morphology, which suggests that polychaete annelids considerably diversified in the Cambrian.

  14. EVOLUTION. A four-legged snake from the Early Cretaceous of Gondwana.

    PubMed

    Martill, David M; Tischlinger, Helmut; Longrich, Nicholas R

    2015-07-24

    Snakes are a remarkably diverse and successful group today, but their evolutionary origins are obscure. The discovery of snakes with two legs has shed light on the transition from lizards to snakes, but no snake has been described with four limbs, and the ecology of early snakes is poorly known. We describe a four-limbed snake from the Early Cretaceous (Aptian) Crato Formation of Brazil. The snake has a serpentiform body plan with an elongate trunk, short tail, and large ventral scales suggesting characteristic serpentine locomotion, yet retains small prehensile limbs. Skull and body proportions as well as reduced neural spines indicate fossorial adaptation, suggesting that snakes evolved from burrowing rather than marine ancestors. Hooked teeth, an intramandibular joint, a flexible spine capable of constricting prey, and the presence of vertebrate remains in the guts indicate that this species preyed on vertebrates and that snakes made the transition to carnivory early in their history. The structure of the limbs suggests that they were adapted for grasping, either to seize prey or as claspers during mating. Together with a diverse fauna of basal snakes from the Cretaceous of South America, Africa, and India, this snake suggests that crown Serpentes originated in Gondwana. PMID:26206932

  15. Eocene bunoselenodont Artiodactyla from southern Thailand and the early evolution of Ruminantia in South Asia

    NASA Astrophysics Data System (ADS)

    Métais, Grégoire; Chaimanee, Yaowalak; Jaeger, J.-J.; Ducrocq, Stéphane

    2007-06-01

    Although Asia is thought to have played a critical role in the basal radiation of Ruminantia, the fossil record of early selenodont artiodactyls remains poorly documented in this region. Dental remains of a new bunoselenodont artiodactyl are described from the late Eocene of Krabi, southern Thailand. This new form, Krabitherium waileki gen. et sp. nov, is tentatively referred to the Tragulidae (Ruminantia) on the basis of several dental features, including a weak Tragulus fold and the presence of a deep groove on the anterior face of the entoconid. Although this new form is suggestive of the enigmatic ? Gelocus gajensis Pilgrim 1912 from the “base of the Gaj” (lower Chitarwata Formation) of the Bugti Hills (Central Pakistan), K. waileki most likely represents an early representative of a relatively bunodont group of tragulids that includes the genus Dorcabune, known from the Miocene of south Asia. This addition to the Eocene record of early ruminants attests to the antiquity of the group in Southeast Asia and lends support to the hypothesis that the Tragulidae represents one of the first offshoots in the evolutionary history of Ruminantia.

  16. Early evolution of limb regeneration in tetrapods: evidence from a 300-million-year-old amphibian

    PubMed Central

    Fröbisch, Nadia B.; Bickelmann, Constanze; Witzmann, Florian

    2014-01-01

    Salamanders are the only tetrapods capable of fully regenerating their limbs throughout their entire lives. Much data on the underlying molecular mechanisms of limb regeneration have been gathered in recent years allowing for new comparative studies between salamanders and other tetrapods that lack this unique regenerative potential. By contrast, the evolution of animal regeneration just recently shifted back into focus, despite being highly relevant for research designs aiming to unravel the factors allowing for limb regeneration. We show that the 300-million-year-old temnospondyl amphibian Micromelerpeton, a distant relative of modern amphibians, was already capable of regenerating its limbs. A number of exceptionally well-preserved specimens from fossil deposits show a unique pattern and combination of abnormalities in their limbs that is distinctive of irregular regenerative activity in modern salamanders and does not occur as variants of normal limb development. This demonstrates that the capacity to regenerate limbs is not a derived feature of modern salamanders, but may be an ancient feature of non-amniote tetrapods and possibly even shared by all bony fish. The finding provides a new framework for understanding the evolution of regenerative capacity of paired appendages in vertebrates in the search for conserved versus derived molecular mechanisms of limb regeneration. PMID:25253458

  17. Sex-specific adaptation drives early sex chromosome evolution in Drosophila

    PubMed Central

    Zhou, Qi; Bachtrog, Doris

    2014-01-01

    Most species’ sex chromosomes are derived from ancient autosomes and show few signatures of their origins. We studied the sex chromosomes of Drosophila miranda, where a neo-Y chromosome originated only about 1 million years (MY) ago. Whole genome and transcriptome analysis reveals massive degeneration of the neo-Y, that male-beneficial genes on the neo-Y are more likely to undergo accelerated protein-evolution, and that neo-Y genes evolve biased expression towards male-specific tissues, i.e. the shrinking gene content of the neo-Y becomes masculinized. In contrast, while older X chromosomes show a paucity of genes expressed in male tissues, neo-X genes highly expressed in male-specific tissues undergo increased rates of protein evolution if haploid in males. Thus, the response to sex-specific selection can shift at different stages of X differentiation, resulting in masculinization or demasculinization of the X-chromosomal gene content. PMID:22822149

  18. Selection by differential molecular survival: a possible mechanism of early chemical evolution.

    PubMed Central

    de Duve, C

    1987-01-01

    A model is proposed to account for selective chemical evolution, progressing from a relatively simple initial set of abiotic synthetic phenomena up to the elaborately sophisticated processes that are almost certainly required to produce the complex molecules, such as replicatable RNA-like oligonucleotides, needed for a Darwinian form of selection to start operating. The model makes the following assumptions: (i) that a small number of micromolecular substances were present at high concentration; (ii) that a random assembly mechanism combined these molecules into a variety of multimeric compounds comprising a wide repertoire of rudimentary catalytic activities; and (iii) that a lytic system capable of breaking down the assembled products existed. The model assumes further that catalysts supplied with substrates were significantly protected against breakdown. It is shown that, by granting these assumptions, an increasingly complex network of metabolic pathways would progressively be established. At the same time, the catalysts concerned would accumulate selectively to become choice substrates for elongation and other modifications that could enhance their efficiency, as well as their survival. Chemical evolution would thus proceed by a dual process of metabolic extension and catalytic innovation. Such a process should be largely deterministic and predictable from initial conditions. PMID:3479788

  19. A new symmetrodont mammal (Trechnotheria: Zhangheotheriidae) from the Early Cretaceous of China and trechnotherian character evolution.

    PubMed

    Bi, Shundong; Zheng, Xiaoting; Meng, Jin; Wang, Xiaoli; Robinson, Nicole; Davis, Brian

    2016-01-01

    We report the discovery of Anebodon luoi, a new genus and species of zhangheotheriid symmetrodont mammal from the Lujiatun site of the Lower Cretaceous Yixian Formation, China. The fossil is represented by an associated partial skull and dentaries with a nearly complete dentition, and with a dental formula of I4/3 C1/1 P5/4 M3/4. This new taxon lacks the high molar count typical of derived symmetrodonts, differing from the well-represented zhangheotheriids Zhangheotherium and Maotherium in having a postcanine dental formula that resembles more primitive tinodontid symmetrodonts on the one hand, and sister taxa to therians such as Peramus on the other. Upper and lower distal premolars are strongly molariform and are captured undergoing replacement, clarifying positional homology among related taxa. We also describe the rostrum and, for the first time in a symmetrodont, much of the orbital mosaic. Importantly, our new taxon occupies a basal position within the Zhangheotheriidae and permits discussion of trechnotherian character evolution, ultimately shedding additional light on the evolution of therians. PMID:27215593

  20. A new symmetrodont mammal (Trechnotheria: Zhangheotheriidae) from the Early Cretaceous of China and trechnotherian character evolution

    PubMed Central

    Bi, Shundong; Zheng, Xiaoting; Meng, Jin; Wang, Xiaoli; Robinson, Nicole; Davis, Brian

    2016-01-01

    We report the discovery of Anebodon luoi, a new genus and species of zhangheotheriid symmetrodont mammal from the Lujiatun site of the Lower Cretaceous Yixian Formation, China. The fossil is represented by an associated partial skull and dentaries with a nearly complete dentition, and with a dental formula of I4/3 C1/1 P5/4 M3/4. This new taxon lacks the high molar count typical of derived symmetrodonts, differing from the well-represented zhangheotheriids Zhangheotherium and Maotherium in having a postcanine dental formula that resembles more primitive tinodontid symmetrodonts on the one hand, and sister taxa to therians such as Peramus on the other. Upper and lower distal premolars are strongly molariform and are captured undergoing replacement, clarifying positional homology among related taxa. We also describe the rostrum and, for the first time in a symmetrodont, much of the orbital mosaic. Importantly, our new taxon occupies a basal position within the Zhangheotheriidae and permits discussion of trechnotherian character evolution, ultimately shedding additional light on the evolution of therians. PMID:27215593

  1. EARLY DYNAMICAL EVOLUTION OF THE SOLAR SYSTEM: PINNING DOWN THE INITIAL CONDITIONS OF THE NICE MODEL

    SciTech Connect

    Batygin, Konstantin; Brown, Michael E.

    2010-06-20

    In the recent years, the 'Nice' model of solar system formation has attained an unprecedented level of success in reproducing much of the observed orbital architecture of the solar system by evolving the planets to their current locations from a more compact configuration. Within the context of this model, the formation of the classical Kuiper Belt requires a phase during which the ice giants have a high eccentricity. An outstanding question of this model is the initial configuration from which the solar system started out. Recent work has shown that multi-resonant initial conditions can serve as good candidates, as they naturally prevent vigorous type-II migration. In this paper, we use analytical arguments, as well as self-consistent numerical N-body simulations to identify fully resonant initial conditions, whose dynamical evolution is characterized by an eccentric phase of the ice giants, as well as planetary scattering. We find a total of eight such initial conditions. Four of these primordial states are compatible with the canonical 'Nice' model, while the others imply slightly different evolutions. The results presented here should prove useful in further development of a comprehensive model for solar system formation.

  2. Biogeography in deep time - What do phylogenetics, geology, and paleoclimate tell us about early platyrrhine evolution?

    PubMed

    Kay, Richard F

    2015-01-01

    Molecular data have converged on a consensus about the genus-level phylogeny of extant platyrrhine monkeys, but for most extinct taxa and certainly for those older than the Pleistocene we must rely upon morphological evidence from fossils. This raises the question as to how well anatomical data mirror molecular phylogenies and how best to deal with discrepancies between the molecular and morphological data as we seek to extend our phylogenies to the placement of fossil taxa. Here I present parsimony-based phylogenetic analyses of extant and fossil platyrrhines based on an anatomical dataset of 399 dental characters and osteological features of the cranium and postcranium. I sample 16 extant taxa (one from each platyrrhine genus) and 20 extinct taxa of platyrrhines. The tree structure is constrained with a "molecular scaffold" of extant species as implemented in maximum parsimony using PAUP with the molecular-based 'backbone' approach. The data set encompasses most of the known extinct species of platyrrhines, ranging in age from latest Oligocene (∼26 Ma) to the Recent. The tree is rooted with extant catarrhines, and Late Eocene and Early Oligocene African anthropoids. Among the more interesting patterns to emerge are: (1) known early platyrrhines from the Late Oligocene through Early Miocene (26-16.5Ma) represent only stem platyrrhine taxa; (2) representatives of the three living platyrrhine families first occur between 15.7 Ma and 13.5 Ma; and (3) recently extinct primates from the Greater Antilles (Cuba, Jamaica, Hispaniola) are sister to the clade of extant platyrrhines and may have diverged in the Early Miocene. It is probable that the crown platyrrhine clade did not originate before about 20-24 Ma, a conclusion consistent with the phylogenetic analysis of fossil taxa presented here and with recent molecular clock estimates. The following biogeographic scenario is consistent with the phylogenetic findings and climatic and geologic evidence: Tropical South

  3. Magnetostratigraphy and sedimentary evolution of the late Miocene to early Pleistocene sediments, Quseir region, Egyptian Red Sea

    NASA Astrophysics Data System (ADS)

    Lean, Candida B.; Hounslow, Mark W.; Vine, Fred J.; Harwood, Gill M.; Elvidge, Liz; Fisk, Kevin; Kendall, Alan C.; Montgomery, Paul

    1998-05-01

    An integrated sedimentological and magnetostratigraphic study has allowed a detailed understanding of the late Miocene to early Pleistocene evolution of the sediments in the Quseir region of the Egyptian Red Sea coast. Palaeomagnetic samples were collected from sections in six wadis, covering the Shagara Formation, the Gabir and Samh members of the Wardan Formation, and the Abu Dabbab Formation evaporites. Remanence properties are carried by magnetite, haematite and goethite. The characteristic remanence is typically carried by detrital magnetite and haematite, with more recent overprints predominantly associated with haematite and goethite, produced by the weathering of diagenetic pyrite. The magnetostratigraphy has allowed the following detailed age assignments for the lithostratigraphic units. The Shagara Formation ranges in age from late Pliocene (late Piacenzian) to middle Pleistocene (0.6-2.5Ma). The Gabir Member is latest Messinian to earliest Piacenzian in age (~3.5-5.5Ma) and the Samh Member, late Tortonian to mid-Messinian (~6.0-7.5Ma). The age of the top of the Abu Dabbab Formation is probably mid-Tortonian (~8Ma). Disconformities occur between all the lithostratigraphic units, with a local angular unconformity between the Shagara and Wardan Formations. Lowstands in global sea level appear to have a strong influence on the timing of these disconformities. Characteristic mixed alluvial and reef facies of the Shagara formation are a response to the ephemeral wetter climate following the initiation of northern hemisphere glaciation at ~2.4Ma, enhanced by rift-margin uplift of basement complexes to the west. This tectonic activity was concentrated in the early Piacenzian. The marine Gabir Member was deposited during the early Pliocene and latest Messinian high-sea-level stands. The late Tortonian/early Messinian age and sedimentological character of the Samh Member indicates this unit was affected by marine flooding events, which ultimately produced, during

  4. HIV evolution in early infection: selection pressures, patterns of insertion and deletion, and the impact of apobec

    SciTech Connect

    Korber, Bette; Bhattacharya, Tanmoy; Giorgi, Elena; Gaschen, B; Daniels, M

    2009-01-01

    The pattern of viral diversification in newly infected individuals provides information about the host environment and immune responses typically experienced by the newly transmitted virus. For example, sites that tend to evolve rapidly across multiple early-infection patients could be involved in enabling escape from common early immune responses, represent adaptation for rapid growth in a newly infected host, or reversion from less fit forms of the virus that were selected for immune escape in previous hosts. Here we investigated the diversification of HIV -I env coding sequences in 81 very early B SUbtype infections previously shown to have resulted from transmission or expansion of single viruses (n=78) or two closely related viruses (n=3). In these cases the sequence of the infecting virus can be estimated accurately, enabling inference of both the direction of substitutions as well as distinction between insertion and deletion events. By integrating information across multiple acutely infected hosts, we find evidence of adaptive evolution of HIV-1 envand identified a subset of codon sites that diversified more rapidly than can be explained by a model of neutral evolution. Of 24 such rapidly diversifying sites, 14 were either (i) clustered and embedded in CTL epitopes that were verified experimentally or predicted based on the individual's HLA or (ii) in a nucleotide context indicative of APOBEC mediated G-to-A substitutions, despite having excluded heavily hypermutated sequences prior to the analysis. In several cases, a rapidly evolving site was both embedded in an APOBEC motif and in a CTL epitope, suggesting that APOBEC may facilitate early immune escape. Ten rapidly diversifying sites could not be explained by CTL escape or APOBEC hypermutation, including the most frequently mutated site, in the fusion peptide of gp4l. We also examined the distribution, extent, and sequence context of insertions and deletions and provide evidence that the length variation

  5. The evolution of Phanerozoic seawater - Isotope paleothermometry finds consensus on Early Paleozoic warmth and constant seawater δ18O

    NASA Astrophysics Data System (ADS)

    Grossman, E. L.; Henkes, G. A.; Passey, B. H.; Shenton, B.; Yancey, T. E.; Perez-Huerta, A.

    2015-12-01

    Evolution of metazoan life is closely linked to the Phanerozoic evolution of ocean temperatures and chemistry. Oxygen isotopic evidence for early Phanerozoic paleotemperatures has been equivocal, with decreasing δ18O values with age being interpreted as warmer early oceans, decreasing seawater δ18O with age, or increasing diagenetic alteration in older samples. Here we compare an updated compilation of oxygen isotope data for carbonate and phosphate fossils and microfossils (Grossman, 2012, Geol. Time Scale, Elsevier, 195-220) with a compilation of new and existing clumped isotope data. Importantly, these data are curated based on sample preservation with special consideration given to screening techniques, and tectonic and burial history. Burial history is critical in the preservation of carbonate clumped isotope temperatures in particular, which can undergo reordering in the solid state. We use a model derived for reordering kinetics (Henkes et al., 2014, Geochim. Cosmochim. Acta 139:362-382) to screen clumped isotope data for the effects of solid-state burial alteration. With minor but significant exceptions (Late Cretaceous, Early Triassic), average δ18O values (4 m.y. window, 2 m.y. steps) for post-Devonian brachiopods, belemnites, and foraminifera, representing tropical-subtropical surface ocean conditions, yield average isotopic temperatures below 30°C (assuming a seawater δ18O value [ -1‰ VSMOW] of an "ice-free" world). In contrast, Ordovician to Devonian data show sustained temperatures of 35-40°C. Likewise, isotopic paleotemperatures from conodont apatite, known to be resistant to isotopic exchange, follow the same pattern. Clumped isotope data derived from Paleozoic brachiopod shells that experienced minimal burial (< 100 °C) and <1% reordering according to the taxon-specific clumped isotope reordering model yield typical temperatures of 25-30°C for the Carboniferous, and 35-40°C for the Ordovician-Silurian. Inserting clumped temperatures and

  6. Early evolution and dynamics of Earth from a molten initial stage

    NASA Astrophysics Data System (ADS)

    Lourenço, Diogo L.; Tackley, Paul J.

    2014-05-01

    It is now well established that most of the terrestrial planets underwent a magma ocean stage during their accretion. On Earth, it is probable that at the end of accretion, giant impacts like the hypothesised Moon-forming impact, together with other sources of heat such as conversion of gravitational energy of formation into heat, heat losses from the core at the core-mantle boundary, radioactive decay, electromagnetic induction heating and tidal heating, melted a substantial part of the mantle. The thermal and chemical evolution of the resulting magma ocean most certainly had dramatic consequences on the history of the planet, influencing the chemical composition of the mantle after differentiation, the style of tectonic regime prevailing in the solid-state mantle and its habitability. Considerable research has been done on magma oceans using 1-D models (e.g.: Abe, PEPI 1997; Solomatov, Treat. Geophys. 2007; Elkins-Tanton, EPSL 2008). However, its dynamics, evolution from a molten state to the present day solid state, and crystallisation are still not fully understood and are more complex than a 1-D formulation. Recent advances in computational methods and resources allow us to address numerically more complex problems, with higher resolution and multiple physics incorporated. Moreover, new developments in mineral physics that indicate that melt can be denser than solid at high pressures (e.g.: de Koker et al., EPSL 2013) can have very important impacts on the classical views of the solidification of magma oceans (Labrosse et al., Nature 2007). The goal of our study is to understand and characterise the influence of melting on the long-term thermo-chemical evolution of rocky planet interiors, starting from an initial molten state (magma ocean). Our approach is to test existing published 1-D parameterisations of magma ocean dynamics and extend them into 2-D models. We will address this problem using the numerical code StagYY (Tackley, PEPI 2008), which uses a

  7. Chemical evolution in the early phases of massive star formation. II. Deuteration

    NASA Astrophysics Data System (ADS)

    Gerner, T.; Shirley, Y. L.; Beuther, H.; Semenov, D.; Linz, H.; Albertsson, T.; Henning, Th.

    2015-07-01

    The chemical evolution in high-mass star-forming regions is still poorly constrained. Studying the evolution of deuterated molecules allows distinguishing between subsequent stages of high-mass star formation regions based on the strong temperature dependence of deuterium isotopic fractionation. We observed a sample of 59 sources including 19 infrared dark clouds, 20 high-mass protostellar objects, 11 hot molecular cores and 9 ultra-compact Hii regions in the (3-2) transitions of the four deuterated molecules, DCN, DNC, DCO+, and N2D+ as well as their non-deuterated counterparts. The overall detection fraction of DCN, DNC, and DCO+ is high and exceeds 50% for most of the stages. N2D+ was only detected in a few infrared dark clouds and high-mass protostellar objects. This may be related to problems in the bandpass at the transition frequency and to low abundances in the more evolved, warmer stages. We find median D/H ratios of 0.02 for DCN, 0.005 for DNC, 0.0025 for DCO+, and 0.02 for N2D+. While the D/H ratios of DNC, DCO+, and N2D+ decrease with time, DCN/HCN peaks at the hot molecular core stage. We only found weak correlations of the D/H ratios for N2D+ with the luminosity of the central source and the FWHM of the line, and no correlation with the H2 column density. In combination with a previously observed set of 14 other molecules (Paper I), we fitted the calculated column densities with an elaborate 1D physico-chemical model with time-dependent D-chemistry including ortho- and para-H2 states. Good overall fits to the observed data were obtained with the model. This is one of the first times that observations and modeling were combined to derive chemically based best-fit models for the evolution of high-mass star formation including deuteration. Appendix A is available in electronic form at http://www.aanda.org

  8. The evolution of Indian psychiatric research: An examination of the early decades of the Indian Journal of Psychiatry

    PubMed Central

    Radhakrishnan, Rajiv; Andrade, Chittaranjan

    2010-01-01

    Research in psychiatry has travelled far since the inception of the Indian Journal of Psychiatry (IJP) in 1949. We reviewed publications in the IJP during its initial three decades to identify path breaking articles and trends in research. We present the evolution of research design in the IJP from cases studies to randomized controlled trials. We identify the earliest studies in different fields, ranging from drug trials to social interventions, and from women’s mental health to geriatric psychiatry. We consider special issues such as the measurement of psychopathology specific to the Indian context, studies of treatments specific to Indian traditions, epidemiology of psychiatric disorders in India, and innovations in service delivery. Students interested in the history of Indian psychiatric research will be rewarded by the richness and variety of thought evidenced in the publications in the early decades of the IJP. PMID:21836678

  9. Spectrophotometric Redshifts in the Faint Infrared Grism Survey

    NASA Astrophysics Data System (ADS)

    Pharo, John; Malhotra, Sangeeta; Rhoads, James E.

    2016-06-01

    We have combined HST grism spectroscopy and deep broadband imaging to measure spectro-photometric redshifts (SPZs) of faint galaxies. Using a technique pioneered by Ryan et al. 2007, one can combine spectra and photometry to yield an SPZ that is more accurate than pure photometric redshifts, and can probe more deeply than ground-based spectroscopic redshifts. By taking mid-resolution spectra from the HST Faint Infrared Grism Survey (FIGS), SPZs can be found for measurements potentially down to 27th magnitude (the typical brightness of a dwarf galaxy at redshift ∼1.5). A galaxy’s redshift is vital for understanding its place in the growth and evolution of the universe. The measurement of high-accuracy SPZs for FIGS sources will improve the faint-end and high-redshift portions of the luminosity function, and make possible a robust analysis of the FIGS fields for signs of Large Scale Structure (LSS). The improved redshift and distance measurements allowed for the identification of a structure at z=0.83 in one of the FIGS fields.

  10. On the relationship between early solar activity and the evolution of terrestrial planet atmospheres

    NASA Technical Reports Server (NTRS)

    Repin, Robert O.

    1989-01-01

    Mass fractionation during hydrodynamic escape of hydrogen-rich primordial atmospheres form Venus, earth, and Mars can account for most of the salient features of mass distributions in their present-day atmospheres. The principal assumptions and results of an escape-fractionation model for the evolution of terrestrial planet atmospheres from primary to final states are qualitatively described, with emphasis on the astrophysical conditions needed to enable the loss process. A substantial and rapidly declining flux of energetic solar radiation into atmospheric exospheres is required, initially (at solar ages of about 1-10 million years) two to three orders of magnitude more intense than that supplied by extreme-ultraviolet emission from the contemporary sun. The solar accretion disk must have dissipated if such radiation is to penetrate the system midplane to planetray distances. On both criteria, hydrodynamic escape from planets appears plausible in the astrophysical environment of the naked T-Tauri stars.

  11. The early heat loss evolution of Mars and their implications for internal and environmental history.

    PubMed

    Ruiz, Javier

    2014-01-01

    The time around 3.7 Ga ago was an epoch when substantial changes in Mars occurred: a substantial decline in aqueous erosion/degradation of landscape features; a change from abundant phyllosilicate formation to abundant acidic and evaporitic mineralogy; a change from olivine-rich volcanism to olivine-pyroxene volcanism; and maybe the cessation of the martian dynamo. Here I show that Mars also experienced profound changes in its internal dynamics in the same approximate time, including a reduction of heat flow and a drastic increasing of lithosphere strength. The reduction of heat flow indicates a limited cooling (or even a heating-up) of the deep interior for post-3.7 Ga times. The drastic increasing of lithosphere strength indicates a cold lithosphere above the inefficiently cooled (or even heated) interior. All those changes experienced by Mars were most probably linked and suggest the existence of profound interrelations between interior dynamics and environmental evolution of this planet. PMID:24614056

  12. Tectonic evolution of Kazakhstan and Tien Shan in Neoproterozoic and Early-Middle Paleozoic

    NASA Astrophysics Data System (ADS)

    Samygin, S. G.; Kheraskova, T. N.; Kurchavov, A. M.

    2015-05-01

    Geological information on Kazakhstan and the Tien Shan obtained up to the present time has been considered and integrated in order to demonstrate the main features of continental massifs, basins with oceanic crust, island arcs, marginal volcanic-plutonic belts, and transform fault zones differing in type and age. We ascertained the character and probable causes of their evolution and transformations resulting in the origination and development of mosaic structural assembly at margin of the Paleoasian ocean that existed from Neoproterozoic. The main stages of the geodynamic history of Paleozoides in Kazakhstan and Tien Shan are characterized, and a model of the probable course of regional tectonic events has been proposed. This model is illustrated by published paleomagnetic data and a series of paleotectonic reconstructions for time intervals 950-900, 850-800, 750-700, 650-630, 570-550, 530-515, 500-470, 460-440, and 390-380 Ma.

  13. Plant genetics. Early allopolyploid evolution in the post-Neolithic Brassica napus oilseed genome.

    PubMed

    Chalhoub, Boulos; Denoeud, France; Liu, Shengyi; Parkin, Isobel A P; Tang, Haibao; Wang, Xiyin; Chiquet, Julien; Belcram, Harry; Tong, Chaobo; Samans, Birgit; Corréa, Margot; Da Silva, Corinne; Just, Jérémy; Falentin, Cyril; Koh, Chu Shin; Le Clainche, Isabelle; Bernard, Maria; Bento, Pascal; Noel, Benjamin; Labadie, Karine; Alberti, Adriana; Charles, Mathieu; Arnaud, Dominique; Guo, Hui; Daviaud, Christian; Alamery, Salman; Jabbari, Kamel; Zhao, Meixia; Edger, Patrick P; Chelaifa, Houda; Tack, David; Lassalle, Gilles; Mestiri, Imen; Schnel, Nicolas; Le Paslier, Marie-Christine; Fan, Guangyi; Renault, Victor; Bayer, Philippe E; Golicz, Agnieszka A; Manoli, Sahana; Lee, Tae-Ho; Thi, Vinh Ha Dinh; Chalabi, Smahane; Hu, Qiong; Fan, Chuchuan; Tollenaere, Reece; Lu, Yunhai; Battail, Christophe; Shen, Jinxiong; Sidebottom, Christine H D; Wang, Xinfa; Canaguier, Aurélie; Chauveau, Aurélie; Bérard, Aurélie; Deniot, Gwenaëlle; Guan, Mei; Liu, Zhongsong; Sun, Fengming; Lim, Yong Pyo; Lyons, Eric; Town, Christopher D; Bancroft, Ian; Wang, Xiaowu; Meng, Jinling; Ma, Jianxin; Pires, J Chris; King, Graham J; Brunel, Dominique; Delourme, Régine; Renard, Michel; Aury, Jean-Marc; Adams, Keith L; Batley, Jacqueline; Snowdon, Rod J; Tost, Jorg; Edwards, David; Zhou, Yongming; Hua, Wei; Sharpe, Andrew G; Paterson, Andrew H; Guan, Chunyun; Wincker, Patrick

    2014-08-22

    Oilseed rape (Brassica napus L.) was formed ~7500 years ago by hybridization between B. rapa and B. oleracea, followed by chromosome doubling, a process known as allopolyploidy. Together with more ancient polyploidizations, this conferred an aggregate 72× genome multiplication since the origin of angiosperms and high gene content. We examined the B. napus genome and the consequences of its recent duplication. The constituent An and Cn subgenomes are engaged in subtle structural, functional, and epigenetic cross-talk, with abundant homeologous exchanges. Incipient gene loss and expression divergence have begun. Selection in B. napus oilseed types has accelerated the loss of glucosinolate genes, while preserving expansion of oil biosynthesis genes. These processes provide insights into allopolyploid evolution and its relationship with crop domestication and improvement. PMID:25146293

  14. Pairwise Comparisons of Mitochondrial DNA Sequences in Subdivided Populations and Implications for Early Human Evolution

    PubMed Central

    Marjoram, P.; Donnelly, P.

    1994-01-01

    We consider the effect on the distribution of pairwise differences between mitochondrial DNA sequences of the incorporation into the underlying population genetics model of two particular effects that seem realistic for human populations. The first is that the population size was roughly constant before growing to its current level. The second is that the population is geographically subdivided rather than panmictic. In each case these features tend to encourage multimodal distributions of pairwise differences, in contrast to existing, unimodal datasets. We argue that population genetics models currently used to analyze such data may thus fail to reflect important features of human mitochondrial DNA evolution. These may include selection on the mitochondrial genome, more realistic mutation mechanisms, or special population or migration dynamics. Particularly in view of the variability inherent in the single available human mitochondrial genealogy, it is argued that until these effects are better understood, inferences from such data should be rather cautious. PMID:8150290

  15. New Postcranial Material of the Early Caseid Casea broilii Williston, 1910 (Synapsida: Caseidae) with a Review of the Evolution of the Sacrum in Paleozoic Non-Mammalian Synapsids

    PubMed Central

    LeBlanc, Aaron R. H.; Reisz, Robert R.

    2014-01-01

    Here we use the description of a new specimen of the small caseid synapsid Casea broilii that preserves the sacral, pelvic and hind limb regions in great detail and in three dimensions, as a unique opportunity to reevaluate the early stages in the evolution of the sacrum in the lineage that led to mammals. We place this new material in the context of sacral evolution in early caseid synapsids and conclude that the transition from two to three sacral vertebrae occurred in small-bodied species, suggesting that it was not an adaptation to heavy weight bearing. Furthermore, we compare descriptions of sacral anatomy among known early synapsids, including caseids, ophiacodontids, edaphosaurids, varanopids, and sphenacodontians and review sacral evolution in early synapsids. Based on the descriptions of new species of caseids, edaphosaurids, and varanopids over the past several decades, it is clear that a sacrum consisting of three vertebrae evolved independently at least four times in synapsids during the Late Carboniferous and Early Permian. Furthermore, similarities in the morphologies of the sacral vertebrae and ribs of these early synapsids lead us to conclude that an anterior caudal vertebra had been incorporated into the sacral series convergently in these groups. Given the repeated acquisition of a three-vertebra sacrum in early synapsids and no apparent link to body size, we argue that this sacral anatomy was related to more efficient terrestrial locomotion than to increased weight bearing. PMID:25545624

  16. New postcranial material of the early caseid Casea broilii Williston, 1910 (Synapsida: Caseidae) with a review of the evolution of the sacrum in Paleozoic non-mammalian synapsids.

    PubMed

    LeBlanc, Aaron R H; Reisz, Robert R

    2014-01-01

    Here we use the description of a new specimen of the small caseid synapsid Casea broilii that preserves the sacral, pelvic and hind limb regions in great detail and in three dimensions, as a unique opportunity to reevaluate the early stages in the evolution of the sacrum in the lineage that led to mammals. We place this new material in the context of sacral evolution in early caseid synapsids and conclude that the transition from two to three sacral vertebrae occurred in small-bodied species, suggesting that it was not an adaptation to heavy weight bearing. Furthermore, we compare descriptions of sacral anatomy among known early synapsids, including caseids, ophiacodontids, edaphosaurids, varanopids, and sphenacodontians and review sacral evolution in early synapsids. Based on the descriptions of new species of caseids, edaphosaurids, and varanopids over the past several decades, it is clear that a sacrum consisting of three vertebrae evolved independently at least four times in synapsids during the Late Carboniferous and Early Permian. Furthermore, similarities in the morphologies of the sacral vertebrae and ribs of these early synapsids lead us to conclude that an anterior caudal vertebra had been incorporated into the sacral series convergently in these groups. Given the repeated acquisition of a three-vertebra sacrum in early synapsids and no apparent link to body size, we argue that this sacral anatomy was related to more efficient terrestrial locomotion than to increased weight bearing. PMID:25545624

  17. Early Mesozoic structural evolution of the eastern West Qinling, northwest China

    NASA Astrophysics Data System (ADS)

    Wu, Guo-Li; Meng, Qing-Ren; Duan, Liang; Li, Lin

    2014-09-01

    This paper aims to reconstruct Early Mesozoic structural development of the eastern West Qinling by integrating structural and geochronologic analyses. The results show that the eastern West Qinling experienced two-phase deformations, separated by a period of tectonic quiescence. Large-scale south-directed displacement of thrust sheets in association with folding characterized the first-phase deformation in Late Triassic time, leading to the formation of the West Qinling fold-and-thrust belt that is composed primarily of Paleozoic-Triassic strata. This fold-and-thrust belt is in general south-convexing arc-shaped, with an accumulated south-directed displacement being over 100 km. The folding and thrusting ended up during the Norian of the Late Triassic Epoch and were immediately followed by widespread granite intrusions. Marked uplift and erosion occurred in the Early Jurassic, resulting in exhumation of the Late Triassic granites. Transpressional deformation took place in the eastern West Qinling in the Middle Jurassic on account of occurrences of strike-slip faulting and refolding. In the easternmost part of the West Qinling exists a Permian-Triassic turbidite wedge that is bordered by a right-slip fault on the northeast and by a left-slip fault on the south, indicating a westward movement that was accommodated by slip faulting. It is argued that collision of the North and South China blocks was responsible for formation of the West Qinling fold-and-thrust belt in the Late Triassic, whereas Middle Jurassic transgression is considered as the result of westward extrusion of Permian-Triassic turbiditic materials from the East Qinling owing to renewed intracontinental convergence between the North and South China blocks. A tectonic model is advanced for Early Mesozoic tectonic development of the West Qinling.

  18. Functional evolution of critically ill patients undergoing an early rehabilitation protocol

    PubMed Central

    Murakami, Fernanda Murata; Yamaguti, Wellington Pereira; Onoue, Mirian Akemi; Mendes, Juliana Mesti; Pedrosa, Renata Santos; Maida, Ana Lígia Vasconcellos; Kondo, Cláudia Seiko; de Salles, Isabel Chateaubriand Diniz; de Brito, Christina May Moran; Rodrigues, Miguel Koite

    2015-01-01

    Objective Evaluation of the functional outcomes of patients undergoing an early rehabilitation protocol for critically ill patients from admission to discharge from the intensive care unit. Methods A retrospective cross-sectional study was conducted that included 463 adult patients with clinical and/or surgical diagnosis undergoing an early rehabilitation protocol. The overall muscle strength was evaluated at admission to the intensive care unit using the Medical Research Council scale. Patients were allocated to one of four intervention plans according to the Medical Research Council score, the suitability of the plan’s parameters, and the increasing scale of the plan expressing improved functional status. Uncooperative patients were allocated to intervention plans based on their functional status. The overall muscle strength and/or functional status were reevaluated upon discharge from the intensive care unit by comparison between the Intervention Plans upon admission (Planinitial) and discharge (Planfinal). Patients were classified into three groups according to the improvement of their functional status or not: responsive 1 (Planfinal > Planinitial), responsive 2 (Planfinal = Planinitial) and unresponsive (Planfinal < Planinitial). Results In total, 432 (93.3%) of 463 patients undergoing the protocol responded positively to the intervention strategy, showing maintenance and/or improvement of the initial functional status. Clinical patients classified as unresponsive were older (74.3 ± 15.1 years of age; p = 0.03) and had longer lengths of intensive care unit (11.6 ± 14.2 days; p = 0.047) and hospital (34.5 ± 34.1 days; p = 0.002) stays. Conclusion The maintenance and/or improvement of the admission functional status were associated with shorter lengths of intensive care unit and hospital stays. The results suggest that the type of diagnosis, clinical or surgical, fails to define the positive response to an early rehabilitation protocol. PMID:26340157

  19. The Thermal Evolution of the Western Equatorial Pacific During the Midde and Early Pleistocene

    NASA Astrophysics Data System (ADS)

    Medina, M. A.; Lea, D. W.; Spero, H. J.

    2004-12-01

    Magnesium/calcium data from planktonic foraminifera in the equatorial Pacific sediment cores suggested that tropical Pacific sea surface temperatures (SST's) were about 3 deg.C colder than modern conditions during glacial episodes of the last 500 thousand years (ky). We have extended the Western Equatorial Pacific (WEP) Globigerinoides ruber Mg/Ca and d18O records, from the Ontong Java Plateau, Ocean Drilling Program Hole 806B (0 19.11'N, 159 21.69'E, 2520m), back to 1.3 ma. For temperature conversion we used a G. ruber calibration based on core-tops from the tropical Pacific (Lea and Martin, 1996), which yields the following relationship: Mg/Ca(mmol/mol)= 0.30exp[0.089 X SST deg. C)]. Our SST record shows that the previously observed 3 deg C-colder SST's than modern conditions during glacial episodes are generally the rule for the entire 1.3 ma period. Glacial-interglacial temperature differences as great as 4 deg. C are observed, even in the Early Pleistocene (1-1.8 ma). Preliminary observations suggest the presence of ~40 Ky SST cycles during the Early Pleistocene, of similar amplitude to the dominant SST cycles seen in Late Pleistocene Tropical records. Early Pleistocene WEP SST's, as suggested by our record, oscillated between 26 and 30 deg. C. MIS 11 stands out as the most prominent feature of the WEP SST record. The potential bias on temperature estimates due to the influence of changes in lysocline depth (Farrell and Prell, 1989) and decrease preservation with depth (Lea et al., 2000) is ± 0.8 deg.C. Preliminary point to point comparison between the SST and the d18O records shows that Mg/Ca-based temperatures lead over d18O by about 3 ky as previously determined by Lea et al. (2000).

  20. Constraining early to middle Eocene climate evolution of the southwest Pacific and Southern Ocean

    NASA Astrophysics Data System (ADS)

    Dallanave, Edoardo; Bachtadse, Valerian; Crouch, Erica M.; Tauxe, Lisa; Shepherd, Claire L.; Morgans, Hugh E. G.; Hollis, Christopher J.; Hines, Benjamin R.; Sugisaki, Saiko

    2016-01-01

    Studies of early Paleogene climate suffer from the scarcity of well-dated sedimentary records from the southern Pacific Ocean, the largest ocean basin during this time. We present a new magnetostratigraphic record from marine sediments that outcrop along the mid-Waipara River, South Island, New Zealand. Fully oriented samples for paleomagnetic analyses were collected along 45 m of stratigraphic section, which encompasses magnetic polarity Chrons from C23n to C21n (˜ 51.5- 47 Ma). These results are integrated with foraminiferal, calcareous nannofossil, and dinoflagellate cyst (dinocyst) biostratigraphy from samples collected in three different expeditions along a total of ˜80 m of section. Biostratigraphic data indicates relatively continuous sedimentation from the lower Waipawan to the upper Heretaungan New Zealand stages (i.e., lower Ypresian to lower Lutetian, 55.5 to 46 Ma). We provide the first magnetostratigraphically-calibrated age of 48.88 Ma for the base of the Heretaungan New Zealand stage (latest early Eocene). To improve the correlation of the climate record in this section with other Southern Ocean records, we reviewed the magnetostratigraphy of Ocean Drilling Program (ODP) Site 1172 (East Tasman Plateau) and Integrated Ocean Drilling Program (IODP) Site U1356 (Wilkes Land Margin, Antarctica). A paleomagnetic study of discrete samples could not confirm any reliable magnetic polarity reversals in the early Eocene at Site 1172. We use the robust magneto-biochronology of a succession of dinocyst bioevents that are common to mid-Waipara, Site 1172, and Site U1356 to assist correlation between the three records. A new integrated chronology offers new insights into the nature and completeness of the southern high-latitude climate histories derived from these sites.

  1. Evolution of Electron Transport Chains During the Anaerobic to Aerobic Transition on Early Earth

    NASA Astrophysics Data System (ADS)

    Sepúlveda, R.; Ortiz, R.; Holmes, D. S.

    2015-12-01

    Sepulveda, R., Ortiz R. and Holmes DS. Center for Bioinformatics and Genome Biology, Fundacion Ciencia y Vida, and Facultad de Ciencias Biologicas, Universidad Andres Bello, Santiago, Chile.According to several models, life emerged on earth in an anoxic environment where oxygen was not available as a terminal electron acceptor for energy generating reactions. After the Great Oxidation Event (GOE) about 2.4 billion years ago, or perhaps even before the GOE, oxygen became the most widespread and efficient terminal electron acceptor and was accompanied by the evolution of a number of redox proteins that could deliver electrons to reduce oxygen to water. Where did these proteins come from? One hypothesis is that they evolved by the neofunctionalization of previously existing redox proteins that had been used in anaerobic conditions as terminal electron donors to reduce compounds such as perchlorate, nitric oxide or iron. We have used a number of bioinformatic tools to explore a large number of genomes looking for discernable signals of such redeployment of function. A Perl pipeline was designed to detect sequence similarity, conserved gene context, remote homology detection, identification of domains and functional evolution of electron carrier proteins from extreme acidophiles, including the small blue copper protein rusticyanin (involved in FeII oxidation), cytochrome oxidase subunit II and quinol-dependent nitric oxide reductase (qNOR). The protein folds and copper binding sites of rusticyanin are conserved in cytochrome oxidase aa3 subunit II, a protein complex that is responsible for the final passage of electrons to reduce oxygen. Therefore, we hypothesize that rusticyanin, cytochrome oxidase II and qNOR are evolutionarily related. Acknowledgments: Fondecyt 1130683.

  2. A synthesis of the theories and concepts of early human evolution.

    PubMed

    Maslin, Mark A; Shultz, Susanne; Trauth, Martin H

    2015-03-01

    Current evidence suggests that many of the major events in hominin evolution occurred in East Africa. Hence, over the past two decades, there has been intensive work undertaken to understand African palaeoclimate and tectonics in order to put together a coherent picture of how the environment of Africa has varied over the past 10 Myr. A new consensus is emerging that suggests the unusual geology and climate of East Africa created a complex, environmentally very variable setting. This new understanding of East African climate has led to the pulsed climate variability hypothesis that suggests the long-term drying trend in East Africa was punctuated by episodes of short alternating periods of extreme humidity and aridity which may have driven hominin speciation, encephalization and dispersals out of Africa. This hypothesis is unique as it provides a conceptual framework within which other evolutionary theories can be examined: first, at macro-scale comparing phylogenetic gradualism and punctuated equilibrium; second, at a more focused level of human evolution comparing allopatric speciation, aridity hypothesis, turnover pulse hypothesis, variability selection hypothesis, Red Queen hypothesis and sympatric speciation based on sexual selection. It is proposed that each one of these mechanisms may have been acting on hominins during these short periods of climate variability, which then produce a range of different traits that led to the emergence of new species. In the case of Homo erectus (sensu lato), it is not just brain size that changes but life history (shortened inter-birth intervals, delayed development), body size and dimorphism, shoulder morphology to allow thrown projectiles, adaptation to long-distance running, ecological flexibility and social behaviour. The future of evolutionary research should be to create evidence-based meta-narratives, which encompass multiple mechanisms that select for different traits leading ultimately to speciation. PMID:25602068

  3. A synthesis of the theories and concepts of early human evolution

    PubMed Central

    Maslin, Mark A.; Shultz, Susanne; Trauth, Martin H.

    2015-01-01

    Current evidence suggests that many of the major events in hominin evolution occurred in East Africa. Hence, over the past two decades, there has been intensive work undertaken to understand African palaeoclimate and tectonics in order to put together a coherent picture of how the environment of Africa has varied over the past 10 Myr. A new consensus is emerging that suggests the unusual geology and climate of East Africa created a complex, environmentally very variable setting. This new understanding of East African climate has led to the pulsed climate variability hypothesis that suggests the long-term drying trend in East Africa was punctuated by episodes of short alternating periods of extreme humidity and aridity which may have driven hominin speciation, encephalization and dispersals out of Africa. This hypothesis is unique as it provides a conceptual framework within which other evolutionary theories can be examined: first, at macro-scale comparing phylogenetic gradualism and punctuated equilibrium; second, at a more focused level of human evolution comparing allopatric speciation, aridity hypothesis, turnover pulse hypothesis, variability selection hypothesis, Red Queen hypothesis and sympatric speciation based on sexual selection. It is proposed that each one of these mechanisms may have been acting on hominins during these short periods of climate variability, which then produce a range of different traits that led to the emergence of new species. In the case of Homo erectus (sensu lato), it is not just brain size that changes but life history (shortened inter-birth intervals, delayed development), body size and dimorphism, shoulder morphology to allow thrown projectiles, adaptation to long-distance running, ecological flexibility and social behaviour. The future of evolutionary research should be to create evidence-based meta-narratives, which encompass multiple mechanisms that select for different traits leading ultimately to speciation. PMID:25602068

  4. Evolution of the Early Proterozoic Colorado province: Constraints from U-Pb geochronology

    NASA Astrophysics Data System (ADS)

    Reed, John C., Jr.; Bickford, M. E.; Premo, Wayne R.; Aleinikoff, John N.; Pallister, John S.

    1987-09-01

    The Colorado province represents an addition of a belt of rocks more than 500 km wide to the southern margin of the Archean Wyoming craton during the Early Proterozoic, between about 1790 and 1660 Ma. Correspondence in ages between metamorphism, deformation, and plutonism; association of volcanic rocks with comagmatic calc-alkalic plutons; and lack of older basement are all consistent with the interpretation that the rocks of the province are products of arc magmatism and cannibalistic sedimentation along a convergent margin at the southern edge of the craton. Note: Additional material for this article is Supplementary Data 8731, available on request from the GSA Documents Secretary (see footnote 1).

  5. Oxygen and Hydrogen Peroxide in the Early Evolution of Life on Earth: In silico Comparative Analysis of Biochemical Pathways

    PubMed Central

    Ślesak, Halina; Kruk, Jerzy

    2012-01-01

    Abstract In the Universe, oxygen is the third most widespread element, while on Earth it is the most abundant one. Moreover, oxygen is a major constituent of all biopolymers fundamental to living organisms. Besides O2, reactive oxygen species (ROS), among them hydrogen peroxide (H2O2), are also important reactants in the present aerobic metabolism. According to a widely accepted hypothesis, aerobic metabolism and many other reactions/pathways involving O2 appeared after the evolution of oxygenic photosynthesis. In this study, the hypothesis was formulated that the Last Universal Common Ancestor (LUCA) was at least able to tolerate O2 and detoxify ROS in a primordial environment. A comparative analysis was carried out of a number of the O2-and H2O2-involving metabolic reactions that occur in strict anaerobes, facultative anaerobes, and aerobes. The results indicate that the most likely LUCA possessed O2-and H2O2-involving pathways, mainly reactions to remove ROS, and had, at least in part, the components of aerobic respiration. Based on this, the presence of a low, but significant, quantity of H2O2 and O2 should be taken into account in theoretical models of the early Archean atmosphere and oceans and the evolution of life. It is suggested that the early metabolism involving O2/H2O2 was a key adaptation of LUCA to already existing weakly oxic zones in Earth's primordial environment. Key Words: Hydrogen peroxide—Oxygen—Origin of life—Photosynthesis—Superoxide dismutase—Superoxide reductase. Astrobiology 12, 775–784. PMID:22970865

  6. The oldest known priapulid-like scalidophoran animal and its implications for the early evolution of cycloneuralians and ecdysozoans.

    PubMed

    Liu, Yunhuan; Xiao, Shuhai; Shao, Tiequan; Broce, Jesse; Zhang, Huaqiao

    2014-05-01

    Morphological phylogenetic analyses suggest that scalidophorans (priapulids, loriciferans, and kinorhynchs) and nematoids (nematodes and nematomorphs) form the ecdysozoan clade Cycloneuralia, which is a sister group to panarthropods. It has been proposed that extant priapulids and Cambrian priapulid-like scalidophorans, because of their conserved evolution, have the potential to illuminate the ancestral morphology, ecology, and developmental biology of highly derived ecdysozoans such as nematods and arthropods. As such, Cambrian fossils, particularly Markuelia and possibly olivooids, can inform the early evolution of scalidophorans, cycloneuralians, and ecdysozoans. However, the scalidophoran Markuelia is known exclusively as embryo fossils, and the olivooids have been alternatively interpreted as cnidarians or cycloneuralians. Here, we describe a post-embryonic scalidophoran fossil Eopriapulites sphinx new genus and species, which represents the oldest known scalidophoran, from the early Cambrian Period (∼535 Ma) in South China. E. sphinx is similar to modern scalidophorans in having an introvert armed with hollow scalids, a collar with coronal scalids, and a pharynx with pharyngeal teeth, but its scalids and pharyngeal teeth are arranged in a hexaradial pattern. Phylogenetically resolved as a stem-group scalidophoran, E. sphinx shares a hexaradial pattern with the hexaradial arrangement of certain anatomical structures in kinorhynchs, loriciferans, nematoids, and Cambrian fossils such as Eolympia pediculata, which could also be a scalidophoran. Thus, the bodyplan of ancestral cycloneuralians may have had a component of hexaradial symmetry (i.e., some but not necessarily all anatomical parts are hexaradially arranged). If panarthropods are nested within paraphyletic cycloneuralians, as several molecular phylogenetic analyses suggest, the ancestral ecdysozoans may have been a legless worm possibly with a component of hexaradial symmetry. PMID:24754444

  7. The dual targeting ability of type II NAD(P)H dehydrogenases arose early in land plant evolution

    PubMed Central

    2013-01-01

    Background Type II NAD(PH) dehydrogenases are located on the inner mitochondrial membrane of plants, fungi, protists and some primitive animals. However, recent observations have been made which identify several Arabidopsis type II dehydrogenases as dual targeted proteins. Targeting either mitochondria and peroxisomes or mitochondria and chloroplasts. Results Members of the ND protein family were identified in various plant species. Phylogenetic analyses and subcellular targeting predictions were carried out for all proteins. All ND proteins from three model plant species Arabidopsis, rice and Physcomitrella were cloned as N- and C-terminal GFP fusions and subcellular localisations were determined. Dual targeting of plant type II dehydrogenases was observed to have evolved early in plant evolution and to be widespread throughout different plant species. In all three species tested dual targeting to both mitochondria and peroxisomes was found for at least one NDA and NDB type protein. In addition two NDB type proteins from Physcomitrella were also found to target chloroplasts. The dual targeting of NDC type proteins was found to have evolved later in plant evolution. Conclusions The functions of type II dehydrogenases within plant cells will have to be re-evaluated in light of this newly identified subcellular targeting information. PMID:23841539

  8. Negative association between parental care and sibling cooperation in earwigs: a new perspective on the early evolution of family life?

    PubMed

    Kramer, J; Thesing, J; Meunier, J

    2015-07-01

    The evolution of family life requires net fitness benefits for offspring, which are commonly assumed to mainly derive from parental care. However, an additional source of benefits for offspring is often overlooked: cooperative interactions among juvenile siblings. In this study, we examined how sibling cooperation and parental care could jointly contribute to the early evolution of family life. Specifically, we tested whether the level of food transferred among siblings (sibling cooperation) in the European earwig Forficula auricularia (1) depends on the level of maternal food provisioning (parental care) and (2) is translated into offspring survival, as well as female investment into future reproduction. We show that higher levels of sibling food transfer were associated with lower levels of maternal food provisioning, possibly reflecting a compensatory relationship between sibling cooperation and maternal care. Furthermore, the level of sibling food transfer did not influence offspring survival, but was associated with negative effects on the production of the second and terminal clutch by the tending mothers. These findings indicate that sibling cooperation could mitigate the detrimental effects on offspring survival that result from being tended by low-quality mothers. More generally, they are in line with the hypothesis that sibling cooperation is an ancestral behaviour that can be retained to compensate for insufficient levels of parental investment. PMID:25975926

  9. Multiregion Whole-Exome Sequencing Uncovers the Genetic Evolution and Mutational Heterogeneity of Early-Stage Metastatic Melanoma.

    PubMed

    Harbst, Katja; Lauss, Martin; Cirenajwis, Helena; Isaksson, Karolin; Rosengren, Frida; Törngren, Therese; Kvist, Anders; Johansson, Maria C; Vallon-Christersson, Johan; Baldetorp, Bo; Borg, Åke; Olsson, Håkan; Ingvar, Christian; Carneiro, Ana; Jönsson, Göran

    2016-08-15

    Cancer genome sequencing has shed light on the underlying genetic aberrations that drive tumorigenesis. However, current sequencing-based strategies, which focus on a single tumor biopsy, fail to take into account intratumoral heterogeneity. To address this challenge and elucidate the evolutionary history of melanoma, we performed whole-exome and transcriptome sequencing of 41 multiple melanoma biopsies from eight individual tumors. This approach revealed heterogeneous somatic mutations in the range of 3%-38% in individual tumors. Known mutations in melanoma drivers BRAF and NRAS were always ubiquitous events. Using RNA sequencing, we found that the majority of mutations were not expressed or were expressed at very low levels, and preferential expression of a particular mutated allele did not occur frequently. In addition, we found that the proportion of ultraviolet B (UVB) radiation-induced C>T transitions differed significantly (P < 0.001) between early and late mutation acquisition, suggesting that different mutational processes operate during the evolution of metastatic melanoma. Finally, clinical history reports revealed that patients harboring a high degree of mutational heterogeneity were associated with more aggressive disease progression. In conclusion, our multiregion tumor-sequencing approach highlights the genetic evolution and non-UVB mutational signatures associated with melanoma development and progression, and may provide a more comprehensive perspective of patient outcome. Cancer Res; 76(16); 4765-74. ©2016 AACR. PMID:27216186

  10. Chronologic and isotopic framework for Early Proterozoic crustal evolution in the eastern Mojave Desert region, SE California

    SciTech Connect

    Wooden, J.L.; Miller, D.M. )

    1990-11-10

    The Early Proterozoic geologic evolution of the eastern Mojave Desert region, as defined by characteristics of its supracrustal rocks, granitoids, metamorphism, structural history, and Pb and Nd isotopic signature, contrasts sharply with other Proterozoic provinces of the southwestern US. The oldest supracrustal rocks of the Mojave Desert region contain zircons over 2.0 Ga, corroborating Nd isotopic evidence for a much older crust here than elsewhere in the southwestern US. Granitoids widely emplaced within these supracrustal rocks range from 1.76 to 1.64 Ga. The earlier plutons and surrounding supracrustal rocks were metamorphosed to granulite and high amphibolite facies throughout the province at about 1,705 Ma in a migmatite-producing event that the authors term (informally) the Ivanpah orogeny. Subsequent granitoids, emplaced from 1.69 to 1.67 Ga, were voluminous along a north trending belt in the middle of the Mojave province. Younger plutons were emplaced at about 1.66 Ga in several places and at about 1.64 Ga along the extreme southern part of the province. Commonalities between the Proterozoic evolutions of the Mojave and Arizona crustal provinces do not conclusively establish the time that the provinces were juxtaposed; the data only suggest that the juxtaposition occurred about 1.76 and 1.64 Ga.

  11. REVIEW ARTICLE: Spectrophotometric applications of digital signal processing

    NASA Astrophysics Data System (ADS)

    Morawski, Roman Z.

    2006-09-01

    Spectrophotometry is more and more often the method of choice not only in analysis of (bio)chemical substances, but also in the identification of physical properties of various objects and their classification. The applications of spectrophotometry include such diversified tasks as monitoring of optical telecommunications links, assessment of eating quality of food, forensic classification of papers, biometric identification of individuals, detection of insect infestation of seeds and classification of textiles. In all those applications, large numbers of data, generated by spectrophotometers, are processed by various digital means in order to extract measurement information. The main objective of this paper is to review the state-of-the-art methodology for digital signal processing (DSP) when applied to data provided by spectrophotometric transducers and spectrophotometers. First, a general methodology of DSP applications in spectrophotometry, based on DSP-oriented models of spectrophotometric data, is outlined. Then, the most important classes of DSP methods for processing spectrophotometric data—the methods for DSP-aided calibration of spectrophotometric instrumentation, the methods for the estimation of spectra on the basis of spectrophotometric data, the methods for the estimation of spectrum-related measurands on the basis of spectrophotometric data—are presented. Finally, the methods for preprocessing and postprocessing of spectrophotometric data are overviewed. Throughout the review, the applications of DSP are illustrated with numerous examples related to broadly understood spectrophotometry.

  12. Early tetrapod evolution and the progressive integration of Permo-Carboniferous terrestrial ecosystems

    SciTech Connect

    Beerbower, J.R. . Dept. of Geological Science); Olson, E.C. . Dept. of Biology); Hotton, N. III . Dept. of Paleobiology)

    1992-01-01

    Variation among Permo-Carboniferous tetrapod assemblages demonstrates major transformations in pathways and rates of energy and nutrient transfer, in integration of terrestrial ecosystems and in predominant ecologic modes. Early Carboniferous pathways were through plant detritus to aquatic and terrestrial detritivores and thence to arthropod and vertebrate meso-and macro-predators. Transfer rates (and efficiency) were low as was ecosystem integration; the principal ecologic mode was conservation. Late Carboniferous and Early Permian assemblages demonstrate an expansion in herbivory, primarily in utilization of low-fiber plant tissue by insects. But transfer rates, efficiency and integration were still limited because the larger portion of plant biomass, high-fiber tissues, still went into detrital pathways; high-fiber'' herbivores, i.e., tetrapods, were neither abundant or diverse, reflecting limited resources, intense predation and limited capabilities for processing fiber-rich food. The abundance and diversity of tetrapod herbivores in upper Permian assemblages suggests a considerable transfer of energy from high-fiber tissues through these animals to tetrapod predators and thus higher transfer rates and efficiencies. It also brought a shift in ecological mode toward acquisition and regulation and tightened ecosystem integration.

  13. Aqueous Chemical Modeling of Sedimentation on Early Mars with Application to Surface-Atmosphere Evolution

    NASA Technical Reports Server (NTRS)

    Catling, David C.

    2004-01-01

    This project was to investigate models for aqueous sedimentation on early Mars from fluid evaporation. Results focused on three specific areas: (1) First, a fluid evaporation model incorporating iron minerals was developed to compute the evaporation of a likely solution on early Mars derived from the weathering of mafic rock. (2) Second, the fluid evaporation model was applied to salts within Martian meteorites, specifically salts in the nakhlites and ALH84001. Evaporation models were found to be consistent with the mineralogy of salt assemblages-anhydrite, gypsum, Fe-Mg-Ca carbonates, halite, clays-- and the concentric chemical fractionation of Ca-to Mg-rich carbonate rosettes in ALH84001. We made progress in further developing our models of fluid concentration by contributing to updating the FREZCHEM model. (3) Third, theoretical investigation was done to determine the thermodynamics and kinetics involved in the formation of gray, crystalline hematite. This mineral, of probable ancient aqueous origin, has been observed in several areas on the surface of Mars by the Thermal Emission Spectrometer on Mars Global Surveyor. The "Opportunity" Mars Exploration Rover has also detected gray hematite at its landing site in Meridiani Planum. We investigated how gray hematite can be formed via atmospheric oxidation, aqueous precipitation and subsequent diagenesis, or hydrothermal processes. We also studied the geomorphology of the Aram Chaos hematite region using Mars Orbiter Camera (MOC) images.

  14. Early hominid evolution and ecological change through the African Plio-Pleistocene.

    PubMed

    Reed, K E

    1997-01-01

    The habitats in which extinct hominids existed has been a key issue in addressing the origin and extinction of early hominids, as well as in understanding various morphological and behavioral adaptations. Many researchers postulated that early hominids lived in an open savanna (Dart, 1925; Robinson, 1963; Howell, 1978). However, Vrba (1985, 1988) has noted that a major global climatic and environmental shift from mesic, closed to xeric, open habitats occurred in the late African Pliocene (approximately 2.5 m.y.a.), thus implying that the earliest hominids existed in these mesic, wooded environs. This climatic shift is also suggested to have contributed to a pulse in speciation events with turnovers of many bovid and possibly hominid species. Previous environmental reconstructions of hominid localities have concentrated on taxonomic identities and taxonomic uniformitarianism to provide habitat reconstructions (e.g., Vrba, 1975; Shipman & Harris, 1988). In addition, relative abundances of species are often used to reconstruct a particular environment, when in fact taphonomic factors could be affecting the proportions of taxa. This study uses the morphological adaptations of mammalian assemblages found with early hominids to reconstruct the habitat based on each species' ecological adaptations, thus minimizing problems introduced by taxonomy and taphonomy. Research presented here compares east and south African Plio-Pleistocene mammalian fossil assemblages with 31 extant mammalian communities from eight different habitat types. All communities are analyzed through ecological diversity methods, that is, each species trophic and locomotor adaptations are used to reconstruct an ecological community and derive its vegetative habitat. Reconstructed habitats show that Australopithecus species existed in fairly wooded, well-watered regions. Paranthropus species lived in similar environs and also in more open regions, but always in habitats that include wetlands. Homo is the

  15. Early Diagenesis of Lower Pliensbachian Sediments from the Algarve Basin (Portugal): Characterisation and Relation with Tectonic Evolution

    NASA Astrophysics Data System (ADS)

    Ribeiro, Carlos; Terrinha, Pedro; Rosario Azevedo, M.; Ouajhain, Brahim

    2010-05-01

    The Lower Jurassic (Lower Pliensbachian) sedimentary record of the western end of the Algarve Basin (Portugal) is made of decimetric thick layers of limestone and dolomitized limestone with chert nodules and inter-layered chert beds. Most of the observable lithologies are the product of an early diagenetic evolution and the original lithological content of the formation included limestones, marls and calciclastic limestones. In this area the sedimentation was controlled by the tectonic stretching responsible for the evolution of the Algarve Basin, as well as by short-lived events of tectonic inversion. These episodes of tectonic inversion were responsible for the some uplift with the development of unconformities, sometimes with erosional surfaces separating the different sedimentary packages. The early diagenesis affecting the Lower Pliensbachian sediments is characterized by: (i) a mechanical event controlled by the syn-sedimentary stretching, responsible for the development of calciclastic dikes and nodules alignements; (ii) the substitution of the carbonates from the most permeable calciclastic limestone layers by silica, leading to the development of the observed cherts; (iii) the dolomitization of the preserved limestones; and (iv) the infilling of joints and normal fault planes by silica-rich fluids leading to the development of quartz veins. This set of diagenetic transformations took place before the Upper Pliensbachian which lacks the evidences of their occurrence. The whole-rock geochemical data of the carbonate and siliceous sediments of the Lower Pliensbachian revealed some affinities between both lithological types namely the lack of Ce anomalies and the presence of La anomalies in the REE patterns of all samples. The similarities between the carbonate lithologies which diagenetic evolution is marked by the replacement of calcite by dolomite and the siliceous sediments derived from the replacement of calcite by quartz establish a chemical connection

  16. Biogeography of Triassic tetrapods: evidence for provincialism and driven sympatric cladogenesis in the early evolution of modern tetrapod lineages.

    PubMed

    Ezcurra, Martin D

    2010-08-22

    Triassic tetrapods are of key importance in understanding their evolutionary history, because several tetrapod clades, including most of their modern lineages, first appeared or experienced their initial evolutionary radiation during this Period. In order to test previous palaeobiogeographical hypotheses of Triassic tetrapod faunas, tree reconciliation analyses (TRA) were performed with the aim of recovering biogeographical patterns based on phylogenetic signals provided by a composite tree of Middle and Late Triassic tetrapods. The TRA found significant evidence for the presence of different palaeobiogeographical patterns during the analysed time spans. First, a Pangaean distribution is observed during the Middle Triassic, in which several cosmopolitan tetrapod groups are found. During the early Late Triassic a strongly palaeolatitudinally influenced pattern is recovered, with some tetrapod lineages restricted to palaeolatitudinal belts. During the latest Triassic, Gondwanan territories were more closely related to each other than to Laurasian ones, with a distinct tetrapod fauna at low palaeolatitudes. Finally, more than 75 per cent of the cladogenetic events recorded in the tetrapod phylogeny occurred as sympatric splits or within-area vicariance, indicating that evolutionary processes at the regional level were the main drivers in the radiation of Middle and Late Triassic tetrapods and the early evolution of several modern tetrapod lineages. PMID:20392730

  17. Cerro Grande volcano: the evolution of a Miocene stratocone in the early Trans-Mexican Volcanic Belt

    NASA Astrophysics Data System (ADS)

    Gómez-Tuena, Arturo; Carrasco-Núñez, Gerardo

    2000-03-01

    Cerro Grande volcano is a well-preserved, low-angle composite volcano that evolved between 11 and 9 Ma. It represents the beginning of volcanism in the eastern sector of the early Trans-Mexican Volcanic Belt. Extensive field, stratigraphic and petrologic work revealed a complex volcanic evolution that can be summarized in six principal stages. (I) construction of a shield-like lava cone; (II) generation of unusual lithic-rich ignimbrites, apparently related to powerful eruptions that caused rapid and significant vent erosion — these eruptions could have resulted from shallow magma-water interactions; (III) eruption of peripheral fissural lava flows following a NNW-SSE-trending fissure system; (IV) period of dome growth and explosive collapse; (V) short period of repose followed by open-vent explosive magmatic and hydromagmatic eruptions; (VI) radial eruption of lava flows, related to a ring-fissural system. Geochemistry data of late Miocene volcanics show a continental arc magmatic origin, and show that crystal fractionation contributed strongly to magma differentiation. Several lava flows were erupted with a persistent NNW-SSE-trending orientation, and the entire late Miocene geologic record is affected by highly dislocated normal faults with the same orientation; this may indicate that late Miocene volcanism was under tectonic control. Finally, late Miocene volcanics, and the inception of the early Trans-Mexican Volcanic Belt, could be related to a shallow subduction angle influenced by a significant increase in the convergence rate along the Middle American Trench at about 20 Ma.

  18. Exceptional preservation reveals gastrointestinal anatomy and evolution in early actinopterygian fishes

    PubMed Central

    Argyriou, Thodoris; Clauss, Marcus; Maxwell, Erin E.; Furrer, Heinz; Sánchez-Villagra, Marcelo R.

    2016-01-01

    Current knowledge about the evolutionary morphology of the vertebrate gastrointestinal tract (GIT) is hindered by the low preservation potential of soft tissues in fossils. Exceptionally preserved cololites of individual †Saurichthys from the Middle Triassic of Switzerland provide unique insights into the evolutionary morphology of the GIT. The GIT of †Saurichthys differed from that of other early actinopterygians, and was convergent to that of some living sharks and rays, in exhibiting up to 30 turns of the spiral valve. Dissections and literature review demonstrate the phylogenetic diversity of GIT features and signs of biological factors that influence its morphology. A phylogenetically informed analysis of a dataset containing 134 taxa suggests that body size and phylogeny are important factors affecting the spiral valve turn counts. The high number of turns in the spiral valve of †Saurichthys and some recent sharks and rays reflect both energetically demanding lifestyles and the evolutionary histories of the groups. PMID:26732746

  19. Star formation in globular clusters and dwarf galaxies and implications for the early evolution of galaxies

    NASA Technical Reports Server (NTRS)

    Lin, Douglas N. C.; Murray, Stephen D.

    1991-01-01

    Based upon the observed properties of globular clusters and dwarf galaxies in the Local Group, we present important theoretical constraints on star formation in these systems. These constraints indicate that protoglobular cluster clouds had long dormant periods and a brief epoch of violent star formation. Collisions between protocluster clouds triggered fragmentation into individual stars. Most protocluster clouds dispersed into the Galactic halo during the star formation epoch. In contrast, the large spread in stellar metallicity in dwarf galaxies suggests that star formation in their pregenitors was self-regulated: we propose the protocluster clouds formed from thermal instability in the protogalactic clouds and show that a population of massive stars is needed to provide sufficient UV flux to prevent the collapsing protogalactic clouds from fragmenting into individual stars. Based upon these constraints, we propose a unified scenario to describe the early epochs of star formation in the Galactic halo as well as the thick and thin components of the Galactic disk.

  20. A virus-like molecule in the early stage of encoded molecular evolution

    NASA Astrophysics Data System (ADS)

    Nemoto, Naoto; Yanagawa, Hiroshi; Husimi, Yuzuru

    1996-10-01

    The recent advances of the evolutionary molecular engineering revealed the effectiveness of bonding strategy for assignment of the phenotype to its genotype, which non-enveloped viruses such as simple bacteriophages adopt. On the other hand, cellular organisms adopt another kind of the strategy, namely the compartmentalzation of both genotype and phenotype molecules in a single compartment enclosed with a cell membrane. The simplest strategy is that adopted by ribozymes in the RNA world. A single molecule carries both genotype and its phenotype. Based on the definition of “virus”-type and “cell”-type of the assignment strategy, we propose a virus-early/cell-late model of the history of life.

  1. Exceptional preservation reveals gastrointestinal anatomy and evolution in early actinopterygian fishes.

    PubMed

    Argyriou, Thodoris; Clauss, Marcus; Maxwell, Erin E; Furrer, Heinz; Sánchez-Villagra, Marcelo R

    2016-01-01

    Current knowledge about the evolutionary morphology of the vertebrate gastrointestinal tract (GIT) is hindered by the low preservation potential of soft tissues in fossils. Exceptionally preserved cololites of individual †Saurichthys from the Middle Triassic of Switzerland provide unique insights into the evolutionary morphology of the GIT. The GIT of †Saurichthys differed from that of other early actinopterygians, and was convergent to that of some living sharks and rays, in exhibiting up to 30 turns of the spiral valve. Dissections and literature review demonstrate the phylogenetic diversity of GIT features and signs of biological factors that influence its morphology. A phylogenetically informed analysis of a dataset containing 134 taxa suggests that body size and phylogeny are important factors affecting the spiral valve turn counts. The high number of turns in the spiral valve of †Saurichthys and some recent sharks and rays reflect both energetically demanding lifestyles and the evolutionary histories of the groups. PMID:26732746

  2. Melanoidin and aldocyanoin microspheres - Implications for chemical evolution and early Precambrian micropaleontology

    NASA Technical Reports Server (NTRS)

    Kenyon, D. H.; Nissenbaum, A.

    1976-01-01

    Two new classes of organic microspheres are described. One of them (melanoidin) is synthesized from amino acids and sugars in heated aqueous solutions. The other (aldocyanoin) is formed in aqueous solutions of ammonium cyanide and formaldehyde at room temperature. The general properties of these microspheres, including conditions of synthesis, size and shape, mechanical and pH stability, and solubility, are compared with corresponding properties of other protocell model systems. It is concluded that melanoidin and aldocyanoin microspheres are plausible candidates for precellular units in the primitive hydrosphere. Since the bulk of the organic carbon in early Precambrian sediments is insoluble kerogen-melanoidin, it is suggested that some Precambrian microfossils may be abiotic melanoidin microspheres.

  3. Was skin cancer a selective force for black pigmentation in early hominin evolution?

    PubMed Central

    Greaves, Mel

    2014-01-01

    Melanin provides a crucial filter for solar UV radiation and its genetically determined variation influences both skin pigmentation and risk of cancer. Genetic evidence suggests that the acquisition of a highly stable melanocortin 1 receptor allele promoting black pigmentation arose around the time of savannah colonization by hominins at some 1–2 Ma. The adaptive significance of dark skin is generally believed to be protection from UV damage but the pathologies that might have had a deleterious impact on survival and/or reproductive fitness, though much debated, are uncertain. Here, I suggest that data on age-associated cancer incidence and lethality in albinos living at low latitudes in both Africa and Central America support the contention that skin cancer could have provided a potent selective force for the emergence of black skin in early hominins. PMID:24573849

  4. COMFEN 3.0 - Evolution of an Early Design Tool for Commercial Facades and Fenestration Systems

    SciTech Connect

    McClintock Facade Consulting LLC, Walnut Creek, CA; McQuillen Interactive LLC, Santa Cruz, CA; Selkowitz, Stephen; Mitchell, Robin; McClintock, Maurya; McQuillen, Daniel; McNeil, Andrew; Yazdanian, Mehry

    2011-03-09

    Achieving a net-zero energy building cannot be done solely by improving the efficiency of the engineering systems. It also requires consideration of the essential nature of the building including factors such as architectural form, massing, orientation and enclosure. Making informed decisions about the fundamental character of a building requires assessment of the effects of the complex interaction of these factors on the resulting performance of the building. The complexity of these interactions necessitates the use of modeling and simulation tools to dynamically analyze the effects of the relationships, yet decisions about the building fundamentals are often made in the earliest stages of design, before a `building? exists to model. To address these issues, Lawrence Berkeley National Laboratory (LBNL) has developed an early-design energy modeling tool (COMFEN) specifically to help make informed decisions about building facade fundamentals by considering the design of the building envelope, orientation and massing on building performance. COMFEN focuses on the concept of a ?space? or ?room? and uses the EnergyPlus, and RadianceTM engines and a simple, graphic user interface to allow the user to explore the effects of changing key early-design input variables on energy consumption, peak energy demand, and thermal and visual comfort. Comparative results are rapidly presented in a variety of graphic and tabular formats to help users move toward optimal facade and fenestration design choices.While COMFEN 1.0 utilized an ExcelTM-based user interface, COMFEN 3.0 has been reworked to include a simple, more intuitive, yet powerful Graphic User Interface (GUI), a broader range of libraries for associated system and component choices and deliver a wider range of graphic outputs and options. This paper (and presentation) outlines the objectives in developing and further refining COMFEN, the mechanics of the program, and plans for future development.

  5. The origin and early evolution of metatherian mammals: the Cretaceous record.

    PubMed

    Williamson, Thomas E; Brusatte, Stephen L; Wilson, Gregory P

    2014-01-01

    Metatherians, which comprise marsupials and their closest fossil relatives, were one of the most dominant clades of mammals during the Cretaceous and are the most diverse clade of living mammals after Placentalia. Our understanding of this group has increased greatly over the past 20 years, with the discovery of new specimens and the application of new analytical tools. Here we provide a review of the phylogenetic relationships of metatherians with respect to other mammals, discuss the taxonomic definition and diagnosis of Metatheria, outline the Cretaceous history of major metatherian clades, describe the paleobiology, biogeography, and macroevolution of Cretaceous metatherians, and provide a physical and climatic background of Cretaceous metatherian faunas. Metatherians are a clade of boreosphendian mammals that must have originated by the Late Jurassic, but the first unequivocal metatherian fossil is from the Early Cretaceous of Asia. Metatherians have the distinctive tightly interlocking occlusal molar pattern of tribosphenic mammals, but differ from Eutheria in their dental formula and tooth replacement pattern, which may be related to the metatherian reproductive process which includes an extended period of lactation followed by birth of extremely altricial young. Metatherians were widespread over Laurasia during the Cretaceous, with members present in Asia, Europe, and North America by the early Late Cretaceous. In particular, they were taxonomically and morphologically diverse and relatively abundant in the Late Cretaceous of western North America, where they have been used to examine patterns of biogeography, macroevolution, diversification, and extinction through the Late Cretaceous and across the Cretaceous-Paleogene (K-Pg) boundary. Metatherian diversification patterns suggest that they were not strongly affected by a Cretaceous Terrestrial Revolution, but they clearly underwent a severe extinction across the K-Pg boundary. PMID:25589872

  6. The origin and early evolution of metatherian mammals: the Cretaceous record

    PubMed Central

    Williamson, Thomas E.; Brusatte, Stephen L.; Wilson, Gregory P.

    2014-01-01

    Abstract Metatherians, which comprise marsupials and their closest fossil relatives, were one of the most dominant clades of mammals during the Cretaceous and are the most diverse clade of living mammals after Placentalia. Our understanding of this group has increased greatly over the past 20 years, with the discovery of new specimens and the application of new analytical tools. Here we provide a review of the phylogenetic relationships of metatherians with respect to other mammals, discuss the taxonomic definition and diagnosis of Metatheria, outline the Cretaceous history of major metatherian clades, describe the paleobiology, biogeography, and macroevolution of Cretaceous metatherians, and provide a physical and climatic background of Cretaceous metatherian faunas. Metatherians are a clade of boreosphendian mammals that must have originated by the Late Jurassic, but the first unequivocal metatherian fossil is from the Early Cretaceous of Asia. Metatherians have the distinctive tightly interlocking occlusal molar pattern of tribosphenic mammals, but differ from Eutheria in their dental formula and tooth replacement pattern, which may be related to the metatherian reproductive process which includes an extended period of lactation followed by birth of extremely altricial young. Metatherians were widespread over Laurasia during the Cretaceous, with members present in Asia, Europe, and North America by the early Late Cretaceous. In particular, they were taxonomically and morphologically diverse and relatively abundant in the Late Cretaceous of western North America, where they have been used to examine patterns of biogeography, macroevolution, diversification, and extinction through the Late Cretaceous and across the Cretaceous-Paleogene (K-Pg) boundary. Metatherian diversification patterns suggest that they were not strongly affected by a Cretaceous Terrestrial Revolution, but they clearly underwent a severe extinction across the K-Pg boundary. PMID:25589872

  7. Histology and affinity of anaspids, and the early evolution of the vertebrate dermal skeleton.

    PubMed

    Keating, Joseph N; Donoghue, Philip C J

    2016-03-16

    The assembly of the gnathostome bodyplan constitutes a formative episode in vertebrate evolutionary history, an interval in which the mineralized skeleton and its canonical suite of cell and tissue types originated. Fossil jawless fishes, assigned to the gnathostome stem-lineage, provide an unparalleled insight into the origin and evolution of the skeleton, hindered only by uncertainty over the phylogenetic position and evolutionary significance of key clades. Chief among these are the jawless anaspids, whose skeletal composition, a rich source of phylogenetic information, is poorly characterized. Here we survey the histology of representatives spanning anaspid diversity and infer their generalized skeletal architecture. The anaspid dermal skeleton is composed of odontodes comprising spheritic dentine and enameloid, overlying a basal layer of acellular parallel fibre bone containing an extensive shallow canal network. A recoded and revised phylogenetic analysis using equal and implied weights parsimony resolves anaspids as monophyletic, nested among stem-gnathostomes. Our results suggest the anaspid dermal skeleton is a degenerate derivative of a histologically more complex ancestral vertebrate skeleton, rather than reflecting primitive simplicity. Hypotheses that anaspids are ancestral skeletonizing lampreys, or a derived lineage of jawless vertebrates with paired fins, are rejected. PMID:26962140

  8. Diversity in early crustal evolution: 4100 Ma zircons in the Cathaysia Block of southern China.

    PubMed

    Xing, Guang-Fu; Wang, Xiao-Lei; Wan, Yusheng; Chen, Zhi-Hong; Jiang, Yang; Kitajima, Kouki; Ushikubo, Takayuki; Gopon, Phillip

    2014-01-01

    Zircons are crucial to understanding the first 500 Myr of crustal evolution of Earth. Very few zircons of this age (>4050 Ma) have been found other than from a ~300 km diameter domain of the Yilgarn Craton, Western Australia. Here we report SIMS U-Pb and O isotope ratios and trace element analyses for two ~4100 Ma detrital zircons from a Paleozoic quartzite at the Longquan area of the Cathaysia Block. One zircon ((207)Pb/(206)Pb age of 4127 ± 4 Ma) shows normal oscillatory zonation and constant oxygen isotope ratios (δ(18)O = 5.8 to 6.0‰). The other zircon grain has a ~4100 Ma magmatic core surrounded by a ~4070 Ma metamorphic mantle. The magmatic core has elevated δ(18)O (7.2 ± 0.2‰), high titanium concentration (53 ± 3.4 ppm) and a positive cerium anomaly, yielding anomalously high calculated oxygen fugacity (FMQ + 5) and a high crystallization temperature (910°C). These results are unique among Hadean zircons and suggest a granitoid source generated from dry remelting of partly oxidizing supracrustal sediments altered by surface waters. The ~4100 Ma dry melting and subsequent ~4070 Ma metamorphism provide new evidence for the diversity of the Earth's earliest crust. PMID:24888297

  9. A view of early vertebrate evolution inferred from the phylogeny of polystome parasites (Monogenea: Polystomatidae).

    PubMed Central

    Verneau, Olivier; Bentz, Sophie; Sinnappah, Neeta Devi; du Preez, Louis; Whittington, Ian; Combes, Claude

    2002-01-01

    The Polystomatidae is the only family within the Monogenea to parasitize sarcopterygians such as the Australian lungfish Neoceratodus poisteri and freshwater tetrapods (lissamphibians and chelonians). We present a phylogeny based on partial 18S rDNA sequences of 26 species of Polystomatidae and three taxon from the infrasubclass Oligonchoinea (= Polyopisthocotylea) obtained from the gills of teleost fishes. The basal position of the polystome from lungfish within the Polystomatidae suggests that the family arose during the evolutionary transition between actinopterygians and sarcopterygians, ca. 425 million years (Myr) ago. The monophyly of the polystomatid lineages from chelonian and lissamphibian hosts, in addition to estimates of the divergence times, indicate that polystomatids from turtles radiated ca. 191 Myr ago, following a switch from an aquatic amniote presumed to be extinct to turtles, which diversified in the Upper Triassic. Within polystomatids from lissamphibians, we observe a polytomy of four lineages, namely caudatan, neobatrachian, pelobatid and pipid polystomatid lineages, which occurred ca. 246 Myr ago according to molecular divergence-time estimates. This suggests that the first polystomatids of amphibians originated during the evolution and diversification of lissamphibian orders and suborders ca. 250 Myr ago. Finally, we report a vicariance event between two major groups of neobatrachian polystomes, which is probably linked to the separation of South America from Africa ca. 100 Myr ago. PMID:11886648

  10. The early heat loss evolution of Mars and their implications for internal and environmental history

    PubMed Central

    Ruiz, Javier

    2014-01-01

    The time around 3.7 Ga ago was an epoch when substantial changes in Mars occurred: a substantial decline in aqueous erosion/degradation of landscape features; a change from abundant phyllosilicate formation to abundant acidic and evaporitic mineralogy; a change from olivine-rich volcanism to olivine-pyroxene volcanism; and maybe the cessation of the martian dynamo. Here I show that Mars also experienced profound changes in its internal dynamics in the same approximate time, including a reduction of heat flow and a drastic increasing of lithosphere strength. The reduction of heat flow indicates a limited cooling (or even a heating-up) of the deep interior for post-3.7 Ga times. The drastic increasing of lithosphere strength indicates a cold lithosphere above the inefficiently cooled (or even heated) interior. All those changes experienced by Mars were most probably linked and suggest the existence of profound interrelations between interior dynamics and environmental evolution of this planet. PMID:24614056

  11. The Place of RNA in the Origin and Early Evolution of the Genetic Machinery

    PubMed Central

    Wächtershäuser, Günter

    2014-01-01

    The extant genetic machinery revolves around three interrelated polymers: RNA, DNA and proteins. Two evolutionary views approach this vital connection from opposite perspectives. The RNA World theory posits that life began in a cold prebiotic broth of monomers with the de novo emergence of replicating RNA as functionally self-contained polymer and that subsequent evolution is characterized by RNA → DNA memory takeover and ribozyme → enzyme catalyst takeover. The FeS World theory posits that life began as an autotrophic metabolism in hot volcanic-hydrothermal fluids and evolved with organic products turning into ligands for transition metal catalysts thereby eliciting feedback and feed-forward effects. In this latter context it is posited that the three polymers of the genetic machinery essentially coevolved from monomers through oligomers to polymers, operating functionally first as ligands for ligand-accelerated transition metal catalysis with later addition of base stacking and base pairing, whereby the functional dichotomy between hereditary DNA with stability on geologic time scales and transient, catalytic RNA with stability on metabolic time scales existed since the dawn of the genetic machinery. Both approaches are assessed comparatively for chemical soundness. PMID:25532530

  12. The evolution of the ozone collar in the Antarctic lower stratosphere during early August 1994

    SciTech Connect

    Mariotti, A.; Mechoso, C.R.; Legras, B.; Daniel, V.

    2000-02-01

    The ozone evolution in the lower stratosphere of the Southern Hemisphere during the period 5--10 August 1994 is analyzed. The analysis focuses on the ozone collar (the band of maximum values in ozone mixing ratio around the Antarctic ozone hole at these altitudes) and the development of collar filaments. Ozone mixing ratios provided by the Microwave Limb Sounder (MLS) on board the Upper Atmosphere Research Satellite and by an ER-2 aircraft participating in the Airborne Southern Hemisphere Ozone Experiment/Measurements for Assessing the Effects of stratospheric Aircraft campaign are compared with values at corresponding locations in high-resolution isentropic maps obtained by using the numerical scheme of contour advection with surgery (CAS). The CAS reconstructed ozone maps provide a view of the way in which air masses are exported from the outskirts of the collar to form the tongues of higher mixing ratios observed at lower latitudes on MLS synoptic maps. There is an overall consistency between the datasets insofar as the collar location is concerned. This location seems to be primarily defined by the local properties of the flow. Nevertheless the CAS reconstructed collar tends to become weaker than that depicted by MLS data. By means of radioactive calculation estimates, it is argued that diabatic descent may be responsible for maintaining the ozone concentration approximately constant in the collar while filaments isentropically disperse collarlike mixing ratios from this region toward lower latitudes.

  13. Histology and affinity of anaspids, and the early evolution of the vertebrate dermal skeleton

    PubMed Central

    Keating, Joseph N.; Donoghue, Philip C. J.

    2016-01-01

    The assembly of the gnathostome bodyplan constitutes a formative episode in vertebrate evolutionary history, an interval in which the mineralized skeleton and its canonical suite of cell and tissue types originated. Fossil jawless fishes, assigned to the gnathostome stem-lineage, provide an unparalleled insight into the origin and evolution of the skeleton, hindered only by uncertainty over the phylogenetic position and evolutionary significance of key clades. Chief among these are the jawless anaspids, whose skeletal composition, a rich source of phylogenetic information, is poorly characterized. Here we survey the histology of representatives spanning anaspid diversity and infer their generalized skeletal architecture. The anaspid dermal skeleton is composed of odontodes comprising spheritic dentine and enameloid, overlying a basal layer of acellular parallel fibre bone containing an extensive shallow canal network. A recoded and revised phylogenetic analysis using equal and implied weights parsimony resolves anaspids as monophyletic, nested among stem-gnathostomes. Our results suggest the anaspid dermal skeleton is a degenerate derivative of a histologically more complex ancestral vertebrate skeleton, rather than reflecting primitive simplicity. Hypotheses that anaspids are ancestral skeletonizing lampreys, or a derived lineage of jawless vertebrates with paired fins, are rejected. PMID:26962140

  14. Evolution of endogenous hormone concentration in embryogenic cultures of carrot during early expression of somatic embryogenesis.

    PubMed

    Jiménez, V M; Guevara, E; Herrera, J; Bangerth, F

    2005-01-01

    Embryogenic callus and suspension cultures of carrot (Daucus carota L., cv. Nantaise), growing on/in medium including 1 mg/l 2,4-dichlorophenoxy acetic acid (2,4-D), were transferred to medium with or without this plant growth regulator, to impair or induce, respectively, further development of somatic embryos. The endogenous hormone levels of the cultures were determined over 7 days by means of radio-immunoassay, to characterize their evolution in the initial stages of embryo development. In general, levels of indoleacetic acid (IAA) and abscisic acid (ABA) showed only short-lived differences among treatments during this time in both types of tissue analyzed (i.e., a peak of IAA in callus cultures in the absence of 2,4-D, 48 h after medium change, and higher ABA contents 144 h after subculture of suspension cultures in the presence of 2,4-D). Gibberellins (1, 3 and 20) were detected only in suspension cultures devoid of 2,4-D, starting 24 h after subculture. Concerning the evaluated cytokinins-zeatin/zeatin riboside and N6(Delta2-isopentenyl) adenine/N6(Delta2-isopentenyl) adenosine-the most remarkable observation is that high levels of the former generally coincided with low concentrations of the latter, indicating a shift from precursor to the active form, and vice versa. PMID:15375630

  15. Leptogenesis in the symmetric phase of the early universe: Baryon asymmetry and hypermagnetic helicity evolution

    SciTech Connect

    Semikoz, V. B. Smirnov, A. Yu.

    2015-02-15

    We investigate the evolution of the baryon asymmetry of the Universe (BAU) in its symmetric phase before the electroweak phase transition (EWPT) induced by leptogenesis in the hypermagnetic field of an arbitrary structure and with a maximum hypermagnetic helicity density. The novelty of this work is that the BAU has been calculated for a continuous hypermagnetic helicity spectrum. The observed BAU B{sub obs} = 10{sup −10} that can be in large-scale hypermagnetic fields satisfying the wave number inequality k ≤ k{sub max} grows with increasing k{sub max}. We will also show that the initial right-handed electron asymmetry ξ{sub eR}(η{sub 0}) used in our leptogenesis model as a free parameter cannot take too large values, ξ{sub eR}(η{sub 0}) = 10{sup −4}, because this leads to a negative BAU by the EWPT time. In contrast, a sufficiently small initial right-handed electron asymmetry, ξ{sub eR}(η{sub 0}), provides its further growth and the corresponding BAU growth from zero to some positive value, including the observed B{sub obs} = 10{sup −10}.

  16. Early sexual origins of homeoprotein heterodimerization and evolution of the plant KNOX/BELL family.

    PubMed

    Lee, Jae-Hyeok; Lin, Huawen; Joo, Sunjoo; Goodenough, Ursula

    2008-05-30

    Developmental mechanisms that yield multicellular diversity are proving to be well conserved within lineages, generating interest in their origins in unicellular ancestors. We report that molecular regulation of the haploid-diploid transition in Chlamydomonas, a unicellular green soil alga, shares common ancestry with differentiation pathways in land plants. Two homeoproteins, Gsp1 and Gsm1, contributed by gametes of plus and minus mating types respectively, physically interact and translocate from the cytosol to the nucleus upon gametic fusion, initiating zygote development. Their ectopic expression activates zygote development in vegetative cells and, in a diploid background, the resulting zygotes undergo a normal meiosis. Gsm1/Gsp1 dyads share sequence homology with and are functionally related to KNOX/BELL dyads regulating stem-cell (meristem) specification in land plants. We propose that combinatorial homeoprotein-based transcriptional control, a core feature of the fungal/animal radiation, may have originated in a sexual context and enabled the evolution of land-plant body plans. PMID:18510927

  17. Jupiter’s decisive role in the inner Solar System’s early evolution

    PubMed Central

    Batygin, Konstantin; Laughlin, Greg

    2015-01-01

    The statistics of extrasolar planetary systems indicate that the default mode of planet formation generates planets with orbital periods shorter than 100 days and masses substantially exceeding that of the Earth. When viewed in this context, the Solar System is unusual. Here, we present simulations which show that a popular formation scenario for Jupiter and Saturn, in which Jupiter migrates inward from a > 5 astronomical units (AU) to a ≈ 1.5 AU before reversing direction, can explain the low overall mass of the Solar System’s terrestrial planets, as well as the absence of planets with a < 0.4 AU. Jupiter’s inward migration entrained s ≳ 10−100 km planetesimals into low-order mean motion resonances, shepherding and exciting their orbits. The resulting collisional cascade generated a planetesimal disk that, evolving under gas drag, would have driven any preexisting short-period planets into the Sun. In this scenario, the Solar System’s terrestrial planets formed from gas-starved mass-depleted debris that remained after the primary period of dynamical evolution. PMID:25831540

  18. Spectrophotometric Estimation of Raltegravir Potassium in Tablets

    PubMed Central

    Kore, P. P.; Gamepatil, M. M.; Nimje, H. M.; Baheti, K. G.

    2014-01-01

    Ultra violet spectrophotometric estimation of the raltegravir potassium, an integrase inhibitor antiretroviral agent was estimated by Ultra violet absorption maxima method at λmax of 328 nm and UV area under curve method in the wave length range of 323-333 nm. The Beer's law obeyed in the concentration range of 3-55 μg/ml and correlation coefficients were found to be more than 0.996 for both methods. The results of the analysis were 100.58±0.99 and 99.69±0.59 by absorption maxima and area under curve method respectively. Both the methods were validated as per ICH guidelines. PMID:25593392

  19. Spectrophotometric determination of azathioprine in pharmaceutical formulations.

    PubMed

    Lakshmi, C S; Reddy, M N

    1998-12-01

    Four simple and sensitive visible spectrophotometric methods (A-D) have been described for the assay of azathioprine (ATP) either in pure form or in pharmaceutical formulations. Methods A and B are based on the oxidation of ATP with excess N-bromosuccinimide (NBS) or chloramine-T (CAT) and determining the consumed NBS or CAT with a decrease in colour intensity of celestine blue (CB) (method A) or gallocyanine (GC) (method B), respectively. Methods C and D are based on the diazotisation of reduced azathioprine (RATP) with excess nitrous acid and estimating either the consumed nitrous acid (HNO(2)) with cresyl fast violet acetate (CFVA) (method C) or by coupling reaction of the diazonium salt formed with N-1-naphthyl ethylene diamine dihydrochloride (NED) (method D). All of the variables have been optimized and the reactions presented. The concentration measurements are reproducible within a relative standard deviation of 1.0%. Recoveries are 99.2-100.3%. PMID:18967434

  20. Spectrophotometric Estimation of Azithromycin in Tablets

    PubMed Central

    Jayanna, B. K.; Nagendrappa, G.; Arunkumar; Gowda, N.

    2012-01-01

    The present manuscript describes a simple, sensitive, accurate, precise and economical visible spectrophotometric method for the estimation of azithromycin from tablet formulation. The method is based on the reduction of potassium permanganate in alkaline medium with azithromycin. The measurement of decrease in absorbance of potassium permanganate at 547 nm was done, as it decolourises upon reduction by azithromycin. The method was used to determine between 2 and 20 μg/ml of azithromycin in the final measured solution. There is no interference from the ingredients commonly found in azithromycin tablets with this method. The results for the determination of azithromycin in tablets were in good agreement with the labelled quantities and related analytical parameters are calculated. PMID:23626394

  1. Spectrophotometric estimation of risperidone in tablets.

    PubMed

    Jayanna, B K; Devaraj, T D; Roopa, K P; Nagendrappa, G; Kumar, H R Arun; Gowda, N

    2014-09-01

    A simple, rapid and highly sensitive spectrophotometric method is developed for the determination of risperidone in tablet formulation. The method is based on the oxidation of drug using potassium permanganate in alkaline medium and excess potassium permanganate oxidizes 1,10-phenanthroline Fe(II). The measurement of decrease in absorbance of 1,10-phenanthroline Fe (II) was done at 415 nm. The beer's law is obeyed in the concentration range of 5.0 to 40.0 μg/ml and molar absorptivity is found to be 7.3932 × 10(4) l/mol/cm. The proposed method is well suited for the pharmaceutical formulations. PMID:25425761

  2. Spectrophotometric estimation of azithromycin in tablets.

    PubMed

    Jayanna, B K; Nagendrappa, G; Arunkumar; Gowda, N

    2012-07-01

    The present manuscript describes a simple, sensitive, accurate, precise and economical visible spectrophotometric method for the estimation of azithromycin from tablet formulation. The method is based on the reduction of potassium permanganate in alkaline medium with azithromycin. The measurement of decrease in absorbance of potassium permanganate at 547 nm was done, as it decolourises upon reduction by azithromycin. The method was used to determine between 2 and 20 μg/ml of azithromycin in the final measured solution. There is no interference from the ingredients commonly found in azithromycin tablets with this method. The results for the determination of azithromycin in tablets were in good agreement with the labelled quantities and related analytical parameters are calculated. PMID:23626394

  3. Chronology of the Final Marine Regression in the Eastern Ebro Basin: Late Eocene to Early Oligocene Tectonosedimentary Evolution. (NE Spain)

    NASA Astrophysics Data System (ADS)

    Costa, E.; Garces, M.; Saez, A.; Lopez-Blanco, M.; Beamud, E.; Gomez-Paccard, M.; Cabrera, L.

    2007-12-01

    The Ebro Basin is a triangular shaped foreland basin surrounded by three alpine ranges: the Pyrenees to the north, the Iberian Range to the SW and the Catalan Coastal Range to the SE. During the early Paleocene started the development of the Ebro Basin by flexural subsidence related to the growth of its margins as a consequence of the continental collision of Iberia and Europe. Connection of the Ebro Basin with the open sea was maintained until late Eocene, when ongoing convergence along the Pyrenean margin lead to the final closure of its western connection with the Atlantic Ocean. Since then, a long endorheic period of uninterrupted continental sedimentation leads to the accumulation of a thick sequence composed by alluvial and lacustrine facies. In foreland basins, tectonics plays a fundamental role in the sedimentation, by generating relief in the margins and accommodation space in the basin. Therefore, it is generally assumed that the main sedimentary breaks have a tectonic origin. The tectonic control on the sedimentation has been successfully established along the margins of the Ebro Basin through the study of the geometries of the syntectonic sediments. However, away from the margins, in distal alluvial and lacustrine environments some other factors related to the climate can also exert control on the sedimentation. In order to interpret the sedimentary record of the Ebro Basin in terms of tectonosedimentary and paleoclimatic evolution, we have sampled two magnetostratigraphic sections (1000 m and 600 m, thick) on Eocene-Oligocene continental sequences. Samples were collected at 2-5 m stratigraphic intervals. Stepwise thermal demagnetisation of the NRM of up to 2 samples per site has yielded a local magnetic polarity stratigraphy. Unambiguous correlation with the geomagnetic polarity time scale was feasible based on the presence of late Eocene to early Oligocene mammal fossil localities and previous magnetostratigraphic studies spanning the complete

  4. Stratigraphic interpretation of the Kulu Formation (Early Miocene, Rusinga Island, Kenya) and its implications for primate evolution.

    PubMed

    Peppe, Daniel J; McNulty, Kieran P; Cote, Susanne M; Harcourt-Smith, William E H; Dunsworth, Holly M; Van Couvering, John A

    2009-05-01

    Early Miocene fossils from Rusinga Island, Kenya, provide some of the best evidence for catarrhine evolution and diversification, and, together with more than eighty-five other mammalian species, form an important comparative reference for understanding faunal succession in East Africa. While there is consensus over the stratigraphic position of most of Rusinga's volcaniclastic deposits, the lacustrine Kulu Formation has been placed in various parts of the geological sequence by different researchers. To resolve this discrepancy, we conducted detailed geological analyses which indicate that the Kulu Formation was formed in the Early Miocene during a period of volcanic inactivity and subsidence following the early, mainly explosive hyper-alkaline phase of the Kisingiri complex and prior to the final eruptions of nephelinitic lavas. The underlying Hiwegi and older formations were locally deformed and deeply eroded before sedimentation began in the Kulu basin, so that the Kulu sediments may be significantly younger than the 17.8 Ma Hiwegi Formation and not much older than the overlying Kiangata Agglomerata-Lunene Lava series, loosely dated to ca. 15 Ma. The overall similarities between Kulu and Hiwegi faunas imply long-term ecological stability in this region. Our stratigraphic interpretation suggests that the Kulu fauna is contemporaneous with faunas from West Turkana, implying that differences between these assemblages-particularly in the primate communities--reflect paleobiogeographic and/or paleocological differences. Finally, the position of the Kulu Formation restricts the time frame during which the substantial faunal turnover seen in the differences between the primate and mammalian communities of Rusinga and Maboko Islands could have occurred. PMID:19427023

  5. Tracking the Distribution of 26Al and 60Fe during the Early Phases of Star and Disk Evolution

    NASA Astrophysics Data System (ADS)

    Kuffmeier, Michael; Frostholm Mogensen, Troels; Haugbølle, Troels; Bizzarro, Martin; Nordlund, Åke

    2016-07-01

    The short-lived 26Al and 60Fe radionuclides are synthesized and expelled into the interstellar medium by core-collapse supernova events. The solar system’s first solids, calcium–aluminum refractory inclusions (CAIs), contain evidence for the former presence of the 26 Al nuclide defining the canonical 26Al/27 Al ratio of ˜ 5× {10}-5. A different class of objects temporally related to canonical CAIs are CAIs with fractionation and unidentified nuclear effects (FUN CAIs), which record a low initial 26Al/27Al of 10‑6. The contrasting level of 26Al between these objects is often interpreted as reflecting the admixing of the 26Al nuclides during the early formative phase of the Sun. We use giant molecular cloud scale adaptive mesh-refinement numerical simulations to trace the abundance of 26Al and 60Fe in star-forming gas during the early stages of accretion of individual low-mass protostars. We find that the 26Al/27Al and 60Fe/56Fe ratios of accreting gas within a vicinity of 1000 au of the stars follow the predicted decay curves of the initial abundances at the time of star formation without evidence of spatial or temporal heterogeneities for the first 100 kyr of star formation. Therefore, the observed differences in 26Al/27Al ratios between FUN and canonical CAIs are likely not caused by admixing of supernova material during the early evolution of the proto-Sun. Selective thermal processing of dust grains is a more viable scenario to account for the heterogeneity in 26Al/27Al ratios at the time of solar system formation.

  6. Evolution of the Early Triassic marine depositional environment in the Croatian Dinarides

    NASA Astrophysics Data System (ADS)

    Aljinović, Dunja; Smirčić, Duje; Horacek, Micha; Richoz, Sylvain; Krystyn, Leopold; Kolar-Jurkovšek, Tea; Jurkovšek, Bogdan

    2014-05-01

    In the central part of the Dinarides in Croatia, the Early Triassic depositional sequence was investigated by means of litho-, bio- and chemostratigraphy at locality Plavno (ca. 1.000m thick). Conodont and δ13C-isotope analysis were a powerfull tool to determine stage and substage boundaries. The succession begins with the second conodont zone of the Griesbachian Isarcicella staeschei and I. isarcica with low δ13C-values and a steadily increase towards the Griesbachian-Dienerian boundary. Around that boundary a minor, short, negative excursion occurs. In the Dienerian the δ13C-values increase with a steepening of the slope towards the Dienerian-Smithian boundary. Around that boundary a maximum of +5o in shallow water carbonate occurs followed by a steep and continuous drop to low, often negative values in the Smithian. Just before the Smithian-Spathian boundary a steep rise to a second maximum is documented. It is followed by decline in the Spathian and a gentle increase to a rounded peak at the Spathian-Anisian boundary. In lithological sense Plavno succession has threefold division: 1) carbonates representing the oldest Early Triassic strata (early Griesbachian); 2) dominantly red clastics (shales, siltstones and sandstones) with intercalation of oncoid/ooid or bioclast rich grainstones (uppermost Griesbachian, Dienerian and Smithian) and 3) dominantly grey carbonaceous lime mudstones, marls and calcisiltites with ammonoids representing Spathian strata. In the oldest strata (Griesbachian) in macrocrystalline subhedral dolomites rare microspheres and foraminifers Earlandia and Cornuspira point to the stressful conditions related to the end Permian mass extinction. In the uppermost Griesbachian and Dienerian strata, within dominantly clastic deposition, rare coarse oncoliths with typical microbial cortices occur. Their presence fits to the interpretation of biotical-induced precipitation related to PTB extinction and can suggest still stressful condition. The

  7. Origin and early evolution of neural circuits for the control of ciliary locomotion

    PubMed Central

    Jékely, Gáspár

    2011-01-01

    Behaviour evolved before nervous systems. Various single-celled eukaryotes (protists) and the ciliated larvae of sponges devoid of neurons can display sophisticated behaviours, including phototaxis, gravitaxis or chemotaxis. In single-celled eukaryotes, sensory inputs directly influence the motor behaviour of the cell. In swimming sponge larvae, sensory cells influence the activity of cilia on the same cell, thereby steering the multicellular larva. In these organisms, the efficiency of sensory-to-motor transformation (defined as the ratio of sensory cells to total cell number) is low. With the advent of neurons, signal amplification and fast, long-range communication between sensory and motor cells became possible. This may have first occurred in a ciliated swimming stage of the first eumetazoans. The first axons may have had en passant synaptic contacts to several ciliated cells to improve the efficiency of sensory-to-motor transformation, thereby allowing a reduction in the number of sensory cells tuned for the same input. This could have allowed the diversification of sensory modalities and of the behavioural repertoire. I propose that the first nervous systems consisted of combined sensory-motor neurons, directly translating sensory input into motor output on locomotor ciliated cells and steering muscle cells. Neuronal circuitry with low levels of integration has been retained in cnidarians and in the ciliated larvae of some marine invertebrates. This parallel processing stage could have been the starting point for the evolution of more integrated circuits performing the first complex computations such as persistence or coincidence detection. The sensory-motor nervous systems of cnidarians and ciliated larvae of diverse phyla show that brains, like all biological structures, are not irreducibly complex. PMID:21123265

  8. Birth place of life on the Hadean Earth and early evolution of life on a tightrope

    NASA Astrophysics Data System (ADS)

    Maruyama, S.

    2014-12-01

    The surface environment of the Hadean Earth is the key to the beginning of life. For the emergence of life, primordial Earth has to evolve with the following conditions. 1) Primordial Earth was formed without an atmosphere and ocean components where ultra-reductive materials such as Fe3P were formed. 2) At about 4.4Ga, atmosphere and ocean components were delivered to the Earth through heavy bombardment of asteroid bodies. 3) Direct reaction between komatiite and primordial atmosphere, associated with pseudo-plate tectonics, fixed atmospheric CO2 into the crust, which resulted in decreased density of atmospheric CO2; because of this, a primordial ocean appeared, and the Earth did not become a burning planet like Venus. 4) The primordial ocean was too toxic because of high salinity, ultra acidity, and high concentrations of heavy metal elements. 5) It was impossible to bear life in such a toxic ocean. However, the mass of the primordial ocean was small, e.g. only 3-5km depth, which enabled a landmass to appear on Hadean Earth. The surface environment was highly diversified with numerous lakes and river systems interacting with the landmass (i.e., primordial continent), providing varied and dynamic conditions (ultra-reductive to acidic environment) where prebiotic chemical evolution progressed. 6) On the other hand, plate tectonics started once the primordial ocean was formed. Due to the chemical reaction between the rocks and ocean, the toxic ocean gradually neutralized. Considering these tight conditions towards the emergence of life, the birth of life progressed on the tightrope of the Hadean Earth.

  9. The early evolution of southwestern Pennsylvania's regional math/science collaborative from the leadership perspective

    NASA Astrophysics Data System (ADS)

    Bunt, Nancy R.

    Designed as a regional approach to the coordination of efforts and focusing of resources in fragmented southwestern Pennsylvania, the Collaborative's story is narrated by its founding director. Drawing from office archives, including letters of invitation, meeting notes, and participant evaluations of each event, the study describes the genesis of the Collaborative. It begins with identification of the problem and the resulting charge by a founding congress. It details the building of an organizational framework, the creation of a shared vision, the development of a blueprint for action, and the decision-making involved in determining how to strengthen mathematics and science education in the region. The study notes several influences on the Collaborative's leadership. Considering the role of other collaboratives, the study notes that knowledge of the Los Angeles Educational Partnership's LA SMART jump-started the Collaborative's initial planning process. Knowledge of San Francisco's SEABA influenced the size and naming of the Collaborative's Journal. Fred Newmann's definition of authentic instruction, learning and assessment are reflected in the shared vision and belief statements of the Collaborative. The five disciplines of Peter Senge influenced the nature of the organizational framework as well as the day-to-day operations of the Collaborative. The study also notes that the five organizational tensions identified in Ann Lieberman's work on "intentional learning communities" were present in every aspect of the evolution of the Collaborative. The study suggests that leaders of evolving collaboratives: (1) engage all relevant stakeholders in assessing the current situation and defining a desired future state, (2) take advantage of the lessons learned by others and the resources available at the state and national levels to design strategies and build action plans, (3) model the practices to be inspired in the learning community, (4) constantly gather feedback on

  10. Gravitational collapse and the thermal evolution of low-metallicity gas clouds in the early Universe

    NASA Astrophysics Data System (ADS)

    Chiaki, Gen; Yoshida, Naoki; Hirano, Shingo

    2016-08-01

    We study gravitational collapse of low-metallicity gas clouds and the formation of protostars by three-dimensional hydrodynamic simulations. Grain growth, non-equilibrium chemistry, molecular cooling, and chemical heating are solved in a self-consistent manner for the first time. We employ the realistic initial conditions for the abundances of metal and dust, and the dust size distribution obtained from recent Population III supernova calculations. We also introduce the state-of-the-art particle splitting method based on the Voronoi tessellation and achieve an extremely high mass resolution of ˜ 10-5 M⊙ (10 Earth masses) in the central region. We follow the thermal evolution of several clouds with various metallicities. We show that the condition for cloud fragmentation depends not only on the gas metallicity but also on the collapse timescale. In many cases, the cloud fragmentation is prevented by the chemical heating owing to molecular hydrogen formation even though dust cooling becomes effective. Meanwhile, in several cases, efficient OH and H2O cooling promotes the cloud elongation, and then cloud "filamentation" is driven by dust thermal emission as a precursor of eventual fragmentation. While the filament fragmentation is driven by rapid gas cooling with metallicity ≳ 10-5 Z⊙, fragmentation occurs in a different manner by the self-gravity of a circumstellar disk with metallicity ≲ 10-5 Z⊙. We use a semi-analytic model to estimate the number fraction of the clouds which undergo the filament fragmentation to be 20-40% with metallicity 10-5-10-4 Z⊙. Overall, our simulations show a viable formation path of the recently discovered Galactic low-mass stars with extremely small metallicities.

  11. Early evolution of the lungfish pectoral fin endoskeleton: evidence from the Middle Devonian (Givetian) Pentlandia macroptera

    NASA Astrophysics Data System (ADS)

    Jude, Emma; Johanson, Zerina; Kearsley, Anton; Friedman, Matt

    2014-08-01

    As the closest living relatives of tetrapods, lungfishes are frequently used as extant models for exploring the fin-to-limb transition. These studies have generally given little consideration to fossil taxa. This is because although lungfish fins are relatively common in the fossil record, the internal structure of these fins is virtually unknown. Information on pectoral-fin endoskeletons in fossil representatives of Dipnomorpha (the lungfish total group) is limited to poorly preserved remains in the lungfish Dipterus and Conchopoma and more complete material in the porolepiform Glyptolepis. Here we describe a well-preserved pectoral-fin endoskeleton in the Middle Devonian (Givetian) lungfish Pentlandia macroptera from the John O’Groats fish bed, Caithness, northeastern Scotland. The skeleton is in association with a cleithrum and clavicle, and consists of a series of at least eight mesomeres. Extensive series of preaxial and postaxial radials are present. Some of the radials are jointed, but none branch. No mesomere articulates with multiple radials on either its pre- or post-axial face. The first two mesomeres, corresponding to the humerus and ulna, bear well-developed axial processes. Uniquely among dipnomorphs, a distinct ossification centre corresponding to the radius is present in Pentlandia. A review of anatomy and development of the pectoral-fin endoskeleton in the living Neoceratodus is presented based on cleared and stained material representing different size stages. These developmental data, in conjunction with new details of primitive lungfish conditions based on Pentlandia, highlight many of the derived features of the pectoral-fin skeleton of Neoceratodus, and clarify patterns of appendage evolution within the dipnomorphs more generally.

  12. Unresolved problems on the origin and early evolution of land plants.

    PubMed

    Bennici, Andrea

    2007-01-01

    The origin of land plants or embryophytes from the Charophyceae is generally accepted today by the botanists. In fact, numerous morphological, cytological, ultrastructural, biochemical and molecular characters are shared in these organisms. A fundamental problem is still constituted by the evolution of the sporophyte, i.e. the appearance of two different phase cycles (gametophyte/sporophyte alternance), although two theories ("antithetic" and "homologous") try to explain this evolutionary event.However, another phylogenetic dilemma is represented, in my opinion, either by the formation of bryophytes or by the transition from these first land plants to the pteridophytes, considering them at whole organism level. The bryophyte gametophyte is the most elaborate of the land plants. It presents several complex characters, principally the growth developmental form, the appearance of multicellular sex organs, antheridia and archegonia. Also the sporophyte shows a complicated structure that is not found in the other land plants or tracheophytes. The sporangium, in particular, exhibits some intricate morphological traits such as the peristome of true mosses for spore dispersion, the elaters of liverworts and the indeterminate growth in the hornworts. The pteridophytes are represented especially by their dominant sporophyte. This latter has the capacity to produce multiple sporangia and, in many cases, two kinds of spores which develop in male and female gametophyte (heterosporous pteridophytes). Another important characteristic of this sporophyte is its ability to become independent of the gametophyte. However, one of the most innovative character is the formation of true vascular elements (xylem and phloem). All these very large evolutionary jumps are discussed on the basis of the phyletic gradualistic neo-Darwinian theory and the punctuated equilibrium theory of Eldredge and Gould. In this context other genetic evolutionary mechanisms are also considered.Nevertheless, the

  13. Early Evolution of the Main Belt Informed by the Compositional Diversity of Basaltic Asteroids

    NASA Astrophysics Data System (ADS)

    Leith, Thomas; Moskovitz, Nicholas; Mayne, Rhiannon; DeMeo, Francesca; Takir, Driss

    2015-11-01

    We present near-infrared (0.78-2.45 micron) reflectance spectra for eight outer main belt (a > 2.5 AU) asteroids that have been taxonomically classified as V-types based on visible wavelength data. Three of these objects are spectrally distinct from all classifications in the Bus-DeMeo spectral catalogue, and thus could represent either spectral end members of the V-type taxonomic class or a small population of a new spectral type. The remainder of the sample are classified as V- or R-type. All of these asteroids are dynamically distinct from the Vestoid family, implying that they originated from differentiated planetesimals which have since been destroyed or ejected from the solar system. The 1- and 2-μm band centers of all objects, determined using Modified Gaussian Model fits, were compared to those of 47 Vestoids and fifteen HED meteorites of known composition. Formulas relating Band 1 and Band 2 centers to the pyroxene mineralogies of these asteroids were derived from the sample of HED meteorites and used to determine the Fs numbers of all asteroids. The Fs numbers of the five outer belt V- and R-type asteroids are, on average, between five and ten molar percent lower than those of the Vestoids, implying that these objects formed in a more reducing environment than Vesta. Given the complex evolution of oxygen fugacity in the solar nebula, these compositional results suggest that these outer belt basaltic asteroids formed either interior to Vesta and were later scattered to the outer belt or formed at a later epoch than Vesta.

  14. Evolution of time-keeping mechanisms: early emergence and adaptation to photoperiod

    PubMed Central

    Hut, R. A.; Beersma, D. G. M.

    2011-01-01

    Virtually all species have developed cellular oscillations and mechanisms that synchronize these cellular oscillations to environmental cycles. Such environmental cycles in biotic (e.g. food availability and predation risk) or abiotic (e.g. temperature and light) factors may occur on a daily, annual or tidal time scale. Internal timing mechanisms may facilitate behavioural or physiological adaptation to such changes in environmental conditions. These timing mechanisms commonly involve an internal molecular oscillator (a ‘clock’) that is synchronized (‘entrained’) to the environmental cycle by receptor mechanisms responding to relevant environmental signals (‘Zeitgeber’, i.e. German for time-giver). To understand the evolution of such timing mechanisms, we have to understand the mechanisms leading to selective advantage. Although major advances have been made in our understanding of the physiological and molecular mechanisms driving internal cycles (proximate questions), studies identifying mechanisms of natural selection on clock systems (ultimate questions) are rather limited. Here, we discuss the selective advantage of a circadian system and how its adaptation to day length variation may have a functional role in optimizing seasonal timing. We discuss various cases where selective advantages of circadian timing mechanisms have been shown and cases where temporarily loss of circadian timing may cause selective advantage. We suggest an explanation for why a circadian timing system has emerged in primitive life forms like cyanobacteria and we evaluate a possible molecular mechanism that enabled these bacteria to adapt to seasonal variation in day length. We further discuss how the role of the circadian system in photoperiodic time measurement may explain differential selection pressures on circadian period when species are exposed to changing climatic conditions (e.g. global warming) or when they expand their geographical range to different latitudes or

  15. The evolution of the equatorial thermocline and the early Pliocene El Padre mean state

    NASA Astrophysics Data System (ADS)

    Ford, Heather L.; Ravelo, A. Christina; Dekens, Petra S.; LaRiviere, Jonathan P.; Wara, Michael W.

    2015-06-01

    The tropical Pacific thermocline strength, depth, and tilt are critical to tropical mean state and variability. During the early Pliocene (~3.5 to 4.5 Ma), the Eastern Equatorial Pacific (EEP) thermocline was deeper and the cold tongue was warmer than today, which resulted in a mean state with a reduced zonal sea surface temperature gradient or El Padre. However, it is unclear whether the deep thermocline was a local feature of the EEP or a basin-wide condition with global implications. Our measurements of Mg/Ca of Globorotalia tumida in a western equatorial Pacific site indicate Pliocene subsurface temperatures warmer than today; thus, El Padre included a basin-wide thermocline that was relatively warm, deep, and weakly tilted. At ~4 Ma, thermocline steepening was coupled to cooling of the cold tongue. Since ~4 Ma, the basin-wide thermocline cooled/shoaled gradually, with implications for thermocline feedbacks in tropical dynamics and the interpretation of TEX86-derived temperatures.

  16. Epigenetic reprogramming of fallopian tube fimbriae in BRCA mutation carriers defines early ovarian cancer evolution.

    PubMed

    Bartlett, Thomas E; Chindera, Kantaraja; McDermott, Jacqueline; Breeze, Charles E; Cooke, William R; Jones, Allison; Reisel, Daniel; Karegodar, Smita T; Arora, Rupali; Beck, Stephan; Menon, Usha; Dubeau, Louis; Widschwendter, Martin

    2016-01-01

    The exact timing and contribution of epigenetic reprogramming to carcinogenesis are unclear. Women harbouring BRCA1/2 mutations demonstrate a 30-40-fold increased risk of high-grade serous extra-uterine Müllerian cancers (HGSEMC), otherwise referred to as 'ovarian carcinomas', which frequently develop from fimbrial cells but not from the proximal portion of the fallopian tube. Here we compare the DNA methylome of the fimbrial and proximal ends of the fallopian tube in BRCA1/2 mutation carriers and non-carriers. We show that the number of CpGs displaying significant differences in methylation levels between fimbrial and proximal fallopian tube segments are threefold higher in BRCA mutation carriers than in controls, correlating with overexpression of activation-induced deaminase in their fimbrial epithelium. The differentially methylated CpGs accurately discriminate HGSEMCs from non-serous subtypes. Epigenetic reprogramming is an early pre-malignant event integral to BRCA1/2 mutation-driven carcinogenesis. Our findings may provide a basis for cancer-preventative strategies. PMID:27216078

  17. The Late Permian - Early Triassic Evolution of the Western Barents Sea

    NASA Astrophysics Data System (ADS)

    Planke, S.; Svensen, H.; Faleide, J.; Myklebust, R.

    2013-12-01

    The Permian-Triassic boundary was temporarily associated with formation of the Siberian Traps Large Igneous Province. Major Late Permian and Early Triassic subsidence is documented by seismic reflection data in the East Barents Basin. Further west, basin subsidence and an abrupt change from carbonate and evaporite deposition to clastic sedimentation is recorded by industry seismic and well data in the south and onshore Svalbard in the north. The Permian-Triassic boundary is commonly not preserved either due to non-deposition or erosion, but could be locally preserved in depocenters. A major northwestward prograding clastic delta sourced from the Uralian hinterland reached the Norwegian (western) part of the Barents Sea in the earliest Triassic (Induan). We suggest that the large-scale changes in paleoenviroment, vertical motions, and sedimentary processes in the Barents Sea region were strongly influenced by large-scale changes in mantle dynamics and paleoclimate caused by the Siberian Traps igneous event. By analogy with other Large Igneous Provinces, such as the North Atlantic Volcanic Province, regional uplift and subsidence associated with a rising mantle plume may precede the arrival of the plume at the base of the lithosphere with 10's of millions of years. In contrast, the paleoenvironmental changes and the associated extinction were mainly caused by rapid intrusion of magma into sedimentary basins and voluminous igneous eruptions.

  18. Early evolution of photosynthesis: Clues from nitrogenase and chlorophyll iron proteins

    SciTech Connect

    Burke, D.H.; Hearst, J.E.; Sidow, A. )

    1993-08-01

    Chlorophyll (Chl) is often viewed as having preceded bacteriochlorophyll (BChl) as the primary photoreceptor pigment in early photosynthetic systems because synthesis of Chl requires one fewer enzymatic reduction than does synthesis of BChl. The authors have conducted statistical DNA sequence analyses of the two reductases involved in Chl and BChl synthesis, protochlorophyllide reductase and chlorin reductase. Both are three-subunit enzymes in which each subunit from one reductase shares significant amino acid identity with a subunit of the other, indicating that the two enzymes are derived from a common three-subunit ancestral reductase. The [open quotes]chlorophyll iron protein[close quotes] subunits, encoded by the bchL and bchX genes in the purple bacterium Rhodobacter capsulatus, also share amino acid sequence identity with the nitrogenase iron protein, encoded by nifH. When nitrogenase iron proteins are used as outgroups, the chlorophyll iron protein tree is rooted on the chlorin reductase lineage. This rooting suggests that the last common ancestor of all extant photosynthetic eubacteria contained BChl, not Chl, in its reaction center, and implies that Chl-containing reaction centers were a late invention unique to the cyanobacteria/chloroplast lineage. 48 refs., 4 figs., 2 tabs.

  19. Modeling spontaneous activity across an excitable epithelium: Support for a coordination scenario of early neural evolution

    PubMed Central

    de Wiljes, Oltman O.; van Elburg, Ronald A. J.; Biehl, Michael; Keijzer, Fred A.

    2015-01-01

    Internal coordination models hold that early nervous systems evolved in the first place to coordinate internal activity at a multicellular level, most notably the use of multicellular contractility as an effector for motility. A recent example of such a model, the skin brain thesis, suggests that excitable epithelia using chemical signaling are a potential candidate as a nervous system precursor. We developed a computational model and a measure for whole body coordination to investigate the coordinative properties of such excitable epithelia. Using this measure we show that excitable epithelia can spontaneously exhibit body-scale patterns of activation. Relevant factors determining the extent of patterning are the noise level for exocytosis, relative body dimensions, and body size. In smaller bodies whole-body coordination emerges from cellular excitability and bidirectional excitatory transmission alone. Our results show that basic internal coordination as proposed by the skin brain thesis could have arisen in this potential nervous system precursor, supporting that this configuration may have played a role as a proto-neural system and requires further investigation. PMID:26441620

  20. Early evolution of photoevaporating protoplanetary disks: mid-infrared spectra of the Orion Nebula proplyds

    NASA Astrophysics Data System (ADS)

    Kassis, Marc; Shuping, Ralph; Morris, Mark; Smith, Nathan; Bally, John

    2008-08-01

    We plan to acquire low-resolution spectra at mid-infrared wavelengths of Orion Nebula protoplanetary disk systems using a highly sensitive spectrograph at the Gemini Observatory. Our goal is to determine the grain properties of proto-planetary disks associated with stars having ages <2 Myr. The proposed observations include sampling the emission from proto-planetary disks that are farther away from Trapezium and that we suspect harbor disks with relatively larger grains than the disks very near the Trapezium that we have previously studied at mid-infrared wavelengths. Observed differences in the grain properties will enable us to investigate early critical phases in the development of these disks. To determine the grain properties, low resolution mid-infrared spectra will be used to detect the Si-O stretch band of silicates at 9.7 microns, which may be modeled to determine basic characteristics of the silicate grains including shape, typical size, and crystallinity. These observations will enable us to constrain current grain and disk models for photo-evaporating disks at a range of radii from an external UV source and further our investigations of proto-planetary disks in Orion.

  1. Early evolution of photoevaporating protoplanetary disks: mid-infrared spectra of the Orion Nebula proplyds

    NASA Astrophysics Data System (ADS)

    Kassis, Marc; Y Shuping, Ralph; Morris, Mark; Smith, Nathan; Bally, John

    2007-08-01

    We plan to acquire low-resolution spectra at mid-infrared wavelengths of Orion Nebula proto-planetary disk systems using a highly sensitive spectrograph at the Gemini Observatory. Our goal is to determine the grain properties of proto-planetary disks associated with stars having ages <2 Myr. The proposed observations include sampling the emission from proto-planetary disks that are farther away from θonec and that we suspect harbor disks with relatively larger grains than the disk we have previously studied at mid-infrared wavelengths. Observed differences in the grain properties will enable us to investigate early critical phases in the development of these disks. To determine the grain properties, low resolution mid-infrared spectra will be used to detect the Si-O stretch band of silicates at 9.7 micron, which may be modeled to determine basic characteristics of the silicate grains including shape, typical size, and crystallinity. These observations will enable us to constrain current grain and disk models for photo-evaporating disks and further our investigations of proto- planetary disks in Orion.

  2. The Gamburtsev mountains and the origin and early evolution of the Antarctic Ice Sheet.

    PubMed

    Bo, Sun; Siegert, Martin J; Mudd, Simon M; Sugden, David; Fujita, Shuji; Xiangbin, Cui; Yunyun, Jiang; Xueyuan, Tang; Yuansheng, Li

    2009-06-01

    Ice-sheet development in Antarctica was a result of significant and rapid global climate change about 34 million years ago. Ice-sheet and climate modelling suggest reductions in atmospheric carbon dioxide (less than three times the pre-industrial level of 280 parts per million by volume) that, in conjunction with the development of the Antarctic Circumpolar Current, led to cooling and glaciation paced by changes in Earth's orbit. Based on the present subglacial topography, numerical models point to ice-sheet genesis on mountain massifs of Antarctica, including the Gamburtsev mountains at Dome A, the centre of the present ice sheet. Our lack of knowledge of the present-day topography of the Gamburtsev mountains means, however, that the nature of early glaciation and subsequent development of a continental-sized ice sheet are uncertain. Here we present radar information about the base of the ice at Dome A, revealing classic Alpine topography with pre-existing river valleys overdeepened by valley glaciers formed when the mean summer surface temperature was around 3 degrees C. This landscape is likely to have developed during the initial phases of Antarctic glaciation. According to Antarctic climate history (estimated from offshore sediment records) the Gamburtsev mountains are probably older than 34 million years and were the main centre for ice-sheet growth. Moreover, the landscape has most probably been preserved beneath the present ice sheet for around 14 million years. PMID:19494912

  3. Epigenetic reprogramming of fallopian tube fimbriae in BRCA mutation carriers defines early ovarian cancer evolution

    PubMed Central

    Bartlett, Thomas E.; Chindera, Kantaraja; McDermott, Jacqueline; Breeze, Charles E.; Cooke, William R.; Jones, Allison; Reisel, Daniel; Karegodar, Smita T.; Arora, Rupali; Beck, Stephan; Menon, Usha; Dubeau, Louis; Widschwendter, Martin

    2016-01-01

    The exact timing and contribution of epigenetic reprogramming to carcinogenesis are unclear. Women harbouring BRCA1/2 mutations demonstrate a 30–40-fold increased risk of high-grade serous extra-uterine Müllerian cancers (HGSEMC), otherwise referred to as ‘ovarian carcinomas', which frequently develop from fimbrial cells but not from the proximal portion of the fallopian tube. Here we compare the DNA methylome of the fimbrial and proximal ends of the fallopian tube in BRCA1/2 mutation carriers and non-carriers. We show that the number of CpGs displaying significant differences in methylation levels between fimbrial and proximal fallopian tube segments are threefold higher in BRCA mutation carriers than in controls, correlating with overexpression of activation-induced deaminase in their fimbrial epithelium. The differentially methylated CpGs accurately discriminate HGSEMCs from non-serous subtypes. Epigenetic reprogramming is an early pre-malignant event integral to BRCA1/2 mutation-driven carcinogenesis. Our findings may provide a basis for cancer-preventative strategies. PMID:27216078

  4. Stable isotope evidence for an amphibious phase in early proboscidean evolution

    PubMed Central

    Liu, Alexander G. S. C.; Seiffert, Erik R.; Simons, Elwyn L.

    2008-01-01

    The order Proboscidea includes extant elephants and their extinct relatives and is closely related to the aquatic sirenians (manatees and dugongs) and terrestrial hyracoids (hyraxes). Some analyses of embryological, morphological, and paleontological data suggest that proboscideans and sirenians shared an aquatic or semiaquatic common ancestor, but independent tests of this hypothesis have proven elusive. Here we test the hypothesis of an aquatic ancestry for advanced proboscideans by measuring δ18O in tooth enamel of two late Eocene proboscidean genera, Barytherium and Moeritherium, which are sister taxa of Oligocene-to-Recent proboscideans. The combination of low δ18O values and low δ18O standard deviations in Barytherium and Moeritherium matches the isotopic pattern seen in aquatic and semiaquatic mammals, and differs from that of terrestrial mammals. δ13C values of these early proboscideans suggest that both genera are likely to have consumed freshwater plants, although a component of C3 terrestrial vegetation cannot be ruled out. The simplest explanation for the combined evidence from isotopes, dental functional morphology, and depositional environments is that Barytherium and Moeritherium were at least semiaquatic and lived in freshwater swamp or riverine environments, where they grazed on freshwater vegetation. These results lend new support to the hypothesis that Oligocene-to-Recent proboscideans are derived from amphibious ancestors. PMID:18413605

  5. Stable isotope evidence for an amphibious phase in early proboscidean evolution.

    PubMed

    Liu, Alexander G S C; Seiffert, Erik R; Simons, Elwyn L

    2008-04-15

    The order Proboscidea includes extant elephants and their extinct relatives and is closely related to the aquatic sirenians (manatees and dugongs) and terrestrial hyracoids (hyraxes). Some analyses of embryological, morphological, and paleontological data suggest that proboscideans and sirenians shared an aquatic or semiaquatic common ancestor, but independent tests of this hypothesis have proven elusive. Here we test the hypothesis of an aquatic ancestry for advanced proboscideans by measuring delta(18)O in tooth enamel of two late Eocene proboscidean genera, Barytherium and Moeritherium, which are sister taxa of Oligocene-to-Recent proboscideans. The combination of low delta(18)O values and low delta(18)O standard deviations in Barytherium and Moeritherium matches the isotopic pattern seen in aquatic and semiaquatic mammals, and differs from that of terrestrial mammals. delta(13)C values of these early proboscideans suggest that both genera are likely to have consumed freshwater plants, although a component of C(3) terrestrial vegetation cannot be ruled out. The simplest explanation for the combined evidence from isotopes, dental functional morphology, and depositional environments is that Barytherium and Moeritherium were at least semiaquatic and lived in freshwater swamp or riverine environments, where they grazed on freshwater vegetation. These results lend new support to the hypothesis that Oligocene-to-Recent proboscideans are derived from amphibious ancestors. PMID:18413605

  6. Early-mid-Cretaceous evolution in Tethyan reef communities and sea level

    SciTech Connect

    Scott, R.W.

    1988-01-01

    The replacement of corals by rudists in Early Cretaceous reefal communities spanned a 30-m.y. period when sea level rose and drowned continental shelves. During this time corals formed communities in the deeper parts of reefs and rudists occupied the shallow, high-energy habitats. By Aptian time rudists dominated reefs that fringed interior shelf basins and corals formed reefs with rudists on the outer shelf margins. By late Albian coral communities had virtually disappeared, presumably because of complex environmental changes and cycles of organic productivity. Two important events of eustatic sea level rise are represented by unconformities separating carbonate depositional sequences on the Arabian platform that correlate with sequence boundaries on the Gulf Coast platform. Graphic correlation techniques test the synchroneity of these events. A composite standard time scale dates these sea level rises at 115.8 Ma and 94.6 Ma; a third, intra-Albian event at 104.3 Ma is present in many places and may also be eustatic. Associated with these sea level rises were apparent changes in ocean water chemistry as evidenced by changes in isotopes and trace elements, where diagenetic effects can be discounted. During this time the climate became more humid and atmospheric CO/sub 2/ increased. The concomitant environmental changes in the oceanic conditions presumably stressed the deeper coral communities on reefs. The emergence of rudists as reef contributors had a profound effect on Late Cretaceous depositional conditions and the development of hydrocarbon reservoirs.

  7. Early-mid-Cretaceous evolution in Tethyan reef communities and sea level

    SciTech Connect

    Scott, R.W.

    1988-02-01

    The replacement of corals by rudists in Early Cretaceous reefal communities spanned a 30-m.y. period when sea level rose and drowned continental shelves. During this time corals formed communities in the deeper parts of reefs and rudists occupied the shallow, high-energy habitats. By Aptian time rudists dominated reefs that fringed interior shelf basins and corals formed reefs with rudists on the outer shelf margins. By late Albian coral communities had virtually disappeared, presumably because of complex environmental changes and cycles of organic productivity. Two important events of eustatic sea level rise are represented by unconformities separating carbonate depositional sequences on the Arabian platform that correlate with sequence boundaries on the Gulf Coast platform. Graphic correlation techniques test the synchroneity of these events. A composite standard time scale dates these sea level rises at 115.8 Ma and 94.6 Ma; a third, intra-Albian event at 104.3 Ma is present in many places and may also be eustatic. Associated with these sea level rises were apparent changes in ocean water chemistry as evidenced by changes in isotopes and trace elements, where diagenetic effects can be discounted. During this time the climate became more humid and atmospheric CO/sub 2/ increased. The concomitant environmental changes in the oceanic conditions presumably stressed the deeper coral communities on reefs. The emergence of rudists as reef contributors had a profound effect on Late Cretaceous depositional conditions and the development of hydrocarbon reservoirs.

  8. Laparoscopic cholecystectomy: evolution, early results, and impact on nonsurgical gallstone therapies.

    PubMed

    Brandon, J C; Velez, M A; Teplick, S K; Mueller, P R; Rattner, D W; Broadwater, J R; Lang, N P; Eidt, J F

    1991-08-01

    Laparoscopic cholecystectomy, a surgical technique first performed in France, has gained widespread acceptance among surgeons in the United States. The abdominal cavity is inflated by carbon dioxide, a video monitor is inserted via a laparoscope placed periumbilically, and the gallbladder is freed and removed from the liver bed by using small subcostal ports for access and dissection. Intraoperative cholangiography is routinely performed, but uncertainty exists about how best to manage choledocholithiasis. Compared with traditional cholecystectomy, initial reports describing laparoscopic cholecystectomy cite shorter recovery times because no large incisions are made, thus potentially reducing the cost and morbidity of cholecystectomy. A survey of 614 early cases supports these claims, with a reported complication rate of 1.5% and quick resumption of normal activities by patients. Because of its promise for reduced morbidity, laparoscopic cholecystectomy is challenging open cholecystectomy as the therapeutic gold standard for symptomatic cholelithiasis. Thus, the standard to which the nonsurgical gallstone therapies, such as lithotripsy and contact dissolution, will be compared may shift to laparoscopic cholecystectomy. As the laparoscopic complications are similar to those of traditional cholecystectomy, such as abscesses and bile leaks, their percutaneous treatment should not change. PMID:1830188

  9. A Time Scale for Major Events in Early Mars Crustal Evolution

    NASA Technical Reports Server (NTRS)

    Frey, Herbert V.

    2004-01-01

    The population of visible and buried impact basins > 200 km diameter revealed by high resolution gridded MOLA data and the cumulative frequency curves derived for these pvide a basis for a chronology of major events in early martian history. The relative chronology can be given in terms of N(200) crater retention ages; 'absolute ages' can be assigued using the Hartmann-Neukum (H&N) model chronology. In terms of billions of H&N years, the crustal dichotomy formed by large impact basins at 4.12 +/- 0.08 BYA (N(200) = 3.0-3.2) and the global magnetic field died at about or slightly before the same time (4.15 +/- 0.08 BYA (N(200) = 3.5). In this chronology, the buried lowlands are approx. 120 my younger than the buried highlands, approx. 160 my younger than the highlands overall and approx. 340 my younger than the oldest crater retention surface we see, defined by the largest impact basins.

  10. Two spinal cords in birds: novel insights into early avian evolution

    PubMed Central

    Woodbury, C. J.

    1998-01-01

    Birds can be subdivided into two large superordinal assemblages based on differences in the dorsal horn of the spinal grey matter. Palaeognaths (i.e. ratites and tinamous), along with a few other orders of neognathous birds, exhibit the primitive dorsal horn state characteristic of other amniotes wherein cutaneous nerves form a single map of the body surface across the dorsal horn. In contrast, the vast majority of neognaths exhibit a novel, distinctly bifid dorsal horn wherein cutaneous nerves form not one, but two separate maps of the skin, each lying side-by-side. This unusual dorsal horn organization, which has been highly conserved and represents the derived state in birds, may identify a novel, major avian clade. These findings shed new light on historically problematic taxa and the early evolutionary branching sequence among living birds. Most notably, they reveal that the traditional orders Gruiformes, Columbiformes, Cuculiformes and Piciformes are unnatural assemblages. Further, in addition to palaeognaths, these findings suggest that most gruiforms, including buttonquails and mesites, as well as pigeons, cuckoos, woodpeckers and songbirds, represent ancient lineages whose ancestry predates the majority of 'modern' birds. The phylogeny of living birds may thus be likened more to a dense bush than the traditional tree, with more than half of all living species arising from a basal side branch.

  11. Further constraining galaxy evolution models through the size function of SDSS early-type galaxies

    NASA Astrophysics Data System (ADS)

    Shankar, Francesco; Marulli, Federico; Bernardi, Mariangela; Boylan-Kolchin, Michael; Dai, Xinyu; Khochfar, Sadegh

    2010-06-01

    We discuss how the effective radius Re function (ERF) recently worked out by Bernardi et al. represents a new testbed to improve the current understanding of semi-analytic models of galaxy formation. In particular, we show here that a detailed hierarchical model of structure formation can broadly reproduce the correct peak in the size distribution of local early-type galaxies, although it significantly overpredicts the number of very compact and very large galaxies. This in turn is reflected in the predicted size-mass relation, much flatter than the observed one, due to too large (>~3kpc) low-mass galaxies (<1011Msolar), and to a non-negligible fraction of compact (<~0.5-1kpc) and massive galaxies (>~1011Msolar). We also find that the latter discrepancy is smaller than previously claimed, and limited to only ultra-compact (Re <~ 0.5kpc) galaxies when considering elliptical-dominated samples. We explore several causes behind these effects. We conclude that the former problem might be linked to the initial conditions, given that large and low-mass galaxies are present at all epochs in the model. The survival of compact and massive galaxies might instead be linked to their very old ages and peculiar merger histories. Overall, knowledge of the galactic stellar mass and size distributions allows a better understanding of where and how to improve models.

  12. Oxygen as a Driver of Early Arthropod Micro-Benthos Evolution

    PubMed Central

    Williams, Mark; Vannier, Jean; Corbari, Laure; Massabuau, Jean-Charles

    2011-01-01

    Background We examine the physiological and lifestyle adaptations which facilitated the emergence of ostracods as the numerically dominant Phanerozoic bivalve arthropod micro-benthos. Methodology/Principal Findings The PO2 of modern normoxic seawater is 21 kPa (air-equilibrated water), a level that would cause cellular damage if found in the tissues of ostracods and much other marine fauna. The PO2 of most aquatic breathers at the cellular level is much lower, between 1 and 3 kPa. Ostracods avoid oxygen toxicity by migrating to waters which are hypoxic, or by developing metabolisms which generate high consumption of O2. Interrogation of the Cambrian record of bivalve arthropod micro-benthos suggests a strong control on ecosystem evolution exerted by changing seawater O2 levels. The PO2 of air-equilibrated Cambrian-seawater is predicted to have varied between 10 and 30 kPa. Three groups of marine shelf-dwelling bivalve arthropods adopted different responses to Cambrian seawater O2. Bradoriida evolved cardiovascular systems that favoured colonization of oxygenated marine waters. Their biodiversity declined during intervals associated with black shale deposition and marine shelf anoxia and their diversity may also have been curtailed by elevated late Cambrian (Furongian) oxygen-levels that increased the PO2 gradient between seawater and bradoriid tissues. Phosphatocopida responded to Cambrian anoxia differently, reaching their peak during widespread seabed dysoxia of the SPICE event. They lacked a cardiovascular system and appear to have been adapted to seawater hypoxia. As latest Cambrian marine shelf waters became well oxygenated, phosphatocopids went extinct. Changing seawater oxygen-levels and the demise of much of the seabed bradoriid micro-benthos favoured a third group of arthropod micro-benthos, the ostracods. These animals adopted lifestyles that made them tolerant of changes in seawater O2. Ostracods became the numerically dominant arthropod micro-benthos of

  13. COSMIC EVOLUTION OF VIRIAL AND STELLAR MASS IN MASSIVE EARLY-TYPE GALAXIES

    SciTech Connect

    Lagattuta, David J.; Fassnacht, Christopher D.; Auger, Matthew W.; Marshall, Philip J.; Bradac, Marusa; Treu, Tommaso; Gavazzi, Raphael; Schrabback, Tim; Faure, Cecile; Anguita, Timo

    2010-06-20

    We measure the average mass properties of a sample of 41 strong gravitational lenses at moderate redshift (z {approx} 0.4-0.9) and present the lens redshift for six of these galaxies for the first time. Using the techniques of strong and weak gravitational lensing on archival data obtained from the Hubble Space Telescope, we determine that the average mass overdensity profile of the lenses can be fit with a power-law profile ({Delta}{Sigma} {proportional_to} R {sup -0.86{+-}0.16}) that is within 1{sigma} of an isothermal profile ({Delta}{Sigma} {proportional_to} R {sup -1}) with velocity dispersion {sigma}{sub v} = 260 {+-} 20 km s{sup -1}. Additionally, we use a two-component de Vaucouleurs + Navarro-Frenk-White (NFW) model to disentangle the total mass profile into separate luminous and dark matter components and determine the relative fraction of each component. We measure the average rest frame V-band stellar mass-to-light ratio (Y{sub V} = 4.0 {+-} 0.6 h M{sub sun}/L{sub sun}) and virial mass-to-light ratio ({tau}{sub V} = 300 {+-} 90 h M{sub sun}/L{sub sun}) for our sample, resulting in a virial-to-stellar mass ratio of M{sub vir}/M{sub *} = 75 {+-} 25. Relaxing the NFW assumption, we estimate that changing the inner slope of the dark matter profile by {approx}20% yields a {approx}30% change in stellar mass-to-light ratio. Finally, we compare our results to a previous study using low-redshift lenses to understand how galaxy mass profiles evolve over time. We investigate the evolution of M{sub vir}/M{sub *}(z) = {alpha}(1 + z){sup {beta}}, and find best-fit parameters of {alpha} = 51 {+-} 36 and {beta} = 0.9 {+-} 1.8, constraining the growth of virial-to-stellar mass ratio over the last {approx}7 Gyr. We note that, by using a sample of strong lenses, we are able to constrain the growth of M{sub vir}/M{sub *}(z) without making any assumptions about the initial mass function of the stellar population.

  14. Magmatic evolution of the Early Pliocene Etrüsk stratovolcano, Eastern Anatolian Collision Zone, Turkey

    NASA Astrophysics Data System (ADS)

    Oyan, Vural; Keskin, Mehmet; Lebedev, Vladimir A.; Chugaev, Andrey V.; Sharkov, Evgenii V.

    2016-07-01

    basalt lavas underlying the volcano, via the AFC process, and experienced at least two major magma replenishment episodes at 4.1 Ma and 3.8 Ma during the magma chamber evolution.

  15. On the position of Archigetes and its bearing on the early evolution of the tapeworms.

    PubMed

    Olson, P D; Poddubnaya, L G; Littlewood, D T J; Scholz, T

    2008-08-01

    The tapeworm Archigetes sieboldi Leuckart, 1878 (Platyhelminthes: Cestoda: Caryophyllidea) has been cited as a likely representative of the "protocestode" condition, owing to its lack of segmentation and ability to attain sexual maturity in the invertebrate host (aquatic oligochaetes). The idea has been variously amplified or rejected in the literature, although the actual phylogenetic position of the species has not been investigated until now. New collections of Archigetes sp. from both its vertebrate and invertebrate hosts provided the opportunity to estimate its phylogenetic position with the use of molecular systematics, while prompting new analyses aimed at assessing the early diversification of the Cestoda. Additional collections representing the Amphilinidea, Caryophyllidea, and Gyrocotylidea were combined with published gene sequences to construct data sets of complete 18S (110 taxa) and partial (D1-D3) 28S (107 taxa) rDNA sequences, including 8 neodermatan outgroup taxa. Estimates resulting from Bayesian inference, maximum likelihood, and maximum parsimony analyses of the separate and combined data sets supported a derived position of the genus within the Caryophyllidea, and thus reject the idea that Archigetes sp. may exemplify a "primitive" condition. Topological constraint analyses rejected the hypothesis that Archigetes represents the most basal lineage of the Eucestoda, but did not rule out that it could represent the earliest branching taxon of the Caryophyllidea. In all analyses, the Eucestoda were monophyletic and supported basal positions of the nonsegmented Caryophyllidea and Spathebothriidea relative to other major lineages of the Eucestoda, implying that segmentation is a derived feature of the common ancestor of the di- and tetrafossate eucestodes. However, constraint analyses could not provide unequivocal evidence as to the precise branching patterns of the cestodarian, spathebothriidean, and caryophyllidean lineages. Phylogenetic analyses

  16. Early evolution of comet 67P studied with the RPC-LAP onboard Rosetta

    NASA Astrophysics Data System (ADS)

    Miloch, Wojciech; Edberg, Niklas J. T.; Eriksson, Anders I.; Yang, Lei; Paulsson, Joakim J. P.; Wedlund, Cyril Simon; Odelstad, Elias

    2016-07-01

    The Rosetta mission provides the in-situ measurements of a comet that are closest to a comet's aphelion ever made. The Rosetta Plasma Consortium (RPC) is a set of five instruments on board the spacecraft that specialise in the measurements of the plasma environment of comet 67P. One of the instruments is RPC-LAP, which consists of two Langmuir Probes and can measure the density, temperature, and flow speed of the plasma in the vicinity of the comet. At the early stage of the Rosetta mission, when the spacecraft is far from the nucleus of comet 67P, the ion part of the current-voltage characteristics of RPC-LAP1 is dominated by the photoemission current which surpasses the currents from the dilute solar wind plasma. As Rosetta starts orbiting around the nucleus in September 2014, LAP1 picks up signatures of local plasma density enhancements corresponding to variations of water-group ions observed in the vicinity of the comet. With the help of current-voltage characteristics and the spacecraft potential, we identify and characterise in space and time the entering of this coma-dominated plasma. In particular we determine the transition for entering the ion dominated region characterised by the 6-hour variations in the local plasma density due to the comet rotation. This transition manifests as a steep gradient in the density with respect to the distance to the comet nucleus. We discuss these RPC-LAP results together with the corresponding measurements by other instruments to provide a comprehensive picture of the transition.

  17. Evaluating Different Scenarios for the Formation and Early Evolution of the Asteroid Belt

    NASA Astrophysics Data System (ADS)

    O'Brien, David P.; Walsh, Kevin J.

    2014-11-01

    The asteroid belt is dynamically excited, depleted in mass relative to the surface mass density of the rest of the Solar System, and contains numerous diverse taxonomic classes of asteroids that are partly, but not completely, radially mixed. In the 'classical' scenario of Solar System formation, the excitation, depletion and radial mixing of the asteroid belt is best explained by the effect of planetary embryos that are initially present in the primordial asteroid belt region [1-3]. In the more recent 'Grand Tack' scenario proposed by Walsh et al. [4], the early inward-then-outward migration of Jupiter in the gas disk initially depletes, then repopulates the asteroid belt with material scattered from both interior and exterior to Jupiter. Here we will examine in detail the model asteroid distributions resulting from these two scenarios for a range of parameters, and compare them to observational constraints on the current distribution of asteroids in the Solar System. We will also address the possible effects that late-stage planetesimal-driven migration and resonance-crossing of Jupiter and Saturn in the Nice Model [eg. 5,6] may have on the final asteroid distribution.[1] G.W. Wetherill, Icarus 100, 307-325 (1992)[2] J.-M. Petit et al., Icarus 153, 338-347 (2001)[3] D.P. O'Brien t al., Icarus 191, 434-452 (2007)[4] K.J. Walsh et al., Nature 475, 206-209 (2011)[5] K. Tsiganis et al., Nature 435, 459-461 (2005)[6] A. Morbidelli et al., AJ 140, 1391-1401 (2010)

  18. The Completeness of the Fossil Record of Mesozoic Birds: Implications for Early Avian Evolution

    PubMed Central

    Brocklehurst, Neil; Upchurch, Paul; Mannion, Philip D.; O'Connor, Jingmai

    2012-01-01

    Many palaeobiological analyses have concluded that modern birds (Neornithes) radiated no earlier than the Maastrichtian, whereas molecular clock studies have argued for a much earlier origination. Here, we assess the quality of the fossil record of Mesozoic avian species, using a recently proposed character completeness metric which calculates the percentage of phylogenetic characters that can be scored for each taxon. Estimates of fossil record quality are plotted against geological time and compared to estimates of species level diversity, sea level, and depositional environment. Geographical controls on the avian fossil record are investigated by comparing the completeness scores of species in different continental regions and latitudinal bins. Avian fossil record quality varies greatly with peaks during the Tithonian-early Berriasian, Aptian, and Coniacian–Santonian, and troughs during the Albian-Turonian and the Maastrichtian. The completeness metric correlates more strongly with a ‘sampling corrected’ residual diversity curve of avian species than with the raw taxic diversity curve, suggesting that the abundance and diversity of birds might influence the probability of high quality specimens being preserved. There is no correlation between avian completeness and sea level, the number of fluviolacustrine localities or a recently constructed character completeness metric of sauropodomorph dinosaurs. Comparisons between the completeness of Mesozoic birds and sauropodomorphs suggest that small delicate vertebrate skeletons are more easily destroyed by taphonomic processes, but more easily preserved whole. Lagerstätten deposits might therefore have a stronger impact on reconstructions of diversity of smaller organisms relative to more robust forms. The relatively poor quality of the avian fossil record in the Late Cretaceous combined with very patchy regional sampling means