Science.gov

Sample records for ar structural evolution

  1. Evolution of the northern Sierra Nevada metamorphic belt: Petrological, structural, and Ar/Ar constraints

    SciTech Connect

    Hacker, B.R.

    1993-05-01

    The Sierra Nevada metamorphic belt constitutes an important record of the growth of continental crust from essentially oceanic materials. In the northern Sierra, the central part of the belt is made up of volcanoplutonic arcs and sediment-dominated units inferred to be accretionary wedges or closed ocean basins. The latter are broken formation and melange composed of radiolarian chert, lava, and volcanogenic and continental turbidites. Sedimentary detritus in the largest of these units can be plausibly linked to sources farther east in the Sierra, suggesting that deposition occurred near the eastern Sierran arc. Isoclinal folds, steeply dipping foliations, and steeply plunging down-dip lineations are characteristics structures. The westernmost unit is only feebly recrystallized, and deformation was accomplished principally by stress solution and local redeposition in veins. More easterly, inboard units are compositionally similar, but they recrystallized at pumpellyite-actinolite-and blueschist-facies conditions and deformed via solution-transfer and dislocation creep. Phengite silica contents, the degree of quartz veining, and the locations of pseudo-isograds support an eastward increase in metamorphic pressure and temperature. Metamorphic conditions during the growth of pumpellyite and actinolite ranged from {approximately}150-350 {degrees}C and 200-400 MPa, compatible with recrystallization and deformation in subduction zones or the deeper levels of magmatic arcs. Ar/Ar ages of volcanisclastic rocks and crosscutting plutons constrain the age of deformation and metamorphism in the western part of the region to 174-165 Ma. Deformation and recrystallization in more easterly units may have been coeval or begun as early as Triassic time. 58 refs., 14 figs., 4 tabs.

  2. Morpho-structural evolution of the Cordón Caulle geothermal region, Southern Volcanic Zone, Chile: Insights from gravity and 40Ar / 39Ar dating

    NASA Astrophysics Data System (ADS)

    Sepúlveda, Fabián; Lahsen, Alfredo; Bonvalot, Sylvain; Cembrano, José; Alvarado, Antonia; Letelier, Pablo

    2005-10-01

    the intra-arc zone. A 5.44 ± 0.04 Ma old granodiorite intrusion bracketed by two sub-parallel branches of the regional, margin-parallel Liquiñe-Ofqui Fault Zone (LOFZ) in a prominent pop-up structure, 15 km to the east of Cordón Caulle, accounts for reverse reactivation of the LOFZ and rapid fault-related exhumation of basement rocks (> 1 mm/year). We argue that under compression, reverse reactivation of the LOFZ was facilitated by the combined effect of cyclic increase in fluid pressure induced by magmatic-hydrothermal input, and removal of lithostatic load induced by glacial erosion (> 1.5 mm/year in the vicinity of Cordón Caulle).

  3. 40Ar/ 39Ar mineral age constraints for the tectonothermal evolution of a Variscan suture in southwest Iberia

    NASA Astrophysics Data System (ADS)

    Dallmeyer, R. D.; Fonseca, P. E.; Quesada, C.; Ribeiro, A.

    1993-06-01

    Dallmeyer, R.D., Fonseca, P.E., Quesada, C. and Ribeiro, A., 1993. 40Ar/ 39Ar mineral age constraints for the tectonothermal evolution of a Variscan suture in southwest Iberia. Tectonophysics, 222: 177-194. Mafic units interpreted to represent an internally disrupted ophiolite succession are exposed along a Variscan suture situated between the South Portuguese and Ossa-Morena zones in southern Iberia. Structural characteristics of various units adjacent to the suture zone suggest maintainence of an oblique (transpressional), sinistral tectonic regime during late Paleozoic plate convergence. This involved initial, limited, north-directed subduction beneath the Ossa-Morena zone, and was followed by oblique collision of the South Portuguese Terrane. Metamorphic evolution of rocks adjacent to the suture occurred during maintainence of a moderately high geothermal regime. Five samples of amphibolite were collected within the hanging wall of the suture. These included samples from the ophiolitic terrane and from the Ossa-Morena zone. Two samples were also collected within the post-kinematic Beja Gabbro which intruded the other two tectonic units following their structural juxtaposition and penetrative ductile deformation. Hornblende concentrates from these seven samples record well-defined 40Ar/ 39Ar plateau ages which range between c. 342 and 335 Ma. These results imply that the regional tectonostratigraphic units were maintained at moderate crustal levels until the Visean, and that their juxtaposition and internal ductile deformation occurred in the late Devonian. Subsequent cooling was probably effected by transpressional uplift during oblique collision following closure of intervening oceanic elements.

  4. Unveiling Turrialba (Costa Rica) volcano's latest geological evolution through new 40Ar/39Ar, ages

    NASA Astrophysics Data System (ADS)

    Ruiz Cubillo, P.; Turrin, B. D.; Soto, G. J.; Del Potro, R.; Gagnevin, D.; Gazel, E.; Mora Fernandez, M.; Carr, M. J.; Swisher, C. C.

    2010-12-01

    Step-heating 40Ar/39Ar dating experiments on whole rock matrix were performed on samples from eight key lava flow units from Turrialba, the easternmost volcano of the Central Volcanic Range of Costa Rica. Our results, together with available corrected 14C ages, recent mapping and new geochemical analyses, are part of a study to reconstruct Turrialba’s evolution. The project is being conducted as part of wider studies because of the increase in volcanic activity during the last three years. The geochemical compositions of the lava flow units span the range from basalts to dacites, and commonly have high K2O concentrations, making them good candidates for 40Ar/39Ar radiometric dating. The ages reported here correspond to the Paleo Turrialba (600-250 ka) and Neo Turrialba (< 250 ka) temporal stages. Sample TUR-38 (251 ± 4 ka) belongs to the latest unit of Paleo Turrialba stage, known as Finca Liebres volcano, while the remaining seven samples belong to Neo Turrialba: TUR-30 (99 ± 3 ka), TUR-19 (90 ± 4 ka), TUR-32 (62 ± 2 ka) TUR-33 (61 ± 2 ka), TUR-12 (25 ± 1.9 ka), TUR-36 (10 ± 3 ka) and TUR-08 (3 ± 3 ka). All the obtained ages in this study are in agreement with the local stratigraphy and prior 14C age determinations, adding robustness to our results. According to ages obtained and the areal distribution of the sampled units, the most important construction period of the massif was during the Neo-Turrialba stage which has passed through two important constructing episodes, around 100-60 ka and 10 ka-present. Although our results include some very young ages, all of them meet the established evaluation criteria used for plateau and isochron ages, commonly used for 40Ar/39Ar dating. Furthermore, we used a protocol that closely monitors the mass spectrometer mass discrimination during the measurements to provide additional control. Three of the eight 40Ar/39Ar ages reported here are remarkably young (25 ka or less). Two of those are the samples with the

  5. 40Ar/39Ar thermochronologic constraints on the tectonothermal evolution of the Northern East Humboldt range metamorphic core complex, Nevada

    USGS Publications Warehouse

    McGrew, A.J.; Snee, L.W.

    1994-01-01

    The northern East Humboldt Range (NEHR) of northeastern Nevada exposes a suite of complexly deformed migmatitic, upper amphibolite-facies rocks in the footwall of the Ruby Mountains-East Humboldt Range (RM-EHR) detachment fault. New 40Ar/39Ar data on hornblende, muscovite, biotite, and potassium feldspar help constrain the kinematic and thermal evolution of this terrain during Tertiary extensional exhumation. Hornblende samples from relatively high structural levels yield discordant age spectra that suggest initial cooling during early Tertiary time (63-49 Ma). When coupled with petrological constraints indicating a strongly decompressional P-T-t path above 550??C, the hornblende data suggest that exhumation of the RM-EHR may have initiated in early Tertiary time, approximately coincident with the initial phases of unroofing in the Wood Hills immediately to the east and with the end of thrusting in the late Mesozoic to early Tertiary Sevier orogenic belt of eastern Nevada and western Utah. This temporal coincidence suggests that gravitational collapse of tectonically thickened crust in the internal zone of the Sevier belt could have driven the initial phases of unroofing. Thermal history during the final stage of exhumation of the NEHR is constrained by discordant hornblende cooling ages of 36-29 Ma from deep structural levels and biotite, muscovite, and potassium feldspar cooling ages of 27-21 Ma from a range of structural levels. Comparison of muscovite, biotite, and potassium feldspar cooling ages with previously published fission-track cooling ages implies very rapid cooling rates at temperatures below the closure temperature for muscovite (270??-350??C), but time gaps of > 7 m.y. between hornblende and mica cooling ages suggest that cooling at higher temperatures was more gradual. In addition, comparison of 40Ar 39Ar mica cooling ages with previously published fission-track apatite cooling ages suggests pronounced thermal gradients between the NEHR and

  6. 40Ar/39Ar constraints on the temporal evolution of Graciosa Island, Azores (Portugal)

    NASA Astrophysics Data System (ADS)

    Larrea, Patricia; Wijbrans, Jan R.; Galé, Carlos; Ubide, Teresa; Lago, Marceliano; França, Zilda; Widom, Elisabeth

    2014-02-01

    Lava flows spanning the eruptive record of Graciosa Island (Azores archipelago) and a gabbro xenolith were dated by 40Ar/39Ar in order to constrain the Pleistocene and Holocene volcanic evolution of the island. The results range from 1.05 Ma to 3.9 ka, whereas prior published K-Ar and 14C ages range from 620 to 2 ka. The formation of the Serra das Fontes shield volcano started at minimum 1.05 Ma, and the magmatic system was active for ca. 600 ky, as suggested by the formation of the gabbro xenolith by magmatic differentiation. Evolved magmas making up the Serra das Fontes-Serra Branca composite volcano were generated at ca. 450 ka. After a period of ca. 110 ky of volcanic inactivity and erosion of volcanic edifices, volcanism was reactivated with the formation of the Vitória Unit NW platform. Later, the development of the Vulcão Central Unit started with the formation of monogenetic cones located to the south of the Serra das Fontes-Serra Branca-Vitória Unit. This volcanism became progressively more evolved and was concentrated in a main eruptive center, forming the Vulcão Central stratovolcano with an age older than 50 ka. The caldera related to this stratovolcano is older than 47 ka and was followed by effusion of basaltic magmas into the caldera, resulting in the formation of a lava lake, which ultimately spilled over the caldera rim at ca. 11 ka. The most recent eruptions on Graciosa formed two small pyroclastic cones within the caldera and the Pico do Timão cone within the Vitória Unit at ca 3.9 ka.

  7. Structural evolution

    SciTech Connect

    Burr, M.T.

    1993-03-01

    In this special report, financial executives discuss key trends in power project finance, new funding sources and evolving project structures. Industry wide, financial firms and developers are striving to improve the cost-effectiveness and efficiency of project financing, for projects in both greenfield development and the growing secondary market.

  8. Arsenic resistance strategy in Pantoea sp. IMH: Organization, function and evolution of ars genes

    PubMed Central

    Wang, Liying; Zhuang, Xuliang; Zhuang, Guoqiang; Jing, Chuanyong

    2016-01-01

    Pantoea sp. IMH is the only bacterium found in genus Pantoea with a high As resistance capacity, but its molecular mechanism is unknown. Herein, the organization, function, and evolution of ars genes in IMH are studied starting with analysis of the whole genome. Two ars systems - ars1 (arsR1B1C1H1) and ars2 (arsR2B2C2H2) - with low sequence homology and two arsC-like genes, were found in the IMH genome. Both ars1 and ars2 are involved in the As resistance, where ars1 is the major contributor at 15 °C and ars2 at 30 °C. The difference in the behavior of these two ars systems is attributed to the disparate activities of their arsR promoters at different temperatures. Sequence analysis based on concatenated ArsRBC indicates that ars1 and ars2 clusters may be acquired from Franconibacter helveticus LMG23732 and Serratia marcescens (plasmid R478), respectively, by horizontal gene transfer (HGT). Nevertheless, two arsC-like genes, probably arising from the duplication of arsC, do not contribute to the As resistance. Our results indicate that Pantoea sp. IMH acquired two different As resistance genetic systems by HGT, allowing the colonization of changing ecosystems, and highlighting the flexible adaptation of microorganisms to resist As. PMID:27966630

  9. The Potential for Measuring Slow Crustal Evolution using Ar-Ar Dating of Large K-feldspar Crystals

    NASA Astrophysics Data System (ADS)

    Kelley, S. P.; Flude, S.

    2012-12-01

    There has been a great deal of debate concerning Ar/Ar age profiles in K-feldspar, even gem quality K-feldspar which should exhibit simple diffusion behaviour. Here we explore their potential for measuring very slow crustal evolution and cratonization. Several different models have been evoked which if correct would challenge our capability to recover long thermal histories from Ar/Ar data. We have measured 40Ar/39Ar ages in gem quality K-feldspar grains from Itrongay Madagascar of 435 [1] - 477 [2] Ma using UV-laserprobe to produce both depth profiles (0-20 microns) and spot traverses (0-1000 microns) to test the mechanisms that might control Ar diffusion in nature. Micron scale UV laser depth profiling was used to determine Ar diffusion adjacent to the natural crystal surface (presumed to have formed as the sample crystallised). UV laser spot dating was used to measure the age variations on length scales of 10s of microns to mm and even cm. The high potassium content and age of the Itrongay sample made it possible to measure natural argon age profiles at high precision and high spatial resolution, to address some of the issues surrounding Ar diffusion. The analysis reveals the presence of very long age gradients in the Itrongay feldspar spanning more than 50Ma - ages as low as 415.7±3.0 Ma were measured at the grain margin and as high as 473.8±2.2 Ma in the core. As previous work on Itrongay feldspar has tended to be carried out on mm-sized fragments without knowledge of the original crystal boundaries, the variation in radiometric ages in the published literature is likely due to these internal age variations. We interpret the age profiles as the combination of diffusion and 40K decay to 40Ar over the full range of spatial scales from micron to centimetre. Thermal models for the thermal history of Itrongay K-feldspar appear to be in agreement with previous thermochronology in the area and hold out the hope for unravelling very long and slow crustal evolution

  10. Finding Structure in the ArXiv

    NASA Astrophysics Data System (ADS)

    Alemi, Alexander; Chachra, Ricky; Ginsparg, Paul; Sethna, James

    2014-03-01

    We applied machine learning techniques to the full text of the arXiv articles and report a meaningful low-dimensional representation of this big dataset. Using Google's open source implementation of the continuous skip-gram model, word2vec, the vocabulary used in scientific articles is mapped to a Euclidean vector space that preserves semantic and syntactic relationships between words. This allowed us to develop techniques for automatically characterizing articles, finding similar articles and authors, and segmenting articles into their relevant sections, among other applications.

  11. Investigation of the Gardnos Impact Structure: 40Ar/39Ar Results

    NASA Astrophysics Data System (ADS)

    Grier, J. A.; Swindle, T. D.; Kring, D. A.; Melosh, H. J.

    1995-09-01

    Introduction: The Gardnos structure (Norway) [1], has recently been identified as an impact crater [2,3], despite being deformed by a series of tectonic processes [2]. The age of the structure is uncertain, although attempts to date the impact event have been made on the basis of stratigraphic relationships [2,3]. Unfortunately, these estimates differ by more than 100 million years. The first study suggested that the impact corresponded roughly with the Cambro-Ordovician boundary, ~500 Ma [2], while a second stratigraphic interpretation suggested a Precambrian age of 650 Ma [3]. To try and resolve this discrepancy, we attempted to determine the age of the structure with radiometric techniques, which typically have an error of < 10 Ma. Method: We examined three samples from the crater, in an attempt to determine the age using the 40Ar/39Ar dating method. The samples (plagioclase feldspar, alkali feldspar, and shards of gray, semi-transparent, glassy-looking material) were obtained from the suevite breccia unit of [2]. This unit should be the most promising for 40Ar/39Ar dating, since it is melt bearing, and no other unit is likely to be less affected by subsequent tectonism and sedimentation. Results: Our experiments yielded complicated age spectra interpreted to reflect a thermal event at 385+/-5 Ma and another possible event at 312+/-5 Ma (Fig. 1). All three samples yielded similar results. If the stratigraphic interpretations are correct, it thus seems clear that the impact event itself was not dated. The 385 Ma age corresponds to the end of the Caledonian Orogeny, which significantly altered this section of Norway [4]. It is suspected that late Caledonian folding occurred during this time [4], and we therefore interpret the 385 Ma age as the thermal metamorphic overprint of the Caledonian Orogeny. Another event clearly occurred afterwards, which is responsible for the 312 Ma signature. The cause of this thermal overprint has not yet been identified, since

  12. The USDA-ARS Experimental Watershed Network - Evolution and Lessons Learned

    NASA Astrophysics Data System (ADS)

    Goodrich, D. C.; Heilman, P.; Nichols, M.; Moran, S. M.; Steiner, J. L.; Sadler, J.; Walbridge, M. R.

    2014-12-01

    The USDA - Agricultural Research Service's Experimental Watershed Network grew from dust bowl era efforts of the Soil Conservation Service in 1935 which established field scale watersheds in three states. In the mid-50's five watershed centers with intensively instrumented watersheds at the scale of 100 to 700 km2 were established. Primary network research objectives were to quantify the downstream effects of conservation practices and accumulate rainfall-runoff observations for design of water conservation structures. ARS has operated over 600 watersheds in its history and continues operate roughly 100 watersheds, many of which are nested. With passage of the Clean Water Act in 1972 research and instrumentation evolved to add a variety of observations relevant to water quality issues that varied regionally. The intensive, long-term measurements and observations have led to an extensive process-based understanding of watershed behavior encompassing a diverse range of hydrologic and ecosystem dynamics. Many of the intensively monitored ARS watersheds have, and continue to serve as validation sites for aircraft and satellite based remotely sensed instruments. Recently, many of the ARS Experimental Watershed have become part of the Long-Term Agro-ecosystem Research Network (LTAR). This presentation will review major activities and advances derived from the network in addition to lessons learned in the long-term operation of a national scale network through its evolution from analog to digital instrumentation and internet accessibility.

  13. 40Ar/39Ar dating of the eruptive history of Mount Erebus, Antarctica: volcano evolution

    NASA Astrophysics Data System (ADS)

    Esser, Richard P.; Kyle, Philip R.; McIntosh, William C.

    2004-12-01

    Mt. Erebus, a 3,794-meter-high active polygenetic stratovolcano, is composed of voluminous anorthoclase-phyric tephriphonolite and phonolite lavas overlying unknown volumes of poorly exposed, less differentiated lavas. The older basanite to phonotephrite lavas crop out on Fang Ridge, an eroded remnant of a proto-Erebus volcano and at other isolated locations on the flanks of the Mt. Erebus edifice. Anorthoclase feldspars in the phonolitic lavas are large (~10 cm), abundant (~30 40%) and contain numerous melt inclusions. Although excess argon is known to exist within the melt inclusions, rigorous sample preparation was used to remove the majority of the contaminant. Twenty-five sample sites were dated by the 40Ar/39Ar method (using 20 anorthoclase, 5 plagioclase and 9 groundmass concentrates) to examine the eruptive history of the volcano. Cape Barne, the oldest site, is 1,311±16 ka and represents the first of three stages of eruptive activity on the Mt. Erebus edifice. It shows a transition from sub-aqueous to sub-aerial volcanism that may mark the initiation of proto-Erebus eruptive activity. It is inferred that a further ~300 ky of basanitic/phonotephritic volcanism built a low, broad platform shield volcano. Cessation of the shield-building phase is marked by eruptions at Fang Ridge at ~1,000 ka. The termination of proto-Erebus eruptive activity is marked by the stratigraphically highest flow at Fang Ridge (758±20 ka). Younger lavas (~550 250 ka) on a modern-Erebus edifice are characterized by phonotephrites, tephriphonolites and trachytes. Plagioclase-phyric phonotephrite from coastal and flank flows yield ages between 531±38 and 368±18 ka. The initiation of anorthoclase tephriphonolite occurred in the southwest sector of the volcano at and around Turks Head (243±10 ka). A short pulse of effusive activity marked by crustal contamination occurred ~160 ka as indicated by at least two trachytic flows (157±6 and 166±10 ka). Most

  14. Geochemical and 40Ar/39Ar constraints on the evolution of volcanism in the Woodlark Rift, Papua New Guinea

    NASA Astrophysics Data System (ADS)

    Catalano, Joseph P.

    The tectonic mechanisms producing Pliocene to active volcanism in eastern Papua New Guinea (PNG) have been debated for decades. In order to assess mechanisms that produce volcanism in the Woodlark Rift, we evaluate the evolution of volcanism in eastern PNG using 40Ar/39Ar thermochronology and whole rock geochemistry. Active volcanism in southeastern Papua New Guinea occurs on the Papuan Peninsula (Mt. Lamington, Mt. Victory and Waiwa), in the Woodlark Rift (Dobu Island, SE Goodenough Island, and Western Fergusson Island), and in the Woodlark Basin. In the Woodlark Basin, seafloor spreading is active and decompression melting of the upper mantle is producing basaltic magmatism. However, the cause of Pliocene and younger volcanism in the Woodlark Rift is controversial. Two hypotheses for the tectonic setting have been proposed to explain Pliocene and younger volcanism in the Woodlark Rift: (1) southward subduction of Solomon Sea lithosphere beneath eastern PNG at the Trobriand Tough and (2) decompression melting of mantle, previously modified by subduction, as the lithosphere undergoes extension associated with the opening of the Woodlark Basin. A comparison of 40Ar/39Ar ages with high field strength element (HFSE) concentrations in primary magmas indicates that HFSE concentrations correlate with age in the Woodlark rift. These data support the hypothesis that Pliocene to active volcanism in the Woodlark Rise and D'Entrecasteaux Islands results from decompression melting of a relict mantle wedge. The subduction zone geochemical signatures (negative HFSE anomalies) in Woodlark Rift lavas younger than 4 m.y. are a relict from older subduction beneath eastern Papua, likely in the middle Miocene. As the lithosphere is extended ahead of the tip of the westward propagating seafloor spreading center in the Woodlark Basin, the composition of volcanism is inherited from prior arc magmatism (via flux melting) and through time evolves toward magmatism associated with a rifting

  15. Late Miocene Thermal Evolution of the Eastern Himalayan Syntaxis as Constrained by Biotite 40Ar/39Ar Thermochronology

    NASA Astrophysics Data System (ADS)

    Gong, J.; Ji, J.; Zhou, J.; Tu, J.; Sun, D.; Han, B.; Zhong, D.

    2014-12-01

    We conducted biotite 40Ar/39Ar thermochronological research in the eastern Himalayan syntaxis and the surrounding Gangdese belt that wraps around the syntaxis, aiming to explore the overall cooling pattern and thermal evolution in this hard-to-access region. The compilation of our new dataset and published ages in the region presents a new temporal-spatial pattern: (1) Separated by the boundary faults of the eastern Himalayan syntaxis, a temporal gap at 13-7 Ma exists in the cooling history of the study area, with ages younger than 7 Ma clustering within the syntaxis, while ages older than 13 Ma distributing in the Gangdese belt. The gap could be a manifestation of the reactivated rapid cooling of the syntaxis since 7 Ma on the background of slow cooling all over the region, which temporally constrains the initial propagation of the eastern Himalayan syntaxis. (2) Ages in the syntaxis and the surrounding region show an annulus shape that younging toward Namche Barwa-Gyala Peri peak that is the core of the syntaxis, from 7-4 Ma and 4-2 Ma in the vicinities to 2-1 Ma in the core, which presents a spatially progressive acceleration in the cooling and exhumation towards the core. This observation indicates that the syntaxis experiences an inward acceleration along a vertical stalk rather than large-scale lateral propagation since late Miocene. The new findings argue that cooling revealed by biotite 40Ar/39Ar method was driven by tectonic contraction. We propose a model for the development of the Namche Barwa syntaxis that dominated by impulsive accelerating and subordinated by progressive accelerating driving by gravitational isostasy.

  16. Magnetic Field Evolution and Topology of an AR

    NASA Astrophysics Data System (ADS)

    Mandrini, C. H.; Deng, Y. Y.; Schmieder, B.; Démoulin, P.; Rudawy, P.; Nitta, N.; Newmark, J.; de Forest, C.

    1999-09-01

    Active region 7968 was observed during runs of a coordinated SOHO, Yohkoh and ground-based observatory program (Joint Observing Program, JOP, 17). The region appeared and decayed in a seven day period (June 3 to 10, 1996). In this time, mainly during June 6, it presented a very dynamical behaviour. Flux emerged in between the two main polarities and Arch Filament Systems (AFS) were observed to be linked to this emergence. We analyze the evolution of some over dark arches observed during flux emergence, forming two systems of AFS. Modelling the magnetic field, we find that these systems were associated to field lines having dips tangent to the photosphere (the so called "bald patches", BPs). We discuss their evolution in terms of emergence of the dipped portion of the lines or of magnetic field reconnection.

  17. Evolution of the Southwest Indian continental divergent margin: Constraints from 40Ar-39Ar dating of lateritic paleolandsurfaces

    NASA Astrophysics Data System (ADS)

    Bonnet, Nicolas; Beauvais, Anicet; Chardon, Dominique; Arnaud, Nicolas

    2015-04-01

    The western continental passive margin of Peninsular India is marked by the Western Ghats escarpment, which separates a coastal lowland from an East-dipping highland plateau and is carved both into the 63-Ma old Deccan traps and their Archean basement. Previous studies suggested establishment of the escarpment by differential erosion across an elevated rift shoulder, and thermochronologic models predicted escarpment formation from higher denudation in the coastal lowland than on the plateau until ~ 50 Ma. We provided complementary time constraints on the evolution of the passive margin by 40Ar-39Ar dating of supergene K-Mn oxides (cryptomelane) sampled in lateritic formations exposed on paleosurfaces, which are preserved as relicts on both sides of the escarpment. Three main lateritic paleosurfaces were identified in the highland at altitude ranges of 1200-1000 m (S1), 1000-900 m (S2) and 850-600 m (S3), and a lower paleosurface in the lowland at 150-50 m (S4). All the 40Ar-39Ar ages obtained on either side of the escarpment document major weathering periods for each paleosurface: 53 to 45 Ma (S1-S4) synchronously with the bauxitic weathering, 40 to 32 Ma (S2), 30 to 23 Ma (S3), and 24 to 19 Ma (S4). These ages indicate that most of the incision and dissection of plateau landsurfaces S1, S2, and S3 must therefore have taken place after 45, 32 and 23 Ma respectively, while the coastal lowland surface S4 was incised after 19 Ma. Preservation of laterites as old as 47 Ma in the coastal lowland implies that the escarpment already existed in the Mid-Eocene while intense bauxitic weathering was taking place on both sides of the escarpment. The ages obtained in the lowland are also indicative of limited erosion (~ 4 m Ma-1) at the foot of the escarpment since 45 Ma, and particularly low incipient incision of the lowland (~ 5 m Ma-1) since 19 Ma. Ages obtained on the highland plateau indicate further Neogene denudation inland but at less than 15 m Ma-1 since 45 Ma, and

  18. Structural and Optical Behaviour of Ar+ Implanted Polycarbonate

    NASA Astrophysics Data System (ADS)

    Shekhawat, Nidhi; Aggarwal, Sanjeev; Sharma, Annu; Deshpande, S. K.; Nair, K. G. M.

    2011-07-01

    Effects of 130 keV Ar+ ion implantation on the structural and optical properties of polycarbonate specimens have been studied using Raman, UV-Visible spectroscopy and glancing angle X-ray diffraction techniques. Formation of disordered carbonaceous network in the implanted layers has been observed using Raman and UV-Visible spectroscopy. A sharp decline in band gap values (4.1 eV to 0.63 eV) with increase in implantation dose has been observed. This decrease in optical band gap has been correlated with the formation of disordered structures in the implanted layers of polycarbonate.

  19. Comparative Genomic Analysis Reveals Organization, Function and Evolution of ars Genes in Pantoea spp.

    PubMed Central

    Wang, Liying; Wang, Jin; Jing, Chuanyong

    2017-01-01

    Numerous genes are involved in various strategies to resist toxic arsenic (As). However, the As resistance strategy in genus Pantoea is poorly understood. In this study, a comparative genome analysis of 23 Pantoea genomes was conducted. Two vertical genetic arsC-like genes without any contribution to As resistance were found to exist in the 23 Pantoea strains. Besides the two arsC-like genes, As resistance gene clusters arsRBC or arsRBCH were found in 15 Pantoea genomes. These ars clusters were found to be acquired by horizontal gene transfer (HGT) from sources related to Franconibacter helveticus, Serratia marcescens, and Citrobacter freundii. During the history of evolution, the ars clusters were acquired more than once in some species, and were lost in some strains, producing strains without As resistance capability. This study revealed the organization, distribution and the complex evolutionary history of As resistance genes in Pantoea spp.. The insights gained in this study improved our understanding on the As resistance strategy of Pantoea spp. and its roles in the biogeochemical cycling of As. PMID:28377759

  20. Structure of the N=27 isotones derived from the {sup 44}Ar(d,p){sup 45}Ar reaction

    SciTech Connect

    Gaudefroy, L.; Beaumel, D.; Blumenfeld, Y.; Fortier, S.; Franchoo, S.; Hammache, F.; Roussel, P.; Stanoiu, M.; Tryggestad, E.; Dombradi, Z.; Sohler, D.; Grevy, S.; St Laurent, M. G.; Roussel-Chomaz, P.; Kratz, K. L.; Lukyanov, S. M.; Penionzhkevich, Yu.-E.

    2008-09-15

    The {sup 44}Ar(d,p){sup 45}Ar neutron transfer reaction was performed at 10A MeV. Measured excitation energies, deduced angular momenta, and spectroscopic factors of the states populated in {sup 45}Ar are reported. A satisfactory description of these properties is achieved in the shell model framework using a new sdpf interaction. The model analysis is extended to more exotic even-Z nuclei down to {sub 14}{sup 41}Si{sub 27} to study how collectivity impacts the low-lying structure of N=27 neutron-rich nuclei.

  1. K/Ar ages, magnetic stratigraphy and morphological evolution of La Gomera: implications for the Canary Islands hotspot evolution.

    NASA Astrophysics Data System (ADS)

    Paris, R.; Guillou, H.; Carracedo, J. C.; Pérez Torrado, F. J.

    2003-04-01

    The Canary Islands are a group of seven volcanic islands, 100-700 km west of the Sahara continental margin. The spatial and chronological evolution of the canarian volcanism, from east to west, is due to the progression of the slow-moving african plate on a hotspot. La Gomera is located between the western shield-growing stage islands (La Palma, 1,7 Ma and El Hierro, 1,1 Ma) and the central "rejuvaneted stage" islands (Tenerife, 11,9 Ma and Gran Canaria, 14,5 Ma). After 23 K-Ar ages and paleomagnetism datas, we determine the main volcanic phases of La Gomera : (1) the submarine shield volcano (> 9,5 Ma), (2) the first subaeriel shield volcano (9,43-7,36 Ma), (3) the Vallehermoso stratovolcan, (4) the peripheral "planèzes" and domes forming series (6,67-1,94 Ma) and the Garajonay horizontal series (5,42-4,25 Ma). The stratovolcano and the horizontal series fill a 10 km wide depression that is supposed to be a giant landslide embayment. The scarps of this landslide correspond to the main discontinuity in the island structure. After 4 M.y. of very scarce volcanism, the whole structure of La Gomera is in relief inversion, with a radial pattern of deep barrancos. The erosion rates are lower during the hiatus (< 0,2 m/ka) than during the shield stage (0,2-0,9 m/ka), pointing out the fact that the volcanic construction rates and the erosion rates are strongly correlated. La Gomera is one of the best example of a hiatus stage of hotspot evolution. The volcanic load La Gomera and Tenerife may have delayed the western islands volcanism, favouring a dual-line.

  2. Microstructural evolution in nickel alloy C-276 after Ar-ion irradiation at elevated temperature

    SciTech Connect

    Jin, Shuoxue; He, Xinfu; Li, Tiecheng; Ma, Shuli; Tang, Rui; Guo, Liping

    2012-10-15

    In present work, the irradiation damage in nickel-base alloy C-276 irradiated with Ar-ions was studied. Specimens of C-276 alloy were subjected to an irradiation of Ar-ions (with 120 keV) to dose levels of 6 and 10 dpa at 300 and 550 Degree-Sign C, respectively. The size distributions and densities of dislocation loops caused by irradiation were investigated with transmission electron microscopy. Irradiation hardening due to the formation of the loops was calculated using the dispersed barrier-hardening model, showing that irradiation hardening was greatest at 300 Degree-Sign C/6 dpa. The microstructure evolution induced by Ar-ion irradiation (0-10 dpa) in nickel-base alloy C-276 has been studied using a multi-scale modeling code Radieff constructed based on rate theory, and the size of dislocation loops simulated by Radieff was in good agreement with the experiment. - Highlights: Black-Right-Pointing-Pointer High density of dislocation loops appeared after Ar ions irradiation. Black-Right-Pointing-Pointer Irradiation hardening due to the formation of loops was calculated by the DBH model. Black-Right-Pointing-Pointer Size of loops simulated by Radieff was in good agreement with the experiment.

  3. Determination of Ar Concentration Evolution Within DIII-D Core Plasma by X-ray Ross Filter Method

    NASA Astrophysics Data System (ADS)

    Bogatu, I. N.; Edgell, D. H.; Brooks, N. H.; Snider, R. T.; West, W. P.; Wade, M. R.

    2001-10-01

    Injection of the non-recycling noble gas Ar into the DIII-D divertor is a promising technique for reducing the heat load on the plates; it also seems to improve thermal transport in an advanced operating mode. During such experiments core plasma contamination by migrating Ar can be investigated by measuring the evolution of the Ar concentration profile using the Ross filter method implemented on the fan shaped X-ray poloidal diagnostics on DIII-D. A Ross filter with energy pass band centered on the ArXVII K_α line at 3.14 keV, discriminating Ar K_α line against background radiation, was used on DIII-D. A high sensitivity to the injected quantity of Ar and good discrimination against Ne was observed. We present reconstruction of Ar concentration profiles from the chord-integrated measurements using the measured Te and ne profiles. Using the transport code MIST, the impurity diffusion coefficients can be determined by matching the time evolution of the Ar concentration evolution.

  4. 40Ar/39Ar geochronology, paleomagnetism, and evolution of the Boring volcanic field, Oregon and Washington, USA

    USGS Publications Warehouse

    Fleck, Robert J.; Hagstrum, Jonathan T.; Calvert, Andrew T.; Evarts, Russell C.; Conrey, Richard M.

    2014-01-01

    The 40Ar/39Ar investigations of a large suite of fine-grained basaltic rocks of the Boring volcanic field (BVF), Oregon and Washington (USA), yielded two primary results. (1) Using age control from paleomagnetic polarity, stratigraphy, and available plateau ages, 40Ar/39Ar recoil model ages are defined that provide reliable age results in the absence of an age plateau, even in cases of significant Ar redistribution. (2) Grouping of eruptive ages either by period of activity or by composition defines a broadly northward progression of BVF volcanism during latest Pliocene and Pleistocene time that reflects rates consistent with regional plate movements. Based on the frequency distribution of measured ages, periods of greatest volcanic activity within the BVF occurred 2.7–2.2 Ma, 1.7–0.5 Ma, and 350–50 ka. Grouped by eruptive episode, geographic distributions of samples define a series of northeast-southwest–trending strips whose centers migrate from south-southeast to north-northwest at an average rate of 9.3 ± 1.6 mm/yr. Volcanic activity in the western part of the BVF migrated more rapidly than that to the east, causing trends of eruptive episodes to progress in an irregular, clockwise sense. The K2O and CaO values of dated samples exhibit well-defined temporal trends, decreasing and increasing, respectively, with age of eruption. Divided into two groups by K2O, the centers of these two distributions define a northward migration rate similar to that determined from eruptive age groups. This age and compositional migration rate of Boring volcanism is similar to the clockwise rotation rate of the Oregon Coast Range with respect to North America, and might reflect localized extension on the trailing edge of that rotating crustal block.

  5. The 1.4 Å crystal structure of the ArsD arsenic metallochaperone provides insights into its interaction with the ArsA ATPase†

    PubMed Central

    Ye, Jun; Ajees, A. Abdul; Yang, Jianbo; Rosen, Barry P.

    2010-01-01

    Arsenic is a carcinogen that tops the Superfund list of hazardous chemicals. Bacterial resistance to arsenic is facilitated by ArsD, which delivers As(III) to the ArsA ATPase, the catalytic subunit of the ArsAB pump. Here we report the structure of the arsenic metallochaperone ArsD at 1.4 Å, and a model for its binding of metalloid. There are two ArsD molecules in the asymmetric unit. The overall structure of the ArsD monomer has a thioredoxin fold, with a core of four β-strands flanked by four α-helices. Based on data from structural homologues, ArsD was modeled with and without bound As(III). ArsD binds one arsenic per monomer coordinated with the three sulfur atoms of Cys12, Cys13 and Cys18. Using this structural model, an algorithm was used to dock ArsD and ArsA. The resulting docking model provides testable predictions of the contact points of the two proteins and forms the basis for future experiments. PMID:20507177

  6. The 1.4 Å Crystal Structure of the ArsD Arsenic Metallochaperone Provides Insights into Its Interaction with the ArsA ATPase

    SciTech Connect

    Ye, Jun; Ajees, A. Abdul; Yang, Jianbo; Rosen, Barry P.

    2010-12-07

    Arsenic is a carcinogen that tops the Superfund list of hazardous chemicals. Bacterial resistance to arsenic is facilitated by ArsD, which delivers As(III) to the ArsA ATPase, the catalytic subunit of the ArsAB pump. Here we report the structure of the arsenic metallochaperone ArsD at 1.4 {angstrom} and a model for its binding of metalloid. There are two ArsD molecules in the asymmetric unit. The overall structure of the ArsD monomer has a thioredoxin fold, with a core of four {beta}-strands flanked by four {alpha}-helices. Based on data from structural homologues, ArsD was modeled with and without bound As(III). ArsD binds one arsenic per monomer coordinated with the three sulfur atoms of Cys12, Cys13, and Cys18. Using this structural model, an algorithm was used to dock ArsD and ArsA. The resulting docking model provides testable predictions of the contact points of the two proteins and forms the basis for future experiments.

  7. 75 FR 11936 - Unit Structures LLC, Magnolia, AR; Notice of Termination of Investigation

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-12

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF LABOR Employment and Training Administration Unit Structures LLC, Magnolia, AR; Notice of Termination of... of workers of Unit Structures LLC, Magnolia, Arkansas. The petitioner has requested that the...

  8. The tectonic evolution of Cenozoic extensional basins, northeast Brazil: Geochronological constraints from continental basalt 40Ar/39Ar ages

    NASA Astrophysics Data System (ADS)

    de Souza, Zorano Sérgio; Vasconcelos, Paulo Marcos; Knesel, Kurt Michael; da Silveira Dias, Luiz Gustavo; Roesner, Eduardo Henrique; Cordeiro de Farias, Paulo Roberto; de Morais Neto, João Marinho

    2013-12-01

    The Boa Vista and Cubati Basins, Paraíba, Brazil, are NW-SE extension-related intracratonic basins that resulted from tectonic stresses after the opening of the South Atlantic. These basins contain lacustrine fossiliferous sediments, bentonite beds, and basalt flows that preserve Cenozoic continental records. 40Ar/39Ar ages for six whole-rocks from two distinct basaltic flows underlying the sediments in the Boa Vista basin are 27.3 ± 0.8 and 25.4 ± 1.3 Ma, while three grains from a basaltic flow overlying the sediments yield 22.0 ± 0.2 Ma. The sediments at the nearby Cubati Basin are overlain by a basalt flow with ages of ˜25.4 Ma. Three whole-rocks from an NE-SW-trending trachytic dyke cross cutting the sediments at the Boa Vista Basin yield 40Ar/39Ar ages of ˜12.45 ± 0.06, 12.59 ± 0.07, and 12.58 ± 0.07 Ma. Three whole-rocks from a nearby volcanic plug (Chupador) yield an age of 23.4 ± 0.1 Ma. The geochronological results combined with stratigraphic correlations between the two basins allow bracketing the age of the main sedimentary and bentonic units within the Boa Vista and Cubati Basins between 25.5 ± 1.3 and 24.9 ± 0.1 Ma. The ages, combined with field observations reveal that the formation of the Boa Vista and Cubati basins is associated with mantle-derived magmas channelled through reactivated Precambrian shear zones. Our geochronological results suggest that a temporal link with the Fernando de Noronha and Saint Helena hot spots can be excluded as possible sources of the Boa Vista and Cubati magmas. Rather, the extensional tectonics in the 30-20 Ma interval, long after Gondwana break-up, may be associated with the re-activation of continental-scale shear zones that channelled small batches of mantle-derived magmas.

  9. Mars Atmospheric History Derived from Upper-Atmospheric Structure of 38Ar/36Ar Measured From MAVEN

    NASA Astrophysics Data System (ADS)

    Jakosky, Bruce; Slipski, Marek; Benna, Mehdi; Mahaffy, Paul; Elrod, Meredith K.; Yelle, Roger; Stone, Shane; Alsaeed, Noora

    2016-10-01

    Measurements of the structure of the Martian upper atmosphere made from MAVEN observations allow us to derive homopause and exobase altitudes in the Mars upper atmosphere and to determine the isotopic fractionation that occurs between them. Fractionation in the ratio of 38Ar/36Ar occurs between the homopause and exobase due to diffusive separation. This fractionation, combined with measurements of the bulk atmospheric ratio, is used to determine the total amount of argon lost to space by pick-up-ion sputtering. Our analysis is based on Rayleigh distillation, modified by replenishment of gas to the atmosphere by outgassing, impact, and crustal weathering. Approximately 80 % of the 36Ar that was ever in the atmosphere has been removed through time. This high value requires that a major fraction of Mars atmospheric gas has been lost to space. It points strongly to loss to space as having been the dominant mechanism driving the transition in Martian climate from an early, warm, wet environment to today's cold, dry, thin atmosphere.

  10. Data management and database structure at the ARS Culture Collection

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The organization and management of collection data for the 96,000 strains held in the ARS Culture Collection has been an ongoing process. Originally, the records for the four separate collections were maintained by individual curators in notebooks and/or card files and subsequently on the National C...

  11. Earth-atmosphere evolution based on new determination of Devonian atmosphere Ar isotopic composition

    NASA Astrophysics Data System (ADS)

    Stuart, Finlay M.; Mark, Darren F.; Gandanger, Pierre; McConville, Paul

    2016-07-01

    The isotopic composition of the noble gases, in particular Ar, in samples of ancient atmosphere trapped in rocks and minerals provides the strongest constraints on the timing and rate of Earth atmosphere formation by degassing of the Earth's interior. We have re-measured the isotopic composition of argon in the Rhynie chert from northeast Scotland using a high precision mass spectrometer in an effort to provide constraints on the composition of Devonian atmosphere. Irradiated chert samples yield 40Ar/36Ar ratios that are often below the modern atmosphere value. The data define a 40Ar/36Ar value of 289.5 ± 0.4 at K/36Ar = 0. Similarly low 40Ar/36Ar are measured in un-irradiated chert samples. The simplest explanation for the low 40Ar/36Ar is the preservation of Devonian atmosphere-derived Ar in the chert, with the intercept value in 40Ar-39Ar-36Ar space representing an upper limit. In this case the Earth's atmosphere has accumulated only 3% (5.1 ± 0.4 ×1016 mol) of the total 40Ar inventory since the Devonian. The average accumulation rate of 1.27 ± 0.09 ×108 mol40Ar/yr overlaps the rate over the last 800 kyr. This implies that there has been no resolvable temporal change in the outgassing rate of the Earth since the mid-Palaeozoic despite the likely episodicity of Ar degassing from the continental crust. Incorporating the new Devonian atmosphere 40Ar/36Ar into the Earth degassing model of Pujol et al. (2013) provides the most precise constraints on atmosphere formation so far. The atmosphere formed in the first ∼100 Ma after initial accretion during a catastrophic degassing episode. A significant volume of 40Ar did not start to accumulate in the atmosphere until after 4 Ga which implies that stable K-rich continental crust did not develop until this time.

  12. Preservation of Sub-Microscopic Scale Structural Relics in Biotite: Implications for 40AR/39AR Geochronology

    NASA Astrophysics Data System (ADS)

    Beltrando, M.; Di Vincenzo, G.; Ferraris, C.

    2012-12-01

    , characterized by a concordant central segment, with an error-weighted mean age of 44.9 ± 0.3 Ma. Age profiling on separate grains from sample JT1007, analyzed perpendicularly to the cleavage plane, reveal a broad core-to-rim age variation, with a maximum apparent age of ~66 Ma in the core and a minimum age in the rim as low as ~45. Similar age gradients and concave upward spectra from relict minerals that underwent at least one re-heating event are generally ascribed to incomplete diffusive resetting of the original argon reservoir or to the influx of extraneous argon followed by partial diffusive loss. However, major element compositional variations and the preservation of sub-micron scale magmatic biotite relics within largely re-equilibrated crystals suggest that the observed age spread may be explained by the coexistence of two different argon reservoirs related to the two different microstructural sites. This study suggests that, in addition to the well documented influx of externally-derived argon, anomalously old 40Ar/39Ar ages in metamorphic biotite may also be related to the preservation of sub-microscopic scale mineral relics that escaped complete re-equilibration during the subsequent tectono-metamorphic evolution.

  13. Low-Lying Structure of 50Ar and the N =32 Subshell Closure

    NASA Astrophysics Data System (ADS)

    Steppenbeck, D.; Takeuchi, S.; Aoi, N.; Doornenbal, P.; Matsushita, M.; Wang, H.; Utsuno, Y.; Baba, H.; Go, S.; Lee, J.; Matsui, K.; Michimasa, S.; Motobayashi, T.; Nishimura, D.; Otsuka, T.; Sakurai, H.; Shiga, Y.; Shimizu, N.; Söderström, P.-A.; Sumikama, T.; Taniuchi, R.; Valiente-Dobón, J. J.; Yoneda, K.

    2015-06-01

    The low-lying structure of the neutron-rich nucleus 50Ar has been investigated at the Radioactive Isotope Beam Factory using in-beam γ -ray spectroscopy with 9Be (54Ca, 50Ar +γ )X , 9Be (55Sc, 50Ar +γ )X , and 9Be (56Ti, 50Ar +γ )X multinucleon removal reactions at ˜220 MeV /u . A γ -ray peak at 1178(18) keV is reported and assigned as the transition from the first 2+ state to the 0+ ground state. A weaker, tentative line at 1582(38) keV is suggested as the 41+→21+ transition. The experimental results are compared to large-scale shell-model calculations performed in the s d p f model space using the SDPF-MU effective interaction with modifications based on recent experimental data for exotic calcium and potassium isotopes. The modified Hamiltonian provides a satisfactory description of the new experimental results for 50Ar and, more generally, reproduces the energy systematics of low-lying states in neutron-rich Ar isotopes rather well. The shell-model calculations indicate that the N =32 subshell gap in 50Ar is similar in magnitude to those in 52Ca and 54Ti and, notably, predict an N =34 subshell closure in 52Ar that is larger than the one recently reported in 54Ca.

  14. Tectono-thermal evolution of the Palaeoproterozoic Granites-Tanami Orogen, North Australian Craton: Implications from hornblende and biotite 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Li, Ben; Bagas, Leon; Jourdan, Fred

    2014-10-01

    The Palaeoproterozoic Granites-Tanami Orogen (GTO) hosts a number of gold deposits located in the southern margin of the North Australian Craton. The major stratigraphic succession is the Palaeoproterozoic Tanami Group which is subdivided into the Dead Bullock Formation and conformably overlying Killi Killi Formation. New geochemical data for the ca. 1864 Coora and Groundrush dolerite sills in the Dead Bullock Formation suggests that they have the same characteristics with the enriched back-arc basin basaltic rocks from the former Stubbins Formation, such as tholeiitic affinity, high TiO2 contents (0.94 to 1.24 wt.%) and low Mg# (41-45), slightly enriched LILE (Rb, Th, U, and K), weakly depleted HFSE (Nb, Ta), and relatively flat REE patterns. Their magma was generated by high degree decompressional melting (5-15%) of the asthenosphere source with an input of 3-4% subduction-related material. The petrological and geochemical similarities of igneous rocks provide new evidence for the assignment of the ca. 1864 Ma former Stubbins Formation and the Mount Charles Formations in the Dead Bullock Formation of the Tanami Group. These conclusions confirmed that the extensive Palaeoproterozoic Tanami Group was deposited in a back-arc basin environment. Hornblende and biotite 40Ar/39Ar geochronological study identified three major tectono-thermal events in the GTO since the deposition of the Dead Bullock Formation. The ca. 1840 Ma 40Ar/39Ar cooling age of metamorphic hornblende from the Coora and Groundrush dolerite sills in the Dead Bullock Formation provided precise age constraint for the first Palaeoproterozoic tectono-thermal event during the evolution of the Granites-Tanami back-arc basin. This age is highly consistent with the ca. 1850-1840 Ma subduction and peak metamorphism events in the North Australian Craton (NAC) associated with the Halls Creek Orogeny in the Halls Creek Orogen, and the Tennant Orogeny in the Tennant Creek Inlier. The 40Ar/39Ar age of 1753 ± 8 Ma

  15. Resonance assignments and secondary structure prediction of the As(III) metallochaperone ArsD in solution

    PubMed Central

    Ye, Jun; He, Yanan; Skalicky, Jack; Rosen, Barry P.; Stemmler, Timothy L.

    2012-01-01

    ArsD is a metallochaperone that delivers As(III) to the ArsA ATPase, the catalytic subunit of the ArsAB pump encoded by the arsRDABC operon of Escherichia coli plasmid R773. Conserved ArsD cysteine residues (Cys12, Cys13 and Cys18) construct the As(III) binding site of the protein, however a global structural understanding of this arsenic binding remains unclear. We have obtained NMR assignments for ArsD as a starting point for probing structural changes on the protein that occur in response to metalloid binding and upon formation of a complex with ArsA. The predicted solution structure of ArsD is in agreement with recently published crystallographic structural results. PMID:21063813

  16. Identification of a new androgen receptor (AR) co-regulator BUD31 and related peptides to suppress wild-type and mutated AR-mediated prostate cancer growth via peptide screening and X-ray structure analysis.

    PubMed

    Hsu, Cheng-Lung; Liu, Jai-Shin; Wu, Po-Long; Guan, Hong-Hsiang; Chen, Yuh-Ling; Lin, An-Chi; Ting, Huei-Ju; Pang, See-Tong; Yeh, Shauh-Der; Ma, Wen-Lung; Chen, Chung-Jung; Wu, Wen-Guey; Chang, Chawnshang

    2014-12-01

    Treatment with individual anti-androgens is associated with the development of hot-spot mutations in the androgen receptor (AR). Here, we found that anti-androgens-mt-ARs have similar binary structure to the 5α-dihydrotestosterone-wt-AR. Phage display revealed that these ARs bound to similar peptides, including BUD31, containing an Fxx(F/H/L/W/Y)Y motif cluster with Tyr in the +5 position. Structural analyses of the AR-LBD-BUD31 complex revealed formation of an extra hydrogen bond between the Tyr+5 residue of the peptide and the AR. Functional studies showed that BUD31-related peptides suppressed AR transactivation, interrupted AR N-C interaction, and suppressed AR-mediated cell growth. Combination of peptide screening and X-ray structure analysis may serve as a new strategy for developing anti-ARs that simultaneously suppress both wt and mutated AR function.

  17. Ne+, Ne2+, Ar+, and Ar2+ fine-structure electron-impact excitation data for applications in ultra low temperature plasmas

    NASA Astrophysics Data System (ADS)

    LI, YE; Wang, Qianxia; Pearce, Jonathan; Pindzola, Michael; Loch, Stuart; Stancil, Phillip C.; Cumbee, Renata; Ballance, Connor

    2016-01-01

    Fine-structure electron-impact excitation of ions plays an important role in cooling most interstellar environments and is important for far infrared (IR) and submillimeter (submm) observations. New atomic structure and collisonal data are presented using both semi-relativistic and fully-relativistic R-matrix methods for Ne+, Ne2+, Ar+, and Ar2+. Some illustrative modeling results using the data are also given.

  18. 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.

  19. Mesozoic thermal history and timing of structural events for the Yukon-Tanana Upland, east-central Alaska: 40Ar/39Ar data from metamorphic and plutonic rocks

    USGS Publications Warehouse

    Dusel-Bacon, C.; Lanphere, M.A.; Sharp, W.D.; Layer, P.W.; Hansen, V.L.

    2002-01-01

    We present new 40Ar/39Ar ages for hornblende, muscovite, and biotite from metamorphic and plutonic rocks from the Yukon-Tanana Upland, Alaska. Integration of our data with published 40Ar/39Ar, kinematic, and metamorphic pressure (P) and temperature (T) data confirms and refines the complex interaction of metamorphism and tectonism proposed for the region. The oldest metamorphic episode(s) postdates Middle Permian magmatism and predates the intrusion of Late Triassic (215-212 Ma) granitoids into the Fortymile River assemblage (Taylor Mountain assemblage of previous papers). In the eastern Eagle quadrangle, rapid and widespread Early Jurassic cooling is indicated by ???188-186 Ma 40Ar/39Ar plateau ages for hornblende from plutons that intrude the Fortymile River assemblage, and for metamorphic minerals from the Fortymile River assemblage and the structurally underlying Nasina assemblage. We interpret these Early Jurassic ages to represent cooling resulting from northwest-directed contraction that emplaced the Fortymile River assemblage onto the Nasina assemblage to the north as well as the Lake George assemblage to the south. This cooling was the final stage of a continuum of subduction-related contraction that produced crustal thickening, intermediate- to high-P metamorphism within both the Fortymile River assemblage and the structurally underlying Lake George assemblage, and Late Triassic and Early Jurassic plutonism in the Fortymile River and Nasina assemblages. Although a few metamorphic samples from the Lake George assemblage yield Jurassic 40Ar/39Ar cooling ages, most yield Early Cretaceous 40Ar/39Ar ages: hornblende ???135-115 Ma, and muscovite and biotite ???110-108 Ma. We interpret the Early Cretaceous metamorphic cooling, in most areas, to have resulted from regional extension and exhumation of the lower plate, previously tectonically thickened during Early Jurassic and older convergence.

  20. Accessory mineral U-Th-Pb ages and 40Ar/39Ar eruption chronology, and their bearing on rhyolitic magma evolution in the Pleistocene Coso volcanic field, California

    USGS Publications Warehouse

    Simon, J.I.; Vazquez, J.A.; Renne, P.R.; Schmitt, A.K.; Bacon, C.R.; Reid, M.R.

    2009-01-01

    We determined Ar/Ar eruption ages of eight extrusions from the Pleistocene Coso volcanic field, a long-lived series of small volume rhyolitic domes in eastern California. Combined with ion-microprobe dating of crystal ages of zircon and allanite from these lavas and from granophyre geothermal well cuttings, we were able to track the range of magma-production rates over the past 650 ka at Coso. In ??? 230 ka rhyolites we find no evidence of protracted magma residence or recycled zircon (or allanite) from Pleistocene predecessors. A significant subset of zircon in the ???85 ka rhyolites yielded ages between ???100 and 200 Ma, requiring that generation of at least some rhyolites involves material from Mesozoic basement. Similar zircon xenocrysts are found in an ???200 ka granophyre. The new age constraints imply that magma evolution at Coso can occur rapidly as demonstrated by significant changes in rhyolite composition over short time intervals (???10's to 100's ka). In conjunction with radioisotopic age constraints from other young silicic volcanic fields, dating of Coso rhyolites highlights the fact that at least some (and often the more voluminous) rhyolites are produced relatively rapidly, but that many small-volume rhyolites likely represent separation from long-lived mushy magma bodies. ?? The Author(s) 2009.

  1. Long-lived structural control of Mt. Shasta's plumbing system illuminated by 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Calvert, A. T.; Christiansen, R. L.

    2013-12-01

    Mt. Shasta is the largest stratovolcano in the Cascade Arc, surpassed in volume only by the large rear-arc Medicine Lake and Newberry composite volcanoes. Including the material in the ~350 ka debris avalanche, it has produced more than 500 km3 of andesite and dacite from several superimposed central vents over its 700-850 kyr history. Earlier, between at least 970 to 1170 ka, the Rainbow Mountain volcano of similar composition and size occupied this latitude of the arc ~20 km further east. This shift of magmatic focus from within the arc axis (as defined by 6 Ma and younger calc-alkaline centers) to the arc front is poorly understood, but the current center's location appears structurally controlled. Most identifiable volcanic vents on Mt. Shasta lie within 1 km of a N-S line through the active summit cone. 40Ar/39Ar ages of map units occupying the vent alignment range from the Holocene (5×1 ka) current summit dome to at least the Middle Pleistocene (464×9 ka McKenzie Butte). The vast majority of eruptions have issued from central vents (Sargents Ridge, 300-135 ka; Misery Hill, 100-15 ka; and Hotlum, <10 ka), each 500 to 1000m north of its predecessor. A central vent for the pre-avalanche edifice is impossible to locate precisely, but was possibly on the same N-S trend and certainly no more than 4 km to the west, likely south of the Sargents Ridge central vent. ~15 of ~25 mapped flank vents lie on the alignment and the other ten lie west of the line. No identified volcanic vents lie east of the line until >12 km from Mt. Shasta (Ash Creek Butte, 227 ka; Basalt of McCloud River, 38 ka; The Whaleback, 102 ka), and monogenetic and polygenetic centers further east and northeast. From these observations we infer that: (1) magmas are localized along a ~20 km, long-lived, N-S trending structure running through the summit; (2) the upper crustal structure appears impermeable to magmas and resistant to dikes on its eastern side; (3) the western half of the area beneath

  2. Southernmost Andes and South Georgia Island, North Scotia Ridge: Zircon U-Pb and muscovite {40Ar }/{39Ar } age constraints on tectonic evolution of Southwestern Gondwanaland

    NASA Astrophysics Data System (ADS)

    Mukasa, Samuel B.; Dalziel, Ian W. D.

    1996-11-01

    Zircon U-Pb and muscovite {40Ar }/{39Ar } isotopic ages have been determined on rocks from the southernmost Andes and South Georgia Island, North Scotia Ridge, to provide absolute time constraints on the kinematic evolution of southwestern Gondwanaland, until now known mainly from stratigraphic relations. The U-Pb systematics of four zircon fractions from one sample show that proto-marginal basin magmatism in the northern Scotia arc, creating the peraluminous Darwin granite suite and submarine rhyolite sequences of the Tobifera Formation, had begun by the Middle Jurassic (164.1 ± 1.7 Ma). Seven zircon fractions from two other Darwin granites are discordant with non-linear patterns, suggesting a complex history of inheritances and Pb loss. Reference lines drawn through these points on concordia diagrams give upper intercept ages of ca. 1500 Ma, interpreted as a minimum age for the inherited zircon component. This component is believed to have been derived from sedimentary rocks in the Gondwanaland margin accretionary wedge that forms the basement of the region, or else directly from the cratonic "back stop" of that wedge. Ophiolitic remnants of the Rocas Verdes marginal basin preserved in the Larsen Harbour complex on South Georgia yield the first clear evidence that Gondwanaland fragmentation had resulted in the formation of oceanic crust in the Weddell Sea region by the Late Jurassic (150 ± 1 Ma). The geographic pattern in the observed age range of 8 to 13 million years in these ophiolitic materials, while not definitive, is in keeping with propagation of the marginal basin floor northwestward from South Georgia Island to the Sarmiento Complex in southern Chile. Rocks of the Beagle granite suite, emplaced post-tectonically within the uplifted marginal basin floor, have complex zircon U-Pb systematics with gross discordances dominated by inheritances in some samples and Pb loss in others. Of eleven samples processed, only two had sufficient amounts of zircon for

  3. Structural rejuvenation of the eastern Arabian Shield during continental collision: 40Ar/ 39Ar evidence from the Ar Ridayniyah ophiolitic mélange

    NASA Astrophysics Data System (ADS)

    Al-Saleh, A. M.; Boyle, A. P.

    2001-07-01

    The Ar Ridayniyah ophiolitic mélange is one of a number of such complexes found within or at the peripheries of the Neoproterozoic Al-Amar Suture of the eastern Arabian Shield. This suture is sandwiched between the Ar Rayn island-arc terrane on the east and the much larger Afif continental block to the west, and is thought to represent the site of a 695—680 Ma back-arc basin that separated the two terranes. A thick and monotonous unit of metagraywacke (Abt Schist) underlies most of the suture along with scattered outcrops of metavolcanics and ophiolitic mélange. One of these bodies is the Ar Ridayniyah mélange, which occurs as a longitudinal belt of sheared ultramafic schists enclosing abundant blocks of oceanic serpentinites, as well as subordinate gabbros and basalts. The western boundary of this mélange is defined by the Ar Ridayniyah thrust fault. The 610—600 Ma ages obtained from the metagabbros of this complex are considered to record the reactivation of the Ar Ridayniyah Fault during continental collision, 60 Ma after ophiolite emplacement.

  4. Identification of a new androgen receptor (AR) co-regulator BUD31 and related peptides to suppress wild-type and mutated AR-mediated prostate cancer growth via peptide screening and X-ray structure analysis

    PubMed Central

    Hsu, Cheng-Lung; Liu, Jai-Shin; Wu, Po-Long; Guan, Hong-Hsiang; Chen, Yuh-Ling; Lin, An-Chi; Ting, Huei-Ju; Pang, See-Tong; Yeh, Shauh-Der; Ma, Wen-Lung; Chen, Chung-Jung; Wu, Wen-Guey; Chang, Chawnshang

    2014-01-01

    Treatment with individual anti-androgens is associated with the development of hot-spot mutations in the androgen receptor (AR), including T877A (hydroxyflutamide [HF]) and W741(C/L) (bicalutamide [CDX]). Here, we found that anti-androgens bound mt-ARs (HF-T877A-AR-LBD and CDX-W741L-AR-LBD) have similar binary structure to the 5α-dihydrotestosterone (DHT) bound wild type (wt) AR (DHT-wt-AR-LBD). Phage display revealed that these ARs bound to similar peptides, including BUD31, containing an Fxx(F/H/L/W/Y)Y motif cluster with Tyr in the +5 position. Structural analyses of the AR-LBD-BUD31 complex at 2.1 Å resolution revealed formation of an extra hydrogen bond between the Tyr+5 residue of the peptide and Gln733 of the AR AF2 domain, suggesting that peptides with Fxx(F/H/L/W/Y)Y motifs can interact with wt or mutated ARs. Functional studies showed that BUD31-related peptides suppressed transactivation of both DHT-wt-AR and HF-T877A-AR by interrupting AR N- and C-terminal interactions, thereby inhibiting wt and mutant AR-mediated prostate cancer cell growth. Collectively, these results suggest the combination of peptide screening and X-ray structure analysis as a new strategy for developing anti-androgens that simultaneously suppress both wt and mutated AR function. PMID:25091737

  5. The Magnetic Evolution of AR 6555 which led to Two Impulsive, Relatively Compact, X-Type Flares

    NASA Technical Reports Server (NTRS)

    Fontenla, J. M.; Ambastha, A.; Kalman, B.; Csepura, Gy.

    1995-01-01

    We study the evolution of the vector magnetic field and the sunspot motions observed in AR 6555 during 1991 March 23-26. This region displays two locations of large magnetic shear that were also sites of flare activity. The first location produced two large (X-class) flares during the period covered by our observations. The second location had larger magnetic shear than the first but produced only small (M- and C-class) flares during our observations. We study the evolution of the photospheric magnetic field in relation to the large flares in the first location. These flares occurred around the same included polarity and have very similar characteristics (soft X-ray light curves, energies, etc,). However, the whole active region has changed substantially in the period between them. We found several characteristics of the region that appear related to the occurrence of these flares: (1) The flares occurred near regions of large magnetic 'shear' but not at the locations of maximum shear or maximum field. (2) Potential field extrapolations of the observed field suggest that the topology changed, prior to the first of the two flares, in such a way that a null appeared in the coarse magnetic field. (3) This null was located close to both X-class flares and remained in that location for a few days while the two flares were observed. (4) The flaring region has a pattern of vector field and sunspot motions in which material is 'squeezed' along the polarity inversion line. This pattern is very different from that usually associated with shearing arcades, but it is similar to that suggested previously by Fontenia and Davis. The vertical electric currents, inferred from the transverse field, are consistent with this pattern. (5) A major reconfiguration of the longitudinal field and the vertical electric currents occurred just prior to the first of the two flares. Both changes imply substantial variations of the magnetic structure of the region. On the basis of the available

  6. The magnetic evolution of AR 6555 which lead to two impulsive, readily compact, X-type flares

    NASA Technical Reports Server (NTRS)

    Ambastha, A.; Fontenla, J. M.; Kalman, B.; Csepura, GY.

    1995-01-01

    We study the evolution of the vector magnetic field and the sunspot motions observed in AR 6555 during 23-26 Mar. 1991. This region displays two locations of large magnetic shear that were also sites of flare activity. The first location produced two large (X-class) flares during the period covered by our observations. The second location had larger magnetic shear than the first, but produced only small (M- and C-class) flares during our observations. We study the evolution of the photospheric magnetic field in relation to the large flares in the first location. These flares occurred around the same included polarity, and have very similar characteristics (soft X-ray light curves, energies, etc.). However, the whole active region has changed substantially in the period between them. We found several characteristics of the region that appear related to the occurrence of these flares. (1) The flares occurred near regions of large magnetic 'shear,' but not at the locations of maximum shear or maximum field. (2) Potential field extrapolations of the observed field suggest that the topology changed, prior to the first of the two flares, in such a way that a null appeared in the coarse magnetic field. (3) This null was located close to both X-class flares, and remained in that location for a few days while the two flares were observed. (4) The flaring region has a pattern of vector field and sunspot motions in which material is 'squeezed' along the polarity inversion line. This pattern is very different from that usually associated with shearing arcades, but it is similar to that suggested previously by Fontenla and Davis. The vertical electric currents, inferred from the transverse field, are consistent with this pattern. (5) A major reconfiguration of the longitudinal field and the vertical electric currents occurred just prior to the first of the two flares. Both changes imply substantial variations of the magnetic structure of the region. On the basis of the

  7. Wavelet-based AR-SVM for health monitoring of smart structures

    NASA Astrophysics Data System (ADS)

    Kim, Yeesock; Chong, Jo Woon; Chon, Ki H.; Kim, JungMi

    2013-01-01

    This paper proposes a novel structural health monitoring framework for damage detection of smart structures. The framework is developed through the integration of the discrete wavelet transform, an autoregressive (AR) model, damage-sensitive features, and a support vector machine (SVM). The steps of the method are the following: (1) the wavelet-based AR (WAR) model estimates vibration signals obtained from both the undamaged and damaged smart structures under a variety of random signals; (2) a new damage-sensitive feature is formulated in terms of the AR parameters estimated from the structural velocity responses; and then (3) the SVM is applied to each group of damaged and undamaged data sets in order to optimally separate them into either damaged or healthy groups. To demonstrate the effectiveness of the proposed structural health monitoring framework, a three-story smart building equipped with a magnetorheological (MR) damper under artificial earthquake signals is studied. It is shown from the simulation that the proposed health monitoring scheme is effective in detecting damage of the smart structures in an efficient way.

  8. Substorm evolution of auroral structures

    NASA Astrophysics Data System (ADS)

    Partamies, N.; Juusola, L.; Whiter, D.; Kauristie, K.

    2015-07-01

    Auroral arcs are often associated with magnetically quiet time and substorm growth phases. We have studied the evolution of auroral structures during global and local magnetic activity to investigate the occurrence rate of auroral arcs during different levels of magnetic activity. The ground-magnetic and auroral conditions are described by the magnetometer and auroral camera data from five Magnetometers — Ionospheric radars — All-sky cameras Large Experiment stations in Finnish and Swedish Lapland. We identified substorm growth, expansion, and recovery phases from the local electrojet index (IL) in 1996-2007 and analyzed the auroral structures during the different phases. Auroral structures were also analyzed during different global magnetic activity levels, as described by the planetary Kp index. The distribution of auroral structures for all substorm phases and Kp levels is of similar shape. About one third of all detected structures are auroral arcs. This suggests that auroral arcs occur in all conditions as the main element of the aurora. The most arc-dominated substorm phases occur in the premidnight sector, while the least arc-dominated substorm phases take place in the dawn sector. Arc event lifetimes and expectation times calculated for different substorm phases show that the longest arc-dominated periods are found during growth phases, while the longest arc waiting times occur during expansion phases. Most of the arc events end when arcs evolve to more complex structures. This is true for all substorm phases. Based on the number of images of auroral arcs and the durations of substorm phases, we conclude that a randomly selected auroral arc most likely belongs to a substorm expansion phase. A small time delay, of the order of a minute, is observed between the magnetic signature of the substorm onset (i.e., the beginning of the negative bay) and the auroral breakup (i.e., the growth phase arc changing into a dynamic display). The magnetic onset was

  9. New 40Ar/39Ar dating of the Clearwater Lake impact structures (Québec, Canada) - Not the binary asteroid impact it seems?

    NASA Astrophysics Data System (ADS)

    Schmieder, Martin; Schwarz, Winfried H.; Trieloff, Mario; Tohver, Eric; Buchner, Elmar; Hopp, Jens; Osinski, Gordon R.

    2015-01-01

    The two Clearwater Lake impact structures (Québec, Canada) are generally interpreted as a crater doublet formed by the impact of a binary asteroid. Here, arguments are presented that raise important questions about the proposed double impact scenario. New 40Ar/39Ar dating of two virtually fresh impact melt rock samples from the ⩾36 km West Clearwater Lake impact structure yielded two statistically robust Early Permian plateau ages with a weighted mean of 286.2 ± 2.2 (2.6) Ma (2σ; MSWD = 0.33; P = 0.57). In contrast, 40Ar/39Ar results for two chloritized melt rocks from the ∼26 km East Clearwater Lake impact structure produced disturbed age spectra suggestive of a distinct extraneous argon component. Although individually weakly robust, age spectra corrected for the trapped argon component and inverse isochron plots for the East Clearwater melt rocks consistently yielded apparent ages around ∼460-470 Ma. No Permian signal was found in either of these melt aliquots. Our new 40Ar/39Ar results reproduce earlier 40Ar/39Ar plateau ages (∼283 Ma and ∼465 Ma, respectively) for the two impact structures by Bottomley et al. (1990) and are in conflict with a previous, statistically non-robust Rb-Sr age of 287 [293] ± 26 Ma for East Clearwater. The combined cluster of apparent ages of ∼460-470 Ma, derived from four different samples across the impact melt sheet, is very unlikely to represent a 'false age effect' due to the incorporation of extraneous argon into the melt; instead, it strongly favors a Middle Ordovician age for the East Clearwater impact and impact-induced hydrothermal chloritization. Moreover, the Clearwater impact structures are characterized by different natural remanent magnetizations testifying to separate geologic histories, an effect unexpected in the case of a Permian double impact. Whereas the West Clearwater impact affected Ordovician carbonates incorporated into the impact breccia, drill core reports from the 1960s concluded that

  10. The sup 40 Ar/ sup 39 Ar thermochronology of the eastern Mojave Desert, California, and adjacent western Arizona with implications for the evolution of metamorphic core complexes

    SciTech Connect

    Foster, D.A.; Harrison, T.M. ); Miller, C.F. ); Howard, K.A. )

    1990-11-10

    The application of {sup 40}Ar/{sup 39}Ar thermochronology provides information about the timing and nature of thrusting, plutonism, metamorphism, denudation, and detachment faulting. The {sup 40}Ar/{sup 39}Ar ages of 175 to 125 Ma from the Clipper, Piute, Turtle, Mohave, Bill Williams, and Hualapai Mountains are interpreted to be the result of a middle Mesozoic thermal event(s) caused by crustal thickening. The {sup 40}Ar/{sup 39}Ar data from the Clipper and Piute Mountains suggest that this thermal event was followed by a period of cooling at rates of 1-5C/m.y. Orogenesis culminated during the Late Cretaceous when rocks exposed in the Old Woman-Piute, Chemehuevi, and Sacramento Mountains attained temperatures >500C which reset the K-Ar systems of minerals from Proterozoic rocks. High-grade metamorphism in the Old Woman Mountains area was caused by the intrusion of the Old Woman-Piute batholith at 73 {plus minus} 1 Ma. Cooling rates following batholith emplacement in the Old Woman Mountains were {approximately}100C/m.y. between 73 and 70 Ma and 5-10C/m.y. from 70 to {approximately}30 Ma. By 30 Ma, rocks exposed in the Old Woman-Piute, Marble, Ship, Clipper, and Turtle Mountains were below {approximately}100C. The {sup 49}Ar/{sup 39}Ar ages from the Sacramento Mountains suggest that mylonization caused by the onset of regional extension occurred at 23 {plus minus} 1 Ma. When extension started in the Chemehuevi Mountains, rocks exposed in the southwestern and northeastern portions of footwall to the Chemehuevi detachment fault were at {approximately}180C and {approximately}350C, respectively. Unroofing of the footwalls to detachment faults in the Sacramento and Chemehuevi Mountains resulted in average cooling rates of 10-50C/m.y. between 22 and 15 Ma.

  11. Relationship between magnetic field evolution and flaring sites in AR 6659 in June 1991

    NASA Technical Reports Server (NTRS)

    Schmieder, B.; Hagyard, M. J.; Guoxiang, AI; Hongqi, Zhang; Kalman, B.; Gyori, L.; Rompolt, B.; Demoulin, P.; Machado, M. E.

    1994-01-01

    During the international campaign of June 1991, the active region AR 6659 produced six very large, long-duration flares (X10/12) during its passage across the solar disk. We present the characteristics of four of them (June 4, 6, 9, 15). Precise measurements of the spot motions from Debrecen and Tokyo white-light pictures are used to understand the fragmentation of the main sunspot group with time. This fragmentation leads to a continuous restructuring of the magnetic field pattern while rapid changes are evidenced due to fast new flux emergence (magnetograms of Marshall Space Flight Center (MSFC), Huairou). The first process leads to a shearing of the field lines along which there is energy storage; the second one is the trigger which causes the release of energy by creating a complex topology. We conjecture that these two processes with different time scales are relevant to the production of flares.

  12. Laser probe 40Ar/39Ar dating of pseudotachylyte from the Sudbury Structure: evidence for post-impact thermal overprinting in the North Range

    NASA Astrophysics Data System (ADS)

    Thompson, Lucy M.; Spray, John G.; Kelley, Simon P.

    1998-11-01

    Ten pseudotachylyte samples from the North Range of the 1850 Ma Sudbury impact structure have been analyzed by the 40Ar/39Ar laser spot fusion method. Field and petrological evidence indicate that the pseudotachylytes were formed at 1850 Ma by comminution and frictional melting due to impact-induced faulting. The cryptocrystalline to microcrystalline grain size (<30 _?m) of the pseudotachylyte matrices, and the predominance of orthoclase as the main K-bearing phase, have rendered the rocks particularly susceptible to argon loss. The age determinations range from ?1850 Ma to ?1000 Ma, with some samples yielding multiple ages that cannot be correlated with known geological events in the area. However, if the finite-difference algorithm of Wheeler (1996) is used to calculate combined argon loss and the accumulation of radiogenic argon for the K-bearing phases, it is possible to reproduce the range of observed ages. The model infers that the long-term volume diffusion of Ar has occurred and that, as a result, the Ar system cannot be treated with a conventional closure temperature approach. The algorithm requires burial of the impact structure to 5-6 km depth and 160-180 deg C at 1850 Ma, followed by exhumation at ?1000 Ma. These ages may be equated with two events: Penokean thin-skinned overthrusting in the North Range, immediately following impact, and exhumation ?850 Ma later, coincident with the Grenville orogeny to the southeast. The results suggest that, contrary to previously accepted paradigms, the North Range has been affected by a protracted period of post-impact, low-grade thermal metamorphism. If this event also involved tectonic shortening within the North Range, as has been documented for the South Range, then the original size of the Sudbury impact structure has been underestimated.

  13. Modifying the electronic structure of semiconducting single-walled carbon nanotubes by Ar{sup +} ion irradiation

    SciTech Connect

    Tolvanen, Antti; Buchs, Gilles; Ruffieux, Pascal; Groening, Pierangelo; Groening, Oliver; Krasheninnikov, Arkady V.

    2009-03-15

    Local controllable modification of the electronic structure of carbon nanomaterials is important for the development of carbon-based nanoelectronics. By combining density-functional theory simulations with Ar-ion-irradiation experiments and low-temperature scanning tunneling microscopy and spectroscopy (STM/STS) characterization of the irradiated samples, we study the changes in the electronic structure of single-walled carbon nanotubes due to the impacts of energetic ions. As nearly all irradiation-induced defects look as nondistinctive hillocklike features in the STM images, we compare the experimentally measured STS spectra to the computed local density of states of the most typical defects with an aim to identify the type of defects and assess their abundance and effects on the local electronic structure. We show that individual irradiation-induced defects can give rise to single and multiple peaks in the band gap of the semiconducting nanotubes and that a similar effect can be achieved when several defects are close to each other. We further study the stability of defects and their evolution during STM measurements. Our results not only shed light on the abundance of the irradiation-induced defects in carbon nanotubes and their signatures in STS spectra but also suggest a way the STM can be used for engineering the local electronic structure of defected carbon nanotubes.

  14. Tephra sequences as indicators of magma evolution: 40Ar/ 39Ar ages and geochemistry of tephra sequences in the southwest Nevada volcanic field

    NASA Astrophysics Data System (ADS)

    Huysken, K. T.; Vogel, T. A.; Layer, P. W.

    2001-04-01

    Changes in rock chemistry with 40Ar/ 39Ar ages in tephra layers record the temporal and magmatic history of two volcanic systems in southwestern Nevada. Tephra layers from the Post-Grouse Canyon tephra sequence record three distinct groups. These groups are chemically distinct and have 40Ar/ 39Ar ages of 13.52±0.06, 13.31±0.18, and 12.95±0.10 Ma. The age groups correspond to three distinct chemical groups based on trace element distributions. These chemical groups cannot be related by any reasonable fractional crystallization or magma mixing model and are interpreted as distinct magma batches. The Pre-Rainier Mesa tephra sequence records two 40Ar/ 39Ar ages (12.79±0.10 and 11.84±0.18 Ma). The upper portion of this sequence is equivalent in age and chemistry to part of the overlying Rainier Mesa ash-flow sheet. The lower portion of the sequence is equivalent in age to the underlying Tiva Canyon ash-flow sheet but is chemically distinct from this sheet. The formation of this chemical group is consistent with mixing of low silica Tiva Canyon and high silica, low Th, Rainier Mesa magma. Post-Grouse Canyon magmas were most likely emplaced as a series of small, unrelated magma bodies, which allowed them to evolve independently. The mixed Pre-Rainier Mesa magma was produced by infilling of the Tiva Canyon magma chamber with Rainier Mesa-like magma after eruption of the Tiva Canyon ash-flow sheet at approximately 12.8 Ma. The upper portion of the Pre-Rainier Mesa tephra sequence represents eruption of Rainier Mesa magma less than 0.3 My. before that of the voluminous (1200 km 3) Rainier Mesa ash-flow sheet at approximately 11.71 Ma.

  15. Phylogeny and evolution of RNA structure.

    PubMed

    Gesell, Tanja; Schuster, Peter

    2014-01-01

    Darwin's conviction that all living beings on Earth are related and the graph of relatedness is tree-shaped has been essentially confirmed by phylogenetic reconstruction first from morphology and later from data obtained by molecular sequencing. Limitations of the phylogenetic tree concept were recognized as more and more sequence information became available. The other path-breaking idea of Darwin, natural selection of fitter variants in populations, is cast into simple mathematical form and extended to mutation-selection dynamics. In this form the theory is directly applicable to RNA evolution in vitro and to virus evolution. Phylogeny and population dynamics of RNA provide complementary insights into evolution and the interplay between the two concepts will be pursued throughout this chapter. The two strategies for understanding evolution are ultimately related through the central paradigm of structural biology: sequence ⇒ structure ⇒ function. We elaborate on the state of the art in modeling both phylogeny and evolution of RNA driven by reproduction and mutation. Thereby the focus will be laid on models for phylogenetic sequence evolution as well as evolution and design of RNA structures with selected examples and notes on simulation methods. In the perspectives an attempt is made to combine molecular structure, population dynamics, and phylogeny in modeling evolution.

  16. Geology and metallogeny of the Ar Rayn terrane, eastern Arabian shield: Evolution of a Neoproterozoic continental-margin arc during assembly of Gondwana within the East African orogen

    USGS Publications Warehouse

    Doebrich, J.L.; Al-Jehani, A. M.; Siddiqui, A.A.; Hayes, T.S.; Wooden, J.L.; Johnson, P.R.

    2007-01-01

    The Neoproterozoic Ar Rayn terrane is exposed along the eastern margin of the Arabian shield. The terrane is bounded on the west by the Ad Dawadimi terrane across the Al Amar fault zone (AAF), and is nonconformably overlain on the east by Phanerozoic sedimentary rocks. The terrane is composed of a magmatic arc complex and syn- to post-orogenic intrusions. The layered rocks of the arc, the Al Amar group (>689 Ma to ???625 Ma), consist of tholeiitic to calc-alkaline basaltic to rhyolitic volcanic and volcaniclastic rocks with subordinate tuffaceous sedimentary rocks and carbonates, and are divided into an eastern and western sequence. Plutonic rocks of the terrane form three distinct lithogeochemical groups: (1) low-Al trondhjemite-tonalite-granodiorite (TTG) of arc affinity (632-616 Ma) in the western part of the terrane, (2) high-Al TTG/adakite of arc affinity (689-617 Ma) in the central and eastern part of the terrane, and (3) syn- to post-orogenic alkali granite (607-583 Ma). West-dipping subduction along a trench east of the terrane is inferred from high-Al TTG/adakite emplaced east of low-Al TTG. The Ar Rayn terrane contains significant resources in epithermal Au-Ag-Zn-Cu-barite, enigmatic stratiform volcanic-hosted Khnaiguiyah-type Zn-Cu-Fe-Mn, and orogenic Au vein deposits, and the potential for significant resources in Fe-oxide Cu-Au (IOCG), and porphyry Cu deposits. Khnaiguiyah-type deposits formed before or during early deformation of the Al Amar group eastern sequence. Epithermal and porphyry deposits formed proximal to volcanic centers in Al Amar group western sequence. IOCG deposits are largely structurally controlled and hosted by group-1 intrusions and Al Amar group volcanic rocks in the western part of the terrane. Orogenic gold veins are largely associated with north-striking faults, particularly in and near the AAF, and are presumably related to amalgamation of the Ar Rayn and Ad Dawadimi terranes. Geologic, structural, and metallogenic

  17. Titanium embedded cage structure formation in Al{sub n}Ti{sup +} clusters and their interaction with Ar

    SciTech Connect

    Torres, M. B.; Vega, A.; Balbás, L. C.; Aguilera-Granja, F.

    2014-05-07

    Recently, Ar physisorption was used as a structural probe for the location of the Ti dopant atom in aluminium cluster cations, Al{sub n}Ti{sup +} [Lang et al., J. Am. Soc. Mass Spectrom. 22, 1508 (2011)]. As an experiment result, the lack of Ar complexes for n > n{sub c} determines the cluster size for which the Ti atom is located inside of an Al cage. To elucidate the decisive factors for the formation of endohedrally Al{sub n}Ti{sup +}, experimentalists proposed detailed computational studies as indispensable. In this work, we investigated, using the density functional theory, the structural and electronic properties of singly titanium doped cationic clusters, Al{sub n}Ti{sup +} (n = 16–21) as well as the adsorption of an Ar atom on them. The first endohedral doped cluster, with Ti encapsulated in a fcc-like cage skeleton, appears at n{sub c} = 21, which is the critical number consistent with the exohedral-endohedral transition experimentally observed. At this critical size the non-crystalline icosahedral growth pattern, related to the pure aluminium clusters, with the Ti atom in the surface, changes into a endohedral fcc-like pattern. The map of structural isomers, relative energy differences, second energy differences, and structural parameters were determined and analyzed. Moreover, we show the critical size depends on the net charge of the cluster, being different for the cationic clusters (n{sub c} = 21) and their neutral counterparts (n{sub c} = 20). For the Al {sub n} Ti {sup +} · Ar complexes, and for n < 21, the preferred Ar adsorption site is on top of the exohedral Ti atom, with adsorption energy in very good agreement with the experimental value. Instead, for n = 21, the Ar adsorption occurs on the top an Al atom with very low absorption energy. For all sizes the geometry of the Al{sub n}Ti{sup +} clusters keeps unaltered in the Ar-cluster complexes. This fact indicates that Ar adsorption does not influence the cluster structure, providing support

  18. Crystal structures of Mycobacterium tuberculosis HspAT and ArAT reveal structural basis of their distinct substrate specificities

    PubMed Central

    Nasir, Nazia; Anant, Avishek; Vyas, Rajan; Biswal, Bichitra Kumar

    2016-01-01

    Aminotransferases of subfamily Iβ, which include histidinol phosphate aminotransferases (HspATs) and aromatic amino acid aminotransferases (ArATs), are structurally similar but possess distinct substrate specificities. This study, encompassing structural and biochemical characterisation of HspAT and ArAT from Mycobacterium tuberculosis demonstrates that the residues lining the substrate binding pocket and N-terminal lid are the primary determinants of their substrate specificities. In mHspAT, hydrophilic residues in the substrate binding pocket and N-terminal lid allow the entry and binding of its preferential substrate, Hsp. On the other hand, the hydrophobic nature of both the substrate binding pocket and the N-terminal lid of mArAT is responsible for the discrimination of a polar substrate such as Hsp, while facilitating the binding of Phe and other aromatic residues such as Tyr and Trp. In addition, the present study delineates the ligand induced conformational rearrangements, providing insights into the plasticity of aminotransferases. Furthermore, the study also demonstrates that the adventitiously bound ligand 2-(N-morpholino)ethanesulfonic acid (MES) is indeed a specific inhibitor of HspAT. These results suggest that previously untapped morpholine-ring scaffold compounds could be explored for the design of new anti-TB agents. PMID:26738801

  19. 40Ar/39Ar and (U-Th)/He - 4He/3He geochronology of landscape evolution and channel iron deposit genesis at Lynn Peak, Western Australia

    NASA Astrophysics Data System (ADS)

    Vasconcelos, Paulo M.; Heim, Jonathan A.; Farley, Kenneth A.; Monteiro, Hevelyn; Waltenberg, Kathryn

    2013-09-01

    (U-Th)/He geochronology of authigenic goethite cements from the Lynn Peak channel iron deposit (CID), Hamersley Province, Western Australia, reveals a history of mineral precipitation ranging from ca. 33 to 14 Ma. Massive goethites from nearby weathering profiles at Roy Hill North, a possible source of detrital material during the aggradation of the Lynn Peak channels, yield (U-Th)/He results as old as ca. 64 Ma. The combination of (U-Th)/He geochronology with incremental outgassing 4He/3He studies on proton-irradiated samples reveals that Lynn Peak goethites host radiogenic 4He in low retentivity (LRD) and high retentivity (HRD) domains and that the HRDs account for most of the sample mass and have lost very little of their original 4He over geologic time. Such high retentivity is especially notable given the goethites were collected from the surface, where they were subject to significant heating by solar irradiation. Minor contamination by detrital fragments of potentially 4He-rich primary phases (e.g., rutile, ilmenite, zircon) occurs in some samples. Fortunately, the 4He/3He method permits characterization of this extraneous 4He component, which is small (<10 wt.% of the total 4He in the goethite) and can be corrected out in estimating the goethite formation age. These results indicate that the Lynn Peak channel was already aggraded and undergoing goethite cementation by ca. 33 Ma. The history of aggradation and channel cementation independently measured through 40Ar/39Ar geochronology is consistent with that obtained from the (U-Th)/He and 4He/3He record. Laser incremental-heating 40Ar/39Ar geochronology of detrital and authigenic Mn oxides, primarily cryptomelane (KMn8O16·xH2O), from the same locality in the Lynn Peak channel reveals that detrital oxides are older than ca. 44 Ma (and as old as ca. 65 Ma) and authigenic oxides are younger than ca. 35 Ma and as young as ca. 16 Ma. Authigenic cryptomelane precipitation and channel cementation occurred

  20. Imprint of evolution on protein structures

    NASA Astrophysics Data System (ADS)

    Tiana, Guido; Shakhnovich, Boris E.; Dokholyan, Nikolay V.; Shakhnovich, Eugene I.

    2004-03-01

    We attempt to understand the evolutionary origin of protein folds by simulating their divergent evolution with a three-dimensional lattice model. Starting from an initial seed lattice structure, evolution of model proteins progresses by sequence duplication and subsequent point mutations. A new gene's ability to fold into a stable and unique structure is tested each time through direct kinetic folding simulations. Where possible, the algorithm accepts the new sequence and structure and thus a "new protein structure" is born. During the course of each run, this model evolutionary algorithm provides several thousand new proteins with diverse structures. Analysis of evolved structures shows that later evolved structures are more designable than seed structures as judged by recently developed structural determinant of protein designability, as well as direct estimate of designability for selected structures by thermodynamic sampling of their sequence space. We test the significance of this trend predicted on lattice models on real proteins and show that protein domains that are found in eukaryotic organisms only feature statistically significant higher designability than their prokaryotic counterparts. These results present a fundamental view on protein evolution highlighting the relative roles of structural selection and evolutionary dynamics on genesis of modern proteins.

  1. Evolution of plasma parameters in an Ar-N2/He inductive plasma source with magnetic pole enhancement

    NASA Astrophysics Data System (ADS)

    Maria, Younus; N, U. Rehman; M, Shafiq; M, Naeem; M, Zaka-Ul-Islam; M, Zakaullah

    2017-02-01

    Magnetic pole enhanced inductively coupled plasmas (MaPE-ICPs) are a promising source for plasma-based etching and have a wide range of material processing applications. In the present study Langmuir probe and optical emission spectroscopy were used to monitor the evolution of plasma parameters in a MaPE-ICP Ar-N2/He mixture plasma. Electron density ({n}{{e}}) and temperature ({T}{{e}}), excitation temperature ({T}{{exc}}), plasma potential ({V}{{p}}), skin depth (δ ) and the evolution of the electron energy probability function (EEPF) are reported as a function of radiofrequency (RF) power, pressure and argon concentration in the mixture. It is observed that {n}{{e}} increases while {T}{{e}} decreases with increase in RF power and argon concentration in the mixture. The emission intensity of the argon line at 750.4 nm is also used to monitor the variation of the ‘high-energy tail’ of the EEPF with RF power and gas pressure. The EEPF has a ‘bi-Maxwellian’ distribution at low RF powers and higher pressure in a pure {{{N}}}2 discharge. However, it evolves into a ‘Maxwellian’ distribution at RF powers greater than 70 W for pure {{{N}}}2, and at 50 W for higher argon concentrations in the mixture. The effect of argon concentration on the temperatures of two electron groups in the ‘bi-Maxwellian’ EEPF is examined. The temperature of the low-energy electron group {T}{{L}} shows a decreasing trend with argon addition until the ‘thermalization’ of the two temperatures occurs, while the temperature of high-energy electrons {T}{{H}} decreases continuously.

  2. Evolution of dinosaur epidermal structures.

    PubMed

    Barrett, Paul M; Evans, David C; Campione, Nicolás E

    2015-06-01

    Spectacularly preserved non-avian dinosaurs with integumentary filaments/feathers have revolutionized dinosaur studies and fostered the suggestion that the dinosaur common ancestor possessed complex integumentary structures homologous to feathers. This hypothesis has major implications for interpreting dinosaur biology, but has not been tested rigorously. Using a comprehensive database of dinosaur skin traces, we apply maximum-likelihood methods to reconstruct the phylogenetic distribution of epidermal structures and interpret their evolutionary history. Most of these analyses find no compelling evidence for the appearance of protofeathers in the dinosaur common ancestor and scales are usually recovered as the plesiomorphic state, but results are sensitive to the outgroup condition in pterosaurs. Rare occurrences of ornithischian filamentous integument might represent independent acquisitions of novel epidermal structures that are not homologous with theropod feathers.

  3. Evolution of dinosaur epidermal structures

    PubMed Central

    Barrett, Paul M.; Evans, David C.; Campione, Nicolás E.

    2015-01-01

    Spectacularly preserved non-avian dinosaurs with integumentary filaments/feathers have revolutionized dinosaur studies and fostered the suggestion that the dinosaur common ancestor possessed complex integumentary structures homologous to feathers. This hypothesis has major implications for interpreting dinosaur biology, but has not been tested rigorously. Using a comprehensive database of dinosaur skin traces, we apply maximum-likelihood methods to reconstruct the phylogenetic distribution of epidermal structures and interpret their evolutionary history. Most of these analyses find no compelling evidence for the appearance of protofeathers in the dinosaur common ancestor and scales are usually recovered as the plesiomorphic state, but results are sensitive to the outgroup condition in pterosaurs. Rare occurrences of ornithischian filamentous integument might represent independent acquisitions of novel epidermal structures that are not homologous with theropod feathers. PMID:26041865

  4. The tectono-thermal evolution of the Waterbury dome, western Connecticut, based on U-Pb and 40Ar/39Ar ages

    USGS Publications Warehouse

    Dietsch, Craig; Kunk, Michael J.; Aleinikoff, John; Sutter, John F.

    2010-01-01

    Level 3 nappes were emplaced over the Waterbury dome along an Acadian décollement synchronous with the formation of a D3 thrust duplex in the dome. The décollement truncates the Ky + Kfs-in (migmatite) isograd in the dome core and a St-in isograd in level 3 nappes, indicating that peak metamorphic conditions in the dome core and nappe cover rocks formed in different places at different times. Metamorphic overgrowths on zircon from the felsic orthogneiss in the Waterbury dome have an age of 387 ± 5 Ma. Rocks of all levels and the décollement are folded by D4 folds that have a strongly developed, regional crenulation cleavage and D5 folds. The Waterbury dome was formed by thrust duplexing followed by fold interference during the Acadian orogeny. The 40Ar/39Ar ages of amphibole, muscovite, biotite, and K-feldspar from above and below the décollement are ca. 378 Ma, 355 Ma, 360 Ma (above) and 340 (below), and 288 Ma, respectively. Any kilometer-scale vertical movements between dome and nappe rocks were over by ca. 378 Ma. Core and cover rocks of the Waterbury dome record synchronous, post-Acadian cooling.

  5. Structural, electrical and optical studies of gold nanostructures formed by Ar plasma-assisted sputtering

    NASA Astrophysics Data System (ADS)

    Siegel, J.; Kvítek, O.; Slepička, P.; Náhlík, J.; Heitz, J.; Švorčík, V.

    2012-02-01

    Ultrathin gold layers with different thickness of (10-100 nm) on the glass substrate were obtained by Ar plasma-assisted sputtering. The effects of annealing on gold structures sputtered onto glass substrate were studied using AFM, SEM, UV-Vis methods and electrical measurements. Concentration of free charge carriers were determined from the measured resistance and the Hall constant measured by the Van der Pauw method. We have shown that post-deposition thermal treatment leads in significant change in surface morphology of the sputtered Au structures. Our results suggest that the annealing affects electrical properties of the Au coverage namely electrical sheet resistance, free carriers volume concentration, the saturation of which is in comparison with as-sputtered samples shifted towards thicker structures. While semi-conductive character of as-sputtered samples diminishes close to the Au structure thickness of ca 20 nm, in the case of the annealed structures zero-level saturation is achieved for the thickness of 60 nm.

  6. Structural manipulation of the graphene/metal interface with Ar+ irradiation

    NASA Astrophysics Data System (ADS)

    Åhlgren, E. H.; Hämäläinen, S. K.; Lehtinen, O.; Liljeroth, P.; Kotakoski, J.

    2013-10-01

    Controlled defect creation is a prerequisite for the detailed study of disorder effects in materials. Here, we irradiate a graphene/Ir(111) interface with low-energy Ar+ to study the induced structural changes. Combining computer simulations and scanning-probe microscopy, we show that the resulting disorder manifests mainly in the forms of intercalated metal adatoms and vacancy-type defects in graphene. One prominent feature at higher irradiation energies (from 1 keV up) is the formation of linelike depressions, which consist of sequential graphene defects created by the ion channeling within the interface, much like a stone skipping on water. Lower energies result in simpler defects, down to 100 eV, where more than one defect in every three is a graphene single vacancy.

  7. Evolution of Coextruded Structures in Static Mixers

    NASA Astrophysics Data System (ADS)

    Sollogoub, C.; Guinault, A.; Pedros, M.

    2007-04-01

    Coextrusion allows to combine two thermoplastics in different ways, creating structures with different cross-sectional geometries (side-by-side structure or concentric ring structure). We use static mixers after the feedblock, in order to homogenise these initial structures and obtain different blend morphologies. The control of these morphologies is of prime importance in order to predict the final properties of the polymer blends. The aim of this paper is to study the evolution of some initial coextruded structures in different static mixers. Different static mixers, with adjustable number of mixing elements, are tested. The experimental observations are confronted with numerical simulation results.

  8. Evolution of the Himalayan structures

    SciTech Connect

    Bhatt, K. )

    1990-05-01

    Sedimentologically, the Himalayan sediments were deposited in the Tethyan Sea and represent rocks from the Paleozoic to the Holocene. During the early Paleozoic, localized movements divided the Tethyan Sea into two geosynclines separated by a geoanticline of Precambrian central crystallines. The northern deep basin which contains euogeosynclinal sediments, is known as the Tethyan zone, and the southern shallow basin which has miogeosynclinal sediments, represents the rocks of the Himalayan zone. Structurally, three major zones of tectonic movement have been recognized, all of which show similar structural trend: (1) along the Indus suture zone (ISZ), (2) along the Main Central thrust (MCT), and (3) along the Main Boundary thrust (MBT). The ISZ represents the subduction zone between the Indian and Asian plate. The origin of the MCT is related to initial subduction along the trench area and may have been formed during the Late Cretaceous-early Paleocene due to offscrapping of sediments in the subduction zone. Further compression between the two plates caused southward migration of the subduction zone and formed the MBT, during or after the Pliocene, which brought old Paleozoic rocks of lesser Himalaya in contact with younger Tertiary rocks (Siwaliks) of Sub-Himalaya. Both the MCT and MBT are parts of an imbricated system formed in the subduction zone representing different geological time periods. The present position of the subduction zone indicates that future subduction of Indian plate into the Asian plate and will cause tectonic activation of the MBT and movement along the MCT will diminish.

  9. Conservation of steroidogenic acute regulatory (StAR) protein structure and expression in vertebrates.

    PubMed

    Bauer, M P; Bridgham, J T; Langenau, D M; Johnson, A L; Goetz, F W

    2000-10-25

    Complementary DNAs for the open reading frames of the chicken, Xenopus and zebrafish StAR homologs were cloned along with a partial cDNA of the zebrafish homolog to MLN64, a StAR-related protein. A comparison of the amino acid sequences of piscine, amphibian, avian and mammalian StARs, indicates strong conservation of the protein across divergent vertebrate groups. On Northern blots probed with species specific StAR cDNAs, expression of StAR transcripts was observed in the ovary and adrenal of chicken, and the ovary, testis, kidney and head of zebrafish. The expression of StAR mRNA in various compartments of the hen ovary was consistent with the results of past studies on steroidogenesis; expression was first observed in follicles selected into the preovulatory hierarchy and was greatest in the largest preovulatory follicle. The expression of StAR mRNA was also consistent with aromatase expression in zebrafish ovaries. The conserved deduced protein sequence and expression pattern of StAR transcripts in chicken and zebrafish tissues, strongly suggest that StAR is also involved in the regulation of steroidogenesis in nonmammalian vertebrates.

  10. Evolution of cooperation in spatially structured populations

    PubMed

    Brauchli; Killingback; Doebeli

    1999-10-21

    Using a spatial lattice model of the Iterated Prisoner's Dilemma we studied the evolution of cooperation within the strategy space of all stochastic strategies with a memory of one round. Comparing the spatial model with a randomly mixed model showed that (1) there is more cooperative behaviour in a spatially structured population, (2) PAVLOV and generous variants of it are very successful strategies in the spatial context and (3) in spatially structured populations evolution is much less chaotic than in unstructured populations. In spatially structured populations, generous variants of PAVLOV are found to be very successful strategies in playing the Iterated Prisoner's Dilemma. The main weakness of PAVLOV is that it is exploitable by defective strategies. In a spatial context this disadvantage is much less important than the good error correction of PAVLOV, and especially of generous PAVLOV, because in a spatially structured population successful strategies always build clusters. Copyright 1999 Academic Press.

  11. Evolution of the rheological structure of Mars

    NASA Astrophysics Data System (ADS)

    Azuma, Shintaro; Katayama, Ikuo

    2017-01-01

    The evolution of Mars has been greatly influenced by temporal changes in its rheological structure, which may explain the difference in tectonics between Mars and Earth. Some previous studies have shown the rheological structures of Mars calculated from the flow law of rocks and the predicted thermal structure. However, the Peierls mechanism, which is the dominant deformation mechanism at relatively low temperature, and the evolution of water reservoirs on Mars were not considered in such studies. In this paper, we apply the Peierls mechanism to refine the rheological structure of Mars to show a new history of the planet that considers the most recent reports on its evolution of water reservoirs. Considering the Peierls creep and the evolution of water reservoirs, we attempt to explain why the tectonics of Mars is inactive compared with that of Earth. On early Mars, the lithospheric thickness inferred from the brittle-ductile transition was small, and the lithospheric strength was low ( 200-300 MPa) under wet conditions at 4 Gya. This suggests that plate boundaries could have developed on the early "wet" Mars, which is a prerequisite for the operation of plate tectonics. Our results also imply that the lithospheric strength had significantly increased in the Noachian owing to water loss. Therefore, plate tectonics may have ceased or could no longer be initiated on Mars. At the least, the tectonic style of Mars would have dramatically changed during the Noachian.[Figure not available: see fulltext.

  12. Object Recognition and Random Image Structure Evolution

    ERIC Educational Resources Information Center

    Sadr, Jvid; Sinha, Pawan

    2004-01-01

    We present a technique called Random Image Structure Evolution (RISE) for use in experimental investigations of high-level visual perception. Potential applications of RISE include the quantitative measurement of perceptual hysteresis and priming, the study of the neural substrates of object perception, and the assessment and detection of subtle…

  13. Cross-linked structure of network evolution

    SciTech Connect

    Bassett, Danielle S.; Wymbs, Nicholas F.; Grafton, Scott T.; Porter, Mason A.; Mucha, Peter J.

    2014-03-15

    We study the temporal co-variation of network co-evolution via the cross-link structure of networks, for which we take advantage of the formalism of hypergraphs to map cross-link structures back to network nodes. We investigate two sets of temporal network data in detail. In a network of coupled nonlinear oscillators, hyperedges that consist of network edges with temporally co-varying weights uncover the driving co-evolution patterns of edge weight dynamics both within and between oscillator communities. In the human brain, networks that represent temporal changes in brain activity during learning exhibit early co-evolution that then settles down with practice. Subsequent decreases in hyperedge size are consistent with emergence of an autonomous subgraph whose dynamics no longer depends on other parts of the network. Our results on real and synthetic networks give a poignant demonstration of the ability of cross-link structure to uncover unexpected co-evolution attributes in both real and synthetic dynamical systems. This, in turn, illustrates the utility of analyzing cross-links for investigating the structure of temporal networks.

  14. The Structure of Scientific Evolution.

    PubMed

    Killeen, Peter R

    2013-01-01

    Science is the construction and testing of systems that bind symbols to sensations according to rules. Material implication is the primary rule, providing the structure of definition, elaboration, delimitation, prediction, explanation, and control. The goal of science is not to secure truth, which is a binary function of accuracy, but rather to increase the information about data communicated by theory. This process is symmetric and thus entails an increase in the information about theory communicated by data. Important components in this communication are the elevation of data to the status of facts, the descent of models under the guidance of theory, and their close alignment through the evolving retroductive process. The information mutual to theory and data may be measured as the reduction in the entropy, or complexity, of the field of data given the model. It may also be measured as the reduction in the entropy of the field of models given the data. This symmetry explains the important status of parsimony (how thoroughly the data exploit what the model can say) alongside accuracy (how thoroughly the model represents what can be said about the data). Mutual information is increased by increasing model accuracy and parsimony, and by enlarging and refining the data field under purview.

  15. The Structure of Scientific Evolution

    PubMed Central

    2013-01-01

    Science is the construction and testing of systems that bind symbols to sensations according to rules. Material implication is the primary rule, providing the structure of definition, elaboration, delimitation, prediction, explanation, and control. The goal of science is not to secure truth, which is a binary function of accuracy, but rather to increase the information about data communicated by theory. This process is symmetric and thus entails an increase in the information about theory communicated by data. Important components in this communication are the elevation of data to the status of facts, the descent of models under the guidance of theory, and their close alignment through the evolving retroductive process. The information mutual to theory and data may be measured as the reduction in the entropy, or complexity, of the field of data given the model. It may also be measured as the reduction in the entropy of the field of models given the data. This symmetry explains the important status of parsimony (how thoroughly the data exploit what the model can say) alongside accuracy (how thoroughly the model represents what can be said about the data). Mutual information is increased by increasing model accuracy and parsimony, and by enlarging and refining the data field under purview. PMID:28018043

  16. The conformational structure of adenosine molecules, isolated in low-temperature Ar matrices

    NASA Astrophysics Data System (ADS)

    Ivanov, A. Yu.; Rubin, Yu. V.; Egupov, S. A.; Belous, L. F.; Karachevtsev, V. A.

    2015-11-01

    FTIR spectra of adenosine (Ado) molecules, isolated in low-temperature matrices, are obtained in the infrared range of 3800-400 cm-1, with a resolution of 0.3. MP2 and DT/B3LYP quantum-mechanical methods are used to calculate the population of major structural Ado isomers. It is shown that Ado can withstand prolonged evaporation at a temperature of 465 K without thermal decomposition. The structure five major conformers that are fixed in Ar matrices at 6 K, are established. Ado anti-conformers with intramolecular hydrogen bonds O2'H-N3, are found. The population of these anti-conformers is more than one and a half times less than the syn-conformer population having the intramolecular hydrogen bond O5'H-N3. In low-temperature matrices, the majority of the dominant conformers are fixed with a C2'-endo ribose ring structure. Similar to 2'-deoxyadenosine (dA), Ado conformers with intramolecular hydrogen bonds O3'H-O5 or O5'H-O3 were not found.

  17. Evolution of West Rota Volcano in the Southern Mariana Arc: Evidence from Swathmapping, Seafloor Robotics, and 40Ar/39Ar Geochronology

    NASA Astrophysics Data System (ADS)

    Stern, R. J.; Tamura, Y.; Embley, R. W.; Ishizuka, O.; Merle, S.; Basu, N. K.; Kawabata, H.; Bloomer, S. H.

    2006-12-01

    West Rota volcano (WRV) is a large (25 km base), extinct submarine volcano in the southern Mariana arc. Its shallowest point lies 300m bsl; before caldera collapse WRV probably was a small island. Several bathymetric and sonar backscatter mapping campaigns reveal a large caldera, 6 x 10 km in diameter, with a maximum of 1km relief. WRV lies near the northern termination of a major NNE-trending normal fault. This and a second, parallel fault just west of the volcano separate uplifted, thick crust beneath the frontal arc to the east from subsiding, thin back-arc basin crust to the west. The youthful morphology of basin-margin faults indicate that the southern Mariana arc is tectonically active. Compared to other Mariana arc volcanoes, WRV is remarkable for 4 reasons: 1) It consists of a lower, predominantly andesite section overlain by a bimodal rhyodacite-basalt layered sequence; 2) Andesitic rocks are locally intensely altered and mineralized; 3) It has a large caldera; and 4) WRV is built on a major fault. Large calderas are commonly associated with volcanoes that erupt voluminous felsic lava (WRV rhyodacite pumice contains 72% SiO2). Such volcanoes are common in the Izu and Kermadec arcs but are otherwise unknown from the Marianas and other primitive, intra- oceanic arcs. WRV's caldera diameter of 6x10 km is large compared with Izu and Kermadec felsic calderas. Robotic seafloor examination has concentrated on understanding the volcanic history exposed in the caldera walls. One dive was carried out with ROPOS during TT167 in April 2004 (R785), followed by 4 dives with Hyperdolphin 3K during NT0517 in Oct. 2005 (HD482-484, 489). 40Ar/39Ar dating indicates that andesitic volcanism formed the lower volcanic section ca. 330,000-550,000 years ago, whereas eruption of the upper rhyodacites and basalts occurred 37,000-51,000 years ago. Four sequences of rhyodacite pyroclastics each are 20-75m thick, are unwelded, and show reverse grading, indicating submarine eruption of

  18. He, Ar, O, Sr and Nd isotope constraints on the origin and evolution of Mount Etna magmatism

    NASA Astrophysics Data System (ADS)

    Marty, Bernard; Trull, Thomas; Lussiez, Patricia; Basile, Isabelle; Tanguy, Jean-Claude

    1994-08-01

    The 0.5 Ma history of the origin and evolution of Mount Etna, Sicily has been investigated by analysing the isotopic composition of He, Ar, O, Sr and Nd in 21 selected lava samples. The near constancy of the isotopic compositions of oxygen δ18O = 5.4 +/- 0.3%) and of helium trapped in olivine phenocrysts (6.7 +/- 0.4 Ra) is interpreted as evidence of a single mantle source, despite drastic petrological changes during the volcano's history. He analyzes performed by crushing cogenetic pyroxene and olivine phenocrysts show a tendency to lower He-3/He-4 ratios in pyroxenes. This is best explained by crystallization of pyroxenes at a depth shallower than that of olivines and/or by exchange of helium trapped in pyroxenes with atmospheric or radiogenic He before eruption. Sr-87/Sr-86 ratios of recent lavas tend to increase with time and to correlate with Rb/Th ratios, and, for historical lavas, these variations are tentatively attributed to shallow selective contamination from underlying sediments. Based on the similarity of the He-3/He-4 ratios at Etna to those of European mantle xenoliths, we propose that the 'baseline' geochemical signature of isotopic tracers at Etna reflects the composition of the subcontinental mantle. Comparison to other southern Italian active volcanoes (Etna, Vulcano Ischia, Campi Flegrei, Vesuvius) shows gradual dilution of the predominantly mantle Etnean end member by more radiogenic Sr and He and material with higher δ18O and C/He-3, which is reasonably explained by the progressively important influence of subducted continental crust.

  19. Learning Protein Structure with Peers in an AR-Enhanced Learning Environment

    ERIC Educational Resources Information Center

    Chen, Yu-Chien

    2013-01-01

    Augmented reality (AR) is an interactive system that allows users to interact with virtual objects and the real world at the same time. The purpose of this dissertation was to explore how AR, as a new visualization tool, that can demonstrate spatial relationships by representing three dimensional objects and animations, facilitates students to…

  20. Characterization of the cod (Gadus morhua) steroidogenic acute regulatory protein (StAR) sheds light on StAR gene structure in fish.

    PubMed

    Goetz, Frederick W; Norberg, Birgitta; McCauley, Linda A R; Iliev, Dimitar B

    2004-03-01

    The full-length cDNA for the cod (Gadus morhua) StAR was cloned by RT-PCR and library screening using ovarian RNA. From the library screening, 2 size classes of cDNA were obtained; a 1577 bp cDNA (cStAR1) and a 2851 bp cDNA (cStAR2). The cStAR1 cDNA presumably encodes a protein of 286 amino acids. The cStAR2 cDNA was composed of 6 separated sequences that contained all of the coding regions of cStAR1 when added together, but also contained 5 noncoding regions not observed in cStAR1. Polymerase chain reactions of cod genomic DNA produced products slightly larger than cStAR2. The sequence of these products were the same as cStAR2 but revealed one additional noncoding region (intron). Thus, the fish StAR gene contains the same number of exons (7) and introns (6) as observed in mammals, but is approximately half the size of the mammalian gene. Using Northern analysis and RT-PCR, cStAR1 expression was observed only in testes, ovaries and head kidneys. Polymerase chain reaction products were also observed using cDNA from steroidogenic tissues and primers designed to regions specific for cStAR2, indicating that cStAR2 is expressed in tissues and may account for the presence of larger transcripts observed on Northern blots.

  1. Structural-energetic regularities of tribocontact evolution

    NASA Astrophysics Data System (ADS)

    Fedorov, S.

    2017-02-01

    The contact of friction lives with its own very interesting life. It gets evolved. This evolution of contact changes the states and properties of it. How can we describe the tribocontact evolution? Any nature systems are very well described by thermodynamic method. The contact of friction has the system properties and therefore one may use thermodynamic approach. From thermodynamic point of view friction is a competition of two simultaneous, interconnected and opposite tendencies of accumulating latent (potential) energy of various kinds of defects and damages of contact volumes structures and releasing (dissipation) energy due to various relaxation processes. This friction adaptive-dissipative model for analysis of evolution of tribocontact as elementary tribosystem is examined. This paper was accepted for publication in Proceedings after double peer reviewing process but was not presented at the Conference ROTRIB’16

  2. 40Ar/39Ar age of the Manson impact structure, Iowa, and correlative impact ejecta in the Crow Creek member of the Pierre Shale (Upper Cretaceous), South Dakota and Nebraska

    USGS Publications Warehouse

    Izett, G.A.; Cobban, W.A.; Dalrymple, G.B.; Obradovich, J.D.

    1998-01-01

    A set of 34 laser total-fusion 40Ar/39Ar analyses of sanidine from a melt layer in crater-fill deposits of the Manson impact structure in Iowa has a weighted-mean age of 74.1 ?? 0.1 Ma. This age is about 9.0 m.y. older than 40Ar/39Ar ages of shocked microcline from the Manson impact structure reported previously by others. The 74.1 Ma age of the sanidine, which is a melt product of Precambrian microcline clasts, indicates that the Manson impact structure played no part in the Cretaceous-Tertiary (K-T) mass extinction at 64.5 Ma. Moreover, incremental-heating 40Ar/39Ar ages of the sanidine show that it is essentially free of excess 40Ar and has not been influenced by postcrystallization heating or alteration. An age spectrum of the matrix of the melt layer shows effects of 39Ar recoil, including older ages in the low-temperature increments and younger ages in the high-temperature increments. At 17 places in eastern South Dakota and Nebraska, shocked quartz and feldspar grains are concentrated in the lower part of the Crow Creek Member of the Pierre Shale (Upper Cretaceous). The grains are largest (3.2 mm) in southeastern South Dakota and decrease in size (0.45 mm) to the northwest, consistent with the idea that the Manson impact structure was their source. The ubiquitous presence of shocked grains concentrated in a thin calcarenite at the base of the Crow Creek Member suggests it is an event bed recording an instant of geologic time. Ammonites below and above the Crow Creek Member limit its age to the zone of Didymoceras nebrascense of earliest late Campanian age. Plagioclase from a bentonite bed in this zone in Colorado has a 40Ar/39Ar age of 74.1 ?? 0.1 Ma commensurate with our sanidine age of 74.1 Ma for the Manson impact structure. 40Ar/39Ar ages of bentonite beds below and above the Crow Creek are consistent with our 74.1 ?? 0.1 Ma age for the Manson impact structure and limit its age to the interval ?? 74.5 0.1 to 73.8 ?? 0.1 Ma. Recently, two origins for the

  3. Interior Structure and Evolution of the Planets

    NASA Astrophysics Data System (ADS)

    Hubbard, W. B.

    Basic Concepts Presumed initial composition Comparison with stellar structure Structure of Cold Bodies T=O thermodynamics The P--> infinity limit (white dwarfs) Finite pressure theories Experimental data at high pressure The radius-mass diagram Heat Flow Review of data The Kelvin mechanism Differentiation Radioactivity Tidal Heating Other Diagnostics of Interior Structure Response to rotation Tidal response Magnetic field The Terrestrial Planets The earth and the moon Mercury Venus Mars Summary The Jovian Planets Jupiter A fundamental solar composition reference? Thermal structure and heat flow Evolution of Jupiter Saturn Differences with Jupiter Heat flow Uranus and Neptune Key differences with Jupiter and with each other Thermal structure and heat flow Jovian Planet Satellites Io's heat flow and its relation to Jupiter's structure The Galilean satellites and their relation to Jupiter's origin Conclusion References

  4. Evolution of salt-related structures

    SciTech Connect

    Bishop, R.S.

    1988-01-01

    Several types of structures (piercements, turtles, and nonpiercements) are caused by salt movement. Reconstructions show that the emplacement process is basically the same for many geometrically dissimilar structures, but that the great differences of shape originated from different patterns of sediment loading, salt thickness, and basin evolution. The reconstructions are generalizations derived from numerous real examples to show timing, evolution of dip, origin of thickness changes and overchanges, how the salt-sediment volume exchange occurs, and diagnostic criteria to interpret these events. Such reconstructions help to discriminate between turtles and nonpiercements, to interpret lithofacies, and to unravel the role of sedimentary events on the structural evolution. In addition, they illustrate the mechanism of diapirism, using criteria to help distinguish diapirism in an overburden having strength (the mechanism assumed here) from diapirism in a viscous overburden (the classical buoyancy theory). In general, many piercements may start quite early (even before a density inversion exists) and move primarily by extrusion or may alternate between extrusion and intrusion beneath a thin overburden. The pattern of sedimentation largely determines the pattern of diapirism. In contrast, nonpiercements and turtle structures are passive features and may form whenever salt migrates away from them to an adjacent ''escape hatch.'' For example, nonpiercements may not form by salt rising vertically, but rather by salt moving away horizontally to some point of escape. In other words, the dome remains static while the overburden collapses into the rim syncline.

  5. Interference structures in the differential cross-sections for inelastic scattering of NO by Ar.

    PubMed

    Eyles, C J; Brouard, M; Yang, C-H; Kłos, J; Aoiz, F J; Gijsbertsen, A; Wiskerke, A E; Stolte, S

    2011-06-12

    Inelastic scattering is a fundamental collisional process that plays an important role in many areas of chemistry, and its detailed study can provide valuable insight into more complex chemical systems. Here, we report the measurement of differential cross-sections for the rotationally inelastic scattering of NO(X2Π1/2, v=0, j=0.5, f) by Ar at a collision energy of 530 cm(-1) in unprecedented detail, with full Λ-doublet (hence total NO parity) resolution in both the initial and final rotational quantum states. The observed differential cross-sections depend sensitively on the change in total NO parity on collision. Differential cross-sections for total parity-conserving and changing collisions have distinct, novel quantum-mechanical interference structures, reflecting different sensitivities to specific homonuclear and heteronuclear terms in the interaction potential. The experimental data agree remarkably well with rigorous quantum-mechanical scattering calculations, and reveal the role played by total parity in acting as a potential energy landscape filter.

  6. 40Ar-39Ar Ages of the Large Impact Structures Kara and Manicouagan and their Relevance to the Cretaceous-Tertiary and the Triassic-Jurassic Boundary

    NASA Astrophysics Data System (ADS)

    Trieloff, M.; Jessberger, E. K.

    1992-07-01

    Since the discovery of the iridium enrichment in Cretaceous- Tertiary boundary clays by Alvarez et al. (1980) the search for the crater of the K/T impactor is in progress. Petrographic evidence at the K/T boundary material points towards an impact into an ocean as well as onto the continental crust, multiple K/T impacts are now being considered (Alvarez and Asaro, 1990). One candidate is the Kara crater in northern Siberia of which Kolesnikov et al. (1988) determined a K-Ar isochrone age of 65.6 +- 0.5 Ma, regarding this as indicating that the Kara bolide is at least one of the K/T impactors. Koeberl et al. (1990) determined ^40Ar-^39Ar ages of six impact melts ranging from 70 to 82 Ma and suggested rather an association to the Campanian- Maastrichtian boundary, another important extinction horizon 73 Ma ago (Harland et al., 1982). We dated with the ^40Ar-^39Ar technique four impact melts, KA2- 306, KA2-305, SA1-302 and AN9-182. The spectra have rather well- defined plateaus, shown with highly extended age scales (Fig. 1). The plateau ages range from 69.3 to 71.7 Ma. Our data do not support an association either with the Cretaceous-Tertiary or with the Campanian-Maastrichtian boundary. We deduce an age of 69-71 Ma for the Kara impact structure. Nazarov et al. (1991) have demonstrated by isotopic hydrogen studies that the Kara bolide impacted on dry land, while the last regression at the target area before the end of the Cretaceous occurred 69-70 Ma ago. Our data are consistent with an impact shortly after the regression. We further dated impact metamorphic anorthosite samples (10BD5 and 10BD3C) of the Manicouagan crater, Canada, which may be related to the Triassic-Jurassic boundary (McLaren and Goodfellow, 1990). The samples consist of two different phases, one degassing at low temperatures yielding a plateau age of 212 Ma and another phase which was degassed during the cratering event to varying degrees with apparent ages increasing up to 950 Ma, the age of the

  7. Evolution on folding landscapes in combinatorial structures

    SciTech Connect

    Fraser, S.M.; Reidys, C.M.

    1997-11-01

    In this paper the authors investigate the evolution of molecular structures by random point mutations. They will consider two types of molecular structures: (a) (RNA) secondary structures, and (b) random structures. In both cases structure consists of: (1) a contact graph, and (2) a family of relations imposed on its adjacent vertices. The vertex set of the contact graph is simply the set of all indices of a sequence, and its edges are the bonds. The corresponding relations associated with the edges are viewed as secondary base pairing rules and tertiary interaction rules respectively. Mapping of sequences into secondary and random structures are modeled and analyzed. Here, the set of all sequences that map into a particular structure is modeled as a random graph in the sequence space, the so called neutral network and they study how neutral networks are embedded in sequence space. A basic replication of deletion experiment reveals how effective secondary and random structures can be searched by random point mutations and to what extent the structure effects the dynamics of this optimization process. In particular the authors can report a nonlinear relation between the fraction of tertiary interactions in random structures, and the times taken for a population of sequences to find a high fitness target random structure.

  8. 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.

  9. Ab initio potential energy surface and predicted microwave spectra for Ar--OCS dimer and structures of Arn--OCS (n = 2-14) clusters.

    PubMed

    Zhu, Hua; Guo, Yong; Xue, Ying; Xie, Daiqian

    2006-07-15

    An ab initio potential energy surface for the Ar--OCS dimer was calculated using the coupled-cluster singles and doubles with noniterative inclusion of connected triples [CCSD(T)] with a large basis set containing bond functions. The interaction energies were obtained by the supermolecular approach with the full counterpoise correction for the basis set superposition error. The CCSD(T) potential was found to have two minima corresponding to the T-shaped and the collinear Ar--SCO structures. The two-dimensional discrete variable representation method was employed to calculate the rovibrational energy levels for five isotopomers Ar--OCS, Ar--OC34S, Ar--O13CS, Ar--18OCS, and Ar--17OCS. The calculated pure rotational transition frequencies for the vibrational ground state of the five isotopomers are in good agreement with the observed values. The corresponding microwave spectra show that the b-type transitions (Delta Ka = +/-1) are significantly stronger than the a-type transitions (Delta Ka = 0). Minimum-energy structures of the Ar2--OCS trimer were been determined with MP2 optimization, whereas the minimum-energy structures of the Arn--OCS clusters with n = 3-14 were obtained with the pairwise additive potentials. It was found that there are two minima corresponding to one distorted tetrahedral structure and one planar structure for the ternary complex. The 14 nearest neighbor Ar atoms form the first solvation shell around the OCS molecule.

  10. Finite temperature path integral Monte Carlo simulations of structural and dynamical properties of ArN-CO2 clusters

    NASA Astrophysics Data System (ADS)

    Wang, Lecheng; Xie, Daiqian

    2012-08-01

    We report finite temperature quantum mechanical simulations of structural and dynamical properties of ArN-CO2 clusters using a path integral Monte Carlo algorithm. The simulations are based on a newly developed analytical Ar-CO2 interaction potential obtained by fitting ab initio results to an anisotropic two-dimensional Morse/Long-range function. The calculated distributions of argon atoms around the CO2 molecule in ArN-CO2 clusters with different sizes are consistent to the previous studies of the configurations of the clusters. A first-order perturbation theory is used to quantitatively predict the CO2 vibrational frequency shift in different clusters. The first-solvation shell is completed at N = 17. Interestingly, our simulations for larger ArN-CO2 clusters showed several different structures of the argon shell around the doped CO2 molecule. The observed two distinct peaks (2338.8 and 2344.5 cm-1) in the υ3 band of CO2 may be due to the different arrangements of argon atoms around the dopant molecule.

  11. The Late-Holocene evolution of the Miseno area (south-western Campi Flegrei) as inferred by stratigraphy, petrochemistry and 40Ar/39Ar geochronology:Chapter 6 in Volcanism in the Campania Plain — Vesuvius, Campi Flegrei and Ignimbrites

    USGS Publications Warehouse

    Insinga, Donatella; Calvert, Andrew T.; Lanphere, Marvin A.; Morra, Vincenzo; Perrotta, Annamaria; Sacchi, Marco; Scarpati, Claudio; Saburomaru, James; Fedele, Lorenzo

    2006-01-01

    This study on terrestrial and marine successions increases the understanding of the Late-Holocene volcanological and stratigraphical evolution of the south-western part of Campi Flegrei caldera.Stratigraphic data derived from field studies of two major tuff vents located along the coastal zone, namely Porto Miseno and Capo Miseno, clearly indicate that the Porto Miseno tuff ring slightly predates the Capo Miseno tuff cone. 40Ar/39Ar step-heating experiments, carried out on fresh sanidine separates from pumice samples, yielded a plateau age of 5090±140 yr BP for Capo Miseno and 6490±510 yr BP for Porto Miseno vent, thus confirming field observations.The volcanoclastic input derived from this recent and intense eruptive activity played a major role in the inner-shelf stratigraphic evolution of the Porto Miseno Bay deposits that have been drilled up to 40 m depth off the crater rim. The cored succession is characterised by transgressive marine deposits (mostly volcanic sand) with two intercalated peat layers (t1 and t2), dated at 3560±40 yr BP and 7815±55 yr BP (14C), respectively, interbedded with a 1–5 m thick pumice layer (tephra C). Peat layers have been chronostratigraphically correlated with two widespread paleosols onland while petrochemical analyses allowed us to correlate tephra C with the Capo Miseno tuff cone deposits.The results presented in this study imply a Late-Holocene volcanic activity that is also well preserved in the marine record in this sector of the caldera where a new chronostratigraphic reconstruction of the eruptive events is required in order to better evaluate the hazard assessment of the area.

  12. A monomeric thallium(I) amide in the solid state: synthesis and structure of TlN(Me)ArMes2 (ArMes2 = C6H3-2,6-Mes2).

    PubMed

    Wright, Robert J; Brynda, Marcin; Power, Philip P

    2005-05-16

    Reaction of TlCl and [LiN(Me)Ar(Mes)2](2) [Ar(Mes)2 = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2)] in Et(2)O generated the thallium amide, TlN(Me)Ar(Mes)2 (1). X-ray data showed that it has a monomeric structure with an average Tl-N distance of 2.364(3) Angstroms. There was also a Tl-arene approach [Tl-centroid = 3.026(2) Angstroms (avg)] to a flanking mesityl ring from the terphenyl substituent. DFT calculations showed that this interaction is weak and supported essentially one coordination for thallium. The electronic spectrum of 1 is hypsochromically shifted in comparison to the monomeric TlAr(Trip)2 (Trip = C(6)H(2)-2,4,6-Pr(i)(3)).

  13. Relief history and denudation evolution of the northern Tibet margin: Constraints from 40Ar/39Ar and (U-Th)/He dating and implications for far-field effect of rising plateau

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Feng, Huile; Shi, Wenbei; Zhang, Weibin; Wu, Lin; Yang, Liekun; Wang, Yinzhi; Zhang, Zhigang; Zhu, Rixiang

    2016-04-01

    How does the rising Tibetan Plateau affect its peripheral region? The current understanding of the mechanism of orogenic plateau development is incomplete and thus no consensus yet exists in this regard. However, our new 40Ar/39Ar and (U-Th)/He dataset presented in this study may shed some light on this issue. 40Ar/39Ar dating, on two vertical transects from the massif between Nuomuhong and Golmud, indicates that the Eastern Kunlun Range was built-up and exhumated during the later Triassic initially, and a minimum overburden of 11.7-14.0 km has been eroded since 220 Ma. (U-Th)/He age-elevation relationships (AERs) indicate a rapid exhumation event at 40 Ma following a long period of slow exhumation phase from late Mesozoic to early Eocene time. In this study, two scenarios - one assuming a single stage and the other assuming multiple stages of evolution history - are modeled. Modeling of a multiple stage scenario is reasonable and is able to reflect the "actual" situation, which reveals the entire denudation and relief history of the northern Tibet from late Mesozoic to the present time. After prolonged denudation before 50 Ma, a low topography ( 0.17 times the relief of the present) developed by 50 Ma with an erosion rate of 0.013-0.013+ 0.025 mm/yr. The highest relief ( 1.82 times the relief of the present) of the Cenozoic time came into being at 40 Ma with an erosion rate of 0.052 ± 0.025 mm/yr, which was possibly a result of the collision between India and Eurasia. Subsequently, the relief steadily decreased to the present level due to continued denudation. This suggests that deformation propagation from the continued convergence boundary between India and Eurasia was insignificant after the construction of the highest relief. This observation is broadly consistent with published accounts on the stratigraphic, cooling, and faulting histories of the northern Tibet margin.

  14. Heme oxygenase: evolution, structure, and mechanism.

    PubMed

    Wilks, Angela

    2002-08-01

    Heme oxygenase has evolved to carry out the oxidative cleavage of heme, a reaction essential in physiological processes as diverse as iron reutilization and cellular signaling in mammals, synthesis of essential light-harvesting pigments in cyanobacteria and higher plants, and the acquisition of iron by bacterial pathogens. In all of these processes, heme oxygenase has evolved a similar structural and mechanistic scaffold to function within seemingly diverse physiological pathways. The heme oxygenase reaction is catalytically distinct from that of other hemoproteins such as the cytochromes P450, peroxidases, and catalases, but shares a hemoprotein scaffold that has evolved to generate a distinct activated oxygen species. In the following review we discuss the evolution of the structural and functional properties of heme oxygenase in light of the recent crystal structures of the mammalian and bacterial enzymes.

  15. Structural Evolution of Carbon During Oxidation

    SciTech Connect

    Adel F. Sarofim; Angelo Kandas

    1998-10-28

    The examination of the structural evolution of carbon during oxidation has proven to be of scientific interest. Early modeling work of fluidized bed combustion showed that most of the reactions of interest occurs iOn the micropores, and this work has concentrated on these pores. This work has concentrated on evolution of macroporosity and rnicroporosity of carbons during kinetic controlled oxidation using SAXS, C02 and TEM analysis. Simple studies of fluidized bed combustion of coal chars has shown that many of the events considered fragmentation events previously may in fact be "hidden" or nonaccessible porosity. This makes the study of the microporous combustion characteristics of carbon even more important. The generation of a combustion resistant grid, coupled with measurements of the SAXS and C02 surface areas, fractal analysis and TEM studies has confined that soot particles shrink during their oxidation, as previously suspected. However, this shrinkage results in an overall change in structure. This structure becomes, on a radial basis, much more ordered near the edges, while the center itself becomes transparent to the TEM beam, implying a total lack of structure in this region. Although complex, this carbon structure is probably burning as to keep the density of the soot particles nearly the same. The TEM techniques developed for examination of soots has also been applied to Spherocarb. The Spherocarb during oxidation also increases its ordering,. This ordering, by present theories, would imply that the reactivity would go. However, the reactivity goes up, implying that structure of carbon is secondary in importance to catalytic effects.

  16. Crystallography, evolution, and the structure of viruses.

    PubMed

    Rossmann, Michael G

    2012-03-16

    My undergraduate education in mathematics and physics was a good grounding for graduate studies in crystallographic studies of small organic molecules. As a postdoctoral fellow in Minnesota, I learned how to program an early electronic computer for crystallographic calculations. I then joined Max Perutz, excited to use my skills in the determination of the first protein structures. The results were even more fascinating than the development of techniques and provided inspiration for starting my own laboratory at Purdue University. My first studies on dehydrogenases established the conservation of nucleotide-binding structures. Having thus established myself as an independent scientist, I could start on my most cherished ambition of studying the structure of viruses. About a decade later, my laboratory had produced the structure of a small RNA plant virus and then, in another six years, the first structure of a human common cold virus. Many more virus structures followed, but soon it became essential to supplement crystallography with electron microscopy to investigate viral assembly, viral infection of cells, and neutralization of viruses by antibodies. A major guide in all these studies was the discovery of evolution at the molecular level. The conservation of three-dimensional structure has been a recurring theme, from my experiences with Max Perutz in the study of hemoglobin to the recognition of the conserved nucleotide-binding fold and to the recognition of the jelly roll fold in the capsid protein of a large variety of viruses.

  17. Crystallography, Evolution, and the Structure of Viruses

    PubMed Central

    Rossmann, Michael G.

    2012-01-01

    My undergraduate education in mathematics and physics was a good grounding for graduate studies in crystallographic studies of small organic molecules. As a postdoctoral fellow in Minnesota, I learned how to program an early electronic computer for crystallographic calculations. I then joined Max Perutz, excited to use my skills in the determination of the first protein structures. The results were even more fascinating than the development of techniques and provided inspiration for starting my own laboratory at Purdue University. My first studies on dehydrogenases established the conservation of nucleotide-binding structures. Having thus established myself as an independent scientist, I could start on my most cherished ambition of studying the structure of viruses. About a decade later, my laboratory had produced the structure of a small RNA plant virus and then, in another six years, the first structure of a human common cold virus. Many more virus structures followed, but soon it became essential to supplement crystallography with electron microscopy to investigate viral assembly, viral infection of cells, and neutralization of viruses by antibodies. A major guide in all these studies was the discovery of evolution at the molecular level. The conservation of three-dimensional structure has been a recurring theme, from my experiences with Max Perutz in the study of hemoglobin to the recognition of the conserved nucleotide-binding fold and to the recognition of the jelly roll fold in the capsid protein of a large variety of viruses. PMID:22318719

  18. Acetohydroxyacid synthases: evolution, structure, and function.

    PubMed

    Liu, Yadi; Li, Yanyan; Wang, Xiaoyuan

    2016-10-01

    Acetohydroxyacid synthase, a thiamine diphosphate-dependent enzyme, can condense either two pyruvate molecules to form acetolactate for synthesizing L-valine and L-leucine or pyruvate with 2-ketobutyrate to form acetohydroxybutyrate for synthesizing L-isoleucine. Because the key reaction catalyzed by acetohydroxyacid synthase in the biosynthetic pathways of branched-chain amino acids exists in plants, fungi, archaea, and bacteria, but not in animals, acetohydroxyacid synthase becomes a potential target for developing novel herbicides and antimicrobial compounds. In this article, the evolution, structure, and catalytic mechanism of acetohydroxyacid synthase are summarized.

  19. Coupled Electronic and Structural Relaxation Pathways in the Postexcitation Dynamics of Rydberg States of BaArN Clusters

    NASA Astrophysics Data System (ADS)

    Masson, A.; Heitz, M.-C.; Mestdagh, J.-M.; Gaveau, M.-A.; Poisson, L.; Spiegelman, F.

    2014-09-01

    We investigate, theoretically, the joint relaxation of orbital and structure in postexcitation dynamics of Rydberg states of cluster BaArN (N =250). Mixed quantum-classical dynamics is used to account for the nonadiabatic transitions among more than 160 electronic states, represented via a diatomics-in-molecules Hamiltonian. The simulation illustrates the complex multistep relaxation processes and provides detailed insight in the mechanisms contributing to the final-time experimental photoelectron spectrum.

  20. {ital Ab initio} characterization of the structure and energetics of the ArHF complex

    SciTech Connect

    van Mourik, T.; Dunning, T.H. Jr.

    1997-08-01

    The ArHF complex has been investigated using correlation consistent basis sets at several levels of theory, including Mo/ller{endash}Plesset perturbation theory (MP2, MP3, MP4) and coupled cluster techniques [CCSD, CCSD(T)]. The three stationary points (the primary linear Ar{endash}HF minimum, the secondary linear Ar{endash}FH minimum, and the interposed transition state TS) on the counterpoise-corrected potential energy surface have been characterized. Calculations with the aug-cc-pV5Z basis set predict D{sub e} for the Ar{endash}HF minimum to be (with estimated complete basis set limits in parentheses) {minus}215 ({minus}218)cm{sup {minus}1} for MP4 and {minus}206 ({minus}211)cm{sup {minus}1} for CCSD(T). For the Ar{endash}FH minimum and the TS, calculations with the d-aug-cc-pVQZ sets predict D{sub e}{close_quote}s (and CBS limits) of {minus}97 ({minus}99) and {minus}76 ({minus}78)cm{sup {minus}1} (MP4) and {minus}93 ({minus}94) and {minus}75 ({minus}76)cm{sup {minus}1} [CCSD(T)], respectively. The corresponding values for the H6(4,3,2) potential of Hutson [J. Chem. Phys. {bold 96}, 6752 (1992)] are {minus}211.1{plus_minus}4cm{sup {minus}1}, {minus}108.8{plus_minus}10cm{sup {minus}1}, and {minus}82.6{plus_minus}10cm{sup {minus}1}. While the agreement of our CCSD(T) estimate with Hutson{close_quote}s value is excellent for the global minimum, it is less so for the other two stationary points, suggesting that the H6(4,3,2) potential may be too attractive around the secondary minimum and the transition state. {copyright} {ital 1997 American Institute of Physics.}

  1. Genetic diversity and population structure of the Ethiopian sorghum [Sorghum bicolor (L.) Moench] germplasm collection maintained by the USDA-ARS, National Plant Germplasm System using SSR markers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The genetic diversity and population structure present in the Ethiopia sorghum collection maintained by the USDA-ARS, National Plant Germplasm System (USDA-ARS-NPGS) is unknown. In addition, passport information is absent for 83% of these accessions which limit its evaluation and utility. Therefor...

  2. Planetary surface structure and evolution of Mars

    NASA Technical Reports Server (NTRS)

    Franck, Siegfried

    1991-01-01

    The surface of the planet Mars is characterized by two different hemispheres: old densely cratered structures in the Southern Uplands, and sparsely cratered younger topographically lower regions covering approximately the northern third of the planet's surface. The model for explaining these global surface structures is characterized by the following features: (1) homogeneous accretion of Mars; (2) formation of a metal melt layer; (3) northward translation of the undifferentiated core due to a Rayleigh-Taylor instability; (4) vigorous convection in the southern parts and formation of the Southern Uplands' crust; (5) fragmentation of the primordial core, slowly dissolving rockbergs, beginning of Tharsis uplift and volcanism; (6) formation of the Northern Lowlands' crust from only weakly differentiated silicatic material; and (7) reaching of the present state with symmetrically placed core and further thermal evolution.

  3. The structure and evolution of story networks.

    PubMed

    Karsdorp, Folgert; van den Bosch, Antal

    2016-06-01

    With this study, we advance the understanding about the processes through which stories are retold. A collection of story retellings can be considered as a network of stories, in which links between stories represent pre-textual (or ancestral) relationships. This study provides a mechanistic understanding of the structure and evolution of such story networks: we construct a story network for a large diachronic collection of Dutch literary retellings of Red Riding Hood, and compare this network to one derived from a corpus of paper chain letters. In the analysis, we first provide empirical evidence that the formation of these story networks is subject to age-dependent selection processes with a strong lopsidedness towards shorter time-spans between stories and their pre-texts (i.e. 'young' story versions are preferred in producing new versions). Subsequently, we systematically compare these findings with and among predictions of various formal models of network growth to determine more precisely which kinds of attractiveness are also at play or might even be preferred as explicatory models. By carefully studying the structure and evolution of the two story networks, then, we show that existing stories are differentially preferred to function as a new version's pre-text given three types of attractiveness: (i) frequency-based and (ii) model-based attractiveness which (iii) decays in time.

  4. The structure and evolution of story networks

    PubMed Central

    Karsdorp, Folgert; van den Bosch, Antal

    2016-01-01

    With this study, we advance the understanding about the processes through which stories are retold. A collection of story retellings can be considered as a network of stories, in which links between stories represent pre-textual (or ancestral) relationships. This study provides a mechanistic understanding of the structure and evolution of such story networks: we construct a story network for a large diachronic collection of Dutch literary retellings of Red Riding Hood, and compare this network to one derived from a corpus of paper chain letters. In the analysis, we first provide empirical evidence that the formation of these story networks is subject to age-dependent selection processes with a strong lopsidedness towards shorter time-spans between stories and their pre-texts (i.e. ‘young’ story versions are preferred in producing new versions). Subsequently, we systematically compare these findings with and among predictions of various formal models of network growth to determine more precisely which kinds of attractiveness are also at play or might even be preferred as explicatory models. By carefully studying the structure and evolution of the two story networks, then, we show that existing stories are differentially preferred to function as a new version's pre-text given three types of attractiveness: (i) frequency-based and (ii) model-based attractiveness which (iii) decays in time. PMID:27429767

  5. Early carboniferous wrenching, exhumation of high-grade metamorphic rocks and basin instability in SW Iberia: Constraints derived from structural geology and U-Pb and 40Ar-39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Pereira, M. Francisco; Chichorro, Martim; Silva, J. Brandão; Ordóñez-Casado, Berta; Lee, James K. W.; Williams, Ian S.

    2012-08-01

    New U-Pb and 40Ar-39Ar geochronology and structural data from high- to medium grade metamorphic shear zones of the Ossa-Morena Zone, and structural data from Early Carboniferous basins (Ossa-Morena Zone and South-Portuguese Zone), place additional constraints on the Variscan tectonics in SW Iberia. A zircon U-Pb age of 465 ± 14 Ma (Middle Ordovician) measured on migmatite from the Coimbra-Cordoba shear zone is interpreted as the age of protolith crystallization. This age determination revises the information contained in the geological map of Portugal, in which these rocks were considered to be Proterozoic in age. This paper describes the evolution of Variscan wrench tectonics related to the development of shear zones, exhumation of deep crustal rocks and emplacement of magma in the Ossa-Morena Zone basement. In the Coimbra-Cordoba shear zone (transpressional), migmatites were rapidly exhumed from a depth of 42.5 km to 16.6 km over a period of ca. 10 Ma in the Viséan (ca. 340-330 Ma), indicating oblique slip exhumation rates of 8.5 to 10.6 mm/yr (Campo Maior migmatites) and 3.2 mm/yr (Ouguela gneisses) respectively. In the Évora Massif, the gneisses of the Boa Fé shear zone (transtensional) were exhumed from 18.5 to 7.4 km depth in the period ca. 344-334 Ma (Viséan), with exhumation oblique slip rates of 2.8 to 4.2 mm/yr. At the same time, the Early Carboniferous basins of SW Iberia were filled by turbidites and olistoliths, composed mostly of Devonian rocks. The presence of olistoliths indicates significant tectonic instability during sedimentation with large-scale mass movement, probably in the form of gravity slides. Deformation and metamorphism dated at 356 ± 12 Ma, 321 ± 13 Ma and 322 ± 29 Ma respectively suggests that Variscan wrench movements were active in SW Iberia during the Early Carboniferous for a period of at least 35 Ma.

  6. Electronic structure of Ar+ ion-sputtered thin-film MoS2: A XPS and IPES study

    NASA Astrophysics Data System (ADS)

    Santoni, Antonino; Rondino, Flaminia; Malerba, Claudia; Valentini, Matteo; Mittiga, Alberto

    2017-01-01

    Polycrystalline MoS2 grown by Mo sulphurization was exposed to increasing doses of Ar+ ions at 250 eV starting from 2.2 × 1015 ions/cm2 to 3.92 × 1017 ions/cm2. Electronic structure changes were monitored by X-Ray Photoelectron Spectroscopy (XPS) and Inverse Photolectron Spectroscopy (IPES). No change in the Fermi level position was observed with Ar+ dosing. Ion bombardment resulted in a new visible feature at lower binding energy in the Mo3d core level, while the S2p lineshape showed little changes. The formation of a steady state from 2.49 × 1017 ions/cm2 has been detected. The investigation of the occupied and unoccupied states on the steady-state surface pointed to the simultaneous presence of metallic-like Mo with amorphous MoS2-x.

  7. NEXAFS study on the local structures of DLC thin films formed by Ar cluster ion beam assisted deposition

    NASA Astrophysics Data System (ADS)

    Kanda, Kazuhiro; Kitagawa, Teruyuki; Shimizugawa, Yutaka; Tsubakino, Harushige; Yamada, Isao; Matsui, Shinji

    2003-08-01

    Near-edge X-ray absorption fine structure (NEXAFS) spectra were measured for the optimization of synthesis conditions on the production of diamond-like carbon (DLC) thin films by the Ar gas cluster ion beam (GCIB) assisted deposition of fullerene. The sp2 contents of DLC films were estimated from the analysis of the peak corresponding to the transition of the excitation electron from a carbon 1s orbital to a π* orbital in the NEXAFS spectrum of the carbon K-edge over the excitation energy range 275-320 eV. Substrate temperature and Ar cluster ion acceleration voltage in the synthesis conditions of DLC films were optimized to make the sp2 content minimum.

  8. Combined 40Ar/39Ar and (U-Th)/He geochronological constraints on long-term landscape evolution of the Second Paraná Plateau and its ruiniform surface features, Paraná, Brazil

    NASA Astrophysics Data System (ADS)

    Riffel, Silvana B.; Vasconcelos, Paulo M.; Carmo, Isabela O.; Farley, Kenneth A.

    2015-03-01

    Regional correlation of dated weathered land surfaces provides the necessary constraints to test long-term continental landscape evolution models, but major challenges remain in properly dating these surfaces. The geomorphological province of Second Paraná Plateau, Paraná State, Brazil, is a high elevation (ca. 800 m) land surface characterized by widely distributed deep saprolites and scattered lateritic profiles (e.g., Vila Velha and Serra das Almas). Prolonged exposure to weathering and erosion has promoted the pseudo-karstic and ruiniform features that are characteristic of this landscape. In this study, 40Ar/39Ar laser incremental heating geochronology on 22 grains of supergene Mn oxyhydroxides from lateritic profiles at Vila Velha yielded results ranging from 17.2 ± 0.7 to 9.1 ± 0.7 Ma. (U-Th)/He geochronology on 28 goethite grains from the same profile yielded results ranging from 36.4 ± 3.6 to 1.0 ± 0.1 Ma, with an age cluster lying within the 17.2 ± 0.7 to 7.9 ± 0.8 Ma interval. (U-Th)/He geochronology on 17 goethite grains from the Serra das Almas lateritic profile, located 20 km from Vila Velha, yield results ranging from 35.1 ± 3.5 to 14.1 ± 1.4 Ma. The combined results for the two sites reveal a common weathering history that started ca. 35 Ma, suggesting that the Second Paraná Plateau results from regional fluvial incision and denudation before ~ 35 Ma, followed by a decline in denudation rates and proportionally more intense weathering. Consistent with the laterite profile central ages, weathering was particularly intense during the Miocene (17-8 Ma). Denudation intensified after the Pliocene.

  9. From olivine nephelinite, basanite and basalt to peralkaline trachyphonolite and comendite in the Ankaratra volcanic complex, Madagascar: 40Ar/39Ar ages, phase compositions and bulk-rock geochemical and isotopic evolution

    NASA Astrophysics Data System (ADS)

    Cucciniello, Ciro; Melluso, Leone; le Roex, Anton P.; Jourdan, Fred; Morra, Vincenzo; de'Gennaro, Roberto; Grifa, Celestino

    2017-03-01

    The Ankaratra volcanic field covers an area of 3800 km2 in central Madagascar and comprises of lava flows, lava domes, scoria cones, tuff rings and maars emplaced at different ages (Miocene to Recent). The volcanic products include ultramafic-mafic (olivine-leucite nephelinite, basanite, alkali basalt, hawaiite and tholeiitic basalt), intermediate (mugearite and benmoreite) and felsic rocks (trachyphonolite, quartz trachyte and rhyolite), the latter often peralkaline. The 40Ar/39Ar determinations for mafic lavas yield ages of 17.45 ± 0.12 Ma, 16.63 ± 0.08 Ma and 8.62 ± 0.09 Ma, indicating a prolonged magmatic activity. The mineralogical and geochemical variations suggest that the magmatic evolution of the alkali basalt-hawaiite-mugearite-benmoreite-trachyte series can be accounted for by removal of olivine, feldspars, clinopyroxene, Fe-Ti oxides and accessory phases, producing residual trachytic and trachyphonolitic compositions mineralogically very similar to those of other volcanic areas and tectonic settings. The Ankaratra olivine leucite nephelinites, basanites and tholeiitic basalts do not seem to be associated with significant amounts of evolved comagmatic rocks. The 87Sr/86Sr (0.70504-0.71012), 143Nd/144Nd (0.51259-0.51244) and 206Pb/204Pb (17.705-18.563) isotopic ratios of trachytes and comendite are consistent with open-system processes. However, other trachyphonolites have 143Nd/144Nd (0.51280), 206Pb/204Pb (18.648), 207Pb/204Pb (15.582) and 208Pb/204Pb (38.795) similar to those of mafic rocks, suggesting differentiation processes without appreciable interaction with crustal materials. The Ankaratra volcanism is to be directly linked to a broadly E-W-trending intracontinental extension. A large-scale thermal anomaly, associated with an anomalously hot source region, is not required to explain the Cenozoic magmatism of Madagascar.

  10. 40Ar/39Ar geochronology of hypabyssal igneous rocks in the Maranon Basin of Peru - A record of thermal history, structure, and alteration

    USGS Publications Warehouse

    Prueher, L.M.; Erlich, R.; Snee, L.W.

    2005-01-01

    Hypabyssal andesites and dacites from the Balsapuerto Dome in the Mara?on Basin of Peru record the thermal, tectonic, and alteration history of the area. The Mara?on Basin is one of 19 sub-Andean foreland basins. The hypabyssal rocks in the Balsapuerto Dome are one of four known occurrences of subvolcanic rocks along the deformation front in Peru. This dome is a potential petroleum structural trap. Petroleum seeps near the dome indicate that a source for the petroleum is present, but the extent and amount of petroleum development is unknown. The Balsapuerto hypabyssal rocks are plagioclase-, hornblende-, pyroxene-phyric andesites to dacites. Some parts of the dome are pervasively altered to a hydrothermal assemblage of quartz-sericite-pyrite. 40Ar/39Ar geochronology shows that thermal activity related to emplacement of these subvolcanic rocks took place between 12-10 Ma, subsequent to the major periods of Andean folding and faulting, previously assumed to have occurred about 9 Ma. Eleven argon mineral age-spectrum analyses were completed. Argon apparent ages on amphibole range from 12.7 to 11.6 Ma, and the age spectra are simple, which indicates that the ages are very close to emplacement ages. Potassium feldspar yields an argon age spectrum ranging in age from 12.5 to 11.4 Ma, reflecting the period during which the potassium feldspar closed to argon diffusion between the temperature range of 350?C to about 150?C; thus the potassium feldspar age spectrum reflects a cooling profile throughout this temperature range. This age range is consistent with ages of emplacement for the entire igneous complex indicating that an increased thermal state existed in the area for at least 1.0 m.y. Combined with the coexisting hornblende age, this rock cooled from ~580?C to ~150?C in ~1.2 m.y. resulting in an average cooling rate of 358?C /m.y. White mica, or sericite, formed as a later alteration phase associated with quartz- sericite- pyrite and propylitic alteration in some

  11. Structural evolution and metallicity of lead clusters

    NASA Astrophysics Data System (ADS)

    Götz, Daniel A.; Shayeghi, Armin; Johnston, Roy L.; Schwerdtfeger, Peter; Schäfer, Rolf

    2016-05-01

    The evolution of the metallic state in lead clusters and its structural implications are subject to ongoing discussions. Here we present molecular beam electric deflection studies of neutral PbN (N = 19-25, 31, 36, 54) clusters. Many of them exhibit dipole moments or anomalies of the polarizability indicating a non-metallic state. In order to resolve their structures, the configurational space is searched using the Pool Birmingham Cluster Genetic algorithm based on density functional theory. Spin-orbit effects on the geometries and dipole moments are taken into account by further relaxing them with two-component density functional theory. Geometries and dielectric properties from quantum chemical calculations are then used to simulate beam deflection profiles. Structures are assigned by the comparison of measured and simulated beam profiles. Energy gaps are calculated using time-dependent density functional theory. They are compared to Kubo gaps, which are an indicator of the metallicity in finite particles. Both, experimental and theoretical data suggest that lead clusters are not metallic up to at least 36 atoms.The evolution of the metallic state in lead clusters and its structural implications are subject to ongoing discussions. Here we present molecular beam electric deflection studies of neutral PbN (N = 19-25, 31, 36, 54) clusters. Many of them exhibit dipole moments or anomalies of the polarizability indicating a non-metallic state. In order to resolve their structures, the configurational space is searched using the Pool Birmingham Cluster Genetic algorithm based on density functional theory. Spin-orbit effects on the geometries and dipole moments are taken into account by further relaxing them with two-component density functional theory. Geometries and dielectric properties from quantum chemical calculations are then used to simulate beam deflection profiles. Structures are assigned by the comparison of measured and simulated beam profiles. Energy gaps

  12. The earth tectonosphere, its structure and evolution

    NASA Astrophysics Data System (ADS)

    Belousov, V. V.

    Endogenic geological regimes, which include the tectonic, magmatic, and metamorphic processes, responsible for the structure of the tectonosphere and its evolution are discussed. Heat flow is considered to be the major factor controlling the type of the endogenic regime, with other factors being the temperature distribution in the tectonosphere and the degree and properties of the penetrability of the tectonosphere to melts and fluids. The development of the tectonosphere proceeds on the basis of geochemical impoverishment of the upper mantle by gradual fractionation of its matter. At initial stages of earth development the fractionation occurred by way of degassing; the continental crust thus evolving was rich in incompatible elements and contained large amounts of calc-alkalic magmas. As the upper mantle lost its volatiles, the mechanism of fractionation changed gradually; degassing was being substituted by selective melting, and the composition of magmas became increasingly widespread. These changes were coupled with the destruction of continental crust and the formation of oceanic crust.

  13. Evolution of groups with a hierarchical structure

    NASA Astrophysics Data System (ADS)

    Ohnishi, Teruaki

    2012-12-01

    The universal occurrence of a hierarchical structure and its dynamic behavior in various types of group, living or abstract, are discussed. Here the word “group” refers not only to tangible aggregation but also to invisible aggregation of social psychological and of geopolitical meaning. The evolution of these groups is simulated using a model of agents distributed on the lattices of cellular grids. It is assumed that agents, fearing isolation, interact asymmetrically with each other with regard to exchange of “power”. As an indicator of hierarchy, the Gini coefficient is introduced. Example calculations are made for the aggregation, fusion and fission of animal groups, and for the appearance of a powerful empire and the rise and fall of supremacy. It is shown that such abstract objects evolve with time in accordance with the universal rules of groups common to birds and fish.

  14. Sensitivity of flow evolution on turbulence structure

    NASA Astrophysics Data System (ADS)

    Mishra, Aashwin A.; Iaccarino, Gianluca; Duraisamy, Karthik

    2016-09-01

    Reynolds averaged Navier-Stokes models represent the workhorse for studying turbulent flows in academia and in industry. Such single-point turbulence models have limitations in accounting for the influence of the nonlocal physics and flow history on turbulence evolution. In this context, we investigate the sensitivity inherent in such single-point models due to their characterization of the internal structure of homogeneous turbulent flows solely by the means of the Reynolds stresses. For a wide variety of mean flows under diverse conditions, we study the prediction intervals engendered due to this coarse-grained description. The nature of this variability and its dependence on parameters such as the mean flow topology, the initial Reynolds stress tensor, and the relative influence of linear contra nonlinear physics is identified, analyzed, and explicated.

  15. Models of Protocellular Structure, Function and Evolution

    NASA Technical Reports Server (NTRS)

    New, Michael H.; Pohorille, Andrew; Szostak, Jack W.; Keefe, Tony; Lanyi, Janos K.; DeVincenzi, Donald L. (Technical Monitor)

    2001-01-01

    In the absence of any record of protocells, the most direct way to test our understanding, of the origin of cellular life is to construct laboratory models that capture important features of protocellular systems. Such efforts are currently underway in a collaborative project between NASA-Ames, Harvard Medical School and University of California. They are accompanied by computational studies aimed at explaining self-organization of simple molecules into ordered structures. The centerpiece of this project is a method for the in vitro evolution of protein enzymes toward arbitrary catalytic targets. A similar approach has already been developed for nucleic acids in which a small number of functional molecules are selected from a large, random population of candidates. The selected molecules are next vastly multiplied using the polymerase chain reaction.

  16. Mercury - Internal structure and thermal evolution

    NASA Technical Reports Server (NTRS)

    Siegfried, R. W., II; Solomon, S. C.

    1974-01-01

    Mercury's thermal evolution and internal structure are modeled based on the planet's gross physical properties (which imply a high metallic iron content) and predictions for its chemistry made from the Lewis-Cameron model of condensation of the primitive solar nebula (which implies that Mercury may be composed only of those materials that condensed at temperatures near that of metallic iron condensation in the cooling nebula). Various heat sources, initial temperatures, and thermal conductivities are considered for a homogeneous model and a differentiated two-layer model. Density distributions are calculated from the mean density and estimates of the present-day temperature. The moment of inertia and the hydrostatic value of the second degree harmonic coefficient of Mercury's gravity field are found for the differentiated and undifferentiated models. These results should be useful for preliminary interpretation of the Mariner 10 measurements of Mercury's gravitational field.

  17. Models of protocellular structures, functions and evolution

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew; New, Michael H.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    The central step in the origin of life was the emergence of organized structures from organic molecules available on the early earth. These predecessors to modern cells, called 'proto-cells,' were simple, membrane bounded structures able to maintain themselves, grow, divide, and evolve. Since there is no fossil record of these earliest of life forms, it is a scientific challenge to discover plausible mechanisms for how these entities formed and functioned. To meet this challenge, it is essential to create laboratory models of protocells that capture the main attributes associated with living systems, while remaining consistent with known, or inferred, protobiological conditions. This report provides an overview of a project which has focused on protocellular metabolism and the coupling of metabolism to energy transduction. We have assumed that the emergence of systems endowed with genomes and capable of Darwinian evolution was preceded by a pre-genomic phase, in which protocells functioned and evolved using mostly proteins, without self-replicating nucleic acids such as RNA.

  18. Ar-40 to Ar-39 ages of the large impact structures Kara and Manicouagan and their relevance to the Cretaceous-Tertiary and the Triassic-Jurassic boundary

    NASA Technical Reports Server (NTRS)

    Trieloff, M.; Jessberger, E. K.

    1992-01-01

    Since the discovery of the Ir enrichment in Cretaceous-Tertiary boundary clays in 1980, the effects of a 10-km asteroid impacting on the Earth 65 Ma ago have been discussed as the possible reason for the mass extinction--including the extinction of the dinosaurs--at the end of the Cretaceous. But up to now no crater of this age that is large enough (ca. 200 km in diameter) has been found. One candidate is the Kara Crater in northern Siberia. Kolesnikov et al. determined a K-Ar isochron of 65.6 +/- 0.5 Ma, indistinguishable from the age of the K-T boundary and interpreted this as confirmation of earlier proposals that the Kara bolide would have been at least one of the K-T impactors. Koeberl et al. determined Ar-40 to Ar-39 ages ranging from 70 to 82 Ma and suggested an association to the Campanian-Maastrichtian boundary, another important extinction horizon 73 Ma ago. We dated four impact melts, KA2-306, KA2-305, SA1-302, and AN9-182. Results from the investigation are discussed.

  19. Relationship between Human Evolution and Neurally Mediated Syncope Disclosed by the Polymorphic Sites of the Adrenergic Receptor Gene α2B-AR

    PubMed Central

    Komiyama, Tomoyoshi; Oka, Akira; Kamiguchi, Hiroshi; Nagata, Eiichiro; Sakura, Hiroshi; Otsuka, Kuniaki; Kobayashi, Hiroyuki

    2015-01-01

    The objective of this study was to clarify the effects of disease on neurally mediated syncope (NMS) during an acute stress reaction. We analyzed the mechanism of the molecular interaction and the polymorphisms of the alpha-2 adrenoreceptor (α2B-AR) gene as the potential psychiatric cause of incentive stress. We focused on the following three genotypes of the repeat polymorphism site at Glu 301–303 in the α2B-AR gene: Glu12/12, Glu12/9, and Glu9/9. On the basis of our clinical research, NMS is likely to occur in people with the Glu12/9 heterotype. To verify this, we assessed this relationship with the interaction of Gi protein and adenylate cyclase by in silico analysis of the Glu12/9 heterotype. By measuring the difference in the dissociation time of the Gi-α subunit twice, we found that the Glu12/9 heterotype suppressed the action of adenylate cyclase longer than the Glu homotypes. As this difference in the Glu repeat number effect is thought to be one of the causes of NMS, we investigated the evolutionary significance of the Glu repeat number. Glu8 was originally repeated in simians, while the Glu12 repeats occurred over time during the evolution of bipedalism in humans. Taken with the Glu12 numbers, NMS would likely become a defensive measure to prevent significant blood flow to the human brain. PMID:25860977

  20. Rotational spectra and structure of the Ar2-H2S complex: pulsed nozzle Fourier transform microwave spectroscopic and ab initio studies.

    PubMed

    Mandal, Pankaj K; Ramdass, Dharmender J; Arunan, E

    2005-07-21

    This paper reports the rotational spectrum and structure of the Ar2-H2S complex and its HDS and D2S isotopomers. The ground state structure has heavy-atom C2v symmetry with the two Ar atoms indistinguishable and H2S freely rotating as evinced by the fact that asymmetric top energy levels with Kp=odd levels are missing. The rotational constants for the parent isotopomer are: A=1733.115(1) MHz, B=1617.6160(5) MHz and C=830.2951(2) MHz. Unlike the Ar-H2S complex, the Ar2-H2S does not show an anomalous isotopic shift in rotational constants on deuterium substitution. However, the intermolecular potential is still quite floppy, leading to very different centrifugal distortion constants for the three isotopomers. The Ar-Ar and Ar-c.m.(H2S) distances are determined to be 3.820 A and 4.105 A, respectively. The A rotational constants for Ar2-H2S/HDS/D2S isotopomers are very close to each other and to the B constant of free Ar2, indicating that H2S does not contribute to the moment of inertia about the a-axis. Ab initio calculations at MP2 level with aug-cc-pVQZ basis set lead to an equilibrium C2v minimum structure with the Ar-Ar line perpendicular to the H-H line and the S away from Ar2. The centrifugal distortion constants, calculated using the ab initio force field, are in reasonable agreement with the experimental values. However, they do not show the variation observed for different isotopmers. The binding energy of Ar2-H2S has been determined to be 507 cm-1(6.0 kJ mol-1) by CBS extrapolation after correcting for basis set superposition error. Potential energy scans point out that the barrier for internal rotation of H2S about its b axis is only 10 cm-1 and it is below the zero point energy (13.5 cm-1) in this torsional degree of freedom. Internal rotation of H2S about its a- and c-axes also have small barriers of about 50 cm-1 only, suggesting that H2S is extremely floppy within the complex.

  1. Evolution and structure of sustainability science.

    PubMed

    Bettencourt, Luís M A; Kaur, Jasleen

    2011-12-06

    The concepts of sustainable development have experienced extraordinary success since their advent in the 1980s. They are now an integral part of the agenda of governments and corporations, and their goals have become central to the mission of research laboratories and universities worldwide. However, it remains unclear how far the field has progressed as a scientific discipline, especially given its ambitious agenda of integrating theory, applied science, and policy, making it relevant for development globally and generating a new interdisciplinary synthesis across fields. To address these questions, we assembled a corpus of scholarly publications in the field and analyzed its temporal evolution, geographic distribution, disciplinary composition, and collaboration structure. We show that sustainability science has been growing explosively since the late 1980s when foundational publications in the field increased its pull on new authors and intensified their interactions. The field has an unusual geographic footprint combining contributions and connecting through collaboration cities and nations at very different levels of development. Its decomposition into traditional disciplines reveals its emphasis on the management of human, social, and ecological systems seen primarily from an engineering and policy perspective. Finally, we show that the integration of these perspectives has created a new field only in recent years as judged by the emergence of a giant component of scientific collaboration. These developments demonstrate the existence of a growing scientific field of sustainability science as an unusual, inclusive and ubiquitous scientific practice and bode well for its continued impact and longevity.

  2. Evolution and structure of sustainability science

    PubMed Central

    Bettencourt, Luís M. A.; Kaur, Jasleen

    2011-01-01

    The concepts of sustainable development have experienced extraordinary success since their advent in the 1980s. They are now an integral part of the agenda of governments and corporations, and their goals have become central to the mission of research laboratories and universities worldwide. However, it remains unclear how far the field has progressed as a scientific discipline, especially given its ambitious agenda of integrating theory, applied science, and policy, making it relevant for development globally and generating a new interdisciplinary synthesis across fields. To address these questions, we assembled a corpus of scholarly publications in the field and analyzed its temporal evolution, geographic distribution, disciplinary composition, and collaboration structure. We show that sustainability science has been growing explosively since the late 1980s when foundational publications in the field increased its pull on new authors and intensified their interactions. The field has an unusual geographic footprint combining contributions and connecting through collaboration cities and nations at very different levels of development. Its decomposition into traditional disciplines reveals its emphasis on the management of human, social, and ecological systems seen primarily from an engineering and policy perspective. Finally, we show that the integration of these perspectives has created a new field only in recent years as judged by the emergence of a giant component of scientific collaboration. These developments demonstrate the existence of a growing scientific field of sustainability science as an unusual, inclusive and ubiquitous scientific practice and bode well for its continued impact and longevity. PMID:22114186

  3. Models of Protocellular Structure, Function and Evolution

    NASA Technical Reports Server (NTRS)

    New, Michael H.; Pohorille, Andrew; Szostak, Jack W.; Keefe, Tony; Lanyi, Janos K.

    2001-01-01

    In the absence of any record of protocells, the most direct way to test our understanding of the origin of cellular life is to construct laboratory models that capture important features of protocellular systems. Such efforts are currently underway in a collaborative project between NASA-Ames, Harvard Medical School and University of California. They are accompanied by computational studies aimed at explaining self-organization of simple molecules into ordered structures. The centerpiece of this project is a method for the in vitro evolution of protein enzymes toward arbitrary catalytic targets. A similar approach has already been developed for nucleic acids in which a small number of functional molecules are selected from a large, random population of candidates. The selected molecules are next vastly multiplied using the polymerase chain reaction. A mutagenic approach, in which the sequences of selected molecules are randomly altered, can yield further improvements in performance or alterations of specificities. Unfortunately, the catalytic potential of nucleic acids is rather limited. Proteins are more catalytically capable but cannot be directly amplified. In the new technique, this problem is circumvented by covalently linking each protein of the initial, diverse, pool to the RNA sequence that codes for it. Then, selection is performed on the proteins, but the nucleic acids are replicated. Additional information is contained in the original extended abstract.

  4. Replacement equivalence of H- and argon in small (Ar)nH- clusters from optimized structure calculations

    NASA Astrophysics Data System (ADS)

    Sebastianelli, F.; Baccarelli, I.; Di Paola, C.; Gianturco, F. A.

    2004-08-01

    The structural properties of some of the smaller ionic clusters of argon atoms containing the atomic impurity H-, ArnH- with n from 2 up to 7, are examined using different modeling for the interactions within each cluster and by employing different theoretical treatments, both classical and quantum, for the energetics. The same calculations are also carried out for the corresponding neutral homogeneous clusters Arn+1. The results of the calculations, the physical reliability of the interactions modeling, and the similarities and the difference between the anionic and the neutral complexes are discussed in some detail. The emerging picture shows that, due to specific features of the employed atom-atom potentials, the ArnH- and Arn+1 clusters present very similar structures, where the H- dopant substitutes for one of the outer Ar atoms but does not undergo as yet solvation within such small clusters.

  5. 30S(α , p) Thermonuclear Reaction Rate from Experimental Level Structure of 34Ar

    NASA Astrophysics Data System (ADS)

    Kahl, D.; Chen, A. A.; Kubono, S.; Yamaguchi, H.; Binh, D. N.; Chen, J.; Cherubini, S.; Duy, N. N.; Hashimoto, T.; Hayakawa, S.; Iwasa, N.; Jung, H. S.; Kato, S.; Kwon, Y. K.; Nishimura, S.; Ota, S.; Setoodehnia, K.; Teranishi, T.; Tokieda, H.; Yamada, T.; Yun, C. C.; Zhang, L. Y.

    Type I X-ray bursts are the most frequent thermonuclear explosions in the galaxy. Owing to their recurrence from known astronomical objects, burst morphology is extensively documented, and they are modeled very successfully as neutron-deficient, thermonuclear runaway on the surface of accreting neutron stars. While reaction networks include hundreds of isotopes and thousands of nuclear processes, only a small subset appear to play a pivotal role. One such reaction is the 30S(α , p) reaction, which is believed to be a crucial link in the explosive helium burning which is responsible for the large energy flux. However, very little experimental information is available concerning the cross section itself, nor the 34Ar compound nucleus at the relevant energies. We performed the first study of the entrance channel via 30S alpha resonant elastic scattering using a state-of-the-art, low-energy, 30S radioactive ion beam. The measurement was performed in inverse kinematics using a newly-developed active target. An R-matrix analysis of the excitation function reveals previously unknown resonances, including their quantum properties of spin, parity, width, and energy.

  6. Natural nanomorphous Ni/NiO magnetic multilayers: structure and magnetism of the high-Ar pressure series.

    PubMed

    Pappas, S D; Delimitis, A; Kapaklis, V; Papaioannou, E Th; Poulopoulos, P; Trachylis, D; Velgakis, M J; Politis, C

    2014-08-01

    Natural nanomorphous Ni/NiO multilayers have exhibited interesting magnetic properties, such as an unusual positive surface anisotropy and perpendicular magnetic anisotropy. Most attention has been paid to multilayers prepared by radio frequency magnetron sputtering under relatively low (3 x 10(-3) mbar) Ar pressure. Here we report on the correlation between structural and magnetic properties for a new series of multilayers, prepared under relatively high (3 x 10(-2) mbar) Ar pressure. The crystalline Ni individual layer thickness ranges between 5-8 nm. The amorphous NiO layer thickness is constant, about 1.1 nm thick. X-ray reflectivity showed that in some of the multilayers the high-order Bragg peaks become broader and diminish quickly. Cross-section transmission electron microscopy reveals that this occurs because the first bilayers are formed in accordance to the growth conditions, while the ones near the top are vanished. Despite the deterioration of the interface quality, all samples show tendency for perpendicular magnetic anisotropy even for large bilayer thickness of about 9 nm. Similar tendency is observed even by a 330 nm thick non-multilayered Ni film grown under the same conditions. This observation reveals the important role of strain and magnetoelastic anisotropy as a source of perpendicular magnetic anisotropy in the Ni/NiO multilayers.

  7. Mars’ atmospheric history derived from upper-atmosphere measurements of 38Ar/36Ar

    NASA Astrophysics Data System (ADS)

    Jakosky, B. M.; Slipski, M.; Benna, M.; Mahaffy, P.; Elrod, M.; Yelle, R.; Stone, S.; Alsaeed, N.

    2017-03-01

    The history of Mars’ atmosphere is important for understanding the geological evolution and potential habitability of the planet. We determine the amount of gas lost to space through time using measurements of the upper-atmospheric structure made by the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft. We derive the structure of 38Ar/36Ar between the homopause and exobase altitudes. Fractionation of argon occurs as a result of loss of gas to space by pickup-ion sputtering, which preferentially removes the lighter atom. The measurements require that 66% of the atmospheric argon has been lost to space. Thus, a large fraction of Mars’ atmospheric gas has been lost to space, contributing to the transition in climate from an early, warm, wet environment to today’s cold, dry atmosphere.

  8. Geochronological constraints on the age of a Permo-Triassic impact event: U-Pb and 40Ar/39Ar results for the 40 km Araguainha structure of central Brazil

    NASA Astrophysics Data System (ADS)

    Tohver, E.; Lana, C.; Cawood, P. A.; Fletcher, I. R.; Jourdan, F.; Sherlock, S.; Rasmussen, B.; Trindade, R. I. F.; Yokoyama, E.; Souza Filho, C. R.; Marangoni, Y.

    2012-06-01

    Impact cratering has been a fundamental geological process in Earth history with major ramifications for the biosphere. The complexity of shocked and melted rocks within impact structures presents difficulties for accurate and precise radiogenic isotope age determination, hampering the assessment of the effects of an individual event in the geological record. We demonstrate the utility of a multi-chronometer approach in our study of samples from the 40 km diameter Araguainha impact structure of central Brazil. Samples of uplifted basement granite display abundant evidence of shock deformation, but U/Pb ages of shocked zircons and the 40Ar/39Ar ages of feldspar from the granite largely preserve the igneous crystallization and cooling history. Mixed results are obtained from in situ40Ar/39Ar spot analyses of shocked igneous biotites in the granite, with deformation along kink-bands resulting in highly localized, partial resetting in these grains. Likewise, spot analyses of perlitic glass from pseudotachylitic breccia samples reflect a combination of argon inheritance from wall rock material, the age of the glass itself, and post-impact devitrification. The timing of crater formation is better assessed using samples of impact-generated melt rock where isotopic resetting is associated with textural evidence of melting and in situ crystallization. Granular aggregates of neocrystallized zircon form a cluster of ten U-Pb ages that yield a “Concordia” age of 247.8 ± 3.8 Ma. The possibility of Pb loss from this population suggests that this is a minimum age for the impact event. The best evidence for the age of the impact comes from the U-Th-Pb dating of neocrystallized monazite and 40Ar/39Ar step heating of three separate populations of post-impact, inclusion-rich quartz grains that are derived from the infill of miarolitic cavities. The 206Pb/238U age of 254.5 ± 3.2 Ma (2σ error) and 208Pb/232Th age of 255.2 ± 4.8 Ma (2σ error) of monazite, together with the

  9. Electronic and crystalline structure of Si/SiO 2 interface modified by ArF excimer laser

    NASA Astrophysics Data System (ADS)

    Cháb, V.; Lukeš, I.; Ondřejček, M.; Jiříček, P.

    The native oxide layers on Si(100) surface were irradiated under UHV conditions by an ArF excimer laser pulses with energy density varied between melting and evaporating thresholds. The resulting changes were studied by LEED, AES and UPS. The increase of the energy density up to evaporation threshold results in the recrystallisation of native oxide layer. The pulses with energy densities just above the evaporation threshold ablate the top layer leaving an ordered and atomicaly clean surface. The observed (1x1) surface reconstruction is probably stabilised by strains introduced during rapid melting and quenching of the topmost layers. The surface electronic structure is dominated by random satisfaction of dangling bonds swearing a well defined surface states observed on (2x1)Si(100) surface.

  10. Structural and Optical Properties Studies Of Ar{sup 2+} Ion Implanted Mn Deposited GaAs

    SciTech Connect

    Tripthi, S.; Dubey, R. L.; Dubey, S. K.; Yadav, A. D.

    2010-12-01

    Mn thin film deposited GaAs samples were implanted with 250 keV Ar{sup +2} ions for various fluences 5x10{sup 15}, 1x10{sup 16} and 5x10{sup 16} ions cm{sup -2}. Optical and structural properties of the samples have been investigated by using ultraviolet spectroscopy and X-ray diffraction techniques. Optical absorbance of the implanted samples was found to decrease with increase in argon ion fluence. XRD spectra of the samples implanted for ion fluences 5x10{sup 15} and 1x10{sup 16} showed the formation of (GaMn)As at 2{theta} value of 65.34 deg. The XRD spectrum of sample 1x10{sup 16} cm{sup -2} annealed at 450 deg. C showed the formation of magnetic phases.

  11. The relativistic equations of stellar structure and evolution

    NASA Technical Reports Server (NTRS)

    Thorne, K. S.

    1977-01-01

    The general-relativistic equations of stellar structure and evolution are reformulated in a notation which makes easy contact with Newtonian theory. Also, a general-relativistic version of the mixing-length formalism for convection is presented.

  12. The Evolution of Baryons in Cosmic Large Scale Structure

    NASA Astrophysics Data System (ADS)

    Snedden, Ali; Arielle Phillips, Lara; Mathews, Grant James; Coughlin, Jared; Suh, In-Saeng; Bhattacharya, Aparna

    2015-01-01

    The environments of galaxies play a critical role in their formation and evolution. We study these environments using cosmological simulations with star formation and supernova feedback included. From these simulations, we parse the large scale structure into clusters, filaments and voids using a segmentation algorithm adapted from medical imaging. We trace the star formation history, gas phase and metal evolution of the baryons in the intergalactic medium as function of structure. We find that our algorithm reproduces the baryon fraction in the intracluster medium and that the majority of star formation occurs in cold, dense filaments. We present the consequences this large scale environment has for galactic halos and galaxy evolution.

  13. Modification of the optical and structural properties of ZnO nanowires by low-energy Ar+ ion sputtering

    PubMed Central

    2013-01-01

    The effects of low-energy (≤2 kV) Ar+ irradiation on the optical and structural properties of zinc oxide (ZnO) nanowires (NWs) grown by a simple and cost-effective low-temperature technique were investigated. Both photoluminescence spectra from ZnO NW-coated films and cathodoluminescence analysis of individual ZnO NWs demonstrated obvious evidences of ultraviolet/visible luminescent enhancement with respect to irradiation fluence. Annihilation of the thinner ZnO NWs after the ion bombardment was appreciated by means of high-resolution scanning electron microscopy and transmission electron microscopy (TEM), which results in an increasing NW mean diameter for increasing irradiation fluences. Corresponding structural analysis by TEM pointed out not only significant changes in the morphology but also in the microstructure of these NWs, revealing certain radiation-sensitive behavior. The possible mechanisms accounting for the decrease of the deep-level emissions in the NWs with the increasing irradiation fluences are discussed according to their structural modifications. PMID:23570658

  14. Modification of the optical and structural properties of ZnO nanowires by low-energy Ar+ ion sputtering.

    PubMed

    Allah, Rabie Fath; Ben, Teresa; González, David; Hortelano, Vanesa; Martínez, Oscar; Plaza, Jose Luis

    2013-04-09

    The effects of low-energy (≤2 kV) Ar+ irradiation on the optical and structural properties of zinc oxide (ZnO) nanowires (NWs) grown by a simple and cost-effective low-temperature technique were investigated. Both photoluminescence spectra from ZnO NW-coated films and cathodoluminescence analysis of individual ZnO NWs demonstrated obvious evidences of ultraviolet/visible luminescent enhancement with respect to irradiation fluence. Annihilation of the thinner ZnO NWs after the ion bombardment was appreciated by means of high-resolution scanning electron microscopy and transmission electron microscopy (TEM), which results in an increasing NW mean diameter for increasing irradiation fluences. Corresponding structural analysis by TEM pointed out not only significant changes in the morphology but also in the microstructure of these NWs, revealing certain radiation-sensitive behavior. The possible mechanisms accounting for the decrease of the deep-level emissions in the NWs with the increasing irradiation fluences are discussed according to their structural modifications.

  15. Structures of hydrazones, (E)-2-(1,3-benzothiazolyl)-NHsbnd Ndbnd CHsbnd Ar, [Ar = 4-(pyridin-2-yl)phenyl, pyrrol-2-yl, thien-2-yl and furan-2-yl]: Difference in conformations and intermolecular hydrogen bonding

    NASA Astrophysics Data System (ADS)

    Lindgren, Eric B.; Yoneda, Julliane D.; Leal, Katia Z.; Nogueira, Antônio F.; Vasconcelos, Thatyana R. A.; Wardell, James L.; Wardell, Solange M. S. V.

    2013-03-01

    Structures of hydrazones, (E)-2-(1,3-benzothiazolyl)-NHsbnd Ndbnd CHsbnd Ar(Ar = pyridine-2-yl (1), pyrrol-2-yl (2), thien-2-yl (3) and furan-2-yl (4), prepared from 2-hydrazinyl-1,3-benzothiazole and ArCHO, followed by recrystallisation from alcohol solutions, are reported. No significant intramolecular hydrogen bonds are present in any of the four molecules. Different conformations were found between 2 and 3, on one hand and for 4, on the other. Thus for 4, the oxygen atom of the furanyl ring is on the same side of the molecule as is the sulfur atom of the benzothiazole unit, while in contrast, each of the heteroatoms of the thienyl and pyrrole rings lies on opposite sides to the benzothiazole sulphur atom. In addition to the conformational variations, differences are noted in the connections between molecules. Despite the presence in each case of N(hydrazono)sbnd H---N(benzothiazolo) intermolecular hydrogen bonds, molecules of 4 are linked into spiral chains, while molecules of 2 and 3 (and indeed all compounds having Ar = substituted phenyl) form symmetric dimers. Further intermolecular interactions, albeit weaker ones, are found in 2 [Csbnd H··N and Nsbnd H··π], 3 [Csbnd H··π] and 4 [π··π], while dimers of 1 remain essentially free. Calculations carried out using the DFT(B3LYP)/6-311++G(d,p) method indicated that the conformations determined by crystallography for 2-4 were the more stable.

  16. Microstructural Evolution of Nanocrystalline Diamond Films Due to CH4/Ar/H2 Plasma Post-Treatment Process.

    PubMed

    Lin, Sheng-Chang; Yeh, Chien-Jui; Manoharan, Divinah; Leou, Keh-Chyang; Lin, I-Nan

    2015-10-07

    Plasma post-treatment process was observed to markedly enhance the electron field emission (EFE) properties of ultrananocrystalline diamond (UNCD) films. TEM examinations reveal that the prime factor which improves the EFE properties of these films is the coalescence of ultrasmall diamond grains (∼5 nm) forming large diamond grains about hundreds of nanometers accompanied by the formation of nanographitic clusters along the grain boundaries due to the plasma post-treatment process. OES studies reveal the presence of large proportion of atomic hydrogen and C2 (or CH) species, which are the main ingredients that altered the granular structure of the UNCD films. In the post-treatment process, the plasma interacts with the diamond films by a diffusion process. The recrystallization of diamond grains started at the surface region of the material, and the interaction zone increased with the post-treatment period. The entire diamond film can be converted into a nanocrystalline granular structure when post-treated for a sufficient length of time.

  17. Melt evolution beneath a rifted craton edge: 40Ar/39Ar geochronology and Sr-Nd-Hf-Pb isotope systematics of primitive alkaline basalts and lamprophyres from the SW Baltic Shield

    NASA Astrophysics Data System (ADS)

    Tappe, Sebastian; Smart, Katie A.; Stracke, Andreas; Romer, Rolf L.; Prelević, Dejan; van den Bogaard, Paul

    2016-01-01

    A new high-precision 40Ar/39Ar anorthoclase feldspar age of 176.7 ± 0.5 Ma (2-sigma) reveals that small-volume alkaline basaltic magmatism occurred at the rifted SW margin of the Baltic Shield in Scania (southern Sweden), at a time of global plate reorganization associated with the inception of Pangea supercontinent break-up. Our combined elemental and Sr-Nd-Hf-Pb isotope dataset for representative basanite and nephelinite samples (>8 wt.% MgO) from 16 subvolcanic necks of the 30 by 40 km large Jurassic volcanic field suggests magma derivation from a moderately depleted mantle source (87Sr/86Sri = 0.7034-0.7048; εNdi = +4.4 to +5.2; εHfi = +4.7 to +8.1; 206Pb/204Pbi = 18.8-19.5). The mafic alkaline melts segregated from mixed peridotite-pyroxenite mantle with a potential temperature of ∼1400 °C at 2.7-4.2 GPa (∼90-120 km depths), which places ultimate melt generation within the convecting upper mantle, provided that the lithosphere-asthenosphere boundary beneath the southern Baltic Shield margin was at ⩽100 km depth during Mesozoic-Cenozoic rifting. Isotopic shifts and incompatible element enrichment relative to Depleted Mantle reflect involvement of at least 20% recycled oceanic lithosphere component (i.e., pyroxenite) with some minor continent-derived sediment during partial melting of well-stirred convecting upper mantle peridotite. Although pargasitic amphibole-rich metasomatized lithospheric mantle is excluded as the main source of the Jurassic magmas from Scania, hydrous ultramafic veins (i.e., hornblendite) may have caused subtle modifications to the compositions of passing sublithospheric melts. For example, modeling suggests that the more radiogenic Hf (εHfi = +6.3 to +8.1) and Pb (206Pb/204Pbi = 18.9-19.5) isotopic compositions of the more sodic and H2O-rich nephelinites, compared with relatively homogenous basanites (εHfi = +4.7 to +6.1; 206Pb/204Pbi = 18.8-18.9), originate from minor interactions between rising asthenospheric melts and

  18. Structural evolution of small ruthenium cluster anions

    SciTech Connect

    Waldt, Eugen; Hehn, Anna-Sophia; Ahlrichs, Reinhart; Kappes, Manfred M.; Schooss, Detlef

    2015-01-14

    The structures of ruthenium cluster anions have been investigated using a combination of trapped ion electron diffraction and density functional theory computations in the size range from eight to twenty atoms. In this size range, three different structural motifs are found: Ru{sub 8}{sup −}–Ru{sub 12}{sup −} have simple cubic structures, Ru{sub 13}{sup −}–Ru{sub 16}{sup −} form double layered hexagonal structures, and larger clusters form close packed motifs. For Ru{sub 17}{sup −}, we find hexagonal close packed stacking, whereas octahedral structures occur for Ru{sub 18}{sup −}–Ru{sub 20}{sup −}. Our calculations also predict simple cubic structures for the smaller clusters Ru{sub 4}{sup −}–Ru{sub 7}{sup −}, which were not accessible to electron diffraction measurements.

  19. Trichome structure and evolution in Neotropical lianas

    PubMed Central

    Nogueira, Anselmo; El Ottra, Juliana Hanna Leite; Guimarães, Elza; Machado, Silvia Rodrigues; Lohmann, Lúcia G.

    2013-01-01

    Background and Aims Trichomes are epidermal outgrowths generally associated with protection against herbivores and/or desiccation that are widely distributed from ferns to angiosperms. Patterns of topological variation and morphological evolution of trichomes are still scarce in the literature, preventing valid comparisons across taxa. This study integrates detailed morphoanatomical data and the evolutionary history of the tribe Bignonieae (Bignoniaceae) in order to gain a better understanding of current diversity and evolution of trichome types. Methods Two sampling schemes were used to characterize trichome types: (1) macromorphological characterization of all 105 species currently included in Bignonieae; and (2) micromorphological characterization of 16 selected species. Individual trichome morphotypes were coded as binary in each vegetative plant part, and trichome density and size were coded as multistate. Ancestral character state reconstructions were conducted using maximum likelihood (ML) assumptions. Key Results Two main functional trichome categories were found: non-glandular and glandular. In glandular trichomes, three morphotypes were recognized: peltate (Pg), stipitate (Sg) and patelliform/cupular (P/Cg) trichomes. Non-glandular trichomes were uniseriate, uni- or multicellular and simple or branched. Pg and P/Cg trichomes were multicellular and non-vascularized with three clearly distinct cell layers. Sg trichomes were multicellular, uniseriate and long-stalked. ML ancestral character state reconstructions suggested that the most recent common ancestor (MRCA) of Bignonieae probably had non-glandular, Pg and P/Cg trichomes, with each trichome type presenting alternative histories of appearance on the different plant parts. For example, the MRCA of Bignonieae probably had non-glandular trichomes on the stems, prophylls, petiole, petiolule and leaflet veins while P/Cg trichomes were restricted to leaflet blades. Sg trichomes were not present in the MRCA

  20. An Introduction to the Theory of Stellar Structure and Evolution

    NASA Astrophysics Data System (ADS)

    Prialnik, Dina

    2000-07-01

    Using fundamental physics, the theory of stellar structure and evolution is able to predict how stars are born, how their complex internal structure changes, what nuclear fuel they burn, and their ultimate fate. This undergraduate textbook provides a clear, methodical introduction to the theory of stellar structure and evolution. Starting from general principles and axioms, step-by-step coverage leads students to a global, comprehensive understanding of the subject. Throughout, the book uniquely places emphasis on the basic physical principles governing stellar structure and evolution. All processes are explained in clear and simple terms with all the necessary mathematics included. Exercises and their full solutions allow students to test their understanding. This book requires only a basic background in physics and mathematics and assumes no prior knowledge of astronomy. It provides a stimulating introduction for undergraduates in astronomy, physics, planetary science and applied mathematics taking a course on the physics of stars.

  1. Voltammetry as a tool for monitoring micellar structural evolution?

    PubMed

    Charlton; Doherty

    2000-02-15

    Self-assembled systems such as micelles and liquid crystals are currently of interest as templates for the controlled formation of nanoscale structures. Knowledge of the mesophase structure, structural evolution, and interparticle interaction is of great importance in understanding the behavior of such systems especially for applications such as nanoreactors. Here, we compare the use of cyclic voltammetry, chronoamperometry, and the rotating disk electrode (RDE) for the determination of micellar hydrodynamic radii and show that only the steady-state RDE yields values directly comparable with nonelectrochemical techniques. The RDE is applied for the determination of cetyltrimethylammonium chloride micellar structure and observing micellar structural evolution as well as evaluating the usual intermicellar interactions. The results clearly show (a) the collapse of the micellar shear plane toward the hard-sphere surface with increasing electrolyte concentration, (b) the electrolyte-dependent spherical expansion of the micellar hard-spheres due to increasing aggregation (N) number, (c) the structural transition from spherical to rodlike micelles, and (d) micellar elongation. As well as structural evolution, the evolutionary changes in interaction processes are also observed, i.e. the transition from Coulombic interactions to excluded volume interaction. This paper describes in detail the voltammetric measurement of these processes and explicates the necessary experimental conditions for successful observation of micellar structural evolution.

  2. Evolution of extortion in structured populations

    NASA Astrophysics Data System (ADS)

    Szolnoki, Attila; Perc, Matjaž

    2014-02-01

    Extortion strategies can dominate any opponent in an iterated prisoner's dilemma game. But if players are able to adopt the strategies performing better, extortion becomes widespread and evolutionary unstable. It may sometimes act as a catalyst for the evolution of cooperation, and it can also emerge in interactions between two populations, yet it is not the evolutionarily stable outcome. Here we revisit these results in the realm of spatial games. We find that pairwise imitation and birth-death dynamics return known evolutionary outcomes. Myopic best response strategy updating, on the other hand, reveals counterintuitive solutions. Defectors and extortioners coarsen spontaneously, which allows cooperators to prevail even at prohibitively high temptations to defect. Here extortion strategies play the role of a Trojan horse. They may emerge among defectors by chance, and once they do, cooperators become viable as well. These results are independent of the interaction topology, and they highlight the importance of coarsening, checkerboard ordering, and best response updating in evolutionary games.

  3. Prolongation structures of nonlinear evolution equations

    NASA Technical Reports Server (NTRS)

    Wahlquist, H. D.; Estabrook, F. B.

    1975-01-01

    A technique is developed for systematically deriving a 'prolongation structure' - a set of interrelated potentials and pseudopotentials - for nonlinear partial differential equations in two independent variables. When this is applied to the Korteweg-de Vries equation, a new infinite set of conserved quantities is obtained. Known solution techniques are shown to result from the discovery of such a structure: related partial differential equations for the potential functions, linear 'inverse scattering' equations for auxiliary functions, Backlund transformations. Generalizations of these techniques will result from the use of irreducible matrix representations of the prolongation structure.

  4. Joint evolution of specialization and dispersal in structured metapopulations.

    PubMed

    Nurmi, Tuomas; Parvinen, Kalle

    2011-04-21

    We study the joint evolution of dispersal and specialization concerning resource usage in a mechanistically underpinned structured discrete-time metapopulation model. We show that dispersal significantly affects the evolution of specialization and that specialization is a key factor that determines the possibility of evolutionary branching in dispersal propensity. Allowing both dispersal propensity and specialization to evolve as a consequence of natural selection is necessary in order to understand the evolutionary dynamics. The joint evolution of dispersal and specialization forms a natural evolutionary path leading to the coexistence of generalists and specialists. We show that in this process, the number of different patch types and the resource distribution are essential.

  5. Nucleolar Methyltransferase Fibrillarin: Evolution of Structure and Functions.

    PubMed

    Shubina, M Y; Musinova, Y R; Sheval, E V

    2016-09-01

    Fibrillarin is one of the most studied nucleolar proteins. Its main functions are methylation and processing of pre-rRNA. Fibrillarin is a highly conserved protein; however, in the course of evolution from archaea to eukaryotes, it acquired an additional N-terminal glycine and arginine-rich (GAR) domain. In this review, we discuss the evolution of fibrillarin structure and its relation to the functions of the protein in prokaryotes and eukaryotes.

  6. The mesoproterozoic Beaverhead impact structure and its tectonic setting, Montana-Idaho: 40Ar/39 and U-Pb isotopic constraints

    USGS Publications Warehouse

    Kellogg, K.S.; Snee, L.W.; Unruh, D.M.

    2003-01-01

    New 40Ar/39Ar and uranium-lead (U-Pb) zircon data from the Beaverhead impact structure, first identified by extensive shatter coning of Proterozoic quartzite and gneiss from the Beaverhead Mountains near the Montana-Idaho border, indicate that the structure formed at or after 900 Ma. The 40Ar/39Ar age spectra from fine-grained muscovite and biotite from a breccia zone in high-grade gneiss show significant argon loss but yield dates for highest-temperature steps that cluster between 899 and 908 Ma. The dated minerals probably formed by recrystallization of impact glass, so on both geologic and isotopic grounds, the dates probably represent the minimum age of impact. U-Pb data for zircons from the same breccia are strongly discordant and yield an upper intercept apparent age of 2464 ?? 56 Ma and a lower intercept apparent age of 779 ?? 69 Ma. Another brecciated gneiss about 7 km to the northeast that does not contain secondary mica does contain zircons that yield a concordant apparent age of 2455 ?? 9 Ma. Nearby gneiss that neither is brecciated nor contains shatter cones yields an apparent age of 2451 ?? 46 Ma. The 40Ar/39Ar results constrain the age of the shatter-coned quartzite and indicate that it is >900 Ma and possibly correlative with the Gunsight Formation of the Mesoproterozoic Lemhi Group. The upper intercept U-Pb age of ???2450 Ma from all three dated samples also shows that the Paleoproterozoic basement rocks of the area are among the youngest in the mostly Archean Wyoming province of North America. The impact site lies near the margin of the province, along the northeast-trending Great Falls tectonic zone, and the relatively young crustal age may reflect Early Proterozoic marginal accretion.

  7. Structural stages and evolution of the Urals

    NASA Astrophysics Data System (ADS)

    Puchkov, V. N.

    2013-02-01

    Five main structural and historical stages are established in the territory of the Urals: 1) Archean-Paleoproterozoic, a time of formation of the Volgo-Uralia subcontinent and its amalgamation with the other blocks of the craton of Baltica; 2) Riphean-Vendian (Meso- and Neoproterozoic), а stage that was finished with formation of Timanides; 3) Paleozoic-Early Mesozoic stage, corresponding to the development of the Uralides; 4) Mid-Jurassic-to Miocene platform stage; 5) Pliocene-Quaternary neo-orogenic stage. In this paper stratigraphic data are discussed, schemes of the structural zonation are presented, and the problems of the structural geology and geodynamics of sedimentary and magmatic complexes are discussed in a chronological order. Ideologically, the paper is based on plate and plume tectonics, in their modern versions.

  8. Structure, dynamics, assembly, and evolution of protein complexes.

    PubMed

    Marsh, Joseph A; Teichmann, Sarah A

    2015-01-01

    The assembly of individual proteins into functional complexes is fundamental to nearly all biological processes. In recent decades, many thousands of homomeric and heteromeric protein complex structures have been determined, greatly improving our understanding of the fundamental principles that control symmetric and asymmetric quaternary structure organization. Furthermore, our conception of protein complexes has moved beyond static representations to include dynamic aspects of quaternary structure, including conformational changes upon binding, multistep ordered assembly pathways, and structural fluctuations occurring within fully assembled complexes. Finally, major advances have been made in our understanding of protein complex evolution, both in reconstructing evolutionary histories of specific complexes and in elucidating general mechanisms that explain how quaternary structure tends to evolve. The evolution of quaternary structure occurs via changes in self-assembly state or through the gain or loss of protein subunits, and these processes can be driven by both adaptive and nonadaptive influences.

  9. Clouds on Neptune: Motions, Evolution, and Structure

    NASA Technical Reports Server (NTRS)

    Sromovsky, Larry A.; Morgan, Thomas (Technical Monitor)

    2001-01-01

    The aims of our original proposal were these: (1) improving measurements of Neptune's circulation, (2) understanding the spatial distribution of cloud features, (3) discovery of new cloud features and understanding their evolutionary process, (4) understanding the vertical structure of zonal cloud patterns, (5) defining the structure of discrete cloud features, and (6) defining the near IR albedo and light curve of Triton. Towards these aims we proposed analysis of existing 1996 groundbased NSFCAM/IRTF observations and nearly simultaneous WFPC2 observations from the Hubble Space Telescope. We also proposed to acquire new observations from both HST and the IRTF.

  10. Communication: Determining the structure of the N₂Ar van der Waals complex with laser-based channel-selected Coulomb explosion.

    PubMed

    Wu, Chengyin; Wu, Cong; Song, Di; Su, Hongmei; Xie, Xiguo; Li, Min; Deng, Yongkai; Liu, Yunquan; Gong, Qihuang

    2014-04-14

    We experimentally reconstructed the structure of the N2Ar van der Waals complex with the technique of laser-based channel-selected Coulomb explosion imaging. The internuclear distance between the N2 center of mass and the Ar atom, i.e., the length of the van der Waals bond, was determined to be 3.88 Å from the two-body explosion channels. The angle between the van der Waals bond and the N2 principal axis was determined to be 90° from the three-body explosion channels. The reconstructed structure was contrasted with our high level ab initio calculations. The agreement demonstrated the potential application of laser-based Coulomb explosion in imaging transient molecular structure, particularly for floppy van der Waals complexes, whose structures remain difficult to be determined by conventional spectroscopic methods.

  11. Evolution of atomic structure during nanoparticle formation

    PubMed Central

    Tyrsted, Christoffer; Lock, Nina; Jensen, Kirsten M. Ø.; Christensen, Mogens; Bøjesen, Espen D.; Emerich, Hermann; Vaughan, Gavin; Billinge, Simon J. L.; Iversen, Bo B.

    2014-01-01

    Understanding the mechanism of nanoparticle formation during synthesis is a key prerequisite for the rational design and engineering of desirable materials properties, yet remains elusive due to the difficulty of studying structures at the nanoscale under real conditions. Here, the first comprehensive structural description of the formation of a nanoparticle, yttria-stabilized zirconia (YSZ), all the way from its ionic constituents in solution to the final crystal, is presented. The transformation is a complicated multi-step sequence of atomic reorganizations as the material follows the reaction pathway towards the equilibrium product. Prior to nanoparticle nucleation, reagents reorganize into polymeric species whose structure is incompatible with the final product. Instead of direct nucleation of clusters into the final product lattice, a highly disordered intermediate precipitate forms with a local bonding environment similar to the product yet lacking the correct topology. During maturation, bond reforming occurs by nucleation and growth of distinct domains within the amorphous intermediary. The present study moves beyond kinetic modeling by providing detailed real-time structural insight, and it is demonstrated that YSZ nanoparticle formation and growth is a more complex chemical process than accounted for in conventional models. This level of mechanistic understanding of the nanoparticle formation is the first step towards more rational control over nanoparticle synthesis through control of both solution precursors and reaction intermediaries. PMID:25075335

  12. The high temperature structural evolution of hafnia

    NASA Astrophysics Data System (ADS)

    Haggerty, Ryan Paul

    The transformations of HfO2 are often described as analogous with the transformations in ZrO2 because of the similar crystal structures; however the phase transformations in HfO2 occur at higher temperatures. Even though this phase transformation has been extensively studied in ZrO2, the respective transformation in HfO2 is relatively unstudied and the properties that are reported are inconsistent. Much of the difficulty associated with studying HfO2 is related to the high temperatures needed and the sensitivity of the crystal to the environmental partial pressure of O2. HfO2 is expected to be capable of producing the same level of transformation toughening as ZrO2 at temperatures beyond 1000°C, the thermodynamic limit for toughened ZrO2. Despite significant effort the toughening acquired has not met with expectation. By providing information on the structure of HfO2 as it undergoes transformation, this study makes a significant step towards solving this problem. Significant advancements in experimentation have enabled a systematic study of the structure of HfO2 in its monoclinic and tetragonal phases in air. Using a quadrupole lamp furnace and a novel curved image plate detector the structure of HfO2 and ZrO 2 have been characterized by high temperature x-ray diffraction. The structural information provided by these experiments allows the properties of the transformation to be further investigated. Using phenomenological theory of martensite crystallography, the strain associated with the transformation from the tetragonal to the monoclinic phase has been described and provides insight into the lack of transformation toughening found in HfO2. Further characterization includes determination of the transformation temperature in air, the change in volume associated with the transformation and the temperature hysteresis of the transformation. In addition to transformation properties, the thermal expansion of HfO2 and ZrO2 has been thoroughly described as a function

  13. Model of evolution of surface grain structure under ion bombardment

    SciTech Connect

    Knyazeva, Anna G.; Kryukova, Olga N.

    2014-11-14

    Diffusion and chemical reactions in multicomponent systems play an important role in numerous technology applications. For example, surface treatment of materials and coatings by particle beam leads to chemical composition and grain structure change. To investigate the thermal-diffusion and chemical processes affecting the evolution of surface structure, the mathematical modeling is efficient addition to experiment. In this paper two-dimensional model is discussed to describe the evolution of titanium nitride coating on the iron substrate under implantation of boron and carbon. The equation for diffusion fluxes and reaction rate are obtained using Gibbs energy expansion into series with respect to concentration and their gradients.

  14. Are the topsoil structures relevant indicators of alluvial soil evolution ?

    NASA Astrophysics Data System (ADS)

    Salomé, Clémence; Le Bayon, Renée.-Claire; Guenat, Claire; Hallaire, Vincent; Bullinger Weber, Géraldine; Verrecchia, Eric

    2010-05-01

    Floodplains contain a wide range of all steps of soil evolution, which are relevant in order to study the initial steps of soil structuring. Alluvial soils exhibit characteristics of both sediment and / or inherited soil deposition, and in situ soil formation resulting in different types of soil structure, especially in the topsoil layers. In calcareous alluvium deposits, the structuration processes of the topsoil are fast resulting in different structures. In this context, our aim is to verify if these topsoil structures, at macroscopic and microscopic scales, are relevant indicators of in situ soil evolution in a carbonate-rich and calcium saturated environment. We hypothesise that along a soil-vegetation stabilisation gradient both macroscopic and microscopic structures of topsoil reflect this in situ soil evolution. Along this evolutionary gradient the type of structure changes and becomes more stable and widespread within the topsoil. We characterize the topsoil structure in three different vegetation types from the pioneer stage (willow vegetation) on new sediment deposits (carbonate-rich FLUVIOSOLS BRUTS according to the Sound Reference base for soils, 1998) to mature forests (beech, ash, spruce) on stable soils (carbonate-rich FLUVIOSOLS TYPIQUES) at three different altitudes (subalpine to hill levels). In order to evaluate the heterogeneity within each site and between them three replicates are made resulting in a total of 27 soil samples. At the macroscopic scale, topsoil structure is described based on morphological and macroscopic descriptions (humus form, type and size of structure) as well as structure stability (Mean Weight Diameter, MWD) and water stable macro aggregates (WSA%) according to Kemper and Rossenau (1986). At the microscopic scale, polished slabs (dimension of 7cm X 10 cm and 0.5 cm in thickness) are used to quantify pore space using a morphological approach and 2D image analysis. After binarization of the image, leading to the detection

  15. Late Paleozoic structural evolution of Permian basin

    SciTech Connect

    Ewing, T.E.

    1984-04-01

    The southern Permian basin is underlain by the NNW-trending Central Basin disturbed belt of Wolfcamp age (Lower Permian), the deep Delaware basin to its west, and the shallower Midland basin to its eat. The disturbed belt is highly segmented with zones of left-lateral offset. Major segments from south to north are: the Puckett-Grey Ranch zone; the Fort Stockton uplift; the Monahans transverse zone; the Andector ridges and the Eunice ridge; the Hobbs transverse zone; and the Tatum ridges, which abut the broad Roosevelt uplift to the north. The disturbed belt may have originated along rift zones of either Precambrian or Cambrian age. The extent of Lower and Middle Pennsylvanian deformation is unclear; much of the Val Verde basin-Ozona arch structure may have formed then. The main Wolfcamp deformation over thrust the West Texas crustal block against the Delaware block, with local denudation of the uplifted edge and eastward-directed backthrusting into the Midland basin. Latter in the Permian, the area was the center of a subcontinental bowl of subsidence - the Permian basin proper. The disturbed belt formed a pedestal for the carbonate accumulations which created the Central Basin platform. The major pre-Permian reservoirs of the Permian basin lie in large structural and unconformity-bounded traps on uplift ridges and domes. Further work on the regional structural style may help to predict fracture trends, to assess the timing of oil migration, and to evaluate intrareservoir variations in the overlying Permian giant oil fields.

  16. Modelling the Evolution of Social Structure

    PubMed Central

    Sutcliffe, A. G.; Dunbar, R. I. M.; Wang, D.

    2016-01-01

    Although simple social structures are more common in animal societies, some taxa (mainly mammals) have complex, multi-level social systems, in which the levels reflect differential association. We develop a simulation model to explore the conditions under which multi-level social systems of this kind evolve. Our model focuses on the evolutionary trade-offs between foraging and social interaction, and explores the impact of alternative strategies for distributing social interaction, with fitness criteria for wellbeing, alliance formation, risk, stress and access to food resources that reward social strategies differentially. The results suggest that multi-level social structures characterised by a few strong relationships, more medium ties and large numbers of weak ties emerge only in a small part of the overall fitness landscape, namely where there are significant fitness benefits from wellbeing and alliance formation and there are high levels of social interaction. In contrast, ‘favour-the-few’ strategies are more competitive under a wide range of fitness conditions, including those producing homogeneous, single-level societies of the kind found in many birds and mammals. The simulations suggest that the development of complex, multi-level social structures of the kind found in many primates (including humans) depends on a capacity for high investment in social time, preferential social interaction strategies, high mortality risk and/or differential reproduction. These conditions are characteristic of only a few mammalian taxa. PMID:27427758

  17. Evolution of atomic structure during nanoparticle formation

    DOE PAGES

    Tyrsted, Christoffer; Lock, Nina; Jensen, Kirsten M. Ø.; ...

    2014-04-14

    Understanding the mechanism of nanoparticle formation during synthesis is a key prerequisite for the rational design and engineering of desirable materials properties, yet remains elusive due to the difficulty of studying structures at the nanoscale under real conditions. Here, the first comprehensive structural description of the formation of a nanoparticle, yttria-stabilized zirconia (YSZ), all the way from its ionic constituents in solution to the final crystal, is presented. The transformation is a complicated multi-step sequence of atomic reorganizations as the material follows the reaction pathway towards the equilibrium product. Prior to nanoparticle nucleation, reagents reorganize into polymeric species whose structuremore » is incompatible with the final product. Instead of direct nucleation of clusters into the final product lattice, a highly disordered intermediate precipitate forms with a local bonding environment similar to the product yet lacking the correct topology. During maturation, bond reforming occurs by nucleation and growth of distinct domains within the amorphous intermediary. The present study moves beyond kinetic modeling by providing detailed real-time structural insight, and it is demonstrated that YSZ nanoparticle formation and growth is a more complex chemical process than accounted for in conventional models. This level of mechanistic understanding of the nanoparticle formation is the first step towards more rational control over nanoparticle synthesis through control of both solution precursors and reaction intermediaries.« less

  18. Structure, diversity and evolution of myriapod hemocyanins.

    PubMed

    Pick, Christian; Scherbaum, Samantha; Hegedüs, Elöd; Meyer, Andreas; Saur, Michael; Neumann, Ruben; Markl, Jürgen; Burmester, Thorsten

    2014-04-01

    Oxygen transport in the hemolymph of many arthropods is mediated by hemocyanins, large copper-containing proteins that are well-studied in Chelicerata and Crustacea, but had long been considered unnecessary in the subphylum of Myriapoda. Only recently has it become evident that hemocyanins are present in Scutigeromorpha (Chilopoda) and Spirostreptida (Diplopoda). Here we present evidence for a more widespread occurrence of hemocyanin in the myriapods. By means of RT-PCR, western blotting and database searches, hemocyanins were identified in the symphylans Hanseniella audax and Symphylella vulgaris, the chilopod Scolopendra subspinipes dehaani and the diplopod Polydesmus angustus. No hemocyanins were found in the diplopods Polyxenus lagurus, Cylindroiulus punctatus, Glomeris marginata, Glomeris pustulata and Arthrosphaera brandtii, or the chilopods Lithobius forficatus, Geophilus flavus and Strigamia maritima. This suggests multiple independent losses in myriapod taxa. Two independent hemocyanin subunits were found that were already present in the myriapod stem line. We specifically investigated the structure of the hemocyanin of P. angustus, which consists of three distinct subunits that occur in an approximately equimolar ratio. As deduced by 3D electron microscopy, the quaternary structure is a 3 × 6-mer that resembles the half structure of the 6 × 6-mer hemocyanin from Scutigera coleoptrata. It was analyzed more closely by homology modeling of 1 × 6-mers and their rigid-body fitting to the electron density map of the 3 × 6-mer. In addition, we obtained the cDNA sequence of a putative myriapod phenoloxidase. Phenoloxidases are related to the arthropod hemocyanins, but diverged before radiation of the arthropod subphyla.

  19. EVOLUTION OF FAST MAGNETOACOUSTIC PULSES IN RANDOMLY STRUCTURED CORONAL PLASMAS

    SciTech Connect

    Yuan, D.; Li, B.; Pascoe, D. J.; Nakariakov, V. M.; Keppens, R. E-mail: bbl@sdu.edu.cn

    2015-02-01

    We investigate the evolution of fast magnetoacoustic pulses in randomly structured plasmas, in the context of large-scale propagating waves in the solar atmosphere. We perform one-dimensional numerical simulations of fast wave pulses propagating perpendicular to a constant magnetic field in a low-β plasma with a random density profile across the field. Both linear and nonlinear regimes are considered. We study how the evolution of the pulse amplitude and width depends on their initial values and the parameters of the random structuring. Acting as a dispersive medium, a randomly structured plasma causes amplitude attenuation and width broadening of the fast wave pulses. After the passage of the main pulse, secondary propagating and standing fast waves appear. Width evolution of both linear and nonlinear pulses can be well approximated by linear functions; however, narrow pulses may have zero or negative broadening. This arises because narrow pulses are prone to splitting, while broad pulses usually deviate less from their initial Gaussian shape and form ripple structures on top of the main pulse. Linear pulses decay at an almost constant rate, while nonlinear pulses decay exponentially. A pulse interacts most efficiently with a random medium with a correlation length of about half of the initial pulse width. This detailed model of fast wave pulses propagating in highly structured media substantiates the interpretation of EIT waves as fast magnetoacoustic waves. Evolution of a fast pulse provides us with a novel method to diagnose the sub-resolution filamentation of the solar atmosphere.

  20. Earth's interdependent thermal, structural, and chemical evolution

    NASA Astrophysics Data System (ADS)

    Hofmeister, A.; Criss, R. E.

    2012-12-01

    The popular view that 30-55% of Earth's global power is primordial, with deep layers emanating significant power, rests on misunderstandings and models that omit magmatism and outgassing. These processes link Earth's chemical and thermal evolution, while creating layers, mainly because magmas transport latent heat and radioactive isotopes rapidly upwards. We link chemistry to heat flow, measured and theoretical, to understand the interior layering and workings. Quasi-steady state conditions describe most of Earth's history: (1) Accretion was cold and was not a source of deep heat. (2) Friction during core formation cannot have greatly heated the interior (thermodynamics plus buoyancy). (3) Conduction is the governing microscopic mechanism in the deep Earth. (4) Using well-constrained values of thermal conductivity (k), we find that homogeneously distributed radionuclides provide extremely high internal temperature (T) under radial symmetry. Moreover, for any given global power, sequestering heat producing elements into the upper mantle reduces Earth's central temperature by a factor of 10 from a homogeneous distribution. Hence, (5) core formation was a major cooling event. From modern determinations of k(T) we provide a reference conductive geotherm. Present-day global power of 30 TW from heat flux measurements and sequestering of heat producing elements in the upper mantle and transition zone, produces nearly isothermal T = 5300 K below 670 km, which equals experimentally determined freezing of pure Fe0 at the inner core boundary. Core freezing buffers the interior temperatures, while the Sun constrains the surface temperature, providing steady state conditions: Earth's deep interior is isothermal due to these constraints, low flux and high k. Our geotherms point to a stagnant lower mantle and convection above 670 km. Rotational flattening cracks the brittle lithosphere, providing paths for buoyant magmas to ascend. Release of latent heat augments the conductive

  1. Arc-oblique fault systems: their role in the Cenozoic structural evolution and metallogenesis of the Andes of central Chile

    NASA Astrophysics Data System (ADS)

    Piquer, Jose; Berry, Ron F.; Scott, Robert J.; Cooke, David R.

    2016-08-01

    The evolution of the Main Cordillera of Central Chile is characterized by the formation and subsequent inversion of an intra-arc volcano-tectonic basin. The world's largest porphyry Cu-Mo deposits were emplaced during basin inversion. Statistically, the area is dominated by NE- and NW-striking faults, oblique to the N-striking inverted basin-margin faults and to the axis of Cenozoic magmatism. This structural pattern is interpreted to reflect the architecture of the pre-Andean basement. Stratigraphic correlations, syn-extensional deposits and kinematic criteria on fault surfaces show several arc-oblique structures were active as normal faults at different stages of basin evolution. The geometry of syn-tectonic hydrothermal mineral fibers, in turn, demonstrates that most of these structures were reactivated as strike-slip ± reverse faults during the middle Miocene - early Pliocene. Fault reactivation age is constrained by 40Ar/39Ar dating of hydrothermal minerals deposited during fault slip. The abundance and distribution of these minerals indicates fault-controlled hydrothermal fluid flow was widespread during basin inversion. Fault reactivation occurred under a transpressive regime with E- to ENE-directed shortening, and was concentrated around major plutons and hydrothermal centers. At the margins of the former intra-arc basin, deformation was largely accommodated by reverse faulting, whereas in its central part strike-slip faulting was predominant.

  2. Gonadotropin-releasing hormone in invertebrates: structure, function, and evolution.

    PubMed

    Tsai, Pei-San

    2006-08-01

    Gonadotropin-releasing hormone (GnRH) is central to the initiation and maintenance of reproduction in vertebrates. GnRH is found in all major groups of Phylum Chordata, including the protochordates. Studies on functional and structural evolution of GnRH have, in the past, focused exclusively on chordates. However, the recent structural elucidation of an octopus GnRH-like molecule and increasing evidence that GnRH-like substances are present in multiple invertebrate phyla suggest GnRH is an ancient peptide that arose prior to the divergence of protostomes and deuterostomes. The extraordinary conservation of GnRH structure and function raises interesting questions regarding the functional role assumed by GnRH over the course of evolution. This review will focus on the current understanding of GnRH structure and function in non-chordate invertebrates. Special emphasis will be placed upon the possible and speculated functions of GnRH in mollusks.

  3. Rehabilitation Counselor Education Accreditation: History, Structure, and Evolution

    ERIC Educational Resources Information Center

    Shaw, Linda R.; Kuehn, Marvin D.

    2009-01-01

    This review examines some of the critical factors that influenced the evolution of rehabilitation counselor education accreditation. The article discusses the history and structure of the accreditation process and the activities that have occurred to maintain the relevancy and viability of the process. Major issues that the Council on…

  4. The relativistic equations of stellar structure and evolution

    NASA Technical Reports Server (NTRS)

    Thorne, K. S.

    1975-01-01

    The general relativistic equations of stellar structure and evolution are reformulated in a notation which makes easy contact with Newtonian theory. A general relativistic version of the mixing-length formalism for convection is presented. It is argued that in work on spherical systems, general relativity theorists have identified the wrong quantity as total mass-energy inside radius r.

  5. Velocity structure and evolution of the moon

    NASA Technical Reports Server (NTRS)

    Toksoz, M. N.; Dainty, A. M.; Solomon, S. C.; Anderson, K. R.

    1973-01-01

    Seismic data from the Apollo Passive Seismic Network stations are analyzed to determine the velocity structure and to infer the composition and physical properties of the lunar interior. Data from artificial impacts (SIBV booster and LM-ascent stage) cover a distance range of 9 to 1750 km. Travel times and amplitudes, as well as theoretical seismograms, are used to derive a velocity model for the outer 150 km of the moon. The P-wave velocity model confirms an earlier report of a lunar crust in the eastern part of Oceanus Procellarum. The crust is about 60 km thick and may consist of two layers in the mare regions. Possible values for the P-wave velocity in the uppermost mantle are between 7.6 and 9.0 km/sec. The 9 km/sec velocity represents either a localized heterogeneous unit, or a thin layer less than about 40 km in thickness. The elastic properties of the deep interior, as inferred from the seismograms of natural events (meteoroid impacts and moonquakes) occurring at great distances, indicate that there is an increase in attenuation and a possible decrease of velocity at depths below about 1000 km.

  6. Structure, Function, and Evolution of Rice Centromeres

    SciTech Connect

    Jiang, Jiming

    2010-02-04

    The centromere is the most characteristic landmark of eukaryotic chromosomes. Centromeres function as the site for kinetochore assembly and spindle attachment, allowing for the faithful pairing and segregation of sister chromatids during cell division. Characterization of centromeric DNA is not only essential to understand the structure and organization of plant genomes, but it is also a critical step in the development of plant artificial chromosomes. The centromeres of most model eukaryotic species, consist predominantly of long arrays of satellite DNA. Determining the precise DNA boundary of a centromere has proven to be a difficult task in multicellular eukaryotes. We have successfully cloned and sequenced the centromere of rice chromosome 8 (Cen8), representing the first fully sequenced centromere from any multicellular eukaryotes. The functional core of Cen8 spans ~800 kb of DNA, which was determined by chromatin immunoprecipitation (ChIP) using an antibody against the rice centromere-specific H3 histone. We discovered 16 actively transcribed genes distributed throughout the Cen8 region. In addition to Cen8, we have characterized eight additional rice centromeres using the next generation sequencing technology. We discovered four subfamilies of the CRR retrotransposon that is highly enriched in rice centromeres. CRR elements are constitutively transcribed and different CRR subfamilies are differentially processed by RNAi. These results suggest that different CRR subfamilies may play different roles in the RNAi-mediated pathway for formation and maintenance of centromeric chromatin.

  7. Molecular Evolution, Structure, and Function of Peroxidasins

    PubMed Central

    Soudi, Monika; Zamocky, Marcel; Jakopitsch, Christa; Furtmüller, Paul G; Obinger, Christian

    2012-01-01

    Peroxidasins represent the subfamily 2 of the peroxidase-cyclooxygenase superfamily and are closely related to chordata peroxidases (subfamily 1) and peroxinectins (subfamily 3). They are multidomain proteins containing a heme peroxidase domain with high homology to human lactoperoxidase that mediates one- and two-electron oxidation reactions. Additional domains of the secreted and glycosylated metalloproteins are type C-like immunoglobulin domains, typical leucine-rich repeats, as well as a von Willebrand factor C module. These are typical motifs of extracellular proteins that mediate protein–protein interactions. We have reconstructed the phylogeny of this new family of oxidoreductases and show the presence of four invertebrate clades as well as one vertebrate clade that includes also two different human representatives. The variability of domain assembly in the various clades was analyzed, as was the occurrence of relevant catalytic residues in the peroxidase domain based on the knowledge of catalysis of the mammalian homologues. Finally, the few reports on expression, localization, enzymatic activity, and physiological roles in the model organisms Drosophila melanogaster, Caenorhabditis elegans, and Homo sapiens are critically reviewed. Roles attributed to peroxidasins include antimicrobial defense, extracellular matrix formation, and consolidation at various developmental stages. Many research questions need to be solved in future, including detailed biochemical/physical studies and elucidation of the three dimensional structure of a model peroxidasin as well as the relation and interplay of the domains and the in vivo functions in various organisms including man. PMID:22976969

  8. Structural evolution of Colloidal Gels under Flow

    NASA Astrophysics Data System (ADS)

    Boromand, Arman; Maia, Joao; Jamali, Safa

    Colloidal suspensions are ubiquitous in different industrial applications ranging from cosmetic and food industries to soft robotics and aerospace. Owing to the fact that mechanical properties of colloidal gels are controlled by its microstructure and network topology, we trace the particles in the networks formed under different attraction potentials and try to find a universal behavior in yielding of colloidal gels. Many authors have implemented different simulation techniques such as molecular dynamics (MD) and Brownian dynamics (BD) to capture better picture during phase separation and yielding mechanism in colloidal system with short-ranged attractive force. However, BD neglects multi-body hydrodynamic interactions (HI) which are believed to be responsible for the second yielding of colloidal gels. We envision using dissipative particle dynamics (DPD) with modified depletion potential and hydrodynamic interactions, as a coarse-grain model, can provide a robust simulation package to address the gel formation process and yielding in short ranged-attractive colloidal systems. The behavior of colloidal gels with different attraction potentials under flow is examined and structural fingerprints of yielding in these systems will be discussed.

  9. The nonsinglet structure function evolution by Laplace method

    SciTech Connect

    Boroun, G. R. E-mail: boroun@razi.ac.ir; Zarrin, S.

    2015-12-15

    We derive a general scheme for the evolution of the nonsinglet structure function at the leadingorder (LO) and next-to-leading-order (NLO) by using the Laplace-transform technique. Results for the nonsinglet structure function are compared with MSTW2008, GRV, and CKMT parameterizations and also EMC experimental data in the LO and NLO analysis. The results are in good agreement with the experimental data and other parameterizations in the low- and large-x regions.

  10. The structure and evolution of plankton communities

    NASA Astrophysics Data System (ADS)

    Longhurst, Alan R.

    New understanding of the circulation of ancient oceans is not yet matched by progress in our understanding of their pelagic ecology, though it was the planktonic ecosystems that generated our offshore oil and gas reserves. Can we assume that present-day models of ecosystem function are also valid for ancient seas? This question is addressed by a study of over 4000 plankton samples to derive a comprehensive, global description of zooplankton community structure in modern oceans: this shows that copepods form only 50% of the biomass of all plankton, ranging from 70% in polar to 35% in tropical seas. Comparable figures are derived from 14 other taxonomic categories of zooplankton. For trophic groupings, the data indicate globally: geletinous predators - 14%; gelatinous herbivores - 4%; raptorial predators - 33%; macrofiltering herbivores - 20%; macrofiltering omnivores - 25%; and detritivores - 3%. A simple, idealized model for the modern pelagic ecosystem is derived from these percentages which indicates that metazooplankton are not the most important consumers of pico- and nano-plankton production which itself probably constitutes 90% of primary production in warm oceans. This model is then compared with candidate life-forms available in Palaeozoic and Mesozoic oceans to determine to what extent it is also valid for ancient ecosystems: it is concluded that it is probably unnecessary to postulate models fundamentally differing from it in order to accommodate the life-forms, both protozoic and metazoic, known to have populated ancient seas. Remarkably few life-forms have existed which cannot be paralleled in the modern ocean, which contains remarkably few life-forms which cannot be paralleled in the Palaeozoic ocean. As a first assumption, then, it is reasonable to assume that energy pathways were similar in ancient oceans to those we study today.

  11. PIECE: a database for plant gene structure comparison and evolution

    PubMed Central

    Wang, Yi; You, Frank M.; Lazo, Gerard R.; Luo, Ming-Cheng; Thilmony, Roger; Gordon, Sean; Kianian, Shahryar F.; Gu, Yong Q.

    2013-01-01

    Gene families often show degrees of differences in terms of exon–intron structures depending on their distinct evolutionary histories. Comparative analysis of gene structures is important for understanding their evolutionary and functional relationships within plant species. Here, we present a comparative genomics database named PIECE (http://wheat.pw.usda.gov/piece) for Plant Intron and Exon Comparison and Evolution studies. The database contains all the annotated genes extracted from 25 sequenced plant genomes. These genes were classified based on Pfam motifs. Phylogenetic trees were pre-constructed for each gene category. PIECE provides a user-friendly interface for different types of searches and a graphical viewer for displaying a gene structure pattern diagram linked to the resulting bootstrapped dendrogram for each gene family. The gene structure evolution of orthologous gene groups was determined using the GLOOME, Exalign and GECA software programs that can be accessed within the database. PIECE also provides a web server version of the software, GSDraw, for drawing schematic diagrams of gene structures. PIECE is a powerful tool for comparing gene sequences and provides valuable insights into the evolution of gene structure in plant genomes. PMID:23180792

  12. Ab initio study of the structures and electronic states of small neutral and ionic DABCO--Ar(n) clusters.

    PubMed

    Mathivon, Kevin; Linguerri, Roberto; Hochlaf, Majdi

    2014-03-01

    In the present theoretical work, we investigated the stationary points (minima and transition states) on the ground state potential energy surfaces of neutral and ionic 1,4-diazabicyclo[2.2.2]octane (DABCO)--Ar(n)⁰,⁺¹ (n = 1-4) clusters. As established in our systematic work on DABCO--Ar cluster (Mathivon et al., J Chem Phys 139:164306, 2013), the (R)MP2/aug-cc-pVDZ level is accurate enough for validating the prediction of stable forms. For n = 1 and 2, further computations at the MP2/aug-cc-pVTZ level confirm these assumptions. We show that some of the already known isomers of these heteroclusters derived using lower levels of theory are not realistic. More interestingly, our work reveals that DABCO is subject to slight deformations when binding to a small number of Ar atoms. Moreover, we computed the potential energy surfaces of the lowest singlet electronic states of DABCO--Ar(n)(n = 1-3) and of DABCO⁺--Ar(n)(n = 1-3), and the transition moments for the Sp(p = 1-3) ← S0 neutral transitions. These electronic states are found to be Rydberg in nature. The shape of their potentials is mainly repulsive with slight stabilization in the S2 potentials. Finally, the effects of microsolvation of DABCO in Ar clusters in ground and electronic excited states are discussed. The photophysical and photochemical dynamics of these electronic states may be complex.

  13. Formation and evolution of structure in loop cosmology.

    PubMed

    Bojowald, Martin; Kagan, Mikhail; Singh, Parampreet; Hernández, Hector H; Skirzewski, Aureliano

    2007-01-19

    Inhomogeneous cosmological perturbation equations are derived in loop quantum gravity, taking into account corrections, in particular, in gravitational parts. This provides a framework for calculating the evolution of modes in structure formation scenarios related to inflationary or bouncing models. Applications here are corrections to the Newton potential and to the evolution of large scale modes which imply nonconservation of curvature perturbations possibly noticeable in a running spectral index. These effects are sensitive to quantization procedures and test the characteristic behavior of correction terms derived from quantum gravity.

  14. Role of p(Z)-π(Ar/Nap) conjugation in structures of 1-(arylchalcogena)naphthalenes for Z = Te versus Se, S and O: experimental and theoretical investigations.

    PubMed

    Nakai, Takahito; Nishino, Mitsuhiro; Hayashi, Satoko; Hashimoto, Masato; Nakanishi, Waro

    2012-07-07

    Magnitudes of the p(Z)-π(Ar/Nap) conjugation were evaluated for 1-(arylchalcogena)naphthalenes (1-(ArZ)Nap, 1-(p-YC(6)H(4)Z)C(10)H(7); 1 (Z = Te), 2 (Se), 3 (S) and 4 (O)). Structures of 1 were determined by X-ray analysis for Y = NMe(2) (b), OMe (c) and CN (i). For 1b and 1c that have electron donating Y, the Z-C(Ar) bond is located on the naphthyl plane with Z-C(Nap) being perpendicular to the aryl plane, which we define as (B: pd). On the other hand, the structure of 1i with electron donating Y is (A: pl), of which Z-C(Ar) is placed almost perpendicular to the naphthyl plane with Z-C(Nap) being located on the aryl plane. Each structure of 1a (Y = H), 1b, 1c, 1d (Me), 1e (F), 1f (Cl), 1g (Br), 1h (COOEt), 1i and 1j (NO(2)) was determined by NMR in chloroform-d. Structures of 1 in the solutions are (B: pd) for b, c and e that have electron donating Y, (A: pl) for f-j with electron accepting Y, and in equilibrium between (B: pd) and (A: pl) for a and d of which Y are rather neutral. The results for 2-4 are very similar to those of 1 in solutions. Quantum chemical calculations were performed on 1-4 with Y of a, b' (NH(2)), d, f and j. Magnitudes of the p(Z)-π(Ar/Nap) conjugation were well-evaluated by NBO (natural bond orbital) analysis. The values were 12.6 and 13.0 kcal mol(-1) for the typical forms of (A: pl) and (B: pd) of 1a, respectively, resulting in a much smaller energy difference between the two (0.4 kcal mol(-1)), which should correspond to the observed result. It is well-demonstrated that the p(Te)-π(Ar/Nap) conjugation operates effectively in 1, although the magnitudes increase in the order of Z = Te < Se < S < O. Thermal effect of the Gibbs free energies is shown to play an important role in the energy profiles of 1a-4a.

  15. 40Ar/39Ar Geochronology, Isotope Geochemistry (Sr, Nd, Pb), and petrology of alkaline lavas near Yampa, Colorado: migration of alkaline volcanism and evolution of the northern Rio Grande rift

    USGS Publications Warehouse

    Cosca, Michael A.; Thompson, Ren A.; Lee, John P.; Turner, Kenzie J.; Neymark, Leonid A.; Premo, Wayne R.

    2014-01-01

    Volcanic rocks near Yampa, Colorado (USA), represent one of several small late Miocene to Quaternary alkaline volcanic fields along the northeast margin of the Colorado Plateau. Basanite, trachybasalt, and basalt collected from six sites within the Yampa volcanic field were investigated to assess correlations with late Cenozoic extension and Rio Grande rifting. In this paper we report major and trace element rock and mineral compositions and Ar, Sr, Nd, and Pb isotope data for these volcanic rocks. High-precision 40Ar/39Ar geochronology indicates westward migration of volcanism within the Yampa volcanic field between 6 and 4.5 Ma, and the Sr, Nd, and Pb isotope values are consistent with a primary source in the Proterozoic subcontinental lithospheric mantle. Relict olivine phenocrysts have Mg- and Ni-rich cores, whereas unmelted clinopyroxene cores are Na and Si enriched with finely banded Ca-, Mg-, Al-, and Ti-enriched rims, thus tracing their crystallization history from a lithospheric mantle source region to one in contact with melt prior to eruption. A regional synthesis of Neogene and younger volcanism within the Rio Grande rift corridor, from northern New Mexico to southern Wyoming, supports a systematic overall southwest migration of alkaline volcanism. We interpret this Neogene to Quaternary migration of volcanism toward the northeast margin of the Colorado Plateau to record passage of melt through subvertical zones within the lithosphere weakened by late Cenozoic extension. If the locus of Quaternary alkaline magmatism defines the current location of the Rio Grande rift, it includes the Leucite Hills, Wyoming. We suggest that alkaline volcanism in the incipient northern Rio Grande rift, north of Leadville, Colorado, represents melting of the subcontinental lithospheric mantle in response to transient infiltration of asthenospheric mantle into deep, subvertical zones of dilational crustal weakness developed during late Cenozoic extension that have been

  16. Parallel Structural Evolution of Mitochondrial Ribosomes and OXPHOS Complexes.

    PubMed

    van der Sluis, Eli O; Bauerschmitt, Heike; Becker, Thomas; Mielke, Thorsten; Frauenfeld, Jens; Berninghausen, Otto; Neupert, Walter; Herrmann, Johannes M; Beckmann, Roland

    2015-04-09

    The five macromolecular complexes that jointly mediate oxidative phosphorylation (OXPHOS) in mitochondria consist of many more subunits than those of bacteria, yet, it remains unclear by which evolutionary mechanism(s) these novel subunits were recruited. Even less well understood is the structural evolution of mitochondrial ribosomes (mitoribosomes): while it was long thought that their exceptionally high protein content would physically compensate for their uniquely low amount of ribosomal RNA (rRNA), this hypothesis has been refuted by structural studies. Here, we present a cryo-electron microscopy structure of the 73S mitoribosome from Neurospora crassa, together with genomic and proteomic analyses of mitoribosome composition across the eukaryotic domain. Surprisingly, our findings reveal that both structurally and compositionally, mitoribosomes have evolved very similarly to mitochondrial OXPHOS complexes via two distinct phases: A constructive phase that mainly acted early in eukaryote evolution, resulting in the recruitment of altogether approximately 75 novel subunits, and a reductive phase that acted during metazoan evolution, resulting in gradual length-reduction of mitochondrially encoded rRNAs and OXPHOS proteins. Both phases can be well explained by the accumulation of (slightly) deleterious mutations and deletions, respectively, in mitochondrially encoded rRNAs and OXPHOS proteins. We argue that the main role of the newly recruited (nuclear encoded) ribosomal- and OXPHOS proteins is to provide structural compensation to the mutationally destabilized mitochondrially encoded components. While the newly recruited proteins probably provide a selective advantage owing to their compensatory nature, and while their presence may have opened evolutionary pathways toward novel mitochondrion-specific functions, we emphasize that the initial events that resulted in their recruitment was nonadaptive in nature. Our framework is supported by population genetic

  17. Structure and Evolution of the Foreign Exchange Networks

    NASA Astrophysics Data System (ADS)

    Kwapień, J.; Gworek, S.; Drożdż, S.

    2009-01-01

    We investigate topology and temporal evolution of the foreign currency exchange market viewed from a weighted network perspective. Based on exchange rates for a set of 46 currencies (including precious metals), we construct different representations of the FX network depending on a choice of the base currency. Our results show that the network structure is not stable in time, but there are main clusters of currencies, which persist for a long period of time despite the fact that their size and content are variable. We find a long-term trend in the network's evolution which affects the USD and EUR nodes. In all the network representations, the USD node gradually loses its centrality, while, on contrary, the EUR node has become slightly more central than it used to be in its early years. Despite this directional trend, the overall evolution of the network is noisy.

  18. Evolution of specialization in resource utilization in structured metapopulations.

    PubMed

    Nurmi, Tuomas; Geritz, Stefan; Parvinen, Kalle; Gyllenberg, Mats

    2008-07-01

    We study the evolution of resource utilization in a structured discrete-time metapopulation model with an infinite number of patches, prone to local catastrophes. The consumer faces a trade-off in the abilities to consume two resources available in different amounts in each patch. We analyse how the evolution of specialization in the utilization of the resources is affected by different ecological factors: migration, local growth, local catastrophes, forms of the trade-off and distribution of the resources in the patches. Our modelling approach offers a natural way to include more than two patch types into the models. This has not been usually possible in the previous spatially heterogeneous models focusing on the evolution of specialization.

  19. Modeling the mesozoic-cenozoic structural evolution of east texas

    USGS Publications Warehouse

    Pearson, Ofori N.; Rowan, Elisabeth L.; Miller, John J.

    2012-01-01

    The U.S. Geological Survey (USGS) recently assessed the undiscovered technically recoverable oil and gas resources within Jurassic and Cretaceous strata of the onshore coastal plain and State waters of the U.S. Gulf Coast. Regional 2D seismic lines for key parts of the Gulf Coast basin were interpreted in order to examine the evolution of structural traps and the burial history of petroleum source rocks. Interpretation and structural modeling of seismic lines from eastern Texas provide insights into the structural evolution of this part of the Gulf of Mexico basin. Since completing the assessment, the USGS has acquired additional regional seismic lines in east Texas; interpretation of these new lines, which extend from the Texas-Oklahoma state line to the Gulf Coast shoreline, show how some of the region's prominent structural elements (e.g., the Talco and Mount Enterprise fault zones, the East Texas salt basin, and the Houston diapir province) vary along strike. The interpretations also indicate that unexplored structures may lie beneath the current drilling floor. Structural restorations based upon interpretation of these lines illustrate the evolution of key structures and show the genetic relation between structural growth and movement of the Jurassic Louann Salt. 1D thermal models that integrate kinetics and burial histories were also created for the region's two primary petroleum source rocks, the Oxfordian Smackover Formation and the Cenomanian-Turonian Eagle Ford Shale. Integrating results from the thermal models with the structural restorations provides insights into the distribution and timing of petroleum expulsion from the Smackover Formation and Eagle Ford Shale in eastern Texas.

  20. The evolution of protein structures and structural ensembles under functional constraint.

    PubMed

    Siltberg-Liberles, Jessica; Grahnen, Johan A; Liberles, David A

    2011-10-28

    Protein sequence, structure, and function are inherently linked through evolution and population genetics. Our knowledge of protein structure comes from solved structures in the Protein Data Bank (PDB), our knowledge of sequence through sequences found in the NCBI sequence databases (http://www.ncbi.nlm.nih.gov/), and our knowledge of function through a limited set of in-vitro biochemical studies. How these intersect through evolution is described in the first part of the review. In the second part, our understanding of a series of questions is addressed. This includes how sequences evolve within structures, how evolutionary processes enable structural transitions, how the folding process can change through evolution and what the fitness impacts of this might be. Moving beyond static structures, the evolution of protein kinetics (including normal modes) is discussed, as is the evolution of conformational ensembles and structurally disordered proteins. This ties back to a question of the role of neostructuralization and how it relates to selection on sequences for functions. The relationship between metastability, the fitness landscape, sequence divergence, and organismal effective population size is explored. Lastly, a brief discussion of modeling the evolution of sequences of ordered and disordered proteins is entertained.

  1. Ar-Ar_Redux: rigorous error propagation of 40Ar/39Ar data, including covariances

    NASA Astrophysics Data System (ADS)

    Vermeesch, P.

    2015-12-01

    Rigorous data reduction and error propagation algorithms are needed to realise Earthtime's objective to improve the interlaboratory accuracy of 40Ar/39Ar dating to better than 1% and thereby facilitate the comparison and combination of the K-Ar and U-Pb chronometers. Ar-Ar_Redux is a new data reduction protocol and software program for 40Ar/39Ar geochronology which takes into account two previously underappreciated aspects of the method: 1. 40Ar/39Ar measurements are compositional dataIn its simplest form, the 40Ar/39Ar age equation can be written as: t = log(1+J [40Ar/39Ar-298.5636Ar/39Ar])/λ = log(1 + JR)/λ Where λ is the 40K decay constant and J is the irradiation parameter. The age t does not depend on the absolute abundances of the three argon isotopes but only on their relative ratios. Thus, the 36Ar, 39Ar and 40Ar abundances can be normalised to unity and plotted on a ternary diagram or 'simplex'. Argon isotopic data are therefore subject to the peculiar mathematics of 'compositional data', sensu Aitchison (1986, The Statistical Analysis of Compositional Data, Chapman & Hall). 2. Correlated errors are pervasive throughout the 40Ar/39Ar methodCurrent data reduction protocols for 40Ar/39Ar geochronology propagate the age uncertainty as follows: σ2(t) = [J2 σ2(R) + R2 σ2(J)] / [λ2 (1 + R J)], which implies zero covariance between R and J. In reality, however, significant error correlations are found in every step of the 40Ar/39Ar data acquisition and processing, in both single and multi collector instruments, during blank, interference and decay corrections, age calculation etc. Ar-Ar_Redux revisits every aspect of the 40Ar/39Ar method by casting the raw mass spectrometer data into a contingency table of logratios, which automatically keeps track of all covariances in a compositional context. Application of the method to real data reveals strong correlations (r2 of up to 0.9) between age measurements within a single irradiation batch. Propertly taking

  2. Structure and sequence based analysis of alpha-amylase evolution.

    PubMed

    Singh, Swati; Guruprasad, Lalitha

    2014-01-01

    α-Amylases hydrolyze α- 1,4-glycosidic bonds during assimilation of biological macromolecules. The amino acid sequences of these enzymes in thousands of diverse organisms are known and the 3D structures of several proteins have been solved. The 3D structure analysis of these universal enzymes from diverse organisms has been studied by the generation of phylogenetic trees and structure based sequence analysis to generate a metric for the degree of conservation that is responsible for individual speciation. Greater similarities are observed between reference NCBI tree and structure based phylogenetic tree compared to sequence based phylogenetic tree indicating that structures truly represent the functional aspects of proteins than from the sequence information alone. We report differences in the profile specific conserved and insertion/deletion regions, factors responsible for the Ca(2+) and Cl(-) ion binding and the disulfide connectivity pattern that discriminate the enzymes over evolution.

  3. Evolution of tertiary structure of viral RNA dependent polymerases.

    PubMed

    Černý, Jiří; Černá Bolfíková, Barbora; Valdés, James J; Grubhoffer, Libor; Růžek, Daniel

    2014-01-01

    Viral RNA dependent polymerases (vRdPs) are present in all RNA viruses; unfortunately, their sequence similarity is too low for phylogenetic studies. Nevertheless, vRdP protein structures are remarkably conserved. In this study, we used the structural similarity of vRdPs to reconstruct their evolutionary history. The major strength of this work is in unifying sequence and structural data into a single quantitative phylogenetic analysis, using powerful a Bayesian approach. The resulting phylogram of vRdPs demonstrates that RNA-dependent DNA polymerases (RdDPs) of viruses within Retroviridae family cluster in a clearly separated group of vRdPs, while RNA-dependent RNA polymerases (RdRPs) of dsRNA and +ssRNA viruses are mixed together. This evidence supports the hypothesis that RdRPs replicating +ssRNA viruses evolved multiple times from RdRPs replicating +dsRNA viruses, and vice versa. Moreover, our phylogram may be presented as a scheme for RNA virus evolution. The results are in concordance with the actual concept of RNA virus evolution. Finally, the methods used in our work provide a new direction for studying ancient virus evolution.

  4. PROTOPLANETARY DISK STRUCTURE WITH GRAIN EVOLUTION: THE ANDES MODEL

    SciTech Connect

    Akimkin, V.; Wiebe, D.; Pavlyuchenkov, Ya.; Zhukovska, S.; Semenov, D.; Henning, Th.; Vasyunin, A.; Birnstiel, T. E-mail: dwiebe@inasan.ru E-mail: zhukovska@mpia.de E-mail: henning@mpia.de E-mail: tbirnstiel@cfa.harvard.edu

    2013-03-20

    We present a self-consistent model of a protoplanetary disk: 'ANDES' ('AccretioN disk with Dust Evolution and Sedimentation'). ANDES is based on a flexible and extendable modular structure that includes (1) a 1+1D frequency-dependent continuum radiative transfer module, (2) a module to calculate the chemical evolution using an extended gas-grain network with UV/X-ray-driven processes and surface reactions, (3) a module to calculate the gas thermal energy balance, and (4) a 1+1D module that simulates dust grain evolution. For the first time, grain evolution and time-dependent molecular chemistry are included in a protoplanetary disk model. We find that grain growth and sedimentation of large grains onto the disk midplane lead to a dust-depleted atmosphere. Consequently, dust and gas temperatures become higher in the inner disk (R {approx}< 50 AU) and lower in the outer disk (R {approx}> 50 AU), in comparison with the disk model with pristine dust. The response of disk chemical structure to the dust growth and sedimentation is twofold. First, due to higher transparency a partly UV-shielded molecular layer is shifted closer to the dense midplane. Second, the presence of big grains in the disk midplane delays the freeze-out of volatile gas-phase species such as CO there, while in adjacent upper layers the depletion is still effective. Molecular concentrations and thus column densities of many species are enhanced in the disk model with dust evolution, e.g., CO{sub 2}, NH{sub 2}CN, HNO, H{sub 2}O, HCOOH, HCN, and CO. We also show that time-dependent chemistry is important for a proper description of gas thermal balance.

  5. Structure and evolution of fossil H II regions

    NASA Technical Reports Server (NTRS)

    Mccray, R.; Schwarz, J.

    1971-01-01

    The structure and evolution of a fossil H II region created by a burst of ionizing radiation from a supernova is considered. The cooling time scale for the shell is about 10 to the 6th power years. Superposition of million-year-old fossil H II regions may account for the temperature and ionization of the interstellar medium. Fossil H II regions are unstable to growth of thermal condensations. Highly ionized filamentary structures form and dissipate in about 10,000 years. Partially ionized clouds form and dissipate in about 10 to the 6th power years.

  6. Structure scalars and evolution equations in f( G) cosmology

    NASA Astrophysics Data System (ADS)

    Sharif, M.; Fatima, H. Ismat

    2017-01-01

    In this paper, we study the dynamics of self-gravitating fluid using structure scalars for spherical geometry in the context of f( G) cosmology. We construct structure scalars through orthogonal splitting of the Riemann tensor and deduce a complete set of equations governing the evolution of dissipative anisotropic fluid in terms of these scalars. We explore different causes of density inhomogeneity which turns out to be a necessary condition for viable models. It is explicitly shown that anisotropic inhomogeneous static spherically symmetric solutions can be expressed in terms of these scalar functions.

  7. Structural measures to track the evolution of SNOMED CT hierarchies.

    PubMed

    Wei, Duo; Helen Gu, Huanying; Perl, Yehoshua; Halper, Michael; Ochs, Christopher; Elhanan, Gai; Chen, Yan

    2015-10-01

    The Systematized Nomenclature of Medicine Clinical Terms (SNOMED CT) is an extensive reference terminology with an attendant amount of complexity. It has been updated continuously and revisions have been released semi-annually to meet users' needs and to reflect the results of quality assurance (QA) activities. Two measures based on structural features are proposed to track the effects of both natural terminology growth and QA activities based on aspects of the complexity of SNOMED CT. These two measures, called the structural density measure and accumulated structural measure, are derived based on two abstraction networks, the area taxonomy and the partial-area taxonomy. The measures derive from attribute relationship distributions and various concept groupings that are associated with the abstraction networks. They are used to track the trends in the complexity of structures as SNOMED CT changes over time. The measures were calculated for consecutive releases of five SNOMED CT hierarchies, including the Specimen hierarchy. The structural density measure shows that natural growth tends to move a hierarchy's structure toward a more complex state, whereas the accumulated structural measure shows that QA processes tend to move a hierarchy's structure toward a less complex state. It is also observed that both the structural density and accumulated structural measures are useful tools to track the evolution of an entire SNOMED CT hierarchy and reveal internal concept migration within it.

  8. Structural Measures to Track the Evolution of SNOMED CT Hierarchies

    PubMed Central

    Wei, Duo; Gu, Huanying (Helen); Perl, Yehoshua; Halper, Michael; Ochs, Christopher; Elhanan, Gai; Chen, Yan

    2015-01-01

    The Systematized Nomenclature of Medicine Clinical Terms (SNOMED CT) is an extensive reference terminology with an attendant amount of complexity. It has been updated continuously and revisions have been released semi-annually to meet users’ needs and to reflect the results of quality assurance (QA) activities. Two measures based on structural features are proposed to track the effects of both natural terminology growth and QA activities based on aspects of the complexity of SNOMED CT. These two measures, called the structural density measure and accumulated structural measure, are derived based on two abstraction networks, the area taxonomy and the partial-area taxonomy. The measures derive from attribute relationship distributions and various concept groupings that are associated with the abstraction networks. They are used to track the trends in the complexity of structures as SNOMED CT changes over time. The measures were calculated for consecutive releases of five SNOMED CT hierarchies, including the Specimen hierarchy. The structural density measure shows that natural growth tends to move a hierarchy’s structure toward a more complex state, whereas the accumulated structural measure shows that QA processes tend to move a hierarchy’s structure toward a less complex state. It is also observed that both the structural density and accumulated structural measures are useful tools to track the evolution of an entire SNOMED CT hierarchy and reveal internal concept migration within it. PMID:26260003

  9. Evolution of baryons in cosmic large scale structure

    NASA Astrophysics Data System (ADS)

    Snedden, Ali

    We introduce a new self-consistent structure finding algorithm that parses large scale cosmological structure into clusters, filaments and voids. This algorithm probes the structure at multiple scales and classifies the appropriate regions with the most probable structure type and size. We use this structure finding algorithm to parse and follow the evolution of poor clusters, filaments and voids in large scale simulations. We trace the complete evolution of the baryons in the gas phase and the star formation history within each structure. We vary the structure measure threshold to probe the complex inner structure of star forming regions in poor clusters, filaments and voids. We find the majority of star formation occurs in cold condensed gas in filaments at all redshifts and that it peaks at intermediate redshifts (z ~ 3). We also show that much of the star formation above a redshift z = 3 occurs in low contrast regions of filaments, but as the density contrast increases at lower redshift, star formation switches to high contrast regions or the inner parts of filaments. Since filaments bridge between void and cluster regions, this suggests that the majority of star formation occurs in galaxies in intermediate density regions prior to the accretion onto poor clusters. We find that at the present epoch, the gas phase distribution is 43.1%, 30.0%, 24.7% and 2.2% in the diffuse, WHIM, hot halo and condensed phases, respectively. Most of the WHIM is found to be in filamentary structures. Moreover 8.77%, 79.1%, 2.11% and 9.98% of the gas is located in poor clusters, filaments, voids and unassigned regions respectively. We find that both filaments and poor clusters are multiphase environments at redshift z = 0.

  10. Polyhedra structures and the evolution of the insect viruses

    PubMed Central

    Ji, Xiaoyun; Axford, Danny; Owen, Robin; Evans, Gwyndaf; Ginn, Helen M.; Sutton, Geoff; Stuart, David I.

    2015-01-01

    Polyhedra represent an ancient system used by a number of insect viruses to protect virions during long periods of environmental exposure. We present high resolution crystal structures of polyhedra for seven previously uncharacterised types of cypoviruses, four using ab initio selenomethionine phasing (two of these required over 100 selenomethionine crystals each). Approximately 80% of residues are structurally equivalent between all polyhedrins (pairwise rmsd ⩽1.5 Å), whilst pairwise sequence identities, based on structural alignment, are as little as 12%. These structures illustrate the effect of 400 million years of evolution on a system where the crystal lattice is the functionally conserved feature in the face of massive sequence variability. The conservation of crystal contacts is maintained across most of the molecular surface, except for a dispensable virus recognition domain. By spreading the contacts over so much of the protein surface the lattice remains robust in the face of many individual changes. Overall these unusual structural constraints seem to have skewed the molecule’s evolution so that surface residues are almost as conserved as the internal residues. PMID:26291392

  11. Structure and Age Jointly Influence Rates of Protein Evolution

    PubMed Central

    Toll-Riera, Macarena; Bostick, David; Albà, M. Mar; Plotkin, Joshua B.

    2012-01-01

    What factors determine a protein's rate of evolution are actively debated. Especially unclear is the relative role of intrinsic factors of present-day proteins versus historical factors such as protein age. Here we study the interplay of structural properties and evolutionary age, as determinants of protein evolutionary rate. We use a large set of one-to-one orthologs between human and mouse proteins, with mapped PDB structures. We report that previously observed structural correlations also hold within each age group – including relationships between solvent accessibility, designabililty, and evolutionary rates. However, age also plays a crucial role: age modulates the relationship between solvent accessibility and rate. Additionally, younger proteins, despite being less designable, tend to evolve faster than older proteins. We show that previously reported relationships between age and rate cannot be explained by structural biases among age groups. Finally, we introduce a knowledge-based potential function to study the stability of proteins through large-scale computation. We find that older proteins are more stable for their native structure, and more robust to mutations, than younger ones. Our results underscore that several determinants, both intrinsic and historical, can interact to determine rates of protein evolution. PMID:22693443

  12. Successive reactivation of older structures under variable heat flow conditions evidenced by K-Ar fault gouge dating in Sierra de Ambato, northern Argentine broken foreland

    NASA Astrophysics Data System (ADS)

    Nóbile, Julieta C.; Collo, Gilda; Dávila, Federico M.; Martina, Federico; Wemmer, Klaus

    2015-12-01

    The Argentine broken foreland has been the subject of continuous research to determine the uplift and exhumation history of the region. High-elevation mountains are the result of N-S reverse faults that disrupted a W-E Miocene Andean foreland basin. In the Sierra de Ambato (northern Argentine broken foreland) the reverse faults offset Neogene sedimentary rocks (Aconquija Fm., ˜9 Ma) and affect the basement comprising Paleozoic metamorphic rocks that have been dated at ˜477-470 Ma. In order to establish a chronology of these faults affecting the previous continuous basin we date the formation age of clay minerals associated with fault gouge using the K-Ar dating technique. Clay mineral formation is a fundamental process in the evolution of faults under the brittle regime (<<300 °C). K-Ar ages (9 fractions from 3 samples collected along a transect in the Sierra de Ambato) vary from Late Devonian to Late Triassic (˜360-220 Ma). This age distribution can be explained by a long lasting brittle deformation history with a minimum age of ˜360 Ma and a last clay minerals forming event at ˜220 Ma. Moreover, given the progression of apparent ages decreasing from coarse to fine size fractions (˜360-311 Ma for 2-1 μm grain size fraction, ˜326-286 Ma for 1-0.2 μm and ˜291-219 Ma of <0.2 μm), we modeled discrete deformation events at ˜417 Ma (ending of the Famatinian cycle), ˜317-326 Ma (end of Gondwanic orogeny), and ˜194-279 Ma (Early Permian - Jurassic deformation). According to our data, the Neogene reactivation would not have affected the K-Ar system neither generated a significant clay minerals crystallization in the fault gouge, although an exhumation of more than 2 Km is recorded in this period from stratigraphic data.

  13. Protein structure comparison using the markov transition model of evolution.

    PubMed

    Kawabata, T; Nishikawa, K

    2000-10-01

    A number of automatic protein structure comparison methods have been proposed; however, their similarity score functions are often decided by the researchers' intuition and trial-and-error, and not by theoretical background. We propose a novel theory to evaluate protein structure similarity, which is based on the Markov transition model of evolution. Our similarity score between structures i and j is defined as log P(j --> i)/P(i), where P(j --> i) is the probability that structure j changes to structure i during the evolutionary process, and P(i) is the probability that structure i appears by chance. This is a reasonable definition of structure similarity, especially for finding evolutionarily related (homologous) similarity. The probability P(j --> i) is estimated by the Markov transition model, which is similar to the Dayhoff's substitution model between amino acids. To estimate the parameters of the model, homologous protein structure pairs are collected using sequence similarity, and the numbers of structure transitions within the pairs are counted. Next these numbers are transformed to a transition probability matrix of the Markov transition. Transition probabilities for longer time are obtained by multiplying the probability matrix by itself several times. In this study, we generated three types of structure similarity scores: an environment score, a residue-residue distance score, and a secondary structure elements (SSE) score. Using these scores, we developed the structure comparison program, Matras (MArkovian TRAnsition of protein Structure). It employs a hierarchical alignment algorithm, in which a rough alignment is first obtained by SSEs, and then is improved with more detailed functions. We attempted an all-versus-all comparison of the SCOP database, and evaluated its ability to recognize a superfamily relationship, which was manually assigned to be homologous in the SCOP database. A comparison with the FSSP database shows that our program can

  14. 40Ar/39Ar and U-Pb Ages and Isotopic Data for Oligocene Ignimbrites, Calderas, and Granitic Plutons, Southern Stillwater Range and Clan Alpine Mountains: Insights into the Volcanic-Plutonic Connection and Crustal Evolution in Western Nevada

    NASA Astrophysics Data System (ADS)

    John, D. A.; Watts, K. E.; Henry, C.; Colgan, J. P.; Cousens, B.

    2014-12-01

    Calderas in the southern Stillwater Range (SSR) and Clan Alpine Mountains (CAM) were formed during the mid-Tertiary ignimbrite flareup and subsequently tilted (40->90°) by large-magnitude extension. New geologic mapping, geochemistry, and 40Ar/39Ar and SHRIMP U-Pb zircon dating document 2 periods of magmatism resulting in 4 nested calderas and related granitoid plutons in sections up to 10 km thick. The first period included pre-caldera rhyolite lava domes (30(?) Ma), ~5 km of pre- and post-collapse intermediate lavas and rhyolite tuff that filled the Job Canyon caldera (~29.4 to 28.8 Ma), and the >4-5 km thick, geochemically similar IXL pluton (28.9±0.4 Ma) that intruded the Job Canyon caldera. The second period included pre-caldera rhyolite lava domes and dikes (~25.5 Ma) and 3 ignimbrite units in 3 calderas: tuff of the Louderback Mountains (low-silica rhyolite; ≥600 m thick; ~25.2 Ma); tuff of Poco Canyon (high-silica rhyolite; up to 4.3 km thick; 25.27±0.05 Ma); and ≥2000 km3 tuff of Elevenmile Canyon (trachydacite to rhyolite; up to 4.5 km thick; 25.12±0.01 Ma). The composite Freeman Creek pluton (granite, 24.8±0.4 Ma; granodiorite, 25.0±0.2 Ma) and Chalk Mountain rhyolite porphyry (25.2±0.2 Ma) and granite (24.8±0.3 Ma) plutons intruded the Poco Canyon and Elevenmile Canyon calderas. Early (30 Ma) rhyolites have the least radiogenic compositions (Sri~0.7040), whereas other units are relatively homogeneous (Sri~0.7050, ENd~0.0). Oxygen isotope compositions for SSR and CAM calderas are highly variable (d18Oquartz=5.6-8.2‰, d18Osanidine=5.5-7.0‰, d18Ozircon= 4.1-6.3‰), corresponding to a magmatic range of 5.7-7.9‰. U-Pb dating of zircons indicates homogeneous age populations and few/no xenocrysts and antecrysts. These data show that (1) thick plutons (>2-5 km) underlie compositionally and temporally related caldera-filling ignimbrites, (2) caldera-forming cycles are isotopically variable, requiring divergent magmatic sources in relatively

  15. Parallel structural evolution of auxin response factors in the angiosperms.

    PubMed

    Finet, Cédric; Fourquin, Chloé; Vinauger, Marion; Berne-Dedieu, Annick; Chambrier, Pierre; Paindavoine, Sandrine; Scutt, Charles P

    2010-09-01

    Here we analyze the structural evolution of the paralogous transcription factors ETTIN (ETT/ARF3) and AUXIN RESPONSE FACTOR 4 (ARF4), which control the development of floral organs and leaves in the model angiosperm Arabidopsis. ETT is truncated at its C terminus, and consequently lacks two regulatory domains present in most other ARFs, including ARF4. Our analysis indicates ETT and ARF4 to have been generated by the duplication of a non-truncated ARF gene prior to the radiation of the extant angiosperms. We furthermore show that either ETT or ARF4 orthologs have become modified to encode truncated ARF proteins, lacking C-terminal regulatory domains, in representatives of three groups that separated early in angiosperm evolution: Amborellales, Nymphaeales and the remaining angiosperm clade. Interestingly, the production of truncated ARF4 transcripts in Amborellales occurs through an alternative splicing mechanism, rather than through a permanent truncation, as in the other groups studied. To gain insight into the potential functional significance of truncations to ETT and ARF4, we tested the capacity of native, truncated and chimeric coding sequences of these genes to restore a wild-type phenotype to Arabidopsis ett mutants. We discuss the results of this analysis in the context of the structural evolution of ARF genes in the angiosperms.

  16. Pelvic fins in teleosts: structure, function and evolution.

    PubMed

    Yamanoue, Y; Setiamarga, D H E; Matsuura, K

    2010-10-01

    The pelvic fins of teleosts are paired appendages that are considered to be homologous to the hind limbs of tetrapods. Because they are less important for swimming, their morphology and function can be flexibly modified, and such modifications have probably facilitated the adaptations of teleosts to various environments. Recently, among these modifications, pelvic-fin loss has gained attention in evolutionary developmental biology. Pelvic-fin loss, however, has only been investigated in a few model species, and various biological aspects of pelvic fins in teleosts in general remain poorly understood. This review summarizes the current state of knowledge regarding pelvic fins, such as their structure, function and evolution, to elucidate their contribution to the considerable diversity of teleosts. This information could be invaluable for future investigations into various aspects of pelvic fins, which will provide clues to understanding the evolution, diversity and adaptations of teleosts.

  17. NASA Structure and Evolution of the Universe Theme: Science Overview

    NASA Technical Reports Server (NTRS)

    White, Nicholas E.; Margon, Bruce

    2001-01-01

    The NASA Office of Space Science Structure and Evolution of the Universe (SEU) theme covers a wide variety of scientific investigations, from the nearest bodies to the farthest observable distances just after the time of the Big Bang. SEU supports experiments that sense radiation of all wavelengths, together with particle and gravitational wave detection. Recently completed road mapping and strategic planning exercises have identified a number of near- and medium-term space initiatives for the 2003-2023 time frame. Each of these experiments pushes the state of the art technically, but will return incredible new insights on the formation and evolution of the universe, as well as probe fundamental laws of physics in regimes never before tested. The scientific goals and technological highlights of each mission are described.

  18. Influence of Ar-irradiation on structural and nanomechanical properties of pure zirconium measured by means of GIXRD and nanoindentation techniques

    NASA Astrophysics Data System (ADS)

    Kurpaska, L.; Gapinska, M.; Jasinski, J.; Lesniak, M.; Sitarz, M.; Nowakowska-Langier, K.; Jagielski, J.; Wozniak, K.

    2016-12-01

    An effect of Ar-irradiation on structural and nanomechanical properties of pure zirconium at room temperature was investigated. In order to simulate the radiation damage, the argon ions were implanted into the pure zirconium coupons with fluences ranging from 1 × 1015 to 1 × 1017 cm-2. Prior to irradiation, zirconium samples were chemically polished with a solution of HF/HNO3/H2O. Structural properties of the implanted layer were studied using Grazing Incidence X-Ray Diffraction (GIXRD) technique. The nanomechanical properties of the material were measured by means of nanoindentation technique. The obtained results revealed correlation between Ar-implantation fluence, hardness and structural properties (as confirmed by the modification of the diffraction peaks). Material hardening and peak shift & broadening in GIXD spectra were associated with the local increase of micro-strains, which is related to the increased density of type - dislocation loops. Presented study confirms that the structural changes induced by ion irradiation are directly linked to the mechanical response of the sample.

  19. Structure Evolution and Electric Properties of TaN Films Deposited on Al2O3-BASED Ceramic and Glass Substrates by Magnetron Reactive Sputtering

    NASA Astrophysics Data System (ADS)

    Zhou, Yan Ming; Ma, Yang Zhao; Xie, Zhong; He, Ming Zhi

    2014-03-01

    Structure evolution and electric properties of tantalum nitride (TaN) films deposited on Al2O3-based ceramic and glass substrates by magnetron reactive sputtering were carried out as a function of the N2-to-Ar flow ratio. The TaN thin films on Al2O3-based ceramic substrates grow with micronclusters composed of numerous nanocrystallites, contains from single-phase of Ta2N grains to TaN, and exhibits high defect density, sheet resistance and negative TCR as the N2-to-Ar flow ratio continuously increases. However, the films on the glass substrates grow in the way of sandwich close-stack, contains from single-phase of Ta2N grains to TaN and Ta3N5 phases with the increase of N2-to-Ar flow ratio. These results indicate that the N2-to-Ar flow ratio and surface characteristic difference of substrates play a dominant effect on the structure and composition of the TaN films, resulting in different electrical properties for the films on Al2O3-based ceramic and the samples on glass substrates.

  20. Structure of the ArsI C-As Lyase: Insights into the Mechanism of Degradation of Organoarsenical Herbicides and Growth Promoters.

    PubMed

    Nadar, Venkadesh Sarkarai; Yoshinaga, Masafumi; Pawitwar, Shashank S; Kandavelu, Palani; Sankaran, Banumathi; Rosen, Barry P

    2016-06-05

    Arsenic is a ubiquitous and carcinogenic environmental element that enters the biosphere primarily from geochemical sources, but also through anthropogenic activities. Microorganisms play an important role in the arsenic biogeochemical cycle by biotransformation of inorganic arsenic into organic arsenicals and vice versa. ArsI is a microbial non-heme, ferrous-dependent dioxygenase that transforms toxic methylarsenite [MAs(III)] to less toxic and carcinogenic inorganic arsenite [As(III)] by C-As bond cleavage. An ArsI ortholog, TcArsI, from the thermophilic bacterium Thermomonospora curvata was expressed, purified, and crystallized. The structure was solved in both the apo form and with Ni(II), Co(II), or Fe(III). The MAs(III) binding site is a vicinal cysteine pair in a flexible loop. A structure with the loop occupied with β-mercaptoethanol mimics binding of MAs(III). The structure of a mutant protein (Y100H/V102F) was solved in two different crystal forms with two other orientations of the flexible loop. These results suggest that a loop-gating mechanism controls the catalytic reaction. In the ligand-free open state, the loop is exposed to solvent, where it can bind MAs(III). The loop moves toward the active site, where it forms a closed state that orients the C-As bond for dioxygen addition and cleavage. Elucidation of the enzymatic mechanism of this unprecedented C-As lyase reaction will enhance our understanding of recycling of environmental organoarsenicals.

  1. Habitat structure and the evolution of diffusible siderophores in bacteria.

    PubMed

    Kümmerli, Rolf; Schiessl, Konstanze T; Waldvogel, Tuija; McNeill, Kristopher; Ackermann, Martin

    2014-12-01

    Bacteria typically rely on secreted metabolites, potentially shareable at the community level, to scavenge resources from the environment. The evolution of diffusible, shareable metabolites is, however, difficult to explain because molecules can get lost, or be exploited by cheating mutants. A key question is whether natural selection can act on molecule structure to control loss and shareability. We tested this possibility by collating information on diffusivity properties of 189 secreted iron-scavenging siderophores and the natural habitats occupied by the siderophore-producing species. In line with evolutionary theory, we found that highly diffusible siderophores have preferentially evolved in species living in structured habitats, such as soil and hosts, because structuring can keep producers and their shareable goods together. Poorly diffusible siderophores, meanwhile, have preferentially evolved in species living in unstructured habitats, such as seawater, indicating that these metabolites are less shareable and more likely provide direct benefits to the producers.

  2. Petrology and K/Ar ages of volcanics dredged from the Eolian seamounts: implications for geodynamic evolution of the southern Tyrrhenian basin

    NASA Astrophysics Data System (ADS)

    Beccaluva, L.; Gabbianelli, G.; Lucchini, F.; Rossi, P. L.; Savelli, C.

    1985-07-01

    Tyrrhenian marginal basin and characteristically analogous, in timing, to the tectonic and magmatic evolution of the western Pacific island arc and back arc basin systems, where an earlier opening of the marginal basin was followed by an arc volcanism on the rifted-off migrating plate. The chronological zonation inside limited sectors of the structure coupled with the widespread age of volcanism of different serial affinity along the whole structure and the counterclockwise rejuvenation of the within-serial magmatic activity, could be related to deformation (via torsion, segmentation and lateral stretching) and progressive steepening of the subducted slab resulting in the present concavity of the Benioff zone which corresponds to a maximal oroclinal distortion of the Apenninic-Maghrebian chain.

  3. Structural evolution of carbon during oxidation. Final report

    SciTech Connect

    Sarofim, A.F.

    1998-04-01

    The examination of the structural evolution of carbon during oxidation has proven to be of scientific interest. Early modeling work of fluidized bed combustion showed that most of the reactions of interest occurs in the micropores, and this work has concentrated on these pores. This work has concentrated on evolution of macroporosity and microporosity of carbons during kinetic controlled oxidation using SAXS, CO{sub 2} and TEM analysis. Simple studies of fluidized bed combustion of coal chars has shown that many of the events considered fragmentation events previously may in fact be {open_quotes}hidden{close_quotes} or nonaccessible porosity. This makes the study of the microporous combustion characteristics of carbon even more important. The generation of a combustion resistant grid, coupled with measurements of the SAXS and CO{sub 2} surface areas, fractal analysis and TEM. Studies has confirmed that soot particles shrink during their oxidation, as previously suspected. However, this shrinkage results in an overall change in structure. This structure becomes, on a radial basis, much more ordered near the edges, while the center itself becomes transparent to the TEM beam, implying a total lack of structure in this region. Although complex, this carbon structure is probably burning as to keep the density of the soot particles nearly the same. The TEM techniques developed for examination of soots has also been applied to Spherocarb. The Spherocarb during oxidation also increases its ordering. This ordering, by present theories, would imply that the reactivity would go. However, the reactivity goes up, implying that structure of carbon is secondary in importance to catalytic effects.

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

    NASA Astrophysics Data System (ADS)

    Bucurescu, D.; Zamfir, N. V.

    2017-01-01

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

  5. Triadic conceptual structure of the maximum entropy approach to evolution.

    PubMed

    Herrmann-Pillath, Carsten; Salthe, Stanley N

    2011-03-01

    Many problems in evolutionary theory are cast in dyadic terms, such as the polar oppositions of organism and environment. We argue that a triadic conceptual structure offers an alternative perspective under which the information generating role of evolution as a physical process can be analyzed, and propose a new diagrammatic approach. Peirce's natural philosophy was deeply influenced by his reception of both Darwin's theory and thermodynamics. Thus, we elaborate on a new synthesis which puts together his theory of signs and modern Maximum Entropy approaches to evolution in a process discourse. Following recent contributions to the naturalization of Peircean semiosis, pointing towards 'physiosemiosis' or 'pansemiosis', we show that triadic structures involve the conjunction of three different kinds of causality, efficient, formal and final. In this, we accommodate the state-centered thermodynamic framework to a process approach. We apply this on Ulanowicz's analysis of autocatalytic cycles as primordial patterns of life. This paves the way for a semiotic view of thermodynamics which is built on the idea that Peircean interpretants are systems of physical inference devices evolving under natural selection. In this view, the principles of Maximum Entropy, Maximum Power, and Maximum Entropy Production work together to drive the emergence of information carrying structures, which at the same time maximize information capacity as well as the gradients of energy flows, such that ultimately, contrary to Schrödinger's seminal contribution, the evolutionary process is seen to be a physical expression of the Second Law.

  6. Evolution in a spatially structured population subject to rare epidemics.

    PubMed

    Socolar, J E; Richards, S; Wilson, W G

    2001-04-01

    We study a model that gives rise to spatially inhomogeneous population densities in a system of host individuals subject to rare, randomly distributed disease events. For stationary hosts that disperse offspring over short distances, evolutionary dynamics can lead to persistent populations with a variety of spatial structures. A mean-field analysis is shown to account for the behavior observed in simulations of a one-dimensional system, where the evolutionarily stable state corresponds to the solution of a straightforward optimization problem. In two dimensions, evolution drives the system to a stable critical state that is less well understood.

  7. Evolution of community structure in the world trade web

    NASA Astrophysics Data System (ADS)

    Tzekina, I.; Danthi, K.; Rockmore, D. N.

    2008-06-01

    In this note we study the bilateral merchandise trade flows between 186 countries over the 1948 2005 period using data from the International Monetary Fund. We use the network visualization package Pajek to identify network structure and behavior across thresholds and over time. In particular, we focus on the evolution of trade “islands” in a world trade network in which countries are linked with directed edges weighted according to the fraction of total dollars sent from one country to another. We find mixed evidence for globalization.

  8. Synthesis and textural evolution of alumina particles with mesoporous structures

    SciTech Connect

    Liu Xun; Peng Tianyou; Yao Jinchun; Lv Hongjin; Huang Cheng

    2010-06-15

    Alumina particles with mesostructures were synthesized through a chemical precipitation method by using different inorganic aluminum salts followed by a heterogeneous azeotropic distillation and calcination process. The obtained mesoporous {gamma}-alumina particles were systematically characterized by the X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption measurement. Effects of the aluminum salt counter anion, pH value and the azeotropic distillation process on the structural or textural evolution of alumina particles were investigated. It is found that Cl{sup -} in the reaction solution can restrain the textural evolution of the resultant precipitates into two-dimensional crystallized pseudoboehmite lamellae during the heterogeneous azeotropic distillation, and then transformed into {gamma}-Al{sub 2}O{sub 3} particles with mesostructures after further calcination at 1173 K, whereas coexisting SO{sub 4}{sup 2-} can promote above morphology evolution and then transformed into {gamma}-Al{sub 2}O{sub 3} nanofibers after calcination at 1173 K. Moreover nearly all materials retain relatively high specific surface areas larger than 100 m{sup 2} g{sup -1} even after calcinations at 1173 K. - Graphical abstract: Co-existing Cl{sup -} is beneficial for the formation of {gamma}-alumina nanoparticles with mesostructures during the precipitation process. Interparticle and intraparticle mesopores can be derived from acidic solution and near neutral solution, respectively.

  9. Evolution and structure of Mercury's interior from MESSENGER observations

    NASA Astrophysics Data System (ADS)

    Tosi, Nicola

    2015-04-01

    During the past four years, the MESSENGER mission (MErcury Surface, Space Environment, GEochemistry and Ranging) has delivered a wealth of information that has been dramatically advancing the understanding of the geological, chemical, and physical state of Mercury. Taking into account the latest constraints on the interior structure, surface composition, volcanic and tectonic history, we employed numerical models to simulate the thermo-chemical evolution of the planet's interior [1]. Typical evolution scenarios that allow the observational constraints to be satisfied consist of an initial phase of mantle heating accompanied by planetary expansion and the production of a substantial amount of partial melt. The evolution subsequent to 2 Ga is characterised by secular cooling that proceeds approximately at a constant rate and implies that contraction should be still ongoing. Most of the models also predict mantle convection to cease after 3-4 Ga, indicating that Mercury may be no longer dynamically active. In addition, the topography, measured by laser altimetry and the gravity field, obtained from radio-tracking, represent fundamental observations that can be interpreted in terms of the chemical and mechanical structure of the interior. The observed geoid-to-topography ratios at intermediate wavelengths are well explained by the isostatic compensation of the topography associated with lateral variations of the crustal thickness, whose mean value can be estimated to be ~35 km, broadly confirming the predictions of the evolution simulations [2]. Finally, we will show that the degree-2 and 4 of the topography and geoid spectra can be explained in terms of the long-wavelength deformation of the lithosphere resulting from deep thermal anomalies caused by the large latitudinal and longitudinal variations in temperature experienced by Mercury's surface. [1] Tosi N., M. Grott, A.-C. Plesa and D. Breuer (2013). Thermo-chemical evolution of Mercury's interior. Journal of

  10. Structural evolution in the crystallization of rapid cooling silver melt

    SciTech Connect

    Tian, Z.A.; Dong, K.J.; Yu, A.B.

    2015-03-15

    The structural evolution in a rapid cooling process of silver melt has been investigated at different scales by adopting several analysis methods. The results testify Ostwald’s rule of stages and Frank conjecture upon icosahedron with many specific details. In particular, the cluster-scale analysis by a recent developed method called LSCA (the Largest Standard Cluster Analysis) clarified the complex structural evolution occurred in crystallization: different kinds of local clusters (such as ico-like (ico is the abbreviation of icosahedron), ico-bcc like (bcc, body-centred cubic), bcc, bcc-like structures) in turn have their maximal numbers as temperature decreases. And in a rather wide temperature range the icosahedral short-range order (ISRO) demonstrates a saturated stage (where the amount of ico-like structures keeps stable) that breeds metastable bcc clusters. As the precursor of crystallization, after reaching the maximal number bcc clusters finally decrease, resulting in the final solid being a mixture mainly composed of fcc/hcp (face-centred cubic and hexagonal-closed packed) clusters and to a less degree, bcc clusters. This detailed geometric picture for crystallization of liquid metal is believed to be useful to improve the fundamental understanding of liquid–solid phase transition. - Highlights: • A comprehensive structural analysis is conducted focusing on crystallization. • The involved atoms in our analysis are more than 90% for all samples concerned. • A series of distinct intermediate states are found in crystallization of silver melt. • A novelty icosahedron-saturated state breeds the metastable bcc state.

  11. Structural evolution of carbon dioxide under high pressure.

    PubMed

    Lu, Cheng; Miao, Maosheng; Ma, Yanming

    2013-09-25

    Using an efficient structure search method based on a particle swarm optimization algorithm, we study the structural evolution of solid carbon dioxide (CO2) under high pressure. Our results show that, although it undertakes many structural transitions under pressure, CO2 is quite resistive to structures with C beyond 4-fold coordination. For the first time, we are able to identify two 6-fold structures of solid CO2 with Pbcn and Pa3 symmetries that become stable at pressures close to 1 TPa. Both structures consist of a network of C-O octahedra, showing hypervalence of the central C atoms. The C-O bond length varies from 1.30 to 1.34 Å at the 4-fold to 6-fold transition, close to the C-O distance in the transition state of a corresponding S(N)2 reaction. It has been a longstanding and challenging objective to stabilize C in a hypervalent state, particularly when it is bonded with nonmetallic elements. Most of the work so far has focused on synthesizing organic molecules with a high coordination number of C. Our results provide a good measure of the resistivity of C toward forming hypervalent compounds with nonmetallic elements and of the barrier of reaction involving C-O bonds.

  12. Insights into gas-phase structural conformers of hydrated rubidium and cesium cations, M(+)(H2O)(n)Ar (M = Rb, Cs; n = 3-5), using infrared photodissociation spectroscopy.

    PubMed

    Ke, Haochen; van der Linde, Christian; Lisy, James M

    2014-02-27

    Infrared photodissociation (IRPD) spectra of M(+)(H2O)nAr (M = Rb, Cs; n = 3-5) with simultaneous monitoring of [Ar] and [Ar+H2O] fragmentation channels are reported. The comparison between the spectral features in the two channels and corresponding energy analysis provide spectral assignments of the stable structural conformers and insight into the competition between ion-water electrostatic and water-water hydrogen bonding interactions. Results show that as the level of hydration increases, the water-water interaction exhibits the tendency to dominate over the ion-water interaction. Cyclic water tetramer and water pentamer substructures appear in Cs(+)(H2O)4Ar and Cs(+)(H2O)5Ar systems, respectively. However, cyclic water tetramer and pentamer structures were not observed for Rb(+)(H2O)4Ar and Rb(+)(H2O)5Ar systems, respectively, due to the stronger influence of the rubidium ion-water electrostatic interaction. The energy analysis, including the available internal energy and the IR photon energy, helped provide an experimental estimate of water binding energies.

  13. Evolution of deep collapse caldera: from structural to gravitational process

    NASA Astrophysics Data System (ADS)

    Geshi, N.; Acocella, V.; Ruch, J.

    2012-04-01

    We discuss the evolution of deep-subsiding caldera mainly controlled by gravitational process. Progress of caldera subsidence increases its subsidence/diameter ratio (S/D ratio). We investigate the surface features of calderas undergoing significant subsidence with regard to their diameter. First, we consider the evolution of the 2000 Miyakejima caldera, from double-concentric ring faults at earlier collapsing stages, to a gravitational-erosion dominant stage at a mature stage. When the topographic S/D approaches 0.33, the topographic S/D (hereafter S/Dt) becomes significantly different from the structural S/D (hereafter S/Ds), owing to the gravitational erosion on the caldera wall and accumulation of the debris on the floor. As collapse progresses, the peripheral block bounded by the inner reverse fault and outer normal fault extends and tilts towards the caldera center; it finally collapses towards the caldera floor and the double-ring faults disappeares. Subsidence of the caldera floor induces the gravitational erosion of the wall. This process increases the topographic diameter and the filling of the floor decreases the topographic depth. Consequently, the S/Dt decreases, while the continuous caldera subsidence increases the S/Ds. This evolution finds close similarities with the caldera collapses of Krakatau (1883), Katmai (1912), Fernandina (1968), Tolbachik (1975-76), Pinatubo (1991) and Dolomieu (2007). Analogue experiments mimic the observed variation, evolving from a depression controlled by the activity of the double-ring faults to that controlled by the gravitational slumping of the wall and sedimentation at the floor. The transition occurs for S/Dt ~0.34. These results show that the control on the shape of mature calderas (S/Ds>0.07) and approaching S/Dt=0.3 passes from a mainly structural to a mainly gravitational type. Both S/Dt and S/Ds are needed to describe the evolution of a collapse and the processes accompanying it. Evaluating the S/Dt and S

  14. Saturn layered structure and homogeneous evolution models with different EOSs

    NASA Astrophysics Data System (ADS)

    Nettelmann, Nadine; Püstow, Robert; Redmer, Ronald

    2013-07-01

    The core mass of Saturn is commonly assumed to be 10-25M⊕ as predicted by interior models with various equations of state (EOSs) and the Voyager gravity data, and hence larger than that of Jupiter (0-10M⊕). We here re-analyze Saturn's internal structure and evolution by using more recent gravity data from the Cassini mission and different physical equations of state: the ab initio LM-REOS which is rather soft in Saturn's outer regions but stiff at high pressures, the standard Sesame-EOS which shows the opposite behavior, and the commonly used SCvH-i EOS. For all three EOS we find similar core mass ranges, i.e. of 0-20M⊕ for SCvH-i and Sesame EOS and of 0-17M⊕ for LM-REOS. Assuming an atmospheric helium mass abundance of 18%, we find maximum atmospheric metallicities, Zatm of 7× solar for SCvH-i and Sesame-based models and a total mass of heavy elements, MZ of 25-30M⊕. Some models are Jupiter-like. With LM-REOS, we find MZ = 16-20M⊕, less than for Jupiter, and Zatm ≲ 3× solar. For Saturn, we compute moment of inertia values λ = 0.2355(5). Furthermore, we confirm that homogeneous evolution leads to cooling times of only ˜2.5 Gyr, independent on the applied EOS. Our results demonstrate the need for accurately measured atmospheric helium and oxygen abundances, and of the moment of inertia for a better understanding of Saturn's structure and evolution.

  15. The structural and property evolution of cellulose during carbonization

    NASA Astrophysics Data System (ADS)

    Rhim, Yo-Rhin

    The understanding of the structure and related property evolution during carbonization is imperative in engineering carbon materials for specific functionalities. High purity cellulose was used as a model precursor to help understand the conversion of organic compounds to hard carbons. Several characterization techniques were employed to follow the structural, compositional and property changes during the thermal transformation of microcrystalline cellulose to carbon over the temperature range of 250°C to 2000°C. These studies revealed several stages of composition and microstructure evolution during carbonization supported by the observation of five distinct regions of electrical and thermal properties. In Region I, from 250°C to 400°C, depolymerisation of cellulose molecules caused the evolution of volatile gases and decrease in dipole polarization. This also led to the reduction of overall AC electrical conductivity and specific heat. In Region II, from 450°C to 500°C, the formation and growth of conducting sp 2 carbon clusters resulted in increases in overall AC electrical conductivity and thermal diffusivity with rising temperature. For heat treatment temperatures of 550°C and 600°C, Region III, carbon clusters grew into aggregates of curved carbon layers leading to interfacial polarization and onset of percolation. AC electrical and thermal conductivities are enhanced due to electron hopping and improved phonon transport among carbon clusters. With temperatures rising from 650°C to 1000°C, Region IV, DC conductivity began to emerge and increased sharply along with thermal conductivity with further percolation of carbon clusters as lateral growth of carbon layers continued. Lastly, from 1200°C to 2000°C, Region V, DC electrical conductivity remained constant due to a fully percolated system.

  16. Radial evolution of density structure in the solar corona

    NASA Astrophysics Data System (ADS)

    Woo, Richard; Habbal, Shadia Rifai

    White-light measurements made by the SOHO coronagraphs (LASCO for Large Angle Spectrometric Coronagraph) and the HAO Mauna Loa Mk III K-coronameter are combined to follow the evolution of path-integrated density structure in the solar corona overlying both coronal hole and quiet Sun regions from 1.15 to 5.5 Ro. The global imaging provided by these two instruments confirms and strengthens earlier results discovered by spacecraft radio ranging measurements [Woo and Habbal, 1999], that the imprint of density structure at the Sun — as manifested in the background latitudinal density profile closest to the Sun at 1.15 Ro — is carried essentially radially into interplanetary space with the same density gradient. The only exceptions are coronal streamers that evolve into the heliospheric current sheet within a few solar radii of the Sun.

  17. Coronal Mass Ejections : A Study of Structural Evolution and Classification

    NASA Astrophysics Data System (ADS)

    Lowder, Chris; Habbal, S. R.; Morgan, H.

    2007-05-01

    Coronal Mass Ejections (or CMEs) are known for their majestic, yet explosive, outflow from the Sun. Although different criteria are often used for their classification, this paper seeks to classify them based on the following factors: (1) The velocity of the CME; (2) the structure of the CME itself, and (3) the angular separation of the "legs" of the CME as it expands. Given that the outer edge and the inner core of the CME move at different velocities, this difference can track the structural evolution of the outburst. Using data from solar minimum and maximum, CMEs will be analyzed and a new classification scheme will be developed based on the characteristics outlined above. This research was conducted as part of an NSF funded REU program at the Institute for Astronomy at the University of Hawaii.

  18. The Structure and Evolution of Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Slane, Patrick O.

    2010-01-01

    The extended nebulae formed as pulsar winds expand into their surroundings provide information about the composition of the winds, the injection history from the host pulsar, and the material into which the nebulae are expanding. Observations from across the electromagnetic spectrum provide constraints on the evolution of the nebulae, the density and composition of the surrounding ejecta, the geometry of the central engines, and the long-term fate of the energetic particles produced in these systems. Such observations reveal the presence of jets and wind termination shocks, time-varying compact emission structures, shocked supernova ejecta, and newly formed dust. Here I provide a broad overview of the structure of pulsar wind nebulae, with specific examples from observations extending from the radio band to very high energy gamma-rays that demonstrate our ability to constrain the history and ultimate fate of the energy released in the spin-down of young pulsars.

  19. Dynamic structural network evolution in compressed granular systems

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Lia; Puckett, James; Daniels, Karen; Bassett, Danielle

    The heterogeneous dynamic behavior of granular packings under shear or compression is not well-understood. In this study, we use novel techniques from network science to investigate the structural evolution that occurs in compressed granular systems. Specifically, we treat particles as network nodes, and pressure-dependent forces between particles as layer-specific network edges. Then, we use a generalization of community detection methods to multilayer networks, and develop quantitative measures that characterize changes in the architecture of the force network as a function of pressure. We observe that branchlike domains reminiscent of force chains evolve differentially as pressure is applied: topological characteristics of these domains at rest predict their coalescence or dispersion under pressure. Our methods allow us to study the dynamics of mesoscale structure in granular systems, and provide a direct way to compare data from systems under different external conditions or with different physical makeup.

  20. Structure evolution in layers of polymer blend nanoparticles.

    PubMed

    Raczkowska, Joanna; Montenegro, Rivelino; Budkowski, Andrzej; Landfester, Katharina; Bernasik, Andrzej; Rysz, Jakub; Czuba, Paweł

    2007-06-19

    The early stages of phase evolution, not available for nanometer polymer blend films spin-cast from solutions of incompatible mixtures, have been examined for films prepared from nanoparticles of deuterated polystyrene/ poly(methyl methacrylate) blends (1:1 mass fraction of dPS/PMMA) with PS-PMMA diblock copolymer additives. The initial phase arrangement, confined to the size of nanoparticles, has provided the homogeneity of the initial film composition. The early stages of structure formation, promoted by annealing and traced with atomic and lateral force microscopy (AFM, LFM) as well as secondary ion mass spectroscopy (SIMS), resulted in bilayers, observed commonly for as-prepared solvent-cast blends. The initiated capillary instability of the upper dPS-rich layer depended on copolymer additives, which enhanced the lateral structures pinning the dewetting process.

  1. The structure and evolution of X-ray clusters

    NASA Technical Reports Server (NTRS)

    Jones, C.; Mandel, E.; Schwarz, J.; Forman, W.; Murray, S. S.; Harnden, F. R., Jr.

    1979-01-01

    Observations of the structure of the X-ray emission from 12 nearby rich clusters of galaxies are presented and interpreted in terms of dynamic cluster evolution. X-ray structures revealed by the Einstein Observatory imaging proportional counter in the range 0.25 to 3.0 keV were analyzed and used to classify the clusters based on their X-ray morphologies. Four categories are observed, consisting of spiral-rich clusters with low X-ray temperatures and velocity dispersions with broad and highly clumped emission, spiral-poor clusters with high X-ray temperatures and velocity dispersions with smoothly varying emission broadly or sharply peaked around a dominant galaxy, and clusters with emission typical of a cD galaxy in a poor cluster or group. The broad, highly clumped cluster emission is interpreted as a result of an early evolutionary stage, while the cD and centrally enhanced emissions represent successive later stages in X-ray galactic cluster evolution.

  2. ArArCALC—software for 40Ar/ 39Ar age calculations

    NASA Astrophysics Data System (ADS)

    Koppers, Anthony A. P.

    2002-06-01

    ArArCALC is a Microsoft Excel ® 97-2000-XP application for performing calculations in 40Ar/ 39Ar geochronology. It is coded in Visual Basic for Applications and can be used under the Windows ® 95/98/NT/2000/ME/XP operating systems. ArArCALC provides an easy-to-use graphical interface for the calculation of age plateaus, total fusion ages and isochrons following the regression of 40Ar/ 39Ar mass spectrometry data. Results are stored in single Excel workbooks including nine different data tables and four different diagrams. Analytical, internal and external errors are calculated based on error propagation of all input parameters, analytical data and applied corrections. Finally, the age calculation results can be recalibrated with reference to the primary K-Ar standards (e.g. GA-1550, MMhb-1) in order to obtain more consistent absolute40Ar/ 39Ar age determinations. ArArCALC is distributed as freeware.

  3. Structure of the Mu transpososome illuminates evolution of DDE recombinases

    PubMed Central

    Montaño, Sherwin P.; Pigli, Ying Z.; Rice, Phoebe A.

    2012-01-01

    Studies of bacteriophage Mu transposition paved the way for understanding retroviral integration and V(D)J recombination as well as many other DNA transposition reactions. Here we report the structure of Mu transposase (MuA) in complex with bacteriophage DNA ends and target DNA, determined from data that extend anisotropically to 5.2/5.2/3.7Å resolution, in conjunction with previously-determined structures of individual domains. The highly intertwined structure illustrates why chemical activity depends on formation of the synaptic complex, and reveals that individual domains play different roles when bound to different sites. It also suggests explanations for the increased stability of the final product complex and for its preferential recognition by the ATP-dependent unfoldase ClpX. Although MuA and many other recombinases share a structurally conserved “DDE” catalytic domain, comparisons among the limited set of available complex structures suggest that some conserved features, such as catalysis in trans and target DNA bending, arose through convergent evolution because they are important for function. PMID:23135398

  4. A Dynamic Model for the Evolution of Protein Structure.

    PubMed

    Tal, Guy; Boca, Simina Maria; Mittenthal, Jay; Caetano-Anollés, Gustavo

    2016-05-01

    Domains are folded structures and evolutionary building blocks of protein molecules. Their three-dimensional atomic conformations, which define biological functions, can be coarse-grained into levels of a hierarchy. Here we build global dynamical models for the evolution of domains at fold and fold superfamily (FSF) levels. We fit the models with data from phylogenomic trees of domain structures and evaluate the distributions of the resulting parameters and their implications. The trees were inferred from a census of domain structures in hundreds of genomes from all three superkingdoms of life. The models used birth-death differential equations with the global abundances of structures as state variables, with one set of equations for folds and another for FSFs. Only the transitions present in the tree are assumed possible. Each fold or FSF diversifies in variants, eventually producing a new fold or FSF. The parameters specify rates of generation of variants and of new folds or FSFs. The equations were solved for the parameters by simplifying the trees to a comb-like topology, treating branches as emerging directly from a trunk. We found that the rate constants for folds and FSFs evolved similarly. These parameters showed a sharp transient change at about 1.5 Gyrs ago. This time coincides with a period in which domains massively combined in proteins and their arrangements distributed in novel lineages during the rise of organismal diversification. Our simulations suggest that exploration of protein structure space occurs through coarse-grained discoveries that undergo fine-grained elaboration.

  5. Structural framework, stratigraphy, and evolution of Brazilian marginal basins

    SciTech Connect

    Ojeda, H.A.O.

    1982-06-01

    The structural framework of the Brazilian continental margin is basically composed of eight structural types: antithetic tilted step-fault blocks, synthetic untilted step-fault blocks, structural inversion axes, hinges with compensation grabens, homoclinal structures, growth faults with rollovers, diapirs, and igneous structures. The antithetic tilted and synthetic untilted step-fault blocks are considered as synchronous, complementary structural systems, separated by an inversion axis. Two evaporitic cycles (Paripueira and Ibura) were differentiated in the Sergipe-Alagoas type basin and tentatively correlated to the evaporitic section of other Brazilian marginal basis. Four phases are considered in the evolution of the Brazilian marginal basins: pre-rift, rift, transitional, and drift. During the pre-rift phase (Late Jurassic-Early Cretaceous), continental sediments were deposited in peripheral intracratonic basins. In the rift phase (Early Cretaceous), the breakup of the continental crust of the Gondwana continent gave rise to a central graben and rift valleys where lacustrine sediments were deposited. The transitional phase (Aptian) developed under relative tectonic stability, when evaporitic and clastic lacustrine sequences were being deposited. In the drift phase (Albian to Holocene), a regionl homoclinal structure developed, consisting of two distinct sedimentary sequences, a lower clastic-carbonate and an upper clastic. From the Albian to the Holocene Epoch, structures associated to plastic displacement of salt or shale developed in many Brazilian marginal basins. Two phases of major igneous activity occurred: one in the Early Cretaceous associated with the rift phase of the Gondwana continent, and the other in the Tertiary during the migration phase of the South American and African plates.

  6. Studying the Thermal and Structural Evolution of Planetary Bodies

    NASA Astrophysics Data System (ADS)

    Karimi, Mohammadali

    The focus of this research is to study the thermal and structural evolution of three planetary bodies, Mars, Venus and the asteroid Vesta. The almost uniform spatial distribution of craters on the surfaces of planets makes them excellent candidates to examine the evolution of planets as a whole. By modeling the viscoelastic deformation of craters at the surface and subsurface with the Finite Element Method (FEM), this study investigated the role of lower crustal flow in crater relaxation, and since lower crustal flow is sensitive to the thermal state, it serves as a probe into the thermal evolution of planets. The thermal history of Mars was explored by modeling the evolution of large craters and Quasi-Circular Depressions (QCDs) in the Southern Highlands and Northern Lowlands, respectively. Because of the spatial distribution of craters, this study yielded a thermal map for Mars that is more complete and less biased regionally relative to other studies. The results revealed a higher background heat flux for the Northern Lowlands relative to the Southern Highlands during the most ancient Noachian epoch, which suggests a thermal fingerprint to whatever process that formed the hemispherical crustal dichotomy, the oldest and most prominent geomorphic feature on Mars. Next, the largest crater on the surface of Venus, Mead, also appears to have undergone significant lower crustal flow. Modeling the viscoelastic deformation of Mead puts constraints on the thermal state of our sister planet in the vicinity of the basin. The background heat flux of Venus estimated here is higher than globally average values predicted by previous thermal models. Moreover, this study showed that Venus's crust and mantle seem to be dry relative to those of the Earth. Last, modeling the evolution of two large craters in the south polar region of Vesta (Rheasilvia and Veneneia) showed that the shallow topography and large central peak of these craters are likely the products of a planetary

  7. 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)

  8. The ArsD As(III) metallochaperone

    PubMed Central

    Ajees, A. Abdul; Yang, Jianbo

    2013-01-01

    Arsenic, a toxic metalloid widely existing in the environment, causes a variety of health problems. The ars operon encoded by Escherichia coli plasmid R773 has arsD and arsA genes, where ArsA is an ATPase that is the catalytic subunit of the ArsAB As(III) extrusion pump, and ArsD is an arsenic chaperone for ArsA. ArsD transfers As(III) to ArsA and increases the affinity of ArsA for As(III), allowing resistance to environmental concentrations of arsenic. Cys12, Cys13 and Cys18 in ArsD form a three sulfur-coordinated As(III) binding site that is essential for metallochaperone activity. ATP hydrolysis by ArsA is required for transfer of As(III) from ArsD to ArsA, suggesting that transfer occurs with a conformation of ArsA that transiently forms during the catalytic cycle. The 1.4 Å x-ray crystal structure of ArsD shows a core of four β-strands flanked by four α-helices in a thioredoxin fold. Docking of ArsD with ArsA was modeled in silico. Independently ArsD mutants exhibiting either weaker or stronger interaction with ArsA were selected. The locations of the mutations mapped on the surface of ArsD are consistent with the docking model. The results suggest that the interface with ArsA involves one surface of α1 helix and metalloid binding site of ArsD. PMID:21188475

  9. Structural Evolution of Silica Gel and Silsesquioxane Using Thermal Curing.

    PubMed

    Hu, Nan; Rao, YuanQiao; Sun, Shengtong; Hou, Lei; Wu, Peiyi; Fan, Shaojuan; Ye, Bangjiao

    2016-08-01

    The curing of coatings of two types of siloxane containing materials, silica gel and silsesquioxane, at a modest temperature (<280℃) was studied with in situ heating Fourier transform infrared spectroscopy (FT-IR) in combination with perturbation correlation moving window (PCMW) and two-dimensional correlation spectroscopy (2D-COS) analyses. The result revealed detailed structural evolution of these two different gels. When the silica gel was heated, (Si-O)6 rings appeared from the random Si-O-Si network formed after sol gel reaction, followed by condensation of silanol groups. Upon further heating, the existing (Si-O)4 rings were broken down and converted into (Si-O)6 structures, and finally isolated silanols appeared. The transition from (Si-O)4 rings to (Si-O)6 rings was observed by IR and further confirmed with positron annihilation lifetime spectroscopy (PALS). In comparison, during the curing of hybrid silsesquioxane, the condensation of silanols happens immediately upon heating without the rearrangement of Si-O-Si network. Afterwards, the fraction of (Si-O)6 ring structure increased. (Si-O)4 structures exhibited higher stability in hybrid silsesquioxanes. In addition, the amount of silanols in silsesquioxane continued to reduce without the generation of isolated silanol in the end. The different curing behavior of silsesquioxanes from silica gel originates from the organic groups in silsesquioxanes, which lowers the cross-linking density and reduces the rigidity of siloxane network.

  10. Directed Evolution and Structural Characterization of a Simvastatin Synthase

    SciTech Connect

    Gao, Xue; Xie, Xinkai; Pashkov, Inna; Sawaya, Michael R.; Laidman, Janel; Zhang, Wenjun; Cacho, Ralph; Yeates, Todd O.; Tang, Yi; UCLA

    2010-02-02

    Enzymes from natural product biosynthetic pathways are attractive candidates for creating tailored biocatalysts to produce semisynthetic pharmaceutical compounds. LovD is an acyltransferase that converts the inactive monacolin J acid (MJA) into the cholesterol-lowering lovastatin. LovD can also synthesize the blockbuster drug simvastatin using MJA and a synthetic {alpha}-dimethylbutyryl thioester, albeit with suboptimal properties as a biocatalyst. Here we used directed evolution to improve the properties of LovD toward semisynthesis of simvastatin. Mutants with improved catalytic efficiency, solubility, and thermal stability were obtained, with the best mutant displaying an {approx}11-fold increase in an Escherichia coli-based biocatalytic platform. To understand the structural basis of LovD enzymology, seven X-ray crystal structures were determined, including the parent LovD, an improved mutant G5, and G5 cocrystallized with ligands. Comparisons between the structures reveal that beneficial mutations stabilize the structure of G5 in a more compact conformation that is favorable for catalysis.

  11. Structural evolution of the methane cation in subfemtosecond photodynamics

    NASA Astrophysics Data System (ADS)

    Mondal, T.; Varandas, A. J. C.

    2015-07-01

    An ab initio quantum dynamics study has been performed to explore the structural rearrangement of ground state CH 4+ in subfemtosecond resolved photodynamics. The method utilizes time-dependent wave-packet propagation on the X ˜ 2 T 2 electronic manifold of the title cation in full dimensionality, including nonadiabatic coupling of the three electronic sheets. Good agreement is obtained with recent experiments [Baker et al., Science 312, 424 (2006)] which use high-order harmonic generation to probe the attosecond proton dynamics. The novel results provide direct theoretical support of the observations while unravelling the underlying details. With the geometrical changes obtained by calculating the expectation values of the nuclear coordinates as a function of time, the structural evolution is predicted to begin through activation of the totally symmetric a1 and doubly degenerate e modes. While the former retains the original Td symmetry of the cation, the Jahn-Teller active e mode conducts it to a D2d structure. At ˜1.85 fs, the intermediate D2d structure is further predicted to rearrange to local C2v minimum geometry via Jahn-Teller active bending vibrations of t2 symmetry.

  12. The evolution of chloroplast genome structure in ferns.

    PubMed

    Wolf, Paul G; Roper, Jessie M; Duffy, Aaron M

    2010-09-01

    The plastid genome (plastome) is a rich source of phylogenetic and other comparative data in plants. Most land plants possess a plastome of similar structure. However, in a major group of plants, the ferns, a unique plastome structure has evolved. The gene order in ferns has been explained by a series of genomic inversions relative to the plastome organization of seed plants. Here, we examine for the first time the structure of the plastome across fern phylogeny. We used a PCR-based strategy to map and partially sequence plastomes. We found that a pair of partially overlapping inversions in the region of the inverted repeat occurred in the common ancestor of most ferns. However, the ancestral (seed plant) structure is still found in early diverging branches leading to the osmundoid and filmy fern lineages. We found that a second pair of overlapping inversions occurred on a branch leading to the core leptosporangiates. We also found that the unique placement of the gene matK in ferns (lacking a flanking intron) is not a result of a large-scale inversion, as previously thought. This is because the intron loss maps to an earlier point on the phylogeny than the nearby inversion. We speculate on why inversions may occur in pairs and what this may mean for the dynamics of plastome evolution.

  13. Rb, Sr and strontium isotopic composition, K/Ar age and large ion lithophile trace element abundances in rocks and glasses from the Wanapitei Lake impact structure

    NASA Technical Reports Server (NTRS)

    Winzer, S. R.; Lum, R. K. L.; Schuhmann, S.

    1976-01-01

    Shock metamorphosed rocks and shock-produced melt glasses from the Wanapitei Lake impact structure have been examined petrographically and by electron microprobe. Eleven clasts exhibiting varying degrees of shock metamorphism and eight impact-produced glasses have been analyzed for Rb, Sr and Sr isotopic composition. Five clasts and one glass have also been analyzed for large ion lithophile (LIL) trace element abundances including Li, Rb, Sr, and Ba and the REE's. The impact event forming the Wanapitei Lake structure occurred 37 m.y. ago based on K/Ar dating of glass and glassy whole-rock samples. Rb/Sr isotopic dating failed to provide a meaningful whole-rock or internal isochron. The isotopic composition of the glasses can be explained by impact-produced mixing and melting of metasediments.

  14. Neogene geomorphic and climatic evolution of the central San Juan Mountains, Colorado: K/Ar age and stable isotope data on supergene alunite and jarosite from the Creede mining district

    USGS Publications Warehouse

    Rye, Robert O.; Bethke, Philip M.; Lanphere, Marvin A.; Steven, Thomas A.

    2000-01-01

    K/Ar age determinations or supergene alunite and jarosite, formed during Neogene weathering of the epithermal silver and base-metal ores of the Creede mining district, have been combined with geologic evidence to estimate the timing of regional uplift of the southern Rocky Mountains and related canyon cutting. In addition, oxygen and hydrogen isotopic studies suggest climate changes in the central San Juan Mountains during the past 5 m.y. Alunite [ideally (K,Na)Al3(SO4)2(OH)6] and jarosite [ideally KFe3(SO4)2(OH)6] can be dated by K/Ar or 40Ar/39Ar techniques and both contain OH and SO4 sites that enable four stable isotope analyses (δD, δ18OOH, and δ34S) to be made. This supergene alunite and jarosite formed by weathering of sulfide-rich ore bodies may record the evolution of the chemical and hydrologic processes affecting ancient oxidized acid ground water, as well as details of climate history and geomorphic evolution. Fine-grained (1-10 μm) supergene alunite and jarosite occur in minor fractures in the upper, oxidized parts of the 25 Ma sulfide-bearing veins of the Creede mining district, and jarosite also occurs in adjacent oxidized Ag-bearing clastic sediments. K/Ar ages for alunite range from 4.8 to 3.1 Ma, and for jarosite range from 2.6 to 0.9 Ma. The δD values for alunite and jarosite show opposite correlations with elevation, and values for jarosite correlate with age. Calculated δDH2O values of alunite fluids approach but are larger than those of present-day meteoric water. Calculated δDH2O values for jarosite fluids are more variable; the values of the youngest jarosites are lowest and are similar to those of present-day meteoric water in the district. The narrow δD-δ18OSO4 values of alunites reflects oxidation of sulfide below the water table. The greater range in these values for jarosites reflects oxidation of sulfide under vadose conditions. The ages of alunite mark the position of the paleo-water table at the end of a period of moderate

  15. Structure and evolution of the hAT transposon superfamily.

    PubMed

    Rubin, E; Lithwick, G; Levy, A A

    2001-07-01

    The maize transposon Activator (Ac) was the first mobile DNA element to be discovered. Since then, other elements were found that share similarity to Ac, suggesting that it belongs to a transposon superfamily named hAT after hobo from Drosophila, Ac from maize, and Tam3 from snapdragon. We addressed the structure and evolution of hAT elements by developing new tools for transposon mining and searching the public sequence databases for the hallmarks of hAT elements, namely the transposase and short terminal inverted repeats (TIRs) flanked by 8-bp host duplications. We found 147 hAT-related sequences in plants, animals, and fungi. Six conserved blocks could be identified in the transposase of most hAT elements. A total of 41 hAT sequences were flanked by TIRs and 8-bp host duplications and, out of these, 34 sequences had TIRs similar to the consensus determined in this work, suggesting that they are active or recently active transposons. Phylogenetic analysis and clustering of hAT sequences suggest that the hAT superfamily is very ancient, probably predating the plant-fungi-animal separation, and that, unlike previously proposed, there is no evidence that horizontal gene transfer was involved in the evolution of hAT elements.

  16. Evolution on a volcanic conveyor belt: using phylogeographic reconstructions and K-Ar-based ages of the Hawaiian Islands to estimate molecular evolutionary rates.

    PubMed

    Fleischer, R C; McIntosh, C E; Tarr, C L

    1998-04-01

    The Hawaiian Islands form as the Pacific Plate moves over a 'hot spot' in the earth's mantle where magma extrudes through the crust to build huge shield volcanos. The islands subside and erode as the plate carries them to the north-west, eventually to become coral atolls and seamounts. Thus islands are ordered linearly by age, with the oldest islands in the north-west (e.g. Kauai at 5.1 Ma) and the youngest in the south-east (e.g. Hawaii at 0.43 Ma). K-Ar estimates of the date of an island's formation provide a maximum age for the taxa inhabiting the island. These ages can be used to calibrate rates of molecular change under the following assumptions: (i) K-Ar dates are accurate; (ii) tree topologies show that derivation of taxa parallels the timing of island formation; (iii) populations do not colonize long after island emergence; (iv) the coalescent point for sister taxa does not greatly predate the formation of the colonized younger island; (v) saturation effects and (vi) among-lineage rate variation are minimal or correctable; and (vii) unbiased standard errors of distances and regressions can be estimated from multiple pairwise comparisons. We use the approach to obtain overall corrected rate calibrations for: (i) part of the mitochondrial cytochrome b gene in Hawaiian drepanidines (0.016 sequence divergence/Myr); (ii) the Yp1 gene in Hawaiian Drosophila (0.019/Myr Kambysellis et al. 1995); and (iii) parts of the mitochondrial 12S and 16S rRNA and tRNAval in Laupala crickets (0.024-0.102/Myr, Shaw 1996). We discuss the reliability of the estimates given the assumptions (i-vii) above and contrast the results with previous calibrations of Adh in Hawaiian Drosophila and chloroplast DNA in lobeliods.

  17. Sm-Nd, K-Ar and petrologic study of some kimberlites from eastern United States and their implication for mantle evolution

    USGS Publications Warehouse

    Basu, A.R.; Rubury, E.; Mehnert, H.; Tatsumoto, M.

    1984-01-01

    We provide new data on Sm-Nd systematics, K-Ar dating and the major element chemistry of kimberlites from the eastern United States (mostly from central New York State) and their constituent mineral phases of olivine, clinopyroxene, garnet, phlogopite and perovskite. In addition, we report Nd-isotopes in a few kimberlites from South Africa, Lesotho and from the eastern part of China. The major element compositions of the New York dike rocks and of their constituent minerals including a xenolith of eclogite are comparable with those from the Kimberley area in South Africa. The K-Ar age of emplacement of the New York dikes is further established to be 143 Ma. We have analyzed the Nd-isotopic composition of the following kimberlites and related rocks: Nine kimberlite pipes from South Africa and Lesotho, two from southern India; one from the U.S.S.R., fifteen kimberlite pipes and related dike rocks from eastern and central U.S. and two pipes from the Shandong Province of eastern China. The age of emplacement of these kimberlites ranges from 1300 million years to 90 million years. The initial Nd-isotopic compositions of these kimberlitic rocks expressed as e{open}NdIwith respect to a chondritic bulk-earth growth-curve show a range between 0 and +4, with the majority of the kimberlites being in the range 0 to +2. This range is not matched by any other suite of mantle-derived igneous rocks. This result strengthens our earlier conclusion that kimberlitic liquids are derived from a relatively primeval and unique mantle reservoir with a nearly chondritic Sm/Nd ratio. ?? 1984 Springer-Verlag.

  18. Thermal and Structural Evolution of a Partially Differentiated Titan

    NASA Astrophysics Data System (ADS)

    Bland, Michael T.; McKinnon, W. B.

    2012-10-01

    Titan’s moment of inertia (C/MR2) has been measured by Cassini to be 0.34, indicating either partial differentiation, or full differentiation with a low-density (hydrated) silicate core. Fully differentiated models have been constructed [Castillo-Rogez and Lunine, 2010], but require specific geochemical assumptions (e.g., rapid accretion, minimal core dehydration). In contrast, the alternative, partially differentiated models have not yet been fully vetted. Here we investigate the thermal stability of such partially differentiated internal structures by evaluating whether complete differentiation can be avoided. Our model assumes an initial three-layer internal structure consisting of a pure ice layer, mixed ice-rock layer, and silicate core, and calculates the temperature of each layer following the numerical approach in Bland et al. (2008, 2009). The model allows melting in the pure ice and mixed layer, and dehydration of the initially hydrated silicate core (leading to densification and absorption of latent heat). Melting of the mixed layer liberates silicate material, which is assumed to sink to the top of the silicate layer over time scales short relative to simulation time scales (in reality some may mx back into the convecting mixed ice-rock layer). Simulations so far indicate that melting of Titan’s pure ice shell is common early in Solar System history, and that melting frequently extends into Titan’s nominal mixed ice-rock layer. Such melting leads to irreversible unmixing of some of the mixed ice-rock layer. Nearly complete dehydration of the silicate core occurs when condritic K is retained in the rock component. The structural evolution decreases Titan’s initial moment of inertia; however, long-lived radiogenic species are generally incapable of completely melting and separating Titan’s mixed layer. To date, thermally stable structural models with C/MR2 as large as 0.33 have been achieved. We continue to investigate how realistic ocean and

  19. Diversity, structure and convergent evolution of the global sponge microbiome.

    PubMed

    Thomas, Torsten; Moitinho-Silva, Lucas; Lurgi, Miguel; Björk, Johannes R; Easson, Cole; Astudillo-García, Carmen; Olson, Julie B; Erwin, Patrick M; López-Legentil, Susanna; Luter, Heidi; Chaves-Fonnegra, Andia; Costa, Rodrigo; Schupp, Peter J; Steindler, Laura; Erpenbeck, Dirk; Gilbert, Jack; Knight, Rob; Ackermann, Gail; Victor Lopez, Jose; Taylor, Michael W; Thacker, Robert W; Montoya, Jose M; Hentschel, Ute; Webster, Nicole S

    2016-06-16

    Sponges (phylum Porifera) are early-diverging metazoa renowned for establishing complex microbial symbioses. Here we present a global Porifera microbiome survey, set out to establish the ecological and evolutionary drivers of these host-microbe interactions. We show that sponges are a reservoir of exceptional microbial diversity and major contributors to the total microbial diversity of the world's oceans. Little commonality in species composition or structure is evident across the phylum, although symbiont communities are characterized by specialists and generalists rather than opportunists. Core sponge microbiomes are stable and characterized by generalist symbionts exhibiting amensal and/or commensal interactions. Symbionts that are phylogenetically unique to sponges do not disproportionally contribute to the core microbiome, and host phylogeny impacts complexity rather than composition of the symbiont community. Our findings support a model of independent assembly and evolution in symbiont communities across the entire host phylum, with convergent forces resulting in analogous community organization and interactions.

  20. Microscopic derivation of IBM and structural evolution in nuclei

    SciTech Connect

    Nomura, Kosuke

    2011-05-06

    A Hamiltonian of the interacting boson model (IBM) is derived based on the mean-field calculations with nuclear energy density functionals (EDFs). The multi-nucleon dynamics of the surface deformation is simulated in terms of the boson degrees of freedom. The interaction strengths of the IBM Hamiltonian are determined by mapping the potential energy surfaces (PESs) of a given EDF with quadrupole degrees of freedom onto the corresponding PES of IBM. A fermion-to-boson mapping for a rotational nucleus is discussed in terms of the rotational response, which reflects a specific time-dependent feature. Ground-state correlation energy is evaluated as a signature of structural evolution. Some examples resulting from the present spectroscopic calculations are shown for neutron-rich Pt, Os and W isotopes including exotic ones.

  1. A teaching module about stellar structure and evolution

    NASA Astrophysics Data System (ADS)

    Colantonio, Arturo; Galano, Silvia; Leccia, Silvio; Puddu, Emanuella; Testa, Italo

    2017-01-01

    In this paper, we present a teaching module about stellar structure, functioning and evolution. Drawing from literature in astronomy education, we designed the activities around three key ideas: spectral analysis, mechanical and thermal equilibrium, energy and nuclear reactions. The module is divided into four phases, in which the key ideas for describing stars' functioning and physical mechanisms are gradually introduced. The activities (20 hours) build on previously learned laws in mechanics, thermodynamics, and electromagnetism and help students combine them meaningfully in order to get a complete picture of processes that happens in stars. The module was piloted with two intact classes of secondary school students (N = 59 students, 17-18 years old), using a ten-question multiple-choice questionnaire as research instrument. Results support the effectiveness of the proposed activities. Implications for the teaching of advanced physics topics using stars as fruitful context are briefly discussed.

  2. Structure Evolution of Metal Nanoparticles in Water Environment

    NASA Astrophysics Data System (ADS)

    Gao, Yi; Zhu, Beien

    Metal nanoparticles have drawn extensive attentions in materials science due to their widespread applications in electronics, engineering and catalysis. A very fundamental question is their structure evolution and surface segregation. Many recent observations have shown that reactive gases or supports may have strong effects on the morphology change and surface segregation. However, the effect of water--the most common solvent and environment--has not received enough attention. Here, we will give two examples to show water adsorption could induce the morphology change and strong surface segregation tendencies for the metal nanoparticles. This finding not only prompts us to re-examine the potential effects of water on metal nanoparticles, but would be also very helpful as a guide for the further theoretical and experimental studies in this field.

  3. Diversity, structure and convergent evolution of the global sponge microbiome

    PubMed Central

    Thomas, Torsten; Moitinho-Silva, Lucas; Lurgi, Miguel; Björk, Johannes R.; Easson, Cole; Astudillo-García, Carmen; Olson, Julie B.; Erwin, Patrick M.; López-Legentil, Susanna; Luter, Heidi; Chaves-Fonnegra, Andia; Costa, Rodrigo; Schupp, Peter J.; Steindler, Laura; Erpenbeck, Dirk; Gilbert, Jack; Knight, Rob; Ackermann, Gail; Victor Lopez, Jose; Taylor, Michael W.; Thacker, Robert W.; Montoya, Jose M.; Hentschel, Ute; Webster, Nicole S.

    2016-01-01

    Sponges (phylum Porifera) are early-diverging metazoa renowned for establishing complex microbial symbioses. Here we present a global Porifera microbiome survey, set out to establish the ecological and evolutionary drivers of these host–microbe interactions. We show that sponges are a reservoir of exceptional microbial diversity and major contributors to the total microbial diversity of the world's oceans. Little commonality in species composition or structure is evident across the phylum, although symbiont communities are characterized by specialists and generalists rather than opportunists. Core sponge microbiomes are stable and characterized by generalist symbionts exhibiting amensal and/or commensal interactions. Symbionts that are phylogenetically unique to sponges do not disproportionally contribute to the core microbiome, and host phylogeny impacts complexity rather than composition of the symbiont community. Our findings support a model of independent assembly and evolution in symbiont communities across the entire host phylum, with convergent forces resulting in analogous community organization and interactions. PMID:27306690

  4. Evolution of surface structure in laser-preheated perturbed materials

    NASA Astrophysics Data System (ADS)

    Di Stefano, C. A.; Merritt, E. C.; Doss, F. W.; Flippo, K. A.; Rasmus, A. M.; Schmidt, D. W.

    2017-02-01

    We report an experimental and computational study investigating the effects of laser preheat on the hydrodynamic behavior of a material layer. In particular, we find that perturbation of the surface of the layer results in a complex interaction, in which the bulk of the layer develops density, pressure, and temperature structure and in which the surface experiences instability-like behavior, including mode coupling. A uniform one-temperature preheat model is used to reproduce the experimentally observed behavior, and we find that this model can be used to capture the evolution of the layer, while also providing evidence of complexities in the preheat behavior. This result has important consequences for inertially confined fusion plasmas, which can be difficult to diagnose in detail, as well as for laser hydrodynamics experiments, which generally depend on assumptions about initial conditions in order to interpret their results.

  5. Structural evolution of a two-component organogel.

    PubMed

    Singh, Mohit; Tan, Grace; Agarwal, Vivek; Fritz, Gerhard; Maskos, Karol; Bose, Arijit; John, Vijay; McPherson, Gary

    2004-08-31

    Dry reverse micelles of AOT in isooctane spontaneously undergo a microstructural transition to an organogel upon the addition of a phenolic dopant, p-chlorophenol. This microstructural evolution has been studied through a combination of light scattering, small-angle neutron scattering (SANS), NMR, and rheology. Several equilibrium stages between the system of dry reverse micelles of AOT and a 1:1 AOT/p-chlorophenol (molar ratio) gel in isooctane have been examined. To achieve this, p-chlorophenol is added progressively to the dilute solutions of AOT in isooctane, and this concentration series is then analyzed. The dry micelles of AOT in isooctane do not undergo any detectable structural change up to a certain p-chlorophenol concentration. Upon a very small increment in the concentration of p-chlorophenol beyond this "threshold" concentration, large strandlike aggregates are observed which then evolve to the three-dimensional gel network.

  6. 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.

  7. Constraints on Composition, Structure and Evolution of the Lithosphere

    NASA Astrophysics Data System (ADS)

    Bianchini, Gianluca; Bonadiman, Costanza; Aulbach, Sonja; Schutt, Derek

    2015-05-01

    The idea for this special issue was triggered at the Goldschmidt Conference held in Florence (August 25-30, 2013), where we convened a session titled "Integrated Geophysical-Geochemical Constraints on Composition and Structure of the Lithosphere". The invitation to contribute was extended not only to the session participants but also to a wider spectrum of colleagues working on related topics. Consequently, a diverse group of Earth scientists encompassing geophysicists, geodynamicists, geochemists and petrologists contributed to this Volume, providing a comprehensive overview on the nature and evolution of lithospheric mantle by combining studies that exploit different types of data and interpretative approaches. The integration of geochemical and geodynamic datasets and their interpretation represents the state of the art in our knowledge of the lithosphere and beyond, and could serve as a blueprint for future strategies in concept and methodology to advance our knowledge of this and other terrestrial reservoirs.

  8. Structure and Evolution of Internally Heated Hot Jupiters

    NASA Astrophysics Data System (ADS)

    Komacek, Thaddeus D.; Youdin, Andrew N.

    2015-11-01

    The transit radii of many close-in extrasolar giant planets, or "hot Jupiters," are systematically larger than those expected from models considering only cooling from an initial high-entropy state. Though these planets receive strong irradiation, with equilibrium temperatures of 1000-2500 Kelvin, the absorption of stellar incident flux in the upper atmosphere alone cannot explain these anomalous radii. More promising mechanisms involve irradiation-driven meteorological activity, which penetrates much deeper into the planet than direct stellar heating. This circulation can lead to large-scale mixing and downward transport of kinetic energy, both processes whereby a fraction of the stellar incident power is transported downwards to the interior of the planet. Here we consider how deposition of heat at different pressure levels or structural locations within a planet affects the resulting evolution. To do so, we run global gas giant evolutionary models with with the stellar structure code MESA including additional energy dissipation. We find that relatively shallow atmospheric heating alone can explain the transit radii of the hot Jupiter sample, but heating in the convective zone is an order of magnitude more efficient regardless of exact location. Additionally, a small difference in atmospheric heating location can have a significant effect on radius evolution, especially near the radiative-convective boundary. The most efficient location to heat the planet is at the radiative-convective boundary or deeper. We expect that shear instabilities at this interface may naturally explain energy dissipation at the radiative-convective boundary, which typically lies at a pressure of ~1 kilobar after 5 Gyr for a planet with the mass and incident stellar flux of HD 209458b. Hence, atmospheric processes are most efficient at explaining the bloated radii of hot Jupiters if they can transport incident stellar power downwards to the top of the inner convective zone.

  9. Structural evolution of turbostratic carbon: Implications in H2 storage

    NASA Astrophysics Data System (ADS)

    Ruz, Priyanka; Banerjee, Seemita; Pandey, M.; Sudarsan, V.; Sastry, P. U.; Kshirsagar, R. J.

    2016-12-01

    Structural evolution of turbostratic carbon samples as a function of annealing temperature has been investigated in detail using small angle X-ray scattering (SAXS), solid state nuclear magnetic resonance (NMR) and Raman spectroscopic techniques. From these studies, it is established that, samples heated at lower temperatures (700 °C and 800 °C) consist carbon particles with rough surfaces forming structure of surface fractal in nature. Whereas the sample heated at higher temperature (900 °C) consists of larger clusters with nearly smooth surface as well as smaller size particles forming dense mass fractal structure. For this sample, solid state NMR and Raman Spectroscopic studies indicate an increased extent of overlapping of 2pz orbital of carbon atoms due to improved long range ordering and clustering. Hydrogen adsorption studies further substantiated that energetically more homogeneous surface exists for particles of 900 °C heated sample as compared to those of 700 °C and 800 °C heated samples. A highest hydrogen storage capacity of 0.152 H/M has been observed at 123 K and 45 bar pressure for the sample heated at 900 °C.

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  11. The Structure and Evolution of Cold Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Diemand, Jürg; Moore, Ben

    2011-02-01

    In the standard cosmological model a mysterious cold dark matter (CDM) component dominates the formation of structures. Numerical studies of the f ormation of CDM halos have produced several robust results that allow unique tests of the hierarchical clustering paradigm. Universal properties of halos, including their mass profiles and substructure properties are roughly consistent with observational data from the scales of dwarf galaxies to galaxy clusters. Resolving the fine grained structure of halos has enabled us to make predictions for ongoing and planned direct and indirect dark matter detection experiments. While simulations of pure CDM halos are now very accurate and in good agreement (recently claimed discrepancies are addressed in detail in this review), we are still unable to make robust, quantitative predictions about galaxy formation and about how the dark matter distribution changes in the process. Whilst discrepancies between observations and simulations have been the subject of much debate in the literature, galaxy formation and evolution needs to be understood in more detail in order to fully test the CDM paradigm. Whatever the true nature of the dark matter particle is, its clustering properties must not be too different from a cold neutralino like particle to maintain all the successes of the model in matching large scale structure data and the global properties of halos which are mostly in good agreement with observations.

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

    PubMed Central

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

    2017-01-01

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

  13. The influence of halo evolution on galaxy structure

    NASA Astrophysics Data System (ADS)

    White, Simon

    2015-03-01

    If Einstein-Newton gravity holds on galactic and larger scales, then current observations demonstrate that the stars and interstellar gas of a typical bright galaxy account for only a few percent of its total nonlinear mass. Dark matter makes up the rest and cannot be faint stars or any other baryonic form because it was already present and decoupled from the radiation plasma at z = 1000, long before any nonlinear object formed. The weak gravito-sonic waves so precisely measured by CMB observations are detected again at z = 4 as order unity fluctuations in intergalactic matter. These subsequently collapse to form today's galaxy/halo systems, whose mean mass profiles can be accurately determined through gravitational lensing. High-resolution simulations link the observed dark matter structures seen at all these epochs, demonstrating that they are consistent and providing detailed predictions for all aspects of halo structure and growth. Requiring consistency with the abundance and clustering of real galaxies strongly constrains the galaxy-halo relation, both today and at high redshift. This results in detailed predictions for galaxy assembly histories and for the gravitational arena in which galaxies live. Dark halos are not expected to be passive or symmetric but to have a rich and continually evolving structure which will drive evolution in the central galaxy over its full life, exciting warps, spiral patterns and tidal arms, thickening disks, producing rings, bars and bulges. Their growth is closely related to the provision of new gas for galaxy building.

  14. Instrumentation development for planetary in situ 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Davidheiser-Kroll, B.; Morgan, L. E.; Munk, M.; Warner, N. H.; Gupta, S.; Slaybaugh, R.; Harkness, P.; Mark, D. F.

    2015-12-01

    The chronology of the Solar System, particularly the timing of formation of extraterrestrial bodies and their features, is a major outstanding problem in planetary science. Although various chronological methods for in situ geochronology have been proposed (e.g. Rb-Sr, K-Ar), and even applied (K-Ar, Farley et al., 2014), the reliability, accuracy, and applicability of the 40Ar/39Ar method makes it by far the most desirable chronometer for dating extraterrestrial bodies. The method however relies on the neutron irradiation of samples, and thus a neutron source. We will discuss the challenges and feasibility of deploying a passive neutron source to planetary surfaces for the in situ application of the 40Ar/39Ar chronometer. Requirements in generating and shielding neutrons, as well as analyzing samples are discussed, along with an exploration of limitations such as mass, power, and cost. Two potential solutions for the in situ extraterrestrial deployment of the 40Ar/39Ar method will be presented. Although this represents a challenging task, developing the technology to apply the 40Ar/39Ar method on planetary surfaces would represent a major advance towards constraining the timescale of solar system formation and evolution.

  15. Halo formation and evolution: unifying physical properties with structure

    NASA Astrophysics Data System (ADS)

    Ernest, Alllan David; Collins, Matthew P.

    2015-08-01

    The assembly of matter in the universe proliferates a variety of structures with diverse properties. For example, massive halos of clusters of galaxies have temperatures often an order of magnitude or more higher than the individual galaxy halos within the cluster, or the temperatures of isolated galaxy halos. Giant spiral galaxies contain large quantities of both dark matter and hot gas while other structures like globular clusters appear to have little or no dark matter or gas. Still others, like the dwarf spheroidal galaxies have low gravity and little hot gas, but ironically contain some of the largest fractions of dark matter in the universe. Star forming rates (SFRs) also vary: compare for example the SFRs of giant elliptical galaxies, globular clusters, spiral and starburst galaxies. Furthermore there is evidence that the various structure types have existed over a large fraction of cosmic history. How can this array of variation in properties be reconciled with galaxy halo formation and evolution?We propose a model of halo formation [1] and evolution [2] that is consistent with both primordial nucleosynthesis (BBN) and the isotropies in the cosmic microwave background (CMB). The model uses two simple parameters, the total mass and size of a structure, to (1) explain why galaxies have the fractions of dark matter that they do (including why dwarf spheroidals are so dark matter dominated despite their weak gravity), (2) enable an understanding of the black hole-bulge/black hole-dark halo relations, (3) explain how fully formed massive galaxies can occur so early in cosmic history, (4) understand the connection between spiral and elliptical galaxies (5) unify the nature of globular clusters, dwarf spheroidal galaxies and bulges and (6) predict the temperatures of hot gas halos and understand how cool galaxy halos can remain stable in the hot environments of cluster-galaxy halos.[1] Ernest, A. D., 2012, in Prof. Ion Cotaescu (Ed) Advances in Quantum Theory, pp

  16. Structure and Evolution of Kuiper Belt Objects and Dwarf Planets

    NASA Astrophysics Data System (ADS)

    McKinnon, W. B.; Prialnik, D.; Stern, S. A.; Coradini, A.

    Kuiper belt objects (KBOs) accreted from a mélange of volatile ices, carbonaceous matter, and rock of mixed interstellar and solar nebular provenance. The transneptunian region, where this accretion took place, was likely more radially compact than today. This and the influence of gas drag during the solar nebula epoch argue for more rapid KBO accretion than usually considered. Early evolution of KBOs was largely the result of heating due to radioactive decay, the most important potential source being 26Al, whereas long-term evolution of large bodies is controlled by the decay of U, Th, and 40K. Several studies are reviewed dealing with the evolution of KBO models, calculated by means of one-dimensional numerical codes that solve the heat and mass balance equations. It is shown that, depending on parameters (principally rock content and porous conductivity), KBO interiors may have reached relatively high temperatures. The models suggest that KBOs likely lost ices of very volatile species during early evolution, whereas ices of less-volatile species should be retained in cold, less-altered subsurface layers. Initially amorphous ice may have crystallized in KBO interiors, releasing volatiles trapped in the amorphous ice, and some objects may have lost part of these volatiles as well. Generally, the outer layers are far less affected by internal evolution than the inner part, which in the absence of other effects (such as collisions) predicts a stratified composition and altered porosity distribution. Kuiper belt objects are thus unlikely to be "the most pristine objects in the solar system," but they do contain key information as to how the early solar system accreted and dynamically evolved. For large (dwarf planet) KBOs, long-term radiogenic heating alone may lead to differentiated structures -- rock cores, ice mantles, volatile-ice-rich "crusts," and even oceans. Persistence of oceans and (potential) volcanism to the present day depends strongly on body size and

  17. K-shell and extreme ultraviolet spectroscopic signatures of structured Ar puff Z-pinch loads with high K-shell x-ray yield

    NASA Astrophysics Data System (ADS)

    Failor, B. H.; Sze, H. M.; Banister, J. W.; Levine, J. S.; Qi, N.; Apruzese, J. P.; Lojewski, D. Y.

    2007-02-01

    Structured 12-cm-diam Ar gas-puff loads have recently produced Z-pinch implosions with reduced Rayleigh-Taylor instability growth and increased ≈3mm, consistent with the observed load inductance change and an imploded-mass consisting of a ≈1.5-mm-diam, hot, ⩾20% of load mass) increases the rise and fall times of the XUV emission to ⩾40ns, consistent with a more adiabatic compression and heating of the load. Axial measurements show that, despite differences in the XUV and K-shell emission time histories, the K-shell x-ray yield is insensitive to axial variations in load mass.

  18. Effect of spatial structure on the evolution of cooperation.

    PubMed

    Roca, Carlos P; Cuesta, José A; Sánchez, Angel

    2009-10-01

    Spatial structure is known to have an impact on the evolution of cooperation, and so it has been intensively studied during recent years. Previous work has shown the relevance of some features, such as the synchronicity of the updating, the clustering of the network, or the influence of the update rule. This has been done, however, for concrete settings with particular games, networks, and update rules, with the consequence that some contradictions have arisen and a general understanding of these topics is missing in the broader context of the space of 2x2 games. To address this issue, we have performed a systematic and exhaustive simulation in the different degrees of freedom of the problem. In some cases, we generalize previous knowledge to the broader context of our study and explain the apparent contradictions. In other cases, however, our conclusions refute what seems to be established opinions in the field, as for example the robustness of the effect of spatial structure against changes in the update rule, or offer new insights into the subject, e.g., the relation between the intensity of selection and the asymmetry between the effects on games with mixed equilibria.

  19. Evolution and Structural Analyses of Glossina morsitans (Diptera; Glossinidae) Tetraspanins.

    PubMed

    Murungi, Edwin K; Kariithi, Henry M; Adunga, Vincent; Obonyo, Meshack; Christoffels, Alan

    2014-11-12

    Tetraspanins are important conserved integral membrane proteins expressed in many organisms. Although there is limited knowledge about the full repertoire, evolution and structural characteristics of individual members in various organisms, data obtained so far show that tetraspanins play major roles in membrane biology, visual processing, memory, olfactory signal processing, and mechanosensory antennal inputs. Thus, these proteins are potential targets for control of insect pests. Here, we report that the genome of the tsetse fly, Glossina morsitans (Diptera: Glossinidae) encodes at least seventeen tetraspanins (GmTsps), all containing the signature features found in the tetraspanin superfamily members. Whereas six of the GmTsps have been previously reported, eleven could be classified as novel because their amino acid sequences do not map to characterized tetraspanins in the available protein data bases. We present a model of the GmTsps by using GmTsp42Ed, whose presence and expression has been recently detected by transcriptomics and proteomics analyses of G. morsitans. Phylogenetically, the identified GmTsps segregate into three major clusters. Structurally, the GmTsps are largely similar to vertebrate tetraspanins. In view of the exploitation of tetraspanins by organisms for survival, these proteins could be targeted using specific antibodies, recombinant large extracellular loop (LEL) domains, small-molecule mimetics and siRNAs as potential novel and efficacious putative targets to combat African trypanosomiasis by killing the tsetse fly vector.

  20. Tatooine Nurseries: Structure and Evolution of Circumbinary Protoplanetary Disks

    NASA Astrophysics Data System (ADS)

    Vartanyan, David; Garmilla, José A.; Rafikov, Roman R.

    2016-01-01

    Recent discoveries of circumbinary planets by the Kepler mission provide motivation for understanding their birthplaces—protoplanetary disks around stellar binaries with separations ≲ 1 {{AU}}. We explore properties and evolution of such circumbinary disks focusing on modification of their structure caused by tidal coupling to the binary. We develop a set of analytical scaling relations describing viscous evolution of the disk properties, which are verified and calibrated using 1D numerical calculations with realistic inputs. Injection of angular momentum by the central binary suppresses mass accretion onto the binary and causes radial distribution of the viscous angular momentum flux {F}J to be different from that in a standard accretion disk around a single star with no torque at the center. Disks with no mass accretion at the center develop an {F}J profile that is flat in radius. Radial profiles of temperature and surface density are also quite different from those in disks around single stars. Damping of the density waves driven by the binary and viscous dissipation dominates heating of the inner disk (within 1-2 AU), pushing the ice line beyond 3-5 AU, depending on disk mass and age. Irradiation by the binary governs disk thermodynamics beyond ˜10 AU. However, self-shadowing by the hot inner disk may render central illumination irrelevant out to ˜20 AU. Spectral energy distribution of a circumbinary disk exhibits a distinctive bump around 10 μm, which may facilitate identification of such disks around unresolved binaries. Efficient tidal coupling to the disk drives orbital inspiral of the binary and may cause low-mass and relatively compact binaries to merge into a single star within the disk lifetime. We generally find that circumbinary disks present favorable sites for planet formation (despite their wider zone of volatile depletion), in agreement with the statistics of Kepler circumbinary planets.

  1. Two-cell detonation: losses effects on cellular structure and propagation in rich H2-NO2/N2O4-Ar mixtures

    NASA Astrophysics Data System (ADS)

    Virot, F.; Khasainov, B.; Desbordes, D.; Presles, H.-N.

    2010-12-01

    Detonation experiments in H2-NO2/N2O4-Ar mixtures (Equivalence ratio 1.2 and initial pressure lower than 0.1 MPa) confined in a tube of internal diameter 52 mm reveal two propagation regimes depending on initial pressure: (1) a quasi-CJ regime is observed along with a double cellular structure at high pressures; (2) at lower pressures, a low velocity detonation regime is observed with a single structure. Transition between this two regimes happens when the spinning detonation of the larger cell vanishes. Each detonation regime is characterized by velocity and pressure measurements and cellular structure records. Coherence between all experimental data for each experiment leads in assumption that losses are responsible for the transition between one regime to another. In a second part, we study such behaviour for a two-step mixture through numerical simulations using a global two-step chemical kinetics and a simple losses model. Numerical simulations qualitatively agree with experiments. Both detonation regimes with their own cellular structures are reproduced.

  2. Effects of 200 keV Ar-ions irradiation on the structural and optical properties of reactively sputtered CrN films

    NASA Astrophysics Data System (ADS)

    Novaković, M.; Popović, M.; Zhang, K.; Rakočević, Z.; Bibić, N.

    2016-12-01

    Modification in structural and optical properties of chromium-nitride (CrN) films induced by argon ion irradiation and thermal annealings were investigated using various experimental techniques. CrN films deposited by d. c. reactive sputtering on Si substrate were implanted with 200 keV argon ions, at fluences of 5-20 × 1015 ions/cm2. As-implanted samples were then annealed in vacuum, for 2 h at 700 °C. Rutherford backscattering spectrometry, X-ray diffraction, cross-sectional (high-resolution) transmission electron microscopy and spectroscopic ellipsometry (SE) measurements were carried out in order to study structural and optical properties of the layers. After irradiation with 200 keV Ar ions a damaged surface layer of nanocrystalline structure was generated, which extended beyond the implantation profile, but left an undamaged bottom zone. Partial loss of columnar structure observed in implanted samples was recovered after annealing at 700 °C and CrN started to decompose to Cr2N. This layer geometry determined from transmission electron microscopy was inferred in the analysis of SE data using the combined Drude and Tauc-Lorentz model, and the variation of the optical bandgap was deduced. The results are discussed on the basis of the changes induced in the microstructure. It was found that the optical properties of the layers are strongly dependent on the defects' concentration of CrN.

  3. Diverse structural evolution at z > 1 in cosmologically simulated galaxies

    NASA Astrophysics Data System (ADS)

    Snyder, Gregory F.; Lotz, Jennifer; Moody, Christopher; Peth, Michael; Freeman, Peter; Ceverino, Daniel; Primack, Joel; Dekel, Avishai

    2015-08-01

    From mock Hubble Space Telescope images, we quantify non-parametric statistics of galaxy morphology, thereby predicting the emergence of relationships among stellar mass, star formation, and observed rest-frame optical structure at 1 < z < 3. We measure automated diagnostics of galaxy morphology in cosmological simulations of the formation of 22 central galaxies with 9.3 < log10M*/M⊙ < 10.7. These high-spatial-resolution zoom-in calculations enable accurate modelling of the rest-frame UV and optical morphology. Even with small numbers of galaxies, we find that structural evolution is neither universal nor monotonic: galaxy interactions can trigger either bulge or disc formation, and optically bulge-dominated galaxies at this mass may not remain so forever. Simulated galaxies with M* > 1010M⊙ contain relatively more disc-dominated light profiles than those with lower mass, reflecting significant disc brightening in some haloes at 1 < z < 2. By this epoch, simulated galaxies with specific star formation rates below 10- 9.7 yr- 1 are more likely than normal star-formers to have a broader mix of structural types, especially at M* > 1010 M⊙. We analyse a cosmological major merger at z ˜ 1.5 and find that the newly proposed Multimode-Intensity-Deviation (MID) morphology diagnostics trace later merger stages while Gini-M20 trace earlier ones. MID is sensitive also to clumpy star-forming discs. The observability time of typical MID-enhanced events in our simulation sample is <100 Myr. A larger sample of cosmological assembly histories may be required to calibrate such diagnostics in the face of their sensitivity to viewing angle, segmentation algorithm, and various phenomena such as clumpy star formation and minor mergers.

  4. Tectonic structure and evolution of the Atlantic continental margin

    SciTech Connect

    Klitgord, K.D.; Schouten, H.; Hutchinson, D.R.

    1985-01-01

    The Atlantic continental margin developed across the boundary between continental and oceanic crust as rifting and then sea-floor spreading broke apart and separated the North American and African plates, forming the Atlantic Ocean Basin. Continental rifting began in Late Triassic with reactivation of Paleozoic thrust faults as normal faults and with extension across a broad zone of subparallel rift basins. Extension became localized in Early to Middle Jurassic along the zone that now underlies the large marginal basins, and other rift zones, such as the Newark, Hartford, and Fundy basins, were abandoned. Rifting and crustal stretching between the two continents gave way to sea-floor spreading Middle Jurassic and the formation of oceanic crust. This tectonic evolution resulted in formation of distinctive structural features. The marginal basins are underlain by a thinner crust and contain a variety of fault-controlled structures, including half-grabens, seaward- and landward-tilted blocks, faults that die out within the crust, and faults that penetrate the entire crust. This variable structure probably resulted from the late Triassic-Early Jurassic pattern of normal, listric, and antithetic faults that evolved from the Paleozoic thrust fault geometry. The boundary between marginal basins and oceanic crust is marked approximately by the East Coast Magnetic Anomaly (ECMA). A major basement fault is located in the Baltimore Canyon trough at the landward edge of the ECMA and a zone of seaward dipping reflectors is found just seaward of the ECMA off Georges Bank. The fracture zone pattern in Mesozoic oceanic crust can be traced landward to the ECMA.

  5. Revised error propagation of 40Ar/39Ar data, including covariances

    NASA Astrophysics Data System (ADS)

    Vermeesch, Pieter

    2015-12-01

    The main advantage of the 40Ar/39Ar method over conventional K-Ar dating is that it does not depend on any absolute abundance or concentration measurements, but only uses the relative ratios between five isotopes of the same element -argon- which can be measured with great precision on a noble gas mass spectrometer. The relative abundances of the argon isotopes are subject to a constant sum constraint, which imposes a covariant structure on the data: the relative amount of any of the five isotopes can always be obtained from that of the other four. Thus, the 40Ar/39Ar method is a classic example of a 'compositional data problem'. In addition to the constant sum constraint, covariances are introduced by a host of other processes, including data acquisition, blank correction, detector calibration, mass fractionation, decay correction, interference correction, atmospheric argon correction, interpolation of the irradiation parameter, and age calculation. The myriad of correlated errors arising during the data reduction are best handled by casting the 40Ar/39Ar data reduction protocol in a matrix form. The completely revised workflow presented in this paper is implemented in a new software platform, Ar-Ar_Redux, which takes raw mass spectrometer data as input and generates accurate 40Ar/39Ar ages and their (co-)variances as output. Ar-Ar_Redux accounts for all sources of analytical uncertainty, including those associated with decay constants and the air ratio. Knowing the covariance matrix of the ages removes the need to consider 'internal' and 'external' uncertainties separately when calculating (weighted) mean ages. Ar-Ar_Redux is built on the same principles as its sibling program in the U-Pb community (U-Pb_Redux), thus improving the intercomparability of the two methods with tangible benefits to the accuracy of the geologic time scale. The program can be downloaded free of charge from

  6. Evaluation of different emission inventories on the O3 and CO evolution within the CTM MOCAGE during the Pre-ChArMEx TRAQA campaign

    NASA Astrophysics Data System (ADS)

    Parmentier, Jonathan; El Amraoui, Laaziz; Attié, Jean-Luc; Josse, Béatrice; Arteta, Joaquim; Joly, Mathieu; Marécal, Virginie; Plu, Matthieu

    2014-05-01

    The chemistry-transport model MOCAGE, using meteorological forcings can use different emission inventories to describe and model numerous trace gases in the atmosphere. Each emission inventory has its specific resolution and its own variability. We present a study of the influence of two different inventories on the MOCAGE simulations. We use the IPCC (Intergovernmental Panel on Climate Change) and the MACC (Monitoring Atmospheric Composition and Climate) inventories. This comparison concerns the atmospheric species of ozone and carbon monoxide. For this study, we performed a new nested domain within the version of MOCAGE at global scale(called MEDI02). This new domain has high horizontal resolution (0.2°x0.2°) and is centred on the Mediterranean basin. To guarantee the consistency of different chemical species in both domains, the boarders of the nested domain are controlled by the global domain. The evaluation of both emission inventories will be done by comparing MOCAGE fields to those measured during the Pre-ChArMEx TRAQA campaign 2012. The TRAQA (TRAnsport à longue distance et Qualité de l'Air sur le bassin méditerranéen) campaign took place on the Mediterranean basin from June 26 to July 11, 2012. During this experiment the ATR-42 aircraft of Météo-France and atmospheric balloons, operated by CNES, have been used to measure trace gases and aerosols. More than 60h of flight measurements and as many as during 7 Intensive Observation Periods (IOPs) with radio-sounding balloons and Boundary Layer Pressurized Balloons (BLPB).

  7. Quadrupole collectivity beyond N = 28: intermediate-energy Coulomb excitation of (47,48)Ar.

    PubMed

    Winkler, R; Gade, A; Baugher, T; Bazin, D; Brown, B A; Glasmacher, T; Grinyer, G F; Meharchand, R; McDaniel, S; Ratkiewicz, A; Weisshaar, D

    2012-05-04

    We report on the first experimental study of quadrupole collectivity in the very neutron-rich nuclei (47,48)Ar using intermediate-energy Coulomb excitation. These nuclei are located along the path from doubly magic Ca to collective S and Si isotopes, a critical region of shell evolution and structural change. The deduced B(E2) transition strengths are confronted with large-scale shell-model calculations in the sdpf shell using the state-of-the-art SDPF-Uand EPQQM effective interactions. The comparison between experiment and theory indicates that a shell-model description of Ar isotopes around N=28 remains a challenge.

  8. Quadrupole Collectivity beyond N=28: Intermediate-Energy Coulomb Excitation of Ar47,48

    NASA Astrophysics Data System (ADS)

    Winkler, R.; Gade, A.; Baugher, T.; Bazin, D.; Brown, B. A.; Glasmacher, T.; Grinyer, G. F.; Meharchand, R.; McDaniel, S.; Ratkiewicz, A.; Weisshaar, D.

    2012-05-01

    We report on the first experimental study of quadrupole collectivity in the very neutron-rich nuclei Ar47,48 using intermediate-energy Coulomb excitation. These nuclei are located along the path from doubly magic Ca to collective S and Si isotopes, a critical region of shell evolution and structural change. The deduced B(E2) transition strengths are confronted with large-scale shell-model calculations in the sdpf shell using the state-of-the-art SDPF-Uand EPQQM effective interactions. The comparison between experiment and theory indicates that a shell-model description of Ar isotopes around N=28 remains a challenge.

  9. The structural evolution of the deep continental lithosphere

    NASA Astrophysics Data System (ADS)

    Cooper, C. M.; Miller, Meghan S.; Moresi, Louis

    2017-01-01

    Continental lithosphere houses the oldest and thickest regions of the Earth's surface. Locked within this deep and ancient rock record lies invaluable information about the dynamics that has shaped and continue to shape the planet. Much of that history has been dominated by the forces of plate tectonics which has repeatedly assembled super continents together and torn them apart - the Wilson Cycle. While the younger regions of continental lithosphere have been subject to deformation driven by plate tectonics, it is less clear whether the ancient, stable cores formed and evolved from similar processes. New insight into continental formation and evolution has come from remarkable views of deeper lithospheric structure using enhanced seismic imaging techniques and the increase in large volumes of broadband data. Some of the most compelling observations are that the continental lithosphere has a broad range in thicknesses (< 100 to > 300 km), has complex internal structure, and that the thickest portion appears to be riddled with seismic discontinuities at depths between 80 and 130 km. These internal structural features have been interpreted as remnants of lithospheric formation during Earth's early history. If they are remnants, then we can attempt to investigate the structure present in the deep lithosphere to piece together information about early Earth dynamics much as is done closer to the surface. This would help delineate between the differing models describing the dynamics of craton formation, particularly whether they formed in the era of modern plate tectonics, a transitional mobile-lid tectonic regime, or are the last fragments of an early, stagnant-lid planet. Our review paper (re)introduces readers to the conceptual definitions of the lithosphere and the complex nature of the upper boundary layer, then moves on to discuss techniques and recent seismological observations of the continental lithosphere. We then review geodynamic models and hypotheses for the

  10. Oldest human footprints dated by Ar/Ar

    NASA Astrophysics Data System (ADS)

    Scaillet, Stéphane; Vita-Scaillet, Grazia; Guillou, Hervé

    2008-11-01

    Fossilized human trackways are extremely rare in the geologic record. These bear indirect but invaluable testimony of human/hominid locomotion in open air settings and can provide critical information on biomechanical changes relating to bipedalism evolution throughout the primitive human lineage. Among these, the "Devil's footsteps" represent one of the best preserved human footprints suite recovered so far in a Pleistocene volcanic ash of the Roccamonfina volcano (southern Italy). Until recently, the age of these footprints remained speculative and indirectly correlated with a loosely dated caldera-forming eruption that produced the Brown Leucitic Tuff. Despite extensive hydrothermal alteration of the pyroclastic deposit and variable contamination with excess 40Ar, detailed and selective 40Ar/ 39Ar laser probe analysis of single leucite crystals recovered from the ash deposit shows that the pyroclastic layer and the footprints are 345 ± 6 kyr old (1 σ), confirming for the first time that these are the oldest human trackways ever dated, and that they were presumably left by the modern human predecessor, Homo heidelbergensis, close to Climatic Termination IV.

  11. Effect of local structures on structural evolution during crystallization in undercooled metallic glass-forming liquids.

    PubMed

    Wu, Z W; Li, M Z; Wang, W H; Song, W J; Liu, K X

    2013-02-21

    The effect of local structures on structural evolution during the crystallization of undercooled ZrCu metallic glass-forming liquid was studied via molecular dynamics simulations. It is found that body-centered-cubic (bcc)-like clusters play a key role in structural evolution during crystallization. In contrast to previous speculations, the number of bcc-like crystal nuclei does not change much before the onset of crystallization. Instead, the development of a bcc-like critical nucleus during annealing leads to a strong spatial correlation with other nuclei in its surroundings, forming a crystalline structure template. It is also found that the size distribution of bcc-like nuclei follows a power-law form with an exponential cutoff in the early stage of annealing, but changes to a pure power-law behavior just before the onset of crystallization. This implies that the crystalline structure template has fractal feature and the undercooled liquids evolve to a self-organized critical state before the onset of crystallization, which might trigger the subsequent rapid crystallization. According to the graph theory analysis, it is also found that the observed large scatter of the onset time of crystallization in different liquid samples results from the connectivity of the bcc-like clusters.

  12. MC carbide structures in M(lc2)ar-M247. M.S. Thesis - Final Report

    NASA Technical Reports Server (NTRS)

    Wawro, S. W.

    1982-01-01

    The morphologies and distribution of the MC carbides in Mar-M247 ingot stock and castings were investigated using metallographic, X-ray diffraction and energy-dispersive X-ray analysis techniques. The MC carbides were found to form script structures during solidification. The script structures were composed of three distinct parts. The central cores and elongated arms of the MC carbide script structures had compositions (Ti, Cr, Hf, Ta, W)C and lattice parameters of 4.39 A. The elongated script arms terminated in enlarged, angular "heads". The heads had compositions (Ti, Hf, Ta, W)C and lattice parameters of approximately 4.50 A. The heads had a higher Hf content than the cores and arms. The size of the script structures, as well as the relative amount of head-type to core and arm-type MC carbide, was found to be determined by solidification conditions. No carryover of the MC carbides from the ingot stock to the remelted and cast material was observed.

  13. Evolution of sperm structure and energetics in passerine birds.

    PubMed

    Rowe, Melissah; Laskemoen, Terje; Johnsen, Arild; Lifjeld, Jan T

    2013-02-22

    Spermatozoa exhibit considerable interspecific variability in size and shape. Our understanding of the adaptive significance of this diversity, however, remains limited. Determining how variation in sperm structure translates into variation in sperm performance will contribute to our understanding of the evolutionary diversification of sperm form. Here, using data from passerine birds, we test the hypothesis that longer sperm swim faster because they have more available energy. We found that sperm with longer midpieces have higher levels of intracellular adenosine triphosphate (ATP), but that greater energy reserves do not translate into faster-swimming sperm. Additionally, we found that interspecific variation in sperm ATP concentration is not associated with the level of sperm competition faced by males. Finally, using Bayesian methods, we compared the evolutionary trajectories of sperm morphology and ATP content, and show that both traits have undergone directional evolutionary change. However, in contrast to recent suggestions in other taxa, we show that changes in ATP are unlikely to have preceded changes in morphology in passerine sperm. These results suggest that variable selective pressures are likely to have driven the evolution of sperm traits in different taxa, and highlight fundamental biological differences between taxa with internal and external fertilization, as well as those with and without sperm storage.

  14. Structural evolution of zirconium carbide under ion irradiation

    NASA Astrophysics Data System (ADS)

    Gosset, D.; Dollé, M.; Simeone, D.; Baldinozzi, G.; Thomé, L.

    2008-02-01

    Zirconium carbide is one of the candidate materials to be used for some fuel components of the high temperature nuclear reactors planned in the frame of the Gen-IV project. Few data exist regarding its behaviour under irradiation. We have irradiated ZrC samples at room temperature with slow heavy ions (4 MeV Au, fluence from 10 11 to 5 × 10 15 cm -2) in order to simulate neutron irradiations. Grazing incidence X-Ray diffraction (GIXRD) and transmission electron microscopy (TEM) analysis have been performed in order to study the microstructural evolution of the material versus ion fluence. A high sensitivity to oxidation is observed with the formation of zirconia precipitates during the ion irradiations. Three damage stages are observed. At low fluence (<10 12 cm -2), low modifications are observed. At intermediate fluence, high micro-strains appear together with small faulted dislocation loops. At the highest fluence (>10 14 cm -2), the micro-strains saturate and the loops coalesce to form a dense dislocation network. No other structural modification is observed. The material shows a moderate cell parameter increase, corresponding to a 0.6 vol.% swelling, which saturates around 10 14 ions/cm 2, i.e., a few Zr dpa. As a result, in spite of a strong covalent bonding component, ZrC seems to have a behaviour under irradiation close to cubic metals.

  15. Evolution of the macromolecular structure of sporopollenin during thermal degradation.

    PubMed

    Bernard, S; Benzerara, K; Beyssac, O; Balan, E; Brown, G E

    2015-10-01

    Reconstructing the original biogeochemistry of organic microfossils requires quantifying the extent of the chemical transformations they experienced during burial and maturation processes. In the present study, fossilization experiments have been performed using modern sporopollenin chosen as an analogue for the resistant biocompounds possibly constituting the wall of many organic microfossils. Sporopollenin powder has been processed thermally under argon atmosphere at different temperatures (up to 1000 °C) for varying durations (up to 900 min). Solid residues of each experiment have been characterized using infrared, Raman and synchrotron-based XANES spectroscopies. Results indicate that significant defunctionalisation and aromatization affect the molecular structure of sporopollenin with increasing temperature. Two distinct stages of evolution with temperature are observed: in a first stage, sporopollenin experiences dehydrogenation and deoxygenation simultaneously (below 500 °C); in a second stage (above 500 °C) an increasing concentration in aromatic groups and a lateral growth of aromatic layers are observed. With increasing heating duration (up to 900 min) at a constant temperature (360 °C), oxygen is progressively lost and conjugated carbon-carbon chains or domains grow progressively, following a log-linear kinetic behavior. Based on the comparison with natural spores fossilized within metasediments which experienced intense metamorphism, we show that the present experimental simulations may not perfectly mimic natural diagenesis and metamorphism. Yet, performing such laboratory experiments provides key insights on the processes transforming biogenic molecules into molecular fossils.

  16. 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.

  17. Thermal structure and evolution of tidally-locked Super Earths

    NASA Astrophysics Data System (ADS)

    Gelman, S.; Elkins-Tanton, L. T.; Seager, S.

    2008-12-01

    Over 260 extrasolar planets have been discovered, many of which are massive (often many times the mass of Jupiter) and orbiting very close to their parent star. Of particular interest to researchers, however, are the handful of discovered planets that are within 20 Earth masses, due to their potential for habitability. We present a model of the internal temperature structure of such tidally-locked 'Super Earth' exoplanets. The planets of interest have a terrestrial, rocky composition, with a hot side facing its star at all times, and a cold side facing away. Heat circulation through an atmosphere is assumed to be negligible due to the planets' proximity to the star, which causes potential atmospheres to be evaporated; therefore, the primary modes of heat transfer within the planet are convection and conduction, with absorption on the hot side of the flux from the star, and black-body radiation to space in all directions. We have modified a spherical axisymmetric version of the finite element code ConMan (SSAXC), which was first created to model the internal thermal evolution of Earth's mantle. The results from this code are plotted and a thermal profile, with potentially molten rock on one side and very cool rock on the other with a temperature gradient connecting the two, allows us to determine where potentially habitable regions would exist on the planet. Finally, an approximation of what typical mantle rocks would be melted at predicted temperatures and pressures are compared with these plotted internal gradients.

  18. The structure and evolution of buyer-supplier networks.

    PubMed

    Mizuno, Takayuki; Souma, Wataru; Watanabe, Tsutomu

    2014-01-01

    In this paper, we investigate the structure and evolution of customer-supplier networks in Japan using a unique dataset that contains information on customer and supplier linkages for more than 500,000 incorporated non-financial firms for the five years from 2008 to 2012. We find, first, that the number of customer links is unequal across firms; the customer link distribution has a power-law tail with an exponent of unity (i.e., it follows Zipf's law). We interpret this as implying that competition among firms to acquire new customers yields winners with a large number of customers, as well as losers with fewer customers. We also show that the shortest path length for any pair of firms is, on average, 4.3 links. Second, we find that link switching is relatively rare. Our estimates indicate that the survival rate per year for customer links is 92 percent and for supplier links 93 percent. Third and finally, we find that firm growth rates tend to be more highly correlated the closer two firms are to each other in a customer-supplier network (i.e., the smaller is the shortest path length for the two firms). This suggests that a non-negligible portion of fluctuations in firm growth stems from the propagation of microeconomic shocks - shocks affecting only a particular firm - through customer-supplier chains.

  19. The Structure and Evolution of Buyer-Supplier Networks

    PubMed Central

    Mizuno, Takayuki; Souma, Wataru; Watanabe, Tsutomu

    2014-01-01

    In this paper, we investigate the structure and evolution of customer-supplier networks in Japan using a unique dataset that contains information on customer and supplier linkages for more than 500,000 incorporated non-financial firms for the five years from 2008 to 2012. We find, first, that the number of customer links is unequal across firms; the customer link distribution has a power-law tail with an exponent of unity (i.e., it follows Zipf's law). We interpret this as implying that competition among firms to acquire new customers yields winners with a large number of customers, as well as losers with fewer customers. We also show that the shortest path length for any pair of firms is, on average, 4.3 links. Second, we find that link switching is relatively rare. Our estimates indicate that the survival rate per year for customer links is 92 percent and for supplier links 93 percent. Third and finally, we find that firm growth rates tend to be more highly correlated the closer two firms are to each other in a customer-supplier network (i.e., the smaller is the shortest path length for the two firms). This suggests that a non-negligible portion of fluctuations in firm growth stems from the propagation of microeconomic shocks – shocks affecting only a particular firm – through customer-supplier chains. PMID:25000368

  20. Mutation rates and the evolution of germline structure

    PubMed Central

    2016-01-01

    Genome sequencing studies of de novo mutations in humans have revealed surprising incongruities in our understanding of human germline mutation. In particular, the mutation rate observed in modern humans is substantially lower than that estimated from calibration against the fossil record, and the paternal age effect in mutations transmitted to offspring is much weaker than expected from our long-standing model of spermatogenesis. I consider possible explanations for these discrepancies, including evolutionary changes in life-history parameters such as generation time and the age of puberty, a possible contribution from undetected post-zygotic mutations early in embryo development, and changes in cellular mutation processes at different stages of the germline. I suggest a revised model of stem-cell state transitions during spermatogenesis, in which ‘dark’ gonial stem cells play a more active role than hitherto envisaged, with a long cycle time undetected in experimental observations. More generally, I argue that the mutation rate and its evolution depend intimately on the structure of the germline in humans and other primates. This article is part of the themed issue ‘Dating species divergences using rocks and clocks'. PMID:27325834

  1. Interactive diversity promotes the evolution of cooperation in structured populations

    NASA Astrophysics Data System (ADS)

    Su, Qi; Li, Aming; Zhou, Lei; Wang, Long

    2016-10-01

    Evolutionary games on networks traditionally assume that each individual adopts an identical strategy to interact with all its neighbors in each generation. Considering the prevalent diversity of individual interactions in the real society, here we propose the concept of interactive diversity, which allows individuals to adopt different strategies against different neighbors in each generation. We investigate the evolution of cooperation based on the edge dynamics rather than the traditional nodal dynamics in networked systems. The results show that, without invoking any other mechanisms, interactive diversity drives the frequency of cooperation to a high level for a wide range of parameters in both well-mixed and structured populations. Even in highly connected populations, cooperation still thrives. When interactive diversity and large topological heterogeneity are combined together, however, in the relaxed social dilemma, cooperation level is lower than that with just one of them, implying that the combination of many promotive factors may make a worse outcome. By an analytical approximation, we get the condition under which interactive diversity provides more advantages for cooperation than traditional evolutionary dynamics does. Numerical simulations validating the approximation are also presented. Our work provides a new line to explore the latent relation between the ubiquitous cooperation and individuals’ distinct responses in different interactions. The presented results suggest that interactive diversity should receive more attention in pursuing mechanisms fostering cooperation.

  2. Structural evolution and petroleum productivity of the Baltic basin

    SciTech Connect

    Ulmishek, G.F. )

    1991-08-01

    The Baltic basin is an oval depression located in the western part of the Russian craton; it occupies the eastern Baltic Sea and adjacent onshore areas. The basin contains more than 5,000 m of sedimentary rocks ranging from latest Proterozoic to Tertiary in age. These rocks consist of four tectonostratigraphic sequences deposited during major tectonic episodes of basin evolution. Principal unconformities separate the sequences. The basin is underlain by a rift probably filled with Upper Proterozoic rocks. Vendian and Lower Cambrian rocks (Baikalian sequence) form two northeast-trending depressions. The principal stage of the basin development was during deposition of a thick Middle Cambrian-Lower Devonian (Caledonian) sequence. This stage was terminated by the most intense deformations in the basin history. The Middle Devonian-Carboniferous (Hercynian) and Permian-Tertiary (Kimmerian-Alpine) tectonic and depositional cycles only slightly modified the basin geometry and left intact the main structural framework of underlying rocks. The petroleum productivity of the basin is related to the Caledonian tectonostratigraphic sequence that contains both source rocks and reservoirs. However, maturation of source rocks, migration of oil, and formation of fields took place mostly during deposition of the Hercynian sequence.

  3. Structure and evolution of the global seafood trade network

    NASA Astrophysics Data System (ADS)

    Gephart, Jessica A.; Pace, Michael L.

    2015-12-01

    The food production system is increasingly global and seafood is among the most highly traded commodities. Global trade can improve food security by providing access to a greater variety of foods, increasing wealth, buffering against local supply shocks, and benefit the environment by increasing overall use efficiency for some resources. However, global trade can also expose countries to external supply shocks and degrade the environment by increasing resource demand and loosening feedbacks between consumers and the impacts of food production. As a result, changes in global food trade can have important implications for both food security and the environmental impacts of production. Measurements of globalization and the environmental impacts of food production require data on both total trade and the origin and destination of traded goods (the network structure). While the global trade network of agricultural and livestock products has previously been studied, seafood products have been excluded. This study describes the structure and evolution of the global seafood trade network, including metrics quantifying the globalization of seafood, shifts in bilateral trade flows, changes in centrality and comparisons of seafood to agricultural and industrial trade networks. From 1994 to 2012 the number of countries trading in the network remained relatively constant, while the number of trade partnerships increased by over 65%. Over this same period, the total quantity of seafood traded increased by 58% and the value increased 85% in real terms. These changes signify the increasing globalization of seafood products. Additionally, the trade patterns in the network indicate: increased influence of Thailand and China, strengthened intraregional trade, and increased exports from South America and Asia. In addition to characterizing these network changes, this study identifies data needs in order to connect seafood trade with environmental impacts and food security outcomes.

  4. Multistage structural evolution of Northern Karakorum (Hunza region, Pakistan)

    NASA Astrophysics Data System (ADS)

    Zanchi, Andrea; Gritti, Damiano

    1996-07-01

    Detailed mapping and structural work in Upper Hunza Valley, Pakistan, have enlightened the tectonics and the structural evolution of the sedimentary cover of Northern Karakorum. This includes the Northern Sedimentary Belt (NSB) with the Guhjal and Sost Units (Permian-Cretaceous), cropping out north of the Karakorum Axial Batholith (KAB); the NSB is bounded to the north by the Misgar Unit, consisting of slates of unknown age. In the Sost Unit a mid-Cretaceous deformed belt is sealed with a strong angular unconformity by the Late Cretaceous formations. Folds within the mid-Cretaceous belt possibly indicate north-vergent transport. Stacking of NE- to N-vergent thrusts sheets postdates the deposition of Cretaceous sediments, which are largely included within tectonic slices developed along the southern flank of the Sost stack. The southern part of the stack is in turn intruded by the Palaeogene Kuk pluton belonging to the Batura Unit of the KAB. S- to SSE-vergent thrusting was successively active, stacking steep north-dipping thrust sheets along the northern side of the Sost Unit, forming a complex antiformal stack, well exposed around Sost. High angle pure dip-slip reverse and oblique dextral motions are recorded by fault-slip data and calc-mylonites along major faults, forming a transpressive fault zone close to the contact between the Sost and Misgar Units. During this stage, the Misgar Unit was thrusted southward above the Sost Unit along the Northern Fault. Prosecution of dextral motion was also active afterwards along the boundary between the two units. The importance of wrench tectonics is also indicated by widespread activation of E-W sinistral strike-slip faults in the whole study area, generally moving along pre-existent fault planes.

  5. Structural Evolution of the Incipient Okavango Rift Zone, NW Botswana

    NASA Astrophysics Data System (ADS)

    Atekwana, E. A.; Kinabo, B. D.; Modisi, M. P.; Hogan, J. P.; Wheaton, D. D.

    2005-05-01

    strongly influenced by the position of these pre-existing faults. Evidence of fault linkage is seen along some of the faults. Linked segments of faults are well defined and some are > 200 km long. We suggest from this result that fault linkage and propagation occurred very early and prior to significant basin development. We conclude that basement fabric seems to be a controlling factor at least in the early stages of basin architecture and structural evolution of ORZ.

  6. Evolution of cosmic structures in different environments in the quasispherical Szekeres model

    SciTech Connect

    Bolejko, Krzysztof

    2007-02-15

    This paper investigates evolution of cosmic structures in different environments. For this purpose the quasispherical Szekeres model is employed. The Szekeres model is an exact solution of the Einstein field equations within which it is possible to describe more than one structure. In this way investigations of the evolution of the cosmic structures presented here can be freed from such assumptions as a small value of the density contrast. Also, studying the evolution of two or three structures within one framework enables us to follow the interaction between these structures and their impact on the evolution. Main findings include a conclusion that small voids surrounded by large overdensities evolve slower than large, isolated voids do. On the other hand, large voids enhance the evolution of adjacent galaxy superclusters which evolve much faster than isolated superclusters.

  7. Paleostress maps and structural evolution of the Pontides

    NASA Astrophysics Data System (ADS)

    Hippolyte, Jean-Claude; Espurt, Nicolas; Kaymakci, Nuretdin; Sangu, Ercan; Müller, Carla

    2014-05-01

    In the frame of DARIUS programme we worked from 2010 to 2012 in the central and eastern Pontides. We aimed at understanding the timing and the characteristics of the extensional and compressional episodes that occurred along the southern margin of the Black Sea (Pontides belt). We used stress inversion technique (Angelier's softwares) for analyzing fault kinematics and characterizing the successive tectonic episodes in terms of paleostresses. The age of the tectonic episodes was constrained by combining structural analysis with nannoplankton dating of the sedimentary units. 1) In the central Pontides, structural analysis shows that deposition of the Barremian-Albian terrigenous sediments of the "syn-rift" Çaglayan Group was controlled by large normal faults under an ESE-WNW extension probably related to the SE-directed opening of the western Black Sea Basin. In contrast, the Coniacian-Santonian and the Paleocene "post-rift" sequences were deposited under NE-SW extension probably related to the SW-directed opening of the eastern Black Sea Basin. At the beginning of Eocene the stress regime changed from extensional to compressional which resulted in the formation of syn-compressional basins. In order to illustrate the two-dimensional structural evolution of the central Pontides we built a NNE-trending 75 km long balanced and restored cross section between Boyabat and Sinop cities. The section is constrained by 183 sites of field data, 5 seismic lines and 8 wells. We model the Pontides as a bi-vergent structure resulting from the structural inversion of Cretaceous normal faults of the southern Black Sea margin. Apatite fission track data along this section suggest that inversion started in the earliest Eocene (~55 Ma). Eocene-Miocene shortening reached ~28 km. 2) In the eastern Pontides, an early Campanian to late Paleocene NW-SE extension was followed by three successive compressional events. A Paleocene to early Eocene NW-SE compression resulted in the formation of

  8. Structure and evolution of high-mass stellar mergers

    NASA Astrophysics Data System (ADS)

    Glebbeek, Evert; Gaburov, Evghenii; Portegies Zwart, Simon; Pols, Onno R.

    2013-10-01

    In young dense clusters repeated collisions between massive stars may lead to the formation of a very massive star (above 100 M⊙). In the past, the study of the long-term evolution of merger remnants has mostly focused on collisions between low-mass stars (up to about 2 M⊙) in the context of blue-straggler formation. The evolution of collision products of more massive stars has not been as thoroughly investigated. In this paper, we study the long-term evolution of a number of stellar mergers formed by the head-on collision of a primary star with a mass of 5-40 M⊙ with a lower mass star at three points in its evolution in order to better understand their evolution. We use smooth particle hydrodynamics calculations to model the collision between the stars. The outcome of this calculation is reduced to one dimension and imported into a stellar evolution code. We follow the subsequent evolution of the collision product through the main sequence at least until the onset of helium burning. We find that little hydrogen is mixed into the core of the collision products, in agreement with previous studies of collisions between low-mass stars. For collisions involving evolved stars, we find that during the merger the surface nitrogen abundance can be strongly enhanced. The evolution of most of the collision products proceeds analogously to that of normal stars with the same mass, but with a larger radius and luminosity. However, the evolution of collision products that form with a hydrogen-depleted core is markedly different from that of normal stars with the same mass. They undergo a long-lived period of hydrogen-shell burning close to the main-sequence band in the Hertzsprung-Russell diagram and spend the initial part of core-helium burning as compact blue supergiants.

  9. Structure and evolution of the magnetochrome domains: no longer alone

    PubMed Central

    Arnoux, Pascal; Siponen, Marina I.; Lefèvre, Christopher T.; Ginet, Nicolas; Pignol, David

    2014-01-01

    Magnetotactic bacteria (MTB) can swim along Earth's magnetic field lines, thanks to the alignment of dedicated cytoplasmic organelles. These organelles, termed magnetosomes, are proteolipidic vesicles filled by a 35–120 nm crystal of either magnetite or greigite. The formation and alignment of magnetosomes are mediated by a group of specific genes, the mam genes, encoding the magnetosome-associated proteins. The whole process of magnetosome biogenesis can be divided into four sequential steps; (i) cytoplasmic membrane invagination, (ii) magnetosomes alignment, (iii) iron crystal nucleation and (iv) species-dependent mineral size and shape control. Since both magnetite and greigite are a mix of iron (III) and iron (II), iron redox state management within the magnetosome vesicle is a key issue. Recently, studies have started pointing out the importance of a MTB-specific c-type cytochrome domain found in several magnetosome-associated proteins (MamE, P, T, and X). This magnetochrome (MCR) domain is almost always found in tandem, and this tandem is either found alone (MamT), in combination with a PDZ domain (MamP), a domain of unknown function (MamX) or with a trypsin combined to one or two PDZ domains (MamE). By taking advantage of new genomic data available on MTB and a recent structural study of MamP, which helped define the MCR domain boundaries, we attempt to retrace the evolutionary history within and between the different MCR-containing proteins. We propose that the observed tandem repeat of MCR is the result of a convergent evolution and attempt to explain why this domain is rarely found alone. PMID:24723915

  10. Structural evolution in mechanically alloyed Al-Fe powders

    SciTech Connect

    Mukhopadhyay, D.K.; Suryanarayana, C.; Froes, F.H.

    1995-08-01

    The structural evolution in mechanically alloyed binary aluminum-iron powder mixtures containing 1, 4, 7.3, 10.7, and 25 at pct Fe was investigated using X-ray diffraction (XRD) and electron microscopic techniques. The constitution (number and identity of phases present), microstructure (crystal size, particle size), and transformation behavior of the powders on annealing were studied. The solid solubility of Fe in Al has been extended up to at least 4.5 at. pct, which is close to that observed using rapid solidification (RS) (4.4 at. pct), compared with the equilibrium value of 0.025 at. pct Fe at room temperature. Nanometer-sized grains were observed in as-milled crystalline powders in all compositions. Increasing the ball-to-powder weight ratio (BPR) resulted in a faster rate of decrease of crystal size. A fully amorphous phase was obtained in the Al-25 at. pct Fe composition, and a mixed amorphous phase plus solid solution of Fe in Al was developed in the Al-10.7 at. pct Fe alloy, agreeing well with the predictions made using the semiempirical Miedema model. Heat treatment of the mechanically alloyed powders containing the supersaturated solid solution or the amorphous phase resulted in the formation of the Al{sub 3}Fe intermetallic in all but the Al-25 at. pct Fe powders. In the Al-25 at. pct Fe powder, formation of nanocrystalline Al{sub 5}Fe{sub 2} was observed directly by milling. Electron microscope studies of the shock-consolidated mechanically alloyed Al-10.7 and 25 at. pct Fe powders indicated that nanometer-sized grains were retained after compaction.

  11. Food web structure and the evolution of ecological communities

    NASA Astrophysics Data System (ADS)

    Quince, Christopher; Higgs, Paul G.; McKane, Alan J.

    Simulations of the coevolution of many interacting species are performed using the Webworld model. The model has a realistic set of predator-prey equations that describe the population dynamics of the species for any structure of the food web. The equations account for competition between species for the same resources, and for the diet choice of predators between alternative prey according to an evolutionarily stable strategy. The set of species present undergoes long-term evolution d ue to speciation and extinction events. We summarize results obtained on the macro-evolutionary dynamics of speciations and extinctions, and on the statistical properties of the food webs that are generated by the model. Simulations begin from small numbers of species and build up to larger webs with relatively constant species number on average. The rate of origination and extinction of species are relatively high, but remain roughly balanced throughout the simulations. When a 'parent' species undergoes sp eciation, the 'child' species usually adds to the same trophic level as the parent. The chance of the child species surviving is significantly higher if the parent is on the second or third trophic level than if it is on the first level, most likely due to a wider choice of possible prey for species on higher levels. Addition of a new species sometimes causes extinction of existing species. The parent species has a high probability of extinction because it has strong competition with the new species. Non-pa rental competitors of the new species also have a significantly higher extinction probability than average, as do prey of the new species. Predators of the new species are less likely than average to become extinct.

  12. Understanding the Structure and Evolution of Nearby Disk Galaxies

    NASA Astrophysics Data System (ADS)

    Zheng, Zheng

    2014-01-01

    In order to understand the structure and evolution of disk galaxies, we studied the stellar and gaseous components as well as the star formation rate in nearby disk galaxies. We used PS1 medium deep survey images to derive five-band (grizy) surface brightness profiles down to 30 ABmag/arcsec^2 for about 700 galaxies. From these stellar mass and mass-to-light ratio radial profiles are derived. The stellar mass radial profiles tend to bend-up at large radii, this often traces an extended old stellar population. The mass-to-light ratio profiles tend to rise outside the r25 radii. We also find a larger fraction of up-bending surface brightness profiles than Polen & Trujillo (2006). This may be because their sample is biased towards low surface brightness galaxies. We used HIPASS data as well as VLA HI 21cm data to study the gas component and dynamics of disk galaxies. We used the GALEX UV images to study the star formation of a HI-selected star-forming sample of about 400 galaxies, compiling a database of FUV and NUV radial profiles and related parameters. We used this to study the star forming efficiency (SFE, star formation rate per unit area divided by gas surface mass density) of the sample galaxies. We found that the UV based SFE has a tighter relationship with HI mass than an H_alpha based SFE as typically used in previous studies and the UV SFE is flat across wide range of stellar mass. We constructed a simple model to predict the distribution of interstellar medium and star formation rate in an equilibrium disk with constant two-fluid Toomre Q. This model can reproduces the SFE relations we derived.

  13. Population structure and evolution of pathogenicity of Yersinia pseudotuberculosis.

    PubMed

    Ch'ng, Shear Lane; Octavia, Sophie; Xia, Qiuyu; Duong, An; Tanaka, Mark M; Fukushima, Hiroshi; Lan, Ruiting

    2011-02-01

    Yersinia pseudotuberculosis is an enteric human pathogen but is widespread in the environment. Pathogenicity is determined by a number of virulence factors, including the virulence plasmid pYV, the high-pathogenicity island (HPI), and the Y. pseudotuberculosis-derived mitogen (YPM), a superantigen. The presence of the 3 virulence factors varies among Y. pseudotuberculosis isolates. We developed a multilocus sequence typing (MLST) scheme to address the population structure of Y. pseudotuberculosis and the evolution of its pathogenicity. The seven housekeeping genes selected for MLST were mdh, recA, sucA, fumC, aroC, pgi, and gyrB. An MLST analysis of 83 isolates of Y. pseudotuberculosis, representing 19 different serotypes and six different genetic groups, identified 61 sequence types (STs) and 12 clonal complexes. Out of 26 allelic changes that occurred in the 12 clonal complexes, 13 were mutational events while 13 were recombinational events, indicating that recombination and mutation contributed equally to the diversification of the clonal complexes. The isolates were separated into 2 distinctive clusters, A and B. Cluster A is the major cluster, with 53 STs (including Y. pestis strains), and is distributed worldwide, while cluster B is restricted to the Far East. The YPM gene is widely distributed on the phylogenetic tree, with ypmA in cluster A and ypmB in cluster B. pYV is present in cluster A only but is sporadically absent in some cluster A isolates. In contrast, an HPI is present only in a limited number of lineages and must be gained by lateral transfer. Three STs carry all 3 virulence factors and can be regarded as high-pathogenicity clones. Isolates from the same ST may not carry all 3 virulence factors, indicating frequent gain or loss of these factors. The differences in pathogenicity among Y. pseudotuberculosis strains are likely due to the variable presence and instability of the virulence factors.

  14. Assessment of molecular diversity and population structure of the Ethiopian sorghum [Sorghum bicolor L. (Moench)] germplasm collection maintained by the USDA-ARS National Plant Germplasm System using SSR markers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The genetic diversity and population structure present in the Ethiopian sorghum collection maintained at the USDA-ARS National Plant Germplasm System (NPGS) has not been studied. In addition, 83% of the accessions in the Ethiopian collection lack passport information which has constrained their eval...

  15. Three-dimensional structure and evolution of the Sierra Barrier Jet: A CalWater case study from 14-16 February 2011

    NASA Astrophysics Data System (ADS)

    Kingsmill, D.; Neiman, P. J.; Yuter, S. E.; Hughes, M. R.; Moore, B.

    2011-12-01

    Atmospheric rivers (ARs) are narrow corridors of enhanced water vapor transport within extratropical cyclones. Although focused research during the last few years has yielded quantitative linkages between ARs and both the regional water supply and extreme precipitation events, questions remain regarding the modification and redistribution of precipitation in ARs by California's coastal mountains and Sierra Nevada. For example, rain rates are strongly correlated with the magnitude of the cross-barrier flow (and hence water vapor flux and uplift) at upper windward slope locations. However, at lowland locations they are poorly correlated due to the influence of low-level barrier airflows within the atmosphere. The most important of these barrier airflows is likely the Sierra Barrier Jet (SBJ), which is a dominant feature in Sierra Nevada storms. Winds reaching the mountain range often are partially stalled and, in part, diverted along the range rather than directed up and over. Knowledge of the impact of the resulting terrain-parallel barrier jets on orographic storms remains elusive. An incomplete understanding of the physics of and joint interactions between ARs and blocked flows limits our ability to identify the factors affecting the distribution and intensity of precipitation in California's Central Valley and along the Sierra's windward slopes. This study addresses these issues. The most recent CalWater field campaign took place in northern California during the winter of 2011. A wide array of aerosol, cloud physics and meteorological measurements were collected. Documentation of SBJs and associated ARs was facilitated by a suite of scanning and profiling Doppler radars (wind retrievals and precipitation structure), balloon soundings (in situ thermodynamic and wind measurements) and GPS receivers (integrated water vapor retrievals). This presentation will provide an overview of the three-dimensional structure and evolution of the SBJ and AR observed during 14

  16. Real Time Pore Structure Evolution during Olivine Mineral Carbonation

    NASA Astrophysics Data System (ADS)

    Zhu, W.; Fusseis, F.; Lisabeth, H. P.; Xiao, X.

    2014-12-01

    Aqueous carbonation of ultramafic rocks has been proposed as a promising method for long-term, secure sequestration of carbon dioxide. While chemical kinetics data indicate that carbonation reaction in olivine is one of the fastest among the mg-bearing minerals, in practice, the factors that limit the extent and rate of carbonation in ultramafic rocks are fluid supply and flux. On the one hand, reaction products could produce passivating layer that prohibits further reactions. On the other hand, the increases in solid volume during carbonation could lead to cracking and create new fluid paths. Whether carbonation in ultramafic rocks is self-limiting or self-sustaining has been hotly debated. Experimental evidence of precipitation of reaction products during olivine carbonation was reported. To date, reaction-driven cracking has not been observed. In this paper, we present the first real-time pore structure evolution data using the x-ray synchrotron microtomography. Sodium bicarbonate (NaHCO3) solution was injected into porous olivine aggregates and in-situ pore structure change during olivine carbonation at a constant confining pressure (12 MPa) and a temperature of 200oC was captured at 30 min. interval for ~160 hours. Shortly after the experiment started, filling-in of the existing pores by precipitation of reaction products was visible. The size of the in-fills kept increasing as reactions continued. After ~48 hours, cracking around the in-fill materials became visible. After ~60 hours, these cracks started to show a clear polygonal pattern, similar to the crack patterns usually seen on the surface of drying mud. After ~72 hours, some of the cracks coalesced into large fractures that cut-through the olivine aggregates. New fractures continued to develop and at the end of the experiment, the sample was completely disintegrated by these fractures. We also conducted nanotomography experiments on a sub-volume of the reacted olivine aggregate. Orthogonal sets of

  17. Construction of a chimeric ArsA-ArsB protein for overexpression of the oxyanion-translocating ATPase.

    PubMed

    Dou, D; Owolabi, J B; Dey, S; Rosen, B P

    1992-12-25

    Resistance to toxic oxyanions of arsenic and antimony in Escherichia coli is conferred by the conjugative R-factor R773, which encodes an ATP-driven anion extrusion pump. The ars operon is composed of three structural genes, arsA, arsB, and arsC. Although transcribed as a single unit, the three genes are differentially expressed as a result of translational differences, such that the ArsA and ArsC proteins are produced in high amounts relative to the amount of ArsB protein made. Consequently, biochemical characterization of the ArsB protein, which is an integral membrane protein containing the anion-conducting pathway, has been limited, precluding studies of the mechanism of this oxyanion pump. To overexpress the arsB gene, a series of changes were made. First, the second codon, an infrequently used leucine codon, was changed to a more frequently utilized codon. Second, a GC-rich stem-loop (delta G = -17 kcal/mol) between the third and twelfth codons was destabilized by changing several of the bases of the base-paired region. Third, the re-engineered arsB gene was fused 3' in frame to the first 1458 base pairs of the arsA gene to encode a 914-residue chimeric protein (486 residues of the ArsA protein plus 428 residues of the mutated ArsB protein) containing the entire re-engineered ArsB sequence except for the initiating methionine. The ArsA-ArsB chimera has been overexpressed at approximately 15-20% of the total membrane proteins. Cells producing the chimeric ArsA-ArsB protein with an arsA gene in trans excluded 73AsO2- from cells, demonstrating that the chimera can function as a component of the oxyanion-translocating ATPase.

  18. Influence of N2 partial pressure on structural and microhardness properties of TiN/ZrN multilayers deposited by Ar/N2 vacuum arc discharge

    NASA Astrophysics Data System (ADS)

    Naddaf, M.; Abdallah, B.; Ahmad, M.; A-Kharroub, M.

    2016-08-01

    The influence of N2 partial pressure on structural, mechanical and wetting properties of multilayered TiN/ZrN thin films deposited on silicon substrates by vacuum arc discharge of (N2 + Ar) gas mixtures is investigated. X-ray diffraction (XRD) results show that the average texturing coefficient of (1 1 1) orientation and the grain size of both TiN and ZrN individual layers increase with increasing the N2 partial pressure. The Rutherford back scattering (RBS) measurements and analysis reveal that incorporation of the nitrogen in the film increases with increasing the N2 partial pressure and both TiN and ZrN individual layers have a nitrogen over-stoichiometry for N2 partial pressure ⩾50%. The change in the film micro-hardness is correlated to the changes in crystallographic texture, grain size, stoichiometry and the residual stress in the film as a function of the N2 partial pressure. In particular, stoichiometry of ZrN and TiN individual is found to play the vital role in determining the multilayer hardness. The multilayer film deposited at N2 partial pressure of 25% has the best stoichiometric ratio of both TiN and ZrN layers and the highest micro-hardness of about 32 GPa. In addition, water contact angle (WCA) measurements and analysis show a decrease in the work of adhesion on increasing the N2 partial pressure.

  19. Paleozoic accretionary orogenesis in the eastern Beishan orogen: constraints from zircon U-Pb and 40Ar/39Ar geochronology

    NASA Astrophysics Data System (ADS)

    Ao, Songjian; Xiao, Wenjiao; Windley, Brian; Mao, Qigui

    2016-04-01

    The continental growth mechanism of the Altaids in Central Asia is still in controversy between models of continuous subduction-accretion versus punctuated accretion by closure of multiple oceanic basins. The Beishan orogenic belt, located in the southern Altaids, is a natural laboratory to address this controversy. Key questions that are heavily debated are: the closure time and subduction polarity of former oceans, the emplacement time of ophiolites, and the styles of accretion and collision. This paper reports new structural data, zircon ages and Ar-Ar dates from the eastern Beishan Orogen that provide information on the accretion process and tectonic affiliation of various terranes. Our geochronological and structural results show that the younging direction of accretion was northwards and the subduction zone dipped southwards under the northern margin of the Shuangyingshan micro-continent. This long-lived and continuous accretion process formed the Hanshan accretionary prism. Our field investigations show that the emplacement of the Xiaohuangshan ophiolite was controlled by oceanic crust subduction beneath the forearc accretionary prism of the Shuangyingshan-Mazongshan composite arc to the south. Moreover, we address the age and terrane affiliation of lithologies in the eastern Beishan orogen through detrital zircon geochronology of meta-sedimentary rocks. We provide new information on the ages, subduction polarities, and affiliation of constituent structural units, as well as a new model of tectonic evolution of the eastern Beishan orogen. The accretionary processes and crustal growth of Central Asia were the result of multiple sequences of accretion and collision of manifold terranes. Reference: Ao, S.J., Xiao, W., Windley, B.F., Mao, Q., Han, C., Zhang, J.e., Yang, L., Geng, J., Paleozoic accretionary orogenesis in the eastern Beishan orogen: Constraints from zircon U-Pb and 40Ar/39Ar geochronology. Gondwana Research, doi: http://dx.doi.org/10.1016/j

  20. Models of the Protocellular Structures, Functions and Evolution

    NASA Technical Reports Server (NTRS)

    Pohorille, Andrew; New, Michael; Keefe, Anthony; Szostak, Jack W.; Lanyi, Janos F.; DeVincenzi, Donald L. (Technical Monitor)

    2000-01-01

    In the absence of extinct or extant record of protocells, the most direct way to test our understanding of the origin of cellular life is to construct laboratory models that capture important features of protocellular systems. Such efforts are currently underway in a collaborative project between NASA-Ames, Harvard medical School and University of California. They are accompanied by computational studies aimed at explaining self-organization of simple molecules into ordered structures. The centerpiece of this project is a method for the in vitro evolution of protein enzymes toward arbitrary catalytic targets. A similar approach has already been developed for nucleic acids: First, a very large population of candidate molecules is generated using a random synthetic approach. Next, the small numbers of molecules that can accomplish the desired task are selected. These molecules are next vastly multiplied using the polymerase chain reaction. A mutagenic approach, in which the sequences of selected molecules are randomly altered, can yield further improvements in performance or alterations of specificities. Unfortunately, the catalytic potential of nucleic acids is rather limited. Proteins are more catalytically capable but cannot be directly amplified. In the new technique, this problem is circumvented by covalently linking each protein of the initial, diverse, pool to the RNA sequence that codes for it. Then, selection is performed on the proteins, but the nucleic acids are replicated. To date, we have obtained "a proof of concept" by evolving simple, novel proteins capable of selectively binding adenosine tri-phosphate (ATP). Our next goal is to create an enzyme that can phosphorylate amino acids and another to catalyze the formation of peptide bonds in the absence of nucleic acid templates. This latter reaction does not take place in contemporary cells. once developed, these enzymes will be encapsulated in liposomes so that they will function in a simulated cellular

  1. Evolution of Anabaenopeptin Peptide Structural Variability in the Cyanobacterium Planktothrix

    PubMed Central

    Entfellner, Elisabeth; Frei, Mark; Christiansen, Guntram; Deng, Li; Blom, Jochen; Kurmayer, Rainer

    2017-01-01

    , Tyrosine, and Lysine in the exocyclic position of the AP-molecule. The increased structural diversity resulted from the evolution of apnA A1 genotypes through a small number of positively selected point mutations that occurred repeatedly and independently from phylogenetic association. PMID:28261178

  2. The Campi Flegrei Deep Drilling Project (CFDDP): New insight on caldera structure, evolution and hazard implications for the Naples area (Southern Italy)

    NASA Astrophysics Data System (ADS)

    De Natale, Giuseppe; Troise, Claudia; Mark, Darren; Mormone, Angela; Piochi, Monica; Di Vito, Mauro A.; Isaia, Roberto; Carlino, Stefano; Barra, Diana; Somma, Renato

    2016-12-01

    The 501 m deep hole of the Campi Flegrei Deep Drilling Project, located west of the Naples metropolitan area and inside the Campi Flegrei caldera, gives new insight to reconstruct the volcano-tectonic evolution of this highly populated volcano. It is one of the highest risk volcanic areas in the world, but its tectonic structure, eruptive history, and size of the largest eruptions are intensely debated in the literature. New stratigraphic and 40Ar/39Ar geochronological dating allow us to determine, for the first time, the age of intracaldera deposits belonging to the two highest magnitude caldera-forming eruptions (i.e., Campanian Ignimbrite, CI, 39 ka, and Neapolitan Yellow Tuff, NYT, 14.9 ka) and to estimate the amount of collapse. Tuffs from 439 m of depth yield the first 40Ar/39Ar age of ca. 39 ka within the caldera, consistent with the CI. Volcanic rocks from the NYT were, moreover, detected between 250 and 160 m. Our findings highlight: (i) a reduction of the area affected by caldera collapse, which appears to not include the city of Naples; (ii) a small volume of the infilling caldera deposits, particularly for the CI, and (iii) the need for reassessment of the collapse amounts and mechanisms related to larger eruptions. Our results also imply a revaluation of volcanic risk for the eastern caldera area, including the city of Naples. The results of this study point out that large calderas are characterized by complex collapse mechanisms and dynamics, whose understanding needs more robust constraints, which can be obtained from scientific drilling.

  3. Shadowed off-axis production of Ge nanoparticles in Ar gas atmosphere by pulsed laser deposition: Morphological, structural and charge trapping properties

    NASA Astrophysics Data System (ADS)

    Martín-Sánchez, J.; Capan, I.; Chahboun, A.; Pinto, S. R. C.; Vieira, E. M. F.; Rolo, A. G.; Gomes, M. J. M.

    2013-09-01

    In this work, a novel customized shadowed off-axis deposition set-up is used to perform an original study of Ge nanoparticles (NPs) formation in an inert Ar gas atmosphere by pulsed laser deposition at room temperature varying systematically the background Ar gas pressure (Pbase(Ar)), target-substrate distance (d) and laser repetition rate (f). The influence of these parameters on the final NPs size distributions is investigated and a fairly uniform droplets-free and non-agglomerated NPs distribution with average height = 2.8 ± 0.6 nm is obtained for optimized experimental conditions (Pbase(Ar) = 1 mbar; d = 3 cm; f = 10 Hz) with a fine control in the NPs density (from 3.2 × 109 cm-2 to 1.1 × 1011 cm-2). The crystalline quality of as-deposited NPs investigations demonstrate a strong dependence with the Ar gas pressure and a crystalline to amorphous phase volume fraction χc > 50% is found for Pbase(Ar) = 2 mbar. The NPs functionality for charge trapping applications has been successfully demonstrated by capacitance-voltage (C-V) electrical measurements.

  4. A comparative study of the structure and bonding in heavier pnictinidene complexes [(ArE)M(CO)n] (E = As, Sb and Bi; M = Cr, Mo, W and Fe).

    PubMed

    Vránová, Iva; Kremláček, Vít; Erben, Milan; Turek, Jan; Jambor, Roman; Růžička, Aleš; Alonso, Mercedes; Dostál, Libor

    2017-03-14

    N,C,N-Chelated pnictinidenes ArE [where E = As (1), Sb (2) or Bi (3); Ar = C6H3-2,6-(CH[double bond, length as m-dash]Nt-Bu)2] were used as ligands for the coordination of transition metal carbonyls. Thus, the reaction of 1-3 with [M(CO)5THF] (where M = Cr, W) or [Mo(CO)5(Me3N)] gave complexes [(ArE)M(CO)5] [where E = As and M = Cr (1a), Mo (1b), W (1c); E = Sb and M = Cr (2a), Mo (2b), W (2c); E = Bi and M = Cr (3a), Mo (3b), W (3c)]. Analogously, the treatment of 1-3 with [Fe2(CO)9] resulted in the formation of the complexes [(ArE)Fe(CO)4] [where E = As (1d), Sb (2d) or Bi (3d)]. All compounds were characterized by (1)H and (13)C NMR spectroscopy, Raman, IR and UV-Vis spectroscopy. The molecular structures of the majority of the compounds (except 1b and 1c) were also determined by the single-crystal X-ray diffraction analysis. Furthermore, the structure and bonding of the title compounds have also been thoroughly investigated using a computational approach.

  5. Differential evolution: crystal structure determination of a triclinic polymorph of adipamide from powder diffraction data.

    PubMed

    Seaton, Colin C; Tremayne, Maryjane

    2002-04-21

    The crystal structure of a previously unknown triclinic polymorph of adipamide has been solved from laboratory X-ray powder diffraction data using a new direct space global optimisation method based on differential evolution.

  6. 40Ar/39Ar and K-Ar data bearing on the metamorphic and tectonic history of western New England.

    USGS Publications Warehouse

    Sutter, J.F.; Ratcliffe, N.M.; Mukasa, S.B.

    1985-01-01

    40Ar/39Ar ages of coexisting biotite and hornblende from Proterozoic Y gneisses of the Berkshire and Green Mt massifs, as well as 40Ar/39Ar and K/Ar mineral and whole-rock ages from Palaeozoic metamorphic rocks, suggest that the thermal peaks for the dominant metamorphic recrystallization in western New England occurred 465 + or - 5 m.y. (Taconian). 40Ar/39Ar age data from a poorly-defined terrain along the eastern strip of the area suggests that the area has been retrograded during a metamorphism that peaked at least 376 + or - 5 m.y. (Acadian). Available age and petrological data from western New England indicate the presence of at least three separate metamorphic-structure domains of Taconic age: 1) a small area of relict high-P and low-T metamorphism, 2) a broad area of normal Barrovian metamorphism from chlorite to garnet grade characterized by a gentle metamorphic gradient and, 3) a rather narrow belt of steep-gradient, Barrovian series metamorphic rocks. Areas of maximum metamorphic intensity within the last domain coincide with areas of maximum crustal thickening in the later stage of Taconic orogeny. -L.di H

  7. The concurrent evolution of cooperation and the population structures that support it.

    PubMed

    Powers, Simon T; Penn, Alexandra S; Watson, Richard A

    2011-06-01

    The evolution of cooperation often depends upon population structure, yet nearly all models of cooperation implicitly assume that this structure remains static. This is a simplifying assumption, because most organisms possess genetic traits that affect their population structure to some degree. These traits, such as a group size preference, affect the relatedness of interacting individuals and hence the opportunity for kin or group selection. We argue that models that do not explicitly consider their evolution cannot provide a satisfactory account of the origin of cooperation, because they cannot explain how the prerequisite population structures arise. Here, we consider the concurrent evolution of genetic traits that affect population structure, with those that affect social behavior. We show that not only does population structure drive social evolution, as in previous models, but that the opportunity for cooperation can in turn drive the creation of population structures that support it. This occurs through the generation of linkage disequilibrium between socio-behavioral and population-structuring traits, such that direct kin selection on social behavior creates indirect selection pressure on population structure. We illustrate our argument with a model of the concurrent evolution of group size preference and social behavior.

  8. Shallow nitrogen ion implantation: Evolution of chemical state and defect structure in titanium

    NASA Astrophysics Data System (ADS)

    Manojkumar, P. A.; Chirayath, V. A.; Balamurugan, A. K.; Krishna, Nanda Gopala; Ilango, S.; Kamruddin, M.; Amarendra, G.; Tyagi, A. K.; Raj, Baldev

    2016-09-01

    Evolution of chemical states and defect structure in titanium during low energy nitrogen ion implantation by Plasma Immersion Ion Implantation (PIII) process is studied. The underlying process of chemical state evolution is investigated using secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The implantation induced defect structure evolution as a function of dose is elucidated using variable energy positron annihilation Doppler broadening spectroscopy (PAS) and the results were corroborated with chemical state. Formation of 3 layers of defect state was modeled to fit PAS results.

  9. Structural limits for evolutive capacities in complex molecular systems.

    PubMed

    Bergareche, A M; Ostolaza, J F

    1990-01-01

    The possibilities of evolution for a system with and without a code of translation from nucleic acids into proteins are evaluated. Our interest is mainly centred on the enzymatic RNA case since this molecule has, at the same time, reproductive and functional properties. After scanning the evolutive capacities of the enzymatic RNAs, including the possibility to play the role of "synthetase" which would match nucleic acids with amino acids as a transition step towards a code, we will try to show that due to their own functional limitative factors, the matching system (code) is necessary. This would be the only way to transform the formal complexity--complexity which has not entered into action before the translation process--into functional information to drive the instructive self-reproductive process. Once this stage is reached, the system could evolve without a limit.

  10. Structural Relationship Between Piton des Neiges and Piton de la Fournaise Volcanoes: New K-Ar Data and Geomorphological Study of the Takamaka Region (East Reunion Island, Indian Ocean)

    NASA Astrophysics Data System (ADS)

    Salvany, T.; Lahitte, P.; Gillot, P.; Kluska, J.

    2007-12-01

    Reunion Island (Indian ocean) is a volcanic complex resulting from hotspot activity composed of three coalescent eruptive systems. The first subaerial volcano (la Montagne massif), which only outcrops in the NW part has been dated between 2.2 and 1.8 Ma (McDougall, 1971). After a major flank collapse of this volcano (Gillot et al., 1994), Piton des Neiges (PNv) edificated from 1.2 Ma to 30 ka (McDougall., 1971; Gillot et al.,1982). then, Piton de la Fournaise volcano (PFv), one of the most active on Earth, started its activity about 530 kyr ago (Gillot et al., 1989; 1990) and was affected by 3 eastward flank collapses (Gillot et al., 1994). Its present complex morphology is characterized by large scale erosional depressions, (Cirques) cut in the volcanic structures, such as Cilaos, Mafate or Salazie in PNv, Grand Bassin between the two volcanoes, and Grand Pays in PFv. Due to the tropical conditions, deeply incised valleys are present throughout the island. The eastern part of the island (Takamaka area), where we show that products of both PNv and PFv overlap, is one of the most rainy place in the world. It is deeply incised and has been highly eroded during the coeval building stages of PFv and PNv since at least 530 kyr. In order to constrain the relationship between the PNv and PFv volcanoes and to characterise the morphological evolution of this area, we realized a new geochronological study of the different massifs based on the accurate K- Ar technique devoted to the dating of very young rocks (Cassignol technique; Gillot et Cornette, 1986). A preserved structure between the two volcano, Morne de l'Etang, is dated between 1.36 +/- 0.02 Ma, which is older than the primary known activity of Piton des Neiges (about 1.2 Ma; McDougall, 1971), to 0.97 +/- 0.02 Ma. It may either correspond to a remnant and older part of PNv or it belongs to the Proto Fournaise 'les Alizés' volcano', which existence is still debated. Our analysis also emphasizes the fact that PFv

  11. Deciphering the brittle evolution of SW Norway through a combined structural, mineralogical and geochronological approach

    NASA Astrophysics Data System (ADS)

    Scheiber, Thomas; Viola, Giulio; Fredin, Ola; Zwingmann, Horst; Wilkinson, Camilla Maya; Ganerød, Morgan

    2016-04-01

    SW Norway has experienced a complex brittle history after cessation of the Caledonian orogeny, and the recent discoveries of major hydrocarbon reserves in heavily fractured and weathered basement offshore SW Norway has triggered a renewed interest in understanding this complex tectonic evolution. In this contribution we present results from a multidisciplinary study combining lineament analysis, field work, paleo-stress inversion, mineralogical characterization and radiometric dating in the Bømlo area of SW Norway in order to develop a tectonic model for the brittle evolution of this important region. The study area mainly consists of the Rolvsnes granodiorite (U-Pb zircon age of ca. 466 Ma), which is devoid of penetrative ductile deformation features. The first identified brittle faults are muscovite-bearing top-to-the-NNW thrusts and E-W striking dextral strike-slip faults decorated with stretched biotite. These are mechanically compatible and are assigned to the same NNW-SSE transpressional regime. Ar-Ar muscovite and biotite dates of ca. 450 Ma (Late Ordovician) indicate fault activity in the course of a Taconian-equivalent orogenic event. During the subsequent Silurian Laurentia-Baltica collision variably oriented, lower-grade chlorite and epidote-coated faults formed in response to a ENE-WSW compressional stress regime. A large number of mainly N-S striking normal faults consist of variably thick fault gouge cores with illite, quartz, kaolinite, calcite and epidote mineralizations, accommodating mainly E-W extension. K-Ar dating of illites separated from representative fault gouges and zones of altered granodiorite constrain deformation ranging from the Permian to the Late Jurassic, indicating a long history of crustal extension where faults were repeatedly activated. In addition, a set of ca. SW-NE striking faults associated with alteration zones give Cretaceous dates, either representing a young phase of NW-SE extension or reactivation of previously formed

  12. Structural evolution of fold-thrust structures in analog models deformed in a large geotechnical centrifuge

    NASA Astrophysics Data System (ADS)

    Noble, Todd E.; Dixon, John M.

    2011-02-01

    We investigate the structural evolution of fault-propagation folds and fold-thrust systems with scaled analog modeling carried out using the 5.5 m radius geotechnical centrifuge at C-CORE, St. John's NL. The experiments presented here are the first of their kind, scaled ten times larger than predecessors and deformed using a custom rig with load monitoring and displacement control. Plane-layered models approximately 1 m long and representing 50 km sections are shortened horizontally under an enhanced gravity field of 160 g. The large model scale allows for a proportionally large number of bedding laminations that act as strain markers. This allows detailed analysis of strain partitioning and interplay, both at the scale of a fold-thrust system and the individual fold-thrust structure. Layer-parallel shortening ("LPS") and rotation of fault-bounded blocks are revealed by mapping contraction fault populations and bedding-contraction fault intersection angles. Low-angle contraction faulting and LPS are found to be dominant at early stages of development and rotation of fault-bounded blocks occurs during progressive folding of the hanging-wall panel during fault-propagation folding. Displacement-distance data obtained from major thrusts in the model show relative stretch values, and consequently fault slip/propagation ratios, that are similar to natural structures.

  13. 39Ar- 40Ar ages of martian nakhlites

    NASA Astrophysics Data System (ADS)

    Park, Jisun; Garrison, Daniel H.; Bogard, Donald D.

    2009-04-01

    We report 39Ar- 40Ar ages of whole rock (WR) and plagioclase and pyroxene mineral separates of nakhlites MIL 03346 and Y-000593, and of WR samples of nakhlites NWA 998 and Nakhla. All age spectra are complex and indicate variable degrees of 39Ar recoil and variable amounts of trapped 40Ar in the samples. Thus, we examine possible Ar-Ar ages in several ways. From consideration of both limited plateau ages and isochron ages, we prefer Ar-Ar ages of NWA 998 = 1334 ± 11 Ma, MIL 03346 = 1368 ± 83 Ma (mesostasis) and 1334 ± 54 Ma (pyroxene), Y-000593 = 1367 ± 7 Ma, and Nakhla = 1357 ± 11 Ma, (2 σ errors). For NWA 998 and MIL 03346 the Ar-Ar ages are within uncertainties of preliminary Rb-Sr isochron ages reported in the literature. These Ar-Ar ages for Y-000593 and Nakhla are several Ma older than Sm-Nd ages reported in the literature. We conclude that the major factor in producing Ar-Ar ages slightly too old is the presence of small amounts of trapped martian or terrestrial 40Ar on weathered grain surfaces that was degassed along with the first several percent of 39Ar. A total K- 40Ar isochron for WR and mineral data from five nakhlites analyzed by us, plus Lafayette data in the literature, gives an isochron age of 1325 ± 18 Ma (2 σ). We emphasize the precision of this isochron over the value of the isochron age. Our Ar-Ar data are consistent with a common formation age for nakhlites. The cosmic-ray exposure (CRE) age for NWA 998 of ˜12 Ma is also similar to CRE ages for other nakhlites.

  14. Evolution of technologies applied to space and aeronautic structures

    NASA Astrophysics Data System (ADS)

    Abiven, H.

    Advanced materials in aerospace structures and their use in reusable launch vehicles are discussed. It is found that composite materials can be used for structures with temperatures up to 400 C, and for most structures with heat shielding. For structures with temperatures up to 1000 C, metals such as Norsial, based on rene alloys could be used. It is concluded that a combination of silicon and carbon composites with Aerocoat/TH hydrotranspiration heat shielding give a heat flux resistant structure with no thermal dilation problems.

  15. Evolution of the structure and function of the vertebrate tongue

    PubMed Central

    Iwasaki, Shin-ichi

    2002-01-01

    Abstract Studies of the comparative morphology of the tongues of living vertebrates have revealed how variations in the morphology and function of the organ might be related to evolutional events. The tongue, which plays a very important role in food intake by vertebrates, exhibits significant morphological variations that appear to represent adaptation to the current environmental conditions of each respective habitat. This review examines the fundamental importance of morphology in the evolution of the vertebrate tongue, focusing on the origin of the tongue and on the relationship between morphology and environmental conditions. Tongues of various extant vertebrates, including those of amphibians, reptiles, birds and mammals, were analysed in terms of gross anatomy and microanatomy by light microscopy and by scanning and transmission electron microscopy. Comparisons of tongue morphology revealed a relationship between changes in the appearance of the tongue and changes in habitat, from a freshwater environment to a terrestrial environment, as well as a relationship between the extent of keratinization of the lingual epithelium and the transition from a moist or wet environment to a dry environment. The lingual epithelium of amphibians is devoid of keratinization while that of reptilians is keratinized to different extents. Reptiles live in a variety of habitats, from seawater to regions of high temperature and very high or very low humidity. Keratinization of the lingual epithelium is considered to have been acquired concomitantly with the evolution of amniotes. The variations in the extent of keratinization of the lingual epithelium, which is observed between various amniotes, appear to be secondary, reflecting the environmental conditions of different species. PMID:12171472

  16. Track structure: time evolution from physics to chemistry.

    PubMed

    Dingfelder, M

    2006-01-01

    This review discusses interaction cross sections of charged particles (electrons, protons, light ions) with atoms and molecules. The focus is on biological relevant targets like liquid water which serves as a substitute of soft tissue in most Monte Carlo codes. The spatial distribution of energy deposition patterns by different radiation qualities and their importance to the time evolution from the physical to the chemical stage or radiation response is discussed. The determination of inelastic interaction cross sections for charged particles in condensed matter is discussed within the relativistic plane-wave Born approximation and semi-empirical models. The dielectric-response-function of liquid water is discussed.

  17. Superhydrophobic hierarchically structured surfaces in biology: evolution, structural principles and biomimetic applications.

    PubMed

    Barthlott, W; Mail, M; Neinhuis, C

    2016-08-06

    A comprehensive survey of the construction principles and occurrences of superhydrophobic surfaces in plants, animals and other organisms is provided and is based on our own scanning electron microscopic examinations of almost 20 000 different species and the existing literature. Properties such as self-cleaning (lotus effect), fluid drag reduction (Salvinia effect) and the introduction of new functions (air layers as sensory systems) are described and biomimetic applications are discussed: self-cleaning is established, drag reduction becomes increasingly important, and novel air-retaining grid technology is introduced. Surprisingly, no evidence for lasting superhydrophobicity in non-biological surfaces exists (except technical materials). Phylogenetic trees indicate that superhydrophobicity evolved as a consequence of the conquest of land about 450 million years ago and may be a key innovation in the evolution of terrestrial life. The approximate 10 million extant species exhibit a stunning diversity of materials and structures, many of which are formed by self-assembly, and are solely based on a limited number of molecules. A short historical survey shows that bionics (today often called biomimetics) dates back more than 100 years. Statistical data illustrate that the interest in biomimetic surfaces is much younger still. Superhydrophobicity caught the attention of scientists only after the extreme superhydrophobicity of lotus leaves was published in 1997. Regrettably, parabionic products play an increasing role in marketing.This article is part of the themed issue 'Bioinspired hierarchically structured surfaces for green science'.

  18. Unusual structure, fluxionality, and reaction mechanism of carbonyl hydrosilylation by silyl hydride complex [(ArN=)Mo(H)(SiH2Ph)(PMe3)3].

    PubMed

    Khalimon, Andrey Y; Ignatov, Stanislav K; Okhapkin, Andrey I; Simionescu, Razvan; Kuzmina, Lyudmila G; Howard, Judith A K; Nikonov, Georgii I

    2013-06-24

    The reactions of bis(borohydride) complexes [(RN=)Mo(BH4)2(PMe3)2] (4: R = 2,6-Me2C6H3; 5: R = 2,6-iPr2C6H3) with hydrosilanes afford new silyl hydride derivatives [(RN=)Mo(H)(SiR'3)(PMe3)3] (3: R = Ar, R'3 = H2Ph; 8: R = Ar', R'3 = H2Ph; 9: R = Ar, R'3 = (OEt)3; 10: R = Ar, R'3 = HMePh). These compounds can also be conveniently prepared by reacting [(RN=)Mo(H)(Cl)(PMe3)3] with one equivalent of LiBH4 in the presence of a silane. Complex 3 undergoes intramolecular and intermolecular phosphine exchange, as well as exchange between the silyl ligand and the free silane. Kinetic and DFT studies show that the intermolecular phosphine exchange occurs through the predissociation of a PMe3 group, which, surprisingly, is facilitated by the silane. The intramolecular exchange proceeds through a new non-Bailar-twist pathway. The silyl/silane exchange proceeds through an unusual Mo(VI) intermediate, [(ArN=)Mo(H)2(SiH2Ph)2(PMe3)2] (19). Complex 3 was found to be the catalyst of a variety of hydrosilylation reactions of carbonyl compounds (aldehydes and ketones) and nitriles, as well as of silane alcoholysis. Stoichiometric mechanistic studies of the hydrosilylation of acetone, supported by DFT calculations, suggest the operation of an unexpected mechanism, in that the silyl ligand of compound 3 plays an unusual role as a spectator ligand. The addition of acetone to compound 3 leads to the formation of [trans-(ArN)Mo(OiPr)(SiH2Ph)(PMe3)2] (18). This latter species does not undergo the elimination of a Si-O group (which corresponds to the conventional Ojima's mechanism of hydrosilylation). Rather, complex 18 undergoes unusual reversible β-CH activation of the isopropoxy ligand. In the hydrosilylation of benzaldehyde, the reaction proceeds through the formation of a new intermediate bis(benzaldehyde) adduct, [(ArN=)Mo(η(2)-PhC(O)H)2(PMe3)], which reacts further with hydrosilane through a η(1)-silane complex, as studied by DFT calculations.

  19. PIECE: A database for plant gene structure comparison and evolution

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Gene families often show degrees of differences in terms of exon-intron structures depending on their distinct evolutionary histories. Comparative analysis of gene structures is important for understanding their evolutionary and functional relationships within plant species. Here, we present a com...

  20. Integrating 40Ar-39Ar, 87Rb-87Sr and 147Sm-143Nd geochronology of authigenic illite to evaluate tectonic reactivation in an intraplate setting, central Australia

    NASA Astrophysics Data System (ADS)

    Middleton, Alexander W.; Uysal, I. Tonguç; Bryan, Scott E.; Hall, Chris M.; Golding, Suzanne D.

    2014-06-01

    The Warburton-Cooper basins, central Australia, include a multitude of reactivated fracture-fault networks related to a complex, and poorly understood, tectonic evolution. We investigated authigenic illites from a granitic intrusion and sedimentary rocks associated with prominent structural features (Gidgealpa-Merrimelia-Innamincka Ridge and the Nappamerri Trough). These were analysed by 40Ar-39Ar, 87Rb-87Sr and 147Sm-143Nd geochronology to explore the thermal and tectonic histories of central Australian basins. The combined age data provide evidence for three major periods of fault reactivation throughout the Phanerozoic. While Carboniferous (323.3 ± 9.4 Ma) and Late Triassic ages (201.7 ± 9.3 Ma) derive from basin-wide hydrothermal circulation, Cretaceous ages (∼128 to ∼86 Ma) reflect episodic fluid flow events restricted to the synclinal Nappamerri Trough. Such events result from regional extensional tectonism derived from the transferral of far-field stresses to mechanically and thermally weakened regions of the Australian continent. Specifically, Cretaceous ages reflect continent-wide transmission of tensional stress from a >2500 km long rifting event on the eastern (and southern) Australian margin associated with break-up of Gondwana and opening of the Tasman Sea. By integrating 40Ar-39Ar, 87Rb-87Sr and 147Sm-143Nd dating, this study highlights the use of authigenic illite in temporally constraining the tectonic evolution of intracontinental basins that would otherwise remain unknown. Furthermore, combining Sr- and Ar-isotopic systems enables more accurate dating of authigenesis whilst significantly reducing geochemical pitfalls commonly associated with these radioisotopic dating methods.

  1. Internal symmetry in protein structures: prevalence, functional relevance and evolution.

    PubMed

    Balaji, Santhanam

    2015-06-01

    Symmetry has been found at various levels of biological organization in the protein structural universe. Numerous evolutionary studies have proposed connections between internal symmetry within protein tertiary structures, quaternary associations and protein functions. Recent computational methods, such as SymD and CE-Symm, facilitate a large-scale detection of internal symmetry in protein structures. Based on the results from these methods, about 20% of SCOP folds, superfamilies and families are estimated to have structures with internal symmetry (Figure 1d). All-β and membrane proteins fold classes contain a relatively high number of unique instances of internal symmetry. In addition to the axis of symmetry, anecdotal evidence suggests that, the region of connection or contact between symmetric units could coincide with functionally relevant sites within a fold. General principles that underlie protein internal symmetry and their connections to protein structural integrity and functions remain to be elucidated.

  2. New Insights about Enzyme Evolution from Large Scale Studies of Sequence and Structure Relationships*

    PubMed Central

    Brown, Shoshana D.; Babbitt, Patricia C.

    2014-01-01

    Understanding how enzymes have evolved offers clues about their structure-function relationships and mechanisms. Here, we describe evolution of functionally diverse enzyme superfamilies, each representing a large set of sequences that evolved from a common ancestor and that retain conserved features of their structures and active sites. Using several examples, we describe the different structural strategies nature has used to evolve new reaction and substrate specificities in each unique superfamily. The results provide insight about enzyme evolution that is not easily obtained from studies of one or only a few enzymes. PMID:25210038

  3. New insights about enzyme evolution from large scale studies of sequence and structure relationships.

    PubMed

    Brown, Shoshana D; Babbitt, Patricia C

    2014-10-31

    Understanding how enzymes have evolved offers clues about their structure-function relationships and mechanisms. Here, we describe evolution of functionally diverse enzyme superfamilies, each representing a large set of sequences that evolved from a common ancestor and that retain conserved features of their structures and active sites. Using several examples, we describe the different structural strategies nature has used to evolve new reaction and substrate specificities in each unique superfamily. The results provide insight about enzyme evolution that is not easily obtained from studies of one or only a few enzymes.

  4. Crystal structure, spectroscopic investigations and quantum chemical calculation studies of (3aR,6S,7aR)-7a-bromo-6-methyl-2-[(4-methylphenyl)sulfonyl]-1,2,3,6,7,7a-hexahydro-3a,6-epoxyisoindole: A combined experimental and theoretical studies

    NASA Astrophysics Data System (ADS)

    Alaşalvar, Can; Demircan, Aydın; Koşar, Başak; Pekacar, Ali İhsan; Büyükgüngör, Orhan

    2016-11-01

    The crystal structure and spectroscopic properties of (3aR,6S,7aR)-7a-bromo-6-methyl-2-[(4-methylphenyl)sulfonyl]-1,2,3,6,7,7a-hexahydro-3a,6-epoxyisoindole were determined by X-ray diffraction, IR and 13CNMR and 1H NMR spectroscopy techniques. We investigate molecular and crystal structure of the new sulfonamide, which was derived from an environmental friendly cyclization reaction in water. This work allow to the development of a stereo-selective tandem allylamine isomerization/Diels Alder cyclo-addition sequence led to rapid assembly of complex nitrogen containing heterocycles. The molecular geometry from X-ray determination, vibrational frequencies and NMR shifts values of the title compound in the ground state have been calculated by using CAM-B3LYP and B3LYP methods with 6-311++G(d,p) basis sets. The calculated results show that the optimized geometry can well regenerate the crystal structure and theoretical vibrational frequencies and chemical shift data are in good agreement with experimental data. Besides, it is examined nonlinear optic properties, molecular electrostatic potential map and HOMO-LUMO orbitals of the molecule.

  5. Probing the Evolution of the Shell Structures in Exotic Nuclei

    SciTech Connect

    De Angelis, Giacomo

    2008-11-11

    Magic numbers are a key feature in finite Fermion systems since they are strongly related to the underlying mean field. The size of the shell gaps and their evolution far from stability can be linked to the shape and symmetry of the nuclear mean field. Moreover the study of nuclei with large neutron/proton ratio allow to probe the density dependence of the effective interaction. Changes of the nuclear density and size in nuclei with increasing N/Z ratios are expected to lead to different nuclear symmetries and excitations. In this contribution I will discuss some selected examples which show the big potential of stable beams and of binary reactions for the study of the properties of the neutron-rich nuclear many body systems.

  6. Evolution of the magnetic field structure of the Crab pulsar.

    PubMed

    Lyne, Andrew; Graham-Smith, Francis; Weltevrede, Patrick; Jordan, Christine; Stappers, Ben; Bassa, Cees; Kramer, Michael

    2013-11-01

    Pulsars are highly magnetized rotating neutron stars and are well known for the stability of their signature pulse shapes, allowing high-precision studies of their rotation. However, during the past 22 years, the radio pulse profile of the Crab pulsar has shown a steady increase in the separation of the main pulse and interpulse components at 0.62° ± 0.03° per century. There are also secular changes in the relative strengths of several components of the profile. The changing component separation indicates that the axis of the dipolar magnetic field, embedded in the neutron star, is moving toward the stellar equator. This evolution of the magnetic field could explain why the pulsar does not spin down as expected from simple braking by a rotating dipolar magnetic field.

  7. Shifting the Starspot Paradigm through Imaging Magnetic Structures and Evolution

    NASA Astrophysics Data System (ADS)

    Roettenbacher, Rachael M.

    2016-08-01

    Magnetism is present in stars across all masses and evolutionary states. For cool stars with a convective outer envelope, stellar magnetic fields are generated through complex interactions between the convective layer and radiative core due to rotation. Magnetism in cool stars fuels stellar activity, in particular as starspots. Using starspots as a proxy, this work concentrates on imaging stellar magnetism. With state-of-the-art observations and imaging techniques, I investigate shifting the spot paradigm of localized starspots blemishing an otherwise bright surface (analogous to the solar photosphere) to a surface hosting a widespread network of magnetically-suppressed convection. This network is capable of affecting measurements of fundamental stellar parameters, such as radius and temperature, leading to inaccurate mass and age estimates. To accomplish this shift, I use precision Kepler data and a light-curve inversion algorithm for studies of stellar differential rotation and starspot evolution. Additionally, with long-baseline interferometric data collected with the Michigan Infrared Combiner (MIRC) at Georgia State University's Center for High Angular Resolution Astronomy (CHARA) Array, I target the bright, spotted, giant primary stars of close binary (RS CVn) systems. For these stars, I combine interferometric detections with radial velocity data to measure orbital and stellar parameters, which are used in concert with long-term photometric light curves to observe ellipsoidal variations, measure gravity darkening, and isolate the starspot signatures. In direct imaging using the interferometric data, I observe a spotted RS CVn star through an entire rotation period to detect canonical starspots, a polar starspot, and globally-suppressed convection. The regions of magnetically-suppressed convection cover a large fraction of the surface, potentially impacting estimates of stellar parameters. The combination of these efforts provides a start to a new era of

  8. Evidence for shock heating and constraints on Martian surface temperatures revealed by 40Ar/ 39Ar thermochronometry of Martian meteorites

    NASA Astrophysics Data System (ADS)

    Cassata, William S.; Shuster, David L.; Renne, Paul R.; Weiss, Benjamin P.

    2010-12-01

    The thermal histories of Martian meteorite are important for the interpretation of petrologic, geochemical, geochronological, and paleomagnetic constraints that they provide on the evolution of Mars. In this paper, we quantify 40Ar/ 39Ar ages and Ar diffusion kinetics of Martian meteorites Allan Hills (ALH) 84001, Nakhla, and Miller Range (MIL) 03346. We constrain the thermal history of each meteorite and discuss the resulting implications for their petrology, paleomagnetism, and geochronology. Maskelynite in ALH 84001 yields a 40Ar/ 39Ar isochron age of 4163 ± 35 Ma, which is indistinguishable from recent Pb-Pb ( Bouvier et al., 2009a) and Lu-Hf ages ( Lapen et al., 2010). The high precision of this result arises from clear resolution of a reproducible trapped 40Ar/ 36Ar component in maskelynite in ALH 84001 ( 40Ar/ 36Ar = 632 ± 90). The maskelynite 40Ar/ 39Ar age predates the Late Heavy Bombardment and likely represents the time at which the original natural remanent magnetization (NRM) component observed in ALH 84001 was acquired. Nakhla and MIL 03346 yield 40Ar/ 39Ar isochron ages of 1332 ± 24 and 1339 ± 8 Ma, respectively, which we interpret to date crystallization. Multi-phase, multi-domain diffusion models constrained by the observed Ar diffusion kinetics and 40Ar/ 39Ar age spectra suggest that localized regions within both ALH 84001 and Nakhla were intensely heated for brief durations during shock events at 1158 ± 110 and 913 ± 9 Ma, respectively. These ages may date the marginal melting of pyroxene in each rock, mobilization of carbonates and maskelynite in ALH 84001, and NRM overprints observed in ALH 84001. The inferred peak temperatures of the shock heating events (>1400 °C) are sufficient to mobilize Ar, Sr, and Pb in constituent minerals, which may explain some of the dispersion observed in 40Ar/ 39Ar, Rb-Sr, and U-Th-Pb data toward ages younger than ˜4.1 Ga. The data also place conservative upper bounds on the long-duration residence

  9. Genetic mapping of the interface between the ArsD metallochaperone and the ArsA ATPase

    PubMed Central

    Yang, Jianbo; Ajees, Abdul; Salam, Abdul; Rosen, Barry P.

    2011-01-01

    Summary The ArsD metallochaperone delivers trivalent metalloids, As(III) or Sb(III), to the ArsA ATPase, the catalytic subunit of the ArsAB As(III) efflux pump. Transfer of As(III) increases the affinity of ArsA for As(III), allowing resistance to environmental arsenic concentrations. As(III) transfer is channeled from chaperone to ATPase, implying that ArsD and ArsA form an interface at their metal binding sites. A genetic approach was used to test this hypothesis. Thirteen ArsD mutants exhibiting either weaker or stronger interaction with ArsA were selected by either repressed transactivator yeast two-hybrid or reverse yeast two-hybrid assays. Additionally, Lys-37 and Lys-62 were identified as being involved in ArsD function by site-directed mutagenesis and chemical modification. Substitution at either position with arginine was tolerated, suggesting participation of a positive charge. By yeast two-hybrid analysis K37A and K62A mutants lost interaction with ArsA. All fifteen mutations were mapped on the surface of the ArsD structure, and their locations are consistent with a structural model generated by in silico docking. Four are close to metalloid binding site residues Cys-12, Cys-13 and Cys18, and seven are on the surface of helix 1. These results suggest that the interface involves one surface of helix 1 and the metalloid binding site. PMID:21299644

  10. Re-evaluation of polyphase kinematic and 40Ar/39Ar cooling history of Moldanubian hot nappe at the eastern margin of the Bohemian Massif

    NASA Astrophysics Data System (ADS)

    Racek, M.; Lexa, O.; Schulmann, K.; Corsini, M.; Štípská, P.; Maierová, P.

    2017-03-01

    A structural and geochronological 40Ar/39Ar study was performed in kilometre-scale middle and lower crustal lens-shaped domains dominated by a preserved subvertical foliation, surrounded by horizontally foliated migmatites. These domains occur within the Moldanubian nappe overlying the Brunia microcontinent at the eastern margin of the European Variscides. Three main deformation phases were recognized: subvertical S2 fabric trending NW-SE in lower crustal rocks and NE-SW in mid-crustal rocks. It is reworked by HT/MT horizontal fabric S3 along margins of crustal domains and in surrounding migmatites. S3 bears a prolate NE lineation parallel to the S2-S3 intersection in the lower crustal domain. In the middle crustal units, L3 is weak, connected to oblate strain and trends NE-SW parallel to the S2-S3 intersection. D4 non-coaxial shear deformation is mainly localized at the boundary between the Moldanubian nappe and Brunia and bears strong top to the NNE shear criteria. In order to constrain kinematics of the D3 deformation, strain modelling was performed to show that the Moldanubian hot nappe was frontally thrust over the Brunia indentor. The renewed D4 tangential movement only heterogeneously reactivates the horizontal S3. This evolution is recorded in 40Ar/39Ar amphibole cooling ages, which show two statistically significant Carboniferous peaks at 342 and 332 Ma, which are also reflected by published detrital muscovite 40Ar/39Ar ages in the adjacent foreland basin. This geochronological record is correlated with progressive erosion of the topographically elevated upper crustal part of the Moldanubian nappe during D3 frontal thrusting, followed by greenschist facies D4 transpressive reactivation and subsequent erosion of high-grade parts of the nappe.

  11. The evolution of structured illumination microscopy in studies of HIV.

    PubMed

    Marno, Kelly; Al'Zoubi, Lara; Pearson, Matthew; Posch, Markus; McKnight, Áine; Wheeler, Ann P

    2015-10-15

    The resolution limit of conventional light microscopy has proven to be limiting for many biological structures such as viruses including Human immunodeficiency virus (HIV). Individual HIV virions are impossible to study using confocal microscopy as they are well below the 200 nm resolution limit of conventional light microscopes. Structured illumination microscopy (SIM) allows a twofold enhancement in image resolution compared to standard widefield illumination and so provides an excellent tool for study of HIV. Viral capsids (CAs) vary between 110 and 146 nm so this study challenges the performance of SIM microscopes. SIM microscopy was first developed in 2000, commercialised in 2007 and rapidly developed. Here we present the changes in capabilities of the SIM microscopes for study of HIV localisation as the instrumentation for structured illumination microscopy has evolved over the past 8 years.

  12. SUBSIDENCE, CRUSTAL STRUCTURE, AND THERMAL EVOLUTION OF GEORGES BANK BASIN.

    USGS Publications Warehouse

    Swift, B. Ann; Sawyer, D.S.; Grow, J.A.; Klitgord, Kim D.

    1987-01-01

    A geographical study of Georges Bank basin defines a deep crustal structure that is interpreted in terms of the basin's tectonic and thermal history. Gravity models along three basin cross sections delineate two zones of crustal thinning at the basement hinge zone and oceanic crustal margins. These two zones bound rift-stage crust (about 25 km thick) which underlies the central portion of the basin. Subsidence analysis of the basin, using data from multichannel seismic reflection lines and two COST wells, suggests a rifting and (uniform) extensional origin. Two-dimensional finite difference modeling of the basin defines a crustal structure that concurs with the gravity and subsidence studies. The resulting isotherms show no major changes in the thermal structure since the Late Jurassic. In some areas of the basin, temperature sufficient for oil generation are determined from maturation studies of Jurassic sediments. Hydrocarbon generation is questionable, however, because of the probable lack of proper and sufficient kerogen in the Jurassic deposits.

  13. Local atomic structure modulations activate metal oxide as electrocatalyst for hydrogen evolution in acidic water

    PubMed Central

    Li, Yu Hang; Liu, Peng Fei; Pan, Lin Feng; Wang, Hai Feng; Yang, Zhen Zhong; Zheng, Li Rong; Hu, P.; Zhao, Hui Jun; Gu, Lin; Yang, Hua Gui

    2015-01-01

    Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry. PMID:26286479

  14. Local atomic structure modulations activate metal oxide as electrocatalyst for hydrogen evolution in acidic water

    NASA Astrophysics Data System (ADS)

    Li, Yu Hang; Liu, Peng Fei; Pan, Lin Feng; Wang, Hai Feng; Yang, Zhen Zhong; Zheng, Li Rong; Hu, P.; Zhao, Hui Jun; Gu, Lin; Yang, Hua Gui

    2015-08-01

    Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry.

  15. Local atomic structure modulations activate metal oxide as electrocatalyst for hydrogen evolution in acidic water.

    PubMed

    Li, Yu Hang; Liu, Peng Fei; Pan, Lin Feng; Wang, Hai Feng; Yang, Zhen Zhong; Zheng, Li Rong; Hu, P; Zhao, Hui Jun; Gu, Lin; Yang, Hua Gui

    2015-08-19

    Modifications of local structure at atomic level could precisely and effectively tune the capacity of materials, enabling enhancement in the catalytic activity. Here we modulate the local atomic structure of a classical but inert transition metal oxide, tungsten trioxide, to be an efficient electrocatalyst for hydrogen evolution in acidic water, which has shown promise as an alternative to platinum. Structural analyses and theoretical calculations together indicate that the origin of the enhanced activity could be attributed to the tailored electronic structure by means of the local atomic structure modulations. We anticipate that suitable structure modulations might be applied on other transition metal oxides to meet the optimal thermodynamic and kinetic requirements, which may pave the way to unlock the potential of other promising candidates as cost-effective electrocatalysts for hydrogen evolution in industry.

  16. The pig X and Y Chromosomes: structure, sequence, and evolution

    PubMed Central

    Skinner, Benjamin M.; Sargent, Carole A.; Churcher, Carol; Hunt, Toby; Herrero, Javier; Loveland, Jane E.; Dunn, Matt; Louzada, Sandra; Fu, Beiyuan; Chow, William; Gilbert, James; Austin-Guest, Siobhan; Beal, Kathryn; Carvalho-Silva, Denise; Cheng, William; Gordon, Daria; Grafham, Darren; Hardy, Matt; Harley, Jo; Hauser, Heidi; Howden, Philip; Howe, Kerstin; Lachani, Kim; Ellis, Peter J.I.; Kelly, Daniel; Kerry, Giselle; Kerwin, James; Ng, Bee Ling; Threadgold, Glen; Wileman, Thomas; Wood, Jonathan M.D.; Yang, Fengtang; Harrow, Jen; Affara, Nabeel A.; Tyler-Smith, Chris

    2016-01-01

    We have generated an improved assembly and gene annotation of the pig X Chromosome, and a first draft assembly of the pig Y Chromosome, by sequencing BAC and fosmid clones from Duroc animals and incorporating information from optical mapping and fiber-FISH. The X Chromosome carries 1033 annotated genes, 690 of which are protein coding. Gene order closely matches that found in primates (including humans) and carnivores (including cats and dogs), which is inferred to be ancestral. Nevertheless, several protein-coding genes present on the human X Chromosome were absent from the pig, and 38 pig-specific X-chromosomal genes were annotated, 22 of which were olfactory receptors. The pig Y-specific Chromosome sequence generated here comprises 30 megabases (Mb). A 15-Mb subset of this sequence was assembled, revealing two clusters of male-specific low copy number genes, separated by an ampliconic region including the HSFY gene family, which together make up most of the short arm. Both clusters contain palindromes with high sequence identity, presumably maintained by gene conversion. Many of the ancestral X-related genes previously reported in at least one mammalian Y Chromosome are represented either as active genes or partial sequences. This sequencing project has allowed us to identify genes—both single copy and amplified—on the pig Y Chromosome, to compare the pig X and Y Chromosomes for homologous sequences, and thereby to reveal mechanisms underlying pig X and Y Chromosome evolution. PMID:26560630

  17. The pig X and Y Chromosomes: structure, sequence, and evolution.

    PubMed

    Skinner, Benjamin M; Sargent, Carole A; Churcher, Carol; Hunt, Toby; Herrero, Javier; Loveland, Jane E; Dunn, Matt; Louzada, Sandra; Fu, Beiyuan; Chow, William; Gilbert, James; Austin-Guest, Siobhan; Beal, Kathryn; Carvalho-Silva, Denise; Cheng, William; Gordon, Daria; Grafham, Darren; Hardy, Matt; Harley, Jo; Hauser, Heidi; Howden, Philip; Howe, Kerstin; Lachani, Kim; Ellis, Peter J I; Kelly, Daniel; Kerry, Giselle; Kerwin, James; Ng, Bee Ling; Threadgold, Glen; Wileman, Thomas; Wood, Jonathan M D; Yang, Fengtang; Harrow, Jen; Affara, Nabeel A; Tyler-Smith, Chris

    2016-01-01

    We have generated an improved assembly and gene annotation of the pig X Chromosome, and a first draft assembly of the pig Y Chromosome, by sequencing BAC and fosmid clones from Duroc animals and incorporating information from optical mapping and fiber-FISH. The X Chromosome carries 1033 annotated genes, 690 of which are protein coding. Gene order closely matches that found in primates (including humans) and carnivores (including cats and dogs), which is inferred to be ancestral. Nevertheless, several protein-coding genes present on the human X Chromosome were absent from the pig, and 38 pig-specific X-chromosomal genes were annotated, 22 of which were olfactory receptors. The pig Y-specific Chromosome sequence generated here comprises 30 megabases (Mb). A 15-Mb subset of this sequence was assembled, revealing two clusters of male-specific low copy number genes, separated by an ampliconic region including the HSFY gene family, which together make up most of the short arm. Both clusters contain palindromes with high sequence identity, presumably maintained by gene conversion. Many of the ancestral X-related genes previously reported in at least one mammalian Y Chromosome are represented either as active genes or partial sequences. This sequencing project has allowed us to identify genes--both single copy and amplified--on the pig Y Chromosome, to compare the pig X and Y Chromosomes for homologous sequences, and thereby to reveal mechanisms underlying pig X and Y Chromosome evolution.

  18. Evolution of the Alboran Sea hydrographic structures during July 1993

    NASA Astrophysics Data System (ADS)

    Lafuente, Jesús García.; Cano, Natalio; Vargas, Manuel; Rubín, Juan P.; Hernández-Guerra, Alonso

    1998-01-01

    During the ICTIOALBORAN-0793 multidisciplinary oceanographic survey carried out in July 1993 by the Instituto Español de Oceanografı´a (IEO) in the Alboran Sea, some anomalous features were detected. One was the presence of a small cyclonic eddy in the western Alboran Basin, close to the African coast. The upper layer of the eddy consisted of Mediterranean Surface Water and was separated from its supposed source (the northern Alboran Sea) by the Atlantic Jet. Another feature was the probable temporary interruption of the flow of fresh Atlantic Water (S≈36.5) into the eastern Alboran Basin and its replacement by a modified (saltier) Atlantic Water. These features can be explained assuming a time evolution of the surface circulation in the Alboran Sea forced by speed variations in the inflowing Atlantic Water through the Strait of Gibraltar. A collection of satellite images covering the survey period and across-strait sea level difference data, indicative of the geostrophic velocity of the inflow through the Strait, were used to check this assumption. Both sets of data supplied independent but compatible information in the sense that they complemented each other and gave support to the proposed evolving model. Finally, some speculative ideas attempting to correlate the inferred variability in the Alboran Sea with the state of the baroclinic water exchange through the Strait of Gibraltar (maximal or submaximal) are discussed.

  19. Disease evolution on networks: the role of contact structure.

    PubMed Central

    Read, Jonathan M; Keeling, Matt J

    2003-01-01

    Owing to their rapid reproductive rate and the severe penalties for reduced fitness, diseases are under immense evolutionary pressure. Understanding the evolutionary response of diseases in new situations has clear public-health consequences, given the changes in social and movement patterns over recent decades and the increased use of antibiotics. This paper investigates how a disease may adapt in response to the routes of transmission available between infected and susceptible individuals. The potential transmission routes are defined by a computer-generated contact network, which we describe as either local (highly clustered networks where connected individuals are likely to share common contacts) or global (unclustered networks with a high proportion of long-range connections). Evolution towards stable strategies operates through the gradual random mutation of disease traits (transmission rate and infectious period) whenever new infections occur. In contrast to mean-field models, the use of contact networks greatly constrains the evolutionary dynamics. In the local networks, high transmission rates are selected for, as there is intense competition for susceptible hosts between disease progeny. By contrast, global networks select for moderate transmission rates because direct competition between progeny is minimal and a premium is placed upon persistence. All networks show a very slow but steady rise in the infectious period. PMID:12713743

  20. Spectral properties of the temporal evolution of brain network structure.

    PubMed

    Wang, Rong; Zhang, Zhen-Zhen; Ma, Jun; Yang, Yong; Lin, Pan; Wu, Ying

    2015-12-01

    The temporal evolution properties of the brain network are crucial for complex brain processes. In this paper, we investigate the differences in the dynamic brain network during resting and visual stimulation states in a task-positive subnetwork, task-negative subnetwork, and whole-brain network. The dynamic brain network is first constructed from human functional magnetic resonance imaging data based on the sliding window method, and then the eigenvalues corresponding to the network are calculated. We use eigenvalue analysis to analyze the global properties of eigenvalues and the random matrix theory (RMT) method to measure the local properties. For global properties, the shifting of the eigenvalue distribution and the decrease in the largest eigenvalue are linked to visual stimulation in all networks. For local properties, the short-range correlation in eigenvalues as measured by the nearest neighbor spacing distribution is not always sensitive to visual stimulation. However, the long-range correlation in eigenvalues as evaluated by spectral rigidity and number variance not only predicts the universal behavior of the dynamic brain network but also suggests non-consistent changes in different networks. These results demonstrate that the dynamic brain network is more random for the task-positive subnetwork and whole-brain network under visual stimulation but is more regular for the task-negative subnetwork. Our findings provide deeper insight into the importance of spectral properties in the functional brain network, especially the incomparable role of RMT in revealing the intrinsic properties of complex systems.

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

    SciTech Connect

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

    2015-01-10

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

  2. Spectral properties of the temporal evolution of brain network structure

    NASA Astrophysics Data System (ADS)

    Wang, Rong; Zhang, Zhen-Zhen; Ma, Jun; Yang, Yong; Lin, Pan; Wu, Ying

    2015-12-01

    The temporal evolution properties of the brain network are crucial for complex brain processes. In this paper, we investigate the differences in the dynamic brain network during resting and visual stimulation states in a task-positive subnetwork, task-negative subnetwork, and whole-brain network. The dynamic brain network is first constructed from human functional magnetic resonance imaging data based on the sliding window method, and then the eigenvalues corresponding to the network are calculated. We use eigenvalue analysis to analyze the global properties of eigenvalues and the random matrix theory (RMT) method to measure the local properties. For global properties, the shifting of the eigenvalue distribution and the decrease in the largest eigenvalue are linked to visual stimulation in all networks. For local properties, the short-range correlation in eigenvalues as measured by the nearest neighbor spacing distribution is not always sensitive to visual stimulation. However, the long-range correlation in eigenvalues as evaluated by spectral rigidity and number variance not only predicts the universal behavior of the dynamic brain network but also suggests non-consistent changes in different networks. These results demonstrate that the dynamic brain network is more random for the task-positive subnetwork and whole-brain network under visual stimulation but is more regular for the task-negative subnetwork. Our findings provide deeper insight into the importance of spectral properties in the functional brain network, especially the incomparable role of RMT in revealing the intrinsic properties of complex systems.

  3. Expanding plasma structure and its evolution toward long wavelengths

    SciTech Connect

    Sgro, A. G.; Peter Gary, S.; Lemons, D. S.

    1989-09-01

    The expansion of a plasma slab across an initially uniform magnetic field is simulated by the use of a two-dimensional electromagnetic hybrid (particle ions, fluid electrons of nonzero mass) computer code. The expanding plasma develops magnetic-field-aligned structure on time scales faster than an ion gyroperiod. Through the full duration of the /ital m//sub /ital i////ital m//sub /ital e// =100 simulation, the structure wavelength is well predicted by the wavelength at maximum growth rate from the linear Vlasov theory of the lower hybrid drift instability modified by deceleration. At /ital m//sub /ital i////ital m//sub /ital e// =400, the late time structure wavelength is about 1.5 times the early time value. At /ital m//sub /ital i////ital m//sub /ital e// =1836, the structure wavelength at early times is close to that corresponding to the maximum growth rate of linear theory, while at later times the structure wavelength becomes about twice as long as its early time value. These three results suggest that the ratio of the late time wavelength to the early time value gradually increases with /ital m//sub /ital i////ital m//sub /ital e//. Extrapolation of this scaling to larger /ital m//sub /ital i////ital m//sub /ital e// values is consistent with structure wavelengths observed in an expanding aluminum plasma experiment (J. Appl. Phys. J. /bold 20/, 157 (1981)), as well as the observed wavelength in the expanding barium plasma of the AMPTE magnetotail experiment (J. Geophys. Res. /bold 92/, 5777 (1987)).

  4. Ar/Ar Dating Independent of Monitor Standard Ages

    NASA Astrophysics Data System (ADS)

    Boswell, S.; Hemming, S. R.

    2015-12-01

    Because the reported age of an analyzed sample is dependent on the age of the co-irradiated monitor standard(s), Ar/Ar dating is a relative dating technique. There is disagreement at the 1% scale in the age of commonly used monitor standards, and there is a great need to improve the inter-laboratory calibrations. Additionally, new approaches and insights are needed to meet the challenge of bringing the Ar/Ar chronometer to the highest possible precision and accuracy. In this spirit, we present a conceptual framework for Ar/Ar dating that does not depend on the age of monitor standards, but only on the K content of a solid standard. The concept is demonstrated by introducing a re-expressed irradiation parameter (JK) that depends on the ratio of 39ArK to 40Ar* rather than the 40Ar*/39ArK ratio. JK is equivalent to the traditional irradiation parameter J and is defined as JK = (39Ar/40K) • (λ/λe). The ultimate precision and accuracy of the method will depend on how precisely and accurately the 39Ar and 40K can be estimated, and will require isotope dilution measurements of both from the same aliquot. We are testing the workability of our technique at the 1% level by measuring weighed and irradiated hornblende and biotite monitor standards using GLO-1 glauconite to define a calibration curve for argon signals versus abundance.

  5. K/Ar dating of lunar soils. II

    NASA Technical Reports Server (NTRS)

    Alexander, E. C., Jr.; Bates, A.; Coscio, M. R., Jr.; Dragon, J. C.; Murthy, V. R.; Pepin, R. O.; Venkatesan, T. R.

    1976-01-01

    An attempt is made to identify those K/Ar techniques which extract the most reliable chronological information from lunar soils and to define the situations in which the best data are obtainable. Results are presented for determinations of the exposure and K/Ar ages of five lunar soil samples, which were performed by applying correlation techniques for a two-component argon structure to stepwise-heated and neutron-irradiated aliquots of grain-sized separates. It is found that ages deduced from Ar-40/surface-correlated Ar-36 vs K-40/surface-correlated Ar-36 and analogous plots of data from grain-sized separates appear to be the best available K/Ar ages of submature to mature lunar soils, that ages deduced from Ar-40 vs Ar-36 and analogous plots which assume a uniform K content can be significantly in error, and that stepwise-heating (Ar-40)-(Ar-39) experiments yield useful information only for simple immature soils where the K-Ar systematics are dominated by a single component.

  6. Structural constraints on the evolution of the collagen fibril: convergence on a 1014-residue COL domain

    PubMed Central

    Slatter, David Anthony; Farndale, Richard William

    2015-01-01

    Type I collagen is the fundamental component of the extracellular matrix. Its α1 gene is the direct descendant of ancestral fibrillar collagen and contains 57 exons encoding the rod-like triple-helical COL domain. We trace the evolution of the COL domain from a primordial collagen 18 residues in length to its present 1014 residues, the limit of its possible length. In order to maintain and improve the essential structural features of collagen during evolution, exons can be added or extended only in permitted, non-random increments that preserve the position of spatially sensitive cross-linkage sites. Such sites cannot be maintained unless the twist of the triple helix is close to 30 amino acids per turn. Inspection of the gene structure of other long structural proteins, fibronectin and titin, suggests that their evolution might have been subject to similar constraints. PMID:25994354

  7. Highly Conserved Elements and Chromosome Structure Evolution in Mitochondrial Genomes in Ciliates

    PubMed Central

    Gershgorin, Roman A.; Gorbunov, Konstantin Yu.; Zverkov, Oleg A.; Rubanov, Lev I.; Seliverstov, Alexandr V.; Lyubetsky, Vassily A.

    2017-01-01

    Recent phylogenetic analyses are incorporating ultraconserved elements (UCEs) and highly conserved elements (HCEs). Models of evolution of the genome structure and HCEs initially faced considerable algorithmic challenges, which gave rise to (often unnatural) constraints on these models, even for conceptually simple tasks such as the calculation of distance between two structures or the identification of UCEs. In our recent works, these constraints have been addressed with fast and efficient solutions with no constraints on the underlying models. These approaches have led us to an unexpected result: for some organelles and taxa, the genome structure and HCE set, despite themselves containing relatively little information, still adequately resolve the evolution of species. We also used the HCE identification to search for promoters and regulatory elements that characterize the functional evolution of the genome. PMID:28264444

  8. Correlation between atomic structure evolution and strength in a bulk metallic glass at cryogenic temperature.

    PubMed

    Tan, J; Wang, G; Liu, Z Y; Bednarčík, J; Gao, Y L; Zhai, Q J; Mattern, N; Eckert, J

    2014-01-28

    A model Zr41.25Ti13.75Ni10Cu12.5Be22.5 (at.%) bulk metallic glass (BMG) is selected to explore the structural evolution on the atomic scale with decreasing temperature down to cryogenic level using high energy X-ray synchrotron radiation. We discover a close correlation between the atomic structure evolution and the strength of the BMG and find out that the activation energy increment of the concordantly atomic shifting at lower temperature is the main factor influencing the strength. Our results might provide a fundamental understanding of the atomic-scale structure evolution and may bridge the gap between the atomic-scale physics and the macro-scale fracture strength for BMGs.

  9. Gene3D: modelling protein structure, function and evolution.

    PubMed

    Yeats, Corin; Maibaum, Michael; Marsden, Russell; Dibley, Mark; Lee, David; Addou, Sarah; Orengo, Christine A

    2006-01-01

    The Gene3D release 4 database and web portal (http://cathwww.biochem.ucl.ac.uk:8080/Gene3D) provide a combined structural, functional and evolutionary view of the protein world. It is focussed on providing structural annotation for protein sequences without structural representatives--including the complete proteome sets of over 240 different species. The protein sequences have also been clustered into whole-chain families so as to aid functional prediction. The structural annotation is generated using HMM models based on the CATH domain families; CATH is a repository for manually deduced protein domains. Amongst the changes from the last publication are: the addition of over 100 genomes and the UniProt sequence database, domain data from Pfam, metabolic pathway and functional data from COGs, KEGG and GO, and protein-protein interaction data from MINT and BIND. The website has been rebuilt to allow more sophisticated querying and the data returned is presented in a clearer format with greater functionality. Furthermore, all data can be downloaded in a simple XML format, allowing users to carry out complex investigations at their own computers.

  10. Early Structural Evolution of Native Cytochrome c after Solvent Removal

    PubMed Central

    Steinberg, Michal Z.; Elber, Ron; McLafferty, Fred W.; Gerber, R. Benny; Breuker, Kathrin

    2009-01-01

    Electrospray ionization transfers thermally labile biomolecules, such as proteins, from solution into the gas phase, where they can be studied by mass spectrometry. Covalent bonds are generally preserved during and after the phase transition, but it is less clear to what extent noncovalent interactions are affected by the new gaseous environment. Here, we present atomic-level computational data on the structural rearrangement of native cytochrome c immediately after solvent removal. The first structural changes after desolvation occur surprisingly early, on a timescale of picoseconds. For the time segment of up to 4.2 ns investigated here, we observed no significant breaking of native noncovalent bonds; instead, we found formation of new noncovalent bonds. This generally involves charged residues on the protein surface, resulting in transiently stabilized intermediate structures with a global fold that is essentially the same as that in solution. Comparison with data from native electron capture dissociation experiments corroborates both its mechanistic postulations and our computational predictions, and suggests that global structural changes take place on a millisecond timescale not covered by our simulations. PMID:18785672

  11. Atomimetic Mechanical Structures with Nonlinear Topological Domain Evolution Kinetics.

    PubMed

    Frazier, Michael J; Kochmann, Dennis M

    2017-03-21

    A mechanical metamaterial, a simple, periodic mechanical structure, is reported, which reproduces the nonlinear dynamic behavior of materials undergoing phase transitions and domain switching at the structural level. Tunable multistability is exploited to produce switching and transition phenomena whose kinetics are governed by the same Allen-Cahn law commonly used to describe material-level, structural-transition processes. The reported purely elastic mechanical system displays several key features commonly found in atomic- or mesoscale physics of solids. The rotating-mass network shows qualitatively analogous features as, e.g., ferroic ceramics or phase-transforming solids, and the discrete governing equation is shown to approach the phase field equation commonly used to simulate the above processes. This offers untapped opportunities for reproducing material-level, dissipative and diffusive kinetic phenomena at the structural level, which, in turn, invites experimental realization and paves the road for new active, intelligent, or phase-transforming mechanical metamaterials bringing small-scale processes to the macroscopically observable scale.

  12. 40Ar/39Ar Dating of Volcanic Glass

    NASA Astrophysics Data System (ADS)

    Morgan, L. E.; Renne, P. R.; Watkins, J. M.

    2007-12-01

    Application of the 40Ar/39Ar method to volcanic glasses has been somewhat stigmatized following several studies demonstrating secondary mobility of K and Ar. Much of the stigma is unwarranted, however, since most studies only impugned the reliability of the K-Ar and 40Ar/39Ar techniques when applied to glass shards rather than obsidian clasts with low surface area to volume ratios. We provide further evidence for problematic K loss and/or 39Ar recoil ejection from glass shards in 40Ar/39Ar step heating results for comagmatic feldspars and shards. In an extreme case, the plateau age of the feldspars (0.17 ± 0.03 Ma at 2σ) is significantly younger than the plateau age of the glass (0.85 ± 0.05 Ma at 2σ). If the feldspar age is reasonably interpreted as the eruption age of the ash, it is likely that the glass shards experienced K and/or 39Ar loss. Electron microprobe analyses of the glass shards have low totals (~93%) and no systematic lateral variability (i.e., diffusion gradients) in K, suggesting that the lengthscale of the glass shards is smaller than the lengthscale of K diffusion. Obsidian clasts should not be as susceptible to K loss since any hydrated (K-depleted) volume represents a small fraction of the total material and can often be physically removed prior to analysis. Samples described here are detrital obsidian clasts from the Afar region of Ethiopia. Evidence from Fourier Transform Infrared Spectroscopy (FTIR), and previous work by Anovitz (1999), confirm that the scale of water and potassium mobility are often small in comparison to the size of obsidian clasts but large enough to effect the bulk composition of glass shards. This expectation is confirmed in another tuff wherein comagmatic obsidian clasts and sanidine phenocrysts yield indistinguishable 40Ar/39Ar ages of 4.4 Ma High abundances of non-radiogenic 40Ar, and kinetic fractionation of Ar isotopes during quenching and/or laboratory degassing resulting in incomplete equilibration between

  13. Combined K-Ar and 40Ar/39Ar dating of the upper Jaramillo reversal

    NASA Astrophysics Data System (ADS)

    Guillou, Herve; Carracedo, Juan Carlos; Kissel, Catherine; Laj, Carlo; Nomade, Sebastien; Perez Torrado, Francisco Jose; Rodriguez Gonzalez, Alejandro; Wandres, Camille

    2013-04-01

    The Jaramillo subchron was first evidenced in 1966 (Doell and Dalrymple) through the Rhyolotic domes of the Valles Caldera, New Mexico (USA). 40Ar/39Ar studies achieved by Spell et McDougall (1992), Spell et Harrison (1993), Izett and Obradovich (1994) and Singer et al. (1994) defined the base of this subchron at 1053±6 ka, and the ceiling at 986±5 ka. Channell et al. (2009) delimited the age of the Jaramillo subchron by astronomic calibration (base 1071 ka, top 990 ka). To provide additional absolute ages on this geomagnetic period, which is critical to improve our knowledge of the earth magnetic field behaviour, we have carried out a study combining paleomagnetism and isotopic dating of a lava sequence from Tenerife island. This sequence of basaltic lava flows is some 500 m thick. The first 400 m present, based on field magnetometer measurements, normal polarity lavas, with dykes of normal and reverse polarity, passing at the top to reverse polarity lavas. Preliminary K-Ar ages bracketed this sequence between 1018 ± 18 ka and 978 ± 17 ka. Therefore, the upper Jaramillo reversal at least appeared to be potentially recorded in this sequence. A more detailed paleomagnetic study was then carried out to more precisely delimit the reversal itself (see Laj et al., session EMRP3.4). We have undertaken 40Ar/39Ar incremental heating and unspiked K-Ar experiments on groundmass from four transitionally magnetized flows. The first transitional flow is K-Ar dated at 993 ± 18 ka and 40Ar/39Ar dated at 991 ± 13 ka, the second at 981 ± 17 ka (K-Ar) and 1000 ± 13 ka (40Ar/39Ar), the third at 950 ± 17 ka (K-Ar) and 1000 ± 8 ka (40Ar/39Ar) and the fourth at 984 ± 17 ka (K-Ar) and 977 ± 12 (40Ar/39Ar). 40Ar/39Ar ages and K-Ar ages (relative to FCT 28.02 Ma) are indistinguishable at 2σ. The age of the upper boundary of the Jaramillo event calculated combining 40Ar/39Ar ages and K-Ar ages is 992 ± 6 ka, in agreement with previous estimates.

  14. Photoionization of Ar VIII

    NASA Astrophysics Data System (ADS)

    Liang, Liang; Jiang, Wen-xian; Zhou, Chao

    2017-01-01

    The photoionization cross section, energy levels and widths of 22 Rydberg series (in the autoionization region) for Na-like Ar VIII were investigated by using of R-matrix method. The relativistic distorted-wave method is used to calculate the radial functions, and QB method of Quigly-Berrington [Quigley et al. 1998] is employed to calculate the resonance levels and widths. We have identified the formant in the figure of the photoionization cross section.

  15. STRUCTURE AND EVOLUTION OF PRE-MAIN-SEQUENCE CIRCUMSTELLAR DISKS

    SciTech Connect

    Isella, Andrea; Carpenter, John M.; Sargent, Anneila I.

    2009-08-10

    We present new subarcsecond ({approx}0.''7) Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations of the 1.3 mm continuum emission from circumstellar disks around 11 low- and intermediate-mass pre-main-sequence stars. High-resolution observations for three additional sources were obtained from the literature. In all cases the disk emission is spatially resolved. We adopt a self-consistent accretion disk model based on the similarity solution for the disk surface density and constrain the dust radial density distribution on spatial scales of about 40 AU. Disk surface densities appear to be correlated with the stellar ages where the characteristic disk radius increases from {approx}20 AU to {approx}100 AU over about 5 Myr. This disk expansion is accompanied by a decrease in the mass accretion rate, suggesting that our sample disks form an evolutionary sequence. Interpreting our results in terms of the temporal evolution of a viscous {alpha}-disk, we estimate (1) that at the beginning of the disk evolution about 60% of the circumstellar material was located inside radii of 25-40 AU, (2) that disks formed with masses from 0.05 to 0.4 M {sub sun}, and (3) that the viscous timescale at the disk initial radius is about 0.1-0.3 Myr. Viscous disk models tightly link the surface density {sigma}(R) with the radial profile of the disk viscosity {nu}(R) {proportional_to} R {sup {gamma}}. We find values of {gamma} ranging from -0.8 to 0.8, suggesting that the viscosity dependence on the orbital radius can be very different in the observed disks. Adopting the {alpha} parameterization for the viscosity, we argue that {alpha} must decrease with the orbital radius and that it may vary between 0.5 and 10{sup -4}. From the inferred disk initial radii we derive specific angular momenta, j, for parent cores of (0.8 - 4) x 10{sup -4} km s{sup -1} pc. Comparison with the values of j in dense cores suggests that about 10% of core angular momentum and 30% of the core

  16. The evolution of structure and feedback with Arcus

    NASA Astrophysics Data System (ADS)

    Brenneman, Laura W.; Smith, Randall K.; Bregman, J.; Kaastra, J.; Brickhouse, N.; Allured, R.; Foster, A.; Wolk, S.; Wilms, J.; Valencic, L.; Willingale, R.; Grant, C.; Bautz, M.; Heilmann, R.; Huenemoerder, D.; Miller, E.; Nowak, M.; Schattenburg, M.; Schulz, N.; Burwitz, V.; Nandra, K.; Sanders, J.; Bookbinder, J.; Petre, R.; Ptak, A.; Smale, A.; Burrows, D.; Poppenhaeger, K.; Costantini, E.; DeRoo, C.; McEntaffer, R.; Mushotzky, R.; Miller, J. M.; Temi, P.

    2016-07-01

    Arcus is a NASA/MIDEX mission under development in response to the anticipated 2016 call for proposals. It is a freeflying, soft X-ray grating spectrometer with the highest-ever spectral resolution in the 8-51 Å (0.24 - 1.55 keV) energy range. The Arcus bandpass includes the most sensitive tracers of diffuse million-degree gas: spectral lines from O VII and O VIII, H- and He-like lines of C, N, Ne and Mg, and unique density- and temperature-sensitive lines from Si and Fe ions. These capabilities enable an advance in our understanding of the formation and evolution of baryons in the Universe that is unachievable with any other present or planned observatory. The mission will address multiple key questions posed in the Decadal Survey1 and NASA's 2013 Roadmap2: How do baryons cycle in and out of galaxies? How do black holes and stars influence their surroundings and the cosmic web via feedback? How do stars, circumstellar disks and exoplanet atmospheres form and evolve? Arcus data will answer these questions by leveraging recent developments in off-plane gratings and silicon pore optics to measure X-ray spectra at high resolution from a wide range of sources within and beyond the Milky Way. CCDs with strong Suzaku heritage combined with electronics based on the Swift mission will detect the dispersed X-rays. Arcus will support a broad astrophysical research program, and its superior resolution and sensitivity in soft X-rays will complement the forthcoming Athena calorimeter, which will have comparably high resolution above 2 keV.

  17. Primordial abundance of 40Ar

    NASA Astrophysics Data System (ADS)

    Sripada, V. S. Murty

    Primordial abundance of the isotope (40) Ar is still not known accurately. Recent results from Genesis could also not provide (40) Ar/ (36) Ar value of solar wind, due mainly to the overwhelming (40) Ar blank. A major part of (40) Ar is contributed by the radioactive decay of (40) K (half life = 1.25 Ga), even in the nebula, as the nebula grew old. Any attempt to determine this quantity needs a sample that satisfies the following criteria: A primitive mineral/phase that formed very early in the nebula, that can trap a large amount of noble gas (Ar); and a phase that acquires minimum amount (or total absence) of in situ produced components (cosmogenic and radiogenic) of Ar. Carbon phases in the ureilite meteorites and Phase Q from chondrites best fit this criteria. The minimum (40) Ar/ (36) Ar value so far observed in Phase Q is 0.2. Also, the relatively lower value of 1.035±±0.002 for trapped (129) Xe/ (132) Xe in ureilites, as compared to 1.042±±0.002 in Phase Q suggests that trapping of gases in ureilites might have predated that of Phase Q. If this interpretation is valid, ureilites are a better host of most primitive nebular Ar. Earlier attempts on ureilite studies in 1970s have yielded the lowest (40) Ar/ (36) Ar ratio in the meteorite Dayalpur, the major uncertainty for this value mostly coming from blank correction for (40) Ar/ (36) Ar. Recent developments in low blank extraction systems and more sensitive multi-collector noble gas mass spectrometers, as compared to 1970s have prompted us to make a fresh attempt in measuring this important quantity. We have analysed a number of ureilite acid residues by stepwise temperature extraction, using both pyrolysis and combustion techniques, for Ar to ascertain the trapped (40) Ar/ (36) Ar ratio in the solar nebula. These acid residues are mostly made of C rich phases, with only trace amounts of K (radiogenic parent of (40) Ar) and target elements for the production of cosmogenic Ar component. They mostly contain

  18. Morphological bubble evolution induced by air diffusion on submerged hydrophobic structures

    NASA Astrophysics Data System (ADS)

    Lv, Pengyu; Xiang, Yaolei; Xue, Yahui; Lin, Hao; Duan, Huiling

    2017-03-01

    Bubbles trapped in the cavities always play important roles in the underwater applications of structured hydrophobic surfaces. Air exchange between bubbles and surrounding water has a significant influence on the morphological bubble evolution, which in turn frequently affects the functionalities of the surfaces, such as superhydrophobicity and drag reduction. In this paper, air diffusion induced bubble evolution on submerged hydrophobic micropores under reduced pressures is investigated experimentally and theoretically. The morphological behaviors of collective and single bubbles are observed using confocal microscopy. Four representative evolution phases of bubbles are captured in situ. After depressurization, bubbles will not only grow and coalesce but also shrink and split although the applied pressure remains negative. A diffusion-based model is used to analyze the evolution behavior and the results are consistent with the experimental data. A criterion for bubble growth and shrinkage is also derived along with a phase diagram, revealing that the competition of effective gas partial pressures across the two sides of the diffusion layer dominates the bubble evolution process. Strategies for controlling the bubble evolution behavior are also proposed based on the phase diagram. The current work provides a further understanding of the general behavior of bubble evolution induced by air diffusion and can be employed to better designs of functional microstructured hydrophobic surfaces.

  19. Evolution of Dust Structures from Room to Cryogenic Temperatures

    SciTech Connect

    Antipov, S. N.; Asinovskii, E. I.; Kirillin, A. V.; Markovets, V. V.; Petrov, O. F.; Fortov, V. E.

    2008-09-07

    In this work dusty plasma of dc glow discharge at the temperatures in the range of 4.2-300 K was experimentally and numerically investigated. As it was shown in the experiments, the deep cooling of discharge tube walls leads to dramatic change of dusty plasma properties. In particular, sufficient increase of dust particle kinetic temperature (by about an order) and dust density (by several orders) was observed at low (cryogenic) temperatures. At 4.2 K, this can lead to the forming of a super dense dust structures with novel properties. Numerical simulations of charging process, dust charge fluctuation and screening of dust particle charge in plasma were made in dependence with the neutral gas temperature and dust density. The main attention was given to proper ion-atom collision analysis that allows us to investigate mechanisms of dust structure transformation observed in the cryogenic experiments.

  20. Structure evolution and thermoelectric properties of carbonized polydopamine thin films

    DOE PAGES

    Li, Haoqi; Aulin, Yaroslav V.; Frazer, Laszlo; ...

    2017-02-13

    Carbonization of nature-inspired polydopamine can yield thin films with high electrical conductivity. Understanding of the structure of carbonized PDA (cPDA) is therefore highly desired. In this study, neutron diffraction, Raman spectroscopy, and other techniques indicate that cPDA samples are mainly amorphous with some short-range ordering and graphite-like structure that emerges with increasing heat treatment temperature. The electrical conductivity and the Seebeck coefficient show different trends with heat treatment temperature, while the thermal conductivity remains insensitive. Finally, the largest room-temperature ZT of 2 × 10–4 was obtained on samples heat-treated at 800 °C, which is higher than that of reduced graphenemore » oxide.« less

  1. Structural evolution of an alkali sulfate activated slag cement

    NASA Astrophysics Data System (ADS)

    Mobasher, Neda; Bernal, Susan A.; Provis, John L.

    2016-01-01

    In this study, the effect of sodium sulfate content and curing duration (from fresh paste up to 18 months) on the binder structure of sodium sulfate activated slag cements was evaluated. Isothermal calorimetry results showed an induction period spanning the first three days after mixing, followed by an acceleration-deceleration peak corresponding to the formation of bulk reaction products. Ettringite, a calcium aluminium silicate hydrate (C-A-S-H) phase, and a hydrotalcite-like Mg-Al layered double hydroxide have been identified as the main reaction products, independent of the Na2SO4 dose. No changes in the phase assemblage were detected in the samples with curing from 1 month up to 18 months, indicating a stable binder structure. The most significant changes upon curing at advanced ages observed were growth of the AFt phase and an increase in silicate chain length in the C-A-S-H, resulting in higher strength.

  2. Effect of Interface Structure on the Microstructural Evolution of Ceramics

    DTIC Science & Technology

    2007-11-06

    surface physics is the surface structural transition from a low-temperature atomically smooth state to a high - temperature rough one. The former has an...being present during sintering.60 Furthermore, investigations using high resolution electron microscopy showed that even solid-state sintered ceramic...the average has a very harmful effect on the strength of this material. A small amount of TaC, VC or other carbides is usually added to inhibit AGG in

  3. Structure and evolution of the northern Potwar deformed zone, Pakistan

    SciTech Connect

    Jaswal, T.M.; Lillie, R.J.; Lawrence, R.D.

    1997-02-01

    The northern Potwar deformed zone (NPDZ) is part of the active foreland fold and thrust belt of the Salt Range and Potwar Plateau in northern Pakistan. About 500 km of seismic reflection profiles are integrated with surface geologic and drilling data to examine the deformation style and structure of the NPDZ with particular emphasis on history of deformation of the Dhurnal oil field. The seismic lines suggest that the overall structure of the eastern NPDZ is a duplex structure developed beneath a passive roof thrust. The roof thrust is generated from a tipline in the Miocene Murree Formation, and the sole thrust is initiated from the same Eocambrian evaporate zone that extends 80 km southward beneath the Soan syncline and Salt Range. The Dhurnal oil field structure is a pop-up at the southern margin of the NPDZ, and developed beneath the passive roof thrust. The passive roof thrust crops out just north of Dhurnal on the steep, northern limb of the Soan syncline. An overstep passive roof thrust (Sakhwal fault) is interpreted west of Dhurnal; this fault developed due to southward progression of the deformation front beneath the earlier passive roof thrust. Very gentle basement dip and almost zero topographic slope in the NPDZ suggest that the Eocambrian salt provides effective decoupling at the present position of the NPDZ. The strong deformation in the NPDZ appears to have developed farther north, in an area where the evaporates may be lacking. Since 2 Ma, the NPDZ moved farther south over the evaporates without further deformation, whereas erosion removed any former topographic slope. Restoring a balanced cross section suggests that the minimum shortening across the NPDZ is more than 55 km. Assuming that this shortening occurred between 5.1 and 2 Ma, the shortening rate is about 18 mm/yr.

  4. Structural evolution and hydrocarbon accumulation of Luxi Depression

    SciTech Connect

    Li Hongliang; Qian Hua Xiao; Angui Lei )

    1996-01-01

    Located in the eastern Inner Mongolia Autonomous Region, China, Luxi Depression covers an area of 760 km[sup 2] and is one of the more than 250 small rifts of Northeast Rift System, the basement of which is Hercynian told belt. The Depression has undergone two Late Jurassic events: rifting and depression. The rifting sedimentation (the main period) may be divided into four stages: in the initial tensional faulting stage (Yixian Age) are accumulated a set of mantle-sourced volcanic rocks; in the fast subsiding stage (Jiufotang Age) the sedimentary system is distributed in belts under the control of boundary faults; in the steep area alluvial fans and near-shore sublacustrine fans are developed; in the gentle area braided deltas are developed; in the central deep area dark mudstones and sublacustrine gravity flows are developed. Meanwhile the rollover structures began to form on the down-thrown walls of the faults and the drape structures are formed on the convex side of the volcanic rocks. The stable subsiding stage (Shahai Age) is mainly a shallow-semi-deep lacustrine system; the rollover structures are generally finished (Fuxin Age). Most of the fill of the re-rising shrinking stage are near-shallow-lake and marsh facies sedimentation. There are five kinds of oil reservoirs distributed around the oil-generating depressions: rollover anticline, structure-lithology reservoir, updip pinch out, lenticular sandstone, and impermeable sandstone seals. Such reservoir formation models are relatively representative in rift system and can be a model for oil and gas exploration in similar depressions.

  5. Structural evolution and hydrocarbon accumulation of Luxi Depression

    SciTech Connect

    Li Hongliang; Qian Hua Xiao; Angui Lei

    1996-12-31

    Located in the eastern Inner Mongolia Autonomous Region, China, Luxi Depression covers an area of 760 km{sup 2} and is one of the more than 250 small rifts of Northeast Rift System, the basement of which is Hercynian told belt. The Depression has undergone two Late Jurassic events: rifting and depression. The rifting sedimentation (the main period) may be divided into four stages: in the initial tensional faulting stage (Yixian Age) are accumulated a set of mantle-sourced volcanic rocks; in the fast subsiding stage (Jiufotang Age) the sedimentary system is distributed in belts under the control of boundary faults; in the steep area alluvial fans and near-shore sublacustrine fans are developed; in the gentle area braided deltas are developed; in the central deep area dark mudstones and sublacustrine gravity flows are developed. Meanwhile the rollover structures began to form on the down-thrown walls of the faults and the drape structures are formed on the convex side of the volcanic rocks. The stable subsiding stage (Shahai Age) is mainly a shallow-semi-deep lacustrine system; the rollover structures are generally finished (Fuxin Age). Most of the fill of the re-rising shrinking stage are near-shallow-lake and marsh facies sedimentation. There are five kinds of oil reservoirs distributed around the oil-generating depressions: rollover anticline, structure-lithology reservoir, updip pinch out, lenticular sandstone, and impermeable sandstone seals. Such reservoir formation models are relatively representative in rift system and can be a model for oil and gas exploration in similar depressions.

  6. Structural insights into the evolution of an antibody combining site

    SciTech Connect

    Wedemayer, G.J.; Patten, P.A.; Wang, L.H.; Schultz, P.G.; Stevens, R.C. |

    1997-06-13

    The crystal structures of a germline antibody Fab fragment and its complex with hapten have been solved at 2.1 {angstrom} resolution. These structures are compared with the corresponding crystal structures of the affinity-matured antibody, 48G7, which has a 30,000 times higher affinity for hapten as a result of nine replacement somatic mutations. Significant changes in the configuration of the combining site occur upon binding of hapten to the germline antibody, whereas hapten binds to the mature antibody by a lock-and-key fit mechanism. The reorganization of the combining site that was nucleated by hapten binding is further optimized by somatic mutations that occur up to 15 {angstrom} from bound hapten. These results suggest that the binding potential of the primary antibody repertoire may be significantly expanded by the ability of germline antibodies to adopt more than one combining-site configuration, with both antigen binding and somatic mutation stabilizing the configuration with optimal hapten complementarily.

  7. Evolution of polymer photovoltaic performances from subtle chemical structure variations.

    PubMed

    Yan, Han; Li, Denghua; Lu, Kun; Zhu, Xiangwei; Zhang, Yajie; Yang, Yanlian; Wei, Zhixiang

    2012-11-21

    Conjugated polymers are promising replacements for their inorganic counterparts in photovoltaics due to their low cost, ease of processing, and straightforward thin film formation. New materials have been able to improve the power conversion efficiency of photovoltaic cells up to 8%. However, rules for rational material design are still lacking, and subtle chemical structure variations usually result in large performance discrepancies. The present paper reports a detailed study on the crystalline structure, morphology, and in situ optoelectronic properties of blend films of polythiophene derivatives and [6,6]-phenyl C61-butyric acid methyl ester by changing the alkyl side chain length and position of polythiophene. The correlation among the molecular structure, mesoscopic morphology, mesoscopic optoelectronic property and macroscopic device performance (highest efficiency above 4%) was directly established. Both solubility and intermolecular interactions should be considered in rational molecular design. Knowledge obtained from this study can aid the selection of appropriate processing conditions that improve blend film morphology, charge transport property, and overall solar cell efficiency.

  8. Evolution of sexual dimorphism in phenotypic covariance structure in Phymata.

    PubMed

    Punzalan, David; Rowe, Locke

    2015-06-01

    Sexual dimorphism is a consequence of both sex-specific selection and potential constraints imposed by a shared genetic architecture underlying sexually homologous traits. However, genetic architecture is expected to evolve to mitigate these constraints, allowing the sexes to approach their respective optimal mean phenotype. In addition, sex-specific selection is expected to generate sexual dimorphism of trait covariance structure (e.g., the phenotypic covariance matrix, P), but previous empirical work has not fully addressed this prediction. We compared patterns of phenotypic divergence, for three traits in seven taxa in the insect genus Phymata (Reduviidae), to ask whether sexual dimorphism in P is common and whether its magnitude relates to the extent of sexual dimorphism in trait means. We found that sexual dimorphism in both mean and covariance structure was pervasive but also that the multivariate distance between sex-specific means was correlated with sex differences in the leading eigenvector of P, while accounting for uncertainty in phylogenetic relationships. Collectively, our findings suggest that sexual dimorphism in covariance structure may be a common but underappreciated feature of dioecious populations.

  9. Structural evolution and petroleum potential of the Norwegian Barents Sea

    SciTech Connect

    Nilsen, K.T.

    1995-08-01

    The tectonic history of the Norwegian Barents Sea has provided potential hydrocarbon traps in clastic reservoirs associated with rotated fault blocks, compressional anticlines and salt domes. Significant stratigraphic potential also resides in Paleozoic carbonates. Drilling in the Hammerfest Basin has yielded large gas discoveries in rotated fault blocks, but other trapping concepts remain relatively untested. The undrilled arm north of 74{degrees} 30 minutes N, currently being mapped by the Norwegian Petroleum Directorate using exclusive seismic and geological data from shallow boreholes, represents a significant area for future exploration. Prospectivity is critically dependent on the scaling of traps following Neogene uplift of large areas of the Barents platform. The area is dominated by structural trends inherited from the Caledonian and older orogens. Carboniferous rifting established a system of half grabens and intervening highs, followed by late Permian faulting in the west which initiated regional subsidence continuing into the early Jurassic. Fault reactivation in early Triassic times triggered salt diapirism and provided structural control for the formation of Triassic shelf margins. During the late Jurassic-early Cretaceous western basins underwent tectonic subsidence, while the northeastern platform arm was subject to gentle compression. In the late Cretaceous salt was reactivated in the Nordkapp Basin and compressional structures developed west of the Loppa High. Further subsidence of the western basins was promoted by late Mesozoic and early Tertiary transtensional movements along the North Atlantic rift system. Subsequent regional compression in these basins, and basin inversion east of the Loppa High, are of post-Eocene age.

  10. Gravitational Lenses and the Structure and Evolution of Galaxies

    NASA Technical Reports Server (NTRS)

    Kochanek, Christopher

    2003-01-01

    The grant has supported the completion of 16 papers and 4 conference proceedings to date. During the first year of the project we completed five papers, each of which represents a new direction in the theory and interpretation of gravitational lenses. In the first paper, "The Importance of Einstein Rings", we developed the first theory for the formation and structure of the Einstein rings formed by lensing extended sources like the host galaxies of quasar and radio sources. We applied the theory to three lenses with lensed host galaxies. For the time delay lens PG 1115+080 we found that the structure of the Einstein ring ruled out models of the gravitational potential which permitted a large Hubble constant (70 km/s Mpc). In the second paper, :Cusped Mass Models Of Gravitational Lenses", we introduced a new class of lens models where the central density is characterized by a cusp ( rho proportional to tau(sup -gamma), 1 less than gamma less than 2) as in most modern models and theories of galaxies rather than a finite core radius. In the third paper, "Global Probes of the Impact of Baryons on Dark Matter Halos", we made the first globally consistent models for the separation distribution of gravitational lenses including both galaxy and cluster lenses. We show that the key physics for the origin of the sharp separation cutoff in the separation distribution near 3 arc sec is the effect of the cooling baryons in galaxies on the density structure of the system.

  11. The relativistic equations of stellar structure and evolution. Stars with degenerate neutron cores. 1: Structure of equilibrium models

    NASA Technical Reports Server (NTRS)

    Thorne, K. S.; Zytkow, A. N.

    1976-01-01

    The general relativistic equations of stellar structure and evolution are reformulated in a notation which makes easy contact with Newtonian theory. Also, a general relativistic version of the mixing-length formalism for convection is presented. Finally, it is argued that in previous work on spherical systems general relativity theorists have identified the wrong quantity as "total mass-energy inside radius r."

  12. Evolution, structure and function of hydrologic subsystems in hillslopes

    NASA Astrophysics Data System (ADS)

    Troch, P. A.; Brooks, P.; Chorover, J.; Huxman, T.; McDonnell, J. J.; Rasmussen, C.; Sivapalan, M.

    2007-12-01

    Hillslopes offer a useful elementary scale to construct catchment hydrologic models, and to understand the role of water in the landscape. However, hillslopes exhibit enormous complexity and heterogeneity, much of which is not easily observable. The complexity is driven by the interactions between water, biogeochemistry, ecology and soils, within the constraints set by the climate and the geologic history of the system. These interactions create complex, non-random patterns and structures in space-time. Current models have difficulty accounting for these interactions and unobserved structural complexity. A new approach may ask: why do the complex structures exist at all? Taking the view that the hydrology of a landscape has evolved along with its soils, ecology and geomorphology, we may ask if the hydrologic subsystem of a hillslope has a functional role in the maintenance of the overall system. This functional role may be expressed as an organizing principle - a constraint on possible ways that the hydrologic flowpaths may be organized such that the functional role is met. If a relationship can be established between an organizing principle and the structure of hydrologic flow-paths and storages, it can form the basis for developing closure relations at the hillslope scale that have meaningful relationships to the underlying dynamics. In this way, heterogeneity and complexity of hillslopes are no longer problems to be overcome, but rather are keys to making meaningful predictions. Formulating and testing organizing principles will necessarily require the synthesis of knowledge from many disciplines. One approach is to construct artificial hillslopes in a controlled environment, and use them to ask, given a set of observable constraints (climate, soil, ecologic and biogeochemical parameters) which structures and responses are "behavioral" - in the sense that they fulfill the function set by the organizing principle. Such artificial hillslopes will be constructed at

  13. Thermally induced structural evolution and performance of mesoporous block copolymer-directed alumina perovskite solar cells.

    PubMed

    Tan, Kwan Wee; Moore, David T; Saliba, Michael; Sai, Hiroaki; Estroff, Lara A; Hanrath, Tobias; Snaith, Henry J; Wiesner, Ulrich

    2014-05-27

    Structure control in solution-processed hybrid perovskites is crucial to design and fabricate highly efficient solar cells. Here, we utilize in situ grazing incidence wide-angle X-ray scattering and scanning electron microscopy to investigate the structural evolution and film morphologies of methylammonium lead tri-iodide/chloride (CH3NH3PbI(3-x)Cl(x)) in mesoporous block copolymer derived alumina superstructures during thermal annealing. We show the CH3NH3PbI(3-x)Cl(x) material evolution to be characterized by three distinct structures: a crystalline precursor structure not described previously, a 3D perovskite structure, and a mixture of compounds resulting from degradation. Finally, we demonstrate how understanding the processing parameters provides the foundation needed for optimal perovskite film morphology and coverage, leading to enhanced block copolymer-directed perovskite solar cell performance.

  14. A laser-probe 40Ar/ 39Ar study of pseudotachylite from the Tambach Fault Zone, Kenya: direct isotopic dating of brittle faults

    NASA Astrophysics Data System (ADS)

    Sherlock, S. C.; Hetzel, R.

    2001-01-01

    Understanding the tectonic evolution of orogenic belts and intracratonic areas depends on our ability to determine the age of tectonic features on a variety of scales. This study demonstrates the value of the laser-probe 40Ar/ 39Ar dating technique, which, if applied to fault-derived pseudotachylites, may be used to directly determine the age of brittle faults. The laser-probe technique affords high spatial resolution, enabling a greater opportunity for discriminating between pseudotachylite matrix, host-rock clasts and alteration products that are often present in varying proportions within pseudotachylites. The laser-probe 40Ar/ 39Ar technique has been applied to pseudotachylite samples from the Tambach Fault Zone (TFZ), a major NW-SE trending strike-slip fault within the Kenyan part of the Late Proterozoic/Early Palaeozoic Mozambique Belt. The pseudotachylites of the TFZ were previously thought to have formed either (i) at about 530-430 Ma, or (ii) during the Cenozoic evolution of the Kenya Rift. In the latter case, seismic slip on the rift-bounding normal fault would have generated the pseudotachylites, due to the reactivation of old NW-SE trending structures in the basement. Based on our new data, we interpret the pseudotachylite formation age to be 400 Ma. This rules out the possibility that the pseudotachylites are related to the formation of the Kenya Rift. Although the inherited basement faults may have been locally reactivated as transfer faults, reactivation of these structures during rifting did not occur beyond the margins of the Kenya Rift.

  15. Comparative Structural Models of Similarities and Differences between "Vehicle" and "Target" in Order to Teach Darwinian "Evolution"

    ERIC Educational Resources Information Center

    Marcelos, Maria Fatima; Nagem, Ronaldo L.

    2010-01-01

    Our objective is to contribute to the teaching of Classical Darwinian "Evolution" by means of a study of analogies and metaphors. Throughout the history of knowledge about "Evolution" and in Science teaching, tree structures have been used an analogs to refer to "Evolution," such as by Darwin in the "Tree of Life" passage contained in "On The…

  16. Evolution of Nucleotide Punctuation Marks: From Structural to Linear Signals

    PubMed Central

    El Houmami, Nawal; Seligmann, Hervé

    2017-01-01

    We present an evolutionary hypothesis assuming that signals marking nucleotide synthesis (DNA replication and RNA transcription) evolved from multi- to unidimensional structures, and were carried over from transcription to translation. This evolutionary scenario presumes that signals combining secondary and primary nucleotide structures are evolutionary transitions. Mitochondrial replication initiation fits this scenario. Some observations reported in the literature corroborate that several signals for nucleotide synthesis function in translation, and vice versa. (a) Polymerase-induced frameshift mutations occur preferentially at translational termination signals (nucleotide deletion is interpreted as termination of nucleotide polymerization, paralleling the role of stop codons in translation). (b) Stem-loop hairpin presence/absence modulates codon-amino acid assignments, showing that translational signals sometimes combine primary and secondary nucleotide structures (here codon and stem-loop). (c) Homopolymer nucleotide triplets (AAA, CCC, GGG, TTT) cause transcriptional and ribosomal frameshifts. Here we find in recently described human mitochondrial RNAs that systematically lack mono-, dinucleotides after each trinucleotide (delRNAs) that delRNA triplets include 2x more homopolymers than mitogenome regions not covered by delRNA. Further analyses of delRNAs show that the natural circular code X (a little-known group of 20 translational signals enabling ribosomal frame retrieval consisting of 20 codons {AAC, AAT, ACC, ATC, ATT, CAG, CTC, CTG, GAA, GAC, GAG, GAT, GCC, GGC, GGT, GTA, GTC, GTT, TAC, TTC} universally overrepresented in coding versus other frames of gene sequences), regulates frameshift in transcription and translation. This dual transcription and translation role confirms for X the hypothesis that translational signals were carried over from transcriptional signals.

  17. Evolution of Nucleotide Punctuation Marks: From Structural to Linear Signals.

    PubMed

    El Houmami, Nawal; Seligmann, Hervé

    2017-01-01

    We present an evolutionary hypothesis assuming that signals marking nucleotide synthesis (DNA replication and RNA transcription) evolved from multi- to unidimensional structures, and were carried over from transcription to translation. This evolutionary scenario presumes that signals combining secondary and primary nucleotide structures are evolutionary transitions. Mitochondrial replication initiation fits this scenario. Some observations reported in the literature corroborate that several signals for nucleotide synthesis function in translation, and vice versa. (a) Polymerase-induced frameshift mutations occur preferentially at translational termination signals (nucleotide deletion is interpreted as termination of nucleotide polymerization, paralleling the role of stop codons in translation). (b) Stem-loop hairpin presence/absence modulates codon-amino acid assignments, showing that translational signals sometimes combine primary and secondary nucleotide structures (here codon and stem-loop). (c) Homopolymer nucleotide triplets (AAA, CCC, GGG, TTT) cause transcriptional and ribosomal frameshifts. Here we find in recently described human mitochondrial RNAs that systematically lack mono-, dinucleotides after each trinucleotide (delRNAs) that delRNA triplets include 2x more homopolymers than mitogenome regions not covered by delRNA. Further analyses of delRNAs show that the natural circular code X (a little-known group of 20 translational signals enabling ribosomal frame retrieval consisting of 20 codons {AAC, AAT, ACC, ATC, ATT, CAG, CTC, CTG, GAA, GAC, GAG, GAT, GCC, GGC, GGT, GTA, GTC, GTT, TAC, TTC} universally overrepresented in coding versus other frames of gene sequences), regulates frameshift in transcription and translation. This dual transcription and translation role confirms for X the hypothesis that translational signals were carried over from transcriptional signals.

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

    PubMed

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

    2017-01-01

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

  19. The structure and evolution of a wintertime occluded front

    NASA Astrophysics Data System (ADS)

    Saarikivi, Pirkko; Puhakka, Timo

    1990-01-01

    A study, making use of serial radiosonde soundings, weather radar measurements and aircraft reports, has been made of the structure of a deeply occluded wintertime front. The sounding interval during the frontal passage was exceptionally short. The synoptic-scale front-relative flow could be described using the concepts of cyclone warm and cold conveyor belt flows (WCB and CCB) only in its initial stages. During the final stages of the occlusion process, the WCB became diffuse, the CCB weakened and penetrated below the occluded front, and a third relatively dry, cool, and diffluent airflow of mid-tropospheric origin was established above the occluded front. The subsynoptic structure of the occlusion was characterized by a warm frontal zone and, lying above it, a series of "warm tongues" and "cold surges" with a wavelength of about 100km. The related circulations were also responsible for the formation of the observed banded structures in the snowfall, and agreed with the observed distributions of wind, humidity and temperature. As a whole, the warm tongues and the cold surges together with their related circulations transferred warm moist air upwards and northwards as required in the occlusion process. The observed wavelength, as well as the thermal and kinematic features of the circulations agreed well with the theory of conditional symmetric instability (CSI), though in this case, only small areas with pure CSI were found. The most significant area with CSI was found behind the occluded surface front at the top of the moist layer, while the other areas of CSI, found at higher elevations both above and on the occluded frontal surface were clearly smaller. This was considered to be related to the time history and the life-cycle of the roll circulations probably produced by the CSI.

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

    PubMed Central

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

    2017-01-01

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

  1. Monogamy, strongly bonded groups, and the evolution of human social structure.

    PubMed

    Chapais, Bernard

    2013-01-01

    Human social evolution has most often been treated in a piecemeal fashion, with studies focusing on the evolution of specific components of human society such as pair-bonding, cooperative hunting, male provisioning, grandmothering, cooperative breeding, food sharing, male competition, male violence, sexual coercion, territoriality, and between-group conflicts. Evolutionary models about any one of those components are usually concerned with two categories of questions, one relating to the origins of the component and the other to its impact on the evolution of human cognition and social life. Remarkably few studies have been concerned with the evolution of the entity that integrates all components, the human social system itself. That social system has as its core feature human social structure, which I define here as the common denominator of all human societies in terms of group composition, mating system, residence patterns, and kinship structures. The paucity of information on the evolution of human social structure poses substantial problems because that information is useful, if not essential, to assess both the origins and impact of any particular aspect of human society.

  2. The evolution of field-induced structure of confined ferrofluid emulsions

    SciTech Connect

    Mou, T.; Flores, G.A.; Liu, J. . Dept. of Physics and Astronomy); Bibette, J. ); Richard, J. )

    1994-09-01

    The authors report a real-time study of the evolution of the structure of confined ferrofluid emulsions during the ''liquid-solid'' phase transition. A monodisperse oil-in-water ferrofluid emulsion is used. The structure evolution of the emulsion after rapidly applying a magnetic field is probed by the static light scattering. The scattering pattern exhibits pronounced rings reflecting the formation of chains and their coalescence to columns or even ''worm'' structures. The scattering ring is found to decrease in size and brighten in intensity with time. To monitor the structure evolution in time, both the ring peak position in scattering wave vector, q[sub max], and the peak intensity, I[sub max], are measured as a function of time. Both q[sub max] and I[sub max] saturate in less than 0.5 seconds after applying a magnetic field. At a constant cell thickness of 25 [mu]m, the evolution of structure is essentially independent of volume fraction ranging from 0.015 to 0.13. In addition, a very good scaling is found in the scattered light intensity as a function of the scattering wave vector.

  3. Maintenance of a Protein Structure in the Dynamic Evolution of TIMPs over 600 Million Years

    PubMed Central

    Nicosia, Aldo; Maggio, Teresa; Costa, Salvatore; Salamone, Monica; Tagliavia, Marcello; Mazzola, Salvatore; Gianguzza, Fabrizio; Cuttitta, Angela

    2016-01-01

    Deciphering the events leading to protein evolution represents a challenge, especially for protein families showing complex evolutionary history. Among them, TIMPs represent an ancient eukaryotic protein family widely distributed in the animal kingdom. They are known to control the turnover of the extracellular matrix and are considered to arise early during metazoan evolution, arguably tuning essential features of tissue and epithelial organization. To probe the structure and molecular evolution of TIMPs within metazoans, we report the mining and structural characterization of a large data set of TIMPs over approximately 600 Myr. The TIMPs repertoire was explored starting from the Cnidaria phylum, coeval with the origins of connective tissue, to great apes and humans. Despite dramatic sequence differences compared with highest metazoans, the ancestral proteins displayed the canonical TIMP fold. Only small structural changes, represented by an α-helix located in the N-domain, have occurred over the evolution. Both the occurrence of such secondary structure elements and the relative solvent accessibility of the corresponding residues in the three-dimensional structures raises the possibility that these sites represent unconserved element prone to accept variations. PMID:26957029

  4. Tectonic evolution and mantle structure of the Caribbean

    NASA Astrophysics Data System (ADS)

    van Benthem, Steven; Govers, Rob; Spakman, Wim; Wortel, Rinus

    2013-04-01

    In the broad context of investigating the relationship between deep structure & processes and surface expressions, we study the Caribbean plate and underlying mantle. We investigate whether predictions of mantle structure from tectonic reconstructions are in agreement with a detailed tomographic image of seismic P-wave velocity structure under the Caribbean region. In the upper mantle, positive seismic anomalies are imaged under the Lesser Antilles and Puerto Rico. These anomalies are interpreted as remnants of Atlantic lithosphere subduction and confirm tectonic reconstructions that suggest at least 1100 km of convergence at the Lesser Antilles island arc during the past ~45 Myr. The imaged Lesser-Antilles slab consists of a northern and southern anomaly, separated by a low velocity anomaly across most of the upper mantle, which we interpret as the subducted North-South America plate boundary. The southern edge of the imaged Lesser Antilles slab agrees with vertical tearing of South America lithosphere. The northern Lesser Antilles slab is continuous with the Puerto Rico slab along the northeastern plate boundary. This results in an amphitheater-shaped slab and it is interpreted as westward subducting North America lithosphere that remained attached to the surface along the northern boundary. At the Muertos Trough, however, material is imaged until a depth of only 100 km, suggesting a small amount of subduction. The location and length of the imaged South Caribbean slab agrees with proposed subduction of Caribbean lithosphere under the northern South America plate. An anomaly related to proposed Oligocene subduction at the Nicaragua rise is absent in the tomographic model. Beneath Panama, a subduction window exists across the upper mantle, which is related to the cessation of subduction of the Nazca plate under Panama since 9.5 Ma and possibly the preceding subduction of the extinct Cocos-Nazca spreading center. In the lower mantle two large anomaly patterns are

  5. Reaction centres: the structure and evolution of biological solar power.

    PubMed

    Heathcote, Peter; Fyfe, Paul K; Jones, Michael R

    2002-02-01

    Reaction centres are complexes of pigment and protein that convert the electromagnetic energy of sunlight into chemical potential energy. They are found in plants, algae and a variety of bacterial species, and vary greatly in their composition and complexity. New structural information has highlighted features that are common to the different types of reaction centre and has provided insights into some of the key differences between reaction centres from different sources. New ideas have also emerged on how contemporary reaction centres might have evolved and on the possible origin of the first chlorophyll-protein complexes to harness the power of sunlight.

  6. Galactic Structure and Evolution: a decade of surveys

    NASA Astrophysics Data System (ADS)

    Gilmore, G.

    2004-12-01

    Surveys of the local and distant Universe are the means to test and improve our models of galaxy formation. Substantial successes in the models are evident, while there is also considerable recent progress in identifying what remains to be learned. The key weaknesses of present models are related to merging histories, and small-scale structures, which are both significantly at variance with observations. Observers are polite, and often emphasise their agreements with models. data is objective, and shows us the way to focus future surveys, to allow improved understanding and knowledge.

  7. The structure and evolution of ancient impact basins on Mars

    NASA Technical Reports Server (NTRS)

    Schultz, P. H.; Schultz, R. A.; Rogers, J.

    1982-01-01

    It is pointed out that characteristic styles of degradation and modification of obvious Martian basins make it possible to recognize more subtle expressions. This approach is seen as providing not only additional basins to the existing inventory but also fundamental clues for initial impact basin structure and stratigraphy. It also reveals the long-lasting influence of basin formation on the crust of Mars in spite of extensive erosion and resurfacing. Consideration is given to five clear examples of modified impact basins, and regions around each that have undergone similar processes (fracturing, collapse, channeling) are delineated. These processes among the different basins are then compared, and similar zones of modification are correlated with concentric basin rings. Consideration is then given to the implications of these observations for current models of basin formation and to the role of impact basins in controlling regional tectonics. The results indicate that large multiring impact scars leave a major but sometimes subtle imprint on the geologic structure of stable crustal regions on Mars.

  8. 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.

  9. Structure and function evolution of thiolate monolayers on gold

    SciTech Connect

    Edwards, Grant Alvin

    2006-01-01

    The use of n-alkanethiolate self-assembled monolayers on gold has blossomed in the past few years. These systems have functioned as models for common interfaces. Thiolate monolayers are ideal because they are easily modified before or after deposition. The works contained within this dissertation include interfacial characterization (infrared reflection absorption spectroscopy, ellipsometry, contact angle, scanning probe microscopy, and heterogeneous electron-transfer kinetics) and various modeling scenarios. The results of these characterizations present ground-breaking insights into the structure, function, and reproducible preparation of these monolayers. Surprisingly, three interfacial properties (electron-transfer, contact angle, and ellipsometry) were discovered to depend directly on the odd-even character of the monolayer components. Molecular modeling was utilized to investigate adlayer orientation, and suggests that these effects are adlayer structure specific. Finally, the electric force microscopy and theoretical modeling investigations of monolayer samples are presented, which show that the film dielectric constant, thickness, and dipole moment directly affect image contrast. In addition, the prospects for utilization of this emerging technique are outlined.

  10. Structure and Function Evolution of Thiolate Monolayers on Gold

    SciTech Connect

    Edwards, Grant Alvin

    2006-01-01

    The use of n-alkanethiolate self-assembled monolayers on gold has blossomed in the past few years. These systems have functioned as models for common interfaces. Thiolate monolayers are ideal because they are easily modified before or after deposition. The works contained within this dissertation include interfacial characterization (inbred reflection absorption spectroscopy, ellipsometry, contact angle, scanning probe microscopy, and heterogeneous electron-transfer kinetics) and various modeling scenarios. The results of these characterizations present ground-breaking insights into the structure, function, and reproducible preparation of these monolayers. Surprisingly, three interfacial properties (electron-transfer, contact angle, and ellipsometry) were discovered to depend directly on the odd-even character of the monolayer components. Molecular modeling was utilized to investigate adlayer orientation, and suggests that these effects are adlayer structure specific. Finally, the electric force microscopy and theoretical modeling investigations of monolayer samples are presented, which show that the film dielectric constant, thickness, and dipole moment directly affect image contrast. In addition, the prospects for utilization of this emerging technique are outlined.

  11. Nanoscale structural oscillations in perovskite oxides induced by oxygen evolution.

    PubMed

    Han, Binghong; Stoerzinger, Kelsey A; Tileli, Vasiliki; Gamalski, Andrew D; Stach, Eric A; Shao-Horn, Yang

    2017-01-01

    Understanding the interaction between water and oxides is critical for many technological applications, including energy storage, surface wetting/self-cleaning, photocatalysis and sensors. Here, we report observations of strong structural oscillations of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) in the presence of both H2O vapour and electron irradiation using environmental transmission electron microscopy. These oscillations are related to the formation and collapse of gaseous bubbles. Electron energy-loss spectroscopy provides direct evidence of O2 formation in these bubbles due to the incorporation of H2O into BSCF. SrCoO3-δ was found to exhibit small oscillations, while none were observed for La0.5Sr0.5CoO3-δ and LaCoO3. The structural oscillations of BSCF can be attributed to the fact that its oxygen 2p-band centre is close to the Fermi level, which leads to a low energy penalty for oxygen vacancy formation, high ion mobility, and high water uptake. This work provides surprising insights into the interaction between water and oxides under electron-beam irradiation.

  12. Nanoscale structural oscillations in perovskite oxides induced by oxygen evolution

    DOE PAGES

    Han, Binghong; Stoerzinger, Kelsey A.; Tileli, Vasiliki; ...

    2016-10-03

    Understanding the interaction between water and oxides is critical for many technological applications, including energy storage, surface wetting/self-cleaning, photocatalysis and sensors. In this paper, we report observations of strong structural oscillations of Ba0.5Sr0.5Co0.8Fe0.2O3$-$δ (BSCF) in the presence of both H2O vapour and electron irradiation using environmental transmission electron microscopy. These oscillations are related to the formation and collapse of gaseous bubbles. Electron energy-loss spectroscopy provides direct evidence of O2 formation in these bubbles due to the incorporation of H2O into BSCF. SrCoO3$-$δ was found to exhibit small oscillations, while none were observed for La0.5Sr0.5CoO3$-$δ and LaCoO3. The structural oscillations ofmore » BSCF can be attributed to the fact that its oxygen 2p-band centre is close to the Fermi level, which leads to a low energy penalty for oxygen vacancy formation, high ion mobility, and high water uptake. This work provides surprising insights into the interaction between water and oxides under electron-beam irradiation.« less

  13. Nanoscale structural oscillations in perovskite oxides induced by oxygen evolution

    SciTech Connect

    Han, Binghong; Stoerzinger, Kelsey A.; Tileli, Vasiliki; Gamalski, Andrew  D.; Stach, Eric A.; Shao-Horn, Yang

    2016-10-03

    Understanding the interaction between water and oxides is critical for many technological applications, including energy storage, surface wetting/self-cleaning, photocatalysis and sensors. In this paper, we report observations of strong structural oscillations of Ba0.5Sr0.5Co0.8Fe0.2O3$-$δ (BSCF) in the presence of both H2O vapour and electron irradiation using environmental transmission electron microscopy. These oscillations are related to the formation and collapse of gaseous bubbles. Electron energy-loss spectroscopy provides direct evidence of O2 formation in these bubbles due to the incorporation of H2O into BSCF. SrCoO3$-$δ was found to exhibit small oscillations, while none were observed for La0.5Sr0.5CoO3$-$δ and LaCoO3. The structural oscillations of BSCF can be attributed to the fact that its oxygen 2p-band centre is close to the Fermi level, which leads to a low energy penalty for oxygen vacancy formation, high ion mobility, and high water uptake. This work provides surprising insights into the interaction between water and oxides under electron-beam irradiation.

  14. Structure, molecular evolution, and hydrolytic specificities of largemouth bass pepsins.

    PubMed

    Miura, Yoko; Suzuki-Matsubara, Mieko; Kageyama, Takashi; Moriyama, Akihiko

    2016-02-01

    The nucleotide sequences of largemouth bass pepsinogens (PG1, 2 and 3) were determined after molecular cloning of the respective cDNAs. Encoded PG1, 2 and 3 were classified as fish pepsinogens A1, A2 and C, respectively. Molecular evolutionary analyses show that vertebrate pepsinogens are classified into seven monophyletic groups, i.e. pepsinogens A, F, Y (prochymosins), C, B, and fish pepsinogens A and C. Regarding the primary structures, extensive deletion was obvious in S'1 loop residues in fish pepsin A as well as tetrapod pepsin Y. This deletion resulted in a decrease in hydrophobic residues in the S'1 site. Hydrolytic specificities of bass pepsins A1 and A2 were investigated with a pepsin substrate and its variants. Bass pepsins preferred both hydrophobic/aromatic residues and charged residues at the P'1 sites of substrates, showing the dual character of S'1 sites. Thermodynamic analyses of bass pepsin A2 showed that its activation Gibbs energy change (∆G(‡)) was lower than that of porcine pepsin A. Several sites of bass pepsin A2 moiety were found to be under positive selection, and most of them are located on the surface of the molecule, where they are involved in conformational flexibility. The broad S'1 specificity and flexible structure of bass pepsin A2 are thought to cause its high proteolytic activity.

  15. Nanoscale structural oscillations in perovskite oxides induced by oxygen evolution

    NASA Astrophysics Data System (ADS)

    Han, Binghong; Stoerzinger, Kelsey A.; Tileli, Vasiliki; Gamalski, Andrew D.; Stach, Eric A.; Shao-Horn, Yang

    2017-01-01

    Understanding the interaction between water and oxides is critical for many technological applications, including energy storage, surface wetting/self-cleaning, photocatalysis and sensors. Here, we report observations of strong structural oscillations of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) in the presence of both H2O vapour and electron irradiation using environmental transmission electron microscopy. These oscillations are related to the formation and collapse of gaseous bubbles. Electron energy-loss spectroscopy provides direct evidence of O2 formation in these bubbles due to the incorporation of H2O into BSCF. SrCoO3-δ was found to exhibit small oscillations, while none were observed for La0.5Sr0.5CoO3-δ and LaCoO3. The structural oscillations of BSCF can be attributed to the fact that its oxygen 2p-band centre is close to the Fermi level, which leads to a low energy penalty for oxygen vacancy formation, high ion mobility, and high water uptake. This work provides surprising insights into the interaction between water and oxides under electron-beam irradiation.

  16. Structural evolution of the Mejerda zone, northern Tunisia

    SciTech Connect

    Baird, A.; Grocott, J. ); Grant, G. ); Moody, R.; Sandman, R. )

    1991-08-01

    The Mejerda zone lies southeast of the Tellian Atlas and has been regarded as part of the reactivated foreland to this late Palaeogene to Neogene thrust belt. Folds have a northeast-southwest (Atlas) trend to the zone contains Triassic, Jurassic, Cretaceous, and Tertiary sediments, including source and reservoir rocks. Northeast-southwest trending Miocene-Pliocene-Pleistocene basin in the zone have attracted petroleum exploration. In the Mejerda zone, Triassic rocks are generally held to have been emplaced diapirically. However, they often outcrop in thin, fault-bounded sheets and not in diapiric domelike structures. Furthermore, there is no unequivocal evidence for the existence of extensive salt deposits in the zone, either at outcrop or in boreholes. Instead, the Triassic rocks are red clastics with some gypsum and black dolomites. Balanced cross sections show that a thin-skinned thrust model with a decollement in the Triassic is consistent with the surface geology of the Mejerda zone. In this model the Triassic rocks decorate low-angle thrust faults. Shortening is estimated to be 40-50%, and the zone is part of the Atlas thrust belt and not a reactivated foreland. As well as thrust-generated old-over-young stratigraphic superpositions, many tectonic contacts in the Mejerda zone place young rocks on old. Such superpositions may be caused by out-of-sequence thrusts but more likely reflect northwest-southeast extension following thrusting. This extension formed the longitudinal Miocene-Pliocene-Pleistocene basins which conceal thrust-belt structures.

  17. The Ninole Basalt - Implications for the structural evolution of Mauna Loa volcano, Hawaii

    USGS Publications Warehouse

    Lipman, P.W.; Rhodes, J.M.; Dalrymple, G.B.

    1990-01-01

    Lava flows of the Ninole Basalt, the oldest rocks exposed on the south side of the island of Hawaii, provide age and compositional constraints on the evolution of Mauna Loa volcano and the southeastward age progression of Hawaiian volcanism. Although the tholeiitic Ninole Basalt differs from historic lavas of Mauna Loa volcano in most major-element contents (e.g., variably lower K, Na, Si; higher Al, Fe, Ti, Ca), REE and other relatively immobile minor elements are similar to historic and prehistoric Mauna Loa lavas, and the present major-element differences are mainly due to incipient weathering in the tropical environment. New K-Ar whole-rock ages, from relatively fresh roadcut samples, suggest that the age of the Ninole Basalt is approximately 0.1-0.2 Ma, although resolution is poor because of low contents of K and radiogenic Ar. Originally considered the remnants of a separate volcano, the Ninole Hills are here interpreted as faulted remnants of the old south flank of Mauna Loa. Deep canyons in the Ninole Hills, eroded after massive landslide failure of flanks of the southwest rift zone, have been preserved from burial by younger lava due to westward migration of the rift zone. Landslide-induced depressurization of the southwest rift zone may also have induced phreatomagmatic eruptions that could have deposited widespread Basaltic ash that overlies the Ninole Basalt. Subaerial presence of the Ninole Basalt documents that the southern part of Hawaii Island had grown to much of its present size above sea level by 0.1-0.2 Ma, and places significant limits on subsequent enlargement of the south flank of Mauna Loa. ?? 1990 Springer-Verlag.

  18. Atmospheric chemical and thermal structure evolution after one Titan year

    NASA Astrophysics Data System (ADS)

    Coustenis, Athena; Bampasidis, Georgios; Achterberg, Richard; Lavvas, Panayiotis; Vinatier, Sandrine; Nixon, Conor; Jennings, Donald; Teanby, Nicolas; Flasar, F. Michael; Carlson, Ronald; Orton, Glenn; Romani, Paul; Guandique, Ever

    2013-04-01

    Our radiative transfer code (ARTT) was applied to Cassini Composite Infrared Spectrometer (CIRS) data taken during Titan flybys from 2004-2010 and to the 1980 Voyager 1 flyby values inferred from the re-analysis of the Infrared Radiometer Spectrometer (IRIS) spectra [1], as well as to the intervening ground- and space- based observations (such as with ISO, [2]), providing us with a new view of the stratospheric evolution over a Titanian year (V1 encounter Ls=9° was reached in mid-2010). CIRS nadir and limb spectral [3,4] show variations in temperature and chemical composition in the stratosphere during the Cassini mission, before and after the Northern Spring Equinox (NSE). We find indication for a weakening of the temperature gradient with warming of the stratosphere and cooling of the lower mesosphere. In addition, we infer precise concentrations for the trace gases and their main isotopologues and find that the chemical composition in Titan's stratosphere varied significantly with latitude during the 6 terrestrial years investigated here, with increased mixing ratios towards the northern latitudes. In particular, we find a maximum enhancement of several gases observed at northern latitudes up to 50°N around mid-2009, at the time of the NSE. We find that this raise is followed by a rapid decrease in chemical inventory in 2010 probably due to changes in the cross vortex mixing or northward migration of the vortex boundary [5,6,7] consistent with the weakening thermal gradient. The finding also ties into the location of the maximum temperature gradient, which appears to be moving northward over the winter/spring season. The return of today's abundances close to the Voyager values (at the same season) is an indication that, as for the Earth, the solar radiation dominates over the other energy sources even at 10AU [8]. Nevertheless, the differences observed for some complex hydrocarbons in the North pole indicate that the other processes could be at play as well

  19. Tectonic evolution and mantle structure of the Caribbean

    NASA Astrophysics Data System (ADS)

    Benthem, Steven; Govers, Rob; Spakman, Wim; Wortel, Rinus

    2013-06-01

    investigate whether predictions of mantle structure from tectonic reconstructions are in agreement with a detailed tomographic image of seismic P wave velocity structure under the Caribbean region. In the upper mantle, positive seismic anomalies are imaged under the Lesser Antilles and Puerto Rico. These anomalies are interpreted as remnants of Atlantic lithosphere subduction and confirm tectonic reconstructions that suggest at least 1100 km of convergence at the Lesser Antilles island arc during the past ~45 Myr. The imaged Lesser Antilles slab consists of a northern and southern anomaly, separated by a low-velocity anomaly across most of the upper mantle, which we interpret as the subducted North America-South America plate boundary. The southern edge of the imaged Lesser Antilles slab agrees with vertical tearing of South America lithosphere. The northern Lesser Antilles slab is continuous with the Puerto Rico slab along the northeastern plate boundary. This results in an amphitheater-shaped slab, and it is interpreted as westward subducting North America lithosphere that remained attached to the surface along the northeastern boundary of the Caribbean plate. At the Muertos Trough, however, material is imaged until a depth of only 100 km, suggesting a small amount of subduction. The location and length of the imaged South Caribbean slab agrees with proposed subduction of Caribbean lithosphere under the northern South America plate. An anomaly related to proposed Oligocene subduction at the Nicaragua rise is absent in the tomographic model. Beneath Panama, a subduction window exists across the upper mantle, which is related to the cessation of subduction of the Nazca plate under Panama since 9.5 Ma and possibly the preceding subduction of the extinct Cocos-Nazca spreading center. In the lower mantle, two large anomaly patterns are imaged. The westernmost anomaly agrees with the subduction of Farallon lithosphere. The second lower mantle anomaly is found east of

  20. Deep Structure and Evolution of the Cyprus Arc, With Implications for the Tectonic Evolution of Anatolia

    NASA Astrophysics Data System (ADS)

    Wortel, M. J.; Spakman, W.; Govers, R.; Ben-Avraham, Z.

    2006-12-01

    This study addresses the easternmost segment of the convergent plate boundary in the Mediterranean, encompassing the Cyprus arc and its connection to the Arabia-Eurasia collision zone and the Dead Sea fault. Seismic activity along the arc is limited (certainly relative to the adjacent Hellenic arc). Although marine geophysical surveys have elucidated many pertinent features of the region, the plate boundary configuration is not well understood. Therefore, we use seismic tomography results to study the deep structure of this plate boundary segment. We find that the deep structure of the eastern part of the Cyprus arc, exhibiting a broad zone of sinistral deformation at the surface, is very similar to the eastern segment of the Hellenic subduction zone. A slab related anomaly is missing here in the upper mantle, and this part can be identified as a STEP fault zone (Subduction-Transform Edge Propagator; see Govers and Wortel, EPSL, v. 236, p. 505-523, 2005), allowing S-SW directed slab retreat. We propose that the inception of the STEP fault and the associated back-arc extension is triggered by the continental collision and subsequent slab detachment in the Bitlis suture to the east. From a quantitative analysis of tomographic anomalies in the mantle below the Bitlis suture zone (Hafkenscheid et al., JGR, v. 111, 2006) slab detachment is inferred to have taken place at 8-12 Ma, the younger end of this age range being more pertinent for the westernmost Bitlis segment. Slab detachment creates an edge to the subducting slab, which is a favourable condition for the inception of a STEP fault. The slab in the central part of the Cypus arc has become detached possibly resulting from the collision with the Eratosthenes Seamount in the (Late) Pliocene. Only in the northwestern segment of the arc below the Antalya Basin and the Isparta Angle the slab appears to be continuous. The short duration of the time window between inception of STEP faulting and collision with the

  1. Patterning and evolution of floral structures - marking time.

    PubMed

    McKim, Sarah; Hay, Angela

    2010-08-01

    The diversity of flowering structures dazzles the eye, dominates the landscape, and invites evolutionary questions regarding the development of such variety. Comparative work in a number of genetically tractable plant species has addressed how diverse floral architectures develop, and started to reveal the balance between conservation and divergence of the patterning mechanisms responsible for when and where flowers form on a plant. We highlight findings from Petunia where conserved LFY/UFO function is under species-specific regulation, and a novel mechanism involving WOX homeodomain proteins for modulating cyme development in diverse nightshades. We also draw attention to recent findings in Arabidopsis of miRNA and chromatin-based timing mechanisms controlling floral development, and illustrate how genetic studies in Arabidopsis relatives can reveal how evolutionary changes in such mechanisms generate diversity in form.

  2. Properties and evolution of dense structures in the interstellar medium

    NASA Astrophysics Data System (ADS)

    Parikka, Anna

    2015-09-01

    In this thesis I present a study of two kinds of dense ISM structures: compact cold sources detected by Planck and dense condensations in a photodissociation region (PDR), namely the Orion Bar detected by ground-based and Herschel telescopes. Both kinds of structures are closely related to star formation. The cold sources are investigated as potentially gravitationally bound, prestellar, objects. The Orion Bar is a highly FUV-illuminated (G0=10^4) prototypical PDR, with several known protoplanetary disks, illuminated by the young Trapezium stars. First I introduce a paper published in A&A: The Physical state of selected cold clumps. In this paper we compared the Herschel dust continuum observations from the open time key program Galactic Cold Cores to ground based molecular line observations from the 20-m radio telescope of the Onsala Space Observatory in Sweden. The clumps were selected based on their brightness and low dust color temperatures (T=10-15 K). We calculated the virial and Bonnor-Ebert masses and compared them to the masses calculated from the observations. The results indicate that most of the observed cold clumps are not necessarily prestellar.Then I move on to the warm and dense condensations of the ISM. In my study of the Orion Bar, I use observations from PACS instrument on board Herschel from the open time program Unveiling the origin and excitation mechanisms of the warm CO, OH and CH+. I present maps of 110"x110" of the methylidyne cation (CH+ J=3-2), OH doublets at 84 μm, and high-J CO (J=19-18). This is the first time that these PDR tracers are presented in such a high spatial resolution and high signal-to-noise ratio. The CH+ and OH have critical densities (10^10 cm-3) and upper level energy temperatures (250 K). In addition the endothermicity of the CH+ + H2 reaction (4300 K) that forms CH+ is comparable to the activation barrier of the O + H2 reaction (4800 K) forming OH. Given these similarities it is interesting to compare their

  3. Halo formation and evolution: unification of structure and physical properties

    NASA Astrophysics Data System (ADS)

    Ernest, Allan D.; Collins, Matthew P.

    2016-08-01

    The assembly of matter in the universe proliferates a wide variety of halo structures, often with enigmatic consequences. Giant spiral galaxies, for example, contain both dark matter and hot gas, while dwarf spheroidal galaxies, with weaker gravity, contain much larger fractions of dark matter, but little gas. Globular clusters, superficially resembling these dwarf spheroidals, have little or no dark matter. Halo temperatures are also puzzling: hot cluster halos contain cooler galaxy halos; dwarf galaxies have no hot gas at all despite their similar internal processes. Another mystery is the origin of the gas that galaxies require to maintain their measured star formation rates (SFRs). We outline how gravitational quantum theory solves these problems, and enables baryons to function as weakly-interacting-massive-particles (WIMPs) in Lambda Cold Dark Matter (LCDM) theory. Significantly, these dark-baryon ensembles may also be consistent with primordial nucleosynthesis (BBN) and cosmic microwave background (CMB) anisotropies.

  4. Structural Evolution of a Granular Pack under Manual Tapping

    NASA Astrophysics Data System (ADS)

    Iikawa, Naoki; Bandi, Mahesh M.; Katsuragi, Hiroaki

    2015-09-01

    We experimentally study a two-dimensional (2D) granular pack of photoelastic disks subject to vertical manual tapping. Using bright- and dark-field images, we employ gradient-based image analysis methods to analyze various structural quantities. These include the packing fraction (ϕ), force per disk (Fd), and force chain segment length (l) as functions of the tapping number (τ). The increase in the packing fraction with the tapping number is found to exponentially approach an asymptotic value. An exponential distribution is observed for the cumulative numbers of both the force per disk Fd:Ncum(Fd) = AFexp ( - Fd/F0), and the force chain segment length l:Ncum(l) = Alexp ( - l/l0). Whereas the coefficient AF varies with τ for Fd, l shows no dependence on τ. The τ dependences of Fd and ϕ allow us to posit a linear relationship between the total force of the granular pack Ftot*(τ ) and ϕ(τ).

  5. STREGA@VST: Structure and Evolution of the Galaxy .

    NASA Astrophysics Data System (ADS)

    Marconi, M.; Musella, I.; Ripepi, V.; De Martino, D.; Silvotti, R.; Capaccioli, M.; Cappellaro, E.; Cignoni, M.; Dall'Ora, M.; Di Criscienzo, M.; Iodice, E.; Ruoppo, A.; Bono, G.; Brocato, E.; Caputo, F.; Carollo, D.; Castellani, M.; Castellani, V.; Cioni, M. R.; Degli Innocenti, S.; Momany, Y.; Monelli, M.; Piotto, G.; Prada Moroni, P. G.; Raimondo, G.

    In this article we present the survey STREGA, that has been proposed as part of the VST GTO (VLT Survey Telescope Guarantee Time of Observation) that will be given to the INAF-OAC in exchange for the construction of the telescope (see Alcalàet al., this volume). This survey will cover an area of about 150 sq. deg., searching for the southern portion of the Fornax stream, also allowing to study the properties of Disk and Halo White Dwarfs and interacting binaries in different fields at increasing galactic latitudes and to provide an ideal database for star counts and for the comparison with Galactic model predictions. The final aim is to constrain the structure and the evolutionary properties of the Milky Way. For the Fornax Stream this proposal is coordinated with a LBT Science Verification Pilot Project (P.I.: G. Bono).

  6. Evolution and Structural Organization of the C Proteins of Paramyxovirinae

    PubMed Central

    Karlin, David G.

    2014-01-01

    The phosphoprotein (P) gene of most Paramyxovirinae encodes several proteins in overlapping frames: P and V, which share a common N-terminus (PNT), and C, which overlaps PNT. Overlapping genes are of particular interest because they encode proteins originated de novo, some of which have unknown structural folds, challenging the notion that nature utilizes only a limited, well-mapped area of fold space. The C proteins cluster in three groups, comprising measles, Nipah, and Sendai virus. We predicted that all C proteins have a similar organization: a variable, disordered N-terminus and a conserved, α-helical C-terminus. We confirmed this predicted organization by biophysically characterizing recombinant C proteins from Tupaia paramyxovirus (measles group) and human parainfluenza virus 1 (Sendai group). We also found that the C of the measles and Nipah groups have statistically significant sequence similarity, indicating a common origin. Although the C of the Sendai group lack sequence similarity with them, we speculate that they also have a common origin, given their similar genomic location and structural organization. Since C is dispensable for viral replication, unlike PNT, we hypothesize that C may have originated de novo by overprinting PNT in the ancestor of Paramyxovirinae. Intriguingly, in measles virus and Nipah virus, PNT encodes STAT1-binding sites that overlap different regions of the C-terminus of C, indicating they have probably originated independently. This arrangement, in which the same genetic region encodes simultaneously a crucial functional motif (a STAT1-binding site) and a highly constrained region (the C-terminus of C), seems paradoxical, since it should severely reduce the ability of the virus to adapt. The fact that it originated twice suggests that it must be balanced by an evolutionary advantage, perhaps from reducing the size of the genetic region vulnerable to mutations. PMID:24587180

  7. Structure, function and evolution of the gas exchangers: comparative perspectives

    PubMed Central

    Maina, JN

    2002-01-01

    Over the evolutionary continuum, animals have faced similar fundamental challenges of acquiring molecular oxygen for aerobic metabolism. Under limitations and constraints imposed by factors such as phylogeny, behaviour, body size and environment, they have responded differently in founding optimal respiratory structures. A quintessence of the aphorism that ‘necessity is the mother of invention’, gas exchangers have been inaugurated through stiff cost–benefit analyses that have evoked transaction of trade-offs and compromises. Cogent structural–functional correlations occur in constructions of gas exchangers: within and between taxa, morphological complexity and respiratory efficiency increase with metabolic capacities and oxygen needs. Highly active, small endotherms have relatively better-refined gas exchangers compared with large, inactive ectotherms. Respiratory structures have developed from the plain cell membrane of the primeval prokaryotic unicells to complex multifunctional ones ofthe modern Metazoa. Regarding the respiratory medium used to extract oxygen from, animal life has had only two choices – water or air – within the biological range of temperature and pressure the only naturally occurring respirable fluids. In rarer cases, certain animalshave adapted to using both media. Gills (evaginated gas exchangers) are the primordial respiratory organs: they are the archetypal water breathing organs. Lungs (invaginated gas exchangers) are the model air breathing organs. Bimodal (transitional) breathers occupy the water–air interface. Presentation and exposure of external (water/air) and internal (haemolymph/blood) respiratory media, features determined by geometric arrangement of the conduits, are important features for gas exchange efficiency: counter-current, cross-current, uniform pool and infinite pool designs have variably developed. PMID:12430953

  8. Structure trees and species trees: what they say about morphological development and evolution.

    PubMed

    Geeta, R

    2003-01-01

    The evolutionary history of morphological structures generally is equated with that of the taxa that carry them. It is argued here that, analogous to genes, developmental genetic pathways underlying morphological structures may be subject to developmental evolutionary changes that result, for instance, in duplication (serial homology analogous to gene duplication and paralogy). Entities that undergo evolution are expected to be related to each other as a tree. Just as with molecular evolution, "structure trees" and species trees sometimes may be incongruent, with implications for morphological homology concepts. Detection of structure trees through morphological evolutionary analyses may point to an entity that is maintained through evolution, possibly in part because it is a developmentally integrated structure ("individualized"). This idea is illustrated in a morphological evolutionary analysis of leaf primordia. These analyses suggest that leaf primordia in monocots and close relatives are related to each other as a tree and, therefore, are developmentally integrated, evolving entities. Among monocot primordia this tree structure breaks down, and it is concluded that there is no entity, the "monocot leaf primordium." However, one group of primordia is identified within monocots that have uniform characteristics and that are well represented by model species maize and rice. Such analyses of structure trees can facilitate the extrapolation and interpretation of results from molecular developmental and other comparative studies.

  9. Observational constraints on the structure and evolution of quasars

    NASA Astrophysics Data System (ADS)

    Kelly, Brandon C.

    2008-01-01

    I use X-ray and optical data to investigate the structure of quasars, and its dependence on luminosity, redshift, black hole mass, and Eddington ratio. In order to facilitate my work, I develop new statistical methods of accounting for measurement error, non-detections, and survey selection functions. The main results of this thesis follow. (1) The statistical uncertainty in the broad line mass estimates can lead to significant artificial broadening of the observed distribution of black hole mass. (2) The z = 0.2 broad line quasar black hole mass function falls off approximately as a power law with slope ~ 2 for M BH [Special characters omitted.] 10 8 [Special characters omitted.] . (3) Radio-quiet quasars become more X-ray quiet as their optical/UV luminosity, black hole mass, or Eddington ratio increase, and more X-ray loud at higher redshift. These correlations imply that quasars emit a larger fraction of their bolometric luminosity through the accretion disk component, as compared to the corona component, as black hole mass and Eddington ratio increase. (4) The X- ray spectral slopes of radio-quiet quasars display a non-monotonic trend with Eddington ratio, where the X-ray continuum softens with increasing Eddington ratio until L/L Edd ~ 0.3, and then begins to harden. This observed non- monotonic trend may be caused by a change in the structure of the disk/corona system at L/L Edd ~ 0.3, possibly due to increased radiation pressure. (5) The characteristic time scales of quasar optical flux variations increase with increasing M BH , and are consistent with disk orbital or thermal time scales. In addition the amplitude of short time scale variability decreases with increasing M BH . I interpret quasar optical light curves as being driven by thermal fluctuations, which in turn are driven by some other underlying stochastic process with characteristic time scale long compared to the disk thermal time scale. The stochastic model I use is able to explain both short

  10. Structural evolution of dilute magnetic (Sn,Mn)Se films grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Kanzyuba, Vasily; Dong, Sining; Liu, Xinyu; Li, Xiang; Rouvimov, Sergei; Okuno, Hanako; Mariette, Henri; Zhang, Xueqiang; Ptasinska, Sylwia; Tracy, Brian D.; Smith, David J.; Dobrowolska, Margaret; Furdyna, Jacek K.

    2017-02-01

    We describe the structural evolution of dilute magnetic (Sn,Mn)Se films grown by molecular beam epitaxy on GaAs (111) substrates, as revealed by transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. When the Mn concentration is increased, the lattice of the ternary (Sn,Mn)Se films evolves quasi-coherently from a SnSe2 two-dimensional (2D) crystal structure into a more complex quasi-2D lattice rearrangement, ultimately transforming into the magnetically concentrated antiferromagnetic MnSe 3D rock-salt structure as Mn approaches 50 at. % of this material. These structural transformations are expected to underlie the evolution of magnetic properties of this ternary system reported earlier in the literature.

  11. Detailed Structure Study of an H2/N2O/Ar Flame Employing Molecular Beam Mass Spectrometry, Laser Spectroscopy, and Modeling

    DTIC Science & Technology

    1993-10-01

    vimcalidoaints pme in th b iadfan 2 0 +M aN2 + 0+M j-une #ad dbacumed 14 SUWIFT TERMS it. NUMBER OF PAGFS mussvcm y "Vm wy molecula bea S=Wb&ng hy&qgeuMduus 50__...cetkmical (neduAnis for this system al low: tem rtirs Ftsztc i tisreport are twti~au awW~ p(Om.fic eurmcuu nte fOf a ..i.-4f grh M-t(tric 11fl’.bO/Ar bunr -ai

  12. Kinematic morphology of large-scale structure: evolution from potential to rotational flow

    SciTech Connect

    Wang, Xin; Szalay, Alex; Aragón-Calvo, Miguel A.; Neyrinck, Mark C.; Eyink, Gregory L.

    2014-09-20

    As an alternative way to describe the cosmological velocity field, we discuss the evolution of rotational invariants constructed from the velocity gradient tensor. Compared with the traditional divergence-vorticity decomposition, these invariants, defined as coefficients of the characteristic equation of the velocity gradient tensor, enable a complete classification of all possible flow patterns in the dark-matter comoving frame, including both potential and vortical flows. We show that this tool, first introduced in turbulence two decades ago, is very useful for understanding the evolution of the cosmic web structure, and in classifying its morphology. Before shell crossing, different categories of potential flow are highly associated with the cosmic web structure because of the coherent evolution of density and velocity. This correspondence is even preserved at some level when vorticity is generated after shell crossing. The evolution from the potential to vortical flow can be traced continuously by these invariants. With the help of this tool, we show that the vorticity is generated in a particular way that is highly correlated with the large-scale structure. This includes a distinct spatial distribution and different types of alignment between the cosmic web and vorticity direction for various vortical flows. Incorporating shell crossing into closed dynamical systems is highly non-trivial, but we propose a possible statistical explanation for some of the phenomena relating to the internal structure of the three-dimensional invariant space.

  13. The Evolution of Thin-Film Structure in pi-Conjugated System: Implications for Devices

    DTIC Science & Technology

    2015-07-09

    AFRL-OSR-VA-TR-2015-0157 The Evolution of Thin-Film Structure in pi-Conjugated System Elsa Reichmanis GEORGIA TECH RESEARCH CORPORATION Final Report...NUMBER 5e.  TASK NUMBER 5f.  WORK UNIT NUMBER 7.  PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) GEORGIA TECH RESEARCH CORPORATION 505 10TH ST NW

  14. Morpho-structural evolution of a volcanic island developed inside an active oceanic rift: S. Miguel Island (Terceira Rift, Azores)

    NASA Astrophysics Data System (ADS)

    Sibrant, A. L. R.; Hildenbrand, A.; Marques, F. O.; Weiss, B.; Boulesteix, T.; Hübscher, C.; Lüdmann, T.; Costa, A. C. G.; Catalão, J. C.

    2015-08-01

    The evolution of volcanic islands is generally marked by fast construction phases alternating with destruction by a variety of mass-wasting processes. More specifically, volcanic islands located in areas of intense regional deformation can be particularly prone to gravitational destabilisation. The island of S. Miguel (Azores) has developed during the last 1 Myr inside the active Terceira Rift, a major tectonic structure materializing the present boundary between the Eurasian and Nubian lithospheric plates. In this work, we depict the evolution of the island, based on high-resolution DEM data, stratigraphic and structural analyses, high-precision K-Ar dating on separated mineral phases, and offshore data (bathymetry and seismic profiles). The new results indicate that: (1) the oldest volcanic complex (Nordeste), composing the easternmost part of the island, was dominantly active between ca. 850 and 750 ka, and was subsequently affected by a major south-directed flank collapse. (2) Between at least 500 ka and 250 ka, the landslide depression was massively filled by a thick lava succession erupted from volcanic cones and domes distributed along the main E-W collapse scar. (3) Since 250 kyr, the western part of this succession (Furnas area) was affected by multiple vertical collapses; associated plinian eruptions produced large pyroclastic deposits, here dated at ca. 60 ka and less than 25 ka. (4) During the same period, the eastern part of the landslide scar was enlarged by retrogressive erosion, producing the large Povoação valley, which was gradually filled by sediments and young volcanic products. (5) The Fogo volcano, in the middle of S. Miguel, is here dated between ca. 270 and 17 ka, and was affected by, at least, one southwards flank collapse. (6) The Sete Cidades volcano, in the western end of the island, is here dated between ca. 91 and 13 ka, and experienced mutliple caldera collapses; a landslide to the North is also suspected from the presence of a

  15. FINE STRUCTURE OF FLARE RIBBONS AND EVOLUTION OF ELECTRIC CURRENTS

    SciTech Connect

    Sharykin, I. N.; Kosovichev, A. G.

    2014-06-10

    Emission of solar flares across the electromagnetic spectrum is often observed in the form of two expanding ribbons. The standard flare model explains flare ribbons as footpoints of magnetic arcades, emitting due to interaction of energetic particles with the chromospheric plasma. However, the physics of this interaction and properties of the accelerated particles are still unknown. We present results of multiwavelength observations of the C2.1 flare of 2013 August 15, observed with the New Solar Telescope of the Big Bear Solar Observatory, and the Solar Dynamics Observatory, GOES, and Fermi spacecraft. The observations reveal previously unresolved sub-arcsecond structure of flare ribbons in regions of strong magnetic field consisting from numerous small-scale bright knots. We observe a red-blue asymmetry of H{sub α} flare ribbons with a width as small as ∼100 km. We discuss the relationship between the ribbons and vertical electric currents estimated from vector magnetograms, and show that Joule heating can be responsible for energization of H{sub α} knots in the ribbons.

  16. Models of planetary structure and evolution: The case of Io

    NASA Technical Reports Server (NTRS)

    Spohn, T.

    1985-01-01

    The interior structure of Jupiter's satellite Io is probably layered with a liquid core surrounded by a rigid mantle, a partially molten asthenosphere and a thin rigid lithosphere. The core radius could roughly equal half the planetary radius if the core is mostly FeS and if the mantle's compressibility is close to that of Earth's upper mantle rocks. The lithosphere thickness is controlled by the balance of the heat flux q sub e across the lithosphere with the tidal heating rate H within the lithosphere and the heat flux q; from the interior into the lithosphere. The maximum thickness determined by a balance of q sub e with H is probably much smaller than the lithosphere thickness that maximizes H. Thus, if Io's interior was once melted and if it's resonant orbital state is ancient it will freeze from the inside out. The time scale of internal and latent heat removal in a molten Io is 10 to the eighth power. Io's strong volcanic activity suggests the persistence of a partially molten asthenosphere to the present time.

  17. Structural Evolution of a Recoverable Rhodium Hydrogenation Catalyst

    SciTech Connect

    Shaw, Wendy J.; Chen, Yongsheng; Fulton, John L.; Linehan, John C.; Gutowska, Anna; Bitterwolf, Thomas E.

    2008-06-01

    N-isopropylacrylamide was utilized as a ligand to affect recoverability into a rhodium hydrogenation catalyst. The catalyst ligand structure was characterized in situ using NMR, XAFS and IR. Model compounds including glycine, cysteamine and methionine methyl ester were also investigated to aid in the interpretation. The investigation revealed a ligand switch from RNH2 to RSR’ when the catalyst is placed in water as opposed to organic solvents. The catalyst continued to transform with time, creating Rh clusters of up to 4 rhodium atoms, with no Rh metal detected. Over the time and solvents investigated, the catalyst ligands evolve from 1-Cl, 1-NH2, and 2-CO’s to 3-Rh, 1-RSR’ and 1-CO. Upon introduction of the alkene for hydrogenation catalysis, the Rh cluster is lost, favoring instead the interaction with the reactant. The kinetics of the hydrogenation reaction were measured using a novel high pressure flow through NMR system and the catalyst was found to have a TOF of 3000/hr at 25 ºC. This work was supported by the Laboratory Directed Research and Development Program at the Pacific Northwest National Laboratory operated by Battelle for the U.S. Department of Energy.

  18. Gravitational Lenses and the Structure and Evolution of Galaxies

    NASA Technical Reports Server (NTRS)

    Oliversen, Ronald J. (Technical Monitor); Kochanek, Christopher

    2004-01-01

    During the first year of the project we completed five papers, each of which represents a new direction in the theory and interpretation of gravitational lenses. In the first paper, The Importance of Einstein Rings, we developed the first theory for the formation and structure of the Einstein rings formed by lensing extended sources like the host galaxies of quasar and radio sources. In the second paper, Cusped Mass Models Of Gravitational Lenses, we introduced a new class of lens models. In the third paper, Global Probes of the Impact of Baryons on Dark Matter Halos, we made the first globally consistent models for the separation distribution of gravitational lenses including both galaxy and cluster lenses. The last two papers explore the properties of two lenses in detail. During the second year we have focused more closely on the relationship of baryons and dark matter. In the third year we have been further examining the relationship between baryons and dark matter. In the present year we extended our statistical analysis of lens mass distributions using a self-similar model for the halo mass distribution as compared to the luminous galaxy.

  19. Evolution of the structure of iron meteorites under terrestrial climate

    NASA Astrophysics Data System (ADS)

    Yakovlev, G.; Grokhovsky, V.

    2014-07-01

    Introduction: Meteoritic iron is affected by many factors in terrestrial conditions. First of all, abundance of water induces an oxidization process. Despite rather high nickel concentration in meteoritic iron, rust is forming on a surface of extraterrestrial matter. But also transformation processes occur inside meteorites at rather low climatic temperatures (0.15 of the melting temperature). Such reaction has been observed for the first time in the Bilibino meteorite [1]. Experiments: Structural changes in kamacite were investigated in ancient iron meteorite falls (Aliskerovo IIIAB, Bilibino IIAB). All of them demonstrate uncompleted recrystallization. Polished sections were analyzed using inverted optical microscope Axiovert 40 MAT and SEM SIGMA VP with EDS and EBSD units. Results: Different percentage of recrystallization was found in Aliskerovo and Bilibino meteorites. 4 % of the section surface in Aliskerovo is occupied by recrystallization products. This value for Bilibino is equal to 80 %. It was noticed that recrystallization started from the kamacite-rhabdite boundaries in the Bilibino meteorite and from the kamacite-schreibersite boundaries in the Aliskerovo meteorite. There are strongly-etched sites in the recrystallized zones. One can suggest that these sites are traces of former boundaries. It is possible to think that the boundaries were moving with jumps because of the position of these sites in the recrystallized zone. Also it was noticed that there is a net of cracks before the recrystallization reaction front. A possible reason for this phenomenon is a wedge of extra material which generates an elastic stress field in the vicinity of the grain boundary [2]. All these phenomena can be explained using the Kirkendall effect on the grain boundary: the boundary shift is the result of the different concentrations of vacancies between the boundary sides.

  20. Structural evolution of NiAg heterogeneous alloys upon annealing

    NASA Astrophysics Data System (ADS)

    Proux, O.; Mimault, J.; Revenant-Brizard, C.; Regnard, J. R.; Mevel, B.

    1999-01-01

    NiAg heterogeneous alloys were studied by x-ray diffraction and x-ray absorption spectroscopy at the Ni K-edge using a total electron yield detection. In the as-deposited 0953-8984/11/1/013/img8 alloys of 0.10 and 0.15 Ni atomic fraction, most of the Ni atoms are in substitutional sites in the Ag matrix. At higher Ni concentration, the Ni atoms outside the Ag-rich phase become numerous enough to group together in small clusters. An important disorder in the neighbourhood of Ni atoms is demonstrated. At low annealing temperature (up to 0953-8984/11/1/013/img9C), in 0953-8984/11/1/013/img10 and 0953-8984/11/1/013/img11, some Ni atoms are still present in substitutional sites in the Ag matrix and the small Ni particles are under strain. A very short-range order exists in this state. After a 0953-8984/11/1/013/img9C annealing, the Ni particles grow, and the Ag-rich phase remains in a steady structural state. After a higher annealing (0953-8984/11/1/013/img13C), the local Ni atomic environment becomes well ordered and typical of the pure Ni FCC phase. The Ag-rich crystallites are impoverished in Ni atoms and grow with elimination of defects. Ni grains are generally smaller than 1 nm for as-deposited alloys and reach several nanometres after a 0953-8984/11/1/013/img13C annealing for 10 min.

  1. Effects of Melt Processing on Evolution of Structure in PEEK

    NASA Technical Reports Server (NTRS)

    Georgiev, Georgi; Dai, Patrick Shuanghua; Oyebode, Elizabeth; Cebe, Peggy; Capel, Malcolm

    1999-01-01

    We report on the effects of melt processing temperature on structure formation in Poly(ether-ether-ketone), PEEK. Real time Small Angle X-ray Scattering, SAXS, and thermal analysis are used to follow the melting behavior after various stages of processing. Assignment of peaks to structural entities within the material, the relative perfection of the crystals, and the possibility of their reorganization, are all influenced by the melt processing history. With the advent of high intensity synchrotron sources of X-radiation, polymer scientists gain a research tool which, when used along with thermal analysis, provides additional structural information about the crystals during growth and subsequent melting. PEEK is an engineering thermoplastic polymer with a very high glass transition temperature (145 C) and crystal melting point (337 C). PEEK has been the subject of recent studies by X-ray scattering in which melt and cold crystallization were followed in real-time. X-ray scattering and thermal studies have been used to address the formation of dual endothermic response which has been variously ascribed to lamellar insertion, dual crystal populations, or melting followed by re-crystallization. Another important issue is whether all of the amorphous phase is located in interlamellar regions, or alternatively whether some is located in "pockets" away from the crystalline lamellar stacks. The interpretation of scattering from lamellar stacks varies depending upon whether such amorphous pockets are formed. Some groups believe all of the amorphous phase is interlamellar. This leads to selection of a smaller thickness for the crystals. Other groups suggest that most amorphous phase is not interlamellar, and this leads to the suggestion that the crystal thickness is larger than the amorphous layer within the stacks. To investigate these ideas, we used SAXS and Differential Scanning Calorimetry to compare results of single and dual stage melt crystallization of PEEK using a

  2. Structure and Evolution of the Central Andes of Peru

    NASA Astrophysics Data System (ADS)

    Gonzalez, L.; Pfiffner, O. A.

    2009-04-01

    part of the Western Cordillera, near Huaraz, a vertical fault puts a Late Miocene to Early Pliocene batholith (Cordillera Blanca) in direct contact to Miocene volcanics (Calipuy group, Cordillera Negra). The structure of the Central Highlands is characterized by relatively open folds in the Paleozoic to Mesozoic strata. Overlying Quaternary deposits are tilted and locally even folded. Eocene to Miocene undeformed granitoids intrude these structures. A swarm of NNW-SSE striking and steeply dipping faults separate the Eastern Cordillera from the Highlands. Some of these faults suggest block faulting. However, near Huancayo a clear indication of strike-slip motion could be found. The Neoproterozoic basement rocks and the Early Paleozoic sediments are unconformably overlain by Late Paleozoic sediments which in turn are folded. Within the Subandine zone, the structural style is characterized by east directed imbricate thrusting. The thrust faults cut down into the crystalline basement going west, suggesting a detachment within upper crustal crystalline basement rocks. In the Central Peruvian Andes, compressional deformation events progressed from west to east. Early Cretaceous plutons of the coast batholith intruded folded Jurassic to Early Cretaceous volcaniclastic rocks of the Casma group and suggest an Early Cretaceous phase of shortening in the Pacific coastal area of the Western Cordillera (referred to as Mochica phase in the literature). Within the Western Cordillera, a major phase of pre-Eocene erosion removed a substantial amount of the tight upright folds. The youngest strata folded are of Late Cretaceous to Early Paleocene age (Red Beds). The overlying volcanics are slightly younger (middle Eocene) and bracket the tight folding, referred to as Inca phase, to Late Paleocene to Early Eocene times. This is corroborated by Eocene to Miocene granitic intrusions in the adjacent fold-and-thrust belt. Still younger deformations, referred to as Quechua Phase, produced

  3. Effects of Melt Processing on Evolution of Structure in PEEK

    NASA Technical Reports Server (NTRS)

    Georgiev, Georgi; Dai, Patrick Shuanghua; Oyebode, Elizabeth; Cebe, Peggy; Capel, Malcolm

    1999-01-01

    We report on the effects of melt processing temperature on structure formation in Poly(ether-ether-ketone), PEEK. Real time Small Angle X-ray Scattering, SAXS, and thermal analysis are used to follow the melting behavior after various stages of processing. Assignment of peaks to structural entities within the material, the relative perfection of the crystals, and the possibility of their reorganization, are all influenced by the melt processing history. With the advent of high intensity synchrotron sources of X-radiation, polymer scientists gain a research tool which, when used along with thermal analysis, provides additional structural information about the crystals during growth and subsequent melting. PEEK is an engineering thermoplastic polymer with a very high glass transition temperature (145 C) and crystal melting point (337 C). PEEK has been the subject of recent studies by X-ray scattering in which melt and cold crystallization were followed in real-time. X-ray scattering and thermal studies have been used to address the formation of dual endothermic response which has been variously ascribed to lamellar insertion, dual crystal populations, or melting followed by re-crystallization. Another important issue is whether all of the amorphous phase is located in interlamellar regions, or alternatively whether some is located in "pockets" away from the crystalline lamellar stacks. The interpretation of scattering from lamellar stacks varies depending upon whether such amorphous pockets are formed. Some groups believe all of the amorphous phase is interlamellar. This leads to selection of a smaller thickness for the crystals. Other groups suggest that most amorphous phase is not interlamellar, and this leads to the suggestion that the crystal thickness is larger than the amorphous layer within the stacks. To investigate these ideas, we used SAXS and Differential Scanning Calorimetry to compare results of single and dual stage melt crystallization of PEEK using a

  4. 40Ar/39Ar ages in deformed potassium feldspar: evidence of microstructural control on Ar isotope systematics

    NASA Astrophysics Data System (ADS)

    Reddy, Steven M.; Potts, Graham J.; Kelley, Simon P.

    2001-05-01

    Detailed field and microstructural studies have been combined with high spatial resolution ultraviolet laser 40Ar/39Ar dating of naturally deformed K-feldspar to investigate the direct relationship between deformation-related microstructure and Ar isotope systematics. The sample studied is a ~1,000 Ma Torridonian arkose from Skye, Scotland, that contains detrital feldspars previously metamorphosed at amphibolite-facies conditions ~1,700 Ma. The sample was subsequently deformed ~430 Ma ago during Caledonian orogenesis. The form and distribution of deformation-induced microstructures within three different feldspar clasts has been mapped using atomic number contrast and orientation contrast imaging, at a range of scales, to identify intragrain variations in composition and lattice orientation. These variations have been related to thin section and regional structural data to provide a well-constrained deformation history for the feldspar clasts. One hundred and forty-three in-situ 40Ar/39Ar analyses measured using ultraviolet laser ablation record a range of apparent ages (317-1030 Ma). The K-feldspar showing the least strain records the greatest range of apparent ages from 420-1,030 Ma, with the oldest apparent ages being found close to the centre of the feldspar away from fractures and the detrital grain boundary. The most deformed K-feldspar yields the youngest apparent ages (317-453 Ma) but there is no spatial relationship between apparent age and the detrital grain boundary. Within this feldspar, the oldest apparent ages are recorded from orientation domain boundaries and fracture surfaces where an excess or trapped 40Ar component resides. Orientation contrast images at a similar scale to the Ar analyses illustrate a significant deformation-related microstructural difference between the feldspars and we conclude that deformation plays a significant role in controlling Ar systematics of feldspars at both the inter- and intragrain scales even at relatively low

  5. Morphological diversity and evolution of egg and clutch structure in amphibians

    USGS Publications Warehouse

    Altig, Ronald; McDiarmid, Roy W.

    2007-01-01

    The first part of this synthesis summarizes the morphology of the jelly layers surrounding an amphibian ovum. We propose a standard terminology and discuss the evolution of jelly layers. The second part reviews the morphological diversity and arrangement of deposited eggs?the ovipositional mode; we recognize 5 morphological classes including 14 modes. We discuss some of the oviductal, ovipositional, and postovipositional events that contribute to these morphologies. We have incorporated data from taxa from throughout the world but recognize that other types will be discovered that may modify understanding of these modes. Finally, we discuss the evolutionary context of the diversity of clutch structure and present a first estimate of its evolution.

  6. Refinement of the time-space evolution of the giant Mio-Pliocene Río Blanco-Los Bronces porphyry Cu-Mo cluster, Central Chile: new U-Pb (SHRIMP II) and Re-Os geochronology and 40Ar/39Ar thermochronology data

    NASA Astrophysics Data System (ADS)

    Deckart, Katja; Clark, Alan H.; Cuadra, Patricio; Fanning, Mark

    2013-01-01

    Representing one of the largest known (estimated >5 Gt at 1 % Cu and 0.02 % Mo) porphyry system, the Río Blanco-Los Bronces deposit incorporates at least five hypabyssal intrusive and hydrothermal centres, extending for about 5 km from the Río Blanco and Los Bronces mines in the north, through the Don Luis mine, to the Sur Sur mine, La Americana and Los Sulfatos in the south. The new geochronology data, which now include data on different molybdenite vein types, confirm the U-Pb ages of the pre-mineralisation intrusions but slightly increase their age range from 8.8 to 8.2 Ma. The distinct magmatic pulses of the mineralisation-associated porphyritic intrusives (Late Porphyries) indicate an age interval instead of the previously suggested individual ages: the quartz monzonite porphyry ranges from 7.7 to 6.1 Ma (Sur Sur 5.74 ± 0.13 Ma), the feldspar porphyry shows an interval from 5.8 to 5.2 Ma and the Don Luis porphyry from 5.2 to 5.0 Ma. The new Re-Os data on distinct molybdenite vein types confirm the protracted history of Cu(-Mo) mineralisation, inferred previously. The vein development occurred at least from 5.94 to 4.50 Ma, indicating a time-span of 1.5 Ma for the hydrothermal activity. Hydrothermal minerals dated by the 40Ar/39Ar method are generally too young to record the age of early, high-temperature mineralisation. The majority of the 40Ar/39Ar data in the Río Blanco porphyry cluster record reheating by either the youngest member of the Late Porphyry suite or the post-mineralisation dacite or rhyolite plug formations at around 4.9-4.7 Ma.

  7. Subtype-specific structural constraints in the evolution of influenza A virus hemagglutinin genes

    PubMed Central

    Gultyaev, Alexander P.; Spronken, Monique I.; Richard, Mathilde; Schrauwen, Eefje J. A.; Olsthoorn, René C. L.; Fouchier, Ron A. M.

    2016-01-01

    The influenza A virus genome consists of eight RNA segments. RNA structures within these segments and complementary (cRNA) and protein-coding mRNAs may play a role in virus replication. Here, conserved putative secondary structures that impose significant evolutionary constraints on the gene segment encoding the surface glycoprotein hemagglutinin (HA) were investigated using available sequence data on tens of thousands of virus strains. Structural constraints were identified by analysis of covariations of nucleotides suggested to be paired by structure prediction algorithms. The significance of covariations was estimated by mutual information calculations and tracing multiple covariation events during virus evolution. Covariation patterns demonstrated that structured domains in HA RNAs were mostly subtype-specific, whereas some structures were conserved in several subtypes. The influence of RNA folding on virus replication was studied by plaque assays of mutant viruses with disrupted structures. The results suggest that over the whole length of the HA segment there are local structured domains which contribute to the virus fitness but individually are not essential for the virus. Existence of subtype-specific structured regions in the segments of the influenza A virus genome is apparently an important factor in virus evolution and reassortment of its genes. PMID:27966593

  8. The evolution of alternative cryptic female choice strategies in age-structured populations.

    PubMed

    Jones, Adam G

    2002-12-01

    Cryptic female choice is a potentially important aspect of the sexual selection process. According to the theory of sexual dialectics, postcopulation manipulation of relative male fertilization success can provide an avenue by which females can circumvent attempts by males to control female reproduction. Here I use stochastic models to investigate the evolution of cryptic female choice in populations with and without age structure. In populations without age structure, cryptic female choice will evolve only when (1) precopulatory mate choice by females is inefficient, (2) variation in male fitness is correlated with a trait upon which a female can base her choice of mates, and (3) the cost of multiple mating is not too high. In populations with age structure, similar conditions apply. However, selection sometimes favors females that employ alternative strategies of female choice at different ages. These results help to define the types of biological systems in which we should expect to see the evolution of cryptic female choice. They also illustrate that the evolution of choice strategies in females may be complex and may mirror in some important respects the evolution of alternative mating tactics in males.

  9. Valence-band electronic structure evolution of graphene oxide upon thermal annealing for optoelectronics

    SciTech Connect

    Yamaguchi, Hisato; Ogawa, Shuichi; Watanabe, Daiki; Hozumi, Hideaki; Gao, Yongqian; Eda, Goki; Mattevi, Cecilia; Fujita, Takeshi; Yoshigoe, Akitaka; Ishizuka, Shinji; Adamska, Lyudmyla; Yamada, Takatoshi; Dattelbaum, Andrew M.; Gupta, Gautam; Doorn, Stephen K.; Velizhanin, Kirill A.; Teraoka, Yuden; Chen, Mingwei; Htoon, Han; Chhowalla, Manish; Mohite, Aditya D.; Takakuwa, Yuji

    2016-09-01

    We report valence band electronic structure evolution of graphene oxide (GO) upon its thermal reduction. Degree of oxygen functionalization was controlled by annealing temperatures, and an electronic structure evolution was monitored using real-time ultraviolet photoelectron spectroscopy. We observed a drastic increase in density of states around the Fermi level upon thermal annealing at ~600 °C. The result indicates that while there is an apparent band gap for GO prior to a thermal reduction, the gap closes after an annealing around that temperature. This trend of band gap closure was correlated with electrical, chemical, and structural properties to determine a set of GO material properties that is optimal for optoelectronics. The results revealed that annealing at a temperature of ~500 °C leads to the desired properties, demonstrated by a uniform and an order of magnitude enhanced photocurrent map of an individual GO sheet compared to as-synthesized counterpart.

  10. Valence-band electronic structure evolution of graphene oxide upon thermal annealing for optoelectronics

    DOE PAGES

    Yamaguchi, Hisato; Ogawa, Shuichi; Watanabe, Daiki; ...

    2016-09-01

    We report valence band electronic structure evolution of graphene oxide (GO) upon its thermal reduction. Degree of oxygen functionalization was controlled by annealing temperatures, and an electronic structure evolution was monitored using real-time ultraviolet photoelectron spectroscopy. We observed a drastic increase in density of states around the Fermi level upon thermal annealing at ~600 °C. The result indicates that while there is an apparent band gap for GO prior to a thermal reduction, the gap closes after an annealing around that temperature. This trend of band gap closure was correlated with electrical, chemical, and structural properties to determine a setmore » of GO material properties that is optimal for optoelectronics. The results revealed that annealing at a temperature of ~500 °C leads to the desired properties, demonstrated by a uniform and an order of magnitude enhanced photocurrent map of an individual GO sheet compared to as-synthesized counterpart.« less

  11. SEASONAL EFFECTS ON COMET NUCLEI EVOLUTION: ACTIVITY, INTERNAL STRUCTURE, AND DUST MANTLE FORMATION

    SciTech Connect

    De Sanctis, M. C.; Capria, M. T.; Lasue, J.

    2010-07-15

    Rotational properties can strongly influence a comet's evolution in terms of activity, dust mantling, and internal structure. In this paper, we investigate the effects of various rotation axis directions on the activity, internal structure, and dust mantling of cometary nuclei. The numerical code developed is able to reproduce different shapes and spin axis inclinations, taking into account both the latitudinal and the longitudinal variations of illumination, using a quasi-three-dimensional approach. The results obtained show that local variations in the dust and gas fluxes can be induced by the different spin axis directions and completely different behaviors of the comet evolution can result in the same cometary shape by using different obliquities of the models. The internal structures of cometary nuclei are also influenced by comet obliquity, as well as dust mantling. Gas and dust production rates show diversities related to the comet seasons.

  12. New insights into the evolution and structure of Colletotrichum plant-like subtilisins (CPLSs)

    PubMed Central

    Armijos Jaramillo, Vinicio D; Vargas, Walter A; Sukno, Serenella A; Thon, Michael R

    2013-01-01

    The Colletotrichum plant-like subtilisins (CPLSs) are a family of proteins found only in species of the phytopathogenic fungus Colletotrichum. CPLSs have high similarity to plant subtilisins and our previous work has shown that they were acquired by an ancient horizontal gene transfer event from plants. The rapid growth of sequence data in public databases enabled us to reexamine the structure and evolution of the CPLSs. A new plant subtilisin structural model aided us in refining the tertiary structure of CPLSs. Also, new information about protein interactions of plant subtilisin has provided new insights into the putative function of CPLSs. The availability of new genome sequences of members of the genus Colletotrichum gave us the opportunity to further validate our hypothesis that the CPLSs are unique to the Colletotrichum lineage. Together, this information furthers our knowledge of the potential role of the CPLSs in pathogenicity and the role of HGT in the genome evolution of plant pathogenic fungi. PMID:24563701

  13. Quantitative tracking of grain structure evolution in a nanocrystalline metal during cyclic loading

    NASA Astrophysics Data System (ADS)

    Panzarino, Jason F.; Ramos, Jesus J.; Rupert, Timothy J.

    2015-02-01

    Molecular dynamics simulations were used to quantify mechanically induced structural evolution in nanocrystalline Al with an average grain size of 5 nm. A polycrystalline sample was cyclically strained at different temperatures, while a recently developed grain tracking algorithm was used to measure the relative contributions of novel deformation mechanisms such as grain rotation and grain sliding. Sample texture and grain size were also tracked during cycling, to show how nanocrystalline plasticity rearranges overall grain structure and alters the grain boundary network. While no obvious texture is developing during cycling, the processes responsible for plasticity act collectively to alter the interfacial network. Cyclic loading led to the formation of many twin boundaries throughout the sample as well as the occasional coalescence of neighboring grains, with higher temperatures causing more evolution. A temperature-dependent cyclic strengthening effect was observed, demonstrating that both the structure and properties of nanocrystalline metals can be dynamic during loading.

  14. PIECE 2.0: an update for the plant gene structure comparison and evolution database

    PubMed Central

    Wang, Yi; Xu, Ling; Thilmony, Roger; You, Frank M.; Gu, Yong Q.; Coleman-Derr, Devin

    2017-01-01

    PIECE (Plant Intron Exon Comparison and Evolution) is a web-accessible database that houses intron and exon information of plant genes. PIECE serves as a resource for biologists interested in comparing intron–exon organization and provides valuable insights into the evolution of gene structure in plant genomes. Recently, we updated PIECE to a new version, PIECE 2.0 (http://probes.pw.usda.gov/piece or http://aegilops.wheat.ucdavis.edu/piece). PIECE 2.0 contains annotated genes from 49 sequenced plant species as compared to 25 species in the previous version. In the current version, we also added several new features: (i) a new viewer was developed to show phylogenetic trees displayed along with the structure of individual genes; (ii) genes in the phylogenetic tree can now be also grouped according to KOG (The annotation of Eukaryotic Orthologous Groups) and KO (KEGG Orthology) in addition to Pfam domains; (iii) information on intronless genes are now included in the database; (iv) a statistical summary of global gene structure information for each species and its comparison with other species was added; and (v) an improved GSDraw tool was implemented in the web server to enhance the analysis and display of gene structure. The updated PIECE 2.0 database will be a valuable resource for the plant research community for the study of gene structure and evolution. PMID:27742820

  15. Fidelity of parent-offspring transmission and the evolution of social behavior in structured populations.

    PubMed

    Débarre, F

    2017-02-28

    The theoretical investigation of how spatial structure affects the evolution of social behavior has mostly been done under the assumption that parent-offspring strategy transmission is perfect, i.e., for genetically transmitted traits, that mutation is very weak or absent. Here, we investigate the evolution of social behavior in structured populations under arbitrary mutation probabilities. We consider populations of fixed size N, structured such that in the absence of selection, all individuals have the same probability of reproducing or dying (neutral reproductive values are the all same). Two types of individuals, A and B, corresponding to two types of social behavior, are competing; the fidelity of strategy transmission from parent to offspring is tuned by a parameter μ. Social interactions have a direct effect on individual fecundities. Under the assumption of small phenotypic differences (implying weak selection), we provide a formula for the expected frequency of type A individuals in the population, and deduce conditions for the long-term success of one strategy against another. We then illustrate our results with three common life-cycles (Wright-Fisher, Moran Birth-Death and Moran Death-Birth), and specific population structures (graph-structured populations). Qualitatively, we find that some life-cycles (Moran Birth-Death, Wright-Fisher) prevent the evolution of altruistic behavior, confirming previous results obtained with perfect strategy transmission. We also show that computing the expected frequency of altruists on a regular graph may require knowing more than just the graph's size and degree.

  16. NF-kB overexpression and decreased immunoexpression of AR in the muscular layer is related to structural damages and apoptosis in cimetidine-treated rat vas deferens

    PubMed Central

    2013-01-01

    Background Cimetidine, histamine H2 receptors antagonist, has caused adverse effects on the male hormones and reproductive tract due to its antiandrogenic effect. In the testes, peritubular myoid cells and muscle vascular cells death has been associated to seminiferous tubules and testicular microvascularization damages, respectively. Either androgen or histamine H2 receptors have been detected in the mucosa and smooth muscular layer of vas deferens. Thus, the effect of cimetidine on this androgen and histamine-dependent muscular duct was morphologically evaluated. Methods The animals from cimetidine group (CMTG; n=5) received intraperitoneal injections of 100 mg/kg b.w. of cimetidine for 50 days; the control group (CG) received saline solution. The distal portions of vas deferens were fixed in formaldehyde and embedded in paraffin. Masson´s trichrome-stained sections were subjected to morphological and the following morphometrical analyzes: epithelial perimeter and area of the smooth muscular layer. TUNEL (Terminal deoxynucleotidyl-transferase mediated dUTP Nick End Labeling) method, NF-kB (nuclear factor kappa B) and AR (androgen receptors) immunohistochemical detection were also carried out. The birefringent collagen of the muscular layer was quantified in picrosirius red-stained sections under polarized light. The muscular layer was also evaluated under Transmission Electron Microscopy (TEM). Results In CMTG, the mucosa of vas deferens was intensely folded; the epithelial cells showed numerous pyknotic nuclei and the epithelial perimeter and the area of the muscular layer decreased significantly. Numerous TUNEL-labeled nuclei were found either in the epithelial cells, mainly basal cells, or in the smooth muscle cells which also showed typical features of apoptosis under TEM. While an enhanced NF-kB immunoexpression was found in the cytoplasm of muscle cells, a weak AR immunolabeling was detected in these cells. In CMTG, no significant difference was observed

  17. Evolution of Yield Stress during Structural Relaxation for the Epoxy 828DEA

    NASA Astrophysics Data System (ADS)

    Arechederra, Gabriel; McCoy, John; Kropka, Jamie

    The evolution of yield stress from structural relaxation of diethanolamine cured diglycidyl ether of bisphenol-A, 828DEA, was tracked using uniaxial compression experiments. Samples were aged isothermally for up to 3 months at 5 temperatures ranging from deep in the glass to above Tg. Since 828DEA has remaining reactive potential, it is anticipated that the Tg will continue to evolve throughout the course of the study as new chemical crosslinks are formed. Consequently, it is important to track the evolution of Tg as well as the progression of the fictive temperature in order to interpret the evolution of yield stress. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE.

  18. Effect of Ar+ ion post-irradiation on crystal structure, magnetic behavior and optical band gap of Co-implanted ZnO wafers

    NASA Astrophysics Data System (ADS)

    Xu, N. N.; Li, G. P.; Lin, Q. L.; Liu, H.; Bao, L. M.

    2016-12-01

    Single crystals wurtzite ZnO with (001) orientation were implanted with Co+ ions at room temperature (RT). To tune their magnetic behavior as well as the band gap of the implanted wafers, Ar+ ion post-irradiation (PI) was performed using the calculated energy and ion dose. The formed Co clusters present in the high dose Co-implanted ZnO wafer were observed to be absent after the PI, which is quite different from the low dose doped one. It is found that all the implanted samples showed a giant magnetic moment and a narrowing optical band gap, and that the post-irradiated ones exhibited an even further redshifted absorption edge and ferromagnetic behavior but with saturation magnetization (MS) drastically decreased.

  19. Formation and evolution of tweed structures on high-purity aluminum polycrystalline foils under cyclic tension

    SciTech Connect

    Kuznetsov, P. V.; Vlasov, I. V.; Sklyarova, E. A.; Smekalina, T. V.

    2015-10-27

    Peculiarities of formation and evolution of tweed structures on the surface of high-purity aluminum polycrystalline foils under cyclic tension were studied using an atom force microscope and a white light interferometer. Tweed structures of micron and submicron sizes were found on the foils at different number of cycles. In the range of 42,000 < N < 95,000 cycles destruction of tweed patterns is observed, which leads to their disappearance from the surface of the foils. Formation of tweed structures of various scales is discussed in terms of the Grinfeld instability.

  20. AR Signaling in Breast Cancer

    PubMed Central

    Rahim, Bilal; O’Regan, Ruth

    2017-01-01

    Androgen receptor (AR, a member of the steroid hormone receptor family) status has become increasingly important as both a prognostic marker and potential therapeutic target in breast cancer. AR is expressed in up to 90% of estrogen receptor (ER) positive breast cancer, and to a lesser degree, human epidermal growth factor 2 (HER2) amplified tumors. In the former, AR signaling has been correlated with a better prognosis given its inhibitory activity in estrogen dependent disease, though conversely has also been shown to increase resistance to anti-estrogen therapies such as tamoxifen. AR blockade can mitigate this resistance, and thus serves as a potential target in ER-positive breast cancer. In HER2 amplified breast cancer, studies are somewhat conflicting, though most show either no effect or are associated with poorer survival. Much of the available data on AR signaling is in triple-negative breast cancer (TNBC), which is an aggressive disease with inferior outcomes comparative to other breast cancer subtypes. At present, there are no approved targeted therapies in TNBC, making study of the AR signaling pathway compelling. Gene expression profiling studies have also identified a luminal androgen receptor (LAR) subtype that is dependent on AR signaling in TNBC. Regardless, there seems to be an association between AR expression and improved outcomes in TNBC. Despite lower pathologic complete response (pCR) rates with neoadjuvant therapy, patients with AR-expressing TNBC have been shown to have a better prognosis than those that are AR-negative. Clinical studies targeting AR have shown somewhat promising results. In this paper we review the literature on the biology of AR in breast cancer and its prognostic and predictive roles. We also present our thoughts on therapeutic strategies. PMID:28245550

  1. AR Signaling in Breast Cancer.

    PubMed

    Rahim, Bilal; O'Regan, Ruth

    2017-02-24

    Androgen receptor (AR, a member of the steroid hormone receptor family) status has become increasingly important as both a prognostic marker and potential therapeutic target in breast cancer. AR is expressed in up to 90% of estrogen receptor (ER) positive breast cancer, and to a lesser degree, human epidermal growth factor 2 (HER2) amplified tumors. In the former, AR signaling has been correlated with a better prognosis given its inhibitory activity in estrogen dependent disease, though conversely has also been shown to increase resistance to anti-estrogen therapies such as tamoxifen. AR blockade can mitigate this resistance, and thus serves as a potential target in ER-positive breast cancer. In HER2 amplified breast cancer, studies are somewhat conflicting, though most show either no effect or are associated with poorer survival. Much of the available data on AR signaling is in triple-negative breast cancer (TNBC), which is an aggressive disease with inferior outcomes comparative to other breast cancer subtypes. At present, there are no approved targeted therapies in TNBC, making study of the AR signaling pathway compelling. Gene expression profiling studies have also identified a luminal androgen receptor (LAR) subtype that is dependent on AR signaling in TNBC. Regardless, there seems to be an association between AR expression and improved outcomes in TNBC. Despite lower pathologic complete response (pCR) rates with neoadjuvant therapy, patients with AR-expressing TNBC have been shown to have a better prognosis than those that are AR-negative. Clinical studies targeting AR have shown somewhat promising results. In this paper we review the literature on the biology of AR in breast cancer and its prognostic and predictive roles. We also present our thoughts on therapeutic strategies.

  2. INTERPRETING ERUPTIVE BEHAVIOR IN NOAA AR 11158 VIA THE REGION'S MAGNETIC ENERGY AND RELATIVE-HELICITY BUDGETS

    SciTech Connect

    Tziotziou, Kostas; Georgoulis, Manolis K.; Liu Yang

    2013-08-01

    In previous works, we introduced a nonlinear force-free method that self-consistently calculates the instantaneous budgets of free magnetic energy and relative magnetic helicity in solar active regions (ARs). Calculation is expedient and practical, using only a single vector magnetogram per computation. We apply this method to a time series of 600 high-cadence vector magnetograms of the eruptive NOAA AR 11158 acquired by the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory over a five-day observing interval. Besides testing our method extensively, we use it to interpret the dynamical evolution in the AR, including eruptions. We find that the AR builds large budgets of both free magnetic energy and relative magnetic helicity, sufficient to power many more eruptions than the ones it gave within the interval of interest. For each of these major eruptions, we find eruption-related decreases and subsequent free-energy and helicity budgets that are consistent with the observed eruption (flare and coronal mass ejection (CME)) sizes. In addition, we find that (1) evolution in the AR is consistent with the recently proposed (free) energy-(relative) helicity diagram of solar ARs, (2) eruption-related decreases occur before the flare and the projected CME-launch times, suggesting that CME progenitors precede flares, and (3) self terms of free energy and relative helicity most likely originate from respective mutual terms, following a progressive mutual-to-self conversion pattern that most likely stems from magnetic reconnection. This results in the non-ideal formation of increasingly helical pre-eruption structures and instigates further research on the triggering of solar eruptions with magnetic helicity firmly placed in the eruption cadre.

  3. Molecular analysis of Arthrobacter myovirus vB_ArtM-ArV1: we blame it on the tail.

    PubMed

    Kaliniene, Laura; Šimoliūnas, Eugenijus; Truncaitė, Lidija; Zajančkauskaitė, Aurelija; Nainys, Juozas; Kaupinis, Algirdas; Valius, Mindaugas; Meškys, Rolandas

    2017-01-25

    This is the first report on a myophage that infects Arthrobacter A novel virus vB_ArtM-ArV1 (ArV1) was isolated from soil using Arthrobacter sp. 68b strain for phage propagation. Transmission electron microscopy showed its resemblance to members of the family Myoviridae: ArV1 has an isometric head (∼74 nm in diameter) and a contractile non-flexible tail (∼192 nm). Phylogenetic and comparative sequence analyses, however, revealed that ArV1 has more genes in common with phages from the family Siphoviridae than it does with any myovirus characterized to date. The genome of ArV1 is a linear, circularly permuted, double-stranded DNA molecule (71,200 bp) with a GC content of 61.6 %. The genome codes for 101 ORFs, yet contains no tRNA genes. More than 50% of ArV1 genes encode unique proteins that either have no reliable identity to database entries, or have homologues only in Arthrobacter phages, both sipho- and myoviruses. Using bioinformatics approaches, 13 ArV1 structural genes were identified, including those coding for head, tail, tail fiber, and baseplate proteins. A further 6 ArV1 ORFs were annotated as putative structural proteins based on the results of proteomic analysis. Phylogenetic analysis based on the alignment of four conserved virion proteins revealed that Arthrobacter myophages form a discreet clade that seems to occupy a somewhat intermediate position between myo- and siphoviruses. Thus, the data presented here will help to advance our understanding of genetic diversity and evolution of phages that constitute the order Caudovirales IMPORTANCE: Bacteriophages, which likely have originated in the early Precambrian Era, represent the most numerous population on the planet. Approximately 95% of known phages are tailed viruses that comprise three families: Podoviridae (short tail), Siphoviridae (long noncontractile tail), and Myoviridae (contractile tail). Based on the current hypothesis, myophages, which may have evolved from siphophages, are thought to

  4. Transverse zones controlling the structural evolution of the Zipaquira Anticline (Eastern Cordillera, Colombia): Regional implications

    NASA Astrophysics Data System (ADS)

    García, Helbert; Jiménez, Giovanny

    2016-08-01

    We report paleomagnetic, magnetic fabric and structural results from 21 sites collected in Cretaceous marine mudstones and Paleogene continental sandstones from the limbs, hinge and transverse zones of the Zipaquira Anticline (ZA). The ZA is an asymmetrical fold with one limb completely overturned by processes like gravity and salt tectonics, and marked by several axis curvatures. The ZA is controlled by at least two (2) transverse zones known as the Neusa and Zipaquira Transverse Zones (NTZ and ZTZ, respectively). Magnetic mineralogy methods were applied at different sites and the main carriers of the magnetic properties are paramagnetic components with some sites being controlled by hematite and magnetite. Magnetic fabric analysis shows rigid-body rotation for the back-limb in the ZA, while the forelimb is subjected to internal deformation. Structural and paleomagnetic data shows the influence of the NTZ and ZTZ in the evolution of the different structures like the ZA and the Zipaquira, Carupa, Rio Guandoque, Las Margaritas and Neusa faults, controlling several factors as vergence, extension, fold axis curvature and stratigraphic detatchment. Clockwise rotations unraveled a block segmentation following a discontinuos model caused by transverse zones and one site reported a counter clockwise rotation associated with a left-lateral strike slip component for transverse faults (e.g. the Neusa Fault). We propose that diverse transverse zones have been active since Paleogene times, playing an important role in the tectonic evolution of the Cundinamarca sub-basin and controlling the structural evolution of folds and faults with block segmentation and rotations.

  5. Differential evolution: Global search problem in LEED-IV surface structural analysis

    SciTech Connect

    Nascimento, V.B.; Plummer, E.W.

    2015-02-15

    The search process associated with the quantitative theory–experiment comparison in Low Energy Electron Diffraction surface structural analysis can be very time consuming, especially in the case of complex materials with many atoms in the unit cell. Global search algorithms need to be employed to locate the global minimum of the reliability factor in the multi-dimensional structural parameter space. In this study we investigate the use of the Differential Evolution algorithm in Low Energy Electron Diffraction structural analysis. Despite the simplicity of its mechanism the Differential Evolution algorithm presents an impressive performance when applied to ultra-thin films of BaTiO{sub 3}(001) in a theory–theory comparison. A scaling relation of N{sup (1.47} {sup ±} {sup 0.08)} was obtained, where N is the total number of parameters to be optimized. - Highlights: • We investigated the use of the Differential Evolution algorithm (DE) for the LEED search problem. • The DE method was applied to the optimization of the surface structure of the BaTiO{sub 3}(001) ultra-thin films. • A very favorable scaling relation of N{sup 1.47} was obtained, where N is the total number of parameters to be optimized.

  6. The spatial evolution of stellar structures in the LMC/SMC

    NASA Astrophysics Data System (ADS)

    Bastian, Nate; Gieles, Mark; Ercolano, Barbara; Gutermuth, Robert

    2009-03-01

    We present an analysis of the spatial distribution of various stellar populations within the Large and Small Magellanic Clouds. We use optically selected stellar samples with mean ages between ~9 and ~1000 Myr, and existing stellar cluster catalogues to investigate how stellar structures form and evolve within the LMC/SMC. We use two statistical techniques to study the evolution of structure within these galaxies, the Q-parameter and the two-point correlation function (TPCF). In both galaxies we find the stars are born with a high degree of substructure (i.e. are highly fractal) and that the stellar distribution approaches that of the “background” population on timescales similar to the crossing times of the galaxy (~ 80 Myr & ~ 150 Myr for the SMC/LMC respectively). By comparing our observations to simple models of structural evolution we find that “popping star clusters” do not significantly influence structural evolution in these galaxies. Instead we argue that general galactic dynamics are the main drivers, and that substructure will be erased in approximately the crossing time, regardless of spatial scale, from small clusters to whole galaxies. This can explain why many young Galactic clusters have high degrees of substructure, while others are smooth and centrally concentrated. We conclude with a general discussion on cluster “infant mortality”, in an attempt to clarify the time/spatial scales involved.

  7. Evolution of the mammalian middle ear and jaw: adaptations and novel structures

    PubMed Central

    Anthwal, Neal; Joshi, Leena; Tucker, Abigail S

    2013-01-01

    Having three ossicles in the middle ear is one of the defining features of mammals. All reptiles and birds have only one middle ear ossicle, the stapes or columella. How these two additional ossicles came to reside and function in the middle ear of mammals has been studied for the last 200 years and represents one of the classic example of how structures can change during evolution to function in new and novel ways. From fossil data, comparative anatomy and developmental biology it is now clear that the two new bones in the mammalian middle ear, the malleus and incus, are homologous to the quadrate and articular, which form the articulation for the upper and lower jaws in non-mammalian jawed vertebrates. The incorporation of the primary jaw joint into the mammalian middle ear was only possible due to the evolution of a new way to articulate the upper and lower jaws, with the formation of the dentary-squamosal joint, or TMJ in humans. The evolution of the three-ossicle ear in mammals is thus intricately connected with the evolution of a novel jaw joint, the two structures evolving together to create the distinctive mammalian skull. PMID:22686855

  8. The suitability of concentration addition for predicting the effects of multi-component mixtures of up to 17 anti-androgens with varied structural features in an in vitro AR antagonist assay

    SciTech Connect

    Ermler, Sibylle; Scholze, Martin; Kortenkamp, Andreas

    2011-12-15

    The risks associated with human exposures to chemicals capable of antagonising the effects of endogenous androgens have attracted considerable recent interest. Exposure is typically to large numbers of chemicals with androgen receptor (AR) antagonist activity, yet there is limited evidence of the combined effects of multi-component mixtures of these chemicals. A few in vitro studies with mixtures of up to six AR antagonists suggest that the concept of concentration addition (CA) provides good approximations of experimentally observed mixture effects, but studies with larger numbers of anti-androgens, and with more varied structural features, are missing. Here we show that the mixture effects of up to 17 AR antagonists, comprising compounds as diverse as UV-filter substances, parabens, perfluorinated compounds, bisphenol-A, benzo({alpha})pyrene, synthetic musks, antioxidants and polybrominated biphenyls, can be predicted well on the basis of the anti-androgenicity of the single components using the concept of CA. We tested these mixtures in an in vitro AR-dependent luciferase reporter gene assay, based on MDA-kb2 cells. The effects of further mixtures, composed of four and six anti-androgens, could be predicted accurately by CA. However, there was a shortfall from expected additivity with a ten-component mixture at two different mixture ratios, but attempts to attribute these deviations to differential expression of hormone-metabolising CYP isoforms did not produce conclusive results. CA provides good approximations of in vitro mixture effects of anti-androgens with varying structural features. -- Highlights: Black-Right-Pointing-Pointer Humans are exposed to a large number of androgen receptor antagonists. Black-Right-Pointing-Pointer There is limited evidence of the combined effects of anti-androgenic chemicals. Black-Right-Pointing-Pointer We modelled the predictability of combined effects of up to 17 anti-androgens. Black-Right-Pointing-Pointer We tested the

  9. Call for Development of New Mineral Standards for 40Ar/39Ar Dating

    NASA Astrophysics Data System (ADS)

    Deino, A. L.; Turrin, B. D.; Renne, P. R.; Hemming, S. R.

    2015-12-01

    Age determination via the 40Ar/39Ar dating method relies on the intercomparison of measured 40Ar*/39ArK ratios of geological unknowns with those of co-irradiated mineral standards. Good analytical procedure dictates that these ratios (and the evolution of the Ar ion beams underpinning them) be as similar as practical for the greatest accuracy. Unfortunately, throughout several intervals of the geological time scale this 'best practice' cannot be achieved with existing widely used standards. Only two internationally utilized sanidine standards are available for the middle to late Cenozoic: the Alder Creek Rhyolite sanidine (ACs), at ~1.2 Ma (Turrin et al., 1994; Nomade et al., 2005), and the Fish Canyon Tuff sanidine (FCs) at ~28.2 Ma (e.g., Kuiper et al., 2008; Renne et al, 2011). The situation is even worse throughout much of the rest of the Phanerozoic, as the next oldest standard in common use is the Hb3gr hornblende standard with an age of ~1.1 Ga (Turner, 1971; Jourdan et al., 2006). We propose, as a community effort, the development a set of standards covering the entire target range of high-precision 40Ar/39Ar dating, i.e. the Phanerozoic. Their ages would be stepped in a regular fashion with no more than approximately a factor of 3 between standards, such that in the worse case the 40Ar*/39Ar ratios of standards and unknown need differ by no more than a factor of two. While somewhat arbitrary, an approximately 3 X age progression allows the entire time scale to be covered by a manageable number of standards. Anchoring the progression in the widely used ACs, FCs, and Hb3gr (in bold, below) yields the following set of suggested standard ages: 0.4, 1.2, 3.3, 9.4, 28.2, 95, 320, and 1100 Ma. A suitable standard should be highly reproducible in age at the grain-to-grain and sub-grain levels, and highly radiogenic. The mineral should be abundant and easily separated from the host rock. These criteria may be most easily achieved by focusing on sanidine phenocrysts

  10. Analysis of the secondary structure of ITS1 in Pectinidae: implications for phylogenetic reconstruction and structural evolution.

    PubMed

    Wang, Shi; Bao, Zhenmin; Li, Ning; Zhang, Lingling; Hu, Jingjie

    2007-01-01

    It is at present difficult to accurately position gaps in sequence alignment and to determine substructural homology in structure alignment when reconstructing phylogenies based on highly divergent sequences. Therefore, we have developed a new strategy for inferring phylogenies based on highly divergent sequences. In this new strategy, the whole secondary structure presented as a string in bracket notation is used as phylogenetic characters to infer phylogenetic relationships. It is no longer necessary to decompose the secondary structure into homologous substructural components. In this study, reliable phylogenetic relationships of eight species in Pectinidae were inferred from the structure alignment, but not from sequence alignment, even with the aid of structural information. The results suggest that this new strategy should be useful for inferring phylogenetic relationships based on highly divergent sequences. Moreover, the structural evolution of ITS1 in Pectinidae was also investigated. The whole ITS1 structure could be divided into four structural domains. Compensatory changes were found in all four structural domains. Structural motifs in these domains were identified further. These motifs, especially those in D2 and D3, may have important functions in the maturation of rRNAs.

  11. AR-39-AR-40 "Age" of Basaltic Shergottite NWA-3171

    NASA Technical Reports Server (NTRS)

    Bogard, Donald D.; Park, Jisun

    2007-01-01

    North-West-Africa 3171 is a 506 g, relatively fresh appearing, basaltic shergottite with similarities to Zagami and Shergotty, but not obviously paired with any of the other known African basaltic shergottites. Its exposure age has the range of 2.5-3.1 Myr , similar to those of Zagami and Shergotty. We made AR-39-AR-40 analyses of a "plagioclase" (now shock-converted to maskelynite) separate and of a glass hand-picked from a vein connected to shock melt pockets.. Plagioclase was separated using its low magnetic susceptibility and then heavy liquid with density of <2.85 g/cm(exp 3). The AR-39-AR-40 age spectrum of NWA-317 1 plag displays a rise in age over 20-100% of the 39Ar release, from 0.24 Gyr to 0.27 Gy.

  12. 40Ar/39Ar Studies of Antarctic Micrometeorites

    NASA Astrophysics Data System (ADS)

    Saxton, J. M.; Knott, S. F.; Turner, G.; Maurette, M.

    1992-07-01

    We have used the ^40Ar/^39Ar technique to study eight dust particles, in the size range 50-100 microns, collected by filtering Antarctic blue ice (Maurette et al. 1989). The particles were pressed into aluminium foil and their compositions estimated using SEM/EDX techniques. Six were found to have approximately chondritic Mg/Fe/Si ratios, suggesting an extraterrestrial origin. The remaining two particles appeared to be composed mostly of iron and we are not sure of their origin. The particles were then irradiated with a fast neutron fluence of approximately 6 x 10^18 cm^-2, and the argon in them extracted using a pulsed laser delivering about 100 mJ per pulse. We attempted to step heat most of the particles by initially defocusing the beam to reduce the heating effect. In four cases, a sufficient amount of gas was released for step heating to be profitable. The results for five of the chondritic particles are shown in the figure. One yielded a very small amount of gas and is not plotted. The high temperature step is shown for those particles that were step heated. In this diagram, air plots on the y-axis (^36Ar/^40Ar = 0.00338), a purely radiogenic component plots on the x-axis, and addition of ^36Ar moves a point vertically upwards. Four particles have ^36Ar/^40Ar ratios higher than air. This confirms their extraterrestrial origin. We believe the 36Ar is most probably derived from solar energetic particles; only 10^2-10^3 years exposure at 1 AU would be required to produce the level of ^36Ar we observe (10^-12-10^-13 ccSTP), assuming that no 36Ar is lost during atmospheric passage. This is comfortably less than the time taken for a particle of this size to drift in from 2AU to 1AU due to the Poynting Robertson effect, which is of the order 10^5 years. The concentration ^36Ar content is of the order of 10^-7-10^-6 g^-1, which is comparable to the levels of trapped ^36Ar found in primitive meteorites. This interpretation of the source of the ^36Ar would seem to

  13. Understanding the Global Structure and Evolution of Coronal Mass Ejections in the Solar Wind

    NASA Technical Reports Server (NTRS)

    Riley, Pete

    2004-01-01

    This report summarizes the technical progress made during the first six months of the second year of the NASA Living with a Star program contract Understanding the global structure and evolution of coronal mass ejections in the solar wind, between NASA and Science Applications International Corporation, and covers the period November 18, 2003 - May 17,2004. Under this contract SAIC has conducted numerical and data analysis related to fundamental issues concerning the origin, intrinsic properties, global structure, and evolution of coronal mass ejections in the solar wind. During this working period we have focused on a quantitative assessment of 5 flux rope fitting techniques. In the following sections we summarize the main aspects of this work and our proposed investigation plan for the next reporting period. Thus far, our investigation has resulted in 6 refereed scientific publications and we have presented the results at a number of scientific meetings and workshops.

  14. Structural Evolutions of STOCK Markets Controlled by Generalized Entropy Principles of Complex Systems

    NASA Astrophysics Data System (ADS)

    Wang, Yi Jiao; Feng, Qing Yi; Chai, Li He

    As one of the most important financial markets and one of the main parts of economic system, the stock market has become the research focus in economics. The stock market is a typical complex open system far from equilibrium. Many available models that make huge contribution to researches on market are strong in describing the market however, ignoring strong nonlinear interactions among active agents and weak in reveal underlying dynamic mechanisms of structural evolutions of market. From econophysical perspectives, this paper analyzes the complex interactions among agents and defines the generalized entropy in stock markets. Nonlinear evolutionary dynamic equation for the stock markets is then derived from Maximum Generalized Entropy Principle. Simulations are accordingly conducted for a typical case with the given data, by which the structural evolution of the stock market system is demonstrated. Some discussions and implications are finally provided.

  15. Simultaneous optimization of enzyme activity and quaternary structure by directed evolution

    PubMed Central

    Vamvaca, Katherina; Butz, Maren; Walter, Kai U.; Taylor, Sean V.; Hilvert, Donald

    2005-01-01

    Natural evolution has produced efficient enzymes of enormous structural diversity. We imitated this natural process in the laboratory to augment the efficiency of an engineered chorismate mutase with low activity and an unusual hexameric topology. By applying two rounds of DNA shuffling and genetic selection, we obtained a 400-fold more efficient enzyme, containing three non-active-site mutations. Detailed biophysical characterization of the evolved variant suggests that it exists predominantly as a trimer in solution, but is otherwise similarly stable as the parent hexamer. The dramatic structural and functional effects achieved by a small number of seemingly innocuous substitutions highlights the utility of directed evolution for modifying protein–protein interactions to produce novel quaternary states with optimized activities. PMID:15987889

  16. Evolution of patterned step structure on vicinal Si(111) surface during high temperature annealing

    NASA Astrophysics Data System (ADS)

    Kan, Hung-Chih; Kwon, Taesoon; Phaneuf, Raymond

    2007-03-01

    We present the results of numerical simulations of the evolution of patterned step structures on vicinal Si(111) surfaces during high temperature annealing, which presumably drives the surface far away from equilibrium. We use a mesoscopic model [1] to describe the motion of individual steps under the effects of sublimation, step stiffness (line tension), and step-step interaction. The qualitative consistency between our simulation and experiment [2] suggest that thermodynamic driving force, such as the step-stiffness and step-step interaction dominate the evolution of the step structure during high temperature annealing. [1] J. D. Weeks, D.-J. Lui, and H.-C. Jeong, in Dynamics of Crystal Surfaces and Interfaces, edited by P. M. Duxbury and T.J. Pence (Plenum Press, New York and London 1997), pp. 199-216 [2] T. Kwon, H-C. Kan, R. J. Phaneuf, Appl. Phys. Lett. 88, 071914 (2006) .

  17. Convergent evolution in structural elements of proteins investigated using cross profile analysis

    PubMed Central

    2012-01-01

    Background Evolutionary relations of similar segments shared by different protein folds remain controversial, even though many examples of such segments have been found. To date, several methods such as those based on the results of structure comparisons, sequence-based classifications, and sequence-based profile-profile comparisons have been applied to identify such protein segments that possess local similarities in both sequence and structure across protein folds. However, to capture more precise sequence-structure relations, no method reported to date combines structure-based profiles, and sequence-based profiles based on evolutionary information. The former are generally regarded as representing the amino acid preferences at each position of a specific conformation of protein segment. They might reflect the nature of ancient short peptide ancestors, using the results of structural classifications of protein segments. Results This report describes the development and use of "Cross Profile Analysis" to compare sequence-based profiles and structure-based profiles based on amino acid occurrences at each position within a protein segment cluster. Using systematic cross profile analysis, we found structural clusters of 9-residue and 15-residue segments showing remarkably strong correlation with particular sequence profiles. These correlations reflect structural similarities among constituent segments of both sequence-based and structure-based profiles. We also report previously undetectable sequence-structure patterns that transcend protein family and fold boundaries, and present results of the conformational analysis of the deduced peptide of a segment cluster. These results suggest the existence of ancient short-peptide ancestors. Conclusions Cross profile analysis reveals the polyphyletic and convergent evolution of β-hairpin-like structures, which were verified both experimentally and computationally. The results presented here give us new insights into the

  18. Transcriptional and posttranscriptional regulation of Bacillus sp. CDB3 arsenic-resistance operon ars1

    PubMed Central

    Yu, Xuefei; Zheng, Wei; Bhat, Somanath; Aquilina, J. Andrew

    2015-01-01

    Bacillus sp. CDB3 possesses a novel eight-gene ars cluster (ars1, arsRYCDATorf7orf8) with some unusual features in regard to expression regulation. This study demonstrated that the cluster is a single operon but can also produce a short three-gene arsRYC transcript. A hairpin structure formed by internal inverted repeats between arsC and arsD was shown to diminish the expression of the full operon, thereby probably acting as a transcription attenuator. A degradation product of the arsRYC transcript was also identified. Electrophoretic mobility shift analysis demonstrated that ArsR interacts with the ars1 promoter forming a protein-DNA complex that could be impaired by arsenite. However, no interaction was detected between ArsD and the ars1 promoter, suggesting that the CDB3 ArsD protein may not play a regulatory role. Compared to other ars gene clusters, regulation of the Bacillus sp. CDB3 ars1 operon is more complex. It represents another example of specific mRNA degradation in the transporter gene region and possibly the first case of attenuator-mediated regulation of ars operons. PMID:26355338

  19. Atmospheric Forcing and the Structure and Evolution of the Upper Ocean in the Bay of Bengal

    DTIC Science & Technology

    2014-09-30

    Atmospheric Forcing and the Structure and Evolution of the Upper Ocean in the Bay of Bengal J. Thomas Farrar and Robert A. Weller Woods Hole...Oceanographic Institution 266 Woods Hole Rd. Clark 212A (MS# 29) Woods Hole, MA 02543-1050 phone: (508) 289-2691 fax: (508) 457-2163 email: jfarrar...AND ADDRESS(ES) Woods Hole Oceanographic Institution,266 Woods Hole Rd, Woods Hole ,MA,02543 8. PERFORMING ORGANIZATION REPORT NUMBER 9

  20. Temperature evolution of the crystal structure of MnTiO{sub 3}

    SciTech Connect

    Maurya, R. K. Singh, Navneet; Bindu, R.

    2015-06-24

    Temperature dependent x-ray diffraction studies were carried on MnTiO{sub 3}. The evolution of the structural parameters as a function of temperature reveal strong link with its magnetism. The results indicate onset of the antiferromagnetic interaction well above the Neel temperature. The present studies will be helpful in understanding the multiferroic property exhibited by this system especially where hybridization plays a very important role.

  1. Monitoring Data-Structure Evolution in Distributed Message-Passing Programs

    NASA Technical Reports Server (NTRS)

    Sarukkai, Sekhar R.; Beers, Andrew; Woodrow, Thomas S. (Technical Monitor)

    1996-01-01

    Monitoring the evolution of data structures in parallel and distributed programs, is critical for debugging its semantics and performance. However, the current state-of-art in tracking and presenting data-structure information on parallel and distributed environments is cumbersome and does not scale. In this paper we present a methodology that automatically tracks memory bindings (not the actual contents) of static and dynamic data-structures of message-passing C programs, using PVM. With the help of a number of examples we show that in addition to determining the impact of memory allocation overheads on program performance, graphical views can help in debugging the semantics of program execution. Scalable animations of virtual address bindings of source-level data-structures are used for debugging the semantics of parallel programs across all processors. In conjunction with light-weight core-files, this technique can be used to complement traditional debuggers on single processors. Detailed information (such as data-structure contents), on specific nodes, can be determined using traditional debuggers after the data structure evolution leading to the semantic error is observed graphically.

  2. Structure and evolution of the large scale solar and heliospheric magnetic fields. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Hoeksema, J. T.

    1984-01-01

    Structure and evolution of large scale photospheric and coronal magnetic fields in the interval 1976-1983 were studied using observations from the Stanford Solar Observatory and a potential field model. The solar wind in the heliosphere is organized into large regions in which the magnetic field has a componenet either toward or away from the sun. The model predicts the location of the current sheet separating these regions. Near solar minimum, in 1976, the current sheet lay within a few degrees of the solar equator having two extensions north and south of the equator. Soon after minimum the latitudinal extent began to increase. The sheet reached to at least 50 deg from 1978 through 1983. The complex structure near maximum occasionally included multiple current sheets. Large scale structures persist for up to two years during the entire interval. To minimize errors in determining the structure of the heliospheric field particular attention was paid to decreasing the distorting effects of rapid field evolution, finding the optimum source surface radius, determining the correction to the sun's polar field, and handling missing data. The predicted structure agrees with direct interplanetary field measurements taken near the ecliptic and with coronameter and interplanetary scintillation measurements which infer the three dimensional interplanetary magnetic structure. During most of the solar cycle the heliospheric field cannot be adequately described as a dipole.

  3. Protein design by fusion: implications for protein structure prediction and evolution

    SciTech Connect

    Skorupka, Katarzyna; Han, Seong Kyu; Nam, Hyun-Jun; Kim, Sanguk; Faham, Salem

    2013-11-19

    Domain fusion is a useful tool in protein design. Here, the structure of a fusion of the heterodimeric flagella-assembly proteins FliS and FliC is reported. Although the ability of the fusion protein to maintain the structure of the heterodimer may be apparent, threading-based structural predictions do not properly fuse the heterodimer. Additional examples of naturally occurring heterodimers that are homologous to full-length proteins were identified. These examples highlight that the designed protein was engineered by the same tools as used in the natural evolution of proteins and that heterodimeric structures contain a wealth of information, currently unused, that can improve structural predictions.

  4. Mineralogy and Ar-Ar Age of the Tarahumara IIE Iron, with Reference to the Origin of Alkali-Rich Materials

    NASA Technical Reports Server (NTRS)

    Takeda, Hiroshi; Bogard, Donald D.; Otsuki, Mayumi; Ishii, Teruaki

    2003-01-01

    Silicate inclusions in nine known IIE irons show diversity in mineralogy, and Colomera, Kodaikanal, Elga and Miles contain alkali-rich silicate inclusions. Bogard et al. showed evidence of a complex parent body evolution for IIE irons based on Ar-39-Ar-40 ages. Colomera contained a sanidine-rich surface inclusion and the K-enrichment trends in the Na-rich inclusions are different from those of other IIEs. To elucidate the origin of K-rich materials, we studied the mineral