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Sample records for phase evolution originating

  1. The Early Phases of Genetic Code Origin: Conjectures on the Evolution of Coded Catalysis

    NASA Astrophysics Data System (ADS)

    Di Giulio, Massimo

    2003-10-01

    A review of the most significant contributions on the early phases of genetic code origin is presented. After stressing the importance of the key intermediary role played in protein synthesis, by peptidyl-tRNA, which is attributed with a primary function in ancestral catalysis, the general lines leading to the codification of the first amino acids in the genetic code are discussed. This is achieved by means of a model of protoribosome evolution which sees protoribosome as the central organiser of ancestral biosynthesis and the mediator of the encounter between compounds (metabolite-pre-tRNAs) and catalysts (peptidyl-pre-tRNAs). The encounter between peptidyl-pre-tRNA catalysts in protoribosome is favoured by metabolic pre-mRNAs and later resulted (given the high temperature at which this evolution is supposed to have taken place) in the evolution of mRNAs with codons of the type GNS. These mRNAs codified only for those amino acids that the coevolution theory of genetic code origin sees as the precursors of all other amino acids. Some aspects of the model here discussed might be rendered real by the transfer-messenger RNA molecule (tmRNA) which is here considered a molecular fossil of ancestral protein synthesis.

  2. Field driven ferromagnetic phase evolution originating from the domain boundaries in antiferromagnetically coupled perpendicular anitsotropy films

    SciTech Connect

    Jones, Juanita; Hauet, Thomas; Gunther, Christian; Hovorka, Ondrej; Berger, Andreas; Im, Mi-Young; Fischer, Peter; Hellwig, Olav

    2008-05-01

    Strong perpendicular anisotropy systems consisting of Co/Pt multilayer stacks that are antiferromagnetically coupled via thin Ru or NiO layers have been used as model systems to study the competition between local interlayer exchange and long-range dipolar interactions [1,2]. Magnetic Force Microscopy (MFM) studies of such systems reveal complex magnetic configurations with a mix of antiferromagnetic (AF) and ferromagnetic (FM) phases. However, MFM allows detecting surface stray fields only and can interact strongly with the magnetic structure of the sample, thus altering the original domain configuration of interest [3,4]. In the current study they combine magnetometry and state-of-the-art soft X-ray transmission microscopy (MXTM) to investigate the external field driven FM phase evolution originating from the domain boundaries in such antiferromagnetically coupled perpendicular anisotropy films. MXTM allows directly imaging the perpendicular component of the magnetization in an external field at sub 100 nm spatial resolution without disturbing the magnetic state of the sample [5,6]. Here they compare the domain evolution for two similar [Co(4{angstrom})/Pt(7{angstrom})]x-1/{l_brace}Co(4{angstrom})/Ru(9{angstrom})/[Co(4{angstrom})/Pt(7{angstrom})]x-1{r_brace}16 samples with slightly different Co/Pt stack thickness, i.e. slightly different strength of internal dipolar fields. After demagnetization they obtain AF domains with either sharp AF domain walls for the thinner multilayer stacks or 'tiger-tail' domain walls (one dimensional FM phase) for the thicker stacks. When increasing the external field strength the sharp domain walls in the tinner stack sample transform into the one-dimensional FM phase, which then serves as nucleation site for further FM stripe domains that spread out into all directions to drive the system towards saturation. Energy calculations reveal the subtle difference between the two samples and help to understand the observed transition, when

  3. Musical emotions: Functions, origins, evolution

    NASA Astrophysics Data System (ADS)

    Perlovsky, Leonid

    2010-03-01

    Theories of music origins and the role of musical emotions in the mind are reviewed. Most existing theories contradict each other, and cannot explain mechanisms or roles of musical emotions in workings of the mind, nor evolutionary reasons for music origins. Music seems to be an enigma. Nevertheless, a synthesis of cognitive science and mathematical models of the mind has been proposed describing a fundamental role of music in the functioning and evolution of the mind, consciousness, and cultures. The review considers ancient theories of music as well as contemporary theories advanced by leading authors in this field. It addresses one hypothesis that promises to unify the field and proposes a theory of musical origin based on a fundamental role of music in cognition and evolution of consciousness and culture. We consider a split in the vocalizations of proto-humans into two types: one less emotional and more concretely-semantic, evolving into language, and the other preserving emotional connections along with semantic ambiguity, evolving into music. The proposed hypothesis departs from other theories in considering specific mechanisms of the mind-brain, which required the evolution of music parallel with the evolution of cultures and languages. Arguments are reviewed that the evolution of language toward becoming the semantically powerful tool of today required emancipation from emotional encumbrances. The opposite, no less powerful mechanisms required a compensatory evolution of music toward more differentiated and refined emotionality. The need for refined music in the process of cultural evolution is grounded in fundamental mechanisms of the mind. This is why today's human mind and cultures cannot exist without today's music. The reviewed hypothesis gives a basis for future analysis of why different evolutionary paths of languages were paralleled by different evolutionary paths of music. Approaches toward experimental verification of this hypothesis in

  4. Musical emotions: functions, origins, evolution.

    PubMed

    Perlovsky, Leonid

    2010-03-01

    Theories of music origins and the role of musical emotions in the mind are reviewed. Most existing theories contradict each other, and cannot explain mechanisms or roles of musical emotions in workings of the mind, nor evolutionary reasons for music origins. Music seems to be an enigma. Nevertheless, a synthesis of cognitive science and mathematical models of the mind has been proposed describing a fundamental role of music in the functioning and evolution of the mind, consciousness, and cultures. The review considers ancient theories of music as well as contemporary theories advanced by leading authors in this field. It addresses one hypothesis that promises to unify the field and proposes a theory of musical origin based on a fundamental role of music in cognition and evolution of consciousness and culture. We consider a split in the vocalizations of proto-humans into two types: one less emotional and more concretely-semantic, evolving into language, and the other preserving emotional connections along with semantic ambiguity, evolving into music. The proposed hypothesis departs from other theories in considering specific mechanisms of the mind-brain, which required the evolution of music parallel with the evolution of cultures and languages. Arguments are reviewed that the evolution of language toward becoming the semantically powerful tool of today required emancipation from emotional encumbrances. The opposite, no less powerful mechanisms required a compensatory evolution of music toward more differentiated and refined emotionality. The need for refined music in the process of cultural evolution is grounded in fundamental mechanisms of the mind. This is why today's human mind and cultures cannot exist without today's music. The reviewed hypothesis gives a basis for future analysis of why different evolutionary paths of languages were paralleled by different evolutionary paths of music. Approaches toward experimental verification of this hypothesis in

  5. Planetary Origin Evolution and Structure

    NASA Technical Reports Server (NTRS)

    Stevenson, David J.

    2005-01-01

    This wide-ranging grant supported theoretical modeling on many aspects of the formation, evolution and structure of planets and satellites. Many topics were studied during this grant period, including the evolution of icy bodies; the origin of magnetic fields in Ganymede; the thermal histories of terrestrial planets; the nature of flow inside giant planets (especially the coupling to the magnetic field) and the dynamics of silicate/iron mixing during giant impacts and terrestrial planet core formation. Many of these activities are ongoing and have not reached completion. This is the nature of this kind of research.

  6. Origins and Evolution of Life

    NASA Astrophysics Data System (ADS)

    Gargaud, Muriel; López-García, Purificación; Martin, Hervé

    2011-01-01

    Part I. What Is Life?: 1. Problems raised by a definition of life M. Morange; 2. Some remarks about uses of cosmological anthropic 'principles' D. Lambert; 3. Minimal cell: the biologist point of view C. Brochier-Armanet; 4. Minimal cell: the computer scientist point of view H. Bersini; 5. Origins of life: computing and simulation approaches B. Billoud; Part II. Astronomical and Geophysical Context of the Emergence of Life: 6. Organic molecules in interstellar medium C. Ceccarelli and C. Cernicharo; 7. Cosmochemical evolution and the origin of life: insights from meteorites S. Pizzarello; 8. Astronomical constraints on the emergence of life M. Gounelle and T. Montmerle; 9. Formation of habitable planets J. Chambers; 10. The concept of galactic habitable zone N. Prantzos; 11. The young Sun and its influence on planetary atmospheres M. Güdel and J. Kasting; 12. Climates of the Earth G. Ramstein; Part III. Role of Water in the Emergence of Life: 13. Liquid water: a necessary condition to all forms of life K. Bartik, G. Bruylants, E. Locci and J. Reisse; 14. The role of water in the formation and evolution of planets T. Encrenaz; 15. Water on Mars J. P. Bibring; Part IV. From Non-Living Systems to Life: 16. Energetic constraints on prebiotic pathways: application to the emergence of translation R. Pascal and L. Boiteau; 17. Comparative genomics and early cell evolution A. Lazcano; 18. Origin and evolution of metabolisms J. Peretó; Part V. Mechanisms for Life Evolution: 19. Molecular phylogeny: inferring the patterns of evolution E. Douzery; 20. Horizontal gene transfer: mechanisms and evolutionary consequences D. Moreira; 21. The role of symbiosis in eukaryotic evolution A. Latorre, A. Durbán, A. Moya and J. Peretó; Part VI. Life in Extreme Conditions: 22. Life in extreme conditions: Deinococcus radiodurans, an organism able to survive prolonged desiccation and high doses of ionising radiation S. Sommer and M. Toueille; 23. Molecular effects of UV and ionizing

  7. Prevolutionary dynamics and the origin of evolution.

    PubMed

    Nowak, Martin A; Ohtsuki, Hisashi

    2008-09-30

    Life is that which replicates and evolves. The origin of life is also the origin of evolution. A fundamental question is when do chemical kinetics become evolutionary dynamics? Here, we formulate a general mathematical theory for the origin of evolution. All known life on earth is based on biological polymers, which act as information carriers and catalysts. Therefore, any theory for the origin of life must address the emergence of such a system. We describe prelife as an alphabet of active monomers that form random polymers. Prelife is a generative system that can produce information. Prevolutionary dynamics have selection and mutation, but no replication. Life marches in with the ability of replication: Polymers act as templates for their own reproduction. Prelife is a scaffold that builds life. Yet, there is competition between life and prelife. There is a phase transition: If the effective replication rate exceeds a critical value, then life outcompetes prelife. Replication is not a prerequisite for selection, but instead, there can be selection for replication. Mutation leads to an error threshold between life and prelife.

  8. Prevolutionary dynamics and the origin of evolution

    PubMed Central

    Nowak, Martin A.; Ohtsuki, Hisashi

    2008-01-01

    Life is that which replicates and evolves. The origin of life is also the origin of evolution. A fundamental question is when do chemical kinetics become evolutionary dynamics? Here, we formulate a general mathematical theory for the origin of evolution. All known life on earth is based on biological polymers, which act as information carriers and catalysts. Therefore, any theory for the origin of life must address the emergence of such a system. We describe prelife as an alphabet of active monomers that form random polymers. Prelife is a generative system that can produce information. Prevolutionary dynamics have selection and mutation, but no replication. Life marches in with the ability of replication: Polymers act as templates for their own reproduction. Prelife is a scaffold that builds life. Yet, there is competition between life and prelife. There is a phase transition: If the effective replication rate exceeds a critical value, then life outcompetes prelife. Replication is not a prerequisite for selection, but instead, there can be selection for replication. Mutation leads to an error threshold between life and prelife. PMID:18791073

  9. Origin and evolution of the giant planets

    NASA Technical Reports Server (NTRS)

    Bodenheimer, P.

    1982-01-01

    A discussion is presented of two major giant planet origin hypotheses: (1) protoplanet formation in the solar nebula in the form of a gravitationally unstable, gaseous subcondensation, subsequently evolving as a chemically homogeneous object until a stage at which a solid core may form; and (2) solid core formation by accumulation of planetesimals, followed by the accretion of solar-composition gas onto the core until it becomes unstable to collapse. Under either of the scenarios, evolution is found to comprise an early, cool phase in hydrostatic equilibrium, a hydrodynamic collapse, and a final phase of hydrostatic contraction and cooling to the present state. Attention is given to the physical processes that are most important in the determination of evolutionary characteristics. A concluding note on the cases of Uranus and Neptune is also given.

  10. Origin and thermal evolution of icy satellites

    NASA Astrophysics Data System (ADS)

    Coradini, Angioletta; Federico, Costanzo; Forni, Olivier; Magni, Gianfranco

    1995-07-01

    The paper reviews the problem of formation and evolution of the so-called “regular satellites “ of the giant planets, and it consists of two parts: the first describes the possible origin of the satellites, the second studies their evolution, attempting to stress the relations of the present status of the satellites with their evolutionary history. The formation of regular satellite systems around giant planets is probably related to the formation of the central planet. Some characteristics of regular satellite systems are quite similar, and suggest a common origin in a disk present around the central body. This disk can originate through different mechanisms which we will describe, paying attention to the so-called “accretion disk” model, in which the satellite-forming material is captured. The disk phase links the formation of the primary body with the formation of satellites. The subsequent stages of the disk's evolution can lead first to the formation of intermediate size bodies, and through the collisional evolution of these bodies, to the birth of satellite “embryos” able to gravitationally capture smaller bodies. Given the scenario in which icy satellites may be formed by homogeneous accretion of planetesimals made of a mixtures of ice and silicates, if no melting occurs during accretion, the satellites have a homogeneous ice-rock composition. For the smaller satellites this homogeneous structure should not be substantially modified; only sporadic local events, such as large impacts, can modify the surface structure of the smaller satellites. For the larger satellites, if some degree of melting appears during accretion, a differentiation of the silicate part occurs, the amount of differentiation and hence the core size depending on the fraction of gravitational potential energy retained during the accumulation process. Melting and differentiation soon after the accretion, for the larger satellites, could also depend on the convective evolution in

  11. Origin and evolution of ordinary chondrite meteorites

    NASA Technical Reports Server (NTRS)

    Scott, E. R. D.; Taylor, G. J.; Keil, K.

    1985-01-01

    The effects of heating on the chemical composition, minerology, and texture of chondrite meteorites are discussed chondrite origin and evolution. Various asteroidal and nebular heating mechanisms are considered to account meteorite compositions.

  12. Origins, Evolution, and Fate of Brown Dwarfs

    NASA Technical Reports Server (NTRS)

    Martin, Eduardo

    2003-01-01

    Research related to the origins, evolution and fate of brown dwarfs is presented. The topics include: 1) Imaging surveys for brown dwarfs; 2) Companion detection techniques; 3) Measurements of fundamental properties of brown dwarfs; 4) Classification schemes for ultracool dwarfs; 5) Origins and evolution of brown dwarfs; 6) Ultracool atmospheres and interiors; 7) Time variable phenomena in brown dwarfs; 8) Comparisons between brown dwarfs and planets; 9) Substellar mass functions; and 10) Future facilities.

  13. Musical Emotions: Functions, Origins, Evolution

    DTIC Science & Technology

    2010-01-01

    27 [93] Perlovsky LI, Kozma R, editors. Neurodynamics of higher-level cognition and consciousness. Heidelberg, Germany: Springer-Verlag; 2006. [94...Perlovsky L, Kozma R. Editorial. Neurodynamics of cognition and consciousness. Heidelberg, Germany: Springer-Verlag; ISBN 978-3-540- 73266-2, 2006. [95...mind, nor evolutionary reasons for music origins. Music seems to be an enigma. Nevertheless, a synthesis of cognitive science and mathematical models of

  14. Eukaryotic evolution: early origin of canonical introns.

    PubMed

    Simpson, Alastair G B; MacQuarrie, Erin K; Roger, Andrew J

    2002-09-19

    Spliceosomal introns, one of the hallmarks of eukaryotic genomes, were thought to have originated late in evolution and were assumed not to exist in eukaryotes that diverged early -- until the discovery of a single intron with an aberrant splice boundary in the primitive 'protozoan' Giardia. Here we describe introns from a close relative of Giardia, Carpediemonas membranifera, that have boundary sequences of the normal eukaryotic type, indicating that canonical introns are likely to have arisen very early in eukaryotic evolution.

  15. Origin and evolution of the Saturn system

    NASA Technical Reports Server (NTRS)

    Pollack, J. B.; Consolmagno, G.

    1983-01-01

    A review is provided of current concepts concerning the formation of the Saturn system and the subsequent history of the planet, its satellites, and rings. Emphasis is placed upon numerical models of Saturn's evolution and interior models of its satellites. Alternative theories are presented and assessed for the origins of the Saturn system, the rings of Saturn, and the atmosphere of Titan.

  16. Planets and their atmospheres - Origin and evolution

    NASA Astrophysics Data System (ADS)

    Lewis, J. S.; Prinn, R. G.

    The origin, evolution, and composition of the planetary atmospheres are examined in an introductory review of ground-based and in situ observations and theoretical models. Chapters are devoted to the retention of volatiles by planets; evolutionary processes (such as hydrogen loss, accretion and outgassing, dissolution, photo-condensation, reactions with planetary surfaces, biochemical transformations, and atmospheric escape); and the present characteristics of the planetary, lunar-size-object, and asteroid atmospheres. Graphs, diagrams, and tables of numerical data are provided.

  17. Origin and evolution of spliceosomal introns

    PubMed Central

    2012-01-01

    Evolution of exon-intron structure of eukaryotic genes has been a matter of long-standing, intensive debate. The introns-early concept, later rebranded ‘introns first’ held that protein-coding genes were interrupted by numerous introns even at the earliest stages of life's evolution and that introns played a major role in the origin of proteins by facilitating recombination of sequences coding for small protein/peptide modules. The introns-late concept held that introns emerged only in eukaryotes and new introns have been accumulating continuously throughout eukaryotic evolution. Analysis of orthologous genes from completely sequenced eukaryotic genomes revealed numerous shared intron positions in orthologous genes from animals and plants and even between animals, plants and protists, suggesting that many ancestral introns have persisted since the last eukaryotic common ancestor (LECA). Reconstructions of intron gain and loss using the growing collection of genomes of diverse eukaryotes and increasingly advanced probabilistic models convincingly show that the LECA and the ancestors of each eukaryotic supergroup had intron-rich genes, with intron densities comparable to those in the most intron-rich modern genomes such as those of vertebrates. The subsequent evolution in most lineages of eukaryotes involved primarily loss of introns, with only a few episodes of substantial intron gain that might have accompanied major evolutionary innovations such as the origin of metazoa. The original invasion of self-splicing Group II introns, presumably originating from the mitochondrial endosymbiont, into the genome of the emerging eukaryote might have been a key factor of eukaryogenesis that in particular triggered the origin of endomembranes and the nucleus. Conversely, splicing errors gave rise to alternative splicing, a major contribution to the biological complexity of multicellular eukaryotes. There is no indication that any prokaryote has ever possessed a spliceosome

  18. Origin and evolution of spliceosomal introns.

    PubMed

    Rogozin, Igor B; Carmel, Liran; Csuros, Miklos; Koonin, Eugene V

    2012-04-16

    Evolution of exon-intron structure of eukaryotic genes has been a matter of long-standing, intensive debate. The introns-early concept, later rebranded 'introns first' held that protein-coding genes were interrupted by numerous introns even at the earliest stages of life's evolution and that introns played a major role in the origin of proteins by facilitating recombination of sequences coding for small protein/peptide modules. The introns-late concept held that introns emerged only in eukaryotes and new introns have been accumulating continuously throughout eukaryotic evolution. Analysis of orthologous genes from completely sequenced eukaryotic genomes revealed numerous shared intron positions in orthologous genes from animals and plants and even between animals, plants and protists, suggesting that many ancestral introns have persisted since the last eukaryotic common ancestor (LECA). Reconstructions of intron gain and loss using the growing collection of genomes of diverse eukaryotes and increasingly advanced probabilistic models convincingly show that the LECA and the ancestors of each eukaryotic supergroup had intron-rich genes, with intron densities comparable to those in the most intron-rich modern genomes such as those of vertebrates. The subsequent evolution in most lineages of eukaryotes involved primarily loss of introns, with only a few episodes of substantial intron gain that might have accompanied major evolutionary innovations such as the origin of metazoa. The original invasion of self-splicing Group II introns, presumably originating from the mitochondrial endosymbiont, into the genome of the emerging eukaryote might have been a key factor of eukaryogenesis that in particular triggered the origin of endomembranes and the nucleus. Conversely, splicing errors gave rise to alternative splicing, a major contribution to the biological complexity of multicellular eukaryotes. There is no indication that any prokaryote has ever possessed a spliceosome or

  19. The Origin of MoS2 Significantly Influences Its Performance for the Hydrogen Evolution Reaction due to Differences in Phase Purity.

    PubMed

    Chua, Xing Juan; Tan, Shu Min; Chia, Xinyi; Sofer, Zdenek; Luxa, Jan; Pumera, Martin

    2017-03-02

    Molybdenum disulfide (MoS2 ) is at the forefront of materials research. It shows great promise for electrochemical applications, especially for hydrogen evolution reaction (HER) catalysis. There is a significant discrepancy in the literature on the reported catalytic activity for HER catalysis on MoS2 . Here we test the electrochemical performance of MoS2 obtained from seven sources and we show that these sources provide MoS2 of various phase purity (2H and 3R, and their mixtures) and composition, which is responsible for their different electrochemical properties. The overpotentials for HER at -10 mA cm(-2) for MoS2 from seven different sources range from -0.59 V to -0.78 V vs. reversible hydrogen electrode (RHE). This is of very high importance as with much interest in 2D-MoS2 , the use of the top-down approach would usually involve the application of commercially available MoS2 . These commercially available MoS2 are rarely characterized for composition and phase purity. These key parameters are responsible for large variance of reported catalytic properties of MoS2 .

  20. Origins and evolution of eukaryotic RNA interference

    PubMed Central

    Shabalina, Svetlana A.; Koonin, Eugene V.

    2009-01-01

    Small interfering RNAs (siRNAs) and genome-encoded microRNAs (miRNAs) silence genes via complementary interactions with mRNAs. With thousands of miRNA genes identified and genome sequences of diverse eukaryotes available for comparison, the opportunity emerges for insights into origin and evolution of RNA interference (RNAi). The miRNA repertoires of plants and animals appear to have evolved independently. However, conservation of the key proteins involved in RNAi suggests that the last common ancestor of modern eukaryotes possessed siRNA-based mechanisms. Prokaryotes have a RNAi-like defense system that is functionally analogous but not homologous to eukaryotic RNAi. The protein machinery of eukaryotic RNAi seems to have been pieced together from ancestral proteins of archaeal, bacterial and phage origins that are involved in DNA repair and RNA-processing pathways. PMID:18715673

  1. Origin and Evolution of Rickettsial Plasmids

    PubMed Central

    El Karkouri, Khalid; Pontarotti, Pierre; Raoult, Didier; Fournier, Pierre-Edouard

    2016-01-01

    Background Rickettsia species are strictly intracellular bacteria that have undergone a reductive genomic evolution. Despite their allopatric lifestyle, almost half of the 26 currently validated Rickettsia species have plasmids. In order to study the origin, evolutionary history and putative roles of rickettsial plasmids, we investigated the evolutionary processes that have shaped 20 plasmids belonging to 11 species, using comparative genomics and phylogenetic analysis between rickettsial, microbial and non-microbial genomes. Results Plasmids were differentially present among Rickettsia species. The 11 species had 1 to 4 plasmid (s) with a size ranging from 12 kb to 83 kb. We reconstructed pRICO, the last common ancestor of the current rickettsial plasmids. pRICO was vertically inherited mainly from Rickettsia/Orientia chromosomes and diverged vertically into a single or multiple plasmid(s) in each species. These plasmids also underwent a reductive evolution by progressive gene loss, similar to that observed in rickettsial chromosomes, possibly leading to cryptic plasmids or complete plasmid loss. Moreover, rickettsial plasmids exhibited ORFans, recent gene duplications and evidence of horizontal gene transfer events with rickettsial and non-rickettsial genomes mainly from the α/γ-proteobacteria lineages. Genes related to maintenance and plasticity of plasmids, and to adaptation and resistance to stress mostly evolved under vertical and/or horizontal processes. Those involved in nucleotide/carbohydrate transport and metabolism were under the influence of vertical evolution only, whereas genes involved in cell wall/membrane/envelope biogenesis, cycle control, amino acid/lipid/coenzyme and secondary metabolites biosynthesis, transport and metabolism underwent mainly horizontal transfer events. Conclusion Rickettsial plasmids had a complex evolution, starting with a vertical inheritance followed by a reductive evolution associated with increased complexity via

  2. The origin and evolution of Homo sapiens.

    PubMed

    Stringer, Chris

    2016-07-05

    If we restrict the use of Homo sapiens in the fossil record to specimens which share a significant number of derived features in the skeleton with extant H. sapiens, the origin of our species would be placed in the African late middle Pleistocene, based on fossils such as Omo Kibish 1, Herto 1 and 2, and the Levantine material from Skhul and Qafzeh. However, genetic data suggest that we and our sister species Homo neanderthalensis shared a last common ancestor in the middle Pleistocene approximately 400-700 ka, which is at least 200 000 years earlier than the species origin indicated from the fossils already mentioned. Thus, it is likely that the African fossil record will document early members of the sapiens lineage showing only some of the derived features of late members of the lineage. On that basis, I argue that human fossils such as those from Jebel Irhoud, Florisbad, Eliye Springs and Omo Kibish 2 do represent early members of the species, but variation across the African later middle Pleistocene/early Middle Stone Age fossils shows that there was not a simple linear progression towards later sapiens morphology, and there was chronological overlap between different 'archaic' and 'modern' morphs. Even in the late Pleistocene within and outside Africa, we find H. sapiens specimens which are clearly outside the range of Holocene members of the species, showing the complexity of recent human evolution. The impact on species recognition of late Pleistocene gene flow between the lineages of modern humans, Neanderthals and Denisovans is also discussed, and finally, I reconsider the nature of the middle Pleistocene ancestor of these lineages, based on recent morphological and genetic data.This article is part of the themed issue 'Major transitions in human evolution'.

  3. Origin and evolution of lysyl oxidases

    PubMed Central

    Grau-Bové, Xavier; Ruiz-Trillo, Iñaki; Rodriguez-Pascual, Fernando

    2015-01-01

    Lysyl oxidases (LOX) are copper-dependent enzymes that oxidize primary amine substrates to reactive aldehydes. The best-studied role of LOX enzymes is the remodeling of the extracellular matrix (ECM) in animals by cross-linking collagens and elastin, although intracellular functions have been reported as well. Five different LOX enzymes have been identified in mammals, LOX and LOX-like (LOXL) 1 to 4, showing a highly conserved catalytic carboxy terminal domain and more divergence in the rest of the sequence. Here we have surveyed a wide selection of genomes in order to infer the evolutionary history of LOX. We identified LOX proteins not only in animals, but also in many other eukaryotes, as well as in bacteria and archaea – which reveals a pre-metazoan origin for this gene family. LOX genes expanded during metazoan evolution resulting in two superfamilies, LOXL2/L3/L4 and LOX/L1/L5. Considering the current knowledge on the function of mammalian LOX isoforms in ECM remodeling, we propose that LOXL2/L3/L4 members might have preferentially been involved in making cross-linked collagen IV-based basement membrane, whereas the diversification of LOX/L1/L5 forms contributed to chordate/vertebrate-specific ECM innovations, such as elastin and fibronectin. Our work provides a novel view on the evolution of this family of enzymes. PMID:26024311

  4. Origin and Evolution of Saturn's Small Satellites

    NASA Astrophysics Data System (ADS)

    Charnoz, Sebastien; Salmon, J.; Crida, A.; Brahic, A.

    2009-09-01

    All Saturn’ small satellites, orbiting below Mimas'orbit, share some common physical and dynamical properties : they have strong water absorption bands (Poulet & Cuzzi, 2002 Icarus 160, 350-358, Cuzzi et al., in press) , they have strange and elongated shapes and are under dense (Charnoz et al, 2007 Science 318, 1622, Porco et al. 2007 Science 318, 1602). They are also dynamically coupled with Saturn rings. In addition, due to their small size, they should not be primordial because of the meteoroid bombardment. They dynamically evolve under the tidal torque of the planet and the rings, in addition to satellite's perturbations. A theory of their origin still needs to be done. We show in the present work that these small satellites may be the natural result of the viscous spreading of Saturn's rings. Using a new 1D coupled hydrodynamic + dynamical evolution code, we compute that the rings viscous spreading may naturally form a population of 10-50 km size satellites, with and orbital organisation similar to the today population of small satellites. Self-regulation processes are at work limiting the maximum mass of small satellite to about the mass of Janus, consistently with observations. This satellite formation scenario of a new kind (due to the viscous spreading of a disk) seems to explain the composition, the shape, the total mass, and the low density of Saturn's small satellites. It would give also an interesting explanation to the origin of the F ring. In conclusion, Saturn's small satellites may be considered as a specific category of satellites whose origin is very different either from Saturn's main satellites of Saturn's captured satellites. They could be the "children” of the rings.

  5. 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.

  6. Origin and evolution of planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Lewis, John S.

    1992-01-01

    This report concerns several research tasks related to the origin and evolution of planetary atmospheres and the large-scale distribution of volatile elements in the Solar System. These tasks and their present status are as follows: (1) we have conducted an analysis of the volatility and condensation behavior of compounds of iron, aluminum, and phosphorus in the atmosphere of Venus in response to publish interpretations of the Soviet Venera probe XRF experiment data, to investigate the chemistry of volcanic gases, injection of volatiles by cometary and asteroidal impactors, and reactions in the troposphere; (2) we have completed and are now writing up our research on condensation-accretion modeling of the terrestrial planets; (3) we have laid the groundwork for a detailed study of the effects of water transport in the solar nebula on the bulk composition, oxidation state, and volatile content of preplanetary solids; (4) we have completed an extensive laboratory study of cryovolcanic materials in the outer solar system; (5) we have begun to study the impact erosion and shock alteration of the atmosphere of Mars resulting from cometary and asteroidal bombardment; and (6) we have developed a new Monte Carlo model of the cometary and asteroidal bombardment flux on the terrestrial planets, including all relevant chemical and physical processes associated with atmospheric entry and impact, to assess both the hazards posed by this bombardment to life on Earth and the degree of cross-correlation between the various phenomena (NO(x) production, explosive yield, crater production, iridium signature, etc.) that characterize this bombardment. The purpose of these investigations has been to contribute to the developing understanding of both the dynamics of long-term planetary atmosphere evolution and the short-term stability of planetary surface environments.

  7. Origin and early evolution of angiosperms.

    PubMed

    Soltis, Douglas E; Bell, Charles D; Kim, Sangtae; Soltis, Pamela S

    2008-01-01

    Contributions from paleobotany, phylogenetics, genomics, developmental biology, and developmental genetics have yielded tremendous insight into Darwin's "abominable mystery"--the origin and rapid diversification of the angiosperms. Analyses of morphological and molecular data reveal a revised "anthophyte clade" consisting of the fossils glossopterids, Pentoxylon, Bennettitales, and Caytonia as sister to angiosperms. Molecular estimates of the age of crown group angiosperms have converged on 140-180 million years ago (Ma), older than the oldest fossils (132 Ma), suggesting that older fossils remain to be discovered. Whether the first angiosperms were forest shrubs (dark-and-disturbed hypothesis) or aquatic herbs (wet-and-wild hypothesis) remains unclear. The near-basal phylogenetic position of Nymphaeales (water lilies), which may include the well-known fossil Archaefructus, certainly indicates that the aquatic habit arose early. After initial, early "experiments," angiosperms radiated rapidly (evolution. Although the flower is the central feature of the angiosperms, its origin and subsequent diversification remain major questions. Variation in spatial expression of floral regulators may control major differences in floral morphology between basal angiosperms and eudicot models.

  8. Origin and evolution of high throughput screening

    PubMed Central

    Pereira, D A; Williams, J A

    2007-01-01

    This article reviews the origin and evolution of high throughput screening (HTS) through the experience of an individual pharmaceutical company, revealing some of the mysteries of the early stages of drug discovery to the wider pharmacology audience. HTS in this company (Pfizer, Groton, USA) had its origin in natural products screening in 1986, by substituting fermentation broths with dimethyl sulphoxide solutions of synthetic compounds, using 96-well plates and reduced assay volumes of 50-100μl. A nominal 30mM source compound concentration provided high μM assay concentrations. Starting at 800 compounds each week, the process reached a steady state of 7200 compounds per week by 1989. Screening in the Applied Biotechnology and Screening Group was centralized with screens operating in lock-step to maximize efficiency. Initial screens were full files run in triplicate. Autoradiography and image analysis were introduced for 125I receptor ligand screens. Reverse transcriptase (RT) coupled with quantitative PCR and multiplexing addressed several targets in a single assay. By 1992 HTS produced ‘hits' as starting matter for approximately 40% of the Discovery portfolio. In 1995, the HTS methodology was expanded to include ADMET targets. ADME targets required each compound to be physically detected leading to the development of automated high throughput LC-MS. In 1996, 90 compounds/week were screened in microsomal, protein binding and serum stability assays. Subsequently, the mutagenic Ames assay was adapted to a 96-well plate liquid assay and novel algorithms permitted automated image analysis of the micronucleus assay. By 1999 ADME HTS was fully integrated into the discovery cycle. PMID:17603542

  9. Quantum Darwinian Evolution Implies Tumor Origination

    NASA Astrophysics Data System (ADS)

    Cooper, W. Grant

    2011-03-01

    Quantum uncertainty limits operating on metastable amino DNA protons drive the arrangement, keto-amino ? enol-imine, which contributes to time-dependent stochastic mutations. Product enol-imine protons participate in coupled quantum oscillations at frequencies of about 1013 s-1 until ``measured by'' an evolutionarily selected quantum reader, the transcriptase. This introduces entanglement states between coherent protons and transcriptase components, which ultimately yield an ensemble of decohered, non-reequilibrated enol and imine isomers that participate in ``molecular clock'' base substitutions at G'-C' and *G-*C sites. This introduces a quantum Darwinian evolution model which (a) simulates incidence of cancer data and (b) implies insight into quantum origins of evolutionary extinction. Data identify an inherited ``genetic space,'' s, which is initially mutation-free and satisfies the inequality, 1 = s = 0.97. When accumulated stochastic mutations cause s-values to approach their evolutionarily allowed threshold limit, s 0.97 + e, age-related degenerative disease is manifested. This implies a gain in evolutionary advantage which protects the gene pool against acquiring unsafe levels of mutation. Data requiring coherent states imply that classical duplex DNA contains an embedded microphysical subset of electron lone-pairs and hydrogen bonded protons that govern time-dependent genetic specificity in terms of quantum probability laws.

  10. Origin and evolution of the Saturn system

    NASA Technical Reports Server (NTRS)

    Pollack, J. B.; Consolmagno, G.

    1984-01-01

    As was the case for Jupiter, Saturn formed either as a result of a gas instability within the solar nebula or the accretion of a solid core that induced an instability within the surrounding solar nebula. In either case, the proto-planet's history is divided into three major stages: early, quasi-hydrostatic evolution (stage 1); hydrodynamical collapse (stage 2); and late, quasi-hydrostatic contraction (stage 3). During stage 1, Saturn had a radius of several hundred times that of its present radius, R(s), while stage 3 began when Saturn had a radius of 3.5 R(s). Stages 1 and 2 lasted 10(6) to 10(7) years and 1 year, respectively, while stage 3 is continuing through the present epoch. During the early history of the Saturn system, giant impact events may have catastrophically disrupted most of the original satellites of Saturn. Such disruption, followed by reaccretion, may be responsible, in part for the occurrence of Trojans and co-orbital moons in the Saturn system, the apparent presence of a stochastic component in the trend of satellite density with radial distance, and the present population of ring particles.

  11. Origin and evolution of the Saturn system

    NASA Technical Reports Server (NTRS)

    Pollack, J. B.; Consolmagno, G.

    1984-01-01

    As was the case for Jupiter, Saturn formed either as a result of a gas instability within the solar nebula or the accretion of a solid core that induced an instability within the surrounding solar nebula. In either case, the proto-planet's history is divided into three major stages: early, quasi-hydrostatic evolution (stage 1); hydrodynamical collapse (stage 2); and late, quasi-hydrostatic contraction (stage 3). During stage 1, Saturn had a radius of several hundred times that of its present radius, R(s), while stage 3 began when Saturn had a radius of 3.5 R(s). Stages 1 and 2 lasted one-million to 10-million years and one year, respectively, while stage 3 is continuing through the present epoch. During the early history of the Saturn system, giant impact events may have catastrophically disrupted most of the original satellites of Saturn. Such disruption, followed by reaccretion, may be responsible, in part for the occurrence of Trojans and co-orbital moons in the Saturn system, the apparent presence of a stochastic component in the trend of satellite density with radial distance, and the present population of ring particles.

  12. The Journal of Anatomy: origin and evolution.

    PubMed

    Morriss-Kay, Gillian

    2016-07-01

    The Journal of Anatomy was launched 150 years ago as the Journal of Anatomy and Physiology, in an age when anatomy and physiology were not regarded as separate disciplines. European science in general was advancing rapidly at the time (it was 7 years after publication of Darwin's Origin of Species), and the recent demise of the Natural History Review meant that there was no English language publication covering these subjects. The founding editors were George Murray Humphry of Cambridge and William Turner of Edinburgh, together with Alfred Newton of Cambridge and Edward Perceval Wright of Dublin (the last two served only for a year). The pivotal event leading to the Journal's foundation was the 1866 meeting of the British Association, at which Humphry delivered the 'Address in Physiology' (printed in the first issue). Turner, who was also present at the 1866 British Association meeting, remained as a member of the editorial team for 50 years and was a major contributor of Journal articles. The title was changed to Journal of Anatomy in October 1916, when it was taken under the wing, in terms of both management and ownership, by the Anatomical Society. This article reviews the early years of the Journal's publication in more detail than later years because of the historical interest of this less familiar material. The subject matter, which has remained surprisingly consistent over the years, is illustrated by examples from some notable contributions. The evolution of illustration techniques is surveyed from 1866 to the present day; the final section provides brief summaries of all of the chief editors.

  13. Origin and evolution of photosynthetic reaction centers

    NASA Astrophysics Data System (ADS)

    Olson, John M.; Pierson, Beverly K.

    1987-09-01

    The prototype reaction center may have used protoporphyrin-IX associated with small peptides to transfer electrons or protons across the primitive cell membrane. The precursor of all contemporary reaction centers contained chlorophylla molecules as both primary electron donor and initial electron acceptor and an Fe-S center as secondary acceptor (RC-1 type). The biosynthetic pathway for chlorophylla evolved along with the evolution of a better organized reaction center associated with cytochromes and quinones in a primitive cyclic electron transport system. This reaction center probably functioned initially in photoassimilation, but was easily adapted to CO2 fixation using H2 and H2S as reductants. During this phase bacteriochlorophyllg may have evolved from chlorophylla in response to competition for light, and thereby initiated the gram-positive line of eubacteria. A second reaction center (RC-2) evolved from RC-1 between 3.5 and 2.5 Ga ago in response to the competition for reductants for CO2 fixation. The new organism containing RC-2 in series with RC-1 would have been able to use poor reducing agents such as the abundant aqueous ferrous ion in place of H2 and H2S. This new organism is proposed to be the common ancestor of all phototrophic eubacteria except those related to the gram-positive bacteria. All organisms containing bacteriochlorophylla lost either RC-1 or RC-2, while those organisms containing chlorophylla (ancestors of cyanobacteria) added a water-splitting enzyme to RC-2 between 3.0 and 2.5 Ga ago in order to use H2O in place of hydrated ferrous ion as electron donor for autotrophic photosynthesis.

  14. Origin and Evolution of Planetary Satellites

    NASA Astrophysics Data System (ADS)

    Hamilton, Douglas

    We propose here to continue our promising investigations into satellite systems in order to elucidate general planetary formation processes. We will investigate the origin and evolution of planetary satellites with both numerical and analytical methods, focusing first on Jupiter's Galilean satellites and then on the large saturnian moons. Our objective is to determine the state of these systems immediately after their formation; these constraints will be useful to researchers who simulate satellite formation and will provide guidance for scientists interested in tidal evolution of exoplanets. There are a number of important parallels between the formation of planetary systems and the subsequent development of planetary satellite systems. Although planetary formation has been studied in much greater detail, there are abundant and perhaps more detailed clues to general formation processes awaiting discovery in the satellite systems of the four giant planets. Thus these systems are important local sources of information that can be mined for insight into critical formation processes. We will use our sophisticated N-Body codes to investigate satellite formation and evolutionary processes with the following key goals: Determine the initial configuration of Jupiter's Galilean satellites by using their current inclinations as fossil clues to past resonance passages Determine the timing of dynamical events affecting the Galilean satellites and put strong constraints on the tidal Q values of Io, Europa, and Jupiter and iii) Investigate the resonant history of the saturnian satellites Mimas through Iapetus, paying particular attention to free inclinations and eccentricities. Andrew Howard/UC Berkeley A Window on Planet Formation from Precise Physical Properties of Kepler Planets and Stars The Kepler mission has detected more than 1200 planets and is transforming our understanding of planet formation, migration, and evolution. From the ensemble of Kepler planets, we have

  15. Origin and Evolution of Planetary Satellites

    NASA Astrophysics Data System (ADS)

    Hamilton, Douglas

    We propose here to continue our promising investigations into satellite systems in order to elucidate general planetary formation processes. We will investigate the origin and evolution of planetary satellites with both numerical and analytical methods, focusing first on Jupiter's Galilean satellites and then on the large saturnian moons. Our objective is to determine the state of these systems immediately after their formation; these constraints will be useful to researchers who simulate satellite formation and will provide guidance for scientists interested in tidal evolution of exoplanets. There are a number of important parallels between the formation of planetary systems and the subsequent development of planetary satellite systems. Although planetary formation has been studied in much greater detail, there are abundant and perhaps more detailed clues to general formation processes awaiting discovery in the satellite systems of the four giant planets. Thus these systems are important local sources of information that can be mined for insight into critical formation processes. We will use our sophisticated N-Body codes to investigate satellite formation and evolutionary processes with the following key goals: Determine the initial configuration of Jupiter's Galilean satellites by using their current inclinations as fossil clues to past resonance passages Determine the timing of dynamical events affecting the Galilean satellites and put strong constraints on the tidal Q values of Io, Europa, and Jupiter and iii) Investigate the resonant history of the saturnian satellites Mimas through Iapetus, paying particular attention to free inclinations and eccentricities. Andrew Howard/UC Berkeley - A Window on Planet Formation from Precise Physical Properties of Kepler Planets and Stars The Kepler mission has detected more than 1200 planets and is transforming our understanding of planet formation, migration, and evolution. From the ensemble of Kepler planets, we have

  16. Chemical evolution and the origin of life

    NASA Technical Reports Server (NTRS)

    Oro, J.

    1983-01-01

    A review is presented of recent advances made in the understanding of the formation of carbon compounds in the universe and the occurrence of processes of chemical evolution. Topics discussed include the principle of evolutionary continuity, evolution as a fundamental principle of the physical universe, the nuclear synthesis of biogenic elements, organic cosmochemistry and interstellar molecules, the solar nebula and the solar system in chemical evolution, the giant planets and Titan in chemical evolution, and comets and their interaction with the earth. Also examined are carbonaceous chondrites, environment of the primitive earth, energy sources available on the primitive earth, the synthesis of biochemical monomers and oligomers, the abiotic transcription of nucleotides, unified prebiotic and enzymatic mechanisms, phospholipids and membranes, and protobiological evolution.

  17. Origin and Evolution of the Mitochondrial Proteome

    PubMed Central

    Kurland, C. G.; Andersson, S. G. E.

    2000-01-01

    The endosymbiotic theory for the origin of mitochondria requires substantial modification. The three identifiable ancestral sources to the proteome of mitochondria are proteins descended from the ancestral α-proteobacteria symbiont, proteins with no homology to bacterial orthologs, and diverse proteins with bacterial affinities not derived from α-proteobacteria. Random mutations in the form of deletions large and small seem to have eliminated nonessential genes from the endosymbiont-mitochondrial genome lineages. This process, together with the transfer of genes from the endosymbiont-mitochondrial genome to nuclei, has led to a marked reduction in the size of mitochondrial genomes. All proteins of bacterial descent that are encoded by nuclear genes were probably transferred by the same mechanism, involving the disintegration of mitochondria or bacteria by the intracellular membranous vacuoles of cells to release nucleic acid fragments that transform the nuclear genome. This ongoing process has intermittently introduced bacterial genes to nuclear genomes. The genomes of the last common ancestor of all organisms, in particular of mitochondria, encoded cytochrome oxidase homologues. There are no phylogenetic indications either in the mitochondrial proteome or in the nuclear genomes that the initial or subsequent function of the ancestor to the mitochondria was anaerobic. In contrast, there are indications that relatively advanced eukaryotes adapted to anaerobiosis by dismantling their mitochondria and refitting them as hydrogenosomes. Accordingly, a continuous history of aerobic respiration seems to have been the fate of most mitochondrial lineages. The initial phases of this history may have involved aerobic respiration by the symbiont functioning as a scavenger of toxic oxygen. The transition to mitochondria capable of active ATP export to the host cell seems to have required recruitment of eukaryotic ATP transport proteins from the nucleus. The identity of the

  18. Origin and thermal evolution of Mars

    NASA Technical Reports Server (NTRS)

    Schubert, G.; Solomon, Sean C.; Turcotte, D. L.; Drake, M. J.; Sleep, N. H.

    1993-01-01

    The thermal evolution of Mars is governed by subsolidus mantle convection beneath a thick lithosphere. Models of the interior evolution are developed by parameterizing mantle convective heat transport in terms of mantle viscosity, the superadiabatic temperature rise across the mantle and mantle heat production. Geological, geophysical, and geochemical observations of the composition and structure of the interior and of the timing of major events in Martian evolution, such as global differentiation, atmospheric outgassing and the formation of the hemispherical dichotomy and Tharsis, are used to constrain the model computations. Isotope systematics of SNC meteorites suggest core formation essentially contemporaneously with the completion of accretion. Other aspects of this investigation are discussed.

  19. The Origin and Evolution of Interstellar Dust

    NASA Technical Reports Server (NTRS)

    Dwek, Eli; Houches, Les

    2006-01-01

    In this lecture I will discuss the many different manifestation of interstellar dust, and current dust models that satisfy interstellar extinction, diffuse infrared emission, and interstellar abundances constraints. Dust is made predominantly in AGB stars and Type I1 supernovae, and I will present observational evidence for the presence of dust in these sources. I will then present chemical evolution models that follow the abundance of dust which is determined by the combined processes of formation, destruction by interstellar shock waves, and accretion in molecular clouds. The model will be applied to the evolution of PAHs and the evolution of dust in the high-redshift galaxy (z=6.42) JD11.

  20. Insect Evolution: The Origin of Wings.

    PubMed

    Ross, Andrew

    2017-02-06

    The debate on the evolution of wings in insects has reached a new level. The study of primitive fossil insect nymphs has revealed that wings developed from a combination of the dorsal part of the thorax and the body wall.

  1. Origin and Evolution of the Cometary Reservoirs

    NASA Astrophysics Data System (ADS)

    Dones, Luke; Brasser, Ramon; Kaib, Nathan; Rickman, Hans

    2015-12-01

    Comets have three known reservoirs: the roughly spherical Oort Cloud (for long-period comets), the flattened Kuiper Belt (for ecliptic comets), and, surprisingly, the asteroid belt (for main-belt comets). Comets in the Oort Cloud were thought to have formed in the region of the giant planets and then placed in quasi-stable orbits at distances of thousands or tens of thousands of AU through the gravitational effects of the planets and the Galaxy. The planets were long assumed to have formed in place. However, the giant planets may have undergone two episodes of migration. The first would have taken place in the first few million years of the Solar System, during or shortly after the formation of the giant planets, when gas was still present in the protoplanetary disk around the Sun. The Grand Tack (Walsh et al. in Nature 475:206-209, 2011) models how this stage of migration could explain the low mass of Mars and deplete, then repopulate the asteroid belt, with outer-belt asteroids originating between, and outside of, the orbits of the giant planets. The second stage of migration would have occurred later (possibly hundreds of millions of years later) due to interactions with a remnant disk of planetesimals, i.e., a massive ancestor of the Kuiper Belt. Safronov (Evolution of the Protoplanetary Cloud and Formation of the Earth and the Planets, 1969) and Fernández and Ip (Icarus 58:109-120, 1984) proposed that the giant planets would have migrated as they interacted with leftover planetesimals; Jupiter would have moved slightly inward, while Saturn and (especially) Uranus and Neptune would have moved outward from the Sun. Malhotra (Nature 365:819-821, 1993) showed that Pluto's orbit in the 3:2 resonance with Neptune was a natural outcome if Neptune captured Pluto into resonance while it migrated outward. Building on this work, Tsiganis et al. (Nature 435:459-461, 2005) proposed the Nice model, in which the giant planets formed closer together than they are now, and

  2. Theory of the Origin, Evolution, and Nature of Life

    PubMed Central

    Andrulis, Erik D.

    2011-01-01

    Life is an inordinately complex unsolved puzzle. Despite significant theoretical progress, experimental anomalies, paradoxes, and enigmas have revealed paradigmatic limitations. Thus, the advancement of scientific understanding requires new models that resolve fundamental problems. Here, I present a theoretical framework that economically fits evidence accumulated from examinations of life. This theory is based upon a straightforward and non-mathematical core model and proposes unique yet empirically consistent explanations for major phenomena including, but not limited to, quantum gravity, phase transitions of water, why living systems are predominantly CHNOPS (carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur), homochirality of sugars and amino acids, homeoviscous adaptation, triplet code, and DNA mutations. The theoretical framework unifies the macrocosmic and microcosmic realms, validates predicted laws of nature, and solves the puzzle of the origin and evolution of cellular life in the universe. PMID:25382118

  3. Origin and thermal evolution of Mars

    NASA Technical Reports Server (NTRS)

    Schubert, Gerald; Soloman, S. C.; Turcotte, D. L.; Drake, M. J.; Sleep, N. H.

    1990-01-01

    The thermal evolution of Mars is governed by subsolidus mantle convection beneath a thick lithosphere. Models of the interior evolution are developed by parameterizing mantle convective heat transport in terms of mantle viscosity, the superadiabatic temperature rise across the mantle, and mantle heat production. Geological, geophysical, and geochemical observations of the compositon and structure of the interior and of the timing of major events in Martian evolution are used to constrain the model computations. Such evolutionary events include global differentiation, atmospheric outgassing, and the formation of the hemispherical dichotomy and Tharsis. Numerical calculations of fully three-dimensional, spherical convection in a shell the size of the Martian mantle are performed to explore plausible patterns of Martian mantel convection and to relate convective features, such as plumes, to surface features, such as Tharsis. The results from the model calculations are presented.

  4. Origin and evolution of metabolic pathways

    NASA Astrophysics Data System (ADS)

    Fani, Renato; Fondi, Marco

    2009-03-01

    The emergence and evolution of metabolic pathways represented a crucial step in molecular and cellular evolution. In fact, the exhaustion of the prebiotic supply of amino acids and other compounds that were likely present in the ancestral environment, imposed an important selective pressure, favoring those primordial heterotrophic cells which became capable of synthesizing those molecules. Thus, the emergence of metabolic pathways allowed primitive organisms to become increasingly less-dependent on exogenous sources of organic compounds. Comparative analyses of genes and genomes from organisms belonging to Archaea, Bacteria and Eukarya revealed that, during evolution, different forces and molecular mechanisms might have driven the shaping of genomes and the arisal of new metabolic abilities. Among these gene elongations, gene and operon duplications undoubtedly played a major role since they can lead to the (immediate) appearance of new genetic material that, in turn, might undergo evolutionary divergence giving rise to new genes coding for new metabolic abilities. Gene duplication has been invoked in the different schemes proposed to explain why and how the extant metabolic pathways have arisen and shaped. Both the analysis of completely sequenced genomes and directed evolution experiments strongly support one of them, i.e. the patchwork hypothesis, according to which metabolic pathways have been assembled through the recruitment of primitive enzymes that could react with a wide range of chemically related substrates. However, the analysis of the structure and organization of genes belonging to ancient metabolic pathways, such as histidine biosynthesis and nitrogen fixation, suggested that other different hypothesis, i.e. the retrograde hypothesis or the semi-enzymatic theory, may account for the arisal of some metabolic routes.

  5. The origin, evolution and signatures of primordial magnetic fields

    NASA Astrophysics Data System (ADS)

    Subramanian, Kandaswamy

    2016-07-01

    The universe is magnetized on all scales probed so far. On the largest scales, galaxies and galaxy clusters host magnetic fields at the micro Gauss level coherent on scales up to ten kpc. Recent observational evidence suggests that even the intergalactic medium in voids could host a weak  ˜  10-16 Gauss magnetic field, coherent on Mpc scales. An intriguing possibility is that these observed magnetic fields are a relic from the early universe, albeit one which has been subsequently amplified and maintained by a dynamo in collapsed objects. We review here the origin, evolution and signatures of primordial magnetic fields. After a brief summary of magnetohydrodynamics in the expanding universe, we turn to magnetic field generation during inflation and phase transitions. We trace the linear and nonlinear evolution of the generated primordial fields through the radiation era, including viscous effects. Sensitive observational signatures of primordial magnetic fields on the cosmic microwave background, including current constraints from Planck, are discussed. After recombination, primordial magnetic fields could strongly influence structure formation, especially on dwarf galaxy scales. The resulting signatures on reionization, the redshifted 21 cm line, weak lensing and the Lyman-α forest are outlined. Constraints from radio and γ-ray astronomy are summarized. Astrophysical batteries and the role of dynamos in reshaping the primordial field are briefly considered. The review ends with some final thoughts on primordial magnetic fields.

  6. The Origin and Evolution of Dinosaurs

    NASA Astrophysics Data System (ADS)

    Sereno, Paul C.

    Phylogenetic studies and new fossil evidence have yielded fundamental insights into the pattern and timing of dinosaur evolution and the emergence of functionally modern birds. The dinosaurian radiation began in the Middle Triassic and significantly predates their rise to global dominance by the end of the period. The phylogenetic history of ornithischian and saurichian dinosaurs reveals evolutionary trends such as increasing body size. Adaptations to herbivory dinosaurs were not tightly correlated with marked floral changes. Dinosaurian biogeography during the era of continental breakup principally involved dispersal and regional extinction.

  7. The origin and evolution of cell types.

    PubMed

    Arendt, Detlev; Musser, Jacob M; Baker, Clare V H; Bergman, Aviv; Cepko, Connie; Erwin, Douglas H; Pavlicev, Mihaela; Schlosser, Gerhard; Widder, Stefanie; Laubichler, Manfred D; Wagner, Günter P

    2016-12-01

    Cell types are the basic building blocks of multicellular organisms and are extensively diversified in animals. Despite recent advances in characterizing cell types, classification schemes remain ambiguous. We propose an evolutionary definition of a cell type that allows cell types to be delineated and compared within and between species. Key to cell type identity are evolutionary changes in the 'core regulatory complex' (CoRC) of transcription factors, that make emergent sister cell types distinct, enable their independent evolution and regulate cell type-specific traits termed apomeres. We discuss the distinction between developmental and evolutionary lineages, and present a roadmap for future research.

  8. Origin and Evolution of the Elements

    NASA Astrophysics Data System (ADS)

    McWilliam, Andrew; Rauch, Michael

    2004-09-01

    Introduction; List of participants; 1. Mount Wilson Observatory contributions to the study of cosmic abundances of the chemical elements George W. Preston; 2. Synthesis of the elements in stars: B2FH and beyond E. Margaret Burbidge; 3. Stellar nucleosynthesis: a status report 2003 David Arnett; 4. Advances in r-process nucleosynthesis John J. Cowan and Christopher Sneden; 5. Element yields of intermediate-mass stars Richard B. C. Henry; 6. The impact of rotation on chemical abundances in red giant branch stars Corinne Charbonnel; 7. s-processing in AGB stars and the composition of carbon stars Maurizio Busso, Oscar Straniero, Roberto Gallino, and Carlos Abia; 8. Models of chemical evolution Francesca Matteucci; 9. Model atmospheres and stellar abundance analysis Bengt Gustafsson; 10. The light elements: lithium, beryllium, and boron Ann Merchant Boesgaard; 11. Extremely metal-poor stars John E. Norris; 12. Thin and thick galactic disks Poul E. Nissen; 13. Globular clusters and halo field stars Christopher Sneden, Inese I. Ivans and Jon P. Fulbright; 14. Chemical evolution in ω Centauri Verne V. Smith; 15. Chemical composition of the Magellanic Clouds, from young to old stars Vanessa Hill; 16. Detailed composition of stars in dwarf spheroidal galaxies Matthew D. Shetrone; 17. The evolutionary history of Local Group irregular galaxies Eva K. Grebel; 18. Chemical evolution of the old stellar populations of M31 R. Michael Rich; 19. Stellar winds of hot massive stars nearby and beyond the Local Group Fabio Bresolin and Rolf P. Kudritzki; 20. Presolar stardust grains Donald D. Clayton and Larry R. Nittler; 21. Interstellar dust B. T. Draine; 22. Interstellar atomic abundances Edward B. Jenkins; 23. Molecules in the interstellar medium Tommy Wiklind; 24. Metal ejection by galactic winds Crystal L. Martin; 25. Abundances from the integrated light of globular clusters and galaxies Scott C. Trager; 26. Abundances in spiral and irregular galaxies Donald R. Garnett; 27

  9. The origin and evolution of model organisms

    NASA Technical Reports Server (NTRS)

    Hedges, S. Blair

    2002-01-01

    The phylogeny and timescale of life are becoming better understood as the analysis of genomic data from model organisms continues to grow. As a result, discoveries are being made about the early history of life and the origin and development of complex multicellular life. This emerging comparative framework and the emphasis on historical patterns is helping to bridge barriers among organism-based research communities.

  10. Phase Transformations and Microstructural Evolution: Part I

    DOE PAGES

    Clarke, Amy Jean

    2015-08-29

    The activities of the Phase Transformations Committee of the Materials Processing & Manufacturing Division (MPMD) of The Minerals, Metals & Materials Society (TMS) are oriented toward understanding the fundamental aspects of phase transformations. Emphasis is placed on the thermodynamic driving forces for phase transformations, the kinetics of nucleation and growth, interfacial structures and energies, transformation crystallography, surface reliefs, and, above all, the atomic mechanisms of phase transformations. Phase transformations and microstructural evolution are directly linked to materials processing, properties, and performance, including in extreme environments, of structural metal alloys. In this paper, aspects of phase transformations and microstructural evolution aremore » highlighted from the atomic to the microscopic scale for ferrous and non-ferrous alloys. Many papers from this issue are highlighted with small summaries of their scientific achievements given.« less

  11. Phase Transformations and Microstructural Evolution: Part II

    DOE PAGES

    Clarke, Amy Jean

    2015-10-30

    The activities of the Phase Transformations Committee of the Materials Processing & Manufacturing Division (MPMD) of The Minerals, Metals & Materials Society (TMS) are oriented toward understanding the fundamental aspects of phase transformations. Emphasis is placed on the thermodynamic driving forces for phase transformations, the kinetics of nucleation and growth, interfacial structures and energies, transformation crystallography, surface reliefs, and, above all, the atomic mechanisms of phase transformations. Phase transformations and microstructural evolution are directly linked to materials processing, properties, and performance. In this issue, aspects of liquid–solid and solid-state phase transformations and microstructural evolution are highlighted. Many papers in thismore » issue are highlighted by this paper, giving a brief summary of what they bring to the scientific community.« less

  12. Phase Transformations and Microstructural Evolution: Part II

    SciTech Connect

    Clarke, Amy Jean

    2015-10-30

    The activities of the Phase Transformations Committee of the Materials Processing & Manufacturing Division (MPMD) of The Minerals, Metals & Materials Society (TMS) are oriented toward understanding the fundamental aspects of phase transformations. Emphasis is placed on the thermodynamic driving forces for phase transformations, the kinetics of nucleation and growth, interfacial structures and energies, transformation crystallography, surface reliefs, and, above all, the atomic mechanisms of phase transformations. Phase transformations and microstructural evolution are directly linked to materials processing, properties, and performance. In this issue, aspects of liquid–solid and solid-state phase transformations and microstructural evolution are highlighted. Many papers in this issue are highlighted by this paper, giving a brief summary of what they bring to the scientific community.

  13. Phase Transformations and Microstructural Evolution: Part I

    SciTech Connect

    Clarke, Amy Jean

    2015-08-29

    The activities of the Phase Transformations Committee of the Materials Processing & Manufacturing Division (MPMD) of The Minerals, Metals & Materials Society (TMS) are oriented toward understanding the fundamental aspects of phase transformations. Emphasis is placed on the thermodynamic driving forces for phase transformations, the kinetics of nucleation and growth, interfacial structures and energies, transformation crystallography, surface reliefs, and, above all, the atomic mechanisms of phase transformations. Phase transformations and microstructural evolution are directly linked to materials processing, properties, and performance, including in extreme environments, of structural metal alloys. In this paper, aspects of phase transformations and microstructural evolution are highlighted from the atomic to the microscopic scale for ferrous and non-ferrous alloys. Many papers from this issue are highlighted with small summaries of their scientific achievements given.

  14. Origin and evolution of the Amazonian craton

    NASA Technical Reports Server (NTRS)

    Gibbs, A. K.; Wirth, K. R.

    1986-01-01

    The Amazonian craton appears to be formed and modifed by processes much like those of the better-known Precambrian cratons, but the major events did not always follow conventional sequences nor did they occur synchronously with those of other cratons. Much of the craton's Archean style continental crust formation, recorded in granite-greenstone and high-grade terranes, occurred in the Early Proterozoic: a period of relative quiescence in many other Precambrian regions. The common Archean to Proterozoic transition in geological style did not occur here, but an analogous change from abundant marine volcanism to dominantly continental sedimentary and eruptive styles occurred later. Amazonian geology is summarized, explaining the evolution of the craton.

  15. Evolution and function of de novo originated genes.

    PubMed

    Wu, Dong-Dong; Zhang, Ya-Ping

    2013-05-01

    De novo origination has recently been appreciated to be an important mechanism contributing to the origin of genes. Evidence indicates that de novo originated genes can evolve important and even essential functions rapidly. We present an "adaptation following neutrality" process to explain the evolution of essential function of new genes. How new de novo originated genes become involved in pathways and interact with other old genes, and the exact functions of these new genes, however, remains largely undocumented. Examinations of the function of de novo origin and the function of noncoding RNA genes should become more frequent and appreciated in the future studies.

  16. The origins and evolution of leadership.

    PubMed

    King, Andrew J; Johnson, Dominic D P; Van Vugt, Mark

    2009-10-13

    How groups of individuals achieve coordination and collective action is an important topic in the natural sciences, but until recently the role of leadership in this process has been largely overlooked. In contrast, leadership is arguably one of the most important themes in the social sciences, permeating all aspects of human social affairs: the election of Barack Obama, the war in Iraq, and the collapse of the banks are all high-profile events that draw our attention to the fundamental role of leadership and followership. Converging ideas and developments in both the natural and social sciences suggest that leadership and followership share common properties across humans and other animals, pointing to ancient roots and evolutionary origins. Here, we draw upon key insights from the animal and human literature to lay the foundation for a new science of leadership inspired by an evolutionary perspective. Identifying the origins of human leadership and followership, as well as which aspects are shared with other animals and which are unique, offers ways of understanding, predicting, and improving leadership today.

  17. The origin and evolution of word order

    PubMed Central

    Gell-Mann, Murray; Ruhlen, Merritt

    2011-01-01

    Recent work in comparative linguistics suggests that all, or almost all, attested human languages may derive from a single earlier language. If that is so, then this language—like nearly all extant languages—most likely had a basic ordering of the subject (S), verb (V), and object (O) in a declarative sentence of the type “the man (S) killed (V) the bear (O).” When one compares the distribution of the existing structural types with the putative phylogenetic tree of human languages, four conclusions may be drawn. (i) The word order in the ancestral language was SOV. (ii) Except for cases of diffusion, the direction of syntactic change, when it occurs, has been for the most part SOV > SVO and, beyond that, SVO > VSO/VOS with a subsequent reversion to SVO occurring occasionally. Reversion to SOV occurs only through diffusion. (iii) Diffusion, although important, is not the dominant process in the evolution of word order. (iv) The two extremely rare word orders (OVS and OSV) derive directly from SOV. PMID:21987807

  18. Origin and Evolution of Europa's Oxygen Exosphere

    NASA Astrophysics Data System (ADS)

    Oza, Apurva V.; Leblanc, Francois; Schmidt, Carl; Johnson, Robert E.

    2016-10-01

    Europa's icy surface is constantly bombarded by sulfur and oxygen ions originating from the Io plasma torus. The momentum transferred to molecules in Europa's surface results in the sputtering of water ice, populating a water product exosphere. We simulate Europa's neutral exosphere using a ballistic 3D Monte Carlo routine and find that the O2 exosphere, while global, is not uniformly symmetric in Europa local time. The O2 exosphere, sourced at a rate of ~ 5 kg/s with a disk-averaged column density of NO2 ~ 2.5 x 1014 O2/cm2, preferentially accumulates towards Europa's dusk. These dawn-dusk atmospheric inhomogeneities escalate as the surface-bounded O2 dissociates into an atomic O corona via electron impact. The inhomogeneities persist and evolve throughout the satellite's orbit, implying a diurnal cycle of the exosphere, recently evidenced by a detailed HST oxygen aurorae campaign (Roth et al. 2016). We conclude that the consistently observed 50% increase in FUV auroral emission from dusk to dawn is principally driven by the day-to-night thermal diffusion of O2 coupled with the Coriolis acceleration. This leads to a dawn-to-dusk gradient, peaking at Europa's leading hemisphere. This exospheric oxygen cycle, dependent on both orbital longitude and magnetic latitude, is fundamentally due to the bulk-sputtering vector changing with respect to the subsolar and subjovian points throughout the orbit. In principle, a similar mechanism should be present at other tidally-locked, rapidly orbiting satellite exospheres.

  19. The origin and evolution of phototropins

    PubMed Central

    Li, Fay-Wei; Rothfels, Carl J.; Melkonian, Michael; Villarreal, Juan C.; Stevenson, Dennis W.; Graham, Sean W.; Wong, Gane K.-S.; Mathews, Sarah; Pryer, Kathleen M.

    2015-01-01

    Plant phototropism, the ability to bend toward or away from light, is predominantly controlled by blue-light photoreceptors, the phototropins. Although phototropins have been well-characterized in Arabidopsis thaliana, their evolutionary history is largely unknown. In this study, we complete an in-depth survey of phototropin homologs across land plants and algae using newly available transcriptomic and genomic data. We show that phototropins originated in an ancestor of Viridiplantae (land plants + green algae). Phototropins repeatedly underwent independent duplications in most major land-plant lineages (mosses, lycophytes, ferns, and seed plants), but remained single-copy genes in liverworts and hornworts—an evolutionary pattern shared with another family of photoreceptors, the phytochromes. Following each major duplication event, the phototropins differentiated in parallel, resulting in two specialized, yet partially overlapping, functional forms that primarily mediate either low- or high-light responses. Our detailed phylogeny enables us to not only uncover new phototropin lineages, but also link our understanding of phototropin function in Arabidopsis with what is known in Adiantum and Physcomitrella (the major model organisms outside of flowering plants). We propose that the convergent functional divergences of phototropin paralogs likely contributed to the success of plants through time in adapting to habitats with diverse and heterogeneous light conditions. PMID:26322073

  20. Sixth Symposium on Chemical Evolution and the Origin and Evolution of Life

    NASA Technical Reports Server (NTRS)

    Acevedo, Sara (Editor); DeVincenzi, Donald L. (Editor); Chang, Sherwood (Editor)

    1998-01-01

    The 6th Symposium on Chemical Evolution and the Origin and Evolution of Life was convened at NASA Ames Research Center, November 17-20, 1997. This Symposium is convened every three years under the auspices of NASA's Exobiology Program Office. All Principal Investigators funded by this Program present their most recent research accomplishments at the Symposium. Scientific papers were presented in the following areas: cosmic evolution of the biogenic elements, prebiotic evolution (both planetary and chemical), evolution of early organisms and evolution of organisms in extreme environments, solar system exploration, and star and planet formation. The Symposium was attended by over 200 scientists from NASA centers and Universities nationwide.

  1. Origin and Evolution of the Moon

    NASA Astrophysics Data System (ADS)

    Zhong, Cuixiang

    2014-01-01

    Since the Moon is the only natural satellite of the Earth, the research on the formation of the Moon can not only find out the formation mechanism of the satellites of Solar System planets but also reveal the evolution law of galaxies in the universe. Hence many hypotheses have been proposed for the Moon's formation, including fission,capture,condensation,and impact event hypothesis, but they all have problems. Recently, the author of this abstract discovered the formation mechanism of the Moon, which can be called ``evolution theory'', and described as follows: During some violent volcanic eruptions of the Earth, some rock debris such as pumice through deep rock hole could achieve a velocity no less than the first cosmic velocity (7.9 km/s) to enter an orbit around the Earth, one of the biggest debris is the young Moon. The orbit of the young Moon might be much closer to the Earth than it is today. There were a lot of ejecta from the Earth in the space. Hence, the Moon has merged these ejecta to become larger and larger, and farther and farther away from the Earth.This can be proved as follows: When the Moon moved around the Earth normally, the centrifugal force produced by the Moon's rotation around the Earth and the Earth's gravitation pull on the Moon had the same size. Let M be the mass of the Earth, m 1 be the mass of the Moon, r m be the radius of the Moon, r be the centroid distance between the Earth and the Moon, v be the tangential velocity of the Moon around the Earth, then Gm 1 M/r 2=m 1 v 2/r, therefore $v=\\sqrt{GM/r}$ . Near the orbit of the Moon, there were also many smaller prograde planetesimals moving around the Earth in circular orbits of radius r x (r-r m \\sqrt{GM/r}$ , which implies v x > v, these planetesimals would finally catch and merge with the Moon.Especially,if a planetesimals was large enough, it would impact the Moon forcefully, making the Moon's velocity increase to a larger

  2. Origin and evolution of asthenospheric layers

    NASA Astrophysics Data System (ADS)

    Czechowski, Leszek; Grad, Marek

    2013-04-01

    is probably in the range from 3 to 5. We investigate the processes of formation and evolution of low viscosity layers ("asthenospheric layers") in the upper mantle. The time scale of the temperature changes is of the order of 10 Myr. The characteristic time of stress changes could be much shorter depending on tectonic processes. Eventually processes of formation and vanishing of low viscosity layers is very dynamical. In a relatively short time (below 1 Myr) the pattern the viscosity distribution and velocity gradient could change substantially. Using results from deep seismic sounding and surface wave tomography we have found that below some regions there are structures in the mantle that could be a forming/vanishing low viscosity layers. Reflectors in the lower lithosphere are observed beneath Trans-European suture zone between Precambrian and Palaeozoic platforms. In a thick Baltic shield lithosphere (200 km or more) low velocity zones and seismic reflectors are observed in the depth range 60-100 km, which could be interpreted as mechanical low Vp velocity zones, in contrast to thermal velocity zone in deeper asthenosphere.

  3. Origin and Evolution of the Cometary Reservoirs

    NASA Astrophysics Data System (ADS)

    Dones, L.; Kaib, N. A.; Brasser, R.

    2014-12-01

    Comets have three known reservoirs: the roughly spherical Oort Cloud (for long-period comets), the flattened Kuiper Belt (for ecliptic comets), and, surprisingly, the asteroid belt (for main-belt comets). Comets in the Oort Cloud are thought to have formed in the region of the giant planets and then placed in quasi-stable orbits at distances of thousands or tens of thousands of AU through the gravitational effects of the planets and the Galaxy. Originally the planets were thought to have formed in place. However, Fernández and Ip (1984) proposed that Jupiter would have migrated slightly inward, while Saturn and (especially) Uranus and Neptune would have migrated outward as they interacted with a massive disk of planetesimals. Malhotra (1993) showed that Pluto's orbit in the 3:2 resonance with Neptune was a natural outcome if Neptune captured Pluto into resonance while it migrated outward. Building on this work, Tsiganis et al. (2005) proposed the "Nice" model, in which the giant planets formed closer together than they are now, and, perhaps many hundreds of Myr later, underwent a dynamical instability that led to a flood of comets and asteroids throughout the Solar System (Gomes et al. 2005). In this scenario, it is somewhat a matter of luck whether an icy planetesimal ends up in the Kuiper Belt or Oort Cloud (Brasser and Morbidelli 2013), as a Trojan asteroid (Morbidelli et al. 2005, Nesvorný and Vokrouhlický 2009, Nesvorný et al. 2013), or as a distant "irregular" satellite of a giant planet (Nesvorný et al. 2007). Comets could even have been captured into the asteroid belt (Levison et al. 2009). The remarkable finding of two "inner Oort cloud" bodies, Sedna and 2012 VP113 (Brown et al. 2004, Sheppard and Trujillo 2014), suggests that the Sun formed in a denser environment, i.e., in a star cluster (Brasser et al. 2006, Kaib and Quinn 2008, Brasser et al. 2012). My talk will focus on how, in spite of this unexpected complexity, we can attempt to surmise the

  4. [Thermodynamics of the origin of life, evolution and aging].

    PubMed

    Gladyshev, G P

    2014-01-01

    Briefly discusses the history of the search of thermodynamic approach to explain the origin of life, evolution and aging of living beings. The origin of life is the result of requirement by the quasi-equilibrium hierarchical thermodynamics, in particular, the supramolecular thermodynamics. The evolution and aging of living beings is accompanied with changes of chemical and supramolecular compositions of living bodies, as well as with changes in the composition and structure of all hierarchies of the living world. The thermodynamic principle of substance stability predicts the existence of a single genetic code in our universe. The thermodynamic theory optimizes physiology and medicine and recommends antiaging diets and medicines. Hierarchical thermodynamics forms the design diversity of culture and art. The thermodynamic theory of origin of life, evolution and aging is the development of Clausius-Gibbs thermodynamics. Hierarchical thermodynamics is the mirror of Darwin-Wallace's-theory.

  5. 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

  6. Origin and use of crystallization phase diagrams

    PubMed Central

    Rupp, Bernhard

    2015-01-01

    Crystallization phase diagrams are frequently used to conceptualize the phase relations and also the processes taking place during the crystallization of macromolecules. While a great deal of freedom is given in crystallization phase diagrams owing to a lack of specific knowledge about the actual phase boundaries and phase equilibria, crucial fundamental features of phase diagrams can be derived from thermodynamic first principles. Consequently, there are limits to what can be reasonably displayed in a phase diagram, and imagination may start to conflict with thermodynamic realities. Here, the commonly used ‘crystallization phase diagrams’ are derived from thermodynamic excess properties and their limitations and appropriate use is discussed. PMID:25760697

  7. Equations of State: Gateway to Planetary Origin and Evolution (Invited)

    NASA Astrophysics Data System (ADS)

    Melosh, J.

    2013-12-01

    Research over the past decades has shown that collisions between solid bodies govern many crucial phases of planetary origin and evolution. The accretion of the terrestrial planets was punctuated by planetary-scale impacts that generated deep magma oceans, ejected primary atmospheres and probably created the moons of Earth and Pluto. Several extrasolar planetary systems are filled with silicate vapor and condensed 'tektites', probably attesting to recent giant collisions. Even now, long after the solar system settled down from its violent birth, a large asteroid impact wiped out the dinosaurs, while other impacts may have played a role in the origin of life on Earth and perhaps Mars, while maintaining a steady exchange of small meteorites between the terrestrial planets and our moon. Most of these events are beyond the scale at which experiments are possible, so that our main research tool is computer simulation, constrained by the laws of physics and the behavior of materials during high-speed impact. Typical solar system impact velocities range from a few km/s in the outer solar system to 10s of km/s in the inner system. Extrasolar planetary systems expand that range to 100s of km/sec typical of the tightly clustered planetary systems now observed. Although computer codes themselves are currently reaching a high degree of sophistication, we still rely on experimental studies to determine the Equations of State (EoS) of materials critical for the correct simulation of impact processes. The recent expansion of the range of pressures available for study, from a few 100 GPa accessible with light gas guns up to a few TPa from current high energy accelerators now opens experimental access to the full velocity range of interest in our solar system. The results are a surprise: several groups in both the USA and Japan have found that silicates and even iron melt and vaporize much more easily in an impact than previously anticipated. The importance of these findings is

  8. Metastable Phase Evolution in Oxide Systems

    NASA Astrophysics Data System (ADS)

    Levi, Carlos G.

    2005-03-01

    Multi-component ceramics are often synthesized by routes that facilitate mixing at the molecular scale and subsequently generate a solid product at low homologous temperatures. Examples include chemical and physical vapor deposition, thermal spray, and pyrolytic decomposition of precursor solutions. In these processes the solid evolves rapidly from a highly energized state, typically in a temperature regime wherein long-range diffusion is largely constrained and the equilibrium configuration can be kinetically suppressed. The resulting product may exhibit various forms of metastability such as amorphization, nanocrystallinity, extended solid solubility and alternate crystalline forms. The approach allows access to novel combinations of structure and composition with unprecedented defect structures that, if reasonably durable, could have properties of potential technological interest. Understanding phase selection and evolution is facilitated by having a suitable reference framework depicting the thermodynamic hierarchy of the phases available to the system under the relevant processing conditions. When transformations are partitionless the phase menu and hierarchy can be readily derived from the relative position of the T0 curves/surfaces for the different pairs of phases. The result is a phase hierarchy map, which is an analog of the phase diagram for partitionless equilibrium. Such maps can then be used to assess the kinetic effects on the selection of metastable states and their subsequent evolution. This presentation will discuss the evolution of metastable phases in oxides, with emphasis on systems involving fluorite phases and their ordered or distorted derivatives. The concepts will be illustrated primarily with zirconia-based systems, notably those of interest in thermal barrier coatings, fuel cells and ferroelectrics (ZrO2-MO3/2, where M = Y, Sc, the lanthanides and combinations thereof, as well as ZrO2-YO3/2-TiO2, ZrO2-TiO2-PbO, etc.). Of particular

  9. The origin and dynamic evolution of chemical information transfer

    PubMed Central

    Steiger, Sandra; Schmitt, Thomas; Schaefer, H. Martin

    2011-01-01

    Although chemical communication is the most widespread form of communication, its evolution and diversity are not well understood. By integrating studies of a wide range of terrestrial plants and animals, we show that many chemicals are emitted, which can unintentionally provide information (cues) and, therefore, act as direct precursors for the evolution of intentional communication (signals). Depending on the content, design and the original function of the cue, there are predictable ways that selection can enhance the communicative function of chemicals. We review recent progress on how efficacy-based selection by receivers leads to distinct evolutionary trajectories of chemical communication. Because the original function of a cue may channel but also constrain the evolution of functional communication, we show that a broad perspective on multiple selective pressures acting upon chemicals provides important insights into the origin and dynamic evolution of chemical information transfer. Finally, we argue that integrating chemical ecology into communication theory may significantly enhance our understanding of the evolution, the design and the content of signals in general. PMID:21177681

  10. Dual-phase evolution in complex adaptive systems

    PubMed Central

    Paperin, Greg; Green, David G.; Sadedin, Suzanne

    2011-01-01

    Understanding the origins of complexity is a key challenge in many sciences. Although networks are known to underlie most systems, showing how they contribute to well-known phenomena remains an issue. Here, we show that recurrent phase transitions in network connectivity underlie emergent phenomena in many systems. We identify properties that are typical of systems in different connectivity phases, as well as characteristics commonly associated with the phase transitions. We synthesize these common features into a common framework, which we term dual-phase evolution (DPE). Using this framework, we review the literature from several disciplines to show that recurrent connectivity phase transitions underlie the complex properties of many biological, physical and human systems. We argue that the DPE framework helps to explain many complex phenomena, including perpetual novelty, modularity, scale-free networks and criticality. Our review concludes with a discussion of the way DPE relates to other frameworks, in particular, self-organized criticality and the adaptive cycle. PMID:21247947

  11. Introduction to 'Origin and evolution of the nervous system'.

    PubMed

    Strausfeld, Nicholas J; Hirth, Frank

    2015-12-19

    In 1665, Robert Hooke demonstrated in Micrographia the power of the microscope and comparative observations, one of which revealed similarities between the arthropod and vertebrate eyes. Utilizing comparative observations, Saint-Hilaire in 1822 was the first to propose that the ventral nervous system of arthropods corresponds to the dorsal nervous system of vertebrates. Since then, studies on the origin and evolution of the nervous system have become inseparable from studies about Metazoan origins and the origins of organ systems. The advent of genome sequence data and, in turn, phylogenomics and phylogenetics have refined cladistics and expanded our understanding of Metazoan phylogeny. However, the origin and evolution of the nervous system is still obscure and many questions and problems remain. A recurrent problem is whether and to what extent sequence data provide reliable guidance for comparisons across phyla. Are genetic data congruent with the geological fossil records? How can we reconcile evolved character loss with phylogenomic records? And how informative are genetic data in relation to the specification of nervous system morphologies? These provide some of the background and context for a Royal Society meeting to discuss new data and concepts that might achieve insights into the origin and evolution of brains and nervous systems.

  12. Origin of Evolution versus Origin of Life: A Shift of Paradigm

    PubMed Central

    Tessera, Marc

    2011-01-01

    The question of the primordial ancestor must be approached through the search for the origin of evolution, not through the search for the origin of life. There is a major issue with the concept of life because it is impossible to define, thus is not a scientific but a metaphysical concept. On the contrary, evolution may be defined by as few as three conditions. These do not necessarily involve biopolymers. However, such an approach must give clues to explain the emergence of distinct lineages to allow Darwinian natural selection. A plausible solution exists within an autotrophic lipidic vesicle-based model that is presented. The model requires the existence of hydrothermal sites such as the Lost City Hydrothermal Field leading to specific constraints. For this reason Mars and Europa may be questioned as possible cradles of evolution. If we replace the search for the origin of life by the one for the origin of evolution our priority first is to find a consensus on the minimal conditions that would allow evolution to emerge and persist anywhere in the universe. PMID:21747687

  13. Origin of evolution versus origin of life: a shift of paradigm.

    PubMed

    Tessera, Marc

    2011-01-01

    The question of the primordial ancestor must be approached through the search for the origin of evolution, not through the search for the origin of life. There is a major issue with the concept of life because it is impossible to define, thus is not a scientific but a metaphysical concept. On the contrary, evolution may be defined by as few as three conditions. These do not necessarily involve biopolymers. However, such an approach must give clues to explain the emergence of distinct lineages to allow Darwinian natural selection. A plausible solution exists within an autotrophic lipidic vesicle-based model that is presented. The model requires the existence of hydrothermal sites such as the Lost City Hydrothermal Field leading to specific constraints. For this reason Mars and Europa may be questioned as possible cradles of evolution. If we replace the search for the origin of life by the one for the origin of evolution our priority first is to find a consensus on the minimal conditions that would allow evolution to emerge and persist anywhere in the universe.

  14. Evolution of structure during phase transitions

    SciTech Connect

    Martin, J.E.; Wilcoxon, J.P.; Anderson, R.A.

    1996-03-01

    Nanostructured materials can be synthesized by utilizing the domain growth that accompanies first-order phase separation. Structural control can be achieved by appropriately selecting the quench depth and the quench time, but in order to do this in a mindful fashion one must understand the kinetics of domain growth. The authors have completed detailed light scattering studies of the evolution of structure in both temperature- and field-quenched phase transitions in two and three dimensional systems. They have studied these systems in the quiescent state and in shear and have developed theoretical models that account for the experimental results.

  15. Chemical Evolution and the Origin of Life: Bibliography 1975

    NASA Technical Reports Server (NTRS)

    West, Martha W. (Compiler); Koch, Rowena A. (Compiler); Chang, Sherwood (Compiler)

    1977-01-01

    This bibliography is the sixth annual supplement to the comprehensive bibliography on the same subject which was published in Space Life Sci.We would like to draw attention to a recently published cumulative bibliography on this same subject: Biochemical Origin of Life: Chemistry and Life. Soil and Water and Its Relationship to Origin of Life. MR - Studies of Prebiotic Polypeptides. Energy, Matter, and Life. Prospects for the Future Orientation of Scientific Research. Photochemical Formation of Self Sustaining Coacervates. Photochemical Formation of Self-Sustaining Coacervates. Comparative Study of Abiogenesis of Cysteine and Other Amino Acids Catalyzed by Various Metal Ions. Protein Structure and the Molecular Evolution of Biological Energy Conversion. Origin of Life. Clues from Relations Between Chemical Compositions of Living Organisms and Natural Environments. Shock Synthesis of Amino Acids II.', Origins of Life 6(1-2). Dynamics of the Chemical Evolution of Earth's Primitive Atmosphere. The Mechanisms of Amino Acids Synthesis by High Temperature Shock-Waves. Theory of Chemical Evolution. Physical Foundations of Probability of Biogenesis.

  16. Origin and evolution of fleshy fruit in woody bamboos.

    PubMed

    Ruiz-Sanchez, Eduardo; Sosa, Victoria

    2015-10-01

    Several hypotheses have been suggested to explain the origin of fleshy fruit in monocots. One is that they originated in the understory of tropical regions and another is that fleshy fruit originated in tropical rainforests where high year-round rainfall implies that seasonality is not a limiting factor. Here we identify the time of origin and ecological preferences of woody bamboos to understand the evolution of the fleshy fruit known as the bacoid caryopsis. Bayesian Inference, Maximum Likelihood and molecular dating analyses were run based on eight plastid and two nuclear regions for 68 bamboo species. Climate data and soil parameters were gathered for 464 localities for these species. The ancestral type of caryopsis was reconstructed by parsimony. According to these analyses the bacoid caryopsis may have evolved independently seven times from the Late Miocene to the Early Pliocene and Mid-Pliocene to Mid-Pleistocene via convergent evolution. Our results suggest that in bamboos neither current climatic variables nor soil parameters were significantly correlated with the appearance of this type of fruit, nor do they have a phylogenetic signal. It is remarkable, however, that the first appearance of the bacoid caryopsis in bamboos might be associated with historical preferences for warmer and wetter climate during the Miocene. Further research is needed to identify whether other factors, such as vivipary or dispersal by small animals, rather than climate, could be responsible for the evolution of this trait in woody bamboos.

  17. The origin and evolution of the woolly mammoth.

    PubMed

    Lister, A M; Sher, A V

    2001-11-02

    The mammoth lineage provides an example of rapid adaptive evolution in response to the changing environments of the Pleistocene. Using well-dated samples from across the mammoth's Eurasian range, we document geographical and chronological variation in adaptive morphology. This work illustrates an incremental (if mosaic) evolutionary sequence but also reveals a complex interplay of local morphological innovation, migration, and extirpation in the origin and evolution of a mammalian species. In particular, northeastern Siberia is identified as an area of successive allopatric innovations that apparently spread to Europe, where they contributed to a complex pattern of stasis, replacement, and transformation.

  18. Origin and evolution of planetary and satellite atmospheres

    SciTech Connect

    Atreya, S.K.; Pollack, J.B.; Matthews, M.S.

    1989-01-01

    The present volume on the origin and evolution of planet and satellite atmospheres discusses the chemistry of interstellar gas and grains, planetary accretion, cometary composition, the inventories of asteroid volatiles, key similarities and differences among the terrestrial planets' atmospheric compositions, and planets' atmospheric escape and water loss. Also discussed are planetary atmosphere-planetary interior evolutionary coupling, the atmospheric composition of the outer planets, the structure and composition of giant planet interiors, the tenuous atmosphere of Io, the sources of the atmospheres of the outer solar system's satellites, the present state and chemical evolution of the Titan, Triton, and Pluto atmospheres, and the thermal structure and heat balance of the outer planets.

  19. Origin and evolution of the genetic code: the universal enigma.

    PubMed

    Koonin, Eugene V; Novozhilov, Artem S

    2009-02-01

    The genetic code is nearly universal, and the arrangement of the codons in the standard codon table is highly nonrandom. The three main concepts on the origin and evolution of the code are the stereochemical theory, according to which codon assignments are dictated by physicochemical affinity between amino acids and the cognate codons (anticodons); the coevolution theory, which posits that the code structure coevolved with amino acid biosynthesis pathways; and the error minimization theory under which selection to minimize the adverse effect of point mutations and translation errors was the principal factor of the code's evolution. These theories are not mutually exclusive and are also compatible with the frozen accident hypothesis, that is, the notion that the standard code might have no special properties but was fixed simply because all extant life forms share a common ancestor, with subsequent changes to the code, mostly, precluded by the deleterious effect of codon reassignment. Mathematical analysis of the structure and possible evolutionary trajectories of the code shows that it is highly robust to translational misreading but there are numerous more robust codes, so the standard code potentially could evolve from a random code via a short sequence of codon series reassignments. Thus, much of the evolution that led to the standard code could be a combination of frozen accident with selection for error minimization although contributions from coevolution of the code with metabolic pathways and weak affinities between amino acids and nucleotide triplets cannot be ruled out. However, such scenarios for the code evolution are based on formal schemes whose relevance to the actual primordial evolution is uncertain. A real understanding of the code origin and evolution is likely to be attainable only in conjunction with a credible scenario for the evolution of the coding principle itself and the translation system.

  20. Urey Prize Lecture - Planetary evolution and the origin of life

    NASA Technical Reports Server (NTRS)

    Mckay, Christopher P.

    1991-01-01

    One of the principal questions concerning planetary evolution and life's origins relates to the early-earth organic material's origination in situ, outer solar system importation, or simple irrelevance to the emergence of organisms. Additional considerations encompass the character of interstellar organic material and its relationship to outer solar system organic compounds, and the possibility of life's emergence in the early Mars. Attention is given to the essentiality of liquid water for life-forms, in the role not only of a reaction medium among molecules but that of a basis for hydrophylic and hydrophobic groups' bonding.

  1. Origins of Solar Systems Workshop: The Origin, Evolution, and Detectability of Short Period Comets

    NASA Technical Reports Server (NTRS)

    Stern, S. Alan

    1993-01-01

    The origin of the short period comets (SPC) (periods less than 200 years), the dynamical formation of their present reservoir(s), the cause and rate of their transport to the inner planetary region where they can be detected, and the magnitude of selection effects in their discovery are important research questions directly coupled to the goals of understanding the origin and evolution of the Solar System. To address these questions in an intensive way, an interdisciplinary, five month long Workshop from Jan. to May 1993 at Southwest Research Institute (SwRI) in San Antonio was convened. The goal of this Workshop was to advance the state of understanding about the origins, dynamical evolution, and present location of short period comets and their reservoir(s).

  2. High rates of evolution preceded the origin of birds.

    PubMed

    Puttick, Mark N; Thomas, Gavin H; Benton, Michael J

    2014-05-01

    The origin of birds (Aves) is one of the great evolutionary transitions. Fossils show that many unique morphological features of modern birds, such as feathers, reduction in body size, and the semilunate carpal, long preceded the origin of clade Aves, but some may be unique to Aves, such as relative elongation of the forelimb. We study the evolution of body size and forelimb length across the phylogeny of coelurosaurian theropods and Mesozoic Aves. Using recently developed phylogenetic comparative methods, we find an increase in rates of body size and body size dependent forelimb evolution leading to small body size relative to forelimb length in Paraves, the wider clade comprising Aves and Deinonychosauria. The high evolutionary rates arose primarily from a reduction in body size, as there were no increased rates of forelimb evolution. In line with a recent study, we find evidence that Aves appear to have a unique relationship between body size and forelimb dimensions. Traits associated with Aves evolved before their origin, at high rates, and support the notion that numerous lineages of paravians were experimenting with different modes of flight through the Late Jurassic and Early Cretaceous.

  3. HIGH RATES OF EVOLUTION PRECEDED THE ORIGIN OF BIRDS

    PubMed Central

    Puttick, Mark N; Thomas, Gavin H; Benton, Michael J; Polly, P David

    2014-01-01

    The origin of birds (Aves) is one of the great evolutionary transitions. Fossils show that many unique morphological features of modern birds, such as feathers, reduction in body size, and the semilunate carpal, long preceded the origin of clade Aves, but some may be unique to Aves, such as relative elongation of the forelimb. We study the evolution of body size and forelimb length across the phylogeny of coelurosaurian theropods and Mesozoic Aves. Using recently developed phylogenetic comparative methods, we find an increase in rates of body size and body size dependent forelimb evolution leading to small body size relative to forelimb length in Paraves, the wider clade comprising Aves and Deinonychosauria. The high evolutionary rates arose primarily from a reduction in body size, as there were no increased rates of forelimb evolution. In line with a recent study, we find evidence that Aves appear to have a unique relationship between body size and forelimb dimensions. Traits associated with Aves evolved before their origin, at high rates, and support the notion that numerous lineages of paravians were experimenting with different modes of flight through the Late Jurassic and Early Cretaceous. PMID:24471891

  4. Origin and evolution of contact binaries of W UMa type

    NASA Astrophysics Data System (ADS)

    Rahunen, T.; Vilhu, O.

    Angular momentum loss estimates for single stars are employed to discuss three theories for contact binary evolution. Two of the theories of the metamorphoses of W UMa stars involve the fission of a rapidly rotating star at the end of the pre-main sequence contraction phase, resulting in a constant level of angular momentum and small mass ratios. The second sequence comprises an evolution of the companion from angular momentum loss from a detached or semidetached binary. Chromospheric Ca(+) emission observations are noted to correlate with rotational velocity predicted for the second type of evolution of angular momentum loss rate. The models display cyclic behavior on a time scale of one to ten million years, although the contact never breaks. It is concluded that the constant angular momentum models require a formation process which yield unequal components, while the detached, followed by contact, process is the most natural production mechanism.

  5. Leishmania: origin, evolution and future since the Precambrian.

    PubMed

    Tuon, Felipe Francisco; Neto, Vicente Amato; Amato, Valdir Sabbaga

    2008-11-01

    This brief review discusses the history of leishmaniasis, considering its origin from the Paleoartic, Neoartic or Neotropic. We reassess some of the theories of the likely origin of this protozoan since the beginning of life on Earth, passing through the Mesozoic and continuing to the appearance of humans. The relationship between this parasite or its ancestors, possible vectors and hosts with regard to ecological modifications is discussed. Recent molecular techniques have helped to elucidate some of the evolutionary questions regarding Leishmania, but have also brought doubts about the origin and evolution of this human parasite. PCR has been used for studies in the new discipline of paleoparasitology, helping to elucidate some of the remaining evolutionary questions. Understanding of this global condition is fundamental in determining the best approach to use against the parasite, specifically for the development of an efficient vaccine.

  6. On the Origin and Evolution of Galactic Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Lesch, H.; Chiba, M.

    The existence of large-scale magnetic fields in galaxies is still a challenge for theoretical astrophysics. Are magnetic fields of primordial origin, produced somehow during the initial stages of cosmic evolution or are they intrinsically produced by the galaxies themselves? Especially observations of m G fields in high redshift (z = 2-3) damped Lyman alpha clouds, which are supposed to be the progenitors of disk galaxies, raise questions about the origin of such strong fields only one or two Gigayears after the Big Bang. Recent observations of galactic magnetic fields in nearby disk galaxies as well as in high redshift objects are reviewed and the role of electrodynamical coupling of the fields and the gas motions in different stages of galaxy evolution is emphasized. By presenting two different scenarios-action of a turbulent dynamo in axisymmetric differentially rotating disks and magnetic field amplification by non-axisymmetric dynamical processes (protogalactic collapse and subsequent excitation of spiral arms and bars) - we illustrate the basic problems of magnetic field production and amplification in galactic systems. It is shown that origin and amplification via dynamical processes leads to appropriate time scales and efficiencies to account for the strong magnetic fields in high redshift objects as well as the field structure in nearby disk galaxies. We describe the implications for galaxy formation if such strong fields exist in the epoch prior to galaxy formation. Finally we discuss our conclusion that the origin and evolution of galactic magnetic fields can only be understood by considering the time-varying velocity field of the conductor, the galactic interstellar medium in all stages of a galactic lifetime, in detail.

  7. Origin and evolution of carnivorism in the Ascomycota (fungi).

    PubMed

    Yang, Ence; Xu, Lingling; Yang, Ying; Zhang, Xinyu; Xiang, Meichun; Wang, Chengshu; An, Zhiqiang; Liu, Xingzhong

    2012-07-03

    Carnivorism is one of the basic life strategies of fungi. Carnivorous fungi possess the ability to trap and digest their preys by sophisticated trapping devices. However, the origin and development of fungal carnivorism remains a gap in evolution biology. In this study, five protein-encoding genes were used to construct the phylogeny of the carnivorous fungi in the phylum Ascomycota; these fungi prey on nematodes by means of specialized trapping structures such as constricting rings and adhesive traps. Our analysis revealed a definitive pattern of evolutionary development for these trapping structures. Molecular clock calibration based on two fossil records revealed that fungal carnivorism diverged from saprophytism about 419 Mya, which was after the origin of nematodes about 550-600 Mya. Active carnivorism (fungi with constricting rings) and passive carnivorism (fungi with adhesive traps) diverged from each other around 246 Mya, shortly after the occurrence of the Permian-Triassic extinction event about 251.4 Mya. The major adhesive traps evolved around 198-208 Mya, which was within the time frame of the Triassic-Jurassic extinction event about 201.4 Mya. However, no major carnivorous ascomycetes divergence was correlated to the Cretaceous-Tertiary extinction event, which occurred more recently (about 65.5 Mya). Therefore, a causal relationship between mass extinction events and fungal carnivorism evolution is not validated in this study. More evidence including additional fossil records is needed to establish if fungal carnivorism evolution was a response to mass extinction events.

  8. Origin and evolution of carnivorism in the Ascomycota (fungi)

    PubMed Central

    Yang, Ence; Xu, Lingling; Yang, Ying; Zhang, Xinyu; Xiang, Meichun; Wang, Chengshu; An, Zhiqiang; Liu, Xingzhong

    2012-01-01

    Carnivorism is one of the basic life strategies of fungi. Carnivorous fungi possess the ability to trap and digest their preys by sophisticated trapping devices. However, the origin and development of fungal carnivorism remains a gap in evolution biology. In this study, five protein-encoding genes were used to construct the phylogeny of the carnivorous fungi in the phylum Ascomycota; these fungi prey on nematodes by means of specialized trapping structures such as constricting rings and adhesive traps. Our analysis revealed a definitive pattern of evolutionary development for these trapping structures. Molecular clock calibration based on two fossil records revealed that fungal carnivorism diverged from saprophytism about 419 Mya, which was after the origin of nematodes about 550–600 Mya. Active carnivorism (fungi with constricting rings) and passive carnivorism (fungi with adhesive traps) diverged from each other around 246 Mya, shortly after the occurrence of the Permian–Triassic extinction event about 251.4 Mya. The major adhesive traps evolved around 198–208 Mya, which was within the time frame of the Triassic–Jurassic extinction event about 201.4 Mya. However, no major carnivorous ascomycetes divergence was correlated to the Cretaceous–Tertiary extinction event, which occurred more recently (about 65.5 Mya). Therefore, a causal relationship between mass extinction events and fungal carnivorism evolution is not validated in this study. More evidence including additional fossil records is needed to establish if fungal carnivorism evolution was a response to mass extinction events. PMID:22715289

  9. Origin and evolution of life on terrestrial planets.

    PubMed

    Brack, A; Horneck, G; Cockell, C S; Bérces, A; Belisheva, N K; Eiroa, Carlos; Henning, Thomas; Herbst, Tom; Kaltenegger, Lisa; Léger, Alain; Liseau, Réne; Lammer, Helmut; Selsis, Franck; Beichman, Charles; Danchi, William; Fridlund, Malcolm; Lunine, Jonathan; Paresce, Francesco; Penny, Alan; Quirrenbach, Andreas; Röttgering, Huub; Schneider, Jean; Stam, Daphne; Tinetti, Giovanna; White, Glenn J

    2010-01-01

    The ultimate goal of terrestrial planet-finding missions is not only to discover terrestrial exoplanets inside the habitable zone (HZ) of their host stars but also to address the major question as to whether life may have evolved on a habitable Earth-like exoplanet outside our Solar System. We note that the chemical evolution that finally led to the origin of life on Earth must be studied if we hope to understand the principles of how life might evolve on other terrestrial planets in the Universe. This is not just an anthropocentric point of view: the basic ingredients of terrestrial life, that is, reduced carbon-based molecules and liquid H(2)O, have very specific properties. We discuss the origin of life from the chemical evolution of its precursors to the earliest life-forms and the biological implications of the stellar radiation and energetic particle environments. Likewise, the study of the biological evolution that has generated the various life-forms on Earth provides clues toward the understanding of the interconnectedness of life with its environment.

  10. Molecular evolution of Pediculus humanus and the origin of clothing.

    PubMed

    Kittler, Ralf; Kayser, Manfred; Stoneking, Mark

    2003-08-19

    The human head louse (Pediculus humanus capitis) and body louse (P. humanus corporis or P. h. humanus) are strict, obligate human ectoparasites that differ mainly in their habitat on the host : the head louse lives and feeds exclusively on the scalp, whereas the body louse feeds on the body but lives in clothing. This ecological differentiation probably arose when humans adopted frequent use of clothing, an important event in human evolution for which there is no direct archaeological evidence. We therefore used a molecular clock approach to date the origin of body lice, assuming that this should correspond with the frequent use of clothing. Sequences were obtained from two mtDNA and two nuclear DNA segments from a global sample of 40 head and body lice, and from a chimpanzee louse to use as an outgroup. The results indicate greater diversity in African than non-African lice, suggesting an African origin of human lice. A molecular clock analysis indicates that body lice originated not more than about 72,000 +/- 42,000 years ago; the mtDNA sequences also indicate a demographic expansion of body lice that correlates with the spread of modern humans out of Africa. These results suggest that clothing was a surprisingly recent innovation in human evolution.

  11. Origin and evolution of MIR1444 genes in Salicaceae

    PubMed Central

    Wang, Meizhen; Li, Caili; Lu, Shanfa

    2017-01-01

    miR1444s are functionally significant miRNAs targeting polyphenol oxidase (PPO) genes for cleavage. MIR1444 genes were reported only in Populus trichocarpa. Through the computational analysis of 215 RNA-seq data, four whole genome sequences of Salicaceae species and deep sequencing of six P. trichocarpa small RNA libraries, we investigated the origin and evolution history of MIR1444s. A total of 23 MIR1444s were identified. Populus and Idesia species contain two MIR1444 genes, while Salix includes only one. Populus and Idesia MIR1444b genes and Salix MIR1444s were phylogenetically separated from Populus and Idesia MIR1444a genes. Ptr-miR1444a and ptr-miR1444b showed sequence divergence. Compared with ptr-miR1444b, ptr-miR1444a started 2 nt upstream of precursor, resulting in differential regulation of PPO targets. Sequence alignments showed that MIR1444 genes exhibited extensive similarity to their PPO targets, the characteristics of MIRs originated from targets through an inverted gene duplication event. Genome sequence comparison showed that MIR1444 genes in Populus and Idesia were expanded through the Salicoid genome duplication event. A copy of MIR1444 gene was lost in Salix through DNA segment deletion during chromosome rearrangements. The results provide significant information for the origin of plant miRNAs and the mechanism of Salicaceae gene evolution and divergence. PMID:28071760

  12. 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.

  13. Orbital evolution and origin of the Martian satellites

    SciTech Connect

    Szeto, A.M.K.

    1983-07-01

    The orbital evolution of the Martian satellites is considered from a dynamical point of view. Celestial mechanics relevant to the calculation of satellite orbital evolution is introduced and the physical parameters to be incorporated in the modeling of tidal dissipation are discussed. Results of extrapolating the satellite orbits backward and forward in time are presented and compared with those of other published work. Collision probability calculations and results for the Martian satellite system are presented and discussed. The implications of these calculations for the origin scenarios of the satellites are assessed. It is concluded that Deimos in its present form could not have been captured, for if it had been, it would have collided with Phobos at some point. An accretion model is therefore preferred over capture, although such a model consistent with the likely carbonaceous chondritic composition of the satellites has yet to be established. 91 references.

  14. 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

  15. Origin and evolution of sulfadoxine resistant Plasmodium falciparum.

    PubMed

    Vinayak, Sumiti; Alam, Md Tauqeer; Mixson-Hayden, Tonya; McCollum, Andrea M; Sem, Rithy; Shah, Naman K; Lim, Pharath; Muth, Sinuon; Rogers, William O; Fandeur, Thierry; Barnwell, John W; Escalante, Ananias A; Wongsrichanalai, Chansuda; Ariey, Frederick; Meshnick, Steven R; Udhayakumar, Venkatachalam

    2010-03-26

    The Thailand-Cambodia border is the epicenter for drug-resistant falciparum malaria. Previous studies have shown that chloroquine (CQ) and pyrimethamine resistance originated in this region and eventually spread to other Asian countries and Africa. However, there is a dearth in understanding the origin and evolution of dhps alleles associated with sulfadoxine resistance. The present study was designed to reveal the origin(s) of sulfadoxine resistance in Cambodia and its evolutionary relationship to African and South American dhps alleles. We sequenced 234 Cambodian Plasmodium falciparum isolates for the dhps codons S436A/F, A437G, K540E, A581G and A613S/T implicated in sulfadoxine resistance. We also genotyped 10 microsatellite loci around dhps to determine the genetic backgrounds of various alleles and compared them with the backgrounds of alleles prevalent in Africa and South America. In addition to previously known highly-resistant triple mutant dhps alleles SGEGA and AGEAA (codons 436, 437, 540, 581, 613 are sequentially indicated), a large proportion of the isolates (19.3%) contained a 540N mutation in association with 437G/581G yielding a previously unreported triple mutant allele, SGNGA. Microsatellite data strongly suggest the strength of selection was greater on triple mutant dhps alleles followed by the double and single mutants. We provide evidence for at least three independent origins for the double mutants, one each for the SGKGA, AGKAA and SGEAA alleles. Our data suggest that the triple mutant allele SGEGA and the novel allele SGNGA have common origin on the SGKGA background, whereas the AGEAA triple mutant was derived from AGKAA on multiple, albeit limited, genetic backgrounds. The SGEAA did not share haplotypes with any of the triple mutants. Comparative analysis of the microsatellite haplotypes flanking dhps alleles from Cambodia, Kenya, Cameroon and Venezuela revealed an independent origin of sulfadoxine resistant alleles in each of these regions.

  16. On the origins of novelty in development and evolution.

    PubMed

    Moczek, Armin P

    2008-05-01

    The origin of novel traits is what draws many to evolutionary biology, yet our understanding of the mechanisms that underlie the genesis of novelty remains limited. Here I review definitions of novelty including its relationship to homology. I then discuss how ontogenetic perspectives may allow us to move beyond current roadblocks in our understanding of the mechanics of innovation. Specifically, I explore the roles of canalization, plasticity and threshold responses during development in generating a reservoir of cryptic genetic variation free to drift and accumulate in natural populations. Environmental or genetic perturbations that exceed the buffering capacity of development can then release this variation, and, through evolution by genetic accommodation, result in rapid diversification, recurrence of lost phenotypes as well as the origins of novel features. I conclude that, in our quest to understand the nature of innovation, the nature of development deserves to take center stage.

  17. Quantum Tunnelling to the Origin and Evolution of Life

    PubMed Central

    Trixler, Frank

    2013-01-01

    Quantum tunnelling is a phenomenon which becomes relevant at the nanoscale and below. It is a paradox from the classical point of view as it enables elementary particles and atoms to permeate an energetic barrier without the need for sufficient energy to overcome it. Tunnelling might seem to be an exotic process only important for special physical effects and applications such as the Tunnel Diode, Scanning Tunnelling Microscopy (electron tunnelling) or Near-field Optical Microscopy operating in photon tunnelling mode. However, this review demonstrates that tunnelling can do far more, being of vital importance for life: physical and chemical processes which are crucial in theories about the origin and evolution of life can be traced directly back to the effects of quantum tunnelling. These processes include the chemical evolution in stellar interiors and within the cold interstellar medium, prebiotic chemistry in the atmosphere and subsurface of planetary bodies, planetary habitability via insolation and geothermal heat as well as the function of biomolecular nanomachines. This review shows that quantum tunnelling has many highly important implications to the field of molecular and biological evolution, prebiotic chemistry and astrobiology. PMID:24039543

  18. Quantum Tunnelling to the Origin and Evolution of Life.

    PubMed

    Trixler, Frank

    2013-08-01

    Quantum tunnelling is a phenomenon which becomes relevant at the nanoscale and below. It is a paradox from the classical point of view as it enables elementary particles and atoms to permeate an energetic barrier without the need for sufficient energy to overcome it. Tunnelling might seem to be an exotic process only important for special physical effects and applications such as the Tunnel Diode, Scanning Tunnelling Microscopy (electron tunnelling) or Near-field Optical Microscopy operating in photon tunnelling mode. However, this review demonstrates that tunnelling can do far more, being of vital importance for life: physical and chemical processes which are crucial in theories about the origin and evolution of life can be traced directly back to the effects of quantum tunnelling. These processes include the chemical evolution in stellar interiors and within the cold interstellar medium, prebiotic chemistry in the atmosphere and subsurface of planetary bodies, planetary habitability via insolation and geothermal heat as well as the function of biomolecular nanomachines. This review shows that quantum tunnelling has many highly important implications to the field of molecular and biological evolution, prebiotic chemistry and astrobiology.

  19. Human origins and evolution: Cold Spring Harbor, deja vu.

    PubMed

    White, T D

    2009-01-01

    The Cold Spring Harbor Symposia of the 1950s were key to integrating human evolutionary studies into biology. That integration provided a solid foundation for systematic and functional interpretations of an expanding base of fossil and molecular evidence during the latter half of the 20th century. Today, the paleontological record of human evolution amassed during the last 150 years illuminates the human clade on life's tree. However, the rise of Hennegian parsimony cladistics and punctuationalism during the end of the last century witnessed the partial abandonment of classificatory conventions cemented by Mayr, Simpson, Dobzhansky, and others at Cold Spring Harbor. This has led to an artificial, postmillennial amplification of apparent species diversity in the hominid clade. Work on a stratigraphically thick and temporally deep sedimentary sequence in the Middle Awash study area of Ethiopia's Afar Depression reveals an assembly order of hominid anatomies and behaviors that was impossible for Darwin to discern. Large parts of that record appear to reflect phyletic evolution, consistent with the lessons and expectations of Cold Spring Harbor in 1950. Molecular biology cannot reveal the assembly sequences or contexts of human origins and evolution without reference to adequate geological, geochronological, paleobiological, and archaeological records. Today's consilience of these disparate data sets would have impressed Charles Darwin.

  20. The clonal origin and clonal evolution of epithelial tumours

    PubMed Central

    Garcia, Sergio Britto; Novelli, Marco; Wright, Nicholas A

    2000-01-01

    While the origin of tumours, whether from one cell or many, has been a source of fascination for experimental oncologists for some time, in recent years there has been a veritable explosion of information about the clonal architecture of tumours and their antecedents, stimulated, in the main, by the ready accessibility of new molecular techniques. While most of these new results have apparently confirmed the monoclonal origin of human epithelial (and other) tumours, there are a significant number of studies in which this conclusion just cannot be made. Moreover, analysis of many articles show that the potential impact of such considerations as patch size and clonal evolution on determinations of clonality have largely been ignored, with the result that a number of these studies are confounded. However, the clonal architecture of preneoplastic lesions provide some interesting insights — many lesions which might have been hitherto regarded as hyperplasias are apparently clonal in derivation. If this is indeed true, it calls into some question our hopeful corollary that a monoclonal origin presages a neoplastic habitus. Finally, it is clear, for many reasons, that methods of analysis which involve the disaggregation of tissues, albeit microdissected, are far from ideal and we should be putting more effort into techniques where the clonal architecture of normal tissues, preneoplastic and preinvasive lesions and their derivative tumours can be directly visualized in situ. PMID:10762440

  1. Origin and evolution of laminin gene family diversity.

    PubMed

    Fahey, Bryony; Degnan, Bernard M

    2012-07-01

    Laminins are a family of multidomain glycoproteins that are important contributors to the structure of metazoan extracellular matrices. To investigate the origin and evolution of the laminin family, we characterized the full complement of laminin-related genes in the genome of the sponge, Amphimedon queenslandica. As a representative of the Demospongiae, a group consistently placed within the earliest diverging branch of animals by molecular phylogenies, Amphimedon is uniquely placed to provide insight into early steps in the evolution of metazoan gene families. Five Amphimedon laminin-related genes possess the conserved molecular features, and most of the domains found in bilaterian laminins, but all display domain architectures distinct from those of the canonical laminin chain types known from model bilaterians. This finding prompted us to perform a comparative genomic analysis of laminins and related genes from a choanoflagellate and diverse metazoans and to conduct phylogenetic analyses using the conserved Laminin N-terminal domain in order to explore the relationships between genes with distinct architectures. Laminin-like genes appear to have originated in the holozoan lineage (choanoflagellates + metazoans + several other unicellular opisthokont taxa), with several laminin domains originating later and appearing only in metazoan (animal) or eumetazoan (placozoans + ctenophores + cnidarians + bilaterians) laminins. Typical bilaterian α, β, and γ laminin chain forms arose in the eumetazoan stem and another chain type that is conserved in Amphimedon, the cnidarian, Nematostella vectensis, and the echinoderm, Strongylocentrotus purpuratus, appears to have been lost independently from the placozoan, Trichoplax adhaerens, and from multiple bilaterians. Phylogenetic analysis did not clearly reconstruct relationships between the distinct laminin chain types (with the exception of the α chains) but did reveal how several members of the netrin family were

  2. Origin and geochemical evolution of the Michigan basin brine

    SciTech Connect

    Wilson, T.P.

    1989-01-01

    Chemical and isotopic data were collected on 126 oil field brine samples and were used to investigate the origin and geochemical evolution of water in 8 geologic formations in the Michigan basin. Two groups of brine are found in the basin, the Na-Ca-Cl brine in the upper Devonian formations, and Ca-Na-Cl brine from the lower Devonian and Silurian aged formations. Water in the upper Devonian Berea, Traverse, and Dundee formations originated from seawater concentrated into halite facies. This brine evolved by halite precipitation, dolomitization, aluminosilicate reactions, and the removal of SO{sub 4} by bacterial action or by CaSO{sub 4} precipitation. The stable isotopic composition (D, O) is thought to represent dilution of evapo-concentrated seawater by meteoric water. Water in the lower Devonian Richfield, Detroit River Group, and Niagara-Salina formations is very saline Ca-Na-Cl brine. Cl/Br suggest it originated from seawater concentrated through the halite and into the MgSO{sub 4} salt facies, with an origin linked to the Silurian and Devonian salt deposits. Dolomitization and halite precipitation increased the Ca/Na, aluminosilicate reactions removed K, and bacterial action or CaSO{sub 4} precipitation removed SO{sub 4} from this brine. Water chemistry in the Ordovician Trenton-Black River formations indicates dilution of evapo-concentrated seawater by fresh or seawater. Possible saline end-members include Ordovician seawater, present-day upper Devonian brine, or Ca-Cl brine from the deeper areas in the basin.

  3. Evolution of the Archaea: emerging views on origins and phylogeny.

    PubMed

    Fournier, Gregory P; Dick, Amanda A; Williams, David; Gogarten, J Peter

    2011-01-01

    Of the three domains of life, the Archaea are the most recently discovered and, from the perspective of systematics, perhaps the least understood. More than three decades after their discovery, there is still no overwhelming consensus as to their phylogenetic status, with diverse evidence supporting in varying degrees their monophyly, paraphyly, or even polyphyly. As a further complication, their evolutionary history is inextricably linked to the origin of Eukarya, one of the most challenging problems in evolutionary biology. This exclusive relationship between the eukaryal nucleocytoplasm and the Archaea is further supported by a new methodology for rooting the ribosomal Tree of Life based on amino acid composition. Novel approaches such as utilizing horizontal gene transfers as synchronizing events and branch length analysis of deep paralogs will help to clarify temporal relationships between these lineages, and may prove useful in evaluating the numerous conflicting hypotheses related to the evolution of the Archaea and Eukarya.

  4. 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.

  5. Giant viruses in the environment: their origins and evolution.

    PubMed

    Yamada, Takashi

    2011-07-01

    The recent identification of giant viruses has raised important questions, not only regarding their origin and evolution, but also regarding the differentiation between viruses and living organisms. These viruses possess large genomes encoding genes potentially involved in various metabolic processes and even protein synthesis, indicating their putative autonomy. Giant viruses of the Phycodnaviridae and Mimiviridae families appear to share a common evolutionary ancestor with members of the nucleo-cytoplasmic large DNA viruses. Many giant viruses are associated with protists in aquatic environments and might have evolved in protist cells. They may therefore play important roles in material cycling in natural ecosystems. With the advent of environmental metagenomic projects, there will be more chances to encounter novel giant viruses in the future.

  6. 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.

  7. Himalayan Origin and Evolution of Myricaria (Tamaricaeae) in the Neogene

    PubMed Central

    Zhang, Ming-Li; Meng, Hong-Hu; Zhang, Hong-Xiang; Vyacheslav, Byalt V.; Sanderson, Stewart C.

    2014-01-01

    Background Myricaria consists of about twelve-thirteen species and occurs in Eurasian North Temperate zone, most species in the Qinghai-Tibet Plateau (QTP) and adjacent areas. Methodology/Principal Findings Twelve species of Myricaria plus two other genera Tamarix and Reaumuria in Tamaricaceae, were sampled, and four markers, ITS, rps16, psbB-psbH, and trnL-trnF were sequenced. The relaxed Bayesian molecular clock BEAST method was used to perform phylogenetic analysis and molecular dating, and Diva, S-Diva, and maximum likelihood Lagrange were used to estimate the ancestral area. The results indicated that Myricaria could be divided into four phylogenetic clades, which correspond to four sections within the genus, of them two are newly described in this paper. The crown age of Myricaria was dated to early Miocene ca. 20 Ma, at the probable early uplifting time of the Himalayas. The Himalayas were also shown as the center of origin for Myricaria from the optimization of ancestral distribution. Migration and dispersal of Myricaria were indicated to have taken place along the Asian Mountains, including the Himalayas, Kunlun, Altun, Hendukosh, Tianshan, Altai, and Caucasus etc., westward to Europe, eastward to Central China, and northward to the Mongolian Plateau. Conclusions/Significance Myricaria spatiotemporal evolution presented here, especially the Himalayan origin at early Miocene ca. 20 Ma, and then migrated westward and eastward along the Asian mountains, offers a significant evolutionary case for QTP and Central Asian biogeography. PMID:24905234

  8. Origin and evolution of valleys on Martian volcanoes

    SciTech Connect

    Gulick, V.C.; Baker, V.R. )

    1990-08-30

    Morphological analyses of six Martian volcanoes, Ceraunius Tholus, Hecates Tholus, Alba Patera, Hadriaca Patera, Apollinaris Patera, and Tyrrhena Patera, indicate that fluvial processes were the dominant influence in the initiation and subsequent development of many dissecting valleys. Lava processes and possibly volcanic density flows were also important as valley-forming processes. Fluvial valleys are especially well developed on Alba Patera, Ceraunius Tholus, and Hecates Tholus. These valleys are inset into the surrounding landscape. They formed in regions of subdued lava flow morphology, contain tributaries, and tend to widen slightly in the downstream direction. Lava channels on Alba Patera are located on the crest of lava flows and have a discontinuous, irregular surface morphology, and distributary patterns. These channels sometimes narrow toward their termini. Possible volcanic density flow channels are located on the northern flank of Ceraunius Tholus. Valleys dissecting Apollinaris Patera, Hadriaca Patera, and Tyrrhena Patera appear to have a complex evolution, probably a mixed fluvial and lava origin. They are inset into a subdued (possibly mantled) surface, lack tributaries, and either have fairly constant widths or widen slightly downvalley. Valleys surrounding the caldera of Apollinaris appear to have formed by fluvial and possibly by volcanic density flow processes, while those on the Apollinaris fan structure may have a mixed lava and fluvial origin. Valleys on Tyrrhena have broad flat floors and theater heads, which have been extensively enlarged, probably by sapping.

  9. Mitogenomic analyses provide new insights into cetacean origin and evolution.

    PubMed

    Arnason, Ulfur; Gullberg, Anette; Janke, Axel

    2004-05-26

    The evolution of the order Cetacea (whales, dolphins, porpoises) has, for a long time, attracted the attention of evolutionary biologists. Here we examine cetacean phylogenetic relationships on the basis of analyses of complete mitochondrial genomes that represent all extant cetacean families. The results suggest that the ancestors of recent cetaceans had an explosive evolutionary radiation 30-35 million years before present. During this period, extant cetaceans divided into the two primary groups, Mysticeti (baleen whales) and Odontoceti (toothed whales). Soon after this basal split, the Odontoceti diverged into the four extant lineages, sperm whales, beaked whales, Indian river dolphins and delphinoids (iniid river dolphins, narwhals/belugas, porpoises and true dolphins). The current data set has allowed test of two recent morphological hypotheses on cetacean origin. One of these hypotheses posits that Artiodactyla and Cetacea originated from the extinct group Mesonychia, and the other that Mesonychia/Cetacea constitutes a sister group to Artiodactyla. The current results are inconsistent with both these hypotheses. The findings suggest that the claimed morphological similarities between Mesonychia and Cetacea are the result of evolutionary convergence rather than common ancestry.

  10. Origin and evolution of developmental enhancers in the mammalian neocortex

    PubMed Central

    Emera, Deena; Yin, Jun; Reilly, Steven K.; Gockley, Jake; Noonan, James P.

    2016-01-01

    Morphological innovations such as the mammalian neocortex may involve the evolution of novel regulatory sequences. However, de novo birth of regulatory elements active during morphogenesis has not been extensively studied in mammals. Here, we use H3K27ac-defined regulatory elements active during human and mouse corticogenesis to identify enhancers that were likely active in the ancient mammalian forebrain. We infer the phylogenetic origins of these enhancers and find that ∼20% arose in the mammalian stem lineage, coincident with the emergence of the neocortex. Implementing a permutation strategy that controls for the nonrandom variation in the ages of background genomic sequences, we find that mammal-specific enhancers are overrepresented near genes involved in cell migration, cell signaling, and axon guidance. Mammal-specific enhancers are also overrepresented in modules of coexpressed genes in the cortex that are associated with these pathways, notably ephrin and semaphorin signaling. Our results also provide insight into the mechanisms of regulatory innovation in mammals. We find that most neocortical enhancers did not originate by en bloc exaptation of transposons. Young neocortical enhancers exhibit smaller H3K27ac footprints and weaker evolutionary constraint in eutherian mammals than older neocortical enhancers. Based on these observations, we present a model of the enhancer life cycle in which neocortical enhancers initially emerge from genomic background as short, weakly constrained “proto-enhancers.” Many proto-enhancers are likely lost, but some may serve as nucleation points for complex enhancers to evolve. PMID:27114548

  11. Origin and evolution of developmental enhancers in the mammalian neocortex.

    PubMed

    Emera, Deena; Yin, Jun; Reilly, Steven K; Gockley, Jake; Noonan, James P

    2016-05-10

    Morphological innovations such as the mammalian neocortex may involve the evolution of novel regulatory sequences. However, de novo birth of regulatory elements active during morphogenesis has not been extensively studied in mammals. Here, we use H3K27ac-defined regulatory elements active during human and mouse corticogenesis to identify enhancers that were likely active in the ancient mammalian forebrain. We infer the phylogenetic origins of these enhancers and find that ∼20% arose in the mammalian stem lineage, coincident with the emergence of the neocortex. Implementing a permutation strategy that controls for the nonrandom variation in the ages of background genomic sequences, we find that mammal-specific enhancers are overrepresented near genes involved in cell migration, cell signaling, and axon guidance. Mammal-specific enhancers are also overrepresented in modules of coexpressed genes in the cortex that are associated with these pathways, notably ephrin and semaphorin signaling. Our results also provide insight into the mechanisms of regulatory innovation in mammals. We find that most neocortical enhancers did not originate by en bloc exaptation of transposons. Young neocortical enhancers exhibit smaller H3K27ac footprints and weaker evolutionary constraint in eutherian mammals than older neocortical enhancers. Based on these observations, we present a model of the enhancer life cycle in which neocortical enhancers initially emerge from genomic background as short, weakly constrained "proto-enhancers." Many proto-enhancers are likely lost, but some may serve as nucleation points for complex enhancers to evolve.

  12. On the origin and evolution of life in the Galaxy

    NASA Astrophysics Data System (ADS)

    McCabe, Michael; Lucas, Holly

    2010-10-01

    A simple stochastic model for evolution, based upon the need to pass a sequence of n critical steps is applied to both terrestrial and extraterrestrial origins of life. In the former case, the time at which humans have emerged during the habitable period of Earth suggests a value of n=4. Progressively adding earlier evolutionary transitions gives an optimum fit when n=5, implying either that their initial transitions are not critical or that habitability began around 6 Ga ago. The origin of life on Mars or elsewhere within the Solar System is excluded by the latter case and the simple anthropic argument is that extraterrestrial life is scarce in the Universe because it does not have time to evolve. Alternatively, the timescale can be extended if the migration of basic progenotic material to Earth is possible. If extra transitions are included in the model to allow for Earth migration, then the start of habitability needs to be even earlier than 6 Ga ago. Our present understanding of Galactic habitability and dynamics does not exclude this possibility. We conclude that Galactic punctuated equilibrium, proposed as a way round the anthropic problem, is not the only way of making life more common in the Galaxy.

  13. The origin and evolution of the Cretaceous Benue Trough (Nigeria)

    NASA Astrophysics Data System (ADS)

    Benkhelil, J.

    The intracontinental Benue Trough was initiated during the Lower Cretaceous in relation with the Atlantic Ocean opening. The first stage of its evolution started in the Aptian, forming isolated basins with continental sedimentation. In the Albian times, a great delta developed in the Upper Benue Trough, while the first marine transgression coming from the opening Gulf of Guinea occurred in the south and reached the Middle Benue. The widespread Turonian transgression made the Atlantic and Tethys waters communicate through the Sahara, Niger basins and the Benue Trough. The tectonic evolution of the Benue Trough was closely controlled by transcurrent faulting through an axial fault system, developing local compressional and tensional regimes and resulting in basins and basement horsts along releasing and restraining bends of the faults. Two major compressional phases occurred: in the Abakaliki area (southern Benue) during the Santonian; and at the end of the Cretaceous in the Upper Benue Trough. In Abakaliki, the sedimentary infilling was severely deformed through folding and flattening, and moderate folding and fracturing occurred in the northeast. The Cretaceous magmatism was restricted to main fault zones in most of the trough but was particularly active in the Abakaliki Trough, where it has alkaline affinities. From Albian to Santonian, the magmatism was accompanied in part of the Abakaliki Trough by a low-grade metamorphism. Geophysical data indicate a crustal thinning beneath the Benue Trough and, at a superficial level, an axial basement high flanked by two elongated deep basins including isolated sub-basins. The model of the tectonic evolution of the trough is based upon a general sinistral wrenching along the trough responsible for the structural arrangement and the geometry of the sub-basins. During the early stages of the Gulf of Guinea opening the Benue Trough was probably the expression on land of the Equatorial Fracture Zones.

  14. The integumentary skeleton of tetrapods: origin, evolution, and development

    PubMed Central

    Vickaryous, Matthew K; Sire, Jean-Yves

    2009-01-01

    Although often overlooked, the integument of many tetrapods is reinforced by a morphologically and structurally diverse assemblage of skeletal elements. These elements are widely understood to be derivatives of the once all-encompassing dermal skeleton of stem-gnathostomes but most details of their evolution and development remain confused and uncertain. Herein we re-evaluate the tetrapod integumentary skeleton by integrating comparative developmental and tissue structure data. Three types of tetrapod integumentary elements are recognized: (1) osteoderms, common to representatives of most major taxonomic lineages; (2) dermal scales, unique to gymnophionans; and (3) the lamina calcarea, an enigmatic tissue found only in some anurans. As presently understood, all are derivatives of the ancestral cosmoid scale and all originate from scleroblastic neural crest cells. Osteoderms are plesiomorphic for tetrapods but demonstrate considerable lineage-specific variability in size, shape, and tissue structure and composition. While metaplastic ossification often plays a role in osteoderm development, it is not the exclusive mode of skeletogenesis. All osteoderms share a common origin within the dermis (at or adjacent to the stratum superficiale) and are composed primarily (but not exclusively) of osseous tissue. These data support the notion that all osteoderms are derivatives of a neural crest-derived osteogenic cell population (with possible matrix contributions from the overlying epidermis) and share a deep homology associated with the skeletogenic competence of the dermis. Gymnophionan dermal scales are structurally similar to the elasmoid scales of most teleosts and are not comparable with osteoderms. Whereas details of development are lacking, it is hypothesized that dermal scales are derivatives of an odontogenic neural crest cell population and that skeletogenesis is comparable with the formation of elasmoid scales. Little is known about the lamina calcarea. It is

  15. Origins and evolution of viruses of eukaryotes: The ultimate modularity.

    PubMed

    Koonin, Eugene V; Dolja, Valerian V; Krupovic, Mart

    2015-05-01

    Viruses and other selfish genetic elements are dominant entities in the biosphere, with respect to both physical abundance and genetic diversity. Various selfish elements parasitize on all cellular life forms. The relative abundances of different classes of viruses are dramatically different between prokaryotes and eukaryotes. In prokaryotes, the great majority of viruses possess double-stranded (ds) DNA genomes, with a substantial minority of single-stranded (ss) DNA viruses and only limited presence of RNA viruses. In contrast, in eukaryotes, RNA viruses account for the majority of the virome diversity although ssDNA and dsDNA viruses are common as well. Phylogenomic analysis yields tangible clues for the origins of major classes of eukaryotic viruses and in particular their likely roots in prokaryotes. Specifically, the ancestral genome of positive-strand RNA viruses of eukaryotes might have been assembled de novo from genes derived from prokaryotic retroelements and bacteria although a primordial origin of this class of viruses cannot be ruled out. Different groups of double-stranded RNA viruses derive either from dsRNA bacteriophages or from positive-strand RNA viruses. The eukaryotic ssDNA viruses apparently evolved via a fusion of genes from prokaryotic rolling circle-replicating plasmids and positive-strand RNA viruses. Different families of eukaryotic dsDNA viruses appear to have originated from specific groups of bacteriophages on at least two independent occasions. Polintons, the largest known eukaryotic transposons, predicted to also form virus particles, most likely, were the evolutionary intermediates between bacterial tectiviruses and several groups of eukaryotic dsDNA viruses including the proposed order "Megavirales" that unites diverse families of large and giant viruses. Strikingly, evolution of all classes of eukaryotic viruses appears to have involved fusion between structural and replicative gene modules derived from different sources along

  16. Prebiological evolution and the physics of the origin of life

    NASA Astrophysics Data System (ADS)

    Delaye, Luis; Lazcano, Antonio

    2005-03-01

    The basic tenet of the heterotrophic theory of the origin of life is that the maintenance and reproduction of the first living systems depended primarily on prebiotically synthesized organic molecules. It is unlikely that any single mechanism can account for the wide range of organic compounds that may have accumulated on the primitive Earth, suggesting that the prebiotic soup was formed by contributions from endogenous syntheses in reducing environments, metal sulphide-mediated synthesis in deep-sea vents, and exogenous sources such as comets, meteorites and interplanetary dust. The wide range of experimental conditions under which amino acids and nucleobases can be synthesized suggests that the abiotic syntheses of these monomers did not take place under a narrow range defined by highly selective reaction conditions, but rather under a wide variety of settings. The robustness of this type of chemistry is supported by the occurrence of most of these biochemical compounds in the Murchison meteorite. These results lend strong credence to the hypothesis that the emergence of life was the outcome of a long, but not necessarily slow, evolutionary processes. The origin of life may be best understood in terms of the dynamics and evolution of sets of chemical replicating entities. Whether such entities were enclosed within membranes is not yet clear, but given the prebiotic availability of amphiphilic compounds this may have well been the case. This scheme is not at odds with the theoretical models of self-organized emerging systems, but what is known of biology suggest that the essential traits of living systems could have not emerged in the absence of genetic material able to store, express and, upon replication, transmit to its progeny information capable of undergoing evolutionary change. How such genetic polymer first evolved is a central issue in origin-of-life studies.

  17. Prebiological evolution and the physics of the origin of life.

    PubMed

    Delaye, Luis; Lazcano, Antonio

    2005-03-01

    The basic tenet of the heterotrophic theory of the origin of life is that the maintenance and reproduction of the first living systems depended primarily on prebiotically synthesized organic molecules. It is unlikely that any single mechanism can account for the wide range of organic compounds that may have accumulated on the primitive Earth, suggesting that the prebiotic soup was formed by contributions from endogenous syntheses in reducing environments, metal sulphide-mediated synthesis in deep-sea vents, and exogenous sources such as comets, meteorites and interplanetary dust. The wide range of experimental conditions under which amino acids and nucleobases can be synthesized suggests that the abiotic syntheses of these monomers did not take place under a narrow range defined by highly selective reaction conditions, but rather under a wide variety of settings. The robustness of this type of chemistry is supported by the occurrence of most of these biochemical compounds in the Murchison meteorite. These results lend strong credence to the hypothesis that the emergence of life was the outcome of a long, but not necessarily slow, evolutionary processes. The origin of life may be best understood in terms of the dynamics and evolution of sets of chemical replicating entities. Whether such entities were enclosed within membranes is not yet clear, but given the prebiotic availability of amphiphilic compounds this may have well been the case. This scheme is not at odds with the theoretical models of self-organized emerging systems, but what is known of biology suggest that the essential traits of living systems could have not emerged in the absence of genetic material able to store, express and, upon replication, transmit to its progeny information capable of undergoing evolutionary change. How such genetic polymer first evolved is a central issue in origin-of-life studies.

  18. Second Symposium on Chemical Evolution and the Origin of Life

    SciTech Connect

    Devincenzi, D.L.; Dufour, P.A.

    1986-05-01

    Recent findings by NASA Exobiology investigators are reported. Scientific papers are presented in the following areas: cosmic evolution of biogenic compounds, prebiotic evolution (planetary and molecular), early evolution of life (biological and geochemical), evolution of advanced life, solar system exploration, and the Search for Extraterrestrial Intelligence (SETI).

  19. Second Symposium on Chemical Evolution and the Origin of Life

    NASA Technical Reports Server (NTRS)

    Devincenzi, D. L. (Editor); model. (Editor)

    1986-01-01

    Recent findings by NASA Exobiology investigators are reported. Scientific papers are presented in the following areas: cosmic evolution of biogenic compounds, prebiotic evolution (planetary and molecular), early evolution of life (biological and geochemical), evolution of advanced life, solar system exploration, and the Search for Extraterrestrial Intelligence (SETI).

  20. ORIGIN: Metal Creation and Evolution from the Cosmic Dawn

    NASA Technical Reports Server (NTRS)

    Kouveliotou, C.; vanderHorst, A.; Weisskopf, M.; White, N.; denHerder, J. W.; Costantini, E.; denHartog, R.; Hermsen, W.; in'tZhand, J.; Kaastra, J.; dePlaa, J.; Jonker, P.; deKorte, P.; Piro, L.; Cocchi, M.; Colasanti, L.; Corsi, A.; DeRosa, A.; DelSanto, M.; DiCosimo, S.; Gendre, B.; Macculi, C.; Natalucci, L.; Ubertini, P.; Ohashi, T.

    2012-01-01

    ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z=10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts (z approx. 0.2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs. The ORIGIN mission includes a Transient Event Detector (coded mask with a sensitivity of 0.4 photon/sq cm/s in 10 s in the 5-150 keV band) to identify and localize 2000 GRBs over a five year mission, of which approx.65 GRBs have a redshift >7. The Cryogenic Imaging Spectrometer, with a spectral resolution of 2.5 eV, a field of view of 30 arcmin and large effective area below 1 keV has the sensitivity to study clusters up to a significant fraction of the virial radius and to map the denser parts of the WHIM (factor 30 higher than achievable with current instruments). The payload is complemented by a Burst InfraRed Telescope to enable onboard red-shift determination of GRBs (hence securing proper follow up of high-z bursts

  1. ORIGIN: metal creation and evolution from the cosmic dawn

    NASA Astrophysics Data System (ADS)

    den Herder, Jan-Willem; Piro, Luigi; Ohashi, Takaya; Kouveliotou, Chryssa; Hartmann, Dieter H.; Kaastra, Jelle S.; Amati, L.; Andersen, M. I.; Arnaud, M.; Attéia, J.-L.; Bandler, S.; Barbera, M.; Barcons, X.; Barthelmy, S.; Basa, S.; Basso, S.; Boer, M.; Branchini, E.; Branduardi-Raymont, G.; Borgani, S.; Boyarsky, A.; Brunetti, G.; Budtz-Jorgensen, C.; Burrows, D.; Butler, N.; Campana, S.; Caroli, E.; Ceballos, M.; Christensen, F.; Churazov, E.; Comastri, A.; Colasanti, L.; Cole, R.; Content, R.; Corsi, A.; Costantini, E.; Conconi, P.; Cusumano, G.; de Plaa, J.; De Rosa, A.; Del Santo, M.; Di Cosimo, S.; De Pasquale, M.; Doriese, R.; Ettori, S.; Evans, P.; Ezoe, Y.; Ferrari, L.; Finger, H.; Figueroa-Feliciano, T.; Friedrich, P.; Fujimoto, R.; Furuzawa, A.; Fynbo, J.; Gatti, F.; Galeazzi, M.; Gehrels, N.; Gendre, B.; Ghirlanda, G.; Ghisellini, G.; Gilfanov, M.; Giommi, P.; Girardi, M.; Grindlay, J.; Cocchi, M.; Godet, O.; Guedel, M.; Haardt, F.; den Hartog, R.; Hepburn, I.; Hermsen, W.; Hjorth, J.; Hoekstra, H.; Holland, A.; Hornstrup, A.; van der Horst, A.; Hoshino, A.; in't Zand, J.; Irwin, K.; Ishisaki, Y.; Jonker, P.; Kitayama, T.; Kawahara, H.; Kawai, N.; Kelley, R.; Kilbourne, C.; de Korte, P.; Kusenko, A.; Kuvvetli, I.; Labanti, M.; Macculi, C.; Maiolino, R.; Hesse, M. Mas; Matsushita, K.; Mazzotta, P.; McCammon, D.; Méndez, M.; Mignani, R.; Mineo, T.; Mitsuda, K.; Mushotzky, R.; Molendi, S.; Moscardini, L.; Natalucci, L.; Nicastro, F.; O'Brien, P.; Osborne, J.; Paerels, F.; Page, M.; Paltani, S.; Pedersen, K.; Perinati, E.; Ponman, T.; Pointecouteau, E.; Predehl, P.; Porter, S.; Rasmussen, A.; Rauw, G.; Röttgering, H.; Roncarelli, M.; Rosati, P.; Quadrini, E.; Ruchayskiy, O.; Salvaterra, R.; Sasaki, S.; Sato, K.; Savaglio, S.; Schaye, J.; Sciortino, S.; Shaposhnikov, M.; Sharples, R.; Shinozaki, K.; Spiga, D.; Sunyaev, R.; Suto, Y.; Takei, Y.; Tanvir, N.; Tashiro, M.; Tamura, T.; Tawara, Y.; Troja, E.; Tsujimoto, M.; Tsuru, T.; Ubertini, P.; Ullom, J.; Ursino, E.; Verbunt, F.; van de Voort, F.; Viel, M.; Wachter, S.; Watson, D.; Weisskopf, M.; Werner, N.; White, N.; Willingale, R.; Wijers, R.; Yamasaki, N.; Yoshikawa, K.; Zane, S.

    2012-10-01

    ORIGIN is a proposal for the M3 mission call of ESA aimed at the study of metal creation from the epoch of cosmic dawn. Using high-spectral resolution in the soft X-ray band, ORIGIN will be able to identify the physical conditions of all abundant elements between C and Ni to red-shifts of z = 10, and beyond. The mission will answer questions such as: When were the first metals created? How does the cosmic metal content evolve? Where do most of the metals reside in the Universe? What is the role of metals in structure formation and evolution? To reach out to the early Universe ORIGIN will use Gamma-Ray Bursts (GRBs) to study their local environments in their host galaxies. This requires the capability to slew the satellite in less than a minute to the GRB location. By studying the chemical composition and properties of clusters of galaxies we can extend the range of exploration to lower redshifts ( z ˜0.2). For this task we need a high-resolution spectral imaging instrument with a large field of view. Using the same instrument, we can also study the so far only partially detected baryons in the Warm-Hot Intergalactic Medium (WHIM). The less dense part of the WHIM will be studied using absorption lines at low redshift in the spectra for GRBs. The ORIGIN mission includes a Transient Event Detector (coded mask with a sensitivity of 0.4 photon/cm2/s in 10 s in the 5-150 keV band) to identify and localize 2000 GRBs over a five year mission, of which ˜65 GRBs have a redshift >7. The Cryogenic Imaging Spectrometer, with a spectral resolution of 2.5 eV, a field of view of 30 arcmin and large effective area below 1 keV has the sensitivity to study clusters up to a significant fraction of the virial radius and to map the denser parts of the WHIM (factor 30 higher than achievable with current instruments). The payload is complemented by a Burst InfraRed Telescope to enable onboard red-shift determination of GRBs (hence securing proper follow up of high-z bursts) and also

  2. Developmental genes and the origin and evolution of Metazoa

    NASA Technical Reports Server (NTRS)

    Jacobs, D. K.

    1994-01-01

    The author discusses the role of developmental genes in evolution of life and the use of molecular approaches to confirm morphologic homology, to aid in understanding developmental mechanisms of evolution of novel structures, and to investigate some aspects of the evolution of life. Topics examined include developmental genes and homology; the role of co-optation and divergence, homeosis, and heterochrony as mechanisms of evolution; and life history evolution and model organisms.

  3. The origin and evolution of adamantanes and diamantanes in petroleum

    NASA Astrophysics Data System (ADS)

    Fang, Chenchen; Xiong, Yongqiang; Li, Yun; Chen, Yuan; Liu, Jinzhong; Zhang, Haizu; Adedosu, Taofik Adewale; Peng, Ping'an

    2013-11-01

    This study investigates the origin and evolution of adamantanes and diamantanes in petroleum, based on the results of pyrolysis experiments on different group components of crude oil and quantitative analyses of diamondoids in the pyrolysates. Results show that the formation and evolution of lower diamondoids in petroleum occurs in three main stages: (1) early generation during the formation of oil (< ca. 0.8-1.0% EasyRo), (2) generation during the cracking of oil (>1.0% EasyRo), and (3) destruction during the late period of oil cracking. The lower diamondoids that formed during the early generation stage include free diamondoids present in the original oil and diamondoids released or transformed from group fractions of oil at relatively low levels of maturity (< ca. 0.8-1.0% EasyRo). During the process of oil cracking, all four group fractions (saturated, aromatic, resin, and asphaltene fractions) can produce adamantanes and diamantanes. Overall, adamantanes are generated primarily within the maturity range 1.0-2.3% EasyRo, and diamantanes within the maturity range 1.6-2.7% EasyRo. Group composition of the oil is probably a major factor controlling the yield and distribution of diamondoids in the main generation stage. The yield ratios of diamondoids can be used as maturity indices to assess the thermal maturity of oil, while the isomerization ratios of diamondoids are potential source facies indices for the generation stage of diamondoids. The destruction of diamondoids is observed at thermal maturity ranges >2.3% EasyRo in adamantanes and >2.7% EasyRo in diamantanes. The thermal stability of diamondoid compounds becomes a critical factor influencing the isomerization index of diamondoids during the destruction stage. The isomerization ratios of some diamondoids (e.g., MAI, DMAI-1, DMAI-2, TMAI-1, TMAI-2, and EAI) are well correlated with maturity within certain maturity ranges, indicating that isomerization indices provide good estimates of the thermal maturity

  4. Origin of noncoding DNA sequences: molecular fossils of genome evolution.

    PubMed

    Naora, H; Miyahara, K; Curnow, R N

    1987-09-01

    The total amount of noncoding sequences on chromosomes of contemporary organisms varies significantly from species to species. We propose a hypothesis for the origin of these noncoding sequences that assumes that (i) an approximately equal to 0.55-kilobase (kb)-long reading frame composed the primordial gene and (ii) a 20-kb-long single-stranded polynucleotide is the longest molecule (as a genome) that was polymerized at random and without a specific template in the primordial soup/cell. The statistical distribution of stop codons allows examination of the probability of generating reading frames of approximately equal to 0.55 kb in this primordial polynucleotide. This analysis reveals that with three stop codons, a run of at least 0.55-kb equivalent length of nonstop codons would occur in 4.6% of 20-kb-long polynucleotide molecules. We attempt to estimate the total amount of noncoding sequences that would be present on the chromosomes of contemporary species assuming that present-day chromosomes retain the prototype primordial genome structure. Theoretical estimates thus obtained for most eukaryotes do not differ significantly from those reported for these specific organisms, with only a few exceptions. Furthermore, analysis of possible stop-codon distributions suggests that life on earth would not exist, at least in its present form, had two or four stop codons been selected early in evolution.

  5. The origin and early evolution of life on Earth.

    PubMed

    Oró, J; Miller, S L; Lazcano, A

    1990-01-01

    We do not have a detailed knowledge of the processes that led to the appearance of life on Earth. In this review we bring together some of the most important results that have provided insights into the cosmic and primitive Earth environments, particularly those environments in which life is thought to have originated. To do so, we first discuss the evidence bearing on the antiquity of life on our planet 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. This is followed by a discussion on the environmental models of the Hadean and early Archean Earth, as well as on the prebiotic formation of organic monomers and polymers essential to life. We then consider the processes that may have led to the appearance in the Archean of the first cells, and how these processes may have affected the early steps of biological evolution. Finally, the significance of these results to the study of the distribution of life in the Universe is discussed.

  6. Can Chimpanzee Biology Highlight Human Origin and Evolution?

    PubMed Central

    Roffman, Itai; Nevo, Eviatar

    2010-01-01

    The closest living relatives of humans are their chimpanzee/bonobo (Pan) sister species, members of the same subfamily “Homininae”. This classification is supported by over 50 years of research in the fields of chimpanzee cultural diversity, language competency, genomics, anatomy, high cognition, psychology, society, self-consciousness and relation to others, tool use/production, as well as Homo level emotions, symbolic competency, memory recollection, complex multifaceted problem-solving capabilities, and interspecies communication. Language competence and symbolism can be continuously bridged from chimpanzee to man. Emotions, intercommunity aggression, body language, gestures, facial expressions, and vocalization of intonations seem to parallel between the sister taxa Homo and Pan. The shared suite of traits between Pan and Homo genus demonstrated in this article integrates old and new information on human–chimpanzee evolution, bilateral informational and cross-cultural exchange, promoting the urgent need for Pan cultures in the wild to be protected, as they are part of the cultural heritage of mankind. Also, we suggest that bonobos, Pan paniscus, based on shared traits with Australopithecus, need to be included in Australopithecine’s subgenus, and may even represent living-fossil Australopithecines. Unfolding bonobo and chimpanzee biology highlights our common genetic and cultural evolutionary origins. PMID:23908781

  7. Can chimpanzee biology highlight human origin and evolution?

    PubMed

    Roffman, Itai; Nevo, Eviatar

    2010-07-01

    The closest living relatives of humans are their chimpanzee/bonobo (Pan) sister species, members of the same subfamily "Homininae". This classification is supported by over 50 years of research in the fields of chimpanzee cultural diversity, language competency, genomics, anatomy, high cognition, psychology, society, self-consciousness and relation to others, tool use/production, as well as Homo level emotions, symbolic competency, memory recollection, complex multifaceted problem-solving capabilities, and interspecies communication. Language competence and symbolism can be continuously bridged from chimpanzee to man. Emotions, intercommunity aggression, body language, gestures, facial expressions, and vocalization of intonations seem to parallel between the sister taxa Homo and Pan. The shared suite of traits between Pan and Homo genus demonstrated in this article integrates old and new information on human-chimpanzee evolution, bilateral informational and cross-cultural exchange, promoting the urgent need for Pan cultures in the wild to be protected, as they are part of the cultural heritage of mankind. Also, we suggest that bonobos, Pan paniscus, based on shared traits with Australopithecus, need to be included in Australopithecine's subgenus, and may even represent living-fossil Australopithecines. Unfolding bonobo and chimpanzee biology highlights our common genetic and cultural evolutionary origins.

  8. Tessera terrain, Venus: Characterization and models for origin and evolution

    SciTech Connect

    Bindschadler, D.L.; Head, J.W. )

    1991-04-10

    Tessera terrain is the dominant tectonic landform in the northern high latitudes of Venus mapped by the Venera 15 and 16 orbiters and is concentrated in the region between the mountain ranges of western Ishtar Terra and Aphrodite Terra. Tesserae are characterized by regionally high topography, a high degree of small scale surface roughness, and sets of intersecting tectonic features. Available Pioneer Venus line of sight gravity data suggest that tessera terrain is compensated at shallow depths relative to many topographic highs on Venus and may be supported by crustal thickness variations. Three types of tessera terrain can be defined on the basis of structural patterns: subparallel ridged terrains (T{sub sr}), trough and ridge terrain (T{sub tr}), and disrupted terrain (T{sub ds}). Observed characteristics of tessera terrain are compared to predictions of models in order to begin to address the question of its origin and evolution. Formational models, in which high topography is created along with surface deformation, include (1) horizontal convergence, (2) mantle upwelling, (3) crustal underplating, and (4) a seafloor spreading analogy. Modification models, in which deformation occurs as a response to the presence of elevated regions, consist of (1) gravity sliding and (2) gravitational relaxation. The authors find that horizontal convergence and late stage gravitational relaxation are the most consistent with basic observations for subparallel ridged terrain and disrupted terrain. Understanding of the basic structural characteristics of trough and ridge terrain is more tentative, and models involving a spreading process or convergence and relaxation merit further study.

  9. Origin and genetic evolution of the vertebrate skeleton.

    PubMed

    Wada, Hiroshi

    2010-02-01

    The current understanding of the origin and evolution of the genetic cassette for the vertebrate skeletal system is reviewed. Molecular phylogenetic analyses of fibrillar collagen genes, which encode the main component of both cartilage and mineralized bone, suggest that genome duplications in vertebrate ancestors were essential for producing distinct collagen fibers for cartilage and mineralized bone. Several data Indicate co-expression of the ancestral copy of fibrillar collagen with the SoxE and Runx transcription factors. Therefore, the genetic cassette may have already existed in protochordate ancestors, and may operate in the development of the pharyngeal gill skeleton. Accompanied by genome duplications in vertebrate ancestors, this genetic cassette may have also been duplicated and co-opted for cartilage and bone. Subsequently, the genetic cassette for cartilage recruited novel genetic material via domain shuffling. Aggrecan, acquired by means of domain shuffling, performs an essential role in cartilage as a shock absorber. In contrast, the cassette for bone recruited new genetic material produced by tandem duplication of the SPARC/osteonectin genes. Some of the duplicated copies of SPARC/osteonectin became secretory Cabinding phosphoproteins (SCPPs) performing a central role in mineralization by regulating the calcium phosphate concentration. Comparative genome analysis revealed similar molecular evolutionary histories for the genetic cassettes for cartilage and bone, namely duplication of the ancestral genetic cassette and recruitment of novel genetic material.

  10. Milgram's Obedience to Authority experiments: origins and early evolution.

    PubMed

    Russell, Nestar John Charles

    2011-03-01

    Stanley Milgram's Obedience to Authority experiments remain one of the most inspired contributions in the field of social psychology. Although Milgram undertook more than 20 experimental variations, his most (in)famous result was the first official trial run - the remote condition and its 65% completion rate. Drawing on many unpublished documents from Milgram's personal archive at Yale University, this article traces the historical origins and early evolution of the obedience experiments. Part 1 presents the previous experiences that led to Milgram's conception of his rudimentary research idea and then details the role of his intuition in its refinement. Part 2 traces the conversion of Milgram's evolving idea into a reality, paying particular attention to his application of the exploratory method of discovery during several pilot studies. Both parts illuminate Milgram's ad hoc introduction of various manipulative techniques and subtle tension-resolving refinements. The procedural adjustments continued until Milgram was confident that the first official experiment would produce a high completion rate, a result contrary to expectations of people's behaviour. Showing how Milgram conceived of, then arrived at, this first official result is important because the insights gained may help others to determine theoretically why so many participants completed this experiment.

  11. Origins and evolution of viruses of eukaryotes: The ultimate modularity

    SciTech Connect

    Koonin, Eugene V.; Dolja, Valerian V.; Krupovic, Mart

    2015-05-15

    Viruses and other selfish genetic elements are dominant entities in the biosphere, with respect to both physical abundance and genetic diversity. Various selfish elements parasitize on all cellular life forms. The relative abundances of different classes of viruses are dramatically different between prokaryotes and eukaryotes. In prokaryotes, the great majority of viruses possess double-stranded (ds) DNA genomes, with a substantial minority of single-stranded (ss) DNA viruses and only limited presence of RNA viruses. In contrast, in eukaryotes, RNA viruses account for the majority of the virome diversity although ssDNA and dsDNA viruses are common as well. Phylogenomic analysis yields tangible clues for the origins of major classes of eukaryotic viruses and in particular their likely roots in prokaryotes. Specifically, the ancestral genome of positive-strand RNA viruses of eukaryotes might have been assembled de novo from genes derived from prokaryotic retroelements and bacteria although a primordial origin of this class of viruses cannot be ruled out. Different groups of double-stranded RNA viruses derive either from dsRNA bacteriophages or from positive-strand RNA viruses. The eukaryotic ssDNA viruses apparently evolved via a fusion of genes from prokaryotic rolling circle-replicating plasmids and positive-strand RNA viruses. Different families of eukaryotic dsDNA viruses appear to have originated from specific groups of bacteriophages on at least two independent occasions. Polintons, the largest known eukaryotic transposons, predicted to also form virus particles, most likely, were the evolutionary intermediates between bacterial tectiviruses and several groups of eukaryotic dsDNA viruses including the proposed order “Megavirales” that unites diverse families of large and giant viruses. Strikingly, evolution of all classes of eukaryotic viruses appears to have involved fusion between structural and replicative gene modules derived from different sources

  12. Environmental evolution: Effects of the origin and evolution of life on Planet Earth

    SciTech Connect

    Margulis, L.; Olendzenski, L.

    1992-01-01

    This book is a multiauthored textbook in planetary evolutionary biogeochemistry, emphasizing the major effects biota have had on the planetary environment and based on a long standing, one semister course at Boston University. A series of chapters described planetary atmospheres in the inner solar system, alternative views on the chemical origin of life, present-day microbial communities and the structures they build, the endosymbiotic origin of eukaryotic cells, and the fossil record of the late Precambrian. Four concluding chapters discuss the Phanerozoic, including the Gaia hypotheseis, plate tectonics, plant secondary compounds, and the role of chromosome fission in mammaliean evolution. A section on assignments, presentations, supplementary material, and background reading, and a comprehensive glossary are included.

  13. THE STRUCTURE, ORIGIN, AND EVOLUTION OF INTERSTELLAR HYDROCARBON GRAINS

    SciTech Connect

    Chiar, J. E.; Ricca, A.; Tielens, A. G. G. M.; Adamson, A. J. E-mail: Alessandra.Ricca@1.nasa.gov E-mail: aadamson@gemini.edu

    2013-06-10

    Many materials have been considered for the carrier of the hydrocarbon absorption bands observed in the diffuse interstellar medium (ISM). In order to refine the model for ISM hydrocarbon grains, we analyze the observed aromatic (3.28, 6.2 {mu}m) and aliphatic (3.4 {mu}m) hydrocarbon absorption features in the diffuse ISM along the line of sight toward the Galactic center Quintuplet Cluster. Observationally, sp {sup 2} bonds can be measured in astronomical spectra using the 6.2 {mu}m CC aromatic stretch feature, whereas the 3.4 {mu}m aliphatic feature can be used to quantify the fraction of sp {sup 3} bonds. The fractional abundance of these components allows us to place the Galactic diffuse ISM hydrocarbons on a ternary phase diagram. We conclude that the Galactic hydrocarbon dust has, on average, a low H/C ratio and sp {sup 3} content and is highly aromatic. We have placed the results of our analysis within the context of the evolution of carbon dust in the ISM. We argue that interstellar carbon dust consists of a large core of aromatic carbon surrounded by a thin mantle of hydrogenated amorphous carbon (a-C:H), a structure that is a natural consequence of the processing of stardust grains in the ISM.

  14. 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.

  15. Origin and evolution of influenza virus hemagglutinin genes.

    PubMed

    Suzuki, Yoshiyuki; Nei, Masatoshi

    2002-04-01

    Influenza A, B, and C viruses are the etiological agents of influenza. Hemagglutinin (HA) is the major envelope glycoprotein of influenza A and B viruses, and hemagglutinin-esterase (HE) in influenza C viruses is a protein homologous to HA. Because influenza A virus pandemics in humans appear to occur when new subtypes of HA genes are introduced from aquatic birds that are known to be the natural reservoir of the viruses, an understanding of the origin and evolution of HA genes is of particular importance. We therefore conducted a phylogenetic analysis of HA and HE genes and showed that the influenza A and B virus HA genes diverged much earlier than the divergence between different subtypes of influenza A virus HA genes. The rate of amino acid substitution for A virus HAs from duck, a natural reservoir, was estimated to be 3.19 x 10(-4) per site per year, which was slower than that for human and swine A virus HAs but similar to that for influenza B and C virus HAs (HEs). Using this substitution rate from the duck, we estimated that the divergences between different subtypes of A virus HA genes occurred from several thousand to several hundred years ago. In particular, the earliest divergence time was estimated to be about 2,000 years ago. Also, the A virus HA gene diverged from the B virus HA gene about 4,000 years ago and from the C virus HE gene about 8,000 years ago. These time estimates are much earlier than the previous ones.

  16. Geometric phases, evolution loops and generalized oscillator potentials

    NASA Technical Reports Server (NTRS)

    Fernandez, David J.

    1995-01-01

    The geometric phases for dynamical processes where the evolution operator becomes the identity (evolution loops) are studied. The case of time-independent Hamiltonians with equally spaced energy levels is considered; special emphasis is made on the potentials having the same spectrum as the harmonic oscillator potential (the generalized oscillator potentials) and their recently found coherent states.

  17. Geometric Phase for Adiabatic Evolutions of General Quantum States

    SciTech Connect

    Wu, Biao; Liu, Jie; Niu, Qian; Singh, David J

    2005-01-01

    The concept of a geometric phase (Berry's phase) is generalized to the case of noneigenstates, which is applicable to both linear and nonlinear quantum systems. This is particularly important to nonlinear quantum systems, where, due to the lack of the superposition principle, the adiabatic evolution of a general state cannot be described in terms of eigenstates. For linear quantum systems, our new geometric phase reduces to a statistical average of Berry's phases. Our results are demonstrated with a nonlinear two-level model.

  18. Phase avalanches in near-adiabatic evolutions

    SciTech Connect

    Vertesi, T.; Englman, R.

    2006-02-15

    In the course of slow, nearly adiabatic motion of a system, relative changes in the slowness can cause abrupt and high magnitude phase changes, ''phase avalanches,'' superimposed on the ordinary geometric phases. The generality of this effect is examined for arbitrary Hamiltonians and multicomponent (>2) wave packets and is found to be connected (through the Blaschke term in the theory of analytic signals) to amplitude zeros in the lower half of the complex time plane. Motion on a nonmaximal circle on the Poincare-sphere suppresses the effect. A spectroscopic transition experiment can independently verify the phase-avalanche magnitudes.

  19. Micromechanics and constitutive models for soft active materials with phase evolution

    NASA Astrophysics Data System (ADS)

    Wang, Binglian

    Soft active materials, such as shape memory polymers, liquid crystal elastomers, soft tissues, gels etc., are materials that can deform largely in response to external stimuli. Micromechanics analysis of heterogeneous materials based on finite element method is a typically numerical way to study the thermal-mechanical behaviors of soft active materials with phase evolution. While the constitutive models that can precisely describe the stress and strain fields of materials in the process of phase evolution can not be found in the databases of some commercial finite element analysis (FEA) tools such as ANSYS or Abaqus, even the specific constitutive behavior for each individual phase either the new formed one or the original one has already been well-known. So developing a computationally efficient and general three dimensional (3D) thermal-mechanical constitutive model for soft active materials with phase evolution which can be implemented into FEA is eagerly demanded. This paper first solved this problem theoretically by recording the deformation history of each individual phase in the phase evolution process, and adopted the idea of effectiveness by regarding all the new formed phase as an effective phase with an effective deformation to make this theory computationally efficient. A user material subroutine (UMAT) code based on this theoretical constitutive model has been finished in this work which can be added into the material database in Abaqus or ANSYS and can be easily used for most soft active materials with phase evolution. Model validation also has been done through comparison between micromechanical FEA and experiments on a particular composite material, shape memory elastomeric composite (SMEC) which consisted of an elastomeric matrix and the crystallizable fibre. Results show that the micromechanics and the constitutive models developed in this paper for soft active materials with phase evolution are completely relied on.

  20. Mimas: Constraints on Origin and Evolution from Libration Data

    NASA Astrophysics Data System (ADS)

    Neveu, Marc; Rhoden, Alyssa R.

    2016-10-01

    In stark contrast with its neighbor moon Enceladus, Mimas is surprisingly geologically quiet, despite an orbital configuration prone to levels of tidal dissipation 30 times higher. While Mimas' lack of activity could be due to a stiff, frigid interior, libration data from the Cassini spacecraft suggest its interior is not homogeneous [1]. Here, we present 1-D models of Mimas' thermal and structural evolution under two accretion scenarios: primordial, undifferentiated formation in the Saturnian subnebula [2]; and late, layered formation from a debris ring created by the disruption of one or more previous moons [3]. In the primordial scenario, our simulations yield two possible outcomes. If tidal dissipation proceeds at levels higher than those obtained using an Andrade rheology [4], Mimas differentiates and an ocean persists until the present day. This should quickly circularize its orbit, but the current orbit is eccentric. In addition, Mimas lacks surface fractures that should result from strong tidal stresses in an ice shell atop an ocean [5]. If dissipation proceeds at lower levels obtained using a Maxwell rheology, it is too weak to drive differentiation; this does not match the observed libration [1]. In the late accretion scenario, Mimas forms already differentiated. As a result, even its deepest ice is within only 100 km of the frigid surface, and poorly insulated by overlying thermally conductive crystalline ice. Thus, all ice remains cold and poorly dissipative, even if dissipation is an order of magnitude above that provided by the Andrade rheology [4]. If Mimas' rocky core is slightly non-hydrostatic [1], this matches the observed libration. We conclude that Mimas' libration is compatible with a late origin from a debris ring, but not with primordial accretion. Consistent with findings from many authors (e.g. [6]), these models cannot produce an ocean on Enceladus unless its orbital eccentricity is higher than observed.References:[1] Tajeddine et al

  1. [Evolution of the origin of strain of Shancigu (Rhizoma Pleionis)].

    PubMed

    Li, Guangyan; Song, Xiangwen; Han, Bangxing; Fang, Shiying

    2015-05-01

    Shancigu (Rhizome Pleionis) was first recorded in the Ben cao shiyi (Supplements to Chinese Materia Medica). The source of the strain of this medicinal was unclear because of its too simple description in the medical books in the Tang and Song dynasties. Its original plant could be Cremastra appendiculata (D.Don) Makino, Tulipa edulis (Miq.) Baker and so on. The original plant of Shanciguwas Tulipaedulis since the Ming dynasty to the Republican period. The name of "Guangcigu" began to appear in the Republican period because of the changes of its processing method. The original plants evolved into Cremastra appendiculata, Pleione bulbocodioides (Franch.) Rolfe and Pleione yunnanensis Rolfe, with Tulipa edulisas the original plant of Guangcigu (Bulbus of Tulipasedulis). It is found that only the Tulipaedulis is the unequivocal origin with the longest medicinal history through sorting out of the original plants of Shancigu. Hence, it is suggested that Tulipa edulis should be recovered as the original strain of Shancigu.

  2. Unique Pitch Evolution in the Smectic -C-alpha* Phase

    SciTech Connect

    Liu,Z.; McCoy, B.; Wang, S.; Pindak, R.; Caliebe, W.; Barois, P.; Fernandes, P.; Nguyen, H.; Hsu, C.; Wang, .

    2007-01-01

    Employing resonant x-ray diffraction, we observed unique pitch evolutions in the smectic-C{alpha}* phase in mixtures of two antiferroelectric liquid crystals. Our results show that the pitch in this phase continuously evolves across 4 layers, contradicting a theoretical model that predicts that the smectic-C{sub FI2}* phase intervenes in the smectic-C{alpha}* phase. The phase sequences we found can be explained by another model that includes one type of long-range interaction among smectic layers.

  3. Primordial stellar evolution - The protostar phase

    NASA Technical Reports Server (NTRS)

    Stahler, S. W.; Palla, F.; Salpeter, E. E.

    1986-01-01

    The structure and evolution of a protostar forming from a cloud composed of pure hydrogen and helium gas are calculated. Using an accretion rate of 0.0044 solar mass/yr, the collapse of the cloud is followed numerically as a sequence of steady state accretion flows onto the hydrostatic core, which grows from an initial mass of 0.01 solar mass to 10.5 solar masses. The core is surrounded by an optically thick radiative precursor for most of its evolution. The core radius reaches 47 solar radii when the mass is 1 solar mass. For sufficiently massive cores, the deep interior contracts strongly, driving out a 'luminosity wave' which reaches the surface when the mass is 8 solar masses. This results in a large increase in core radius, the establishment of surface convection, and the disappearance of the radiative precursor. The dependence of core radius on the mass and accretion rate is analytically derived, and a new table or Rosseland mean opacities for metal-free gas is presented.

  4. On the Origin and Evolution of s-PROCESS Elements

    NASA Astrophysics Data System (ADS)

    Schramm, David N.; Tinsley, Beatrice M.

    The evolution of s-process abundances in the solar neighborhood is studied, using alternative stellar production sites and Galactic models. Production in either low-mass or medium-mass stars, as suggested in Ulrich's alternative models for FG Sge for example, can account for the solar-system abundances. Either case is consistent with independent limits on subsequent neutron exposure of nuclei produced in explosive oxygen and silicon burning and of r-process material. The cases could be distinguished by observations of the ratios of s-process to primary metal abundances in stars of different ages. The predictions are not strongly dependent on the model used for Galactic evolution.

  5. Evolution: ctenophore genomes and the origin of neurons.

    PubMed

    Marlow, Heather; Arendt, Detlev

    2014-08-18

    Recent sequencing of ctenophore genomes opens a new era in the study of this unique and phylogenetically distant group. The presence of neurodevelopmental genes, pre- and postsynaptic modules, and transmitter molecules is consistent with a single origin of neurons.

  6. Tumor archaeology: tracking leukemic evolution to its origins.

    PubMed

    Dick, John E

    2014-05-28

    Unearthing of the BRAF mutation in self-renewing hematopoietic stem cells reveals an unexpected origin for hairy cell leukemia-a mature B cell malignancy-and a potential new therapeutic target (Chung et al., this issue).

  7. Texture Evolution and Phase Transformation in Titanium Investigated by In-Situ Neutron Diffraction

    SciTech Connect

    Ma, Dong; Stoica, Alexandru Dan; An, Ke; Yang, Ling; Bei, Hongbin; Mills, Rebecca A; Skorpenske, Harley David; Wang, Xun-Li

    2011-01-01

    We report in-situ neutron diffraction studies of texture evolution and the (hcp) (bcc) phase transformation in commercially pure cold-drawn titanium upon continuous heating and cooling, complemented by differential scanning calorimetry (DSC) measurements. We show that the recrystallization of the phase at elevated temperature enhanced the preexisting fiber texture, which eventually facilitated the nucleation and growth of the phase favored by the Burgers orientation relationship, i.e., {0001} //{110} . More strikingly, upon completion of the transformation, the {110} texture (or preferred orientation) in was eliminated immediately by the rapid grain growth of intergranular allotriomorphs. This resulted in the loss of the original -texture when Ti was transformed back to from to upon subsequent cooling, distinct from the known texture memory effect for rolling textures in titanium. Our present work provides useful experimental results for understanding the mechanisms of texture evolution and phase transformation in titanium and its alloys and, by and large, low-symmetry alloys such as zirconium.

  8. Comparing Common Origins: Using Biotechnology To Teach Evolution.

    ERIC Educational Resources Information Center

    McLaughlin, John; Glasson, George

    2001-01-01

    Presents an innovative, inquiry-oriented lesson plan for using biotechnology to teach evolution. Using acrylamide gel electrophoresis, students learn how to isolate and compare different proteins from the muscle tissue of readily available seafood specimens to determine phylogenetic relationships. Uses a 5E (engagement, exploration, explanation,…

  9. What Teachers Should Know about the Evolution-Intentional Design Debate on the Origin of Life.

    ERIC Educational Resources Information Center

    Brekke, Stewart E.

    This paper discusses the beginning of life on Earth, the formation of life forms, evolution, and the origin of life. The paper suggests that how life first appeared on earth is not known and may never be known. (YDS)

  10. Impact origin of the Sudbury structure: Evolution of a theory

    NASA Technical Reports Server (NTRS)

    Lowman, Paul D., Jr.

    1992-01-01

    This paper reviews the origin, development, and present status of the widely accepted theory, proposed by Robert S. Dietz in 1962, that the Sudbury structure was formed by meteoritic or asteroidal impact. The impact theory for the origin of the Sudbury structure seems supported by a nearly conclusive body of evidence. However, even assuming an impact origin to be correct, at least three major questions require further study: (1) the original size and shape of the crater, before tectonic deformation and erosion; (2) the source of the melt now forming the Sudbury Igneous Complex; and (3) the degree, if any, to which the Ni-Cu-platinum group elements are meteoritic. The history of the impact theory illustrates several under-appreciated aspects of scientific research: (1) the importance of cross-fertilization between space research and terrestrial geology; (2) the role of the outsider in stimulating thinking by insiders; (3) the value of small science, at least in the initial stages of an investigation, Dietz's first field work having been at his own expense; and (4) the value of analogies (here, between the Sudbury Igneous Complex and the maria), which although incorrect in major aspects, may trigger research on totally new lines. Finally, the Sudbury story illustrates the totally unpredictable and, by implication, unplannable nature of basic research, in that insight to the origin of the world's then-greatest Ni deposit came from the study of tektites and the Moon.

  11. Thermodynamic geometry: Evolution, correlation and phase transition

    NASA Astrophysics Data System (ADS)

    Bellucci, S.; Tiwari, B. N.

    2011-06-01

    Under the fluctuation of the electric charge and atomic mass, this paper considers the theory of the thin film depletion layer formation of an ensemble of finitely excited, non-empty d/f-orbital heavy materials, from the thermodynamic geometric perspective. At each state of the local adiabatic evolutions, we examine the nature of the thermodynamic parameters, viz., electric charge and mass, changing at each respective embedding. The definition of the intrinsic Riemannian geometry and differential topology offers the properties of (i) local heat capacities, (ii) global stability criterion and (iv) global correlation length. Under the Gaussian fluctuations, such an intrinsic geometric consideration is anticipated to be useful in the statistical coating of the thin film layer of a desired quality-fine high cost material on a low cost durable coatant. From the perspective of everyday applications, thermodynamic geometry is thus intrinsically self-consistent with the theory of local and global economic optimizations. Following the above procedure, the quality of the thin layer depletion could self-consistently be examined to produce quality products economically.

  12. The origin and evolution of mutations in Acute Myeloid Leukemia

    PubMed Central

    Welch, John S.; Ley, Timothy J.; Link, Daniel C.; Miller, Christopher A.; Larson, David E.; Koboldt, Daniel C.; Wartman, Lukas D.; Lamprecht, Tamara L.; Liu, Fulu; Xia, Jun; Kandoth, Cyriac; Fulton, Robert S.; McLellan, Michael D.; Dooling, David J.; Wallis, John W.; Chen, Ken; Harris, Christopher C.; Schmidt, Heather K.; Kalicki-Veizer, Joelle M.; Lu, Charles; Zhang, Qunyuan; Lin, Ling; O’Laughlin, Michelle D.; McMichael, Joshua F.; Delehaunty, Kim D.; Fulton, Lucinda A.; Magrini, Vincent J.; McGrath, Sean D.; Demeter, Ryan T.; Vickery, Tammi L.; Hundal, Jasreet; Cook, Lisa L.; Swift, Gary W.; Reed, Jerry P.; Alldredge, Patricia A.; Wylie, Todd N.; Walker, Jason R.; Watson, Mark A.; Heath, Sharon E.; Shannon, William D.; Varghese, Nobish; Nagarajan, Rakesh; Payton, Jacqueline E.; Baty, Jack D.; Kulkarni, Shashikant; Klco, Jeffery M.; Tomasson, Michael H.; Westervelt, Peter; Walter, Matthew J.; Graubert, Timothy A.; DiPersio, John F.; Ding, Li; Mardis, Elaine R.; Wilson, Richard K.

    2012-01-01

    Summary Most mutations in cancer genomes are thought to be acquired after the initiating event, which may cause genomic instability, driving clonal evolution. However, for acute myeloid leukemia (AML), normal karyotypes are common, and genomic instability is unusual. To better understand clonal evolution in AML, we sequenced the genomes of AML samples with a known initiating event (PML-RARA) vs. normal karyotype AML samples, and the exomes of hematopoietic stem/progenitor cells (HSPCs) from healthy people. Collectively, the data suggest that most of the mutations found in AML genomes are actually random events that occurred in HSPCs before they acquired the initiating mutation; the mutational history of that cell is “captured” as the clone expands. In many cases, only one or two additional, cooperating mutations are needed to generate the malignant founding clone. Cells from the founding clone can acquire additional cooperating mutations, yielding subclones that can contribute to disease progression and/or relapse. PMID:22817890

  13. Origin and evolution of the Saturn system: Observational consequences

    NASA Technical Reports Server (NTRS)

    Pollack, J. B.

    1978-01-01

    A number of important cosmogonic questions concerning the Saturn system can be addressed with a Saturn-orbiter-dual-probe spacecraft mission. These questions include: The origin of the Saturn system; the source of Saturn's excess luminosity; the mechanism by which the irregular satellites were captured; the influence of Saturn's early luminosity on the composition of its regular satellites; and the origin of the rings. The first two topics can be studied by measurements made from an entry probe into Saturn's atmosphere, while the remaining issues can be investigated by measurements conducted from an orbiter. Background information is provided on these five questions describing the critical experiments needed to help resolve them.

  14. Fourth Symposium on Chemical Evolution and the Origin and Evolution of Life

    NASA Technical Reports Server (NTRS)

    Wharton, Robert A., Jr. (Editor); Andersen, Dale T. (Editor); Bzik, Sara E. (Editor); Rummel, John D. (Editor)

    1991-01-01

    This symposium was held at the NASA Ames Research Center, Moffett Field, California, July 24-27, 1990. The NASA exobiology investigators reported their recent research findings. Scientific papers were presented in the following areas: cosmic evolution of biogenic compounds, prebiotic evolution (planetary and molecular), early evolution of life (biological and geochemical), evolution of advanced life, solar system exploration, and the Search for Extraterrestrial Intelligence (SETI).

  15. PLANET TOPERS: Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their ReservoirS

    NASA Astrophysics Data System (ADS)

    Dehant, V.; Asael, D.; Baland, R. M.; Baludikay, B. K.; Beghin, J.; Belza, J.; Beuthe, M.; Breuer, D.; Chernonozhkin, S.; Claeys, Ph.; Cornet, Y.; Cornet, L.; Coyette, A.; Debaille, V.; Delvigne, C.; Deproost, M. H.; De WInter, N.; Duchemin, C.; El Atrassi, F.; François, C.; De Keyser, J.; Gillmann, C.; Gloesener, E.; Goderis, S.; Hidaka, Y.; Höning, D.; Huber, M.; Hublet, G.; Javaux, E. J.; Karatekin, Ö.; Kodolanyi, J.; Revilla, L. Lobo; Maes, L.; Maggiolo, R.; Mattielli, N.; Maurice, M.; McKibbin, S.; Morschhauser, A.; Neumann, W.; Noack, L.; Pham, L. B. S.; Pittarello, L.; Plesa, A. C.; Rivoldini, A.; Robert, S.; Rosenblatt, P.; Spohn, T.; Storme, J.-Y.; Tosi, N.; Trinh, A.; Valdes, M.; Vandaele, A. C.; Vanhaecke, F.; Van Hoolst, T.; Van Roosbroek, N.; Wilquet, V.; Yseboodt, M.

    2016-11-01

    The Interuniversity Attraction Pole (IAP) `PLANET TOPERS' (Planets: Tracing the Transfer, Origin, Preservation, and Evolution of their Reservoirs) addresses the fundamental understanding of the thermal and compositional evolution of the different reservoirs of planetary bodies (core, mantle, crust, atmosphere, hydrosphere, cryosphere, and space) considering interactions and feedback mechanisms. Here we present the first results after 2 years of project work.

  16. PLANET TOPERS: Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their ReservoirS.

    PubMed

    Dehant, V; Asael, D; Baland, R M; Baludikay, B K; Beghin, J; Belza, J; Beuthe, M; Breuer, D; Chernonozhkin, S; Claeys, Ph; Cornet, Y; Cornet, L; Coyette, A; Debaille, V; Delvigne, C; Deproost, M H; De WInter, N; Duchemin, C; El Atrassi, F; François, C; De Keyser, J; Gillmann, C; Gloesener, E; Goderis, S; Hidaka, Y; Höning, D; Huber, M; Hublet, G; Javaux, E J; Karatekin, Ö; Kodolanyi, J; Revilla, L Lobo; Maes, L; Maggiolo, R; Mattielli, N; Maurice, M; McKibbin, S; Morschhauser, A; Neumann, W; Noack, L; Pham, L B S; Pittarello, L; Plesa, A C; Rivoldini, A; Robert, S; Rosenblatt, P; Spohn, T; Storme, J -Y; Tosi, N; Trinh, A; Valdes, M; Vandaele, A C; Vanhaecke, F; Van Hoolst, T; Van Roosbroek, N; Wilquet, V; Yseboodt, M

    2016-11-01

    The Interuniversity Attraction Pole (IAP) 'PLANET TOPERS' (Planets: Tracing the Transfer, Origin, Preservation, and Evolution of their Reservoirs) addresses the fundamental understanding of the thermal and compositional evolution of the different reservoirs of planetary bodies (core, mantle, crust, atmosphere, hydrosphere, cryosphere, and space) considering interactions and feedback mechanisms. Here we present the first results after 2 years of project work.

  17. Origins and Evolution of the TPSR Alliance Community of Practice

    ERIC Educational Resources Information Center

    Balague, Gloria

    2016-01-01

    Teaching for personal and social responsibility (TPSR) is unconventional in nature, and this article describes the origins of the program and the many hurdles it had to overcome. It is not strictly a form of kinesiology, social work or education. It focuses instead on the whole person: kids' needs, interests and vulnerabilities. But TPSR also…

  18. The evolution of milk secretion and its ancient origins.

    PubMed

    Oftedal, O T

    2012-03-01

    Lactation represents an important element of the life history strategies of all mammals, whether monotreme, marsupial, or eutherian. Milk originated as a glandular skin secretion in synapsids (the lineage ancestral to mammals), perhaps as early as the Pennsylvanian period, that is, approximately 310 million years ago (mya). Early synapsids laid eggs with parchment-like shells intolerant of desiccation and apparently dependent on glandular skin secretions for moisture. Mammary glands probably evolved from apocrine-like glands that combined multiple modes of secretion and developed in association with hair follicles. Comparative analyses of the evolutionary origin of milk constituents support a scenario in which these secretions evolved into a nutrient-rich milk long before mammals arose. A variety of antimicrobial and secretory constituents were co-opted into novel roles related to nutrition of the young. Secretory calcium-binding phosphoproteins may originally have had a role in calcium delivery to eggs; however, by evolving into large, complex casein micelles, they took on an important role in transport of amino acids, calcium and phosphorus. Several proteins involved in immunity, including an ancestral butyrophilin and xanthine oxidoreductase, were incorporated into a novel membrane-bound lipid droplet (the milk fat globule) that became a primary mode of energy transfer. An ancestral c-lysozyme lost its lytic functions in favor of a role as α-lactalbumin, which modifies a galactosyltransferase to recognize glucose as an acceptor, leading to the synthesis of novel milk sugars, of which free oligosaccharides may have predated free lactose. An ancestral lipocalin and an ancestral whey acidic protein four-disulphide core protein apparently lost their original transport and antimicrobial functions when they became the whey proteins β-lactoglobulin and whey acidic protein, which with α-lactalbumin provide limiting sulfur amino acids to the young. By the late

  19. Models of Ceres' Surface as a Function of Origin and Evolution Scenarios

    NASA Astrophysics Data System (ADS)

    Castillo, J. C.; Frank, E.; Grazier, K.; Raymond, C. A.

    2012-12-01

    After its spectacular encounter with Vesta, the Dawn spacecraft is now on its way to the largest object in the main belt, Ceres. The last few years have seen a growing interest in the origin and evolution of this object and increased observational constraints on its geophysical properties and surface chemistry. In 2005, McCord and Sotin (2005) introduced the idea that Ceres could have held a deep ocean for some period of time. Rivkin (2006) discovered carbonates at the surface of Ceres, evidence for chemistry in aqueous environments, an idea reinforced by and Milliken and Rivkin's (2009) suggestion that brucite is a major component of Ceres' surface. See also Rivkin et al. (this conference) for the state of the art on Ceres' surface composition inferred from astronomical observations. In parallel, recent developments in Solar system dynamical evolution (Walsh et al. 2011; Grazier et al. 2012) and cosmochemistry models (Dodson-Robinson et al. 2009) and measurements (d'Alexander et al. 2012) indicate that asteroid volatiles may have been supplied from different sources and included second-phase low-eutectic impurities such as ammonia hydrates. Hence, the upcoming rendezvous of Dawn at Ceres offers the prospect of obtaining constraints on the origin of volatiles in the main belt and the habitability potential of large wet asteroids such as Ceres. Ceres' surface chemistry is the product of multiple parameters and processes: (1) the composition of accreted materials, volatile composition, and the possibility for hydrothermal activity in planetesimals prior to accretion in Ceres (i.e., in objects of the size of chondrite parent bodies); (2) evolution of the rock and ocean chemistry as a consequence of one or several episodes of hydrothermal activity (Castillo-Rogez and McCord 2010), (3) the transportation mechanism that may encompass solid-state convection or cryovolcanism and act as a possible filter against certain species in the ocean; (4) exogenic processing (esp. UV

  20. Biomaterial evolution parallels behavioral innovation in the origin of orb-like spider webs

    NASA Astrophysics Data System (ADS)

    Blackledge, Todd A.; Kuntner, Matjaž; Marhabaie, Mohammad; Leeper, Thomas C.; Agnarsson, Ingi

    2012-11-01

    Correlated evolution of traits can act synergistically to facilitate organism function. But, what happens when constraints exist on the evolvability of some traits, but not others? The orb web was a key innovation in the origin of >12,000 species of spiders. Orb evolution hinged upon the origin of novel spinning behaviors and innovations in silk material properties. In particular, a new major ampullate spidroin protein (MaSp2) increased silk extensibility and toughness, playing a critical role in how orb webs stop flying insects. Here, we show convergence between pseudo-orb-weaving Fecenia and true orb spiders. As in the origin of true orbs, Fecenia dragline silk improved significantly compared to relatives. But, Fecenia silk lacks the high compliance and extensibility found in true orb spiders, likely due in part to the absence of MaSp2. Our results suggest how constraints limit convergent evolution and provide insight into the evolution of nature's toughest fibers.

  1. Untangling the origin of viruses and their impact on cellular evolution.

    PubMed

    Nasir, Arshan; Sun, Feng-Jie; Kim, Kyung Mo; Caetano-Anollés, Gustavo

    2015-04-01

    The origin and evolution of viruses remain mysterious. Here, we focus on the distribution of viral replicons in host organisms, their morphological features, and the evolution of highly conserved protein and nucleic acid structures. The apparent inability of RNA viral replicons to infect contemporary akaryotic species suggests an early origin of RNA viruses and their subsequent loss in akaryotes. A census of virion morphotypes reveals that advanced forms were unique to viruses infecting a specific supergroup, while simpler forms were observed in viruses infecting organisms in all forms of cellular life. Results hint toward an ancient origin of viruses from an ancestral virus harboring either filamentous or spherical virions. Finally, phylogenetic trees built from protein domain and tRNA structures in thousands of genomes suggest that viruses evolved via reductive evolution from ancient cells. The analysis presents a complete account of the evolutionary history of cells and viruses and identifies viruses as crucial agents influencing cellular evolution.

  2. The universal relation of galactic chemical evolution: the origin of the mass-metallicity relation

    SciTech Connect

    Zahid, H. Jabran; Dima, Gabriel I.; Kudritzki, Rolf-Peter; Kewley, Lisa J.; Geller, Margaret J.; Hwang, Ho Seong; Silverman, John D.; Kashino, Daichi

    2014-08-20

    We examine the mass-metallicity relation for z ≲ 1.6. The mass-metallicity relation follows a steep slope with a turnover, or 'knee', at stellar masses around 10{sup 10} M {sub ☉}. At stellar masses higher than the characteristic turnover mass, the mass-metallicity relation flattens as metallicities begin to saturate. We show that the redshift evolution of the mass-metallicity relation depends only on the evolution of the characteristic turnover mass. The relationship between metallicity and the stellar mass normalized to the characteristic turnover mass is independent of redshift. We find that the redshift-independent slope of the mass-metallicity relation is set by the slope of the relationship between gas mass and stellar mass. The turnover in the mass-metallicity relation occurs when the gas-phase oxygen abundance is high enough that the amount of oxygen locked up in low-mass stars is an appreciable fraction of the amount of oxygen produced by massive stars. The characteristic turnover mass is the stellar mass, where the stellar-to-gas mass ratio is unity. Numerical modeling suggests that the relationship between metallicity and the stellar-to-gas mass ratio is a redshift-independent, universal relationship followed by all galaxies as they evolve. The mass-metallicity relation originates from this more fundamental universal relationship between metallicity and the stellar-to-gas mass ratio. We test the validity of this universal metallicity relation in local galaxies where stellar mass, metallicity, and gas mass measurements are available. The data are consistent with a universal metallicity relation. We derive an equation for estimating the hydrogen gas mass from measurements of stellar mass and metallicity valid for z ≲ 1.6 and predict the cosmological evolution of galactic gas masses.

  3. Clinical Sequencing Uncovers Origins and Evolution of Lassa Virus.

    PubMed

    Andersen, Kristian G; Shapiro, B Jesse; Matranga, Christian B; Sealfon, Rachel; Lin, Aaron E; Moses, Lina M; Folarin, Onikepe A; Goba, Augustine; Odia, Ikponmwonsa; Ehiane, Philomena E; Momoh, Mambu; England, Eleina M; Winnicki, Sarah; Branco, Luis M; Gire, Stephen K; Phelan, Eric; Tariyal, Ridhi; Tewhey, Ryan; Omoniwa, Omowunmi; Fullah, Mohammed; Fonnie, Richard; Fonnie, Mbalu; Kanneh, Lansana; Jalloh, Simbirie; Gbakie, Michael; Saffa, Sidiki; Karbo, Kandeh; Gladden, Adrianne D; Qu, James; Stremlau, Matthew; Nekoui, Mahan; Finucane, Hilary K; Tabrizi, Shervin; Vitti, Joseph J; Birren, Bruce; Fitzgerald, Michael; McCowan, Caryn; Ireland, Andrea; Berlin, Aaron M; Bochicchio, James; Tazon-Vega, Barbara; Lennon, Niall J; Ryan, Elizabeth M; Bjornson, Zach; Milner, Danny A; Lukens, Amanda K; Broodie, Nisha; Rowland, Megan; Heinrich, Megan; Akdag, Marjan; Schieffelin, John S; Levy, Danielle; Akpan, Henry; Bausch, Daniel G; Rubins, Kathleen; McCormick, Joseph B; Lander, Eric S; Günther, Stephan; Hensley, Lisa; Okogbenin, Sylvanus; Schaffner, Stephen F; Okokhere, Peter O; Khan, S Humarr; Grant, Donald S; Akpede, George O; Asogun, Danny A; Gnirke, Andreas; Levin, Joshua Z; Happi, Christian T; Garry, Robert F; Sabeti, Pardis C

    2015-08-13

    The 2013-2015 West African epidemic of Ebola virus disease (EVD) reminds us of how little is known about biosafety level 4 viruses. Like Ebola virus, Lassa virus (LASV) can cause hemorrhagic fever with high case fatality rates. We generated a genomic catalog of almost 200 LASV sequences from clinical and rodent reservoir samples. We show that whereas the 2013-2015 EVD epidemic is fueled by human-to-human transmissions, LASV infections mainly result from reservoir-to-human infections. We elucidated the spread of LASV across West Africa and show that this migration was accompanied by changes in LASV genome abundance, fatality rates, codon adaptation, and translational efficiency. By investigating intrahost evolution, we found that mutations accumulate in epitopes of viral surface proteins, suggesting selection for immune escape. This catalog will serve as a foundation for the development of vaccines and diagnostics. VIDEO ABSTRACT.

  4. 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.

  5. The origin and evolution of the ectodermal placodes.

    PubMed

    Graham, Anthony; Shimeld, Sebastian M

    2013-01-01

    Many of the features that distinguish the vertebrates from other chordates are found in the head. Prominent amongst these differences are the paired sense organs and associated cranial ganglia. Significantly, these structures are derived developmentally from the ectodermal placodes. It has therefore been proposed that the emergence of the ectodermal placodes was concomitant with and central to the evolution of the vertebrates. More recent studies, however, indicate forerunners of the ectodermal placodes can be readily identified outside the vertebrates, particularly in urochordates. Thus the evolutionary history of the ectodermal placodes is deeper and more complex than was previously appreciated with the full repertoire of vertebrate ectodermal placodes, and their derivatives, being assembled over a protracted period rather than arising collectively with the vertebrates.

  6. [Origin and evolution of peptide-protein bioregulators].

    PubMed

    Chipens, G I; Freĭdlin, I S; Skliarova, S N

    1987-01-01

    Possible evolutionary pathways of cellular regulatory systems are discussed. Analysis of animal evolution suggests that peptide and protein bioregulators emerged at an early stage during formation of biochemical systems in prokaryotic cells involving protein synthesis on ribosomes, the processes of exo- and endocytosis and limited proteolysis reactions. Primary autocrine bioregulators are compared with growth factors. Models for cellular bioregulation are discussed in which both cell receptors and peptide/protein ligands, primarily immunoglobins, act as prehormones. Their internalization and limited proteolysis can lead to formation of low-molecular peptides (tetines) acting as autocrine or paracrine bioregulators. Basing on the concept of biochemical universality, it is suggested that the effects of many growth factors, hormones, immunoglobulins, mono- and lymphokins are mediated by identical or similar (carrying the same signatures) fragments which are produced in cells due to limited proteolysis reactions and which are directly involved in activation of biochemical systems in these cells.

  7. 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

  8. Origin, Methods, and Evolution of the Three Nurses’ Health Studies

    PubMed Central

    Bertoia, Monica L.; Lenart, Elizabeth B.; Stampfer, Meir J.; Willett, Walter C.; Speizer, Frank E.; Chavarro, Jorge E.

    2016-01-01

    We have summarized the evolution of the Nurses’ Health Study (NHS), a prospective cohort study of 121 700 married registered nurses launched in 1976; NHS II, which began in 1989 and enrolled 116 430 nurses; and NHS3, which began in 2010 and has ongoing enrollment. Over 40 years, these studies have generated long-term, multidimensional data, including lifestyle- and health-related information across the life course and an extensive repository of various biological specimens. We have described the questionnaire data collection, disease follow-up methods, biorepository resources, and data management and statistical procedures. Through integrative analyses, these studies have sustained a high level of scientific productivity and substantially influenced public health recommendations. We have highlighted recent interdisciplinary research projects and discussed future directions for collaboration and innovation. PMID:27459450

  9. Clinical sequencing uncovers origins and evolution of Lassa virus

    PubMed Central

    Andersen, Kristian G.; Shapiro, B. Jesse; Matranga, Christian B.; Sealfon, Rachel; Lin, Aaron E.; Moses, Lina M.; Folarin, Onikepe A.; Goba, Augustine; Odia, Ikponmwonsa; Ehiane, Philomena E.; Momoh, Mambu; England, Eleina M.; Winnicki, Sarah; Branco, Luis M.; Gire, Stephen K.; Phelan, Eric; Tariyal, Ridhi; Tewhey, Ryan; Omoniwa, Omowunmi; Fullah, Mohammed; Fonnie, Richard; Fonnie, Mbalu; Kanneh, Lansana; Jalloh, Simbirie; Gbakie, Michael; Saffa, Sidiki; Karbo, Kandeh; Gladden, Adrianne D.; Qu, James; Stremlau, Matthew; Nekoui, Mahan; Finucane, Hilary K.; Tabrizi, Shervin; Vitti, Joseph J.; Birren, Bruce; Fitzgerald, Michael; McCowan, Caryn; Ireland, Andrea; Berlin, Aaron M.; Bochicchio, James; Tazon-Vega, Barbara; Lennon, Niall J.; Ryan, Elizabeth M.; Bjornson, Zach; Milner, Danny A.; Lukens, Amanda K.; Broodie, Nisha; Rowland, Megan; Heinrich, Megan; Akdag, Marjan; Schieffelin, John S.; Levy, Danielle; Akpan, Henry; Bausch, Daniel G.; Rubins, Kathleen; McCormick, Joseph B.; Lander, Eric S.; Günther, Stephan; Hensley, Lisa; Okogbenin, Sylvanus; Schaffner, Stephen F.; Okokhere, Peter O.; Khan, S. Humarr; Grant, Donald S.; Akpede, George O.; Asogun, Danny A.; Gnirke, Andreas; Levin, Joshua Z.; Happi, Christian T.; Garry, Robert F.; Sabeti, Pardis C.

    2015-01-01

    Summary The 2013-2015 West African epidemic of Ebola virus disease (EVD) reminds us how little is known about biosafety level-4 viruses. Like Ebola virus, Lassa virus (LASV) can cause hemorrhagic fever with high case fatality rates. We generated a genomic catalog of almost 200 LASV sequences from clinical and rodent reservoir samples. We show that whereas the 2013-2015 EVD epidemic is fueled by human-to-human transmissions, LASV infections mainly result from reservoir-to-human infections. We elucidated the spread of LASV across West Africa and show that this migration was accompanied by changes in LASV genome abundance, fatality rates, codon adaptation, and translational efficiency. By investigating intrahost evolution, we found that mutations accumulate in epitopes of viral surface proteins, suggesting selection for immune escape. This catalog will serve as a foundation for the development of vaccines and diagnostics. PMID:26276630

  10. Evolution of the Moon's orbit and the origin of life

    NASA Technical Reports Server (NTRS)

    Turcotte, D. L.; Nordmann, J. C.; Cisne, J. L.

    1974-01-01

    Indications about the past history of the lunar orbit that are yielded by palaeontological data derived from periodicities in fossil corals are shown to suggest that the moon approached the earth 2,850 plus or minus 250 Myr BP. Convergent evidence in the geological record indicates that a pulse of high temperature volcanism occurred about 2800 Myr BP. The implied catastrophe roughly coincides with the first records of life. It seems within the realm of possibility that a global thermal event might have been involved in the origin of life.

  11. NASA Strategic Roadmap: Origin, Evolution, Structure, and Destiny of the Universe

    NASA Technical Reports Server (NTRS)

    White, Nicholas E.

    2005-01-01

    The NASA strategic roadmap on the Origin, Evolution, Structure and Destiny of the Universe is one of 13 roadmaps that outline NASA s approach to implement the vision for space exploration. The roadmap outlines a program to address the questions: What powered the Big Bang? What happens close to a Black Hole? What is Dark Energy? How did the infant universe grow into the galaxies, stars and planets, and set the stage for life? The roadmap builds upon the currently operating and successful missions such as HST, Chandra and Spitzer. The program contains two elements, Beyond Einstein and Pathways to Life, performed in three phases (2005-2015, 2015-2025 and >2025) with priorities set by inputs received from reviews undertaken by the National Academy of Sciences and technology readiness. The program includes the following missions: 2005-2015 GLAST, JWST and LISA; 2015-2025 Constellation-X and a series of Einstein Probes; and >2025 a number of ambitious vision missions which will be prioritized by results from the previous two phases.

  12. Origin and Evolution of Plastids and Photosynthesis in Eukaryotes

    PubMed Central

    McFadden, Geoffrey I.

    2014-01-01

    Recent progress in understanding the origins of plastids from endosymbiotic cyanobacteria is reviewed. Establishing when during geological time the endosymbiosis occurred remains elusive, but progress has been made in defining the cyanobacterial lineage most closely related to plastids, and some mechanistic insight into the possible existence of cryptic endosymbioses perhaps involving Chlamydia-like infections of the host have also been presented. The phylogenetic affinities of the host remain obscure. The existence of a second lineage of primary plastids in euglyphid amoebae has now been confirmed, but the quasipermanent acquisition of plastids by animals has been shown to be more ephemeral than initially suspected. A new understanding of how plastids have been integrated into their hosts by transfer of photosynthate, by endosymbiotic gene transfer and repatriation of gene products back to the endosymbiont, and by regulation of endosymbiont division is presented in context. PMID:24691960

  13. The origin and evolution of terrestrial and Martian rock labyrinths

    NASA Technical Reports Server (NTRS)

    Brook, G. A.

    1984-01-01

    The morphological characteristics and evolutionary development of rock labyrinths on Earth (in sandstone, volcanics, and carbonates) are compared with those on Mars. On Earth rock labyrinths originate as parallel, an echelon, or intersecting narrow grabens, or develop where fault and joint networks are selectively eroded. Labyrinths frequently contain both downfaulted and erosional elements. Closed labyrinths contain depressions; open labyrinths do not, they are simple part of a fluvial network generally of low order. As closed labyrinths made up of intersecting grabens or made up of connected erosional depressions are extremely common on Mars, the research focussed on an understanding of these labyrinth types. Field investigations were carried out in Canyonlands National Park, Utah, and in the Chirachahua Mountains of Arizona. Martian labyrinths were investigated using Viking orbiter images. In addition, research was undertaken on apparent thermokarst features in Lunae Planum and Chryse Planitia where closed depressions are numerous and resemble atlas topography.

  14. The origins and evolution of freeze-etch electron microscopy

    PubMed Central

    Heuser, John E.

    2011-01-01

    The introduction of the Balzers freeze-fracture machine by Moor in 1961 had a much greater impact on the advancement of electron microscopy than he could have imagined. Devised originally to circumvent the dangers of classical thin-section techniques, as well as to provide unique en face views of cell membranes, freeze-fracturing proved to be crucial for developing modern concepts of how biological membranes are organized and proved that membranes are bilayers of lipids within which proteins float and self-assemble. Later, when freeze-fracturing was combined with methods for freezing cells that avoided the fixation and cryoprotection steps that Moor still had to use to prepare the samples for his original invention, it became a means for capturing membrane dynamics on the millisecond time-scale, thus allowing a deeper understanding of the functions of biological membranes in living cells as well as their static ultrastructure. Finally, the realization that unfixed, non-cryoprotected samples could be deeply vacuum-etched or even freeze-dried after freeze-fracturing opened up a whole new way to image all the other molecular components of cells besides their membranes and also provided a powerful means to image the interactions of all the cytoplasmic components with the various membranes of the cell. The purpose of this review is to outline the history of these technical developments, to describe how they are being used in electron microscopy today and to suggest how they can be improved in order to further their utility for biological electron microscopy in the future. PMID:21844598

  15. Origin and evolution of the deep thermochemical structure beneath Eurasia

    NASA Astrophysics Data System (ADS)

    Flament, N.; Williams, S.; Müller, R. D.; Gurnis, M.; Bower, D. J.

    2017-01-01

    A unique structure in the Earth's lowermost mantle, the Perm Anomaly, was recently identified beneath Eurasia. It seismologically resembles the large low-shear velocity provinces (LLSVPs) under Africa and the Pacific, but is much smaller. This challenges the current understanding of the evolution of the plate-mantle system in which plumes rise from the edges of the two LLSVPs, spatially fixed in time. New models of mantle flow over the last 230 million years reproduce the present-day structure of the lower mantle, and show a Perm-like anomaly. The anomaly formed in isolation within a closed subduction network ~22,000 km in circumference prior to 150 million years ago before migrating ~1,500 km westward at an average rate of 1 cm year-1, indicating a greater mobility of deep mantle structures than previously recognized. We hypothesize that the mobile Perm Anomaly could be linked to the Emeishan volcanics, in contrast to the previously proposed Siberian Traps.

  16. On the possible origin and evolution of the genetic code

    NASA Technical Reports Server (NTRS)

    Jukes, T. H.

    1974-01-01

    The genetic code is examined for indications of possible preceding codes that existed during early evolution. Eight of the 20 amino acids are coded by 'quartets' of codons with fourfold degeneracy, and 16 such quartets can exist, so that an earlier code could have provided for 15 or 16 amino acids, rather than 20. If twofold degeneracy is postulated for the first position of the codon, there could have been ten amino acids in the code. It is speculated that these may have been phenylalanine, valine, proline, alanine, histidine, glutamine, glutanic acid, aspartic acid, cysteine and glycine. There is a notable deficiency of arginine in proteins, despite the fact that it has six codons. Simultaneously, there is more lysine in proteins than would be expected from its two codons, if the four bases in mRNA are equiprobable and are arranged randomly. It is speculated that arginine is an 'intruder' into the genetic code, and that it may have displayed another amino acid such as ornithine, or may even have displayed lysine from some of its previous codon assignments. As a result, natural selection has favored lysine against the fact that it has only two codons.

  17. Origin and evolution of the deep thermochemical structure beneath Eurasia

    PubMed Central

    Flament, N.; Williams, S.; Müller, R. D.; Gurnis, M.; Bower, D. J.

    2017-01-01

    A unique structure in the Earth's lowermost mantle, the Perm Anomaly, was recently identified beneath Eurasia. It seismologically resembles the large low-shear velocity provinces (LLSVPs) under Africa and the Pacific, but is much smaller. This challenges the current understanding of the evolution of the plate–mantle system in which plumes rise from the edges of the two LLSVPs, spatially fixed in time. New models of mantle flow over the last 230 million years reproduce the present-day structure of the lower mantle, and show a Perm-like anomaly. The anomaly formed in isolation within a closed subduction network ∼22,000 km in circumference prior to 150 million years ago before migrating ∼1,500 km westward at an average rate of 1 cm year−1, indicating a greater mobility of deep mantle structures than previously recognized. We hypothesize that the mobile Perm Anomaly could be linked to the Emeishan volcanics, in contrast to the previously proposed Siberian Traps. PMID:28098137

  18. The origin and evolution of chordate nervous systems

    PubMed Central

    Holland, Linda Z.

    2015-01-01

    In the past 40 years, comparisons of developmental gene expression and mechanisms of development (evodevo) joined comparative morphology as tools for reconstructing long-extinct ancestral forms. Unfortunately, both approaches typically give congruent answers only with closely related organisms. Chordate nervous systems are good examples. Classical studies alone left open whether the vertebrate brain was a new structure or evolved from the anterior end of an ancestral nerve cord like that of modern amphioxus. Evodevo plus electron microscopy showed that the amphioxus brain has a diencephalic forebrain, small midbrain, hindbrain and spinal cord with parts of the genetic mechanisms for the midbrain/hindbrain boundary, zona limitans intrathalamica and neural crest. Evodevo also showed how extra genes resulting from whole-genome duplications in vertebrates facilitated evolution of new structures like neural crest. Understanding how the chordate central nervous system (CNS) evolved from that of the ancestral deuterostome has been truly challenging. The majority view is that this ancestor had a CNS with a brain that gave rise to the chordate CNS and, with loss of a discrete brain, to one of the two hemichordate nerve cords. The minority view is that this ancestor had no nerve cord; those in chordates and hemichordates evolved independently. New techniques such as phylostratigraphy may help resolve this conundrum. PMID:26554041

  19. The origin and evolution of chordate nervous systems.

    PubMed

    Holland, Linda Z

    2015-12-19

    In the past 40 years, comparisons of developmental gene expression and mechanisms of development (evodevo) joined comparative morphology as tools for reconstructing long-extinct ancestral forms. Unfortunately, both approaches typically give congruent answers only with closely related organisms. Chordate nervous systems are good examples. Classical studies alone left open whether the vertebrate brain was a new structure or evolved from the anterior end of an ancestral nerve cord like that of modern amphioxus. Evodevo plus electron microscopy showed that the amphioxus brain has a diencephalic forebrain, small midbrain, hindbrain and spinal cord with parts of the genetic mechanisms for the midbrain/hindbrain boundary, zona limitans intrathalamica and neural crest. Evodevo also showed how extra genes resulting from whole-genome duplications in vertebrates facilitated evolution of new structures like neural crest. Understanding how the chordate central nervous system (CNS) evolved from that of the ancestral deuterostome has been truly challenging. The majority view is that this ancestor had a CNS with a brain that gave rise to the chordate CNS and, with loss of a discrete brain, to one of the two hemichordate nerve cords. The minority view is that this ancestor had no nerve cord; those in chordates and hemichordates evolved independently. New techniques such as phylostratigraphy may help resolve this conundrum.

  20. The origin and evolution of dust clouds in Central Asia

    USGS Publications Warehouse

    Smirnov, V.V.; Gillette, Dale A.; Golitsyn, G.S.; MacKinnon, D.J.

    1994-01-01

    Data from a high resolution radiometer AVHRR (580-680 nm optical lengthwaves) installed on the "NOAA-11" satellite as well as TV (500-700 nm) and IR (8000-12000 nm) equipment of the Russia satellite "Meteor-2/16" were used to study the evolution of dust storms for 1-30 September 1989 in Tajikistan, Uzbekistan, Turkmenistan and Afghanistan. These data help to validate the hypothesis, that long-term dusted boundary layer (duration of the order of a day or more), but of comparatively not high optical density (4-10 km meteorological visibility range at the 20-50 km background), is formed after the northwest intrusions into a region of intensive cold fronts at the surface wind velocities of 7-15 m/s. Stability of dust clouds of vertical power to 3-3.5 km (up to an inversion level) is explained by an action of collective buoyancy factors at heating the dust particles of 2-4 ??m in mean diameter by solar radiation. The more intensive intrusions stimulate a formation of simultaneously dust and water clouds. The last partially reduce the solar radiation (by the calculations of the order of 30-50%) and decrease the role of buoyancy factors. Thus, initiated is the intensive but short-term dusted boundary layer at horizontal visibility of 50-200 m. ?? 1994.

  1. Phase Transition in Sexual Reproduction and Biological Evolution

    NASA Astrophysics Data System (ADS)

    Zawierta, Marta; Waga, Wojciech; Mackiewicz, Dorota; Biecek, Przemysław; Cebrat, Stanisław

    Using Monte Carlo model of biological evolution it is discovered that populations can switch between two different strategies of their genomes' evolution: Darwinian purifying selection and complementing the haplotypes. The first one is exploited in the large panmictic populations while the second one in the small highly inbred populations. The choice depends on the crossover frequency. There is a power law relation between the critical value of crossover frequency and the size of panmictic population. Under constant inbreeding this critical value of crossover does not depend on the population size and has a character of phase transition. Close to this value sympatric speciation is observed.

  2. The Origins and Evolution of Molecules in Icy Solids

    NASA Technical Reports Server (NTRS)

    Hudson, Reggie L.; Moore, Marla H.

    2010-01-01

    Astronomical observations of the past few decades have revealed the existence of a variety of molecules in extraterrestrial ices. These molecules include H2O, CO, and CO2, and organics such as CH4, CH30H, and C2H6. Some ices are dominated by polar molecules, while non-polar species appear to dominate others. Observations, mainly in the radio and IR regions, have allowed the inference of other solid-phase molecules whose formation remains difficult to explain by gas-phase chemistry alone. Several laboratory research groups have reported on extensive experiments on the solid-phase reaction chemistry of icy materials, generally as initiated by either ionizing radiation or vacuum-UV photons. These experiments not only permit molecular identifications to be made from astronomical observations, but also allow predictions of yet unidentified molecules. This laboratory approach has evolved over more than 30 years with much of the earliest work focusing on complex mixtures thought to represent either cometary or interstellar ices. Although those early experiments documented a rich solid-state photo- and radiation chemistry, they revealed few details of reactions for particular molecules, partly due to the multi-component nature of the samples. Since then, model systems have been examined that allow the chemistry of individual species and specific reactions to be probed. Reactions involving most of the smaller astronomical molecules have now been studied and specific processes identified. Current laboratory work suggests that a variety of reactions occur in extraterrestrial ices, including acid-base processes, radical dimerizations, proton transfers, oxidations, reductions, and isomerizations. This workshop presentation will focus on chemical reactions relevant to solar system and interstellar ices. While most of the work will be drawn from that to which the speaker has contributed, results from other laboratories also will be included. Suggestions for future studies will be

  3. Evolution in fossil lineages: paleontology and The Origin of Species.

    PubMed

    Hunt, Gene

    2010-12-01

    Of all of the sources of evidence for evolution by natural selection, perhaps the most problematic for Darwin was the geological record of organic change. In response to the absence of species-level transformations in the fossil record, Darwin argued that the fossil record was too incomplete, too biased, and too poorly known to provide strong evidence against his theory. Here, this view of the fossil record is evaluated in light of 150 years of subsequent paleontological research. Although Darwin's assessment of the completeness and resolution of fossiliferous rocks was in several ways astute, today the fossil record is much better explored, documented, and understood than it was in 1859. In particular, a reasonably large set of studies tracing evolutionary trajectories within species can now be brought to bear on Darwin's expectation of gradual change driven by natural selection. An unusually high-resolution sequence of stickleback-bearing strata records the transformation of this lineage via natural selection. This adaptive trajectory is qualitatively consistent with Darwin's prediction, but it occurred much more rapidly than he would have guessed: almost all of the directional change was completed within 1,000 generations. In most geological sequences, this change would be too rapid to resolve. The accumulated fossil record at more typical paleontological scales (10(4)-10(6) years) reveals evolutionary changes that are rarely directional and net rates of change that are perhaps surprisingly slow, two findings that are in agreement with the punctuated-equilibrium model. Finally, Darwin's view of the broader history of life is reviewed briefly, with a focus on competition-mediated extinction and recent paleontological and phylogenetic attempts to assess diversity dependence in evolutionary dynamics.

  4. Insights into the origin and evolution of the plant hormone signaling machinery.

    PubMed

    Wang, Chunyang; Liu, Yang; Li, Si-Shen; Han, Guan-Zhu

    2015-03-01

    Plant hormones modulate plant growth, development, and defense. However, many aspects of the origin and evolution of plant hormone signaling pathways remain obscure. Here, we use a comparative genomic and phylogenetic approach to investigate the origin and evolution of nine major plant hormone (abscisic acid, auxin, brassinosteroid, cytokinin, ethylene, gibberellin, jasmonate, salicylic acid, and strigolactone) signaling pathways. Our multispecies genome-wide analysis reveals that: (1) auxin, cytokinin, and strigolactone signaling pathways originated in charophyte lineages; (2) abscisic acid, jasmonate, and salicylic acid signaling pathways arose in the last common ancestor of land plants; (3) gibberellin signaling evolved after the divergence of bryophytes from land plants; (4) the canonical brassinosteroid signaling originated before the emergence of angiosperms but likely after the split of gymnosperms and angiosperms; and (5) the origin of the canonical ethylene signaling pathway postdates shortly the emergence of angiosperms. Our findings might have important implications in understanding the molecular mechanisms underlying the emergence of land plants.

  5. Insights into the Origin and Evolution of the Plant Hormone Signaling Machinery1

    PubMed Central

    Wang, Chunyang; Liu, Yang; Li, Si-Shen; Han, Guan-Zhu

    2015-01-01

    Plant hormones modulate plant growth, development, and defense. However, many aspects of the origin and evolution of plant hormone signaling pathways remain obscure. Here, we use a comparative genomic and phylogenetic approach to investigate the origin and evolution of nine major plant hormone (abscisic acid, auxin, brassinosteroid, cytokinin, ethylene, gibberellin, jasmonate, salicylic acid, and strigolactone) signaling pathways. Our multispecies genome-wide analysis reveals that: (1) auxin, cytokinin, and strigolactone signaling pathways originated in charophyte lineages; (2) abscisic acid, jasmonate, and salicylic acid signaling pathways arose in the last common ancestor of land plants; (3) gibberellin signaling evolved after the divergence of bryophytes from land plants; (4) the canonical brassinosteroid signaling originated before the emergence of angiosperms but likely after the split of gymnosperms and angiosperms; and (5) the origin of the canonical ethylene signaling pathway postdates shortly the emergence of angiosperms. Our findings might have important implications in understanding the molecular mechanisms underlying the emergence of land plants. PMID:25560880

  6. Complexation and phase evolution at dimethylformamide-Ag(111) interfaces

    SciTech Connect

    Song, Wentao; Leung, Kevin; Shao, Qian; Gaskell, Karen J.; Reutt-Robey, Janice E.

    2016-09-15

    The interaction of solvent molecules with metallic surfaces impacts many interfacial chemical processes. We investigate the chemical and structure evolution that follows adsorption of the polar solvent dimethylformamide (DMF) on Ag(111). An Ag(DMF)2 coordination complex forms spontaneously by DMF etching of Ag(111), yielding mixed films of the complexes and DMF. Utilizing ultrahigh vacuum scanning tunneling microscopy (UHV-STM), in combination with X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) computations, we map monolayer phases from the 2-D gas regime, consisting of a binary mixture of DMF and Ag(DMF)2, through the saturation monolayer limit, in which these two chemical species phase separate into ordered islands. Structural models for the near-square DMF phase and the chain-like Ag(DMF)2 phase are presented and supported by DFT computation. Interface evolution is summarized in a surface pressure-composition phase diagram, which allows structure prediction over arbitrary experimental conditions. In conclusion, this work reveals new surface coordination chemistry for an important electrolyte-electrode system, and illustrates how surface pressure can be used to tune monolayer phases.

  7. The Origin and Evolution of Deep Plasmaspheric Notches

    NASA Technical Reports Server (NTRS)

    Gallagher, D. L.; Adrian, M. L.; Liemohn, M.

    2004-01-01

    Deep plasmaspheric notches can extend over more than 2 RE in radial distance and 3 hours MLT in the magnetic equatorial plane. They appear to be among the largest evacuated features in the exterior plasmaspheric boundary. They can last for days and exhibit varying structure. It appears that low-density channels resulting from the entrainment of the plasmaspheric convection plume during storm-time recovery share the same origin as notches. Notches rather than channels result from differences in storm- time conditions. Strong convection tends to result in low-density channels, while weaker convection and limited erosion results in notches. Eighteen events in 2000 have been analyzed. Among these events, notches were found to drift as slowly as 72% of corotation. In only one case was a notch found to drift at the corotation rate within measurement error. On average, notches drift at about 2 1.5 hours per day or 90% of the co-rotational rate. Notches also sometimes exhibit an interior structure that appears as an extended prominence of dense plasma, which forms a W-like feature in IMAGEEUV images when viewed from Earth-center. Modeling suggests such features may be caused by small-scale potential structures that result from the localized injection of ring current plasma. Plasma filling rates during recovery and drainage during a minor storm are reported.

  8. Human enterobiasis in evolution: origin, specificity and transmission.

    PubMed

    Hugot, J P; Reinhard, K J; Gardner, S L; Morand, S

    1999-09-01

    The co-evolutionary pathway seems to be the most plausible hypothesis for the explanation of the origin of human pinworms. Of the two modes of transmission of oxyurids among humans which have been documented, the direct oral/anal route is also observed in other Primates and seems to have been favoured by selection. As indirect air-borne transmission has also been shown for human enterobiasis, the question of "How this alternative to the standard transmission method could have arisen" is examined. The results of comparative studies of prevalence of Enterobius in human coprolites, in villages of Neolithic age of the arid west of North America, show that a higher prevalence of pinworms is correlated with the lower total amount of air-exchange in caves relative to other structures. The air-borne route of transmission of pinworms among humans is interpreted as an innovation in the human/Enterobius pair. This mode of transfer could have been favoured during the time when humans changed their behaviour from a hunting-gathering to a more sedentary existence, initially associated with cave habitats.

  9. Origin and evolution of the Earth's atmosphere and hydrosphere

    SciTech Connect

    Akbari, G.E.

    1984-01-01

    The composition of the outgassed fluid has been a point of serious debate. A model developed by Melton and Giardini has been used. In this model, the fluid inclusions in diamonds have been taken as original samples of the outgassed fluids. The model uses first order kinetics of the degassing processes of H2, CH4, N2, CO and Ar, and zero order kinetics for the degassing processes of H2O and CO2. Samples with compositions similar to the fluid included in diamonds were exposed to electric discharge, UV radiation and gamma radiation to formulate the equilibrium composition of the Earth's atmosphere. Small amounts of organic and inorganic compounds were formed in the samples by the radiation. The Melton/Giardini model was used to calculate the composition and pressure of primitive atmosphere of the Earth as a function of time, beginning 4.5 b.y. ago. Since light gases such as H2 and He escape from the Earth, and other degassed material undergoes numerous chemical and physical reactions, the Earth's atmosphere was quite different from the predicted composition using the uncorrected Melton/Giardini model.

  10. Origins and evolution of the Etruscans' mtDNA.

    PubMed

    Ghirotto, Silvia; Tassi, Francesca; Fumagalli, Erica; Colonna, Vincenza; Sandionigi, Anna; Lari, Martina; Vai, Stefania; Petiti, Emmanuele; Corti, Giorgio; Rizzi, Ermanno; De Bellis, Gianluca; Caramelli, David; Barbujani, Guido

    2013-01-01

    The Etruscan culture is documented in Etruria, Central Italy, from the 8(th) to the 1(st) century BC. For more than 2,000 years there has been disagreement on the Etruscans' biological origins, whether local or in Anatolia. Genetic affinities with both Tuscan and Anatolian populations have been reported, but so far all attempts have failed to fit the Etruscans' and modern populations in the same genealogy. We extracted and typed the hypervariable region of mitochondrial DNA of 14 individuals buried in two Etruscan necropoleis, analyzing them along with other Etruscan and Medieval samples, and 4,910 contemporary individuals from the Mediterranean basin. Comparing ancient (30 Etruscans, 27 Medieval individuals) and modern DNA sequences (370 Tuscans), with the results of millions of computer simulations, we show that the Etruscans can be considered ancestral, with a high degree of confidence, to the current inhabitants of Casentino and Volterra, but not to the general contemporary population of the former Etruscan homeland. By further considering two Anatolian samples (35 and 123 individuals) we could estimate that the genetic links between Tuscany and Anatolia date back to at least 5,000 years ago, strongly suggesting that the Etruscan culture developed locally, and not as an immediate consequence of immigration from the Eastern Mediterranean shores.

  11. Universal genome in the origin of metazoa: thoughts about evolution.

    PubMed

    Sherman, Michael

    2007-08-01

    Recent advances in paleontology, genome analysis, genetics and embryology raise a number of questions about the origin of Animal Kingdom. These questions include:(1) seemingly simultaneous appearance of diverse Metazoan phyla in Cambrian period, (2) similarities of genomes among Metazoan phyla of diverse complexity, (3) seemingly excessive complexity of genomes of lower taxons and (4) similar genetic switches of functionally similar but non-homologous developmental programs. Here I propose an experimentally testable hypothesis of Universal Genome that addresses these questions. According to this model, (a) the Universal Genome that encodes all major developmental programs essential for various phyla of Metazoa emerged in a unicellular or a primitive multicellular organism shortly before the Cambrian period; (b) The Metazoan phyla, all having similar genomes, are nonetheless so distinct because they utilize specific combinations of developmental programs. This model has two major predictions, first that a significant fraction of genetic information in lower taxons must be functionally useless but becomes useful in higher taxons, and second that one should be able to turn on in lower taxons some of the complex latent developmental programs, e.g., a program of eye development or antibody synthesis in sea urchin. An example of natural turning on of a complex latent program in a lower taxon is discussed.

  12. The principle of cooperation and life's origin and evolution

    NASA Technical Reports Server (NTRS)

    Oro, J.; Armangue, G.; Mar, A.

    1986-01-01

    In simple terms a living entity is a negentropic system that replicates, mutates and evoluves. A number of suggestions have been made, such as directed panspermia, atmospheric photosynthesis, genetic overtaking from inorganic processes, etc., as alternative models to the accepted Oparin-Haldane-Urey model of the origin of life on Earth. This has probably occurred because in spite of tremendous advances in the prebiotic synthesis of biochemical compounds, the fundamental problem of the appearance of the first life--a primordial replicating cell-ancestral to all other forms of extant life, has remained elusive. This is indeed a reflection on the different fundamental nature of the problem involved. Regardless of which were the fundamental processes which occurred on the primitive Earth, it has to end up with the fundamental characteristics of an ancestral protocell. The problem of the emergence of the first ancestral cell was one of synergistic macromolecular cooperation, as it has been discussed by authors recently (COSPAR XXV Plenary Meeting). An analogous situation must have occurred at the time of the appearance of the first eucaryotic organism. Procaryotic life appeared probably during the first 600 million years of Earth history when the Earth was sufficiently cool and continually bombarded (in the late accretion period) by comets and minor bodies of the solar system, when the sea had not yet acquired its present form.

  13. Origin and evolution of dengue virus type 3 in Brazil.

    PubMed

    de Araújo, Josélio Maria Galvão; Bello, Gonzalo; Romero, Hector; Nogueira, Rita Maria Ribeiro

    2012-01-01

    The incidence of dengue fever and dengue hemorrhagic fever in Brazil experienced a significant increase since the emergence of dengue virus type-3 (DENV-3) at the early 2000s. Despite the major public health concerns, there have been very few studies of the molecular epidemiology and time-scale of this DENV lineage in Brazil. In this study, we investigated the origin and dispersion dynamics of DENV-3 genotype III in Brazil by examining a large number (n=107) of E gene sequences sampled between 2001 and 2009 from diverse Brazilian regions. These Brazilian sequences were combined with 457 DENV-3 genotype III E gene sequences from 29 countries around the world. Our phylogenetic analysis reveals that there have been at least four introductions of the DENV-3 genotype III in Brazil, as signified by the presence of four phylogenetically distinct lineages. Three lineages (BR-I, BR-II, and BR-III) were probably imported from the Lesser Antilles (Caribbean), while the fourth one (BR-IV) was probably introduced from Colombia or Venezuela. While lineages BR-I and BR-II succeeded in getting established and disseminated in Brazil and other countries from the Southern Cone, lineages BR-III and BR-IV were only detected in one single individual each from the North region. The phylogeographic analysis indicates that DENV-3 lineages BR-I and BR-II were most likely introduced into Brazil through the Southeast and North regions around 1999 (95% HPD: 1998-2000) and 2001 (95% HPD: 2000-2002), respectively. These findings show that importation of DENV-3 lineages from the Caribbean islands into Brazil seems to be relatively frequent. Our study further suggests that the North and Southeast Brazilian regions were the most important hubs of introduction and spread of DENV-3 lineages and deserve an intense epidemiological surveillance.

  14. Bladed Terrain on Pluto: Possible Origins and Evolutions

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey M.; Howard, Alan D.; Umurhan, Orkan M.; White, Oliver L.; Schenk, Paul; Beyer, Ross A.; McKinnon, William B.; Spencer, John R.; Singer, Kelsi N.; Grundy, William N.; Nimmo, Francis; Young, Leslie Ann; Stern, Alan; Weaver, Harold A., Jr.; Olkin, Catherine; Smith, Kimberly Ennico; Collins, Geoffrey C.

    2016-01-01

    Pluto's Bladed Terrain (centered roughly 20 deg N, 225 deg E) covers the flanks and crests of the informally named Tartarus Dorsa with numerous roughly aligned blade-like ridges oriented approx. North-South; it may also stretch considerably farther east onto the non-close approach hemisphere but that inference is tentative. Individual ridges are typically several hundred meters high, and are spaced 5 to 10 km crest to crest, separated by V-shaped valleys. Many ridges merge at acute angles to form Y-shape junctions in plan view. The principle composition of the blades themselves we suspect is methane or a methane-rich mixture. (Methane is spectroscopically strongly observed on the optical surfaces of blades.) Nitrogen ice is very probably too soft to support their topography. Cemented mixtures of volatile and non-volatile ices may also provide a degradable but relief supporting "bedrock" for the blades, perhaps analogous to Callisto. Currently we are considering several hypotheses for the origins of the deposit from which Bladed Terrain has evolved, including aeolian disposition, atmospheric condensation, updoming and exhumation, volcanic intrusions or extrusions, crystal growth, among others. We are reviewing several processes as candidate creators or sculptors of the blades. Perhaps they are primary depositional patterns such as dunes, or differential condensation patterns (like on Callisto), or fissure extrusions. Or alternatively perhaps they are the consequence of differential erosion (such as sublimation erosion widening and deepening along cracks), variations in substrate properties, mass wasting into the subsurface, or sculpted by a combination of directional winds and solar isolation orientation. We will consider the roles of the long-term increasing solar flux and short periods of warm thick atmospheres. Hypotheses will be ordered based on observational constrains and modeling to be presented at the conference.

  15. Bladed Terrain on Pluto: Possible Origins and Evolutions

    NASA Astrophysics Data System (ADS)

    Moore, Jeffrey M.; Howard, Alan D.; Umurhan, Orkan M.; White, Oliver; Schenk, Paul M.; Beyer, Ross A.; McKinnon, William B.; Spencer, John R.; Singer, Kelsi N.; Grundy, William M.; Nimmo, Francis; Young, Leslie; Stern, S. Alan; Weaver, Harold A.; Olkin, Catherine B.; Ennico, Kimberly; Collins, Geoffrey; New Horizons Science Team

    2016-10-01

    Pluto's Bladed Terrain (centered roughly 20°N, 225°E) covers the flanks and crests of the informally named Tartarus Dorsa with numerous roughly aligned blade-like ridges oriented ~North-South; it may also stretch considerably farther east onto the non-close approach hemisphere but that inference is tentative. Individual ridges are typically several hundred meters high, and are spaced 5 to 10 km crest to crest, separated by V-shaped valleys. Many ridges merge at acute angles to form Y-shape junctions in plan view. The principle composition of the blades themselves we suspect is methane or a methane-rich mixture. (Methane is spectroscopically strongly observed on the optical surfaces of blades.) Nitrogen ice is very probably too soft to support their topography. Cemented mixtures of volatile and non-volatile ices may also provide a degradable but relief supporting "bedrock" for the blades, perhaps analogous to Callisto. Currently we are considering several hypotheses for the origins of the deposit from which Bladed Terrain has evolved, including aeolian disposition, atmospheric condensation, updoming and exhumation, volcanic intrusions or extrusions, crystal growth, among others. We are reviewing several processes as candidate creators or sculptors of the blades. Perhaps they are primary depositional patterns such as dunes, or differential condensation patterns (like on Callisto), or fissure extrusions. Or alternatively perhaps they are the consequence of differential erosion (such as sublimation erosion widening and deepening along cracks), variations in substrate properties, mass wasting into the subsurface, or sculpted by a combination of directional winds and solar isolation orientation. We will consider the roles of the long-term increasing solar flux and short periods of warm thick atmospheres. Hypotheses will be ordered based on observational constrains and modeling to be presented at the conference.

  16. Phosphotyrosine phosphatase R3 receptors: Origin, evolution and structural diversification.

    PubMed

    Chicote, Javier U; DeSalle, Rob; García-España, Antonio

    2017-01-01

    Subtype R3 phosphotyrosine phosphatase receptors (R3 RPTPs) are single-spanning membrane proteins characterized by a unique modular composition of extracellular fibronectin repeats and a single cytoplasmatic protein tyrosine phosphatase (PTP) domain. Vertebrate R3 RPTPs consist of five members: PTPRB, PTPRJ, PTPRH and PTPRO, which dephosphorylate tyrosine residues, and PTPRQ, which dephosphorylates phophoinositides. R3 RPTPs are considered novel therapeutic targets in several pathologies such as ear diseases, nephrotic syndromes and cancer. R3 RPTP vertebrate receptors, as well as their known invertebrate counterparts from animal models: PTP52F, PTP10D and PTP4e from the fruitfly Drosophila melanogaster and F44G4.8/DEP-1 from the nematode Caenorhabditis elegans, participate in the regulation of cellular activities including cell growth and differentiation. Despite sharing structural and functional properties, the evolutionary relationships between vertebrate and invertebrate R3 RPTPs are not fully understood. Here we gathered R3 RPTPs from organisms covering a broad evolutionary distance, annotated their structure and analyzed their phylogenetic relationships. We show that R3 RPTPs (i) have probably originated in the common ancestor of animals (metazoans), (ii) are variants of a single ancestral gene in protostomes (arthropods, annelids and nematodes); (iii) a likely duplication of this ancestral gene in invertebrate deuterostomes (echinodermes, hemichordates and tunicates) generated the precursors of PTPRQ and PTPRB genes, and (iv) R3 RPTP groups are monophyletic in vertebrates and have specific conserved structural characteristics. These findings could have implications for the interpretation of past studies and provide a framework for future studies and functional analysis of this important family of proteins.

  17. Phosphotyrosine phosphatase R3 receptors: Origin, evolution and structural diversification

    PubMed Central

    Chicote, Javier U.; DeSalle, Rob; García-España, Antonio

    2017-01-01

    Subtype R3 phosphotyrosine phosphatase receptors (R3 RPTPs) are single-spanning membrane proteins characterized by a unique modular composition of extracellular fibronectin repeats and a single cytoplasmatic protein tyrosine phosphatase (PTP) domain. Vertebrate R3 RPTPs consist of five members: PTPRB, PTPRJ, PTPRH and PTPRO, which dephosphorylate tyrosine residues, and PTPRQ, which dephosphorylates phophoinositides. R3 RPTPs are considered novel therapeutic targets in several pathologies such as ear diseases, nephrotic syndromes and cancer. R3 RPTP vertebrate receptors, as well as their known invertebrate counterparts from animal models: PTP52F, PTP10D and PTP4e from the fruitfly Drosophila melanogaster and F44G4.8/DEP-1 from the nematode Caenorhabditis elegans, participate in the regulation of cellular activities including cell growth and differentiation. Despite sharing structural and functional properties, the evolutionary relationships between vertebrate and invertebrate R3 RPTPs are not fully understood. Here we gathered R3 RPTPs from organisms covering a broad evolutionary distance, annotated their structure and analyzed their phylogenetic relationships. We show that R3 RPTPs (i) have probably originated in the common ancestor of animals (metazoans), (ii) are variants of a single ancestral gene in protostomes (arthropods, annelids and nematodes); (iii) a likely duplication of this ancestral gene in invertebrate deuterostomes (echinodermes, hemichordates and tunicates) generated the precursors of PTPRQ and PTPRB genes, and (iv) R3 RPTP groups are monophyletic in vertebrates and have specific conserved structural characteristics. These findings could have implications for the interpretation of past studies and provide a framework for future studies and functional analysis of this important family of proteins. PMID:28257417

  18. Science as a (TRANSITORY?) Phase in Human Evolution

    NASA Astrophysics Data System (ADS)

    Leibowitz, Elia

    One of the key elements of human knowledge in the last 150 years is the recognition that the universe, as well as each of its components, are in a permanent stage of evolution. Mankind and human affairs are of course no exceptions. Human beings owe their biological supremacy to the possession of a form of inheritance quite unlike that of other animals: exogenetic heredity. They have a non genetic channel for transmitting information from one generation to another, namely, the entire apparatus of culture. As information is correlated with brain structure, culture is a non genetic means to create patterns in human brains. It therefore plays a major role in human evolution. This apparatus by itself is however also undergoing a process of evolution. Using examples of astronomical, cosmological and other cultural concepts and argumentations, I shall show that throughout recorded human history, 4 distinct phases can be recognized in the evolution of this non genetic apparatus. The latest phase, the beginning of which is symbolized by the life and work of Galileo, is the "scientific" era. At the turn of the millenium, humankind is possibly at a transition state, from the "scientific" towards a new phase that may be termed a "public relation" or "propaganda" era. Causes for this transition can be found among recent developments in mass media and communications. These, in turn, are correlated with modern, 20th century trends in economy, technology and sociology that are other dominants factors in this transition. The apparent decline of the "scientific" culture may have profound consequences on the future evolution of mankind.

  19. Complexation and phase evolution at dimethylformamide-Ag(111) interfaces

    DOE PAGES

    Song, Wentao; Leung, Kevin; Shao, Qian; ...

    2016-09-15

    The interaction of solvent molecules with metallic surfaces impacts many interfacial chemical processes. We investigate the chemical and structure evolution that follows adsorption of the polar solvent dimethylformamide (DMF) on Ag(111). An Ag(DMF)2 coordination complex forms spontaneously by DMF etching of Ag(111), yielding mixed films of the complexes and DMF. Utilizing ultrahigh vacuum scanning tunneling microscopy (UHV-STM), in combination with X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) computations, we map monolayer phases from the 2-D gas regime, consisting of a binary mixture of DMF and Ag(DMF)2, through the saturation monolayer limit, in which these two chemical species phasemore » separate into ordered islands. Structural models for the near-square DMF phase and the chain-like Ag(DMF)2 phase are presented and supported by DFT computation. Interface evolution is summarized in a surface pressure-composition phase diagram, which allows structure prediction over arbitrary experimental conditions. In conclusion, this work reveals new surface coordination chemistry for an important electrolyte-electrode system, and illustrates how surface pressure can be used to tune monolayer phases.« less

  20. Mathematical Methods for the Analysis of Polycrystal Phase Evolutions

    NASA Astrophysics Data System (ADS)

    Zlokazov, V. B.; Bobrikov, I. A.; Balagurov, A. M.

    2016-02-01

    Two methods for an automatic analysis of the temporal evolution of a multiphase polycrystalline sample are described: The Upeak method, analyzing the spectra formally, i.e., carrying the peak search in them, and so describing the evolution in terms of spectral peaks, or having made additionally the autoindexing of the found peaks, preparing the crystallographic information for the Rietveld analysis. The Rietveld method, using an already available crystallographic information about the phase reflections, and describing the unit cell and atomic characteristics of each phase, and the mutual phase contributions to the total intensity for each item of the analyzed sequence of neutron scattering spectra. The paper describes difficulties of an automatic analysis securing the convergence of a non-linear and at the same time non-stationary fitting. The evolution of the polycrystalline compound CuFe2O4 with the temperature T in the range from 300 to 500 degrees Celsius illustrates the performance of the methods.

  1. Genome increase as a clock for the origin and evolution of life

    PubMed Central

    Sharov, Alexei A

    2006-01-01

    Background The size of non-redundant functional genome can be an indicator of biological complexity of living organisms. Several positive feedback mechanisms including gene cooperation and duplication with subsequent specialization may result in the exponential growth of biological complexity in macro-evolution. Results I propose a hypothesis that biological complexity increased exponentially during evolution. Regression of the logarithm of functional non-redundant genome size versus time of origin in major groups of organisms showed a 7.8-fold increase per 1 billion years, and hence the increase of complexity can be viewed as a clock of macro-evolution. A strong version of the exponential hypothesis is that the rate of complexity increase in early (pre-prokaryotic) evolution of life was at most the same (or even slower) than observed in the evolution of prokaryotes and eukaryotes. Conclusion The increase of functional non-redundant genome size in macro-evolution was consistent with the exponential hypothesis. If the strong exponential hypothesis is true, then the origin of life should be dated 10 billion years ago. Thus, the possibility of panspermia as a source of life on earth should be discussed on equal basis with alternative hypotheses of de-novo life origin. Panspermia may be proven if bacteria similar to terrestrial ones are found on other planets or satellites in the solar system. Reviewers This article was reviewed by Eugene V. Koonin, Chris Adami and Arcady Mushegian. PMID:16768805

  2. Origin and Evolution of Limestone Caves of Chhattisgarh and Orissa, India: Role of Geomorphic, Tectonic and Hydrological Processes

    NASA Astrophysics Data System (ADS)

    Gautam, P. K.; Allu, N. C.; Ramesh, R.; Yadava, M. G.; Panigrahi, C. P.

    2014-12-01

    Carbonate rocks undergo karstic process and karst morphology is a key to understand the nature and genesis of caves. The primary energy source for the formation of karst landforms is hydrological cycle. Geomorphic features along with hydrological characteristics provide important information not only on karst formation but also climate and environmental conditions. In this paper, we present the tectonic and geomorphic features that played a role in evolution of caves located in Chhattisgarh and Orissa States of India. The geomorphic and tectonic aspects of Kotumsar, Kailash, and Gupteshwar caves are discussed in relation to the origin and evolution of these caves. Caves are located near the water falls. The area is folded and faulted along the Eastern Ghat Mobile Belt (EGMB) due to tectonic reactivation. Shaly-limestone beds exhibit vertical dipping near Gupteshwar cave, and steeply inclined near Kotumsar and Kailash caves. Indrāvati and Sabari/Kolab tributaries of the Godavari River drain the area. The landscape evolution and the origin of caves in the region is a multistage process, where the lithology, orogeny, fluvial action, and monsoon are the main agents, which is similar to the four state model (Ford and Ewers, 1978). The river basin evolution and regional tectonism also caused the initiation of karstification in the region. The evolution of caves is believed to have taken place in Pre-Pliocene under more humid conditions that coincided with the initiation of monsoon in India. Further, during the Quaternary wet-dry/cold-warm phases altered physical and chemical weathering of limestone rocks. Contrasting relief features of Bastar plateau have also helped the extensive cave formation in the region. The dissolution along weak planes initiated the openings of caves, further enlarged by geomorphic agents. Both monsoon and tectonics have caused fluctuations in water levels along river courses, which acted as active agents in evolution of caves.

  3. Independent origins and rapid evolution of the placenta in the fish genus Poeciliopsis.

    PubMed

    Reznick, David N; Mateos, Mariana; Springer, Mark S

    2002-11-01

    The evolution of complex organs is a source of controversy because they require the contributions of many adaptations to function properly. We argue that placentas are complex, that they have evolved multiple times in Poeciliopsis, and that there are closely related sister taxa that have either no placentas or intermediate stages in the evolution of a placenta. Furthermore, placentas can evolve in 750,000 years or less, on the same time scale as suggested by theoretical calculations for the evolution of complex eyes. Independent origins of such complexity, accompanied by sister taxa that either lack or have intermediate stages in the evolution of the trait, present an opportunity to study the evolution of novelty and complexity from a comparative, evolutionary perspective.

  4. Orbital Evolution of Mass-transferring Eccentric Binary Systems. I. Phase-dependent Evolution

    NASA Astrophysics Data System (ADS)

    Dosopoulou, Fani; Kalogera, Vicky

    2016-07-01

    Observations reveal that mass-transferring binary systems may have non-zero orbital eccentricities. The time evolution of the orbital semimajor axis and eccentricity of mass-transferring eccentric binary systems is an important part of binary evolution theory and has been widely studied. However, various different approaches to and assumptions on the subject have made the literature difficult to comprehend and comparisons between different orbital element time evolution equations not easy to make. Consequently, no self-consistent treatment of this phase has ever been included in binary population synthesis codes. In this paper, we present a general formalism to derive the time evolution equations of the binary orbital elements, treating mass loss and mass transfer as perturbations of the general two-body problem. We present the self-consistent form of the perturbing acceleration and phase-dependent time evolution equations for the orbital elements under different mass loss/transfer processes. First, we study the cases of isotropic and anisotropic wind mass loss. Then, we proceed with non-isotropic ejection and accretion in a conservative as well as a non-conservative manner for both point masses and extended bodies. We compare the derived equations with similar work in the literature and explain the existing discrepancies.

  5. 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

  6. The 1st Symposium on Chemical Evolution and the Origin and Evolution of Life

    NASA Technical Reports Server (NTRS)

    Devincenzi, D. L. (Editor); Pleasant, L. G. (Editor)

    1982-01-01

    This symposium provided an opportunity for all NASA Exobiology principal investigators to present their most recent research in a scientific meeting forum. Papers were presented in the following exobiology areas: extraterrestrial chemistry primitive earth, information transfer, solar system exploration, planetary protection, geological record, and early biological evolution.

  7. A phylogenomic data-driven exploration of viral origins and evolution

    PubMed Central

    Nasir, Arshan; Caetano-Anollés, Gustavo

    2015-01-01

    The origin of viruses remains mysterious because of their diverse and patchy molecular and functional makeup. Although numerous hypotheses have attempted to explain viral origins, none is backed by substantive data. We take full advantage of the wealth of available protein structural and functional data to explore the evolution of the proteomic makeup of thousands of cells and viruses. Despite the extremely reduced nature of viral proteomes, we established an ancient origin of the “viral supergroup” and the existence of widespread episodes of horizontal transfer of genetic information. Viruses harboring different replicon types and infecting distantly related hosts shared many metabolic and informational protein structural domains of ancient origin that were also widespread in cellular proteomes. Phylogenomic analysis uncovered a universal tree of life and revealed that modern viruses reduced from multiple ancient cells that harbored segmented RNA genomes and coexisted with the ancestors of modern cells. The model for the origin and evolution of viruses and cells is backed by strong genomic and structural evidence and can be reconciled with existing models of viral evolution if one considers viruses to have originated from ancient cells and not from modern counterparts. PMID:26601271

  8. Origin and evolution of metabolic sub-cellular compartmentalization in eukaryotes.

    PubMed

    Gabaldón, Toni; Pittis, Alexandros A

    2015-12-01

    A high level of subcellular compartmentalization is a hallmark of eukaryotic cells. This intricate internal organization was present already in the common ancestor of all extant eukaryotes, and the determination of the origins and early evolution of the different organelles remains largely elusive. Organellar proteomes are determined through regulated pathways that target proteins produced in the cytosol to their final subcellular destinations. This internal sorting of proteins can vary across different physiological conditions, cell types and lineages. Evolutionary retargeting - the alteration of a subcellular localization of a protein in the course of evolution - has been rampant in eukaryotes and involves any possible combination of organelles. This fact adds another layer of difficulty to the reconstruction of the origins and evolution of organelles. In this review we discuss current themes in relation to the origin and evolution of organellar proteomes. Throughout the text, a special focus is set on the evolution of mitochondrial and peroxisomal proteomes, which are two organelles for which extensive proteomic and evolutionary studies have been performed.

  9. Origin and evolution of metabolic sub-cellular compartmentalization in eukaryotes

    PubMed Central

    Gabaldón, Toni; Pittis, Alexandros A.

    2015-01-01

    A high level of subcellular compartmentalization is a hallmark of eukaryotic cells. This intricate internal organization was present already in the common ancestor of all extant eukaryotes, and the determination of the origins and early evolution of the different organelles remains largely elusive. Organellar proteomes are determined through regulated pathways that target proteins produced in the cytosol to their final subcellular destinations. This internal sorting of proteins can vary across different physiological conditions, cell types and lineages. Evolutionary retargeting – the alteration of a subcellular localization of a protein in the course of evolution – has been rampant in eukaryotes and involves any possible combination of organelles. This fact adds another layer of difficulty to the reconstruction of the origins and evolution of organelles. In this review we discuss current themes in relation to the origin and evolution of organellar proteomes. Throughout the text, a special focus is set on the evolution of mitochondrial and peroxisomal proteomes, which are two organelles for which extensive proteomic and evolutionary studies have been performed. PMID:25869000

  10. First Steps in Eukaryogenesis: Physical Phenomena in the Origin and Evolution of Chromosome Structure

    NASA Astrophysics Data System (ADS)

    Chela-Flores, Julian

    1998-04-01

    Our present understanding of the origin and evolution of chromosomes differs considerably from current understanding of the origin and evolution of the cell itself. Chromosome origins have been less prominent in research, as the emphasis has not shifted so far appreciably from the phenomenon of primeval nucleic acid encapsulation to that of the origin of gene organization, expression, and regulation. In this work we discuss some reasons why preliminary steps in this direction are being taken. We have been led to examine properties that have contributed to raise the ancestral prokaryotic programmes to a level where we can appreciate in eukaryotes a clear departure from earlier themes in the evolution of the cell from the last common ancestor. We shift our point of view from evolution of cell morphology to the point of view of the genes. In particular, we focus attention on possible physical bases for the way transmission of information has evolved in eukaryotes, namely, the inactivation of whole chromosomes. The special case of the inactivation of the X chromosome in mammals is discussed, paying particular attention to the physical process of the spread of X inactivation in monotremes (platypus and echidna). When experimental data is unavailable some theoretical analysis is possible based on the idea that in certain cases collective phenomena in genetics, rather than chemical detail, are better correlates of complex chemical processes.

  11. Chemical evolution and the origin of life: cumulative keyword subject index 1970-1986

    NASA Technical Reports Server (NTRS)

    Roy, A. C.; Powers, J. V.; Rummel, J. D. (Principal Investigator)

    1990-01-01

    This cumulative subject index encompasses the subject indexes of the bibliographies on Chemical Evolution and the Origin of Life that were first published in 1970 and have continued through publication of the 1986 bibliography supplement. Early bibliographies focused on experimental and theoretical material dealing directly with the concepts of chemical evolution and the origin of life, excluding the broader areas of exobiology, biological evolution, and geochemistry. In recent years, these broader subject areas have also been incorporated as they appear in literature searches relating to chemical evolution and the origin of life, although direct attempts have not been made to compile all of the citations in these broad areas. The keyword subject indexes have also undergone an analogous change in scope. Compilers of earlier bibliographies used the most specific term available in producing the subject index. Compilers of recent bibliographies have used a number of broad terms relating to the overall subject content of each citation and specific terms where appropriate. The subject indexes of these 17 bibliographies have, in general, been cumulatively compiled exactly as they originally appeared. However, some changes have been made in an attempt to correct errors, combine terms, and provide more meaningful terms.

  12. Understanding Freedom of Speech in America: The Origin & Evolution of the 1st Amendment.

    ERIC Educational Resources Information Center

    Barnes, Judy

    In this booklet the content and implications of the First Amendment are analyzed. Historical origins of free speech from ancient Greece to England before the discovery of America, free speech in colonial America, and the Bill of Rights and its meaning for free speech are outlined. The evolution of the First Amendment is described, and the…

  13. A Comparison of Manual and Computer Searches of the Chemical Evolution and Origin of Life Literature.

    ERIC Educational Resources Information Center

    Gill, Elizabeth Deas

    Parallel machine and manual literature searches on the subject of chemical evolution and the origin of life were compared on six characteristics: (1) precision, (2) recall, (3) novelty, (4) uniqueness, (5) time cost per citation, and (6) dollar cost per citation. The manual search outperformed the machine on precision, novelty, uniqueness, and…

  14. Complex quantum network geometries: Evolution and phase transitions

    NASA Astrophysics Data System (ADS)

    Bianconi, Ginestra; Rahmede, Christoph; Wu, Zhihao

    2015-08-01

    Networks are topological and geometric structures used to describe systems as different as the Internet, the brain, or the quantum structure of space-time. Here we define complex quantum network geometries, describing the underlying structure of growing simplicial 2-complexes, i.e., simplicial complexes formed by triangles. These networks are geometric networks with energies of the links that grow according to a nonequilibrium dynamics. The evolution in time of the geometric networks is a classical evolution describing a given path of a path integral defining the evolution of quantum network states. The quantum network states are characterized by quantum occupation numbers that can be mapped, respectively, to the nodes, links, and triangles incident to each link of the network. We call the geometric networks describing the evolution of quantum network states the quantum geometric networks. The quantum geometric networks have many properties common to complex networks, including small-world property, high clustering coefficient, high modularity, and scale-free degree distribution. Moreover, they can be distinguished between the Fermi-Dirac network and the Bose-Einstein network obeying, respectively, the Fermi-Dirac and Bose-Einstein statistics. We show that these networks can undergo structural phase transitions where the geometrical properties of the networks change drastically. Finally, we comment on the relation between quantum complex network geometries, spin networks, and triangulations.

  15. [Human origin and evolution. A review of advances in paleoanthropology, comparative genetics, and evolutionary psychology].

    PubMed

    Markov, A V

    2009-01-01

    In his main work, "On the origin of species", Darwin has refrained from discusion of the origin of man; be only mentioned that his theory would "throw light" on this problem. This famous Darwin's phrase turned out to be one of the most succesful scientific predictions. In the present paper some of the most important recent adavnces in paleoanthroplogy, comparative genetics and evolutionary psychology are reviewed. These three disciplines currently contribute most to our knowledge of anthropogenesis. The review demonstrates that Darwin's ideas not only "threw light" on human origin and evolution; they provided a comprehensive framework for a great variety of studies concerning different aspects of anthropogenesis.

  16. Introduction to ‘Origin and evolution of the nervous system’

    PubMed Central

    Strausfeld, Nicholas J.; Hirth, Frank

    2015-01-01

    In 1665, Robert Hooke demonstrated in Micrographia the power of the microscope and comparative observations, one of which revealed similarities between the arthropod and vertebrate eyes. Utilizing comparative observations, Saint-Hilaire in 1822 was the first to propose that the ventral nervous system of arthropods corresponds to the dorsal nervous system of vertebrates. Since then, studies on the origin and evolution of the nervous system have become inseparable from studies about Metazoan origins and the origins of organ systems. The advent of genome sequence data and, in turn, phylogenomics and phylogenetics have refined cladistics and expanded our understanding of Metazoan phylogeny. However, the origin and evolution of the nervous system is still obscure and many questions and problems remain. A recurrent problem is whether and to what extent sequence data provide reliable guidance for comparisons across phyla. Are genetic data congruent with the geological fossil records? How can we reconcile evolved character loss with phylogenomic records? And how informative are genetic data in relation to the specification of nervous system morphologies? These provide some of the background and context for a Royal Society meeting to discuss new data and concepts that might achieve insights into the origin and evolution of brains and nervous systems. PMID:26554035

  17. Phase nucleation and evolution mechanisms in heterogeneous solids

    NASA Astrophysics Data System (ADS)

    Udupa, Anirudh

    Phase nucleation and evolution is a problem of critical importance in many applications. As the length scales are reduced, it becomes increasingly important to consider interfacial and micro-structural effects that can be safely ignored at larger length scales owing to randomness. The theory of phase nucleation has been addressed usually by the classical nucleation theory, which was originally derived for single component fluid systems, after making an assumption of equilibrium. The criterion has not been rigorously derived for solids, which are far from equilibrium due to dissipation by multiple physical drivers. In this thesis, a thermodynamically sound nucleation criterion is derived for systems with multiple interacting physical phenomena and multiple dissipating mechanisms. This is done, using the tools of continuum mechanics, by determining the change in free energy upon the introduction of a new nucleus into the system. The developed theory is demonstrated to be a generalization of the classical nucleation theory (CNT). The developed theory is then applied to the problem of electromigration driven void nucleation, a serious reliability concern for the microelectronics industry. The void grows and eventually severs the line making the chip nonfunctional. There are two classes of theories at present in the electromigration literature to address the problem of void nucleation, the vacancy supersaturation theory and the entropic dissipation theory, both of which are empirical and based on intuition developed from experimental observations. When the developed theory was applied to the problem of electromigration, it was found to be consistent with the vacancy supersaturation theory, but provided the correct energetic quantity, the chemical potential, which has contribution from both the vacancy concentration as well as the hydrostatic stress. An experiment, consisting of electromigration tests on serpentine lines, was developed to validate the developed

  18. Microstructure evolution and densification of alumina in liquid phase sintering

    NASA Astrophysics Data System (ADS)

    Dong, Weimin

    The microstructure evolution and densification of alumina during liquid phase sintering were quantified. Quantification included the evolution of pore-size distribution, the redistribution of liquid phase, the densification kinetics, and the fraction of closed and open pores. The results revealed that the small and large pores were filled simultaneously. This is inconsistent with Shaw's model in which liquid fills preferentially the smaller low-coordination-number pores in order to reach a low-energy configuration. The results also recommended that the pressure build-up of the trapped gases in pores due to the closure of open pores might have a significantly negative contribution to the driving force, and consequently cause the termination of the densification of alumina. To demonstrate whether the trapped gases played an important role in the microstructure evolution and the densification of alumina during liquid phase sintering, the following two experiments have been conducted. First, alumina preforms containing artificial pores were penetrated by glass. The results indicated that the trapped gases in pores had a considerable influence on the pore filling process, and ultimately caused the termination of the densification of the alumina preforms. Second, alumina compacts containing different amount of glass were sintered in vacuum. The alumina compact containing 20 vol. % reached full density during vacuum sintering, indicating that the pressure build-up of the trapped gases in pores was the main factor causing the termination of the densification of alumina in the final stage of liquid phase sintering. The limiting relative densities of compacts were calculated theoretically on the basis of a comprehensive analysis of the variation of the capillary pressure and gas pressure in pores with pore size and pore number. The capillary pressure and gas pressure in alumina compact during liquid phase sintering were analyzed on the basis of the above theoretical models

  19. SPHEREx: Understanding the Origin and Evolution of Galaxies Through the Extragalactic Background Light

    NASA Astrophysics Data System (ADS)

    Zemcov, Michael B.; SPHEREx Science Team

    2016-01-01

    The near IR extragalactic background light (EBL) encodes the integrated light production over cosmic history, so traces the total emission from all galaxies along the line of sight up to ancient first-light objects present during the epoch of reionization (EOR). The EBL can be constrained both through direct photometric measurements and through measurements of anisotropies in the EBL which take advantage of the fact that extragalactic populations produce fluctuations with distinct spatial and spectral characteristics from local foregrounds. Because the amplitude of the linear clustering signal is proportional to the total photon emission, large-scale EBL anisotropies are an important tracer of star formation history. In particular, EBL anisotropies trace the underlying clustering of faint emission sources, such as low mass objects present during the EOR, dwarf galaxies, and intra-halo light (IHL), all of which are components not readily detected in point source surveys. The fluctuation amplitude measured independently by a number of recent experiments exceeds that expected from the large-scale clustering of known galaxy populations, indicating the presence of a large integrated brightness from these faint and diffuse components. SPHEREx, a mission in NASA's Small Explorer (SMEX) program that was selected for Phase A in July 2015, is an all-sky survey satellite designed to address all three science goals in NASA's astrophysics division: to probe the origin and destiny of our Universe; to explore whether planets around other stars could harbor life; and to explore the origin and evolution of galaxies. SPHEREx will produce extremely deep maps of the ~200 square degrees around the celestial poles in lambda/d lambda~40 bins. These will be ideal for EBL anisotropy measurements, either by averaging into broad spectral bands, or as a possible science enhancement option, by performing tomography of cosmic large scale structure using line tracers such as Lya, Ha, Hb, O

  20. Evolution of angiosperm seed disperser mutualisms: the timing of origins and their consequences for coevolutionary interactions between angiosperms and frugivores.

    PubMed

    Eriksson, Ove

    2016-02-01

    The origins of interactions between angiosperms and fruit-eating seed dispersers have attracted much attention following a seminal paper on this topic by Tiffney (1984). This review synthesizes evidence pertaining to key events during the evolution of angiosperm-frugivore interactions and suggests some implications of this evidence for interpretations of angiosperm-frugivore coevolution. The most important conclusions are: (i) the diversification of angiosperm seed size and fleshy fruits commenced around 80 million years ago (Mya). The diversity of seed sizes, fruit sizes and fruit types peaked in the Eocene around 55 to 50 Mya. During this first phase of the interaction, angiosperms and animals evolving frugivory expanded into niche space not previously utilized by these groups, as frugivores and previously not existing fruit traits appeared. From the Eocene until the present, angiosperm-frugivore interactions have occurred within a broad frame of existing niche space, as defined by fruit traits and frugivory, motivating a separation of the angiosperm-frugivore interactions into two phases, before and after the peak in the early Eocene. (ii) The extinct multituberculates were probably the most important frugivores during the early radiation phase of angiosperm seeds and fleshy fruits. Primates and rodents are likely to have been important in the latter part of this first phase. (iii) Flying frugivores, birds and bats, evolved during the second phase, mainly during the Oligocene and Miocene, thus exploiting an existing diversity of fleshy fruits. (iv) A drastic climate shift around the Eocene-Oligocene boundary (around 34 Mya) resulted in more semi-open woodland vegetation, creating patchily occurring food resources for frugivores. This promoted evolution of a 'flying frugivore niche' exploited by birds and bats. In particular, passerines became a dominant frugivore group worldwide. (v) Fleshy fruits evolved at numerous occasions in many angiosperm families

  1. Dynamical Phase Transition in a Model for Evolution with Migration

    NASA Astrophysics Data System (ADS)

    Waclaw, Bartłomiej; Allen, Rosalind J.; Evans, Martin R.

    2010-12-01

    We study a simple quasispecies model for evolution in two different habitats, with different fitness landscapes, coupled through one-way migration. Our key finding is a dynamical phase transition at a critical value of the migration rate, at which the time to reach the steady state diverges. The genetic composition of the population is qualitatively different above and below the transition. Using results from localization theory, we show that the critical migration rate may be very small—demonstrating that evolutionary outcomes can be very sensitive to even a small amount of migration.

  2. Phase coexistence and pressure-temperature phase evolution of VO2(A ) nanorods near the semiconductor-semiconductor transition

    NASA Astrophysics Data System (ADS)

    Samanta, Sudeshna; Li, Quanjun; Cheng, Benyuan; Huang, Yanwei; Pei, Cuiying; Wang, Qinglin; Ma, Yanzhang; Wang, Lin

    2017-01-01

    A comprehensive understanding of the physical origins of the phase transition behaviors of transition metal oxides is still complex due to the interplay among competing interactions of comparable strengths tuning their nature. Widespread interest in such phase transitions has motivated explorations of nanocrystalline vanadium dioxide (VO2) in various forms and a long-running debate persists over the roles played by electron-electron correlation with lattice distortion. External stimuli like pressure and temperature have strong effects on the appearance, stability, and spacial distribution of the high-resistive (HR) and low-resistive (LR) phases accompanying their structural modification. Our comprehensive experiments establish the pressure-induced and thermally driven evolution of phase coexistence in VO2(A ) nanorods. Our experimental evidence supports coexisting HR and LR phases, where compression suppressed coexistence at ˜7 GPa, followed by a semiconductor-semiconductor transition at around ˜10 GPa with the absence of pressure-induced metallization. X-ray diffraction revealed lattice distortion with local microscopic strain inhomogeneity in the nanorods, without any discontinuity in the pressure-volume data. We further investigated the vibrational modes and relaxations of the samples related to their thermal expansions. We also found that the pressure-dependent hierarchy of microstructural densification contributed significantly to the resulting transport properties.

  3. Phase-space evolution of x-ray coherence in phase-sensitive imaging.

    PubMed

    Wu, Xizeng; Liu, Hong

    2008-08-01

    X-ray coherence evolution in the imaging process plays a key role for x-ray phase-sensitive imaging. In this work we present a phase-space formulation for the phase-sensitive imaging. The theory is reformulated in terms of the cross-spectral density and associated Wigner distribution. The phase-space formulation enables an explicit and quantitative account of partial coherence effects on phase-sensitive imaging. The presented formulas for x-ray spectral density at the detector can be used for performing accurate phase retrieval and optimizing the phase-contrast visibility. The concept of phase-space shearing length derived from this phase-space formulation clarifies the spatial coherence requirement for phase-sensitive imaging with incoherent sources. The theory has been applied to x-ray Talbot interferometric imaging as well. The peak coherence condition derived reveals new insights into three-grating-based Talbot-interferometric imaging and gratings-based x-ray dark-field imaging.

  4. Exploration of the origin and evolution of globular proteins by mRNA display.

    PubMed

    Yanagawa, Hiroshi

    2013-06-04

    The questions of how proteins first appeared on the primitive earth and how they evolved into functional proteins are fundamental. If we can understand the origins and evolution of proteins, we should be able to create novel functional proteins. Evolutionary protein engineering or directed protein evolution has been used to create artificial proteins with novel functions by repeated mutation, selection, and amplification, mimicking Darwinian evolution in the laboratory. For this purpose, display technology, such as mRNA display, to link genotype with phenotype is extremely important. Here I focus on three hypotheses regarding the origin and evolution of proteins. First, Eigen's GNC hypothesis proposes that the early genetic code began from the directionless codons GNC and GNN, where N denotes U, C, A, or G. Second, Ohno's gene duplication theory proposes that gene duplication produces two functionally redundant, paralogous genes, of which one retains the original function, leaving the second free to evolve adaptively. Third, Gilbert's exon shuffling theory proposes that new genes are formed through shuffling of small segments corresponding to exons. I then review various experimental approaches to evolutionary protein engineering using mRNA display, such as the creation of functional proteins from random sequences with limited sets of amino acids, randomly mutated folded proteins, and block-shuffled sequence proteins, and I discuss the results in relation to these three hypotheses.

  5. The Evolution of Stellar Rotation and the Origin of Be Stars

    NASA Astrophysics Data System (ADS)

    Katsuta, Yutaka; Okazaki, Atsuo T.; Fujimoto, Masayuki Y.

    2013-06-01

    The evolution of rotation rate of stars is caused by the structural changes in the stellar interior as well as by the gain and loss of angular momentum through mass loss and accretion. The stellar rotation rate is determined by the stellar moment of inertia for a given angular momentum. The variation in the internal moment of inertia due to expansion and/or contraction of shells may produce differential rotation in the interior. From the study of hydrodynamical stability, however, it is predicted that instabilities prevail in differentially rotating stars and resultant turbulent viscosity may effectively eliminate the differential rotation to bring the stellar interior into more or less uniform rotation. Under the uniform rotation, the internal distribution of angular momentum is determined solely by that of moment of inertia. In this paper, we analyze the evolutionary characteristics of stellar moment of inertia, in particular, focusing on the variation with the surface radius and discuss the influence on the evolution of stellar rotation and the relevance to the origin of Be stars. As stars evolvefrom main sequence, their central region contracts, whereas the outer parts expand first due to the difference in the mean molecular weight produced by the central nuclear burning, and then, due to the entropy difference produced by shell burning. The stellar moment of inertia, I, also augments with the surface radius R, and yet, the increase rate of I with R differs according to the evolutionary stages because of changes in the characteristic of stellar structure; the increase of I is slower than R^{1.5} during the early stage of expansion while it is accelerated to be greater than the latter in the later stage of expansion due to shell burning. Accordingly, the ratio of stellar rotation rate to the surface critical rotation rate augments during the early phase, while it turns to decrease during the shell burning phase. Consequently, the stellar rotation rate may reach

  6. Structure evolution and phase transition in odd-mass nuclei

    NASA Astrophysics Data System (ADS)

    Bucurescu, D.; Zamfir, N. V.

    2017-01-01

    The evolution of level structures due to the unique parity orbitals g9 /2, h11 /2, and i13 /2 in odd-mass nuclei from Zn to Am is studied within a unified framework, by correlations between ratios of excitation energies in both odd-mass nuclei and their even-even core nuclei. These plots reveal regularities that can be understood in terms of the particle-plus-rotor model, as evolutions along its three limiting coupling schemes: weak coupling, decoupling, and strong coupling, and transitions between them. Peculiar transitions between the decoupling and strong coupling schemes are found in both i13 /2 structures of neutron-odd nuclei and h11 /2 structures of proton-odd nuclei, at neutron numbers around 90 and 70, respectively. These are correlated with the critical shape phase transitions from vibrator to rotor from the even-even nuclei in the same regions and are characterized as critical phase transitions too. This behavior is corroborated with a nonmonotonic behavior of the differential variation of the two-neutron separation energies in the same nuclear regions.

  7. Morphology and crystal phase evolution of GeO 2 in liquid phase deposition process

    NASA Astrophysics Data System (ADS)

    Jing, Chengbin; Sun, Wei; Wang, Wei; Li, Yi; Chu, Junhao

    2012-01-01

    Morphology and crystal phase evolution of GeO 2 in liquid phase deposition (LPD) process is investigated. Rod-like solid phases precipitate out of solution ahead of truncated cube-like phases. SEM, XRD and TEM analyses reveal that the two sorts of solid phases are tetragonal GeO 2 and hexagonal GeO 2, respectively. The tetragonal GeO 2 phases start to experience a re-dissolving process as soon as the hexagonal phases come into being. The prior precipitation of the rod-like phase arises from a relatively low solute saturation of tetragonal GeO 2. Fast growth of a tetragonal GeO 2 phase along [111] direction leads to development of a rod-like shape. The re-dissolving phenomenon does not agree with the classic growth kinetics of crystals but is strongly favored by our calculations based on thermodynamics. The GeO 2 solutes are released in a fluctuant way by germanate ions, which promotes the occurrence of the re-dissolution phenomenon. The current researches open a door for room-temperature LPD growth of not only the hexagonal GeO 2 particles and film but also the one-dimensional tetragonal GeO 2 product.

  8. Oxygen and animal evolution: did a rise of atmospheric oxygen "trigger" the origin of animals?

    PubMed

    Mills, Daniel B; Canfield, Donald E

    2014-12-01

    Recent studies challenge the classical view that the origin of animal life was primarily controlled by atmospheric oxygen levels. For example, some modern sponges, representing early-branching animals, can live under 200 times less oxygen than currently present in the atmosphere - levels commonly thought to have been maintained prior to their origination. Furthermore, it is increasingly argued that the earliest animals, which likely lived in low oxygen environments, played an active role in constructing the well-oxygenated conditions typical of the modern oceans. Therefore, while oxygen is still relevant to understanding early animal evolution, the relationships between the two might be less straightforward than previously thought.

  9. Interhemispheric interaction and beliefs on our origin: degree of handedness predicts beliefs in creationism versus evolution.

    PubMed

    Niebauer, Christopher Lee; Christman, Stephen D; Reid, Scott A; Garvey, Kilian J

    2004-10-01

    It has been suggested that strongly handed individuals have attenuated systems for updating beliefs compared to mixed handers (Niebauer, Aselage, & Schutte, 2002). The current research extended this theory to individual differences in updating beliefs concerning our origins. Although the theory of evolution has gained overwhelming success in the sciences, a significant percentage of the population believes in biblical creationist accounts of human origins that are inconsistent with accepted, contemporary scientific views. If strongly handed individuals possess attenuated systems for updating beliefs, they might be more likely to believe in creationism. In two studies, strongly handed participants were more likely to believe in creationism while mixed-handed participants were more likely to believe in evolution. A model of how interhemispheric interaction functions in maintaining and updating beliefs is discussed. Specifically, mixed-handedness seems to be associated with a lower threshold for updating beliefs.

  10. The Lingula genome provides insights into brachiopod evolution and the origin of phosphate biomineralization

    PubMed Central

    Luo, Yi-Jyun; Takeuchi, Takeshi; Koyanagi, Ryo; Yamada, Lixy; Kanda, Miyuki; Khalturina, Mariia; Fujie, Manabu; Yamasaki, Shin-ichi; Endo, Kazuyoshi; Satoh, Noriyuki

    2015-01-01

    The evolutionary origins of lingulid brachiopods and their calcium phosphate shells have been obscure. Here we decode the 425-Mb genome of Lingula anatina to gain insights into brachiopod evolution. Comprehensive phylogenomic analyses place Lingula close to molluscs, but distant from annelids. The Lingula gene number has increased to ∼34,000 by extensive expansion of gene families. Although Lingula and vertebrates have superficially similar hard tissue components, our genomic, transcriptomic and proteomic analyses show that Lingula lacks genes involved in bone formation, indicating an independent origin of their phosphate biominerals. Several genes involved in Lingula shell formation are shared by molluscs. However, Lingula has independently undergone domain combinations to produce shell matrix collagens with EGF domains and carries lineage-specific shell matrix proteins. Gene family expansion, domain shuffling and co-option of genes appear to be the genomic background of Lingula's unique biomineralization. This Lingula genome provides resources for further studies of lophotrochozoan evolution. PMID:26383154

  11. Evolution of social learning does not explain the origin of human cumulative culture.

    PubMed

    Enquist, Magnus; Ghirlanda, Stefano

    2007-05-07

    Because culture requires transmission of information between individuals, thinking about the origin of culture has mainly focused on the genetic evolution of abilities for social learning. Current theory considers how social learning affects the adaptiveness of a single cultural trait, yet human culture consists of the accumulation of very many traits. Here we introduce a new modeling strategy that tracks the adaptive value of many cultural traits, showing that genetic evolution favors only limited social learning owing to the accumulation of maladaptive as well as adaptive culture. We further show that culture can be adaptive, and refined social learning can evolve, if individuals can identify and discard maladaptive culture. This suggests that the evolution of such "adaptive filtering" mechanisms may have been crucial for the birth of human culture.

  12. The origin and evolution of the sexes: Novel insights from a distant eukaryotic linage.

    PubMed

    Mignerot, Laure; Coelho, Susana M

    2016-01-01

    Sexual reproduction is an extraordinarily widespread phenomenon that assures the production of new genetic combinations in nearly all eukaryotic lineages. Although the core features of sexual reproduction (meiosis and syngamy) are highly conserved, the control mechanisms that determine whether an individual is male or female are remarkably labile across eukaryotes. In genetically controlled sexual systems, gender is determined by sex chromosomes, which have emerged independently and repeatedly during evolution. Sex chromosomes have been studied in only a handful of classical model organism, and empirical knowledge on the origin and evolution of the sexes is still surprisingly incomplete. With the advent of new generation sequencing, the taxonomic breadth of model systems has been rapidly expanding, bringing new ideas and fresh views on this fundamental aspect of biology. This mini-review provides a quick state of the art of how the remarkable richness of the sexual characteristics of the brown algae is helping to increase our knowledge about the evolution of sex determination.

  13. Origin and Evolution of a Chimeric Fusion Gene in Drosophila subobscura, D. madeirensis and D. guanche

    PubMed Central

    Jones, Corbin D.; Custer, Andrew W.; Begun, David J.

    2005-01-01

    An understanding of the mutational and evolutionary mechanisms underlying the emergence of novel genes is critical to studies of phenotypic and genomic evolution. Here we describe a new example of a recently formed chimeric fusion gene that occurs in Drosophila guanche, D. madeirensis, and D. subobscura. This new gene, which we name Adh-Twain, resulted from an Adh mRNA that retrotransposed into the Gapdh-like gene, CG9010. Adh-Twain is transcribed; its 5′ promoters and transcription patterns appear similar to those of CG9010. Population genetic and phylogenetic analyses suggest that the amino acid sequence of Adh-Twain evolved rapidly via directional selection shortly after it arose. Its more recent history, however, is characterized by slower evolution consistent with increasing functional constraints. We present a model for the origin of this new gene and discuss genetic and evolutionary factors affecting the evolution of new genes and functions. PMID:15781692

  14. The case for planetary sample return missions - Origin and evolution of the moon and its environment

    SciTech Connect

    Ryder, G.; Spudis, P.D.; Taylor, G.J. USGS, Flagstaff, AZ New Mexico Univ., Albuquerque )

    1989-11-01

    The most important questions concerning the origin and evolution of the moon and its environment are reviewed, and the ways that studying lunar samples could help answer them, are discussed. Recommendations are made about methods for obtaining samples and the best lunar sites for obtaining them using simple, unmanned sample returners. Lunar geologic field sites that require intensive field work with human interaction are also considered. 16 refs.

  15. Transition to the radiative phase in supernova remnant evolution

    NASA Astrophysics Data System (ADS)

    Wright, Eric Boyd

    1999-11-01

    The evolution of a supernova remnant (SNR) through the transition from an adiabatic Sedov-Taylor blastwave to a radiative pressure-driven snowplow phase is studied through a series of one-, two- and three-dimensional hydrodynamic (HD) and magnetohydrodynamic (MHD) simulations. This transition is marked by a catastrophic collapse of the postshock gas, forming a thin, dense shell behind the forward shock. Previous studies have shown that the thin, dense shell of gas present during this transition is susceptible to both radiative and dynamical instabilities. One-dimensional HD studies indicate the presence of a radial oscillation between the forward shock and the thin shell, due to the rapid cooling of the gas in the immediate postshock region. Two-dynamical HD simulations of this transition indicate the presence of violent dynamical instabilities that alter the initially spherical morphology of the blastwave, specifically, the Pressure-driven Thin Shell Overstability (PDTSO) and the Non-linear Thin Shell Instability (NTSI). Hydrodynamical simulations, by their very nature, ignore the effects of magnetic forces on moving fluids. In general, interstellar magnetic fields will be weak enough that their effects may be safely ignored. However, the transition to the radiative phase in SNR evolution is often triggered when the blastwave interacts with dense clouds of gas in the interstellar medium (ISM). The resulting compression of the gas during the transition also compresses the magnetic fields in the cloud, possibly enhancing the field sufficiently to play a role in the further evolution of the SNR. To better understand the role of the NTSI during the transition, and to study the effects of magnetic fields on the instability itself, we performed idealized two- and three-dimensional MHD simulations. The results of the two-dimensional simulations were found to depend strongly on the orientation of the ambient magnetic field when the postshock field is dynamically

  16. 3R phase of MoS2 and WS2 outperforms the corresponding 2H phase for hydrogen evolution.

    PubMed

    Toh, Rou Jun; Sofer, Zdeněk; Luxa, Jan; Sedmidubský, David; Pumera, Martin

    2017-03-09

    Herein, we compare the bulk, 2H and 3R phases of two most prevalent TMD materials: MoS2 and WS2. The 3R phase outperforms its 2H phase counterpart in hydrogen evolution reaction catalysis and is even comparable with the exfoliated, 1T phase in the case of MoS2.

  17. Origin and Evolution of Eukaryotic Large Nucleo-Cytoplasmic DNA Viruses

    PubMed Central

    Koonin, Eugene V.; Yutin, Natalya

    2010-01-01

    Background/Aims The nucleo-cytoplasmic large DNA viruses (NCLDV) constitute an apparently monophyletic group that consists of 6 families of viruses infecting a broad variety of eukaryotes. A comprehensive genome comparison and maximum-likelihood reconstruction of NCLDV evolution reveal a set of approximately 50 conserved genes that can be tentatively mapped to the genome of the common ancestor of this class of eukaryotic viruses. We address the origins and evolution of NCLDV. Results Phylogenetic analysis indicates that some of the major clades of NCLDV infect diverse animals and protists, suggestive of early radiation of the NCLDV, possibly concomitant with eukaryogenesis. The core NCLDV genes seem to have originated from different sources including homologous genes of bacteriophages, bacteria and eukaryotes. These observations are compatible with a scenario of the origin of the NCLDV at an early stage of the evolution of eukaryotes through extensive mixing of genes from widely different genomes. Conclusions The common ancestor of the NCLDV probably evolved from a bacteriophage as a result of recruitment of numerous eukaryotic and some bacterial genes, and concomitant loss of the majority of phage genes except for a small core of genes coding for proteins essential for virus genome replication and virion formation. PMID:20551680

  18. Origin and dynamical evolution of Neptune Trojans - II. Long-term evolution

    NASA Astrophysics Data System (ADS)

    Lykawka, P. S.; Horner, J.; Jones, B. W.; Mukai, T.

    2011-03-01

    Following our earlier work studying the formation of the Neptunian Trojan population during the planet's migration, we present results examining the eventual fate of the Trojan clouds produced in that work. A large number of Trojans were followed under the gravitational influence of the giant planets for a period of at least 1 Gyr. We find that the stability of Neptunian Trojans seems to be strongly correlated to their initial post-migration orbital elements, with those objects that survive as Trojans for billions of years, displaying negligible orbital evolution. The great majority of these survivors began the integrations with small eccentricities (e < 0.2) and small libration amplitudes (A < 30°-40°). The survival rate of 'pre-formed' Neptunian Trojans [which in general survived on dynamically cold orbits (e < 0.1, i < 5°-10°)] varied between ˜5 and 70 per cent, depending on the precise detail of their initial orbits. In contrast, the survival rate of 'captured' Trojans (on final orbits spread across a larger region of the e-i element space) was markedly lower, ranging between 1-10 per cent after 4 Gyr. Taken in concert with our earlier work and the broad i-distribution of the observed Trojan population, we note that planetary formation scenarios, which involve the slow migration (a few tens of millions of years) of Neptune from an initial planetary architecture that is both resonant and compact (aN < 18 au), provide the most promising fit of those we considered to the observed Trojan population. In such scenarios, we find that the present-day Trojan population would number ˜1 per cent of that which was present at the end of the planet's migration (i.e. survival rate of ˜1 per cent), with the bulk being sourced from captured, rather than pre-formed objects. We note, however, that even those scenarios still fail to reproduce the presently observed portion of the Neptune Trojan population moving on orbits with e < 0.1 but i > 20°. Dynamical integrations of

  19. Rapid evolution of stability and productivity at the origin of a microbial mutualism

    SciTech Connect

    Hillesland, Kristina L.; Stahl, David A.

    2009-12-01

    Mutualistic interactions are taxonomically and functionally diverse. Despite their ubiquity, the basic ecological and evolutionary processes underlying their origin and maintenance are poorly understood. A major reason for this has been the lack of an experimentally tractable model system. We examine the evolution of an experimentally imposed obligate mutualism between sulfate-reducing and methanogenic microorganisms that have no known history of prior interaction. Twenty-four independent pairings (cocultures) of the bacterium Desulfovibrio vulgaris and the archaeon Methanococcus maripaludis were established and followed for 300 community doublings in two environments, one allowing for the development of a heterogeneous distribution of resources and the other not. Evolved cocultures grew up to 80percent faster and were up to 30percent more productive (biomass yield per mole substrate) than the ancestors. The evolutionary process was marked by periods of significant instability leading to extinction of two of the cocultures, but resulted in more stable, efficient, and productive mutualisms for most replicated pairings. Comparisons of evolved cocultures with those assembled from one evolved and one ancestral mutualist showed that evolution of both species contributed to improved productivity. Surprisingly, however, overall improvements in growth rate and yield were less than the sum of individual contributions, suggesting antagonistic interactions between mutations from the coevolved populations. Physical constraints on the transfer of metabolites in the evolution environment affected the evolution of M. maripaludis but not D. vulgaris. Together, these results show that challenges can imperil nascent obligate mutualisms and demonstrate the evolutionary responses that enable their persistence and future evolution.

  20. Evolution of molecular crystal optical phonons near structural phase transitions

    NASA Astrophysics Data System (ADS)

    Michki, Nigel; Niessen, Katherine; Xu, Mengyang; Markelz, Andrea

    Molecular crystals are increasingly important photonic and electronic materials. For example organic semiconductors are lightweight compared to inorganic semiconductors and have inexpensive scale up processing with roll to roll printing. However their implementation is limited by their environmental sensitivity, in part arising from the weak intermolecular interactions of the crystal. These weak interactions result in optical phonons in the terahertz frequency range. We examine the evolution of intermolecular interactions near structural phase transitions by measuring the optical phonons as a function of temperature and crystal orientation using terahertz time-domain spectroscopy. The measured orientation dependence of the resonances provides an additional constraint for comparison of the observed spectra with the density functional calculations, enabling us to follow specific phonon modes. We observe crystal reorganization near 350 K for oxalic acid as it transforms from dihydrate to anhydrous form. We also report the first THz spectra for the molecular crystal fructose through its melting point.

  1. Co-option and dissociation in larval origins and evolution: the sea urchin larval gut.

    PubMed

    Love, Alan C; Lee, Abigail E; Andrews, Mary E; Raff, Rudolf A

    2008-01-01

    The origin of marine invertebrate larvae has been an area of controversy in developmental evolution for over a century. Here, we address the question of whether a pelagic "larval" or benthic "adult" morphology originated first in metazoan lineages by testing the hypothesis that particular gene co-option patterns will be associated with the origin of feeding, indirect developing larval forms. Empirical evidence bearing on this hypothesis is derivable from gene expression studies of the sea urchin larval gut of two closely related but differently developing congenerics, Heliocidaris tuberculata (feeding indirect-developing larva) and H. erythrogramma (nonfeeding direct developer), given two subsidiary hypotheses. (1) If larval gut gene expression in H. tuberculata was co-opted from an ancestral adult expression pattern, then the gut expression pattern will remain in adult H. erythrogramma despite its direct development. (2) Genes expressed in the larval gut of H. tuberculata will not have a coordinated expression pattern in H. erythrogramma larvae due to loss of a functional gut. Five structural genes expressed in the invaginating archenteron of H. tuberculata during gastrulation exhibit substantially different expression patterns in H. erythrogramma with only one remaining endoderm specific. Expression of these genes in the adult of H. erythrogramma and larval gut of H. tuberculata, but not in H. erythrogramma larval endoderm, supports the hypothesis that they first played roles in the formation of adult structures and were subsequently recruited into larval ontogeny during the origin and evolution of feeding planktotrophic deuterostome larvae.

  2. Magnetotail and Ionospheric Evolution during the Substorm Growth Phase

    NASA Astrophysics Data System (ADS)

    Hsieh, M.; Otto, A.

    2013-12-01

    The growth phase of geomagnetic substorms is characterized by the equatorward motion of the growth phase arc close to or even into the region of diffuse aurora characteristic for a dipolar magnetic field. The presented results use a model of current sheet thinning based on midnight magnetic flux depletion (MMFD) in the near-Earth tail which is caused by sunward convection to replenish magnetic flux that is eroded on the dayside by magnetic reconnection during periods of southward IMF. The results use a three-dimensional mesocale MHD simulation of the near-Earth tail. This paper examines the changes of the near-Earth magnetotail region mapped into the ionopshere. Of specific interest are the changes in magnetic flux, flux tube entropy, field-aligned currents, convection, and the size and location of the respective ionospheric footprints of the magnetotail structure and properties. The mapping method is based on the Tsyganenko [1996] magnetic field model combined with magnetic flux conservation. It is found that the mapped magnetotail properties move equatorward by about 2 to 3 degrees during the growth phase. The removal of magnetic flux in the near-Earth tail causes a contraction of the ionospheric footprints of this tail region such that all of the mapped magnetotail structures move equatorward. The thin current is mapped into the region where magnetic flux is strongly depleted, and in close proximity with strong and narrow region 1 and 2 sense field-aligned currents. Our ionospheric maps also show a sharp transition between the dipole and stretched magnetic field and an evolution of thinning and convergent motion of field-aligned currents in the late growth phase.

  3. Molecular Origins of Mesoscale Ordering in a Metalloamphiphile Phase

    PubMed Central

    2015-01-01

    Controlling the assembly of soft and deformable molecular aggregates into mesoscale structures is essential for understanding and developing a broad range of processes including rare earth extraction and cleaning of water, as well as for developing materials with unique properties. By combined synchrotron small- and wide-angle X-ray scattering with large-scale atomistic molecular dynamics simulations we analyze here a metalloamphiphile–oil solution that organizes on multiple length scales. The molecules associate into aggregates, and aggregates flocculate into meso-ordered phases. Our study demonstrates that dipolar interactions, centered on the amphiphile headgroup, bridge ionic aggregate cores and drive aggregate flocculation. By identifying specific intermolecular interactions that drive mesoscale ordering in solution, we bridge two different length scales that are classically addressed separately. Our results highlight the importance of individual intermolecular interactions in driving mesoscale ordering. PMID:27163014

  4. Evolving Ideas on the Origin and Evolution of Flowers: New Perspectives in the Genomic Era

    PubMed Central

    Chanderbali, Andre S.; Berger, Brent A.; Howarth, Dianella G.; Soltis, Pamela S.; Soltis, Douglas E.

    2016-01-01

    The origin of the flower was a key innovation in the history of complex organisms, dramatically altering Earth’s biota. Advances in phylogenetics, developmental genetics, and genomics during the past 25 years have substantially advanced our understanding of the evolution of flowers, yet crucial aspects of floral evolution remain, such as the series of genetic and morphological changes that gave rise to the first flowers; the factors enabling the origin of the pentamerous eudicot flower, which characterizes ∼70% of all extant angiosperm species; and the role of gene and genome duplications in facilitating floral innovations. A key early concept was the ABC model of floral organ specification, developed by Elliott Meyerowitz and Enrico Coen and based on two model systems, Arabidopsis thaliana and Antirrhinum majus. Yet it is now clear that these model systems are highly derived species, whose molecular genetic-developmental organization must be very different from that of ancestral, as well as early, angiosperms. In this article, we will discuss how new research approaches are illuminating the early events in floral evolution and the prospects for further progress. In particular, advancing the next generation of research in floral evolution will require the development of one or more functional model systems from among the basal angiosperms and basal eudicots. More broadly, we urge the development of “model clades” for genomic and evolutionary-developmental analyses, instead of the primary use of single “model organisms.” We predict that new evolutionary models will soon emerge as genetic/genomic models, providing unprecedented new insights into floral evolution. PMID:27053123

  5. Evolving Ideas on the Origin and Evolution of Flowers: New Perspectives in the Genomic Era.

    PubMed

    Chanderbali, Andre S; Berger, Brent A; Howarth, Dianella G; Soltis, Pamela S; Soltis, Douglas E

    2016-04-01

    The origin of the flower was a key innovation in the history of complex organisms, dramatically altering Earth's biota. Advances in phylogenetics, developmental genetics, and genomics during the past 25 years have substantially advanced our understanding of the evolution of flowers, yet crucial aspects of floral evolution remain, such as the series of genetic and morphological changes that gave rise to the first flowers; the factors enabling the origin of the pentamerous eudicot flower, which characterizes ∼70% of all extant angiosperm species; and the role of gene and genome duplications in facilitating floral innovations. A key early concept was the ABC model of floral organ specification, developed by Elliott Meyerowitz and Enrico Coen and based on two model systems,Arabidopsis thalianaandAntirrhinum majus Yet it is now clear that these model systems are highly derived species, whose molecular genetic-developmental organization must be very different from that of ancestral, as well as early, angiosperms. In this article, we will discuss how new research approaches are illuminating the early events in floral evolution and the prospects for further progress. In particular, advancing the next generation of research in floral evolution will require the development of one or more functional model systems from among the basal angiosperms and basal eudicots. More broadly, we urge the development of "model clades" for genomic and evolutionary-developmental analyses, instead of the primary use of single "model organisms." We predict that new evolutionary models will soon emerge as genetic/genomic models, providing unprecedented new insights into floral evolution.

  6. A hypothesis on the biological origins and social evolution of music and dance

    PubMed Central

    Wang, Tianyan

    2015-01-01

    The origins of music and musical emotions is still an enigma, here I propose a comprehensive hypothesis on the origins and evolution of music, dance, and speech from a biological and sociological perspective. I suggest that every pitch interval between neighboring notes in music represents corresponding movement pattern through interpreting the Doppler effect of sound, which not only provides a possible explanation for the transposition invariance of music, but also integrates music and dance into a common form—rhythmic movements. Accordingly, investigating the origins of music poses the question: why do humans appreciate rhythmic movements? I suggest that human appreciation of rhythmic movements and rhythmic events developed from the natural selection of organisms adapting to the internal and external rhythmic environments. The perception and production of, as well as synchronization with external and internal rhythms are so vital for an organism's survival and reproduction, that animals have a rhythm-related reward and emotion (RRRE) system. The RRRE system enables the appreciation of rhythmic movements and events, and is integral to the origination of music, dance and speech. The first type of rewards and emotions (rhythm-related rewards and emotions, RRREs) are evoked by music and dance, and have biological and social functions, which in turn, promote the evolution of music, dance and speech. These functions also evoke a second type of rewards and emotions, which I name society-related rewards and emotions (SRREs). The neural circuits of RRREs and SRREs develop in species formation and personal growth, with congenital and acquired characteristics, respectively, namely music is the combination of nature and culture. This hypothesis provides probable selection pressures and outlines the evolution of music, dance, and speech. The links between the Doppler effect and the RRREs and SRREs can be empirically tested, making the current hypothesis scientifically

  7. A hypothesis on the biological origins and social evolution of music and dance.

    PubMed

    Wang, Tianyan

    2015-01-01

    The origins of music and musical emotions is still an enigma, here I propose a comprehensive hypothesis on the origins and evolution of music, dance, and speech from a biological and sociological perspective. I suggest that every pitch interval between neighboring notes in music represents corresponding movement pattern through interpreting the Doppler effect of sound, which not only provides a possible explanation for the transposition invariance of music, but also integrates music and dance into a common form-rhythmic movements. Accordingly, investigating the origins of music poses the question: why do humans appreciate rhythmic movements? I suggest that human appreciation of rhythmic movements and rhythmic events developed from the natural selection of organisms adapting to the internal and external rhythmic environments. The perception and production of, as well as synchronization with external and internal rhythms are so vital for an organism's survival and reproduction, that animals have a rhythm-related reward and emotion (RRRE) system. The RRRE system enables the appreciation of rhythmic movements and events, and is integral to the origination of music, dance and speech. The first type of rewards and emotions (rhythm-related rewards and emotions, RRREs) are evoked by music and dance, and have biological and social functions, which in turn, promote the evolution of music, dance and speech. These functions also evoke a second type of rewards and emotions, which I name society-related rewards and emotions (SRREs). The neural circuits of RRREs and SRREs develop in species formation and personal growth, with congenital and acquired characteristics, respectively, namely music is the combination of nature and culture. This hypothesis provides probable selection pressures and outlines the evolution of music, dance, and speech. The links between the Doppler effect and the RRREs and SRREs can be empirically tested, making the current hypothesis scientifically

  8. Evolution of a phase separated gravity independent bioreactor

    NASA Astrophysics Data System (ADS)

    Villeneuve, Peter E.; Dunlop, Eric H.

    The evolution of a phase-separated gravity-independent bioreactor is described. The initial prototype, a zero head-space manifold silicone membrane based reactor, maintained large diffusional resistances. Obtaining oxygen transfer rates needed to support carbon-recycling aerobic microbes is impossible if large resistances are maintained. Next generation designs (Mark I and II) mimic heat exchanger design to promote turbulence at the tubing-liquid interface, thereby reducing liquid and gas side diffusional resistances. While oxygen transfer rates increased by a factor of ten, liquid channeling prevented further increases. To overcome these problems, a Mark III reactor was developed which maintains inverted phases, i.e., media flows inside the silicone tubing, oxygen gas is applied external to the tubing. This enhances design through changes in gas side driving force concentration and liquid side turbulence levels. Combining an applied external pressure of four atmospheres with increased Reynolds numbers resulted in oxygen transfer intensities of 232 mmol O2/l/h (1000 times greater than first prototype and comparable to a conventional fermenter). A 1.0 liter Mark III reactor can potentially deliver oxygen supplies necessary to support cell cultures needed to recycle a 10 astronaut carbon load continuously.

  9. Texture evolution during nitinol martensite detwinning and phase transformation

    SciTech Connect

    Cai, S.; Schaffer, J. E.; Ren, Y.

    2013-12-09

    Nitinol has been widely used to make medical devices for years due to its unique shape memory and superelastic properties. However, the texture of the nitinol wires has been largely ignored due to inherent complexity. In this study, in situ synchrotron X-ray diffraction has been carried out during uniaxial tensile testing to investigate the texture evolution of the nitinol wires during martensite detwinning, variant reorientation, and phase transformation. It was found that the thermal martensitic nitinol wire comprised primarily an axial (1{sup ¯}20), (120), and (102)-fiber texture. Detwinning initially converted the (120) and (102) fibers to the (1{sup ¯}20) fiber and progressed to a (1{sup ¯}30)-fiber texture by rigid body rotation. At strains above 10%, the (1{sup ¯}30)-fiber was shifted to the (110) fiber by (21{sup ¯}0) deformation twinning. The austenitic wire exhibited an axial (334)-fiber, which transformed to the near-(1{sup ¯}30) martensite texture after the stress-induced phase transformation.

  10. Texture evolution during nitinol martensite detwinning and phase transformation

    NASA Astrophysics Data System (ADS)

    Cai, S.; Schaffer, J. E.; Ren, Y.; Yu, C.

    2013-12-01

    Nitinol has been widely used to make medical devices for years due to its unique shape memory and superelastic properties. However, the texture of the nitinol wires has been largely ignored due to inherent complexity. In this study, in situ synchrotron X-ray diffraction has been carried out during uniaxial tensile testing to investigate the texture evolution of the nitinol wires during martensite detwinning, variant reorientation, and phase transformation. It was found that the thermal martensitic nitinol wire comprised primarily an axial (1¯20), (120), and (102)-fiber texture. Detwinning initially converted the (120) and (102) fibers to the (1¯20) fiber and progressed to a (1¯30)-fiber texture by rigid body rotation. At strains above 10%, the (1¯30)-fiber was shifted to the (110) fiber by (21¯0) deformation twinning. The austenitic wire exhibited an axial (334)-fiber, which transformed to the near-(1¯30) martensite texture after the stress-induced phase transformation.

  11. Evolution of a phase separated gravity independent bioreactor

    NASA Technical Reports Server (NTRS)

    Villeneuve, Peter E.; Dunlop, Eric H.

    1992-01-01

    The evolution of a phase-separated gravity-independent bioreactor is described. The initial prototype, a zero head-space manifold silicone membrane based reactor, maintained large diffusional resistances. Obtaining oxygen transfer rates needed to support carbon-recycling aerobic microbes is impossible if large resistances are maintained. Next generation designs (Mark I and II) mimic heat exchanger design to promote turbulence at the tubing-liquid interface, thereby reducing liquid and gas side diffusional resistances. While oxygen transfer rates increased by a factor of ten, liquid channeling prevented further increases. To overcome these problems, a Mark III reactor was developed which maintains inverted phases, i.e., media flows inside the silicone tubing, oxygen gas is applied external to the tubing. This enhances design through changes in gas side driving force concentration and liquid side turbulence levels. Combining an applied external pressure of 4 atm with increased Reynolds numbers resulted in oxygen transfer intensities of 232 mmol O2/l per hr (1000 times greater than the first prototype and comparable to a conventional fermenter). A 1.0 liter Mark III reactor can potentially deliver oxygen supplies necessary to support cell cultures needed to recycle a 10-astronaut carbon load continuously.

  12. Phase transitions in the evolution of gene regulatory networks

    NASA Astrophysics Data System (ADS)

    Skanata, Antun; Kussell, Edo

    The role of gene regulatory networks is to respond to environmental conditions and optimize growth of the cell. A typical example is found in bacteria, where metabolic genes are activated in response to nutrient availability, and are subsequently turned off to conserve energy when their specific substrates are depleted. However, in fluctuating environmental conditions, regulatory networks could experience strong evolutionary pressures not only to turn the right genes on and off, but also to respond optimally under a wide spectrum of fluctuation timescales. The outcome of evolution is predicted by the long-term growth rate, which differentiates between optimal strategies. Here we present an analytic computation of the long-term growth rate in randomly fluctuating environments, by using mean-field and higher order expansion in the environmental history. We find that optimal strategies correspond to distinct regions in the phase space of fluctuations, separated by first and second order phase transitions. The statistics of environmental randomness are shown to dictate the possible evolutionary modes, which either change the structure of the regulatory network abruptly, or gradually modify and tune the interactions between its components.

  13. Origin and evolution of metal P-type ATPases in Plantae (Archaeplastida)

    PubMed Central

    Hanikenne, Marc; Baurain, Denis

    2013-01-01

    Metal ATPases are a subfamily of P-type ATPases involved in the transport of metal cations across biological membranes. They all share an architecture featuring eight transmembrane domains in pairs of two and are found in prokaryotes as well as in a variety of Eukaryotes. In Arabidopsis thaliana, eight metal P-type ATPases have been described, four being specific to copper transport and four displaying a broader metal specificity, including zinc, cadmium, and possibly copper and calcium. So far, few efforts have been devoted to elucidating the origin and evolution of these proteins in Eukaryotes. In this work, we use large-scale phylogenetics to show that metal P-type ATPases form a homogenous group among P-type ATPases and that their specialization into either monovalent (Cu) or divalent (Zn, Cd…) metal transport stems from a gene duplication that took place early in the evolution of Life. Then, we demonstrate that the four subgroups of plant metal ATPases all have a different evolutionary origin and a specific taxonomic distribution, only one tracing back to the cyanobacterial progenitor of the chloroplast. Finally, we examine the subsequent evolution of these proteins in green plants and conclude that the genes thoroughly characterized in model organisms are often the result of lineage-specific gene duplications, which calls for caution when attempting to infer function from sequence similarity alone in non-model organisms. PMID:24575101

  14. Origin of the hungry caterpillar: Evolution of fasting in slug moths (Insecta: Lepidoptera: Limacodidae).

    PubMed

    Zaspel, J M; Weller, S J; Epstein, M E

    2016-01-01

    Studies of caterpillar defense strategy evolution typically focus on aposematic coloration, gregarious behavior, and/or chemical defense. In the slug moth family Limacodidae, the evolution of chemical defense is coupled to the life history trait of first instar feeding behaviors. In nettle caterpillars, the first instars fast and molt into a second instar that feeds. In contrast, gelatines and monkey slug larval forms feed in the first instar. This study focused on whether the evolution of fasting associated with the nettle morphology was a derived trait of single or multiple origins. Twenty-nine species of Limacodidae (including one Chrysopolominae) representing 27 genera and four outgroup species with known first and final instar morphologies and behaviors were included. Four out-group species representing Megalopygidae (1 sp), Dalceridae (1 sp) and Aididae (2 sp) were included. These were sequenced for three molecular markers for a total of 4073 bp, mitochondrial COI (∼1500 bp), 18S (∼1900 bp) and the D2 region of 28S (approximately 670 bp). Maximum likelihood and Bayesian analyses were conducted. The resulting phylogeny and comparative analysis of feeding strategy revealed that the nettle caterpillar morphology and behavior of larval fasting may have a single origin.

  15. Origin and evolution of the Notch signalling pathway: an overview from eukaryotic genomes

    PubMed Central

    Gazave, Eve; Lapébie, Pascal; Richards, Gemma S; Brunet, Frédéric; Ereskovsky, Alexander V; Degnan, Bernard M; Borchiellini, Carole; Vervoort, Michel; Renard, Emmanuelle

    2009-01-01

    Background Of the 20 or so signal transduction pathways that orchestrate cell-cell interactions in metazoans, seven are involved during development. One of these is the Notch signalling pathway which regulates cellular identity, proliferation, differentiation and apoptosis via the developmental processes of lateral inhibition and boundary induction. In light of this essential role played in metazoan development, we surveyed a wide range of eukaryotic genomes to determine the origin and evolution of the components and auxiliary factors that compose and modulate this pathway. Results We searched for 22 components of the Notch pathway in 35 different species that represent 8 major clades of eukaryotes, performed phylogenetic analyses and compared the domain compositions of the two fundamental molecules: the receptor Notch and its ligands Delta/Jagged. We confirm that a Notch pathway, with true receptors and ligands is specific to the Metazoa. This study also sheds light on the deep ancestry of a number of genes involved in this pathway, while other members are revealed to have a more recent origin. The origin of several components can be accounted for by the shuffling of pre-existing protein domains, or via lateral gene transfer. In addition, certain domains have appeared de novo more recently, and can be considered metazoan synapomorphies. Conclusion The Notch signalling pathway emerged in Metazoa via a diversity of molecular mechanisms, incorporating both novel and ancient protein domains during eukaryote evolution. Thus, a functional Notch signalling pathway was probably present in Urmetazoa. PMID:19825158

  16. 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.

  17. Constructive Approaches for Understanding the Origin of Self-Replication and Evolution

    PubMed Central

    Ichihashi, Norikazu; Yomo, Tetsuya

    2016-01-01

    The mystery of the origin of life can be divided into two parts. The first part is the origin of biomolecules: under what physicochemical conditions did biomolecules such as amino acids, nucleotides, and their polymers arise? The second part of the mystery is the origin of life-specific functions such as the replication of genetic information, the reproduction of cellular structures, metabolism, and evolution. These functions require the coordination of many different kinds of biological molecules. A direct strategy to approach the second part of the mystery is the constructive approach, in which life-specific functions are recreated in a test tube from specific biological molecules. Using this approach, we are able to employ design principles to reproduce life-specific functions, and the knowledge gained through the reproduction process provides clues as to their origins. In this mini-review, we introduce recent insights gained using this approach, and propose important future directions for advancing our understanding of the origins of life. PMID:27420098

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

    PubMed

    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.

  19. Abrupt deceleration of molecular evolution linked to the origin of arborescence in ferns.

    PubMed

    Korall, Petra; Schuettpelz, Eric; Pryer, Kathleen M

    2010-09-01

    Molecular rate heterogeneity, whereby rates of molecular evolution vary among groups of organisms, is a well-documented phenomenon. Nonetheless, its causes are poorly understood. For animals, generation time is frequently cited because longer-lived species tend to have slower rates of molecular evolution than their shorter-lived counterparts. Although a similar pattern has been uncovered in flowering plants, using proxies such as growth form, the underlying process has remained elusive. Here, we find a deceleration of molecular evolutionary rate to be coupled with the origin of arborescence in ferns. Phylogenetic branch lengths within the “tree fern” clade are considerably shorter than those of closely related lineages, and our analyses demonstrate that this is due to a significant difference in molecular evolutionary rate. Reconstructions reveal that an abrupt rate deceleration coincided with the evolution of the long-lived tree-like habit at the base of the tree fern clade. This suggests that a generation time effect may well be ubiquitous across the green tree of life, and that the search for a responsible mechanism must focus on characteristics shared by all vascular plants. Discriminating among the possibilities will require contributions from various biological disciplines,but will be necessary for a full appreciation of molecular evolution.

  20. Human development x: Explanation of macroevolution--top-down evolution materializes consciousness. The origin of metamorphosis.

    PubMed

    Hermansen, Tyge Dahl; Ventegodt, Søren; Merrick, Joav

    2006-12-15

    In this paper, we first give a short discussion of the macroevolution viewing life as information-directed, complex, dynamic systems. On this basis, we give our explanation of the origin of life and discuss the top-down evolution of molecules, proteins, and macroevolution. We discuss these subjects according to our new holistic biological paradigm. In view of this, we discuss the macroevolution of the organism, the species, the biosphere, and human society. After this, we discuss the shift in evolution from natural selection to a new proposed process of nature called the "metamorphous top-down" evolution. We discuss the capability of the evolutionary shift to govern some of the processes that lead to the formation of new species. We discuss the mechanisms we think are behind this proposed shift in evolution and conclude that this event is able to explain the huge biological diversity of nature in combination with evolutionary natural selection. We also discuss this event of nature as an isolated, but integrated, part of the universe. We propose the most important genetic and biochemical process that we think is behind the evolutionary shift as a complicated symbiosis of mechanisms leading to metamorphosis in all biological individuals, from bacteria to humans. The energetic superorbital that manifests the consciousness governs all these processes through quantum chemical activity. This is the key to evolutionary shift through the consciousness, and we propose to call this process "adult human metamorphosis".

  1. Origin and evolution of transporter substrate specificity within the NPF family

    PubMed Central

    Jørgensen, Morten Egevang; Xu, Deyang; Crocoll, Christoph; Ramírez, David; Motawia, Mohammed Saddik; Olsen, Carl Erik; Nour-Eldin, Hussam Hassan; Halkier, Barbara Ann

    2017-01-01

    Despite vast diversity in metabolites and the matching substrate specificity of their transporters, little is known about how evolution of transporter substrate specificities is linked to emergence of substrates via evolution of biosynthetic pathways. Transporter specificity towards the recently evolved glucosinolates characteristic of Brassicales is shown to evolve prior to emergence of glucosinolate biosynthesis. Furthermore, we show that glucosinolate transporters belonging to the ubiquitous NRT1/PTR FAMILY (NPF) likely evolved from transporters of the ancestral cyanogenic glucosides found across more than 2500 species outside of the Brassicales. Biochemical characterization of orthologs along the phylogenetic lineage from cassava to A. thaliana, suggests that alterations in the electrogenicity of the transporters accompanied changes in substrate specificity. Linking the evolutionary path of transporter substrate specificities to that of the biosynthetic pathways, exemplify how transporter substrate specificities originate and evolve as new biosynthesis pathways emerge. DOI: http://dx.doi.org/10.7554/eLife.19466.001 PMID:28257001

  2. Origin and evolution of transporter substrate specificity within the NPF family.

    PubMed

    Jørgensen, Morten Egevang; Xu, Deyang; Crocoll, Christoph; Ramírez, David; Motawia, Mohammed Saddik; Olsen, Carl Erik; Nour-Eldin, Hussam Hassan; Halkier, Barbara Ann

    2017-03-03

    Despite vast diversity in metabolites and the matching substrate specificity of their transporters, little is known about how evolution of transporter substrate specificities is linked to emergence of substrates via evolution of biosynthetic pathways. Transporter specificity towards the recently evolved glucosinolates characteristic of Brassicales is shown to evolve prior to emergence of glucosinolate biosynthesis. Furthermore, we show that glucosinolate transporters belonging to the ubiquitous NRT1/PTR FAMILY (NPF) likely evolved from transporters of the ancestral cyanogenic glucosides found across more than 2500 species outside of the Brassicales. Biochemical characterization of orthologs along the phylogenetic lineage from cassava to A. thaliana, suggests that alterations in the electrogenicity of the transporters accompanied changes in substrate specificity. Linking the evolutionary path of transporter substrate specificities to that of the biosynthetic pathways, exemplify how transporter substrate specificities originate and evolve as new biosynthesis pathways emerge.

  3. Evolution and the eye: the Darwin bicentennial and the sesquicentennial of the origin of species.

    PubMed

    Fishman, Ronald S

    2008-11-01

    Evolution is an essential concept for anyone who considers science to be the best way to understand the natural world. It is as fully established as any scientific principle can be and is the great unifying theme in all of biology, as integral to understanding life-forms as gravity is to understanding the cosmos. On the bicentennial of the birth of Charles Darwin in 1809, and 150 years after the publication of On the Origin of Species by Means of Natural Selection in 1859, we should remember the main features of eye evolution and the prominent place the eye holds in the development and refinement of evolutionary theory. A few highlights include the antiquity of rhodopsin, the ready capacity of an eye to evolve, the effect of eyes on the diversification of life-forms, and the promising influence of genetics on developmental and evolutionary biology.

  4. The origin and early evolution of whales: macroevolution documented on the Indian subcontinent.

    PubMed

    Bajpai, S; Thewissen, J G M; Sahni, A

    2009-11-01

    The origin of whales (order Cetacea) from a four-footed land animal is one of the best understood examples of macroevolutionary change. This evolutionary transition has been substantially elucidated by fossil finds from the Indian subcontinent in the past decade and a half. Here, we review the first steps of whale evolution, i.e. the transition from a land mammal to obligate marine predators, documented by the Eocene cetacean families of the Indian subcontinent: Pakicetidae, Ambulocetidae, Remingtonocetidae, Protocetidae, and Basilosauridae, as well as their artiodactyl sister group, the Raoellidae. We also discuss the influence that the excellent fossil record has on the study of the evolution of organ systems, in particular the locomotor and hearing systems.

  5. The Origin and Evolution of Halo Bias in Linear and Nonlinear Regimes

    NASA Astrophysics Data System (ADS)

    Kravtsov, Andrey V.; Klypin, Anatoly A.

    1999-08-01

    attribute the strong antibias observed in the halo correlation function and power spectrum to these effects. The results of this study show that despite the apparent complexity, the origin and evolution of bias can be understood in terms of the processes that drive the formation and evolution of dark matter halos. These processes conspire to produce a halo distribution quite different from the overall distribution of matter, yet remarkably similar to the observed distribution of galaxies.

  6. 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.

  7. Speculations on the origin and evolution of the Utopia-Elysium lowlands of Mars

    NASA Technical Reports Server (NTRS)

    Frey, Herbert V.; Schultz, Richard A.

    1990-01-01

    This paper proposes a qualitative model for the origin of the Utopia-Elysium northern lowlands on eastern Mars in terms of the long-term evolution of two large overlapping impact basins. The model, which is consistent with both the observed geologic constraints and more quantitative results obtained by numerical modeling of smaller (Orientale-size) impact basins, is shown to qualitatively account for the major topographic variation seen in the Utopia-Elysium region, including the overall 'lowness' of the area and localized depressions.

  8. New Insights Into the Origin and Evolution of the Hikurangi Oceanic Plateau

    NASA Astrophysics Data System (ADS)

    Hoernle, Kaj; Hauff, Folkmar; Werner, Reinhard; Mortimer, Nicholas

    2004-10-01

    Oceanic plateaus and continental flood basalts, collectively referred to as large igneous provinces (LIPs), represent the most voluminous volcanic events on Earth. In contrast to continental LIPs, relatively little is known about the surface and internal structure, range in age and chemical composition, origin, and evolution of oceanic plateaus, which occur throughout the world's oceans. One of the major goals of the R/V Sonne SO168 ZEALANDIA expedition (deport Wellington, 3 December 2002, return Christchurch, 15 January 2003) was to investigate the Hikurangi oceanic plateau off the east coast of New Zealand.

  9. [The evolution of the origin and connotation of the word Ma Zhui ("anesthesia")].

    PubMed

    Li, Chun-yu; Guo, Bin; Jia, Jin-tai

    2009-09-01

    It has been a long time since people recognized the word "Ma Zhui (anesthesia)" which was also recorded in the medical literature of past generations, for example: anesthesia powder, the magic prescription of toad powder of Huatuo, magic sleeping powder, 'knock-out' drops etc. In 1846, etherization was applied in clinic successfully, since then modern anesthesiology has had a process of more than 150 years during which the concept of the word "anesthesia" changed constantly. Reviewing the evolution of the origin and the concept of the word "anesthesia" can be of benefit to recognize and understand the concept and nature of "anesthesia" to improve clinical anesthesia.

  10. Supernovae from yellow, blue supergiants: origin and consequences for stellar evolution

    NASA Astrophysics Data System (ADS)

    Meynet, Georges; Georgy, Cyril; Saio, Hideyuki; Kudritzki, Rolf-Peter; Groh, Jose

    2015-08-01

    A few core collapse supernovae progenitors have been found to be yellow or blue supergiants. We shall discuss possible scenarios involving single and close binary evolution allowing to explain this kind of core collapse supernova progenitors. According to stellar models for both single and close binaries, blue supergiants, at the end of their nuclear lifetimes and thus progenitors of core collapse supernovae, present very different characteristics for what concerns their surface compositions, rotational surface velocities and pulsational properties with respect to blue supergiants in their core helium burning phase. We discuss how the small observed scatter of the flux-weighted gravity-luminosity (FWGL) relation of blue supergiants constrains the evolution of massive stars after the Main-Sequence phase and the nature of the progenitors of supernovae in the mass range between 12 and 40 solar masses. The present day observed surface abundances of blue supergiants, of their pulsational properties, as well as the small scatter of the FWGL relation provide strong constraints on both internal mixing and mass loss in massive stars and therefore on the end point of their evolution.

  11. The analysis of translation-related gene set boosts debates around origin and evolution of mimiviruses

    PubMed Central

    Colson, Philippe; La Scola, Bernard

    2017-01-01

    The giant mimiviruses challenged the well-established concept of viruses, blurring the roots of the tree of life, mainly due to their genetic content. Along with other nucleo-cytoplasmic large DNA viruses, they compose a new proposed order—named Megavirales—whose origin and evolution generate heated debate in the scientific community. The presence of an arsenal of genes not widespread in the virosphere related to important steps of the translational process, including transfer RNAs, aminoacyl-tRNA synthetases, and translation factors for peptide synthesis, constitutes an important element of this debate. In this review, we highlight the main findings to date about the translational machinery of the mimiviruses and compare their distribution along the distinct members of the family Mimiviridae. Furthermore, we discuss how the presence and/or absence of the translation-related genes among mimiviruses raises important insights to boost the debate on their origin and evolutionary history. PMID:28207761

  12. The cytochrome P450 genesis locus: the origin and evolution of animal cytochrome P450s

    PubMed Central

    Nelson, David R.; Goldstone, Jared V.; Stegeman, John J.

    2013-01-01

    The neighbourhoods of cytochrome P450 (CYP) genes in deuterostome genomes, as well as those of the cnidarians Nematostella vectensis and Acropora digitifera and the placozoan Trichoplax adhaerens were examined to find clues concerning the evolution of CYP genes in animals. CYP genes created by the 2R whole genome duplications in chordates have been identified. Both microsynteny and macrosynteny were used to identify genes that coexisted near CYP genes in the animal ancestor. We show that all 11 CYP clans began in a common gene environment. The evidence implies the existence of a single locus, which we term the ‘cytochrome P450 genesis locus’, where one progenitor CYP gene duplicated to create a tandem set of genes that were precursors of the 11 animal CYP clans: CYP Clans 2, 3, 4, 7, 19, 20, 26, 46, 51, 74 and mitochondrial. These early CYP genes existed side by side before the origin of cnidarians, possibly with a few additional genes interspersed. The Hox gene cluster, WNT genes, an NK gene cluster and at least one ARF gene were close neighbours to this original CYP locus. According to this evolutionary scenario, the CYP74 clan originated from animals and not from land plants nor from a common ancestor of plants and animals. The CYP7 and CYP19 families that are chordate-specific belong to CYP clans that seem to have originated in the CYP genesis locus as well, even though this requires many gene losses to explain their current distribution. The approach to uncovering the CYP genesis locus overcomes confounding effects because of gene conversion, sequence divergence, gene birth and death, and opens the way to understanding the biodiversity of CYP genes, families and subfamilies, which in animals has been obscured by more than 600 Myr of evolution. PMID:23297357

  13. Reconstructing the Origin of Oxygenic Photosynthesis: Do Assembly and Photoactivation Recapitulate Evolution?

    PubMed Central

    Cardona, Tanai

    2016-01-01

    Due to the great abundance of genomes and protein structures that today span a broad diversity of organisms, now more than ever before, it is possible to reconstruct the molecular evolution of protein complexes at an incredible level of detail. Here, I recount the story of oxygenic photosynthesis or how an ancestral reaction center was transformed into a sophisticated photochemical machine capable of water oxidation. First, I review the evolution of all reaction center proteins in order to highlight that Photosystem II and Photosystem I, today only found in the phylum Cyanobacteria, branched out very early in the history of photosynthesis. Therefore, it is very unlikely that they were acquired via horizontal gene transfer from any of the described phyla of anoxygenic phototrophic bacteria. Second, I present a new evolutionary scenario for the origin of the CP43 and CP47 antenna of Photosystem II. I suggest that the antenna proteins originated from the remodeling of an entire Type I reaction center protein and not from the partial gene duplication of a Type I reaction center gene. Third, I highlight how Photosystem II and Photosystem I reaction center proteins interact with small peripheral subunits in remarkably similar patterns and hypothesize that some of this complexity may be traced back to the most ancestral reaction center. Fourth, I outline the sequence of events that led to the origin of the Mn4CaO5 cluster and show that the most ancestral Type II reaction center had some of the basic structural components that would become essential in the coordination of the water-oxidizing complex. Finally, I collect all these ideas, starting at the origin of the first reaction center proteins and ending with the emergence of the water-oxidizing cluster, to hypothesize that the complex and well-organized process of assembly and photoactivation of Photosystem II recapitulate evolutionary transitions in the path to oxygenic photosynthesis. PMID:26973693

  14. Origins Space Telescope: Galaxy and Black Hole Evolution over Cosmic Time

    NASA Astrophysics Data System (ADS)

    Pope, Alexandra; Origins Space Telescope Study Team

    2017-01-01

    The Origins Space Telescope (OST) is the mission concept for the Far-Infrared Surveyor, a study in development by NASA in preparation for the 2020 Astronomy and Astrophysics Decadal Survey. Origins is planned to be a large aperture, actively-cooled telescope covering a wide span of the mid- to far-infrared spectrum. Its imagers and spectrographs will enable a variety of surveys of the sky that will discover and characterize the most distant galaxies, Milky-Way, exoplanets, and the outer reaches of our Solar system. Origins will enable flagship-quality general observing programs led by the astronomical community in the 2030s. The Science and Technology Definition Team (STDT) would like to hear your science needs and ideas for this mission. The team can be contacted at firsurveyor_info@lists.ipac.caltech.edu. This presentation will provide a summary of the science case related to galaxy formation and evolution. Origins will investigate the connection between black hole growth and star formation, understand the role of feedback from supernovae and active galactic nuclei, probe the multiphase interstellar medium, and chart the rise of metals over cosmic time.

  15. The Role of Transposable Elements in the Origin and Evolution of MicroRNAs in Human

    PubMed Central

    Qin, Sheng; Jin, Ping; Zhou, Xue; Chen, Liming; Ma, Fei

    2015-01-01

    MicroRNAs (miRNAs) are crucial regulators of gene expression at the post-transcriptional level in eukaryotes via targeting gene 3'-untranslated regions. Transposable elements (TEs) are considered as natural origins of some miRNAs. However, what miRNAs are and how these miRNAs originate and evolve from TEs remain unclear. We identified 409 TE-derived miRNAs (386 overlapped with TEs and 23 un-overlapped with TEs) which are derived from TEs in human. This indicates that the TEs play important roles in origin of miRNAs in human. In addition, we found that the proportions of miRNAs derived from TEs (MDTEs) in human are more than other vertebrates especially non-mammal vertebrates. Furthermore, we classified MDTEs into three types and found that TE head or tail sequences along with adjacent genomic sequences contribute to generation of human miRNAs. Our current study will improve the understanding of origin and evolution of human miRNAs. PMID:26115450

  16. Restriction and Recruitment—Gene Duplication and the Origin and Evolution of Snake Venom Toxins

    PubMed Central

    Hargreaves, Adam D.; Swain, Martin T.; Hegarty, Matthew J.; Logan, Darren W.; Mulley, John F.

    2014-01-01

    Snake venom has been hypothesized to have originated and diversified through a process that involves duplication of genes encoding body proteins with subsequent recruitment of the copy to the venom gland, where natural selection acts to develop or increase toxicity. However, gene duplication is known to be a rare event in vertebrate genomes, and the recruitment of duplicated genes to a novel expression domain (neofunctionalization) is an even rarer process that requires the evolution of novel combinations of transcription factor binding sites in upstream regulatory regions. Therefore, although this hypothesis concerning the evolution of snake venom is very unlikely and should be regarded with caution, it is nonetheless often assumed to be established fact, hindering research into the true origins of snake venom toxins. To critically evaluate this hypothesis, we have generated transcriptomic data for body tissues and salivary and venom glands from five species of venomous and nonvenomous reptiles. Our comparative transcriptomic analysis of these data reveals that snake venom does not evolve through the hypothesized process of duplication and recruitment of genes encoding body proteins. Indeed, our results show that many proposed venom toxins are in fact expressed in a wide variety of body tissues, including the salivary gland of nonvenomous reptiles and that these genes have therefore been restricted to the venom gland following duplication, not recruited. Thus, snake venom evolves through the duplication and subfunctionalization of genes encoding existing salivary proteins. These results highlight the danger of the elegant and intuitive “just-so story” in evolutionary biology. PMID:25079342

  17. Restriction and recruitment-gene duplication and the origin and evolution of snake venom toxins.

    PubMed

    Hargreaves, Adam D; Swain, Martin T; Hegarty, Matthew J; Logan, Darren W; Mulley, John F

    2014-08-01

    Snake venom has been hypothesized to have originated and diversified through a process that involves duplication of genes encoding body proteins with subsequent recruitment of the copy to the venom gland, where natural selection acts to develop or increase toxicity. However, gene duplication is known to be a rare event in vertebrate genomes, and the recruitment of duplicated genes to a novel expression domain (neofunctionalization) is an even rarer process that requires the evolution of novel combinations of transcription factor binding sites in upstream regulatory regions. Therefore, although this hypothesis concerning the evolution of snake venom is very unlikely and should be regarded with caution, it is nonetheless often assumed to be established fact, hindering research into the true origins of snake venom toxins. To critically evaluate this hypothesis, we have generated transcriptomic data for body tissues and salivary and venom glands from five species of venomous and nonvenomous reptiles. Our comparative transcriptomic analysis of these data reveals that snake venom does not evolve through the hypothesized process of duplication and recruitment of genes encoding body proteins. Indeed, our results show that many proposed venom toxins are in fact expressed in a wide variety of body tissues, including the salivary gland of nonvenomous reptiles and that these genes have therefore been restricted to the venom gland following duplication, not recruited. Thus, snake venom evolves through the duplication and subfunctionalization of genes encoding existing salivary proteins. These results highlight the danger of the elegant and intuitive "just-so story" in evolutionary biology.

  18. The Origin and Evolution of Interstellar Dust in the Local and High-Redshift Universe

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2011-01-01

    In this talk I will begin by reviewing our current state of knowledge regarding the origin and evolution of dust in the local solar neighborhood. Using chemical evolution models, I will discuss their many different input parameters and their uncertainties. An important consequence of these models is the delayed injection of dust from AGB stars, compared to supernova-condensed dust, into the interstellar medium. I will show that these stellar evolutionary effects on dust composition are manifested in the infrared spectra of local galaxies. The delayed production of dust in AGB stars has also important consequences for the origin of the large amount of dust detected in high-redshift galaxies, when the universe was less that - 1 Gyr old. Supernovae may have been the only viable dust sources in those galaxies. Recent observations of SN1987a show a significant mass of dust in the ejecta of this SN. Is that production rate high enough to account for the observed dust mass in these galaxies? If not, what are the alternative viable sources of dust, and how do they depend on the nature of the galaxy (starburst or AGN) and its star formation history.

  19. The Origin and Evolution of Interstellar Dust in the Local and High-redshift Universe

    NASA Technical Reports Server (NTRS)

    Dwek, Eliahu

    2012-01-01

    In this talk I will begin by reviewing our current state of knowledge regarding the origin and evolution of dust in the local solar neighborhood. using chemical evolution models, I will discuss their many different input parameters and their uncertainties. An important consequence of these models is the delayed injection of dust from AGB stars, compared to supernova-condensed dust, into the interstellar medium. I will show that these stellar evolutionary effects on dust composition are manifested in the infrared spectra of local galaxies. The delayed production of dust in AGB stars has also important consequences for the origin of the large amount of dust detected in high-redshift galaxies, when the universe was less that approx. 1 Gyr old. Supernovae may have been the only viable dust sources in those galaxies. Recent observations of sN1987a show a significant mass of dust in the ejecta of this SN. Is that production rate high enough to account for the observed dust mass in these galaxies? If not, what are the alternative viable sources of dust, and how do they depend on the nature of the galaxy (starburst or AGN) and its star formation history .

  20. Origin of a major infectious disease in vertebrates: The timing of Cryptosporidium evolution and its hosts.

    PubMed

    Garcia-R, Juan C; Hayman, David T S

    2016-11-01

    Protozoan parasites of the genus Cryptosporidium infect all vertebrate groups and display some host specificity in their infections. It is therefore possible to assume that Cryptosporidium parasites evolved intimately aside with vertebrate lineages. Here we propose a scenario of Cryptosporidium-Vertebrata coevolution testing the hypothesis that the origin of Cryptosporidium parasites follows that of the origin of modern vertebrates. We use calibrated molecular clocks and cophylogeny analyses to provide and compare age estimates and patterns of association between these clades. Our study provides strong support for the evolution of parasitism of Cryptosporidium with the rise of the vertebrates about 600 million years ago (Mya). Interestingly, periods of increased diversification in Cryptosporidium coincides with diversification of crown mammalian and avian orders after the Cretaceous-Palaeogene (K-Pg) boundary, suggesting that adaptive radiation to new mammalian and avian hosts triggered the diversification of this parasite lineage. Despite evidence for ongoing host shifts we also found significant correlation between protozoan parasites and vertebrate hosts trees in the cophylogenetic analysis. These results help us to understand the underlying macroevolutionary mechanisms driving evolution in Cryptosporidium and may have important implications for the ecology, dynamics and epidemiology of cryptosporidiosis disease in humans and other animals.

  1. Investigating the Origin and Evolution of Venus with in Situ Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Trainer, M. G.; Mahaffy, P. R.; Brinckerhoff, W. B.; Johnson, N. M.; Glaze, L. S.

    2016-01-01

    The exploration of Venus continues to be a top priority of planetary science. The Planetary Decadal Survey goals for inner-planet exploration seek to discern the origin and diversity of terrestrial planets, understand how the evolution of terrestrial planets relates to the evolution of life, and explore the processes that control climate on Earth-like planets. These goals can only be realized through continued and extensive exploration of Venus, the most mysterious of the terrestrial planets, remarkably different from the Earth despite the gross similarities between these "twin planets". It is unknown if this apparent divergence was intrinsic, programmed during accretion from distinct nebular reservoirs, or a consequence of either measured or catastrophic processes during planetary evolution. Even if the atmosphere of Venus is a more "recent" development, its relationship to the resurfacing of the planet's enigmatic surface is not well understood. Resolving such uncertainties directly addresses the hypothesis of a more clement, possibly water-rich era in Venus' past as well as whether Earth could become more Venus-like in the future.

  2. Clonal origins and parallel evolution of regionally synchronous colorectal adenoma and carcinoma

    PubMed Central

    Rhee, Je-Keun; Jung, Seung-Hyun; Lee, Sung Hak; Baek, In-Pyo; Kim, Min Sung; Lee, Sug Hyung; Chung, Yeun-Jun

    2015-01-01

    Although the colorectal adenoma-to-carcinoma sequence represents a classical cancer progression model, the evolution of the mutational landscape underlying this model is not fully understood. In this study, we analyzed eight synchronous pairs of colorectal high-grade adenomas and carcinomas, four microsatellite-unstable (MSU) and four -stable (MSS) pairs, using whole-exome sequencing. In the MSU adenoma-carcinoma pairs, we observed no subclonal mutations in adenomas that became fixed in paired carcinomas, suggesting a ‘parallel’ evolution of synchronous adenoma-to-carcinoma, rather than a ‘stepwise’ evolution. The abundance of indel (in MSU and MSS pairs) and microsatellite instability (in MSU pairs) was noted in the later adenoma- or carcinoma-specific mutations, indicating that the mutational processes and functional constraints operative in early and late colorectal carcinogenesis are different. All MSU cases exhibited clonal, truncating mutations in ACVR2A, TGFBR2, and DNA mismatch repair genes, but none were present in APC or KRAS. In three MSS pairs, both APC and KRAS mutations were identified as both early and clonal events, often accompanying clonal copy number changes. An MSS case uniquely exhibited clonal ERBB2 amplification, followed by APC and TP53 mutations as carcinoma-specific events. Along with the previously unrecognized clonal origins of synchronous colorectal adenoma-carcinoma pairs, our study revealed that the preferred sequence of mutational events during colorectal carcinogenesis can be context-dependent. PMID:26336987

  3. Investigating the Origin and Evolution of Venus with In Situ Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Trainer, M. G.; Mahaffy, P. R.; Brinckerhoff, W. B.; Johnson, N. M.; Glaze, L. S.

    2014-01-01

    The exploration of Venus continues to be a top priority of planetary science. The Planetary Decadal Survey goals for inner-planet exploration seek to discern the origin and diversity of terrestrial planets, understand how the evolution of terrestrial planets relates to the evolution of life, and explore the processes that control climate on Earth-like planets [1]. These goals can only be realized through continued and extensive exploration of Venus, the most mysterious of the terrestrial planets, remarkably different from the Earth despite the gross similarities between these twin planets. It is unknown if this apparent divergence was intrinsic, programmed during accretion from distinct nebular reservoirs, or a consequence of either measured or catastrophic processes during planetary evolution. Even if the atmosphere of Venus is a more recent development, its relationship to the resurfacing of the planets enigmatic surface is not well understood. Resolving such uncertainties directly addresses the hypothesis of a more clement, possibly water-rich era in Venus past as well as whether Earth could become more Venus-like in the future.

  4. Investigating the Origin and Evolution of Venus with In Situ Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Trainer, M. G.; Mahaffy, P. R.; Brinckerhoff, W. B.; Johnson, N. M.; Glaze, L. S.

    2015-01-01

    The exploration of Venus continues to be a top priority of planetary science. The Planetary Decadal Survey goals for inner-planet exploration seek to discern the origin and diversity of terrestrial planets, understand how the evolution of terrestrial planets relates to the evolution of life, and explore the processes that control climate on Earth-like planets. These goals can only be realized through continued and extensive exploration of Venus, the most mysterious of the terrestrial planets, remarkably different from the Earth despite the gross similarities between these "twin planets". It is unknown if this apparent divergence was intrinsic, programmed during accretion from distinct nebular reservoirs, or a consequence of either measured or catastrophic processes during planetary evolution. Even if the atmosphere of Venus is a more "recent" development, its relationship to the resurfacing of the planet's enigmatic surface is not well understood. Resolving such uncertainties directly addresses the hypothesis of a more clement, possibly water-rich era in Venus' past as well as whether Earth could become more Venus-like in the future.

  5. CRevolution 2—Origin and evolution of the Colorado River system, workshop abstracts

    USGS Publications Warehouse

    : Beard, L. Sue; Karlstrom, Karl E.; Young, Richard A.; Billingsley, George H.

    2011-01-01

    A 2010 Colorado River symposium, held in Flagstaff, Arizona, involved 70 participants who engaged in intense debate about the origin and evolution of the Colorado River system. This symposium, built upon two previous decadal scientific meetings, focused on forging scientific consensus, where possible, while articulating continued controversies regarding the Cenozoic evolution of the Colorado River System and the landscapes of the Colorado Plateau-Rocky Mountain region that it drains. New developments involved hypotheses that Neogene mantle flow is driving plateau tilting and differential uplift and new and controversial hypotheses for the pre-6 Ma presence and evolution of ancestral rivers that may be important in the history and birth of the present Colorado River. There is a consensus that plateau tilt and uplift models must be tested with multidisciplinary studies involving differential incision studies and additional geochronology and thermochronology to determine the relative importance of tectonic and geomorphic forces that shape the spectacular landscapes of the Colorado Plateau, Arizona and region. In addition to the scientific goals, the meeting participants emphasized the iconic status of Grand Canyon for geosciences and the importance of good communication between the research community, the geoscience education/interpretation community, the public, and the media. Building on a century-long tradition, this region still provides a globally important natural laboratory for studies of the interactions of erosion and tectonism in shaping the landscape of elevated plateaus.

  6. [Role of transposons in origin and evolution of plant XY sex chromosomes].

    PubMed

    Shufen, Li; Sha, Li; Chuanliang, Deng; Longdou, Lu; Wujun, Gao

    2015-02-01

    The XY sex-determination system is crucial for plant reproduction. However, little is known about the mechanism of the origin and evolution of the XY sex chromosomes. It has been believed that a pair of autosomes is evolved to produce young sex chromosomes (neo-X chromosome and neo-Y chromosome) by loss of function or gain of function mutation, which influences the development of pistil or stamen. With the aggravation of the recombination suppression between neo-X and neo-Y and consequent expanding of the non-recombination region, the proto-sex chromosomes were finally developed to heteromorphic sex chromosomes. Accumulation of repetitive sequences and DNA methylation were probably involved in this process. Transposons, as the most abundant repetitive sequences in the genome, might be the initial motivation factors for the evolution of sex chromosome. Moreover, transposons may also increase heterochromatin expansion and recombination suppression of sex chromosome by local epigenetics modification. In this review, we summarize the function of transposon accumulation and the relationship between transposon and heterochromatization in the evolution of plant sex chromosome.

  7. Saltatory evolution of the ectodermal neural cortex gene family at the vertebrate origin.

    PubMed

    Feiner, Nathalie; Murakami, Yasunori; Breithut, Lisa; Mazan, Sylvie; Meyer, Axel; Kuraku, Shigehiro

    2013-01-01

    The ectodermal neural cortex (ENC) gene family, whose members are implicated in neurogenesis, is part of the kelch repeat superfamily. To date, ENC genes have been identified only in osteichthyans, although other kelch repeat-containing genes are prevalent throughout bilaterians. The lack of elaborate molecular phylogenetic analysis with exhaustive taxon sampling has obscured the possible link of the establishment of this gene family with vertebrate novelties. In this study, we identified ENC homologs in diverse vertebrates by means of database mining and polymerase chain reaction screens. Our analysis revealed that the ENC3 ortholog was lost in the basal eutherian lineage through single-gene deletion and that the triplication between ENC1, -2, and -3 occurred early in vertebrate evolution. Including our original data on the catshark and the zebrafish, our comparison revealed high conservation of the pleiotropic expression pattern of ENC1 and shuffling of expression domains between ENC1, -2, and -3. Compared with many other gene families including developmental key regulators, the ENC gene family is unique in that conventional molecular phylogenetic inference could identify no obvious invertebrate ortholog. This suggests a composite nature of the vertebrate-specific gene repertoire, consisting not only of de novo genes introduced at the vertebrate origin but also of long-standing genes with no apparent invertebrate orthologs. Some of the latter, including the ENC gene family, may be too rapidly evolving to provide sufficient phylogenetic signals marking orthology to their invertebrate counterparts. Such gene families that experienced saltatory evolution likely remain to be explored and might also have contributed to phenotypic evolution of vertebrates.

  8. Saltatory Evolution of the Ectodermal Neural Cortex Gene Family at the Vertebrate Origin

    PubMed Central

    Feiner, Nathalie; Murakami, Yasunori; Breithut, Lisa; Mazan, Sylvie; Meyer, Axel; Kuraku, Shigehiro

    2013-01-01

    The ectodermal neural cortex (ENC) gene family, whose members are implicated in neurogenesis, is part of the kelch repeat superfamily. To date, ENC genes have been identified only in osteichthyans, although other kelch repeat-containing genes are prevalent throughout bilaterians. The lack of elaborate molecular phylogenetic analysis with exhaustive taxon sampling has obscured the possible link of the establishment of this gene family with vertebrate novelties. In this study, we identified ENC homologs in diverse vertebrates by means of database mining and polymerase chain reaction screens. Our analysis revealed that the ENC3 ortholog was lost in the basal eutherian lineage through single-gene deletion and that the triplication between ENC1, -2, and -3 occurred early in vertebrate evolution. Including our original data on the catshark and the zebrafish, our comparison revealed high conservation of the pleiotropic expression pattern of ENC1 and shuffling of expression domains between ENC1, -2, and -3. Compared with many other gene families including developmental key regulators, the ENC gene family is unique in that conventional molecular phylogenetic inference could identify no obvious invertebrate ortholog. This suggests a composite nature of the vertebrate-specific gene repertoire, consisting not only of de novo genes introduced at the vertebrate origin but also of long-standing genes with no apparent invertebrate orthologs. Some of the latter, including the ENC gene family, may be too rapidly evolving to provide sufficient phylogenetic signals marking orthology to their invertebrate counterparts. Such gene families that experienced saltatory evolution likely remain to be explored and might also have contributed to phenotypic evolution of vertebrates. PMID:23843192

  9. Evolution of dinoflagellate unigenic minicircles and the partially concerted divergence of their putative replicon origins.

    PubMed

    Zhang, Zhaoduo; Cavalier-Smith, Thomas; Green, Beverley R

    2002-04-01

    Dinoflagellate chloroplast genes are unique in that each gene is on a separate minicircular chromosome. To understand the origin and evolution of this exceptional genomic organization we completely sequenced chloroplast psbA and 23S rRNA gene minicircles from four dinoflagellates: three closely related Heterocapsa species (H. pygmaea, H. rotundata, and H. niei) and the very distantly related Amphidinium carterae. We also completely sequenced a Protoceratium reticulatum minicircle with a 23S rRNA gene of novel structure. Comparison of these minicircles with those previously sequenced from H. triquetra and A. operculatum shows that in addition to the single gene all have noncoding regions of approximately a kilobase, which are likely to include a replication origin, promoter, and perhaps segregation sequences. The noncoding regions always have a high potential for folding into hairpins and loops. In all six dinoflagellate strains for which multiple minicircles are fully sequenced, parts of the noncoding regions, designated cores, are almost identical between the psbA and 23S rRNA minicircles, but the remainder is very different. There are two, three, or four cores per circle, sometimes highly related in sequence, but no sequence identity is detectable between cores of different species, even within one genus. This contrast between very high core conservation within a species, but none among species, indicates that cores are diverging relatively rapidly in a concerted manner. This is the first well-established case of concerted evolution of noncoding regions on numerous separate chromosomes. It differs from concerted evolution among tandemly repeated spacers between rRNA genes, and that of inverted repeats in plant chloroplast genomes, in involving only the noncoding DNA cores. We present two models for the origin of chloroplast gene minicircles in dinoflagellates from a typical ancestral multigenic chloroplast genome. Both involve substantial genomic reduction and

  10. Effect of Phase Contiguity and Morphology on the Evolution of Deformation Texture in Two-Phase Alloys

    NASA Astrophysics Data System (ADS)

    Gurao, N. P.; Suwas, Satyam

    2017-02-01

    Deformation texture evolution in two-phase xFe- yNi-(100- x- y)Cr model alloys and Ti-13Nb-13Zr alloy was studied during rolling to develop an understanding of micro-mechanisms of deformation in industrially relevant two-phase FCC-BCC steels and HCP-BCC titanium alloys, respectively. It was found that volume fraction and contiguity of phases lead to systematic changes in texture, while morphology affects the strength of texture. There was a characteristic change in texture from typical Brass-type to a weaker Copper-type texture in the austenite phase accompanied with a change from alpha fiber to gamma fiber in ferrite phase for Fe-Ni-Cr alloys with increase in fraction of harder ferrite phase. However, similar characteristic texture evolution was noted in both α and β phase irrespective of the different initial morphologies in Ti-13Nb-13Zr alloy. Viscoplastic self-consistent simulations with two-phase scheme were able to qualitatively predict texture evolution in individual phases. It is proposed that the transition from iso-strain-type behavior for equiaxed microstructure at low strain to iso-stress-type behavior at higher strain is aided by the presence of higher volume fraction of the second phase and increasing aspect ratio of individual phases in two-phase alloys.

  11. Phase transitions as the origin of large scale structure in the universe

    NASA Technical Reports Server (NTRS)

    Turok, Neil

    1989-01-01

    A review of the formation of large scale structure through gravitational growth of primordial perturbations is given. This is followed by a discussion of how symmetry breaking phase transitions in the early universe might have produced the required perturbations, in particular through the formation and evolution of a network of cosmic strings.

  12. Origin and Evolution of Water Oxidation before the Last Common Ancestor of the Cyanobacteria

    PubMed Central

    Cardona, Tanai; Murray, James W.; Rutherford, A. William

    2015-01-01

    Photosystem II, the water oxidizing enzyme, altered the course of evolution by filling the atmosphere with oxygen. Here, we reconstruct the origin and evolution of water oxidation at an unprecedented level of detail by studying the phylogeny of all D1 subunits, the main protein coordinating the water oxidizing cluster (Mn4CaO5) of Photosystem II. We show that D1 exists in several forms making well-defined clades, some of which could have evolved before the origin of water oxidation and presenting many atypical characteristics. The most ancient form is found in the genome of Gloeobacter kilaueensis JS-1 and this has a C-terminus with a higher sequence identity to D2 than to any other D1. Two other groups of early evolving D1 correspond to those expressed under prolonged far-red illumination and in darkness. These atypical D1 forms are characterized by a dramatically different Mn4CaO5 binding site and a Photosystem II containing such a site may assemble an unconventional metal cluster. The first D1 forms with a full set of ligands to the Mn4CaO5 cluster are grouped with D1 proteins expressed only under low oxygen concentrations and the latest evolving form is the dominant type of D1 found in all cyanobacteria and plastids. In addition, we show that the plastid ancestor had a D1 more similar to those in early branching Synechococcus. We suggest each one of these forms of D1 originated from transitional forms at different stages toward the innovation and optimization of water oxidation before the last common ancestor of all known cyanobacteria. PMID:25657330

  13. Origin and Evolution of Water Oxidation before the Last Common Ancestor of the Cyanobacteria.

    PubMed

    Cardona, Tanai; Murray, James W; Rutherford, A William

    2015-05-01

    Photosystem II, the water oxidizing enzyme, altered the course of evolution by filling the atmosphere with oxygen. Here, we reconstruct the origin and evolution of water oxidation at an unprecedented level of detail by studying the phylogeny of all D1 subunits, the main protein coordinating the water oxidizing cluster (Mn4CaO5) of Photosystem II. We show that D1 exists in several forms making well-defined clades, some of which could have evolved before the origin of water oxidation and presenting many atypical characteristics. The most ancient form is found in the genome of Gloeobacter kilaueensis JS-1 and this has a C-terminus with a higher sequence identity to D2 than to any other D1. Two other groups of early evolving D1 correspond to those expressed under prolonged far-red illumination and in darkness. These atypical D1 forms are characterized by a dramatically different Mn4CaO5 binding site and a Photosystem II containing such a site may assemble an unconventional metal cluster. The first D1 forms with a full set of ligands to the Mn4CaO5 cluster are grouped with D1 proteins expressed only under low oxygen concentrations and the latest evolving form is the dominant type of D1 found in all cyanobacteria and plastids. In addition, we show that the plastid ancestor had a D1 more similar to those in early branching Synechococcus. We suggest each one of these forms of D1 originated from transitional forms at different stages toward the innovation and optimization of water oxidation before the last common ancestor of all known cyanobacteria.

  14. Progressive and Biased Divergent Evolution Underpins the Origin and Diversification of Peridinin Dinoflagellate Plastids.

    PubMed

    Dorrell, Richard G; Klinger, Christen M; Newby, Robert J; Butterfield, Erin R; Richardson, Elisabeth; Dacks, Joel B; Howe, Christopher J; Nisbet, Ellen R; Bowler, Chris

    2016-11-04

    Dinoflagellates are algae of tremendous importance to ecosystems and to public health. The cell biology and genome organization of dinoflagellate species is highly unusual. For example, the plastid genomes of peridinin-containing dinoflagellates encode only a minimal number of genes arranged on small elements termed "minicircles". Previous studies of peridinin plastid genes have found evidence for divergent sequence evolution, including extensive substitutions, novel insertions and deletions, and use of alternative translation initiation codons. Understanding the extent of this divergent evolution has been hampered by the lack of characterized peridinin plastid sequences. We have identified over 300 previously unannotated peridinin plastid mRNAs from published transcriptome projects, vastly increasing the number of sequences available. Using these data, we have produced a well-resolved phylogeny of peridinin plastid lineages, which uncovers several novel relationships within the dinoflagellates. This enables us to define changes to plastid sequences that occurred early in dinoflagellate evolution, and that have contributed to the subsequent diversification of individual dinoflagellate clades. We find that the origin of the peridinin dinoflagellates was specifically accompanied by elevations both in the overall number of substitutions that occurred on plastid sequences, and in the Ka/Ks ratio associated with plastid sequences, consistent with changes in selective pressure. These substitutions, alongside other changes, have accumulated progressively in individual peridinin plastid lineages. Throughout our entire dataset, we identify a persistent bias toward non-synonymous substitutions occurring on sequences encoding photosystem I subunits and stromal regions of peridinin plastid proteins, which may have underpinned the evolution of this unusual organelle.

  15. Phylogenetic approach for inferring the origin and functional evolution of bacterial ADP-ribosylation superfamily.

    PubMed

    Chellapandi, P; Sakthishree, S; Bharathi, M

    2013-09-01

    Bacterial ADP-ribosyltransferases (BADPRTs) are extensively contributed to determine the strain-specific virulence state and pathogenesis in human hosts. Understanding molecular evolution and functional diversity of the BADPRTs is an important standpoint to describe the fundamental behind in the vaccine designing for bacterial infections. In the present study, we have evaluated the origin and functional evolution of conserved domains within the BADPRTs by analyzing their sequence-function relationship. To represent the evolution history of BADPRTs, phylogenetic trees were constructed based on their protein sequence, structure and conserved domains using different evolutionary programs. Sequence divergence and genetic diversity were studied herein to deduce the functional evolution of conserved domains across the family and superfamily. The results of sequence similarity search have shown that three hypothetical proteins (above 90%) were identical to the members of BADPRTs and their functions were annotated by phylogenetic approach. Phylogenetic analysis of this study has revealed the family members of BADPRTs were phylogenetically related to one another, functionally diverged within the same family, and dispersed into closely related bacteria. The presence of core substitution pattern in the conserved domains would determine the family-specific function of BADPRTs. Functional diversity of the BADPRTs was exclusively distinguished by Darwinian positive selection (diphtheria toxin C and pertussis toxin S) and neutral selection (arginine ADP-ribosyltransferase, enterotoxin A and binary toxin A) acting on the existing domains. Many of the family members were sharing their sequence-specific features from members in the arginine ADP-ribosyltransferase family. Conservative functions of members in the BADPRTs have shown to be expanded only within closely related families, and retained as such in pathogenic bacteria by evolutionary process (domain duplication or

  16. Unraveling the origins of electromechanical response in mixed-phase Bismuth Ferrite

    SciTech Connect

    Vasudevan, Rama K; Okatan, M. B.; Liu, Y. Y.; Jesse, Stephen; Yang, J.-C.; Liang, W. -I.; Chu, Ying-Hao; Li, J. Y.; Kalinin, Sergei V; Valanoor, Nagarajan V

    2013-01-01

    The origin of giant electromechanical response in a mixed-phase rhombohedral-tetragonal BiFeO3 thin film is probed using sub-coercive scanning probe microscopy based multiple-harmonic measurements. Significant contributions to the strain arise from a second-order harmonic response localized at the phase boundaries. Strain and dissipation data, backed by thermodynamic calculations suggest that the source of the enhanced electromechanical response is the motion of phase boundaries. These findings elucidate the key role of labile phase boundaries, both natural and artificial, in achieving thin films with giant electromechanical properties.

  17. Phase field modeling of the defect evolution and failure

    NASA Astrophysics Data System (ADS)

    Xie, Yuesong

    The plastic recovery processes in ultrafine and nano grained metals and the yield criteria and failure mechanisms in polymer matrix composite are the two major topics in this work. In the first part of the work, a phase field dislocation dynamics (PFDD) approach is introduced, which tracks the evolution of the dislocations in ultrafine and nano grained metals and takes into account the elastic interaction between dislocations, obstacles and the applied resolved shear stress on a single slip plane. Two phenomena, the reverse plastic strain during cyclic loading and plastic strain recovery upon unloading, are studied. One major finding of our simulations is that these two plastic recovery processes are related to the formation of dislocation structures during loading, and additional grain size inhomogeneity will increase the amount of plastic strain recovered. In the second part of the work, a phase field damage model (PFDM) is presented to study the onset of yielding and crack propagation in polymer matrix composite. The effect of two damage parameters, the fracture toughness Gc and crack length scale parameter l0, are first investigated. The former is shown to determine the energy needed during crack propagation and the latter is observed to control the crack nucleation process. Moreover, two asymmetric damage models are compared regarding their yield surfaces and it is found that the model of Miehe et al. leads to a linear pressure modified von Mises relation. Next, the PFDM reveals that the yield criterion in amorphous polymers should be described in terms of local stress and strains fields and cannot be extended directly from applied stress field values. Furthermore, it is demonstrated that the same damage model can be used to study the failure under shear yielding and crazing conditions. And if local defects in the samples such as voids are included explicitly in the simulations, the PFDM is able to explain the breakdown of the pressure modified von Mises

  18. Comparative Mitogenomic Analyses of Praying Mantises (Dictyoptera, Mantodea): Origin and Evolution of Unusual Intergenic Gaps

    PubMed Central

    Zhang, Hong-Li; Ye, Fei

    2017-01-01

    Praying mantises are a diverse group of predatory insects. Although some Mantodea mitogenomes have been reported, a comprehensive comparative and evolutionary genomic study is lacking for this group. In the present study, four new mitogenomes were sequenced, annotated, and compared to the previously published mitogenomes of other Mantodea species. Most Mantodea mitogenomes share a typical set of mitochondrial genes and a putative control region (CR). Additionally, and most intriguingly, another large non-coding region (LNC) was detected between trnM and ND2 in all six Paramantini mitogenomes examined. The main section in this common region of Paramantini may have initially originated from the corresponding control region for each species, whereas sequence differences between the LNCs and CRs and phylogenetic analyses indicate that LNC and CR are largely independently evolving. Namely, the LNC (the duplicated CR) may have subsequently degenerated during evolution. Furthermore, evidence suggests that special intergenic gaps have been introduced in some species through gene rearrangement and duplication. These gaps are actually the original abutting sequences of migrated or duplicated genes. Some gaps (G5 and G6) are homologous to the 5' and 3' surrounding regions of the duplicated gene in the original gene order, and another specific gap (G7) has tandem repeats. We analysed the phylogenetic relationships of fifteen Mantodea species using 37 concatenated mitochondrial genes and detected several synapomorphies unique to species in some clades. PMID:28367101

  19. Revising the Taxonomic Distribution, Origin and Evolution of Ribosome Inactivating Protein Genes

    PubMed Central

    Lapadula, Walter J.; Sánchez Puerta, María Virginia; Juri Ayub, Maximiliano

    2013-01-01

    Ribosome inactivating proteins are enzymes that depurinate a specific adenine residue in the alpha-sarcin-ricin loop of the large ribosomal RNA, being ricin and Shiga toxins the most renowned examples. They are widely distributed in plants and their presence has also been confirmed in a few bacterial species. According to this taxonomic distribution, the current model about the origin and evolution of RIP genes postulates that an ancestral RIP domain was originated in flowering plants, and later acquired by some bacteria via horizontal gene transfer. Here, we unequivocally detected the presence of RIP genes in fungi and metazoa. These findings, along with sequence and phylogenetic analyses, led us to propose an alternative, more parsimonious, hypothesis about the origin and evolutionary history of the RIP domain, where several paralogous RIP genes were already present before the three domains of life evolved. This model is in agreement with the current idea of the Last Universal Common Ancestor (LUCA) as a complex, genetically redundant organism. Differential loss of paralogous genes in descendants of LUCA, rather than multiple horizontal gene transfer events, could account for the complex pattern of RIP genes across extant species, as it has been observed for other genes. PMID:24039805

  20. Electronic phase separation transition as the origin of the superconductivity and pseudogap phase of cuprates

    NASA Astrophysics Data System (ADS)

    de Mello, E. V. L.; Kasal, R. B.; Passos, C. A. C.

    2009-06-01

    To deal with the physics of cuprate superconductivity we propose an electronic phase separation transition that segregates the holes into high and low density domains. The calculated grain boundary potential favors the development of intragrain superconducting amplitudes. The zero resistivity transition arises only when the intergrain Josephson coupling EJ is of the order of the thermal energy and phase locking takes place among the superconducting grains. We show that this approach explains the pseudogap and superconducting phases and it also reproduces some recent scanning tunneling microscopy data.

  1. Electronic phase separation transition as the origin of the superconductivity and pseudogap phase of cuprates.

    PubMed

    de Mello, E V L; Kasal, R B; Passos, C A C

    2009-06-10

    To deal with the physics of cuprate superconductivity we propose an electronic phase separation transition that segregates the holes into high and low density domains. The calculated grain boundary potential favors the development of intragrain superconducting amplitudes. The zero resistivity transition arises only when the intergrain Josephson coupling E(J) is of the order of the thermal energy and phase locking takes place among the superconducting grains. We show that this approach explains the pseudogap and superconducting phases and it also reproduces some recent scanning tunneling microscopy data.

  2. Age, origin and evolution of Antarctic debris-covered glaciers: Implications for landscape evolution and long-term climate change

    NASA Astrophysics Data System (ADS)

    Mackay, Sean Leland

    Antarctic debris-covered glaciers are potential archives of long-term climate change. However, the geomorphic response of these systems to climate forcing is not well understood. To address this concern, I conducted a series of field-based and numerical modeling studies in the McMurdo Dry Valleys of Antarctica (MDV), with a focus on Mullins and Friedman glaciers. I used data and results from geophysical surveys, ice-core collection and analysis, geomorphic mapping, micro-meteorological stations, and numerical-process models to (1) determine the precise origin and distribution of englacial and supraglacial debris within these buried-ice systems, (2) quantify the fundamental processes and feedbacks that govern interactions among englacial and supraglacial debris, (3) establish a process-based model to quantify the inventory of cosmogenic nuclides within englacial and supraglacial debris, and (4) isolate the governing relationships between the evolution of englacial /supraglacial debris and regional climate forcing. Results from 93 field excavations, 21 ice cores, and 24 km of ground-penetrating radar data show that Mullins and Friedman glaciers contain vast areas of clean glacier ice interspersed with inclined layers of concentrated debris. The similarity in the pattern of englacial debris bands across both glaciers, along with model results that call for negligible basal entrainment, is best explained by episodic environmental change at valley headwalls. To constrain better the timing of debris-band formation, I developed a modeling framework that tracks the accumulation of cosmogenic 3He in englacial and supraglacial debris. Results imply that ice within Mullins Glacier increases in age non-linearly from 12 ka to ˜220 ka in areas of active flow (up to >> 1.6 Ma in areas of slow-moving-to-stagnant ice) and that englacial debris bands originate with a periodicity of ˜41 ka. Modeling studies suggest that debris bands originate in synchronicity with changes in

  3. Rotation in the Pleiades with K2. III. Speculations on Origins and Evolution

    NASA Astrophysics Data System (ADS)

    Stauffer, John; Rebull, Luisa; Bouvier, Jerome; Hillenbrand, Lynne A.; Collier-Cameron, Andrew; Pinsonneault, Marc; Aigrain, Suzanne; Barrado, David; Bouy, Herve; Ciardi, David; Cody, Ann Marie; David, Trevor; Micela, Giusi; Soderblom, David; Somers, Garrett; Stassun, Keivan G.; Valenti, Jeff; Vrba, Frederick J.

    2016-11-01

    We use high-quality K2 light curves for hundreds of stars in the Pleiades to better understand the angular momentum evolution and magnetic dynamos of young low-mass stars. The K2 light curves provide not only rotational periods but also detailed information from the shape of the phased light curve that was not available in previous studies. A slowly rotating sequence begins at {(V-{K}{{s}})}0 ˜ 1.1 (spectral type F5) and ends at {(V-{K}{{s}})}0 ˜ 3.7 (spectral type K8), with periods rising from ˜2 to ˜11 days in that interval. A total of 52% of the Pleiades members in that color interval have periods within 30% of a curve defining the slow sequence; the slowly rotating fraction decreases significantly redward of {(V-{K}{{s}})}0 = 2.6. Nearly all of the slow-sequence stars show light curves that evolve significantly on timescales less than the K2 campaign duration. The majority of the FGK Pleiades members identified as photometric binaries are relatively rapidly rotating, perhaps because binarity inhibits star-disk angular momentum loss mechanisms during pre-main-sequence evolution. The fully convective late M dwarf Pleiades members (5.0 < {(V-{K}{{s}})}0 < 6.0) nearly always show stable light curves, with little spot evolution or evidence of differential rotation. During pre-main-sequence evolution from ˜3 Myr (NGC 2264 age) to ˜125 Myr (Pleiades age), stars of 0.3 {M}⊙ shed about half of their angular momentum, with the fractional change in period between 3 and 125 Myr being nearly independent of mass for fully convective stars. Our data also suggest that very low mass binaries form with rotation periods more similar to each other and faster than would be true if drawn at random from the parent population of single stars.

  4. The origin and evolution of maize in the Southwestern United States.

    PubMed

    da Fonseca, Rute R; Smith, Bruce D; Wales, Nathan; Cappellini, Enrico; Skoglund, Pontus; Fumagalli, Matteo; Samaniego, José Alfredo; Carøe, Christian; Ávila-Arcos, María C; Hufnagel, David E; Korneliussen, Thorfinn Sand; Vieira, Filipe Garrett; Jakobsson, Mattias; Arriaza, Bernardo; Willerslev, Eske; Nielsen, Rasmus; Hufford, Matthew B; Albrechtsen, Anders; Ross-Ibarra, Jeffrey; Gilbert, M Thomas P

    2015-01-08

    The origin of maize (Zea mays mays) in the US Southwest remains contentious, with conflicting archaeological data supporting either coastal(1-4) or highland(5,6) routes of diffusion of maize into the United States. Furthermore, the genetics of adaptation to the new environmental and cultural context of the Southwest is largely uncharacterized(7). To address these issues, we compared nuclear DNA from 32 archaeological maize samples spanning 6,000 years of evolution to modern landraces. We found that the initial diffusion of maize into the Southwest about 4,000 years ago is likely to have occurred along a highland route, followed by gene flow from a lowland coastal maize beginning at least 2,000 years ago. Our population genetic analysis also enabled us to differentiate selection during domestication for adaptation to the climatic and cultural environment of the Southwest, identifying adaptation loci relevant to drought tolerance and sugar content.

  5. Diversity in the origins of proteostasis networks- a driver for protein function in evolution

    PubMed Central

    Powers, Evan T.; Balch, William E.

    2013-01-01

    Although a protein’s primary sequence largely determines its function, proteins can adopt different folding states in response to changes in the environment, some of which may be deleterious to the organism. All organisms, including Bacteria, Archaea and Eukarya, have evolved a protein homeostasis network, or proteostasis network, that consists of chaperones and folding factors, degradation components, signalling pathways and specialized compartmentalized modules that manage protein folding in response to environmental stimuli and variation. Surveying the origins of proteostasis networks reveals that they have co-evolved with the proteome to regulate the physiological state of the cell, reflecting the unique stresses that different cells or organisms experience, and that they have a key role in driving evolution by closely managing the link between the phenotype and the genotype. PMID:23463216

  6. Chromatographic separation as selection process for prebiotic evolution and the origin of the genetic code.

    PubMed

    Lehmann, U

    1985-01-01

    A model for the evolution of a translation apparatus has been suggested where oligonucleotides in a hairpin conformation act as primordial adapters. Specifically activated amino acids are assumed to be attached to these hairpin molecules. For the specific activation, a chromatographic separation of, e.g. ala and CMP from gly and GMP can be accomplished on silica (e.g. of volcanic origin) with aqueous salt solutions. Other adsorbents like clays (kaolin, bentonite, montmorillonite), different silicates (florisil, magnesium trisilicate, calcium silicate, talc), hydroxyapatite, barium sulfate, calcium carbonate, calcium fluoride and titanoxide have been examined as model systems for the separation of nucleotides, nucleosides and amino acids on mineral surfaces. The possible role of chromatographic separation of amino acids for the formation of proteinoids, composed of selected amino acids, is also considered.

  7. Origin and Initial Evolution of Coronal Mass Ejections Observed by SDO, STEREO, and IRIS

    NASA Astrophysics Data System (ADS)

    Cheng, Xin

    2016-07-01

    Magnetic flux rope (MFR) is a coherent magnetic structure with all magnetic field lines wrapping around its central axis. It has been supposed to exist in various celestial circumstances like the magnetotail of the Earth, the ionosphere of Venus, the Nebula, and the black hole system. In the solar atmosphere, the MFR is even believed to be a fundamental structure of coronal mass ejections, existing prior to and driving the solar eruptions. In this talk, I will present the observational signature of MFR; discuss its origin through analyzing EUV images, 3D magnetic field configurations, and thermal structures of associated active regions. Furthermore, the kinematic evolution of MFR and its role in the early dynamic process of coronal mass ejections are also included.

  8. Stochastic Chemical Evolution of Sub-Halos and the Origin of r-Process Elements

    NASA Astrophysics Data System (ADS)

    Ojima, Takuya; Ishimaru, Yuhri; Wanajo, Shinya; Prantzos, Nikos

    The main origin of r-process elements is still uncertain, but recent nucleosynthesis studies show that neutron star mergers (NSMs) are capable of naturally explaining the solar r-process abundance. Though, previous chemical evolution models hold conflict with the NSM scenario because the long NSM coalescence timescale causes an [r/Fe] enhancement at higher metallicity compared to the observed Galactic halo stars in the [r/Fe] vs [Fe/H] plane. However, it is not the case if assuming the formation of the Galactic halo by clusterings of sub-halos with varying star formation histories. We construct a chemical evolution model of sub-halos, where NSM occurring in each sub-halos are computed stochastically. Our results are in good agreement with the Galactic halo stars, explaining the observed dispersion and trend. Also, the abundance ratio pattern of the low mass sub-halos is in consistency with Reticulum II, a dwarf galaxy that might have been contaminated by a single r-process event.

  9. The twin-arginine subunit C in Oscarella: origin, evolution, and potential functional significance.

    PubMed

    Pett, Walker; Lavrov, Dennis V

    2013-09-01

    The twin-arginine translocation (Tat) pathway is a protein transport system that moves completely folded proteins across lipid membranes. Genes encoding components of the pathway have been found in the genomes of many Bacteria, Archaea, and eukaryotic organelles including chloroplasts, plant mitochondria, and the mitochondria of many protists. However, with a single exception, Tat genes are absent from the mitochondrial genomes of all animals. The only exception comes from the homoscleromorph sponges in the family Oscarellidae, whose mitochondrial genomes encode a gene for tatC, the largest subunit of the complex. Here, we explore the origin and evolution of the mitochondrial tatC gene in Oscarellidae, and use bioinformatic approaches to evaluate its functional significance. We conclude that tatC in Homoscleromorpha sponges was likely inherited from the ancestral proto-mitochondrial genome, implying multiple independent losses of the mitochondrial Tat pathway during the evolution of opisthokonts. In addition, bioinformatic evidence suggests that tatC comprises the entire Tat pathway in Oscarellidae, and that the Rieske Fe/S protein of mitochondrial complex III is its likely substrate.

  10. The molecular origin and evolution of dim-light vision in mammals.

    PubMed

    Bickelmann, Constanze; Morrow, James M; Du, Jing; Schott, Ryan K; van Hazel, Ilke; Lim, Steve; Müller, Johannes; Chang, Belinda S W

    2015-11-01

    The nocturnal origin of mammals is a longstanding hypothesis that is considered instrumental for the evolution of endothermy, a potential key innovation in this successful clade. This hypothesis is primarily based on indirect anatomical inference from fossils. Here, we reconstruct the evolutionary history of rhodopsin--the vertebrate visual pigment mediating the first step in phototransduction at low-light levels--via codon-based model tests for selection, combined with gene resurrection methods that allow for the study of ancient proteins. Rhodopsin coding sequences were reconstructed for three key nodes: Amniota, Mammalia, and Theria. When expressed in vitro, all sequences generated stable visual pigments with λMAX values similar to the well-studied bovine rhodopsin. Retinal release rates of mammalian and therian ancestral rhodopsins, measured via fluorescence spectroscopy, were significantly slower than those of the amniote ancestor, indicating altered molecular function possibly related to nocturnality. Positive selection along the therian branch suggests adaptive evolution in rhodopsin concurrent with therian ecological diversification events during the Mesozoic that allowed for an exploration of the environment at varying light levels.

  11. Introduction: CRevolution 2: origin and evolution of the Colorado River System II

    USGS Publications Warehouse

    Karlstrom, Karl E.; Beard, L. Sue; House, Kyle; Young, Richard A.; Aslan, Andres; Billingsley, George; Pederson, Joel

    2012-01-01

    A 2010 Colorado River symposium held in Flagstaff, Arizona, in May 2010, had 70 participants who engaged in intense debate about the origin and evolution of the Colorado River system. This symposium, built on two previous decadal scientific meetings, focused on forging scientific consensus where possible, while also articulating continued controversies regarding the Cenozoic evolution of the Colorado River System and the landscapes of the Colorado Plateau–Rocky Mountain region that it drains. New developments involved hypotheses that Neogene mantle flow is driving plateau tilting and differential uplift, with consensus that multidisciplinary studies involving differential incision studies and additional geochronology and thermochronology are needed to test the relative importance of tectonic and geomorphic forcings in shaping the spectacular landscapes of the Colorado Plateau region. In addition to the scientific goals, the meeting participants emphasized the iconic status of Grand Canyon for geosciences, and the importance of good communication between the research community, the geoscience education/interpretation community, the public, and the media. Building on a century-long tradition, this region still provides a globally important natural laboratory for studies of the interactions of erosion and tectonism in the shaping landscape of elevated plateaus.

  12. Reassortment Networks and the evolution of pandemic H1N1 swine-origin influenza.

    PubMed

    Bokhari, Shahid H; Pomeroy, Laura W; Janies, Daniel A

    2012-01-01

    Prior research developed Reassortment Networks to reconstruct the evolution of segmented viruses under both reassortment and mutation. We report their application to the swine-origin pandemic H1N1 virus (S-OIV). A database of all influenza A viruses, for which complete genome sequences were available in Genbank by October 2009, was created and dynamic programming was used to compute distances between all corresponding segments. A reassortment network was created to obtain the minimum cost evolutionary paths from all viruses to the exemplar S-OIV A/California/04/2009. This analysis took 35 hours on the Cray Extreme Multithreading (XMT) supercomputer, which has special hardware to permit efficient parallelization. Six specific H1N1/H1N2 bottleneck viruses were identified that almost always lie on minimum cost paths to S-OIV. We conjecture that these viruses are crucial to S-OIV evolution and worthy of careful study from a molecular biology viewpoint. In phylogenetics, ancestors are typically medians that have no functional constraints. In our method, ancestors are not inferred, but rather chosen from previously observed viruses along a path of mutation and reassortment leading to the target virus. This specificity and functional constraint render our results actionable for further experiments in vitro and in vivo.

  13. Evolution and the origin of the visual retinoid cycle in vertebrates.

    PubMed

    Kusakabe, Takehiro G; Takimoto, Noriko; Jin, Minghao; Tsuda, Motoyuki

    2009-10-12

    Absorption of a photon by visual pigments induces isomerization of 11-cis-retinaldehyde (RAL) chromophore to all-trans-RAL. Since the opsins lacking 11-cis-RAL lose light sensitivity, sustained vision requires continuous regeneration of 11-cis-RAL via the process called 'visual cycle'. Protostomes and vertebrates use essentially different machinery of visual pigment regeneration, and the origin and early evolution of the vertebrate visual cycle is an unsolved mystery. Here we compare visual retinoid cycles between different photoreceptors of vertebrates, including rods, cones and non-visual photoreceptors, as well as between vertebrates and invertebrates. The visual cycle systems in ascidians, the closest living relatives of vertebrates, show an intermediate state between vertebrates and non-chordate invertebrates. The ascidian larva may use retinochrome-like opsin as the major isomerase. The entire process of the visual cycle can occur inside the photoreceptor cells with distinct subcellular compartmentalization, although the visual cycle components are also present in surrounding non-photoreceptor cells. The adult ascidian probably uses RPE65 isomerase, and trans-to-cis isomerization may occur in distinct cellular compartments, which is similar to the vertebrate situation. The complete transition to the sophisticated retinoid cycle of vertebrates may have required acquisition of new genes, such as interphotoreceptor retinoid-binding protein, and functional evolution of the visual cycle genes.

  14. Accelerated protein evolution and origins of human-specific features: Foxp2 as an example.

    PubMed

    Zhang, Jianzhi; Webb, David M; Podlaha, Ondrej

    2002-12-01

    Genes responsible for human-specific phenotypes may have been under altered selective pressures in human evolution and thus exhibit changes in substitution rate and pattern at the protein sequence level. Using comparative analysis of human, chimpanzee, and mouse protein sequences, we identified two genes (PRM2 and FOXP2) with significantly enhanced evolutionary rates in the hominid lineage. PRM2 is a histone-like protein essential to spermatogenesis and was previously reported to be a likely target of sexual selection in humans and chimpanzees. FOXP2 is a transcription factor involved in speech and language development. Human FOXP2 experienced a >60-fold increase in substitution rate and incorporated two fixed amino acid changes in a broadly defined transcription suppression domain. A survey of a diverse group of placental mammals reveals the uniqueness of the human FOXP2 sequence and a population genetic analysis indicates possible adaptive selection behind the accelerated evolution. Taken together, our results suggest an important role that FOXP2 may have played in the origin of human speech and demonstrate a strategy for identifying candidate genes underlying the emergences of human-specific features.

  15. Origin and evolution of eukaryotic chaperonins: phylogenetic evidence for ancient duplications in CCT genes.

    PubMed

    Archibald, J M; Logsdon, J M; Doolittle, W F

    2000-10-01

    Chaperonins are oligomeric protein-folding complexes which are divided into two distantly related structural classes. Group I chaperonins (called GroEL/cpn60/hsp60) are found in bacteria and eukaryotic organelles, while group II chaperonins are present in archaea and the cytoplasm of eukaryotes (called CCT/TriC). While archaea possess one to three chaperonin subunit-encoding genes, eight distinct CCT gene families (paralogs) have been characterized in eukaryotes. We are interested in determining when during eukaryotic evolution the multiple gene duplications producing the CCT subunits occurred. We describe the sequence and phylogenetic analysis of five CCT genes from TRICHOMONAS: vaginalis and seven from GIARDIA: lamblia, representatives of amitochondriate protist lineages thought to have diverged early from other eukaryotes. Our data show that the gene duplications producing the eight CCT paralogs took place prior to the organismal divergence of TRICHOMONAS: and GIARDIA: from other eukaryotes. Thus, these divergent protists likely possess completely hetero-oligomeric CCT complexes like those in yeast and mammalian cells. No close phylogenetic relationship between the archaeal chaperonins and specific CCT subunits was observed, suggesting that none of the CCT gene duplications predate the divergence of archaea and eukaryotes. The duplications producing the CCTdelta and CCTepsilon subunits, as well as CCTalpha, CCTbeta, and CCTeta, are the most recent in the CCT gene family. Our analyses show significant differences in the rates of evolution of archaeal chaperonins compared with the eukaryotic CCTs, as well as among the different CCT subunits themselves. We discuss these results in light of current views on the origin, evolution, and function of CCT complexes.

  16. The origin and evolution of the surfactant system in fish: insights into the evolution of lungs and swim bladders.

    PubMed

    Daniels, Christopher B; Orgeig, Sandra; Sullivan, Lucy C; Ling, Nicholas; Bennett, Michael B; Schürch, Samuel; Val, Adalberto Luis; Brauner, Colin J

    2004-01-01

    Several times throughout their radiation fish have evolved either lungs or swim bladders as gas-holding structures. Lungs and swim bladders have different ontogenetic origins and can be used either for buoyancy or as an accessory respiratory organ. Therefore, the presence of air-filled bladders or lungs in different groups of fishes is an example of convergent evolution. We propose that air breathing could not occur without the presence of a surfactant system and suggest that this system may have originated in epithelial cells lining the pharynx. Here we present new data on the surfactant system in swim bladders of three teleost fish (the air-breathing pirarucu Arapaima gigas and tarpon Megalops cyprinoides and the non-air-breathing New Zealand snapper Pagrus auratus). We determined the presence of surfactant using biochemical, biophysical, and morphological analyses and determined homology using immunohistochemical analysis of the surfactant proteins (SPs). We relate the presence and structure of the surfactant system to those previously described in the swim bladders of another teleost, the goldfish, and those of the air-breathing organs of the other members of the Osteichthyes, the more primitive air-breathing Actinopterygii and the Sarcopterygii. Snapper and tarpon swim bladders are lined with squamous and cuboidal epithelial cells, respectively, containing membrane-bound lamellar bodies. Phosphatidylcholine dominates the phospholipid (PL) profile of lavage material from all fish analyzed to date. The presence of the characteristic surfactant lipids in pirarucu and tarpon, lamellar bodies in tarpon and snapper, SP-B in tarpon and pirarucu lavage, and SPs (A, B, and D) in swim bladder tissue of the tarpon provide strong evidence that the surfactant system of teleosts is homologous with that of other fish and of tetrapods. This study is the first demonstration of the presence of SP-D in the air-breathing organs of nonmammalian species and SP-B in actinopterygian

  17. Origin of the cilium: novel approaches to examine a centriolar evolution hypothesis.

    PubMed

    Alliegro, Mark C; Satir, Peter

    2009-01-01

    Recently, a new hypothesis was proposed regarding the evolution of the cilium from an enveloped RNA virus (Satir et al., 2007, Cell Motil. Cytoskeleton 64, 906). The hypothesis predicts that there may be specific centriolar or basal body RNAs with sequences reminiscent of retroviruses, and/or that the nuclear genes for certain centriole-specific proteins would have viral origins. Four independent laboratories have reported the existence of centrosomal RNA (cnRNA). Methods for studying cnRNA are described. We analyzed evidence of relatedness of known full-length cnRNAs to extant viral molecules. Out of 14 cnRNAs studied, 12 have similarity to entries in viral databases, all but one of these with E-values of < or = 1e(-4). Some centrosomal, and possibly uniquely centriolar, proteins also have relatives in viral databases that meet the criteria accepted to indicate a relationship by descent. Nine general cytoskeleton proteins exhibited no significant similarity to viral proteins. The speculation that centrioles are invaders of RNA viral origin in the evolving eukaryotic cell is strengthened by these findings.

  18. Golden jubilee year of Stanley Miller experiment and chemical evolution and origin of life

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Sandip K.

    2013-06-01

    I give a brief review of how some of the major players in the subject approached the problem of the origin of pre-biotic molecules on Earth. For paucity of space, I will start with the developments starting with Stanley Miller's experiment on abiotic synthesis of amino acids till the most recent work on numerical simulation of hydro-chemical processes of collapsing clouds and the evolution of complex bio-molecules. We are evidently far away from actually solving the problem of origin of life. What is clear, however, is that the formation of complex amino acids in interstellar region is indeed possible, independently, in many star forming regions inside protostellar disks. Possibly, the delivery of these important ingredients to the earth was done by comets and meteorites. Finally, I conclude that since only a small part of the universe is involved for a relatively short time to create the present life-form, far more complex and possibly 'super-civilized' systems are possible in this universe, and could even be present elsewhere.

  19. 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.

  20. Early Origin and Evolution of the Angelman Syndrome Ubiquitin Ligase Gene Ube3a

    PubMed Central

    Sato, Masaaki

    2017-01-01

    The human Ube3a gene encodes an E3 ubiquitin ligase and exhibits brain-specific genomic imprinting. Genetic abnormalities that affect the maternal copy of this gene cause the neurodevelopmental disorder Angelman syndrome (AS), which is characterized by severe mental retardation, speech impairment, seizure, ataxia and some unique behavioral phenotypes. In this review article, I highlight the evolution of the Ube3a gene and its imprinting to provide evolutionary insights into AS. Recent comparative genomic studies have revealed that Ube3a is most phylogenetically similar to HECTD2 among the human HECT (homologous to the E6AP carboxyl terminus) family of E3 ubiquitin ligases, and its distant evolutionary origin can be traced to common ancestors of fungi and animals. Moreover, a gene more similar to Ube3a than HECTD2 is found in a range of eukaryotes from amoebozoans to basal metazoans, but is lost in later lineages. Unlike in mice and humans, Ube3a expression is biallelic in birds, monotremes, marsupials and insects. The imprinting domain that governs maternal expression of Ube3a was formed from non-imprinted elements following multiple chromosomal rearrangements after diversification of marsupials and placental mammals. Hence, the evolutionary origins of Ube3a date from long before the emergence of the nervous system, although its imprinted expression was acquired relatively recently. These observations suggest that exogenous expression and functional analyses of ancient Ube3a orthologs in mammalian neurons will facilitate the evolutionary understanding of AS. PMID:28326016

  1. Constrained lability in floral evolution: counting convergent origins of hummingbird pollination in Penstemon and Keckiella.

    PubMed

    Wilson, Paul; Wolfe, Andrea D; Armbruster, W Scott; Thomson, James D

    2007-01-01

    In the clade of Penstemon and segregate genera, pollination syndromes are well defined among the 284 species. Most display combinations of floral characters associated with pollination by Hymenoptera, the ancestral mode of pollination for this clade. Forty-one species present characters associated with hummingbird pollination, although some of these ornithophiles are also visited by insects. The ornithophiles are scattered throughout the traditional taxonomy and across phylogenies estimated from nuclear (internal transcribed spacer (ITS)) and chloroplast DNA (trnCD/TL) sequence data. Here, the number of separate origins of ornithophily is estimated, using bootstrap phylogenies and constrained parsimony searches. Analyses suggest 21 separate origins, with overwhelming support for 10 of these. Because species sampling was incomplete, this is probably an underestimate. Penstemons therefore show great evolutionary lability with respect to acquiring hummingbird pollination; this syndrome acts as an attractor to which species with large sympetalous nectar-rich flowers have frequently been drawn. By contrast, penstemons have not undergone evolutionary shifts backwards or to other pollination syndromes. Thus, they are an example of both striking evolutionary lability and constrained evolution.

  2. Genome wide exploration of the origin and evolution of amino acids

    PubMed Central

    2010-01-01

    Background Even after years of exploration, the terrestrial origin of bio-molecules remains unsolved and controversial. Today, observation of amino acid composition in proteins has become an alternative way for a global understanding of the mystery encoded in whole genomes and seeking clues for the origin of amino acids. Results In this study, we statistically monitored the frequencies of 20 alpha-amino acids in 549 taxa from three kingdoms of life: archaebacteria, eubacteria, and eukaryotes. We found that the amino acids evolved independently in these three kingdoms; but, conserved linkages were observed in two groups of amino acids, (A, G, H, L, P, Q, R, and W) and (F, I, K, N, S, and Y). Moreover, the amino acids encoded by GC-poor codons (F, Y, N, K, I, and M) were found to "lose" their usage in the development from single cell eukaryotic organisms like S. cerevisiae to H. sapiens, while the amino acids encoded by GC-rich codons (P, A, G, and W) were found to gain usage. These findings further support the co-evolution hypothesis of amino acids and genetic codes. Conclusion We proposed a new chronological order of the appearance of amino acids (L, A, V/E/G, S, I, K, T, R/D, P, N, F, Q, Y, M, H, W, C). Two conserved evolutionary paths of amino acids were also suggested: A→G→R→P and K→Y. PMID:20230639

  3. Origin and evolution of the integumentary skeleton in non-tetrapod vertebrates

    PubMed Central

    Sire, Jean-Yves; Donoghue, Philip C J; Vickaryous, Matthews K

    2009-01-01

    Most non-tetrapod vertebrates develop mineralized extra-oral elements within the integument. Known collectively as the integumentary skeleton, these elements represent the structurally diverse skin-bound contribution to the dermal skeleton. In this review we begin by summarizing what is known about the histological diversity of the four main groups of integumentary skeletal tissues: hypermineralized (capping) tissues; dentine; plywood-like tissues; and bone. For most modern taxa, the integumentary skeleton has undergone widespread reduction and modification often rendering the homology and relationships of these elements confused and uncertain. Fundamentally, however, all integumentary skeletal elements are derived (alone or in combination) from only two types of cell condensations: odontogenic and osteogenic condensations. We review the origin and diversification of the integumentary skeleton in aquatic non-tetrapods (including stem gnathostomes), focusing on tissues derived from odontogenic (hypermineralized tissues, dentines and elasmodine) and osteogenic (bone tissues) cell condensations. The novelty of our new scenario of integumentary skeletal evolution resides in the demonstration that elasmodine, the main component of elasmoid scales, is odontogenic in origin. Based on available data we propose that elasmodine is a form of lamellar dentine. Given its widespread distribution in non-tetrapod lineages we further propose that elasmodine is a very ancient tissue in vertebrates and predict that it will be found in ancestral rhombic scales and cosmoid scales. PMID:19422423

  4. 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.

  5. Are Petals Sterile Stamens or Bracts? The Origin and Evolution of Petals in the Core Eudicots

    PubMed Central

    Ronse De Craene, Louis P.

    2007-01-01

    Background The aim of this paper is to discuss the controversial origins of petals from tepals or stamens and the links between the morphological expression of petals and floral organ identity genes in the core eudicots. Scope I challenge the widely held classical view that petals are morphologically derived from stamens in the core eudicots, and sepals from tepals or bracts. Morphological data suggest that tepal-derived petals have evolved independently in the major lineages of the core eudicots (i.e. asterids, Santalales and rosids) from Berberidopsis-like prototypes, and that staminodial petals have arisen only in few isolated cases where petals had been previously lost (Caryophyllales, Rosales). The clear correlation between continuous changes in petal morphology, and a scenario that indicates numerous duplications to have taken place in genes controlling floral organ development, can only be fully understood within a phylogenetic context. B-gene expression plays a fundamental role in the evolution of the petals by controlling petaloidy, but it does not clarify petal homology. Conclusions An increased synorganization of the flower in the core eudicots linked with the establishment of floral whorls restricts the petaloid gene expression to the second whorl, reducing the similarities of petals with tepals from which they were originally derived. An increased flower size linked with secondary polyandry or polycarpelly may lead to a breakdown of the restricted gene expression and a reversal to ancestral characteristics of perianth development. An altered ‘sliding boundary’ hypothesis is proposed for the core eudicots to explain shifts in petaloidy of the perianth and the event of staminodial petals. The repetitive changes of function in the perianth of the core eudicots are linked with shifts in petaloidy to the outer perianth whorl, or losses of petal or sepal whorls that can be secondarily compensated for by the inclusion of bracts in the flower. The origin

  6. Speculations on the origin and evolution of the Utopia-Elysium lowlands of Mars

    SciTech Connect

    Frey, H.V.; Schultz, R.A. )

    1990-08-30

    The origin of the overall low and variable topographic character of the northern plains is a fundamental aspect of the Martian crustal dichotomy. A model for the development of the Utopia-Elysium lowlands in eastern Mars in terms of the long-term evolution of large, overlapping impact basins is presented. The effects of relaxation of basin topography, volcanic flooding and loading of the basins with subsequent subsidence and downwarping, and the growth of a long-lived major tectonovolcanic center in the overlap region between the proposed Utopia and Elysium impact basins are qualitatively described. In an early hot, thin (<50 km thick) lithosphere with low mantle viscosity (<10{sup 22} P), relaxation of topographic relief was probably rapid (<10{sup 4} years) by comparison with the likely time between the two largest impacts (>10{sup 6} years). The later Utopia Basin impact drastically altered the structure of the earlier Elysium Basin, uplifting portions of what had been the central depression. The heating and fracturing due to the impacts was most intense in the region of overlap, which probably provided an easy conduit for volcanic eruptions in this area. Loading by Early Hesperian and older basin volcanic caused widespread subsidence which may have extended beyond the basin rim and which was responsible for the generally low character of the northern plains, despite the minimum 2-3 km volcanic fill present there. Prolonged volcanism would likely keep the overlap region hotter longer, opposing later general subsidence of the impact basin floor where it had cooled. The authors suggest this model may be applicable to the origin of the northern lowlands elsewhere on Mars and that overlapping large impacts may be important in the establishment of the fundamental topographic and crustal dichtomy and the origin of major tectonovolcanic complexes on the planet.

  7. Evolution of Modern Birds Revealed by Mitogenomics: Timing the Radiation and Origin of Major Orders

    PubMed Central

    Pacheco, M. Andreína; Battistuzzi, Fabia U.; Lentino, Miguel; Aguilar, Roberto F.; Kumar, Sudhir; Escalante, Ananias A.

    2011-01-01

    Mitochondrial (mt) genes and genomes are among the major sources of data for evolutionary studies in birds. This places mitogenomic studies in birds at the core of intense debates in avian evolutionary biology. Indeed, complete mt genomes are actively been used to unveil the phylogenetic relationships among major orders, whereas single genes (e.g., cytochrome c oxidase I [COX1]) are considered standard for species identification and defining species boundaries (DNA barcoding). In this investigation, we study the time of origin and evolutionary relationships among Neoaves orders using complete mt genomes. First, we were able to solve polytomies previously observed at the deep nodes of the Neoaves phylogeny by analyzing 80 mt genomes, including 17 new sequences reported in this investigation. As an example, we found evidence indicating that columbiforms and charadriforms are sister groups. Overall, our analyses indicate that by improving the taxonomic sampling, complete mt genomes can solve the evolutionary relationships among major bird groups. Second, we used our phylogenetic hypotheses to estimate the time of origin of major avian orders as a way to test if their diversification took place prior to the Cretaceous/Tertiary (K/T) boundary. Such timetrees were estimated using several molecular dating approaches and conservative calibration points. Whereas we found time estimates slightly younger than those reported by others, most of the major orders originated prior to the K/T boundary. Finally, we used our timetrees to estimate the rate of evolution of each mt gene. We found great variation on the mutation rates among mt genes and within different bird groups. COX1 was the gene with less variation among Neoaves orders and the one with the least amount of rate heterogeneity across lineages. Such findings support the choice of COX 1 among mt genes as target for developing DNA barcoding approaches in birds. PMID:21242529

  8. The origin of the incommesurate phase in the spin Peierls compound TiOCl

    NASA Astrophysics Data System (ADS)

    Dobry, Ariel; Mastrogiuseppe, Diego; Gazza, Claudio

    2011-03-01

    TiOX (X=Cl,Br) are recently characterized Spin-Peierls compounds. They are unusual due to the appearance of an intermediate incommensurate phase between the dimerized and the uniform ones. We show that the incommensurate phase is stabilized by a linear dependency of the phononic dispersion near the dimerized mode. A model based on antiferromagnetic chains with position dependent exchanges accounts for the evolution of the atomic coordinates with temperature within the incommensurate phase. The magnetic gap closes in the intermediate phase. Finally, we find that the magnetic static structure factor has incommensurate peaks situated at twice the wave vector of the structural ones. These peaks could be found in future elastic neutron scattering measurements.

  9. Model for resistance evolution in shape memory alloys including R-phase

    NASA Astrophysics Data System (ADS)

    Brammajyosula, Ravindra; Buravalla, Vidyashankar; Khandelwal, Ashish

    2011-03-01

    The electrical resistance behavior of a shape memory alloy (SMA) wire can be used for sensing the state of an SMA device. Hence, this study investigates the resistance evolution in SMAs. A lumped parameter model with cosine kinetics to capture the resistance variation during the phase transformation is developed. Several SMA materials show the presence of trigonal or rhombohedral (R) phase as an intermediate phase, apart from the commonly recognized austenite and martensite phases. Most of the SMA models ignore the R-phase effect in their prediction of thermomechanical response. This may be acceptable since the changes in thermomechanical response associated with the R-phase are relatively less. However, the resistivity related effects are pronounced in the presence of the R-phase and its appearance introduces non-monotonicity in the resistivity evolution. This leads to additional complexities in the use of resistance signal for sensing and control. Hence, a lumped model is developed here for resistance evolution including the R-phase effects. A phase-diagram-based model is proposed for predicting electro-thermomechanical response. Both steady state hysteretic response and transient response are modeled. The model predictions are compared with the available test data. Numerical studies have shown that the model is able to capture all the essential features of the resistance evolution in SMAs in the presence of the R-phase.

  10. Tracing the origin of functional and conserved domains in the human proteome: implications for protein evolution at the modular level

    PubMed Central

    Pal, Lipika R; Guda, Chittibabu

    2006-01-01

    Background The functional repertoire of the human proteome is an incremental collection of functions accomplished by protein domains evolved along the Homo sapiens lineage. Therefore, knowledge on the origin of these functionalities provides a better understanding of the domain and protein evolution in human. The lack of proper comprehension about such origin has impelled us to study the evolutionary origin of human proteome in a unique way as detailed in this study. Results This study reports a unique approach for understanding the evolution of human proteome by tracing the origin of its constituting domains hierarchically, along the Homo sapiens lineage. The uniqueness of this method lies in subtractive searching of functional and conserved domains in the human proteome resulting in higher efficiency of detecting their origins. From these analyses the nature of protein evolution and trends in domain evolution can be observed in the context of the entire human proteome data. The method adopted here also helps delineate the degree of divergence of functional families occurred during the course of evolution. Conclusion This approach to trace the evolutionary origin of functional domains in the human proteome facilitates better understanding of their functional versatility as well as provides insights into the functionality of hypothetical proteins present in the human proteome. This work elucidates the origin of functional and conserved domains in human proteins, their distribution along the Homo sapiens lineage, occurrence frequency of different domain combinations and proteome-wide patterns of their distribution, providing insights into the evolutionary solution to the increased complexity of the human proteome. PMID:17090320

  11. Study on the opinion of university students about the themes of the origin of Universe and evolution of life

    NASA Astrophysics Data System (ADS)

    de Souza, Rogério F.; de Carvalho, Marcelo; Matsuo, Tiemi; Zaia, Dimas A. M.

    2010-04-01

    This paper reports the results of a questionnaire administered to university students, about several questions involving the origin of the Universe and life and biological evolution, as well as questions related to more common scientific themes. As few as between 2.4% (philosophy students) and 14% (geography students) did not accept the theory of evolution, because they believed in creation as described in the Bible. However, between 41.5% (philosophy students) and 71.3% (biology students) did not see any conflict between religion and evolution. About 80% of the students believed that the relationship between lung cancer and smoking is well established by science, but this number falls to 65% for biological evolution and 28.9% for the big bang theory. It should be pointed out that for 24.5% and 7.4% of the students the big bang theory and biological evolution, respectively, are poorly established by science. The students who self-reported being Christian but not Roman Catholic are more conservative in the acceptance of biological evolution and the old age of Earth and the Universe than are other groups of students. Other factors, such as family income and the level of education of parents, appear to influence the students' acceptance of themes related to the origin of the Universe and biological evolution.

  12. The origin and evolution of genomic imprinting and viviparity in mammals

    PubMed Central

    Renfree, Marilyn B.; Suzuki, Shunsuke; Kaneko-Ishino, Tomoko

    2013-01-01

    Genomic imprinting is widespread in eutherian mammals. Marsupial mammals also have genomic imprinting, but in fewer loci. It has long been thought that genomic imprinting is somehow related to placentation and/or viviparity in mammals, although neither is restricted to mammals. Most imprinted genes are expressed in the placenta. There is no evidence for genomic imprinting in the egg-laying monotreme mammals, despite their short-lived placenta that transfers nutrients from mother to embryo. Post natal genomic imprinting also occurs, especially in the brain. However, little attention has been paid to the primary source of nutrition in the neonate in all mammals, the mammary gland. Differentially methylated regions (DMRs) play an important role as imprinting control centres in each imprinted region which usually comprises both paternally and maternally expressed genes (PEGs and MEGs). The DMR is established in the male or female germline (the gDMR). Comprehensive comparative genome studies demonstrated that two imprinted regions, PEG10 and IGF2-H19, are conserved in both marsupials and eutherians and that PEG10 and H19 DMRs emerged in the therian ancestor at least 160 Ma, indicating the ancestral origin of genomic imprinting during therian mammal evolution. Importantly, these regions are known to be deeply involved in placental and embryonic growth. It appears that most maternal gDMRs are always associated with imprinting in eutherian mammals, but emerged at differing times during mammalian evolution. Thus, genomic imprinting could evolve from a defence mechanism against transposable elements that depended on DNA methylation established in germ cells. PMID:23166401

  13. Acrobat ants go global--origin, evolution and systematics of the genus Crematogaster (Hymenoptera: Formicidae).

    PubMed

    Blaimer, Bonnie B

    2012-11-01

    This study unravels the evolution and biogeographic history of the globally distributed ant genus Crematogaster on the basis of a molecular phylogeny, reconstructed from five nuclear protein-coding genes and a total of 3384 bp of sequence data. A particular emphasis is placed on the evolutionary history of these ants in the Malagasy region. Bayesian and likelihood analyses performed on a dataset of 124 Crematogaster ingroup taxa lend strong support for three deeply diverging phylogenetic lineages within the genus: the Orthocrema clade, the Global Crematogaster clade and the Australo-Asian Crematogaster clade. The 15 previous subgenera within Crematogaster are mostly not monophyletic. Divergence dating analyses and ancestral range reconstructions suggest that Crematogaster evolved in South-East Asia in the mid-Eocene (40-45 ma). The three major lineages also originated in this region in the late Oligocene/early Miocene (~24-30 ma). A first dispersal out of S-E Asia by an Orthocrema lineage is supported for 22-30 ma to the Afrotropical region. Successive dispersal events out of S-E Asia began in the early, and continued throughout the late Miocene. The global distribution of Crematogaster was achieved by subsequent colonizations of all major biogeographic regions by the Orthocrema and the Global Crematogaster clade. Molecular dating estimates and ancestral range evolution are discussed in the light of palaeogeographic changes in the S-E Asian region and an evolving ocean circulation system throughout the Eocene, Oligocene and Miocene. Eight dispersal events to/from Madagascar by Crematogaster are supported, with most events occurring in the late Miocene to Pliocene (5.0-9.5 ma). These results suggest that Crematogaster ants possess exceptional dispersal and colonization abilities, and emphasize the need for detailed investigations of traits that have contributed to the global evolutionary success of these ants.

  14. Origin and Evolution of Titan's Nitrogen Atmosphere - A Cassini-Huygens Perspective

    NASA Astrophysics Data System (ADS)

    Atreya, Sushil K.

    2014-05-01

    Prior to Cassini-Huygens, it was debated how Titan acquired its earth-like atmosphere of nitrogen [1]. This talk will review the history of Titan's atmosphere, models, and the unique role of Cassini-Huygens in understanding the origin and evolution of an atmosphere of nitrogen on Titan. After hydrogen and helium, nitrogen is the fourth most abundant element in the solar system. In the colder outer solar system beyond 5 AU, nitrogen is bound to hydrogen in the giant planets. Thus ammonia (NH3), not N2, is the dominant reservoir of nitrogen in these objects. The satellites that form in the relatively warm and dense subnebula of the gas giant planets, Jupiter and Saturn, may acquire nitrogen as NH3 during their accretion [2], although some models had proposed N2, not NH3, as the stable form of nitrogen in the subnebulae. The latter is reflected in the atmosphere of Triton, which almost certainly accreted nitrogen directly as N2, since N2 can be the stable form of nitrogen in the very cold environment of Neptune. Before Cassini-Huygens, it was debated whether Titan, the largest moon of Saturn, also acquired its nitrogen directly as N2, putting it in the same class as Neptune's moon Triton half its size, or the nitrogen on Titan was secondary atmosphere, produced from a nitrogen bearing molecule, putting Titan in the class with terrestrial planets. The evidence from Cassini-Huygens to be discussed in this talk leaves no doubt that Titan's nitrogen atmosphere is secondary [3]. Probable scenarios of the sustenance, evolution and reduction or demise of this atmosphere will also be explored. References: [1]Owen T. (2000), Planet. Space Sci. 48, 747-752. [2]Prinn R.G., Fegley B. (1981), Astrophys J. 249, 308-317. [3]Atreya S.K., Lorenz R.D., Waite J.H. (2009), pp 177-199, in Titan (R.H. Brown et al., eds.) Springer.

  15. Evolution and Origin of HRS, a Protein Interacting with Merlin, the Neurofibromatosis 2 Gene Product

    PubMed Central

    Omelyanchuk, Leonid V.; Pertseva, Julia A.; Burns, Sarah S.; Chang, Long-Sheng

    2009-01-01

    Hepatocyte growth factor receptor tyrosine kinase substrate (HRS) is an endosomal protein required for trafficking receptor tyrosine kinases from the early endosome to the lysosome. HRS interacts with Merlin, the Neurofibromatosis 2 (NF2) gene product, and this interaction may be important for Merlin’s tumor suppressor activity. Understanding the evolution, origin, and structure of HRS may provide new insight into Merlin function. We show that HRS homologs are present across a wide range of Metazoa with the yeast Vps27 protein as their most distant ancestor. The phylogenetic tree of the HRS family coincides with species evolution and divergence, suggesting a unique function for HRS. Sequence alignment shows that various protein domains of HRS, including the VHS domain, the FYVE domain, the UIM domain, and the clathrin-binding domain, are conserved from yeast to multicellular organisms. The evolutionary transition from unicellular to multicellular organisms was accompanied by the appearance of a binding site for Merlin, which emerges in the early Metazoa after its separation from flatworms. In addition to the region responsible for growth suppression, the Merlin-binding and STAM-binding domains of HRS are conserved among multicellular organisms. The residue equivalent to tyrosine-377, which is phosphorylated in the human HRS protein, is highly conserved throughout the HRS family. Three additional conserved boxes lacking assigned functions are found in the HRS proteins of Metazoa. While boxes 1 and 3 may constitute the Eps-15-and Snx1-binding sites, respectively, box 2, containing the residue equivalent to tyrosine-377, is likely to be important for HRS phosphorylation. While several functional domains are conserved throughout the HRS family, the STAM-binding, Merlin-binding, and growth suppression domains evolved in the early Metazoa around the time the Merlin protein emerged. As these domains appear during the transition to multicellularity, their functional

  16. The origin and evolution of genomic imprinting and viviparity in mammals.

    PubMed

    Renfree, Marilyn B; Suzuki, Shunsuke; Kaneko-Ishino, Tomoko

    2013-01-05

    Genomic imprinting is widespread in eutherian mammals. Marsupial mammals also have genomic imprinting, but in fewer loci. It has long been thought that genomic imprinting is somehow related to placentation and/or viviparity in mammals, although neither is restricted to mammals. Most imprinted genes are expressed in the placenta. There is no evidence for genomic imprinting in the egg-laying monotreme mammals, despite their short-lived placenta that transfers nutrients from mother to embryo. Post natal genomic imprinting also occurs, especially in the brain. However, little attention has been paid to the primary source of nutrition in the neonate in all mammals, the mammary gland. Differentially methylated regions (DMRs) play an important role as imprinting control centres in each imprinted region which usually comprises both paternally and maternally expressed genes (PEGs and MEGs). The DMR is established in the male or female germline (the gDMR). Comprehensive comparative genome studies demonstrated that two imprinted regions, PEG10 and IGF2-H19, are conserved in both marsupials and eutherians and that PEG10 and H19 DMRs emerged in the therian ancestor at least 160 Ma, indicating the ancestral origin of genomic imprinting during therian mammal evolution. Importantly, these regions are known to be deeply involved in placental and embryonic growth. It appears that most maternal gDMRs are always associated with imprinting in eutherian mammals, but emerged at differing times during mammalian evolution. Thus, genomic imprinting could evolve from a defence mechanism against transposable elements that depended on DNA methylation established in germ cells.

  17. Origin and geochemical evolution of groundwater in a closed-basin clayey aquitard, Northern Mexico

    NASA Astrophysics Data System (ADS)

    Ortega-Guerrero, Adrián

    2003-12-01

    Groundwater flow cross-sectional modeling in combination with major ion and trace element chemistry, stable isotopes of water ( 18O and 2H) and geochemical modeling were used to investigate the origin and evolution of groundwater in a Quaternary lacustrine clay-rich aquitard in the closed basin of the 'La Laguna Region', Northern Mexico. This study pertains to the Viesca Lake, one of a series of ephemeral ancient lakes that existed in this basin until the early 1900s. The Viesca aquitard overlies a regional marine Mesozoic sequence that outcrops in the surrounding mountains. Groundwater samples were collected from springs, pumping wells in a carbonate aquifer and from former industrial production wells in the aquitard. Numerical results indicate a classical gravity flow system, where the carbonate aquifer discharged about 90% of the groundwater, as springs, that fed the former Viesca Lake. Isotope content of groundwater, in the carbonate aquifer, shows that groundwater has a local meteoric origin; and its chemical evolution is mainly associated to progressive dissolution of gypsum and oxidation of pyrite along the flow paths. In contrast, groundwater in the aquitard presented enrichment of heavy isotopes 2H and 18O, indicating that this water resulted from the evaporation of the carbonate groundwater aquifer. The maximum concentrations of sulfate (77,700 mg L -1), chloride (45,400 mg L -1) and sodium (45,000 mg L -1) in the groundwater from the aquitard were between three and four orders of magnitude greater than the fresh groundwater. Sulfate behaved as a conservative ion, contrasting with concentration of sulfate in groundwater from other aquitards in the world; which is usually reduced. Chemical patterns and enrichment of stable isotopes in groundwater from the aquitard follow general evaporation trends observed for other closed or semi-closed basins worldwide. Redox related parameters (NO 3-N, NH 4+, Mn 2+, total Fe and TOC) and redox-sensitive trace elements

  18. Structural evolution of calcite at high temperatures: Phase V unveiled

    PubMed Central

    Ishizawa, Nobuo; Setoguchi, Hayato; Yanagisawa, Kazumichi

    2013-01-01

    The calcite form of calcium carbonate CaCO3 undergoes a reversible phase transition between Rc and Rm at ~1240 K under a CO2 atmosphere of ~0.4 MPa. The joint probability density function obtained from the single-crystal X-ray diffraction data revealed that the oxygen triangles of the CO3 group in the high temperature form (Phase V) do not sit still at specified positions in the space group Rm, but migrate along the undulated circular orbital about carbon. The present study also shows how the room temperature form (Phase I) develops into Phase V through an intermediate form (Phase IV) in the temperature range between ~985 K and ~1240 K. PMID:24084871

  19. Understanding the origin and evolution of water in the Moon through lunar sample studies.

    PubMed

    Anand, Mahesh; Tartèse, Romain; Barnes, Jessica J

    2014-09-13

    A paradigm shift has recently occurred in our knowledge and understanding of water in the lunar interior. This has transpired principally through continued analysis of returned lunar samples using modern analytical instrumentation. While these recent studies have undoubtedly measured indigenous water in lunar samples they have also highlighted our current limitations and some future challenges that need to be overcome in order to fully understand the origin, distribution and evolution of water in the lunar interior. Another exciting recent development in the field of lunar science has been the unambiguous detection of water or water ice on the surface of the Moon through instruments flown on a number of orbiting spacecraft missions. Considered together, sample-based studies and those from orbit strongly suggest that the Moon is not an anhydrous planetary body, as previously believed. New observations and measurements support the possibility of a wet lunar interior and the presence of distinct reservoirs of water on the lunar surface. Furthermore, an approach combining measurements of water abundance in lunar samples and its hydrogen isotopic composition has proved to be of vital importance to fingerprint and elucidate processes and source(s) involved in giving rise to the lunar water inventory. A number of sources are likely to have contributed to the water inventory of the Moon ranging from primordial water to meteorite-derived water ice through to the water formed during the reaction of solar wind hydrogen with the lunar soil. Perhaps two of the most striking findings from these recent studies are the revelation that at least some portions of the lunar interior are as water-rich as some Mid-Ocean Ridge Basalt source regions on Earth and that the water in the Earth and the Moon probably share a common origin.

  20. Origins and emergent evolution of life: the colloid microsphere hypothesis revisited.

    PubMed

    Egel, Richard

    2014-04-01

    Self-replicating molecules, in particular RNA, have long been assumed as key to origins of life on Earth. This notion, however, is not very secure since the reduction of life's complexity to self-replication alone relies on thermodynamically untenable assumptions. Alternative, earlier hypotheses about peptide-dominated colloid self-assembly should be revived. Such macromolecular conglomerates presumably existed in a dynamic equilibrium between confluent growth in sessile films and microspheres detached in turbulent suspension. The first organic syntheses may have been driven by mineral-assisted photoactivation at terrestrial geothermal fields, allowing photo-dependent heterotrophic origins of life. Inherently endowed with rudimentary catalyst activities, mineral-associated organic microstructures can have evolved adaptively toward cooperative 'protolife' communities, in which 'protoplasmic continuity' was maintained throughout a graded series of 'proto-biofilms', 'protoorganisms' and 'protocells' toward modern life. The proneness of organic microspheres to merge back into the bulk of sessile films by spontaneous fusion can have made large populations promiscuous from the beginning, which was important for the speed of collective evolution early on. In this protein-centered scenario, the emergent coevolution of uncoded peptides, metabolic cofactors and oligoribonucleotides was primarily optimized for system-supporting catalytic capabilities arising from nonribosomal peptide synthesis and nonreplicative ribonucleotide polymerization, which in turn incorporated other reactive micromolecular organics as vitamins and cofactors into composite macromolecular colloid films and microspheres. Template-dependent replication and gene-encoded protein synthesis emerged as secondary means for further optimization of overall efficieny later on. Eventually, Darwinian speciation of cell-like lineages commenced after minimal gene sets had been bundled in transmissible genomes from

  1. Origin and evolution of nitrogen on Titan, Enceladus, Triton, and Pluto

    NASA Astrophysics Data System (ADS)

    Atreya, S. K.; Niemann, H. B.; Mahaffy, P. R.; Owen, T. C.

    Nitrogen, together with carbon, hydrogen, oxygen, phosphorus and sulfur (CHNOPS), plays a central role in life as we know it. Indeed, molecular nitrogen is the most abundant component of the terrestrial atmosphere, and second only to carbon dioxide on Mars and Venus. The Voyager and Cassini-Huygens observations show that copious nitrogen is present on Titan also, comprising some 95% by volume of this moon's 1500 millibar atmosphere. After water vapor, it may be the most abundant (4%) of the gases around tiny Enceladus, as revealed by the recent Cassini observations. A thin nitrogen atmosphere is found even on the coldest of the solar system bodies, Triton and Pluto. The available evidence on nitrogen isotopes and the heavy noble gases [Niemann et al., Nature, doi:10.1038/nature04122, 2005] suggests that Titan acquired its nitrogen largely in the form of ammonia. Subsequent chemical evolution, beginning with the photolysis of NH3 on primordial Titan, led to the nitrogen atmosphere we see on Titan today [Atreya et al., Science 201, 611, 1978]. This is also the scenario for the origin of nitrogen on the terrestrial planets. Contrary to Titan, the colder outer solar system objects, Triton and Pluto, neither had the luxury of receiving much ammonia in the first place, nor of photolyzing whatever little ammonia they did receive in the planetesimals that formed them. On the other hand, it is plausible the planetesimals were capable of trapping and delivering molecular nitrogen directly to Triton and Pluto, unlike Titan. The origin of nitrogen on Enceladus is somewhat enigmatic. A scenario similar to Titan's, but with a role for the interior processes, may be at work. In this paper, we will discuss the source and loss of nitrogen for the above objects, and why Ganymede, the largest moon in the solar system, is nitrogen starved.

  2. Understanding the origin and evolution of water in the Moon through lunar sample studies

    PubMed Central

    Anand, Mahesh; Tartèse, Romain; Barnes, Jessica J.

    2014-01-01

    A paradigm shift has recently occurred in our knowledge and understanding of water in the lunar interior. This has transpired principally through continued analysis of returned lunar samples using modern analytical instrumentation. While these recent studies have undoubtedly measured indigenous water in lunar samples they have also highlighted our current limitations and some future challenges that need to be overcome in order to fully understand the origin, distribution and evolution of water in the lunar interior. Another exciting recent development in the field of lunar science has been the unambiguous detection of water or water ice on the surface of the Moon through instruments flown on a number of orbiting spacecraft missions. Considered together, sample-based studies and those from orbit strongly suggest that the Moon is not an anhydrous planetary body, as previously believed. New observations and measurements support the possibility of a wet lunar interior and the presence of distinct reservoirs of water on the lunar surface. Furthermore, an approach combining measurements of water abundance in lunar samples and its hydrogen isotopic composition has proved to be of vital importance to fingerprint and elucidate processes and source(s) involved in giving rise to the lunar water inventory. A number of sources are likely to have contributed to the water inventory of the Moon ranging from primordial water to meteorite-derived water ice through to the water formed during the reaction of solar wind hydrogen with the lunar soil. Perhaps two of the most striking findings from these recent studies are the revelation that at least some portions of the lunar interior are as water-rich as some Mid-Ocean Ridge Basalt source regions on Earth and that the water in the Earth and the Moon probably share a common origin. PMID:25114308

  3. Origins and Emergent Evolution of Life: The Colloid Microsphere Hypothesis Revisited

    NASA Astrophysics Data System (ADS)

    Egel, Richard

    2014-04-01

    Self-replicating molecules, in particular RNA, have long been assumed as key to origins of life on Earth. This notion, however, is not very secure since the reduction of life's complexity to self-replication alone relies on thermodynamically untenable assumptions. Alternative, earlier hypotheses about peptide-dominated colloid self-assembly should be revived. Such macromolecular conglomerates presumably existed in a dynamic equilibrium between confluent growth in sessile films and microspheres detached in turbulent suspension. The first organic syntheses may have been driven by mineral-assisted photoactivation at terrestrial geothermal fields, allowing photo-dependent heterotrophic origins of life. Inherently endowed with rudimentary catalyst activities, mineral-associated organic microstructures can have evolved adaptively toward cooperative `protolife' communities, in which `protoplasmic continuity' was maintained throughout a graded series of `proto-biofilms', `protoorganisms' and `protocells' toward modern life. The proneness of organic microspheres to merge back into the bulk of sessile films by spontaneous fusion can have made large populations promiscuous from the beginning, which was important for the speed of collective evolution early on. In this protein-centered scenario, the emergent coevolution of uncoded peptides, metabolic cofactors and oligoribonucleotides was primarily optimized for system-supporting catalytic capabilities arising from nonribosomal peptide synthesis and nonreplicative ribonucleotide polymerization, which in turn incorporated other reactive micromolecular organics as vitamins and cofactors into composite macromolecular colloid films and microspheres. Template-dependent replication and gene-encoded protein synthesis emerged as secondary means for further optimization of overall efficieny later on. Eventually, Darwinian speciation of cell-like lineages commenced after minimal gene sets had been bundled in transmissible genomes from

  4. Origin and Evolution of Nitrogen on Titan, Enceladus, Triton, and Pluto

    NASA Technical Reports Server (NTRS)

    Atreya, S. K.; Niemann, H. B.; Mahaffy, P. R.; Owen, T. C.

    2007-01-01

    Nitrogen, together with carbon, hydrogen, oxygen, phosphorus and sulfur (CHNOPS), plays a central role in life as we know it. Indeed, molecular nitrogen is the most abundant component of the terrestrial atmosphere, and second only to carbon dioxide on Mars and Venus. The Voyager and Cassini-Huygens observations show that copious nitrogen is present on Titan also, comprising some 95% by volume of this moon's 1500 millibar atmosphere. After water vapor, it may be the most abundant (4%) of the gases around tiny Enceladus, as revealed by the recent Cassini observations. A thin nitrogen atmosphere is found even on the coldest of the solar system bodies, Triton and Pluto. The available evidence on nitrogen isotopes and the heavy noble gases suggests that Titan acquired its nitrogen largely in the form of ammonia. Subsequent chemical evolution, beginning with the photolysis of NH3 on primordial Titan, led to the nitrogen atmosphere we see on Titan today. This is also the scenario for the origin of nitrogen on the terrestrial planets. Contrary to Titan, the colder outer solar system objects, Triton and Pluto, neither had the luxury of receiving much arnmonia in the first place, nor of photolyzing whatever little ammonia they did receive in the planetesimals that formed them. On the other hand, it is plausible the planetesimals were capable of trapping and delivering molecular nitrogen directly to Triton and Pluto, unlike Titan. The origin of nitrogen on Enceladus is somewhat enigmatic. A scenario similar to Titan's, but with a role for the interior processes, may be at work. In this paper, we will discuss the source and loss of nitrogen for the above objects, and why Ganymede, the largest moon in the solar system, is nitrogen starved.

  5. Origin and Evolution of Allopolyploid Wheatgrass Elymus fibrosus (Schrenk) Tzvelev (Poaceae: Triticeae) Reveals the Effect of Its Origination on Genetic Diversity

    PubMed Central

    Gu, Hai-Lan; Wu, Pan-Pan; Yi, Xu; Wang, Wei-Jie; Shi, Han-Feng; Wu, De-Xiang; Sun, Genlou

    2016-01-01

    Origin and evolution of tetraploid Elymus fibrosus (Schrenk) Tzvelev were characterized using low-copy nuclear gene Rpb2 (the second largest subunit of RNA polymerase II), and chloroplast region trnL–trnF (spacer between the tRNA Leu (UAA) gene and the tRNA-Phe (GAA) gene). Ten accessions of E. fibrosus along with 19 Elymus species with StH genomic constitution and diploid species in the tribe Triticeae were analyzed. Chloroplast trnL–trnF sequence data suggested that Pseudoroegneria (St genome) was the maternal donor of E. fibrosus. Rpb2 data confirmed the presence of StH genomes in E. fibrosus, and suggested that St and H genomes in E. fibrosus each is more likely originated from single gene pool. Single origin of E. fibrosus might be one of the reasons causing genetic diversity in E. fibrosus lower than those in E. caninus and E. trachycaulus, which have similar ecological preferences and breeding systems with E. fibrosus, and each was originated from multiple sources. Convergent evolution of St and H copy Rpb2 sequences in some accessions of E. fibrosus might have occurred during the evolutionary history of this allotetraploid. PMID:27936163

  6. Iron: A Key Element for Understanding the Origin and Evolution of Interstellar Dust

    NASA Astrophysics Data System (ADS)

    Dwek, Eli

    2016-07-01

    The origin and depletion of iron differ from all other abundant refractory elements that make up the composition of interstellar dust. Iron is primarily synthesized in Type Ia supernovae (SNe Ia) and in core collapse supernovae (CCSN), and is present in the outflows from AGB stars. Only the latter two are observed to be sources of interstellar dust since searches for dust in SN Ia have provided strong evidence for the absence of any significant mass of dust in their ejecta. Consequently, more than 65% of the iron is injected into the ISM in gaseous form. Yet ultraviolet and X-ray observations along many lines of sight in the ISM show that iron is severely depleted in the gas phase as compared to expected solar abundances. The missing iron, comprising about 90% of the total, is believed to be locked up in interstellar dust. This suggests that most of the missing iron must have precipitated from the ISM gas by a cold accretion onto preexisting silicate, carbon, or composite grains. Iron is thus the only element that requires most of its growth to occur outside the traditional stellar condensation sources. This is a robust statement that does not depend on our evolving understanding of the dust destruction efficiency in the ISM. Reconciling the physical, optical, and chemical properties of such composite grains with their many observational manifestations is a major challenge for understanding the nature and origin of interstellar dust.

  7. Origin of the phase transition in IrTe2: structural modulation and local bonding instability

    SciTech Connect

    Cao, Huibo; Chakoumakos, Bryan C; Yan, Jiaqiang; Zhou, Haidong; Custelcean, Radu; Mandrus, D.; McGuire, Michael A; Singh, David J; Chen, Xin; Yang, Hui

    2013-01-01

    We used X-ray/neutron diffraction to determine the low temperature (LT) structure of IrTe2. A structural modulation was observed with a wavevector of k =(1/5, 0, 1/5) below Ts285 K, accompanied by a structural transition from a trigonal to a triclinic lattice. We also performed the first principles calculations for high temperature (HT) and LT structures, which elucidate the nature of the phase transition and the LT structure. A local bonding instability associated with the Te 5p states is likely the origin of the structural phase transition in IrTe2.

  8. New Insights into the Structure, Origin, and Evolution of Pluto and Charon

    NASA Astrophysics Data System (ADS)

    McKinnon, W. B.; Stern, A.; Weaver, H. A., Jr.; Spencer, J. R.; Nimmo, F.; Lisse, C. M.; Umurhan, O. M.; Moore, J. M.; Buie, M. W.; Porter, S.; Olkin, C.; Young, L. A.; Ennico Smith, K.

    2015-12-01

    The July 2015 New Horizons flyby has removed a long-standing obstacle to understanding the cosmogony of the Pluto-Charon system: the uncertain radius of Pluto. Combined with precise astrometric fits to the barycenter of the Pluto-Charon binary from HST observations of the more distant, small satellites (M. Brozović et al., Icarus 246, 317-329, 2015), the densities of both Pluto and Charon are now known. At the 10% level, the densities of Pluto and Charon are rather similar, as opposed to the more divergent density estimates of years past in which Charon was thought to be substantially icier. In the context of a giant impact origin for binaries, a rock-poor Charon corresponds to an iron-poor Moon in the terrestrial case, with differentiated precursors being implied in both cases. A rock-rich Charon, however, implies that the precursor impacting bodies were at most only partially differentiated — possessing relatively thin ice shells (R.M. Canup, Astron. J. 141, 35, 2011). This suggests some combination of relatively slow and/or late accretion in the ancestral Kuiper belt. A more rock-rich Charon also implies a more vigorous geological history, all other things being equal. For Pluto, the evolution to the surface of a substantial mass of supervolatile ices increases the likelihood that internal volatiles such as ammonia and methanol have been sequestered in an internal, aqueous layer (or ocean).

  9. Evolution of a complex behavior: the origin and initial diversification of foliar galling by Permian insects

    NASA Astrophysics Data System (ADS)

    Schachat, Sandra R.; Labandeira, Conrad C.

    2015-04-01

    A central notion of the early evolution of insect galling is that this unique behavior was uncommon to rare before the diversification of angiosperms 135 to 125 m.yr. ago. However, evidence accumulated during recent years shows that foliar galls were diverse and locally abundant as early as the Permian Period, 299 to 252 m.yr. ago. In particular, a diversity of leaf galling during the Early Permian has recently been documented by the plant-damage record of foliar galls and, now, our interpretation of the body-fossil record of culprit insect gallers. Small size is a prerequisite for gallers. Wing-length measurements of Permian insects indicate that several small-bodied hemipteroid lineages originated early during the Permian, some descendant lineages of which gall the leaves of seed plants to the present day. The earliest foliar gallers likely were Protopsyllidiidae (Hemiptera) and Lophioneuridae (Thripida). Much of the Early Permian was a xeric interval, and modern galls are most common in dry, extra-tropical habitats such as scrubland and deserts. Plant-damage, insect body fossils, and the paleoclimate record collectively support the ecological expansion of foliar galling during the Early Permian and its continued expansion through the Late Permian.

  10. Elsevier Trophoblast Research Award Lecture: origin, evolution and future of placenta miRNAs.

    PubMed

    Morales-Prieto, D M; Ospina-Prieto, S; Schmidt, A; Chaiwangyen, W; Markert, U R

    2014-02-01

    MicroRNAs (miRNAs) regulate the expression of a large number of genes in plants and animals. Placental miRNAs appeared late in evolution and can be found only in mammals. Nevertheless, these miRNAs are constantly under evolutionary pressure. As a consequence, miRNA sequences and their mRNA targets may differ between species, and some miRNAs can only be found in humans. Their expression can be tissue- or cell-specific and can vary time-dependently. Human placenta tissue exhibits a specific miRNA expression pattern that dynamically changes during pregnancy and is reflected in the maternal plasma. Some placental miRNAs are involved in or associated with major pregnancy disorders, such as preeclampsia, intrauterine growth restriction or preterm delivery and, therefore, have a strong potential for usage as sensitive and specific biomarkers. In this review we summarize current knowledge on the origin of placental miRNAs, their expression in humans with special regard to trophoblast cells, interspecies differences, and their future as biomarkers. It can be concluded that animal models for human reproduction have a different panel of miRNAs and targets, and can only partly reflect or predict the situation in humans.

  11. Evolution of a complex behavior: the origin and initial diversification of foliar galling by Permian insects.

    PubMed

    Schachat, Sandra R; Labandeira, Conrad C

    2015-04-01

    A central notion of the early evolution of insect galling is that this unique behavior was uncommon to rare before the diversification of angiosperms 135 to 125 m.yr. ago. However, evidence accumulated during recent years shows that foliar galls were diverse and locally abundant as early as the Permian Period, 299 to 252 m.yr. ago. In particular, a diversity of leaf galling during the Early Permian has recently been documented by the plant-damage record of foliar galls and, now, our interpretation of the body-fossil record of culprit insect gallers. Small size is a prerequisite for gallers. Wing-length measurements of Permian insects indicate that several small-bodied hemipteroid lineages originated early during the Permian, some descendant lineages of which gall the leaves of seed plants to the present day. The earliest foliar gallers likely were Protopsyllidiidae (Hemiptera) and Lophioneuridae (Thripida). Much of the Early Permian was a xeric interval, and modern galls are most common in dry, extra-tropical habitats such as scrubland and deserts. Plant-damage, insect body fossils, and the paleoclimate record collectively support the ecological expansion of foliar galling during the Early Permian and its continued expansion through the Late Permian.

  12. Origin and evolution of the dependent lineages in the genetic caste determination system of Pogonomyrmex ants.

    PubMed

    Sirviö, Anu; Pamilo, Pekka; Johnson, Robert A; Page, Robert E; Gadau, Jürgen

    2011-03-01

    Hybridizing harvester ants of the Pogonomyrmex barbatus/rugosus complex have an exceptional genetic caste determination (GCD) mechanism. We combined computer simulations, population genomics, and linkage mapping using >1000 nuclear AFLP markers and a partial mtDNA sequence to explore the genetic architecture and origin of the dependent lineages. Our samples included two pairs of hybridizing lineages, and the mitochondrial and nuclear data showed contradicting affinities between them. Clustering of individual genotypes based on nuclear markers indicated some exceptions to the general GCD system, that is, interlineage hybrid genes as well as some pure-line workers. A genetic linkage map of P. rugosus showed one of the highest recombination rates ever measured in insects (14.0 cM/Mb), supporting the view that social insects are characterized by high recombination rates. The population data had 165 markers in which sibling pairs showed a significant genetic difference depending on the caste. The differences were scattered in the genome; 13 linkage groups had loci with F(ST)>0.9 between the hybridizing lineages J1 and J2.The mapping results and the population data indicate that the dependent lineages have been initially formed through hybridization at different points in time but the role of introgression has been insignificant in their later evolution.

  13. The origin and geologic evolution of the East Continent Rift Basin

    SciTech Connect

    Drahovzal, J.A. . Kentucky Geological Survey)

    1992-01-01

    The East Continent Rift Basin (ECRB) is a newly recognized, dominantly sedimentary-volcanic Proterozoic rift basin that apparently represents the southern extension of the Keweenawan Midcontinent Rift. The ECRB extends from central Michigan at least as far south as south-central Kentucky. The inferred age of the rift fill is approximately 1,000 Ma. Evidence supporting a rift origin for the ECRB includes: interbedding of continental flood basalts and felsic volcanics with siliciclastics; sedimentary fill consisting of distal, arid-climate alluvial fan sediments that lack metamorphic lithologies; close proximity and similar lithologic succession to the Keweenawan rift-fill rocks of the Michigan Basin; and inferred marginal block faulting of Granite-Rhyolite Province rocks near the western edge of the ECRB. ECRB evolution is interpreted as follows: (1) formation of Granite-Rhyolite Province rocks (1,500--1,340 Ma); (2) Keweenawan crustal extension and rifting with development of central mafic complexes, emplacement of volcanic rocks, and deposition of siliciclastic fill from eroded marginal Granite-Rhyolite Province tilted fault blocks (ca 1,000 Ma); (3) overthrusting of the Grenville allochthon and associated foreland thrusting and folding of the rift sequence rocks together with deposition of foreland basin sediments (975---890 Ma); (4) Late Proterozoic erosional removal of the foreland basin sediments and interpreted wrench faulting along the Grenville Front (post-975 to pre-570 Ma); and (5) tectonic inversion, with the ECRB area remaining relatively high during major cambrian subsidence in central Kentucky (590--510 Ma).

  14. NEAR-EARTH BINARIES AND TRIPLES: ORIGIN AND EVOLUTION OF SPIN-ORBITAL PROPERTIES

    SciTech Connect

    Fang, Julia; Margot, Jean-Luc

    2012-01-15

    In the near-Earth asteroid population, binary and triple systems have been discovered with mutual orbits that have significant eccentricities as well as large semimajor axes. All known systems with eccentric orbits and all widely separated primary-satellite pairs have rapidly rotating satellites. Here, we study processes that can elucidate the origin of these spin-orbital properties. Binary formation models based on rotational fissioning can reproduce asynchronous satellites on orbits with high eccentricities and a wide range of separations, but do not match observed properties. We explore whether any evolutionary mechanisms can link the spin and orbital parameters expected from post-fission dynamics to those observed today. We investigate four processes: tidal torques, radiative perturbations (BYORP), close planetary encounters, and Kozai oscillations. We find that a combination of post-fission dynamics and tidal evolution can explain nearly all the spin-orbit properties in a sample of nine well-characterized near-Earth binaries and triples. The other mechanisms may act as well but are not required to explain the observed data. Lastly, we describe evolutionary pathways between observed spin-orbital states including synchronous and circular, asynchronous and circular, and asynchronous and eccentric configurations.

  15. Activity origin and catalyst design principles for electrocatalytic hydrogen evolution on heteroatom-doped graphene

    NASA Astrophysics Data System (ADS)

    Jiao, Yan; Zheng, Yao; Davey, Kenneth; Qiao, Shi-Zhang

    2016-10-01

    The hydrogen evolution reaction (HER) is a fundamental process in electrocatalysis and plays an important role in energy conversion through water splitting to produce hydrogen. Effective candidates for HER are often based on noble metals or transition metal dichalcogenides, while carbon-based metal-free electrocatalysts generally demonstrate poorer activity. Here we report evaluation of a series of heteroatom-doped graphene materials as efficient HER electrocatalysts by combining spectroscopic characterization, electrochemical measurements, and density functional theory calculations. Results of theoretical computations are shown to be in good agreement with experimental observations regarding the intrinsic electrocatalytic activity and the HER reaction mechanism. As a result, we establish a HER activity trend for graphene-based materials, and explore their reactivity origin to guide the design of more efficient electrocatalysts. We predict that by rationally modifying particular experimentally achievable physicochemical characteristics, a practically realizable graphene-based material will have the potential to exceed the performance of the metal-based benchmark for HER.

  16. Evolution of a CAM anatomy predates the origins of Crassulacean acid metabolism in the Agavoideae (Asparagaceae).

    PubMed

    Heyduk, Karolina; McKain, Michael R; Lalani, Falak; Leebens-Mack, James

    2016-12-01

    Crassulacean acid metabolism (CAM) is a modified form of photosynthesis that has arisen independently at least 35 times in flowering plants. The occurrence of CAM is often correlated with shifts to arid, semiarid, or epiphytic habits, as well as transitions in leaf morphology (e.g. increased leaf thickness) and anatomy (e.g. increased cell size and packing). We assess shifts between C3 and CAM photosynthesis in the subfamily Agavoideae (Asparagaceae) through phylogenetic analysis of targeted loci captured from the nuclear and chloroplast genomes of over 60 species. Carbon isotope data was used as a proxy for mode of photosynthesis in extant species and ancestral states were estimated on the phylogeny. Ancestral character state mapping suggests three independent origins of CAM in the Agavoideae. CAM species differ from C3 species in climate space and are found to have thicker leaves with densely packed cells. C3 ancestors of CAM species show a predisposition toward CAM-like morphology. Leaf characteristics in the ancestral C3 species may have enabled the repeated evolution of CAM in the Agavoideae subfamily. Anatomical changes, including a tendency toward 3D venation, may have initially arisen in C3 ancestors in response to aridity as a way to increase leaf succulence for water storage.

  17. The origin and evolution of vertebrate sex chromosomes and dosage compensation

    PubMed Central

    Livernois, A M; Graves, J A M; Waters, P D

    2012-01-01

    In mammals, birds, snakes and many lizards and fish, sex is determined genetically (either male XY heterogamy or female ZW heterogamy), whereas in alligators, and in many reptiles and turtles, the temperature at which eggs are incubated determines sex. Evidently, different sex-determining systems (and sex chromosome pairs) have evolved independently in different vertebrate lineages. Homology shared by Xs and Ys (and Zs and Ws) within species demonstrates that differentiated sex chromosomes were once homologous, and that the sex-specific non-recombining Y (or W) was progressively degraded. Consequently, genes are left in single copy in the heterogametic sex, which results in an imbalance of the dosage of genes on the sex chromosomes between the sexes, and also relative to the autosomes. Dosage compensation has evolved in diverse species to compensate for these dose differences, with the stringency of compensation apparently differing greatly between lineages, perhaps reflecting the concentration of genes on the original autosome pair that required dosage compensation. We discuss the organization and evolution of amniote sex chromosomes, and hypothesize that dosage insensitivity might predispose an autosome to evolving function as a sex chromosome. PMID:22086077

  18. Origin and evolution of the long non-coding genes in the X-inactivation center.

    PubMed

    Romito, Antonio; Rougeulle, Claire

    2011-11-01

    Random X chromosome inactivation (XCI), the eutherian mechanism of X-linked gene dosage compensation, is controlled by a cis-acting locus termed the X-inactivation center (Xic). One of the striking features that characterize the Xic landscape is the abundance of loci transcribing non-coding RNAs (ncRNAs), including Xist, the master regulator of the inactivation process. Recent comparative genomic analyses have depicted the evolutionary scenario behind the origin of the X-inactivation center, revealing that this locus evolved from a region harboring protein-coding genes. During mammalian radiation, this ancestral protein-coding region was disrupted in the marsupial group, whilst it provided in eutherian lineage the starting material for the non-translated RNAs of the X-inactivation center. The emergence of non-coding genes occurred by a dual mechanism involving loss of protein-coding function of the pre-existing genes and integration of different classes of mobile elements, some of which modeled the structure and sequence of the non-coding genes in a species-specific manner. The rising genes started to produce transcripts that acquired function in regulating the epigenetic status of the X chromosome, as shown for Xist, its antisense Tsix, Jpx, and recently suggested for Ftx. Thus, the appearance of the Xic, which occurred after the divergence between eutherians and marsupials, was the basis for the evolution of random X inactivation as a strategy to achieve dosage compensation.

  19. PLANET TOPERS: Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their ReservoirS

    NASA Astrophysics Data System (ADS)

    Dehant, Veronique; Breuer, Doris; Claeys, Philippe; Debaille, Vinciane; De Keyser, Johan; Javaux, Emmanuelle; Goderis, Steven; Karatekin, Ozgur; Mattielli, Nadine; Noack, Lena; Spohn, Tilman; Carine Vandaele, Ann; Vanhaecke, Frank; Van Hoolst, Tim; Wilquet, Valerie

    2013-04-01

    The PLANET TOPERS (Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their ReservoirS) group is an Inter-university attraction pole (IAP) addressing the question of habitability in our Solar System. Habitability is commonly understood as "the potential of an environment (past or present) to support life of any kind" (Steele et al., 2005, http://mepag.jpl.nasa.gov/reports/archive.html). Based on the only known example of Earth, the concept refers to whether environmental conditions are available that could eventually support life, even if life does not currently exist (Javaux and Dehant, 2010, Astron. Astrophys. Rev., 18, 383-416, DOI: 10.1007/s00159-010-0030-4). Life includes properties such as consuming nutrients and producing waste, the ability to reproduce and grow, pass on genetic information, evolve, and adapt to the varying conditions on a planet (Sagan, 1970, Encyclopedia Britannica, 22, 964-981). Terrestrial life requires liquid water. The stability of liquid water at the surface of a planet defines a habitable zone (HZ) around a star. In the Solar System, it stretches between Venus and Mars, but excludes these two planets. If the greenhouse effect is taken into account, the habitable zone may have included early Mars while the case for Venus is still debated. Important geodynamic processes affect the habitability conditions of a planet. As envisaged by the group, this IAP develops and closely integrates the geophysical, geological, and biological aspects of habitability with a particular focus on Earth neighboring planets, Mars and Venus. It works in an interdisciplinary approach to understand habitability and in close collaboration with another group, the Helmholtz Alliance "Life and Planet Evolution", which has similar objectives. The dynamic processes, e.g. internal dynamo, magnetic field, atmosphere, plate tectonics, mantle convection, volcanism, thermo-tectonic evolution, meteorite impacts, and erosion, modify the planetary surface

  20. On the origin of residual strain in shape memory alloys: experimental investigation on evolutions in the microstructure of CuAlBe during complex thermomechanical loadings

    NASA Astrophysics Data System (ADS)

    Barati, M.; Arbab Chirani, S.; Kadkhodaei, M.; Saint-Sulpice, L.; Calloch, S.

    2017-02-01

    The behaviors of shape memory alloys (SMAs) strongly depend on the presence of different phases: austenite, thermally-induced martensite and stress-induced martensite. Consequently, it is important to know the phase volume fraction of each phases and their evolution during thermomechanical loadings. In this work, a three-phase proportioning method based on electric resistivity variation of a CuAlBe SMA is proposed. Simple thermomechanical loadings (i. e. pseudoplasticity and pseudoelasticity), one-way shape memory effect, recovery stress, assisted two-way memory effect at different level of stress and cyclic pseudoelasticity tests are investigated. Based on the electric resistivity results, during each loading path, evolution of the microstructure is determined. The origin of residual strain observed during the considered thermomechanical loadings is discussed. A special attention is paid to two-way shape memory effect generated after considered cyclic loadings and its relation with the developed residual strain. These results permit to identify and to validate the macroscopic models of SMAs behaviors.

  1. Genetic-evolutionary studies on cultivated cannas : VI. Origin and evolution of ornamental taxa.

    PubMed

    Khoshoo, T N; Mukherjee, I

    1970-01-01

    Hybridization has played a dominant and decisive role in the origin of ornamental cannas. This has been made possible by the ecospecific differentiation of the parental species, which implies lack of barriers and a good deal of recombination associated with reasonably high fertility.Colour differences between species are controlled by a number of genes and their intensifiers, inhibitors, lethals, etc. From recombination in interspecific hybrids of such a wide range of genes, segregating simultaneously and involving complex segregation, arises a wide array of heterozygous genotypes with new colours and colour combinations, releasing much genetic diversity.Hybridization has also been responsible for transgressive segregation, particularly in length and breadth of staminodia and luxuriance, affecting not only plant height but also flower size. Perhaps the most important single factor responsible for the evolution of ornamental cannas has been the repeated cycles of hybridization which have led to the breakage of size and other barriers; this seems to have been exploited continuously until very large flower size was built up and combined with other useful vegetative and floral characters such as colour and number of flowers per inflorescence, extended blooming period, cold resistance, etc. The efficient vegetative propagation made fixing of the useful genotypes no problem, although they may contain a high degree of heterozygosity and sexual sterility.Along these lines, Année (hybrids between C. indica and C. glauca) and Ehemann (hybrids between C. iridiflora and C. warscwiczii) cannas came into being in 1848 and 1863 respectively. Although both were a distinct improvement over the original species, they were still relatively small-flowered and major improvements came roundabout 1868, when Crozy, Gladiolus or French Dwarf cannas (C. X generalis Bailey) were released. This group arose from hybrids and back crosses of the first two groups and contains diploids

  2. Direct observation of electronic-liquid-crystal phase transitions and their microscopic origin in La1/3Ca2/3MnO3

    PubMed Central

    Tao, J.; Sun, K.; Yin, W.-G.; Wu, L.; Xin, H.; Wen, J. G.; Luo, W.; Pennycook, S. J.; Tranquada, J. M.; Zhu, Y.

    2016-01-01

    The ground-state electronic order in doped manganites is frequently associated with a lattice modulation, contributing to their many interesting properties. However, measuring the thermal evolution of the lattice superstructure with reciprocal-space probes alone can lead to ambiguous results with competing interpretations. Here we provide direct observations of the evolution of the superstructure in La1/3Ca2/3MnO3 in real space, as well as reciprocal space, using transmission electron microscopic (TEM) techniques. We show that the transitions are the consequence of a proliferation of dislocations plus electronic phase separation. The resulting states are well described by the symmetries associated with electronic-liquid-crystal (ELC) phases. Moreover, our results resolve the long-standing controversy over the origin of the incommensurate superstructure and suggest a new structural model that is consistent with recent theoretical calculations. PMID:27874069

  3. Direct observation of electronic-liquid-crystal phase transitions and their microscopic origin in La1/3Ca2/3MnO3

    DOE PAGES

    Tao, J.; Sun, K.; Yin, W. -G.; ...

    2016-11-22

    The ground-state electronic order in doped manganites is frequently associated with a lattice modulation, contributing to their many interesting properties. However, measuring the thermal evolution of the lattice superstructure with reciprocal-space probes alone can lead to ambiguous results with competing interpretations. Here, we provide direct observations of the evolution of the superstructure in La1/3Ca2/3MnO3 in real space, as well as reciprocal space, using transmission electron microscopic (TEM) techniques. We show that the transitions are the consequence of a proliferation of dislocations plus electronic phase separation. The resulting states are well described by the symmetries associated with electronic-liquid-crystal (ELC) phases. Furthermore,more » our results resolve the long-standing controversy over the origin of the incommensurate superstructure and suggest a new structural model that is consistent with recent theoretical calculations.« less

  4. Direct observation of electronic-liquid-crystal phase transitions and their microscopic origin in La1/3Ca2/3MnO3

    NASA Astrophysics Data System (ADS)

    Tao, J.; Sun, K.; Yin, W.-G.; Wu, L.; Xin, H.; Wen, J. G.; Luo, W.; Pennycook, S. J.; Tranquada, J. M.; Zhu, Y.

    2016-11-01

    The ground-state electronic order in doped manganites is frequently associated with a lattice modulation, contributing to their many interesting properties. However, measuring the thermal evolution of the lattice superstructure with reciprocal-space probes alone can lead to ambiguous results with competing interpretations. Here we provide direct observations of the evolution of the superstructure in La1/3Ca2/3MnO3 in real space, as well as reciprocal space, using transmission electron microscopic (TEM) techniques. We show that the transitions are the consequence of a proliferation of dislocations plus electronic phase separation. The resulting states are well described by the symmetries associated with electronic-liquid-crystal (ELC) phases. Moreover, our results resolve the long-standing controversy over the origin of the incommensurate superstructure and suggest a new structural model that is consistent with recent theoretical calculations.

  5. Direct observation of electronic-liquid-crystal phase transitions and their microscopic origin in La1/3Ca2/3MnO3.

    PubMed

    Tao, J; Sun, K; Yin, W-G; Wu, L; Xin, H; Wen, J G; Luo, W; Pennycook, S J; Tranquada, J M; Zhu, Y

    2016-11-22

    The ground-state electronic order in doped manganites is frequently associated with a lattice modulation, contributing to their many interesting properties. However, measuring the thermal evolution of the lattice superstructure with reciprocal-space probes alone can lead to ambiguous results with competing interpretations. Here we provide direct observations of the evolution of the superstructure in La1/3Ca2/3MnO3 in real space, as well as reciprocal space, using transmission electron microscopic (TEM) techniques. We show that the transitions are the consequence of a proliferation of dislocations plus electronic phase separation. The resulting states are well described by the symmetries associated with electronic-liquid-crystal (ELC) phases. Moreover, our results resolve the long-standing controversy over the origin of the incommensurate superstructure and suggest a new structural model that is consistent with recent theoretical calculations.

  6. Kinematic evolution of the southwestern Arabian continental margin: implications for the origin of the Red Sea

    NASA Astrophysics Data System (ADS)

    Voggenreiter, W.; Hötzl, H.

    The tectonic and magnetic evolution of the Jizan coastal plain (Tihama Asir) in southwest Arabia was dominated by SW-NE lithospheric extension related to the development of the Red Sea Rift. A well-exposed, isotopically-dated succession of magmatic rocks (Jizan Group volcanics, Tihama Asir Magmatic Complex) allows a kinematic analysis for this part of the Arabian Red Sea margin. A mafic dyke swarm and several generations of roughly NW-trending normal faults characterized the continental rift stage from Oligocene to early Miocene time. Major uplift of the Arabian graben shoulder probably began about 14 Ma ago. By this time, extension and magmatism ceased in the Jizan area and were followed by an approximately 10 Ma interval of tectonic and magmatic quiescence. A second phase of extension began in the Pliocene and facilitated a vast outpouring of alkaliolivine basalts on the coastal plain. The geometry of faulting in the Jizan area supports a Wernicke-type simple-shear mechanism of continental rifting for the southern Arabian continental margin of the Red Sea.

  7. Chromosome evolution with naked eye: Palindromic context of the life origin

    NASA Astrophysics Data System (ADS)

    Larionov, Sergei; Loskutov, Alexander; Ryadchenko, Eugeny

    2008-03-01

    Based on the representation of the DNA sequence as a two-dimensional (2D) plane walk, we consider the problem of identification and comparison of functional and structural organizations of chromosomes of different organisms. According to the characteristic design of 2D walks we identify telomere sites, palindromes of various sizes and complexity, areas of ribosomal RNA, transposons, as well as diverse satellite sequences. As an interesting result of the application of the 2D walk method, a new duplicated gigantic palindrome in the X human chromosome is detected. A schematic mechanism leading to the formation of such a duplicated palindrome is proposed. Analysis of a large number of the different genomes shows that some chromosomes (or their fragments) of various species appear as imperfect gigantic palindromes, which are disintegrated by many inversions and the mutation drift on different scales. A spread occurrence of these types of sequences in the numerous chromosomes allows us to develop a new insight of some accepted points of the genome evolution in the prebiotic phase.

  8. Chromosome evolution with naked eye: palindromic context of the life origin.

    PubMed

    Larionov, Sergei; Loskutov, Alexander; Ryadchenko, Eugeny

    2008-03-01

    Based on the representation of the DNA sequence as a two-dimensional (2D) plane walk, we consider the problem of identification and comparison of functional and structural organizations of chromosomes of different organisms. According to the characteristic design of 2D walks we identify telomere sites, palindromes of various sizes and complexity, areas of ribosomal RNA, transposons, as well as diverse satellite sequences. As an interesting result of the application of the 2D walk method, a new duplicated gigantic palindrome in the X human chromosome is detected. A schematic mechanism leading to the formation of such a duplicated palindrome is proposed. Analysis of a large number of the different genomes shows that some chromosomes (or their fragments) of various species appear as imperfect gigantic palindromes, which are disintegrated by many inversions and the mutation drift on different scales. A spread occurrence of these types of sequences in the numerous chromosomes allows us to develop a new insight of some accepted points of the genome evolution in the prebiotic phase.

  9. Gravitational instability in two-phase disks and the origin of the moon

    NASA Technical Reports Server (NTRS)

    Thompson, Christopher; Stevenson, David J.

    1988-01-01

    Two-phase disks may be gravitationally unstable at temperatures or surface densities at which a disk composed of either single phase would be highly stable. It is argued that two-phase disks can achieve a marginally unstable state (in addition to a highly unstable state that leads to fragmentation), limited by the ability of the photosphere to radiate the energy dissipated in the disk. A self-consistent prescription for the viscosity induced by the slow instabilities is provided. Two-phase disks are more centrally condensed than single-phase disks, and their secular cooling time may be comparable to their spreading time. A circumterrestrial disk of sufficient mass to form the moon provides a detailed example of all the preceding points. Its stability, structure, and dynamical evolution are investigated, and it is concluded that its spreading time is short (about 100 yr); the moon is formed molten, or partially molten; the moon's initial orbit lies in the earth's equatorial plane; and only a small fraction of the disk mass is lost in a wind, although this may represent a substantial fraction of volatiles. Most of these conclusions are independent of how the disk was formed, e.g., from a giant impact.

  10. Phase transitions as the origin of large scale structure in the universe

    NASA Technical Reports Server (NTRS)

    Turok, Neil

    1988-01-01

    A review of the formation of large scale structure through gravitational growth of primordial perturbations is given. This is followed by a discussion of how symmetry breaking phase transitions in the early universe might have produced the required perturbations, in particular through the formation and evolution of a network of cosmic strings. Finally, the statistical mechanics of string networks, for both cosmic and fundamental strings is discussed, leading to some more speculative ideas on the possible role of fundamental strings (superstrings or heterotic strings) in the very early universe.

  11. Titanium carbide and titania phases on Antarctic ice particles of probable extraterrrestrial origin

    NASA Technical Reports Server (NTRS)

    Zolensky, M. E.; Pun, A.; Thomas, K. L.

    1989-01-01

    Two unique titania-rich particles, found within ancient Antarctic ice have been discovered and characterized, and are believed to be of extraterrestrial origin. Both particles contain abundant submicron-sized crystals of Magneli phases (Ti(n)O(2n-1). In addition, one particle contains a core of TiC. Whereas the Magneli phases would have been stable in the early solar nebula, and so probably formed there, the TiC is more likely to have condensed in the cool, dusty, carbon-rich outer shell of a red giant star. It is suggested that both particles are interplanetary dust particles whose Magneli phases carry a record of the PO2-T conditions of the early solar nebula. It is further suggested that the TiC grain in particle 705 is remnant interstellar dust.

  12. Phase-field modeling of microstructure evolutions in magnetic materials

    PubMed Central

    Koyama, Toshiyuki

    2008-01-01

    Recently, the phase-field method has been extended and utilized across many fields of materials science. Since this method can incorporate, systematically, the effect of the coherency induced by lattice mismatch and the applied stress as well as the external electrical and magnetic fields, it has been applied to many material processes including solidification, solid-state phase transformations and various types of complex microstructure changes. In this paper, we focus on the recent phase-field simulations of real magnetic materials, and the simulation method for magnetic materials is explained comprehensively. Several applications of the phase-field method to clarifying the microstructure changes in magnetic materials, such as Ni2MnGa ferromagnetic shape memory alloy, FePt nanogranular thin film, Co–Sm–Cu rare-earth magnet, Fe–Cr–Co spinodal magnet, and Fe–C steel with external magnetic field, are demonstrated. Furthermore, the general concept of the effective strategy for controlling microstructure in magnetic materials is proposed. PMID:27877924

  13. Phase Transition Behavior in a Neutral Evolution Model

    NASA Astrophysics Data System (ADS)

    King, Dawn; Scott, Adam; Maric, Nevena; Bahar, Sonya

    2014-03-01

    The complexity of interactions among individuals and between individuals and the environment make agent based modeling ideal for studying emergent speciation. This is a dynamically complex problem that can be characterized via the critical behavior of a continuous phase transition. Concomitant with the main tenets of natural selection, we allow organisms to reproduce, mutate, and die within a neutral phenotype space. Previous work has shown phase transition behavior in an assortative mating model with variable fitness landscapes as the maximum mutation size (μ) was varied (Dees and Bahar, 2010). Similarly, this behavior was recently presented in the work of Scott et al. (2013), even on a completely neutral landscape, for bacterial-like fission as well as for assortative mating. Here we present another neutral model to investigate the `critical' phase transition behavior of three mating types - assortative, bacterial, and random - in a phenotype space as a function of the percentage of random death. Results show two types of phase transitions occurring for the parameters of the population size and the number of clusters (an analogue of species), indicating different evolutionary dynamics for system survival and clustering. This research was supported by funding from: University of Missouri Research Board and James S. McDonnell Foundation.

  14. Evolution stings: the origin and diversification of scorpion toxin peptide scaffolds.

    PubMed

    Sunagar, Kartik; Undheim, Eivind A B; Chan, Angelo H C; Koludarov, Ivan; Muñoz-Gómez, Sergio A; Antunes, Agostinho; Fry, Bryan G

    2013-12-13

    The episodic nature of natural selection and the accumulation of extreme sequence divergence in venom-encoding genes over long periods of evolutionary time can obscure the signature of positive Darwinian selection. Recognition of the true biocomplexity is further hampered by the limited taxon selection, with easy to obtain or medically important species typically being the subject of intense venom research, relative to the actual taxonomical diversity in nature. This holds true for scorpions, which are one of the most ancient terrestrial venomous animal lineages. The family Buthidae that includes all the medically significant species has been intensely investigated around the globe, while almost completely ignoring the remaining non-buthid families. Australian scorpion lineages, for instance, have been completely neglected, with only a single scorpion species (Urodacus yaschenkoi) having its venom transcriptome sequenced. Hence, the lack of venom composition and toxin sequence information from an entire continent's worth of scorpions has impeded our understanding of the molecular evolution of scorpion venom. The molecular origin, phylogenetic relationships and evolutionary histories of most scorpion toxin scaffolds remain enigmatic. In this study, we have sequenced venom gland transcriptomes of a wide taxonomical diversity of scorpions from Australia, including buthid and non-buthid representatives. Using state-of-art molecular evolutionary analyses, we show that a majority of CSα/β toxin scaffolds have experienced episodic influence of positive selection, while most non-CSα/β linear toxins evolve under the extreme influence of negative selection. For the first time, we have unraveled the molecular origin of the major scorpion toxin scaffolds, such as scorpion venom single von Willebrand factor C-domain peptides (SV-SVC), inhibitor cystine knot (ICK), disulphide-directed beta-hairpin (DDH), bradykinin potentiating peptides (BPP), linear non-disulphide bridged

  15. Origin of the genetic code: was the original mechanism lost or altered during evolution after the universal genetic code was virtually frozen?

    NASA Astrophysics Data System (ADS)

    Trevors, T. J.

    2011-10-01

    The natural mechanism that organized the corresponding coding between nucleic acids and the corresponding amino acids is still unknown. It is also not known if molecular remnants or relics of this mechanism are present in some living cells as an altered mechanism or the original mechanism was lost during evolution. Prokaryotic organisms may be a plausible location for discovering such a mechanism as they are the ancient species on the Earth. The hypothesis is proposed that the molecular mechanism that generated the universal genetic code was lost, or altered for other functions, once the genetic code was virtually frozen/fixed. By virtually freezing the code, evolution could proceed at a faster pace without generating a new genetic coding system for different species. Different combinations of the code emerged in the evolving species. This is an efficient mechanism of generating new code combinations from an existing genetic code.

  16. Local microstructure evolution at shear bands in metallic glasses with nanoscale phase separation

    PubMed Central

    He, Jie; Kaban, Ivan; Mattern, Norbert; Song, Kaikai; Sun, Baoan; Zhao, Jiuzhou; Kim, Do Hyang; Eckert, Jürgen; Greer, A. Lindsay

    2016-01-01

    At room temperature, plastic flow of metallic glasses (MGs) is sharply localized in shear bands, which are a key feature of the plastic deformation in MGs. Despite their clear importance and decades of study, the conditions for formation of shear bands, their structural evolution and multiplication mechanism are still under debate. In this work, we investigate the local conditions at shear bands in new phase-separated bulk MGs containing glassy nanospheres and exhibiting exceptional plasticity under compression. It is found that the glassy nanospheres within the shear band dissolve through mechanical mixing driven by the sharp strain localization there, while those nearby in the matrix coarsen by Ostwald ripening due to the increased atomic mobility. The experimental evidence demonstrates that there exists an affected zone around the shear band. This zone may arise from low-strain plastic deformation in the matrix between the bands. These results suggest that measured property changes originate not only from the shear bands themselves, but also from the affected zones in the adjacent matrix. This work sheds light on direct visualization of deformation-related effects, in particular increased atomic mobility, in the region around shear bands. PMID:27181922

  17. PLANET TOPERS: Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their ReservoirS

    NASA Astrophysics Data System (ADS)

    Dehant, Véronique; Breuer, Doris; Claeys, Philippe; Debaille, Vinciane; de Keyser, Johan; Javaux, Emmanuelle; Goderis, Steven; Karatekin, Ozgur; Matielli, Nadine; Noack, Lena; Spohn, Tilman; Carine Vandaele, Ann; Vanhaecke, Frank; van Hoolst, Tim; Wilquet, Valérie; The PLANET Topers Team

    2015-04-01

    The PLANET TOPERS (Planets, Tracing the Transfer, Origin, Preservation, and Evolution of their ReservoirS) group is an Inter-university attraction pole (IAP) addressing the question of habitability in our Solar System. Based on the only known example of Earth, the concept refers to whether environmental conditions are available that could eventually support life, even if life does not currently exist. Life is believed to require liquid water, but important geodynamic processes affect the habitability conditions of a planet. The PLANET TOPERS group develops and closely integrates the geophysical, geological, and biological aspects of habitability with a particular focus on Earth neighboring planets, Mars and Venus. Habitability is commonly understood as "the potential of an environment (past or present) to support life of any kind" (Steele et al., 2005). Based on the only known example of Earth, the concept refers to whether environmental conditions are available that could eventually support life, even if life does not currently exist (Javaux and Dehant, 2010). Life includes properties such as consuming nutrients and producing waste, the ability to reproduce and grow, pass on genetic information, evolve, and adapt to the varying conditions on a planet (Sagan, 1970). Terrestrial life requires liquid water. The common view, however, is that extraterrestrial life would probably be based on organic chemistry in a water solvent (Pace, 2001) although alternative biochemistries have been hypothesized. The stability of liquid water at the surface of a planet defines a habitable zone (HZ) around a star. In the Solar System, it stretches between Venus and Mars, but excludes these two planets. If the greenhouse effect is taken into account, the habitable zone may have included early Mars while the case for Venus is still debated. The dynamic processes, e.g. internal dynamo, magnetic field, atmosphere, plate tectonics, mantle convection, volcanism, thermo-tectonic evolution

  18. Origin and evolution of the panarthropod head - A palaeobiological and developmental perspective.

    PubMed

    Ortega-Hernández, Javier; Janssen, Ralf; Budd, Graham E

    2016-12-18

    The panarthropod head represents a complex body region that has evolved through the integration and functional specialization of the anterior appendage-bearing segments. Advances in the developmental biology of diverse extant organisms have led to a substantial clarity regarding the relationships of segmental homology between Onychophora (velvet worms), Tardigrada (water bears), and Euarthropoda (e.g. arachnids, myriapods, crustaceans, hexapods). The improved understanding of the segmental organization in panarthropods offers a novel perspective for interpreting the ubiquitous Cambrian fossil record of these successful animals. A combined palaeobiological and developmental approach to the study of the panarthropod head through deep time leads us to propose a consensus hypothesis for the intricate evolutionary history of this important tagma. The contribution of exceptionally preserved brains in Cambrian fossils - together with the recognition of segmentally informative morphological characters - illuminate the polarity for major anatomical features. The euarthropod stem-lineage provides a detailed view of the step-wise acquisition of critical characters, including the origin of a multiappendicular head formed by the fusion of several segments, and the transformation of the ancestral protocerebral limb pair into the labrum, following the postero-ventral migration of the mouth opening. Stem-group onychophorans demonstrate an independent ventral migration of the mouth and development of a multisegmented head, as well as the differentiation of the deutocerebral limbs as expressed in extant representatives. The anterior organization of crown-group Tardigrada retains several ancestral features, such as an anterior-facing mouth and one-segmented head. The proposed model aims to clarify contentious issues on the evolution of the panarthropod head, and lays the foundation from which to further address this complex subject in the future.

  19. Different Origins or Different Evolutions? Decoding the Spectral Diversity Among C-type Asteroids

    NASA Astrophysics Data System (ADS)

    Vernazza, P.; Castillo-Rogez, J.; Beck, P.; Emery, J.; Brunetto, R.; Delbo, M.; Marsset, M.; Marchis, F.; Groussin, O.; Zanda, B.; Lamy, P.; Jorda, L.; Mousis, O.; Delsanti, A.; Djouadi, Z.; Dionnet, Z.; Borondics, F.; Carry, B.

    2017-02-01

    Anhydrous pyroxene-rich interplanetary dust particles (IDPs) have been proposed as surface analogs for about two-thirds of all C-complex asteroids. However, this suggestion appears to be inconsistent with the presence of hydrated silicates on the surfaces of some of these asteroids, including Ceres. Here, we report the presence of enstatite (pyroxene) on the surface of two C-type asteroids (Ceres and Eugenia) based on their spectral properties in the mid-infrared range. The presence of this component is particularly unexpected in the case of Ceres, because most thermal evolution models predict a surface consisting of hydrated compounds only. The most plausible scenario is that Ceres’ surface has been partially contaminated by exogenous enstatite-rich material, possibly coming from the Beagle asteroid family. This scenario questions a similar origin for Ceres and the remaining C-types, and it possibly supports recent results obtained by the Dawn mission (NASA) that Ceres may have formed in the very outer solar system. Concerning the smaller D ∼ 200 km C-types such as Eugenia, both their derived surface composition (enstatite and amorphous silicates) and low density (<1.5 g cm‑3) suggest that these bodies accreted from the same building blocks, namely chondritic porous, pyroxene-rich IDPs and volatiles (mostly water ice), and that a significant volume fraction of these bodies has remained unaffected by hydrothermal activity likely implying a late accretion. In addition, their current heliocentric distance may best explain the presence or absence of water ice at their surfaces. Finally, we raise the possibility that CI chondrites, Tagish-Lake-like material, or hydrated IDPs may be representative samples of the cores of these bodies.

  20. Origin and post-colonization evolution of the Chatham Islands skink (Oligosoma nigriplantare nigriplantare).

    PubMed

    Liggins, Libby; Chapple, David G; Daugherty, Charles H; Ritchie, Peter A

    2008-07-01

    Island ecosystems provide an opportunity to examine a range of evolutionary and ecological processes. The Chatham Islands are an isolated archipelago situated approximately 800 km east of New Zealand. Geological evidence indicates that the Chatham Islands re-emerged within the last 1-4 million years, following a prolonged period of marine inundation, and therefore the resident flora and fauna is the result of long-distance overwater dispersal. We examine the origin and post-colonization evolution of the Chatham Islands skink, Oligosoma nigriplantare nigriplantare, the sole reptile species occurring on the archipelago. We sampled O. n. nigriplantare from across nine islands within the Chatham Islands group, and representative samples from across the range of its closest relative, the New Zealand mainland common skink (Oligosoma nigriplantare polychroma). Our mitochondrial sequence data indicate that O. n. nigriplantare diverged from O. n. polychroma 5.86-7.29 million years ago. This pre-dates the emergence date for the Chatham Islands, but indicates that O. n. nigriplantare colonized the Chatham Islands via overwater dispersal on a single occasion. Despite the substantial morphological variability evident in O. n. nigriplantare, only relatively shallow genetic divergences (maximum divergence approximately 2%) were found across the Chatham Islands. Our analyses (haplotypic diversity, Phi(ST), analysis of molecular variance, and nested clade phylogeographical analysis) indicated restricted gene flow in O. n. nigriplantare resulting in strong differentiation between islands. However, the restrictions to gene flow might have only arisen recently as there was also a significant pattern of isolation by distance, possibly from when the Chatham Islands were a single landmass during Pleistocene glacial maxima when sea levels were lower. The level of genetic and morphological divergence between O. n. nigriplantare and O. n. polychroma might warrant their recognition as

  1. Multiple origins and nrDNA internal transcribed spacer homeologue evolution in the Glycine tomentella (Leguminosae) allopolyploid complex.

    PubMed Central

    Rauscher, Jason T; Doyle, Jeff J; Brown, A H D

    2004-01-01

    Despite the importance of polyploidy in the evolution of plants, patterns of molecular evolution and genomic interactions following polyploidy are not well understood. Nuclear ribosomal DNA is particularly complex with respect to these genomic interactions. The composition of nrDNA tandem arrays is influenced by intra- and interlocus concerted evolution and their expression is characterized by patterns such as nucleolar dominance. To understand these complex interactions it is important to study them in diverse natural polyploid systems. In this study we use direct sequencing to isolate and characterize nrDNA internal transcribed spacer (ITS) homeologues from multiple accessions of six different races in the Glycine tomentella allopolyploid complex. The results indicate that in most allopolyploid accessions both homeologous nrDNA repeats are present, but that there are significant biases in copy number toward one homeologue, possibly resulting from interlocus concerted evolution. The predominant homeologue often differs between races and between accessions within a race. A phylogenetic analysis of ITS sequences provides evidence for multiple origins in several of the polyploid races. This evidence for diverse patterns of nrDNA molecular evolution and multiple origins of polyploid races will provide a useful system for future studies of natural variation in patterns of nrDNA expression. PMID:15020482

  2. Primordial stellar evolution - The pre-main-sequence phase

    NASA Technical Reports Server (NTRS)

    Stahler, S. W.; Palla, F.; Salpeter, E. E.

    1986-01-01

    The quasi-static contraction of primordial stars composed of pure hydrogen and helium gas is studied by following numerically the evolution of a star of five solar masses from the end of protostellar accretion to the onset of hydrogen burning. Although the protostellar core of this mass is radiatively stable and undergoing nonhomologous contraction, its large surface area and luminosity force the star to a partially convective, homologously contracting state within only 100 yr. Deuterium later ignites at an off-center temperature maximum but fails to produce interior convection. The star follows a conventional premain sequence track in the HR diagram, reaching the ZAMS after 1.2 million yr, with a luminosity of 880 solar luminosities and a radius of 1.2 solar radii.

  3. Dynamic interplay between uranyl phosphate precipitation, sorption, and phase evolution

    DOE PAGES

    Munasinghe, P. Sumudu; Elwood Madden, Megan E.; Brooks, Scott C.; ...

    2015-04-17

    We report that natural examples demonstrate uranyl-phosphate minerals can maintain extremely low levels of aqueous uranium in groundwaters due to their low solubility. Thus, greater understanding of the geochemical factors leading to uranyl phosphate precipitation may lead to successful application of phosphate-based remediation methods. However, the solubility of uranyl phosphate phases varies over >3 orders of magnitude, with the most soluble phases typically observed in lab experiments. To understand the role of common soil/sediment mineral surfaces in the nucleation and transformation of uranyl phosphate minerals under environmentally relevant conditions, we carried out batch experiments with goethite and mica at pHmore » 6 in mixed electrolyte solutions ranging from 1–800 μM U and 1–800 μM P. All experiments ended with uranium concentrations below the USEPA MCL for U, but with 2–3 orders of magnitude difference in uranium concentrations.« less

  4. Dynamic interplay between uranyl phosphate precipitation, sorption, and phase evolution

    SciTech Connect

    Munasinghe, P. Sumudu; Elwood Madden, Megan E.; Brooks, Scott C.; Elwood Madden, Andrew S.

    2015-04-17

    We report that natural examples demonstrate uranyl-phosphate minerals can maintain extremely low levels of aqueous uranium in groundwaters due to their low solubility. Thus, greater understanding of the geochemical factors leading to uranyl phosphate precipitation may lead to successful application of phosphate-based remediation methods. However, the solubility of uranyl phosphate phases varies over >3 orders of magnitude, with the most soluble phases typically observed in lab experiments. To understand the role of common soil/sediment mineral surfaces in the nucleation and transformation of uranyl phosphate minerals under environmentally relevant conditions, we carried out batch experiments with goethite and mica at pH 6 in mixed electrolyte solutions ranging from 1–800 μM U and 1–800 μM P. All experiments ended with uranium concentrations below the USEPA MCL for U, but with 2–3 orders of magnitude difference in uranium concentrations.

  5. Phase transitions and path dependence in urban evolution

    NASA Astrophysics Data System (ADS)

    Wilson, Alan; Dearden, Joel

    2011-03-01

    There is a long history of recognising and interpreting discontinuous change—phase transitions—in urban systems. In this paper, we use the aggregate retail model as an archetype to explore some new ideas. For example, we argue that the dependence of paths of development on initial conditions has been understudied, and we offer a new graphical analysis that demonstrates explicitly their influence on discrete change. We introduce an order parameter, and we plot this on a `results grid' to facilitate the discovery of possible phase transitions. We illustrate the use of these new developments with an application to London. We show how retail developers can change the `initial conditions' at a point in time and possibly bring about phase transitions by their actions. This also shows that it should be possible to account for the history of urban development as a sequence of initial conditions, illustrating path dependence. Secondly, the model could be deployed in relation to a new shopping zone, and the tools developed here used to calculate the minimum size of a new development in order for it to compete. We explore the `minimum size' idea in relation to a new shopping zone in London.

  6. Phase evolution and magnetic properties of HoIn{sub 3−x}Co{sub x}

    SciTech Connect

    Chen, Songlin; Guo, Yongquan He, Qiang

    2015-03-28

    The phase evolution of HoIn{sub 3−x}Co{sub x} exhibits the phase transformations from the original HoIn{sub 3} with cubic structure to the intermediated HoCo{sub 2}In with orthorhombic structure and to the final HoCo{sub 3} with rhombohedral structure. The corresponding magnetic states are found to closely associate with the structural phase transformation of HoIn{sub 3−x}Co{sub x}.With increasing Co contents, HoIn{sub 3−x}Co{sub x} are paramagnetic in region of x < 0.6, mixture of paramagnetic and ferromagnetic in range of 0.6 < x < 1.8, and ferromagnetic in range of 3 > x > 2.4 at room temperature, respectively. The field dependence of magnetization curves follows an equation of M=M{sub s}(1−a/H )+χH, where M{sub s} and χ are corresponding to the saturation moment and susceptibility; a is a parameter related to the external field. The fitting results show that the susceptibility increases with increasing Co contents and M{sub s} depends upon the Co content as well. It implies that the evolution of magnetic phases in HoIn{sub 3−x}Co{sub x} might originate from the change of exchange interaction from the one between the isolated Co spins and the surrounding conduction electrons in Co-poor regime to the one between Co-Co pairs mediated by the conduction electrons in Co-rich regime.

  7. Origin of the Hawaiian rainforest ecosystem and its evolution in long-term primary succession

    NASA Astrophysics Data System (ADS)

    Mueller-Dombois, D.; Boehmer, H. J.

    2013-02-01

    Born among volcanoes in the north central Pacific about 4 million years ago, the Hawaiian rainforest became assembled from spores of algae, fungi, lichens, bryophytes, ferns and from seeds of about 275 flowering plants that over the millenia evolved into ca. 1000 endemic species. Outstanding among the forest builders were the tree ferns (Cibotium spp.) and the 'Ōhi'a lehua trees (Metrosideros spp.), which still dominate the Hawaiian rainforest ecosystem today. The structure of this forest is simple. The canopy in closed mature rainforests is dominated by cohorts of Metrosideros polymorpha and the undergrowth by tree fern species of Cibotium. When a new lava flow cuts through this forest, kipuka are formed, i.e. islands of remnant vegetation. On the new volcanic substrate, the assemblage of plant life-forms is similar as during the evolution of this system. In open juvenile forests, a mat-forming fern, the uluhe fern (Dicranopteris lineraris) becomes established. It inhibits further regeneration of the dominant 'Ōhi'a tree, thereby reinforcing the cohort structure of the canopy guild. In the later part of its life cycle, the canopy guild breaks down often in synchrony. The trigger is hypothesized to be a climatic perturbation. After that disturbance the forest becomes reestablished in about 30-40 yr. As the volcanic surfaces age, they go from a mesotrophic to a eutrophic phase, reaching a biophilic nutrient climax by about 1-25 K yr. Thereafter, a regressive oligotrophic phase follows; the soils become exhausted of nutrients. The shield volcanoes break down. Marginally, forest habitats change into bogs and stream ecosystems. The broader 'Ōhi'a rainforest redeveloping in the more dissected landscapes of the older islands looses stature, often forming large gaps that are invaded by the aluminum tolerant uluhe fern. The 'Ōhi'a trees still thrive on soils rejuvenated from landslides and from Asian dust on the oldest (5 million year old) island Kaua'i but their

  8. SPECTRAL AMPLITUDE AND PHASE EVOLUTION IN PETAWATT LASER PULSES

    SciTech Connect

    Filip, C V

    2010-11-22

    The influence of the active gain medium on the spectral amplitude and phase of amplified pulses in a CPA system is studied. Results from a 10-PW example based on Nd-doped mixed glasses are presented. In conclusion, this study shows that, by using spectral shaping and gain saturation in a mixed-glass amplifier, it is possible to produce 124 fs, 1.4 kJ laser pulses. One detrimental effect, the pulse distortion due to resonant amplification medium, has been investigated and its magnitude as well as its compensation calculated.

  9. Transcriptome analyses of primitively eusocial wasps reveal novel insights into the evolution of sociality and the origin of alternative phenotypes

    PubMed Central

    2013-01-01

    Background Understanding how alternative phenotypes arise from the same genome is a major challenge in modern biology. Eusociality in insects requires the evolution of two alternative phenotypes - workers, who sacrifice personal reproduction, and queens, who realize that reproduction. Extensive work on honeybees and ants has revealed the molecular basis of derived queen and worker phenotypes in highly eusocial lineages, but we lack equivalent deep-level analyses of wasps and of primitively eusocial species, the latter of which can reveal how phenotypic decoupling first occurs in the early stages of eusocial evolution. Results We sequenced 20 Gbp of transcriptomes derived from brains of different behavioral castes of the primitively eusocial tropical paper wasp Polistes canadensis. Surprisingly, 75% of the 2,442 genes differentially expressed between phenotypes were novel, having no significant homology with described sequences. Moreover, 90% of these novel genes were significantly upregulated in workers relative to queens. Differential expression of novel genes in the early stages of sociality may be important in facilitating the evolution of worker behavioral complexity in eusocial evolution. We also found surprisingly low correlation in the identity and direction of expression of differentially expressed genes across similar phenotypes in different social lineages, supporting the idea that social evolution in different lineages requires substantial de novo rewiring of molecular pathways. Conclusions These genomic resources for aculeate wasps and first transcriptome-wide insights into the origin of castes bring us closer to a more general understanding of eusocial evolution and how phenotypic diversity arises from the same genome. PMID:23442883

  10. Identification and analysis of a lytic-phase origin of DNA replication in human herpesvirus 7.

    PubMed Central

    van Loon, N; Dykes, C; Deng, H; Dominguez, G; Nicholas, J; Dewhurst, S

    1997-01-01

    Human herpesvirus 7 (HHV-7) DNA sequences colinear with the HHV-6 lytic-phase origin of DNA replication (oriLyt) were amplified by PCR. Plasmid constructs containing these sequences were replicated in HHV-7-infected cord blood mononuclear cells but not in HHV-6-infected cells. In contrast, plasmids bearing HHV-6 oriLyt were replicated in both HHV-6- and HHV-7-infected cells. Finally, the minimal HHV-7 DNA element necessary for replicator activity was mapped to a 600-bp region which contains two sites with high homology to the consensus binding site for the HHV-6 origin binding protein. At least one of these binding sites was shown to be essential for replicator function of HHV-7 oriLyt. PMID:9060695

  11. Doing the math: Calculating the role of evolution and enculturation in the origins of geometrical and mathematical reasoning.

    PubMed

    Gallagher, Shaun

    2015-12-01

    In this paper I review broadly embodied, phenomenological and evolutionary conceptions of the origin of mathematics. I relate these conceptions to Husserl's work on the origins of geometry, and recent research into the notion of extended expertise and the role of enculturation as they relate to mathematical reasoning. I suggest that the concept of 'affordance space' - the (abstract) range of possibilities provided by any change in body or environment - is a useful construct in working out the contributions of evolution and enculturation to mathematical reasoning.

  12. Changing the Public's Perception of Evolution--Christian Origins of Evolutionary Thought.

    ERIC Educational Resources Information Center

    Bartelt, Karen

    1998-01-01

    Presents the history of the theory of evolution and states that the creationist world view had been abandoned by even religious scientists before 1859. Argues that the public's perception of evolution could be improved by presenting a more complete picture of the theory's development, emphasizing the contributions of Christian--often…

  13. Evolution of the cystatin B gene: implications for the origin of its variable dodecamer tandem repeat in humans.

    PubMed

    Osawa, Motoki; Kaneko, Mika; Horiuchi, Hidekazu; Kitano, Takashi; Kawamoto, Yoshi; Saitou, Naruya; Umetsu, Kazuo

    2003-01-01

    The human cystatin B gene contains a variable number of 12-bp tandem repeats in its promoter region, of which the common alleles contain two or three copies and unusual expansion causes progressive myoclonus epilepsy of the Unverricht-Lundborg type. We undertook a comprehensive analysis of the genomic sequence to address the evolutionary events of this variable repeat. By examination of a contiguous genome sequence spanning 5.0 kb and linkage analysis of detected polymorphic changes, we identified six major intragenic haplotypes in unrelated Japanese subjects. The number of normal repeats was closely correlated with these alleles, indicating that changes in the array should be comparatively rare events during human evolution. To examine the origin of the repeat array further, we also analyzed five primate genomes. Repetitive polymorphism was unlikely in hominoids, and the array originated with the dodecamer itself in the course of primate evolution. The variability conceivably developed after the separation to humans.

  14. Origin of magnetic and dielectric response in single phase nano crystalline BiFeO3

    NASA Astrophysics Data System (ADS)

    Feroze, Asad; Idrees, Muhammad; Nadeem, Muhammad; Siddiqi, Saadat A.; Saleem, Murtaza; Atif, Muhammad; Siddique, Muhammad; Shaukat, Saleem F.

    2016-12-01

    Stoichiometric and single phase synthesis of BiFeO3 is critical both in its particle industrial applications as well as in understanding the origin of its attractive dielectric and magnetic properties. In this study, BiFeO3 has been obtained at temperatures as low as 400 °C. Zero Fe+2/Fe+3 ratio, and absence of bismuth and oxygen non-stoichiometry have been probed by 57Fe Mössbauer spectroscopy. The appearance of different magnetic phases in 57Fe Mössbauer spectrum, MH hysteresis curve and exchange bias effect have been conferred on the basis of magneto-crystalline anisotropy and particle size distribution. Dependence of the dielectric response on the applied electric field reveals that the colossal dielectric response in BiFeO3 is dominated by extrinsic effects at grain-grain interface.

  15. Theoretical and Computational Studies of Condensed-Phase Phenomena: The Origin of Biological Homochirality, and the Liquid-Liquid Phase Transition in Network-Forming Fluids

    NASA Astrophysics Data System (ADS)

    Ricci, Francesco

    This dissertation describes theoretical and computational studies of the origin of biological homochirality, and the existence of a liquid-liquid phase transition in pure-component network-forming fluids. A common theme throughout these studies is the use of sophisticated computer simulation and statistical mechanics techniques to study complex condensed-phase phenomena. In the first part of this dissertation, we use an elementary lattice model with molecular degrees of freedom, and satisfying microscopic reversibility, to investigate the effect of reaction reversibility on the evolution of stochastic symmetry breaking via autocatalysis and mutual inhibition in a closed system. We identify conditions under which the system's evolution towards racemic equilibrium becomes extremely slow, allowing for long-time persistence of a symmetry-broken state. We also identify a "monomer purification" mechanism, due to which a nearly homochiral state can persist for long times, even in the presence of significant reverse reaction rates. Order of magnitude estimates show that with reasonable physical parameters a symmetry broken state could persist over geologically-relevant time scales. In the second part of this dissertation, we study a chiral-symmetry breaking mechanism known as Viedma ripening. We develop a Monte Carlo model to gain further insights into the mechanisms capable of reproducing key experimental signatures associated with this phenomenon. We also provide a comprehensive investigation of how the model parameters impact the system's overall behavior. It is shown that size-dependent crystal solubility alone is insufficient to reproduce most experimental signatures, and that some form of a solid-phase chiral feedback mechanism (e.g., agglomeration) must be invoked in our model. In the third part of this dissertation, we perform rigorous free energy calculations to investigate the possibility of a liquid-liquid phase transition (LLPT) in the Stillinger-Weber (SW

  16. Mapping the northern plains of Mars: origins, evolution and response to climate change

    NASA Astrophysics Data System (ADS)

    Balme, Matthew; Conway, Susan; Costard, François; Gallagher, Colman; van Gasselt, Stephan; Hauber, Ernst; Johnsson, Andreas; Kereszturi, Akos; Platz, Thomas; Ramsdale, Jason; Reiss, Dennis; Séjourné, Antoine; Skinner, James; Swirad, Zuzanna

    2014-05-01

    An ISSI (International Space Science Institute) international team has been convened to study the Northern Plain of Mars. The northern plains are extensive, geologically young, low-lying areas that contrast in age and relief to Mars' older, heavily cratered, southern highlands. Mars' northern plains are characterised by a wealth of landforms and landscapes that have been inferred to be related to the presence of ice or ice-rich material near, beneath, or at the surface. Such landforms include 'scalloped' pits and depressions, polygonally-patterned grounds, and viscous flow features similar in form to terrestrial glacial or ice-sheet landforms. Furthermore, new (within the last few years) impact craters have exposed ice in the northern plains, and spectral data from orbiting instruments have revealed the presence of tens of percent by weight of water within the upper most ~50 cm of the martian surface at high latitudes. The northern plains comprise three linked zones: Acidalia Planitia, Utopia Planitia and Arcadia Planitia. Each region consists of a shallow basin, with the three areas are separated by low topographic divides. Our aim is to study the ice-related geomorphology of each region in order to understand the origins, evolution and response to climate change of ice on Mars. In particular, by comparing and contrasting the three separate basins we hope to determine if the processes that created the ice-related terrains are regional (perhaps basin limited) or global in scope, and whether the differing geology of each basin has an effect on the ice-related features observed there. The ISSI team is using planetary geomorphological mapping to meet this aim. Three long strips, each about 250 km wide and spanning the ~30N to ~80N latitude range have been defined and sub-teams are each mapping a single area. The group contains experts in mapping, GIS and crater counting (details in the size-frequency distribution of impact craters on a planetary surface can reveal

  17. The evolution of milk casein genes from tooth genes before the origin of mammals.

    PubMed

    Kawasaki, Kazuhiko; Lafont, Anne-Gaelle; Sire, Jean-Yves

    2011-07-01

    Caseins are among cardinal proteins that evolved in the lineage leading to mammals. In milk, caseins and calcium phosphate (CaP) form a huge complex called casein micelle. By forming the micelle, milk maintains high CaP concentrations, which help altricial mammalian neonates to grow bone and teeth. Two types of caseins are known. Ca-sensitive caseins (α(s)- and β-caseins) bind Ca but precipitate at high Ca concentrations, whereas Ca-insensitive casein (κ-casein) does not usually interact with Ca but instead stabilizes the micelle. Thus, it is thought that these two types of caseins are both necessary for stable micelle formation. Both types of caseins show high substitution rates, which make it difficult to elucidate the evolution of caseins. Yet, recent studies have revealed that all casein genes belong to the secretory calcium-binding phosphoprotein (SCPP) gene family that arose by gene duplication. In the present study, we investigated exon-intron structures and phylogenetic distributions of casein and other SCPP genes, particularly the odontogenic ameloblast-associated (ODAM) gene, the SCPP-Pro-Gln-rich 1 (SCPPPQ1) gene, and the follicular dendritic cell secreted peptide (FDCSP) gene. The results suggest that contemporary Ca-sensitive casein genes arose from a putative common ancestor, which we refer to as CSN1/2. The six putative exons comprising CSN1/2 are all found in SCPPPQ1, although ODAM also shares four of these exons. By contrast, the five exons of the Ca-insensitive casein gene are all reminiscent of FDCSP. The phylogenetic distribution of these genes suggests that both SCPPPQ1 and FDCSP arose from ODAM. We thus argue that all casein genes evolved from ODAM via two different pathways; Ca-sensitive casein genes likely originated directly from SCPPPQ1, whereas the Ca-insensitive casein genes directly differentiated from FDCSP. Further, expression of ODAM, SCPPPQ1, and FDCSP was detected in dental tissues, supporting the idea that both types of caseins

  18. Chemical evolution of interstellar dust, comets and the origins of life.

    PubMed

    Greenberg, J M; Zhao, N; Hage, J

    1989-04-01

    It now appears that the chemical evolution of the pre-solar system interstellar dust ensures that a major fraction of comets is in the form of complex organic molecules at least partially of a prebiotic nature and that the submicron interstellar dust preserves its chemical integrity as result of forming a very tenuous low density comet structure whose solid matter occupies approximately 1/5 of the total volume. This low density micro structure further provides a physical basis for comets bringing a significant fraction of the original interstellar organic molecules to the earth unmodified by the impact event. Finally, the evidence for a large number of comet collisions with the early earth ensured that the major organic molecular budget on the earth's surface was "continuously" supplied along with water well before 3.8 billion years ago which is the earliest date for life. The chemistry and morphological structure of a comet nucleus as an aggregate of interstellar dust is used to provide comparisons with a variety of comet Halley results: the density of the nucleus and of the dust; the dust cloud model and its consequences on the production of C+ and CN in the coma by small organic grains; the surface albedo and the low nucleus heat conductivity and high surface temperature; the appearance of 10(-14) g and 10(-17) g dust particles along with higher masses; the mass spectra of dust and infrared spectroscopy as evidence for complex organic grain mantles and of very small (approximately 0.01 micrometer) carbonaceous and silicate grains; the appearance of small grains resulting from breakup of larger grains. The cosmic ray dosage of a comet nucleus during its 4.5 billion years in the Oort cloud appears to be many orders of magnitude less than the dosage of the preaggregated interstellar dust by ultraviolet photons except perhaps in the outer few meters of the nucleus of a new comet. The heat conductivity calculated for aggregated dust is certainly less than 10(-4) that

  19. Wide-angle seismic constraints on the nature, origin and evolution of the SW Iberian margins

    NASA Astrophysics Data System (ADS)

    Sallares, V.; Gailler, A.; Gutscher, M.; Martínez-Loriente, S.; Bartolome, R.; Graindorge, D.; Diaz, J.; Gracia, E.

    2011-12-01

    We investigate the crustal structure of the SW Iberian margin along two new refraction and wide-angle reflection seismic profiles acquired during the NEAREST-2008 survey; one crossing from the central Gulf of Cadiz to the Variscan continental margin in the Algarve, Southern Portugal (P1), and the other crossing the Gorringe bank from Tagus Abyssal plain to the Seine Abyssal plain (P2). P1 shows shows a sharp transition between the ~30 km-thick Variscan domain in the north and a ~7 km-thick and ~150 km-wide crustal section that is oceanic in nature. The sharp transition between continental and oceanic crust is best explained by an initial rifting setting as a transform margin during the Early Jurassic that followed the continental break-up in the Central Atlantic. The narrow oceanic basin would have formed during an oblique rifting and seafloor spreading episode between Iberia and Africa that lasted up to the initiation of oceanic spreading in the North Atlantic (earliest Cretaceous). This oceanic plate segment could be the last remnant of an oceanic corridor that once connected the Alpine-Tethys with the Atlantic ocean. This interpretation is consistent with geodynamic models suggesting the existence of a narrow oceanic slab beneath the Gibraltar arc-Alboran basin system. In P2, the most striking observation is that the Tagus and Horseshoe Abyssal plains, as well as the Gorringe bank, show the same basement velocity structure, suggesting a common nature and origin. The velocity and density gradient confirms that the basement in these domains is made of highly serpentinized, exhumed mantle, probably emplaced during the initial phases of rifting at the of the North Atlantic in the Early Cretaceous. In contrast, the Seine Abyssal plain south from Coral Patch show evidences for the presence of a well-developed oceanic crust, similar to that described along P1. Therefore, these new observations provide key constraints to better understand the initial phases of rifting

  20. Proponents of Creationism but not Proponents of Evolution Frame the Origins Debate in Terms of Proof

    NASA Astrophysics Data System (ADS)

    Barnes, Ralph M.; Church, Rebecca A.

    2013-03-01

    In Study 1, 72 internet documents containing creationism, ID (intelligent design), or evolution content were selected for analysis. All instances of proof cognates (the word "proof" and related terms such as "proven", "disproof", etc.) contained within these documents were identified and labeled in terms of the manner in which the terms were used. In Study 2, frequency counts for six terms (proof, evidence, establish, experiment, test, trial) were conducted on a sample of peer-reviewed research articles in the journal Science and the 72 internet documents included in Study 1. Quantitative and qualitative analyses revealed that proponents of creationism were much more likely than proponents of evolution to frame the creationism/evolution issue in terms of proof (ID proponents fell partway between the other two). Proponents of creationism frequently described empirical data favoring their position as proof of their position. Even more frequently, proponents of creationism described evolutionary scientists as being engaged in failed attempts to prove the truth of the evolutionary position. Evolution documents included fewer proof cognates than creationism or ID documents and the few proof cognates found in evolution documents were rarely used to describe the status of the theory of evolution. Qualitative data analysis indicated that proof cognates were often used to indicate certainty. The asymmetry between evolution and creationism documents was limited primarily to proof cognates; there were no major asymmetries for the terms evidence, establish, experiment, test, and trial. The results may reveal differences in the epistemological commitments of the involved parties.

  1. Alleles versus mutations: Understanding the evolution of genetic architecture requires a molecular perspective on allelic origins.

    PubMed

    Remington, David L

    2015-12-01

    Perspectives on the role of large-effect quantitative trait loci (QTL) in the evolution of complex traits have shifted back and forth over the past few decades. Different sets of studies have produced contradictory insights on the evolution of genetic architecture. I argue that much of the confusion results from a failure to distinguish mutational and allelic effects, a limitation of using the Fisherian model of adaptive evolution as the lens through which the evolution of adaptive variation is examined. A molecular-based perspective reveals that allelic differences can involve the cumulative effects of many mutations plus intragenic recombination, a model that is supported by extensive empirical evidence. I discuss how different selection regimes could produce very different architectures of allelic effects under a molecular-based model, which may explain conflicting insights on genetic architecture from studies of variation within populations versus between divergently selected populations. I address shortcomings of genome-wide association study (GWAS) practices in light of more suitable models of allelic evolution, and suggest alternate GWAS strategies to generate more valid inferences about genetic architecture. Finally, I discuss how adopting more suitable models of allelic evolution could help redirect research on complex trait evolution toward addressing more meaningful questions in evolutionary biology.

  2. Speckle evolution with multiple steps of least-squares phase removal

    SciTech Connect

    Chen Mingzhou; Dainty, Chris; Roux, Filippus S.

    2011-08-15

    We study numerically the evolution of speckle fields due to the annihilation of optical vortices after the least-squares phase has been removed. A process with multiple steps of least-squares phase removal is carried out to minimize both vortex density and scintillation index. Statistical results show that almost all the optical vortices can be removed from a speckle field, which finally decays into a quasiplane wave after such an iterative process.

  3. Possible Origins of the `Free T Phase' Seismic Signals Generated by the Kick `em Jenny Volcano

    NASA Astrophysics Data System (ADS)

    Mohais, A.; Mohais, R.

    2006-12-01

    The Kick 'em Jenny submarine volcano located approximately 9km off the North Coast of Grenada in the Lesser Antilles, was discovered in 1939. Since then, it has had a history of twelve recorded eruptions. Geophysicists have determined over the years that many of these eruptions have been accompanied by T- phases occurring in the absence of P and S-phases. Although these authors have characterized these 'free T- phases' and have analyzed the frequency components of the seismic activity, there has been little attention given to the possible origins of these signals. Based on the analysis of the seismic signals of eruptions of Kick 'em Jenny, an attempt is made to determine a possible source of the free T-phases. Previous studies of sample free T-phases showed a spectral peak of 0.7 Hz, corresponding to a period of 1.43 seconds. Although no definitive statement by previous authors was made on this analysis, one may be led to categorise the event as a long period event. When the power spectral densities of a long period event from a volcanic earthquake was compared to that of a free T phase however, there was a marked difference between the two. Within the bandwidth of 1 to 6 Hz, the power spectrum of the T phase of an earthquake exhibits frequency peaks beyond the 10 Hz value as compared to a value less than 1. Also in the 1990 Kick 'em Jenny eruption, there was a period of harmonic tremor preceding the T phase. Harmonic tremor lends itself to the idea of the signal originating from a resonator. One possibility is the resonance of a fluid filled cavity which accompanies the oscillation of magma within a fissure arising from rapid degassing. This may be applicable in the case of Kick 'em Jenny since it is in fact active. The other possibility is the presence of reverberations in the stratified structure of the volcano. Other evidence suggests that in the time domain there is a significant difference between the free T-phase and the earthquake generated T phase, in that

  4. Evolution in eggs and phases: experimental evolution of fecundity and reproductive timing in Caenorhabditis elegans

    PubMed Central

    2016-01-01

    To examine the role of natural selection in fecundity in a variety of Caenorhabditis elegans genetic backgrounds, we used an experimental evolution protocol to evolve 14 distinct genetic strains over 15–20 generations. We were able to generate 790 distinct genealogies, which provided information on both the effects of natural selection and the evolvability of each strain. Among these genotypes are a wild-type (N2) and a collection of mutants with targeted mutations in the daf-c, daf-d and AMPK pathways. Differences are observed in reproductive fitness along with related changes in reproductive timing. The majority of selective effects on fecundity occur during the first few generations of evolution, while the negative selection for reproductive timing occurs on longer time scales. In addition, positive selection on fecundity results in positive and negative strain-dependent selection on reproductive timing. A derivative of population size per generation called reproductive carry-over (RCO) may be informative in terms of developmental selection. While these findings transcend mutations in a specific gene, changes in the RCO measure may nevertheless be products of selection. In conclusion, the broader implications of these findings are discussed, particularly in the context of genotype-fitness maps and the role of uncharacterized mutations in individual variation and evolvability. PMID:28018635

  5. Interface Propagation and Microstructure Evolution in Phase Field Models of Stress-Induced Martensitic Phase Transformations

    DTIC Science & Technology

    2010-01-01

    simulation, the initial conditions are g1 ¼ g2 ¼ 0:1 in a circle of radius 2 nm (an embryo ) at the center of the sample and zero elsewhere. The boundary...in narrow bands around the interfaces if the driving force is less than a critical value, K: Fig. 10. Evolution of an embryo , gi ¼ 0:1, in a circle...concentration curve does not exhibit a hysteresis loop and energy dissipation. 4. In Fig. 22 we display the evolution of an embryo with gi ¼ 0:1 as in

  6. Kinetic phase evolution of spinel cobalt oxide during lithiation

    SciTech Connect

    Li, Jing; He, Kai; Meng, Qingping; Li, Xin; Zhu, Yizhou; Hwang, Sooyeon; Sun, Ke; Gan, Hong; Zhu, Yimei; Mo, Yifei; Stach, Eric A.; Su, Dong

    2016-09-15

    Spinel cobalt oxide has been proposed to undergo a multiple-step reaction during the electrochemical lithiation process. Understanding the kinetics of the lithiation process in this compound is crucial to optimize its performance and cyclability. In this work, we have utilized a low-angle annular dark-field scanning transmission electron microscopy method to visualize the dynamic reaction process in real time and study the reaction kinetics at different rates. We show that the particles undergo a two-step reaction at the single-particle level, which includes an initial intercalation reaction followed by a conversion reaction. At low rates, the conversion reaction starts after the intercalation reaction has fully finished, consistent with the prediction of density functional theoretical calculations. At high rates, the intercalation reaction is overwhelmed by the subsequently nucleated conversion reaction, and the reaction speeds of both the intercalation and conversion reactions are increased. Phase-field simulations show the crucial role of surface diffusion rates of lithium ions in controlling this process. Furthermore, this work provides microscopic insights into the reaction dynamics in non-equilibrium conditions and highlights the effect of lithium diffusion rates on the overall reaction homogeneity as well as the performance.

  7. Kinetic phase evolution of spinel cobalt oxide during lithiation

    DOE PAGES

    Li, Jing; He, Kai; Meng, Qingping; ...

    2016-09-15

    Spinel cobalt oxide has been proposed to undergo a multiple-step reaction during the electrochemical lithiation process. Understanding the kinetics of the lithiation process in this compound is crucial to optimize its performance and cyclability. In this work, we have utilized a low-angle annular dark-field scanning transmission electron microscopy method to visualize the dynamic reaction process in real time and study the reaction kinetics at different rates. We show that the particles undergo a two-step reaction at the single-particle level, which includes an initial intercalation reaction followed by a conversion reaction. At low rates, the conversion reaction starts after the intercalationmore » reaction has fully finished, consistent with the prediction of density functional theoretical calculations. At high rates, the intercalation reaction is overwhelmed by the subsequently nucleated conversion reaction, and the reaction speeds of both the intercalation and conversion reactions are increased. Phase-field simulations show the crucial role of surface diffusion rates of lithium ions in controlling this process. Furthermore, this work provides microscopic insights into the reaction dynamics in non-equilibrium conditions and highlights the effect of lithium diffusion rates on the overall reaction homogeneity as well as the performance.« less

  8. Origin and Evolution of the Self-Organizing Cytoskeleton in the Network of Eukaryotic Organelles

    PubMed Central

    Jékely, Gáspár

    2014-01-01

    The eukaryotic cytoskeleton evolved from prokaryotic cytomotive filaments. Prokaryotic filament systems show bewildering structural and dynamic complexity and, in many aspects, prefigure the self-organizing properties of the eukaryotic cytoskeleton. Here, the dynamic properties of the prokaryotic and eukaryotic cytoskeleton are compared, and how these relate to function and evolution of organellar networks is discussed. The evolution of new aspects of filament dynamics in eukaryotes, including severing and branching, and the advent of molecular motors converted the eukaryotic cytoskeleton into a self-organizing “active gel,” the dynamics of which can only be described with computational models. Advances in modeling and comparative genomics hold promise of a better understanding of the evolution of the self-organizing cytoskeleton in early eukaryotes, and its role in the evolution of novel eukaryotic functions, such as amoeboid motility, mitosis, and ciliary swimming. PMID:25183829

  9. Origin and evolution of the self-organizing cytoskeleton in the network of eukaryotic organelles.

    PubMed

    Jékely, Gáspár

    2014-09-02

    The eukaryotic cytoskeleton evolved from prokaryotic cytomotive filaments. Prokaryotic filament systems show bewildering structural and dynamic complexity and, in many aspects, prefigure the self-organizing properties of the eukaryotic cytoskeleton. Here, the dynamic properties of the prokaryotic and eukaryotic cytoskeleton are compared, and how these relate to function and evolution of organellar networks is discussed. The evolution of new aspects of filament dynamics in eukaryotes, including severing and branching, and the advent of molecular motors converted the eukaryotic cytoskeleton into a self-organizing "active gel," the dynamics of which can only be described with computational models. Advances in modeling and comparative genomics hold promise of a better understanding of the evolution of the self-organizing cytoskeleton in early eukaryotes, and its role in the evolution of novel eukaryotic functions, such as amoeboid motility, mitosis, and ciliary swimming.

  10. On the origins of birds: the sequence of character acquisition in the evolution of avian flight

    PubMed Central

    Garner, J. P.; Taylor, G. K.; Thomas, A. L. R.

    1999-01-01

    Assessment of competing theories for the evolution of avian flight is problematic, and tends to rest too heavily on reconstruction of the mode of life of one or a few specimens representing still fewer species. A more powerful method is to compare the sequence of character acquisition predicted by the various theories with the empirical sequence provided by cladistic phylogeny. Arboreal and cursorial theories incorrectly predict the sequence of character acquisition for several key features of avian evolution. We propose an alternative 'pouncing proavis' model for the evolution of flight. As well as being both biologically and evolutionarily plausible, the pouncing proavis model correctly predicts the evolutionary sequence of all five key features marking the evolution of birds.

  11. Excretion of norsteroids' phase II metabolites of different origin in human.

    PubMed

    Guay, Claudiane; Goudreault, Danielle; Schänzer, Wilhem; Flenker, Ulrich; Ayotte, Christiane

    2009-03-01

    The urinary phase II metabolites of norsteroids, 19-norandrosterone, 19-noretiocholanolone and 19-norepiandrosterone glucuronide and sulphate, were analyzed in samples collected during the pregnancy, following the administration of norsteroids or the consumption of edible parts of non-castrated pig and in athletes' samples in which they were found during routine controls. The level of the sulfo- and glucuroconjugated metabolites was precisely determined by GC/HRMS, after selective hydrolysis. The goal was to evaluate whether the fine analysis of the norsteroid conjugates produced and excreted in different conditions would show a pattern that could be linked to their origin. The delta (13)C values of the metabolites formed following the ingestion of edible parts of non-castrated pig were measured by isotope ratio mass spectrometry. Our results indicated that it is not possible to determine the origin of the urinary metabolites based upon the sole evaluation of the different metabolites and conjugates. The GC/C/IRMS is the only method permitting to distinguish between the exogenous and endogenous origin of the metabolites.

  12. Phase-Field Modeling of Microstructure Evolution in Electron Beam Additive Manufacturing

    NASA Astrophysics Data System (ADS)

    Gong, Xibing; Chou, Kevin

    2015-05-01

    In this study, the microstructure evolution in the powder-bed electron beam additive manufacturing (EBAM) process is studied using phase-field modeling. In essence, EBAM involves a rapid solidification process and the properties of a build partly depend on the solidification behavior as well as the microstructure of the build material. Thus, the prediction of microstructure evolution in EBAM is of importance for its process optimization. Phase-field modeling was applied to study the microstructure evolution and solute concentration of the Ti-6Al-4V alloy in the EBAM process. The effect of undercooling was investigated through the simulations; the greater the undercooling, the faster the dendrite grows. The microstructure simulations show multiple columnar-grain growths, comparable with experimental results for the tested range.

  13. The origin and evolution of dust in interstellar and circumstellar environments

    NASA Technical Reports Server (NTRS)

    Whittet, Douglas C. B.; Leung, Chun M.

    1993-01-01

    This status report covers the period from the commencement of the research program on 1 Jul. 1992 through 30 Apr. 1993. Progress is reported for research in the following areas: (1) grain formation in circumstellar envelopes; (2) photochemistry in circumstellar envelopes; (3) modeling ice features in circumstellar envelopes; (4) episodic dust formation in circumstellar envelopes; (5) grain evolution in the diffuse interstellar medium; and (6) grain evolution in dense molecular clouds.

  14. Hidden parameters in open-system evolution unveiled by geometric phase

    SciTech Connect

    Pawlus, Patrik; Sjoeqvist, Erik

    2010-11-15

    We find a class of open-system models in which individual quantum trajectories may depend on parameters that are undetermined by the full open-system evolution. This dependence is imprinted in the geometric phase associated with such trajectories and persists after averaging. Our findings indicate a potential source of ambiguity in the quantum trajectory approach to open quantum systems.

  15. Microstructural and phase evolution in metakaolin geopolymers with different activators and added aluminosilicate fillers

    NASA Astrophysics Data System (ADS)

    Sarkar, Madhuchhanda; Dana, Kausik; Das, Sukhen

    2015-10-01

    This work aims to investigate the microstructural and phase evolution of alkali activated metakaolin products with different activators and added aluminosilicate filler phases. The added filler phases have different reactivity to the alkali activated metakaolin system. Microstructural evolution in the alkali activated products has been investigated by X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Field Emission Scanning Electron Microscope (FESEM). Variation in strength development in alkali activated metakaolin products was followed by compressive strength measurement test. Microstructural study shows that in case of metakaolin with NaOH activator crystalline sodalite formed in all the product samples irrespective of the added filler phases. The microstructure of these NaOH activated products investigated by FESEM showed crystalline and inhomogeneous morphology. Mixed activator containing both NaOH and sodium silicate in a fixed mass ratio formed predominantly amorphous phase. Microstructure of these samples showed more homogeneity than that of NaOH activated metakaolin products. The study further shows that addition of α-Al2O3 powder, non reactive phase to the alkali activated metakaolin system when used in larger amount increased crystalline phase in the matrix. α-Al2O3 powder addition increased the compressive strength of the product samples for both the activator compositions. Added phase of colloidal silica, reactive to the alkali activated metakaolin system when used in larger amount was found to increase amorphous nature of the matrix. Addition of colloidal silica influenced the compressive strength property differently with different activator compositions.

  16. Analysis of origin and protein-protein interaction maps suggests distinct oncogenic role of nuclear EGFR during cancer evolution

    PubMed Central

    Sharip, Ainur; Abdukhakimova, Diyora; Wang, Xiao; Kim, Alexey; Kim, Yevgeniy; Sharip, Aigul; Orakov, Askarbek; Miao, Lixia; Sun, Qinglei; Chen, Yue; Chen, Zhenbang; Xie, Yingqiu

    2017-01-01

    Receptor tyrosine kinase EGFR usually is localized on plasma membrane to induce progression of many cancers including cancers in children (Bodey et al. In Vivo. 2005, 19:931-41), but it contains a nuclear localization signal (NLS) that mediates EGFR nuclear translocation (Lin et al. Nat Cell Biol. 2001, 3:802-8). Here we report that NLS of EGFR has its old evolutionary origin. Protein-protein interaction maps suggests that nEGFR pathways are different from membrane EGFR and EGF is not found in nEGFR network while androgen receptor (AR) is found, which suggests the evolution of prostate cancer, a well-known AR driven cancer, through changes in androgen- or EGF-dependence. Database analysis suggests that nEGFR correlates with the tumor grades especially in prostate cancer patients. Structural predication analysis suggests that NLS can compromise the differential protein binding to EGFR through stretch linkers with evolutionary mutation from N to V. In experiment, elevation of nEGFR but not membrane EGFR was found in castration resistant prostate cancer cells. Finally, systems analysis of NLS and transmembrane domain (TM) suggests that NLS has old origin while NLS neighboring domain of TM has been undergone accelerated evolution. Thus nEGFR has an old origin resembling the cancer evolution but TM may interfere with NLS driven signaling for natural selection of survival to evade NLS induced aggressive cancers. Our data suggest NLS is a dynamic inducer of EGFR oncogenesis during evolution for advanced cancers. Our model provides novel insights into the evolutionary role of NLS of oncogenic kinases in cancers. PMID:28382154

  17. Creation, Phase Change and Evolution of the Universe Based on the "Convection Bang Hypothesis"

    NASA Astrophysics Data System (ADS)

    Gholibeigian, Hassan; Amirshahkarami, Abdolazim; Gholibeigian, Kazem

    2016-04-01

    In our vision, it is believed that creation and phase change of universe and their coupling began by the gigantic Large Scale Forced Convection System (LSFCS) in very high temperature including a swirling wild wind and energetic particles like gravitons. That wind as the creator of the inflation process was carrying many Quantum Convection Loops (QCLs). Those QCLs have been transformed to black holes as the cores of galaxies. Convection Bang (CB) Model for creation, phase change and evolution of the Universe is constituted based on three assumptions as follows: The first is: "Gravity Hypothesis" that describes the gravity fields generation by the LSFCSs of the heat and mass inside the planets, stars, galaxies and clusters. The LSFCS changes the material properties of the domain and produces coupling of the matched electromagnetic and gravity fields. Gravity hypothesis is a new way to understand gravitation phenomenon which is different from the both Newton's law of gravity and Einstein's theory of general relativity approaches [Gholibeigian et. al, AGU Fall Meeting 2015, P11A-2056 ]. The second is: "Substantial Motion" theory of Iranian philosopher, Mulla Sadra (1571/2-1640), which describes space-time, time's relativity for all atoms (bodies) which are different from each other [Gholibeigian, APS April Meeting 2015, abstract #L1.027], atom's (body) volume squeezing, black hole's mass lightening while increases the velocities of its involved masses inward (a paradox with general relativity), and changes of material properties and geometries in speed of near light speed [Gholibeigian, APS March Meeting 2016, abstract #]. The third is: "Animated Sub-particles" model. These sub-particles (sub-strings) are origin of life and creator of the momentums of the fundamental particles and forces, and basic link of the information transfer to them, [Gholibeigian, APS April Meeting 2015, abstract #L1.027]. In this model, there are four proposed animated sub-particles of mater

  18. The Evolution of Swift/BAT blazars and the origin of the MeV background

    SciTech Connect

    Ajello, M.; Costamante, L.; Sambruna, R.M.; Gehrels, N.; Chiang, J.; Rau, A.; Escala, A.; Greiner, J.; Tueller, J.; Wall, J.V.; Mushotzky, R.F.; /NASA, Goddard

    2009-10-17

    We use 3 years of data from the Swift/BAT survey to select a complete sample of X-ray blazars above 15 keV. This sample comprises 26 Flat-Spectrum Radio Quasars (FSRQs) and 12 BL Lac objects detected over a redshift range of 0.03 < z < 4.0. We use this sample to determine, for the first time in the 15-55 keV band, the evolution of blazars. We find that, contrary to the Seyfert-like AGNs detected by BAT, the population of blazars shows strong positive evolution. This evolution is comparable to the evolution of luminous optical QSOs and luminous X-ray selected AGNs. We also find evidence for an epoch-dependence of the evolution as determined previously for radio-quiet AGNs. We interpret both these findings as a strong link between accretion and jet activity. In our sample, the FSRQs evolve strongly, while our best-fit shows that BL Lacs might not evolve at all. The blazar population accounts for 10-20% (depending on the evolution of the BL Lacs) of the Cosmic X-ray background (CXB) in the 15-55 keV band. We find that FSRQs can explain the entire CXB emission for energies above 500 keV solving the mystery of the generation of the MeV background. The evolution of luminous FSRQs shows a peak in redshift (z{sub c} = 4.3 {+-} 0.5) which is larger than the one observed in QSOs and X-ray selected AGNs. We argue that FSRQs can be used as tracers of massive elliptical galaxies in the early Universe.

  19. Granitoids of different geodynamic settings of Baikal region (Russia) their geochemical evolution and origin

    NASA Astrophysics Data System (ADS)

    Antipin, Viktor; Sheptyakova, Natalia

    2016-04-01

    In the southern folded framing of the Siberian craton the granitoid magmatism of different ages involves batholiths, small low-depth intrusions and intrusion-dyke belts with diverse mineral and geochemical characteristics of rocks. Granitoid formation could be related to the Early Paleozoic collision stage and intra-plate magmatism of the Late Paleozoic age of the geologic development of Baikal area. The Early Paleozoic granitoids of Khamar-Daban Ridge and Olkhon region revealed their closeness in age and composition. They were referred to syncollision S-type formations derived from gneiss-schistose substratum of metamorphic sequences. The magmatic rocks were classified into various geochemical types comprising formations of normal Na-alkalinity (migmatites and plagiogranites), calc-alkaline and subalkaline (K-Na granitoids, granosyenites and quartz syenites) series. It is significant, that plagiomigmatites and plagiogranites in all elements repeat the shape of the chart of normalized contents marked for trend of K-Na granitoids, but at considerably lower level of concentrations of all elements. This general pattern of element distribution might indicate similar anatectic origin of both granitoid types, but from crustal substrata distinguished by composition and geochemical features. Comparative geochemical analysis pointed out that the source of melts of the Early Paleozoic granitoids of the Olkhon (505-477 Ma) and Khamar-Daban (516-490 Ma) complexes of the Baikal region could be the crustal substratum, which is obviously the criterion for their formation in the collisional geodynamic setting. Using the Late Paleozoic subalkaline magmatism proceeding at the Khamar-Daban Range (Khonzurtay pluton, 331 Ma) as an example, it was found that the formation of monzodiorite-syenite-leucogranite series was considerably contributed by the processes of hybridism and assimilation through mixing of the upper mantle basaltoid magma derived melts of granitic composition. The

  20. Microstructure evolution and mechanical behavior of a high strength dual-phase steel under monotonic loading

    SciTech Connect

    Nesterova, E.V.; Bouvier, S.; Bacroix, B.

    2015-02-15

    Transmission electron microscopy (TEM) microstructures of a high-strength dual-phase steel DP800 have been examined after moderate plastic deformations in simple shear and uniaxial tension. Special attention has been paid to the effect of the intergranular hard phase (martensite) on the microstructure evolution in the near-grain boundary regions. Quantitative parameters of dislocation patterning have been determined and compared with the similar characteristics of previously examined single-phase steels. The dislocation patterning in the interiors of the ferrite grains in DP800 steel is found to be similar to that already observed in the single-phase IF (Interstitial Free) steel whereas the martensite-affected zones present a delay in patterning and display very high gradients of continuous (gradual) disorientations associated with local internal stresses. The above stresses are shown to control the work-hardening of dual-phase materials at moderate strains for monotonic loading and are assumed to influence their microstructure evolution and mechanical behavior under strain-path changes. - Highlights: • The microstructure evolution has been studied by TEM in a DP800 steel. • It is influenced by both martensite and dislocations in the initial state. • The DP800 steel presents a high work-hardening rate due to internal stresses.

  1. Cannibalism can drive the evolution of behavioural phase polyphenism in locusts.

    PubMed

    Guttal, Vishwesha; Romanczuk, Pawel; Simpson, Stephen J; Sword, Gregory A; Couzin, Iain D

    2012-10-01

    During outbreaks, locust swarms can contain millions of insects travelling thousands of kilometers while devastating vegetation and crops. Such large-scale spatial organization is preceded locally by a dramatic density-dependent phenotypic transition in multiple traits. Behaviourally, low-density 'solitarious' individuals avoid contact with one another; above a critical local density, they undergo a rapid behavioural transition to the 'gregarious phase' whereby they exhibit mutual attraction. Although proximate causes of this phase polyphenism have been widely studied, the ultimate driving factors remain unclear. Using an individual-based evolutionary model, we reveal that cannibalism, a striking feature of locust ecology, could lead to the evolution of density-dependent behavioural phase-change in juvenile locusts. We show that this behavioural strategy minimizes risk associated with cannibalistic interactions and may account for the empirically observed persistence of locust groups during outbreaks. Our results provide a parsimonious explanation for the evolution of behavioural plasticity in locusts.

  2. Microstructural and chemical evolution near anode triple phase boundary in Ni/YSZ solid oxide fuel cells

    SciTech Connect

    Chen, Yun; Chen, Song; Hacket, Gregory; Finklea, Harry; Song, Zueyan; Gerdes, Kirk

    2011-12-01

    In this study, we report the microstructural and chemical evolution of anode grain boundaries and triple phase boundary (TPB) junctions of Ni/YSZ anode supported solid oxide fuel cells. A NiO phase was found to develop along the Ni/YSZ interfaces extending to TPBs in the operated cells. The thickness of the NiO ribbon phase remains constant at ~5 nm in hydrogen for operating durations up to 540 h. When operating on synthesis gas, an increase in interphase thickness was observed from ~11 nm for 24 h of operation to ~51 nm for 550 h of operation. YSZ phases are observed to be stable in H2 over 540 h of operation. However, for the cell operated in syngas for 550 h, a 5–10 nm tetragonal YSZ (t-YSZ) interfacial layer was identified that originated from the Ni/YSZ interfaces. Yttrium species seem to segregate to the interfaces during operation, leading to the formation of t-YSZ in the Y-depleted regions.

  3. Microstructural and chemical evolution near anode triple phase boundary in Ni/YSZ solid oxide fuel cells

    SciTech Connect

    Chen, Yun; Chen, Song; Hackett, Gregory; Finklea, Harry; Song, Xueyan; Gerdes, Kirk

    2011-12-12

    In this study, we report the micro-structural and chemical evolution of anode grain boundaries and triple phase boundary (TPB) junctions of Ni/YSZ anode supported solid oxide fuel cells. A NiO phase was found to develop along the Ni/YSZ interfaces extending to TPBs in the operated cells. The thickness of the NiO ribbon phase remains constant at ~ 5 nm in hydrogen for operating durations up to 540 h. When operating on synthesis gas, an increase in interphase thickness was observed from ~ 11 nm for 24 h of operation to ~ 51 nm for 550 h of operation. YSZ phases are observed to be stable in H{sub 2} over 540 h of operation. However, for the cell operated in syngas for 550 h, a 5–10 nm tetragonal YSZ (t-YSZ) interfacial layer was identified that originated from the Ni/YSZ interfaces. Yttrium species seem to segregate to the interfaces during operation, leading to the formation of t-YSZ in the Y-depleted regions.

  4. Research program for a search of the origin of Darwinian evolution. Research program for a vesicle-based model of the origin of Darwinian evolution on prebiotic early Earth

    NASA Astrophysics Data System (ADS)

    Tessera, Marc

    2017-03-01

    The search for origin of `life' is made even more complicated by differing definitions of the subject matter, although a general consensus is that an appropriate definition should center on Darwinian evolution (Cleland and Chyba 2002). Within a physical approach which has been defined as a level-4 evolution (Tessera and Hoelzer 2013), one mechanism could be described showing that only three conditions are required to allow natural selection to apply to populations of different system lineages. This approach leads to a vesicle- based model with the necessary properties. Of course such a model has to be tested. Thus, after a brief presentation of the model an experimental program is proposed that implements the different steps able to show whether this new direction of the research in the field is valid and workable.

  5. Research program for a search of the origin of Darwinian evolution : Research program for a vesicle-based model of the origin of Darwinian evolution on prebiotic early Earth.

    PubMed

    Tessera, Marc

    2017-03-01

    The search for origin of 'life' is made even more complicated by differing definitions of the subject matter, although a general consensus is that an appropriate definition should center on Darwinian evolution (Cleland and Chyba 2002). Within a physical approach which has been defined as a level-4 evolution (Tessera and Hoelzer 2013), one mechanism could be described showing that only three conditions are required to allow natural selection to apply to populations of different system lineages. This approach leads to a vesicle- based model with the necessary properties. Of course such a model has to be tested. Thus, after a brief presentation of the model an experimental program is proposed that implements the different steps able to show whether this new direction of the research in the field is valid and workable.

  6. A constraint-free phase field model for ferromagnetic domain evolution

    PubMed Central

    Yi, Min; Xu, Bai-Xiang

    2014-01-01

    A continuum constraint-free phase field model is proposed to simulate the magnetic domain evolution in ferromagnetic materials. The model takes the polar and azimuthal angles (ϑ1,ϑ2), instead of the magnetization unit vector m(m1,m2,m3), as the order parameters. In this way, the constraint on the magnetization magnitude can be exactly satisfied automatically, and no special numerical treatment on the phase field evolution is needed. The phase field model is developed from a thermodynamic framework which involves a configurational force system for ϑ1 and ϑ2. A combination of the configurational force balance and the second law of thermodynamics leads to thermodynamically consistent constitutive relations and a generalized evolution equation for the order parameters (ϑ1,ϑ2). Beneficial from the constraint-free model, the three-dimensional finite-element implementation is straightforward, and the degrees of freedom are reduced by one. The model is shown to be capable of reproducing the damping-dependent switching dynamics, and the formation and evolution of domains and vortices in ferromagnetic materials under the external magnetic or mechanical loading. Particularly, the calculated out-of-plane component of magnetization in a vortex is verified by the corresponding experimental results, as well as the motion of the vortex under a magnetic field. PMID:25383036

  7. A constraint-free phase field model for ferromagnetic domain evolution.

    PubMed

    Yi, Min; Xu, Bai-Xiang

    2014-11-08

    A continuum constraint-free phase field model is proposed to simulate the magnetic domain evolution in ferromagnetic materials. The model takes the polar and azimuthal angles (ϑ1,ϑ2), instead of the magnetization unit vector m(m1,m2,m3), as the order parameters. In this way, the constraint on the magnetization magnitude can be exactly satisfied automatically, and no special numerical treatment on the phase field evolution is needed. The phase field model is developed from a thermodynamic framework which involves a configurational force system for ϑ1 and ϑ2. A combination of the configurational force balance and the second law of thermodynamics leads to thermodynamically consistent constitutive relations and a generalized evolution equation for the order parameters (ϑ1,ϑ2). Beneficial from the constraint-free model, the three-dimensional finite-element implementation is straightforward, and the degrees of freedom are reduced by one. The model is shown to be capable of reproducing the damping-dependent switching dynamics, and the formation and evolution of domains and vortices in ferromagnetic materials under the external magnetic or mechanical loading. Particularly, the calculated out-of-plane component of magnetization in a vortex is verified by the corresponding experimental results, as well as the motion of the vortex under a magnetic field.

  8. Evolution of Secondary Phases Formed upon Solidification of a Ni-Based Alloy

    NASA Astrophysics Data System (ADS)

    Zuo, Qiang; Liu, Feng; Wang, Lei; Chen, Changfeng

    2013-07-01

    The solidification of UNS N08028 alloy subjected to different cooling rates was studied, where primary austenite dendrites occur predominantly and different amounts of sigma phase form in the interdendritic regions. The solidification path and elemental segregation upon solidification were simulated using the CALPHAD method, where THERMO-CALC software packages and two classical segregation models were employed to predict the real process. It is thus revealed that the interdendritic sigma phase is formed via eutectic reaction at the last stage of solidification. On this basis, an analytical model was developed to predict the evolution of nonequilibrium eutectic phase, while the isolated morphology of sigma phase can be described using divorced eutectic theory. Size, fraction, and morphology of the sigma phase were quantitatively studied by a series of experiments; the results are in good agreement with the model prediction.

  9. Mechanism Analysis of the Inverse Doppler Effect in Two-Dimensional Photonic Crystal based on Phase Evolution.

    PubMed

    Jiang, Qiang; Chen, Jiabi; Wang, Yan; Liang, Binming; Hu, Jinbing; Zhuang, Songlin

    2016-04-22

    Although the inverse Doppler effect has been observed experimentally at optical frequencies in photonic crystal with negative effective refractive index, its explanation is based on phenomenological theory rather than a strict theory. Elucidating the physical mechanism underlying the inverse Doppler shift is necessary. In this article, the primary electrical field component in the photonic crystal that leads to negative refraction was extracted, and the phase evolution of the entire process when light travels through a moving photonic crystal was investigated using static and dynamic finite different time domain methods. The analysis demonstrates the validity of the use of np (the effective refractive index of the photonic crystal in the light path) in these calculations, and reveals the origin of the inverse Doppler effect in photonic crystals.

  10. Mitogenomic perspectives into sciaenid fishes' phylogeny and evolution origin in the New World.

    PubMed

    Xu, Tianjun; Tang, Da; Cheng, Yuanzhi; Wang, Rixin

    2014-04-10

    Sciaenid fishes are widely distributed throughout the coastal waters and estuaries of the world. A total of 23 genera of this family are endemic to the Old World. However, evolutionary relationships among Old World sciaenid fishes and their origin have remained unresolved despite their diversity and importance. Besides, hypotheses that explain the origin and biogeographical distribution of sciaenid fishes are controversial. In this study, the complete mitochondrial genome sequences of seven representative sciaenid species were determined and a well-resolved tree was recovered. This new timescale demonstrated that the sciaenid originated during the late Jurassic to early Cretaceous Period. The estimated origin time of sciaenid fish is 208 Mya, and the origin of Old World sciaenid is estimated at 126 Mya. Reconstruction of ancestral distributions indicated a plesiomorphic distribution and center of origin in the New World, with at least one lineage subsequently dispersed to the Old World. Moreover, we conclude that the common ancestors of Old World sciaenid fishes were derived from species of New World.

  11. The Origins and Evolution of Child Protection in Terms of the History of Ideas

    ERIC Educational Resources Information Center

    Hämäläinen, Juha

    2016-01-01

    Dealing with the methodological challenge of historical expounding, this paper discusses the historical formation of child protection with regard to the history of ideas. The aim is to identify the early intellectual grounds of the idea of child protection. Due to the fact that the genesis and evolution of child protection are shaped by many kinds…

  12. Proponents of Creationism but Not Proponents of Evolution Frame the Origins Debate in Terms of Proof

    ERIC Educational Resources Information Center

    Barnes, Ralph M.; Church, Rebecca A.

    2013-01-01

    In Study 1, 72 internet documents containing creationism, ID (intelligent design), or evolution content were selected for analysis. All instances of proof cognates (the word "proof" and related terms such as "proven", "disproof", etc.) contained within these documents were identified and labeled in terms of the manner in which the terms were used.…

  13. Origins, evolution, and diversification of cleptoparasitic lineages in long-tongued bees.

    PubMed

    Litman, Jessica R; Praz, Christophe J; Danforth, Bryan N; Griswold, Terry L; Cardinal, Sophie

    2013-10-01

    The evolution of parasitic behavior may catalyze the exploitation of new ecological niches yet also binds the fate of a parasite to that of its host. It is thus not clear whether evolutionary transitions from free-living organism to parasite lead to increased or decreased rates of diversification. We explore the evolution of brood parasitism in long-tongued bees and find decreased rates of diversification in eight of 10 brood parasitic clades. We propose a pathway for the evolution of brood parasitic strategy and find that a strategy in which a closed host nest cell is parasitized and the host offspring is killed by the adult parasite represents an obligate first step in the appearance of a brood parasitic lineage; this ultimately evolves into a strategy in which an open host cell is parasitized and the host offspring is killed by a specialized larval instar. The transition to parasitizing open nest cells expanded the range of potential hosts for brood parasitic bees and played a fundamental role in the patterns of diversification seen in brood parasitic clades. We address the prevalence of brood parasitic lineages in certain families of bees and examine the evolution of brood parasitism in other groups of organisms.

  14. The search for life's origins: Progress and future directions in planetary biology and chemical evolution

    NASA Technical Reports Server (NTRS)

    1990-01-01

    The current state is reviewed of the study of chemical evolution and planetary biology and the probable future is discussed of the field, at least for the near term. To this end, the report lists the goals and objectives of future research and makes detailed, comprehensive recommendations for accomplishing them, emphasizing those issues that were inadequately discussed in earlier Space Studies Board reports.

  15. Origins, evolution and diversification of cleptoparasitic lineages in long-tongued bees

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The evolution of parasitic behavior may catalyze the exploitation of new ecological niches yet also binds the fate of a parasite to that of its host. It is thus not clear whether evolutionary transitions from free-living organism to parasite lead to increased or decreased rates of diversification. W...

  16. The origin of the supernumerary subunits and assembly factors of complex I: A treasure trove of pathway evolution.

    PubMed

    Elurbe, Dei M; Huynen, Martijn A

    2016-07-01

    We review and document the evolutionary origin of all complex I assembly factors and nine supernumerary subunits from protein families. Based on experimental data and the conservation of critical residues we identify a spectrum of protein function conservation between the complex I representatives and their non-complex I homologs. This spectrum ranges from proteins that have retained their molecular function but in which the substrate specificity may have changed or have become more specific, like NDUFAF5, to proteins that have lost their original molecular function and critical catalytic residues like NDUFAF6. In between are proteins that have retained their molecular function, which however appears unrelated to complex I, like ACAD9, or proteins in which amino acids of the active site are conserved but for which no enzymatic activity has been reported, like NDUFA10. We interpret complex I evolution against the background of molecular evolution theory. Complex I supernumerary subunits and assembly factors appear to have been recruited from proteins that are mitochondrial and/or that are expressed when complex I is active. Within the evolution of complex I and its assembly there are many cases of neofunctionalization after gene duplication, like ACAD9 and TMEM126B, one case of subfunctionalization: ACPM1 and ACPM2 in Yarrowia lipolytica, and one case in which a complex I protein itself appears to have been the source of a new protein from another complex: NDUFS6 gave rise to cytochrome c oxidase subunit COX4/COX5b. Complex I and its assembly can therewith be regarded as a treasure trove for pathway evolution. This article is part of a Special Issue entitled Respiratory complex I, edited by Volker Zickermann and Ulrich Brandt.

  17. The hidden universal distribution of amino acid biosynthetic networks: a genomic perspective on their origins and evolution

    PubMed Central

    Hernández-Montes, Georgina; Díaz-Mejía, J Javier; Pérez-Rueda, Ernesto; Segovia, Lorenzo

    2008-01-01

    Background Twenty amino acids comprise the universal building blocks of proteins. However, their biosynthetic routes do not appear to be universal from an Escherichia coli-centric perspective. Nevertheless, it is necessary to understand their origin and evolution in a global context, that is, to include more 'model' species and alternative routes in order to do so. We use a comparative genomics approach to assess the origins and evolution of alternative amino acid biosynthetic network branches. Results By tracking the taxonomic distribution of amino acid biosynthetic enzymes, we predicted a core of widely distributed network branches biosynthesizing at least 16 out of the 20 standard amino acids, suggesting that this core occurred in ancient cells, before the separation of the three cellular domains of life. Additionally, we detail the distribution of two types of alternative branches to this core: analogs, enzymes that catalyze the same reaction (using the same metabolites) and belong to different superfamilies; and 'alternologs', herein defined as branches that, proceeding via different metabolites, converge to the same end product. We suggest that the origin of alternative branches is closely related to different environmental metabolite sources and life-styles among species. Conclusion The multi-organismal seed strategy employed in this work improves the precision of dating and determining evolutionary relationships among amino acid biosynthetic branches. This strategy could be extended to diverse metabolic routes and even other biological processes. Additionally, we introduce the concept of 'alternolog', which not only plays an important role in the relationships between structure and function in biological networks, but also, as shown here, has strong implications for their evolution, almost equal to paralogy and analogy. PMID:18541022

  18. Electron microscopic evidence for a tribologically induced phase transformation as the origin of wear in diamond

    SciTech Connect

    Zhang, Xinyi; Schneider, Reinhard; Müller, Erich; Gerthsen, Dagmar; Mee, Manuel; Meier, Sven; Gumbsch, Peter

    2014-02-14

    Tribological testing of a coarse-grained diamond layer, deposited by plasma-enhanced chemical vapor deposition, was performed on a ring-on-ring tribometer with a diamond counterpart. The origin of the wear of diamond and of the low friction coefficient of 0.15 was studied by analyzing the microstructure of worn and unworn regions by transmission and scanning electron microscopy. In the worn regions, the formation of an amorphous carbon layer with a thickness below 100 nm is observed. Electron energy loss spectroscopy of the C-K ionization edge reveals the transition from sp{sup 3}-hybridized C-atoms in crystalline diamond to a high fraction of sp{sup 2}-hybridized C-atoms in the tribo-induced amorphous C-layer within a transition region of less than 5 nm thickness. The mechanically induced phase transformation from diamond to the amorphous phase is found to be highly anisotropic which is clearly seen at a grain boundary, where the thickness of the amorphous layer above the two differently oriented grains abruptly changes.

  19. Origin and evolution of the Laguna Potrok Aike maar (Patagonia, Argentina)

    NASA Astrophysics Data System (ADS)

    Gebhardt, A. C.; de Batist, M.; Niessen, F.; Anselmetti, F. S.; Ariztegui, D.; Ohlendorf, C.; Zolitschka, B.

    2009-04-01

    the hydrological cycle, changes in eolian dust deposition, frequencies and consequences of volcanic activities and other natural forces controlling climatic and environmental responses can be tracked throughout time. Laguna Potrok Aike has thus become a major focus of the International Continental Scientific Drilling Program. Drilling operations were carried out within PASADO (Potrok Aike Maar Lake Sediment Archive Drilling Project) in late 2008 and penetrated ~100 m into the lacustrine sediment. Laguna Potrok Aike is surrounded by a series of subaerial paleo-shorelines of modern to Holocene age that reach up to 21 m above the 2003 AD lake level. An erosional unconformity which can be observed basin-wide along the lake shoulder at about 33 m below the 2003 AD lake level marks the lowest lake level reached during Late Glacial to Holocene times. A high-resolution seismic survey revealed a series of buried, subaquatic paleo-shorelines that hold a record of the complex transgressional history of the past approximately 6800 years, which was temporarily interrupted by two regressional phases from approximately 5800 to 5400 and 4700 to 4000 cal BP. Seismic reflection and refraction data provide insights into the sedimentary infill and the underlying volcanic structure of Laguna Potrok Aike. Reflection data show undisturbed, stratified lacustrine sediments at least in the upper ~100 m of the sedimentary infill. Two stratigraphic boundaries were identified in the seismic profiles (separating subunits I-ab, I-c and I-d) that are likely related to changes in lake level. Subunits I-ab and I-d are quite similar even though velocities are enhanced in subunit I-d. This might point at cementation in subunit I-d. Subunit I-c is restricted to the central parts of the lake and thins out laterally. A velocity-depth model calculated from seismic refraction data reveals a funnel-shaped structure embedded in the sandstone rocks of the surrounding Santa Cruz Formation. This funnel structure

  20. The pre-endosymbiont hypothesis: a new perspective on the origin and evolution of mitochondria.

    PubMed

    Gray, Michael W

    2014-03-01

    Mitochondrial DNA (mtDNA) is unquestionably the remnant of an α-proteobacterial genome, yet only ~10%-20% of mitochondrial proteins are demonstrably α-proteobacterial in origin (the "α-proteobacterial component," or APC). The evolutionary ancestry of the non-α-proteobacterial component (NPC) is obscure and not adequately accounted for in current models of mitochondrial origin. I propose that in the host cell that accommodated an α-proteobacterial endosymbiont, much of the NPC was already present, in the form of a membrane-bound metabolic organelle (the premitochondrion) that compartmentalized many of the non-energy-generating functions of the contemporary mitochondrion. I suggest that this organelle also possessed a protein import system and various ion and small-molecule transporters. In such a scenario, an α-proteobacterial endosymbiont could have been converted relatively directly and rapidly into an energy-generating organelle that incorporated the extant metabolic functions of the premitochondrion. This model (the "pre-endosymbiont hypothesis") effectively represents a synthesis of previous, contending mitochondrial origin hypotheses, with the bulk of the mitochondrial proteome (much of the NPC) having an endogenous origin and the minority component (the APC) having a xenogenous origin.

  1. [What gene and chromosomes say about the origin and evolution of insects and other arthropods].

    PubMed

    Lukhtanov, V A; Kuznetsova, V G

    2010-09-01

    At the turn of the 21st century, the use of molecular and molecular cytogenetic methods led to revolutionary advances in systematics of insects and other arthropods. Analysis of nuclear and mitochondrial genes, as well as investigation of structural rearrangements in the mitochondrial chromosome convincingly supported the Pancrustacea hypothesis, according to which insects originated directly from crustaceans, whereas myriapods are not closely related to them. The presence of the specific telomeric motif TTAGG confirmed the monophyletic origin of arthropods (Arthropoda) and the assignment of tongue worms (Pentastomida) to this type. Several different types of telomeric sequences have been found within the class of insects. Investigation of the molecular organization of these sequences may shed light on the relationships between the orders Diptera, Siphonaptera, and Mecoptera and on the origin of such enigmatic groups as the orders Strepsiptera, Zoraptera and suborder Coleorrhyncha.

  2. 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)

  3. Astrobiology: exploring the origins, evolution, and distribution of life in the Universe

    NASA Technical Reports Server (NTRS)

    Des Marais, D. J.; Walter, M. R.

    1999-01-01

    The search for the origins of life and its presence beyond Earth is strengthened by new technology and by evidence that life tolerates extreme conditions and that planets are widespread. Astrobiologists learn how planets develop and maintain habitable conditions. They combine biological and information sciences to decipher the origins of life. They examine how biota, particularly microorganisms, evolve, at scales from the molecular to the biosphere level, including interactions with long-term planetary changes. Astrobiologists learn how to recognize the morphological, chemical, and spectroscopic signatures of life in order to explore both extraterrestrial samples and electromagnetic spectra reflected from extrasolar planets.

  4. Astrobiology: exploring the origins, evolution, and distribution of life in the Universe.

    PubMed

    Des Marais, D J; Walter, M R

    1999-01-01

    The search for the origins of life and its presence beyond Earth is strengthened by new technology and by evidence that life tolerates extreme conditions and that planets are widespread. Astrobiologists learn how planets develop and maintain habitable conditions. They combine biological and information sciences to decipher the origins of life. They examine how biota, particularly microorganisms, evolve, at scales from the molecular to the biosphere level, including interactions with long-term planetary changes. Astrobiologists learn how to recognize the morphological, chemical, and spectroscopic signatures of life in order to explore both extraterrestrial samples and electromagnetic spectra reflected from extrasolar planets.

  5. The origins and evolution of dwarf males and habitat use in thoracican barnacles.

    PubMed

    Lin, Hsiu-Chin; Høeg, Jens T; Yusa, Yoichi; Chan, Benny K K

    2015-10-01

    Barnacles are exceptional in having various sexual systems (androdioecy, hermaphroditism, dioecy) and with a high morphological diversity of males, though these are always minute (dwarf) compared to their female or hermaphrodite partners. For the first time, we use a multiple DNA marker-based phylogeny to elucidate the ancestral states and evolution of (1) dwarf males, (2) their morphology when present, (3) their attachment site on the partner, and (4) habitat use in thoracican barnacles. Our taxon sampling was especially rich in rare deep-sea Scalpelliformes and comprised species with diverse sexual systems and dwarf male morphologies. Within the thoracican barnacles dwarf male evolution is subject to extensive convergence, but always correlated to similar ecological conditions. Males evolved convergently at least four times from purely hermaphroditic ancestors, in each case correlated with the invasion into habitats with low mating group sizes. The independent evolution of dwarf males in these lineages dovetails with the males having different morphologies and occurring in several different locations on their sexual partner.

  6. The properties, origin and evolution of stellar clusters in galaxy simulations and observations

    NASA Astrophysics Data System (ADS)

    Dobbs, C. L.; Adamo, A.; Few, C. G.; Calzetti, D.; Dale, D. A.; Elmegreen, B. G.; Evans, A. S.; Gouliermis, D. A.; Grasha, K.; Grebel, E. K.; Johnson, K. E.; Kim, H.; Lee, J. C.; Messa, M.; Ryon, J. E.; Smith, L. J.; Thilker, D.; Ubeda, L.; Whitmore, B.

    2017-01-01

    We investigate the properties and evolution of star particles in two simulations of isolated spiral galaxies, and two galaxies from cosmological simulations. Unlike previous numerical work, where typically each star particle represents one `cluster', for the isolated galaxies we are able to model features we term `clusters' with groups of particles. We compute the spatial distribution of stars with different ages, and cluster mass distributions, comparing our findings with observations including the recent LEGUS survey. We find that spiral structure tends to be present in older (100s Myr) stars and clusters in the simulations compared to the observations. This likely reflects differences in the numbers of stars or clusters, the strength of spiral arms, and whether the clusters are allowed to evolve. Where we model clusters with multiple particles, we are able to study their evolution. The evolution of simulated clusters tends to follow that of their natal gas clouds. Massive, dense, long-lived clouds host massive clusters, whilst short-lived clouds host smaller clusters which readily disperse. Most clusters appear to disperse fairly quickly, in basic agreement with observational findings. We note that embedded clusters may be less inclined to disperse in simulations in a galactic environment with continuous accretion of gas on to the clouds than isolated clouds and correspondingly, massive young clusters which are no longer associated with gas tend not to occur in the simulations. Caveats of our models include that the cluster densities are lower than realistic clusters, and the simplistic implementation of stellar feedback.

  7. Positive phase evolution of waves propagating along a photonic crystal with negative index of refraction.

    PubMed

    Martínez, Alejandro; Martí, Javier

    2006-10-16

    We analyze propagation of electromagnetic waves in a photonic crystal at frequencies at which it behaves as an effective medium with a negative index in terms of refraction at its interface with free space. We show that the phase evolution along the propagation direction is positive, despite the fact that the photonic crystal displays negative refraction following Snell's law, and explain it in terms of the Fourier components of the Bloch wave. Two distinct behaviors are found at frequencies far and close to the band edge of the negative-index photonic band. These findings contrast with the negative phase evolution that occurs in left-handed materials, so care has to be taken when applying the term left-handed to photonic crystals.

  8. The origin of the animals and a 'Savannah' hypothesis for early bilaterian evolution.

    PubMed

    Budd, Graham E; Jensen, Sören

    2017-02-01

    The earliest evolution of the animals remains a taxing biological problem, as all extant clades are highly derived and the fossil record is not usually considered to be helpful. The rise of the bilaterian animals recorded in the fossil record, commonly known as the 'Cambrian explosion', is one of the most significant moments in evolutionary history, and was an event that transformed first marine and then terrestrial environments. We review the phylogeny of early animals and other opisthokonts, and the affinities of the earliest large complex fossils, the so-called 'Ediacaran' taxa. We conclude, based on a variety of lines of evidence, that their affinities most likely lie in various stem groups to large metazoan groupings; a new grouping, the Apoikozoa, is erected to encompass Metazoa and Choanoflagellata. The earliest reasonable fossil evidence for total-group bilaterians comes from undisputed complex trace fossils that are younger than about 560 Ma, and these diversify greatly as the Ediacaran-Cambrian boundary is crossed a few million years later. It is generally considered that as the bilaterians diversified after this time, their burrowing behaviour destroyed the cyanobacterial mat-dominated substrates that the enigmatic Ediacaran taxa were associated with, the so-called 'Cambrian substrate revolution', leading to the loss of almost all Ediacara-aspect diversity in the Cambrian. Why, though, did the energetically expensive and functionally complex burrowing mode of life so typical of later bilaterians arise? Here we propose a much more positive relationship between late-Ediacaran ecologies and the rise of the bilaterians, with the largely static Ediacaran taxa acting as points of concentration of organic matter both above and below the sediment surface. The breaking of the uniformity of organic carbon availability would have signalled a decisive shift away from the essentially static and monotonous earlier Ediacaran world into the dynamic and burrowing world

  9. On the origin and evolution of thermophily: reconstruction of functional precambrian enzymes from ancestors of Bacillus.

    PubMed

    Hobbs, Joanne K; Shepherd, Charis; Saul, David J; Demetras, Nicholas J; Haaning, Svend; Monk, Colin R; Daniel, Roy M; Arcus, Vickery L

    2012-02-01

    Thermophily is thought to be a primitive trait, characteristic of early forms of life on Earth, that has been gradually lost over evolutionary time. The genus Bacillus provides an ideal model for studying the evolution of thermophily as it is an ancient taxon and its contemporary species inhabit a range of thermal environments. The thermostability of reconstructed ancestral proteins has been used as a proxy for ancient thermal adaptation. The reconstruction of ancestral "enzymes" has the added advantages of demonstrable activity, which acts as an internal control for accurate inference, and providing insights into the evolution of enzymatic catalysis. Here, we report the reconstruction of the structurally complex core metabolic enzyme LeuB (3-isopropylmalate dehydrogenase, E. C. 1.1.1.85) from the last common ancestor (LCA) of Bacillus using both maximum likelihood (ML) and Bayesian inference. ML LeuB from the LCA of Bacillus shares only 76% sequence identity with its closest contemporary homolog, yet it is fully functional, thermophilic, and exhibits high values for k(cat), k(cat)/K(M), and ΔG(‡) for unfolding. The Bayesian version of this enzyme is also thermophilic but exhibits anomalous catalytic kinetics. We have determined the 3D structure of the ML enzyme and found that it is more closely aligned with LeuB from deeply branching bacteria, such as Thermotoga maritima, than contemporary Bacillus species. To investigate the evolution of thermophily, three descendents of LeuB from the LCA of Bacillus were also reconstructed. They reveal a fluctuating trend in thermal evolution, with a temporal adaptation toward mesophily followed by a more recent return to thermophily. Structural analysis suggests that the determinants of thermophily in LeuB from the LCA of Bacillus and the most recent ancestor are distinct and that thermophily has arisen in this genus at least twice via independent evolutionary paths. Our results add significant fluctuations to the broad

  10. The origin of digital species: The evolution of autonomous agents and lineages in a simulated ecosystem

    NASA Astrophysics Data System (ADS)

    Earon, Ernest J. P.

    As mobile robotics technology continues to advance, the manual development of algorithms and controllers for these systems will become less feasible, if possible at all. As such, it will become increasingly necessary to turn to techniques that allow the automatic design of such systems, both in software and indeed in hardware. Evolutionary methods can provide powerful tools for automatic design as is evidenced by the abundance of diverse natural systems from the simple to the massively sophisticated and coupled. One of the fundamental features, and one of the lesser understood phenomena, in biology is that of speciation. In order to better understand the development and creation of species, and their role in evolution, a method for tracking speciation in simulation is presented. While there is much dispute in the field of biology as to the precise definition of the term species, there is little debate that the natural world is full of distinct subpopulations. Each of these populations has developed unique features for, and solutions to, the problem of surviving in an incredibly complex world. The power of investigating species over individual agents arises from improved robustness of a grouping of like individuals as opposed to single entities more sensitive to very local conditions and interactions. In essence, a species is a more complete view of the fitness and survivability of a genome than a single agent. A simulation engine is presented which allows the study of evolution from a species point of view. Results from simulations offer insight into the role of genetic neutrality in evolution as well as the effect of this neutrality on mechanisms such as mutation pressure. Several results are presented which provide insight into these features which can serve as analogs for similar biological effects as well as features such as genetic cross drift (or convergent evolution of species). Some insight into the such as solution bloating are also detailed. The

  11. Nanoarchitectured Co-Cr-Mo orthopedic implant alloys: nitrogen-enhanced nanostructural evolution and its effect on phase stability.

    PubMed

    Yamanaka, Kenta; Mori, Manami; Chiba, Akihiko

    2013-04-01

    Our previous studies indicate that nitrogen addition suppresses the athermal γ (face-centered cubic, fcc)→ε (hexagonal close-packed, hcp) martensitic transformation of biomedical Co-Cr-Mo alloys and ultimately offers large elongation to failure while maintaining high strength. In the present study, structural evolution and dislocation slip as an elementary process in the martensitic transformation in Co-Cr-Mo alloys were investigated to reveal the origin of their enhanced γ phase stability due to nitrogen addition. Alloy specimens with and without nitrogen addition were prepared. The N-doped alloys had a single-phase γ matrix, whereas the N-free alloys had a γ/ε duplex microstructure. Irrespective of the nitrogen content, dislocations frequently dissociated into Shockley partial dislocations with stacking faults. This indicates that nitrogen has little effect on the stability of the γ phase, which is also predicted by thermodynamic calculations. We discovered short-range ordering (SRO) or nanoscale Cr2N precipitates in the γ matrix of the N-containing alloy specimens, and it was revealed that both SRO and nanoprecipitates function as obstacles to the glide of partial dislocations and consequently significantly affect the kinetics of the γ→ε martensitic transformation. Since the formation of ε martensite plays a crucial role in plastic deformation and wear behavior, the developed nanostructural modification associated with nitrogen addition must be a promising strategy for highly durable orthopedic implants.

  12. Positional information from oscillatory phase shifts : insights from in silico evolution

    NASA Astrophysics Data System (ADS)

    Beaupeux, M.; François, P.

    2016-06-01

    Complex cellular decisions are based on temporal dynamics of pathways, including genetic oscillators. In development, recent works on vertebrae formation have suggested that relative phase of genetic oscillators encode positional information, including differentiation front defining vertebrae positions. Precise mechanisms for this are still unknown. Here, we use computational evolution to find gene network topologies that can compute the phase difference between oscillators and convert it into a decoder morphogen concentration. Two types of networks are discovered, based on symmetry properties of the decoder gene. So called asymmetric networks are studied, and two submodules are identified converting phase information into an amplitude variable. Those networks naturally display a ’shock’ for a well defined phase difference, that can be used to define a wavefront of differentiation. We show how implementation of these ideas reproduce experimental features of vertebrate segmentation.

  13. Two different phase-change origins with chemical- and structural-phase-changes in C doped (1.5 wt.%) In3Sb1Te2

    PubMed Central

    Lee, Y. M.; Lee, S. Y.; Sasaki, T.; Kim, K.; Ahn, D.; Jung, M.-C.

    2016-01-01

    We fabricated C-doped (1.5 wt.%) In3Sb1Te2 (CIST) thin films with amorphous phase (a-CIST) using a sputter method. Two electrical-phase-changes at 250 and 275 °C were observed in the sheet resistance measurement. In order to understand the origin of these electrical-phase-changes, all samples were characterized by XRD, TEM, and HRXPS with synchrotron radiation. In a-CIST, only weak Sb-C bonding was observed. In the first electrical-phase-change at 250 °C, strong Sb-C bonding occurred without an accompanying structural/phase change (still amorphous). On the other hand, the second electrical-phase-change at 275 °C was due to the structural/phase change from amorphous to crystalline without a chemical state change. PMID:27929133

  14. Two different phase-change origins with chemical- and structural-phase-changes in C doped (1.5 wt.%) In3Sb1Te2.

    PubMed

    Lee, Y M; Lee, S Y; Sasaki, T; Kim, K; Ahn, D; Jung, M-C

    2016-12-08

    We fabricated C-doped (1.5 wt.%) In3Sb1Te2 (CIST) thin films with amorphous phase (a-CIST) using a sputter method. Two electrical-phase-changes at 250 and 275 °C were observed in the sheet resistance measurement. In order to understand the origin of these electrical-phase-changes, all samples were characterized by XRD, TEM, and HRXPS with synchrotron radiation. In a-CIST, only weak Sb-C bonding was observed. In the first electrical-phase-change at 250 °C, strong Sb-C bonding occurred without an accompanying structural/phase change (still amorphous). On the other hand, the second electrical-phase-change at 275 °C was due to the structural/phase change from amorphous to crystalline without a chemical state change.

  15. Two different phase-change origins with chemical- and structural-phase-changes in C doped (1.5 wt.%) In3Sb1Te2

    NASA Astrophysics Data System (ADS)

    Lee, Y. M.; Lee, S. Y.; Sasaki, T.; Kim, K.; Ahn, D.; Jung, M.-C.

    2016-12-01

    We fabricated C-doped (1.5 wt.%) In3Sb1Te2 (CIST) thin films with amorphous phase (a-CIST) using a sputter method. Two electrical-phase-changes at 250 and 275 °C were observed in the sheet resistance measurement. In order to understand the origin of these electrical-phase-changes, all samples were characterized by XRD, TEM, and HRXPS with synchrotron radiation. In a-CIST, only weak Sb-C bonding was observed. In the first electrical-phase-change at 250 °C, strong Sb-C bonding occurred without an accompanying structural/phase change (still amorphous). On the other hand, the second electrical-phase-change at 275 °C was due to the structural/phase change from amorphous to crystalline without a chemical state change.

  16. The origin and evolution of r- and s-process elements in the Milky Way stellar disk

    NASA Astrophysics Data System (ADS)

    Battistini, Chiara; Bensby, Thomas

    2016-02-01

    Context. Elements heavier than iron are produced through neutron-capture processes in the different phases of stellar evolution. Asymptotic giant branch (AGB) stars are believed to be mainly responsible for elements that form through the slow neutron-capture process, while the elements created in the rapid neutron-capture process have production sites that are less understood. Knowledge of abundance ratios as functions of metallicity can lead to insight into the origin and evolution of our Galaxy and its stellar populations. Aims: We aim to trace the chemical evolution of the neutron-capture elements Sr, Zr, La, Ce, Nd, Sm, and Eu in the Milky Way stellar disk. This will allow us to constrain the formation sites of these elements, as well as to probe the evolution of the Galactic thin and thick disks. Methods: Using spectra of high resolution (42 000 ≲ R ≲ 65 000) and high signal-to-noise (S/N ≳ 200) obtained with the MIKE and the FEROS spectrographs, we determine Sr, Zr, La, Ce, Nd, Sm, and Eu abundances for a sample of 593 F and G dwarf stars in the solar neighborhood. The abundance analysis is based on spectral synthesis using one-dimensional, plane-parallel, local thermodynamic equilibrium (LTE) model stellar atmospheres calculated with the MARCS 2012 code. Results: We present abundance results for Sr (156 stars), Zr (311 stars), La (242 stars), Ce (365 stars), Nd (395 stars), Sm (280 stars), and Eu (378 stars). We find that Nd, Sm, and Eu show trends similar to what is observed for the α elements in the [X/Fe]-[Fe/H] abundance plane. For [Sr/Fe] and [Zr/Fe], we find decreasing abundance ratios for increasing metallicity, reaching sub-solar values at super-solar metallicities. [La/Fe] and [Ce/Fe] do not show any clear trend with metallicity, and they are close to solar values at all [Fe/H]. The trends of abundance ratios [X/Fe] as a function of stellar ages present different slopes before and after 8 Gyr. Conclusions: The rapid neutron-capture process is

  17. Origin, evolution, and imaging of vortices in proton-hydrogen collisions

    NASA Astrophysics Data System (ADS)

    Schultz, D. R.; Macek, J. H.; Sternberg, J. B.; Ovchinnikov, S. Yu; Lee, T.-G.

    2009-11-01

    Using a novel computational approach, we have elucidated the origin of unexpected vortices in the electronic wavefunction during ion-atom collisions. It is shown how they could be observed in experiments and how they play a new and wide ranging role in angular momentum transfer and other atomic processes.

  18. Laurentian origin for the North Slope of Alaska: Implications for the tectonic evolution of the Arctic

    USGS Publications Warehouse

    Strauss, J. V.; Macdonald, F. A.; Taylor, J. F.; Repetski, John E.; McClelland, W. C.

    2013-01-01

    The composite Arctic Alaska–Chukotka terrane plays a central role in tectonic reconstructions of the Arctic. An exotic, non-Laurentian origin of Arctic Alaska–Chukotka has been proposed based on paleobiogeographic faunal affinities and various geochronological constraints from the southwestern portions of the terrane. Here, we report early Paleozoic trilobite and conodont taxa that support a Laurentian origin for the North Slope subterrane of Arctic Alaska, as well as new Neoproterozoic–Cambrian detrital zircon geochronological data, which are both consistent with a Laurentian origin and profoundly different from those derived from similar-aged strata in the southwestern subterranes of Arctic Alaska–Chukotka. The North Slope subterrane is accordingly interpreted as allochthonous with respect to northwestern Laurentia, but it most likely originated farther east along the Canadian Arctic or Atlantic margins. These data demonstrate that construction of the composite Arctic Alaska–Chukotka terrane resulted from juxtaposition of the exotic southwestern fragments of the terrane against the northern margin of Laurentia during protracted Devonian(?)–Carboniferous tectonism.

  19. On the correlation between phase evolution of lipoplexes/anionic lipid mixtures and DNA release

    NASA Astrophysics Data System (ADS)

    Caracciolo, Giulio; Pozzi, Daniela; Caminiti, Ruggero; Marchini, Cristina; Montani, Maura; Amici, Augusto; Amenitsch, Heinz

    2007-10-01

    We investigated the structural evolution of three lipoplex formulations when interacting with anionic lipids by synchrotron small angle x-ray diffraction, while the extent of DNA release from lipoplexes by anionic lipids was evaluated by gel electrophoresis. Lipoplexes formed lamellar phases when mixed with anionic dioleoylphosphatidylglycerol (DOPG), while promoting the formation of nonbilayer structures when mixed with anionic dioleoylphosphatidic acid (DOPA). However, lipoplexes exhibited a virtually identical extent of DNA release when mixed with DOPG or DOPA. Thus, the recently proposed correlation between the formation of nonlamellar phases in lipoplex/anionic lipid mixtures and the increase of DNA release does not seem to exist.

  20. Structural evolution of epitaxial SrCoOx films near topotactic phase transition

    NASA Astrophysics Data System (ADS)

    Jeen, Hyoungjeen; Lee, Ho Nyung

    2015-12-01

    Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoOx) epitaxially grown by pulsed laser epitaxy (PLE) as a model system to study the oxidation-driven evolution of the structure, electronic, and magnetic properties. We grew coherently strained SrCoO2.5 thin films and performed post-annealing at various temperatures for topotactic conversion into the perovskite phase (SrCoO3-δ). We clearly observed significant changes in electronic transport, magnetism, and microstructure near the critical temperature for the topotactic transformation from the brownmillerite to the perovskite phase. Nevertheless, the overall crystallinity was well maintained without much structural degradation, indicating that topotactic phase control can be a useful tool to control the physical properties repeatedly via redox reactions.

  1. Structural evolution of epitaxial SrCoO{sub x} films near topotactic phase transition

    SciTech Connect

    Jeen, Hyoungjeen; Lee, Ho Nyung

    2015-12-15

    Control of oxygen stoichiometry in complex oxides via topotactic phase transition is an interesting avenue to not only modifying the physical properties, but utilizing in many energy technologies, such as energy storage and catalysts. However, detailed structural evolution in the close proximity of the topotactic phase transition in multivalent oxides has not been much studied. In this work, we used strontium cobaltites (SrCoO{sub x}) epitaxially grown by pulsed laser epitaxy (PLE) as a model system to study the oxidation-driven evolution of the structure, electronic, and magnetic properties. We grew coherently strained SrCoO{sub 2.5} thin films and performed post-annealing at various temperatures for topotactic conversion into the perovskite phase (SrCoO{sub 3-δ}). We clearly observed significant changes in electronic transport, magnetism, and microstructure near the critical temperature for the topotactic transformation from the brownmillerite to the perovskite phase. Nevertheless, the overall crystallinity was well maintained without much structural degradation, indicating that topotactic phase control can be a useful tool to control the physical properties repeatedly via redox reactions.

  2. THE ORIGIN AND EVOLUTION OF METALLICITY GRADIENTS: PROBING THE MODE OF MASS ASSEMBLY AT z {approx_equal} 2

    SciTech Connect

    Jones, Tucker; Ellis, Richard S.; Richard, Johan; Jullo, Eric

    2013-03-01

    We present and discuss measurements of the gas-phase metallicity gradient in four gravitationally lensed galaxies at z = 2.0-2.4 based on adaptive optics-assisted imaging spectroscopy with the Keck II telescope. Three galaxies with well-ordered rotation reveal metallicity gradients with lower gas-phase metallicities at larger galactocentric radii. Two of these display gradients much steeper than found locally, while a third has one similar to that seen in local disk galaxies. The fourth galaxy exhibits complex kinematics indicative of an ongoing merger and reveals an 'inverted' gradient with lower metallicity in the central regions. By comparing our sample to similar data in the literature for lower redshift galaxies, we determine that, on average, metallicity gradients must flatten by a factor of 2.6 {+-} 0.9 between z = 2.2 and the present epoch. This factor is in rough agreement with the size growth of massive galaxies, suggesting that inside-out growth can account for the evolution of metallicity gradients. Since the addition of our new data provides the first indication of a coherent picture of this evolution, we develop a simple model of chemical evolution to explain the collective data. We find that metallicity gradients and their evolution can be explained by the inward radial migration of gas together with a radial variation in the mass loading factor governing the ratio of outflowing gas to the local star formation rate. Average mass loading factors of {approx}< 2 are inferred from our model in good agreement with direct measurements of outflowing gas in z {approx_equal} 2 galaxies.

  3. Transformation abrogates an early G1-phase arrest point required for specification of the Chinese hamster DHFR replication origin.

    PubMed Central

    Wu, J R; Keezer, S M; Gilbert, D M

    1998-01-01

    The origin decision point (ODP) was originally identified as a distinct point during G1-phase when Chinese hamster ovary (CHO) cell nuclei experience a transition that is required for specific recognition of the dihydrofolate reductase (DHFR) origin locus by Xenopus egg extracts. Passage of cells through the ODP requires a mitogen-independent protein kinase that is activated prior to restriction point control. Here we show that inhibition of an early G1-phase protein kinase pathway by the addition of 2-aminopurine (2-AP) prior to the ODP arrests CHO cells in G1-phase. Transformation with simian virus 40 (SV40) abrogated this arrest point, resulting in the entry of cultured cells into S-phase in the presence of 2-AP and a disruption of the normal pattern of initiation sites at the DHFR locus. Cells treated with 2-AP after the ODP initiated replication specifically within the DHFR origin locus. Transient exposure of transformed cells to 2-AP during the ODP transition also disrupted origin choice, whereas non-transformed cells arrested in G1-phase and then passed through a delayed ODP after removal of 2-AP from the medium. We conclude that mammalian cells have many potential sites at which they can initiate replication. Normally, events occurring during the early G1-phase ODP transition determine which of these sites will be the preferred initiation site. However, if chromatin is exposed to S-phase-promoting factors prior to this transition, mammalian cells, like Xenopus and Drosophila embryos, can initiate replication without origin specification. PMID:9501102

  4. A genomic timescale of prokaryote evolution: insights into the origin of methanogenesis, phototrophy, and the colonization of land

    NASA Technical Reports Server (NTRS)

    Battistuzzi, Fabia U.; Feijao, Andreia; Hedges, S. Blair

    2004-01-01

    BACKGROUND: The timescale of prokaryote evolution has been difficult to reconstruct because of a limited fossil record and complexities associated with molecular clocks and deep divergences. However, the relatively large number of genome sequences currently available has provided a better opportunity to control for potential biases such as horizontal gene transfer and rate differences among lineages. We assembled a data set of sequences from 32 proteins (approximately 7600 amino acids) common to 72 species and estimated phylogenetic relationships and divergence times with a local clock method. RESULTS: Our phylogenetic results support most of the currently recognized higher-level groupings of prokaryotes. Of particular interest is a well-supported group of three major lineages of eubacteria (Actinobacteria, Deinococcus, and Cyanobacteria) that we call Terrabacteria and associate with an early colonization of land. Divergence time estimates for the major groups of eubacteria are between 2.5-3.2 billion years ago (Ga) while those for archaebacteria are mostly between 3.1-4.1 Ga. The time estimates suggest a Hadean origin of life (prior to 4.1 Ga), an early origin of methanogenesis (3.8-4.1 Ga), an origin of anaerobic methanotrophy after 3.1 Ga, an origin of phototrophy prior to 3.2 Ga, an early colonization of land 2.8-3.1 Ga, and an origin of aerobic methanotrophy 2.5-2.8 Ga. CONCLUSIONS: Our early time estimates for methanogenesis support the consideration of methane, in addition to carbon dioxide, as a greenhouse gas responsible for the early warming of the Earths' surface. Our divergence times for the origin of anaerobic methanotrophy are compatible with highly depleted carbon isotopic values found in rocks dated 2.8-2.6 Ga. An early origin of phototrophy is consistent with the earliest bacterial mats and structures identified as stromatolites, but a 2.6 Ga origin of cyanobacteria suggests that those Archean structures, if biologically produced, were made by

  5. The origins of language and the evolution of music: A comparative perspective

    NASA Astrophysics Data System (ADS)

    Masataka, Nobuo

    2009-03-01

    According to Darwin [Darwin, CR. The descent of man, and selection in relation to sex. London: John Murray; 1871], the human musical faculty ‘must be ranked amongst the most mysterious with which he is endowed’. Music is a human cultural universal that serves no obvious adaptive purpose, making its evolution a puzzle for evolutionary biologists. This review examines Darwin's hypothesis of similarities between language and music indicating a shared evolutionary history. In particular, the fact that both are human universals, have phrase structure, and entail learning and cultural transmission, suggests that any theory of the evolution of language will have implications for the evolution of music, and vice versa. The argument starts by describing variable predispositional musical capabilities and the ontogeny of prosodic communication in human infants and young children, presenting comparative data regarding communication systems commonly present in living nonhuman primate species. Like language, the human music faculty is based on a suite of abilities, some of which are shared with other primates and some of which appear to be uniquely human. Each of these subcomponents may have a different evolutionary history, and should be discussed separately. After briefly considering possible functions of human music for language acquisition, the review ends by discussing the phylogenetic history of music. It concludes that many strands of evidence support Darwin's hypothesis of an intermediate stage of human evolutionary history, characterized by a communication system that resembled music more closely than language, but was identical to neither. This pre-linguistic system, which could probably referred to as “prosodic protolanguage”, provided a precursor for both modern language and music.

  6. Gene regulatory evolution and the origin of macroevolutionary novelties: insights from the neural crest.

    PubMed

    Van Otterloo, Eric; Cornell, Robert A; Medeiros, Daniel Meulemans; Garnett, Aaron T

    2013-07-01

    The appearance of novel anatomic structures during evolution is driven by changes to the networks of transcription factors, signaling pathways, and downstream effector genes controlling development. The nature of the changes to these developmental gene regulatory networks (GRNs) is poorly understood. A striking test case is the evolution of the GRN controlling development of the neural crest (NC). NC cells emerge from the neural plate border (NPB) and contribute to multiple adult structures. While all chordates have a NPB, only in vertebrates do NPB cells express all the genes constituting the neural crest GRN (NC-GRN). Interestingly, invertebrate chordates express orthologs of NC-GRN components in other tissues, revealing that during vertebrate evolution new regulatory connections emerged between transcription factors primitively expressed in the NPB and genes primitively expressed in other tissues. Such interactions could have evolved by two mechanisms. First, transcription factors primitively expressed in the NPB may have evolved new DNA and/or cofactor binding properties (protein neofunctionalization). Alternately, cis-regulatory elements driving NPB expression may have evolved near genes primitively expressed in other tissues (cis-regulatory neofunctionalization). Here we discuss how gene duplication can, in principle, promote either form of neofunctionalization. We review recent published examples of interspecies gene-swap, or regulatory-element-swap, experiments that test both models. Such experiments have yielded little evidence to support the importance of protein neofunctionalization in the emergence of the NC-GRN, but do support the importance of novel cis-regulatory elements in this process. The NC-GRN is an excellent model for the study of gene regulatory and macroevolutionary innovation.

  7. The origin and early evolution of tracheids in vascular plants: integration of palaeobotanical and neobotanical data.

    PubMed Central

    Friedman, W E; Cook, M E

    2000-01-01

    Although there is clear evidence for the establishment of terrestrial plant life by the end of the Ordovician, the fossil record indicates that land plants remained extremely small and structurally simple until the Late Silurian. Among the events associated with this first major radiation of land plants is the evolution of tracheids, complex water-conducting cells defined by the presence of lignified secondary cell wall thickenings. Recent palaeobotanical analyses indicate that Early Devonian tracheids appear to possess secondary cell wall thickenings composed of two distinct layers: a degradation-prone layer adjacent to the primary cell wall and a degradation-resistant (possibly lignified) layer next to the cell lumen. In order to understand better the early evolution of tracheids, developmental and comparative studies of key basal (and potentially plesiomorphic) extant vascular plants have been initiated. Ultrastructural analysis and enzyme degradation studies of wall structure (to approximate diagenetic alterations of fossil tracheid structure) have been conducted on basal members of each of the two major clades of extant vascular plants: Huperzia (Lycophytina) and Equisetum (Euphyllophytina. This research demonstrates that secondary cell walls of extant basal vascular plants include a degradation-prone layer ('template layer') and a degradation-resistant layer ('resistant layer'). This pattern of secondary cell wall formation in the water-conducting cells of extant vascular plants matches the pattern of wall thickenings in the tracheids of early fossil vascular plants and provides a key evolutionary link between tracheids of living vascular plants and those of their earliest fossil ancestors. Further studies of tracheid development and structure among basal extant vascular plants will lead to a more precise reconstruction of the early evolution of water-conducting tissues in land plants, and will add to the current limited knowledge of spatial, temporal and

  8. The origins of language and the evolution of music: A comparative perspective.

    PubMed

    Masataka, Nobuo

    2009-03-01

    According to Darwin [Darwin, CR. The descent of man, and selection in relation to sex. London: John Murray; 1871], the human musical faculty 'must be ranked amongst the most mysterious with which he is endowed'. Music is a human cultural universal that serves no obvious adaptive purpose, making its evolution a puzzle for evolutionary biologists. This review examines Darwin's hypothesis of similarities between language and music indicating a shared evolutionary history. In particular, the fact that both are human universals, have phrase structure, and entail learning and cultural transmission, suggests that any theory of the evolution of language will have implications for the evolution of music, and vice versa. The argument starts by describing variable predispositional musical capabilities and the ontogeny of prosodic communication in human infants and young children, presenting comparative data regarding communication systems commonly present in living nonhuman primate species. Like language, the human music faculty is based on a suite of abilities, some of which are shared with other primates and some of which appear to be uniquely human. Each of these subcomponents may have a different evolutionary history, and should be discussed separately. After briefly considering possible functions of human music for language acquisition, the review ends by discussing the phylogenetic history of music. It concludes that many strands of evidence support Darwin's hypothesis of an intermediate stage of human evolutionary history, characterized by a communication system that resembled music more closely than language, but was identical to neither. This pre-linguistic system, which could probably referred to as "prosodic protolanguage", provided a precursor for both modern language and music.

  9. The RNA-world and co-evolution hypothesis and the origin of life: Implications, research strategies and perspectives

    NASA Technical Reports Server (NTRS)

    Lahav, Noam

    1993-01-01

    The applicability of the RNA-world and co-evolution hypothesis to the study of the very first stages of the origin of life is discussed. The discussion focuses on the basic differences between the two hypotheses and their implications, with regard to the reconstruction methodology, ribosome emergence, balance between ribozymes and protein enzymes, and their major difficultites. Additional complexities of the two hypotheses, such as membranes and the energy source of the first reactions, are not treated in the present work. A central element in the proposed experimental strategies is the study of the catalytic activites of very small peptides and RNA-like oligomers, according to existing, as well as to yet-to-be-invented scenarios of the two hypothesis under consideration. It is suggested that the novel directed molecular evolution technology, and molecular computational modeling, can be applied to this research. This strategy is assumed to be essential for the suggested goal of future studies of the origin of life, namely, the establishment of a `Primordial Darwinian entity'.

  10. Role of pKa of Nucleobases in the Origins of Chemical Evolution

    PubMed Central

    2012-01-01

    The formation of canonical base pairs through Watson–Crick hydrogen bonding sits at the heart of the genetic apparatus. The specificity of the base pairing of adenine with thymine/uracil and guanine with cytosine preserves accurate information for the biochemical blueprint and replicates the instructions necessary for carrying out biological function. The chemical evolution question of how these five canonical nucleobases were selected over various other possibilities remains intriguing. Since these and alternative nucleobases would have been available for chemical evolution, the reasons for the emergence of this system appear to be primarily functional. While investigating the base-pairing properties of structural nucleic acid analogs, we encountered a relationship between the pKa of a series of nonstandard (and canonical) nucleobases and the pH of the aqueous medium. This relationship appeared to correspond with the propensity of these molecules to self-assemble via Watson–Crick-type base-pairing interactions. A simple correlation of the “magnitude of the difference between the pKa and pH” (pKa–pH correlation) enables a general prediction of which types of heterocyclic recognition elements form hydrogen-bonded base pairs in aqueous media. Using the pKa–pH relationship, we can rationalize why nature chose the canonical nucleobases in terms of hydrophobic and hydrophilic interactions, and further extrapolate its significance within the context of chemical evolution. The connection between the physicochemical properties of bioorganic compounds and the interactions with their aqueous environment directly affects structure and function, at both a molecular and a supramolecular level. A general structure–function pattern emerges in biomolecules and biopolymers in aqueous media near neutral pH. A pKa – pH < 2 generally prompts catalytic functions, central to metabolism, but a difference in pKa – pH > 2 seems to result in the emergence of structure

  11. Ancestor-descendant relationships in evolution: origin of the extant pygmy right whale, Caperea marginata.

    PubMed

    Tsai, Cheng-Hsiu; Fordyce, R Ewan

    2015-01-01

    Ancestor-descendant relationships (ADRs), involving descent with modification, are the fundamental concept in evolution, but are usually difficult to recognize. We examined the cladistic relationship between the only reported fossil pygmy right whale, †Miocaperea pulchra, and its sole living relative, the enigmatic pygmy right whale Caperea marginata, the latter represented by both adult and juvenile specimens. †Miocaperea is phylogenetically bracketed between juvenile and adult Caperea marginata in morphologically based analyses, thus suggesting a possible ADR-the first so far identified within baleen whales (Cetacea: Mysticeti). The †Miocaperea-Caperea lineage may show long-term morphological stasis and, in turn, punctuated equilibrium.

  12. The Origin and Evolution of U.S. Naval Strategic Nuclear Policy to 1960

    DTIC Science & Technology

    1986-12-01

    White House requesting the XAJ-1 be modified to provide an atomic delivery capability for the Navy. After sitting in Forrestal’s ofTice unsigned for...whom he convinced should support legislation in the House that would create a Chief of Naval Operations. The proposal would create a CNO to represent... House . 57 Daniels was unhappy with the wording of the original bill and had it clarified by stating that the C\\0 would work directly for the

  13. 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.

  14. Origin and evolution of GATA2a and GATA2b in teleosts: insights from tongue sole, Cynoglossus semilaevis

    PubMed Central

    Liu, Jinxiang; Jiang, Jiajun; Wang, Zhongkai; He, Yan

    2016-01-01

    Background. Following the two rounds of whole-genome duplication that occurred during deuterostome evolution, a third genome duplication occurred in the lineage of teleost fish and is considered to be responsible for much of the biological diversification within the lineage. GATA2, a member of GATA family of transcription factors, is an important regulator of gene expression in hematopoietic cell in mammals, yet the role of this gene or its putative paralogs in ray-finned fishes remains relatively unknown. Methods. In this study, we attempted to identify GATA2 sequences from the transcriptomes and genomes of multiple teleosts using the bioinformatic tools MrBayes, MEME, and PAML. Following identification, comparative analysis of genome structure, molecular evolution rate, and expression by real-time qPCR were used to predict functional divergence of GATA2 paralogs and their relative transcription in organs of female and male tongue soles (Cynoglossus semilaevis). Results. Two teleost GATA2 genes were identified in the transcriptomes of tongue sole and Japanese flounder (Paralichthysolivaceus). Synteny and phylogenetic analysis confirmed that the two genes likely originated from the teleost-specific genome duplication . Additionally, selection pressure analysis predicted these gene duplicates to have undergone purifying selection and possible divergent new functions. This was supported by differential expression pattern of GATA2a and GATA2b observed in organs of female and male tongue soles. Discussion. Our results indicate that two GATA2 genes originating from the first teleost-specific genome duplication have remained transcriptionally active in some fish species and have likely undergone neofunctionalization. This knowledge provides novel insights into the evolution of the teleost GATA2 genes and constituted important groundwork for further research on the GATA gene family. PMID:27019782

  15. The Origin of Inertia and Matter as a Superradiant Phase Transition of Quantum Vacuum

    NASA Astrophysics Data System (ADS)

    Maxmilian Caligiuri, Luigi

    Mass is one of the most important concepts in physics and its real understanding represents the key for the formulation of any consistent physical theory. During the past years, a very interesting model of inertial and gravitational mass as the result of the reaction interaction between the charged particles (electrons and quarks) contained in a given body and a suitable "fraction" of QED Zero Point Fields confined within an ideal resonant cavity, associated to the same body, has been proposed by Haish, Rueda and Puthoff. More recently, the author showed that this interpretation is consistent with a picture of mass (both inertial and gravitational) as the seat of ZPF standing waves whose presence reduces quantum vacuum energy density inside the resonant cavity ideally associated to the body volume. Nevertheless so far, the ultimate physical origin of such resonant cavity as well as the mechanism able to "select" the fraction of ZPF electromagnetic modes interacting within it, remained unrevealed. In this paper, basing on the framework of QED coherence in condensed matter, we'll show mass can be viewed as the result of a spontaneous superradiant phase transition of quantum vacuum giving rise to a more stable, energetically favored, oscopic quantum state characterized by an ensemble of coherence domains, "trapping" the coherent ZPF fluctuations inside a given volume just acting as a resonant cavity. Our model is then able to explain the "natural" emergence of the ideal resonant cavity speculated by Haish, Rueda and Puthoff and its defining parameters as well as the physical mechanism selecting the fraction of ZPF interacting with the body particles. Finally, a generalization of the model to explain the origin of mass of elementary particles is proposed also suggesting a new understanding of Compton's frequency and De Broglie's wavelength. Our results indicates both inertia and matter could truly originate from coherent interaction between quantum matter-wave and

  16. The Origin and Evolution of the Atmospheres of Venus, Earth and Mars

    NASA Astrophysics Data System (ADS)

    Denlinger, Michael C.

    2005-04-01

    The chemical compositions of the primordial atmospheres of Venus, Earth and Mars have long been a topic of debate between the experts. Some believe that the original atmospheres were a product of outgassed volatiles from the newly accreted terrestrial planets and that these atmospheres consisted primarily of carbon dioxide, nitrogen, water vapor and residual hydrogen and helium (e.g., Lewis and Prinn, Planets and their Atmospheres, Academic Press, Orlando, FL, 1984, pp. 62 63, 81 84, 228 231, 383). Still others think the earliest atmospheres were composed of the gas components of the solar nebula from which the solar system formed (i.e., hydrogen, helium, methane, ammonia and water). I consider the latter to be the correct scenario. Presented herein is a proposed mechanism by which the original atmospheres of Venus, Earth and Mars were transformed to atmospheres rich in carbon dioxide and nitrogen. An explanation is proposed for why water is so common on the surface of Earth and so scarce on the surfaces of Venus and Mars. Also presented are the effects the “great impact” (single cataclysmic event that was responsible for producing the Earth Moon system) had upon the early atmosphere of Earth. The origin, structure and composition of the impacting object are determined through deductive analyses.

  17. Origin and genome evolution of polyploid green toads in Central Asia: evidence from microsatellite markers.

    PubMed

    Betto-Colliard, C; Sermier, R; Litvinchuk, S; Perrin, N; Stöck, M

    2015-03-01

    Polyploidization, which is expected to trigger major genomic reorganizations, occurs much less commonly in animals than in plants, possibly because of constraints imposed by sex-determination systems. We investigated the origins and consequences of allopolyploidization in Palearctic green toads (Bufo viridis subgroup) from Central Asia, with three ploidy levels and different modes of genome transmission (sexual versus clonal), to (i) establish a topology for the reticulate phylogeny in a species-rich radiation involving several closely related lineages and (ii) explore processes of genomic reorganization that may follow polyploidization. Sibship analyses based on 30 cross-amplifying microsatellite markers substantiated the maternal origins and revealed the paternal origins and relationships of subgenomes in allopolyploids. Analyses of the synteny of linkage groups identified three markers affected by translocation events, which occurred only within the paternally inherited subgenomes of allopolyploid toads and exclusively affected the linkage group that determines sex in several diploid species of the green toad radiation. Recombination rates did not differ between diploid and polyploid toad species, and were overall much reduced in males, independent of linkage group and ploidy levels. Clonally transmitted subgenomes in allotriploid toads provided support for strong genetic drift, presumably resulting from recombination arrest. The Palearctic green toad radiation seems to offer unique opportunities to investigate the consequences of polyploidization and clonal transmission on the dynamics of genomes in vertebrates.

  18. Karyotype evolution in apomictic Boechera and the origin of the aberrant chromosomes.

    PubMed

    Mandáková, Terezie; Schranz, M Eric; Sharbel, Timothy F; de Jong, Hans; Lysak, Martin A

    2015-06-01

    Chromosome rearrangements may result in both decrease and increase of chromosome numbers. Here we have used comparative chromosome painting (CCP) to reconstruct the pathways of descending and ascending dysploidy in the genus Boechera (tribe Boechereae, Brassicaceae). We describe the origin and structure of three Boechera genomes and establish the origin of the previously described aberrant Het and Del chromosomes found in Boechera apomicts with euploid (2n = 14) and aneuploid (2n = 15) chromosome number. CCP analysis allowed us to reconstruct the origin of seven chromosomes in sexual B. stricta and apomictic B. divaricarpa from the ancestral karyotype (n = 8) of Brassicaceae lineage I. Whereas three chromosomes (BS4, BS6, and BS7) retained their ancestral structure, five chromosomes were reshuffled by reciprocal translocations to form chromosomes BS1-BS3 and BS5. The reduction of the chromosome number (from x = 8 to x = 7) was accomplished through the inactivation of a paleocentromere on chromosome BS5. In apomictic 2n = 14 plants, CCP identifies the largely heterochromatic chromosome (Het) being one of the BS1 homologues with the expansion of pericentromeric heterochromatin. In apomictic B. polyantha (2n = 15), the Het has undergone a centric fission resulting in two smaller chromosomes - the submetacentric Het' and telocentric Del. Here we show that new chromosomes can be formed by a centric fission and can be fixed in populations due to the apomictic mode of reproduction.

  19. The origin of life: a problem of history, chemistry, and evolution.