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Sample records for phase evolution originating

  1. 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

  2. Religion: Origins and Evolution.

    ERIC Educational Resources Information Center

    Meyer, John K.

    2004-01-01

    We present the purpose of study of the origins and development of affect-relevant and religion-relevant hypotheses, and conjectured prediction of proto-religious sequences in pre-human anthropoids and primitive human cultures. We anticipate more comprehensive study of modern cultural outcomes of these origins and developments.

  3. 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

  4. 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

  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. Origin and early evolution of land plants

    PubMed Central

    2008-01-01

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

  8. Magnetars: Properties, Origin and Evolution

    NASA Astrophysics Data System (ADS)

    Mereghetti, Sandro; Pons, José A.; Melatos, Andrew

    2015-10-01

    Magnetars are neutron stars in which a strong magnetic field is the main energy source. About two dozens of magnetars, plus several candidates, are currently known in our Galaxy and in the Magellanic Clouds. They appear as highly variable X-ray sources and, in some cases, also as radio and/or optical pulsars. Their spin periods (2-12 s) and spin-down rates (˜10-13-10-10 s s-1) indicate external dipole fields of ˜1013-15 G, and there is evidence that even stronger magnetic fields are present inside the star and in non-dipolar magnetospheric components. Here we review the observed properties of the persistent emission from magnetars, discuss the main models proposed to explain the origin of their magnetic field and present recent developments in the study of their evolution and connection with other classes of neutron stars.

  9. 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.

  10. Origin and evolution of Schistosoma japonicum.

    PubMed

    Agatsuma, Takeshi

    2003-12-01

    In his hypothesis on the coevolution of Asian schistosomes and snails, Davis implies that the ancestors of the Schistosoma japonicum and S. indicum species group were African and arrived in Asia via the Indian plate. This paper briefly reviews molecular phylogenetic relationships among species of the genus Schistosoma to test Davis' theory about the origin and evolution of S. japonicum. All analyses using DNA base sequences, mitochondrial genome gene order and C-banding patterns suggest that Schistosoma originated in Asia and not Africa. PMID:14665391

  11. Origins and evolution of spliceosomal introns.

    PubMed

    Rodríguez-Trelles, Francisco; Tarrío, Rosa; Ayala, Francisco J

    2006-01-01

    Research into the origins of introns is at a critical juncture in the resolution of theories on the evolution of early life (which came first, RNA or DNA?), the identity of LUCA (the last universal common ancestor, was it prokaryotic- or eukaryotic-like?), and the significance of noncoding nucleotide variation. One early notion was that introns would have evolved as a component of an efficient mechanism for the origin of genes. But alternative theories emerged as well. From the debate between the "introns-early" and "introns-late" theories came the proposal that introns arose before the origin of genetically encoded proteins and DNA, and the more recent "introns-first" theory, which postulates the presence of introns at that early evolutionary stage from a reconstruction of the "RNA world." Here we review seminal and recent ideas about intron origins. Recent discoveries about the patterns and causes of intron evolution make this one of the most hotly debated and exciting topics in molecular evolutionary biology today. PMID:17094737

  12. 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

  13. The origin and early evolution of roots.

    PubMed

    Kenrick, Paul; Strullu-Derrien, Christine

    2014-10-01

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

  14. 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

  15. Dynamics of lunar origin and orbital evolution

    NASA Technical Reports Server (NTRS)

    Kaula, W. M.; Harris, A. W.

    1975-01-01

    The considerable differences in bulk composition of the moon and the earth have led most investigators to favor the capture hypothesis of lunar origin. However, upon closer examination all forms of the hypothesis still seem much less plausible dynamically than formation by accretion, i.e., acquisition of the moon in many small pieces rather than as predominantly one body. Models of accretion do suggest that the proto-lunar matter had a significantly different history from the proto-earth matter. A better understanding of collisions is needed to infer the compositional consequences of this history. Recent work on the acceleration of the moon's orbit exacerbates the time scale problem of orbital evolution. However, it now is much clearer that the locus of tidal dissipation is in the oceans and hence that the solution to the time scale problem lies in differing oceanic configurations in the past.

  16. The origin and evolution of Homo sapiens.

    PubMed

    Stringer, Chris

    2016-07-01

    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'. PMID:27298468

  17. 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

  18. Origin and evolution of lysyl oxidases.

    PubMed

    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

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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. PMID:27278888

  4. Probing the origin of quasi-periodic oscillations: the short-time-scale evolution of phase lags in GRS 1915+105

    NASA Astrophysics Data System (ADS)

    van den Eijnden, Jakob; Ingram, Adam; Uttley, Phil

    2016-06-01

    We present a model-independent analysis of the short-time-scale energy dependence of low-frequency quasi-periodic oscillations (QPOs) in the X-ray flux of GRS 1915+105. The QPO frequency in this source has previously been observed to depend on photon energy, with the frequency increasing with energy for observations with a high (≳2 Hz) QPO frequency, and decreasing with energy for observations with a low (≲2 Hz) QPO frequency. As this observed energy dependence is currently unexplained, we investigate if it is intrinsic to the QPO mechanism by tracking phase lags on (sub)second time-scales. We find that the phase lag between two broad energy bands systematically increases for 5-10 QPO cycles, after which the QPO becomes decoherent, the phase lag resets and the pattern repeats. This shows that the band with the higher QPO frequency is running away from the other band on short time-scales, providing strong evidence that the energy dependence of the QPO frequency is intrinsic. We also find that the faster the QPO decoheres, the faster the phase lag increases, suggesting that the intrinsic frequency difference contributes to the decoherence of the QPO. We interpret our results within a simple geometric QPO model, where different radii in the inner accretion flow experience Lense-Thirring precession at different frequencies, causing the decoherence of the oscillation. By varying the spectral shape of the inner accretion flow as a function of radius, we are able to qualitatively explain the energy-dependent behaviour of both QPO frequency and phase lag.

  5. 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.

  6. 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.

  7. Origin and evolution of the mitochondrial proteome.

    PubMed

    Kurland, C G; Andersson, S G

    2000-12-01

    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 alpha-proteobacteria symbiont, proteins with no homology to bacterial orthologs, and diverse proteins with bacterial affinities not derived from alpha-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

  8. 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.

  9. 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.

  10. 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

  11. Origin and evolution of the Pacific Superplume

    NASA Astrophysics Data System (ADS)

    Maruyama, S.

    2001-12-01

    The Pacific superplume defined as P- and S-wave velocity anomalies in the mantle underneath the southern Pacific superswell which yields a bundle of 5 hotspots. Moreover, it has been well-known that it has become active during the Cretaceous time to form a series of huge oceanic plateaus such as Ontong-Java and other oceanic Lips. I summarize the history of the Pacific superplume and speculate its origin, based on UHP experiments, tomographic images, and paleogeography back to 1.0Ga. The Pacific superplume was born when the supercontinent Rodinia was rifted to bear the Pacific Ocean in it at 750Ma. Since then it has been activated episodically at 750-700Ma, 550-500Ma, 300-250Ma and 125-85Ma, the last of which has been well-recorded on both ocean-floor and in orogenic belts. During the pulsation period, it should be emphasized that not only superplume but also the ocean-floor spreading became 30-50% faster than that of normal period. Based on UHP experiments at 660km depth and tomographic images in whole mantle, pulsation can be explained by regional mantle overturn, by which more fertile and higher-temperature materials in the lower mantle replace the upper mantle to accelerate both plate tectonics and plume activity However, the birth of superplume may be different from regional mantle overturn. Presence of cold superplume was estimated first underneath Asia by P-wave whole mantle tomography. Paleogeographic reconstruction gives us an image that cold superplume swallow many continents into a black hole to form a supercontinent. A supercontinent formed by a cold superplume must be broken up subsequently by a hot superplume underneath. The upper mantle underneath the supercontinet must be coldest among all parts of upper mantle, because of extensive subduction hence refrigeration. Moreover, subduction carries water underneath the continents, particularly in the case of subduction of cold slab. Transformation of cold to hot superplume took about 200 m.y. after the

  12. 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.

  13. 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

  14. Theory of the origin, evolution, and nature of life.

    PubMed

    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

  15. The origin and evolution of lactation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The presence of mammary glands are the defining morphological feature of mammals, and a successful lactation is crucial to mammalian reproductive strategies. Among mammalian species, the nature of lactation and the composition of milk vary greatly. The evolution of lactation and its diversity amon...

  16. Animal Evolution: The Hard Problem of Cartilage Origins.

    PubMed

    Brunet, Thibaut; Arendt, Detlev

    2016-07-25

    Our skeletons evolved from cartilaginous tissue, but it remains a mystery how cartilage itself first arose in evolution. Characterization of cartilage in cuttlefish and horseshoe crabs reveals surprising commonalities with chordate chondrocytes, suggesting a common evolutionary origin. PMID:27458918

  17. The origin and evolution of atmospheric oxygen

    NASA Technical Reports Server (NTRS)

    Levine, Joel S.

    1988-01-01

    This paper discusses the chemical processes involved in the evolution of the earth's atmospheric oxygen and ozone, as well as the sources, sinks, and transfer rates of oxygen in the present atmosphere. Special attention is given the evolution of atmospheric O3 as a function of the buildup of O2, with the results of calculations presented as the vertical profiles of O3, in terms of the present atmospheric level (PAL) oxygen values. Calculations show that the total O3 column density that is approximately half of the present level was reached when atmospheric oxygen level reached 0.1 PAL. At this level of ozone, the biological shielding of the earth's surface from the UV radiation is believed to have been achieved.

  18. 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.

  19. Origin and evolution of the genus Homo.

    PubMed

    Wood, B

    1992-02-27

    It is remarkable that the taxonomy and phylogenetic relationships of the earliest known representatives of our own genus, Homo, remain obscure. Advances in techniques for absolute dating and reassessments of the fossils themselves have rendered untenable a simple unilineal model of human evolution, in which Homo habilis succeeded the australopithecines and then evolved via H. erectus into H. sapiens-but no clear alternative consensus has yet emerged. PMID:1538759

  20. Physical observations of comets: Their composition, origin and evolution

    NASA Technical Reports Server (NTRS)

    Cochran, Anita L.; Barker, Edwin S.; Cochran, William D.

    1991-01-01

    The composition, origins, and evolution of comets were studied. The composition was studied using spectroscopic observations of primarily brighter comets at moderate and high resolution for the distribution of certain gases in the coma. The origins was addressed through an imaging search for the Kuiper belt of comets. The evolution was addressed by searching for a link between comets and asteroids using an imaging approach to search for an OH coma.

  1. 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

  2. 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.

  3. 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.

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

    PubMed

    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. PMID:27243368

  5. Chemical evolution and the origin of life

    NASA Astrophysics Data System (ADS)

    Oró, J.

    During the last three decades major advances have been made in our understanding of the formation of carbon compounds in the universe and of the occurence of processes of chemical evolution. 1) Carbon and other biogenic elements (C,H,N,O,S and P) are some of the most abundant in the universe. 2) The interstellar medium has been found to contain a diversity of molecules of these elements. 3) Some of these molecules have also been found in comets which are considered the most primordial bodies of the solar system. 4) The atmospheres of the outer planets and their satellites, for example, Titan, are actively involved in the formation of organic compounds which are the precursors of biochemical molecules. 5) Some of these biochemical molecules, such as amino acids, purines and pyrimidines, have been found in carbonaceous chondrites. 6) Laboratory experiments have shown that most of the monomers and oligomers necessary for life can be synthesized under hypothesized but plausible primitive Earth conditions from compounds found in the above cosmic bodies. 7) It appears that the primitive Earth had the necessary and sufficient conditions to allow the chemical synthesis of biomacromolecules and to permit the processes required for the emergence of life on our planet. 8) It is unlikely that the emergence of life occurred in any other body of the solar system, although the examination of the Jovian satellite Europa may provide important clues about the constraints of this evolutionary process. Some of the fundamental principles of chemical evolution are briefly discussed.

  6. Origin and evolution of X chromosome inactivation.

    PubMed

    Gribnau, Joost; Grootegoed, J Anton

    2012-06-01

    Evolution of the mammalian sex chromosomes heavily impacts on the expression of X-encoded genes, both in marsupials and placental mammals. The loss of genes from the Y chromosome forced a two-fold upregulation of dose sensitive X-linked homologues. As a corollary, female cells would experience a lethal dose of X-linked genes, if this upregulation was not counteracted by evolution of X chromosome inactivation (XCI) that allows for only one active X chromosome per diploid genome. Marsupials rely on imprinted XCI, which inactivates always the paternally inherited X chromosome. In placental mammals, random XCI (rXCI) is the predominant form, inactivating either the maternal or paternal X. In this review, we discuss recent new insights in the regulation of XCI. Based on these findings, we propose an X inactivation center (Xic), composed of a cis-Xic and trans-Xic that encompass all elements and factors acting to control rXCI either in cis or in trans. We also highlight that XCI may have evolved from a very small nucleation site on the X chromosome in the vicinity of the Sox3 gene. Finally, we discuss the possible evolutionary road maps that resulted in imprinted XCI and rXCI as observed in present day mammals. PMID:22425180

  7. Compensatory Evolution and the Origins of Innovations

    PubMed Central

    Rajon, Etienne; Masel, Joanna

    2013-01-01

    Cryptic genetic sequences have attenuated effects on phenotypes. In the classic view, relaxed selection allows cryptic genetic diversity to build up across individuals in a population, providing alleles that may later contribute to adaptation when co-opted—e.g., following a mutation increasing expression from a low, attenuated baseline. This view is described, for example, by the metaphor of the spread of a population across a neutral network in genotype space. As an alternative view, consider the fact that most phenotypic traits are affected by multiple sequences, including cryptic ones. Even in a strictly clonal population, the co-option of cryptic sequences at different loci may have different phenotypic effects and offer the population multiple adaptive possibilities. Here, we model the evolution of quantitative phenotypic characters encoded by cryptic sequences and compare the relative contributions of genetic diversity and of variation across sites to the phenotypic potential of a population. We show that most of the phenotypic variation accessible through co-option would exist even in populations with no polymorphism. This is made possible by a history of compensatory evolution, whereby the phenotypic effect of a cryptic mutation at one site was balanced by mutations elsewhere in the genome, leading to a diversity of cryptic effect sizes across sites rather than across individuals. Cryptic sequences might accelerate adaptation and facilitate large phenotypic changes even in the absence of genetic diversity, as traditionally defined in terms of alternative alleles. PMID:23335336

  8. 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.

  9. 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. PMID:19825357

  10. [Evolution of the Origin of Herba Schizonepetae].

    PubMed

    Song, X W; Li, G Y; Wang, D Q; Han, B X

    2016-05-01

    Herba Schizonepetae was firstly recorded in the Sheng nong ben caojing (Shennong's Materia Medica) with the title Jiasu. It could be sure that the original plant of Jiasu is Ocimumbasilicum L. ofLabiatae based on the record of Jiasu's name, morphology, edible property before the Song Dynasty. Beginning from the Ben cao tu jing (Illustrated Classic of Materia Medica) in the Song Dynasty, the source of this drug evolved as SchizonepetatenuisfoliaBriq. ofLabiatae, and it has been in use until now. Hence, the sources of Jiasu should be both O. basilicum L. and the co-existence of S. tenuisfolia Briq in the Qing Dynasty. It is claimed that the hometowns of those herb writers who considered the source ofOcimumbasilicum L. to be the producing areas of cultivation of the edible Ocimumbasilicum L. It was found that the source of Jiasu recorded in the Sheng nong ben cao jing should be O. basilicum L. , hence, it is suggested the title Jiasu should be recorded for the source of O. basilicum L, and the original plant of Herba Schizonepetae was Schizonepetatenuisfolia Briq. of Labiatae, and this medicine should be separately recorded. In fact, Jiasu and Herba Schizonepetae were two different kinds of medicines. PMID:27485864

  11. The origin and evolution of activity analysis.

    PubMed

    Creighton, C

    1992-01-01

    Practitioners of occupational therapy in the early 1900s selected therapeutic activities with an intuitive understanding of their characteristics and operations. The term activity analysis and the methodology for breaking down and examining tasks scientifically, however, were borrowed from industry during World War I. Methods originally used in time and motion study of jobs were applied to vocational retraining and therapeutic crafts; later, they were applied to a broader range of activities. The most systematic early use of activity analysis was in occupational therapy for physical dysfunction, particularly in military hospitals. Development of the concept was gradual until the 1970s, when the delineation of theoretical frames of reference for practice led to important changes. Today, activity analysis is viewed as a multifaceted process that involves both generic and specific components. PMID:1558138

  12. Origin and evolution of Nipah virus.

    PubMed

    Lo Presti, Alessandra; Cella, Eleonora; Giovanetti, Marta; Lai, Alessia; Angeletti, Silvia; Zehender, Gianguglielmo; Ciccozzi, Massimo

    2016-03-01

    Nipah virus, member of the Paramyxoviridae family, is classified as a Biosafety Level-4 agent and category C priority pathogen. Nipah virus disease is endemic in south Asia and outbreaks have been reported in Malaysia, Singapore, India, and Bangladesh. Bats of the genus Pteropus appear to be the natural reservoir of this virus. The aim of this study was to investigate the genetic diversity of Nipah virus, to estimate the date of origin and the spread of the infection. The mean value of Nipah virus N gene evolutionary rate, was 6.5 × 10(-4) substitution/site/year (95% HPD: 2.3 × 10(-4)-1.18 × 10(-3)). The time-scaled phylogenetic analysis showed that the root of the tree originated in 1947 (95% HPD: 1888-1988) as the virus entered in south eastern Asiatic regions. The segregation of sequences in two main clades (I and II) indicating that Nipah virus had two different introductions: one in 1995 (95% HPD: 1985-2002) which correspond to clade I, and the other in 1985 (95% HPD: 1971-1996) which correspond to clade II. The phylogeographic reconstruction indicated that the epidemic followed two different routes spreading to the other locations. The trade of infected pigs may have played a role in the spread of the virus. Bats of the Pteropus genus, that are able to travel to long distances, may have contributed to the spread of the infection. Negatively selected sites, statistically supported, could reflect the stability of the viral N protein. PMID:26252523

  13. The Neogene: Origin, adoption, evolution, and controversy

    NASA Astrophysics Data System (ADS)

    Walsh, Stephen L.

    2008-07-01

    Some stratigraphers have recently insisted that for historical reasons, the Neogene (Miocene + Pliocene) should be extended to the present. However, despite some ambiguity in its application by Moriz Hörnes in the 1850s, the "Neogene" was widely adopted by European geologists to refer to the Miocene and Pliocene of Lyell, but excluding the "Diluvium" (later to become the Pleistocene) and "Alluvium" (later to become the Holocene). During the late 19th and early 20th centuries, the ends of the Neogene, Tertiary and Pliocene evolved in response to the progressive lowering of the beginnings of the Quaternary and Pleistocene. This evolution was a logical result of the widespread views that the most recent "ice ages" were worthy of recognition as a formal unit of the standard geologic time scale, and that the structure of this time scale must be strictly hierarchical. Motivations for the extension of the Neogene to the present include the desire to establish a monopoly for marine biochronology in the definition of standard global chronostratigraphic boundaries. This agenda would also eliminate the Tertiary, Quaternary, and Holocene. These changes are unnecessary. There is every reason to retain the traditional hierarchical structure of the Cenozoic time scale.

  14. 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

  15. The origins and evolution of vertebrate metamorphosis.

    PubMed

    Laudet, Vincent

    2011-09-27

    Metamorphosis, classically defined as a spectacular post-embryonic transition, is well exemplified by the transformation of a tadpole into a frog. It implies the appearance of new body parts (such as the limbs), the resorption of larval features (such as the tail) and the remodelling of many organs (such as the skin or the intestine). In vertebrates, metamorphosis has been well characterized in anuran amphibians, where thyroid hormones orchestrate the intricate and seemingly contradictory changes observed at the cellular and tissue levels. Thyroid hormones control a complex hierarchical cascade of target genes via binding to specific receptors, TRα and TRβ, ligand-activated transcription factors belonging to the nuclear receptor superfamily. Metamorphosis is actually widespread in the vertebrates, though quite diverse in the way it manifests in a particular species. Furthermore, evolutionary and ecological variations of this key event, from paedomorphosis to direct development, provide an excellent illustration of how tinkering with a control pathway can lead to divergent life histories. The study of invertebrate chordates has also shed light on the origin of metamorphosis. The available data suggest that post-embryonic remodelling governed by thyroid hormones is an ancestral feature of chordates. According to this view, metamorphosis of the anurans is an extreme example of a widespread life history transition. PMID:21959163

  16. The origin and evolution of phototropins.

    PubMed

    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

  17. The Origin and Evolution of Ribonucleotide Reduction

    PubMed Central

    Lundin, Daniel; Berggren, Gustav; Logan, Derek T.; Sjöberg, Britt-Marie

    2015-01-01

    Ribonucleotide reduction is the only pathway for de novo synthesis of deoxyribonucleotides in extant organisms. This chemically demanding reaction, which proceeds via a carbon-centered free radical, is catalyzed by ribonucleotide reductase (RNR). The mechanism has been deemed unlikely to be catalyzed by a ribozyme, creating an enigma regarding how the building blocks for DNA were synthesized at the transition from RNA- to DNA-encoded genomes. While it is entirely possible that a different pathway was later replaced with the modern mechanism, here we explore the evolutionary and biochemical limits for an origin of the mechanism in the RNA + protein world and suggest a model for a prototypical ribonucleotide reductase (protoRNR). From the protoRNR evolved the ancestor to modern RNRs, the urRNR, which diversified into the modern three classes. Since the initial radical generation differs between the three modern classes, it is difficult to establish how it was generated in the urRNR. Here we suggest a model that is similar to the B12-dependent mechanism in modern class II RNRs. PMID:25734234

  18. 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

  19. The Origin and Evolution of Rich Clusters

    NASA Astrophysics Data System (ADS)

    Hora, Joseph

    observations will allow us to compare star formation in these massive inner Galaxy regions to star formation near the Sun, and in the outer Galaxy, and therefore to complete a more representative view of star formation. This work will further NASA's goals of learning about the universe and understanding how it began and evolved into what we see today. The knowledge we gain about the formation and evolution of stars in the most massive clusters in the Galaxy will enhance our understanding of these important processes, and the data products we develop will provide an important tool to other researchers, and a key resource for further observations with other NASA missions such as JWST.

  20. 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

  1. 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.

  2. 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

  3. [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. PMID:25306651

  4. 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

  5. Mitochondrial genome evolution and the origin of eukaryotes.

    PubMed

    Lang, B F; Gray, M W; Burger, G

    1999-01-01

    Recent results from ancestral (minimally derived) protists testify to the tremendous diversity of the mitochondrial genome in various eukaryotic lineages, but also reinforce the view that mitochondria, descendants of an endosymbiotic alpha-Proteobacterium, arose only once in evolution. The serial endosymbiosis theory, currently the most popular hypothesis to explain the origin of mitochondria, postulates the capture of an alpha-proteobacterial endosymbiont by a nucleus-containing eukaryotic host resembling extant amitochondriate protists. New sequence data have challenged this scenario, instead raising the possibility that the origin of the mitochondrion was coincident with, and contributed substantially to, the origin of the nuclear genome of the eukaryotic cell. Defining more precisely the alpha-proteobacterial ancestry of the mitochondrial genome, and the contribution of the endosymbiotic event to the nuclear genome, will be essential for a full understanding of the origin and evolution of the eukaryotic cell as a whole. PMID:10690412

  6. 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

  7. 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

  8. 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. PMID:26554035

  9. 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

  10. 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.

  11. 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.

  12. Automodelity of the biological evolution and the hypothesis of self-consistent Galaxy life origin

    NASA Astrophysics Data System (ADS)

    Panov, A.

    The evolution of the Earth's biosphere passed trough a sequence of biospheric revolutions. It is shown, that the arrangement of the biospheric revolutions on the time axis has the property of automodelity in very good approximation. Supposing that the automodel scale of the time of the evolution includes the prebiological chemical evolution as well, we obtain that the estimated duration of the prebiological chemical evolution is about 5.5\\cdot10^9 years. It is much longer then the actual time of the prebiological evolution on the Earth. One possible resolution of the contradiction is that the prebiological evolution took place on the Earth-like planets near the stars much older then the Sun and not on the Earth. The life could be brought to the Earth by the panspermia process. But if the panspermia of life is possible, then the panspermia of the prebiological chemical evolution products must be possible as well. The prebiological panspermia would synchronize the prebiological evolution on different planets in the Galaxy in the stage of the prebiological history of the Galaxy--before the moment when the life had appeared for the first time. Thus the life in the Galaxy in many different places originates almost simultaneously with the same common chemical base and with the same chirality. This event resembles a no-equilibrium phase transition. Thus the origin of life may be self-consistent collective Galaxy process, not a process localized on single planets.

  13. Origin and evolution of outer solar system atmospheres

    NASA Technical Reports Server (NTRS)

    Lunine, J. I.

    1989-01-01

    The origin and evolution of the atmospheres of bodies in the outer solar system is studied on the basis of the abundances of key molecular species. Formation models in which significant infall of icy and rocky planetesimals accompanies planet formation is supported by the enrichment of methane and deuterated species from Jupiter and Neptune. The chemistry of the solar nebula and Titan are discussed. The prospects for obtaining information on the atmosphere of Triton from the Voyager 2 mission are considered. It is found that the mean density of the Pluto-Charon system implies an origin in the rather water-poor solar nebula.

  14. 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.

  15. 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).

  16. Origin, Evolution and Clinical Application of the Thermometer.

    PubMed

    Wright, William F; Mackowiak, Philip A

    2016-05-01

    Although Galileo, Fahrenheit and Celsius are the names generally associated with the origin of the thermometer and its scale, many others were involved in bringing into existence the instrument we use today to monitor body temperature. In fact, the seed from which the thermometer arose was planted long before those credited with inventing it made their contributions, and nurtured by many other investigators during its evolution and clinical application. PMID:27140714

  17. 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.

  18. 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. PMID:24471891

  19. [Original meaning of mai and its academic evolution].

    PubMed

    Sun, Jingwen; Tian, Yanpeng; Guo, Yan; Wang, Chaoyang; Liu, Qingguo

    2015-06-01

    Mai is the important concept in TCM and this term has been found in the early classic work of TCM. With the development and perfection of TCM theory, the original meaning of mai is "blood vessels entirely distrusted in the body". In five dynasties, the meaning of it was supplemented as "distribution of qi and blood in five zang and six fu organs to the four extremities", in which, not only blood but also qi has been included. With the constant understanding on mai, qi and blood, the unique concept of meridian and collateral is gradually generated. In terms of the modern study on the original meaning of mai and the academic evolution of meridian and collateral, it is discovered that qi is predominated and distributed in meridian and collateral as compared with blood. It is very significant to study the original meaning and academic evolution of mai, as well as the origin of the concept of meridian and collateral and to provide the reference support for the terminology standardization and basic study. PMID:26480573

  20. Directed evolution and solid phase enzyme screening

    NASA Astrophysics Data System (ADS)

    Bylina, Edward J.; Grek, Christina L.; Coleman, William J.; Youvan, Douglas C.

    2000-03-01

    A new digital imaging spectrophotometer and a series of colorimetric solid phase arrays have been developed to screen bacterial libraries expressing mutagenized enzymes undergoing directed evolution. This high-throughput solid- phase array system (known as `Kcat Technology') can detect less than a 20% difference in enzyme rates within microcolonies grown at a nearly confluent density of 500 colonies per cm2 on an assay disk. Each microcolony is analyzed simultaneously at single-pixel resolution (1.5 megapixels; 75 micron/pixel), requiring less than 100 nanoliters of substrate per measurement, a 1000-fold reduction over conventional liquid phase assays. Here we report the successful identification of variants of Agrobacterium (beta) -glucosidase--a glycosidase with broad substrate specificity that favors cleavage of glucosides over galactosides--by simultaneously assaying two different substrates tagged with spectrally distinct chromogenic reporters.

  1. Origin and Evolution of Life on Terrestrial Planets

    NASA Astrophysics Data System (ADS)

    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 H2O, 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.

  2. 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. PMID:20307183

  3. 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

  4. 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.

  5. The Origin and Early Evolution of Membrane Channels

    NASA Astrophysics Data System (ADS)

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

    2005-02-01

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

  6. 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

  7. Origin and evolution of the earth-moon system.

    NASA Technical Reports Server (NTRS)

    Alfven, H.; Arrhenius, G.

    1972-01-01

    The general problem of formation of secondary bodies around a central body is studied, and comparison is made with other satellite systems (Jupiter, Saturn, Uranus). The normal satellite systems of Neptune and the earth are reconstructed. The capture theory, the tidal evolution of the lunar orbit, destruction of a normal satellite system, asteroids and the earth-moon system, and accretion and heat structure of the moon are discussed. It is concluded that the moon originated as a planet accreted in a jet stream near the orbit of the earth, and was probably captured in a retrograde orbit.

  8. The nature, origin and evolution of embedded star clusters

    NASA Technical Reports Server (NTRS)

    Lada, Charles J.; Lada, Elizabeth A.

    1991-01-01

    The recent development of imaging infrared array cameras has enabled the first systematic studies of embedded protoclusters in the galaxy. Initial investigations suggest that rich embedded clusters are quite numerous and that a significant fraction of all stars formed in the galaxy may begin their lives in such stellar systems. These clusters contain extremely young stellar objects and are important laboratories for star formation research. However, observational and theoretical considerations suggest that most embedded clusters do not survive emergence from molecular clouds as bound clusters. Understanding the origin, nature, and evolution of embedded clusters requires understanding the intimate physical relation between embedded clusters and the dense molecular cloud cores from which they form.

  9. Origins and Early Evolution of the tRNA Molecule

    PubMed Central

    Tamura, Koji

    2015-01-01

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

  10. 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

  11. Modern human origins in Australasia: replacement or evolution?

    PubMed

    Kramer, A

    1991-12-01

    The controversies surrounding the origins of modern humans have spawned two competing hypotheses, namely Replacement and Multiregional Evolution. The first suggests that modern Homo sapiens evolved first in Africa, as late as 140 ka, and subsequently inhabited the balance of the Old World. Conversely, the second hypothesis posits that modern humans evolved principally from local populations of archaic hominids indigenous to the major regions of the Old World. The hominid mandibular remains (ca. 1 Ma) from Sangiran, central Java, Indonesia, were studied in order to test these hypotheses. Non-metric comparisons were performed between these fossils and aboriginal H. sapiens from Africa and Australia. The Replacement model would be supported by a unique Afro-Australian grouping while Multiregional Evolution would be suggested by a Sangiran-Australasian group which would exclude the modern Africans. These data support the Multiregional Evolution hypothesis in that a plurality (eight) of the seventeen non-metric features link Sangiran to modern Australians, while only three exclusively group the humans from Africa and Australia. These results are suggestive of morphological continuity, which implies the presence of a genetic continuum in Australasia dating back at least one million years. PMID:1776654

  12. 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. PMID:24039543

  13. 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. PMID:19776166

  14. 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

  15. Origin and Dynamics of Morphotropic Phase Boundary in Multiferroic Films

    NASA Astrophysics Data System (ADS)

    Zhang, Jinxing; Zeches, Robert; Sheng, Guang; Seidel, Jan; Yu, Pu; He, Qing; Yang, Chanho; Chu, Yinghao; Chen, Longqing; Ramesh, Ramamoorthy

    2010-03-01

    Materials with morphotropic phase boundary (MPB) compositions attract people's interests because of their huge electromechanical response. The ambiguity of crystal structure, phases and physics behind presents a challenge to interpret the origin of abnormally high piezoelectric coefficient. Recently, epitaxial strain can be used to stabilize the MPB in BiFeO3. [1] However, to better understand the origin of MPB in multiferroic perovskite, it is essential to probe into the strain/polarization coupling mechanism. In this abstract, origin and dynamics of the phase transition in BiFeO3 near MPB have been investigated by exploring the ferroelectric domains. Careful analysis of domain configurations across the phase boundary reveals the rotation of ferroelectric vectors from phase to phase, a new strain/polarization coupling state in nature. The phase transition dynamics are assisted by the re-orientation of ferroelectric polarizations. Phase-field simulation further proves the origin of this MPB is the strain-driven rotation and re-orientation of ferroelectric vectors. This investigation provides new insight into the study of high electromechanical response in MPB-like crystal and helps engineer other lead free-ferroelectrics. Reference: 1. R. J. Zeches, et al., Science 326, 977 (2009).

  16. 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.

  17. 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.

  18. Origin and Evolution of the Sodium -Pumping NADH: Ubiquinone Oxidoreductase

    PubMed Central

    Reyes-Prieto, Adrian; Barquera, Blanca; Juárez, Oscar

    2014-01-01

    The sodium -pumping NADH: ubiquinone oxidoreductase (Na+-NQR) is the main ion pump and the primary entry site for electrons into the respiratory chain of many different types of pathogenic bacteria. This enzymatic complex creates a transmembrane gradient of sodium that is used by the cell to sustain ionic homeostasis, nutrient transport, ATP synthesis, flagellum rotation and other essential processes. Comparative genomics data demonstrate that the nqr operon, which encodes all Na+-NQR subunits, is found in a large variety of bacterial lineages with different habitats and metabolic strategies. Here we studied the distribution, origin and evolution of this enzymatic complex. The molecular phylogenetic analyses and the organizations of the nqr operon indicate that Na+-NQR evolved within the Chlorobi/Bacteroidetes group, after the duplication and subsequent neofunctionalization of the operon that encodes the homolog RNF complex. Subsequently, the nqr operon dispersed through multiple horizontal transfer events to other bacterial lineages such as Chlamydiae, Planctomyces and α, β, γ and δ -proteobacteria. Considering the biochemical properties of the Na+-NQR complex and its physiological role in different bacteria, we propose a detailed scenario to explain the molecular mechanisms that gave rise to its novel redox- dependent sodium -pumping activity. Our model postulates that the evolution of the Na+-NQR complex involved a functional divergence from its RNF homolog, following the duplication of the rnf operon, the loss of the rnfB gene and the recruitment of the reductase subunit of an aromatic monooxygenase. PMID:24809444

  19. 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.

  20. 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. PMID:27114548

  1. 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.

  2. 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

  3. Gut-Origin sepsis; evolution of a concept

    PubMed Central

    Deitch, Edwin A.

    2012-01-01

    The concept of bacterial translocation and gut-origin sepsis as a cause of systemic infectious complications and the multiple organ dysfunction syndrome (MODS) in surgical and ICU patients has emerged over the last several decades, although the exact clinical relevance of these phenomenon continue to be debated. Thus, the goal of this review will be to trace the evolution of gut-origin sepsis and gut-induced MODS and put these disorders and observations into clinical perspective. Additionally, the mechanisms leading to gut-derived complications will be explored as well as therapeutic options to limit or prevent these complications. From this work, several major conclusions emerge. First, that bacterial translocation occurs clinically and is responsible for increased infectious complications in patients undergoing major abdominal surgery. However, the phenomenon of bacterial translocation is not sufficient to explain the development of MODS in ICU patients. Instead, the development of MODS in these high risk patients is likely due to gut injury and the systemic spread of non-microbial, tissue injurious factors that reach the systemic circulation via the intestinal lymphatics. These observations have resulted in the gut lymph hypothesis of MODS. PMID:22534256

  4. 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

  5. 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.

  6. Origin and evolution of high-titanium mare basalts

    NASA Astrophysics Data System (ADS)

    Donohue, Patrick H.

    The Moon is the sole known locality of exposed high-titanium (high-Ti) basalts in the solar system, but their occurrence has implications for the early evolution of the terrestrial planets. High-Ti basalts derive from partial melts of cumulates in the lunar upper mantle. The ilmenite, clinopyroxene, and olivine cumulates from which these basalts form are late-stage products of crystallization of the lunar magma ocean, a planetary-scale melting event that also likely occurred early on in the evolution of Venus, Mercury, the Earth and Mars. Fortunately, despite the ancient nature of mare volcanism, pristine high-Ti basalts are preserved on the relatively inert lunar surface, and the lunar sample collection contains abundant high-Ti basaltic material. Crystals are quantifiable components of the basaltic system, and are a record of the compositional and temporal history of magmatic evolution. Complementary techniques of textural and in-situ trace element geochemical analyses comprise the crystal stratigraphy method used to investigate this history. I use crystal size distributions and spatial distribution profiles to identify crystal populations and quantitatively evaluate rock textures. I use EPMA and LA-ICP-MS analysis of major crystallizing phases to identify processes affecting evolving magmas. I first show that LA-ICP-MS can determine accurate and precise trace elements for ilmenite, which is a major crystallizing phase in high-Ti basalts. The Taurus-Littrow Valley on the Moon contains high-Ti basalts from multiple distinct magmatic source regions. I propose multiple flow events of some regions were sampled during the Apollo missions, and magma partially crystallized for short residence times at shallow depths. Textural characterization of a high-Ti olivine cumulate shows no other samples experienced crystal accumulation. Finally, I investigate two rocklets found in the lunar highlands that were recently classified as basalts. I confirm their basaltic nature

  7. 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).

  8. 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).

  9. 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

  10. 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

  11. 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.

  12. 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

  13. Ammonia Bearing Species on Ceres: Implication on Origin and Evolution

    NASA Astrophysics Data System (ADS)

    De Sanctis, M. C.; Ammannito, E.; Raponi, A.; Marchi, S.; Ciarniello, M.; McSween, H. Y., Jr.; McCord, T. B.; Capaccioni, F.; Capria, M. T.; Carrorro, F. G.; Longobardo, A.; Tosi, F.; Fonte, S.; Giardino, M.; Palomba, E.; Magni, G.; Zambon, F.; Pieters, C. M.; McFadden, L. A.; Raymond, C. A.

    2015-12-01

    The Visible and Infrared Mapping Spectrometer (VIR) on board the Dawn spacecraft observed Ceres' surface acquiring spectra since January 2015. Here we report the average Ceres spectrum, including the spectral range previously precluded from telescopic measurements due to telluric atmospheric absorptions. The data indicate that the surface is very dark: average albedo of 0.090 ±0.006 at 0.55 µm, consistent with HST data (Li et al., 2006). Ceres' average spectrum is characterized by a prominent absorption band at 2.7 micron. Weaker absorption bands are observed between 3.05-3.1, 3.3-3.4 and 3.9-4 micron; the visible and near-IR ranges lack prominent bands. We modelled the spectra of Ceres using Hapke theory. Results of the spectral modelling indicate that extensive water ice is not present in surface spectra acquired so far. The best fit is obtained with a mixture of ammoniated phyllosilicates mixed with other clays, Mg-carbonates, and dark material, like magnetite (De Sanctis et al. 2015, submitted). The presence of ammonia bearing materials across the surface has implications for the origin of Ceres and its internal structure and evolution. Higher spatial resolution spectra are being acquired to address the small scale mineralogy across this dwarf planet. References: Li, et al., Photometric analysis of 1 Ceres and surface mapping from HST observations. Icarus 182, 143-160 (2006). De Sanctis et al., Ammoniated phyllosilicates on dwarf planet Ceres reveal an outer solar system origin, Nature submitted, (2015). This work is supported the Italian Space Agencies, NASA, and from the German Space Agency. Support of the Dawn Instrument, Operations, and Science Teams is acknowledged.

  14. Epigenetics: The origins and evolution of a fashionable topic.

    PubMed

    Deichmann, Ute

    2016-08-01

    The term "epigenetics" was introduced in 1942 by embryologist Conrad Waddington, who, relating it to the 17th century concept of "epigenesis", defined it as the complex of developmental processes between the genotype and phenotype. While in the years that followed, these processes - in particular gene regulation - were tackled, not in the frame of epigenetics but of genetics, research labelled "epigenetics" rose strongly only in the 21st century. Then it consisted of research on chromatin modifications, i.e. chemical modifications of DNA or histone proteins around DNA that do not change the base sequence. This rise was accompanied by far-reaching claims, such as that epigenetics provides a mechanism for "Lamarckian" inheritance. This article highlights the origin of epigenetics, the major phases of epigenetic research, and the changes in the meaning of the term. It also calls into question some of the far-reaching claims that have accompanied the recent rise of epigenetics. PMID:27291929

  15. Human microRNAs originated from two periods at accelerated rates in mammalian evolution.

    PubMed

    Iwama, Hisakazu; Kato, Kiyohito; Imachi, Hitomi; Murao, Koji; Masaki, Tsutomu

    2013-03-01

    MicroRNAs (miRNAs) are short, noncoding RNAs that modulate genes posttranscriptionally. Frequent gains and losses of miRNA genes have been reported to occur during evolution. However, little is known systematically about the periods of evolutionary origin of the present miRNA gene repertoire of an extant mammalian species. Thus, in this study, we estimated the evolutionary periods during which each of 1,433 present human miRNA genes originated within 15 periods, from human to platypus-human common ancestral branch and a class "conserved beyond theria," primarily using multiple genome alignments of 38 species, plus the pairwise genome alignments of five species. The results showed two peak periods in which the human miRNA genes originated at significantly accelerated rates. The most accelerated rate appeared in the period of the initial phase of hominoid lineage, and the second appeared shortly before Laurasiatherian divergence. Approximately 53% of the present human miRNA genes have originated within the simian lineage to human. In particular, approximately 28% originated within the hominoid lineage. The early phase of placental mammal radiation comprises approximately 28%, while no more than 15% of human miRNAs have been conserved beyond placental mammals. We also clearly showed a general trend, in which the miRNA expression level decreases as the miRNA becomes younger. Intriguingly, amid this decreasing trend of expression, we found one significant rise in the expression level that corresponded to the initial phase of the hominoid lineage, suggesting that increased functional acquisitions of miRNAs originated at this particular period. PMID:23171859

  16. 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.

  17. A hypothesis for the origin and evolution of menopause.

    PubMed

    Peccei, J S

    1995-02-01

    Menopause is widely believed by biological anthropologists and life history theorists to have arisen early in human evolution. In this paper, I suggest that female reproductive senescence was the result of the escalating energetic cost of gestation, lactation and childcare that accompanied the continuing encephalization of early hominid offspring and the ensuing increase in infant altriciality, or helplessness, and the concomitant prolongation of juvenile dependence. Natural selection favored females who became prematurely infertile, as the escalating cost of raising each offspring led to maternal depletion and made it more profitable in terms of lifetime reproductive success to continue investing in existing offspring rather than attempting late pregnancies. Results of a mathematical model are presented which show that reproductive senescence can be advantageous even when maximum potential lifespan is only 50 years, if the premature cessation of reproduction allows females to moderately increase the survival and fertility of their existing subadult offspring. These findings suggest that menopause could have originated as much as 1.5 million years ago, and that if menopause is indeed such an old trait, it was more likely the result of selective pressure on females to invest more in their own children, as opposed to their grandchildren. PMID:7752954

  18. 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. PMID:23908781

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. Origin and Evolution of Filament-Prominence Systems

    NASA Astrophysics Data System (ADS)

    Martens, Petrus C.; Zwaan, Cornelis

    2001-09-01

    We present a ``head-to-tail'' linkage model for the formation, evolution, and eruption of solar filaments. The magnetic field structure of our model is based on the observation that filaments form exclusively in filament channels with no apparent magnetic connections above the polarity inversion line. The formation of a filament in this configuration is driven by flux convergence and cancellation, which produces looplike filament segments with a half-turn. Filament segments of like chirality may connect and form long quiescent filaments. Such filaments are stabilized through footpoint anchoring until further cancellation at the footpoints causes their eruption. The eruption restores the original filament channel so that filament formation may resume immediately. We then demonstrate that the combined workings of Hale's polarity law, Joy's law, and differential rotation introduce a strong hemispheric preference in the chirality of filaments formed poleward of the sunspot belt, which is in agreement with observations. We analyze the magnetic fine structure of filaments formed through our model and find consistency with the observed hemispheric preference for barb orientation and a simple explanation for barb formation. Finally, we consider the flux tubes retracted below the surface in the process of filament formation. We show that every cancellation event that generates a filament obeying the hemispheric chirality preference injects a flux tube below the surface with a poloidal field opposite that of the ongoing cycle. We suggest that this pattern of submergence of flux represents the specific mechanism for the reversal of the poloidal flux in a Babcock-Leighton-Durney-type model for the solar dynamo.

  5. Analysis of the Origin and Evolution of the Small Satellites of Pluto

    NASA Astrophysics Data System (ADS)

    Pires Dos Santos, Pryscilla Maria; Morbidelli, A.; Nesvorny, D.; Giuliatti Winter, S. M.

    2012-10-01

    At this time the origin of the small satellites of Pluto remains elusive. In this work we envisioned an alternative scenario. Pluto-Charon was already formed and embedded into a massive planetesimal disk, then planetesimals got captured by Pluto-Charon binary from the heliocentric disk. For a dynamically "cold" disk, temporary capture in the Pluto-Charon system can occur with non-negligible probability. We conjecture that if the captured planetesimals got disrupted during their Pluto-bound phase by a collision with other planetesimals of the disk, then these events could have generated a debris disk. This disk damped under internal collisional evolution, until turning itself into an accretional disk that could form small satellites on circular orbits, co-planar with Charon. Objects large enough to carry a sufficient amount of mass to generate the small satellites of Pluto have collisional lifetimes orders of magnitude longer than the typical capture time ( 100 years). Thus, this scenario, although add new arguments to an unsolved problem, cannot also explain the origin of the small satellites of Pluto, which remains elusive. Additionality, we will also present some preliminary results on the analysis of the evolution of the Pluto system in the framework of the "new" Nice model (see, e.g. Levison et al, 2008). Their results explain very well the distribution of Plutinos, bodies trapped in 2:3 mean motion resonance with Neptune. By assuming that the bodies observed today in the Pluto system were put together before the Late Heavy Bombardment period (Gomes et al, 2005), through encounter histories of Pluto and its members during the dynamical evolution of the giant planets, we analyse if this multiple system is destroyed by such interactions. In fact, understanding the evolution of the plutinos provides hints to the understanding of the history of the outer Solar system.

  6. [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. PMID:26420522

  7. ON THE ORIGIN OF THE EXTREME-ULTRAVIOLET LATE PHASE OF SOLAR FLARES

    SciTech Connect

    Liu Kai; Wang Yuming; Zhang Jie; Cheng Xin

    2013-05-10

    Solar flares typically have an impulsive phase that is followed by a gradual phase as best seen in soft X-ray emissions. A recent discovery based on the EUV Variability Experiment observations on board the Solar Dynamics Observatory (SDO) reveals that some flares exhibit a second large peak separated from the first main phase peak by tens of minutes to hours, which is coined as the flare's EUV late phase. In this paper, we address the origin of the EUV late phase by analyzing in detail two late phase flares, an M2.9 flare on 2010 October 16 and an M1.4 flare on 2011 February 18, using multi-passband imaging observations from the Atmospheric Imaging Assembly on board SDO. We find that (1) the late phase emission originates from a different magnetic loop system, which is much larger and higher than the main phase loop system. (2) The two loop systems have different thermal evolution. While the late phase loop arcade reaches its peak brightness progressively at a later time spanning for more than one hour from high to low temperatures, the main phase loop arcade reaches its peak brightness at almost the same time (within several minutes) in all temperatures. (3) Nevertheless, the two loop systems seem to be connected magnetically, forming an asymmetric magnetic quadruple configuration. (4) Further, the footpoint brightenings in UV wavelengths show a systematic delay of about one minute from the main flare region to the remote footpoint of the late phase arcade system. We argue that the EUV late phase is the result of a long-lasting cooling process in the larger magnetic arcade system.

  8. Origin and Evolution of the Moon: Apollo 2000 Model

    NASA Astrophysics Data System (ADS)

    Schmitt, H. H.

    1999-01-01

    A descriptive formulation of the stages of lunar evolution as an augmentation of the traditional time-stratigraphic approach [21 enables broadened multidisciplinary discussions of issues related to the Moon and planets. An update of this descriptive formulation [3], integrating Apollo and subsequently acquired data, provides additional perspectives on many of the outstanding issues in lunar science. (Stage 1): Beginning (Pre-Nectarian) - 4.57 Ga; (Stage 2): Magma Ocean (Pre-Nectarian) - 4.57-4.2(?) Ga; (Stage 3:) Cratered Highlands (Pre-Nectarian) - 4.4(?) 4.2(?) Ga (Stage 4:) Large Basins - (Pre-Nectarian - Upper Imbrium) 4.3(?)-3.8 Ga; (Stage 4A:) Old Large Basins and Crustal Strengthening (Pre Nectarian) - 4.3(?)-3.92 Ga; (Stage 4B): Young Large Basins (Nectarian - Lower Imbrium) 3.92-3.80 Ga; (Stage 5): Basaltic Maria (Upper Imbrium) - 4.3(?)- 1.0(?) Ga; (Stage 6): Mature Surface (Copernican and Eratosthenian) - 3.80 Ga to Present. Increasingly strong indications of a largely undifferentiated lower lunar mantle and increasingly constrained initial conditions for models of an Earth-impact origin for the Moon suggest that lunar origin by capture of an independently evolved planet should be investigated more vigorously. Capture appears to better explain the geochemical and geophysical details related to the lower mantle of the Moon and to the distribution of elements and their isotopes. For example, the source of the volatile components of the Apollo 17 orange glass apparently would have lain below the degassed and differentiated magma ocean (3) in a relatively undifferentiated primordial lower mantle. Also, a density reversal from 3.7 gm/cubic cm to approximately 3.3 gm/cubic cm is required at the base of the upper mantle to be consistent with the overall density of the Moon. Finally, Hf/W systematics allow only a very narrow window, if any at all for a giant impact to form the Moon. Continued accretionary impact activity during the crystallization of the magma

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. [Reconstruction of possible paths of the origin and morphological evolution of bacteriophages].

    PubMed

    Letarov, A V

    1998-11-01

    The problem of the origin and evolution of viruses and, in particular, the origin and evolution of bacteriophages is of considerable interest. However, so far, this problem has not been solved with quantitative methods of molecular systematics. In the present study, an attempt to reconstruct the possible paths of appearance and evolution of bacteriophages based on their structural features and morphogenesis, as well as general characteristics of their life cycles and genome organization, was carried out. A scheme describing phylogeny of the main bacteriophage groups and evolution of their life cycles is suggested. Existence of two independently evaluating types of morphogenesis ("budding outward" and "budding inward") is postulated. PMID:10096023

  14. The Origin and Evolution of the Solar System.

    ERIC Educational Resources Information Center

    Woolfson, M. M.

    1987-01-01

    Describes the major components of the solar system and proposes several features that a theory about the solar system should include. Contains explanations of several theories about the origin of the solar system. (TW)

  15. 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,…

  16. Multiple cellular origins and molecular evolution of intrahepatic cholangiocarcinoma.

    PubMed

    Wei, Miaoyan; Lü, Lisheng; Lin, Peiyi; Chen, Zhisheng; Quan, Zhiwei; Tang, Zhaohui

    2016-09-01

    Intrahepatic cholangiocarcinoma (ICC) is an aggressive malignancy associated with unfavorable prognosis and for which no effective treatments are available. Its molecular pathogenesis is poorly understood. Genome-wide sequencing and high-throughput technologies have provided critical insights into the molecular basis of ICC while sparking a heated debate on the cellular origin. Cancer exhibits variabilities in origin, progression and cell biology. Recent evidence suggests that ICC has multiple cellular origins, including differentiated hepatocytes; intrahepatic biliary epithelial cells (IBECs)/cholangiocytes; pluripotent stem cells, such as hepatic stem/progenitor cells (HPCs) and biliary tree stem/progenitor cells (BTSCs); and peribiliary gland (PBG). However, both somatic mutagenesis and epigenomic features are highly cell type-specific. Multiple cellular origins may have profoundly different genomic landscapes and key signaling pathways, driving phenotypic variation and thereby posing significant challenges to personalized medicine in terms of achieving the optimal drug response and patient outcome. Considering this information, we have summarized the latest experimental evidence and relevant literature to provide an up-to-date view of the cellular origin of ICC, which will contribute to establishment of a hierarchical model of carcinogenesis and allow for improvement of the anatomical-based classification of ICC. These new insights have important implications for both the diagnosis and treatment of ICC patients. PMID:26940139

  17. 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.

  18. 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.

  19. Origin of Life and Evolution in Biology Textbooks--A Critique.

    ERIC Educational Resources Information Center

    Mills, Gordon C.; And Others

    1993-01-01

    Examines biology textbooks from the list of books approved by the state of Texas. Concludes that there are errors, overstatements, and omissions that tend to enhance the plausibility of accepted hypotheses of the origin of life and evolution. (PR)

  20. 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)

  1. Images of Evolution: Origin of Spontaneous RNA Replication Waves

    NASA Astrophysics Data System (ADS)

    McCaskill, J. S.; Bauer, G. J.

    1993-05-01

    Self-replicating molecules set up traveling concentration waves that propagate in an aqueous enzyme solution. The velocity of each wave provides an accurate (±0.1%) noninvasive measure of fitness for the RNA species currently growing in its front. Evolution may be followed from changes in the front velocity, and these differ from wave to wave. Thousands of controlled evolution reactions in traveling waves have been monitored in parallel to obtain quantitative images of the stochastic process of natural selection. An RNA polymerase (RNA-dependent RNA nucleotidyltransferase, EC 2.7.7.6), extracted from bacteria infected by the Qβ RNA virus, catalyzes the replication. The traveling waves that arise spontaneously without added RNA provide a model system for major evolutionary change.

  2. 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.

  3. Origin and evolution of the parasitic cyclopoid copepods.

    PubMed

    Ho, J S

    1994-12-01

    Six of the 10 recognised families of the order Cyclopoida are parasitic, with 4 of them occurring on marine invertebrates and the remaining 2 on freshwater gastropods and fishes, respectively. A cladistic analysis of the 10 families indicates that evolution of parasitism occurred twice in the history of the cyclopoids. The first attempt was made by the marine epibenthic ancestors seeking food and shelter in sessile tunicates--the ascidians. This event led to the evolution of 2 ascidicolous families: Archinotodelphyidae and Notodelphyidae. The descendant of this lineage had also invaded the mantle cavity of marine bivalve molluscs, eventually leading to the evolution of the Mantridae. The second attempt for the parasitic mode of life was launched by the ancestor which was the sister group of the ancestral cyclopoids--the most successful family of freshwater copepods. This ancestral stock, while living in the coastal zone, split into 2 groups: one group stayed behind in the ocean and colonised again the ascidians; the other groups invaded freshwater and evolved into the fish-parasitising Lernaeidae and the gastropod-parasitising Ozmanidae. PMID:7729982

  4. The atmospheres of the earth and the other planets: Origin, evolution and composition

    NASA Technical Reports Server (NTRS)

    Levine, Joel S.

    1988-01-01

    The current understanding of the composition, chemistry, and structure of the atmospheres of the other planets and the origin, early history, and evolution of the earth's atmosphere is reviewed. The information on the atmospheres of the other planets is based on the successful Mariner, Viking, Pioneer, and Voyager missions to these planets. The information on the origin, early history, and evolution of the atmosphere, which is somewhat speculative, is largely based on numerical studies with geochemical and photochemical models.

  5. 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).

  6. Singularities in the Origin and Evolution of Life

    SciTech Connect

    Duve, Christian de

    2003-11-19

    The history of life is landmarked by a large number of remarkable singularities. The single ancestry of all living beings, the universal genetic code, and the monophyletic origin of eukaryotes are typical examples, but there are many others. The mechanisms responsible for these singularities will be discussed.

  7. Origin, evolution, and biogeography of Juglans: a phylogenetic perspective

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Phylogenetic analyses of extant Juglans (Juglandaceae) using five cpDNA intergenic spacer (IGS) sequences (trnT-trnF, psbA-trnH, atpB-rbcL, trnV-16S rRNA, and trnS-trnfM) were performed to elucidate the origin, diversification, historical biogeography, and evolutionary relationships within the genus...

  8. 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. PMID:25137591

  9. Origin and evolution of TNF and TNF receptor superfamilies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The tumor necrosis factor superfamily (TNFSF) and the TNF receptor superfamily (TNFRSF) have an ancient evolutionary origin that can be traced back to single copy genes within Arthropods. In humans, 18 TNFSF and 29 TNFRSF genes have been identified. Evolutionary models account for the increase in g...

  10. 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…

  11. Origin and evolution of medium chain alcohol dehydrogenases.

    PubMed

    Jörnvall, Hans; Hedlund, Joel; Bergman, Tomas; Kallberg, Yvonne; Cederlund, Ella; Persson, Bengt

    2013-02-25

    Different lines of alcohol dehydrogenases (ADHs) have separate superfamily origins, already recognized but now extended and re-evaluated by re-screening of the latest databank update. The short-chain form (SDR) is still the superfamily with most abundant occurrence, most multiple divergence, most prokaryotic emphasis, and most non-complicated architecture. This pattern is compatible with an early appearance at the time of the emergence of prokaryotic cellular life. The medium-chain form (MDR) is also old but second in terms of all the parameters above, and therefore compatible with a second emergence. However, this step appears seemingly earlier than previously considered, and may indicate sub-stages of early emergences at the increased resolution available from the now greater number of data entries. The Zn-MDR origin constitutes a third stage, possibly compatible with the transition to oxidative conditions on earth. Within all these three lines, repeated enzymogeneses gave the present divergence. MDR-ADH origin(s), at a fourth stage, may also be further resolved in multiple or extended modes, but the classical liver MDR-ADH of the liver type can still be traced to a gene duplication ~550 MYA (million years ago), at the early vertebrate radiation, compatible with the post-eon-shift, "Cambrian explosion". Classes and isozymes correspond to subsequent and recent duplicatory events, respectively. They illustrate a peculiar pattern with functional and emerging evolutionary distinctions between parent and emerging lines, suggesting a parallelism between duplicatory and mutational events, now also visible at separate sub-stages. Combined, all forms show distinctive patterns at different levels and illustrate correlations with global events. They further show that simple molecular observations on patterns, multiplicities and occurrence give much information, suggesting common divergence rules not much disturbed by horizontal gene transfers after the initial origins. PMID

  12. Why Reproduce? A Demonstration of Evolution and the Origin of Life.

    ERIC Educational Resources Information Center

    Journet, Alan R. P.

    1982-01-01

    Describes a simple model to illustrate several aspects of the biochemical origin of life and the process of evolution through natural selection. The model has students predict the outcome of evolution in populations of beads. Instructional strategies using the model are also discussed. (Author/JN)

  13. 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.

    2016-06-01

    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.

  14. 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.

  15. Pre-metazoan origins and evolution of the cadherin adhesome

    PubMed Central

    Murray, Paul S.; Zaidel-Bar, Ronen

    2014-01-01

    ABSTRACT Vertebrate adherens junctions mediate cell–cell adhesion via a “classical” cadherin–catenin “core” complex, which is associated with and regulated by a functional network of proteins, collectively named the cadherin adhesome (“cadhesome”). The most basal metazoans have been shown to conserve the cadherin–catenin “core”, but little is known about the evolution of the cadhesome. Using a bioinformatics approach based on both sequence and structural analysis, we have traced the evolution of this larger network in 26 organisms, from the uni-cellular ancestors of metazoans, through basal metazoans, to vertebrates. Surprisingly, we show that approximately 70% of the cadhesome, including proteins with similarity to the catenins, predate metazoans. We found that the transition to multicellularity was accompanied by the appearance of a small number of adaptor proteins, and we show how these proteins may have helped to integrate pre-metazoan sub-networks via PDZ domain–peptide interactions. Finally, we found the increase in network complexity in higher metazoans to have been driven primarily by expansion of paralogs. In summary, our analysis helps to explain how the complex protein network associated with cadherin at adherens junctions first came together in the first metazoan and how it evolved into the even more complex mammalian cadhesome. PMID:25395670

  16. 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

  17. Origin and evolution of Japanese encephalitis virus in southeast Asia.

    PubMed

    Solomon, Tom; Ni, Haolin; Beasley, David W C; Ekkelenkamp, Miquel; Cardosa, Mary Jane; Barrett, Alan D T

    2003-03-01

    Since it emerged in Japan in the 1870s, Japanese encephalitis has spread across Asia and has become the most important cause of epidemic encephalitis worldwide. Four genotypes of Japanese encephalitis virus (JEV) are presently recognized (representatives of genotypes I to III have been fully sequenced), but its origin is not known. We have determined the complete nucleotide and amino acid sequence of a genotype IV Indonesian isolate (JKT6468) which represents the oldest lineage, compared it with other fully sequenced genomes, and examined the geographical distribution of all known isolates. JKT6468 was the least similar, with nucleotide divergence ranging from 17.4 to 19.6% and amino acid divergence ranging from 4.7 to 6.5%. It included an unusual series of amino acids at the carboxy terminus of the core protein unlike that seen in other JEV strains. Three signature amino acids in the envelope protein (including E327 Leu-->Thr/Ser on the exposed lateral surface of the putative receptor binding domain) distinguished genotype IV strains from more recent genotypes. Analysis of all 290 JEV isolates for which sequence data are available showed that the Indonesia-Malaysia region has all genotypes of JEV circulating, whereas only more recent genotypes circulate in other areas (P < 0.0001). These results suggest that JEV originated from its ancestral virus in the Indonesia-Malaysia region and evolved there into the different genotypes which then spread across Asia. Our data, together with recent evidence on the origins of other emerging viruses, including dengue virus and Nipah virus, imply that tropical southeast Asia may be an important zone for emerging pathogens. PMID:12584335

  18. 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. PMID:26276630

  19. Origin, Methods, and Evolution of the Three Nurses' Health Studies.

    PubMed

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

    2016-09-01

    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

  20. 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

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

    PubMed

    Budd, Graham E

    2015-12-19

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

  2. 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

  3. 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.

  4. 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. PMID:25758413

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

    PubMed Central

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

    2012-01-01

    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. PMID:23150784

  6. 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

  7. The origin and evolution of the genetic code.

    PubMed

    Béland, P; Allen, T F

    1994-10-21

    We argue that a primitive genetic code with only 20 separate words explains that there are 20 coded amino acids in modern life. The existence of 64 words on the modern genetic code requires modern life to read almost exclusively one strand of DNA in one direction. In our primitive code, both the original and the complementary sequence are read in either direction to give the same strings of amino acids. The algebra of complements forces synonymy of primitive codons so as to reduce the 64 independent codons of the modern code to exactly 20 independent separate words in the primitive condition. The synonymy in the modern code is the result of selection rather than algebraic forcing. The primitive code has almost no resilience to base mutations, unlike the third base redundancy of the modern code. Our primitive and the modern code are orthogonal. If palindromic proteins were coded by hairpin DNA or RNA, then (i) no punctuation would be needed; (ii) the reverse reading would give the same secondarily folded protein structure; and (iii) the sugar backbone would be read in the conventional 5' to 3' direction for the original arm and its complement. Modern copying of genetic material is almost always antiparallel. However, occasional parallel copying, as does occur in modern life, would give the complementary hairpin that would also read 5' to 3' along its entire length.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7996862

  8. 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.

  9. Impact of solar system exploration on theories of chemical evolution and the origin of life

    NASA Technical Reports Server (NTRS)

    Devincenzi, D. L.

    1983-01-01

    The impact of solar system exploration on theories regarding chemical evolution and the origin of life is examined in detail. Major findings from missions to Mercury, Venus, the moon, Mars, Jupiter, Saturn, and Titan are reviewed and implications for prebiotic chemistry are discussed. Among the major conclusions are: prebiotic chemistry is widespread throughout the solar system and universe; chemical evolution and the origin of life are intimately associated with the origin and evolution of the solar system; the rate, direction, and extent of prebiotic chemistry is highly dependent upon planetary characteristics; and continued exploration will increase understanding of how life originated on earth and allow better estimates of the likelihood of similar processes occurring elsewhere.

  10. Evolution of bilaterian central nervous systems: a single origin?

    PubMed Central

    2013-01-01

    The question of whether the ancestral bilaterian had a central nervous system (CNS) or a diffuse ectodermal nervous system has been hotly debated. Considerable evidence supports the theory that a CNS evolved just once. However, an alternative view proposes that the chordate CNS evolved from the ectodermal nerve net of a hemichordate-like ancestral deuterostome, implying independent evolution of the CNS in chordates and protostomes. To specify morphological divisions along the anterior/posterior axis, this ancestor used gene networks homologous to those patterning three organizing centers in the vertebrate brain: the anterior neural ridge, the zona limitans intrathalamica and the isthmic organizer, and subsequent evolution of the vertebrate brain involved elaboration of these ancestral signaling centers; however, all or part of these signaling centers were lost from the CNS of invertebrate chordates. The present review analyzes the evidence for and against these theories. The bulk of the evidence indicates that a CNS evolved just once – in the ancestral bilaterian. Importantly, in both protostomes and deuterostomes, the CNS represents a portion of a generally neurogenic ectoderm that is internalized and receives and integrates inputs from sensory cells in the remainder of the ectoderm. The expression patterns of genes involved in medio/lateral (dorso/ventral) patterning of the CNS are similar in protostomes and chordates; however, these genes are not similarly expressed in the ectoderm outside the CNS. Thus, their expression is a better criterion for CNS homologs than the expression of anterior/posterior patterning genes, many of which (for example, Hox genes) are similarly expressed both in the CNS and in the remainder of the ectoderm in many bilaterians. The evidence leaves hemichordates in an ambiguous position – either CNS centralization was lost to some extent at the base of the hemichordates, or even earlier, at the base of the hemichordates

  11. Evolution of bilaterian central nervous systems: a single origin?

    PubMed

    Holland, Linda Z; Carvalho, João E; Escriva, Hector; Laudet, Vincent; Schubert, Michael; Shimeld, Sebastian M; Yu, Jr-Kai

    2013-01-01

    The question of whether the ancestral bilaterian had a central nervous system (CNS) or a diffuse ectodermal nervous system has been hotly debated. Considerable evidence supports the theory that a CNS evolved just once. However, an alternative view proposes that the chordate CNS evolved from the ectodermal nerve net of a hemichordate-like ancestral deuterostome, implying independent evolution of the CNS in chordates and protostomes. To specify morphological divisions along the anterior/posterior axis, this ancestor used gene networks homologous to those patterning three organizing centers in the vertebrate brain: the anterior neural ridge, the zona limitans intrathalamica and the isthmic organizer, and subsequent evolution of the vertebrate brain involved elaboration of these ancestral signaling centers; however, all or part of these signaling centers were lost from the CNS of invertebrate chordates. The present review analyzes the evidence for and against these theories. The bulk of the evidence indicates that a CNS evolved just once - in the ancestral bilaterian. Importantly, in both protostomes and deuterostomes, the CNS represents a portion of a generally neurogenic ectoderm that is internalized and receives and integrates inputs from sensory cells in the remainder of the ectoderm. The expression patterns of genes involved in medio/lateral (dorso/ventral) patterning of the CNS are similar in protostomes and chordates; however, these genes are not similarly expressed in the ectoderm outside the CNS. Thus, their expression is a better criterion for CNS homologs than the expression of anterior/posterior patterning genes, many of which (for example, Hox genes) are similarly expressed both in the CNS and in the remainder of the ectoderm in many bilaterians. The evidence leaves hemichordates in an ambiguous position - either CNS centralization was lost to some extent at the base of the hemichordates, or even earlier, at the base of the hemichordates

  12. 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.

  13. Chemical evolution and the origin of life: bibliography supplement 1985

    NASA Technical Reports Server (NTRS)

    Wade, R. C.; Powers, J. V.; Ponnamperuma, C.

    1989-01-01

    This bibliography is the seventeenth annual supplement to the comprehensive bibliography on the same subject which was published in Space Life Sci. 2(1970), 225-295; 3(1972), 293-304; 4(1973), 309-329 and in Origins of Life 5(1974), 505-527; 6(1975), 285-300; 7(1976), 75-85; 8(1977), 59-66; 9(1978), 67-74; 10(1980), 69-87; 10(1980), 379-404; 11(1981), 273-288; 12(1982), 93-118; 13(1983), 61-80; 15(1984), 55-69; 17(1987), 171-184; 17(1987), 185-206.

  14. 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

  15. Social roles, context and evolution in the origins of depression.

    PubMed

    Brown, George W

    2002-09-01

    This paper reviews the author's research on the social origins of depression begun in the early 1970s. It emphasizes the importance of taking account of the context and meaning of proximal causal factors by the use of investigator-based ratings using intensive interviews and the need to extend research to cover a whole lifetime. The implications of the research program that has involved some twenty inquiries in a variety of cultural settings is discussed in terms of the importance of both a comparative and an evolutionary perspective concerning meaning that bring together the biology involved in an evolutionary perspective emphasizing a common human nature with one that takes account of cultural and individual differences. In short an approach that take seriously a biopsychosocial perspective. PMID:12467252

  16. 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.

  17. 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

  18. 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.

  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. PMID:26554041

  20. Evolution of organogenesis and the origin of altriciality in mammals.

    PubMed

    Werneburg, Ingmar; Laurin, Michel; Koyabu, Daisuke; Sánchez-Villagra, Marcelo R

    2016-07-01

    Mammals feature not only great phenotypic disparity, but also diverse growth and life history patterns, especially in maturity level at birth, ranging from altriciality to precocity. Gestation length, morphology at birth, and other markers of life history are fundamental to our understanding of mammalian evolution. Based on the first synthesis of embryological data and the study of new ontogenetic series, we reconstructed estimates of the ancestral chronology of organogenesis and life-history modes in placental mammals. We found that the ancestor of marsupial and placental mammals was placental-like at birth but had a long, marsupial-like infancy. We hypothesize that mammalian viviparity might have evolved in association with the extension of growth after birth, enabled through lactation, and that mammalian altriciality is inherited from the earliest amniotes. The precocial lifestyle of extant sauropsids and that of many placental mammals were acquired secondarily. We base our conclusions on the best estimates and provide a comprehensive discussion on the methods used and the limitations of our dataset. We provide the most comprehensive embryological dataset ever published, "rescue" old literature sources, and apply available methods and illustrate thus an approach on how to investigate comparatively organogenesis in macroevolution. PMID:27402569

  1. 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.

  2. Diversity and evolution of multiple orc/cdc6-adjacent replication origins in haloarchaea

    PubMed Central

    2012-01-01

    Background While multiple replication origins have been observed in archaea, considerably less is known about their evolutionary processes. Here, we performed a comparative analysis of the predicted (proved in part) orc/cdc6-associated replication origins in 15 completely sequenced haloarchaeal genomes to investigate the diversity and evolution of replication origins in halophilic Archaea. Results Multiple orc/cdc6-associated replication origins were predicted in all of the analyzed haloarchaeal genomes following the identification of putative ORBs (origin recognition boxes) that are associated with orc/cdc6 genes. Five of these predicted replication origins in Haloarcula hispanica were experimentally confirmed via autonomous replication activities. Strikingly, several predicted replication origins in H. hispanica and Haloarcula marismortui are located in the distinct regions of their highly homologous chromosomes, suggesting that these replication origins might have been introduced as parts of new genomic content. A comparison of the origin-associated Orc/Cdc6 homologs and the corresponding predicted ORB elements revealed that the replication origins in a given haloarchaeon are quite diverse, while different haloarchaea can share a few conserved origins. Phylogenetic and genomic context analyses suggested that there is an original replication origin (oriC1) that was inherited from the ancestor of archaea, and several other origins were likely evolved and/or translocated within the haloarchaeal species. Conclusion This study provides detailed information about the diversity of multiple orc/cdc6-associated replication origins in haloarchaeal genomes, and provides novel insight into the evolution of multiple replication origins in Archaea. PMID:22978470

  3. Atmospheres on the terrestrial planets: Clues to origin and evolution

    NASA Astrophysics Data System (ADS)

    Pepin, Robert O.

    2006-11-01

    Earth, Venus and Mars reached their final sizes in the first 100 Myr or so of solar system history. For part of that time the growing planets and the materials forming them were immersed in the Sun-like gases of the solar nebula, and so one would expect that their early volatile inventories were acquired from the nebula. But the compositions of atmospheres presently on these planets are not solar, and therein lies a complex and fascinating story of physical and chemical evolution over the past 4.5 Ga. Records of physical processing survive most clearly in the chemically inert noble gases, and data on the elemental and isotopic abundances of these trace constituents, now from Mars and Venus as well as Earth, point to atmospheric histories punctuated by enormous inputs of energy from early astrophysical sources long since vanished. Observational and theoretical advances during the past 30 years underpin current evolutionary models in which primordial solar-like atmospheric gases are fractionated by gravitational escape, driven on Earth by a giant Moon-forming impact, on Mars by sputtering at high altitudes, and on all three planets by adsorption of intense ultraviolet radiation from the young Sun. Residual atmospheres left behind after these outflows to space are augmented by planetary degassing, including species generated in their interiors by radioactive decay. Interplay over time of these mechanisms for loss and gain of atmospheric gases can account for many of the details of contemporary noble gas distributions. These of course are just models. However they have predictive power for compositions as yet unmeasured, particularly on Venus, and the modeling assumptions are in principle testable by experiment or theory. The fundamental question of whether nature actually shaped the atmospheres in this way is still unanswered, but at least we have an outline of how it might have happened.

  4. 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. PMID:21043781

  5. Origins and Evolution of the Etruscans’ mtDNA

    PubMed Central

    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 8th to the 1st 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. PMID:23405165

  6. 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. PMID:10511967

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. Origin, Internal Structure and Evolution of 4 Vesta

    NASA Astrophysics Data System (ADS)

    Zuber, Maria T.; McSween, Harry Y.; Binzel, Richard P.; Elkins-Tanton, Linda T.; Konopliv, Alexander S.; Pieters, Carle M.; Smith, David E.

    2011-12-01

    Asteroid 4 Vesta is the only preserved intact example of a large, differentiated protoplanet like those believed to be the building blocks of terrestrial planet accretion. Vesta accreted rapidly from the solar nebula in the inner asteroid belt and likely melted due to heat released due to the decay of 26Al. Analyses of meteorites from the howardite-eucrite-diogenite (HED) suite, which have been both spectroscopically and dynamically linked to Vesta, lead to a model of the asteroid with a basaltic crust that overlies a depleted peridotitic mantle and an iron core. Vesta’s crust may become more mafic with depth and might have been intruded by plutons arising from mantle melting. Constraints on the asteroid’s moments of inertia from the long-wavelength gravity field, pole position and rotation, informed by bulk composition estimates, allow tradeoffs between mantle density and core size; cores of up to half the planetary radius can be consistent with plausible mantle compositions. The asteroid’s present surface is expected to consist of widespread volcanic terrain, modified extensively by impacts that exposed the underlying crust or possibly the mantle. Hemispheric heterogeneity has been observed by poorly resolved imaging of the surface that suggests the possibility of a physiographic dichotomy as occurs on other terrestrial planets. Vesta might have had an early magma ocean but details of the early thermal structure are far from clear owing to model uncertainties and paradoxical observations from the HEDs. Petrological analysis of the eucrites coupled with thermal evolution modeling recognizes two possible mechanisms of silicate-metal differentiation leading to the formation of the basaltic achondrites: equilibrium partial melting or crystallization of residual liquid from the cooling magma ocean. A firmer understanding the plethora of complex physical and chemical processes that contribute to melting and crystallization will ultimately be required to

  12. 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. PMID:22970331

  13. Origin and Evolution of Dengue Virus Type 3 in Brazil

    PubMed Central

    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. PMID:22970331

  14. 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.

  15. 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

  16. Origin and evolution of the ligand-binding ability of nuclear receptors.

    PubMed

    Markov, Gabriel V; Laudet, Vincent

    2011-03-01

    The origin of the ligand-binding ability of nuclear receptors is still a matter of discussion. Current opposing models are the early evolution of an ancestral receptor that would bind a specific ligand with high affinity and the early evolution of an ancestral orphan that was a constitutive transcription factor. Here we review the arguments in favour or against these two hypotheses, and we discuss an alternative possibility that the ancestor was a ligand sensor, which would be able to explain the apparently contradictory data generated in previous models for the evolution of ligand binding in nuclear receptors. PMID:21055443

  17. Geochemistry of Bolivian salars, Lipez, southern Altiplano: Origin of solutes and brine evolution

    SciTech Connect

    Risacher, F. ); Fritz, B. )

    1991-03-01

    This paper focuses on poorly understood processes related to saline lakes, or salars, of the southern Bolivian Altiplano. A morphologic classification system is described, and the origin of solutes in the inflow waters is discussed. Next, the actual chemical evolution of these inflow waters is compared with their theoretical evolution based on thermodynamic equilibria. The water chemistry of a specific sequence of evaporating waters is then scrutinized to determine which processes are responsible for a significant discrepancy which is apparent between the measured and the calculated evolution.

  18. 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.

  19. 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.

  20. 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

  1. Phase dependent fracture and damage evolution of polytetrafluoroethylene (PTFE)

    SciTech Connect

    Brown, E. N.; Rae, P.; Orler, E. B.; Thissell, W. R.; Dattelbaum, D. M.

    2004-01-01

    Compared with other polymers, polytetrafluoroethylene (PTFE) presents several advantages for load-bearing structural components including higher strength at elevated temperatures and higher toughness at lowered temperatures. Failure sensitive applications of PTFE include surgical implants, aerospace components, and chemical barriers. Polytetrafluoroethylene is semicrystalline in nature with their linear chains forming complicated phases near room temperature and ambient pressure. The presence of three unique phases near room temperature implies that failure during standard operating conditions may be strongly dependent on the phase. This paper presents a comprehensive and systematic study of fracture and damage evolution in PTFE to elicit the effects of temperature-induced phase on fracture mechanisms. The fracture behavior of PTFE is observed to undergo transitions from brittle-fracture below 19 C to ductile-fracture with crazing and some stable crack growth to plastic flow aver 30 C. The bulk failure properties are correlated to failure mechanisms through fractography and analysis of the crystalline structure.

  2. 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

  3. 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.

  4. 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

  5. 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.

  6. 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…

  7. 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.

  8. 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.

  9. 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…

  10. The origins of the Acheulean: past and present perspectives on a major transition in human evolution.

    PubMed

    de la Torre, Ignacio

    2016-07-01

    The emergence of the Acheulean from the earlier Oldowan constitutes a major transition in human evolution, the theme of this special issue. This paper discusses the evidence for the origins of the Acheulean, a cornerstone in the history of human technology, from two perspectives; firstly, a review of the history of investigations on Acheulean research is presented. This approach introduces the evolution of theories throughout the development of the discipline, and reviews the way in which cumulative knowledge led to the prevalent explanatory framework for the emergence of the Acheulean. The second part presents the current state of the art in Acheulean origins research, and reviews the hard evidence for the appearance of this technology in Africa around 1.7 Ma, and its significance for the evolutionary history of Homo erectusThis article is part of the themed issue 'Major transitions in human evolution'. PMID:27298475

  11. 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

  12. 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

  13. 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.

  14. 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

  15. Influence of phase transformation on stress evolution during growth of metal thin films on silicon.

    PubMed

    Fillon, A; Abadias, G; Michel, A; Jaouen, C; Villechaise, P

    2010-03-01

    In situ stress measurements during two-dimensional growth of low mobility metal films on amorphous Si were used to demonstrate the impact of interface reactivity and phase transformation on stress evolution. Using Mo1-xSix films as examples, the results show that the tensile stress rise, which develops after the film has become crystalline, is correlated with an increase in lateral grain size. The origin of the tensile stress is attributed to the volume change resulting from the alloy crystallization, which occurs at a concentration-dependent critical thickness. PMID:20366996

  16. Phase Evolution During the Carbothermic Reduction Process of Ilmenite Concentrate

    NASA Astrophysics Data System (ADS)

    Gou, Hai-Peng; Zhang, Guo-Hua; Chou, Kuo-Chih

    2015-02-01

    The phase evolution during the carbothermic reduction process of Panzhihua ilmenite concentrate was investigated under argon atmosphere. The Panzhihua ilmenite concentrate briquette with graphite powder was reduced at 1473 K, 1573 K, 1673 K, and 1773 K (1200 °C, 1300 °C, 1400 °C, and 1500 °C) respectively, with the molar ratios of C to FeTiO3 being 4:1 and 5:1. The phase transformation of the briquette reduced at different temperatures was investigated by X-ray diffraction and scanning electron microscope. During the carbothermic reduction process from 1473 K to 1773 K (1200 °C to 1500 °C), it was found that main phases were Fe, Ti3O5, Ti2O3, and TiC x O y . The lowest temperature for the generation of TiC x O y was 1573 K (1300 °C) for both kinds of briquettes with different C contents. The rate controlling step for the carbothermic reduction above 1573 K (1300 °C) obeyed the diffusion model. The reduction degree of the ilmenite was increased by increasing the temperature. With the increase of reaction temperature and reaction time, TiC x O y phase would be reduced to TiC phase.

  17. Phase Evolution During the Carbothermic Reduction Process of Ilmenite Concentrate

    NASA Astrophysics Data System (ADS)

    Gou, Hai-Peng; Zhang, Guo-Hua; Chou, Kuo-Chih

    2014-09-01

    The phase evolution during the carbothermic reduction process of Panzhihua ilmenite concentrate was investigated under argon atmosphere. The Panzhihua ilmenite concentrate briquette with graphite powder was reduced at 1473 K, 1573 K, 1673 K, and 1773 K (1200 °C, 1300 °C, 1400 °C, and 1500 °C) respectively, with the molar ratios of C to FeTiO3 being 4:1 and 5:1. The phase transformation of the briquette reduced at different temperatures was investigated by X-ray diffraction and scanning electron microscope. During the carbothermic reduction process from 1473 K to 1773 K (1200 °C to 1500 °C), it was found that main phases were Fe, Ti3O5, Ti2O3, and TiC x O y . The lowest temperature for the generation of TiC x O y was 1573 K (1300 °C) for both kinds of briquettes with different C contents. The rate controlling step for the carbothermic reduction above 1573 K (1300 °C) obeyed the diffusion model. The reduction degree of the ilmenite was increased by increasing the temperature. With the increase of reaction temperature and reaction time, TiC x O y phase would be reduced to TiC phase.

  18. The phase evolution mechanism in Fe(Se, Te) system

    NASA Astrophysics Data System (ADS)

    Liu, Jixing; Li, Chengshan; Zhang, Shengnan; Feng, Jianqing; Zhang, Pingxiang; Zhou, Lian

    2016-08-01

    The phase evolution mechanism in Fe(Se, Te) system during sintering was investigated with step-by-step heat treatment process. It was noticed that the diffusion processes between Fe and Se (Te) as well as that between Se and Te were both very important to the formation of superconducting Fe(Se, Te) phase with very uniform chemical composition. During heat treatment, solid solutions of (Se, Te)ss with different chemical composition were formed with the diffusion of Se atoms into Te solids and Te atoms into Se melts, simultaneously. Then with the increasing temperature, Fe atoms diffused into (Se, Te)ss, Fe(Se, Te)2 and Fe(Se, Te) phases were formed in sequence with the increasing Fe content. The chemical composition in melts became more and more uniform with the further increasing of sintering temperature and dwell time. Therefore, it was suggested that in order to achieve Fe(Se, Te) phase with high superconducting properties, it was necessary to enhance the diffusion process during sintering. The critical temperature of the sample, which was sintered at 700 °C for 12 h with slow cooling process and an O2-annealing process for 24 h, was above 14.0 K. This Tc value proved that a good superconducting β phase could be obtained under this sintering condition.

  19. In Situ Phase Evolution of Ni/Ti Reactive Multilayers

    NASA Astrophysics Data System (ADS)

    Cavaleiro, A. J.; Ramos, A. S.; Martins, R. M. S.; Baetz, C.; Vieira, M. T.; Braz Fernandes, F. M.

    2014-07-01

    Joining shape-memory alloys (SMA) to other materials is strongly required in order to enlarge their fields of application. Fusion welding induces strong compositional and microstructural changes that significantly affect the shape-memory effect and the superelastic behavior of these alloys. The exothermic and in some cases self-propagating character of some nano-multilayer reactions is explored in this study as an alternative for joining SMA. To follow these very fast reactions, high brilliance sources, such as synchrotron radiation, are required. In situ high-resolution x-ray diffraction data, giving the phase evolution sequence with temperature of the Ni/Ti multilayer thin films under study, are presented. A correlation between the multilayer design and the tendency for the sequence of phase formation is established.

  20. Adaptive evolution of Hoxc13 genes in the origin and diversification of the vertebrate integument.

    PubMed

    Wu, Jianghong; Husile; Sun, Hailian; Wang, Feng; Li, Yurong; Zhao, Cunfa; Zhang, Wenguang

    2013-11-01

    The problem of origination and diversification of integument derivatives in vertebrates is still a challenge. The homeobox (Hox) genes Hoxc13 control integument formation in vertebrate. Hoxc13 show strong expression in the integument development, are highly conserved across vertebrates, and show mutations that are associated with skin and appendages. To test whether the evolution of the integument is associated with positive selection or relaxation of Hoxc13, we obtained these genes in a wide range of vertebrates. In Hoxc13, we found evidence of diversifying selection after speciation during the origin of vertebrates. In addition, we found the glycine-rich regions in Hoxc13 protein in mammals, but not among non-mammalian taxa. Our results strongly implicate that Hoxc13 genes could have played an important role in the evolution of integument structure. PMID:25961277

  1. 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. PMID:15513240

  2. 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

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

    PubMed

    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

  4. The origin and evolution of the great resonance in the Jovian satellite system

    NASA Astrophysics Data System (ADS)

    Wiesel, W.

    1981-04-01

    The problem of the creation and subsequent evolution of the great resonance among the three inner Galilean satellites of Jupiter is studied by using a periodic orbit/Floquet reference solution to the dynamics. It is shown that the only instability the system can experience is associated with the great libration. By numerically integrating an unstable periodic orbit, the resonant state which preceded the periodic orbit is characterized. A second numerical experiment demonstrates that this resonant state can be directly entered under the influence of tidal forces, without the prior formation of an individual 2:1 resonance pair. Finally, the method of adiabatic invariants is used to prove that tidal evolution after capture will reduce the amplitude of the great libration to zero. These results enable the assembly of a complete description of the origin and evolution of the great resonance.

  5. 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.

  6. Origin of Gila seminuda (Teleostei: Cyprinidae) through introgressive hybridization: implications for evolution and conservation.

    PubMed Central

    DeMarais, B D; Dowling, T E; Douglas, M E; Minckley, W L; Marsh, P C

    1992-01-01

    Morphological and genetic characters from cyprinid fishes of the genus Gila were examined to assess a hypothesized hybrid origin of Gila seminuda from the Virgin River, Arizona-Nevada-Utah. The presumed parents, Gila robusta robusta and Gila elegans, are clearly differentiated from one another based on morphology, allozymes, and mtDNA haplotypes. G. seminuda is morphologically intermediate and polymorphic at allozyme loci diagnostic for the parental species. Restriction endonuclease analysis of mtDNA showed G. seminuda nearly identical to G. elegans. These results support an origin of the bisexual taxon G. seminuda through introgressive hybridization. The Gila population in the Moapa River, Nevada, also appears to be of hybrid origin and is considered a distinctive population of G. seminuda. Inter-specific hybridization is potentially an important mode of evolution among western North American fishes, and valid species of hybrid origin may exist in other groups as well. Consideration of this mode of evolution argues for the need to conserve entire species complexes. PMID:1557380

  7. 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.

  8. 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

  9. 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

  10. 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. PMID:27053123

  11. 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

  12. 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

  13. Phase-Field Methods for Structure Evolution in Sheared Multiphase Systems

    NASA Technical Reports Server (NTRS)

    Badalassi, Vittorio; Ceniceros, Hector; Banerjee, Sanjoy

    2002-01-01

    A homogeneous disordered phase separates into ordered structures when quenched into a broken-symmetry phase. The competition of broken-symmetry phases to select an equilibrium state may be studied in terms of coarse-grained order parameters described by a suitable Landau free-energy function. A network of equilibrium-phase domains develops on quenching and coarsens with time with a topology that may be controlled by shear. We use three-dimensional simulations, in which time-dependent models for conserved-order parameters coupled to Navier-Stokes fluid models are solved, to investigate the evolution of such domains, e.g. spinodal decompositions of polymeric materials under shear. The numerical problems are formidable because of the strong nonlinearities inherent in the coupled model, and these are amongst the first 3D calculations undertaken. In linear shear fields we find stable nanostrings, also recently seen in experiments. The affinity of the ordered phases to boundaries plays a role in the form of the structures that develop, with stacked plate-like phase distributions emerging under certain conditions. Such methods appear quite promising for design and analysis of multiphase and complex fluid formulations. The behavior of foams in such conditions is of particular interest in microgravity environments. Additional information can be found in the original extended abstract.

  14. The origin and evolution of Saturn’s 2011-2012 stratospheric vortex

    NASA Astrophysics Data System (ADS)

    Fletcher, Leigh N.; Hesman, B. E.; Achterberg, R. K.; Irwin, P. G. J.; Bjoraker, G.; Gorius, N.; Hurley, J.; Sinclair, J.; Orton, G. S.; Legarreta, J.; García-Melendo, E.; Sánchez-Lavega, A.; Read, P. L.; Simon-Miller, A. A.; Flasar, F. M.

    2012-11-01

    The planet-encircling springtime storm in Saturn’s troposphere (December 2010-July 2011, Fletcher, L.N. et al. [2011]. Science 332, 1413-1414; Sánchez-Lavega, A. et al. [2011]. Nature 475, 71-74; Fischer, G. et al. [2011]. Nature 475, 75-77) produced dramatic perturbations to stratospheric temperatures, winds and composition at mbar pressures that persisted long after the tropospheric disturbance had abated. Thermal infrared (IR) spectroscopy from the Cassini Composite Infrared Spectrometer (CIRS), supported by ground-based IR imaging from the VISIR instrument on the Very Large Telescope and the MIRSI instrument on NASA’s IRTF, is used to track the evolution of a large, hot stratospheric anticyclone between January 2011 and March 2012. The evolutionary sequence can be divided into three phases: (I) the formation and intensification of two distinct warm airmasses near 0.5 mbar between 25 and 35°N (B1 and B2) between January-April 2011, moving westward with different zonal velocities, B1 residing directly above the convective tropospheric storm head; (II) the merging of the warm airmasses to form the large single ‘stratospheric beacon’ near 40°N (B0) between April and June 2011, disassociated from the storm head and at a higher pressure (2 mbar) than the original beacons, a downward shift of 1.4 scale heights (approximately 85 km) post-merger; and (III) the mature phase characterised by slow cooling (0.11 ± 0.01 K/day) and longitudinal shrinkage of the anticyclone since July 2011. Peak temperatures of 221.6 ± 1.4 K at 2 mbar were measured on May 5th 2011 immediately after the merger, some 80 K warmer than the quiescent surroundings. From July 2011 to the time of writing, B0 remained as a long-lived stable stratospheric phenomenon at 2 mbar, moving west with a near-constant velocity of 2.70 ± 0.04 deg/day (-24.5 ± 0.4 m/s at 40°N relative to System III longitudes). No perturbations to visible clouds and hazes were detected during this period. With no

  15. Molecular Origins of Mesoscale Ordering in a Metalloamphiphile Phase.

    PubMed

    Qiao, Baofu; Ferru, Geoffroy; Olvera de la Cruz, Monica; Ellis, Ross J

    2015-12-23

    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

  16. 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

  17. Rapid Concerted Evolution of Nuclear Ribosomal DNA in Two Tragopogon Allopolyploids of Recent and Recurrent Origin

    PubMed Central

    Kovarik, A.; Pires, J. C.; Leitch, A. R.; Lim, K. Y.; Sherwood, A. M.; Matyasek, R.; Rocca, J.; Soltis, D. E.; Soltis, P. S.

    2005-01-01

    We investigated concerted evolution of rRNA genes in multiple populations of Tragopogon mirus and T. miscellus, two allotetraploids that formed recurrently within the last 80 years following the introduction of three diploids (T. dubius, T. pratensis, and T. porrifolius) from Europe to North America. Using the earliest herbarium specimens of the allotetraploids (1949 and 1953) to represent the genomic condition near the time of polyploidization, we found that the parental rDNA repeats were inherited in roughly equal numbers. In contrast, in most present-day populations of both tetraploids, the rDNA of T. dubius origin is reduced and may occupy as little as 5% of total rDNA in some individuals. However, in two populations of T. mirus the repeats of T. dubius origin outnumber the repeats of the second diploid parent (T. porrifolius), indicating bidirectional concerted evolution within a single species. In plants of T. miscellus having a low rDNA contribution from T. dubius, the rDNA of T. dubius was nonetheless expressed. We have apparently caught homogenization of rDNA repeats (concerted evolution) in the act, although it has not proceeded to completion in any allopolyploid population yet examined. PMID:15654116

  18. 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

  19. 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. PMID:26432392

  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. 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.

  2. 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.

  3. Behavioral Plasticity and the Origins of Novelty: The Evolution of the Rattlesnake Rattle.

    PubMed

    Allf, Bradley C; Durst, Paul A P; Pfennig, David W

    2016-10-01

    Environmentally induced behavior (behavioral plasticity) has long been hypothesized to promote the origins of novel morphological traits, but this idea remains controversial. One context in which this hypothesis can be evaluated is animal communication, where behavior and morphology are often linked. Here, we examined the evolution of one of nature's most spectacular communication signals: the rattlesnake rattle. We specifically evaluated whether rattlesnake rattling behavior-and, hence, the rattle-originated from a simple behavior: vibrating the tail when threatened. By reconstructing the ancestral state of defensive tail vibration, we show that this behavior is nearly ubiquitous in the Viperidae (the family that includes rattlesnakes) and widespread in the Colubridae (the largest snake family, nearly all of which are nonvenomous), suggesting a shared origin for the behavior between these families. After measuring tail vibration in 56 species of Viperidae and Colubridae, we show that the more closely related a species was to rattlesnakes, the more similar it was to rattlesnakes in duration and rate of tail vibration. Thus, the rattlesnake rattle might have evolved via elaboration of a simple behavior. These data thereby support the long-standing hypothesis that behavioral plasticity often precedes-and possibly instigates-the evolution of morphological novelty. PMID:27622880

  4. 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

  5. Origin and Evolution of the Uranian and Neptunian Satellites: Some Dynamical Considerations

    NASA Technical Reports Server (NTRS)

    Dermott, S. F.

    1984-01-01

    The satellite system of Neptune is so irregular that some formation mechanism or subsequent dynamical evolution that sets it apart from the other, more regular, satellite systems is obviously indicated. McKinnon argued that satellite capture is the most likely possibility and has shown that tidal circularization of Triton's presumably highly eccentric initial orbit probably resulted in melting of the satellite's interior. The satellite system of Uranus, although somewhat bland, also has a number of special features that indicate an interesting dynamical history. These include the anomalously high orbital inclination of Miranda and the probable coexistence of small satellites and narrow rings inside the plant's Roche limit. The possibility that orbital evolution due to tidal dissipation is involved in both of these phenomena is discussed. Other topics discussed are: the origin of rings; the formation of coorbital satellites; the lack of stable orbit-orbit resonances in the Uranian satellite system; and chaos, tidal heating and the shapes of Miranda and Ariel.

  6. 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. PMID:19001229

  7. On the origin of the eukaryotic chromosome: the role of noncanonical DNA structures in telomere evolution.

    PubMed

    Garavís, Miguel; González, Carlos; Villasante, Alfredo

    2013-01-01

    The transition of an ancestral circular genome to multiple linear chromosomes was crucial for eukaryogenesis because it allowed rapid adaptive evolution through aneuploidy. Here, we propose that the ends of nascent linear chromosomes should have had a dual function in chromosome end protection (capping) and chromosome segregation to give rise to the "proto-telomeres." Later on, proper centromeres evolved at subtelomeric regions. We also propose that both noncanonical structures based on guanine-guanine interactions and the end-protection proteins recruited by the emergent telomeric heterochromatin have been required for telomere maintenance through evolution. We further suggest that the origin of Drosophila telomeres may be reminiscent of how the first telomeres arose. PMID:23699225

  8. On the Origin of the Eukaryotic Chromosome: The Role of Noncanonical DNA Structures in Telomere Evolution

    PubMed Central

    Garavís, Miguel; González, Carlos; Villasante, Alfredo

    2013-01-01

    The transition of an ancestral circular genome to multiple linear chromosomes was crucial for eukaryogenesis because it allowed rapid adaptive evolution through aneuploidy. Here, we propose that the ends of nascent linear chromosomes should have had a dual function in chromosome end protection (capping) and chromosome segregation to give rise to the “proto-telomeres.” Later on, proper centromeres evolved at subtelomeric regions. We also propose that both noncanonical structures based on guanine–guanine interactions and the end-protection proteins recruited by the emergent telomeric heterochromatin have been required for telomere maintenance through evolution. We further suggest that the origin of Drosophila telomeres may be reminiscent of how the first telomeres arose. PMID:23699225

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

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

    PubMed

    Melkikh, Alexey V; Chesnokova, Oksana I

    2012-08-01

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

  15. [The origin and evolution of parasitism on terrestrial vertebrates in insects, mites, and ticks].

    PubMed

    Balashov, Iu S

    2006-01-01

    Coexistence of terrestrial vertebrates and arthropods has been continuing over 200 million years; various forms of parasitism originated independently in various groups of arthropods during this period. The association of Acari and insects with nests and shelters of their hosts (nidicoly) played the main role in the origin of parasitism in these major groups of arthropods. The primary step in the evolution of parasitism was the permanent habitation in nests and borrows of mammals and birds in Mesozoic era. The second step was a substitution of various forms of schizophagy by the regular feeding on products of vital activity and dead parts of host body. The next step was the feeding on various body parts of vertebrate hosts, namely skin, hair, feathers, external excreta, and drops of blood. The final step was the development of the ability to damage skin and suck out the blood of vertebrates. In some taxa of astigmatid mites the parasitism on birds originated from phoresy: hypopi (heteromorphous deutonymphs) obtained the ability to absorb the liquid nutrients from hair follicles and subcutaneous tissues through the cuticle. The development of haematophagous feeding on mammals in several families of Diptera was the second way of the origin of parasitism. Highly mobile dipterans with the piercing-sucking or licking mouthparts were able to change easily from the accidental puncturing of the host skin or licking of the blood, pus, and mucus to the obligatory haematophagy. The evolution of some arthropod taxa did not went beyond a primary domination of spatial relations, as in many astigmatid mites, or trophic relations in the form of micropredatory, as in the haematophagous Diptera. PMID:17144402

  16. 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

  17. 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

  18. The origin and evolution of fragrance in rice (Oryza sativa L.)

    PubMed Central

    Kovach, Michael J.; Calingacion, Mariafe N.; Fitzgerald, Melissa A.; McCouch, Susan R.

    2009-01-01

    Fragrance in the grain is one of the most highly valued grain quality traits in rice, yet the origin and evolution of the betaine aldehyde dehydrogenase gene (BADH2) underlying this trait remains unclear. In this study, we identify eight putatively nonfunctional alleles of the BADH2 gene and show that these alleles have distinct geographic and genetic origins. Despite multiple origins of the fragrance trait, a single allele, badh2.1, is the predominant allele in virtually all fragrant rice varieties today, including the widely recognized Basmati and Jasmine types. Haplotype analysis allowed us to establish a single origin of the badh2.1 allele within the Japonica varietal group and demonstrate the introgression of this allele from Japonica to Indica. Basmati-like accessions were nearly identical to the ancestral Japonica haplotype across a 5.3-Mb region flanking BADH2 regardless of their fragrance phenotype, demonstrating a close evolutionary relationship between Basmati varieties and the Japonica gene pool. These results clarify the relationships among fragrant rice varieties and challenge the traditional assumption that the fragrance trait arose in the Indica varietal group. PMID:19706531

  19. Origins and Evolution of Hepatitis B Virus and Hepatitis D Virus.

    PubMed

    Littlejohn, Margaret; Locarnini, Stephen; Yuen, Lilly

    2016-01-01

    Members of the family Hepadnaviridae fall into two subgroups: mammalian and avian. The detection of endogenous avian hepadnavirus DNA integrated into the genomes of zebra finches has revealed a deep evolutionary origin of hepadnaviruses that was not previously recognized, dating back at least 40 million and possibly >80 million years ago. The nonprimate mammalian members of the Hepadnaviridae include the woodchuck hepatitis virus (WHV), the ground squirrel hepatitis virus, and arctic squirrel hepatitis virus, as well as a number of members of the recently described bat hepatitis virus. The identification of hepatitis B viruses (HBVs) in higher primates, such as chimpanzee, gorilla, orangutan, and gibbons that cluster with the human HBV, as well as a number of recombinant forms between humans and primates, further implies a more complex origin of this virus. We discuss the current theories of the origin and evolution of HBV and propose a model that includes cross-species transmissions and subsequent recombination events on a genetic backbone of genotype C HBV infection. The hepatitis delta virus (HDV) is a defective RNA virus requiring the presence of the HBV for the completion of its life cycle. The origins of this virus remain unknown, although some recent studies have suggested an ancient African radiation. The age of the association between HDV and HBV is also unknown. PMID:26729756

  20. Phase-dependent photocatalytic H2 evolution of copper zinc tin sulfide under visible light.

    PubMed

    Chang, Zhi-Xian; Zhou, Wen-Hui; Kou, Dong-Xing; Zhou, Zheng-Ji; Wu, Si-Xin

    2014-10-28

    CZTS exhibited apparently phase-dependent photocatalytic H2 evolution under visible light. Possible factors for the phase-dependent photocatalytic activity of CZTS were discussed in detail. PMID:25205452

  1. 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.

  2. 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 .

  3. 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

  4. Origin and evolution of the cystic fibrosis transmembrane regulator protein R domain

    PubMed Central

    Sebastian, Aswathy; Rishishwar, Lavanya; Wang, Jianrong; Bernard, Karen F.; Conley, Andrew B.; McCarty, Nael A.; Jordan, I. King

    2013-01-01

    The Cystic Fibrosis Transmembrane Conductance Regulator protein (CFTR) is a member of the ABC transporter superfamily. CFTR is distinguished from all other members of this superfamily by its status as an ion channel as well as the presence of its unique regulatory (R) domain. We investigated the origin and subsequent evolution of the R domain along the CFTR evolutionary lineage. The R domain protein coding sequence originated via the loss of a splice donor site at the 3′ end of exon 14, leading to the subsequent read-through and capture of formerly intronic sequence as novel coding sequence. Inclusion of the remaining part of the R domain coding sequence in the CFTR transcript involved a lineage-specific gain of exonic sequence with no homology to protein coding sequences outside of CFTR and loss of two exons conserved among ABC family members. These events occurred at the base of the Gnathostome evolutionary lineage ~550–650 million years ago. The apparent origination of the R domain de novo from previously non-coding sequence is consistent with its lack of sequence similarity to other domains as well as its intrinsically disordered structure, which has important implications for its function. In particular, this lack of structure may provide for a dynamic and inducible regulatory activity based on transient physical interactions with more structured domains of the protein. Since its acquisition along the CFTR evolutionary lineage, the R domain has evolved more rapidly than any other CFTR domain; however, there is no evidence for positive (adaptive) selection in the evolution of the domain. The R domain does show a distinct pattern of relative evolutionary rates compared to other CFTR domains, which sheds additional light on the connection between its function and evolution. The regulatory function of the R domain is dependent upon a fairly small number of sites that are subject to phosphorylation, and these sites were fixed very early in R domain evolution

  5. Origin and evolution of the cystic fibrosis transmembrane regulator protein R domain.

    PubMed

    Sebastian, Aswathy; Rishishwar, Lavanya; Wang, Jianrong; Bernard, Karen F; Conley, Andrew B; McCarty, Nael A; Jordan, I King

    2013-07-10

    The Cystic Fibrosis Transmembrane Conductance Regulator protein (CFTR) is a member of the ABC transporter superfamily. CFTR is distinguished from all other members of this superfamily by its status as an ion channel as well as the presence of its unique regulatory (R) domain. We investigated the origin and subsequent evolution of the R domain along the CFTR evolutionary lineage. The R domain protein coding sequence originated via the loss of a splice donor site at the 3' end of exon 14, leading to the subsequent read-through and capture of formerly intronic sequence as novel coding sequence. Inclusion of the remaining part of the R domain coding sequence in the CFTR transcript involved a lineage-specific gain of exonic sequence with no homology to protein coding sequences outside of CFTR and loss of two exons conserved among ABC family members. These events occurred at the base of the Gnathostome evolutionary lineage ~550-650 million years ago. The apparent origination of the R domain de novo from previously non-coding sequence is consistent with its lack of sequence similarity to other domains as well as its intrinsically disordered structure, which has important implications for its function. In particular, this lack of structure may provide for a dynamic and inducible regulatory activity based on transient physical interactions with more structured domains of the protein. Since its acquisition along the CFTR evolutionary lineage, the R domain has evolved more rapidly than any other CFTR domain; however, there is no evidence for positive (adaptive) selection in the evolution of the domain. The R domain does show a distinct pattern of relative evolutionary rates compared to other CFTR domains, which sheds additional light on the connection between its function and evolution. The regulatory function of the R domain is dependent upon a fairly small number of sites that are subject to phosphorylation, and these sites were fixed very early in R domain evolution and

  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. PMID:25665642

  7. 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. PMID:27236828

  8. 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

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

    USGS Publications Warehouse

    : Beard, L. Sue, (Edited By); 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.

  10. 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.

  11. 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.

  12. 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.

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

    PubMed

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

    2015-09-29

    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

  14. Stability and phase evolution of mullite in reducing atmosphere

    SciTech Connect

    Naghizadeh, R. Golestani-fard, F.; Rezaie, H.R.

    2011-05-15

    The aim of this study is to investigate the stability of mullite and its phase evolution when heated at 1600-1650 deg. C in reducing atmosphere created by a carbon bed. The stoichiometric mullite (3Al{sub 2}O{sub 3}.2SiO{sub 2}) was synthesized by reacting the proper precursors at 1400 deg. C in air atmosphere. Samples containing the primary mullite and graphite or carbon were prepared by pressing the mix and heated at 1600-1650 deg. C. Products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the stoichiometric mullite could decompose to corundum and alumina-rich mullite. During firing under reducing atmosphere, the stoichiometric mullite became richer in Al{sup 3+} cations. The gaseous SiO compound was found to be released from the sample and reacting with C to form SiC phase. Comparison of general mullite solid solution (Al{sub 4+2x}Si{sub 2-2x}O{sub 10-x}) with alumina-rich mullite obtained from decomposition revealed that x would take different values depending on temperature and atmosphere. The ultimate decomposition product was found to be corundum. - Research Highlights: {yields} This method is a new route for investigation of thermochemical stability of stoichimetric mullite under reducing condition which have done by the authors. {yields} This research has got very good results for stability of mullite at different conditions. {yields} This work has also studied the mechanism of stability of mullite under reducing atmosphere.

  15. 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

  16. 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

  17. 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

  18. Geochemical Evolution of Baru Volcano and the Origin of the Adakite Signal

    NASA Astrophysics Data System (ADS)

    Hidalgo, P. J.; Rooney, T. O.

    2012-12-01

    Subduction zones constitute environments where the exchange of mantle and crustal material is possible. This exchange plays a central role in the evolution of the continental crust and the Earth's mantle and may be probed by examining the geochemical properties of arc magmas. At Baru volcano, volcanic products range from "typical" calc-alkaline arc magmas that swiftly transition to adakitic compositions. This compositional transition may have significant implications for the thermal state of subduction zones. Specifically, are adakites the result of slab melting resulting from increased heat within the mantle wedge/subducting slab, or could volatile fluxing of the mantle be responsible for adakite genesis? At Baru volcano, we have used a robust geochronological and geochemical dataset to examine processes that are responsible for generation of magmas from the Miocene to present. For primitive rocks that span Miocene to Quaternary, we have used Arc-Basalt Simulator II to model water contents and degrees of melting. Our data show a distinct drop in modeled water content (3.5%-6% vs. 2%-5%) and degree of melting (20%-23% vs 10%-15%) between the Miocene period of typical arc volcanism and the Quaternary adakitic volcanism. Despite the lower modeled water contents for magmas during the Quaternary adakitic phase, these water values are significantly enriched over those recorded in melts generated by slab melting processes (<0.7 % H2O), and support previous studies suggesting adakites in the Panama arc may be produced by fractional crystallization of amphibole and garnet. The water content of arc magmas is a critical control in the composition of the fractionating assemblage. At moderate pressures (~12 Kb), elevated magmatic water contents promote amphibole stability and fractionation path that yields normal island arc magmas. However, with decreasing magma water contents garnet may become stable at the expense of amphibole, yielding an adakitic magmatic signature. Our

  19. The origin of the Gouy phase anomaly and its generalization to astigmatic wavefields

    NASA Astrophysics Data System (ADS)

    Visser, T. D.; Wolf, E.

    2010-09-01

    One of the most poorly understood subjects in physical optics is the origin of the Gouy phase (sometimes called "the phase anomaly near focus"). This is evident from the large number of publications on the subject, many of which attribute it to quite different causes. In this paper we show that the Gouy phase anomaly can be clearly understood from elementary properties of normal congruences of light rays and from the relationship between geometrical optics and physical optics. We also show that the Gouy phase anomaly may be regarded as a degenerate case of a rapid π/2 phase change that is found to occur at each focal line of an astigmatic pencil of rays. The intensity distribution in the region of the phase changes is also presented. Furthermore, symmetry relations for both the phase anomaly and the intensity distribution are derived.

  20. The evolution of courtship behaviors through the origination of a new gene in Drosophila

    PubMed Central

    Dai, Hongzheng; Chen, Ying; Chen, Sidi; Mao, Qiyan; Kennedy, David; Landback, Patrick; Eyre-Walker, Adam; Du, Wei; Long, Manyuan

    2008-01-01

    New genes can originate by the combination of sequences from unrelated genes or their duplicates to form a chimeric structure. These chimeric genes often evolve rapidly, suggesting that they undergo adaptive evolution and may therefore be involved in novel phenotypes. Their functions, however, are rarely known. Here, we describe the phenotypic effects of a chimeric gene, sphinx, that has recently evolved in Drosophila melanogaster. We show that a knockout of this gene leads to increased male–male courtship in D. melanogaster, although it leaves other aspects of mating behavior unchanged. Comparative studies of courtship behavior in other closely related Drosophila species suggest that this mutant phenotype of male–male courtship is the ancestral condition because these related species show much higher levels of male–male courtship than D. melanogaster. D. melanogaster therefore seems to have evolved in its courtship behaviors by the recruitment of a new chimeric gene. PMID:18508971

  1. 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

    2015-01-01

    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. PMID:27246050

  2. European origin of placodont marine reptiles and the evolution of crushing dentition in Placodontia.

    PubMed

    Neenan, James M; Klein, Nicole; Scheyer, Torsten M

    2013-01-01

    Sauropterygia was the most successful marine reptile radiation in history, spanning almost the entire Mesozoic and exploiting a wide range of habitats and ecological niches. Here we report a new, exceptionally preserved skull of a juvenile stem placodont from the early Middle Triassic of the Netherlands, thus indicating a western Tethyan (European) origin for Placodontia, the most basal group of sauropterygians. A single row of teeth on an enlarged palatine supports this close relationship, although these are small and pointed instead of broad and flat, as is the case in placodonts, which demonstrate the strongest adaptation to a durophagous diet known in any reptile. Peg-like, slightly procumbent premaxillary teeth and an 'L-shaped' jugal also confirm a close relationship to basal placodonts. The new taxon provides insight into the evolution of placodont dentition, representing a transitional morphology between the plesiomorphic diapsid condition of palatal denticles and the specialized crushing teeth of placodonts. PMID:23535642

  3. 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

  4. 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.

  5. Phylogenomics of Sterol Synthesis: Insights into the Origin, Evolution, and Diversity of a Key Eukaryotic Feature

    PubMed Central

    Desmond, Elie

    2009-01-01

    The availability of complete genomes from a wide sampling of eukaryotic diversity has allowed the application of phylogenomics approaches to study the origin and evolution of unique eukaryotic cellular structures, but these are still poorly applied to study unique eukaryotic metabolic pathways. Sterols are a good example because they are an essential feature of eukaryotic membranes. The sterol pathway has been well dissected in vertebrates, fungi, and land plants. However, although different types of sterols have been identified in other eukaryotic lineages, their pathways have not been fully characterized. We have carried out an extensive analysis of the taxonomic distribution and phylogeny of the enzymes of the sterol pathway in a large sampling of eukaryotic lineages. This allowed us to tentatively indicate features of the sterol pathway in organisms where this has not been characterized and to point out a number of steps for which yet-to-discover enzymes may be at work. We also inferred that the last eukaryotic common ancestor already harbored a large panel of enzymes for sterol synthesis and that subsequent evolution over the eukaryotic tree occurred by tinkering, mainly by gene losses. We highlight a high capacity of sterol synthesis in the myxobacterium Plesiocystis pacifica, and we support the hypothesis that the few bacteria that harbor homologs of the sterol pathway have likely acquired these via horizontal gene transfer from eukaryotes. Finally, we propose a potential candidate for the elusive enzyme performing C-3 ketoreduction (ERG27 equivalent) in land plants and probably in other eukaryotic phyla. PMID:20333205

  6. 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.

  7. Colony size evolution and the origin of eusociality in corbiculate bees (Hymenoptera: Apinae).

    PubMed

    Rodriguez-Serrano, Enrique; Inostroza-Michael, Oscar; Avaria-Llautureo, Jorge; Hernandez, Cristian E

    2012-01-01

    Recently, it has been proposed that the one of the main determinants of complex societies in Hymenoptera is colony size, since the existence of large colonies reduces the direct reproductive success of an average individual, given a decreased chance of being part of the reproductive caste. In this study, we evaluate colony size evolution in corbiculate bees and their relationship with the sociality level shown by these bees. Specifically i) the correlation between colony size and level of sociality considering the phylogenetic relationship to evaluate a general evolutionary tendency, and ii) the hypothetical ancestral forms of several clades within a phylogeny of corbiculate bees, to address idiosyncratic process occurring at important nodes. We found that the level of social complexity in corbiculate bees is phylogenetically correlated with colony size. Additionally, another process is invoked to propose why colony size evolved concurrently with the level of social complexity. The study of this trait improves the understanding of the evolutionary transition from simple to complex societies, and highlights the importance of explicit probabilistic models to test the evolution of other important characters involved in the origin of eusociality. PMID:22808274

  8. Origin and evolution of the colonial volvocales (Chlorophyceae) as inferred from multiple, chloroplast gene sequences.

    PubMed

    Nozaki, H; Misawa, K; Kajita, T; Kato, M; Nohara, S; Watanabe, M M

    2000-11-01

    A combined data set of DNA sequences (6021 bp) from five protein-coding genes of the chloroplast genome (rbcL, atpB, psaA, psaB, and psbC genes) were analyzed for 42 strains representing 30 species of the colonial Volvocales (Volvox and its relatives) and 5 related species of green algae to deduce robust phylogenetic relationships within the colonial green flagellates. The 4-celled family Tetrabaenaceae was robustly resolved as the most basal group within the colonial Volvocales. The sequence data also suggested that all five volvocacean genera with 32 or more cells in a vegetative colony (all four of the anisogamous/oogamous genera, Eudorina, Platydorina, Pleodorina, and Volvox, plus the isogamous genus Yamagishiella) constituted a large monophyletic group, in which 2 Pleodorina species were positioned distally to 3 species of Volvox. Therefore, most of the evolution of the colonial Volvocales appears to constitute a gradual progression in colonial complexity and in types of sexual reproduction, as in the traditional volvocine lineage hypothesis, although reverse evolution must be considered for the origin of certain species of Pleodorina. Data presented here also provide robust support for a monophyletic family Goniaceae consisting of two genera: Gonium and Astrephomene. PMID:11083939

  9. Colony Size Evolution and the Origin of Eusociality in Corbiculate Bees (Hymenoptera: Apinae)

    PubMed Central

    Rodriguez-Serrano, Enrique; Inostroza-Michael, Oscar; Avaria-Llautureo, Jorge; Hernandez, Cristian E.

    2012-01-01

    Recently, it has been proposed that the one of the main determinants of complex societies in Hymenoptera is colony size, since the existence of large colonies reduces the direct reproductive success of an average individual, given a decreased chance of being part of the reproductive caste. In this study, we evaluate colony size evolution in corbiculate bees and their relationship with the sociality level shown by these bees. Specifically i) the correlation between colony size and level of sociality considering the phylogenetic relationship to evaluate a general evolutionary tendency, and ii) the hypothetical ancestral forms of several clades within a phylogeny of corbiculate bees, to address idiosyncratic process occurring at important nodes. We found that the level of social complexity in corbiculate bees is phylogenetically correlated with colony size. Additionally, another process is invoked to propose why colony size evolved concurrently with the level of social complexity. The study of this trait improves the understanding of the evolutionary transition from simple to complex societies, and highlights the importance of explicit probabilistic models to test the evolution of other important characters involved in the origin of eusociality. PMID:22808274

  10. Stochastic evolution of refractory interstellar dust during the chemical evolution of a two-phase interstellar medium

    NASA Technical Reports Server (NTRS)

    Liffman, Kurt; Clayton, Donald D.

    1989-01-01

    The evolution course of refractoary interstellar dust during the chemical evolution of a two-phase interstellar medium (ISM) is studied using a simple model of the chemical evolution of ISM. It is assumed that, in this medium, the stars are born in molecular clouds, but new nucleosynthesis products and stellar return are entered into a complementary diffuse medium; the well-mixed matter of each interstellar phase is repeatedly cycled stochastically through the complementary phase and back. The dust is studied on a particle-by-particle bases as it is sputtered by shock waves in the diffuse medium, accretes an amorphous mantle of gaseous refractory atoms while its local medium joins the molecular cloud medium, and encounters the possibility of astration within molecular clouds. Results are presented relevant to the size spectrum of accreted mantles, its age spectrum and the distinction among its several lifetimes, depletion factors of refractory atoms in the diffuse gas, and isotopic anomalies.

  11. Physical origins of double peak phase matching in GaSe

    NASA Astrophysics Data System (ADS)

    Andreev, Yu. M.; Lanskii, G. V.; Svetlichnyi, V. A.

    2015-12-01

    Double peak phase matching was recorded during experimental study of parametric frequency converters based on GaSe, its solid solutions crystals like GaSe1-xSx and ZnGeP2. Its physical origins are identified as presence of twin, large difference between cut and PM angles, self-heating effect at appropriate conditions, mismatched second (Φ) phase matching angle and microdefects.

  12. Origins.

    ERIC Educational Resources Information Center

    Online-Offline, 1999

    1999-01-01

    Provides an annotated list of resources dealing with the theme of origins of life, the universe, and traditions. Includes Web sites, videos, books, audio materials, and magazines with appropriate grade levels and/or subject disciplines indicated; professional resources; and learning activities. (LRW)

  13. Large-scale gas dynamical processes affecting the origin and evolution of gaseous galactic halos

    NASA Technical Reports Server (NTRS)

    Shapiro, Paul R.

    1991-01-01

    Observations of galactic halo gas are consistent with an interpretation in terms of the galactic fountain model in which supernova heated gas in the galactic disk escapes into the halo, radiatively cools and forms clouds which fall back to the disk. The results of a new study of several large-scale gas dynamical effects which are expected to occur in such a model for the origin and evolution of galactic halo gas will be summarized, including the following: (1) nonequilibrium absorption line and emission spectrum diagnostics for radiatively cooling halo gas in our own galaxy, as well the implications of such absorption line diagnostics for the origin of quasar absorption lines in galactic halo clouds of high redshift galaxies; (2) numerical MHD simulations and analytical analysis of large-scale explosions ad superbubbles in the galactic disk and halo; (3) numerical MHD simulations of halo cloud formation by thermal instability, with and without magnetic field; and (4) the effect of the galactic fountain on the galactic dynamo.

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

    PubMed

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

    2009-04-01

    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

  15. Evolution of Asparagus L. (Asparagaceae): Out-of-South-Africa and multiple origins of sexual dimorphism.

    PubMed

    Norup, Maria F; Petersen, Gitte; Burrows, Sandie; Bouchenak-Khelladi, Yanis; Leebens-Mack, Jim; Pires, J Chris; Linder, H Peter; Seberg, Ole

    2015-11-01

    In the most comprehensive study to date we explored the phylogeny and evolution of the genus Asparagus, with emphasis on the southern African species. We included 211 accessions, representing 77 (92%) of the southern African, 6 (17%) of the tropical African, 10 (56%) of the strictly European and 6 (9%) of the Eurasian species. We analyzed DNA sequences from three plastid regions (trnH-psbA, trnD-T, ndhF) and from the nuclear region phytochrome C (PHYC) with parsimony and maximum likelihood methods, and recovered a monophyletic Asparagus. The phylogeny conflicts with all previous infra-generic classifications. It has many strongly supported clades, corroborated by morphological characters, which may provide a basis for a revised taxonomy. Additionally, the phylogeny indicates that many of the current species delimitations are problematic. Using biogeographic analyses that account for phylogenetic uncertainty (S-DIVA) and take into account relative branch lengths (Lagrange) we confirm the origin of Asparagus in southern Africa, and find no evidence that the dispersal of Asparagus follow the Rand flora pattern. We find that all truly dioecious species of Asparagus share a common origin, but that sexual dimorphism has arisen independently several times. PMID:26079131

  16. Early sexual origins of homeoprotein heterodimerization and evolution of the plant KNOX/BELL family.

    PubMed

    Lee, Jae-Hyeok; Lin, Huawen; Joo, Sunjoo; Goodenough, Ursula

    2008-05-30

    Developmental mechanisms that yield multicellular diversity are proving to be well conserved within lineages, generating interest in their origins in unicellular ancestors. We report that molecular regulation of the haploid-diploid transition in Chlamydomonas, a unicellular green soil alga, shares common ancestry with differentiation pathways in land plants. Two homeoproteins, Gsp1 and Gsm1, contributed by gametes of plus and minus mating types respectively, physically interact and translocate from the cytosol to the nucleus upon gametic fusion, initiating zygote development. Their ectopic expression activates zygote development in vegetative cells and, in a diploid background, the resulting zygotes undergo a normal meiosis. Gsm1/Gsp1 dyads share sequence homology with and are functionally related to KNOX/BELL dyads regulating stem-cell (meristem) specification in land plants. We propose that combinatorial homeoprotein-based transcriptional control, a core feature of the fungal/animal radiation, may have originated in a sexual context and enabled the evolution of land-plant body plans. PMID:18510927

  17. Origin and Molecular Evolution of the Determinant of Methicillin Resistance in Staphylococci ▿

    PubMed Central

    Tsubakishita, Sae; Kuwahara-Arai, Kyoko; Sasaki, Takashi; Hiramatsu, Keiichi

    2010-01-01

    Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most important multidrug-resistant pathogens around the world. MRSA is generated when methicillin-susceptible S. aureus (MSSA) exogenously acquires a methicillin resistance gene, mecA, carried by a mobile genetic element, staphylococcal cassette chromosome mec (SCCmec), which is speculated to be transmissible across staphylococcal species. However, the origin/reservoir of the mecA gene has remained unclear. Finding the origin/reservoir of the mecA gene is important for understanding the evolution of MRSA. Moreover, it may contribute to more effective control measures for MRSA. Here we report on one of the animal-related Staphylococcus species, S. fleurettii, as the highly probable origin of the mecA gene. The mecA gene of S. fleurettii was found on the chromosome linked with the essential genes for the growth of staphylococci and was not associated with SCCmec. The mecA locus of the S. fleurettii chromosome has a sequence practically identical to that of the mecA-containing region (∼12 kbp long) of SCCmec. Furthermore, by analyzing the corresponding gene loci (over 20 kbp in size) of S. sciuri and S. vitulinus, which evolved from a common ancestor with that of S. fleurettii, the speciation-related mecA gene homologues were identified, indicating that mecA of S. fleurettii descended from its ancestor and was not recently acquired. It is speculated that SCCmec came into form by adopting the S. fleurettii mecA gene and its surrounding chromosomal region. Our finding suggests that SCCmec was generated in Staphylococcus cells living in animals by acquiring the intrinsic mecA region of S. fleurettii, which is a commensal bacterium of animals. PMID:20679504

  18. 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.

  19. The origin and evolution of the galaxy mass-metallicity relation

    NASA Astrophysics Data System (ADS)

    Ma, Xiangcheng; Hopkins, Philip F.; Faucher-Giguère, Claude-André; Zolman, Nick; Muratov, Alexander L.; Kereš, Dušan; Quataert, Eliot

    2016-02-01

    We use high-resolution cosmological zoom-in simulations from the Feedback in Realistic Environment (FIRE) project to study the galaxy mass-metallicity relations (MZR) from z = 0-6. These simulations include explicit models of the multiphase ISM, star formation, and stellar feedback. The simulations cover halo masses Mhalo = 109-1013 M⊙ and stellar masses M* = 104-1011 M⊙ at z = 0 and have been shown to produce many observed galaxy properties from z = 0-6. For the first time, our simulations agree reasonably well with the observed mass-metallicity relations at z = 0-3 for a broad range of galaxy masses. We predict the evolution of the MZR from z = 0-6, as log (Z_gas/Z_{{⊙}}) = {12 + log (O/H) - 9.0} = 0.35 [log (M_{*}/M_{{⊙}})-10] + 0.93 exp (-0.43z) - 1.05 and log (Z*/Z⊙) = [Fe/H] + 0.2 = 0.40[log (M*/M⊙) - 10] + 0.67exp ( - 0.50z) - 1.04, for gas-phase and stellar metallicity, respectively. Our simulations suggest that the evolution of MZR is associated with the evolution of stellar/gas mass fractions at different redshifts, indicating the existence of a universal metallicity relation between stellar mass, gas mass, and metallicities. In our simulations, galaxies above M* = 106 M⊙ are able to retain a large fraction of their metals inside the halo, because metal-rich winds fail to escape completely and are recycled into the galaxy. This resolves a longstanding discrepancy between `subgrid' wind models (and semi-analytic models) and observations, where common subgrid models cannot simultaneously reproduce the MZR and the stellar mass functions.

  20. Constraining the Origin and Stellar Evolution of Li Using Giants in M92/NGC 2506, and Dwarfs in NGC 7789

    NASA Astrophysics Data System (ADS)

    Twarog, Bruce A.; Deliyannis, Constantine; Anthony-Twarog, Barbara

    2013-08-01

    Three years ago we began a comprehensive program focused on the collection and analysis of high-dispersion spectra in the Li 6708 Å region for 150-330 stars per cluster from the tip of the RGB to below the MS-turnoff in each of the open clusters NGC 2158, NGC 6819, and NGC 7789. We have combined intermediate-band photometry and spectroscopy of samples typically an order-of-magnitude larger than any previous open cluster study, to map the main sequence and post-main sequence evolution of Li with age and metallicity. Our success in these open clusters leads us to push the study limits to a moderately metal-poor cluster (NGC 2506, [Fe/H]=-0.4) and an exceptionally low-metallicity globular cluster (M92, [Fe/H]=-2.7) by probing the evolution of stars on their giant/subgiants branches. We will also push to dwarfs of NGC 7789 to compare with our results for NGC 6819. With ~ 150 stars to below the HB in M92, and ~100 stars to the turnoff in NGC 2506, we will (a) test the degree to which standard theory correctly predicts subgiant dilution, (b) search for Li-rich stars and empirically constrain the non-standard mixing mechanisms known to be at work on the RGB, and differentiate among proposed models, (c) test the impact of intracluster population inhomogeneities on the dispersion in Li, and (d) constrain the Big Bang Li abundance (Phase 2). With NGC 7789, we will constrain varied mechanisms proposed for the origin of the Li dip.

  1. Redshift controversy in atom interferometry: representation dependence of the origin of phase shift.

    PubMed

    Schleich, Wolfgang P; Greenberger, Daniel M; Rasel, Ernst M

    2013-01-01

    Motivated by the recent debate on whether the Kasevich-Chu atom interferometer can measure the gravitational redshift, we show that in different representations of quantum mechanics chosen for the calculation, the observed phase shift appears as though it originates from different physical phenomena. In particular, we demonstrate that the decomposition of the total phase shift into three dynamical phases, which emerges in a semiclassical approach and is at the very heart of the redshift controversy, does not appear in an exact treatment based on a representation-free analysis. Here only two phenomena determine the phase shift: the difference of the laser phases and the acceleration of the atom. Hence, the Kasevich-Chu interferometer is an accelerometer or gravimeter. PMID:23383761

  2. 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.

  3. 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.

  4. 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. PMID:22796480

  5. 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

  6. Origin and pre-Cenozoic evolution of the Qiangtang terrane basement, central Tibet

    NASA Astrophysics Data System (ADS)

    Zhao, Zhongbao; Bons, Paul D.; Wang, Genhou

    2013-04-01

    Central Tibet, with its high-pressure rocks, is a key area to unravel the evolution of the Proto-, Paleo- and Meso-Tethys. However, due to its remoteness and difficult field conditions, relative little is known of the area. Here we present new evidence on the Paleozoic and Mesozoic evolution of the Qiangtang Terrane, located between the Jinsha suture zone in the north and Banggong-Nujiang suture zone in the south. A >500-km-long east-west trending high-pressure metamorphic belt divides the Qiangtang Terrane into the North Qiangtang Terrane and the South Qiangtang terrane. Different hypotheses have been proposed for the origin and pre-Cenozoic evolution of the Qiangtang Terrane. In the Central Qiangtang Terrane, an unconformity with basal conglomerate separates the basement from overlying middle Ordovician strata. Based on structural analysis of basement and cover units, detailed geochronology (including detrital and magmatic zircons) and comparison with surrounding micro-plates (such as Lhasa Terrane, Himalaya Terrane and Southern China Terrane) we conclude that the basement of the Qiangtang Terrane was connected with Gondwana as a passive margin of the Proto-Tethys during the Early Paleozoic. The occurrence of Late Triassic eclogite and glaucophane-bearing schists in the Central Qiangtang Terrane indicates the existence of a suture zone between the North and South Qiangtang Terrane before the Late Triassic (Liu et al., 2011). This suture zone resulted from closure of the Palaeo-Tethys between the two terranes and obduction of the melange onto the basement of South Qiangtang before 210 Ma. ~275 Ma E-W oriented dyke swarms in the north of the South Qiangtang Terrane indicate opening of the Palaeo-Tethys in a back-arc setting between the North and South Qiangtang Terrane, during roll-back retreat of the Proto-Tethys further north. Late Permian to Early Triassic subduction related volcanism and the 236-219 Ma adakitic volcanic series are related to southward

  7. 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.

  8. 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

  9. 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

  10. 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

  11. 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. PMID:25114308

  12. 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.

  13. The origin of GEMS in IDPs as deduced from microstructural evolution of amorphous silicates with annealing

    NASA Astrophysics Data System (ADS)

    Davoisne, C.; Djouadi, Z.; Leroux, H.; D'Hendecourt, L.; Jones, A.; Deboffle, D.

    2006-03-01

    Aims.We present laboratory studies of the micro-structural evolution of an amorphous ferro-magnesian silicate, of olivine composition, following thermal annealing under vacuum.Methods.The amorphous silicate was prepared as a thin film on a diamond substrate. Annealing under vacuum was performed at temperatures ranging from 870 to 1020 K. After annealing the thin films were extracted from the substrate and analysed by transmission electron microscopy to infer their microstructural and compositional evolution.Results.Spheroidal metallic nano-particles (2-50 nm) are found within the silicate films, which are still amorphous after annealing at 870 K and partially crystallized into forsterite for annealing up to 1020 K. We interpret this microstructure in terms of a reduction of the initial amorphous silicate FeO component, because of the carbon-rich partial pressure in the furnace due to pumping mechanism. Annealing in a controlled oxygen-rich atmosphere confirms this interpretation. Conclusions.The observed microstructures closely resemble those of the GEMS (Glass with Embedded Metal and Sulphides) found in chondritic IDPs (Interplanetary Dust Particles). Since IDPs contain abundant carbonaceous matter, a solid-state reduction reaction may have occurred during heating in the hot inner regions of the proto-solar disc. Related to this, the presence of forsterite grains grown from the amorphous precursor material clearly demonstrates that condensation from gaseous species is not required to explain the occurrence of forsterite around young protostars and in comets. Forsterite grains in these environments can be formed directly in the solid phase by thermal annealing of amorphous ferro-magnesian silicates precursor under reducing conditions. Finally, locking iron as metallic particles within the silicates explains why astronomical silicates always appear observationally Mg-rich.

  14. 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).

  15. 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).

  16. 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.

  17. Origin and evolution of retroelements based upon their reverse transcriptase sequences.

    PubMed Central

    Xiong, Y; Eickbush, T H

    1990-01-01

    To study the evolutionary relationship of reverse transcriptase (RT) containing genetic elements, a phylogenetic tree of 82 retroelements from animals, plants, protozoans and bacteria was constructed. The tree was based on seven amino acid domains totalling 178 residues identified in all RTs. We have also identified these seven domains in the RNA-directed RNA polymerases from various plus-strand RNA viruses. The sequence similarity of these RNA polymerases to RT suggests that these two enzymes evolved from a common ancestor, and thus RNA polymerase can be used as an outgroup to root the RT tree. A comparison of the genetic organization of the various RT containing elements and their position on the tree allows several inferences concerning the origin and evolution of these elements. The most probable ancestor of current retroelements was a retrotransposable element with both gag-like and pol-like genes. On one major branch of the tree, organelle and bacterial sequences (e.g. group II introns and bacterial msDNA) appear to have captured the RT sequences from retrotransposons which lack long terminal repeats (LTRs). On the other major branch, acquisition of LTRs gave rise to two distinct groups of LTR retrotransposons and three groups of viruses: retroviruses, hepadnaviruses and caulimoviruses. Images Fig. 4. PMID:1698615

  18. 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.

  19. 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. PMID:25783809

  20. Origin and evolution of the northern hemisphere disjunction in the moss genus Homalothecium (Brachytheciaceae).

    PubMed

    Huttunen, Sanna; Hedenäs, Lars; Ignatov, Michael S; Devos, Nicolas; Vanderpoorten, Alain

    2008-06-01

    Competing hypotheses that rely either on a stepping-stone dispersal via the North Atlantic or the Bering land bridges, or more recent transoceanic dispersal, have been proposed to explain the disjunct distribution of Mediterranean flora in southern Europe and western North America. These hypotheses were tested with molecular dating using a phylogeny of the moss genus Homalothecium based on ITS, atpB-rbcL, and rpl16 sequence data. The monophyly of two main lineages in Western Palearctic (Europe, central Asia and north Africa) and North America is consistent with the ancient vicariance hypothesis. The monophyly of Madeiran H. sericeum accessions supports the recognition of the Macaronesian endemic H. mandonii. A range of absolute rates of molecular evolution documented in land plants was used as probabilistic calibration prior by a Bayesian inference implementing a relaxed-clock model to derive ages for the nodes of interest. Our age estimates for the divergence of the American and Western Palearctic Homalothecium clade (5.7 Ma, IC 3.52-8.26) and the origin of H. mandonii (2.52 Myr IC 0.86-8.25) are not compatible with the ancient vicariance hypothesis. Age estimates suggests that species distributions result from rare instances of dispersal and subsequent sympatric diversification. The calibrated phylogeny indicates that Homalothecium has undergone a fast radiation during the last 4 Myr, which is consistent with the low levels of morphological divergence among sibling species. PMID:21632398

  1. 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

  2. Reconstruction of the genome origins and evolution of the hybrid lager yeast Saccharomyces pastorianus.

    PubMed

    Dunn, Barbara; Sherlock, Gavin

    2008-10-01

    Inter-specific hybridization leading to abrupt speciation is a well-known, common mechanism in angiosperm evolution; only recently, however, have similar hybridization and speciation mechanisms been documented to occur frequently among the closely related group of sensu stricto Saccharomyces yeasts. The economically important lager beer yeast Saccharomyces pastorianus is such a hybrid, formed by the union of Saccharomyces cerevisiae and Saccharomyces bayanus-related yeasts; efforts to understand its complex genome, searching for both biological and brewing-related insights, have been underway since its hybrid nature was first discovered. It had been generally thought that a single hybridization event resulted in a unique S. pastorianus species, but it has been recently postulated that there have been two or more hybridization events. Here, we show that there may have been two independent origins of S. pastorianus strains, and that each independent group--defined by characteristic genome rearrangements, copy number variations, ploidy differences, and DNA sequence polymorphisms--is correlated with specific breweries and/or geographic locations. Finally, by reconstructing common ancestral genomes via array-CGH data analysis and by comparing representative DNA sequences of the S. pastorianus strains with those of many different S. cerevisiae isolates, we have determined that the most likely S. cerevisiae ancestral parent for each of the independent S. pastorianus groups was an ale yeast, with different, but closely related ale strains contributing to each group's parentage. PMID:18787083

  3. Origins and Evolution of WUSCHEL-Related Homeobox Protein Family in Plant Kingdom

    PubMed Central

    Lian, Gaibin; Ding, Zhiwen; Wang, Qin; Zhang, Dabing; Xu, Jie

    2014-01-01

    WUSCHEL-related homeobox (WOX) is a large group of transcription factors specifically found in plants. WOX members contain the conserved homeodomain essential for plant development by regulating cell division and differentiation. However, the evolutionary relationship of WOX members in plant kingdom remains to be elucidated. In this study, we searched 350 WOX members from 50 species in plant kingdom. Linkage analysis of WOX protein sequences demonstrated that amino acid residues 141–145 and 153–160 located in the homeodomain are possibly associated with the function of WOXs during the evolution. These 350 members were grouped into 3 clades: the first clade represents the conservative WOXs from the lower plant algae to higher plants; the second clade has the members from vascular plant species; the third clade has the members only from spermatophyte species. Furthermore, among the members of Arabidopsis thaliana and Oryza sativa, we observed ubiquitous expression of genes in the first clade and the diversified expression pattern of WOX genes in distinct organs in the second clade and the third clade. This work provides insight into the origin and evolutionary process of WOXs, facilitating their functional investigations in the future. PMID:24511289

  4. 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

  5. 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

  6. 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

  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. Evolution Stings: The Origin and Diversification of Scorpion Toxin Peptide Scaffolds

    PubMed Central

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

    2013-01-01

    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

  9. 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.

  10. 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

  11. Developmental Origin and Evolution of Bacteriocytes in the Aphid–Buchnera Symbiosis

    PubMed Central

    2003-01-01

    Symbiotic relationships between bacteria and insect hosts are common. Although the bacterial endosymbionts have been subjected to intense investigation, little is known of the host cells in which they reside, the bacteriocytes. We have studied the development and evolution of aphid bacteriocytes, the host cells that contain the endosymbiotic bacteria Buchnera aphidicola. We show that bacteriocytes of Acyrthosiphon pisum express several gene products (or their paralogues): Distal-less, Ultrabithorax/Abdominal-A, and Engrailed. Using these markers, we find that a subpopulation of the bacteriocytes is specified prior to the transmission of maternal bacteria to the embryo. In addition, we discovered that a second population of cells is recruited to the bacteriocyte fate later in development. We experimentally demonstrate that bacteriocyte induction and proliferation occur independently of B. aphidicola. Major features of bacteriocyte development, including the two-step recruitment of bacteriocytes, have been conserved in aphids for 80–150 million years. Furthermore, we have investigated two cases of evolutionary loss of bacterial symbionts: in one case, where novel extracellular, eukaryotic symbionts replaced the bacteria, the bacteriocyte is maintained; in another case, where symbionts are absent, the bacteriocytes are initiated but not maintained. The bacteriocyte represents an evolutionarily novel cell fate, which is developmentally determined independently of the bacteria. Three of five transcription factors we examined show novel expression patterns in bacteriocytes, suggesting that bacteriocytes may have evolved to express many additional transcription factors. The evolutionary transition to a symbiosis in which bacteria and an aphid cell form a functional unit, similar to the origin of plastids, has apparently involved extensive molecular adaptations on the part of the host cell. PMID:14551917

  12. Ancient Protostome Origin of Chemosensory Ionotropic Glutamate Receptors and the Evolution of Insect Taste and Olfaction

    PubMed Central

    Cummins, Scott F.; Budd, Aidan; Brawand, David; Kaessmann, Henrik; Gibson, Toby J.; Benton, Richard

    2010-01-01

    Ionotropic glutamate receptors (iGluRs) are a highly conserved family of ligand-gated ion channels present in animals, plants, and bacteria, which are best characterized for their roles in synaptic communication in vertebrate nervous systems. A variant subfamily of iGluRs, the Ionotropic Receptors (IRs), was recently identified as a new class of olfactory receptors in the fruit fly, Drosophila melanogaster, hinting at a broader function of this ion channel family in detection of environmental, as well as intercellular, chemical signals. Here, we investigate the origin and evolution of IRs by comprehensive evolutionary genomics and in situ expression analysis. In marked contrast to the insect-specific Odorant Receptor family, we show that IRs are expressed in olfactory organs across Protostomia—a major branch of the animal kingdom that encompasses arthropods, nematodes, and molluscs—indicating that they represent an ancestral protostome chemosensory receptor family. Two subfamilies of IRs are distinguished: conserved “antennal IRs,” which likely define the first olfactory receptor family of insects, and species-specific “divergent IRs,” which are expressed in peripheral and internal gustatory neurons, implicating this family in taste and food assessment. Comparative analysis of drosophilid IRs reveals the selective forces that have shaped the repertoires in flies with distinct chemosensory preferences. Examination of IR gene structure and genomic distribution suggests both non-allelic homologous recombination and retroposition contributed to the expansion of this multigene family. Together, these findings lay a foundation for functional analysis of these receptors in both neurobiological and evolutionary studies. Furthermore, this work identifies novel targets for manipulating chemosensory-driven behaviours of agricultural pests and disease vectors. PMID:20808886

  13. 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.

  14. 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.

  15. 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.

  16. Origin of shear-induced phase transitions in melts of liquid-crystal polymers

    NASA Astrophysics Data System (ADS)

    Noirez, Laurence

    2005-11-01

    Flow induced mechanical properties are often coupled with instabilities, spurt effects, or induced phase transitions. Recent studies have revealed that side-chain liquid crystal polymers exhibit typically shear-induced phases inside the isotropic (nonmesomorphic) liquid state. We present an experimental approach which brings a new understanding for nonlinear flow behaviors. The strategy consists in comparing the critical times issued from the flow behavior of a liquid-crystal polymer to the equilibrium orientational-order relaxation time was characterized. We demonstrate that shear-induced phases do not originate from a flow coupling to conventional orientational order parameter fluctuations. It does not also correspond to a direct coupling with the viscoelastic terminal time, leading to the conclusion that an additional relaxation process takes place with time scales longer than the terminal time. The identification of a low-frequency elastic plateau by viscoelastic measurements corroborates this conclusion.

  17. The early phases of galaxy formation and evolution

    NASA Astrophysics Data System (ADS)

    Dickinson, Mark

    2016-05-01

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

  18. 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

  19. 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.

  20. Evidence for Tidal Interactions and Mergers as the Origin of Galaxy Morphology Evolution in Compact Groups

    NASA Astrophysics Data System (ADS)

    Coziol, R.; Plauchu-Frayn, I.

    2007-06-01

    We present the results of a morphological study based on NIR images of 25 galaxies, with different levels of nuclear activity (star formation or AGN), in eight compact groups (CGs) of galaxies. We independently perform two different analyses: a study of the deviations of the isophotal levels from pure ellipses and a study of morphological asymmetries. The results yielded by the two analyses are highly consistent. For the first time, it is possible to show that deviations from pure ellipses are produced by inhomogeneous stellar mass distributions related to galaxy interactions and mergers. We find evidence of mass asymmetries in 74% of the galaxies in our sample. In 59% of these cases, the asymmetries come in pairs and are consistent with tidal effects produced by the proximity of companion galaxies. The symmetric galaxies are generally small in size or mass and inactive, and have an early-type morphology. They may have already lost their gas and least-attached envelope of stars to their more massive companions. In 20% of the galaxies we find evidence for cannibalism: a big galaxy swallowing a smaller companion. In 36% of the early-type galaxies the color gradient is positive (blue nucleus) or flat. Summing up these results, as much as 52% of the galaxies in our sample could show evidence of an ongoing or past merger. Our observations also suggest that galaxies in CGs merge more frequently under ``dry'' conditions (that is, once they have lost most of their gas). The high frequency of interacting and merging galaxies observed in our study is consistent with the bias of our sample toward CGs of type B, which represent the most active phase in the evolution of the groups. In these groups we also find a strong correlation between asymmetries and nuclear activity in early-type galaxies. This correlation allows us to identify tidal interactions and mergers as the cause of galaxy morphology transformation in CGs.

  1. 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

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    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.

  4. Microstructural evolution and ductile phase toughening in brazed joints

    NASA Astrophysics Data System (ADS)

    Philips, Noah Robinson

    In typical brazed joints, melting point depressants degrade the structural robustness by concentrating as brittle phases into continuous seams along the centerline. The objective of this dissertation is to sufficiently understand the mechanisms governing the microstructure of a typical braze that approaches for modifying the fabrication to eliminate brittleness can be identified and demonstrated. A characterization of a quaternary braze (Nicrobraze 31) used for stainless steel bonds, containing P and Si melting point depressants, reveals that the thermochemical interactions governing the microstructure include dissolution/reprecipitation, solid-state diffusion, and solidification. It is shown that the Si can be incorporated into a solid solution gamma-Ni(Fe, Si) phase that forms by reprecipitation. A fracture toughness test for intermediate toughness materials is developed to quantify the performance of brazed joints. The test configuration is a wedge driven DCB (Double Cantilever Beam), with design guided by analytical solutions for the energy release rate and compliance. The fracture resistance of a typical braze joint is found to be significantly greater than that for the intermetallic constituents. Approximately half of the toughening is attributed to plastic stretch of the ductile phase within the eutectic. The remainder is attributed to dissipation within a plastic zone that forms in the primary gamma-Ni(Fe, Si) regions. Heat treatments are presented that use ductile phase toughening to mitigate the effect of brittle intermetallics in a Ni-based braze alloy. The development of this beneficial microstructure is based on an understanding of the transient dissolution and isothermal solidification phenomena. By rapid cooling after a short brazing time, gamma-Ni(Fe, Si) is redistributed to the midline where it disrupts the intermetallics and forms a network of ductile ligaments upon fracture. Reinforcement by the modified ductile phase nearly doubles the toughness

  5. 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.

  6. 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…

  7. Morphological Evolution of Electrochemically Plated/Stripped Lithium Microstructures Investigated by Synchrotron X-ray Phase Contrast Tomography.

    PubMed

    Sun, Fu; Zielke, Lukas; Markötter, Henning; Hilger, André; Zhou, Dong; Moroni, Riko; Zengerle, Roland; Thiele, Simon; Banhart, John; Manke, Ingo

    2016-08-23

    Due to its low redox potential and high theoretical specific capacity, Li metal has drawn worldwide research attention because of its potential use in next-generation battery technologies such as Li-S and Li-O2. Unfortunately, uncontrollable growth of Li microstructures (LmSs, e.g., dendrites, fibers) during electrochemical Li stripping/plating has prevented their practical commercialization. Despite various strategies proposed to mitigate LmS nucleation and/or block its growth, a fundamental understanding of the underlying evolution mechanisms remains elusive. Herein, synchrotron in-line phase contrast X-ray tomography was employed to investigate the morphological evolution of electrochemically deposited/dissolved LmSs nondestructively. We present a 3D characterization of electrochemically stripped Li electrodes with regard to electrochemically plated LmSs. We clarify fundamentally the origin of the porous lithium interface growing into Li electrodes. Moreover, cleavage of the separator caused by growing LmS was experimentally observed and visualized in 3D. Our systematic investigation provides fundamental insights into LmS evolution and enables us to understand the evolution mechanisms in Li electrodes more profoundly. PMID:27463258

  8. Dynamical Evolution of Quintessence Cosmology in a Physical Phase Space

    NASA Astrophysics Data System (ADS)

    Qi, Jing-Zhao; Zhang, Ming-Jian; Liu, Wen-Biao

    2016-04-01

    The phase space analysis of cosmological parameters Ω ϕ and γ ϕ is given. Based on this, the well-known quintessence cosmology is studied with an exponential potential V(φ )=V0exp (-λ φ ). Given observational data, the current state of universe could be pinpointed in the phase diagrams, thus making the diagrams more informative. The scaling solution of quintessence usually is not supposed to give the cosmic accelerating expansion, but we prove it could educe the transient acceleration. We also find that the differential equations of system used widely in study of scalar field are incomplete, and then a numerical method is used to figure out the range of application.

  9. 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.

  10. Dynamical Evolution of Quintessence Cosmology in a Physical Phase Space

    NASA Astrophysics Data System (ADS)

    Qi, Jing-Zhao; Zhang, Ming-Jian; Liu, Wen-Biao

    2016-08-01

    The phase space analysis of cosmological parameters Ω ϕ and γ ϕ is given. Based on this, the well-known quintessence cosmology is studied with an exponential potential V(φ )=V0exp (-λ φ ). Given observational data, the current state of universe could be pinpointed in the phase diagrams, thus making the diagrams more informative. The scaling solution of quintessence usually is not supposed to give the cosmic accelerating expansion, but we prove it could educe the transient acceleration. We also find that the differential equations of system used widely in study of scalar field are incomplete, and then a numerical method is used to figure out the range of application.

  11. Dynamic interplay between uranyl phosphate precipitation, sorption, and phase evolution

    DOE PAGESBeta

    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 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

  12. 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.

  13. 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

  14. 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

  15. Classification theorem for principal fibre bundles, Berry's phase, and exact cycle evolution

    SciTech Connect

    Bohm, A.; Boya, L.J.; Mostafazadeh, A. . Center for Particle Physics); Rudolph, G. . Fachbereich Physik)

    1993-03-01

    The relation between the two mathematical interpretations of the geometric (Berry) phase is discussed, using either the fibre bundle over parameter space or over projective Hilbert space. It turns out that these two geometric constructions are linked by the classification theorem for vector bundles. The classification theorem provides the means to classify the parameter space bundles for adiabatic evolution and for non-adiabatic cyclic evolution of the statevectors.

  16. Classification theorem for principal fibre bundles, Berry`s phase, and exact cycle evolution

    SciTech Connect

    Bohm, A.; Boya, L.J.; Mostafazadeh, A.; Rudolph, G.

    1993-03-01

    The relation between the two mathematical interpretations of the geometric (Berry) phase is discussed, using either the fibre bundle over parameter space or over projective Hilbert space. It turns out that these two geometric constructions are linked by the classification theorem for vector bundles. The classification theorem provides the means to classify the parameter space bundles for adiabatic evolution and for non-adiabatic cyclic evolution of the statevectors.

  17. Characterization of the origin and distribution of the minerals and phases in metallurgical cokes

    SciTech Connect

    Sushil Gupta; Maria Dubikova; David French; Veena Sahajwalla

    2007-01-15

    Three industrial metallurgical cokes were examined using X-ray diffraction (XRD) and scanning electron microscopy combined with energy dispersive X-ray analysis (SEM/EDS). The study highlighted the difficulties and implications of identifying the inherent crystalline mineral phases in cokes using XRD such that increasing the ashing temperature led to the formation of anhydrite and destruction of metallic iron: microwave plasma ashing resulted in minimal alteration of the original coke mineralogy apart from the formation of bassanite and possibly jarosite. A preliminary scheme to characterize coke minerals is presented such that, physically, minerals can be classified as fine ({lt}50 {mu}m), coarse (50-100 {mu}m), and agglomerate ({gt}1000 {mu}m); chemically, minerals can be grouped as refractory, semirefractory, and reactive, while on the basis of distribution they can be described as discrete, disseminated, or pore inclusions. Quartz, cristobalite, mullite, and high melting point Al-silicates were found to be the predominant refractory phases while low melting point Al-silicates, e.g., containing high fluxing elements such as K, and Fe were the main semirefractory phases present in all cokes. A variety of iron containing phases including pyrrhotite, troilite, iron oxides, metallic iron, and iron silicates were also invariably present in all cokes while calcium phases were found to occur as sulfide, silicates, and phosphates. In general, iron and calcium phases can be categorized as reactive phases with few exceptions such as oldhamite (CaS). The study highlighted that most of the cokes possess a similar mineralogy, with the main distinction being in their relative abundance, particle size, and nature of distribution in the coke matrix. The study provides a basis to develop a mechanistic understanding of the influence of minerals on coke reactivity and strength at high temperatures. 41 refs., 13 figs., 4 tabs.

  18. Origin and evolution of mountainous regions north of Tibet, Central Asia

    NASA Astrophysics Data System (ADS)

    Cunningham, D.; Zhang, J.

    2013-12-01

    The huge deformation field associated with the Indo-Eurasia collision provides an unrivalled opportunity to investigate the origin and evolution of anomalously high topography in an intraplate, continental interior setting. Mountainous regions north of Tibet and south of the Hangay Dome are hyper-arid with internally drained basins and very low erosion rates. Consequently, the tectonic signal is very strongly expressed in the landscape. Directly north of Tibet, the Beishan is an anomalous plateau region whose first-order topography cannot be explained by Tertiary-Quaternary faulting, although second-order topographic culminations within the plateau are due to Quaternary-Recent transpressional fault displacements. The Beishan appears to be a peripheral bulge due to significant underthrusting of the Tarim-Dunhuang Block beneath the northern margin of Tibet. North of the Beishan region, the Eastern Tien Shan and Gobi Altai are essentially a transpressional basin and range province whose origin is due to thrust and oblique-slip thrust reactivation of older basement structures and diffuse sinistral strike-slip faulting. The angular relationship between SHmax and older structural trends is the first-order control on the kinematics of Quaternary faulting in the region and the style of mountain building. Restraining bends, thrust blocks and diverse transpressional fault arrays generate a complex 3D orogenic architecture that differs significantly from a contractional fold and thrust belt. Late Cenozoic uplift of the Gobi Altai, eastern Tien Shan and Altai orogens is due to diffuse transpressional reactivation of a mechanically weak Paleozoic terrane collage sandwiched between more rigid Precambrian basement blocks, representing the ';soft' core of Central Asia. Southeast of Mongolia and northeast of Tibet, the Lang Shan, Yabrai Shan and Helan Shan mountainous regions comprise footwall block uplifts associated with Ordos Basin extension and the left-lateral strike

  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. 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.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  3. 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.

  4. Phase-field model simulation of ferroelectric/antiferroelectric materials microstructure evolution under multiphysics loading

    NASA Astrophysics Data System (ADS)

    Zhang, Jingyi

    Ferroelectric (FE) and closely related antiferroelectric (AFE) materials have unique electromechanical properties that promote various applications in the area of capacitors, sensors, generators (FE) and high density energy storage (AFE). These smart materials with extensive applications have drawn wide interest in the industrial and scientific world because of their reliability and tunable property. However, reliability issues changes its paradigms and requires guidance from detailed mechanism theory as the materials applications are pushed for better performance. A host of modeling work were dedicated to study the macro-structural behavior and microstructural evolution in FE and AFE material under various conditions. This thesis is focused on direct observation of domain evolution under multiphysics loading for both FE and AFE material. Landau-Devonshire time-dependent phase field models were built for both materials, and were simulated in finite element software Comsol. In FE model, dagger-shape 90 degree switched domain was observed at preexisting crack tip under pure mechanical loading. Polycrystal structure was tested under same condition, and blocking effect of the growth of dagger-shape switched domain from grain orientation difference and/or grain boundary was directly observed. AFE ceramic model was developed using two sublattice theory, this model was used to investigate the mechanism of energy efficiency increase with self-confined loading in experimental tests. Consistent results was found in simulation and careful investigation of calculation results gave confirmation that origin of energy density increase is from three aspects: self-confinement induced inner compression field as the cause of increase of critical field, fringe leak as the source of elevated saturation polarization and uneven defects distribution as the reason for critical field shifting and phase transition speed. Another important affecting aspect in polycrystalline materials is the

  5. The origin and evolution of dense regions in the ISM, and their role in spectral features

    NASA Astrophysics Data System (ADS)

    Falceta-Gonçalves, Diego

    2013-03-01

    In this work we discuss the turbulent evolution of molecular clouds and the formation of dense structures within. Typically, the clumps evolution occurs apart from the secular evolution of the turbulent mother cloud due to its high density and large inertia. Despite of current theoretical assumptions we show, by means of numerical simulations, that the clump lifetimes are greater than previously thought by more than an order of magnitude. The presence of dense and long-lived clumps modifies the spectral line profiles of clouds, which are strongly related to the determination of Larson's relations. We address the main modifications of these if a realistic distribution of dense structures is taken into account.

  6. The Roles of Tidal Evolution and Evaporative Mass Loss in the Origin of CoRoT-7 b

    NASA Technical Reports Server (NTRS)

    Jackson, Brian; Miller, Neil; Barnes, Rory; Raymond, Sean N.; Fortney, Jonathan J.; Greenberg, Richard

    2010-01-01

    CoRoT-7 b is the first confirmed rocky exoplanet, but, with an orbital semimajor axis of 0.0172 au, its origins may be unlike any rocky planet in our Solar System. In this study, we consider the roles of tidal evolution and evaporative mass loss in CoRoT-7 b's history, which together have modified the planet's mass and orbit. If CoRoT-7 b has always been a rocky body, evaporation may have driven off almost half its original mass, but the mass loss may depend sensitively on the extent of tidal decay of its orbit. As tides caused CoRoT-7 b's orbit to decay, they brought the planet closer to its host star, thereby enhancing the mass loss rate. Such a large mass loss also suggests the possibility that CoRoT-7 b began as a gas giant planet and had its original atmosphere completely evaporated. In this case, we find that CoRoT-7 b's original mass probably did not exceed 200 Earth masses (about two-third of a Jupiter mass). Tides raised on the host star by the planet may have significantly reduced the orbital semimajor axis, perhaps causing the planet to migrate through mean-motion resonances with the other planet in the system, CoRoT-7 c. The coupling between tidal evolution and mass loss may be important not only for CoRoT-7 b but also for other close-in exoplanets, and future studies of mass loss and orbital evolution may provide insight into the origin and fate of close-in planets, both rocky and gaseous.

  7. The scientific origin of life. Considerations on the evolution of information, leading to an alternative proposal for explaining the origin of the cell, a semantically closed system.

    PubMed

    Vaneechoutte, M

    2000-01-01

    We hypothesize that the origin of life, that is, the origin of the first cell, cannot be explained by natural selection among self-replicating molecules, as is done by the RNA-world hypothesis. To circumvent the chicken and egg problem associated with semantic closure of the cell--no replication of information molecules (nucleotide strands) without functional enzymes, no functional enzymes without encoding in information molecules--a prebiotic evolutionary process is proposed that, from the informational point of view, must somehow have resembled the current scientific process. The cell was the outcome of interactions of a complex premetabolic community, with information molecules that were devoid of self-replicative properties. In a comparable manner, scientific progress is possible, essentially because of interaction between a complex cultural society and permanent information carriers like printed matter. This may eventually lead to self-replicating technology in which semantic closure occurs anew. Explaining the origin of life as a scientific process might provide a unifying theory for the evolution of information, wherebye at two moments symbolization/encoding of interactions into permanent information occurred: at one moment that of chemical interaction and at another moment that of animal behavior interaction. In one event this encoding led to autonomously duplicating chemistry (the cell), an event that possibly may be one of the outcomes of current scientific progress. PMID:10818565

  8. Effect of ageing on phase evolution and precipitation behaviour of duplex steel

    NASA Astrophysics Data System (ADS)

    Podany, P.; Kover, M.; Dlouhy, J.

    2015-12-01

    The isothermal formation of secondary phases in duplex stainless steel was studied. Samples were isothermally heat treated (aged) at temperatures of 700, 800 and 850°C in a quenching dilatometer. Microstructured evolution of secondary phases was analysed by means of optical and scanning electron microscopes. Both common phases, Chi and Sigma, were observed. The resulting shrinkage curves from dilatometric measurements show the potential for research into the formation of minor phases and the estimation of transformation kinetics in this kind of steel.

  9. 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

  10. Microcanonical thermostatistics as foundation of thermodynamics: The microscopic origin of condensation and phase separations

    NASA Astrophysics Data System (ADS)

    Gross, D. H. E.

    2005-10-01

    Conventional thermo-statistics address infinite homogeneous systems within the canonical ensemble. However, some 150 years ago the original motivation of thermodynamics was the description of steam engines, i.e., boiling water. Its essential physics is the separation of the gas phase from the liquid. Of course, boiling water is inhomogeneous and as such cannot be treated by canonical thermo-statistics. Then it is not astonishing that a phase transition of first order is signaled canonically by a Yang Lee singularity. Thus it is only treated correctly by microcanonical Boltzmann Planck statistics. This is elaborated in the present article. It turns out that the Boltzmann Planck statistics is much richer and gives fundamental insight into statistical mechanics and especially into entropy. This can even be done to some extend rigorously and analytically. The microcanonical entropy has a very simple physical meaning: It measures the microscopic uncertainty that we have about the system, i.e., the number of points in 6N-dim phase, which are consistent with our information about the system. It can rigorously be split into an ideal-gas part and a configuration part which contains all the physics and especially is responsible for all phase transitions. The deep and essential difference between “extensive” and “intensive” control parameters, i.e., microcanonical and canonical statistics, is exemplified by rotating, self-gravitating systems.

  11. 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

  12. 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.

  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. The Puzzle of Italian Rice Origin and Evolution: Determining Genetic Divergence and Affinity of Rice Germplasm from Italy and Asia

    PubMed Central

    Jiang, Zhuxi; Basso, Barbara; Sala, Francesco; Spada, Alberto; Grassi, Fabrizio; Lu, Bao-Rong

    2013-01-01

    The characterization of genetic divergence and relationships of a set of germplasm is essential for its efficient applications in crop breeding and understanding of the origin/evolution of crop varieties from a given geographical region. As the largest rice producing country in Europe, Italy holds rice germplasm with abundant genetic diversity. Although Italian rice varieties and the traditional ones in particular have played important roles in rice production and breeding, knowledge concerning the origin and evolution of Italian traditional varieties is still limited. To solve the puzzle of Italian rice origin, we characterized genetic divergence and relationships of 348 rice varieties from Italy and Asia based on the polymorphisms of microsatellite fingerprints. We also included common wild rice O. rufipogon as a reference in the characterization. Results indicated relatively rich genetic diversity (He = 0.63-0.65) in Italian rice varieties. Further analyses revealed a close genetic relationship of the Italian traditional varieties with those from northern China, which provides strong genetic evidence for tracing the possible origin of early established rice varieties in Italy. These findings have significant implications for the rice breeding programs, in which appropriate germplasm can be selected from a given region and utilized for transferring unique genetic traits based on its genetic diversity and evolutionary relationships. PMID:24265814

  15. The Evolution and Origin of Animal Toll-Like Receptor Signaling Pathway Revealed by Network-Level Molecular Evolutionary Analyses

    PubMed Central

    Qin, Sheng; Chen, Liming; Ma, Fei

    2012-01-01

    Genes carry out their biological functions through pathways in complex networks consisting of many interacting molecules. Studies on the effect of network architecture on the evolution of individual proteins will provide valuable information for understanding the origin and evolution as well as functional conservation of signaling pathways. However, the relationship between the network architecture and the individual protein sequence evolution is yet little known. In current study, we carried out network-level molecular evolution analysis on TLR (Toll-like receptor ) signaling pathway, which plays an important role in innate immunity in insects and mammals, and we found that: 1) The selection constraint of genes was negatively correlated with its position along TLR signaling pathway; 2) all genes in TLR signaling pathway were highly conserved and underwent strong purifying selection; 3) the distribution of selective pressure along the pathway was driven by differential nonsynonymous substitution levels; 4) The TLR signaling pathway might present in a common ancestor of sponges and eumetazoa, and evolve via the TLR, IKK, IκB and NF-κB genes underwent duplication events as well as adaptor molecular enlargement, and gene structure and conservation motif of NF-κB genes shifted in their evolutionary history. Our results will improve our understanding on the evolutionary history of animal TLR signaling pathway as well as the relationship between the network architecture and the sequences evolution of individual protein. PMID:23236523

  16. Phase-field study of spacing evolution during transient growth

    NASA Astrophysics Data System (ADS)

    Gurevich, Sebastian; Amoorezaei, Morteza; Provatas, Nikolas

    2010-11-01

    The primary spacing of a dendritic array grown under transient growth conditions displays a distribution of wavelengths. The average primary spacing is shown, both experimentally and numerically, to evolve between characteristic incubation periods during which the distribution of wavelengths remains essentially stable. Our primary spacing results display a gradual transition period from one spacing range to another, consistent with the fact that the abrupt doubling of spacing predicted by Warren and Langer for an idealized periodic array affects different wavelengths of the distribution at different times. This transition is shown to depend on the rate of change in growth speed using phase-field simulations of directional solidification where the pulling speed is ramped at different rates. In particular, for high rates of change of the pulling speed we observe temporary marginally stable array configurations separated by relatively short lived transitions, while for lower rates of change of the pulling speed the distinction between incubation and transition periods disappears.

  17. 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

  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. The evolution of high-metallicity horizontal-branch stars and the origin of the ultraviolet light in elliptical galaxies

    NASA Technical Reports Server (NTRS)

    Horch, E.; Demarque, P.; Pinsonneault, M.

    1992-01-01

    Evolutionary calculations of high-metallicity horizontal-branch stars show that for the relevant masses and helium abundances, post-HB evolution in the HR diagram does not proceed toward and along the AGB, but rather toward a 'slow blue phase' in the vicinity of the helium-burning main sequence, following the extinction of the hydrogen shell energy source. For solar and twice solar metallicity, the blue phase begins during the helium shell-burning phase (in agreement with the work of Brocato and Castellani and Tornambe); for 3 times solar metallicity, it begins earlier, during the helium core-burning phase. This behavior differs from what takes place at lower metallicities. The implications for high-metallicity old stellar populations in the Galactic bulge and for the integrated colors of elliptical galaxies are discussed.

  1. The statistical model of origin and evolution planets of Solar system and planetary satellities

    NASA Astrophysics Data System (ADS)

    Krot, A.

    new low for Solar system planetary distances is derived (it generalizes the well-known Schmidt low). The new low gives a very good estimation of real planetary distances in Solar system (the relative error of estimation is 0%; absolute error of estimation is 0,5% besides its maximal value is equal to 5% for Earth and Pluto). This low has been applied also to estimation of Jupiter's satellities distances in this work. References: [1] M.M.Nieto, The Tutius-Bode low of planetary distances: its his-tory and theory. Pergamon: Oxford, New York et., 1972. [2] V.S. Safronov, Evolution of Protoplanetary cloud and the formation of the Earth and planets. 1969, Moscow, Nauka, (in Russian); NASA Tech. Transl. F-677, Washington, D.C. 1972. [3] A.V. Vityazev, G.V. Pechrnikova and V.S.Safronov, The Terrestrial planets: origin and early evolution. 1990. Moscow, Nauka (in Russian) [4] A.M.Krot, Achievement in Modern Radioelectronics (Special issue "Cosmic Radiophysics", Moscow), no.8, pp.66-81, 1996 (in Russian). [5] A.M.Krot, Proc. SPIE's 13th Annual Intern.Symp. "AeroSense", vol.3710, pp.1248-1259, Orlando, Florida, USA, April 5-9, 1999. [6] A.M.Krot, Proc. SPIE's 14th Annual Intern.Symp. "AeroSense", vol.4038, pp.1318-1329, Orlando, Florida, USA, April 24-28, 2000. [7] A.M.Krot, Proc. SPIE's 15th Annual Intern. Symposium "AeroSense", vol.4394, pp.1271-1282, Orlando, Florida, USA, April 16-20, 2001. [8] A.M.Krot, Proc. 53rd Intern. Astronautical Congress: The World Space Congress-2002, Houston, Texas, USA, October 10-19, 2002, Preprint IAC-02-J.P.01. - 11 p. [9] A.M.Krot, Proc. 34th Scientific Assembly of the Committee on Space Research (COSPAR)- The 2nd World Space Congress (WSC- 2002), October 10-19, 2002,Houston, Texas, USA. [10] A.M.Krot, Proc. of EGS- AGU-EUG Joint Assembly, Nice, France, April 6-11, 2003, Geophysical Research Abstracts, vol.5, EAE03-À-05568, 2003. [11] A.M. Krot, Proc. of 54 Intern. Astronautical Congress (IAC), September 29-October 3, 2003, Bremen, Germany

  2. Origin and annealing of deep-level defects in GaNAs grown by metalorganic vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Gelczuk, Ł.; Stokowski, H.; Dąbrowska-Szata, M.; Kudrawiec, R.

    2016-05-01

    Deep-level defects were investigated by deep level transient spectroscopy on the as-grown and annealed GaNAs layers of various nitrogen (N) contents. The unintentionally doped (uid) GaNAs layers were grown by metalorganic vapor phase epitaxy with N = 1.4%, 2.0%, 2.2%, and 2.4% on GaAs substrate. The possible origin and evolution of the deep-level defects upon annealing were analyzed with the use of the GaNAs band gap diagram concept [Kudrawiec et al., Appl. Phys. Lett. 101, 082109 (2012)], which assumes that the activation energy of donor traps decreases with N-related downward shift of the conduction band. On the basis of this diagram and in comparison with previous results, the N-related traps were associated with (N-As)As or (N-N)As split interstitials. It was also proposed that one of the electron traps and the hole trap, lying at the same level position in the bandgap of the annealed uid-GaNAs layers, can both act as one generation-recombination center partially responsible for poor optical properties of this alloy.

  3. 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

    2016-03-01

    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.

  4. 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.

  5. 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. PMID:24487053

  6. 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

  7. 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.

  8. The search for life's origins: Progress and future directions in planetary biology and chemical evolution

    NASA Astrophysics Data System (ADS)

    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.

  9. 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...

  10. 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.…

  11. Evolutionary dynamics of cytoplasmic segregation and fusion: Mitochondrial mixing facilitated the evolution of sex at the origin of eukaryotes.

    PubMed

    Radzvilavicius, Arunas L

    2016-09-01

    Sexual reproduction is a trait shared by all complex life, but the complete account of its origin is missing. Virtually all theoretical work on the evolution of sex has been centered around the benefits of reciprocal recombination among nuclear genes, paying little attention to the evolutionary dynamics of multi-copy mitochondrial genomes. Here I develop a mathematical model to study the evolution of nuclear alleles inducing cell fusion in an ancestral population of clonal proto-eukaryotes. Segregational drift maintains high mitochondrial variance between clonally reproducing hosts, but the effect of segregation is opposed by cytoplasmic mixing which tends to reduce variation between cells in favor of higher heterogeneity within the cell. Despite the reduced long-term population fitness, alleles responsible for sexual cell fusion can spread to fixation. The evolution of sex requires negative epistatic interactions between mitochondrial mutations under strong purifying selection, low mutation load and weak mitochondrial-nuclear associations. I argue that similar conditions could have been maintained during the late stages of eukaryogenesis, facilitating the evolution of sexual cell fusion and meiotic recombination without compromising the stability of the emerging complex cell. PMID:27266671

  12. The stochastic evolution of asteroidal regoliths and the origin of brecciated and gas-rich meteorites. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Housen, K. R.

    1981-01-01

    A model is constructed which views regolith evolution on asteroids as a stochastic process. Average values are shown to be poor descriptors of regolith depth. The utility of the average depth is not significantly increased by avoiding large craters or thick ejecta deposits, a procedure adopted in previous regolith studies. The statistical uncertainty associated with regolith depth severely limits the power of regolith models in predicting parent-body size for brecciated meteorites. A Monte Carlo algorithm was used to simulate the random walks and corresponding charged-particle irradiation histories of grains in regoliths. On rocky asteroids, only about 20 percent of the grains was exposed to solar cosmic ray ions. Results based on present-day conditions in the asteroid belt agree well with irradiation features observed in gas-rich meteorites. An origin during epochs of early solar system evolution is not required.

  13. 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.

  14. Application of Phase-field Method in Predicting Gas Bubble Microstructure Evolution in Nuclear Fuels

    SciTech Connect

    Hu, Shenyang Y.; Li, Yulan; Sun, Xin; Gao, Fei; Devanathan, Ramaswami; Henager, Charles H.; Khaleel, Mohammad A.

    2010-04-30

    Fission product accumulation and gas bubble microstructure evolution in nuclear fuels strongly affect thermo-mechanical properties such as thermal conductivity, gas release, volumetric swelling and cracking, and hence the fuel performance. In this paper, a general phase-field model is developed to predict gas bubble formation and evolution. Important materials processes and thermodynamic properties including the generation of gas atoms and vacancies, sinks for vacancies and gas atoms, the elastic interaction among defects, gas re-solution, and inhomogeneity of elasticity and diffusivity are accounted for in the model. The simulations demonstrate the potential application of the phase-field method in investigating 1) heterogeneous nucleation of gas bubbles at defects; 2) effect of elastic interaction, inhomogeneity of material properties, and gas re-solution on gas bubble microstructures; and 3) effective properties from the output of phase-field simulations such as distribution of defects, gas bubbles, and stress fields.

  15. 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. PMID:27048931

  16. 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

  17. [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. PMID:21061630

  18. The Origins and Evolution of the p53 Family of Genes

    PubMed Central

    Belyi, Vladimir A.; Ak, Prashanth; Markert, Elke; Wang, Haijian; Hu, Wenwei; Puzio-Kuter, Anna; Levine, Arnold J.

    2010-01-01

    A common ancestor to the three p53 family members of human genes p53, p63, and p73 is first detected in the evolution of modern‐day sea anemones, in which both structurally and functionally it acts to protect the germ line from genomic instabilities in response to stresses. This p63/p73 common ancestor gene is found in almost all invertebrates and first duplicates to produce a p53 gene and a p63/p73 ancestor in cartilaginous fish. Bony fish contain all three genes, p53, p63, and p73, and the functions of these three transcription factors diversify in the higher vertebrates. Thus, this gene family has preserved its structural features and functional activities for over one billion years of evolution. PMID:20516129

  19. Origin of planetary atmospheres and their role in the evolution of life

    NASA Astrophysics Data System (ADS)

    Bauer, Siegfried J.

    2002-11-01

    The successful synthesis of amino acids in a reducing gas mixture presumably resembling the primary Earth atmosphere, by the Miller-Urey experiment, had a long lasting influence on the general perception of such an early atmosphere. Based on atmospheric escape, such a reducing atmosphere, however, has a lifetime of only millions of years. According to present view the early atmosphere of Earth may have resulted from mantle degassing of volatiles (H2O, CO2, N2), followed by later accumulation of O2 as product of life (photosynthesis). For Mars, with similar degassing products, evolution of life could have been possible in its early history. Non-reducing atmospheres (with liquid water) although not conductive for local synthesis of prebiotic molecules, may provide a benign environment for the evolution of life via ubiquitous supply of "building blocks" from external sources.

  20. 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

  1. A constraint-free phase field model for ferromagnetic domain evolution.

    PubMed

    Yi, Min; Xu, Bai-Xiang

    2014-11-01

    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 (ϑ 1,ϑ 2), instead of the magnetization unit vector m(m 1,m 2,m 3), 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 ϑ 1 and ϑ 2. 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 (ϑ 1,ϑ 2). 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

  2. The Origin and Evolution of the Behavior Analysis Program at the University of Nevada, Reno.

    PubMed

    Hayes, Linda J; Houmanfar, Ramona A; Ghezzi, Patrick M; Williams, W Larry; Locey, Matthew; Hayes, Steven C

    2016-05-01

    The origins of the Behavior Analysis program at the University of Nevada, Reno by way of a self-capitalized model through its transition to a more typical graduate program is described. Details of the original proposal to establish the program and the funding model are described. Some of the unusual features of the program executed in this way are discussed, along with problems engendered by the model. Also included is the diversification of faculty interests over time. The status of the program, now, after 25 years of operation, is presented. PMID:27606197

  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. Symbiosis between hydra and chlorella: molecular phylogenetic analysis and experimental study provide insight into its origin and evolution.

    PubMed

    Kawaida, Hitomi; Ohba, Kohki; Koutake, Yuhki; Shimizu, Hiroshi; Tachida, Hidenori; Kobayakawa, Yoshitaka

    2013-03-01

    Although many physiological studies have been reported on the symbiosis between hydra and green algae, very little information from a molecular phylogenetic aspect of symbiosis is available. In order to understand the origin and evolution of symbiosis between the two organisms, we compared the phylogenetic relationships among symbiotic green algae with the phylogenetic relationships among host hydra strains. To do so, we reconstructed molecular phylogenetic trees of several strains of symbiotic chlorella harbored in the endodermal epithelial cells of viridissima group hydra strains and investigated their congruence with the molecular phylogenetic trees of the host hydra strains. To examine the species specificity between the host and the symbiont with respect to the genetic distance, we also tried to introduce chlorella strains into two aposymbiotic strains of viridissima group hydra in which symbiotic chlorella had been eliminated in advance. We discussed the origin and history of symbiosis between hydra and green algae based on the analysis. PMID:23219706

  5. Climate variability and the energetic pathways of evolution: the origin of endothermy in mammals and birds.

    PubMed

    Portner, Hans O

    2004-01-01

    Large-scale climate oscillations in earth's history have influenced the directions of evolution, last but not least, through mass extinction events. This analysis tries to identify some unifying forces behind the course of evolution that favored an increase in organismic complexity and performance, paralleled by an increase in energy turnover, and finally led to endothermy. The analysis builds on the recent concept of oxygen-limited thermal tolerance and on the hypothesis that unifying principles exist in the temperature-dependent biochemical design of the eukaryotic cell in animals. The comparison of extant water-breathing and air-breathing animal species from various climates provides a cause-and-effect understanding of the trade-offs and constraints in thermal adaptation and their energetic consequences. It is hypothesized that the high costs of functional adaptation to fluctuating temperatures, especially in the cold (cold eurythermy), cause an increase in energy turnover and, at the same time, mobility and agility. These costs are associated with elevated mitochondrial capacities at minimized levels of activation enthalpies for proton leakage. Cold eurythermy is seen as a precondition for the survival of evolutionary crises elicited by repeated cooling events during extreme climate fluctuations. The costs of cold eurythermy appear as the single most important reason why metazoan evolution led to life forms with high energy turnover. They also explain why dinosaurs were able to live in subpolar climates. Finally, they give insight into the pathways, benefits, and trade-offs involved in the evolution of constant, elevated body temperature maintained by endothermy. Eurythermy, which encompasses cold tolerance, is thus hypothesized to be the "missing link" between ectothermy and endothermy. Body temperatures between 32 degrees and 42 degrees C in mammals and birds then result from trade-offs between the limiting capacities of ventilation and circulation and the

  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.; Kim, H.; Johnson, K. E.; Lee, J. C.; Messa, M.; Ryon, J. E.; Smith, L. J.; Ubeda, L.; Whitmore, B.

    2016-09-01

    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 Myrs) 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 onto 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. 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. PMID:25979758

  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. Stalled fork rescue via dormant replication origins in unchallenged S phase promotes proper chromosome segregation and tumor suppression

    PubMed Central

    Kawabata, Tsuyoshi; Luebben, Spencer W.; Yamaguchi, Satoru; Ilves, Ivar; Matise, Ilze; Buske, Tavanna; Botchan, Michael R.; Shima, Naoko

    2011-01-01

    Summary Eukaryotic cells license far more origins than are actually used for DNA replication, thereby generating a large number of dormant origins. Accumulating evidence suggests that such origins play a role in chromosome stability and tumor suppression, though the underlying mechanism is largely unknown. Here, we show that a loss of dormant origins results in an increased number of stalled replication forks even in unchallenged S phase in primary mouse fibroblasts derived from embryos homozygous for the Mcm4Chaos3 allele. We found that this allele reduces the stability of the MCM2-7 complex, but confers normal helicase activity in vitro. Despite the activation of multiple fork recovery pathways, replication intermediates in these cells persist into M phase, increasing the number of abnormal anaphase cells with lagging chromosomes and/or acentric fragments. These findings suggest that dormant origins constitute a major pathway for stalled fork recovery, contributing to faithful chromosome segregation and tumor suppression. PMID:21362550

  10. 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

    2016-01-01

    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. PMID:27102211

  11. Mechanism Analysis of the Inverse Doppler Effect in Two-Dimensional Photonic Crystal based on Phase Evolution

    NASA Astrophysics Data System (ADS)

    Jiang, Qiang; Chen, Jiabi; Wang, Yan; Liang, Binming; Hu, Jinbing; Zhuang, Songlin

    2016-04-01

    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.

  12. Mechanism Analysis of the Inverse Doppler Effect in Two-Dimensional Photonic Crystal based on Phase Evolution

    PubMed Central

    Jiang, Qiang; Chen, Jiabi; Wang, Yan; Liang, Binming; Hu, Jinbing; Zhuang, Songlin

    2016-01-01

    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. PMID:27102211

  13. 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.

  14. Understanding the origin of phase segregation of nano-crystalline in a Be(x)Zn(1-x)O random alloy: a novel phase of Be(1/3)Zn(2/3)O.

    PubMed

    Yong, Dingyu; He, Haiyan; Su, Longxing; Zhu, Yuan; Tang, Zikang; Zeng, Xiao Cheng; Pan, Bicai

    2015-06-01

    The usage of a BexZn1-xO alloy in ultraviolet (UV)-region optoelectronic devices is largely hindered by its intricate phase segregation of crystallites of different sizes. To understand the physical origin of this phase segregation phenomenon on the atomistic scale, we have undertaken an extensive study of the structural evolution of the segregation phases in the BexZn1-xO alloy at finite temperatures by using first-principles calculations combined with the cluster expansion approach. We find that a random alloy of BexZn1-xO tends to segregate into a mix-ordered phase below a critical temperature, by the growth of prototype and nano-sized structures. The segregated phases in BexZn1-xO entail not only ZnO or BeO crystallites, but also two as yet unreported phases with beryllium concentration of 1/3 and 2/3. Both new phases of BexZn1-xO are direct wide-gap semiconductors with band gap values of 4.88 eV and 6.78 eV respectively. We envisioned that the novel Be1/3Zn2/3O crystal is highly promising for solar-blind device applications. PMID:25966302

  15. Phase-field model for compositional and morphological evolution studies in thin film heteroepitaxial systems

    NASA Astrophysics Data System (ADS)

    Singh, Nitin

    A computational tool based on a diffuse-interface approach has been developed to simulate coupled evolution of film surface morphology and compositional evolution during thin film growth. It is well known from numerous experiments especially in Si/Ge and InGaAs/InP thin film systems that relaxation of elastic energy influences the surface morphology during growth. Strain relaxation via composition modulation is also of particular importance in the theory of spinodal decomposition. In this computational model, the influence of coherency stresses, both due to compositional strains (due to the atomic size mismatch of the constituent species) and epitaxial strains on the coupled evolution of composition and morphology of a thin film is considered. The model consists of a film on a substrate system which is in contact with vapor. The film-vapor interface and the compositional interfaces are diffuse in nature, so that it is not necessary to track these interfaces explicitly at each step during evolution. Using a modeling approach that eliminates the need to track sharp interfaces at each step during evolution, not only reduces the computational burden, but also allows for the incorporation of complex physical interaction in the model. The initial focus of the dissertation is on the development of a diffuse-interface model for simulating microstructural evolution in a InxGa 1-xAsySb1-y alloy thin film-substrate system. The regions of instability are mapped on the phase diagram using the regular solution model. The influence of compositional strain and epitaxial strains on microstructure evolution is investigated. The model is further extended to simulate surface morphological evolution and coupled morphology-composition effects. The strain energy in the system is calculated by solving the Cauchy-Navier equations for equilibrium using a linear multigrid method. Generalized nonlinear Cahn-Hilliard equations are used to describe the evolution of the phase-field variables

  16. 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.

  17. Origin, Evolution, and Imaging of Vortices in Proton-Hydrogen Collisions

    SciTech Connect

    Schultz, David Robert; Macek, J. H.; Sternberg, J. B.; Ovchinnikov, S. Yu.; Lee, Teck-Ghee

    2010-01-01

    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. Evolution of microbial dynamics during the maturation phase of the composting of different types of waste.

    PubMed

    Villar, Iria; Alves, David; Garrido, Josefina; Mato, Salustiano

    2016-08-01

    During composting, facilities usually exert greater control over the bio-oxidative phase of the process, which uses a specific technology and generally has a fixed duration. After this phase, the material is deposited to mature, with less monitoring during the maturation phase. While there has been considerable study of biological parameters during the thermophilic phase, there is less research on the stabilization and maturation phase. This study evaluates the effects of the type of starting material on the evolution of microbial dynamics during the maturation phase of composting. Three waste types were used: sludge from the fish processing industry, municipal sewage sludge and pig manure, each independently mixed with shredded pine wood as bulking agent. The composting system for each waste type comprised a static reactor with capacity of 600L for the bio-oxidative phase followed by stabilization and maturation phase in triplicate 200L boxes for 112days. Phospholipid fatty acids, enzyme activities and physico-chemical parameters were measured throughout the maturation phase. The evolution of the total microbial biomass, Gram + bacteria, Gram - bacteria, fungi and enzymatic activities (β-glucosidase, cellulase, protease, acid and alkaline phosphatase) depended significantly on the waste type (p<0.001). The predominant microbial community for each waste type remained present throughout the maturation process, indicating that the waste type determines the microorganisms that are able to develop at this stage. While fungi predominated during fish sludge maturation, manure and municipal sludge were characterized by a greater proportion of bacteria. Both the structure of the microbial community and enzymatic activities provided important information for monitoring the composting process. More attention should be paid to the maturation phase in order to optimize composting. PMID:27236404

  19. 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)

  20. 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

  1. Phase field modeling of microstructure evolution of electrocatalyst-infiltrated solid oxide fuel cell cathodes

    NASA Astrophysics Data System (ADS)

    Liang, Linyun; Li, Qun; Hu, Jiamian; Lee, Shiwoo; Gerdes, Kirk; Chen, Long-Qing

    2015-02-01

    A phase field model is developed to examine microstructural evolution of an infiltrated solid oxide fuel cell cathode. It is employed to generate the three-phase backbone microstructures and morphology of infiltrate nano-particles [La1-xSrxMnO3 (LSM)]. Two-phase Y2O3 + ZrO2 and LSM backbones composed of 0.5-1 μm particles are first generated and then seeded with infiltrate, and evolution is compared for starting infiltrate particle diameters of 5 nm and 10 nm. The computed lifetime triple phase boundary (3PB) density of the infiltrated cathode is then compared to the cathode backbone. Results indicate that initial coarsening of infiltrate nano-particles is the primary evolution process, and infiltrate coarsening is the majority contributor to 3PB reduction. However, at all times, the infiltrated cathode possesses significantly greater 3PB length than even the uncoarsened backbone. Infiltrate particle size effects indicate that the smaller particle size produces greater 3PB length for the same infiltration amount, consistent with intuition. A maximum 3PB enhancement is reached when increasing infiltrate particle loading, and the maximum enhancement depends on infiltrate particle size. It is found that architectural degradation modes will insignificantly affect the lifetime performance of infiltrated cathodes. This work suggests that lifetime optimized particle size/loading combinations are identifiable, and can be precise if additional fundamental data become available.

  2. 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

  3. 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.

  4. 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.

  5. 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. PMID:22537940

  6. The Paramyxea Levine 1979: An original example of evolution towards multicellularity

    NASA Astrophysics Data System (ADS)

    Desportes, Isabelle

    1984-03-01

    The Paramyxea are parasitic in marine invertebrates. Their development is a sporulation involving the differentiation within a stem cell of several sporonts which produce spores made of cells enclosed inside each other. Three genera are recognized according to the number of spores and sporal cells, and the taxonomic position of the host (Polychaeta, Mollusca, Crustacea). The Paramyxea exhibit both protistan and metazoan characters. Their nine singlets centrioles are observed in different Protoctists whereas the fact that their sporal cells acquire distinctive cytological features may be interpreted as an evolution towards multicellularity.

  7. 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. PMID:25589485

  8. Ancestor–descendant relationships in evolution: origin of the extant pygmy right whale, Caperea marginata

    PubMed Central

    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. PMID:25589485

  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. 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. PMID:25864414

  11. 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. PMID:25370211

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

    SciTech Connect

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

    2014-11-28

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

  13. Three R's of bacterial evolution: how replication, repair, and recombination frame the origin of species.

    PubMed

    Brown, E W; LeClerc, J E; Kotewicz, M L; Cebula, T A

    2001-01-01

    The genetic diversity of bacteria results not only from errors in DNA replication and repair but from horizontal exchange and recombination of DNA sequences from similar and disparate species as well. New individuals carrying adaptive changes are thus being spawned constantly among the population at large. When new selection pressures appear, these are the individuals that survive, at the expense of the general population, to forge new populations. Depending on the severity and uniqueness of the selection pressure, this could lead to new speciation. It is becoming more and more evident that, as nucleotide sequences of numerous loci from many bacterial strains continue to amass, horizontal transfer has played a key role in configuring the Escherichia coli chromosome. Here, we examine views, both old and new, for the role of recombination in the evolution of bacterial chromosomes. We present novel phylogenetic evidence for horizontal transfer of three genes involved in DNA replication and repair (mutS, uvrD, and polA). These data reveal a prominent role for horizontal transfer in the evolution of genes known to play a key role in the fidelity of DNA replication and, thus, ultimate survival of the organism. Our data underscore that recombination plays both a diversifying and a homogenizing role in defining the structure of the E. coli genome. PMID:11746762

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

    NASA Astrophysics Data System (ADS)

    Frebel, Anna

    2013-10-01

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

  15. An asymmetric explosion as the origin of spectral evolution diversity in type Ia supernovae.

    PubMed

    Maeda, K; Benetti, S; Stritzinger, M; Röpke, F K; Folatelli, G; Sollerman, J; Taubenberger, S; Nomoto, K; Leloudas, G; Hamuy, M; Tanaka, M; Mazzali, P A; Elias-Rosa, N

    2010-07-01

    Type Ia supernovae form an observationally uniform class of stellar explosions, in that more luminous objects have smaller decline-rates. This one-parameter behaviour allows type Ia supernovae to be calibrated as cosmological 'standard candles', and led to the discovery of an accelerating Universe. Recent investigations, however, have revealed that the true nature of type Ia supernovae is more complicated. Theoretically, it has been suggested that the initial thermonuclear sparks are ignited at an offset from the centre of the white-dwarf progenitor, possibly as a result of convection before the explosion. Observationally, the diversity seen in the spectral evolution of type Ia supernovae beyond the luminosity-decline-rate relation is an unresolved issue. Here we report that the spectral diversity is a consequence of random directions from which an asymmetric explosion is viewed. Our findings suggest that the spectral evolution diversity is no longer a concern when using type Ia supernovae as cosmological standard candles. Furthermore, this indicates that ignition at an offset from the centre is a generic feature of type Ia supernovae. PMID:20596015

  16. Origins of light trans-Fe and r-process elements deduced from Galactic chemical evolution

    NASA Astrophysics Data System (ADS)

    Ishimaru, Yuhri; Arao, Sachie; Wanajo, Shinya; Prantzos, Nicolas

    2014-09-01

    Compact binary mergers are suggested to be the major site of the r-process elements by recent hydrodynamical and nucleosynthesis studies. It has been pointed out, however, that estimated long lifetimes of compact binaries are in conflict with the presence of large scatters in r-process elements of very metal-poor stars (MPS). To resolve this problem, we examine the role of compact binary mergers in the early Galactic chemical evolution on the assumption that our Galactic halo was formed from clusterings of sub-halos. We find that star-to-star scatters of [r/Fe] in MPS can be well explained with this scenario. Observations of MPS also show large enhancement of Sr relative to Ba, suggesting a distinct site of light trans-Fe elements. Recent nucleosynthesis studies show that electron-capture supernovae (ECSNe) can produce heavy elements up to Zr (Wanajo et al. 2011). Using our inhomogeneous chemical evolution model, we discuss that ECSNe can explain observed enhancement of Zn in MPS as well as of Sr, Y, and Zr.

  17. Antibiotic resistance in Neisseria gonorrhoeae: origin, evolution, and lessons learned for the future.

    PubMed

    Unemo, Magnus; Shafer, William M

    2011-08-01

    The strict human pathogen Neisseria gonorrhoeae has caused gonorrhea for thousands of years, and currently gonorrhea is the second most prevalent bacterial sexually transmitted infection worldwide. Given the ancient nature of N. gonorrhoeae and its unique obligate relationship with humankind over the millennia, its remarkable ability to adapt to the host immune system and cause repeated infections, and its propensity to develop resistance to all clinically useful antibiotics, the gonococcus is an ideal pathogen on which to study the evolution of bacterial pathogenesis, including antimicrobial resistance, over the long term and within the host during infection. Recently, the first gonococcus displaying high-level resistance to ceftriaxone, identified in Japan, was characterized in detail. Ceftriaxone is the last remaining option for empirical first-line treatment, and N. gonorrhoeae now seems to be evolving into a true "superbug." In the near future, gonorrhea may become untreatable in certain circumstances. Herein, the history of antibiotics used for treatment of gonorrhea, the evolution of resistance emergence in N. gonorrhoeae, the linkage between resistance and biological fitness of N. gonorrhoeae, lessons learned, and future perspectives are reviewed and discussed. PMID:22239555

  18. Microscopic Origin of the Logarithmic Time Evolution of Aging Processes in Complex Systems

    NASA Astrophysics Data System (ADS)

    Lomholt, Michael A.; Lizana, Ludvig; Metzler, Ralf; Ambjörnsson, Tobias

    2013-05-01

    There exists compelling experimental evidence in numerous systems for logarithmically slow time evolution, yet its full theoretical understanding remains elusive. We here introduce and study a generic transition process in complex systems, based on nonrenewal, aging waiting times. Each state n of the system follows a local clock initiated at t=0. The random time τ between clock ticks follows the waiting time density ψ(τ). Transitions between states occur only at local clock ticks and are hence triggered by the local forward waiting time, rather than by ψ(τ). For power-law forms ψ(τ)≃τ-1-α (0<α<1) we obtain a logarithmic time evolution of the state number ⟨n(t)⟩≃log⁡(t/t0), while for α>2 the process becomes normal in the sense that ⟨n(t)⟩≃t. In the intermediate range 1<α<2 we find the power-law growth ⟨n(t)⟩≃tα-1. Our model provides a universal description for transition dynamics between aging and nonaging states.

  19. Microscopic origin of the logarithmic time evolution of aging processes in complex systems.

    PubMed

    Lomholt, Michael A; Lizana, Ludvig; Metzler, Ralf; Ambjörnsson, Tobias

    2013-05-17

    There exists compelling experimental evidence in numerous systems for logarithmically slow time evolution, yet its full theoretical understanding remains elusive. We here introduce and study a generic transition process in complex systems, based on nonrenewal, aging waiting times. Each state n of the system follows a local clock initiated at t = 0. The random time τ between clock ticks follows the waiting time density ψ(τ). Transitions between states occur only at local clock ticks and are hence triggered by the local forward waiting time, rather than by ψ(τ). For power-law forms ψ(τ) ≃ τ(-1-α) (0 < α < 1) we obtain a logarithmic time evolution of the state number ⟨n(t)⟩ ≃ log(t/t(0)), while for α > 2 the process becomes normal in the sense that ⟨n(t)⟩ ≃ t. In the intermediate range 1 < α < 2 we find the power-law growth ⟨n(t)⟩ ≃ t(α-1). Our model provides a universal description for transition dynamics between aging and nonaging states. PMID:25167457

  20. Domain combination of the vertebrate-like TLR gene family: implications for their origin and evolution.

    PubMed

    Wu, Baojun; Huan, Tianxiao; Gong, Jing; Zhou, Pin; Bai, Zengliang

    2011-12-01

    Domain shuffling, which is an important mechanism in the evolution of multi-domain proteins, has shaped the evolutionary development of the immune system in animals. Toll and Toll-like receptors (TLRs) are a class of proteins that play a key role in the innate and adaptive immune systems. Draft genome sequences provide the opportunity to compare the Toll/TLR gene repertoire among representative metazoans. In this study, we investigated the combination of Toll/interleukin-1 receptor (TIR) and leucine-rich repeat (LRR) domains of metazoan Toll/TLRs. Before Toll with both domains occurred in Cnidaria (sea anemone, Nematostella vectensis), through domain combinations, TIR-only and LRR-only proteins had already appeared in sponges (Amphimedon queenslandica). Although vertebrate-like TIR (V-TIR) domain already appeared in Cnidaria, the vertebrate-like TLR (V-TLR) with both domains appeared much later. The first combination between V-TIR domain and vertebrate-like LRR (V-LRR) domain for V-TLR may have occurred after the divergence of Cnidaria and bilateria. Then, another combination for V-TLR, a recombination of both domains, possibly occurred before or during the evolution of primitive vertebrates. Taken together, two rounds of domain combinations may thus have co-shaped the vertebrate TLRs. PMID:22227927

  1. Respiratory Evolution Facilitated the Origin of Pterosaur Flight and Aerial Gigantism

    PubMed Central

    Claessens, Leon P. A. M.; O'Connor, Patrick M.; Unwin, David M.

    2009-01-01

    Pterosaurs, enigmatic extinct Mesozoic reptiles, were the first vertebrates to achieve true flapping flight. Various lines of evidence provide strong support for highly efficient wing design, control, and flight capabilities. However, little is known of the pulmonary system that powered flight in pterosaurs. We investigated the structure and function of the pterosaurian breathing apparatus through a broad scale comparative study of respiratory structure and function in living and extinct archosaurs, using computer-assisted tomographic (CT) scanning of pterosaur and bird skeletal remains, cineradiographic (X-ray film) studies of the skeletal breathing pump in extant birds and alligators, and study of skeletal structure in historic fossil specimens. In this report we present various lines of skeletal evidence that indicate that pterosaurs had a highly effective flow-through respiratory system, capable of sustaining powered flight, predating the appearance of an analogous breathing system in birds by approximately seventy million years. Convergent evolution of gigantism in several Cretaceous pterosaur lineages was made possible through body density reduction by expansion of the pulmonary air sac system throughout the trunk and the distal limb girdle skeleton, highlighting the importance of respiratory adaptations in pterosaur evolution, and the dramatic effect of the release of physical constraints on morphological diversification and evolutionary radiation. PMID:19223979

  2. Origin and evolution of GATA2a and GATA2b in teleosts: insights from tongue sole, Cynoglossus semilaevis.

    PubMed

    Liu, Jinxiang; Jiang, Jiajun; Wang, Zhongkai; He, Yan; Zhang, Quanqi

    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

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

    PubMed

    Grosch, Eugene G; Hazen, Robert M

    2015-10-01

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

  4. 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

  5. Origin and evolution of protein fold designs inferred from phylogenomic analysis of CATH domain structures in proteomes.

    PubMed

    Bukhari, Syed Abbas; Caetano-Anollés, Gustavo

    2013-01-01

    The spatial arrangements of secondary structures in proteins, irrespective of their connectivity, depict the overall shape and organization of protein domains. These features have been used in the CATH and SCOP classifications to hierarchically partition fold space and define the architectural make up of proteins. Here we use phylogenomic methods and a census of CATH structures in hundreds of genomes to study the origin and diversification of protein architectures (A) and their associated topologies (T) and superfamilies (H). Phylogenies that describe the evolution of domain structures and proteomes were reconstructed from the structural census and used to generate timelines of domain discovery. Phylogenies of CATH domains at T and H levels of structural abstraction and associated chronologies revealed patterns of reductive evolution, the early rise of Archaea, three epochs in the evolution of the protein world, and patterns of structural sharing between superkingdoms. Phylogenies of proteomes confirmed the early appearance of Archaea. While these findings are in agreement with previous phylogenomic studies based on the SCOP classification, phylogenies unveiled sharing patterns between Archaea and Eukarya that are recent and can explain the canonical bacterial rooting typically recovered from sequence analysis. Phylogenies of CATH domains at A level uncovered general patterns of architectural origin and diversification. The tree of A structures showed that ancient structural designs such as the 3-layer (αβα) sandwich (3.40) or the orthogonal bundle (1.10) are comparatively simpler in their makeup and are involved in basic cellular functions. In contrast, modern structural designs such as prisms, propellers, 2-solenoid, super-roll, clam, trefoil and box are not widely distributed and were probably adopted to perform specialized functions. Our timelines therefore uncover a universal tendency towards protein structural complexity that is remarkable. PMID:23555236

  6. Phase-field modeling of void evolution and swelling in materials under irradiation

    SciTech Connect

    Li, Yulan; Hu, Shenyang Y.; Sun, Xin; Gao, Fei; Henager, Charles H.; Khaleel, Mohammad A.

    2011-05-01

    Void swelling is an important phenomenon observed in both nuclear fuels and cladding materials in operating nuclear reactors. In this work we developed a phase-field model to simulate the void nucleation, growth, and the change of void volume fraction. Important material processes including the generation of defects such as vacancies and self-interstitials, their diffusion and annihilation, and void nucleation and evolution have been taken into account in our phase-field model. The thermodynamic and kinetic properties such as chemical free energy, interfacial energy, vacancy mobility, and annihilation rate of vacancies and interstitials are generally expressed as functions of the temperature. The developed model enables one to parametrically study critical void nucleus size, void growth kinetics, and void volume fraction evolutions. Our simulations demonstrated that the volume swelling displays a quasi-bell shape distribution with temperature that was often observed in experiments.

  7. Evolution of the phase content of zirconia powders prepared by sol-gel acid hydrolysis

    SciTech Connect

    Rivas, P.C.; Martinez, J.A.; Caracoche, M.C.; Rodriguez, A.M.; Lopez Garcia, A.R.; Pavlik, R.S. Jr.; Klein, L.C.

    1998-01-01

    The evolution of the phase content in zirconia powders that have been prepared by sol-gel acid hydrolysis has been investigated using the perturbed-angular-correlation (PAC) technique and X-ray diffractometry. As a consequence of performing annealing treatments at increasing temperatures between room temperature and 1,000 C, the amorphous starting material transforms to the tetragonal form and then to the monoclinic form. The metastable tetragonal phase exhibits two hyperfine components, one of which describes very defective zirconium surroundings. The evolution of PAC relative fractions is in agreement with the diffraction results. The durability of the samples in sodium hydroxide seems to increase as the relative amount of the most-defective zirconium surroundings of the tetragonal form increases.

  8. 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. PMID:23253619

  9. alpha'-SiAlON: Phase stability, phase transformations and microstructural evolutions

    NASA Astrophysics Data System (ADS)

    Rosenflanz, Anatoly Zhanovich

    1997-11-01

    Silicon nitride is a prominent member of a ceramic family developed for use in structural applications at ambient and elevated temperatures. It exists in two polymorphic forms, alpha and beta. The predominant form in use today is beta-Sisb3Nsb4. The other form of silicon nitride, alpha-Sisb3Nsb4, is not used even though it is much harder. This is because only beta-Sisb3Nsb4 can be made into a tough and strong ceramic by forming a microstructure that resembles a fiber-reinforced composite. alpha-Sisb3Nsb4, which is unstable at high temperature, can be stabilized by forming solid solutions with Al, O, and interstitial cations, but it always appears with a microstructure of fine, equiaxed grains and has low toughness and strength. Microstructural development of silicon nitride is closely related to phase transformations mediated by a liquid. To help guide the development of new silicon nitride alloys, various aspects of these transformations, and some reverse transformations among them, have been studied. This dissertation sheds light on such issues as the determination of equilibrium phase relations at different temperatures for different compositions, the kinetics of forward and reverse transformations, and the connection of these transformations to the microstructure. Among the outstanding issues that have been resolved by this work are the stability of alphasp'-SiAlON at low temperature and the role of starting powders and rare-earth cations in determining the rate of phase transformations. A new class of alphasp'-SiAlON, which combines the toughness of beta-Sisb3Nsb4 and the hardness of alpha-Sisb3Nsb4, with a whisker-like microstructure, has also been discovered by exploiting the nucleation and growth kinetics of phase transformations.

  10. Positional information from oscillatory phase shifts : insights from in silico evolution.

    PubMed

    Beaupeux, M; François, P

    2016-01-01

    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. PMID:27346171

  11. 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.

  12. Structural evolution of La-Cr-O thin films: Part I. Microstructure and phase development

    SciTech Connect

    Orlovskaya, N.; Coratolo, A.; Lugovy, M.; Johnson, C.D.; Gemmen, R.S.

    2006-12-05

    The structural evolution of La–Cr–O thin films and the formation mechanisms of the LaCrO3 perovskite phase have been studied. X-ray amorphous La–Cr–O protective coatings were deposited by magnetron sputtering on metallic interconnect materials. During the annealing of the material in air a two-step phase transition from La–Cr–O to a monoclinic LaCrO4 monazite and further to an orthorhombic LaCrO3 perovskite phase was observed. The formation of a fine nanoporous structure is a result of the significant increase in density of the final LaCrO3 perovskite in comparison with monazite LaCrO4 phase. While the porous structure was not sought after for this application, these distinctive nanostructures may have numerous applications in catalysis, separation membranes or for other SOFC components.

  13. Homeotic Evolution in the Mammalia: Diversification of Therian Axial Seriation and the Morphogenetic Basis of Human Origins

    PubMed Central

    Filler, Aaron G.

    2007-01-01

    Background Despite the rising interest in homeotic genes, little has been known about the course and pattern of evolution of homeotic traits across the mammalian radiation. An array of emerging and diversifying homeotic gradients revealed by this study appear to generate new body plans and drive evolution at a large scale. Methodology/Principal Findings This study identifies and evaluates a set of homeotic gradients across 250 extant and fossil mammalian species and their antecedents over a period of 220 million years. These traits are generally expressed as co-linear gradients along the body axis rather than as distinct segmental identities. Relative position or occurrence sequence vary independently and are subject to polarity reversal and mirroring. Five major gradient modification sets are identified: (1)–quantitative changes of primary segmental identity pattern that appeared at the origin of the tetrapods ; (2)–frame shift relation of costal and vertebral identity which diversifies from the time of amniote origins; (3)–duplication, mirroring, splitting and diversification of the neomorphic laminar process first commencing at the dawn of mammals; (4)–emergence of homologically variable lumbar lateral processes upon commencement of the radiation of therian mammals and ; (5)–inflexions and transpositions of the relative position of the horizontal septum of the body and the neuraxis at the emergence of various orders of therian mammals. Convergent functional changes under homeotic control include laminar articular engagement with septo-neural transposition and ventrally arrayed lumbar transverse process support systems. Conclusion/Significance Clusters of homeotic transformations mark the emergence point of mammals in the Triassic and the radiation of therians in the Cretaceous. A cluster of homeotic changes in the Miocene hominoid Morotopithecus that are still seen in humans supports establishment of a new “hominiform” clade and suggests a homeotic

  14. Staminal Evolution in the Genus Salvia (Lamiaceae): Molecular Phylogenetic Evidence for Multiple Origins of the Staminal Lever

    PubMed Central

    Walker, Jay B.; Sytsma, Kenneth J.

    2007-01-01

    Background and Aims The genus Salvia has traditionally included any member of the tribe Mentheae (Lamiaceae) with only two stamens and with each stamen expressing an elongate connective. The recent demonstration of the non-monophyly of the genus presents interesting implications for staminal evolution in the tribe Mentheae. In the context of a molecular phylogeny, the staminal morphology of the various lineages of Salvia and related genera is characterized and an evolutionary interpretation of staminal variation within the tribe Mentheae is presented. Methods Two molecular analyses are presented in order to investigate phylogenetic relationships in the tribe Mentheae and the genus Salvia. The first presents a tribal survey of the Mentheae and the second concentrates on Salvia and related genera. Schematic sketches are presented for the staminal morphology of each major lineage of Salvia and related genera. Key Results These analyses suggest an independent origin of the staminal elongate connective on at least three different occasions within the tribe Mentheae, each time with a distinct morphology. Each independent origin of the lever mechanism shows a similar progression of staminal change from slight elongation of the connective tissue separating two fertile thecae to abortion of the posterior thecae and fusion of adjacent posterior thecae. A monophyletic lineage within the Mentheae is characterized consisting of the genera Lepechinia, Melissa, Salvia, Dorystaechas, Meriandra, Zhumeria, Perovskia and Rosmarinus. Conclusions Based on these results the following are characterized: (1) the independent origin of the staminal lever mechanism on at least three different occasions in Salvia, (2) that Salvia is clearly polyphyletic, with five other genera intercalated within it, and (3) staminal evolution has proceeded in different ways in each of the three lineages of Salvia but has resulted in remarkably similar staminal morphologies. PMID:16926227

  15. Control of phase boundary evolution in metal solidification for new thermodynamic parameters of the metal

    NASA Astrophysics Data System (ADS)

    Albu, A. F.

    2016-05-01

    The problem of controlling the phase boundary evolution in the course of solidification of metals with different thermodynamic properties is studied. The underlying mathematical model of the process is based on a three-dimensional nonstationary two-phase initial-boundary value problem of the Stefan type. The control functions are determined by optimal control problems, which are solved numerically with the help of gradient optimization methods. The gradient of the cost function is exactly computed by applying the fast automatic differentiation technique. The research results are described and analyzed. Some of them are illustrated.

  16. The application of the phase space time evolution method to electron shielding

    NASA Technical Reports Server (NTRS)

    Cordaro, M. C.; Zucker, M. S.

    1972-01-01

    A computer technique for treating the motion of charged and neutral particles and called the phase space time evolution method was developed. This technique employs the computer's bookkeeping capacity to keep track of the time development of a phase space distribution of particles. This method was applied to a study of the penetration of electrons. A 1 MeV beam of electrons normally incident on a semi-infinite slab of aluminum was used. Results of the calculation were compared with Monte Carlo calculations and experimental results. Time-dependent PSTE electron penetration results for the same problem are presented.

  17. Evolution of ordered {omega} phases in (Zr{sub 3}Al)-Nb alloys

    SciTech Connect

    Tewari, R.; Mukhopadhyay, P.; Banerjee, S.; Bendersky, L.A.

    1999-03-10

    Microstructural investigations on rapidly solidified Zr{sub 3}Al based alloys (binary Zr{sub 3}Al and ternary Zr{sub 3}Al-3Nb and Zr{sub 3}Al-10Nb) have revealed some unusual phase transformation sequences. The Zr{sub 5}Al{sub 3} phase (D8{sub 8} structure) has been found to occur in both the rapidly solidified ternary alloys unlike in the rapidly solidified stoichiometric Zr{sub 3}Al alloy in which the ZrAl phase (B8{sub 2} structure) has been found to be present. The evolution of the D8{sub 8} phase, which could be regarded as one of the ordered derivatives of the {omega} phase, could be described in terms of a superimposition of replacive and displacive ordering waves in the {beta} phase. The orientation relationship between the {beta} and the D8{sub 8} phases has been established. The microstructural changes occurring in the rapidly solidified Zr{sub 3}Al-Nb alloys during aging have been examined. It has been found that on aging the D8{sub 8} phase gets transformed into the B8{sub 2} phase which, on continued aging, transforms to other metastable and equilibrium phases, depending upon the aging temperature. The observed sequence of phase transformations involving different structurally related phases has been along the direction of progressively close packed structures. The symmetry changes associated with the sequence of {omega} related transformations have been summarized in the form of a symmetry tree.

  18. Pulse evolution and plasma-wave phase velocity in channel-guided laser-plasma accelerators.

    PubMed

    Benedetti, C; Rossi, F; Schroeder, C B; Esarey, E; Leemans, W P

    2015-08-01

    The self-consistent laser evolution of an intense, short-pulse laser exciting a plasma wave and propagating in a preformed plasma channel is investigated, including the effects of pulse steepening and energy depletion. In the weakly relativistic laser intensity regime, analytical expressions for the laser energy depletion, pulse self-steepening rate, laser intensity centroid velocity, and phase velocity of the plasma wave are derived and validated numerically. PMID:26382537

  19. 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.

  20. Structural evolution of epitaxial SrCoOx films near topotactic phase transition

    SciTech Connect

    Jeen, Hyoung Jeen; Lee, Ho Nyung

    2015-12-18

    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 SrCoO2.5thin 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. Furthermore, 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 SrCoOx films near topotactic phase transition

    DOE PAGESBeta

    Jeen, Hyoung Jeen; Lee, Ho Nyung

    2015-12-18

    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 SrCoO2.5thin films and performed post-annealing at various temperatures for topotacticmore » 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. Furthermore, 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.« less

  2. 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.

  3. Phase-Field Simulation of Microstructure Evolution in Industrial A2214 Alloy During Solidification

    NASA Astrophysics Data System (ADS)

    Wei, Ming; Tang, Ying; Zhang, Lijun; Sun, Weihua; Du, Yong

    2015-07-01

    By linking to the thermodynamic and atomic mobility databases in Al alloys well established in our research group, the microstructure evolution in industrial A2214 alloy (Al-4.5Cu-0.5Mg-1.0Si, in wt pct) during solidification process was studied by means of two-dimensional phase-field simulation via MICRostructure Evolution Simulation Software in the framework of the multi-phase-field formalism. The thermophysical parameters including interfacial energies and interfacial mobilities were carefully chosen for reproducing the experimental features. The solidification sequence due to the present phase-field simulation conforms to both equilibrium calculation and Scheil simulation. The predicted microstructure reproduces the experimental data very well. These facts indicate that a quantitative phase-field simulation was achieved in the present work. Moreover, the mechanisms of characteristic patterns and microstructure formation were revealed with the aid of the phase-field simulation. In addition, the effect of cooling rate on the secondary dendrite arm spacing and microsegregation was also investigated through comprehensive comparison with the experimental data.

  4. 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

  5. On the origin of DNA genomes: evolution of the division of labor between template and catalyst in model replicator systems.

    PubMed

    Takeuchi, Nobuto; Hogeweg, Paulien; Koonin, Eugene V

    2011-03-01

    The division of labor between template and catalyst is a fundamental property of all living systems: DNA stores genetic information whereas proteins function as catalysts. The RNA world hypothesis, however, posits that, at the earlier stages of evolution, RNA acted as both template and catalyst. Why would such division of labor evolve in the RNA world? We investigated the evolution of DNA-like molecules, i.e. molecules that can function only as template, in minimal computational models of RNA replicator systems. In the models, RNA can function as both template-directed polymerase and template, whereas DNA can function only as template. Two classes of models were explored. In the surface models, replicators are attached to surfaces with finite diffusion. In the compartment models, replicators are compartmentalized by vesicle-like boundaries. Both models displayed the evolution of DNA and the ensuing division of labor between templates and catalysts. In the surface model, DNA provides the advantage of greater resistance against parasitic templates. However, this advantage is at least partially offset by the disadvantage of slower multiplication due to the increased complexity of the replication cycle. In the compartment model, DNA can significantly delay the intra-compartment evolution of RNA towards catalytic deterioration. These results are explained in terms of the trade-off between template and catalyst that is inherent in RNA-only replication cycles: DNA releases RNA from this trade-off by making it unnecessary for RNA to serve as template and so rendering the system more resistant against evolving parasitism. Our analysis of these simple models suggests that the lack of catalytic activity in DNA by itself can generate a sufficient selective advantage for RNA replicator systems to produce DNA. Given the widespread notion that DNA evolved owing to its superior chemical properties as a template, this study offers a novel insight into the evolutionary origin of DNA

  6. Elastic, not plastic species: Frozen plasticity theory and the origin of adaptive evolution in sexually reproducing organisms

    PubMed Central

    2010-01-01

    Background Darwin's evolutionary theory could easily explain the evolution of adaptive traits (organs and behavioral patterns) in asexual but not in sexual organisms. Two models, the selfish gene theory and frozen plasticity theory were suggested to explain evolution of adaptive traits in sexual organisms in past 30 years. Results The frozen plasticity theory suggests that sexual species can evolve new adaptations only when their members are genetically uniform, i.e. only after a portion of the population of the original species had split off, balanced on the edge of extinction for several generations, and then undergone rapid expansion. After a short period of time, estimated on the basis of paleontological data to correspond to 1-2% of the duration of the species, polymorphism accumulates in the gene pool due to frequency-dependent selection; and thus, in each generation, new mutations occur in the presence of different alleles and therefore change their selection coefficients from generation to generation. The species ceases to behave in an evolutionarily plastic manner and becomes evolutionarily elastic on a microevolutionary time-scale and evolutionarily frozen on a macroevolutionary time-scale. It then exists in this state until such changes accumulate in the environment that the species becomes extinct. Conclusion Frozen plasticity theory, which includes the Darwinian model of evolution as a special case - the evolution of species in a plastic state, not only offers plenty of new predictions to be tested, but also provides explanations for a much broader spectrum of known biological phenomena than classic evolutionary theories. Reviewers This article was reviewed by Rob Knight, Fyodor Kondrashov and Massimo Di Giulio (nominated by David H. Ardell). PMID:20067646

  7. The plasma structure of coronal hole solar wind: Origins and evolution

    NASA Astrophysics Data System (ADS)

    Borovsky, Joseph E.

    2016-06-01

    Whereas slow solar wind is known to be highly structured, the fast (coronal hole origin) wind is usually considered to be homogeneous. Using measurements from Helios 1 + 2, ACE, Wind, and Ulysses, structure in the coronal hole origin solar wind is examined from 0.3 AU to 2.3 AU. Care is taken to collect and analyze intervals of "unperturbed coronal hole plasma." In these intervals, solar wind structure is seen in the proton number density, proton temperature, proton specific entropy, magnetic field strength, magnetic field to density ratio, electron heat flux, helium abundance, heavy-ion charge-state ratios, and Alfvenicity. Typical structure amplitudes are factors of 2, far from homogeneous. Variations are also seen in the solar wind radial velocity. Using estimates of the motion of the solar wind origin footpoint on the Sun for the various spacecraft, the satellite time series measurements are converted to distance along the photosphere. Typical variation scale lengths for the solar wind structure are several variations per supergranule. The structure amplitude and structure scale sizes do not evolve with distance from the Sun from 0.3 to 2.3 AU. An argument is quantified that these variations are the scale expected for solar wind production in open magnetic flux funnels in coronal holes. Additionally, a population of magnetic field foldings (switchbacks, reversals) in the coronal hole plasma is examined: this population evolves with distance from the Sun such that the magnetic field is mostly Parker spiral aligned at 0.3 AU and becomes more misaligned with distance outward.

  8. Origin and evolution of X-ray binaries in globular clusters

    NASA Technical Reports Server (NTRS)

    Grindlay, Jonathan E.

    1986-01-01

    The theoretical model developed by Grindlay (1984 and 1985) and Grindlay and Hertz (1985) to explain the relative numbers of low-luminosity and high-luminosity X-ray sources in Galactic globular clusters is briefly characterized, and the relevant observational evidence is summarized. In the model, high-rate mass transfer onto white dwarfs in about 1 percent of the low-luminosity binary sources produces neutron stars, which then form compact high-luminosity X-ray binaries (by tidal capture in the dense cluster cores); these in turn evolve into hierarchical triple systems. Evidence considered includes observations of the high-luminosity giant-fed X-ray binary in M 15, the results of searches for CVs in globulars, comparisons of X-ray-binary and host-globular evolution, and indications that GX 17 + 2 is a bound triple.

  9. The origin and evolution of the coordinated data analysis workshop process. [for International Magnetospheric Study

    NASA Technical Reports Server (NTRS)

    Vette, J. I.; Sawyer, D. M.; Teague, M. J.; Hei, D. J., Jr.

    1982-01-01

    During the planning stage for the International Magnetospheric Study (IMS), it was stressed that coordinated observations among various satellites and among satellite, ground-based, balloon, and rocket (GBR) experiments were essential in obtaining the required observational data base. In the course of operating the Satellite Situation Center (SSC), it was found to be desirable to assemble a problem-oriented digital data base, consisting of a large number of physical parameters obtained from satellite and GBR sensors, in a computer system which would permit a large number of scientists to manipulate, display, discuss, study and analyze the data together in a coordinated manner. It was felt that such a process might shorten the time required to gain full scientific understanding of the observations. This approach was called the Coordinated Data Analysis Workshop (CDAW) process. Attention is given to the preliminary concept, the the initial implementation of the CDAW process, and aspects of subsequent evolution.

  10. Origin and evolution of prebiotic organic matter as inferred from the Tagish Lake meteorite.

    PubMed

    Herd, Christopher D K; Blinova, Alexandra; Simkus, Danielle N; Huang, Yongsong; Tarozo, Rafael; Alexander, Conel M O'D; Gyngard, Frank; Nittler, Larry R; Cody, George D; Fogel, Marilyn L; Kebukawa, Yoko; Kilcoyne, A L David; Hilts, Robert W; Slater, Greg F; Glavin, Daniel P; Dworkin, Jason P; Callahan, Michael P; Elsila, Jamie E; De Gregorio, Bradley T; Stroud, Rhonda M

    2011-06-10

    The complex suite of organic materials in carbonaceous chondrite meteorites probably originally formed in the interstellar medium and/or the solar protoplanetary disk, but was subsequently modified in the meteorites' asteroidal parent bodies. The mechanisms of formation and modification are still very poorly understood. We carried out a systematic study of variations in the mineralogy, petrology, and soluble and insoluble organic matter in distinct fragments of the Tagish Lake meteorite. The variations correlate with indicators of parent body aqueous alteration. At least some molecules of prebiotic importance formed during the alteration. PMID:21659601

  11. Origin and Evolution of Prebiotic Organic Matter As Inferred from the Tagish Lake Meteorite

    NASA Astrophysics Data System (ADS)

    Herd, Christopher D. K.; Blinova, Alexandra; Simkus, Danielle N.; Huang, Yongsong; Tarozo, Rafael; Alexander, Conel M. O.'D.; Gyngard, Frank; Nittler, Larry R.; Cody, George D.; Fogel, Marilyn L.; Kebukawa, Yoko; Kilcoyne, A. L. David; Hilts, Robert W.; Slater, Greg F.; Glavin, Daniel P.; Dworkin, Jason P.; Callahan, Michael P.; Elsila, Jamie E.; De Gregorio, Bradley T.; Stroud, Rhonda M.

    2011-06-01

    The complex suite of organic materials in carbonaceous chondrite meteorites probably originally formed in the interstellar medium and/or the solar protoplanetary disk, but was subsequently modified in the meteorites’ asteroidal parent bodies. The mechanisms of formation and modification are still very poorly understood. We carried out a systematic study of variations in the mineralogy, petrology, and soluble and insoluble organic matter in distinct fragments of the Tagish Lake meteorite. The variations correlate with indicators of parent body aqueous alteration. At least some molecules of prebiotic importance formed during the alteration.

  12. Origin and Evolution of Prebiotic Organic Matter as Inferred from the Tagish Lake Meteorite

    NASA Technical Reports Server (NTRS)

    Herd, Christopher D.; Blinova, Alexandra; Simkus, Danielle N.; Huang, Yongsong; Tarozo, Rafael; Alexander, Conel M.; Gyngard, Frank; Nittler, Larry R.; Cody, George D.; Fogel, Marilyn L.; Kebukawa, Yoko; Kilcoyne, A. L.; Hilts, Robert W.; Slater, Greg F.; Glavin, Daniel P.; Dworkin, Jason P.; Callahan, Michael P.; Elsila, Jamie E.; De Gregorio, Bradley T.; Stroud, Rhonda M.

    2011-01-01

    The complex suite of organic materials in carbonaceous chondrite meteorites probably originally formed in the interstellar medium and/or the solar protoplanetary disk, but was subsequently modified in the meteorites' asteroidal parent bodies. The mechanisms of formation and modification are still very poorly understood. We carried out a systematic study of variations in the mineralogy, petrology, and soluble and insoluble organic matter in distinct fragments of the Tagish Lake meteorite. The variations correlate with indicators of parent body aqueous alteration and at least some molecules of pre-biotic importance formed during the alteration.

  13. Origin and evolution of the layered deposits in the Valles Marineris, Mars

    NASA Technical Reports Server (NTRS)

    Nedell, Susan S.; Squyres, Steven W.; Andersen, David W.

    1987-01-01

    Four hypotheses are discussed concerning the origin of the layered deposits in the Martian Valles Marineris, whose individual thicknesses range from about 70 to 300 m. The hypothesized processes are: (1) aeolian deposition; (2) deposition of remnants of the material constituting the canyon walls; (3) deposition of volcanic eruptions; and (4) deposition in standing bodies of water. The last process is chosen as most consistent with the rhythm and lateral continuity of the layers, as well as their great thickness and stratigraphic relationship with other units in the canyons. Attention is given to ways in which the sediments could have entered an ice-covered lake; several geologically feasible mechanisms are identified.

  14. On the chronology of lunar origin and evolution. Implications for Earth, Mars and the Solar System as a whole

    NASA Astrophysics Data System (ADS)

    Geiss, Johannes; Rossi, Angelo Pio

    2013-11-01

    An origin of the Moon by a Giant Impact is presently the most widely accepted theory of lunar origin. It is consistent with the major lunar observations: its exceptionally large size relative to the host planet, the high angular momentum of the Earth-Moon system, the extreme depletion of volatile elements, and the delayed accretion, quickly followed by the formation of a global crust and mantle. According to this theory, an impact on Earth of a Mars-sized body set the initial conditions for the formation and evolution of the Moon. The impact produced a protolunar cloud. Fast accretion of the Moon from the dense cloud ensured an effective transformation of gravitational energy into heat and widespread melting. A "Magma Ocean" of global dimensions formed, and upon cooling, an anorthositic crust and a mafic mantle were created by gravitational separation. Several 100 million years after lunar accretion, long-lived isotopes of K, U and Th had produced enough additional heat for inducing partial melting in the mantle; lava extruded into large basins and solidified as titanium-rich mare basalt. This delayed era of extrusive rock formation began about 3.9 Ga ago and may have lasted nearly 3 Ga. A relative crater count timescale was established and calibrated by radiometric dating (i.e., dating by use of radioactive decay) of rocks returned from six Apollo landing regions and three Luna landing spots. Fairly well calibrated are the periods ≈4 Ga to ≈3 Ga BP (before present) and ≈0.8 Ga BP to the present. Crater counting and orbital chemistry (derived from remote sensing in spectral domains ranging from γ- and x-rays to the infrared) have identified mare basalt surfaces in the Oceanus Procellarum that appear to be nearly as young as 1 Ga. Samples returned from this area are needed for narrowing the gap of 2 Ga in the calibrated timescale. The lunar timescale is not only used for reconstructing lunar evolution, but it serves also as a standard for chronologies of the

  15. Theory and modeling of microstructural evolution in polycrystalline materials: Solute segregation, grain growth and phase transformations

    NASA Astrophysics Data System (ADS)

    Ma, Ning

    2005-11-01

    To accurately predict microstructure evolution and, hence, to synthesis metal and ceramic alloys with desirable properties involves many fundamental as well as practical issues. In the present study, novel theoretical and phase field approaches have been developed to address some of these issues including solute drag and segregation transition at grain boundaries and dislocations, grain growth in systems of anisotropic boundary properties, and precipitate microstructure development in polycrystalline materials. The segregation model has allowed for the prediction of a first-order segregation transition, which could be related to the sharp transition of solute concentration of grain boundary as a function of temperature. The incorporating of interfacial energy and mobility as functions of misorientation and inclination in the phase field model has allowed for the study of concurrent grain growth and texture evolution. The simulation results were analyzed using the concept of local grain boundary energy density, which simplified significantly the development of governing equations for texture controlled grain growth in Ti-6Al-4V. Quantitative phase field modeling techniques have been developed by incorporating thermodynamic and diffusivity databases. The models have been validated against DICTRA simulations in simple 1D problems and applied to simulate realistic microstructural evolutions in Ti-6Al-4V, including grain boundary a and globular a growth and sideplate development under both isothermal aging and continuous cooling conditions. The simulation predictions agree well with experimental observations.

  16. The origin, evolution, and trajectory of large dust storms on Mars during Mars years 24-30 (1999-2011)

    NASA Astrophysics Data System (ADS)

    Wang, Huiqun; Richardson, Mark I.

    2015-05-01

    Mars Daily Global Maps (MDGM) derived from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) and Mars Reconnaissance Orbiter (MRO) Mars Color Imager (MARCI) are used to study the distribution and evolution of large dust storms over the period from Mars years 24-30 (1999-2001). Large storms are defined here as discrete dust events visible in image sequences extending over at least 5 sols (Mars days) and where the dust covers areas beyond the origination region. A total of 65 large dust storms meeting these criteria are identified during the observational period and all are observed during the Ls = 135-30° seasonal window. Dust storms originating in the northern and southern hemispheres appear to form two distinct families. All but two of the storms originating in the northern hemisphere are observed in two seasonal windows at Ls = 180-240° and Ls = 305-350°; while all but two of those originating in the southern hemisphere are observed during Ls = 135-245°. None of the large dust storms originating in the northern hemisphere are observed to develop to global scale, but some of them develop into large regional storms with peak area >1 × 107 km2 and duration on the order of several weeks. In comparison, large dust storms originating in the southern hemisphere are typically much smaller, except notably in the two cases that expanded to global scale (the 2001 and 2007 global storms). Distinct locations of preferred storm origination emerge from the dust storm image sequences, including Acidalia, Utopia, Arcadia and Hellas. A route (trajectory) 'graph' for the observed sequences is provided. The routes are highly asymmetric between the two hemispheres. In the south, for non-global dust storms, the main routes are primarily oriented eastwest, whereas in the north, the routes are primarily north-south and zonally-concentrated into meridional channels. In a few impressive cases, storms originating in the northern hemisphere are observed to "flush" through

  17. Conservation and canalization of gene expression during angiosperm diversification accompany the origin and evolution of the flower.

    PubMed

    Chanderbali, André S; Yoo, Mi-Jeong; Zahn, Laura M; Brockington, Samuel F; Wall, P Kerr; Gitzendanner, Matthew A; Albert, Victor A; Leebens-Mack, James; Altman, Naomi S; Ma, Hong; dePamphilis, Claude W; Soltis, Douglas E; Soltis, Pamela S

    2010-12-28

    The origin and rapid diversification of the angiosperms (Darwin's "Abominable Mystery") has engaged generations of researchers. Here, we examine the floral genetic programs of phylogenetically pivotal angiosperms (water lily, avocado, California poppy, and Arabidopsis) and a nonflowering seed plant (a cycad) to obtain insight into the origin and subsequent evolution of the flower. Transcriptional cascades with broadly overlapping spatial domains, resembling the hypothesized ancestral gymnosperm program, are deployed across morphologically intergrading organs in water lily and avocado flowers. In contrast, spatially discrete transcriptional programs in distinct floral organs characterize the more recently derived angiosperm lineages represented by California poppy and Arabidopsis. Deep evolutionary conservation in the genetic programs of putatively homologous floral organs traces to those operating in gymnosperm reproductive cones. Female gymnosperm cones and angiosperm carpels share conserved genetic features, which may be associated with the ovule developmental program common to both organs. However, male gymnosperm cones share genetic features with both perianth (sterile attractive and protective) organs and stamens, supporting the evolutionary origin of the floral perianth from the male genetic program of seed plants. PMID:21149731

  18. Conservation and canalization of gene expression during angiosperm diversification accompany the origin and evolution of the flower

    PubMed Central

    Chanderbali, André S.; Yoo, Mi-Jeong; Zahn, Laura M.; Brockington, Samuel F.; Wall, P. Kerr; Gitzendanner, Matthew A.; Albert, Victor A.; Leebens-Mack, James; Altman, Naomi S.; Ma, Hong; dePamphilis, Claude W.; Soltis, Douglas E.; Soltis, Pamela S.

    2010-01-01

    The origin and rapid diversification of the angiosperms (Darwin's “Abominable Mystery”) has engaged generations of researchers. Here, we examine the floral genetic programs of phylogenetically pivotal angiosperms (water lily, avocado, California poppy, and Arabidopsis) and a nonflowering seed plant (a cycad) to obtain insight into the origin and subsequent evolution of the flower. Transcriptional cascades with broadly overlapping spatial domains, resembling the hypothesized ancestral gymnosperm program, are deployed across morphologically intergrading organs in water lily and avocado flowers. In contrast, spatially discrete transcriptional programs in distinct floral organs characterize the more recently derived angiosperm lineages represented by California poppy and Arabidopsis. Deep evolutionary conservation in the genetic programs of putatively homologous floral organs traces to those operating in gymnosperm reproductive cones. Female gymnosperm cones and angiosperm carpels share conserved genetic features, which may be associated with the ovule developmental program common to both organs. However, male gymnosperm cones share genetic features with both perianth (sterile attractive and protective) organs and stamens, supporting the evolutionary origin of the floral perianth from the male genetic program of seed plants. PMID:21149731

  19. Shared origins of a key enzyme during the evolution of C4 and CAM metabolism

    PubMed Central

    Christin, Pascal-Antoine; Arakaki, Monica; Osborne, Colin P.; Bräutigam, Andrea; Sage, Rowan F.; Hibberd, Julian M.; Kelly, Steven; Covshoff, Sarah; Wong, Gane Ka-Shu; Hancock, Lillian; Edwards, Erika J.

    2014-01-01

    CAM and C4 photosynthesis are two key plant adaptations that have evolved independently multiple times, and are especially prevalent in particular groups of plants, including the Caryophyllales. We investigate the origin of photosynthetic PEPC, a key enzyme of both the CAM and C4 pathways. We combine phylogenetic analyses of genes encoding PEPC with analyses of RNA sequence data of Portulaca, the only plants known to perform both CAM and C4 photosynthesis. Three distinct gene lineages encoding PEPC exist in eudicots (namely ppc-1E1, ppc-1E2 and ppc-2), one of which (ppc-1E1) was recurrently recruited for use in both CAM and C4 photosynthesis within the Caryophyllales. This gene is present in multiple copies in the cacti and relatives, including Portulaca. The PEPC involved in the CAM and C4 cycles of Portulaca are encoded by closely related yet distinct genes. The CAM-specific gene is similar to genes from related CAM taxa, suggesting that CAM has evolved before C4 in these species. The similar origin of PEPC and other genes involved in the CAM and C4 cycles highlights the shared early steps of evolutionary trajectories towards CAM and C4, which probably diverged irreversibly only during the optimization of CAM and C4 phenotypes. PMID:24638902

  20. Pelvis of Gargoyleosaurus (Dinosauria: Ankylosauria) and the Origin and Evolution of the Ankylosaur Pelvis

    PubMed Central

    Carpenter, Kenneth; DiCroce, Tony; Kinneer, Billy; Simon, Robert

    2013-01-01

    Discovery of a pelvis attributed to the Late Jurassic armor-plated dinosaur Gargoyleosaurus sheds new light on the origin of the peculiar non-vertical, broad, flaring pelvis of ankylosaurs. It further substantiates separation of the two ankylosaurs from the Morrison Formation of the western United States, Gargoyleosaurus and Mymoorapelta. Although horizontally oriented and lacking the medial curve of the preacetabular process seen in Mymoorapelta, the new ilium shows little of the lateral flaring seen in the pelvis of Cretaceous ankylosaurs. Comparison with the basal thyreophoran Scelidosaurus demonstrates that the ilium in ankylosaurs did not develop entirely by lateral rotation as is commonly believed. Rather, the preacetabular process rotated medially and ventrally and the postacetabular process rotated in opposition, i.e., lateral and ventrally. Thus, the dorsal surfaces of the preacetabular and postacetabular processes are not homologous. In contrast, a series of juvenile Stegosaurus ilia show that the postacetabular process rotated dorsally ontogenetically. Thus, the pelvis of the two major types of Thyreophora most likely developed independently. Examination of other ornithischians show that a non-vertical ilium had developed independently in several different lineages, including ceratopsids, pachycephalosaurs, and iguanodonts. Therefore, a separate origin for the non-vertical ilium in stegosaurs and ankylosaurs does have precedent. PMID:24244573

  1. The Distribution of Antarctic Subglacial Lake Environments With Implications for Their Origin and Evolution

    NASA Astrophysics Data System (ADS)

    Blankenship, D. D.; Young, D. A.; Carter, S. P.

    2006-12-01

    Ice-penetrating radar records across the Antarctic Ice Sheet show regions with strong flat mirror-like reflections from the subglacial interface that are interpreted to be from subglacial lakes. The majority of subglacial lakes are found in East Antarctica, primarily in topographically low areas of basins beneath the thick ice divides. Occasionally lakes are observed "perched" at higher elevations within local depressions of rough morphological regions. In addition, a correlation between the "onset" of enhanced glacial flow and subglacial lakes was identified. The greatest concentration of known lakes was found in the vicinity of Dome C. A second grouping of lakes lying near Ridge B includes Lake Vostok and several smaller lakes. Subglacial lakes were also discovered near the South Pole, within eastern Wilkes Land, west of the Transantarctic Mountains, and within West Antarctica's Whitmore Mountains. Aside from Lake Vostok, typical lengths of subglacial lakes were found to range from a few to about 20 kilometers. A recent inventory includes 145 subglacial lakes. Approximately 81% of detected lakes lie at elevations less than a few hundred meters above sea level while the majority of the remaining lakes are "perched" at higher elevations. We present the locations from the subglacial lake inventory on local "ice divides" calculated from the satellite derived surface elevations with and find the distance of each lake from these divides. Most significantly, we found that 66% of the lakes identified lie within 50 km of a local ice divide and 88% lie within 100 km of a local divide. In particular, note that lakes located far from the Dome C/Ridge B cluster and even those associated with very narrow catchments lie either on or within a few tens of kilometers of the local divide marked by the catchment boundary. The distance correlation of subglacial lakes with local ice divides leads to a fundamental question for the evolution of subglacial lake environments: Does the

  2. Compositional heterogeneity of lunar impact melts: Issues of origin and evolution

    NASA Astrophysics Data System (ADS)

    Dhingra, Deepak; Pieters, Carle

    2012-07-01

    Impact melt formation and emplacement occurs in a dynamically active environment during the excavation and modification stages of the cratering process [1]. They are typically very mobile and as a result occur in a variety of geographical settings including crater floor, walls, rim and beyond. Diverse morphologies of impact melts on the Moon have been well documented [e.g. 2, 3, 4]. Little attention however, has been given to their compositional nature [e.g. 5, 6]. Impact melts occur in diverse geological settings and display wide variability in their volume, liquid to clast ratio and degrees of crystallinity. All these factors affect their physical and chemical attributes. It is therefore necessary to study the compositional nature of impact melts in order to understand their evolution. We have initiated a global remote sensing survey of impact melts on the Moon integrating their compositional character with morphology to understand their evolution. Our initial results suggest compositional heterogeneity in impact melts at various spatial scales [7]. However, it is yet to be understood if the variation is caused by unmelted clast component, the melted target or both. Inefficient mixing of impact melts has been noted at terrestrial impact craters [8] and might be responsible for the heterogeneous composition of impact melts. We are exploring the role of these factors in different environments. In this context, craters with both homogeneous and heterogeneous targets have been selected. Data from Moon Mineralogy Mapper (M3) have been integrated with Kaguya Terrain Camera (TC) and Lunar Reconnaissance Orbiter Narrow Angle Camera (NAC). The integration of these new datasets will enable detailed study of impact melts. Acknowledgment: This research is supported by NLSI grant no. NNA09DB34A References: [1] Grieve R.A.F. et al. (1977) Impact and Expl. Cratering, Eds. D.J. Roddy et al., Pergamon Press, 791-814 [2] Howard and Wilshire (1975) J. Res. U.S. Geol. Surv., 3, 237

  3. The cratering record at Uranus: Implications for satellite evolution and the origin of impacting objects

    NASA Technical Reports Server (NTRS)

    Strom, Robert G.

    1987-01-01

    The crater size/frequency distributions on the major Uranian satellites show two distinctly different crater populations of different ages. Any hypothesis on the origin of the objects responsible for the period of heavy bombardment must account for the occurrence of different crater populations (size/frequency distributions) in different parts of the solar system. A computerized simulation using short-period comet impact velocities and a modified Holsapple-Schmidt crater scaling law was used to recover the size distribution of cometary nuclei from the observed cratering record. The most likely explanation for the cratering record is that the period of heavy bombardment was caused by different families of accretional remnants indigenous to the system in which the different crater populations occurred.

  4. High-3He plume origin and temporal-spatial evolution of the Siberian flood basalts

    USGS Publications Warehouse

    Basu, A.R.; Poreda, R.J.; Renne, P.R.; Teichmann, F.; Vasiliev, Y.R.; Sobolev, N.V.; Turrin, B.D.

    1995-01-01

    An olivine nephelinite from the lower part of a thick alkalic ultrabasic and mafic sequence of volcanic rocks of the northeastern part of the Siberian flood basalt province (SFBP) yielded a 40ArX39Ar plateau age of 253.3 ?? 2.6 million years, distinctly older than the main tholeiitic pulse of the SFBP at 250.0 million years. Olivine phenocrysts of this rock showed 3He/4He ratios up to 12.7 times the atmospheric ratio; these values suggest a lower mantle plume origin. The neodymium and strontium isotopes, rare earth element concentration patterns, and cerium/lead ratios of the associated rocks were also consistent with their derivation from a near-cnondritic, primitive plume. Geochemical data from the 250-million-year-old volcanic rocks higher up in the sequence indicate interaction of this high-3He SFBP plume with a suboceanic-type upper mantle beneath Siberia.

  5. Origins of Life and the RNA World: Evolution of RNA-Replicase Recognition

    NASA Astrophysics Data System (ADS)

    Guogas, Laura; Hogle, James; Gehrke, Lee

    2004-06-01

    Central to understanding the origin of life is the elucidation of the first replication mechanism. The RNA World hypothesis suggests that the first self-replicating molecules were RNAs and that DNA later superceded RNA as the genetic material. RNA viruses were not subjected to the same evolutionary pressures as cellular organisms; consequently, they likely possess remnants of earlier replication strategies. Our laboratory investigates how members of the RNA virus family Bromoviridae can have structurally distinct 3' end tags yet are specifically recognized by conserved replication enzymes. This work addresses the idea that 3' tRNA tails were functionally replaced in some viruses by an RNA-protein complex. These viruses may serve as a timeline for the transition from the RNA world to DNA and protein based life.

  6. The evolution of blue-greens and the origins of chloroplasts

    NASA Technical Reports Server (NTRS)

    Schwartz, R. M.; Dayhoff, M. O.

    1981-01-01

    All of the available molecular data support the theory that the chloroplasts of eukaryote cells were originally free-living blue-greens. Of great interest is what the relationships are between contemporary types of blue-greens and eukaryote chloroplasts and whether the chloroplasts of the various eukaryotes are the result of one or more than one symbiosis. By combining information from phylogenetic trees based on cytochrome c6 and 2Fe-2S ferredoxin sequences, it is shown that the chloroplasts of a number of eukaryote algae as well as the protist Euglena are polyphyletic; the chloroplasts of green algae and the higher plants may be the result of a single symbiosis.

  7. Mosaic nature of the mitochondrial proteome: Implications for the origin and evolution of mitochondria.

    PubMed

    Gray, Michael W

    2015-08-18

    Comparative studies of the mitochondrial proteome have identified a conserved core of proteins descended from the α-proteobacterial endosymbiont that gave rise to the mitochondrion and was the source of the mitochondrial genome in contemporary eukaryotes. A surprising result of phylogenetic analyses is the relatively small proportion (10-20%) of the mitochondrial proteome displaying a clear α-proteobacterial ancestry. A large fraction of mitochondrial proteins typically has detectable homologs only in other eukaryotes and is presumed to represent proteins that emerged specifically within eukaryotes. A further significant fraction of the mitochondrial proteome consists of proteins with homologs in prokaryotes, but without a robust phylogenetic signal affiliating them with specific prokaryotic lineages. The presumptive evolutionary source of these proteins is quite different in contending models of mitochondrial origin. PMID:25848019

  8. Evolution in situ: hybrid origin and establishment of willows (Salix L.) on alpine glacier forefields

    PubMed Central

    Gramlich, S; Sagmeister, P; Dullinger, S; Hadacek, F; Hörandl, E

    2016-01-01

    Little attention has been paid to the evolutionary consequences of the colonizing dynamics and succession processes following glacier retreat. Here we studied hybrid populations that have recently formed and established on glacier forefields of the European Alps owing to secondary contact of a lowland colonizer with a subalpine species. We analyzed the composition of two hybrid populations between Salix purpurea and Salix helvetica with nine microsatellite markers by using Bayesian methods (structure and NewHybrids), and simulations. We also studied niche differentiation between the hybrids and the parental species based on indicator values, soil pH and water retention potential measurements. Allelic structure of hybrids confirms the assumed parentage and in situ origin of the crosses on two independent sites within the last decades. Both hybrid populations comprised F1 and later generation hybrids (F2 and backcrosses), confirming hybrid fertility. The parental species showed significant differences in niche characteristics for temperature, soil pH, nutrients and moisture. Remarkably, the hybrids exhibited a higher tolerance to cold temperatures, nutrient-poor and acidic soils than either parent. Our results show that willow hybrids originated after glacier retreat and have established persistent populations within a few decades. One factor contributing to hybrid establishment in sympatry with their parents is their ability to occupy more extreme niches than either parental species within a mosaic-like pattern of microhabitats on the forefield. Introgression and/or transgressive segregation may have resulted in novel genotypes that are able to expand the ecological spectrum of either parent. PMID:26980342

  9. On the origin and evolution of electrical signals during frictional stick slip in sheared granular material

    NASA Astrophysics Data System (ADS)

    Leeman, J. R.; Scuderi, M. M.; Marone, C.; Saffer, D. M.; Shinbrot, T.

    2014-05-01

    Electromagnetic signals have been reported in association with geophysical phenomena including earthquakes, landslides, and volcanic events. Mechanisms that suggested to explain seismoelectrical signals include triboelectricity, piezoelectricity, streaming potentials, and the migration of electron holes, yet the origin of such phenomena remains poorly understood. We present results from laboratory experiments regarding the relationship between electrical and mechanical signals for frictional stick-slip events in sheared soda-lime glass bead layers. The results are interpreted in the context of lattice defect migration and granular force chain mechanics. During stick-slip events, we observe two distinct behaviors delineated by the attainment of a frictional stick-slip steady state. During initial shear loading, layers charge during stick-slip events and the potential of the system rises. After steady state stick-slip behavior is attained, the system begins to discharge. Coseismic signals are characterized by potential drops superimposed on a longer-term trend. We suggest that the observed signal is a convolution of two effects: charging of the forcing blocks and signals associated with the stress state of the material. The long-term charging of the blocks is accomplished by grain boundary movement during the initial establishment of force chain networks. Short-term signals associated with stick-slip events may originate from produced electron holes. Applied to tectonic faults, our results suggest that electrical signals generated during frictional failure may provide a way to monitor stress and the onset of earthquake rupture. Potential changes could produce detectable signals that may forecast the early stages of failure, providing a modest warning of the event.

  10. A phylogenetic approach to study the origin and evolution of the CRINKLY4 family.

    PubMed

    Nikonorova, Natalia; Vu, Lam D; Czyzewicz, Nathan; Gevaert, Kris; De Smet, Ive

    2015-01-01

    Cell-cell communication plays a crucial role in plant growth and development and relies to a large extent on peptide ligand-receptor kinase signaling mechanisms. The CRINKLY4 (CR4) family of receptor-like kinases is involved in a wide range of developmental processes in plants, including mediating columella stem cell identity and differentiation in the Arabidopsis thaliana root tip. Members of the CR4 family contain a signal peptide, an extracellular part, a single-pass transmembrane helix and an intracellular cytoplasmic protein kinase domain. The main distinguishing features of the family are the presence of seven "crinkly" repeats and a TUMOR NECROSIS FACTOR RECEPTOR (TNFR)-like domain in the extracellular part. Here, we investigated the evolutionary origin of the CR4 family and explored to what extent members of this family are conserved throughout the green lineage. We identified members of the CR4 family in various dicots and monocots, and also in the lycophyte Selaginella moellendorffii and the bryophyte Physcomitrella patens. In addition, we attempted to gain insight in the evolutionary origin of different CR4-specific domains, and we could detect "crinkly" repeat containing proteins already in single celled algae. Finally, we related the presence of likely functional CR4 orthologs to its best described signaling module comprising CLAVATA3/EMBRYO SURROUNDING REGION-RELATED 40 (CLE40), WUSCHEL RELATED HOMEOBOX 5 (WOX5), CLAVATA 1 (CLV1), and ARABIDOPSIS CR4 (ACR4), and established that this module likely is already present in bryophytes and lycophytes. PMID:26557128

  11. A phylogenetic approach to study the origin and evolution of the CRINKLY4 family

    PubMed Central

    Nikonorova, Natalia; Vu, Lam D.; Czyzewicz, Nathan; Gevaert, Kris; De Smet, Ive

    2015-01-01

    Cell–cell communication plays a crucial role in plant growth and development and relies to a large extent on peptide ligand–receptor kinase signaling mechanisms. The CRINKLY4 (CR4) family of receptor-like kinases is involved in a wide range of developmental processes in plants, including mediating columella stem cell identity and differentiation in the Arabidopsis thaliana root tip. Members of the CR4 family contain a signal peptide, an extracellular part, a single-pass transmembrane helix and an intracellular cytoplasmic protein kinase domain. The main distinguishing features of the family are the presence of seven “crinkly” repeats and a TUMOR NECROSIS FACTOR RECEPTOR (TNFR)-like domain in the extracellular part. Here, we investigated the evolutionary origin of the CR4 family and explored to what extent members of this family are conserved throughout the green lineage. We identified members of the CR4 family in various dicots and monocots, and also in the lycophyte Selaginella moellendorffii and the bryophyte Physcomitrella patens. In addition, we attempted to gain insight in the evolutionary origin of different CR4-specific domains, and we could detect “crinkly” repeat containing proteins already in single celled algae. Finally, we related the presence of likely functional CR4 orthologs to its best described signaling module comprising CLAVATA3/EMBRYO SURROUNDING REGION-RELATED 40 (CLE40), WUSCHEL RELATED HOMEOBOX 5 (WOX5), CLAVATA 1 (CLV1), and ARABIDOPSIS CR4 (ACR4), and established that this module likely is already present in bryophytes and lycophytes. PMID:26557128

  12. Gene flow and biological conflict systems in the origin and evolution of eukaryotes.

    PubMed

    Aravind, L; Anantharaman, Vivek; Zhang, Dapeng; de Souza, Robson F; Iyer, Lakshminarayan M

    2012-01-01

    The endosymbiotic origin of eukaryotes brought together two disparate genomes in the cell. Additionally, eukaryotic natural history has included other endosymbiotic events, phagotrophic consumption of organisms, and intimate interactions with viruses and endoparasites. These phenomena facilitated large-scale lateral gene transfer and biological conflicts. We synthesize information from nearly two decades of genomics to illustrate how the interplay between lateral gene transfer and biological conflicts has impacted the emergence of new adaptations in eukaryotes. Using apicomplexans as example, we illustrate how lateral transfer from animals has contributed to unique parasite-host interfaces comprised of adhesion- and O-linked glycosylation-related domains. Adaptations, emerging due to intense selection for diversity in the molecular participants in organismal and genomic conflicts, being dispersed by lateral transfer, were subsequently exapted for eukaryote-specific innovations. We illustrate this using examples relating to eukaryotic chromatin, RNAi and RNA-processing systems, signaling pathways, apoptosis and immunity. We highlight the major contributions from catalytic domains of bacterial toxin systems to the origin of signaling enzymes (e.g., ADP-ribosylation and small molecule messenger synthesis), mutagenic enzymes for immune receptor diversification and RNA-processing. Similarly, we discuss contributions of bacterial antibiotic/siderophore synthesis systems and intra-genomic and intra-cellular selfish elements (e.g., restriction-modification, mobile elements and lysogenic phages) in the emergence of chromatin remodeling/modifying enzymes and RNA-based regulation. We develop the concept that biological conflict systems served as evolutionary "nurseries" for innovations in the protein world, which were delivered to eukaryotes via lateral gene flow to spur key evolutionary innovations all the way from nucleogenesis to lineage-specific adaptations. PMID:22919680

  13. Evolution in situ: hybrid origin and establishment of willows (Salix L.) on alpine glacier forefields.

    PubMed

    Gramlich, S; Sagmeister, P; Dullinger, S; Hadacek, F; Hörandl, E

    2016-06-01

    Little attention has been paid to the evolutionary consequences of the colonizing dynamics and succession processes following glacier retreat. Here we studied hybrid populations that have recently formed and established on glacier forefields of the European Alps owing to secondary contact of a lowland colonizer with a subalpine species. We analyzed the composition of two hybrid populations between Salix purpurea and Salix helvetica with nine microsatellite markers by using Bayesian methods (structure and NewHybrids), and simulations. We also studied niche differentiation between the hybrids and the parental species based on indicator values, soil pH and water retention potential measurements. Allelic structure of hybrids confirms the assumed parentage and in situ origin of the crosses on two independent sites within the last decades. Both hybrid populations comprised F1 and later generation hybrids (F2 and backcrosses), confirming hybrid fertility. The parental species showed significant differences in niche characteristics for temperature, soil pH, nutrients and moisture. Remarkably, the hybrids exhibited a higher tolerance to cold temperatures, nutrient-poor and acidic soils than either parent. Our results show that willow hybrids originated after glacier retreat and have established persistent populations within a few decades. One factor contributing to hybrid establishment in sympatry with their parents is their ability to occupy more extreme niches than either parental species within a mosaic-like pattern of microhabitats on the forefield. Introgression and/or transgressive segregation may have resulted in novel genotypes that are able to expand the ecological spectrum of either parent. PMID:26980342

  14. Origin and evolution of organisms as deduced from 5S ribosomal RNA sequences.

    PubMed

    Hori, H; Osawa, S

    1987-09-01

    A phylogenetic tree of most of the major groups of organisms has been constructed from the 352 5S ribosomal RNA sequences now available. The tree suggests that there are several major groups of eubacteria that diverged during the early stages of their evolution. Metabacteria (= archaebacteria) and eukaryotes separated after the emergence of eubacteria. Among eukaryotes, red algae emerged first; and, later, thraustochytrids (a Proctista group), ascomycetes (yeast), green plants (green algae and land plants), "yellow algae" (brown algae, diatoms, and chrysophyte algae), basidiomycetes (mushrooms and rusts), slime- and water molds, various protozoans, and animals emerged, approximately in that order. Three major types of photosynthetic eukaryotes--i.e., red algae (= Chlorophyll a group), green plants (Chl. a + b group) and yellow algae (Chl. a + c)--are remotely related to one another. Other photosynthetic unicellular protozoans--such as Cyanophora (Chl. a), Euglenophyta (Chl. a + b), Cryptophyta (Chl. a + c), and Dinophyta (Chl. a + c)--seem to have separated shortly after the emergence of the yellow algae. PMID:2452957

  15. Origin, dynamics and evolution of ocean garbage patches from observed surface drifters

    NASA Astrophysics Data System (ADS)

    van Sebille, Erik; England, Matthew H.; Froyland, Gary

    2012-12-01

    Much of the debris in the near-surface ocean collects in so-called garbage patches where, due to convergence of the surface flow, the debris is trapped for decades to millennia. Until now, studies modelling the pathways of surface marine debris have not included release from coasts or factored in the possibilities that release concentrations vary with region or that pathways may include seasonal cycles. Here, we use observational data from the Global Drifter Program in a particle-trajectory tracer approach that includes the seasonal cycle to study the fate of marine debris in the open ocean from coastal regions around the world on interannual to centennial timescales. We find that six major garbage patches emerge, one in each of the five subtropical basins and one previously unreported patch in the Barents Sea. The evolution of each of the six patches is markedly different. With the exception of the North Pacific, all patches are much more dispersive than expected from linear ocean circulation theory, suggesting that on centennial timescales the different basins are much better connected than previously thought and that inter-ocean exchanges play a large role in the spreading of marine debris. This study suggests that, over multi-millennial timescales, a significant amount of the debris released outside of the North Atlantic will eventually end up in the North Pacific patch, the main attractor of global marine debris.

  16. Uricoteley:its nature and origin during the evolution of tetrapod vertebrates.

    PubMed

    Campbell, J W; Vorhaben, J E; Smith, D D

    1987-09-01

    The hepatic mechanism for detoxication of ammonia formed during amino acid gluconeogenesis in uricotelic vertebrates requires the intramitochondrial synthesis of glutamine by glutamine synthetase. This glutamine then serves as a precursor of uric acid in the cytosol. The evolutionary development of uricoteley thus required the localization of glutamine synthetase in liver mitochondria. The mechanism for the mitochondrial import of glutamine synthetase in uricotelic vertebrate liver is not yet known. Tortoises, extant relatives of the stem reptiles, possess both the ureotelic and uricotelic hepatic systems. It therefore seems likely that the genetic events allowing the mitochondrial localization of glutamine synthetase in liver occurred in the amniote amphibian ancestors of the stem reptiles. The selection of ureoteley by the theropsids and of uricoteley by the sauropsids were major events in the divergence and subsequent evolution of these two lines. Once established in the sauropsid line, uricoteley has persisted through to the higher reptiles, crocodilians, and birds. Uricoteley was in part responsible for the radiation of the archosaurs during the Triassic as a water-conserving mechanism in the adult, thereby allowing them to invade the arid environments of that period. Contrary to dogma, uricoteley was probably of minor significance in the development of the cleidoic egg. Neither mammalian nor avian embryonic liver tissues catabolize amino acids to any great extent, so it is inappropriate to attribute to them a kind of "waste" nitrogen metabolism. PMID:2890702

  17. On the origin, evolution, and nature of programmed cell death: a timeline of four billion years.

    PubMed

    Ameisen, J C

    2002-04-01

    Programmed cell death is a genetically regulated process of cell suicide that is central to the development, homeostasis and integrity of multicellular organisms. Conversely, the dysregulation of mechanisms controlling cell suicide plays a role in the pathogenesis of a wide range of diseases. While great progress has been achieved in the unveiling of the molecular mechanisms of programmed cell death, a new level of complexity, with important therapeutic implications, has begun to emerge, suggesting (i) that several different self-destruction pathways may exist and operate in parallel in our cells, and (ii) that molecular effectors of cell suicide may also perform other functions unrelated to cell death induction and crucial to cell survival. In this review, I will argue that this new level of complexity, implying that there may be no such thing as a 'bona fide' genetic death program in our cells, might be better understood when considered in an evolutionary context. And a new view of the regulated cell suicide pathways emerges when one attempts to ask the question of when and how they may have become selected during evolution, at the level of ancestral single-celled organisms. PMID:11965491

  18. Insight into the evolution and origin of leprosy bacilli from the genome sequence of Mycobacterium lepromatosis

    PubMed Central

    Singh, Pushpendra; Benjak, Andrej; Schuenemann, Verena J.; Herbig, Alexander; Avanzi, Charlotte; Busso, Philippe; Nieselt, Kay; Krause, Johannes; Vera-Cabrera, Lucio; Cole, Stewart T.

    2015-01-01

    Mycobacterium lepromatosis is an uncultured human pathogen associated with diffuse lepromatous leprosy and a reactional state known as Lucio's phenomenon. By using deep sequencing with and without DNA enrichment, we obtained the near-complete genome sequence of M. lepromatosis present in a skin biopsy from a Mexican patient, and compared it with that of Mycobacterium leprae, which has undergone extensive reductive evolution. The genomes display extensive synteny and are similar in size (∼3.27 Mb). Protein-coding genes